Concentration measurement device, reaction device, and concentration measurement method

Abstract

Provided are a concentration measurement device, a reaction device, and a concentration measurement method that can reduce the effect of pressure when measuring the concentration of methane included in a product gas. The concentration measurement device (20) comprises: a thermometer (23) that detects the temperature of a product gas obtained by a methanation reaction between carbon dioxide and hydrogen; a pressure gauge (24) that detects the pressure of the product gas; a flowmeter (22) that detects the flow rate of the product gas or the flow rate of water included in the product gas; and an arithmetic device (21) that calculates the concentration of methane on the basis of the detection results of the thermometer, the pressure gauge, and the flow meter.

Description

Concentration measuring device, reaction device, and concentration measuring method

[0001] The present invention relates to a device, a reactor, and a method for measuring the concentration of methane contained in a product gas obtained by a methanation reaction.

[0002] There is a demand for measuring the concentration of methane contained in the product gas obtained by the methanation reaction of carbon dioxide and hydrogen. The prior art disclosed in Patent Document 1 quantifies the carbon dioxide concentration of the product gas and determines the conversion rate of carbon dioxide to methane.

[0003] Japanese Patent Application Laid-Open No. 2020-33280

[0004] In the prior art, when determining the conversion rate of carbon dioxide to methane, if the carbon dioxide concentration of the product gas is measured with a concentration meter, the measurement result is affected by the pressure of the product gas and therefore lacks accuracy.Measuring the methane concentration in the product gas directly with a concentration meter also has the problem of lacking accuracy, as the measurement result is affected by the pressure of the product gas.

[0005] The present invention has been made to solve this problem, and aims to provide a concentration measuring device, a reaction device, and a concentration measuring method that can reduce the influence of pressure when measuring the concentration of methane contained in the generated gas.

[0006] A first aspect for achieving this object is a device for measuring the concentration of methane contained in a product gas obtained by a methanation reaction of carbon dioxide and hydrogen, which includes a thermometer that detects the temperature of the product gas, a pressure gauge that detects the pressure of the product gas, a flow meter that detects the flow rate of the product gas, and a computing device that calculates the concentration of methane based on the detection results of the thermometer, pressure gauge, and flow meter.

[0007] In the second aspect, in the first aspect, the calculation device calculates the volumetric flow rate of saturated water vapor in the generated gas based on the amount of saturated water vapor in the generated gas at the temperature detected by the thermometer and the pressure of the generated gas detected by the pressure gauge, calculates the flow rate of carbon dioxide based on the flow rate and volumetric flow rate of the generated gas detected by the flow meter, and calculates the concentration of methane contained in the generated gas.

[0008] The third aspect is a device for measuring the concentration of methane contained in a product gas obtained by a methanation reaction of carbon dioxide and hydrogen, and includes a thermometer that detects the temperature of the product gas, a pressure gauge that detects the pressure of the product gas, a flow meter that detects the flow rate of the product gas, a water meter that detects the flow rate of water produced by condensation of the product gas, and a computing device that calculates the concentration of methane based on the detection results of the thermometer, pressure gauge, flow meter, and water meter.

[0009] In a fourth aspect, in the third aspect, the calculation device calculates the volumetric flow rate of saturated water vapor in the generated gas based on the amount of saturated water vapor in the generated gas at the temperature detected by the thermometer and the pressure of the generated gas detected by the pressure gauge, calculates the flow rate of carbon dioxide based on the flow rate and volumetric flow rate detected by the water meter, and calculates the concentration of methane contained in the generated gas based on the flow rate of the generated gas and the flow rate of carbon dioxide detected by the flow meter.

[0010] In a fifth aspect, in any one of the first to fourth aspects, the absolute pressure of the generated gas is 0.1 MPa or more.

[0011] A sixth aspect is a reaction apparatus comprising the concentration measurement device according to any one of the first to fifth aspects and a reactor containing a catalyst that promotes the methanation reaction of carbon dioxide and hydrogen.

