System for producing hydrogen through methanol conversion and recovering high-concentration carbon dioxide

Abstract

The utility model provides a system for producing hydrogen through methanol conversion and recovering high-concentration carbon dioxide, and aims to solve the technical problem that the high-concentration carbon dioxide cannot be recovered in the conventional system for producing hydrogen through methanol. The system comprises a raw material unit, a vaporization overheating unit, a methanol conversion unit, a heat exchange unit, a condensation liquid separation unit and a pressure swing adsorption unit which are sequentially connected through pipelines, the system further comprises a compression unit, an inlet of the compression unit is connected with an outlet of the pressure swing adsorption unit through a pipeline, and an outlet of the compression unit is connected with an inlet of the vaporization overheating unit, an inlet of the methanol conversion unit and an outlet of the methanol conversion unit through pipelines. According to the utility model, the plurality of adsorption towers are connected in series and in parallel in the pressure swing adsorption unit, and the compression unit is connected behind the pressure swing adsorption unit, so that carbon dioxide which is not completely purified in the system is compressed again and is conveyed into the vaporization overheating unit and the methanol conversion unit; and resource utilization of the carbon dioxide is realized while efficient purification of the carbon dioxide is realized.

Description

Technical Field

[0001] The utility model relates to the technical field of reaction gas recovery and treatment in the process of hydrogen production from methanol, and particularly relates to a system for methanol conversion to hydrogen and recovery of high-concentration carbon dioxide. Background Art

[0002] With the booming development of hydrogen energy, the demand for the utilization of green hydrogen is increasing day by day. As a hydrogen energy carrier, methanol is widely used in hydrogen production. However, since methanol contains one carbon atom, CO2 emissions will be generated during the process of hydrogen production from methanol; if the hydrogen produced from methanol produced using fossil energy is discharged, it will also be affected by carbon emissions. Therefore, there is an urgent need for a process for efficient CO2 recovery.

[0003] Currently, the commonly used processes are wet decarbonization and dry pressure swing adsorption decarbonization processes; the wet decarbonization process can achieve high carbon dioxide recovery efficiency and recovery of high-concentration (>98%mol) carbon dioxide, but the process is complex and requires a large amount of heat consumption, which has a greater impact on the investment in small and medium-scale projects; the dry pressure swing adsorption decarbonization process generally adopts decarbonization before hydrogen purification, which can achieve efficient carbon dioxide removal, but the carbon dioxide content in the removed gas is between 85% and 92%, and the carbon dioxide removal effect in the system is not good. Therefore, it poses challenges to simultaneously remove hydrogen and carbon dioxide in the pressure swing adsorption unit and to obtain high-concentration carbon dioxide. Summary of the Invention

[0004] The purpose of the present invention is to solve the problem that in the existing methanol hydrogen production system, high-concentration carbon dioxide cannot be recovered and resourcefully utilized while producing hydrogen. By connecting multiple adsorption towers in series and parallel in the pressure swing adsorption unit and connecting a compression unit after the pressure swing adsorption unit, the carbon dioxide in the system that has not been completely purified is compressed again and sent to the vaporization and superheating unit and the methanol conversion unit, realizing the resourceful utilization of carbon dioxide while achieving efficient purification of carbon dioxide.

[0005] In order to achieve the above purpose, the utility model adopts the following technical scheme:

[0006] A system for methanol conversion to hydrogen and recovery of high-concentration carbon dioxide, comprising a raw material unit, a vaporization and superheating unit, a methanol conversion unit, a heat exchange unit, a condensation and liquid separation unit, and a pressure swing adsorption unit connected in sequence through pipelines; it further includes a compression unit, the inlet of the compression unit is connected to the outlet of the pressure swing adsorption unit through a pipeline, and the outlet of the compression unit is respectively connected to the inlet of the vaporization and superheating unit, the inlet of the methanol conversion unit, and the outlet of the methanol conversion unit through pipelines.

