KELLY KAREN SUE (CA)
KELLY KAREN SUE (CA)
| US10087121B2 | 2018-10-02 | |||
| US20060014841A1 | 2006-01-19 |
| CLAIMS What is claimed is: 1. A process to optimize the carbon yield in the production of synthetic chemicals or fuels from organic feedstock, comprising: a. processing the organic feedstock in a method to generate synthesis gas stream A comprised of at least carbon monoxide, hydrogen and carbon dioxide; b. removing substantially all unwanted solids and gases from synthesis gas stream A such that it consists of only carbon monoxide, hydrogen, carbon dioxide and hydrocarbons to form synthesis gas stream B; c. removing a measured amount of carbon dioxide from synthesis gas stream B based on data from a gas analyzer to form synthesis gas stream C comprised substantially of carbon monoxide, hydrogen, hydrocarbons and a reduced amount of carbon dioxide; d. sending synthesis gas stream C to a reformer which applies heat, pressure and a catalyst such that the hydrocarbons are reformed by a reaction with the carbon dioxide in the synthesis gas into carbon monoxide and hydrogen thus forming synthesis gas stream F consisting substantially of carbon monoxide and hydrogen; e. compressing synthesis gas stream F; f. reacting synthesis gas stream F in a reactor with a catalyst, heat and pressure to form a product; g. selectively obtaining the product by separating it from unreacted gases and formed hydrocarbon gases unrelated to the product; h. combining the unreacted gases and formed hydrocarbon gases to form a mixture; i. removing a sample from the mixture and combining it with the sample from synthesis gas stream B and sending it to the gas analyzer to determine the composition of the combined stream; j. sending the mixture to the reformer in step d. which applies heat, pressure and a catalyst such that the mixture is reformed into substantially carbon monoxide and hydrogen 2. A process to optimize the carbon yield in the production of synthetic chemicals or fuels as in Claim 1 where the organic feedstock is selected from one or any of a group of plant material, a mixture of plastics and organic waste, natural gas, landfill gas, or gas from anaerobic digesters. 3. A process to optimize the carbon yield in the production of synthetic chemicals or fuels as in Claim 1 where the processing method or methods for the organic feedstock is gasification, pyrolysis or hydro- treating. 4. A process to optimize the carbon yield in the production of synthetic chemicals or fuels as in Claim 1 where the process to generate synthesis gas from the feedstock takes place at a temperature range of 200°C to 1200°C. 5. A process to optimize the carbon yield in the production of synthetic chemicals or fuels as in Claim 1 where the process to generate synthesis gas from the feedstock takes place at a pressure range of 0.1 to 10.7 MPa. 6. A process to optimize the carbon yield in the production of synthetic chemicals or fuels as in Claim 1 where the carbon dioxide removal system can be regulated by process controls. 7. A process to optimize the carbon yield in the production of synthetic chemicals or fuels as in Claim 1 the reformer in step d. operates at a temperature range of 800°C to 1000°C and preferably at 875°C and a pressure of 0.1 - 5 MPa, preferably at 0.1 MPa. 8. A process to optimize the carbon yield in the production of synthetic chemicals or fuels as in Claim 1 where in step f. there is one reactor which produces dimethyl ether. 9. A process to optimize the carbon yield in the production of synthetic chemicals or fuels as in Claim 1 where step f. includes multiple reactors and the first reactor produces dimethyl ether and the second reactor produces gasoline range hydrocarbons. 10. A process to optimize the carbon yield in the production of synthetic chemicals or fuels as in Claim 1 where in step f. there is one reactor which is a Fischer-Tropsch reactor. |
PRIORITY DATA
This patent application claims priority under 35 U.S.C. §120 from U.S. Provisional Patent Application No. 62/919,704 filed March 26, 2019 and which is incorporated by reference herein for all purposes.
FIELD OF USE
The present invention generally relates to a process which utilizes carbon more efficiently in the synthetic production of chemicals and fuels including gasoline.
BACKGROUND
The efficient production of synthetic fuels and chemicals from renewable sources is a challenge. The processes are complex, with a number of steps involving not only the synthesis but the efficient use of process heat and the optimization of the process yields through recycles and reforming. Process designers and engineers are continually seeking methods and equipment to maximize efficiency and minimize capital and operating costs.
The starting point for synthetic chemicals and fuels is the creation of a synthesis gas, (“syngas") which is a mixture of carbon dioxide and hydrogen, the two building blocks from which they are typically created. Syngas has been produced from coal since 1780, widely today from natural gas, and currently from renewable sources. Syngas from natural gas is primarily used to produce methanol, the chemical starting point of the plastics industry. Other products from syngas include alkanes, olefins, oxygenates, and alcohols such as ethanol.