[0012] A seventh aspect is the sixth aspect, further comprising a plurality of reactors, a communication passage connecting adjacent reactors and sending product gas generated in a reactor in a preceding stage to a reactor in a subsequent stage, and a separation device separating water from the product gas in the communication passage, wherein the concentration measurement device measures the concentration of methane contained in the product gas generated in a reactor in a stage preceding the subsequent reactor.

[0013] An eighth aspect is a method for measuring the concentration of methane contained in a product gas obtained by a methanation reaction of carbon dioxide and hydrogen, which detects the temperature of the product gas, detects the pressure of the product gas, and detects the flow rate of the product gas or the flow rate of water contained in the product gas, and calculates the methane concentration based on the temperature of the product gas, the pressure of the product gas, and the flow rate of the product gas or the flow rate of water contained in the product gas.

[0014] According to the present invention, the methane concentration is calculated without using a concentration meter based on the temperature of the product gas obtained by the methanation reaction of carbon dioxide and hydrogen, the pressure of the product gas, and the flow rate of the product gas or the flow rate of water contained in the product gas, thereby reducing the influence of the pressure of the product gas and further eliminating the need for a concentration meter.

[0015] 1 is a block diagram of a reaction device according to a first embodiment;FIG. 2 is a block diagram of a reaction device according to a second embodiment;FIG.

[0016] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. Fig. 1 is a block diagram of a reaction apparatus 10 according to a first embodiment. The reaction apparatus 10 comprises a reactor 11 containing a catalyst 12, a carbon dioxide inlet 13 for introducing carbon dioxide into the reactor 11, and a hydrogen inlet 14 for introducing hydrogen into the reactor 11. In the reactor 11 to which a raw material gas containing carbon dioxide and hydrogen is introduced, CO ２ +4H ２ →CH ４ +2H ２ A methanation reaction represented by the chemical reaction formula O proceeds. The reaction device 10 includes a concentration measuring device 20 that measures the concentration of methane contained in the product gas obtained by the methanation reaction.

[0017] Any catalyst suitable for a methanation reaction can be used as the catalyst 12 without any restrictions. Examples of the catalyst 12 include powder, pellets, or a porous structure in which particles are supported on a carrier. Examples of the carrier include powder, pellets, or a porous structure of an oxide containing one or more of alumina, silica, magnesia, titania, zirconia, niobia, silica-alumina, zeolite, and calcium phosphate. The porous structure has permeability that allows the raw material gas to pass through. Furthermore, the raw material gas passes through the gaps between the powder and pellets. Examples of the particles supported on the carrier include metals such as Ni.

[0018] The reaction device 10 includes a plurality of reactors 11 (three in this embodiment) and is provided with a communication passage 15 connecting adjacent reactors 11. The communication passage 15 sends the product gas generated by the methanation reaction in the reactor 11 in the preceding stage to the reactor 11 in the succeeding stage. Since no catalyst 12 is disposed in the communication passage 15, the methanation reaction does not proceed when the product gas passes through the communication passage 15. The number of reactors 11 is not limited to three, and may be two or more.

[0019] A cooler 16 is disposed in the communicating passage 15. A cooler 16 is also disposed downstream of the final reactor 11. The cooler 16 can be any device capable of cooling the product gas, such as a heat exchanger, and is not limited to this. The cooler 16 cools the product gas generated in the preceding reactor 11, and the communicating passage 15 sends the cooled product gas to the subsequent reactor 11. The cooler 16 cools the product gas, for example, to the minimum temperature at which the methanation reaction starts. Because the methanation reaction is an exothermic reaction, if the surface of the catalyst 12 becomes too hot, the reverse reaction becomes dominant and the methane conversion rate decreases. The cooler 16 is provided to reduce the reverse reaction and increase the methane conversion rate.

[0020] A separator 17 that separates water from the produced gas is disposed downstream of the cooler 16 in the communicating passage 15. The cooler 16, disposed upstream of the separator 17, cools the produced gas to the dew point, and the separator 17 separates the water condensed in the cooler 16. When the amount of water contained in the produced gas is reduced by the separator 17, the rate of the forward methanation reaction becomes higher than the rate of the reverse methanation reaction in the reactor 11 downstream of the separator 17, thereby increasing the methane conversion rate.

