CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims the priority benefit of US provisional patent application no. 62/517,186, filed June 9, 2017, and to FI patent application no 20170148, filed November 1, 2017. The present application is related to PCT patent application no. PCT/IB2018/054187, filed June 11, 2018 and titled "Recovery of Chemicals from Fuel Streams." Each of these references is incorporated by reference herein.

BACKGROUND

1. Technical Field

[0001] The present invention relates generally to fluidized bed reactors, particularly to bubbling fluidized bed reactors, and to the recovery and use of volatile species in fluidized bed systems.

2. Description of Related Art

[0002] Typical fluidized bed reactors are based on either so-called circulating fluidized bed (CFB) or so-called bubbling fluidized bed (BFB) designs. CFB reactors typically utilize smaller particles than BFB. A CFB reactor in a combustion application typically has an average particle size between 0.2 and 0.4 mm, whereas a BFB has an average particle size that is approximately 1mm. The larger particles of BFB lend themselves to "bubbling" under economic reaction conditions.

[0003] The small particle sizes of CFB lend themselves to long-distance, convective, gas-entrained "circulation" (like a dust storm). CFB reactors are based on "fast" fluidization, thereby utilizing much higher gas velocities than those associated with the bubbling regime (itself below the turbulent regime). The resulting "dust storm" of entrained particles and fuel in a typical circulation regime is entirely different than the discrete, dense, "bed phase" of a bubbling fluidized bed, notwithstanding the "CFB" nomenclature. In prior CFB systems, circulation of particles from a circulation reactor to a second "storage" reactor and back entails the use of a riser (built into the circulation reactor), followed by separation of the particles from the gas phase (typically with a cyclone). The riser carries the particles upwards over tens of meters, during which reactions and heat exchange (e.g., to heat steam) occur. The particles are later separated from the gas phase and dropped via a downcomer back to the other reactor. The reactors are spatially separated from each other, with ductwork guiding a convective "wind" that carries particles through the ducts between reactors. CFB reactors operate with very high gas velocities and concomitantly entrained particles - ostensibly not even as "beds" per se. A "pre- bed" storage bed may capture and store those particles.

[0004] Typical CFB -circulation designs do not work well (and are often

incompatible with) BFB particles. Circulation of the relatively large BFB particles in prior CFB designs require very high gas velocities to lift the particles in the riser and/or separate them in the cyclone. These high velocities are expensive to generate and difficult to manage. The large, high velocity particles are erosive and readily damage the walls and other surfaces of the plant.

[0005] Conversely, the use of CFB particles in a BFB is also problematic. The use of the relatively smaller CFB particles in a BFB requires the use of relatively low gas velocities (in the bubbling bed) to properly "bubble" the bed of CFB particles. As a result, very large beds are required to achieve desired reaction rates.

[0006] CFB and BFB designs each have their advantages. BFB reactors benefit from certain features associated with their relatively larger BFB particles, notwithstanding that such reactors cannot practically be made into "circulating" reactors. CFB designs provide for circulation between reactors. It would be advantageous to combine the advantages of a CFB (e.g., circulation) with those of a BFB (e.g., bubbling).

[0007] Various references describe adding a fluidization bed to a circulating fluidized bed (CFB) combustor. JP 2005-274015 A, JP 2004-132621A, JP 2005-41959A, JP 2006132885, and US 2010/0024297 describe a CFB combustor having a

riser/cyclone/downcomer circuit to recycle particles from the CFB combustor into another fluidized bed. US 4,823,712 describes the use of screw conveyors to transport solids between beds. Such conveyors are prone to erosion by the solids.

SUMMARY

[0008] Aspects describe a fluidized bed reactor having a splashgenerator configured to impart a directed momentum to a particular portion of the bed, causing an active, controllable circulation/movement of bed solids within the bed. The splashgenerator may be used to increase convection within the bed (e.g., to enhance in-bed transport of fuel within a single bed). The bed solids may have a mean particle diameter that is at least 0.4mm, including at least 0.6 mm, particularly at least 0.75mm, particularly at least 0.9mm. Particles are typically below 2mm, including up to 1.5mm. A splashgenerator may be used to create circulation in a bubbling fluidized bed. [0009] An otherwise contiguous fluidized bed reactor may be divided into zones by a wall that separates at least a portion of the bed into two or more zones, enabling different reactions on either side of the wall. The wall modifies, inhibits, and/or prevents solids transport between the zones under standard fluidization conditions (e.g., the top of the wall may be near, or even above, the normally-fluidized bed height). When combined with a wall, a

splashgenerator in one zone imparts a directed momentum to a portion of the solids in that zone to drive ("splash") those solids (e.g., with fuel, char, and the like) through/over/past the wall into the other zone, where a subsequent reaction may occur. The solids may be splashed over the wall. The solids may be splashed through an opening in the wall. A return passage allows the "splashed-over" bed solids to recirculate back to the first zone. When the splashgenerator is turned off, a high wall substantially prevents bed communication between the zones (except for insubstantial convective flow via a return passage). A first zone may be used to volatilize a fuel with a less oxidizing gas such as N2 and/or steam to create a volatiles stream and char, the resulting char may be driven to the second zone, and the second zone may be used to combust the char with a more oxidizing gas such as air or oxygen.

[0010] Control of solids transport between zones via the splashgenerator-induced momentum may be used to control heat transport from one zone to the other. By integrating such a "compact circulation" functionality into a BFB, benefits of a CFB may be achieved using the bed characteristics (e.g., particle size) of a BFB. Circulation of bed material among the zones in an integrated bed may provide for different gases in different reactions zones with the reactivity of a bubbling bed using BFB particles, a compact design, and low cost. By integrating the zones within a single container, mass transfer (and especially heat transfer) from one zone to the next may be improved as compared to the discrete reactors of prior CFB designs. As compared to prior systems having complex circulation paths (risers, cyclones, separators, downcomers, and the like) various aspects provide for a much simpler, capital-efficient solution, enabling high, controlled reaction rates and/or multiple reaction zones, at lower capital cost, operational cost, and maintenance cost. Because long-distance "windstorm" convection is not required, erosion and other damage may be substantially reduced.