[0007] As a preferred technical scheme:

[0008] Optionally, a low-temperature shift unit is also connected between the methanol conversion unit and the heat exchange unit, and the position where the outlet of the compression unit is connected to the outlet of the methanol conversion unit is located at the inlet of the low-temperature shift unit. The purpose of adding the low-temperature shift in the present invention is to complete the water-gas reaction of CO in the gas under the action of a catalyst, and CO and water vapor are converted into hydrogen and CO2 at a certain temperature.

[0009] Optionally, the pressure swing adsorption unit includes N adsorption towers connected in series and parallel, N≥4, and the series and parallel connection means that the gas outlet end of the previous adsorption tower is connected to the gas inlet end of the next adsorption tower through a pipeline. The multiple adsorption towers alternately perform adsorption, desorption, and adsorption preparation to achieve continuous hydrogen production. During the adsorption → desorption process, a part of pure hydrogen remains in the tower that has completed adsorption. This part of pure hydrogen is used to equalize the pressure and flush the other towers that have just completed desorption respectively. This not only utilizes the residual hydrogen in the adsorption tower, but also slows down the pressure increase rate of the adsorption tower, that is, slows down the metal fatigue rate of the adsorption tower, and at the same time reduces the scouring force on the adsorbent solid. In the present invention, the multiple adsorption towers are connected in a series-parallel form. The purpose is that in one adsorption cycle, the raw material gas first enters adsorption tower A for adsorption and then enters adsorption tower B. The desorbed gas for hydrogen production by pressure swing adsorption enters the pressure swing adsorption decarbonization process after being stabilized in pressure and flow rate through a buffer tank; the desorbed gas first enters the bottom of adsorption tower A, exits from the top of adsorption tower A and enters the bottom of adsorption tower B, and the recovered gas (the CO2 concentration in this gas is less than 5%) is obtained from the top of adsorption tower B; adsorption tower C is in the pressure increase stage, and the recovered gas is used to increase the pressure of the adsorption tower. The pressure increase can be from the bottom of the adsorption tower or from the top of the tower (preferably from the bottom of the tower); adsorption tower D is in the vacuum desorption state, and the adsorbed CO2 and trace CH4 in the adsorption tower are desorbed to obtain by-product CO2 gas, and the gas concentration can reach more than 98%.

[0010] Optionally, the pressure swing adsorption unit further includes a hydrogen production desorbed gas device, a recycled gas recovery device, and a carbon dioxide recovery device. The hydrogen production desorbed gas device is respectively connected to the gas inlet ends of the N adsorption towers, and is used to introduce the off-site desorbed gas into the adsorption tower to be mixed with the raw material gas in the condensation and separation unit, and then flow out from the top of the adsorption tower under the action of the adsorption tower and flow into the recycled gas recovery device. The gas outlet ends of the N adsorption towers are respectively connected to the recycled gas recovery device and the carbon dioxide recovery device through pipelines.

[0011] Optionally, the pressure swing adsorption unit includes a pressure swing adsorption hydrogen production unit and a pressure swing adsorption decarbonization unit, and a gas compressor is also connected between the pressure swing adsorption hydrogen production unit and the pressure swing adsorption decarbonization unit.

[0012] Optionally, the raw material unit includes a demineralized water addition unit and a methanol addition unit.

[0013] Optionally, the gas outlet end of the condensation and liquid separation unit is also connected to the gas inlet end of the vaporization and superheating unit. The unreacted methanol raw material in the condensate is returned to the system to participate in the reaction, improving the utilization rate of raw materials.

[0014] Compared with the prior art, the beneficial effects of the present utility model are as follows:

[0015] 1. The methanol conversion to hydrogen and high-concentration carbon dioxide recovery system of the present utility model can achieve 100% recovery of carbon dioxide, realizing resource utilization.

