CN101289166B - Method and device for co-converting CH4 and CO2 to prepare H2 and CO - Google Patents

Abstract

The invention discloses a method and a device for co-converting CH ₄ and CO ₂ to prepare H ₂ and CO, belonging to the technical fields of petrochemical industry and coal chemical industry. The reaction gas CH ₄ and CO ₂ are premixed at a molar ratio of 1:1 to 4:1; they enter the plasma reactor for reaction; they are separated by the polysulfone membrane H ₂ separator; the CO separator is separated; the remaining gas is sent back to the raw material Gas premixing; cycle production to obtain _H2 and CO. The gas premixer (1), the plasma reactor (2), the _H2 separator (3), and the CO separator (4) are connected in sequence, and the unseparated gas outlet of the CO separator is connected with the inlet of the premixer. The invention also provides a method and device including reaction-separation-separation-reaction-separation-separation two or more times. The invention avoids the reaction termination caused by catalyst deactivation, realizes the preparation of _H2 and CO at low temperature, effectively reduces energy consumption, has high conversion rate of _CH4 and _CO2 , and good product selectivity.

Description

Method and device for co-converting CH4 and CO2 to prepare H2 and CO

technical field

The invention relates to a method and a device for co-converting _CH4 and _CO2 to prepare _H2 and CO at low temperature, and belongs to the technical fields of petrochemical and coal chemical industries.

Background technique

CH ₄ and CO ₂ are the main greenhouse gases. The CO ₂ reforming reaction of CH ₄ can not only realize the simultaneous chemical conversion of the two, but also produce a large amount of synthesis gas for Fischer-Tropsch synthesis and other processes.

At present, the research mainly focuses on the following aspects: thermodynamics research, catalyst loading metal, carrier and additive research, carbon deposition behavior research and reaction kinetics research, etc. According to thermodynamic calculations, it can be known that the reaction is a strong endothermic reaction, at least above 600°C to generate synthesis gas, and to achieve a relatively high conversion rate of CH ₄ and CO ₂ above 850°C. Therefore, traditional catalysts catalyze methane drying The gas reforming reaction is an energy-intensive reaction. In a high-temperature environment, the carrier of the catalyst needs to use a material with stable chemical and physical properties at high temperature, and the form of its interaction with the active component also has an important impact on the catalytic activity of the catalyst. For the catalytic reforming reaction of methane, the metals supported on the catalyst, that is, the active components are mostly transition metals of Group VIII, and nickel metal is the most commonly used, but this type of catalyst has a big drawback, which is very easy to Carbon deposition causes catalyst deactivation, thereby terminating the reaction. Usually, some alkaline earth metal or rare earth metal oxides are added as additives to reduce carbon deposition. Using noble metals as active components can effectively inhibit carbon deposition, but the use of noble metals causes Catalyst costs have risen dramatically. CH ₄ and CO ₂ are substances with high carbon content, and the reaction between the two will inevitably cause greater carbon deposition and deactivation problems.

At present, studies have shown that the conversion of _CH4 and _CO2 at low temperature can be realized by using the characteristics of plasma, but due to the characteristics of plasma itself, this process has poor selectivity for products and limited conversion rate.

The traditional methane dry gas reforming process has the following disadvantages: the reaction can only occur at high temperature, which requires high energy input, resulting in an increase in the cost of the _CO2 chemical conversion process; the requirements for the catalyst are very high, and the carrier is required to have a high Thermal stability, but also to overcome the reaction termination caused by carbon deposition.

The prevalent plasma-catalyzed chemical conversion of _CH4 and _CO2 has the following disadvantages: by plasma reactors operated at atmospheric pressure, product selectivity is poor, synthesis gas yield is low and feedstock gas conversion is low, some utilize radio frequency or microwave The discharge-promoted conversion reactor needs to be operated at a lower negative pressure, which not only increases the requirements for equipment but also affects the throughput of the reactor, which is not conducive to industrial scale-up.

Contents of the invention

The purpose of the present invention is to overcome the disadvantages of high energy consumption and easy carbon deposition in the traditional methane dry gas reforming process, as well as the disadvantages of poor product selectivity and low conversion rate of the plasma itself; Realize a high chemical conversion rate of CH ₄ and CO ₂ ; use a set of reaction-separation-separation cycle process to realize the production of H ₂ and CO at low temperature.

