Reactor for carbon monoxide production via reverse boudouard reaction

Abstract

Implementations of the disclosed subject matter provide a reactor for gasification of biochar with CO2 to produce CO. The reactor may include an inlet for receiving a first feed stream comprising biochar, O2, and CO2. The reactor may include a mixing zone and a combustion zone comprising a moving bed wherein the biochar is combusted with O2 to produce a first product stream comprising CO2, CO, ash particles and unreacted biochar. The reactor may include a gasification zone comprising a fluidized bed, wherein the first product stream may be fluidized with a second feed stream, comprising CO2 to perform a reverse Boudouard reaction to produce a second product stream comprising CO and ash particles. The first feed stream at the inlet may comprise 0-70% of the total CO2 fed to the reactor and the second feed stream may comprise 30-100% of the total CO2 fed to the reactor.

Description

SP 2941 FF - 1 - 5 REACTOR FOR CARBON MONOXIDE PRODUCTION VIA REVERSE BOUDOUARD REACTION TECHNICAL FIELD OF THE INVENTION

[0001] The present invention relates to a reactor design for reverse Boudouard reaction with biochar for net zero 10 CO production. The reactor includes a mixing zone, a combustion zone comprising a moving bed, and a gasification zone comprising a fluidized bed. BACKGROUND OF THE INVENTION

[0002] CO is widely used by the chemical industry in the 15 production of inorganic / organic chemicals and chemical intermediates. Currently, CO is produced from fossil fuels and that has a high carbon intensity. The closest known processes for CO production from CO2(i.e., with low carbon intensity) are the Reverse Water Gas Shift (RWGS) 20 reaction (e.g., thermal, catalytic, or sorption enhanced) and CO2electrolysis (e.g., solid oxide or low temperature). However, the RWGS process produces a mixture of CO and H2(i.e., syngas). Hence, for applications requiring relatively pure CO streams (e.g., 25 CO electrolyzer, Ube process, SHOP) an expensive cold box (e.g., a cryogenic unit) is necessary to separate the CO from the H2. RWGS also requires H2and CO2as input that needs to be produced from renewable energy and this increases the cost and energy intensity of the process. 30 CO2electrolysis to CO requires as input renewable energy and CO2to produce CO. Renewable energy can beintermittent if the source is from solar photovoltaic or wind. These further increase the costs and energy intensity of the CO2electrolyser. The production of CO 35 from biochar and CO2via a reverse Boudouard reaction is5 an attractive front end process to produce low carbon intensity CO for a CO / CO2to ethylene / ethanol electrolyzer.

[0003] Reverse Boudouard is a highly endothermic reaction that takes place at high temperature. Therefore, to 10 improve the overall energy efficiency, it is important to design a reactor that integrates combustion (e.g., to provide heat needed for the reaction) and the reverse Boudouard reaction in the same unit without providing heat externally for the reaction to occur. 15 SUMMARY OF THE INVENTION

[0004] According to an embodiment of the disclosed subject matter, a reactor for gasification of biochar with CO2to produce CO may include at least one inlet for receiving a first feed stream comprising biochar, O2, and CO2. The 20 first feed stream may be injected into the reactor by a gas-solid injector. The reactor may include a mixing zone for mixing the biochar, O2, and CO2, and a combustion zone comprising a moving bed. The biochar may be combusted with O2to produce a first product stream comprising CO2, 25 CO, ash particles and unreacted biochar. The reactor may also include a gasification zone comprising a fluidized bed. In this gasification zone, the first product stream may be fluidized with a second feed stream comprising CO2to perform a reverse Boudouard reaction to produce a 30 second product stream comprising CO and ash particles. The second feed stream may be fed to the gasification zone via a gas distributor. The first feed stream at the inlet may comprise 0-70% of the total CO2fed to the reactor, and the second feed stream in the gasification zone may 35 comprise 30-100% of the total CO2fed to the reactor.

