KR20130112940A - Method for producing syngas containing carbon monoxide(co) and hydrogen(h2) - Google Patents

Abstract

The present invention is carbon dioxide (CO ₂₎ from carbon monoxide (CO) and hydrogen as a method for producing synthesis gas comprising (H _2), carbon dioxide (CO ₂₎ the decomposition of carbon dioxide (CO ₂₎ as the flow through the plasma product To a synthesis gas by reacting the decomposition product with a gaseous hydrocarbon as it is decomposed to a gas, and then the decomposition product flows through the hydrocarbon-containing gas.

Description

METHOD FOR PRODUCING SYNGAS CONTAINING CARBON MONOXIDE (CO) AND HYDROGEN (H2)}

The present invention relates to a method of manufacturing a synthesis gas containing carbon monoxide (CO) and hydrogen (H ₂₎ from carbon dioxide (CO _2).

It is known to use carbon dioxide for the production of syngas, ie a hydrogen gas mixture, more particularly a gas mixture of carbon monoxide and hydrogen, or the production of fuel.

In particular, when using a catalytic production process, the problem arises that the catalyst used does not exhibit sufficient life. One reason for this is due to thermodynamic phenomena and another due to the material properties of the catalyst materials used. For example, there is no chemical conversion at reaction temperatures below 400 ° C. Increasing the reaction temperature favors the formation of carbon thermodynamically, where the catalyst is at risk of coking, which means that the catalyst is no longer available. This can be prevented by elevated reaction temperatures above 900 ° C., but sintering of the catalyst material may likewise limit the lifetime of the catalyst.

The use of what is called a plasma-based dielectric barrier discharge has been proposed, in which case it is even possible to convert the carbon dioxide-methane mixture into a synthesis gas at a temperature of 20 to 30 ° C. However, the problem here is efficiency, because obtaining a significant conversion requires 10 times the energy cost of the reaction enthalpy.

In recent years, it has also been proposed to combine a catalyst and a plasma to produce synthesis gas. In this case, both the conversion and the efficiency of the synthesis gas increased at reaction temperatures above 700 ° C., but the problem of coking, i.e., soot formation and limitations on the catalyst lifetime associated, was still not solved.

Accordingly, the present invention addresses the problem of specifying an improved process for the production of syngas from carbon dioxide.

Such a problem is the invention for producing synthesis gas by decomposing carbon dioxide into decomposition products as the carbon dioxide flows through the plasma, and then reacting the decomposition products with gaseous hydrocarbons as these decomposition products flow through the hydrocarbonaceous gas. Solved by a process of the type specified above.

The process according to the invention contemplates a two-step process sequence for the production of a synthesis gas, ie a gas mixture of carbon monoxide and hydrogen, wherein the gaseous carbon dioxide preferably used in the first step is generated by a plasma generating device. Flowing through a plasma, this plasma advantageously completely converts the carbon dioxide into decomposition products, and the gaseous carbon dioxide used may be in pure form or part of a gas mixture. Here, the temperature reaches thousands of degrees Celsius.

In the second stage, as the decomposition products are supplied to or flow through the hydrocarbonaceous gases, these decomposition products are mixed with the gaseous hydrocarbons, examples of which include various elements as well as elemental carbon and oxygen, carbon or oxygen radicals. Molecular fragments are included. Here, it is preferable to use pure gaseous hydrocarbons. Due to the high temperature of the gaseous decomposition products, endothermic reactions occur with the hydrocarbons providing the synthesis gas during mixing. The mixing time is relatively short, which means that mixing preferably takes place within a few milliseconds (ms).

Thus, the present invention proposes a process route that is thermodynamically preferred for the production of syngas resulting in rapid and efficient chemical conversion. The high mixing and reaction rates of the decomposition products of hydrocarbons and carbon dioxide prevent the heating of the gas mixtures of hydrocarbons and carbon dioxide that are typically used where soot formation will undergo a thermodynamically preferred temperature range.

Preferably, the carbon dioxide and / or the decomposition product flows at a flow rate of 10 to 100 m / s. Such high flow rates first shorten the residence time of carbon dioxide in the plasma, so that the thermodynamic equilibrium of the decomposition reaction (s) of carbon dioxide cannot be established. Therefore, the electrical energy of the plasma is used at a higher rate for the decomposition of carbon dioxide molecules, and a high mixing rate of gaseous hydrocarbons and decomposition products is achieved in the second process step. In this way, the yield of synthesis gas, and thus the efficiency of the process according to the invention, can be increased overall, and the desired carbon monoxide and hydrogen products can be obtained with high selectivity. In exceptional cases, the flow rate may also be higher or lower.

