FIELD OF THE INVENTION

[0001] This invention relates generally to microbial production of hydrogen gas by biological water gas shift reaction using a CO-containing feed gas produced by plasma gasification of opportunity fuels.

BACKGROUND

[0002] Hydrogen (H ₂ ) is an attractive alternative to fossil fuels as a portable, non-polluting source of energy. Today, hydrogen gas is predominantly produced by reforming fossil sources (petroleum, natural gas and coal) to produce synthesis gas (syngas), which is a mixture of hydrogen and carbon monoxide (CO). Syngas is customarily generated by steam or dry reforming or partial oxidation of natural gas or liquid hydrocarbons, by gasification of coal, or by waste-to-energy gasification processes (e.g., biomass gasification). The relative amounts of CO and H ₂ in a syngas product varies depending upon the way it is generated. Existing technologies for separating and purifying the hydrogen component of syngas usually involve pressure swing adsorption (PSA), membrane separation, or chemical reaction on solid iron oxide and calcium oxide beds, with regeneration of the solids. [0003] Different technologies such as electrolysis and thermolysis have been investigated for producing hydrogen from water. Still other technologies used for hydrogen production include inorganic chemical reduction and various biological reactions. The biological production of hydrogen using photosynthetic and fermentative microorganisms has been described. Among these microorganisms are certain photosynthetic bacteria that contain a carbon monoxide oxidation pathway in which the water-gas shift reaction occurs, converting a mole of water and a mole of carbon monoxide into equimolar amounts of hydrogen and carbon dioxide. The water-gas shift reaction has been reported for Rubrivivax gelatinosus, Rhodospirillum rubrum, Rhodopseudomonas palustris, and others.

[0004] As the CO substrate is of low solubility in an aqueous solution, mass transfer of CO into the microbial culture medium is likely the rate-limiting step for the biological water-gas shift reaction. A challenge in developing synthesis gas fermentation processes is providing for efficient gas mass transfer and resolving microbial toxicity issues with respect to CO and CO ₂ gases. [0005] Accordingly, there exists a need for a system of producing high-purity hydrogen in bulk via microbial fermentation-polishing of synthesis gas. Desirably, the system comprises one or more gasifϊers by which synthesis gas may be produced via gasification of opportunity fuels, although utilization of fossil fuels is also suitable. Gasifiers within the system should produce synthesis gas without creating substantial environmentally-undesirable (leaching) slag.

SUMMARY

[0006] In accordance with certain embodiments of the invention, herein disclosed is a biological water gas shift reaction system comprising: a gasifier operable to gasify carbonaceous feed material to produce gaseous product comprising synthesis gas, the gasifier comprising a gasifier inlet for carbonaceous feed material, a gasifier outlet for gaseous product comprising synthesis gas and a gasifier outlet for non-gaseous gasification product, wherein the gasifier is operable at an operating temperature and operating pressure; and a deep shaft reactor fluidly connected to the gasifier and configured for fermentation of a suspension of microorganisms capable of net water-gas splitting, the deep shaft reactor comprising at least one reactor inlet for a fluid comprising fermentation feed gas and a reactor outlet for fermentation product comprising hydrogen gas, wherein the deep shaft reactor has a vertical depth, a shaft width, and a normal operating fill line; and wherein the gasifier outlet for gaseous product is fluidly connected with the at least one reactor inlet for a fluid comprising fermentation feed gas such that at least a portion of the carbon monoxide in the fermentation feed gas may be obtained from the gasifier. In embodiments, the gasifier is a plasma gasifier. The gasifier may be operable at temperatures of at least 2500 ⁰ C. The gasifier may be operable at atmospheric pressure. The gasifier may be operable to produce a non-gaseous product which passes EPA-mandated Toxicity Characteristic Leachate Procedure. In embodiments, the gasifier is operable to gasify carbonaceous feed material selected from opportunity fuels and fossil fuels.

[0007] In applications, the deep shaft reactor is divided into a fast-flow zone and a slow-flow zone by a divider that extends vertically from at or below the normal operating fill line to a first vertical distance from the bottom of the reactor. The system may further comprise means for injecting the fluid comprising fermentation feed gas to at least one location within the fast flow zone of the deep shaft reactor, wherein the means for injecting is configured such that, during operation, gas lift provides an upward linear velocity within the fast flow zone that is greater than a downward linear velocity within the slow flow zone. The means for injecting may comprise at least one high pressure pump and at least one rotary head nozzle. The means for injecting may comprise means for injecting the fluid comprising fermentation feed gas at a plurality of vertical locations along the vertical length of the fast flow zone of the deep shaft reactor. In embodiments of the system, there is no inlet for injection of fluid comprising fermentation feed gas into the slow flow zone of the deep shaft reactor.

[0008] The deep shaft reactor may further comprise a first suspension outlet located below the normal operating fill line and wherein the system further comprises a biomass separation unit configured for separation of biomass from a suspension introduced thereto, to produce a biomass-reduced product comprising a reduced concentration of biomass relative to the suspension and a biomass-increased product comprising an increased concentration of biomass relative to the suspension, and wherein the biomass separation unit comprises a biomass separation unit inlet fluidly connected to the first suspension outlet, an outlet for biomass-reduced product, and an outlet for biomass increased product. In embodiments, the system further comprises a retention chamber operable to produce a fluid substantially saturated with fermentation feed gas, wherein the retention chamber comprises a retention chamber inlet and a retention chamber outlet fluidly connected with the reactor inlet for a fluid comprising fermentation feed gas, whereby the fluid substantially saturated with feed gas may be introduced into the deep shaft reactor, and wherein the retention chamber inlet is fluidly connected with the outlet for biomass-reduced product of the biomass separation unit. The outlet for biomass-reduced product may be fluidly connected to an inlet of the deep shaft reactor whereby at least a portion of the biomass-reduced product may be recycled to the deep shaft reactor. The biomass separation unit may comprise an ultrafiltration module, a microfiltration module, a centrifuge, or a combination thereof. The outlet for biomass- increased product may be fluidly connected to the gasifier inlet for carbonaceous feed material.

[0009] In embodiments, the system further comprises a retention chamber operable to produce a fluid substantially saturated with fermentation feed gas, wherein the retention chamber comprises a retention chamber inlet and a retention chamber outlet fluidly connected with the reactor inlet for a fluid comprising fermentation feed gas, whereby the fluid substantially saturated with feed gas may be introduced into the deep shaft reactor. The deep shaft reactor may be divided into a fast-flow zone and a slow-flow zone by a divider that extends vertically from at or below the normal operating fill line to a first vertical distance from the bottom of the reactor, and may further comprise a CO-deprived suspension outlet positioned a second vertical distance from the bottom of the deep shaft reactor, wherein the first vertical distance is greater than or about equal to the second vertical distance, and the retention chamber inlet may be fluidly connected to the CO-deprived suspension outlet of the deep shaft reactor, such that the fluid saturated with CO in the retention chamber comprises extracted suspension. Extraction apparatus operable to produce a mixture of a fluid and fermentation feed gas comprising carbon monoxide and raise the pressure of the mixture prior to introduction of the mixture into the retention chamber via the retention chamber inlet may be positioned downstream the deep shaft reactor and upstream the retention chamber. The extraction apparatus may comprise a high pressure pump and a venturi having a venturi inlet for fermentation feed gas comprising carbon monoxide.

[0010] In embodiments of the system, the deep shaft reactor further comprises a vacuum degasifier region positioned above the normal fill line and configured such that gas released from the suspension may be extracted therefrom. The outlet for fermentation product gas comprising hydrogen may be located within the vacuum degasifier region. [0011] In applications, the depth of the deep shaft reactor is in the range of from about 50m to about 600m. The deep shaft reactor system may further comprise at least one hydrogen recovery or utilization unit comprising a hydrogen recovery or utilization unit inlet in fluid communication with the outlet for fermentation product comprising hydrogen gas, and configured to increase the purity of the hydrogen in the fermentation product gas or convert at least a portion of the hydrogen in the fermentation product gas to a useful product. The hydrogen recovery or utilization unit may comprise at least one selected from hydrogen pressure swing adsorption units, fuel cells, and gas generator sets.

[0012] In embodiments, the deep shaft reactor further comprises measuring apparatus for determining the concentration of carbon monoxide in the fermentation product gas, and control apparatus for adjusting the volume, the composition, or both of fermentation feed gas introduced into the deep shaft reactor and/or the concentration of biomass in the suspension within the deep shaft reactor, such that substantially all of the carbon monoxide introduced into the deep shaft reactor with the fermentation feed gas is converted to hydrogen and carbon dioxide and the measured concentration of carbon monoxide in the fermentation product gas is maintained at substantially zero. The outlet for fermentation product gas may be fluidly coupled with the at least one inlet for a fluid comprising fermentation feed gas such that the fermentation feed gas may be diluted with fermentation product comprising hydrogen gas if the measured concentration of carbon monoxide in the fermentation product gas is greater than a desired value. [0013] The system may further comprise an illumination assembly configured to photoactivate microorganisms in the suspension. The illumination assembly may be located above the normal operating fill line of the deep shaft reactor.

[0014] The system may further comprise at least one temperature-reduction apparatus positioned downstream of the gasifier and upstream of the fermentation reactor and configured to reduce the temperature of the gaseous product comprising synthesis gas. The temperature -reduction apparatus may comprise an oxidant preheater, an HRSG, or both. [0015] In embodiments, the system further comprises a particulate removal device downstream the gasifier and upstream the deep shaft reactor and configured to reduce the concentration of particulates in the gaseous product comprising synthesis gas. [0016] These and other embodiments of the present invention, and various features and potential advantages will be apparent with reference to the following description and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a schematic of a CO water shift reaction system 10 according to an embodiment of this disclosure.

[0018] Figure 2 is a schematic of an embodiment of upstream gasification zone 100a suitable for use in CO water shift reaction system 10.

[0019] Figure 3 is a schematic of a plasma torch system 140 suitable for use in plasma reactor 105 of upstream gasification zone 100a of Figure 2.

[0020] Figure 4 is a schematic of an embodiment of downstream gasification zone 100b suitable for use in CO water shift reaction system 10.

[0021] Figure 5 is a schematic of a CO water shift reaction system 1OA detailing a deep-shaft reactor 30 according to an embodiment of this disclosure and relation thereof to hydrogen recovery system 110, biomass separation unit 90, retention chamber 80, and plasma gasification subsystem 100.

[0022] Figure 6 is a schematic of a CO water shift reaction system 1OB detailing a deep-shaft reactor 30 according to another embodiment of this disclosure and relation thereof to hydrogen recovery system 110, biomass separation unit 90, retention chamber 80, and plasma gasification subsystem 100.