[0005] Implementations of the disclosed subject matter provide a reactor for gasification of biochar with CO2to5 produce CO. The disclosed reactor design allows for the overall energy efficiency to be maximized by coupling the combustion reaction and biochar / CO2gasification in the same reactor. The disclosed reactor design also allows for maximizing the conversion of biochar and CO2to CO. 10 Additional features, advantages, and embodiments of the disclosed subject matter may be set forth or apparent from consideration of the following detailed description, figures, and claims. Moreover, it is to be understood that both the foregoing summary and the following detailed 15 description are examples and are intended to provide further explanation without limiting the scope of the claims. BRIEF DESCRIPTION OF THE FIGURES

[0006] The accompanying figures, which are included to 20 provide a further understanding of the disclosed subject matter, are incorporated in and constitute a part of this specification. The figures also illustrate embodiments of the disclosed subject matter and together with the detailed description serve to explain the principles of 25 embodiments of the disclosed subject matter. No attempt is made to show structural details in more detail than may be necessary for a fundamental understanding of the disclosed subject matter and various ways in which it may be practiced. 30

[0007] FIG. 1 shows a side view of a reactor according to an implementation of the disclosed subject matter.

[0008] FIG. 2 shows a side view of a reactor according to an implementation of the disclosed subject matter. DETAILED DESCRIPTION OF EMBODIMENTS 35

[0009] The process of converting biochar with CO2to CO can be thought to be analogous to the coal gasification process. In the traditional coal gasification process, coal is reacted with insufficient oxygen and / or steam at5 high temperatures to primarily produce synthesis gas that is a mixture of CO and H2. The coal gasification process has a high CO2intensity because it uses coal (a fossil fuel) as feed and also operates at high temperatures (normally > 1300°C) producing CO2as a product. 10 Furthermore, the coal gasification process needs huge amount of water in the form of steam. One of the promising ways to produce CO with lower CO2intensity is the reverse Boudouard reaction. The reverse Boudouard reaction has been studied extensively over the last 20 years. However, 15 these studies have focused on the kinetics, especially in lab scale facilities. Very few reactor designs for reverse Boudouard reaction have been previously presented in the literature. An example of a prior process is the fluidized bed biomass / coal gasifier as taught by Winkler 20 (see Wolfgang Adlhoch, Hissaki Sato, Joachim Wolff, and Karsten Radtke, “High Temperature Winkler Gasification of Municipal Solid Waste”, 2000 Gasification Technologies Conference, San Francisco, CA, USA, Oct. 8-11, 2000). In a fluidized bed reactor, steam and air are injected as the 25 fluidization / gasification media and react with biomass / coal to produce syngas (CO+H2). In this case, biomass / coal and steam / air are reacted in the same fluidized bed reactor – and therefore the residence time of the gas phase is limited by the fluidized bed. 30 Therefore, the conversion of the gas phase is lower. However, for a reaction with lower reaction rate, for example the reverse Boudouard reaction, it is necessary to achieve a higher conversion and therefore a large volume reactor is needed which leads to higher capex – thus 35 making the process less economically desirable. As such, there is a need for a reactor design for the reverse5 Boudouard reaction that achieves higher conversion while reducing capex.