In the present invention, the plasma can be generated using a plasma generating device which provides a magnitude of the converted electric field strength in the working gas in the range of about 100 V / mm bar to about 10 kV / mm bar. Correspondingly, the converted electric field produces high-energy electrons in the plasma, which promotes or accelerates the decomposition of carbon dioxide. The plasma is preferably not fully thermalized. That is, not in thermodynamic equilibrium. At atmospheric pressure and operating voltage of 10 kV, this means that the electrodes used for plasma generation can be separated from 1 mm to 100 mm. Higher pressures require higher operating voltages or less electrode separation. Plasma generation is of course not limited to this range of configuration parameters and operating conditions. More particularly, it is also possible to operate the plasma at an equivalent electric field strength of less than 100 V / mm bar, in which case a lower efficiency is expected for carbon dioxide decomposition, but on the other hand, the gas flow and More fluid operation is possible with respect to the electricity supply.

Advantageously, the decomposition product is mixed with the hydrocarbonaceous gas in such a way that the temperature of the synthesis gas produced is 1100 ° C. or lower, in particular 700-1000 ° C. Accordingly, after completion of the process, the temperature of the synthesis gas is about 1000 ° C. or lower. This process should advantageously be carried out in such a way that these criteria are met, as well as an important reason for this being thermodynamically preferred equilibrium conditions.

Plasma generation can be achieved using electrodes in direct contact with flowing carbon dioxide, and direct current, alternating current, in particular low frequency alternating current, or pulse-periodic current. The use of pulsed-cycle currents has the advantage that thermal neutronization, ie the establishment of thermodynamic equilibrium, is suppressed, but for this purpose an increase in the cost of supplying electrical energy is inevitable. In the case of a direct current plasma or a low frequency alternating plasma, the electrode can be in direct contact with the plasma, in which case it is preferable to use a graphite electrode.

Alternatively, the generation of the plasma can be achieved using electrodes which are not in direct contact with the flowing carbon dioxide, and pulse-cycle currents, in particular high-frequency pulse-cycle currents, alternating currents, in particular high-frequency alternating currents, or electromagnetic waves, in particular microwaves. Can be. In the case of using microwave or high frequency alternating current in the radio frequency range, it is possible to prevent the direct contact between the plasma and the electrode accordingly, so that no protective gas is required. The use of surface wave plasmas at particularly high flow rates of carbon dioxide or decomposition products or hydrocarbonaceous gas mixtures is preferred.

Particularly advantageously, the waste heat produced in the process is fed to a device for generating steam, in particular to a heat exchanger for generating steam. Thus, the thermal energy generated in the process can be used technically, in which case the generated steam, ie more particularly the generated steam, is more preferably supplied to the decomposition products and / or hydrocarbonaceous gases of carbon dioxide. In this way, undesirable soot formation can be thermodynamically suppressed in the course of cooling the synthesis gas and the chemical equilibrium of the product can be shifted towards hydrogen.

It is possible for the synthesis gas to be fed to a catalyst, in particular a catalyst based on nickel (Ni) or zirconium (Zr), for subsequent reactions. In this way, materials which have not been completely converted during the production process are given the possibility of reaction by catalytic support to provide the synthesis gas. The catalyst can be present, for example, in solid form, for example in solid form in a honeycomb structure, or in powder form. In addition to the aforementioned nickel or zirconium catalysts, it is also possible to use other catalytic materials.

Advantageously, it is possible to feed the synthesis gas in the synthesis reaction, in particular in the synthesis of methanol or dimethyl ether. In this variant of the invention, the thermal energy of the syngas produced is used in a downstream process; Thus, process heat is used efficiently. In subsequent dimethyl ether synthesis it is possible to improve the customary catalytic production process which consists essentially of removing water from methanol to provide dimethyl ether, since typically the use of the required hydrogen is reduced. Likewise, the efficiency of dimethyl ether synthesis can be increased.