[0011] In an embodiment, a fluidized bed reactor (e.g., a BFB) comprises a splashgenerator configured to impart a localized directed momentum to a portion of the bed. The directed momentum is other than that used for normal fluidization of the bed, such that solids acted on by the splashgenerator are preferentially accelerated (splashed) as compared to the surrounding solids. The splashgenerator may be used to increase circulation within the bed (e.g., to circulate fuel away from a fuel inlet, increasing fuel dispersion). The directed momentum may be at least partially horizontal (e.g., like a hot-tub jet) which may enhance horizontal convection in the bed.

[0012] A fluidized bed reactor configured to react a fuel (or other substance) in a fluidized bed of bed solids may comprise a container configured to hold the bed of bed solids and a first wall separating at least a portion (typically at least the bottom) of the bed of bed solids into i) a first reaction zone having a first gas inlet configured to fluidize the bed solids in the first reaction zone with a first gas, and ii) a second reaction zone having a second gas inlet configured to fluidize the bed solids in the second reaction zone with a second gas, particularly different than (e.g., more or less oxidizing than) the first gas. A fuel inlet is typically disposed in at least one of the first and second reaction zones.

[0013] A splashgenerator configured to impart a directed momentum to a portion of the bed solids in the second reaction zone causes a drivenflow of the bed solids from the second reaction zone past the wall into the first reaction zone. A separate passage between the first and second reaction zones provides for a returnflow of the bed solids from the first reaction zone back into the second reaction zone. A passage may comprise an opening in a wall. For a passage having appreciable length, a passage gas inlet may fluidize the bed solids within the passage with a third (same or different) gas.

[0014] The drivenflow from the second zone into the first zone, combined with the returnflow from the first zone back to the second zone, creates a circulation between the two zones. Circulation enables certain functionality of a CFB, even for a BFB bed. As compared to typical CFBs (risers, cyclones, and the like) in which high velocity convection is used to blow particles long distances (meters to tens of meters) on a "wind" of gas through various ducts, the splashzone entrains particles in much shorter paths - merely enough to get past the wall separating the zone (tens of cm, typically less than 1-2 meters). As a result, erosion may be reduced or largely eliminated. Solids can be transported from one zone to another without requiring that they contact metal surfaces at high velocities.

[0015] Various aspects may be combined with a multistage fluidized bed reactor comprising separate stages (typically having separate gas phases separated by a wall).

Independent control of the gas pressure between the stages, combined with an appropriately dimensioned communication passage between the stages, enables a controlled transport of media (gas, bed solids) between the stages.

[0016] In an aspect, the container of bed solids includes a first wall separating at least a portion of the bed into two zones and a second wall that separates at least the gas phases above the zones, enabling the use of different stages in each zone. The walls may be separate or integrated as one wall. The second wall may be located in either reaction zone, and descends to below the normally fluidized bed heights, preventing gaseous communication between the stages (and substantially between zones). An opening in and/or below the second wall (below the surface of the bed solids) provides for a flow of solids between zones. As a result, solids may circulate between reaction zones (drivenflow -> returnflow) while the gas phases over the zones remain separate. Each zone may have its own fluidization gas, ambient pressure, evacuation rate, inlet velocity, temperature, and gas phase composition.

[0017] When not integrated into the same wall, the first wall (separating the bed solids) and the second wall (separating the gas phases) are typically separated by a gap that allows the drivenflow of solids (driven by the splashgenerator) to pass from the second zone to the first zone, but does not allow gaseous communication between the zones.

[0018] For simplicity, different stages are described as a volatilization stage and a combustion stage, although stages may be used differently (e.g., a first stage that is more oxidizing and/or hotter than a second stage) and solids may be driven from either zone. The wall(s) may divide the container into stages, each of which has its own fluidization gas supply. The stages may use the same or different fluidization gases, and each stage may have independent control of fluidization gas, pressure, temperature, and gas phase composition. In some cases, the stages need not have independent pressure control. The first stage may have a more or less oxidizing gas than the second stage. A reactor may include a volatilization stage and a combustion stage. The first wall may separate the beds into a first reaction zone fluidized by a relatively less oxidizing gas (LowOx gas) to create a volatilization stage and second reaction zone fluidized by a relatively more oxidizing gas (HiOx gas) to create a combustion stage. The second wall separates the gaseous phases, such that the stages may have separate gas compositions, pressures, and the like. The gap/passage provide for solids circulation between the stages but prevent gas phase circulation.

[0019] The volatilization stage may comprise a fuel inlet configured to receive the fuel, a first gas inlet disposed at a bottom of the container within volatilization stage, and a LowOx gas supply configured to supply an inert and/or mildly oxidizing gas to the first gas inlet to fluidize the bed of bed solids within the first reaction zone and

pyrolyze/gasify/reform/evaporate or otherwise react (herein: volatilize) the fuel to yield a volatiles stream and a char stream. A volatiles stream outlet is configured to convey the volatiles stream out of the volatilization stage, and a volatiles pressure gauge may be configured to measure pressure within the volatilization stage.

[0020] The combustion stage may comprise a second gas inlet comprising an oxidant inlet disposed at a bottom of the container within the combustion stage, and a HiOx gas supply configured to supply a gas that is more oxidizing than the gas supplied by the LowOx gas supply. The oxidant supply and oxidant inlet are configured to fluidize the bed of bed solids in the combustion stage and combust a char stream received from the volatilization stage (via the returnflow) to yield an exhaust gas. An exhaust gas outlet conveys the exhaust gas out of the combustion stage, and a combustion pressure gauge may be configured to measure pressure within the combustion stage. A means to control gas flow into/out of at least one stage (e.g., a valve, a fan, gas inlet, and/or an oxidant inlet), and a controller coupled to the pressure gauges and the means to control gas flow, provides for the control of the pressures of (e.g., pressure difference between) the stages.

[0021] The walls typically allow controlled solids circulation (e.g., with char, fuel) between the stages via the gap/passage, but prevent communication of the gas phases of the stages (other than that small portion of gas entrained with the solids as they traverse from one stage to the other). A gap/opening allows the drivenflow of solids to flow into the volatilization stage. A corresponding opening in/below the second wall allows the returnflow solids to return to the combustion stage, while the gas phases remain separate. The first reaction zone may be operated at higher pressure than the second reaction zone, yet the momentum created by the splashgenerator can "push" solids against a gas pressure gradient (from the second reaction zone into the first reaction zone). Thus, the gas phases above the volatilization stage (first reaction zone) and combustion stage (second reaction zone) may be independently controlled, and bed transfer between the stages may be independently controlled (e.g., the relative flow rates of the drivenflow (into the volatilization stage) and returnflow (into the combustion stage) in combination with the momentum control of the splashgenerator.