[0010] The present invention is directed to a reactor design for reverse Boudouard reaction with biochar for net zero CO production. The reactor includes a mixing zone, a 10 combustion zone comprising a moving bed, and a gasification zone comprising a fluidized bed. In the present invention, the mixing zone of the designed reactor increases the mass transfer between the gas and solid feed streams. The present invention supplies the heat required 15 for the reverse Boudouard reaction by combusting O2and biochar inside the reactor thereby increasing the heat transfer and the energy efficiency between the reactants and the products. The effective heat transfer between the high temperature combustion zone and the gasification zone 20 ensures low heat loss and high overall energy efficiency. One of the advantages of the reactor design disclosed herein is that the combustion zone comprising a moving bed increases the residence time of biochar / gas phase contact which increases the heat transfer between gas / solid, which 25 increases the overall energy efficiency of the process. The resultant product of the combustion zone comprising the moving bed acts as a reactant for the reverse Boudouard reaction and thus resulting in higher conversion of the reverse Boudouard reaction of the biochar. 30 Furthermore, the CO2, which is the gasification media in reverse Boudouard reaction, is injected into the reactor in multi-stages, resulting in a higher overall residence time for CO2gas and therefore higher gas conversion. This present invention is directed to designing a unique 35 reactor that combines the mixing zone, the combustion zone comprising a moving bed and the gasification zone comprising a fluidized bed in the single reactor in that particular order to maximize conversion and overall energy5 efficiency, that solves the problem of the state of the art processes.

[0011] In particular, the disclosed subject matter provides a novel reactor designed specifically for the reverse Boudouard reaction. The reactor may be divided into at 10 least three zones, wherein each zone is defined as performing a specific function or a specific process. There may be a physical boundary present separating each zone, but this is not always necessary. For example, the mixing zone is referred to the zone wherein the components 15 in the first feed stream mix well with each other. The combustion zone comprising a moving bed is defined as the zone wherein the feed streams undergo predominantly a combustion reaction with the two or more components in the presence of oxygen while flowing down in a moving bed. The 20 gasification zone comprising a fluidized bed is defined as the zone wherein the reverse Boudouard reaction predominantly takes place in the absence of oxygen. Other side reactions may take place in this zone, for example, water gas shift reaction (CO + H2O → CO2+ H2), reverse 25 water gas shift (CO2+ H2→ CO + H2O) or steam gasification reaction (C + H2O → CO + H2). For example, one embodiment of the reactor may include an inner side wall that divides the reactor into a number of, e.g., three or four, relatively separate zones. One such zone 30 is a mixing zone. Another one of these zones may be a combustion zone comprising a moving bed. In the combustion zone, combustion of biochar with O2may dominate – combustion heat may heat the biochar / CO2mixture to a relatively high temperature (e.g., up to 35 1300°C). In said combustion zone comprising the moving bed, biochar pellets may react with CO2to produce CO. The long residence time (also low gas velocity) can ensure5 the conversion of both biochar and CO2. Another zone in the reactor may be a gasification zone comprising a fluidized bed. In the gasification zone comprising a fluidized bed, the remaining biochar particles may be fully mixed with CO2and converted to CO. Any remaining 10 ash fines may then be entrained into the gas flow and removed from the reactor for further separation. The inner sidewall may also provide efficient heat transfer between the high temperature combustion zone and the lower temperature gasification zone comprising a fluidized bed, 15 and because both zones are enclosed in a single reactor, heat loss may be minimized.

[0012] According to an implementation of the disclosed subject matter, a reactor for gasification of biochar with CO2to produce CO may include at least one inlet for 20 receiving a first feed stream. The first feed stream may include biochar, O2, and CO2. The first feed stream may be injected into the reactor by a gas-solid injector. According to an embodiment, the temperature of the first feed stream may be between 20-400°C. The reactor may also 25 include a mixing zone for mixing the biochar, O2, and CO2to improve the conversion of the reverse Boudouard reaction .

[0013] According to an implementation of the disclosed subject matter, the reactor may include a combustion zone. 30 The combustion zone may include a moving bed and the biochar may be combusted with O2to produce a first product stream. The first product stream may include CO2, CO, ash particles and unreacted biochar. In an embodiment, the temperature at the bottom of the 35 combustion zone may be 1200-1500°C.