[0023] Figures 7a and 7b are horizontal cross sections of respective embodiments of a deep shaft reactor 30 as employed in the system of Figure 1. Figure 7a shows an embodiment with one slow-flow zone and one fast-flow zone. Figure 7b shows an embodiment with one slow- flow zone and two fast-flow zones.

[0024] Figure 8a is a top view 400a of a temperature control assembly according to an embodiment of this disclosure.

[0025] Figure 8b is a side view 400b of the temperature control assembly of Figure 8a. [0026] Figure 9a is a schematic of a hydrogen recovery subsystem HOa according to an embodiment of this disclosure.

[0027] Figure 9b is a schematic of a hydrogen recovery subsystem 110b according to another embodiment of this disclosure.

NOTATION AND NOMENCLATURE

[0028] For the purposes of this disclosure, the term "coupled to" includes direct and indirect fluid communication (i.e., flow of gas, liquid or both) between the coupled components. [0029] The terms "suspension" and "mixed liquor" are used herein to refer to the mixture of liquids, gas, and solids present within deep shaft reactor 30 during operation. [0030] For the purposes of this disclosure, the terms "CO fermentation" and "fermentation of carbon monoxide" refer to the production of energy by microorganisms via metabolic pathway(s) that include a net water-gas shift reaction whereby hydrogen and carbon dioxide products are produced using carbon monoxide as the carbon-containing food source.

DETAILED DESCRIPTION

[0031] A system to polish synthesis gas via biological net water shift reaction using feed comprising carbon monoxide therein is provided. Figure 1 is a simplified schematic of a plasma gasification-produced CO water shift reaction system 10 (sometimes referred to as 'CO fermentation system 10') according to this disclosure. Carbon monoxide water shift reaction system 10 comprises deep shaft reactor 30, retention chamber 80, biomass extraction unit 90, hydrogen recovery subsystem 110, and plasma gasification subsystem 100, each of which will be described in detail hereinbelow.

[0032] Within CO water shift reaction system 10, deep-shaft reactor 30 is fluidly connected with hydrogen recovery subsystem 110, via outlet line 88, which connects a headspace 44 of deep-shaft reactor 30 with hydrogen recovery subsection 110. Deep-shaft reactor 30 is also fluidly connected with biomass extraction unit 90 via spent biomass outlet line 89, which connects a position of deep-shaft reactor 30 below operational fill line 43 with biomass extraction unit 90. An outlet line 92 of biomass extraction unit 90 may be connected via a line 93 to an inlet 41a of deep-shaft reactor 30 and/or to a retention chamber 80 via return filtrate line 98. Deep-shaft reactor 30 is further fluidly connected with retention chamber 80. Retention chamber 80 is connected to deep shaft reactor 30 via a retention chamber outlet line 84 which connects an outlet of retention chamber 80 with one or more injection inlets of deep shaft reactor 30. Biomass extraction unit may be fluidly connected with retention chamber 80 via return filtrate line 98, whereby filtrate produced in biomass extraction unit 90 may be combined with feed gas comprising CO and saturated with CO in retention chamber 80 prior to recycle to reactor 30. In embodiments, a reactor outlet line 82 may connect reactor 30 with retention chamber 80. In such embodiments, reactor outlet line 82 may be configured for removal of a portion of suspension from a lower portion (for example, the lower 20%) of deep-shaft reactor 30. In such embodiments, a portion of suspension extracted from reactor 30 via reactor outlet line 82 may be combined with feed gas comprising CO via line 102 and introduced into retention chamber 80, wherein the extracted suspension may be saturated with CO prior to introduction into reactor 30. Retention chamber 80 is further fluidly connected with plasma gasification subsystem 100, for example, via a fermentation feed gas line 102.

[0033] Via the disclosed plasma gasification-produced carbon monoxide fermentation system, carbon monoxide produced via plasma gasification is converted to hydrogen via net biological water-gas shift reaction. The product hydrogen may be sold, used to create electricity, used in the formation of a desired chemical product and/or recycled within the system as described in more detail hereinbelow.

[0034] Furthermore, the CO water shift system also provides a novel new means of reducing green house gas. As the CO ₂ produced by the biomass is neutral (i.e., not considered a greenhouse gas emission), the disclosed system provides novel carbon capture technology. A. Gasification Subsystem 100

[0035] Carbon monoxide water shift reaction system 10 comprises plasma gasification subsystem 100. Plasma gasification subsystem 100 comprises an upstream gasification zone and may comprise a downstream gasification zone. Upstream gasification zone 100a and downstream gasification zone 100b may be configured as depicted in Figures 2 and 4. Figure 2 is a schematic of upstream gasification zone 100a according to an embodiment. Upstream gasification zone 100a comprises plasma gasifier 105. Plasma gasifier 105 may be a plasma gasification vitrification reactor (PGVR), available through Westinghouse Plasma Corporation (a division of Alter Nrg, Madison, PA). Alternatively, plasma gasifier 105 may be any plasma gasifier capable of producing synthesis gas via gasification of a carbon- containing gasifier feed and gasifϊer process gas. The carbon-containing gasifier feed material may be an opportunity fuel, a fossil fuel, or combination thereof. The carbon- containing gasifier feed material may be selected from coal, coal fines, coal mine waste, biomass (forestry products corn stover, bagasse, switchgrass, miscanthus, etc.), municipal solid waste, industrial sludge (liquid and/or solid), auto shredder residue, petcoke, heavy oil sludge, refinery tar, wood chips, used plastics, tires, and combinations thereof. Gasification of carbon-containing feed materials may be more environmentally-friendly than combustion thereof.

[0036] Plasma reactor 105 comprises plasma torch system 140. Desirably, plasma torch system 140 produces superheated gas for gasification of gasifier feed materials at temperatures in the range of from about 1,500 ⁰ C to 5,500 ⁰ C (2,732°F to 10,000 ⁰ F). In applications, gasifier 105 is capable of gasifying feed materials at temperatures of greater than about 2200 ⁰ C (3,992°F), alternatively greater than about 5000 ⁰ C (9,032 ⁰ F), or alternatively greater than 5500 ⁰ C (10,000 ⁰ F), such that inorganics are liquefied and vitrification may produce a non-hazardous glassy slag residue and gasification produces low emissions of undesirable components such as NO _x , SO _x , tars, fly ash, dioxins, and/or furans. Plasma gasification reactor 105 may operate at substantially atmospheric pressure. The one or more plasma torches 240 may be positioned within a lower portion 117 of gasifier 105, whereby plasma heated gas enters gasifier 105 and rises. Gasifier 105 may be configured for operation at low gas velocity such that particulate carryover is low. Lower portion 117 of plasma gasifier 105 may comprise the lower ¹ A of plasma gasifier 105. Plasma gasifier 105 may further comprise one or more gasifier inlets 120 and gasifier feed inlet lines 125 for introducing gasifier feed into gasifier 105, and one or more gasifier product outlets 130 and product outlet lines 135 for extracting gasifier product gas from plasma reactor 105. In embodiments, gasifer feed inlet line(s) 125 are configured to introduce gasifier feed within the top half of plasma gasifier 105, whereby the feed falls by gravity. As mentioned hereinabove, the feed may comprise one or more opportunity or fossil fuels. [0037] In applications, CO water shift reaction system 10 further comprises apparatus for heating/drying of gasifier feed materials, for example, heat transfer apparatus configured for indirect heat transfer from hot gas product in product outlet line(s) 135 and the carbonaceous gasifier feed materials, as shown in the embodiment of Figure 4 and discussed further hereinbelow. However, when gasifier 105 is configured for operation at extreme temperatures, such feed heating apparatus may not be present. Gasifier product gas outlets 130 may be positioned within the top 25% of plasma reactor 105 and are connected to plasma reactor product outlet lines 135.

[0038] Generally, plasma gasifier 105 will comprise a gasification zone 115a, within which gasification of gasifier feed occurs. Above gasification zone 115a is a freeboard zone 115b. The freeboard zone 115b is a substantially solids-free zone, during passage through which (within residence time through which) any ungasified solids fall back into the gasification zone 115a. Freeboard zone 115b may extend from about the level of the one or more gasifier feed inlets 120 to substantially the top 116 of plasma gasifier 105 or to about the level of gasifier product gas outlet 130. Below gasification zone 115a is desirably a slag zone, in which ungasified metal and slag or vitrified product (depending on operating temperatures) are extracted from gasifier 105. For example, solids outlet 150 may be positioned within slag zone 115c and may be connected to solids outlet line(s) 155. Ideally, materials removed from slag zone 115c are environmentally friendly vitrified products which do not leach undesirable components into the environment. Plasma gasifier 105 may be configured to produce a glass- like slag which passes EPA-mandated Toxicity Characteristic Leachate Procedure (TCLP) requirements. The vitrified materials may be sold, for example, as construction building materials, road fill, or may be safely landfilled.

[0039] One or more gasifier process gas inlets 180 are positioned within gasification zone 115a. The gasifier process gas may comprise air, oxygen-enriched air, or substantially pure oxygen. The use of substantially pure oxygen or oxygen-enriched air as gasifier process gas is desirable in applications where a low nitrogen content and/or increased synthesis gas content of the gasification product gas is desired. Plasma gasification reactor 105 may further comprise inlets for components such as water and/or flux, which may be introduced to form vitreous product from melted ash and assist in slag withdrawal (i.e., adjust slag viscosity). The flux may be, for example, limestone.

[0040] Figure 3 is a schematic of a plasma torch system 140 suitable for use in plasma reactor 105. Plasma torch system 140 comprises one or more plasma torches 240. Each plasma torch 240 is configured to produce a superheated gas 145 from a plasma process gas. The process energy is provided by direct heat transfer from an electric arc. Plasma is a scientific term referring to the fourth state of mater which is a very high temperature, ionized, conductive gas created within plasma torch 240 by the interaction of a plasma torch process gas with an electric arc. The plasma state exists within the arc within plasma torch 240. Upon exit from torch 240, the gas exists mainly in its neutral (nonionic, non-plasma) state. [0041] Plasma torch 240 may be connected to plasma torch process gas supply system 143 via plasma torch process gas line 144, for introduction of gas to plasma torch 240. Plasma torch process gas supply system 143 may comprise a gas compressor, gas storage, or both. The plasma torch process gas may be any of a variety of reducing, oxidizing, and inert gases. In applications, plasma arc 145 is a self-stabilized arc and may be a non-transferred arc. Plasma torch 240 may further be connected to power supply system 146 via conduit 147, for supplying of power thereto. Power supply system 146 may comprise a thyristor power supply system for provision of DC power to plasma torch 240. A cooling water system 141 is associated with plasma torch 240 for cooling the electrodes in plasma torch 240. Cooling water system 141 may be configured for supplying cooling water to plasma torch 240 at high pressure. A control system 148 in communication with plasma torch 240 may be configured to control process parameters and operation of the power supply system, the water cooling system, and the plasma process gas supply system. Control system 148 is in communication with plasma torch 240 via one or more conduits 149.

