Methanol synthesis gas on-line analysis and gas proportion feedback regulation system and method

Abstract

The invention discloses a system and a method for online analysis of methanol synthesis gas and feedback regulation of gas proportion. Compared with gas chromatography synthesis gas components synthesized by a traditional methanol process, a Raman spectrum analysis technology is used for replacing gas chromatography in a process scheme; the content of gases such as hydrogen, carbon dioxide, carbon monoxide and the like in the green methanol synthesis gas can be rapidly detected and analyzed on line, the detection time is shortened from more than ten minutes to more than ten seconds, the gas concentration is adjusted in various modes such as a compressor and an adjusting valve in the process method, and through the arrangement of sequential gas taking of the synthesis gas buffer tank, the detection efficiency is improved. And the adjusting device is arranged before the reaction in the synthesis tower, so that the adjusting feedback time of the component concentration of the synthesis gas is shortened.

Description

Technical Field

[0001] The present invention relates to the field of electromechanical equipment, and in particular to a system and method for online analysis and feedback regulation of methanol synthesis gas ratio. Background Art

[0002] Green methanol is a fuel with environmental protection and sustainability characteristics. It can be synthesized by green hydrogen produced by green electricity and carbon dioxide captured from the air. Compared with traditional coal-to-methanol, the green methanol synthesis process does not consume fossil fuels and does not produce solid or liquid waste. However, the production of green hydrogen in the green methanol synthesis process requires the use of renewable energy power to electrolyze water, and the output of green hydrogen will also fluctuate with the fluctuation of renewable energy. In the synthesis of methanol from hydrogen and carbon dioxide synthesis gas, it is necessary to control the ratio of hydrogen to carbon dioxide (carbon-hydrogen ratio) at a stable value. Too high or too low carbon-hydrogen ratio will reduce the reaction rate and cause other by-products to be generated. For green methanol synthesis, since the output of green hydrogen has a certain uncertainty, online detection and rapid adjustment of the carbon-hydrogen ratio of synthesis gas can improve the synthesis conversion rate and conversion rate of green methanol.

[0003] Traditional synthesis gas component detection technology uses gas chromatography, which takes tens of minutes from sampling to issuing a test report. This can no longer meet the needs of green methanol synthesis component detection where working conditions may change at any time. Synthesis gas component adjustment is generally achieved by manually adjusting the opening of related valves to control the intake volume of different component gases to change the synthesis gas carbon-hydrogen ratio. However, depending on the conditions such as the volume of the synthesis gas buffer tank and the location of the sampling point, it also takes a certain amount of time for the carbon-hydrogen ratio to be adjusted from the beginning to a stable state.

[0004] In summary, a methanol synthesis gas online analysis and feedback adjustment gas ratio system and method are needed to solve the shortcomings of the existing technology. Summary of the invention

[0005] In view of the deficiencies in the prior art, the present invention provides a system and method for online analysis and feedback adjustment of gas ratio of methanol synthesis gas, aiming to solve the above problems.

[0006] To achieve the above-mentioned object, the present invention provides the following technical solutions: a methanol synthesis gas online analysis and feedback adjustment gas ratio system, including a hydrogen production device and a carbon capture device, for providing hydrogen and carbon dioxide;

[0007] A hydrogen compressor and a carbon dioxide compressor, used for compressing hydrogen and carbon dioxide to required pressures respectively;

[0008] Hydrogen buffer tank and carbon dioxide buffer tank, used to store compressed hydrogen and carbon dioxide;

[0009] Regulating valves, used to adjust the flow of hydrogen and carbon dioxide;

[0010] A deoxygenation reactor, used to remove oxygen from a mixture of hydrogen and carbon dioxide;

[0011] A syngas buffer tank, used to store deoxygenated syngas, the syngas buffer tank being provided with a plurality of gas extraction stop valves at different heights;

[0012] Online gas concentration detector, used to detect the content of hydrogen, carbon dioxide, carbon monoxide and other gases in the synthesis gas in real time;

[0013] The circulating gas bypass regulating valve is used to adjust the intake volume of low-temperature synthesis gas;

[0014] A synthesis preheater, used to heat the synthesis gas to the reaction temperature;

[0015] Methanol reactor, used to synthesize methanol;

[0016] Methanol condenser, used to condense and separate the synthesis reaction products.