[0016] 2. In the methanol conversion to hydrogen and high-concentration carbon dioxide recovery system of the present utility model, the carbon dioxide concentration in the carbon dioxide gas recovered in the pressure swing adsorption decarbonization unit is greater than 96%.

[0017] 3. In the methanol conversion to hydrogen and high-concentration carbon dioxide recovery system of the present utility model, through the effective gas circulation utilization of multiple series-parallel adsorption towers in the pressure swing adsorption unit for the recovery and concentration of the desorbed gas of carbon dioxide, the recovered hydrogen concentration reaches 99%.

[0018] 4. It has been verified that by using the system of the present utility model, the methanol consumption can be 0.49 kg / Nm 3 ·H2 per cubic meter of hydrogen in the reaction section. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0020] Figure 1 It is the system flow chart of the present utility model;

[0021] Figure 2 It is the structural schematic diagram of the pressure swing adsorption unit of the present utility model;

[0022] Reference numerals:

[0023] 1 - raw material unit; 101 - desalted water addition unit; 102 - methanol addition unit; 2 - vaporization and superheating unit; 3 - methanol conversion unit; 4 - low-temperature conversion unit; 5 - heat exchange unit; 6 - condensation and liquid separation unit; 7 - pressure swing adsorption unit; 701 - pressure swing adsorption hydrogen production unit; 702 - pressure swing adsorption decarbonization unit; 703 - gas compressor; 8 - compression unit;

[0024] 71 - Hydrogen extraction and desorption gas device; 72 - Recirculating gas recovery device; 73 - Carbon dioxide recovery device; 100 - Adsorption tower A; 200 - Adsorption tower B; 300 - Adsorption tower C; 400 - Adsorption tower D. Detailed implementation manner

[0025] In the following, only some exemplary embodiments are simply described. As those skilled in the art can recognize, the described embodiments can be modified in various different ways without departing from the spirit or scope of the present invention. Therefore, the drawings and the description are considered to be exemplary in nature rather than restrictive.

[0026] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship when the product of the present utility model is normally placed, or the orientation or positional relationship commonly understood by those skilled in the art. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation of the present invention.

[0027] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, "a plurality" means two or more unless otherwise specifically defined.

[0028] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected to", "fixed", etc. should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or integrated; it can be a mechanical connection, an electrical connection, or a communication connection; it can be directly connected, or indirectly connected through an intermediate medium, and it can be the internal communication of two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0029] In the present invention, unless otherwise clearly defined and limited, the first feature being "on" or "under" the second feature may include direct contact between the first and second features, or may include the first and second features not being in direct contact but being in contact through additional features therebetween. Moreover, the first feature being "above", "over" and "on top of" the second feature includes the first feature being directly above and obliquely above the second feature, or merely indicating that the first feature has a higher horizontal height than the second feature. The first feature being "under", "beneath" and "underneath" the second feature includes the first feature being directly below and obliquely below the second feature, or merely indicating that the first feature has a lower horizontal height than the second feature.

[0030] The following disclosure provides many different embodiments or examples for implementing different structures of the present invention. To simplify the disclosure of the present invention, the components and settings of specific examples are described below. Of course, they are merely examples and are not intended to limit the present invention. In addition, the present invention may repeat reference numerals and / or reference letters in different examples. This repetition is for the purpose of simplification and clarity, and does not itself indicate the relationship between the various embodiments and / or settings discussed. In addition, the present invention provides examples of various specific processes and materials, but those of ordinary skill in the art may be aware of the application of other processes and / or the use of other materials.

[0031] The embodiments of the present invention / utility model will be described in detail below with reference to the accompanying drawings.