[0042] Gasification subsystem 100 may further comprise downstream gasification zone 100b, downstream of upstream gasification zone 100a. Figure 4 is a schematic of a downstream gasification zone 100b according to an embodiment of this disclosure. Downstream gasification zone 100b may comprise heat recovery/utilization units and/or gasification product gas upgrading units. The gasification product gas exiting plasma gasification reactor 105 via outlet 130 and outlet line 135 may comprise a variety of products depending on the gasifier feed material, the gasification operating parameters (temperature, pressure, residence time, etc.), and the specific capabilities of the plasma gasifier 105 of system 10. For example, gasifier 105 may be configured for production of gasifier product comprising synthesis gas (hydrogen and carbon monoxide), carbon dioxide, nitrogen, ash, methane, ethane, water vapor, tar and/or ash along with trace amounts of components such as SO _x , NO _x , and H ₂ S. Gasifier 105 may be configured to produce gasification product gas exiting plasma reactor 105 via outlet line 135 having a temperature in excess of 900 ⁰ C, alternatively greater than or about 910 ⁰ C. In applications, gasifier 105 is configured to produce synthesis gas in the gasification product having a ratio of hydrogen to carbon monoxide of at least about 0.8; alternatively at least about 0.9; alternatively at least about 0.95. [0043] As deep-shaft reactor 30 is configured as a fermentation reactor comprising microorganisms during CO conversion, the temperature of the gas stream introduced thereto must have a temperature much less than that of gasifier product gas in gasifier product outlet line 135. For example, the microorganisms may operate most efficiently (produce significant hydrogen from CO and water) at temperatures of less than 70 ⁰ C, less than 50 ⁰ C, or less than 40 ⁰ C. Therefore, CO fermentation system 10 may comprise downstream gasification system 100b comprising one or more temperature -reducing stages. For example, in the embodiment of Figure 4, gasifier product outlet line 135 connects plasma gasification reactor 105 with process gas preheater 165. In this manner, the gasification process gas introduced into gasification process gas inlets 180 of plasma gasification reactor 105 may be preheated as desired prior to introduction into plasma gasification reactor 105. If desired, downstream gasification system 100b may be configured such that a portion of the heat may be utilized for drying the gasification feed materials (e.g., biomass sludge) prior to introduction into plasma gasifier 105 via gasifier feed inlet line 125 (not shown in the embodiment of Figure

4).

[0044] Downstream gasification system 100b may comprise oxygen-enhancement unit 166. Oxygen enhancement unit 166 may be any unit suitable for providing oxygen or oxygen- enhanced air for use in plasma gasification reactor 105. For example, oxygen-enhancement unit 166 may be an air separation unit, in which case the gasification process gas comprises substantially oxygen. Alternatively, oxygen-enhancement unit 166 may comprise an oxygen pressure swing adsorption unit, in which case the gasification process gas may comprise oxygen-enriched air, for example, 90% oxygen. Oxygen enhancement unit 166 comprises an air inlet 163 for air, an outlet 164 for gas comprising nitrogen, and an outlet 160 for oxygen- enriched air (or substantially pure oxygen, in the case of an air separation unit). Process gas preheater 165 may be any suitable heat transfer reactor. For example, process gas preheater 165 may be a heat exchange-type reactor, configured such that process gas may travel through, for example, tubes of the heat exchange-type reactor 165 and heat transferred indirectly from the gasification product gas in line 135 to a gasification process gas. [0045] Downstream gasification system 100b may further comprise a particulate removal device 175. Particulate removal device 175 may be directly connected with product outlet line 135 of plasma reactor 105 or, alternatively, may be connected with process gas preheater 165 via a reduced-temperature gasification product line 170. Particulate removal device 175 may be any suitable apparatus capable of removing ash and other particulate matter from the temperature -reduced gasification product in line 170 or gasification product in gasifier outlet line 135. For example, particulate removal device 175 may be a cyclone, an electrostatic precipitator, a baghouse, or any other suitable device known to those of skill in the art. Particulate removal device 175 will have an outlet 185 for the removal of separated particulate matter therefrom, and an outlet line 190 for particulate-reduced gasification product gas.

[0046] Downstream gasification system 100b may further comprise heat recovery unit 195. Heat recovery unit 195 may be any apparatus suitable for the transfer of heat from particulate-reduced gasification product in line 190, for example a heat recovery steam generator or HRSG. For example, heat recovery unit 195 may comprise an inlet 215 for introduction of water or other suitable heat transfer fluid to one or more heat transfer coils 217. Heat recovery unit 195 is operable for transfer of heat from the particulate-reduced gasification product to, for example, a heat transfer fluid within the coil(s) 217 of heat recovery device 195. An outlet 216 of coil(s) 217 may be connected with a steam turbine 218 for introduction of steam produced within heat recovery device 195 into the steam turbine 218 for the generation of electricity 95 a. Alternatively, steam produced via heat recovery unit 195 may be used during cleaning of deep-shaft reactor 30, as described further hereinbelow. The electricity 95 a produced from the hot gasification product gas may be used throughout carbon monoxide water shift reaction system 10, for example, for running oxygen-enhancement unit 166 and/or hydrogen upgrading unit 112, or may be utilized in another associated part of system 10 or sold for profit.

[0047] Heat recovery device 195 comprises an outlet line 200 for particulate- reduced/temperature -reduced gasification gas. Depending on the gasifier feed materials introduced into plasma gasifier 105 via gasifier feed inlet 125, operation and configuration of plasma gasifier 105, the particulate-reduced/temperature -reduced gasification gas will comprise various components in addition to synthesis gas. Depending on the desired composition of the resultant synthesis gas, downstream gasification zone 100b may further comprise one or more synthesis gas clean-up units 210. The one or more synthesis gas cleanup units 210 may be configured to remove non-synthesis gas components from the particulate-reduced/temperature -reduced gasification gas. Any synthesis gas clean-up units known in the art may be utilized, for example, acid gas removal units may be used to remove extraneous carbon dioxide. Such removed carbon dioxide may, depending on plant locations, be sold for purposes such as enhanced oil recovery operations. Downstream gasification system 100b comprises an outlet line 102 for cleaned-up synthesis gas. In applications, the cleaned-up synthesis gas outlet line connects with synthesis gas clean-up unit(s) 210. Desirably, carbon monoxide-containing gas introduced to deep shaft reactor 30 via fermentation feed gas inlet line 102 comprises CO and the levels of other gaseous components are not prohibitively toxic to the microorganisms selected for use in reactor 30. [0048] Plasma gasification subsection 100 may thus be configured to produce a desired synthesis gas composition having a desired temperature. The power provided to plasma torch 140, the gasification feed material, and/or the oxidant utilized in plasma reactor 105 may be selected to produce synthesis gas of a desired composition (H ₂ :CO ratio, N ₂ content, etc). Downstream gasification section 100b may be used to achieve the desired temperature of the gasification-produced synthesis gas.

[0049] It should be noted that downstream gasification zone 100b may not comprise each and every unit described in relation to Figure 4, and the order of the devices may be varied. For example, in some applications, synthesis gas clean-up unit(s) 210 may not be required, particulate separation device 175 may be positioned upstream of heat recovery device 195, or process gas preheater 165 may be absent. B. Deep Shaft Reactor 30 Overview

[0050] Figures 5 and 6 are schematics of carbon monoxide water shift reaction systems 1OA and 1OB respectively, depicting a deep-shaft reactor 30 according to embodiments of this disclosure and relation thereof to hydrogen recovery system 110, biomass separation unit 90, CO saturation retention chamber 80, and plasma gasification subsystem 100. Deep-shaft reactor 30 is adapted for CO water shift reaction using microorganisms which utilize carbon monoxide as a food source, thereby producing hydrogen via the water gas shift (water-gas splitting reaction):

CO + H ₂ O → CO ₂ + H _2. (1)

[0051] The reaction of Equation (1) is mediated by proteins coordinated in an enzymatic pathway, and takes place at ambient temperature and pressure, with the thermodynamic equilibrium (desirably for the production of hydrogen) to the right of Eq. (1). Reactor 30 is operable as follows: microorganisms capable of carrying out the water-gas splitting reaction in Eq. (1) are suspended in an aqueous nutrient medium initially lacking a carbon source, exposed to a light source to activate a metabolic pathway that includes the water-gas shift reaction (1), and then incubated anaerobically in a slow-flowing, carbon monoxide-depleted stream within a downcomer section of reactor 30.

[0052] A fluid is saturated with carbon monoxide in the feed gas comprising monoxide and the saturated fluid is injected into reactor 30 in such a manner that injection of the CO- saturated fluid thereto creates/maintains a fast-flowing, carbon monoxide-rich stream within a riser section 70 of reactor 30. The fluid saturated within retention chamber 80 may be at least a portion of return filtrate from biomass extraction unit 90, as indicated in the embodiment of Figure 5, and/or a portion of the CO-starved microorganisms from downcomer 50 of reactor 30, as indicated in the embodiment of Figure 6. Retention chamber 80 external to reactor 30 provides a CO-saturated filtrate or CO-saturated suspension according to Figures 5 and 6, respectively.

[0053] Following contact with CO-saturated fluid, metabolically activated microorganisms in the CO-enriched fast flow zone of riser 70 metabolize the CO-saturated medium to form fermentation product gas including hydrogen and carbon dioxide. Gas coming out of solution while in the riser 70 creates a gas-lift pump, which enhances circulation of the suspension throughout reactor 30 from the fast- flowing phase within the riser section 70 of reactor 30 back to the slow- flowing phase within the downcomer 50 of reactor 30. Product hydrogen, and other undissolved gas, enters a gaseous headspace 44 above the suspension level 43 of reactor 30 prior to return of the suspension to the downcomer 50. Dimensions/Construction

[0054] Deep-shaft reactor 30 may be configured as a vessel having a top 12a, a bottom 12b, and walls 33. Deep shaft reactor 30 may be an open-ended pressure vessel. The head of pressure provided by the suspension during operation serves to provide pressure variation along the length of the vessel, and promotes circulation of suspension.