[0014] According to an implementation of the disclosed subject matter, the reactor may include a gasification5 zone which may include a fluidized bed. Here the first product stream may be fluidized with a second feed stream via a gas distributor. The second feed stream may include CO2. In the gasification zone, the CO2in the second feed stream may perform a reverse Boudouard reaction to produce 10 a second product stream which may include CO and ash particles. According to an embodiment, the temperature of the second feed stream may be between 20-600°C. In an embodiment, the second feed stream may be fed to the combustion zone. 15

[0015] According to an implementation of the disclosed subject matter, the first feed stream at the inlet of the reactor may comprise 0-70% of the total CO2fed to the reactor, and the second feed stream in the gasification zone may comprise 30-100% of the total CO2fed to the 20 reactor.

[0016] According to an embodiment, the reactor may minimize the heat loss to be about 25% for 1 million metric tons per annum CO production, leading to a higher overall energy efficiency also reducing the CO2intensity of the 25 overall process.

[0017] In an embodiment, the ash in the second product stream may have a particle size in the range of 5-60 micron. These ash particles may be removed from the second product stream. According to an embodiment, the 30 second product stream may be fed to a separator to separate the ash particles from the third product stream comprising CO.

[0018] In another embodiment, the CO2in the first and / or second feed streams may be from a source including the 35 atmosphere, biogenic sources, biomass, and point sources from a chemical plant and / or refinery, and the like.5

[0019] According to an embodiment, the reactor may be operated at a pressure in the range of 1-50 bara.

[0020] For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiments illustrated in the accompanying 10 figures, which are described in more detail below. The embodiments disclosed herein are not intended to be exhaustive or limit the invention to the precise form disclosed in the following detailed description. The invention includes any alterations and further 15 modifications in the illustrated devices and described methods and further applications of the principles of the invention as set forth in the claims.

[0021] FIG. 1 shows a side view of a reactor according to an implementation of the disclosed subject matter. FIG. 1 20 shows an example of a reactor 100 viewed from the side. As shown in FIG. 1, a reactor for gasification of biochar with CO2to produce CO may include at least one inlet 10 for receiving a first feed stream 110 comprising biochar, O2, and CO2. As shown, the first feed stream 110 may be 25 injected into the reactor by a gas-solid injector 15. The reactor 100 may include a mixing zone 20 for mixing the biochar, O2, and CO2, and a combustion zone 30 comprising a moving bed. The biochar may be combusted with O2to produce a first product stream 120 comprising CO2, CO, ash 30 particles and unreacted biochar. The reactor 100 may also include a gasification zone 40 comprising a fluidized bed. In this gasification zone 40, the first product stream 120 may be fluidized with a second feed stream 130 comprising CO2to perform a reverse Boudouard reaction to produce a35 second product stream 140 comprising CO and ash particles. The second feed stream 130 may be fed to the gasification zone 40 via a gas distributor 45. The first feed stream5 110 at the inlet 10 may comprise 0-70% of the total CO2fed to the reactor 100, and the second feed stream 130 in the gasification zone 40 may comprise 30-100% of the total CO2fed to the reactor 100.

[0022] FIG. 1 shows a side view of a reactor according to 10 an implementation of the disclosed subject matter. FIG. 1 shows an example of a reactor 100 viewed from the side. As shown in FIG. 1, a reactor 100 for gasification of biochar with CO2to produce CO may include at least one inlet 10 for receiving a first feed stream 110. The first 15 feed stream 110 may include biochar, O2, and CO2. The first feed stream 110 may be injected into the reactor 100 by a gas-solid injector 15. Although not shown in FIG. 1, the temperature of the first feed stream 110 may be between 20-400°C. The reactor 100 may also include a 20 mixing zone 20 for mixing the biochar, O2, and CO2.

