A method for carrying out a water-gas shift reaction

Abstract

The application discloses a method for carrying out water-gas shift reaction, and belongs to the technical field of carbon monoxide conversion and hydrogen production. The method is to divide reaction raw materials required by water-gas shift reaction into two parts of gas phase and liquid phase, the gas phase reaction raw materials contain carbon monoxide and water vapor, and the liquid phase reaction raw materials contain water. The gas phase reaction raw materials and the liquid phase reaction raw materials are respectively sent into a reactor provided with a catalyst through two paths. The two paths of reaction raw materials are contacted in the reactor and water-gas shift reaction occurs. Under the condition that the input amount of liquid water is appropriate, the water-gas shift reaction can be carried out in a near isothermal state. The water in the liquid phase reaction raw materials does not need to be pre-gasified and is directly sent into the reactor in a liquid state, so that the energy consumption required for conveying the corresponding amount of water vapor is saved. Meanwhile, the molar ratio of water to carbon monoxide in the reactor can be kept at a high level, so that the carbon monoxide is fully converted. The above method is suitable for the gas phase reaction raw materials with a carbon monoxide molar fraction of greater than or equal to 10%.

Description

TECHNICAL FIELD

[0001] The present application relates to a method for carrying out water-gas shift reaction, belonging to the technical field of carbon monoxide conversion and hydrogen production. BACKGROUND

[0002] Water-gas shift refers to the reaction of carbon monoxide and water vapor into hydrogen and carbon dioxide under the action of catalyst, and its reaction formula is: CO + H2O → H2+ CO2. The reaction is used for hydrogen production and adjusting the ratio of hydrogen to carbon monoxide in synthesis gas in industrial production. Existing industrial devices all use adiabatic reactors to carry out gas-solid two-phase reaction at 200-500℃. Among them, the gas phase is the reactant containing carbon monoxide and water vapor, and the solid phase is the catalyst. The gas-solid two-phase water-gas shift is a strong exothermic reaction, and its reaction heat is about 40 kJ / mol. The reaction heat accumulates in the adiabatic reactor, which will greatly increase the temperature. Too high temperature is not conducive to the operation of the device, and will cause the deactivation of the catalyst. Therefore, the industrial production usually adopts a staged multi-stage shift process; before carrying out the next stage of shift reaction, the temperature of the reactant is lowered in advance by heat exchange. Patent documents CN1280180C, CN102001623B, CN102971252B, CN103508416B, CN102992264B, CN103449365B, CN104340958B, CN104098069B, CN105084313B and the like provide specific examples of the above process.

[0003] Compared with the adiabatic water-gas shift reaction process, isothermal water-gas shift can simplify the reaction process. Patent document CN1204038C discloses a carbon monoxide isothermal sulfur-tolerant shift process. The process uses a column tube type or a built-in heat exchange coil reactor to remove the reaction heat from the catalyst bed layer by a heat transfer medium, so as to ensure that the bed layer temperature is close to isothermal. Patent document CN104085855B discloses a dry gas detoxification device outside reverse humidification isothermal carbon monoxide shift process. The process sets a heat exchange curved pipe in the reactor. Patent document CN110550602A discloses a high-concentration carbon monoxide controllable semi-isothermal shift process for carbonyl synthesis. The reactor used in the process is divided into an isothermal reaction zone and an adiabatic reaction zone; a heat exchange column tube is arranged in the isothermal reaction zone and is connected from bottom to top.

[0004] Increasing the water vapor content in the gas phase reactant can promote the progress of the water-gas shift reaction. However, the transportation of water vapor is a high energy consumption process, and blindly increasing the water vapor content will greatly increase the operating cost, so it is not feasible.

[0005] If hydrogen can be removed by membrane separation device at the same time of water gas shift reaction, not only the carbon monoxide conversion rate can be improved, but also high purity hydrogen can be obtained directly. Patent document CN102482079B discloses a method for preparing dilute hydrogen gas mixture. The method uses a membrane reactor to carry out water gas shift reaction; the used membrane is a hydrogen permeable membrane with hydrogen permeation selectivity of at least 30 relative to carbon dioxide. Patent document CN103359688B discloses a method for preparing hydrogen with different purity grades by using coke oven gas. The method uses a membrane reactor to separate hydrogen-containing product while carrying out water gas shift reaction. SUMMARY

[0006] The present application aims to provide a method for efficiently and controllably carrying out water gas shift reaction to overcome the defects of the prior art. In order to achieve this goal, the present application adopts the following technical solutions:

[0007] The reaction raw materials required for water gas shift reaction are divided into gas phase and liquid phase, the gas phase reaction raw materials contain carbon monoxide and water vapor, and the liquid phase reaction raw materials contain water. The gas phase reaction raw materials and the liquid phase reaction raw materials are sent into the reactor containing catalyst through two routes respectively. The two reaction raw materials contact and carry out water gas shift reaction in the reactor.