[0055] In applications, reactor 30 is cylindrical. In certain embodiments, reactor 30 has a long axis Ll oriented vertically between the top 12a and the bottom 12b. In some embodiments, the length Ll to be used for a particular application is optimized based on the pressure sensitivity of the microorganism(s) to be used in reactor 30, and such other factors as CO or CO ₂ toxicity at various pressures.

[0056] In applications, long axis Ll is between about 10 m and about 600 m. In preferred embodiments, deep-shaft reactor 30 has a long axis Ll of greater than about 50m. In applications, Ll may be about 150 meters (492 ft) in some cases. Deep shaft reactor 30 has a short axis D, perpendicular to long axis Ll. Short axis D is the diameter of the vessel in cylindrical embodiments. Reactor 30 may be of non-cylindrical shape, such as, without limitation, rectangular, or polygonal. Deep shaft reactor 30 has a long axis Ll that is at least twice the dimension of the short axis D. In some embodiments, inner diameter D of reactor 30 is up to 6 meters (20 ft), and reactor length Ll is up to 600 meters (2000 ft). Head 40 of reactor 30 may comprise at least a portion of spillover zone 16a, a headspace 44, and illumination assembly 46. Head 40 may extend a distance L5 outward from walls 33 of reactor 30. In this manner, an annular suspension region 48 at the top of reactor 30 may be defined. Such an annular suspension region may be conducive to transfer of product and evolved gases from the suspension in annular suspension region 48 into headspace 44 and subsequent removal therefrom via hydrogen removal system 110, as further described hereinbelow. Such an annular suspension region, by providing a larger surface area of interaction between headspace 44 and annular region 48, may be configured to enhance exposure of the circulating suspension to light during activation, prior to downward flow into the darkened slow- flow zone 50 of reactor 30. Alternatively, the head 40 of reactor 30 has the same diameter D as the shaft defined by walls 33. In some embodiments, reactor head 40 is made to be detachable from deep shaft reactor 30.

[0057] Annular region 48 of reactor head 40 may be fitted with a baffle configured to encourage suspension emerging from riser 70 to traverse a substantial horizontal distance along annular region 48, and facilitate release of H ₂ product into headspace 44 prior to descent of gas-disengaged suspension slowly in downcomer 50, wherein the suspension (again) becomes CO depleted.

[0058] Head 40 includes one or more inlets 41 for introducing nutrients, microorganisms, sterile fresh water injection, sterile recycled filtrate, pH adjusting agents, and other materials into reactor 30. For example, in the embodiment of Figures 5 and 6, head 40 comprises inlet 41a for a water stream comprising fresh and recycled water, an inlet 41b for nutrients, an inlet 41c for fresh microorganisms, and an inlet 41d for chemicals (e.g., pH adjusting base). Lines 41a, 41b, 41c, and 4 Id may be utilized during start-up (and optionally thereafter) to introduce water, nutrients, selected microorganisms, and chemicals to a temperature-controlled reactor 30 to prepare (maintain) a biomass suspension. Although depicted at the top of reactor 30, it is envisioned that inlets 41a-41d may connect through any position of head 40 or walls 33. [0059] Production of hydrogen via Eq. (1) involves concomitant production of equimolar amounts of carbon dioxide acid gas, which may lead to decreased pH, affecting microbial toxicity limitations with respect to CO ₂ , H ₂ or CO. Thus, system 10 may further comprise pH measuring apparatus for determining the pH of suspension within reactor 30, and line 41d may be used to introduce base into reactor 30 to encourage formation of bicarbonate/pH elevation. The bicarbonate which will remain in the liquid phase as compared with gaseous carbon dioxide which would exit reactor 30 via fermentation product gas line 88. In some applications, the pH is controllable with a NaOH injection system to maintain the pH of the suspension within a desired pH range by promoting conversion of excess CO ₂ to soluble bicarbonate. Such a desired pH may be from about 7.5 to about 9.5. In some instances, pH is controllable to about pH 9 by injection of aliquots of a NaOH solution into reactor head 40. Biomass separation unit 90 may be configured to remove soluble bicarbonate, for example, via water dilution, system 10 may comprise a precipitation unit configured to remove bicarbonate by precipitation from the aqueous phase.

[0060] In applications, deep-shaft reactor 30 is disposed below ground level G, for instance in a shaft, borehole, or other vertically oriented compartment in the earth. Alternatively, reactor 30 is at least partially above ground level G. Reactor 30 may be surrounded by a cooling chamber 11 , as described further hereinbelow. Furthermore, an insulation layer (not shown) may be positioned between at least a portion of the surrounding soil and reactor 30. Such an insulation layer may be made of polyurethane and may be positioned within a borehole prior to positioning of the reactor 30 within the borehole, concomitant with positioning of reactor 30 into the borehole, or after placement of reactor 30 within the borehole.

[0061] Walls 33 and bottom 12b of reactor 30 are constructed of any corrosion resistant material and are desirably constructed of a thermally-conductive material. In certain embodiments, the walls 33 and bottom 12b of deep shaft reactor 30 are constructed of aluminum, or stainless steel. The interior of reactor walls 33, the bottom 12b of reactor 30, divider 34, and any parts exposed to bacterial suspension during operation may be made of polished steel or other suitable material or may be clad therewith, such that adhesion and growth of bacteria thereon is discouraged. Reactor 30 comprises any suitable vessel for carrying out a fermentation reaction. In embodiments, reactor 30 is a pressurized vessel, reactor, container or the like configured to contain a fermentation reaction. Reactor Suspension

[0062] Reactor 30 may be configured for hydrogen production via water-gas splitting utilizing any suitable microorganism known in the art to consume carbon monoxide under aqueous anaerobic conditions and release H ₂ according to the reaction portrayed in Equation (1). In embodiments, reactor 30 is configured for fermentation of reactant suspension comprising thermophilic Carboxydothertnus hydrogenofortnans Z-2901; Rubrivivax gelatinosus; or Rhodospirillum rubrum. Some additional bacteria that are potentially suitable for production of hydrogen with the disclosed system include Bdellovibrio sp.; Rhodopseudomonas palustris; Rhodobacter sphaeroides; Citrobacter sp. Y19; Methanosarcina acetivorans c2A; and Bacillus smithii.

[0063] At start-up, water, selected microorganisms, and nutrients are combined in a temperature-controlled reactor to prepare a suspension. Any suitable growth medium for the selected microorganisms may be used, provided that it lacks a carbon source. One such growth medium contains RCVBN medium modified to omit a carbon source (Maness, et al. Appl. Environ. Microbiol. 2002. 68:2633-2636).

[0064] Reactor 30 may be configured for other microorganisms that are capable of fermenting CO to produce H ₂ ; such microorganisms may be identified by screening candidate microorganisms to identify (1) efficiency of CO fed to H ₂ produced; (2) variation of CO toxicity with pressure; (3) variation of CO toxicity with CO concentration; (4) optimum operating temperature; (5) optimum nutrient dosing; (6) optimum operating pH; (7) sensitivity to SOx and NOx contaminants in CO feed gas; and (8) ease of removal from reactor during cleaning.

[0065] Reactor 30 may be operated at pressures (depths of reactor 30) and temperature suitable for optimum conversion of CO to hydrogen by the selected microorganisms. In instances, reactor 30 is configured for operation at operating temperatures of less than 35°C to achieve maximal hydrogen production. A suitable operating temperature may be in the range of from about 30 ⁰ C to 70 ⁰ C. Alternatively, the operating temperature is in the range of from about 35°C to 50 ⁰ C. In some cases the operating temperature is in the range of about 37-53°C. Alternatively about 37°C. The microorganisms may have a preferred pH operating range. As mentioned above, system 10 may comprise pH adjustment inlet line(s) 41c and a pH measuring and control system operable to maintain a desired pH of the suspension within reactor 30. In embodiments, the pH control system is operable to maintain a pH in the range of from about 7 to about 9.5; alternatively, about 9.

[0066] The normal operating level of the suspension during operation of reactor 30 is indicated as fluid level 43. Normal operating suspension level 43 is a vertical distance L2 from bottom 12b of reactor 30. Normal operating suspension level 43 defines a normal reactor suspension volume, defined as the volume of suspension contained within reactor walls 33, reactor bottom 12b, and normal operating suspension level 43 during operation of reactor 30. For the embodiment of Figures 5 and 6, the normal operating suspension volume is π (D/2) ² L ₂ . The operating suspension volume of deep shaft reactor 30 may be between about 50% and about 99% of the total internal volume of reactor 30. Normal operating suspension level 43 comprises a suspension/gas interface within reactor 30 during operation. [0067] During start-up, an aqueous medium containing suitable H ₂ -producing microorganisms is introduced into slow- flow zone 50 of deep shaft reactor 30 to a normal operating level 43. System 10 may further comprise level meters configured to maintain the suspension at about the normal operating fill level 43 during operation of CO fermentation system 10. [0068] Deep shaft reactor 30 further comprises divider 34. In certain instances, divider 34 is a virtual division, wherein the normal operating suspension volume is a unitary volume. In such embodiments, divider 34 is an axis of circulation about which the liquid volume within reactor 30 circulates. Divider 34 may comprise a region of shear, such that fluid flowing downward and fluid flowing upward interact at the interface thereof.

[0069] Generally, divider 34 will be a physical divider, such as a baffle, wall, or other structure within reactor 30 which serves to direct or control liquid phase flow. Divider 34 may be oriented in any direction with respect to long axis Li of reactor 30. In embodiments, divider 34 is oriented vertically, parallel to long axis L ₁ . Divider 34 extends from a distance L3 below suspension level 43 to a distance L4 above bottom 12b of reactor 30. In embodiments, divider 34 is substantially parallel to long axis Li and perpendicular to short axis D. Divider 34 divides the operating reactor volume into a fast-flow or riser section 70 and a slow- flow or downcomer section 50. Riser section 70 and downcomer section 50 may be of about equal volume. Alternatively, the volume and/or cross-sectional area of downcomer section 50 is greater than about the volume/cross-sectional area of riser section 70, to promote relatively slower flow in downcomer 50 relative to riser 70. [0070] A schematic horizontal cross section view of an embodiment of a deep shaft reactor 230 configured as described in Figures 5 and 6 is shown in Figure 7a. Reactor walls 233 enclose one slow-flow zone 250 and one fast-flow zone 270. The slow- and fast- flow zones are divided by a partition or wall 234, which is positioned so that the volume of slow-flow zone 250 is greater than the volume of fast- flow zone 270.