In order to achieve the above object, the technical solution proposed by the present invention is:

A method and device for preparing H _and CO by co-conversion of CH and _CO at low temperature, characterized in that _the method is carried out as follows:

(1) The reaction gas CH ₄ is premixed with CO ₂ ;

(2) The premixed mixed gas enters the plasma reactor, such as the axial dielectric barrier discharge reactor, and chemical conversion occurs at low temperature and atmospheric pressure; in addition to CO and H ₂ , there is unreacted CH ₄ in the product gas And CO ₂ gas, in addition to the reaction to generate synthesis gas, a small amount of high-carbon hydrocarbons are produced, such as C ₂ H ₆ , C ₂ H ₄ , C ₃ H ₈ , etc.;

(3) The mixed gas flowing out from the plasma reactor passes through a _H2 separator, such as a polysulfone membrane hydrogen separator, with an operating pressure difference of 7 to 8 atm and an operating temperature of normal temperature, and most of the _H2 is separated;

(4) Step (3) The remaining gas after the _H2 is separated enters the CO separator, such as a pressure swing adsorption tower utilizing a copper-based CO chemical adsorbent, the operating pressure difference is 1 atm, and the operating temperature is normal temperature for CO separation; Almost all the CO, most of the unreacted CO ₂ and a small amount of CH ₄ separated from CO enter the high-temperature carbon furnace, such as a fluidized bed combustion furnace, and react with excess carbon to generate CO gas;

(5) Step (4) CO is separated and the remaining gas is almost all CH ₄ , and the remaining CH ₄ is returned to the plasma reactor for recycling, and the next reaction-separation-separation cycle is carried out together with the raw material gas, thereby continuously obtaining _H2 and CO.

In step (1) of the above method, the molar ratio of feed gas CH ₄ to CO ₂ is in the range of 1:1 to 4:1.

In the above method, the operating temperature of the whole cycle process is a low temperature of 20° C. to 200° C., and the operating pressure can be realized within the range of 1 atm to 10 atm.

The present invention provides a kind of CH under low temperature _and CO _Co- transformation prepares the device of H _and CO, said device comprises the premixer (1) that is arranged before the entrance of plasma reactor, low-temperature plasma reactor (2) ), the _H2 separator (3) that is arranged at the low-temperature plasma reactor outlet, the CO separator (4) that is arranged at the _H2 separator outlet, the high-temperature carbon furnace (5) that is arranged at the CO separator outlet; The gas outlet of the mixer (1) is connected with the inlet of the plasma reactor, the outlet of the low-temperature plasma reactor (2) is connected with the inlet of the _H2 separator (3), and the _H2 separator (3) has an _H2 separated gas outlet, H ₂ The unseparated gas outlet of the separator (3) is connected to the gas inlet of the CO separator (4), the separated gas outlet of the CO separator is connected to the air inlet of the high-temperature carbon furnace (5), the unseparated gas outlet of the CO separator is connected to the premixed The device inlet is connected.

The invention provides a method for co-converting _CH4 and _CO2 to prepare _H2 and CO at low temperature, which can be realized by circulating reaction in a single set of reaction-separation-separation equipment.

In steps (3) and (4) of the above method, the mixed gas flowing out from the plasma reactor passes through the CO separator and the _H separator respectively, and the order of the two separators can be interchanged. The sequence of the two separators of CO separator and _H2 separator in the corresponding device is exchanged.

The present invention also provides a method for co-converting CH ₄ and CO ₂ to prepare H ₂ and CO at low temperature. The method is realized through reaction-separation-separation-reaction-separation-separation in two or more sets of equipment.