[0022] Bed solids (typically relatively large BFB particles) may be circulated between the two stages while the two stages are part of the same bed, enabling "circulation" at reduced capital and operational expense. Heat transfer, compactness, and energy efficiency may be substantially improved. The relatively low particle velocities minimize the impact of particles against various surfaces (e.g., eroding walls). As a result, reactors may be longer lasting and less prone to wear. Combustion is typically more exothermic than volatilization (which may require heat). Integration of the volatilization and combustion stages into an otherwise contiguous bed typically minimizes undesired heat loss, and a splashgenerator disposed in the combustion stage may effectively transfer heat from the (hotter) combustion bed into the cooler volatilization bed, providing an integrated, controlled series of reactions at high overall efficiency.

[0023] A fuel processing system may comprise a reactor having a splashgenerator, a volatilization stage and a combustion stage, and a separation reactor coupled to the reactor (e.g., a volatiles stream outlet of the volatilization stage). The separation reactor may be configured to receive the volatiles stream from the volatilization stage, and may comprise a heat exchanger, condenser, a cyclone, and/or other separator configured to separate chemical species from the volatiles stream. The separation reactor may separate out a desired chemical species from the volatiles stream, leaving a residual stream. The residual stream may be sent to a different reactor, another combustor, and/or the combustion stage. The chemical species may be used as needed (e.g., combusted, refined, processed, stored).

BRIEF DESCRIPTION OF THE FIGURES

[0024] FIG. 1 is a schematic illustration of a splashgenerator operating in a fluidized bed, per an embodiment.

[0025] FIGS. 2A, 2B, and 2C are schematic illustrations of different views of a compact circulating bubbling fluidized bed reactor, per some embodiments.

[0026] FIG. 3 is a schematic illustration of a two-stage fluidized bed reactor, per some embodiments.

[0027] FIGS. 4A, 4B, 4C, and 4D are schematic illustrations of different views of compact circulating bubbling fluidized bed reactors integrated with a two-stage fluidized bed reactor, per some embodiments.

[0028] FIG. 5 illustrates various optional features, per an embodiment.

[0029] FIG. 6 is a photograph of an experimental fluidized bed having a 2 ^nd reaction zone and a splash generator (not shown) comprising high pressure jets and configured to generate a splashzone, per some embodiments.

DETAILED DESCRIPTION

[0030] Various aspects provide for a compact fluidized bed reactor that combines features previously associated either with circulating fluidized bed (CFB) or with bubbling fluidized bed (BFB) reactors. By separating a BFB into separate zones (e.g., each with its own fluidization gas, pressure, and/or temperature), and imparting a directed momentum to a localized portion of the solids in one zone to "splash" the solids into the other zone, benefits of a CFB may be achieved using the bed characteristics (e.g., particle size) of a BFB. Aspects may provide for significantly improved erosion resistance, longevity, thermal efficiency, and/or control of chemical reactions.

[0031] FIG. 1 is a schematic illustration of a side view of a splashgenerator operating in a fluidized bed, per an embodiment. Reactor 100 comprises a container 301 configured to contain a bed of bed solids. A gas inlet 314 coupled to a gas supply (not shown) is configured to fluidize the bed of solids with a gas, creating a fluidized bed. Reactor 100 may be operated as a BFB or a CFB. A fuel inlet 316 delivers a material to be reacted in the bed (e.g., a fuel).

Reaction typically takes place within the bed, as illustrated by reaction zone 312.

[0032] Reactor 100 includes a splashgenerator 114 configured to impart a directed momentum to a portion of the bed solids in reaction zone 312 (e.g., using high velocity jets of gas, large wave oscillations, acoustic/pressure pulses, and the like). The momentum is typically at least partially upward; the momentum may be at least partially horizontal. The resulting momentum causes a localized portion of the bed solids in zone 312 to be preferentially accelerated, schematically illustrated as a splashzone 120. Splashzone 120 corresponds to a localized portion of the bed having higher velocity, higher magnitude, and/or otherwise different convection than that in the surrounding bed. For simplicity, various figures illustrate splashzone 120 as "above" the bed; it may be within the bed (although such a configuration is not readily illustrated). The momentum imparted by the splashgenerator may be used to control convection, circulation, heat transfer, bed uniformity, stirring, and the like. Splashgenerator 114 may be configured to inject a gas into the bed at a velocity, pressure, and/or flow rate that is higher than the corresponding velocity/pressure/flowrate of the gas inlet 314, including at least 2x, at least 5x, at least lOx higher. The gas injected by the splashgenerator may be the same or different as the fluidizing gas of the gas inlet 314.

[0033] FIGS. 2A, 2B, and 2C are schematic illustrations of different views of a compact circulating bubbling fluidized bed reactor, per some embodiments. FIG. 2A illustrates a side view in cross section. In reactor 200, a container 301 contains a bed of bed solids. A wall 303 separates at least a portion of the bed into a first reaction zone 312 and a second reaction zone 312'. Wall 303 may partially separate the zones (e.g., allowing some convective flow). The wall may not extend entirely to the bottom of the bed or above the surface of the bed, although the wall typically separates at least the lowermost portions of the zones. The wall may substantially entirely separate the beds of the zones (e.g., FIG. 4A).

[0034] A height 210 of wall 303 may be higher than the expected fluidized height of at least the second reaction zone 312' (typically both zones 312/312') to prevent solids flow over the wall during normal fluidization. In FIG. 2A, height 210 is slightly below the normally fluidized heights of zones 312/312'. Height 210 may be below 90%, below 80%, including below 50% of the bed heights of both zones 312/312' . Wall 303 typically allows gaseous communication above the beds between the zones.

[0035] The zones may have different fluidization gases, temperatures, and/or otherwise enable different reactions in different zones. A gas inlet 314 at the bottom of the bed in the first reaction zone is configured to deliver a first gas to fluidize the bed solids in the first reaction zone 312. A gas inlet 314' at the bottom of the bed in the second reaction zone is configured to deliver a second (typically different) gas to fluidize the bed of bed solids in the second reaction zone 312'. The fluidization gas compositions, velocities, temperatures, and the like may be the same or different. Typically, at least one zone (including both) include a fuel inlet 316 to receive a fuel and/or other species to be reacted in the reactor. In this example, fuel inlet 316 delivers fuel to second reaction zone 312'. Various other inlets and outlets are not shown for simplicity.