[0071] In another embodiment, the bioreactor of Figures 5 and 6 is configured as illustrated in Figure 7b. A horizontal cross section of a deep shaft reactor 330 is shown which includes two fast-flow zones 370a, 370b located on opposite sides of reactor 230 and enclosed by reactor walls 333. One slow-flow zone 350 is disposed between the two fast- flow zones 270a, 270b.

[0072] A spillover region 16a located proximal suspension surface 43 has a vertical height L3 and width D (or part D + L5 in embodiments with annular region 48). Spillover region 16a is configured to allow suspension circulation during operation (indicated by the dashed arrows) to proceed over or around divider 34 between riser 70 and downcomer 50. Similarly, flow-through region 16b having a vertical height L4 and width D, that is configured such that circulation (indicated by dashed arrows) continues under, or around divider 34 between riser 70 and downcomer 50. Divider 34 is designed such that circulation of suspension within reactor 30 proceeds in any direction such that reactant suspension in reactor 30 is circulated continuously from an upper region of downcomer 50 to a lower region of downcomer 50 to a lower position within riser 70 to a higher position within riser 70, passing around divider 34, from downcomer 50 to riser 70.

[0073] During operation of fermentation system 10, activated microorganisms in the suspension are incubated in the dark under anaerobic, slow-flow, carbon-monoxide-depleted conditions ("CO-depleted conditions" to produce CO-starved suspension) of downcomer 50. During operation, suspension in downcomer 50 becomes CO-depleted, while that in the riser is CO-enhanced due to the utilization of retention chamber 80, which will be discussed in detail hereinbelow. The desired biochemical reaction (i.e., the water-gas shift reaction) benefits from a CO feed gas starvation, as food-deprived microorganisms are primed for enhanced metabolic activity upon restoration of a food source (i.e., carbon monoxide). The same benefit would not be achieved with a system configured for injection of feed gas into a conventional batch fermentation mixture. CO feed gas starvation is provided by not injecting fermentation feed gas comprising CO into the down flowing or downcomer 50 side of deep shaft reactor 30, thus system 10 is not adapted for fermentation feed gas injection along downcomer 50.

[0074] Reactor 30 is configured such that, during operation, suspension may be circulated repeatedly between downcomer 50 ("downflow chamber"), which comprises CO-depleted suspension 50, and riser 70 ("upflow chamber"), which comprises fast flowing, CO-rich suspension. Referring still to Figures 5 and 6, reactor 30 is configured to drive the suspension through the circulating system by injection of CO-saturated fluid only into the rapid flow zone of riser 70. The undissolved gas, including primarily unconverted CO, and evolved H ₂ and CO ₂ , in fast-flow zone 70 provides gas "lift" to drive circulation of the suspension from fast- flow zone 70 towards head 40. The theory of operation is that the suspension in downcomer 50 (i.e., the slow-flow zone) has a higher density than the liquid- bubble mixture in riser 70 (i.e., fast- flow zone 70). This density differential also promotes circulation from riser 70 to downcomer 50. As the circulating suspension and product gases (including hydrogen and CO ₂ ) ascend in riser 70 (fast-flow zone) to regions of lower hydrostatic pressure (e.g., the upper end of riser 70 and annular liquid region 48) the dissolved off-gas separates as bubbles. When the liquid/bubble mixture from fast-flow zone 70 enters the annular region 48 of reactor head 40, gas disengagement occurs. The disengaged gas accumulates in headspace 44 head 40 until withdrawn using vacuum. [0075] Reactor 30 is designed such that, during operation, a headspace 44 exists above suspension level 43. Operation of reactor 30 is monitored as known in the art (flow meters, PLC, etc.) such that a headspace 44 of a desired volume exists within reactor 30. Headspace 44 may be a volume approximately 1-10% of the operating suspension reactor volume. Headspace 44 is configured as a vacuum degasifier which allows/promotes gases produced/disengaged from the suspension to be removed from reactor 30, as will be discussed further hereinbelow. Vacuum degasification may be designed to promote disengagement and removal of hydrogen gas from the suspension in annular region 48 prior to reentry of the suspension into slow- flow zone 50. Headspace 44 is coupled to fast- flow zone in riser 70, spillover region 16a, and H ₂ recovery subsystem 110.

[0076] Although a deep shaft reactor 30 is described, any other suitable reactor may be employed within biological CO water shift reaction system 10. Such a suitable reactor should be configured for the following: handling large volumes of CO gas (e.g., greater than about 5,000 kg/h), promoting excellent gas to liquid transfer rates, allowing effective control of gas injection control, control, operating at high pressures, allowing for effective cleaning to avoid contamination (e.g., contamination with undesirable microorganisms), temperature control, construction using common, standard parts for easy servicing/maintenance and economy of construction, explosion-resistance, ability to run continuously, and effective mixing throughout the reactor volume. An optional reactor design is the U-Loop reactor. Lighting

[0077] Reactor 30 may comprise a head 40 comprised of (from lowest to highest in elevation) annular suspension region 48, headspace 44, and illumination assembly 46. Illumination assembly 46 may be concealed into the roof (i.e., uppermost region of head 40) of reactor 30 to avoid chemical and humidity damage during operation, while ensuring transmittance of an appropriate wavelength light to suspension in spillover region 16a. Illumination system 46 is designed to photoactivate the hydrogen-producing bacteria during start-up or bacterial replacement within reactor 30. Illumination assembly 46 may comprise one or a plurality of lamps, for example, one or more incandescent lamps. [0078] Illumination assembly 46 is operable to photoactivate the selected microorganisms via initiation of a biological pathway that includes the water-gas shift reaction (1). After an initial exposure of the suspension to illumination effective to stimulate the photosynthetic CO oxidation pathway in the microorganisms, the activated microorganisms may then be grown in darkness, especially when the microorganisms are known to consume hydrogen in the presence of light. No carbon-containing nutrients are provided to the activated microorganisms except for the gaseous CO that is provided to the microorganisms via retention chamber 80. [0079] Illumination assembly 46 may be configured to expose suspension in annular liquid region 48 to light in the visible wavelength range. The duration of light exposure for activation may be controlled as desired via control apparatus based on the parameters of a given application, such as flow rate of the suspension, the intensity of the light, and the exposed surface area of the suspension in head 40. Although fermentation of CO by the water-gas shift reaction will continue in the presence of light, it is thought that endogenous hydrogenases will oxidize the produced H ₂ to support light-dependent CO ₂ fixation. Therefore, reactor 30 may be operable in an absence of light following activation, to enhance the yield of H ₂ product.

[0080] In embodiments, illumination assembly 46 is located external to reactor 30 such that activation of selected microorganisms may be performed prior to introduction of microorganisms into reactor 30.

[0081] Referring again to Figures 5 and 6, in some instances, system 30 comprises a photoactivation control system such that, during operation of CO water shift reaction system 10, should fresh microorganisms be introduced into reactor 30 via microorganism inlet 41c, suspension circulating from fast flow zone 70, through head 40, and downward into slow- flow zone 50 may again be exposed to visible light as it passes through head 40, to ensure activation of the CO oxidation pathway in the recirculated microorganisms and/or make-up microorganisms. The photoactivation control system may be designed such that non-initial exposure to light may be brief. Following such exposure, the control system may be designed to again expose the flowing suspension to darkness. Injection System and Control

[0082] Reactor 30 comprises an injection system whereby carbon-monoxide saturated fluid are injected into reactor 30. This injection system may also be utilized to clean the portions of CO water shift reaction system 10, for example, the interior of riser 70, downcomer 50, and head 40, as discussed further hereinbelow. As indicated in Figures 5 and 6, retention chamber outlet line(s) 84 are connected to inlet nozzles 2 along the walls of riser 70 (or fast- flow zone) of reactor 30. Line(s) 84 are configured for introduction of CO-saturated fluid to one or more pumps 1 which are operable to forcibly inject the CO-saturated fluid into reactor 30 via one or more injection nozzles 2. For example, in the embodiment of Figure 5, line 84 is connected to seven pumps, Ia-Ig. Pumps Ia-Ig are configured to pump the CO-saturated fluid into riser 70 of reactor 30 via seven injection nozzles or sprayers 2a-2g respectively. [0083] The one or more pumps of associated with reactor 30 may be in electronic communication with a controller for regulating the injection characteristics of each injection nozzle or sprayer 2 or the flow rate provided by venturi pump Ih. CO fermentation system 10 may further comprise variable frequency drives associated with each of pumps 1. [0084] The nozzles may be any nozzle known in the art. In applications, suitable nozzles, e.g., nozzles Ia-Ig, (and cleaning nozzles Ii-Ik, and Im which will be discussed further hereinbelow) are high pressure Toftejorg rotary jet heads, available from Alfa Laval (Lund, Sweden). The flow of fluid through the nozzles causes a geared rotation around the vertical and horizontal axes. Sprayers 2 may comprise four changeable nozzles which can rotate in the vertical and horizontal directions simultaneously. Sprayers 2 may be constructed of any suitable material in any suitable form and size.

[0085] Utilization of a plurality of injection nozzles/sprayers 2 and associated pumps 1 allows injection of differing volumes and/or concentrations of fermentation feed gas into the various nozzles. In such embodiments, line 84 may be split into a plurality of lines (not shown in the embodiment of Figures 5 and 6) such that CO-saturated fluid exiting retention chamber 80 via retention chamber outlet line 84 may be introduced at various flow rates and varying concentrations into riser 70. For example, different amounts of gaseous diluent or saturated fluid may be introduced into each or some of the nozzles 2. For example, as toxicity of microorganisms to CO ₂ may be greater at greater depths (pressures), fluid injected into a lower nozzle, such as nozzle 2g, may be of a greater bacterial concentration and/or a reduced CO or CO ₂ concentration as compared with fluid injected to a nozzle positioned closer to ground level G, e.g., nozzle 2a.

[0086] System 10 may further comprise measurement apparatus for determining the concentration of carbon monoxide in the fermentation product gas extracted from headspace 44 via fermentation product gas outlet line 88. In many applications, the selected microorganism(s) are relatively insensitive to CO concentration in the suspension. Therefore, the CO concentration in the fermentation product gas may be adjusted such that substantially all CO is consumed. Thus, system 10 may further comprise a control system in conjunction with measurement apparatus whereby the composition of the fermentation feed gas comprising CO in line 102 may be adjusted so that substantially all CO in the fermentation feed gas is consumed in reactor 30. The control system may be operable to dilute the carbon monoxide feed in line 102 or increase the biomass concentration in the slurry if the measured amount of CO in the fermentation product gas is too high and alternatively, to increase the concentration of the CO feed in line 102 if the bacterial concentration is capable of converting a greater amount of CO to hydrogen. Fermentation product gas outlet line 88 and/or hydrogen PSA outlet line 113 may be fluidly connected with fermentation feed gas inlet line 102 or retention chamber 80, such that a portion of the product hydrogen in fermentation gas product outlet line 88 (the gas extracted from the vacuum degasified region, or headspace 44) or upgraded hydrogen in hydrogen PSA outlet line 113 may be introduced into retention chamber 80 or inlet line 102 should the measured CO in the fermentation product gas be undesirably high, thus providing dilution while maintaining desired gas lift potential.