[0017] Optionally, the online gas concentration detector is a Raman spectrometer, including a laser emitter, a Raman detection cell and a Raman spectrometer, which is used to qualitatively and quantitatively detect gas components.

[0018] Optionally, a perforated partition is provided inside the synthesis gas buffer tank to reduce convection of the gas in the tank.

[0019] Optionally, the carbon-hydrogen ratio of the synthesis gas is adjusted by adjusting the opening of a start-up regulating valve.

[0020] Optionally, a synthesis outlet heat exchanger is provided before the synthesis gas preheater to preheat the synthesis gas and recover heat.

[0021] A method for online analysis of methanol synthesis gas and feedback adjustment of gas ratio, using a system for online analysis of methanol synthesis gas and feedback adjustment of gas ratio, characterized in that it comprises the following steps:

[0022] Step S1: raw material preparation, introducing hydrogen from a hydrogen production device and introducing carbon dioxide from a carbon capture device;

[0023] Step S2: Gas compression: hydrogen and carbon dioxide are compressed to the required pressure by a hydrogen compressor and a carbon dioxide compressor respectively, and sent to their respective hydrogen buffer tanks and carbon dioxide buffer tanks for storage;

[0024] Step S3: gas mixing and deoxygenation treatment, the gas is mixed in the pipeline after the flow rate is adjusted by the regulating valve, and enters the deoxygenation reactor to remove any oxygen that may exist therein;

[0025] Step S4: Synthesis gas buffering: the deoxygenated synthesis gas enters the synthesis gas buffer tank. The buffer tank is provided with first, second and third synthesis gas extraction shut-off valves at different heights, and gas can be extracted from different positions as needed;

[0026] Step S5: Online detection: the gas taken out from the synthesis gas buffer tank is divided into two routes, one of which is the main route. The gas first passes through an online gas concentration detector for gas composition analysis to detect the concentration of hydrogen, carbon dioxide, carbon monoxide and other gases;

[0027] Step S6: heat exchange, the synthesis gas after online detection enters the synthesis outlet heat exchanger (17), performs the first heat exchange with the synthesis tower outlet gas, and then enters the outer shell layer of the synthesis tower to perform the second heat exchange with the inner tube to preheat the synthesis gas;

[0028] Step S7: Synthesis gas preheating and methanol synthesis. The two gases converge into one before the synthesis gas preheater and are preheated to reach the temperature required for the reaction. The preheated synthesis gas enters the methanol reactor and undergoes a chemical reaction under the action of the catalyst to generate methanol.

[0029] Step S8: product separation: the product after the reaction is condensed by a methanol condenser and separated into a condensate and the remaining circulating gas.

[0030] Optionally, the carbon-hydrogen ratio in the synthesis gas in step S3 is adjusted by the following method:

[0031] According to the gas concentration data provided by the online gas concentration detector, the carbon-hydrogen ratio of the synthesis gas is adjusted by adjusting the opening of the pneumatic regulating valve ( and controlling the state of different gas intake stop valves of the synthesis gas buffer tank.

[0032] Optionally, the carbon-hydrogen ratio in the synthesis gas can be further adjusted by adjusting the operating frequency of the hydrogen compressor and the carbon dioxide compressor.

[0033] Optionally, in step S5, when it is detected that the hydrogen concentration is lower than a set value, the opening of the regulating valve after the carbon dioxide compressor is reduced and the gas intake valve at the top of the synthesis gas buffer tank is opened to increase the proportion of hydrogen in the synthesis gas.

[0034] Optionally, in step S5, when it is detected that the hydrogen concentration is higher than a set value, the opening of the regulating valve after the hydrogen compressor is reduced and the gas extraction valve at the bottom of the synthesis gas buffer tank is opened to increase the proportion of carbon dioxide in the synthesis gas.