[0008] Specifically, in the reaction process, the molar ratio of water vapor to carbon monoxide in the gas phase reaction raw materials is ≥0.1, preferably ≥0.15, and more preferably ≥0.2; the molar ratio of water in the liquid phase reaction raw materials to carbon monoxide in the gas phase reaction raw materials is ≥0.5, preferably ≥0.55, and more preferably ≥0.6; the molar ratio of the sum of water vapor in the gas phase reaction raw materials and water in the liquid phase reaction raw materials to carbon monoxide in the gas phase reaction raw materials is ≥1, preferably ≥1.1, and more preferably ≥1.2.

[0009] In the method provided by the present application, the molar fraction of carbon monoxide in the gas phase reaction raw materials is ≥10%, preferably ≥30%, and more preferably ≥50%.

[0010] In the method provided by the present application, the temperature of the gas phase reaction raw materials when entering the reactor is 100-500℃, preferably 150-450℃, and more preferably 250-350℃.

[0011] In the method provided by the present application, the temperature of the liquid phase reaction raw materials when entering the reactor is 5-180℃, preferably 10-150℃, and more preferably 20-120℃.

[0012] In the method provided by the present application, the reaction pressure is 1-20MPa, preferably 2-10MPa, and more preferably 3-8MPa.

[0013] In the method provided by the present application, the standard state volume space velocity of the gas phase reaction raw materials is 100-30000h－1 , preferably 500-20000h －1 , more preferably 1000-10000h －1 .

[0014] According to the need, the technical solution provided by the present application can be further optimized, and the molar ratio of water in the liquid phase reaction raw material to carbon monoxide in the gas phase reaction raw material is ≤0.9.

[0015] According to the need, the technical solution provided by the present application can be further optimized, and the water gas shift reaction is carried out using a liquid phase reaction raw material containing only water.

[0016] According to the need, the technical solution provided by the present application can be further optimized, and the catalyst with a particle size of 1-200mm is selected and loaded in the reactor for the water gas shift reaction.

[0017] The method for carrying out the water gas shift reaction provided by the present application is completely different from the prior art and understanding. The present application has the following beneficial effects:

[0018] First, the liquid water as the reaction raw material absorbs the heat released by the water gas shift reaction and then vaporizes, so that the reaction temperature is kept stable. This overcomes the problem of severe temperature rise in the gas-solid two-phase water gas shift reaction using an adiabatic reactor, and the full conversion of carbon monoxide can be realized in one reaction unit. Since the liquid water is in direct contact with the catalyst, the heat transfer efficiency is much higher than that of the isothermal water gas shift reaction device with heat exchange tubes arranged in the catalyst bed. Under the condition that the input amount of liquid water is appropriate, the water gas shift reaction can be carried out in a nearly isothermal state. This greatly simplifies the reaction device and greatly saves the operation cost.

[0019] Secondly, the water in the liquid phase reaction raw material does not need to be pre-vaporized and is directly sent into the reactor in liquid state, so the energy consumption required for transporting the corresponding amount of water vapor is saved. At the same time, the molar ratio of water to carbon monoxide in the reactor can be kept at a high level, so that the reaction can be promoted by simply increasing the water amount without increasing the energy consumption, and the full conversion of carbon monoxide is promoted. Compared with the method of using a membrane reactor to improve the carbon monoxide conversion rate, the method provided by the present application does not need to configure additional membrane components, and does not bring difficulties to the manufacturing, operation and maintenance of the reaction device. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 is the reactor outlet temperature change curve under the condition that the molar ratio of water in the liquid phase reaction raw material to carbon monoxide in the gas phase reaction raw material is different when the molar ratio of hydrogen to carbon monoxide in the gas phase reaction raw material is 0, the molar ratio of water vapor to carbon monoxide is 0, 0.1, 0.5, 1.

[0021] Figure 2is the reactor outlet temperature change curve when the molar ratio of hydrogen to carbon monoxide in the gas phase reaction raw material is 0.5, the molar ratio of water vapor to carbon monoxide is 0, 0.1, 0.5, 1, and the molar ratio of water to carbon monoxide in the gas phase reaction raw material is different in the liquid phase reaction raw material.