The present invention provides another kind of low temperature under _CH4 and _CO2 co-convert and prepare _H2 and CO device, described device comprises the first gas premixer (1-a), the first low temperature plasma reactor (2- a), the first _H2 separator (3-a), the first CO separator (4-a), the first high temperature carbon furnace (5-a), the second gas premixer (1-b), the first Two plasma reactors (2-b), the second _H2 separator (3-b), the second CO separator (4-b), the second high temperature carbon furnace (5-b); the first gas premixer The outlet of (1-a) links to each other with the first plasma reactor (2-a) inlet, and the outlet of the first low temperature plasma reactor (2-a) links to each other with the first _H separator (3-a), The first _H2 separator (3-a) has a separated gas outlet, the unseparated gas outlet of the first _H2 separator (3-a) is connected to the inlet of the first CO separator (4-a), and the first CO separator The separated gas outlet of the device (4-a) is connected with the high-temperature carbon furnace (5-a) inlet; the unseparated gas outlet of the first CO separator (4-a) and the second gas premixer (1-b) The inlet is connected, the outlet of the second gas premixer (1-b) is connected with the gas inlet of the second plasma reactor (2-b), the gas outlet of the second low temperature plasma reactor (2-b) is connected with the second The _H2 separator (3-b) inlet is connected, the second _H2 separator (3-b) has a separated gas outlet, and the unseparated gas outlet of the second _H2 separator (3-b) is connected to the second CO separator The inlet of (4-b), the outlet of the separated gas of the second CO separator (4-b) is connected with the gas inlet of the second high-temperature carbon furnace (5-b), and the second CO separator (4-b) does not separate the gas The outlet is connected to the gas inlet of the first gas premixer (1-a). As mentioned above, the high conversion of CH ₄ and CO ₂ is realized, and H ₂ and CO are obtained by using the method of reaction-separation-separation-reaction-separation-separation such cycle.

Compared with the prior art, the present invention has the following advantages and outstanding effects:

① It avoids the high energy consumption required to realize methane dry gas reforming by conventional means, and the catalyst deactivation caused by carbon deposition, which leads to the termination of the reaction.

②Effective use of the special means of plasma to achieve high-efficiency conversion of CH ₄ and CO ₂ at low temperature, effectively reducing energy consumption.

③It overcomes the disadvantages of low conversion rate and poor product selectivity when using low-temperature plasma catalytic conversion of _CH4 and _CO2 , and realizes the preparation of _H2 and CO at low temperature by using the cycle process of reaction-separation-separation.

Description of drawings

Fig. 1 is the flowchart of the method of the present invention.

Fig. 2 is a flowchart of another method of the present invention.

Fig. 3 is a schematic diagram of the device of the present invention. Among them, 1. Gas premixer; 2. Low temperature plasma reactor; 3. H ₂ separator; 4. CO separator; 5. High temperature carbon furnace; A. Plasma catalytic conversion product mixed gas; B, H ₂ ; C, mixed gas after _H2 separation; D, CO gas; E, mixed gas after CO separation; G, raw material gas

Fig. 4 is a schematic diagram of another method device of the present invention. In the figure: 1-a, the first gas premixer; 2-a, the first low-temperature plasma reactor; 3-a, the first _H2 separator; 4-a, the first CO separator; 5-a , the first high-temperature carbon furnace; 1-b, the second gas premixer; 2-b, the second low-temperature plasma reactor; 3-b, the second _H2 separator; 4-b, the second CO separator ; 5-b, the second high-temperature carbon furnace; A-1, the mixed gas of plasma catalytic conversion products; B-1, H ₂ ; C-1, the mixed gas after H ₂ separation; D-1, CO gas; E -1, the mixed gas after CO separation; A-2, the mixed gas of plasma catalytic conversion product; B-2, H ₂ ; C-2, the mixed gas after H ₂ separation; D-2, CO gas; E- 2. Mixed gas after CO separation; F, supply raw material gas; G, raw material gas

Detailed ways

The present invention will be further described in detail below in conjunction with the accompanying drawings.

Fig. 1 is the flowchart of the method of the present invention. Fig. 3 is a schematic diagram of the device of the present invention. In Fig. 3, 1, gas premixer; 2, low-temperature plasma reactor; 3, _H separator; 4, CO separator; 5, high-temperature carbon furnace; A, plasma catalytic conversion product mixed gas; B, H ₂ ; C, mixed gas after H ₂ separation; D, CO gas; E, mixed gas after CO separation; G, raw material gas. The gas outlet of the gas premixer (1) is connected to the inlet of the plasma reactor, the outlet of the low-temperature plasma reactor (2) is connected to the inlet of the _H2 separator (3), and the _H2 separator (3) has an _H2 separated gas outlet , H _The unseparated gas outlet of the separator (3) is connected with the gas inlet of the CO separator (4), the separated gas outlet of the CO separator is connected with the air inlet of the high-temperature carbon furnace (5), and the unseparated gas outlet of the CO separator and The inlet of the premixer is connected.