[0035] Beneficial effects of the present invention:

[0036] 1. In the present invention, Raman spectroscopy is used instead of gas chromatography to realize online detection and rapid analysis of the content of hydrogen, carbon dioxide, carbon monoxide and other gases in green methanol synthesis gas, and the detection time is shortened from more than ten minutes to more than ten seconds;

[0037] 2. In the present invention, the gas concentration is adjusted by various means such as a compressor and a regulating valve, and the gas is taken out sequentially through the setting of the synthesis gas buffer tank. A regulating device is set before entering the synthesis tower reaction, thereby shortening the adjustment feedback time of the synthesis gas component concentration. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 A schematic diagram of a system process of the present invention.

[0039] Figure 2 This is a schematic diagram of a device for detecting synthesis gas components using Raman spectroscopy according to the present invention.

[0040] In the figure: 1-circulating gas compressor; 2-hydrogen compressor; 3-carbon dioxide compressor; 4-circulating gas buffer tank; 5-hydrogen buffer tank; 6-carbon dioxide buffer tank; 7-hydrogen flow regulating valve; 8-carbon dioxide flow regulating valve; 9-deoxygenation reactor; 10-synthesis gas buffer tank; 11-first synthesis gas intake stop valve; 12-second synthesis gas intake stop valve; 13-third synthesis gas intake stop valve; 14-circulating gas bypass regulating valve; 15-synthesis gas preheater; 16-synthesis gas analysis and detection device; 17-synthesis outlet heat exchanger; 18-methanol reactor; 19-methanol condenser. DETAILED DESCRIPTION

[0041] In order to more clearly illustrate the embodiments of the invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0042] like Figure 1 and Figure 2 As shown, a methanol synthesis gas online analysis and feedback adjustment gas ratio process system includes the following contents:

[0043] Hydrogen and carbon dioxide are introduced from the hydrogen production device and the carbon capture device respectively, and enter the hydrogen and carbon dioxide buffer tanks 4 and 5 through the hydrogen compressor 2 and the carbon dioxide compressor 3, and then pass through the regulating valves 7 and 8 and control the flow of hydrogen and carbon dioxide respectively by controlling the regulating valves. After the hydrogen and carbon dioxide gases are mixed in the pipeline, they enter the deoxygenation reactor 9 to remove the oxygen in the mixed gas, and then mix with the circulating gas pressurized by the circulating compressor 1, and enter the synthesis gas buffer tank 10. The synthesis gas buffer tank is respectively provided with a first synthesis gas gas withdrawal stop valve 11, a second synthesis gas gas withdrawal stop valve 12, and a third synthesis gas withdrawal stop valve 13 of different heights. The synthesis gas withdrawal stop valves can be opened in sequence to take synthesis gas from different positions of the synthesis gas buffer tank for reaction. The gas after gas extraction is divided into two routes: one is the main route, where the synthesis gas enters the online gas concentration detector 16 for analysis and then enters the synthesis outlet heat exchanger 17 for the first heat exchange with the synthesis tower outlet gas, and then enters the outer shell of the synthesis tower for the second heat exchange with the inner tube; the other is the bypass pipeline, where the intake amount of low-temperature synthesis gas without convection heat exchange is controlled by the circulating gas bypass regulating valve 14. The two routes of gas converge into one route before the synthesis gas preheater 15 and enter the synthesis preheater for heating, and then enter the methanol reactor (synthesis tower) 18 for synthesis reaction, and the product after the reaction is condensed by the methanol condenser 19 and separated into condensate and the remaining circulating gas.

[0044] In this process system, the online detection device uses a Raman spectrometer that can detect gases such as CO, H2, and CO2. Raman spectroscopy uses the principle that molecules emit light of a specific frequency after being irradiated by laser and undergo inelastic scattering. It has the characteristics of being fast, qualitative, and quantitative. Figure 2 As shown, it is composed of a laser emitter, a Raman detection cell, and a Raman spectrometer. The laser emitter can emit light of a wavelength of 785nm, 1064nm, or 1242nm. The main body of the Raman detection cell is a bypass pipe with a thinner diameter leading out from the main synthesis gas line. There is a piece of pressure-resistant quartz glass at both ends of the pipe. The quartz glass is fixed with a hollow high-pressure flange. The laser emitted from the laser can penetrate the quartz glass, reflect multiple times in the detection cell and excite the Raman scattered light of the synthesis gas in the detection cell. Finally, the scattered light enters the Raman spectrometer, and the gas concentration data can be obtained through the analyzer detection.