The invention also relates to an apparatus for producing a synthesis gas comprising carbon monoxide and hydrogen from carbon dioxide, which is configured to carry out the process described above. Such a device comprises at least one first reaction chamber and at least one second reaction chamber, the first reaction chamber comprising at least one plasma generating device for the decomposition of carbon dioxide, wherein at least one carbon dioxide is contained in the first reaction chamber. Fed through a feed line, through which carbon dioxide flows into the decomposition product; The second reaction chamber is connected downstream of the first reaction chamber or directly to the first reaction chamber via one or more lines, the second reaction chamber containing or through hydrocarbon hydrocarbon gas supplied via a feed line. Sex gas flows; Syngas is produced as the cracked product reacts with the gaseous hydrocarbon in the course of the cracked product flowing through the gaseous hydrocarbon, and is sent out through the outlet line. Accordingly, the two-step production process of the present invention for producing syngas with the apparatus of the present invention is that the supplied carbon dioxide is decomposed by the plasma generated therein in the reaction chamber or the first reaction chamber (s), and the reaction It can be designed in such a way that subsequent mixing of the decomposition product of the hydrocarbonaceous gas and carbon dioxide in the chamber or the second reaction chamber (s) takes place. All reaction chambers are equipped with suitable inlet and outlet lines so that gaseous materials used in the production process according to the invention can flow between them. Likewise, it is possible for one or more second reaction chamber (s) to be connected directly to one or more first reaction chamber (s) or direct contact therebetween. It is also possible for the apparatus of the present invention to have two or more separate device units, in particular for syngas production, which are connected in parallel, each of which is one or more of the individual or groupings in the case of multiple corresponding device units. One and one or more second reaction chambers.

The plasma generating device preferably has several plasma sources. This leads to improved mixing of gaseous hydrocarbons and cracked products, the particular reason being that the use of several small plasma sources for the decomposition of carbon dioxide provides a larger proportion of contact area to space. As mentioned above, the plasma source may have different electrical excitations. The converted electric field strength of the plasma source is preferably in the range of about 100 V / mm bar to about 10 kV / mm bar.

Advantageously, one or more lines between the first reaction chambers and the second reaction chambers and / or the second reaction chamber have one or more orifices for the introduction of steam, in particular steam. As described for the process according to the present invention, supplying a small amount of steam can thermodynamically suppress soot formation in the course of cooling the synthesis gas and also shift the product spectrum predominantly to hydrogen.

For the subsequent-reaction of the synthesis gas, there may be a catalyst based on the catalyst, in particular nickel (Ni) or zirconium (Zr), downstream of the second reaction chamber. Thus, it is possible to convert a substance or compound incompletely converted into syngas by means of catalysis, which increases the efficiency of syngas production.

There may also be additional catalyst chambers for carrying out the synthesis reaction, in particular methanol or dimethyl ether synthesis, downstream of any catalyst or second reaction chamber connected downstream of the second reaction chamber. In this way, the thermal energy of the synthesis gas can be used efficiently for the downstream process.

Further advantages, features and details of the present invention are demonstrated from the working examples described below and from the drawings.

1 shows an apparatus for carrying out a process according to the invention according to a first embodiment.
2 shows an apparatus for carrying out a process according to the invention according to a second embodiment.
3 shows an apparatus for carrying out a process according to the invention according to a third embodiment.
4 shows an apparatus for carrying out a process according to the invention according to a fourth embodiment.
5 shows an apparatus for carrying out a process according to the invention according to a fifth embodiment.
6 shows an apparatus for carrying out a process according to the invention according to a sixth embodiment.
7 shows part of an apparatus for carrying out a process according to the invention according to a seventh embodiment.
8 shows an apparatus for carrying out a process according to the invention according to an eighth embodiment.

Figure 1 shows an apparatus 1 for carrying out the process according to the invention to produce a synthesis gas containing carbon monoxide (CO) and hydrogen (H ₂₎ from carbon dioxide (CO ₂₎ according to the first embodiment . The device 1 basically comprises first and second reaction chambers 2, 3, which are connected to one another via a line 4. In addition, dedicated inlet lines 5, 6 are arranged in the reaction chambers 2, 3, and discharge lines 7 are arranged in the second reaction chamber 3.

The first reaction chamber 2 advantageously comprises one or more plasma generating devices 8 having several plasma sources 8 ', as shown in FIG. The plasma generator 8 and the plasma source 8 ′ are connected to the electrical energy supply 16 by an electrical energy supply line 17.