[0036] A splashgenerator 214 is configured to impart a directed momentum to a portion of the bed solids in the second reaction zone 312' (e.g., using jets of gas, wave oscillations, pulses, and the like). The momentum is typically at least partially (and may be entirely) upward (e.g., for a high wall 303). The resulting momentum causes a localized portion of the bed solids in second reaction zone 312' to pass by/through/over/under wall 303 into the first reaction zone 312. One or more walls (not shown) may be used to direct momentum (e.g., funnel waves toward the wall). As compared to the normally fluidized bed height (when fluidized by its respective gas inlet) the added momentum of the splashgenerator may locally increase bed height - "splashing" bed solids and other material over the wall. The directed flow from the splashgenerator typically increases the height 212 of the "receiving" first reaction zone 312 when the splashgenerator is operating (and correspondingly reduces the height 213 of second reaction zone 312') as illustrated schematically. Splashgenerator 214 may be configured to inject a gas into the bed at a velocity, pressure, and/or flow rate that is at least 20% higher than the corresponding velocity/pressure/flowrate of the second gas inlet 314', including at least 50%, including at least 2x, at least 5x, at least lOx higher. The gas injected by the

splashgenerator may be the same or different as the fluidizing gas of the gas inlets. Drivenflow 280 may pass through an opening in wall 303.

[0037] As a result of the directed momentum generated by the splashgenerator, a localized flow of bed solids (drivenflow 280) is driven past/through (or in this illustration, over) wall 303 into first reaction zone 312. For simplicity, FIG. 2A illustrates drivenflow 280 as being associated with a splashzone 220, from which solids "splash over" wall 303, somewhat like a geyser spraying water out of a hole in the earth. In an aspect, first wall 303 has a height (210) greater than an expected normally fluidized bed height 212, 213 of at least one of the reaction zones 312/312' (typically at least the reaction zone having the splashgenerator), such that solids do not traverse the wall during normal fluidization; they must be driven by the splashgenerator, which operates independently of fluidization. [0038] Although integrated into a single container, each zone may be operated as its own, independently controlled bubbling fluidized bed. In contrast to systems that incorporate risers, downcomers, cyclones for recovering bed solids, and the like, the reaction zones are integrated into the same container such that the beds have substantially the same bed heights and "share" solids via liquid-like flow. High flow rates over long distances may be avoided, significantly reducing energy consumption and erosion.

[0039] Wall 303 may be lower than, approximately equal to, or higher than, the "normally fluidized" bed heights, according to a desired amount of non-driven bed flow past the wall. A lower wall allows more "natural convection" bed flow; a higher wall reduces this convection. A wall extending above the bed surface substantially prevents this "natural convection" proximate the wall, and so transport between beds is more tightly controlled by the splashgenerator and corresponding returnflow (below).

[0040] An exemplary BFB reactor may have a stagnant bed height from 30-100 cm, including 40-70 cm, including from 50-60 cm. Fluidization by the gas inlet typically increases a fluidized bed height of the "fluidized" solids by 40-80%, including about 50-70%, over the stagnant bed height. Height 210 of wall 303 may be accordingly chosen to prevent substantial solids flow under normal fluidization conditions. Height 210 of wall 303 may be at least 140% of the expected stagnant bed height, including at least 150%, including at least 160%. For particularly energetic splash generators, height 210 may be 2x the expected stagnant bed height, including at least 3x, including at least 4x. For some reactors (e.g., with highly varying fuel particle sizes), a more energetic splashgenerator may reduce fuel segregation (e.g., ensuring large chunks of fuel pass over wall 303). A less energetic splashgenerator may ensure that larger chunks remain in the first reaction zone until they are small enough to pass to the second reaction zone.

[0041] FIG. 2B illustrates an overhead view of a section of reactor 200, and illustrates a passage 299 through which bed solids return from the first reaction zone 312 back to the second reaction zone 312'. Returnflow 285 of bed solids "returns" the solids driven by drivenflow 280, enabling circulation of solids between separate reaction zones of a single fluidized bed. Flow of solids past wall 303 (drivenflow 280 driven by splashgenerator 214) and corresponding returnflow 285 of the solids provides for a compact "circulating" fluidized bed having the benefits of bubbling fluidized beds - a compact, integrated, circulating, dual-zone bubbling, fluidized bed. When appreciably long, passage 299 is typically fluidized by a passage gas inlet 214' (FIG. 2C), such that solids return via natural convection (flowing downhill according to the pressure gradient created by the drivenflow). A passage may include its own (typically horizontally directed) splashgenerator to increase horizontal velocity of the returnflow.

[0042] FIG. 2C illustrates an overhead view of another section of reactor 200, schematically illustrating the gas inlets at the "bottoms" of the relevant zones of the bed. The different gas inlets (314, 314') fluidize their respective zones, and passage gas inlet 214' fluidizes the returnflow 285 of solids returning from first reaction zone 312 to second reaction zone 312' (FIG. 2B). Passage gas inlet 214' may fluidize the solids in the passage using the same or different gas than that used by one or more of the gas inlets, typically with the same gas as that delivered by gas inlet 314' to fluidize the second reaction zone 312' .

[0043] It may be advantageous to combine a splash generator with a fuel stream processing system as disclosed in US provisional patent application no. 62/517, 186 and/or Finnish patent application no. 20170148. Various aspects may be used to control residence times and reaction rates within a stage, and heat and/or mass transfer between the stages, enabling a wide range of chemical reactions. Pressure control above each stage, gas inlet flow rates, and/or pressure drop across the distributor plates themselves may be combined with flow control via directed and return flows (e.g., using a splashzone between stages) to control residence times, heat transfer rates, mass transfer rates, and the relative concentration of various species.