[0045] Since the methanol synthesis catalyst has a specific and most suitable syngas carbon-hydrogen ratio, after obtaining the gas concentration data, it is necessary to maintain a stable syngas carbon-hydrogen ratio through a regulating device. The regulating device is mainly composed of pneumatic regulating valves 7, 8, compressors and pneumatic gas extraction shut-off valves 11, 12, 13, etc. The syngas buffer tank connected to the gas extraction shut-off valve has a large aspect ratio (slender), and a certain number of perforated partitions are distributed in the tank to reduce gas convection in the tank. When the system is working normally, the middle gas extraction valve 12 is opened and the other gas extraction valves are closed. After working for a long time, there is syngas with a high carbon dioxide content at the bottom of the buffer tank and syngas with a high hydrogen content at the top.

[0046] When the analyzer detects that the hydrogen concentration ratio is less than the set range, the opening of the regulating valve 8 after the carbon dioxide compressor is controlled to decrease, the carbon dioxide flow rate is reduced to increase the hydrogen ratio, and the gas extraction valve 11 at the top of the buffer tank is opened and the other gas extraction valves are closed, so that the gas concentration can be adjusted synchronously at the synthesis gas buffer tank. After the synthesis gas components are stabilized, the gas extraction valve is switched to 12, and the synthesis gas concentration is continuously adjusted through regulating valves 7 and 8 until it is stable. If the above steps still cannot effectively increase the hydrogen concentration of the synthesis gas, reduce the frequency of the carbon dioxide compressor 3 or increase the frequency of the hydrogen compressor 2.

[0047] When the analyzer detects that the hydrogen concentration ratio is higher than the set range, the system controls the opening of the regulating valve 7 after the hydrogen compressor to reduce, reduce the flow of hydrogen and increase the carbon dioxide ratio, and at the same time, the gas extraction valve 13 at the bottom of the buffer tank is opened and the other gas extraction valves are closed to extract the gas with a higher carbon dioxide concentration at the bottom of the tank. After the synthesis gas components are stabilized, the gas extraction valve is switched to 12, and the synthesis gas concentration is continuously adjusted through regulating valves 7 and 8 until it is stable. If the above steps still cannot effectively increase the carbon dioxide concentration of the synthesis gas, reduce the frequency of hydrogen compressor 2 or increase the frequency of carbon dioxide compressor 3.

[0048] A method for online analysis of methanol synthesis gas and feedback adjustment of gas ratio, comprising the following steps:

[0049] Step S1: raw material preparation, introducing hydrogen from a hydrogen production device and introducing carbon dioxide from a carbon capture device;

[0050] Step S2: Gas compression: hydrogen and carbon dioxide are compressed to required pressures by a hydrogen compressor (2) and a carbon dioxide compressor (3), respectively, and sent to respective hydrogen buffer tanks (4) and carbon dioxide buffer tanks (5) for storage;

[0051] Step S3: gas mixing and deoxygenation treatment, the gas is mixed in the pipeline after the flow rate is adjusted by the regulating valve (7, 8), and enters the deoxygenation reactor (9) to remove any oxygen that may be present therein;

[0052] Step S4: Synthesis gas buffering, the deoxygenated synthesis gas enters the synthesis gas buffer tank (10), the buffer tank is provided with first, second and third synthesis gas extraction stop valves (11, 12, 13) of different heights, and gas is extracted from different positions according to needs;

[0053] Step S5: Online detection: the gas taken out from the synthesis gas buffer tank is divided into two routes, one of which is the main route. The gas first passes through an online gas concentration detector (16) for gas composition analysis to detect the concentration of hydrogen, carbon dioxide, carbon monoxide and other gases;

[0054] Step S6: heat exchange, the synthesis gas after online detection enters the synthesis outlet heat exchanger (17), performs the first heat exchange with the synthesis tower outlet gas, and then enters the outer shell layer of the synthesis tower to perform the second heat exchange with the inner tube to preheat the synthesis gas;

[0055] Step S7: Synthesis gas preheating and methanol synthesis. The two gases are combined into one before the synthesis gas preheater (15). After preheating, the synthesis gas reaches the temperature required for the reaction. The preheated synthesis gas enters the methanol reactor (18) and undergoes a chemical reaction under the action of the catalyst to generate methanol.