[0023] Also shown in FIG. 1, the reactor 100 may include a combustion zone 30 comprising a moving bed. In the combustion zone 30, the biochar may be combusted with O2to produce a first product stream 120. The first product 25 stream 120 may include CO2, CO, ash particles and unreacted biochar. Although not shown in FIG. 1, the temperature at the bottom of the combustion zone 30 may be in the range of 1000-1800°C, preferably between 1200- 1500°C. 30

[0024] As shown in FIG. 1, the reactor 100 may include a gasification zone 40 comprising a fluidized bed. Here, the first product stream 120 may be fluidized with a second feed stream 130 via a gas distributor 45. The second feed stream 130 may include CO2. In the gasification zone 40, 35 the CO2in the second feed stream 130 may perform a reverse Boudouard reaction to produce a second product stream 140 which may include CO and ash particles. Although not5 shown in FIG. 1, the temperature of the second feed stream 130 may be between 20-600°C. As an example and as shown in FIG. 1, the second feed stream 130 may also be fed to the combustion zone 30.

[0025] The first feed stream 110 at the inlet 10 of the 10 reactor 100 may comprise 0-70% of the total CO2fed to the reactor 100, and the second feed stream 130 in the gasification zone 40 may comprise 30-100% of the total CO2fed to the reactor 100.

[0026] The ash in the second product stream 140 may have a 15 particle size in the range of 5-60 micron. These ash particles may be removed from the second product stream 140. For example, as shown in FIG. 1, the second product stream 140 may be fed to a separator 50 to separate the ash particles 150 from the third product stream 160 20 comprising CO.

[0027] Although not shown in FIG. 1, the reactor 100 may be operated at a pressure in the range of 1-50 bara.

[0028] FIG. 2 shows a side view of a reactor according to an implementation of the disclosed subject matter. The 25 reactor 100 in FIG. 2 has at least one inlet feed stream 110 entering from the center portion of the reactor. FIG. 2 shows an example of a reactor 100 viewed from the side. As shown in FIG. 2, a reactor 100 for gasification of biochar with CO2to produce CO may include at least one 30 inlet 10 for receiving a first feed stream 110. The first feed stream 110 may include biochar, O2, and CO2. The first feed stream 110 may be injected into the reactor 100 by a gas-solid injector 15. Although not shown in FIG. 2, the temperature of the first feed stream 110 may be 35 between 20-400°C. The reactor 100 may also include a mixing zone 20 for mixing the biochar, O2, and CO2.5

[0029] Also shown in FIG. 2, the reactor 100 may include a combustion zone 30 comprising a moving bed and the biochar may be combusted with O2to produce a first product stream 120. The first product stream 120 may include CO2, CO, ash particles and unreacted biochar. Although not shown 10 in FIG. 2, the temperature at the bottom of the combustion zone 30 may be 1200-1500°C.

[0030] As shown in FIG. 2, the reactor 100 may include a gasification zone 40 comprising a fluidized bed. Here the first product stream 120 may be fluidized with a second 15 feed stream 130 via a gas distributor 45. The second feed stream 130 may include CO2. In the gasification zone 40, the CO2in the second feed stream 130 may perform a reverse Boudouard reaction to produce a second product stream 140 which may include CO and ash particles. Although not 20 shown in FIG. 2, the temperature of the second feed stream 130 may be between 20-600°C. As an example and as shown in FIG. 2, the second feed stream 130 may also be fed to the combustion zone 30.

[0031] The first feed stream 110 at the inlet 10 of the 25 reactor 100 may comprise 0-70% of the total CO2fed to the reactor 100, and the second feed stream 130 in the gasification zone 40 may comprise 30-100% of the total CO2fed to the reactor 100.

[0032] The ash in the second product stream 140 may have a 30 particle size in the range of 5-60 micron. These ash particles may be removed from the second product stream 140. For example, as shown in FIG. 2, the second product stream 140 may be fed to a separator 50 to separate the ash particles 150 from the third product stream 160 35 comprising CO.

[0033] Although not shown in FIG. 2, the reactor 100 may be operated at a pressure in the range of 1-50 bara.5

[0034] For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the Examples carried out of various embodiments of the present invention, which are described in more detail below. The Examples and embodiments disclosed herein are 10 not intended to be exhaustive or limit the invention to the precise form disclosed in the following Examples. The invention includes any alterations and further modifications in the provided Examples and described methods and further applications of the principles of the 15 invention as set forth in the claims.