[0044] A fuel stream processing system may comprise a volatilization stage and a combustion stage. The volatilization stage typically uses a relatively inert, and/or mildly oxidizing gas (e.g. , N ₂ , syngas, steam, C02, and the like). A solid and/or liquid fuel stream flows into the volatilization stage to be reacted to form a volatiles stream and a char stream, which is passed to the combustion stage for combustion. The combustion stage typically uses a gas that is more oxidizing than the gas used in the volatilization stage. A volatilization stage may be retrofit to an existing combustion plant (e.g. , with an additional fuel supply) to enable the extraction of a high-value volatiles stream prior to combustion. In Sweden, the population of biomass-fueled fluidized bed boilers is presently about 80% BFB/20% CFB. As such, the retrofit market may be larger in Sweden for BFB, although both designs offer opportunity.

[0045] A volatiles stream comprises chemical species that may be used directly (e.g., fed into a lime kiln) and/or separated out for subsequent use via a chemicals outlet. The chemical species may include syngas (H2 + CO), raw gas, oils, chemical precursors, hydrocarbons (including oxygenated hydrocarbons), liquid fuels (e.g. , C4-C16) such as biofuels and/or biofuel precursors, volatile polymers, fuel gas, chemical compounds, fine chemicals, and the like. A volatilization stage may be used to separate a fuel into a first fuel source (e.g. , for a separate combustion process, such as an engine or turbine) and a residual char source (e.g. , for combustion in a fluidized bed). A volatiles stream may flow to a separation reactor to separate out various species. A heat exchanger may cool the volatiles stream to condense various (typically >5, including >10, including >100) chemical species from the volatiles stream. The separated chemical species may be subsequently processed and/or utilized. A residual stream (remaining, undesired chemicals which may have fuel value) separated from the desired chemical species may be combusted.

[0046] A volatiles stream may have a range of uses (according to fuel source, pretreatment conditions, and the like) such as for raw gas, syngas, and the like. The volatiles stream may include syngas (e.g. , for use in a subsequent chemical process) gaseous species (e.g. , gaseous fuels), liquid fuels (e.g. , biofuels and/or biofuel precursors), and the like.

[0047] FIG. 3 is a schematic illustration of a two-stage fluidized bed reactor, per some embodiments. A multistage fluidized bed reactor comprises a container 301 integrating a fluidized bed having at least a first (e.g. , volatilization) and second (e.g. , combustion) stages, each bed/stage enabling a different chemical reaction. In this example, a first reaction zone 312 in a first fluidized bed and a second reaction zone 332 in a second fluidized bed provide for different reactions. Stages are described as "volatilization" and "combustion" for simplicity; other series of reactions may also be implemented, according to the choice of gases, temperatures, and the like.

[0048] The gas phases above the first and second stages are separated by a wall 302, which allows the fluidized bed phases to communicate via an opening 304 below/in the wall and/or a passage between beds of the stages. Thus, the fluidized bed phase (e.g. , media and char stream) may pass from the first stage to the second stage, but the gas phase above the first stage is separated from the gas phase above the second stage. The fluidized beds may communicate via an opening in the floor rather than the wall. The fluidization gases, temperatures, flow rates, and ambient gas phases may be independently controlled. A controller coupled to pressure gauges within the stages may control these pressures (e.g. , via a valve on the volatiles stream) to achieve a desired overpressure of the first stage vs. the second stage. Pressure difference between stages may be used to control residence time of fuel particles (e.g., to achieve a desired reaction in the volatilization stage prior to char transfer to the combustion stage). A transfer of fuel and bed material from the first to second stages may be controlled via a sequential decrease and increase in gas pressure in the first stage vs. that in the second stage to "flush" material to the second stage (e.g., periodically, as "breathing" in and blowing out a deep breath). Fuel residence time may also be controlled by adjusting fluidization gas velocities and/or

splashgenerator momentum. [0049] In exemplary FIG. 3, a fluidized bed reactor 300 comprises a container 301 (e.g., an otherwise contiguous single container) configured to hold a bed of bed solids. A wall 302 separates the container into a volatilization stage 310 and a combustion stage 330. Wall 302 has an opening 304 through which bed solids and char may flow. Opening 304 may include a passage and/or a char stream outlet 219 to convey char from the volatilization stage and a char stream inlet 239 to convey the char into the combustion stage, and may include a passage (FIG. 4B). Opening 304 may comprise openings in the floors of each stage coupled by a passage. Wall 302 may include a plurality of walls. The media and char stream pass from the volatilization stage to the combustion stage, where the char is burned. The wall lets the media/char pass between stages, but prevents mixing of the gas phases.

[0050] The volatilization stage has a fuel inlet 316 configured to receive and deliver the fuel into the volatilization stage. The fuel inlet may include a lock hopper and/or other apparatus to transfer solid fuel while controlling gas flow/pressure. Fuel may be fed by gravity and/or auger. Fuel may be delivered to the lock hopper (e.g. , via a feed screw) and a gas pressure within the lock hopper may be controlled to match that of the volatilization stage, such that fuel may be delivered to the volatilization stage at or above the pressure of the volatilization stage.

[0051] The bed solids in the volatilization stage may be fluidized by a flow of gas from a LowOx gas supply 311 delivered via a gas inlet 314 (e.g. , a diffuser plate/distributor plate having holes distributed across the plate to fluidize the bed) to first reaction zone 312. LowOx gas supply 311 supplies a (typically hot) gas chosen according to desired volatilization conditions, fuel source, desired composition of volatiles stream, and the like. LowOx gas supply 311 typically supplies an inert and/or mildly oxidizing gas. In some cases, LowOx gas supply may supply a reducing gas (e.g., H2). Pressure drop across the distributor plate may be controlled (typically in concert with gas pressure above the bed) to achieve a desired bubble size (within the bed), convection pattern, fuel residence time, bed temperature, and the like. Various reactions may be controlled via stage pressure (e.g. , to control bed height, reaction rates, and/or residence times). A typical volatilization stage may have a lower temperature at the top of the bed than at the bottom (although in the absolute bottom of the bed (the first centimeters from the bottom) where the fluidization media enters the bed the temperature is typically lower). A reduced bed height in the volatilization stage typically reduces residence time within.