The mixed gas of _CH4 and _CO2 with a molar ratio of 1:1 to 4:1 enters the low-temperature plasma reactor 2, and _CH4 and _CO2 are ionized to form a plasma atmosphere, which contains a large number of active groups and metastable State ions, so that the two have a chemical reaction, but the conversion rate of the two is limited, and due to the non-directional combination of active groups, the product gas contains not only CO and H ₂ but also a small amount of C ₂ H ₆ , C ₂ H ₄ , C ₃ H ₈ and other carbon hydrocarbons, the mixed gas A enters the H ₂ separator 3, and most of the H ₂ is separated to produce hydrogen B, and the remaining mixed gas C enters the CO after passing through the H ₂ separator Separator 4, almost all CO and CO ₂ and a small amount of CH ₄ and H ₂ are separated, and the separated gas enters the CO gas D produced by burning in the high-temperature carbon furnace 5, and the main component of the separated gas E is CH ₄ , it enters the premixer 1 together with the raw material supply gas G, and returns to the low temperature plasma reactor 2 after premixing to carry out the circulation reaction.

Fig. 2 is a flowchart of another method of the present invention. Fig. 4 is a schematic diagram of another method device of the present invention. Among Fig. 4: 1-a, the first gas premixer; 2-a, the first low temperature plasma reactor; 3-a, the first _H2 separator; 4-a, the first CO separator; 5- a, the first high-temperature carbon furnace; 1-b, the second gas premixer; 2-b, the second low-temperature plasma reactor; 3-b, the second _H2 separator; 4-b, the second CO separation 5-b, the second high-temperature carbon furnace; A-1, the mixed gas of plasma catalytic conversion products; B-1, H ₂ ; C-1, the mixed gas after H ₂ separation; D-1, CO gas; E-1, mixed gas after CO separation; A-2, mixed gas of plasma catalytic conversion product; B-2, H ₂ ; C-2, mixed gas after H ₂ separation; D-2, CO gas; E -2. Mixed gas after CO separation; F. Supply raw material gas; G. Raw material gas. The outlet of the first gas premixer (1-a) is connected with the inlet of the first plasma reactor (2-a), and the outlet of the first low temperature plasma reactor (2-a) is connected with the first _H separator ( 3-a) are connected, the first _H2 separator (3-a) has a separated gas outlet, the unseparated gas outlet of the first _H2 separator (3-a) is connected to the first CO separator (4-a) inlet Connected, the separated gas outlet of the first CO separator (4-a) is connected with the inlet of the high-temperature carbon furnace (5-a); the unseparated gas outlet of the first CO separator (4-a) is connected with the second gas premixer The inlet of (1-b) links to each other, and the outlet of the second gas premixer (1-b) links to each other with the second plasma reactor (2-b) gas inlet, and the second low temperature plasma reactor (2-b) The gas outlet of the second _H2 separator (3-b) is connected to the inlet, the second _H2 separator (3-b) has a separated gas outlet, and the unseparated gas outlet of the second _H2 separator (3-b) Connect the inlet of the second CO separator (4-b), the outlet of the second CO separator (4-b) separated gas is connected with the second high temperature carbon furnace (5-b) gas inlet, the second CO separator (4 -b) The unseparated gas outlet is connected to the gas inlet of the first gas premixer (1-a).