[0087] As mentioned above, CO system 10 may further comprise a PLC, integrated control panel, and variable frequency drives associated with pumps 1. The PLC may be configured to control the gas transfer rate by measuring the CO content in degassing chamber 44 via an integrated control panel. If the CO in the product gas is too high, pump speed may be reduced and/or the CO gas feed to venturi 85 reduced. A portion of the degasifϊer product gas may be recycled from product gas outlet line 88 to fermentation feed gas inlet line 102 to effect reduction in CO fed while maintaining desired gas lift in riser 70. System 10 may further comprise an operating room and touch screens for monitoring operational parameters, as known in the art. Temperature Control System

[0088] CO water shift reaction system 10 may further comprise a temperature control system. The temperature control system may comprise a temperature control unit in thermal communication with reactor 30 and retention chamber 80. Reactor 30 may be surrounded by and spaced an axial distance from by a vessel having the same general shape thereof. For example, in instances where reactor 30 is cylindrical, reactor 30 may be surrounded by and separated an axial distance from a concentric cylinder. As indicated in Figures 5 and 6, reactor 30 may be surrounded by vessel 36 and separated therefrom by a distance L6. Concentric (or similarly-shaped) vessel 36 may be itself surrounded by insulation, e.g. polyurethane, which separates it from the earth of the borehole. As depicted in Figure 8a, walls 33 of reactor 30 have inner sides 33a and outer sides 33b; similarly, concentric vessel 36 has inner sides 36a and outer sides 36b. As depicted in Figures 5 and 6, temperature control fluid may be introduced the region between concentric vessel 36 and the outer sides 33b of reactor walls 33 of reactor 30 via a line 4a. Spent temperature control fluid may be removed from the temperature control region 11 between concentric vessel 36 and the outer sides of reactor walls 33 of reactor 30 via a line 4b. Baffles may be positioned within temperature control region 11 to direct the flow of cooling fluid from the top of reactor 30 along one side to the bottom, along the bottom, and back up the opposite side of reactor 30 and out. Baffles may be welded to outer sides 33b of reactor walls 33 and inner side 36a of concentric vessel 36 (see Figure 8a).

[0089] Inner sides 33a of reactor walls 33 may be constructed of a highly polished stainless steel. Inner sides 33a are configured such that, during operation, at least a portion of inner sides 33a of reactor walls 33 are in contact with suspension. To provide temperature control, outer sides 33b of reactor walls 33 are configured such that, during operation of CO water shift reaction system 10, outer sides 33b are in communication with temperature control region 11. Concentric vessel 36 is configured such that inner sides 36a of concentric vessel 36 are in communication with temperature control region 11 and outer walls 36b are in contact with the surrounding earth or an insulation layer, e.g. polyurethane wrap as described hereinabove. Temperature control region 11 and cooling sleeve or concentric vessel 36 may also be used to sterilize deep shaft reactor 30 via steam cleaning.

[0090] Figure 8a is a top view 400a of a temperature control assembly according to an embodiment of this disclosure. In this embodiment, baffles 410a and 410b are positioned from the surface 12a of reactor 30 to a position a distance X from the bottom 12b of reactor 30 and extend horizontally the entire distance from the outer sides 33b of reactor 30 to the inner sides 36a of concentric vessel 36. Thus the length LI l of the baffles is less than the length L7 of the walls 33 of reactor 30. The baffles may be positioned opposite each other, e.g., for concentric configurations, baffles 410a and 410b may be positioned 180 degrees from one another. In this manner, temperature control region 11 may be divided into two subregions 11a and 1 Ib. There may be any number of subregions provided by any number and arrangement of baffles. For example, in the embodiment of Figure 8a, baffles 410a and 410b divide cooling region 11 into equal volume subregions 11a and l ib. In embodiments, not all subregions of a plurality thereof have the same volume.

[0091] Figure 8b is a side view 400b of the temperature control assembly of Figure 8a. During operation, heating or cooling fluid is introduced to the top of subregion 11a, flows down the length of subregion 11a, transfers to subregion 1 Ib within the distance X from the bottom 12 of reactor 30, and traverses the vertical length of subregion l ib back to the top of subregion l ib where it is extracted as spent temperature control fluid via spent temperature control fluid outlet line 4b.

[0092] In embodiments in which the bacteria fermented within reactor 30 do not produce significant amounts of heat, cooling of reactor 30 may not be necessary. A temperature control system may be desirable, however, in applications in which the ground temperature is very cold, in which applications the temperature control system may be utilized to elevate the temperature of the suspension within reactor 30 to within a desirable or optimum range for bacterial conversion of carbon monoxide. In other instances, a temperature control system is desirable for use in cooling the equipment when steam is used during cleaning operations. Cooling may also be desirable when the bacteria produce a significant amount of heat, in which case the temperature control system may be used to reduce the temperature of the suspension within reactor 30 to a desired or optimum level for bacterial fermentation of carbon monoxide and production of CO therefrom. Cleaning System

[0093] Reactor 30 may also be configured for cleaning in place. Nozzles configured for injection of CO-saturated fluid into riser 70 may be utilized for cleaning in place, or CIP. Additional spray nozzles may be positioned along the slow-flow or downcomer wide of reactor 30, as indicated in Figures 5 and 6. For example, nozzles 2i, 2j, and 2k along with associated high pressure pumps Ii, Ij, and Ik may be fluidly connected with cleaning chemicals via lines 3a and 3c, for example. Should reactor 30 comprise suspension annular region 48, an additional nozzle 2m and associated high pressure pump Im may be positioned along the vertical perimeter of annular suspension region 48, as indicated in Figures 5 and 6. Pump Im and spray nozzle 2m may be fluidly connected with cleaning chemicals via, for example, cleaning lines 3 a and 3b.

[0094] As mentioned hereinabove, the nozzles may be Toftejorg rotating spray devices, available from Alfa Laval (Lund, Sweden). The flow of the fluid (in this application, cleaning fluid or steam) causes the nozzles to make a geared rotation around the vertical and horizontal axes. In the first cycle, the nozzles lay out a coarse pattern on the surface of the vessel being cleaned. Subsequent cycles gradually make the pattern denser until substantially complete coverage is obtained. The jets provide a combination of physical impact and a cascade cleaning solution flow that reaches substantially all of the surfaces in the compartment being cleaned. Toftejorg nozzles are auto-cleaning by directing the cleaning media through the rotating bearing track and onto the neck of the elongated head. [0095] The cleaning system may be operable such that cleaning chemicals may be fluidly connected with riser 70 via cleaning chemical lines 3a and 3d. Line 3d may introduce cleaning chemicals into venturi 85 such that the interior of retention chamber 80 may be exposed to cleaning solution prior to introduction of the cleaning chemicals to reactor 30 via pumps Ia-Ig and nozzles 2a-2g. Alternatively, the cleaning system may be configured such that cleaning chemicals may be introduced directly into each pump along riser 70 or may be introduced into retention chamber outlet line 84. Although not indicated in the embodiment of Figures 5 and 6, conservation of cleaning chemicals may be provided by a cleaning chemical recycle loop and cleaning chemical purification apparatus. The cleaning chemical recycle loop and purification apparatus may be configured so that used cleaning chemicals extracted from the bottom of reactor 30 may be cleaned (e.g., filtered) by the purification apparatus and recycled via the recycle loop for reuse as cleanser. For example, in applications, cleaning chemical purification apparatus may comprise a plate and frame membrane module for (continuous, semi-continuous, or periodic) removal of contaminants from spent cleaning solution prior to reinjection into reactor 30 or retention chamber 80. In such a manner, the cleaning system may be operable for continuous operation via cleaning chemical recirculation. This recycle/reuse of cleaning chemical(s) may reduce the amount of water and/or cleaning chemical(s) utilized during cleaning operations.

[0096] The cleaning chemicals may comprise any suitable cleaning solution and may be, for example, hydrophilic, oleophilic, amphiphilic. The cleaning solution is supplied to the feed streams utilizing at least one vessel with necessary components, such as tubes, pipes, and pumps. Cleaning chemicals may comprise, for example, a bleach solution, NaOH solution, or steam. The composition of the cleaning solution may be varied during a cleaning cycle, depending on the objectives of cleaning needed and the surface to be cleaned. In embodiments, the cleaning solution is heated or cooled prior to being introduced into cleaning nozzles/sprayers 2. Although temperature control may not be needed during regular fermentation, temperature control may be desirable during cleaning operations, e.g., using steam cleaning. In embodiments, a cleaning cycle comprises emptying the vessels to be cleaned, optional rinsing with water, injection of cleaning chemicals, optional rinsing, and finally injection of steam. Maintenance/Elevators

[0097] Although not shown in the embodiment of Figures 5 and 6, one or more maintenance elevators may be positioned from the ground surface G to a depth along the length Ll of reactor 30. Such service elevators may be used to enable service personnel easy access to system components. The elevator or elevators may be positioned within system 10 such that substantially all in-ground mounted equipment is accessible thereby. In embodiments, a service elevator allows access along the riser side of reactor 30. In embodiments, another service elevator allows access to the downcomer side of reactor 30. Serial Reactors 30