[0052] A volatiles stream outlet 318 is configured to convey the volatiles stream out of the volatilization stage (e.g. , to an optional separation reactor 220 for separating useful chemical species). A volatiles pressure gauge 350 measures gas pressure in the volatilization stage, the volatiles stream outlet, and/or the corresponding volatiles line. Useful chemical species 229' are typically extracted from the volatiles stream via chemicals outlet 229, and may leave a residuals stream. A separation reactor may include a heat exchanger 224, a cyclone 225, or other phase separator 226 configured to separate species (e.g. , a filter, bag house, electrostatic precipitator, scrubber, quenching) as needed to separate the volatiles into useful chemical species and a residual stream. A heat exchanger 224 may extract heat from a volatiles stream and preheat the gas flowing to a gas inlet. In some cases, a volatiles stream is rapidly quenched (immediately after volatilization) to prevent polymerization of desirable discrete molecules. A reactor may include an absorption loop that exposes a stream to a liquid that absorbs a species (e.g., an amine C02 scrubber). The liquid is circulated out, the species is removed, and the liquid is reexposed to the stream. In some cases, separation reactor 220 outputs a residuals stream (e.g. , comprising residual chemicals not extracted for other purposes) via residuals stream outlet 228. Residuals stream outlet 228 may be coupled to a corresponding residuals stream inlet 238 of the combustion stage, providing for the combustion of the residuals stream, return of bed solids, and the like.

[0053] A reactor includes a means to control gas flow into and/or out of at least one stage, including multiple stages. Controlling this means in concert with pressure measurements, the controller may control the pressure difference between stages, typically via closed-loop (e.g. , PID) control. In an embodiment, a volatiles outlet valve 370 (e.g. , a butterfly valve) coupled to the volatilization stage outlet 318 is configured to control pressure in the volatilization stage and/or flow out of the volatiles stream outlet (shown upstream of separation reactor 220; it may also be downstream).

[0054] Combustion stage 330 includes an oxidant inlet 334 (e.g. , a diffuser plate) correspondingly disposed with second reaction zone 332. A HiOx gas supply 331 coupled to the oxidant inlet may deliver a relatively more oxidizing gas than that of the LowOx gas supply (typically 02 and/or air) at a flow rate and pressure sufficient to fluidize the bed solids in the combustion stage and combust the char from the volatilization stage. An exhaust gas outlet 337 removes combustion products such as power 337' , chemicals 337" and/or heat 337' ", which may be subsequently harvested from the exhaust gas (e.g. , via a heat exchanger, a turbine, and the like, not shown). A combustion pressure gauge 352 disposed in the combustion stage and/or exhaust measures pressure in the combustion stage. Reactor 300 illustrates an optional 2 ^nd oxidant inlet 333 (e.g. , to provide additional combustion air to supplement oxidant supplied via oxidant inlet 334). Additional gas and/or oxidant inlets may be included with the relevant stage. In this example, a fan 338 fluidically coupled to the exhaust 337 controllably extracts exhaust gas, which may be used to control pressure. [0055] A controller 360 coupled to the pressure gauges (in this case, 350, 352) controls a pressure difference between the stages. In FIG. 3, controller 360 is coupled to a volatiles outlet valve 370 (illustrated upstream of optional separation reactor 220; it may be downstream, particularly downstream of a heat exchanger). In this example, controller 360 controls pressure in the volatilization stage (above first reaction zone 312) via throttling of the valve 370. During operation, controller 360 typically controls pressure of the volatilization stage to be different than that of the combustion stage. Lower pressure in the volatilization stage typically decreases fuel/char residence time; higher pressure typically reduces residence time. Pressures may be controlled via a valve on the flue gas line. Pressure control of bed solids flow (and the resulting mass transfer rates) may be used to control residence time within the stages (e.g. , in a pretreatment stage prior to a combustion stage).

[0056] A combustion stage may include a second fuel inlet 336 (e.g. , to supplement the fuel value of the char), which may include a separate (or the same) fuel supply, typically with its own lock hopper. Second fuel inlet 336 may be the main fuel supply for the combustion stage, with a separate fuel supply implemented for the volatilization stage (e.g. , as a retrofit to an existing combustion stage).

[0057] The hot flue gas from the combustion stage is typically used to generate steam, heat, energy. A portion of the hot flue gas may be routed through an optional heat exchanger 340 to preheat fluidization gas (e.g., flowing into the first stage). Heat exchanger 340 may extract heat from the exhaust gas and transfer the heat to the gas supplied to a stage (in this case, the volatilization stage), which may improve energy efficiency.

[0058] Increased gas pressure in the one stage may increase the transfer of bed material into the other stage. Typically, some natural convection of the bed material recirculates at least some media between stages; pressure may affect this convection. FIG. 3 illustrates an implementation in which the floor heights of the two stages are the same; the floor heights may be different. The volatilization stage may have an internal wall separating the fuel inlet 316 from the volatiles stream outlet 318. This wall may end above the fluidized bed height or descend into the bed (separating the respective gas phases). A baffle within the bed may be used to change circulation within the bed. The combustion stage may have an additional fuel supply 336. In some cases, a residual stream separated out of the volatiles stream by a separation reactor 220 is routed into the combustion stage 330, where it is burned.

[0059] Volatilization stage 310 may be operated to volatilize, gasify, pyrolyze, and/or otherwise partially react a fuel. Combustion stage 330 typically has a higher oxygen partial pressure than the volatilization stage, and is operated to combust matter that was not combusted by the volatilization stage. [0060] FIGS. 4A, 4B, 4C, and 4D are schematic illustrations of different views of a compact circulating bubbling fluidized bed reactor having a splashgenerator and two separate stages, integrated into a single fluidized bed container, per some embodiments. FIGS 4A, 4B, 4C, 4D illustrate the combination of a splashgenerator-controlled solids flow between reaction zones (e.g., as in reactor 200) with separate reaction stages having their own independent gas phase control (e.g., as in reactor 300). One stage has the first gas inlet, the other stage has the second gas inlet, and a wall separates the gas phases above the stages. Various

gaps/openings/passages provide for drivenflow/returnflow between the stages. For simplicity, the stages are described as volatilization and combustion stages.