The use of renewable sources to produce syngas is particularly challenging. Any carbonaceous material, in particular, biomass such as agricultural wastes, forest products, grasses, and other ceiiulosic material, including municipal waste streams, may be converted to syngas. The most common methods are gasification, pyrolysis and hydro-treating, which produce a syngas which is a mixture of not only carbon monoxide and hydrogen, but includes carbon dioxide and carbon particles, and whatever other elements are present in the feedstock, in gaseous form and must be removed before the syngas is processed.
Syngas from biomass, generally speaking, contains carbon monoxide to hydrogen at a 1.2 : 1 ratio, (CO:H 2 = 1.2 : 1 ) This ratio is fairly consistent when the feedstock contains high cellulose and lignin content, regardless of the method used, whether it be gasification, pyrolysis or hydro-treating. The volume of carbon dioxide produced varies with the production method. This ratio of CO:H 2 does not favor the formation of methanol, so when used for that purpose, CO 2 is produced as a by-product. Kelly et al (US 10,087,121 B2) taught that converting the syngas ratio is favorable for production of dimethyl ether, which results in better carbon utilization and reduces the formation of CO 2 .
Typically the newly-formed syngas is cleaned and conditioned before sending to the first reactor in the process. In general, anything other than carbon monoxide and hydrogen are removed to the level possible and practical, but is especially cleaned of those elements which would foul compressors or poison catalysts downstream. Carbon dioxide is generally removed as well, simply to reduce the volume of process gases and to ensure that it does not act as a reagent in the subsequent chemical reactors. The carbon dioxide is typically then vented.
In most synthetic production processes, there is a gas reformer included in the process train. Its purpose is to convert any unreacted gases or products, from a step, or steps in the process train, into syngas. The syngas thus formed are then fed back into the appropriate reactor. Any carbon dioxide formed as a result is typically removed from the newly-formed syngas prior to sending on.
A common method to utilize recycled gases is Autothermal Reforming (ATR). This method produces syngas using methane as example, is as follows:
Chem Eq 1 : C x H y + O 2 + H 2 O H 2 + CO
The advantage of ATR is that the H2:CO can be varied, this is particularly useful for producing dimethyl ether, which requires a 1:1 H2:CO ratio. However, Dry Reforming (DR) has presented an interesting alternative to the ATR. Initially reported in 1928 by Fischer and Tropsch, the process is being investigated to enhance the production of hydrogen from methane. Dry Reforming refers to the process which utilizes heat, pressure, catalysts and the injection of CO 2 with the gas to be reformed. The reaction is:
Chem Eq 2: C x H y + CO 2 -> H 2 + CO
SUMMARY OF INVENTION
The instant invention teaches a novel method to utilize carbon dioxide in the production of any synthesis of chemicals or fuels in which the syngas ratio of carbon monoxide to hydrogen is not ideal for the purpose, and when carbon dioxide and other hydrocarbon gases are present.
The placement of the carbon dioxide removal system (CDRS) in the instant invention is typically placed to remove as much carbon dioxide as possible as the final step following syngas cleanup. A novel aspect of the instant invention is that the volume of carbon dioxide removed from the syngas is controlled, leaving a measured amount therein. The syngas is then fed directly into a Dry Reformer, which is novel placement of this reactor. Typically gas reforming is used to convert any unused gases resulting from catalytic steps in a process, but it is not a part of the main stream.
Also novel is the operation of the Dry Reformer, which also receives recycled gases from downstream reactors. Gas analysis and monitoring of on- line sampling provide feedback control to the CDRS, adjusting the volume of carbon dioxide which will be required to efficiently convert all hydrocarbons into syngas. Ultimately, carbon usage from the feedstock is optimized because of the use of i) CO 2 present in the synthesis gas, which would be otherwise removed and vented, and ii) consumption of CO 2 formed in downstream reactions. Although not all the CO 2 in the various steps in the process can be utilized, mass balances demonstrate that reduced carbon emissions and greater product yields are achieved.
The following description and drawings will clarify the process and the invention. TECHNICAL PROBLEM
The problem to be solved is to eliminate the production and venting of carbon dioxide to the maximum extent possible.
SOLUTION TO PROBLEM
The solution suggested in the instant invention is the novel placement of a gas reformer, using heat, pressure, a catalyst and a measured amount of carbon dioxide. The new syngas stream thus produced adds to the yield of product and reduction in carbon dioxide vented.
ADVANTAGEOUS EFFECTS OF INVENTION
The economics of renewable chemicals and fuels has always been measured against their counterparts produced from fossil sources. The fossil fuel and chemical industry have had many decades to establish functional, efficient and economic processes. Renewables, on the other hand, have not yet achieved that success.
The instant invention will help improve the economic competitiveness of biofuel or biochemical production, and has the added advantage of benefiting the environment by the reduction of carbon emissions.
Another advantage of this invention is that it utilizes equipment already in the marketplace, proven commercially, and therefore is not inhibiting to commercialization.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is a block-flow diagram depicting a general process for conversion of renewable materials into end products.