The mixed gas of _CH4 and _CO2 with a molar ratio of 1:1 to 4:1 enters the low-temperature plasma reactor 2-a, and _CH4 and _CO2 are ionized to form a plasma atmosphere, which contains a large number of active groups and Metastable ions, so that the two have a chemical reaction, but the conversion rate of the two is limited, and due to the non-directional combination of active groups, the product gas contains not only CO and H ₂ but also a small amount of C ₂ H ₆ , C ₂ H ₄ , C ₃ H ₈ and other carbon hydrocarbons, the mixed gas A-1 enters the H ₂ separator 3-a, and most of the H ₂ is separated to produce hydrogen B-1, which is separated by H ₂ The remaining mixed gas C-1 enters the CO separator 4-a, almost all CO and CO ₂ and a small amount of CH ₄ and H ₂ are separated, and the separated gas enters the high-temperature carbon furnace 5-a to burn the produced CO gas D-1, the main component of the separated remaining gas E-1 is CH ₄ , which enters the premixer 1-b together with the raw material supply gas F, and enters the low temperature plasma reactor 2-b after premixing Continue the reaction in the middle, CH ₄ and CO ₂ are ionized to react, the generated mixed gas A-2 enters the H ₂ separator 3-b, and most of the H ₂ is separated, thereby producing hydrogen B-2, After passing through the _H2 separator, the remaining mixed gas C-2 enters the CO separator 4-b, almost all CO and _CO2 and a small amount of _CH4 and _H2 are separated, and the separated gas enters the high-temperature carbon furnace 5-b for burning The CO gas D-2 produced by burning, the main component of the remaining gas E-2 is CH ₄ , which enters the premixer 1-a together with the raw material supply gas G, and returns to the low-temperature plasma after premixing The cyclic reaction is carried out in the reactor 2-a.

Example 1

_CH4 and _CO2 are fed at a molar ratio of 1:1, and the operating pressure of the reactor is 7 atm. In the low-temperature plasma reactor, the conversion rate of _CH4 reaches 50%, and the conversion rate of _CO2 reaches 27%. The selection of CO The selectivity of H ₂ is about 60%, the selectivity of H 2 is about 80%, and the remaining gas is high-carbon hydrocarbons such as C ₂ H ₆ , C ₂ H ₄ , and C ₃ H ₈ . This mixed gas enters the H ₂ separator together, and most of them are _H2 is separated, the purity reaches 90%-95%, and the remaining gas enters the CO separator, almost all CO and part of _CO2 are separated, and a small amount of _CH4 and the remaining _H2 are also separated , and they enter the high-temperature carbon furnace together for burning to obtain CO gas with a purity of more than 95%. Most of the remaining gas after passing through the CO separator is CH ₄ , and a small part is CO ₂ . They return together with the raw material gas. In the low-temperature plasma reactor, the next reaction-separation-separation process is carried out.

Example 2

_CH4 and _CO2 are fed in a molar ratio of 4:1, and the operating pressure of the reactor is 7 atm. In the low-temperature plasma reactor, the conversion rate of _CH4 reaches 14%, and the conversion rate of _CO2 reaches 42%. The selection of CO The selectivity of _H2 is about 80%, _the selectivity of H2 is about 60%, and the remaining gas is high-carbon hydrocarbons such as _C2H6 , _C2H4 , _C3H8 , _etc. This mixed gas enters the _H2 separator together, and _most of them are _H2 is separated, the purity reaches 90%-95%, and the remaining gas enters the CO separator, all CO and all _CO2 are separated, and a small amount of _CH4 and the remaining _H2 are also separated, They enter the high-temperature carbon furnace together for burning to obtain CO gas with a purity of more than 95%. Almost all of the remaining gas after passing through the CO separator is CH ₄ , and they return to the low-temperature plasma reactor together with the raw material gas. Carry out the next reaction-separation-separation process.

Example 3

_CH4 and _CO2 are fed in a molar ratio of 2:1, and the reactor operating pressure is 7atm. In the low-temperature plasma reactor, the conversion rate of _CH4 reaches 22%, and the conversion rate of _CO2 reaches 32%. The selection of CO The selectivity of _{H2 is} about 64%, _{the selectivity} of H2 is about 70%, and the rest of the gas is _C2H6 , _C2H4 , _C3H8 and other high-carbon hydrocarbons. This mixed gas enters the _H2 separator together, and most of them are _H2 is separated, the purity reaches 90%-95%, and the remaining gas enters the CO separator, all CO and all _CO2 are separated, and a small amount of _CH4 and the remaining _H2 are also separated, They enter the high-temperature carbon furnace together for burning to obtain CO gas with a purity of more than 95%. Almost all of the remaining gas after passing through the CO separator is CH ₄ , and they return to the low-temperature plasma reactor together with the raw material gas. Carry out the next reaction-separation-separation process.