[0021] The concentration measuring device 20 is a device that measures the concentration of methane contained in the produced gas. The concentration measuring device 20 measures the concentration of methane contained in the produced gas that flows downstream of the reactor 11 that is in a stage preceding the reactor 11 in the most recent stage. The absolute pressure of the produced gas whose concentration is measured by the concentration measuring device 20 is, for example, 0.1 MPa or higher. The concentration of methane contained in the produced gas from the reactor 11 in the most recent stage can be measured using a concentration meter after the produced gas is reduced in pressure to atmospheric pressure.

[0022] The concentration measuring device 20 includes a calculation device 21, a flow meter 22 that measures the flow rate of the produced gas, a thermometer 23 that detects the temperature of the produced gas, and a pressure meter 24 that detects the pressure of the produced gas. The flow meter 22, the thermometer 23, and the pressure meter 24 input their respective detection results to the calculation device 21.

[0023] The arithmetic unit 21 includes a CPU, a ROM, a RAM, and a backup RAM (none of which are shown). The ROM is a non-volatile memory that stores programs executed by the CPU. The CPU executes arithmetic processing based on the programs stored in the ROM. The RAM is a memory that temporarily stores the results of CPU calculations and data input from each sensor. The backup RAM is a non-volatile memory that stores data to be saved.

[0024] The chemical reaction formula for the methanation reaction is CO ２ +4H ２ →CH ４ +2H ２ O, so CO ２ If the flow rate of H is x [L / min], ２ The flow rate of CO is 4x [L / min]. ２ From CH ４ Considering the conversion rate to ４ The flow rate of the generated gas is 1-x [L / min]. Because the generated gas also contains saturated water vapor, if the amount of saturated water vapor is α [L / min], the flow rate F of the generated gas detected by the flow meter 22 is F = x + 4x + (1-x) + α = 4x + 1 + α [L / min].

[0025] Saturated water vapor amount [g / m ３ ] is a value determined by the temperature of the generated gas detected by the thermometer 23. The ROM of the computing device 21 stores the saturated water vapor amount [g / m ３ The calculation device 21 calculates Q=A·V=A·(2q / P) １／２ The fluid density [g / m ３where Q is the volumetric flow rate = saturated water vapor amount [L / min], A is the cross-sectional area of ​​the communication passage 15, V is the flow velocity, q is the pressure of the produced gas detected by the pressure gauge 24, and P is the fluid density = saturated water vapor amount [g / m ３ ]. Q = A (2q / P) １／２ In the above equation, A is a known constant, so the calculation device 21 calculates the saturated water vapor amount [g / m], which is determined by the pressure of the generated gas detected by the pressure gauge 24 and the temperature detected by the thermometer 23. ３ ] is substituted to calculate the saturated water vapor amount α [L / min] contained in the generated gas.

[0026] The calculation device 21 acquires the flow rate F [L / min] of the generated gas detected by the flow meter 22, and calculates x by substituting the saturated water vapor amount α [L / min] into the algebraic formula F = 4x + 1 + α. ４ Since the flow rate of is 1-x [L / min], the CH contained in the generated gas ４ The concentration [vol %] of CH contained in the generated gas is (1-x) / F. The calculation device 21 substitutes x and F into this algebraic formula to obtain ４ The concentration [vol %] of

[0027] The concentration measuring device 20 measures the concentration of methane contained in the product gas without using a concentration meter, whose measurement results are easily affected by pressure, thereby reducing the influence of pressure when measuring concentration. As a result, it is possible to measure the concentration of methane contained in the high-pressure product gas flowing through the communication passage 15 connecting adjacent reactors 11. By arranging a concentration measuring device 20 for each communication passage 15, it is possible to measure the methane concentration for each reactor 11. Therefore, by comparing the designed methane concentration for each reaction stage with the actual methane concentration, it is possible to detect the deterioration state of the catalyst 12 contained in the reactor 11. Since deteriorated catalysts 12 can be replaced appropriately, maintenance of the reactor 10 is easier. Since it is possible to omit a concentration meter that detects the concentration of components in the product gas, maintenance of the concentration meter, which was previously part of reactor maintenance, is no longer necessary.