This and other embodiments, features, and advantages of the present invention will become more apparent to those skilled in the art when taken with reference to the following detailed description of the invention in conjunction with the accompanying drawing.
DESCRIPTION OF THE INVENTION
Figure 1 at 10 shows the main (preferred) embodiment of the instant invention. Biomass 1 is gasified 2 in a fluidized bed using steam as fluidtzer and oxygen in substoichiometric volumes to produce Synthesis Gas A 3. The hot syngas emerging from the gasifier is typically composed of carbon monoxide, hydrogen, methane, propane, ethane, carbon dioxide, and possibly heavier hydrocarbons greater than C4, and also may contain contaminants, such as carbon particles, sulphur, chlorine, and trace metals and minerals, according to the composition of the feedstock used and the conditions in the gasifier. The syngas is cleaned and conditioned 4 in a series of steps to remove all contaminants, using industry-standard processes and equipment selected on the basis of the composition of the initial feedstock, leaving only gaseous components, to form Syngas B 5. At Sampling Port A 6 a sample of Syngas B is withdrawn and sent to the Gas Analyzer 13 to quantify the composition of the gases in general and the carbon dioxide content in particular. Feedback from this analysis is sent to the controls which regulate the removal of carbon dioxide at the Carbon Dioxide separator 7, to form Syngas C 9 consisting of carbon monoxide, hydrogen, hydrocarbons and a determined amount of carbon dioxide. The mass of carbon dioxide which remains is calculated based on the stoichiometry of the reactions to convert the
hydrocarbons present in the gas stream into synthesis gas. The removed carbon dioxide is vented 8. Syngas C 9 with controlled quantity of carbon dioxide enters the Syngas Reformer 10 and is subjected to heat, pressure and a catalyst which convert the gases, as follows, into Syngas F 11.
Chem Eq 3: Methane: CO2 + CH4 2 H2 + 2 CO
Chem Eq 4: Ethane: C2H6 + 2 CO2 4CO + 3H2
Chem Eq 5: Propane: C3H8 + 3CO2 = 6CO = 4H2
Chem Eq 6: Generally: CxHy + CO2 = CO + H2
Syngas F 11 emerging from the Syngas Reformer is comprised of
predominately carbon monoxide and hydrogen, and may contain unreacted carbon dioxide. As the syngas travels down to the Dimethyl Ether Reactor, it is sampled at Sampling Part B 12 to determine the gas composition. The sample is sent to the on-line Gas Analyzer 13 where it is combined with the sample from Sampling Port A 6. Together these two gas samples are analyzed and provide results which control the conditions in the Carbon Dioxide Removal 7 to remove the correct amount of carbon dioxide to achieve stoichiometric balance of the reactions. The integrated feedback loop formed by the analysis of Syngas B and Syngas F optimizes the quantity of carbon dioxide required to properly reform the hydrocarbon gases and produce the optimum volumes of carbon monoxide and hydrogen, i.e. the ideal syngas mixture for the dimethyl ether reaction which immediately follows. Syngas F 12 enters the dimethyl ether reactor 14 after being appropriately compressed according to the reactor conditions. The reactor is coupled with a separator (not shown separately) which removes any carbon dioxide from the exit products, and which is then vented 15. Dimethyl ether is fed to the gasoline reactor 16 where the dimethyl ether is converted into gasoline range hydrocarbons with skeleton of C5 to C12. Products exiting the reactor are sent to a separator which removes the water 18 formed by the reaction, and sends the light hydrocarbon gases 19, consisting of methane, ethane, propane and butane formed during the reaction back to the Syngas Reformer 10. The gasoline product 20 is sent to storage. it will be evident to those skilled in the art that the placement of the on- line gas sampling and the analysis of the gases provide a sophisticated control interface for controlled carbon dioxide removal early on in the process train.
The advantages of this control result in the more efficient use of the carbon in the feedstock and is in contrast to current industry practices. It is common to remove carbon dioxide at different points in the reaction stream, depending on the end product and reactors involved. Recently the carbon dioxide is used in dry reforming of unconverted or recycled gases, but that is typically done outside the main reaction process steps, with the resulting synthesis gas fed into the reactor(s). The instant invention is more efficient, and because of the control mechanism, can ensure that the carbon it utilized in a controlled manner without having to vent more than absolutely necessary. The instant invention is appropriate for the production of Fischer-Tropsch liquids, which conventionally produces excess carbon dioxide.
INDUSTRIAL APPLICABILITY
The instant invention has valuable industrial applicability to any process which converts renewable material into synthesis gas for further processing to make chemicals or fuels. The placement of the gas reformer immediately after the syngas cleaning allows for immediate and regulated composition of the syngas for the subsequent reaction(s) in the process in this way, the carbon content of the feedstock is utilized to the maximum, instead of being vented as carbon dioxide.
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