[0035] EXAMPLES:

[0036] According to the present invention, an example reactor for the production of carbon monoxide via Reverse Boudouard reaction of a feedstock containing carbon and 20 carbon dioxide along with the addition of oxygen. The first feed stream 110 contains a mixture of biochar, CO2and O2entering the reactor 100. The second feed stream 130 contains CO2. In the reactor 100, the series of reactions takes place the product stream 140 exits the 25 reactor. Table 1 gives an exemplary summary of the process streams for the process that is required to produce 1 million tons / year of CO. Table 1: Summary of Process Streams according to the Example Flowrate, Streams Composition T, oC P, bara kg / h 110CO210000 300 3.5 110 Biochar 28920 300 3.5 110O210560 300 3.5 130CO257232 300 3.5 140CO / CO2 / Ash106712 850 3.2 305

[0037] The foregoing description, for purpose of explanation, has been described with reference to specific embodiments. However, the illustrative discussions above are not intended to be exhaustive or to limit embodiments of the disclosed subject matter to the precise forms 10 disclosed. Many modifications and variations are possible in view of the above teachings. The embodiments were chosen and described in order to explain the principles of embodiments of the disclosed subject matter and their practical applications, to thereby enable others skilled 15 in the art to utilize those embodiments as well as various embodiments with various modifications as may be suited to the particular use contemplated.

Claims

SP 2941 FF - 15 - C L A I M S 1. A reactor for gasification of biochar with CO2to produce CO, the reactor 100 comprising: a) at least one inlet 10 for receiving a first feed stream 110 comprising biochar, O2, and CO2, wherein the first feed stream is injected into the reactor by a gas- solid injector 15, b) a mixing zone 20 for mixing the biochar, O2, andCO2,c) a combustion zone 30 comprising a moving bed, wherein the biochar is combusted with O2to produce a first product stream 120 comprising CO2, CO, ash particles and unreacted biochar, d) a gasification zone 40 comprising a fluidized bed, wherein the first product stream is fluidized with a second feed stream 130 via a gas distributor, comprising CO2to perform a reverse Boudouard reaction to produce a second product stream 140 comprising CO and ash particles, wherein the first feed stream at the inlet comprises 0-70% of the total CO2fed to the reactor, and wherein the second feed stream in the gasification zone comprises 30- 100% of the total CO2fed to the reactor.

2. The reactor for gasification of biochar with CO2to produce CO according to claim 1, wherein second feed stream provides CO2to the combustion zone 30.

3. The reactor for gasification of biochar with CO2to produce CO according to claim 1 or 2, wherein the temperature of the first feed stream is between 20-400°C.

4. The reactor for gasification of biochar with CO2to produce CO according to any of claims 1 to 3, wherein the temperature of the second feed stream is between 20-600°C.

5. The reactor for gasification of biochar with CO2to produce CO according to any of claims 1 to 4, wherein the temperature at the bottom of the combustion zone is 1200- 1500°C.

6. The reactor for gasification of biochar with CO2to produce CO according to any of claims 1 to 5, wherein the ash in the second product stream has a particle size in the range of 5-60 micron.

7. The reactor for gasification of biochar with CO2to produce CO according to any of claims 1 to 6, wherein the temperature in the gasification zone is 800-1000°C.

8. The reactor for gasification of biochar with CO2to produce CO according to any of claims 1 to 7, wherein the second product stream is fed to a separator 50 to separate the ash particles 150 from the third product stream 160 comprising CO.

9. The reactor for gasification of biochar with CO2to produce CO according to any of claims 1 to 8, wherein the CO2in the first and / or second feed streams is from a source selected from the group consisting of: atmosphere, biogenic sources, biomass, and point sources from a chemical plant and / or refinery.

10. The reactor for gasification of biochar with CO2to produce CO according to any of claims 1 to 9, wherein the reactor is operated at a pressure in the range of 1-50 bara.

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