[0022] Figure 3 is the reactor outlet temperature change curve when the molar ratio of hydrogen to carbon monoxide in the gas phase reaction raw material is 1, the molar ratio of water vapor to carbon monoxide is 0, 0.1, 0.5, 1, and the molar ratio of water to carbon monoxide in the gas phase reaction raw material is different in the liquid phase reaction raw material.

[0023] Figure 4 is the reactor outlet temperature change curve when the molar ratio of hydrogen to carbon monoxide in the gas phase reaction raw material is 10, the molar ratio of water vapor to carbon monoxide is 0, 0.1, 0.5, 1, and the molar ratio of water to carbon monoxide in the gas phase reaction raw material is different in the liquid phase reaction raw material.

[0024] Figure 5 is the carbon monoxide equilibrium conversion rate change curve when the molar ratio of hydrogen to carbon monoxide in the gas phase reaction raw material is 0, the molar ratio of water vapor to carbon monoxide is 0, 0.1, 0.5, 1, and the molar ratio of water to carbon monoxide in the gas phase reaction raw material is different in the liquid phase reaction raw material.

[0025] Figure 6 is the carbon monoxide equilibrium conversion rate change curve when the molar ratio of hydrogen to carbon monoxide in the gas phase reaction raw material is 0.5, the molar ratio of water vapor to carbon monoxide is 0, 0.1, 0.5, 1, and the molar ratio of water to carbon monoxide in the gas phase reaction raw material is different in the liquid phase reaction raw material.

[0026] Figure 7 is the carbon monoxide equilibrium conversion rate change curve when the molar ratio of hydrogen to carbon monoxide in the gas phase reaction raw material is 1, the molar ratio of water vapor to carbon monoxide is 0, 0.1, 0.5, 1, and the molar ratio of water to carbon monoxide in the gas phase reaction raw material is different in the liquid phase reaction raw material.

[0027] Figure 8 is the carbon monoxide equilibrium conversion rate change curve when the molar ratio of hydrogen to carbon monoxide in the gas phase reaction raw material is 10, the molar ratio of water vapor to carbon monoxide is 0, 0.1, 0.5, 1, and the molar ratio of water to carbon monoxide in the gas phase reaction raw material is different in the liquid phase reaction raw material. DETAILED DESCRIPTION

[0028] To illustrate the present application, the reaction process is simulated using chemical process simulation software DWSIM (V6.5.4). The simulation obtains the specific values of the reactor outlet temperature and the equilibrium conversion of carbon monoxide under different reaction conditions when the adiabatic water-gas shift reaction reaches thermodynamic equilibrium. The above simulation does not involve the operation details of the reaction and the performance of the catalyst. The reaction conditions selected for simulation are as follows:

[0029] The reaction raw materials are divided into gas phase and liquid phase and sent into the reactor respectively;

[0030] The gas phase reaction raw materials may contain water vapor and hydrogen in addition to carbon monoxide, the temperature is 300℃, and the pressure is 4MPa;

[0031] The liquid phase reaction raw materials only contain water, the temperature is 20℃, and the pressure is 4MPa;

[0032] The reactor is an adiabatic equilibrium reactor.

[0033] The variables investigated in the simulation include:

[0034] The molar ratio of hydrogen to carbon monoxide in the gas phase reaction raw materials is selected as 0, 0.5, 1, and 10;

[0035] The molar ratio of water vapor to carbon monoxide in the gas phase reaction raw materials is selected as 0, 0.1, 0.5, and 1;

[0036] The molar ratio of water in the liquid phase reaction raw materials to carbon monoxide in the gas phase reaction raw materials is selected as 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, and 1.

[0037] The simulation results are shown in the accompanying drawings. Figures 1-8 In the drawings, ■, ●, ▲, and ▼ correspond to the cases where the molar ratio of water vapor to carbon monoxide in the gas phase reaction raw materials is 0, 0.1, 0.5, and 1, respectively.

[0038] In actual operation of industrial production, the composition of the raw materials for water-gas shift varies greatly. In addition to carbon monoxide, water vapor, and hydrogen, the gas phase reaction raw materials may also contain a small amount of carbon dioxide, nitrogen, argon, hydrogen sulfide, etc. In order to simplify the simulation process, these components are ignored. This does not affect the reliability and representativeness of the simulation results.

[0039] From the above simulation results, it can be seen that: Figures 1-8As can be seen from the results, when the adiabatic water gas shift reaction reaches thermodynamic equilibrium under the condition that the molar ratio of water vapor to carbon monoxide in the gas phase reaction raw material is less than 0.1, the reactor outlet temperature is much lower than the temperature of the gas phase reaction raw material (for example, lower than 200°C), or the equilibrium conversion rate of carbon monoxide is very low (for example, lower than 70%). Too low temperature is not conducive to the rapid progress of the water gas shift reaction. Therefore, such conditions cannot meet the needs of the water gas shift reaction.