The first reaction chamber 2 serves to decompose carbon dioxide, which is supplied through the inlet line 5 and through the first reaction chamber 2, for example at a flow rate of about 50 m / s. Flows into decomposition products. This is done at a temperature of several thousand degrees Celsius. The plasma generating apparatus 8 is operated, for example, with a converted electric field strength of 1 kV / mm bar, which ensures that the generated plasma is not completely thermoneutralized, ie not in thermodynamic equilibrium. In order to generate the plasma, it is preferable to use high frequency alternating current in the radio frequency range, because in this manner, the contact between the plasma and the electrode of the plasma generating device 8 is not necessary, and the use of a protective gas is not necessary. . It is also advantageous to use surface wave plasma for the desired high flow rates. More particularly, the plasma power is concentrated in small spaces through which carbon dioxide flows at the high flow rates mentioned above. Thus, the residence time in the electrical energy dissipation zone is short enough that the establishment of thermodynamic equilibrium is suppressed, and a high proportion of electrical energy is used for the decomposition of carbon dioxide.

The cracked product is mixed with the gaseous hydrocarbons fed through line 6 as it flows through line 4 into the second reaction chamber 3, and then converted to syngas, and through line 7 It is sent out from the second reaction chamber 3 as a final product at a temperature of 800 to 900 ° C. Here, too, both decomposition products and gaseous hydrocarbons are advantageously of high flow rate, because this results in high mixing rates. The mixing time is, for example, only a few milliseconds (ms). In line 4 the plasma gas containing decomposition products of carbon dioxide is kept short in order to prevent unwanted heat loss and subsequent reactions in the course of passing into the reaction chamber 3. It can also be omitted completely so that the plasma generating device 8, ie the reaction chamber 2 of the plasma reactor, is in direct contact with the reaction chamber 3.

Advantageously, as shown in FIG. 2, several first reaction chambers 2 having a suitable plasma generating apparatus 8 or plasma reactor may be arranged in the second reaction chamber 3 for reforming. Can be. This achieves the desired large contact area between the plasma gas and the hydrocarbon.

The process according to the invention consists of a thermodynamically preferred process route which leads to a fast and efficient chemical conversion of the materials used in the synthesis gas. At the same time, the process is basically divided into two stages to prevent the gas mixture of carbon dioxide and hydrocarbons from being heated, thereby avoiding the thermodynamically preferred temperature range for soot formation. The reaction chambers 2 and 3 and the energy supply 16 or the electric power supply desired for the operation of the plasma generating apparatus 8 and the plasma source 8 'are compact and inexpensive.

3 shows an apparatus 1 for carrying out a process according to the invention according to a third embodiment. The fundamental difference in the embodiment according to FIG. 1 or 2 is that steam is supplied from the heat exchanger 10 to the second reaction chamber 3 via an additional supply line 9, as a result of which the soot formation is synthesized. In the course of cooling the gas is thermodynamically suppressed and the product spectrum of the syngas produced is shifted predominantly to hydrogen. The heat exchanger 10 can advantageously be operated using process heat generated in the process according to the invention.

FIG. 4 shows a variant in which steam does not go directly to the second reaction chamber 3 but rather to the line 4 connecting the two reaction chambers 2, 3 to premix the decomposition product with steam. will be.

5 shows an apparatus 1 for carrying out a process according to the invention according to a fifth embodiment. Here, the catalyst 11 connected downstream of the second reaction chamber 3 serves to subsequently-react the incompletely converted material, thus achieving a complete conversion of the material used. The catalyst 11 can be composed of, for example, a solid-state catalyst based on a perovskite structure with zirconium as the active element.

FIG. 6 shows, on the basis of the embodiment according to FIG. 5, a downstream process taking place in the reaction chamber 12 connected downstream of the catalyst 11 after passing through the catalyst 11, ie for example methanol synthesis. Or an option to supply synthesis gas to dimethyl ether synthesis. For this purpose, the catalyst 11 is connected to the reaction chamber 12 via line 13. Here, it may be possible to supply hydrogen from reservoir 14 to reaction chamber 12 via line 15 to establish the desired ratio of carbon monoxide to hydrogen in the synthesis gas. Hydrogen can be obtained, for example, via an electrolysis process. Overall, this results in the advantage that the thermal energy obtained in the process according to the invention can be used efficiently for methanol synthesis. The same applies when direct dimethyl ether synthesis takes place in the reaction chamber 12, because, in particular, compared to a two-stage catalytic process for dimethyl ether synthesis known from the prior art, provided by the process according to the invention This is because the process heat here likewise increases the efficiency of the reaction.