[0056] Step S8: Product separation: the product after the reaction is condensed by a methanol condenser (19) and separated into a condensate and the remaining circulating gas.

[0057] In step S3, the carbon-hydrogen ratio in the synthesis gas is adjusted by:

[0058] According to the gas concentration data provided by the online gas concentration detector (16), the carbon-hydrogen ratio of the synthesis gas is adjusted by adjusting the opening of the pneumatic regulating valve (7, 8) and controlling the states of the different gas extraction stop valves (11, 12, 13) of the synthesis gas buffer tank (10).

[0059] The carbon-hydrogen ratio in the synthesis gas can be further adjusted by adjusting the operating frequency of the hydrogen compressor (2) and the carbon dioxide compressor (3).

[0060] In step S5, when it is detected that the hydrogen concentration is lower than the set value, the opening of the regulating valve (8) after the carbon dioxide compressor (3) is reduced, and the gas intake valve (11) at the top of the synthesis gas buffer tank (10) is opened to increase the proportion of hydrogen in the synthesis gas.

[0061] In step S5, when it is detected that the hydrogen concentration is higher than the set value, the opening of the regulating valve (7) after the hydrogen compressor (2) is reduced, and the gas extraction valve (13) at the bottom of the synthesis gas buffer tank (10) is opened to increase the proportion of carbon dioxide in the synthesis gas.

[0062] Compared with gas chromatography analysis of synthesis gas components in traditional methanol synthesis process, the process scheme of the present invention uses Raman spectroscopy analysis technology instead of gas chromatography, which can realize online detection and rapid analysis of the content of gases such as hydrogen, carbon dioxide, carbon monoxide in green methanol synthesis gas, and the detection time is shortened from more than ten minutes to more than ten seconds. The process method uses a compressor, a regulating valve and other methods to adjust the gas concentration, and the setting of sequential gas extraction from the synthesis gas buffer tank is used. An adjustment device is set one step before entering the synthesis tower reaction, which shortens the adjustment feedback time of the concentration of the synthesis gas components.

[0063] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modification, equivalent substitution or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A methanol synthesis gas online analysis and feedback adjustment gas ratio system, characterized in that: include: A hydrogen production unit and a carbon capture unit to provide hydrogen and carbon dioxide; A hydrogen compressor (2) and a carbon dioxide compressor (3), used to compress hydrogen and carbon dioxide to required pressures respectively; A hydrogen buffer tank (4) and a carbon dioxide buffer tank (5) for storing compressed hydrogen and carbon dioxide; Regulating valves (7, 8) for regulating the flow of hydrogen and carbon dioxide; A deoxygenation reactor (9), used for removing oxygen from a mixture of hydrogen and carbon dioxide; A synthesis gas buffer tank (10) is used to store deoxygenated synthesis gas, and the synthesis gas buffer tank is provided with a plurality of gas extraction stop valves (11, 12, 13) at different heights; An online gas concentration detector (16) is used to detect the content of hydrogen, carbon dioxide, carbon monoxide and other gases in the synthesis gas in real time; A circulating gas bypass regulating valve (14) for regulating the intake amount of low-temperature synthesis gas; A synthesis preheater (15) for heating the synthesis gas to a reaction temperature; A methanol reactor (18) for synthesizing methanol; The methanol condenser (19) is used to condense and separate the synthesis reaction products.

2. The methanol synthesis gas online analysis and feedback adjustment gas ratio system according to claim 1 is characterized in that: The online gas concentration detector (16) is a Raman spectrometer, comprising a laser emitter, a Raman detection cell and a Raman spectrometer, and is used to qualitatively and quantitatively detect gas components.

3. The methanol synthesis gas online analysis and feedback gas ratio adjustment system according to claim 1 is characterized in that: The synthesis gas buffer tank (10) is provided with a perforated partition plate inside to reduce the convection of the gas in the tank.