[0040] From Figures 1-8 As can be seen from the results, only when the water content in the liquid phase reaction raw material is appropriate can ideal reaction results be obtained. Specifically, the molar ratio of water in the liquid phase reaction raw material to carbon monoxide in the gas phase reaction raw material should not be less than 0.5, and the molar ratio of the sum of water vapor in the gas phase reaction raw material and water in the liquid phase reaction raw material to carbon monoxide in the gas phase reaction raw material should not be less than 1. At the same time, too high water content in the liquid phase reaction raw material will result in too low reactor outlet temperature. Therefore, the molar ratio of water in the liquid phase reaction raw material to carbon monoxide in the gas phase reaction raw material should not be higher than 0.9.

[0041] The molar ratio of hydrogen to carbon monoxide in the selected gas phase reaction raw material was 0, 0.5, 1 and 10, respectively, and the molar ratio of water vapor to carbon monoxide was 0, 0.1, 0.5 and 1, respectively. The molar fraction of carbon monoxide in the gas phase reaction raw material is shown in Table 1:

[0042] Table 1

[0043] [H2O / CO = 0] [H2O / CO = 0.1] [H2O / CO = 0.5] [H2O / CO = 1] [H2 / CO = 0] 100％ 91％ 67％ 50％ [H2 / CO = 0.5] 67％ 63％ 50％ 40％ [H2 / CO = 1] 50％ 48％ 40％ 33％ [H2 / CO = 10] 9％ 9％ 9％ 8％

[0044] From Figures 1-8 As can be seen from the results and Table 1, when the molar fraction of carbon monoxide in the gas phase reaction raw material is less than 10%, it is impossible to obtain a carbon monoxide equilibrium conversion rate higher than 90%.

[0045] It should be noted that the present application is not limited to the reaction conditions described in the process simulation. The equilibrium reactor model is selected to obtain theoretical reaction results. These simulation results based on thermodynamic analysis can fully demonstrate the advantages of the method provided by the present application. In actual operation, by selecting a catalyst with high activity and high stability, reaction results close to the above theoretical values can be obtained.

[0046] The following examples will further illustrate the present application. However, the present application is not limited to the following examples.

[0047] Example 1

[0048] An adiabatic fixed bed reactor was used to carry out the water gas shift reaction. The reactor adopted a five-stage heat compensation and three-layer heat insulation structure to achieve adiabaticity. The reaction raw material was divided into two routes, gas phase and liquid phase, and was sent into the reactor respectively.

[0049] The water gas shift catalyst with platinum as the active component was sieved and 5-10 mesh (2-4 mm) particles were charged into the adiabatic fixed bed reactor described above. After the reactor was closed, the air in the reactor was replaced with nitrogen and tested for leaks, the gaseous and liquid phase reaction materials were introduced. The reaction pressure was 5 MPa. The gaseous phase reaction material was a mixture of carbon monoxide and water vapor, and the molar ratio of water vapor to carbon monoxide was 0.2. The gaseous phase reaction material was preheated to 400°C and then introduced into the reactor, and the standard state volumetric space velocity was 10000 h －1 The liquid phase reaction material was water, and the temperature was 25°C. The molar ratio of the gaseous phase reaction material to the liquid phase reaction material was 1.5. Under the reaction conditions described above, the molar ratio of water in the liquid phase reaction material to carbon monoxide in the gaseous phase reaction material was 0.8, the molar ratio of the sum of water vapor in the gaseous phase reaction material and water in the liquid phase reaction material to carbon monoxide in the gaseous phase reaction material was 1, and the mole fraction of carbon monoxide in the gaseous phase reaction material was 83%.

[0050] After the reaction was stabilized, the temperature of the product stream exiting the reactor was 230°C, and the carbon monoxide conversion was 91%.

[0051] Example 2

[0052] The reactor and catalyst described in Example 1 were used for the reaction. The reaction pressure was 3 MPa. The gaseous phase reaction material was a mixture of carbon monoxide, hydrogen and water vapor, and the mole fraction of carbon monoxide was 45%, the mole fraction of water vapor was 36%, and the remainder was hydrogen. The gaseous phase reaction material was preheated to 350°C and then introduced into the reactor, and the standard state volumetric space velocity was 8000 h －1 The liquid phase reaction material was water, and the temperature was 25°C. The molar ratio of the gaseous phase reaction material to the liquid phase reaction material was 4. Under the reaction conditions described above, the molar ratio of water vapor in the gaseous phase reaction material to carbon monoxide was 0.8, the molar ratio of water in the liquid phase reaction material to carbon monoxide in the gaseous phase reaction material was 0.56, and the molar ratio of the sum of water vapor in the gaseous phase reaction material and water in the liquid phase reaction material to carbon monoxide in the gaseous phase reaction material was 1.4.