8 shows a further option for scaling of the process according to the invention. Instead of having several first reaction chambers 2 for plasma decomposition of carbon dioxide arranged in a large second reaction chamber 3 for reforming, here the device 1, 1 ′ of the invention is parallel to several units. In this case the apparatus 1, 1 ′ consists of first and second reaction chambers 2, 3, and, optionally, a catalyst 11 or a catalytic reactor, respectively. This ensures that the contact area between the hydrocarbon and the plasma gas containing the decomposition products of carbon dioxide grows to a plant size.

Claims (17)

Carbon dioxide as a method for producing synthesis gas from (CO ₂₎ include carbon monoxide (CO) and hydrogen (H _2), carbon dioxide (CO ₂₎ is as the flow through the plasma by decomposing carbon dioxide (CO ₂₎ as a degradation product And then reacting the decomposition product with a gaseous hydrocarbon to produce syngas as the decomposition product flows through the hydrocarbonaceous gas. The method of claim 1 wherein the carbon dioxide (CO ₂ ) and / or the decomposition product flows at a flow rate of 10 to 100 m / s. A method according to claim 1 or 2, characterized in that the plasma is generated using a plasma generator with a converted electric field strength in the range of 100 V / mm bar to 10 kV / mm bar. 4. The decomposition product is mixed with the hydrocarbonaceous gas according to claim 1, wherein the decomposition product is mixed in such a way that the temperature of the synthesis gas produced is 1100 ° C. or less, in particular 700-1000 ° C. 5. Way. The method according to any one of claims 1 to 4, wherein an electrode is in direct contact with the carbon dioxide through which plasma generation flows, and direct current, alternating current, in particular low frequency alternating current, or pulse-periodic current is used. Achieved. 6. The method of claim 5 wherein plasma generation is achieved using a graphite electrode. 5. The electrode according to claim 1, wherein the plasma generation does not come in direct contact with the flowing carbon dioxide, and pulse-periodic currents, in particular high-frequency pulse-periodic currents, alternating current, in particular high-frequency alternating current, or electromagnetic waves. , In particular, achieved using microwaves. 8. The method according to claim 1, wherein the plasma used is a nonthermalized plasma. 9. 9. Process according to any one of the preceding claims, characterized in that the waste heat produced in the process is fed to an apparatus for steam generation, in particular to a heat exchanger for steam generation. 10. The process according to claim 1, wherein steam, in particular steam, is supplied to the decomposition product of carbon dioxide and / or steam, in particular steam, is supplied to the hydrocarbonaceous gas. 11. The process according to claim 1, wherein the synthesis gas is fed to a catalyst, in particular a catalyst based on nickel (Ni) or zirconium (Zr), for subsequent reactions. The process according to claim 1, wherein the synthesis gas is fed to a synthesis reaction, in particular to methanol or dimethyl ether synthesis. An apparatus for producing a synthesis gas comprising carbon monoxide (CO) and hydrogen (H ₂ ) from carbon dioxide (CO ₂ ), configured to carry out the process of claim 1, wherein the apparatus (1) is At least one first reaction chamber (2) and at least one second reaction chamber (3), wherein the first reaction chamber comprises at least one plasma generating device (8) for the decomposition of carbon dioxide (CO ₂ ), Carbon dioxide is supplied to this first reaction chamber 2 through one or more supply lines through which carbon dioxide flows into the decomposition product; The second reaction chamber 3 is connected downstream of the first reaction chamber 2 or directly to the first reaction chamber 2 via one or more lines 4, and to this second reaction chamber 2. The hydrocarbonaceous gas supplied through the supply line 5 is contained or through which the hydrocarbonaceous gas flows; Apparatus characterized in that the synthesis gas is produced as the decomposition product reacts with the gaseous hydrocarbon in the course of the decomposition product flowing through the gaseous hydrocarbon, and is discharged through the outlet line (7). 12. Apparatus according to claim 11, characterized in that the plasma generating device (8) has several plasma sources (8 '). Device according to claim 13 or 14, characterized in that the at least one line (4) and / or the second reaction chamber (3) has at least one orifice for the introduction of steam, in particular steam. 16. The catalyst 11 according to any one of claims 13 to 15, wherein the catalyst 11, in particular a catalyst based on nickel (Ni) or zirconium (Zr), is used for the second reaction chamber (3) for the post-reaction of the synthesis gas. Device downstream). 16. The reaction chamber as claimed in claim 16, wherein the further reaction chamber 12 for carrying out the synthesis reaction, in particular methanol or dimethyl ether synthesis, comprises a catalyst 11 or a second reaction chamber. And downstream of (3).

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