[0028] By providing a concentration measuring device 20 for each communicating passage 15, it is possible to measure the methane concentration for each reactor 11, and therefore by comparing the methane concentration of the product gas in the reactor 11 at the most upstream stage with the methane concentration for each designed reaction stage, it is possible to detect an abnormality in the concentration of carbon dioxide introduced into the reactor 11 by the carbon dioxide introducing part 13. This makes it possible to detect an abnormality in the raw material gas.

[0029] A second embodiment will be described with reference to Figure 2. In the first embodiment, the flow rate of the produced gas is detected to determine the methane concentration of the produced gas. In contrast, in the second embodiment, the flow rate of water formed by condensation of water vapor contained in the produced gas is detected to determine the methane concentration of the produced gas. In the second embodiment, the same parts as those described in the first embodiment are designated by the same reference numerals, and the following description will be omitted.

[0030] 2 is a block diagram of the reaction apparatus 30 according to the second embodiment. The reaction apparatus 30 includes a concentration measuring device 40. The concentration measuring device 40 measures the concentration of methane contained in the generated gas flowing downstream of the reactor 11 in the first stage relative to the reactor 11 in the last stage.

[0031] The concentration measuring device 40 includes a calculation device 21, a flow meter 22, a thermometer 23, a pressure meter 24, and a water meter 41 (flow meter) that detects the flow rate of water separated by the separation device 17. The flow meter 22 detects the flow rate F of the product gas upstream of the separation device 17. The thermometer 23 and the pressure meter 24 detect the temperature and pressure of the product gas downstream of the separation device 17. The water meter 41, the flow meter 22, the thermometer 23, and the pressure meter 24 input their respective detection results to the calculation device 21.

[0032] The chemical reaction formula for the methanation reaction is CO ２ +4H ２ →CH ４ +2H ２ O, so CO ２ If the flow rate of H is x [L / min], ２ The flow rate of CO is 4x [L / min]. ２ From CH ４ Considering the conversion rate to ４The flow rate of H is 1-x [L / min]. ２ The flow rate of O (gas) is 2(1-x) [L / min].

[0033] The flow rate detected by the water meter 41, i.e., the H separated by the separator 17 ２ If the flow rate of O (liquid) is β [L / min], then β [L / min] = β [g / mol] = β / 18 [mol / min]. Therefore, according to Avogadro's law, the H separated by the separator 17 is ２ The flow rate of O (gas) is β / 18 [mol / min]·22.4 [L / mol]=22.4β / 18 [L / min]. Since the generated gas also contains saturated water vapor, if the amount of saturated water vapor in the generated gas flowing downstream of the separator 17 is α [L / min], the amount of H contained in the generated gas flowing upstream of the separator 17 is ２ The flow rate of O (gas) is 22.4β / 18+α [L / min].

[0034] H contained in the produced gas ２ When the flow rate [L / min] of O (gas) is taken into consideration, the following equation holds: 2(1-x) = 22.4β / 18 + α. As in the first embodiment, the calculation device 21 calculates the saturated water vapor amount [g / m ３ The calculation device 21 calculates the saturated water vapor amount α [L / min] contained in the generated gas from the saturated water vapor amount α and the flow rate β detected by the water meter 41. The calculation device 21 calculates x by substituting the saturated water vapor amount α and the flow rate β detected by the water meter 41 into the formula 2(1−x)=22.4β / 18+α.

[0035] The calculation device 21 acquires the flow rate F [L / min] of the generated gas detected by the flow meter 22. ４ Since the flow rate of is 1-x [L / min], the CH contained in the generated gas ４ The concentration [vol %] of CH contained in the generated gas is (1-x) / F. The calculation device 21 substitutes x and F into this algebraic formula to obtain ４ The concentration [vol %] of

[0036] The concentration measuring device 40 and the reaction device 30 including the concentration measuring device 40 can achieve the same effects as the concentration measuring device 20 and the reaction device 10 in the first embodiment.

[0037] The present invention has been described above based on the embodiments, but the present invention is not limited to the above embodiments, and it can be easily inferred that various improvements and modifications are possible within the scope of the present invention.