4. The methanol synthesis gas online analysis and feedback adjustment gas ratio system according to claim 1 is characterized in that: The carbon-hydrogen ratio of the synthesis gas is adjusted by adjusting the opening of the start-up regulating valve (7, 8).

5. The methanol synthesis gas online analysis and feedback adjustment gas ratio system according to claim 1 is characterized in that: A synthesis outlet heat exchanger (17) is provided before the synthesis gas preheater (15) for preheating the synthesis gas and recovering heat.

6. A method for online analysis and feedback adjustment of gas ratio of methanol synthesis gas, using the system for online analysis and feedback adjustment of gas ratio of methanol synthesis gas as claimed in claim 1, characterized in that: The following steps are involved: Step S1: raw material preparation, introducing hydrogen from a hydrogen production device and introducing carbon dioxide from a carbon capture device; Step S2: Gas compression: hydrogen and carbon dioxide are compressed to required pressures by a hydrogen compressor (2) and a carbon dioxide compressor (3), respectively, and sent to respective hydrogen buffer tanks (4) and carbon dioxide buffer tanks (5) for storage; Step S3: gas mixing and deoxygenation treatment, the gas is mixed in the pipeline after the flow rate is adjusted by the regulating valve (7, 8), and enters the deoxygenation reactor (9) to remove any oxygen that may be present therein; Step S4: Synthesis gas buffering, the deoxygenated synthesis gas enters the synthesis gas buffer tank (10), the buffer tank is provided with first, second and third synthesis gas extraction stop valves (11, 12, 13) of different heights, and gas is extracted from different positions according to needs; Step S5: Online detection: the gas taken out from the synthesis gas buffer tank is divided into two routes, one of which is the main route. The gas first passes through an online gas concentration detector (16) for gas composition analysis to detect the concentration of hydrogen, carbon dioxide, carbon monoxide and other gases; Step S6: heat exchange, the synthesis gas after online detection enters the synthesis outlet heat exchanger (17), performs the first heat exchange with the synthesis tower outlet gas, and then enters the outer shell layer of the synthesis tower to perform the second heat exchange with the inner tube to preheat the synthesis gas; Step S7: Synthesis gas preheating and methanol synthesis. The two gases are combined into one before the synthesis gas preheater (15). After preheating, the synthesis gas reaches the temperature required for the reaction. The preheated synthesis gas enters the methanol reactor (18) and undergoes a chemical reaction under the action of the catalyst to generate methanol. Step S8: Product separation: the product after the reaction is condensed by a methanol condenser (19) and separated into a condensate and the remaining circulating gas.

7. The method for online analysis and feedback adjustment of gas ratio of methanol synthesis gas according to claim 6, characterized in that: In step S3, the carbon-hydrogen ratio in the synthesis gas is adjusted by: According to the gas concentration data provided by the online gas concentration detector (16), the carbon-hydrogen ratio of the synthesis gas is adjusted by adjusting the opening of the pneumatic regulating valve (7, 8) and controlling the states of the different gas extraction stop valves (11, 12, 13) of the synthesis gas buffer tank (10).

8. The method for online analysis and feedback adjustment of gas ratio of methanol synthesis gas according to claim 7, characterized in that: The carbon-hydrogen ratio in the synthesis gas can be further adjusted by adjusting the operating frequency of the hydrogen compressor (2) and the carbon dioxide compressor (3).

9. The method for online analysis and feedback adjustment of gas ratio of methanol synthesis gas according to claim 6, characterized in that: In the step S5, when it is detected that the hydrogen concentration is lower than the set value, the opening of the regulating valve (8) after the carbon dioxide compressor (3) is reduced, and the gas extraction valve (11) at the top of the synthesis gas buffer tank (10) is opened to increase the proportion of hydrogen in the synthesis gas.

10. The method for online analysis and feedback adjustment of gas ratio of methanol synthesis gas according to claim 6, characterized in that: In step S5, when it is detected that the hydrogen concentration is higher than the set value, the opening of the regulating valve (7) after the hydrogen compressor (2) is reduced, and the gas extraction valve (13) at the bottom of the synthesis gas buffer tank (10) is opened at the same time, so as to increase the proportion of carbon dioxide in the synthesis gas.

Images