[0098] Although not depicted in the Figures, in applications CO fermentation system 10 comprises a plurality of deep shaft reactors 30 arranged in series. In such arrangements, a first reactor Rl may have a fermentation feed gas inlet line for feed gas having a CO concentration [Xl], may contain a suspension comprising a microorganism concentration [Ml], and may have a vertical depth Dl; a second reactor R2 of the series may have a fermentation feed gas inlet line for feed gas (gas exiting first reactor Rl) having a CO concentration [X2], may contain a suspension comprising a microorganism concentration [M2], and may have a vertical depth D2; a third reactor R3 of the series may have a fermentation feed gas inlet line for feed gas (gas exiting second reactor R2) having a CO concentration [X3], may contain a suspension comprising a microorganism concentration [M3], and may have a vertical depth D3; and so on. High CO (and/or other gas, e.g., CO ₂ ) concentration may be toxic to the microorganisms. Thus, lower pressure (reduced depth and thus reduced toxicity) may be desired when [CO] in the fermentation feed gas is higher. As the fermentation feed gas fed into subsequent reactors in serial application is lower, subsequent reactors in the series may have deeper depths, D. Furthermore, as the CO concentration, [X] of the fermentation feed gas to subsequent serial reactors is reduced, the subsequent reactors may convert substantially all of the carbon monoxide to hydrogen while operating with a lower microorganism concentration, [M]. Therefore, in applications system 10 comprise a plurality of deep shaft reactors 30 aligned in series and [X1]>[X2]>[X3], and so on. In applications, system 10 comprises a plurality of reactors 30 aligned in series and D1<D2<D3, and so on. In applications, system 10 comprises a plurality of deep shaft reactors 30 aligned in series, and [M1]>[M2]>[M3], and so on. In applications, system 10 comprise a plurality of deep shaft reactors aligned in series and [X1]>[X2]>[X3]... ; D1<D2<D3...; and [M1]>[M2]>[M3]. In this manner, system 10 is designed such that the pressure of operation, the concentration of biomass within each of a plurality of reactors, and/or the CO content of the feed gas to each of a plurality of reactors may be modified (i.e., the depth varied) to provide optimum conditions for bacterial fermentation. Design of system 10 with a plurality of deep shaft reactors in series with various inlet concentrations of CO in the fermentation feed gas and/or various depths allow manipulation of the optimum operating conditions (toxicity points) of the bacteria. Such serial design within CO water shift reaction system 10 may provide flexibility in operation when the gasifier feed materials utilized in gasifier feed inlet line 125 varies, changing the fermentation feed gas obtained therefrom.

C. CO-Saturation Retention Chamber 80

[0099] CO biological water shift reaction system 10 comprises retention chamber 80. Retention chamber 80 is configured to saturate a fluid with CO prior to injection of the fluid into reactor 30. In embodiments, water filtrate extracted from biomass extraction unit 90 is saturated with CO. In embodiments, a portion of CO-starved suspension within reactor 30 is saturated with CO within retention chamber 80. During operation, the dissolved carbon monoxide provides the necessary carbon source for the microorganisms to carry out the net water-gas shift reaction (1), when CO-saturated fluid is injected into the fast-flow zone of riser 70. Saturation of fluid (i.e., return water filtrate and/or carbon-deprived suspension) with fermentation feed gas comprising CO is designed to reduce gas mass transfer limitations within the system and enhance reaction rate. Retention chamber 80 may be positioned either above ground level G, below ground level G, or may be split therebetween. [00100] As depicted in the embodiment of CO water shift reaction system 1OA shown in Figure 5, return water filtrate line 98 may couple biomass extraction unit 90 with retention chamber 80. In this manner, at least a portion of the water filtrate (e.g., from a centrifuge or membrane separation biomass extraction unit 90) may be recycled to reactor 30 via retention chamber 80. In such embodiments, a portion of the water filtrate may also be recycled via water recycle line 93 and inlet 41a to reactor 30.

[00101] A pump Ih and venturi 85 may be used to draw return filtrate from unit 90 and combine the return filtrate with fermentation feed gas comprising carbon monoxide via fermentation feed gas inlet line 102. The return filtrate from unit 90 may be stored in a break tank (not shown in Figure 5) and drawn therefrom as desired. Pump Ih and venturi 85 may also provide pressure to the water filtrate drawn therein. Alternatively, fermentation feed gas inlet line 102 may connect directly to retention chamber 80 in certain applications. Thus, gasification subsystem 100 may be coupled to retention chamber 80 indirectly via fermentation feed gas inlet line 102, venturi 85, and venturi outlet line 86. Alternatively, gasification subsystem 100 may be coupled directly to retention chamber 80 via line 102 (not shown as such in the embodiment of Figure 5), so that fermentation feed gas and return water filtrate may be fed separately into retention chamber 80. Pump Ih and venturi 85 may be preferable in relation to utilizing a compressor, as synthesis gas is explosive and the fermentation feed gas comprising CO may also comprise hydrogen. Furthermore, the fermentation feed gas may be a synthesis gas comprising substantial ash and/or soot. In these applications, compression of the fermentation feed gas would be dangerous and expensive, although theoretically utilizable.

[00102] As depicted in the embodiment of CO water shift reaction system 1OB in Figure 6, downcomer 50 (slow-flow zone) may coupled to retention chamber 80 via CO-starved suspension outlet line 82. CO suspension outlet line 82 may exit a lower portion (lower 20%, for example) of downcomer 50. In such embodiments, CO-saturation of extracted CO- depleted suspension is used to provide feed materials to reactor 30. In embodiments in which return water filtrate serves as fluid to be saturated with CO and fed to reactor 30, an outlet line 82 may be present for extraction of fluid from reactor 30 during cleaning operations, and may not be fluidly connected with retention chamber 80 (for example, as depicted in the embodiment of Figure 5).

[00103] In embodiments in which CO-depleted suspension serves as the fluid to be saturated with CO and introduced to riser 70 of reactor 30, CO-depleted suspension outlet line 82 may be coupled to retention chamber 80. CO-depleted suspension outlet line 82 may be coupled to retention chamber 80 via any means suitable for raising the pressure of the withdrawn suspension and/or combining the removed CO-depleted suspension with fermentation feed gas comprising CO, for dispersion of the fermentation feed gas therein. In such embodiments, another portion of CO-depleted suspension travels around the bottom of divider 34 and passes into riser 70 without exiting reactor 30.

[00104] A pump Ih and venturi 85 may be used to draw CO-depleted suspension from reactor 30 and combine the removed CO-depleted suspension with fermentation feed gas comprising carbon monoxide via fermentation feed gas inlet line 102. Pump Ih and venturi 85 may also provide pressure to the extracted CO-depleted suspension drawn therein. Alternatively, fermentation feed gas inlet line 102 may connect directly to retention chamber 80 in certain applications. Thus, gasification subsystem 100 may be coupled to retention chamber 80 indirectly via fermentation feed gas inlet line 102, venturi 85, and venturi outlet line 86. Alternatively, gasification subsystem 100 may be coupled directly to retention chamber 80 via line 102 (not shown as such in the embodiment of Figure 6). In this configuration, fermentation feed gas and withdrawn CO-depleted suspension may be fed separately into retention chamber 80. As mentioned hereinabove, pump Ih and venturi 85 may be preferable in relation to utilizing a compressor, as synthesis gas is explosive and the fermentation feed gas comprising CO may also comprise hydrogen. Furthermore, the fermentation feed gas may be a synthesis gas comprising substantial ash and/or soot. In these applications, compression of the fermentation feed gas would be dangerous and expensive, although theoretically utilizable.

[00105] The intake end of CO-depleted suspension outlet line 82 may be adjacent to flow- through zone 16b and/or bottom 12b of reactor 30. The intake end of CO-depleted suspension outlet line 82 may be disposed in downcomer 50, in riser 70, or substantially therebetween. Retention chamber outlet line(s) 84, pump(s) 1, and nozzle(s) 2 couple retention chamber 80 to reactor 30.

[00106] Retention chamber 80 is configured to provide retention time for extracted CO- depleted suspension to be exposed to fermentation feed gas introduced into retention chamber 80. Retention chamber 80 may be operable in darkness.

[00107] Retention chamber 80 is configured to provide substantially complete saturation (or supersaturation) of fluid (e.g., return water filtrate and/or CO-deprived suspension) with CO reactant in the fermentation feed gas such that downstream microorganism activity is enhanced. The theory of operation is that, as the suspension is CO-depleted upon contact with CO-saturated fluid, the organisms will super activate following starvation, and subsequently produce hydrogen more efficiently. The activated microorganisms in the CO- enriched zone of riser 70 will produce H ₂ and CO ₂ from the carbon monoxide dissolved into the CO-saturated fluid within retention chamber 80. This metabolic process by which H ₂ is generated may occur in retention chamber 80, during transfer from retention chamber 80 to riser 70 of deep shaft reactor 30, and during circulation through fast-flow zone 70. A majority of the hydrogen production may be expected within riser 70. The production of H ₂ may also occur as the suspension circulates through the lower portion (annular liquid region 48) of reactor head 40. D. Biomass Extraction Unit 90

[00108] The microorganisms of the suspension metabolize and proliferate, in some cases doubling in population after only two hours of processing. CO fermentation system 10 thus further comprises biomass extraction unit 90. Biomass extraction unit 90 is configured to separate excess biomass from an extracted portion of suspension. During operation, all or a portion of the circulating suspension is removed from reactor 30 and treated with biomass extraction unit 90 to remove excess or spent microorganisms. Furthermore, as the fermentation feed gas introduced into reactor 30 via fermentation feed gas inlet line 102 may comprise some dust and/or tar, it may be desirable to extract biomass to remove such materials which may accumulate in the biomass cell structure. Also, bicarbonate will be formed from the biologically-produced carbon dioxide due to utilization of suitable pH, as discussed hereinabove. Removal of at least a portion of suspension may facilitate dilution/removal of the bicarbonate.

[00109] Biomass extraction unit 90 may be positioned above ground level G, below ground level G, or a combination thereof. Biomass extraction unit 90 comprises a spent biomass outlet line 89 which connects biomass extraction unit 90 with a location within the operating reactor volume of reactor 30, i.e., a location within reactor 30 below normal suspension fill line 43. In embodiments, as shown in Figures 5 and 6, spent biomass outlet line 89 is coupled to annular extension region 48 of reactor 30. The removal of at least a portion of the circulating suspension from reactor 30 may be periodic, continuous, or semi-continuous, or may vary depending on measured microorganism concentration within reactor 30. CO water shift reaction system 10 may thus further comprise one or more TDS meters configured to measure the TDS concentration within reactor 30 during operation. When the measured TDS is too high and/or replacement of biomass is desired, at least a portion of the circulating suspension may be extracted from reactor 30 via spent biomass outlet line 89. [00110] Biomass extraction unit 90 is adapted to separate aqueous medium from spent bacteria. Biomass extraction unit 90 further comprises an aqueous phase outlet line 92 and a sludge outlet line 91. Biomass extraction unit 90 may be any suitable device or devices for separating spent bacteria from aqueous media. Biomass extraction unit 90 may be a membrane bioreactor system and/or a centrifuge. Separation may be effected by filtration, centrifugation, or a combination thereof. To resist the likelihood of contaminant introduction into system 10, biomass extraction unit 90 may be an ultrafiltration or micro filtration module comprising at least one ultrafiltration or microfϊltration membrane. Depending on the composition of fermentation feed gas comprising CO (which itself depends somewhat on the gasifier feed material), suspension extracted via spent biomass outlet line 89 may comprise trace toxic elements such as, but not limited to, hydrogen sulfide, and nitrogen compounds such as NO _x . Although the levels of these contaminants in the fermentation feed gas may be low, with continuous operation, such contaminants may accumulate. Depending on the effect of such accumulated contaminants on the biomass, biomass extraction unit 90 may be one of several units utilized to remove such trace contaminants from reactor 30. For example, CO water shift reaction system 10 may comprise additional biomass extraction units 90 for removal of a variety of contaminants.