[0038] In the first embodiment, the methane concentration of the produced gas is calculated by detecting the flow rate, temperature, and pressure of the produced gas flowing downstream of the cooler 16 in the communicating passage 15, but this is not necessarily limited to this. It is of course possible to calculate the methane concentration of the produced gas by detecting the flow rate, temperature, and pressure of the produced gas flowing upstream of the cooler 16 in the communicating passage 15.

[0039] In the embodiment, the case where the separation device 17 is disposed in one of the three communication passages 15 has been described, but this is not necessarily limited to this. It is of course possible to dispose a separation device 17 in each of the three communication passages 15, or to dispose a separation device 17 in two of the three communication passages 15. It is of course possible to dispose a plurality of separation devices 17 in one communication passage 15.

[0040] In the embodiment, the reaction apparatuses 10 and 30 are described as including the separator 17 that separates the water condensed in the cooler 16, but the separator 17 is not limited to this. The separator 17 may be one that separates water vapor without condensing it in the cooler 16 by using a desiccant such as slaked lime, an adsorbent such as activated carbon or zeolite, a water separation membrane, or the like.

[0041] In the embodiment, the cooler 16 cools the produced gas to the minimum temperature at which the methanation reaction starts, but this is not necessarily limited to this. The temperature to which the cooler 16 cools the produced gas may be any temperature lower than the temperature at which the methanation reaction reaches equilibrium.

[0042] Although not described in the embodiment, it is of course possible to heat the gas introduced into the reactor 11 to a temperature equal to or higher than the initiation temperature of the methanation reaction by disposing a heater in the communicating passage 15 or the reactor 11. Examples of heaters include those that heat the generated gas by heating a heat source using the heat of gas combustion or electricity, those that use induction heating, and heat exchangers.

[0043] 10, 30 Reactor 11 Reactor 12 Catalyst 15 Communication path 17 Separator 20, 40 Concentration measuring device 21 Calculation device 22 Flow meter 23 Thermometer 24 Pressure gauge 41 Water meter

Claims

1. A device for measuring the concentration of methane contained in a product gas obtained by a methanation reaction of carbon dioxide and hydrogen, comprising: a thermometer for detecting the temperature of the product gas; a pressure gauge for detecting the pressure of the product gas; a flowmeter for detecting the flow rate of the product gas; and a calculation device for calculating the concentration of the methane based on the detection results of the thermometer, the pressure gauge, and the flowmeter.

2. A device for measuring the concentration of methane contained in a product gas obtained by a methanation reaction of carbon dioxide and hydrogen, comprising: a thermometer for detecting the temperature of the product gas; a pressure gauge for detecting the pressure of the product gas; a flow meter for detecting the flow rate of the product gas; a water meter for detecting the flow rate of water produced by condensation of the product gas; and a calculation device for calculating the concentration of the methane based on the detection results of the thermometer, the pressure gauge, the flow meter, and the water meter.

3. A concentration measuring device as claimed in claim 1 or 2, wherein the generated gas has an absolute pressure of 0.1 MPa or more.

4. A reaction apparatus comprising: the concentration measuring device according to claim 1 or 2; and a reactor containing a catalyst for promoting the methanation reaction of carbon dioxide and hydrogen.

5. A reaction apparatus as described in claim 4, comprising: a plurality of said reactors; a communication passage connecting adjacent reactors and sending a product gas generated in a reactor in a preceding stage to a reactor in a succeeding stage; and a separation device separating water from the product gas in the communication passage, wherein the concentration measuring device measures the concentration of methane contained in the product gas generated in a reactor in a stage preceding the most succeeding stage reactor.

6. A method for measuring the concentration of methane contained in a product gas obtained by a methanation reaction of carbon dioxide and hydrogen, comprising: detecting a temperature of the product gas; detecting a pressure of the product gas; and detecting a flow rate of the product gas or a flow rate of water contained in the product gas; and calculating the concentration of the methane based on the temperature of the product gas, the pressure of the product gas, and the flow rate of the product gas or the flow rate of water contained in the product gas.

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