Claims (8)

_1.CH and CO _Co- conversion to prepare H The method for _CO and CO, characterized in that the method is carried out as follows: (1) The reaction gas CH ₄ and CO ₂ enter the gas premixer for premixing; (2) The premixed mixed gas enters the plasma reactor for reaction; (3) The mixed gas flowing out from the plasma reactor passes through the H ₂ separator to separate H ₂ ; (4) In the step (3), after the _H2 is separated, the remaining gas enters the CO separator for CO separation; the separated gas passes through the high-temperature carbon furnace, and reacts with the excess carbon of the high-temperature carbon furnace to generate the target CO gas; (5) Step (4) CO is separated and the remaining gas is almost all CH ₄ ; the remaining CH ₄ is pre-mixed with the raw material gas and returned to the plasma reactor for recycling, and the next reaction is carried out together with the new raw material gas- Separation-separation cycle, so as to continuously obtain _H2 and CO; The molar ratio of the feed gas _CH4 to _CO2 is 1:1 to 4:1; The operating temperature of the whole process is 20° C. to 200° C., and the operating pressure is 1 atm to 10 atm. 2. CH according to claim 1 ₄ and CO ₂ co-converting to prepare H ₂ and CO method, characterized in that, the plasma reactor is a coaxial dielectric barrier discharge reactor. 3. CH according to claim 1 ₄ and CO ₂ co-conversion method for preparing H ₂ and CO, characterized in that, the H ₂ separator is a polysulfone membrane hydrogen separator. 4. The method for co-conversion of _CH4 and _CO2 to produce _H2 and CO according to claim 1, characterized in that the CO separator is a pressure swing adsorption tower using a copper-based CO chemical adsorbent. 5. The method for preparing H ₂ and CO by co-conversion of CH ₄ and CO ₂ according to claim 1, characterized in that, the high-temperature carbon furnace is a fluidized bed combustion furnace. 6. The method for preparing _H2 and CO by co-conversion of _CH4 and _CO2 according to claim 1, characterized in that the method comprises multiple processes of reaction-separation-separation-reaction-separation-separation. 7. _CH and CO co _- conversion to prepare H _and CO device, characterized in that the device comprises a gas premixer (1), a low temperature plasma reactor (2), _H separator (3), CO separator (4), high temperature carbon furnace (5); The gas outlet of the gas premixer (1) is connected to the inlet of the low temperature plasma reactor, the outlet of the low temperature plasma reactor (2) is connected to the inlet of the _H2 separator (3), and the _H2 separator (3) has _H2 separated gas Outlet, the unseparated gas outlet of the _H2 separator (3) is connected to the gas inlet of the CO separator (4), the separated gas outlet of the CO separator is connected to the air inlet of the high-temperature carbon furnace (5), and the unseparated gas outlet of the CO separator Connect to gas premixer inlet. 8. _CH and CO _co -conversion to prepare H _and CO device, characterized in that the device comprises the first gas premixer (1-a), the first low-temperature plasma reactor (2-a), The first _H2 separator (3-a), the first CO separator (4-a), the first high temperature carbon furnace (5-a), the second gas premixer (1-b), the second low temperature plasma body reactor (2-b), the second _H separator (3-b), the second CO separator (4-b), the second high-temperature carbon furnace (5-b); The outlet of the first gas premixer (1-a) is connected with the inlet of the first low-temperature plasma reactor (2-a), and the outlet of the first low-temperature plasma reactor (2-a) is connected with the first _H2 separator (3-a) is connected, the first _H2 separator (3-a) has a separated gas outlet, and the unseparated gas outlet of the first _H2 separator (3-a) is connected to the first CO separator (4-a) The inlet is connected, and the separated gas outlet of the first CO separator (4-a) is connected with the inlet of the first high-temperature carbon furnace (5-a); the unseparated gas outlet of the first CO separator (4-a) is connected with the second gas The inlet of the premixer (1-b) is connected, the outlet of the second gas premixer (1-b) is connected with the gas inlet of the second low temperature plasma reactor (2-b), and the second low temperature plasma reactor ( The gas outlet of 2-b) is connected with the second _H2 separator (3-b) inlet, and the second _H2 separator (3-b) has a separated gas outlet, and the second _H2 separator (3-b) The unseparated gas outlet is connected to the inlet of the second CO separator (4-b), and the outlet of the separated gas of the second CO separator (4-b) is connected to the gas inlet of the second high-temperature carbon furnace (5-b), and the second CO The unseparated gas outlet of the separator (4-b) is connected to the gas inlet of the first gas premixer (1-a).

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