[0061] Container 301 includes a first wall 303 at least partially separating (in this case, substantially entirely separating) the bed solids into first and second reaction zones 312/332, and a second wall 302 that separates at least the gas phases above the corresponding volatilization and combustion stages 310, 330. An opening 304 in/below the second wall 302 provides for solids flow between the stages while blocking gas flow. In this example, height 210 of wall 303 is higher than the normally fluidized bed heights of both zones 312/332, and fuel inlet 316 delivers fuel to the first reaction zone 312/ volatilization stage 310. The gap/opening 304/305 and passage 299 (FIG. 4B) provide for the circulation of bed solids between the reaction zones while the gases remain substantially independent. The first reaction zone may be operated as a volatilization stage (with a relatively less oxidizing gas) and the second reaction zone may be operated as a combustion stage (with a more oxidizing gas). The drivenflow 280 of solids from the combustion stage and returnflow 285 of solids from the volatilization stage (or vice versa) may be used to circulate solids from the combustion stage to the volatilization stage and back again, while wall 302 enables separate atmospheres, pressures, and the like of the two stages. First wall 303 separates at least a portion of the beds (but not the gases) and a second wall 302 separates the gas phases (but not the beds).

[0062] FIG. 4A illustrates a side view in cross section. In reactor 400, container 301 containing the bed of bed solids includes at least two walls 302, 303. First wall 303 separates at least a portion of the bed into a first reaction zone 312 configured to operate as a first stage 310 comprising the first gas inlet 314 and a second reaction zone 332 configured to operate as a second stage 330 and comprising the second gas inlet (314', 334), each gas inlet fluidizing with its own gas. A gap 305 between the first and second walls provides for a flow of drivenflow 280 of bed solids from the second stage to the first stage, and passage 299 (FIG. 4B) provides for the returnflow 285 of bed solids from the first stage to the second stage. In this example, first wall 303 has a height 210 that extends above the "normally fluidized" bed heights (212, 213, FIG. 2A) of the zones, such that the beds are separated except for drivenflow 280 and returnflow 285 (FIG. 4B).

[0063] A volatilization stage 310 may include at least a majority (typically substantially all) of the first reaction zone 312, and a combustion stage 330 may include at least a majority of (e.g., substantially all) of the second reaction zone 332. Second wall 302 separates the gaseous phase in the volatilization stage 310 (first reaction zone 312) from that of the combustion stage 330 (second reaction zone 332). An opening 304 through and/or below the second wall 302 and below the expected bed height is configured to provide for a flow of the drivenflow 280 (e.g., bed solids and char stream) from the combustion stage 330 to the volatilization stage 310, having been driven past wall 303 by the splashgenerator, but substantially prevents gaseous communication between the reaction zones.

[0064] As combustion is typically exothermic, a splashgenerator may be used to transfer heat from the combustion stage to the volatilization stage, which may reduce the need for gas preheating in the volatilization stage. Typically, the combustion stage is hotter than the volatilization stage, and so control of the splashgenerator-induced momentum may be used to control heat transfer from the combustion stage to the volatilization stage via control of the drivenflow 280 of solids. Such a configuration may also be used to "additionally volatilize" the char, such that slow reactions may completed on a "second lap" through the volatilization stage. A passage 299 (FIG. 4B) provides for the returnflow 285 of bed solids from the volatilization stage to the combustion stage when the splashgenerator is operating.

[0065] The second wall 302 may be disposed in either zone, including within the first reaction zone 312 (e.g., proximate to first wall 303). Drivenflow of solids may be facilitated by locating the splashgenerator in one zone (e.g., second) and the gas-blocking second wall 302 in the other zone (e.g., first), such that drivenflow 280 splashes against the second wall and drops into the gap 305 between the walls. Typically, second wall 302 is located proximate first wall 303 (e.g., within a distance that is less than 20%, including less than 10%, including less than 5%, of the length of first reaction zone 312 (left to right in FIG. 4A)). When walls 302/303 are separate walls, a gap 305 between the first and second walls 302/303 may provide for a flow of the drivenflow 280 of bed solids from the combustion stage 330/second reaction zone 332 past wall 303, through gap 305, through opening 304, into the volatilization stage 310/first reaction zone 312. The gap may include a region having the gas phase of one zone (e.g., combustion stage) and the fluidization gas of the other zone (e.g., the volatilization stage), and so the size of the gap may be minimized according to an expected flow rate of drivenflow. [0066] Gas inlet 314 at the bottom of the bed in first reaction zone 312 is coupled to a LowOx gas supply and configured to deliver a first LowOx (relatively less oxidizing/inert) gas to fluidize the bed solids in the first reaction zone 312 for use of this stage as a volatilization stage. Oxidant inlet 334 at the bottom of the bed in the second reaction zone 332 is coupled to a HiOx gas supply and configured to deliver a second HiOx gas that is relatively more oxidizing than the LowOx gas to fluidize the bed of bed solids in the second reaction zone, which may be operated as a combustion stage. For example, the LowOx gas might be steam, syngas, N2, and/or C02, and the HiOx gas might be C02, air and/or oxygen.

[0067] Splashgenerator 414 imparts a localized directed momentum to the bed solids in the second reaction zone 332 to create a drivenflow 280 of solids past wall 303 into first reaction zone 312, driving solids from the combustion stage to the volatilization stage. In this example, splashgenerator 414 is illustrated generating a momentum that is at least partially horizontal, in this case angled toward the top of first wall 303. A splashgenerator may comprise angled jets configured to inject high velocity gas toward the top of the wall. A splashgenerator may inject a gas that is more oxidizing than that delivered by gas inlet 314, which may be the same or different as that delivered by oxidant inlet 334.

[0068] FIG. 4B illustrates an overhead of a section of reactor 400, showing the passage 299 through which bed solids return (through and/or beneath second wall 302, beneath the bed heights) from the first reaction zone 312 (volatilization stage) back to the second reaction zone 332 (combustion stage). The returnflow 285 of bed solids "returns" the solids driven by drivenflow 280, enabling circulation of solids between separate reaction zones of a single fluidized bed, and thus between stages. Flow of solids past wall 303 (drivenflow 280 driven by splashgenerator 414) and corresponding returnflow 285 of the solids provides for a compact "circulation" of solids from the combustion stage to the volatilization stage and back again. With this compact design, heat generated by combustion in the combustion stage may be efficiently transferred back to the volatilization stage, where it may be used to enable reactions in the volatilization stage. Having released its heat, these solids return to the combustion stage via returnflow 285.

[0069] In reactor 400, a char stream outlet 219 from the volatilization stage and char stream inlet 239 into the combustion stage are schematically illustrated as parts of passage 299, illustrating a flow of char (as part of returnflow 285) from the volatilization stage to the combustion stage. The char is typically burned in the combustion stage, and the heat

(transferred as drivenflow 280) is then used in the volatilization stage.