[0053] After the reaction was stabilized, the temperature of the product stream exiting the reactor was 361°C, and the carbon monoxide conversion was 87%.

Claims

1. A method of carrying out a water gas shift reaction, characterized by, The water gas shift reaction is carried out in an adiabatic fixed bed reactor, the reaction raw material comprises two routes of gas phase and liquid phase, the gas phase reaction raw material contains carbon monoxide and water vapor, the liquid phase reaction raw material contains only water, the gas phase reaction raw material and the liquid phase reaction raw material are contacted in the reactor loaded with catalyst and the water gas shift reaction occurs, the molar ratio of water vapor to carbon monoxide in the gas phase reaction raw material is ≥0.1, the molar ratio of water in the liquid phase reaction raw material to carbon monoxide in the gas phase reaction raw material is ≥0.5, and the molar ratio of the sum of water vapor in the gas phase reaction raw material and water in the liquid phase reaction raw material to carbon monoxide in the gas phase reaction raw material is ≥1.

2. The method of performing a water gas shift reaction according to claim 1, wherein, The molar ratio of water vapor to carbon monoxide in the gas phase reaction raw material is ≥0.15, the molar ratio of water in the liquid phase reaction raw material to carbon monoxide in the gas phase reaction raw material is ≥0.55, and the molar ratio of the sum of water vapor in the gas phase reaction raw material and water in the liquid phase reaction raw material to carbon monoxide in the gas phase reaction raw material is ≥1.

1.

3. The method for carrying out the water gas shift reaction according to claim 1, characterized by, The molar ratio of water vapor to carbon monoxide in the gas phase reaction raw material is ≥0.2, the molar ratio of water in the liquid phase reaction raw material to carbon monoxide in the gas phase reaction raw material is ≥0.6, and the molar ratio of the sum of water vapor in the gas phase reaction raw material and water in the liquid phase reaction raw material to carbon monoxide in the gas phase reaction raw material is ≥1.

2.

4. The method for carrying out the water gas shift reaction according to claim 1, characterized by, The molar fraction of carbon monoxide in the gas phase reaction raw material is ≥10%.

5. The method for carrying out the water gas shift reaction according to claim 1, characterized by, The molar fraction of carbon monoxide in the gas phase reaction raw material is ≥30%.

6. The method for carrying out the water gas shift reaction according to claim 1, characterized by, The molar fraction of carbon monoxide in the gas phase reaction raw material is ≥50%.

7. The method for performing a water gas shift reaction according to claim 1, wherein, The temperature of the gas phase reaction raw material when entering the reactor is 100-500℃.

8. The method for performing a water gas shift reaction according to claim 1, wherein, The temperature of the liquid phase reaction raw material when entering the reactor is 5-180℃.

9. The method for carrying out the water gas shift reaction according to claim 1 or 7 or 8, characterized in that, The temperature of the gas phase reaction raw material when entering the reactor is 150-450℃, and the temperature of the liquid phase reaction raw material when entering the reactor is 10-150℃.

10. The method of performing a water gas shift reaction according to claim 1 or 7 or 8, wherein, The temperature of the gas phase reaction raw material when entering the reactor is 250-350℃, and the temperature of the liquid phase reaction raw material when entering the reactor is 20-120℃.

11. The method of performing a water gas shift reaction according to claim 1, wherein, The reaction pressure is 1-20MPa.

12. The method of performing a water gas shift reaction according to claim 1 or 11, wherein, The reaction pressure is 2-10MPa.

13. The method of performing a water gas shift reaction according to claim 1 or 11, wherein, The reaction pressure is 3-8MPa.

14. The method for performing a water gas shift reaction according to claim 1, wherein, The standard state volume space velocity of the gas phase reaction raw material is 100-30000h －1 .

15. The method of performing a water gas shift reaction according to claim 1 or 14, wherein, The standard state volume space velocity of the gas phase reaction raw material is 500-20000h －1 .

16. The method of performing a water gas shift reaction according to claim 1 or 14, wherein, The standard state volume space velocity of the gas phase reaction raw material is 1000-10000h －1 .

17. The method of performing a water gas shift reaction according to claim 1, wherein, The particle size of the catalyst loaded in the reactor is 1-200mm.

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