[00111] Aqueous phase outlet line 92 may be coupled to recycle water line 93 and/or return filtrate line 98. In this manner at least a portion of the water removed from reactor 30 via spent suspension outlet line 89 may be recycled for reuse within reactor 30 and the production of further hydrogen therefrom. Fresh water line 94 may be coupled to recycle water line 93 as desired. Alternatively, fresh water line 94 may introduce sterile fresh water directly into reactor 30 (not shown in the embodiments of Figures 5 and 6). At least a portion of the aqueous phase comprising separated liquid, and dissolved components of the suspension, may be returned to the CO fermentation reactor 30 via water inlet line 41a, optionally diluted with fresh sterile water, as needed, to reduce the bicarbonate concentration. At least a portion of the aqueous phase comprising separated liquid and dissolved components of the suspension will, in embodiments as depicted in Figure 5, be returned to reactor 30 via line 98 and retention chamber 80 for saturation with CO in the feed gas. As mentioned above, CO water shift reaction system 10 may further comprise a TDS meter for measuring the TDS within the suspension within reactor 30. During operation of CO water shift reaction system 10, the amount of water introduced into reactor 30 via fresh water line 94 and/or recycle water line 93 and water inlet 41a, as well as the amount of nutrients, fresh microorganisms, and chemicals introduced into reactor head 40 via inlet lines 41b, 41c, and 4 Id, may be controlled in response to the measured total dissolved solids or TDS within reactor 30, the level of suspension in annular region 48, or both. A desired TDS level may be in the range of what is biologically acceptable by the microbes and what is allowed to be discharged by local authorities related to local water discharge standards. Recycled effluent from biomass extraction unit(s) 90 may be supplemented with fresh nutrients and sterile water as needed.

[00112] Sludge extracted via sludge outlet line 91 comprises spent microorganisms. The sludge may be utilized in a variety of ways, for example, at least a portion of the sludge extracted via sludge outlet line 91 may be recycled to plasma reactor 105. In such instances, sludge outlet line 91 may be fluidly connected to plasma gasification reactor 105 or gasifϊer inlet feed line 125 for carbon recycle. In this manner, the recycled sludge may be utilized for production of additional fermentation feed gas comprising CO. Alternatively, or additionally, a portion of the spent biomass extracted via sludge outlet line 91 may be disposed of as waste, in accordance with applicable regulations. At least a portion of the portion of the spent biomass extracted via sludge outlet line 91 may be utilized as protein feed in husbandry operations, for example as proteinaceous cattle feed. If not contaminated, portions of the extracted biomass may be utilized to startup additional reactors 30, for example, when CO system 10 comprises a plurality of reactors 30 in series. CO water shift reaction system 10 may further comprise one or more centrifuges (not shown in the Figures) to dewater sludge extracted via sludge outlet line 91. E. Hydrogen Removal Subsystem 110

[00113] CO water shift reaction system 10 further comprises hydrogen recovery/utilization subsection 110. Fermentation product gas outlet line 88 couples a location of reactor 30 within headspace 44 (vacuum degasifier) with hydrogen recovery/utilization subsection 110. Hydrogen recovery/utilization subsystem 110 comprises a means to remove fermentation product gas from headspace 44 of reactor 30. Hydrogen recovery/utilization subsystem 110 may further comprise apparatus for utilization of the hydrogen that exits reactor 30 via fermentation product gas outlet line 88. Such utilization may comprise production of electricity via combustion or fuel cell, sale, product upgrading, and creation of desirable chemical compounds.

[00114] Rapid removal of the fermentation product gas from the suspension deters potential toxic effects of the gases on the microorganisms, and reduces the propensity of undesirable side reaction. Fermentation system 10 may comprise a vacuum degasifϊer whereby evolved gases may be collected and extracted from reactor 30. Such vacuum may be applicable to the suspension as the suspension circulates through the lower portion (or annular liquid region 48) of reactor head 40. During operation, hydrogen product is recovered from the vacuum extracted fermentation product gas removed via fermentation product gas outlet line 88. [00115] Figure 9a is a schematic of an embodiment of hydrogen recovery subsystem HOa according to an embodiment of this disclosure. Hydrogen recovery subsystem HOa comprises a vacuum pump In and gas generator set 111. Vacuum pump In provides vacuum degasifϊcation to headspace 44, drawing product gases comprising hydrogen from reactor 30 via fermentation product gas outlet line 88. The system may be configured for the production of fermentation product gas comprising at least 90% hydrogen, at least about 99% hydrogen, at least about 99.9% hydrogen, or at least about 99.99% hydrogen. The product gas may comprise ultra-pure hydrogen. Given enough time, for example, or using serial reactors 30, fermentation product gas extracted via fermentation product outlet line 88 may comprise little or substantially no CO.

[00116] If fermentation product gas comprising hydrogen comprises about 99% hydrogen, fermentation product gas may be introduced, as in the embodiment of Figure 9a, via pump In into gas generator set 111. Additional fuel line 118 may be configured to introduce additional fuel into Gas Generator (GasGen) set 111. Additional fuel line 118 may introduce additional fuel into line 88 upstream of GasGen set 111 or may introduce additional fuel directly into GasGen Set 111. The additional fuel may be any fuel, for example, methane. Alternatively, if the hydrogen in fermentation product gas is less than about 99% pure, further clean-up (not shown in the embodiment of Figure 9a) may be performed upstream of GasGen set 111. GasGen set 111 is any suitable gas generator capable of converting hydrogen to electricity, which is represented in Figure 9a as line 95b.

[00117] Figure 9b is a schematic of a hydrogen recovery subsystem 110b according to an embodiment of this disclosure. In this embodiment, hydrogen recovery subsystem 110b comprises vacuum pump In, hydrogen pressure swing adsorption unit 112 and fuel cell 114. In this embodiment, fermentation product gas comprising hydrogen is pumped via pump In into hydrogen pressure swing adsorption (or PSA) unit 112. Hydrogen PSA is a PSA unit configured for separation of non-hydrogen components from hydrogen. PSA exhaust gas line 96 is configured to carry exhaust gas separated from the fermentation product gas within PSA 112 out of PSA 112. Depending on CO ₂ and nitrogen compound levels, a chimney (not shown in Figure 9b) may be adapted to vent the exhaust gas to the atmosphere. PSA 112 further comprises an outlet line 113 for high purity hydrogen gas. In embodiments, PSA 112 is capable of producing high purity hydrogen comprising at least 99% hydrogen by weight; alternatively greater than 99.9% hydrogen by weight; alternatively greater than 99.99% hydrogen by weight. Outlet line 113 may fluidly connect PSA 112 with fuel cell 114. Fuel cell 114 may be one or more high or low temperature fuel cells suitable for producing electricity using hydrogen as fuel. For example, fuel cell(s) 114 may be selected from proton exchange membrane fuel cells or PEMs, molten carbonate fuel cells or MCFCs, and solid oxide fuel cells or SOFCs. In embodiments, oxygen produced in oxygen-enrichment unit 166 (when oxygen enrichment unit 166 comprises an ASU) is also introduced via oxygen inlet line 180b into fuel cell 114 for use as oxidant. Fuel cell 114 produces electricity from the hydrogen within the fermentation product gas, as indicated by outlet line 95 c. In general, the higher the temperature, the lower the constraints on fuel mixtures that are suitable for fuel cell(s) 114. Low and intermediate temperature operation fuel cells, e.g. PEM fuel cells, may require very low concentrations of CO, e.g. [CO] < lOppm. Higher temperature fuel cell(s) 114 may have less stringent fuel requirements.

[00118] As with the electricity 95a generated in steam turbine 218, electricity 95b/95c generated in hydrogen recovery subsystem 110 may be used throughout carbon monoxide water shift reaction system 10, for example, for running oxygen-enhancement unit 166 and/or hydrogen upgrading unit 112, or may be utilized in another associated part of system 10 or sold for profit.

[00119] Alternatively, fermentation product gas comprising hydrogen or high purity hydrogen in PSA outlet line 113 may be utilized for a purpose other than electricity generation. For example, the hydrogen may be utilized for chemical production, product upgrading, may be sold for a profit, or other uses.

[00120] Without further elaboration, it is believed that one skilled in the art can, using the description herein, utilize the present invention to its fullest extent. The embodiments described herein are to be construed as illustrative and not as constraining the remainder of the disclosure in any way whatsoever. While the preferred embodiments of the invention have been shown and described, many variations and modifications thereof can be made by one skilled in the art without departing from the spirit and teachings of the invention. Accordingly, the scope of protection is not limited by the description set out above, but is only limited by the claims, including all equivalents of the subject matter of the claims. The disclosures of all patents, patent applications and publications cited herein are hereby incorporated herein by reference, to the extent that they provide procedural or other details consistent with and supplementary to those set forth herein.

References:

Maness, Pin-Ching, Jie Huang, Sharon Smolinski, Vekalet Tek, and Gary Vanzin, "Energy generation from the CO oxidation-hydrogen production pathway in Rubrivivax gelatinosus," June 2005 Applied and Environ. Microbiol. 71 :2870-2874.

Merida, Walter, Pin-Ching Maness, Robert C. Brown and David B. Levin, "Enhanced hydrogen production from indirectly heated, gasified biomass, and removal of carbon gas emissions using a novel biological gas reformer," 2004 Int. J. Hydrogen Energy 29:283-290.

Maness, Pin-Ching, Sharon Smolinski, Anne C. Dillon, Michael J. Heven, and Paul F. Weaver, "Characterization of the oxygen tolerance of a hydrogenase linked to a carbon monoxide oxidation pathway in Rubrivivax gelatinosus," June 2002 68:2633-2636.

Maness, Pin-Ching and Paul F. Weaver, "Hydrogen production from a carbon-monoxide oxidation pathway in Rubrivivax gelatinosus " 2002 Int. J. Hydrogen Energy 27: 1707-1411.