[0070] FIG. 4C illustrates an overhead view of another section of reactor 400, schematically illustrating the "bottoms" of the relevant zones of the bed. The different gas inlets (314, 334) fluidize their respective zones/stages, and a passage gas inlet 414' fluidizes the returnflow 285 of solids (FIG. 4B) returning from first reaction zone 312/volatilization stage 310 to second reaction zone 332/combustion stage 330 (FIG. 4A). Passage gas inlet 414' may fluidize the solids in the passage with the same gas or different gas than that used in either of the reaction zones. Typically, passage gas inlet 414' uses a gas that is more oxidizing than the gas delivered by the first gas inlet 314, which may or may not be the same gas as that delivered by oxidant inlet 334 to fluidize the second reaction zone 332.

[0071] The returnflow passage is typically dimensioned to accommodate an expected flow rate of the drivenflow past the wall without deleterious backpressure. The "natural" back- convection through the passage may be minimized by having a relatively long, narrow passage. A passage may have a length greater than its width, including 2x the width, including 5x the width, including lOx the width. Natural convection between the zones (splashgenerator turned off but gas inlets fluidizing their respective zones) may be controlled (e.g., minimized) via passage shape, dimensions, and the like.

[0072] FIG. 4D is a schematic illustration of an overhead view of a reactor 400' having a very short passage 299 between first and second reaction zones 312/332, per an embodiment. A passage 299 may essentially have zero length (e.g., be the thickness of a wall separating the reaction zones). Such a configuration may provide for a very fast transition from the fluidization gas/ambient atmosphere of the first reaction zone 312 to the fluidization gas/ambient atmosphere of the second reaction zone 332. For example, a first reaction zone 312 may be operated to have a much higher temperature than the second reaction zone 332 (e.g., using preheated gas). The splashgenerator and/or pressure control may be used to constrain the fuel entering the first reaction zone to a very short residence time, after which the fuel

"quenches" to the temperature of second reaction zone 332 after having passed through opening 304 as returnflow 285. Such a configuration may be used to fractionate the fuel, quickly extracting highly volatile species before longer term degradation occurs.

[0073] In this example, reactor 400' comprises a combined wall 302/303 that separates both the gas phases (e.g., above volatilization and combustion stages, FIG.4A) and the bed solids (of first zone 312 fluidized by a first gas and second zone 332 fluidized by a second gas). Passage 299 may comprise an opening 304 in wall 302/303 located below the fluidized bed surface that allows returnflow 285 to flow from the first to second reaction zone while the gas phases remain separated. Opening 304 may or may not extend to the reactor floor.

Combined wall 302/303 may (but need not) have at least a bottom part of wall 303 separating the gas inlets 314/334/314' (FIG. 2C, 4C) and lowermost bed portions of the reaction zones. [0074] The locations of the walls, splashgenerator, and passage/openings may be chosen to enhance circulation around the bed (from one zone to the other). A reactor (e.g., 400') may comprise a first reaction zone built into the second reaction zone (e.g., in a retrofit application). FIG. 4D illustrates an embodiment in which the first reaction zone 312 (which may be a first stage) is substantially contained within the second reaction zone 332 (in this case, surrounded on two sides; it may be surrounded on three or more sides). As opposed to FIG. 4B (in which the returnflow direction is geometrically opposite the drivenflow direction), reactor 400' has returnflow 284 flowing in a direction other than opposite that of drivenflow 280 (in this case, about 90 degrees).

[0075] FIG. 5 illustrates various optional features, per an embodiment. According to the types of reactions in each zone, temperatures, gases, particle behavior, and the like, a reactor may be modified to enable certain types of flow. In some cases, an optional passage wall 503 separating at least a portion (e.g., at least the bottom) of the beds is used to minimize natural convective transport between zones. A passage wall 503 allows returnflow solids to flow over the passage wall 503 when the bed height in the first reaction zone 312 (FIG. 2A) exceeds the height of passage wall 503. As drivenflow 280 "loads" the first reaction zone 312 with solids, bed height increases until the solids can pass over passage wall 503 as returnflow 285 into second reaction zone 312' (FIG. 2A). A passage wall 503 may be at the leading end, trailing end, or within a passage. A passage width 510 and passage length 520 may be chosen according to a desired flow rate within the passage. In some cases, a breadth 530 of splashzone 220 (FIG. 2A) and an expected drivenflow rate are used to design an appropriate combination of passagewidth 510 and passagelength 520.

[0076] An optional Flow Directing Area (FDA) 502 may be incorporated into the container. An FDA is typically a large (as compared to a simple wall) volume through which material cannot pass. An FDA may be hollow and/or insulated. Blocking flow, the FDA forces material to take a longer route (e.g., from one zone/stage to the next). FDA 502 typically blocks both gas and solid flow. FDA 502 may be used to increase passage length 520 (for a given width). FDA 502 may be used to force material to spend a minimum residence time in a given reaction zone before exiting that reaction zone. FDA 502 may be substantially "surrounded" by the beds and gas phases, such that heat loss to the external environment is minimized, notwithstanding the long circulation path within the container.

[0077] EXAMPLE 1

[0078] FIG. 6 is a photograph of an experimental fluidized bed having a 2 ^nd reaction zone 312' and a splash generator 214 (not shown) comprising high pressure jets and configured to generate a splashzone 220, according to some embodiments. As compared with the flow rates and volumes used in a CFB to move particles tens of meters, a relatively low momentum is still sufficient to splash the bubbling bed solids high enough over the normally fluidized bed height (e.g., 10% of the bed height above, 20% of the bed height above, 100% of the bed height above, twice the bed height above, or as illustrated here, approximately 300% of the bed height above). A short distance (e.g., <2m) is sufficient to move between zones, as opposed to the many meters of flow in a circulating "bed." Thus, a drivenflow 280 of solids may be easily controlled, notwithstanding a wall separating the beds extends above the bed height, using a small, localized injection of momentum to splash the solids over the wall.

[0079] Various features described herein may be implemented independently and/or in combination with each other. An explicit combination of features in an embodiment does not preclude the omission of any of these features from other embodiments. The above description is illustrative and not restrictive. Many variations of the invention will become apparent to those of skill in the art upon review of this disclosure. The scope of the invention should, therefore, be determined not with reference to the above description, but instead should be determined with reference to the appended claims along with their full scope of equivalents.