[0032] An embodiment of the present utility model provides a system for methanol conversion to hydrogen and recovery of high-concentration carbon dioxide, as Figure 1 shown, including a raw material unit 1, a vaporization and superheating unit 2, a methanol conversion unit 3, a heat exchange unit 5, a condensation and liquid separation unit 6, a pressure swing adsorption unit 7, and a compression unit 8 that are connected in sequence through pipelines. A low-temperature shift unit 4 is also connected between the methanol conversion unit 3 and the heat exchange unit 5, as Figure 1 shown by the dashed box in

[0033] Among them, the raw material unit 1 includes a desalted water addition unit 101 and a methanol addition unit 102;

[0034] The pressure swing adsorption unit 7 includes a pressure swing adsorption hydrogen production unit 701 and a pressure swing adsorption decarbonization unit 702. A gas compressor 703 is also connected between the pressure swing adsorption hydrogen production unit 701 and the pressure swing adsorption decarbonization unit 702.

[0035] The inlet of the compression unit 8 is connected to the outlet of the pressure swing adsorption decarbonization unit 702 of the pressure swing adsorption unit 7 through a pipeline. The outlet of the compression unit 8 is connected to the inlet of the vaporization and superheating unit 2, the inlet of the methanol conversion unit 3, and the outlet of the methanol conversion unit 3 through pipelines, as Figure 1As shown by the three upward dotted arrows, the position where the outlet of the compression unit 8 is connected to the outlet of the methanol conversion unit 3 is located at the inlet of the low-temperature shift unit 4.

[0036] In the system of the present utility model, the pressure swing adsorption unit 7 realizes pressure swing adsorption by using adsorption towers, including N adsorption towers connected in series and parallel, N≥4, and series and parallel means that the gas outlet end of the previous adsorption tower is connected to the gas inlet end of the next adsorption tower through a pipeline. As Figure 2 shown, the pressure swing adsorption unit 7 further includes a hydrogen extraction desorbed gas device 71, a recycled gas recovery device 72 and a carbon dioxide recovery device 73. The hydrogen extraction desorbed gas device 71 is respectively connected to the gas inlet ends of the N adsorption towers, and the gas outlet ends of the N adsorption towers are respectively connected to the recycled gas recovery device 72 and the carbon dioxide recovery device 73 through pipelines. As Figure 2 shown, N is 4, that is, there are 4 adsorption towers, namely adsorption tower A 100, adsorption tower B 200, adsorption tower C 300 and adsorption tower D 400. The series and parallel connection method is as follows: connect the top of adsorption tower A 100 to the bottom of adsorption tower B 200, and then connect the top of adsorption tower B 200 to the bottom of adsorption tower C 300, and so on. The hydrogen extraction desorbed gas device 71 is respectively connected to the gas inlet ends at the bottoms of adsorption towers A to D. The gas outlet ends at the tops of adsorption towers A to D are connected to the recycled gas recovery device 72, and the gas outlet ends at the bottoms of adsorption towers A to D are also connected to the carbon dioxide recovery device 73. A plurality of control valves are respectively installed on each gas inlet and outlet pipeline to control the gas flow rate.

[0037] Using the system for methanol conversion to hydrogen and recovery of high-concentration carbon dioxide of the present utility model for pressure swing adsorption decarbonization and hydrogen extraction, the specific process is as follows:

[0038] During one adsorption cycle, the raw material gas first enters adsorption tower A for adsorption and then enters adsorption tower B; the end time of the adsorption tower is when the tower and the adsorbed impurities penetrate; pressure swing adsorption preferably uses slightly positive pressure adsorption, and the adsorption pressure is <50 kPaG.

[0039] The working process is as follows: the desorbed gas for hydrogen extraction by pressure swing adsorption enters the pressure swing adsorption decarbonization process after being stabilized in flow rate by a buffer tank; the desorbed gas first enters the bottom of adsorption tower A, exits from the top of adsorption tower A and enters the bottom of adsorption tower B, and the recovered gas (the CO2 concentration in this gas is less than 5%) is obtained from the top of adsorption tower B; adsorption tower C is in the pressure boosting stage, and the recovered gas is used to boost the pressure of the adsorption tower. The pressure boosting can be from the bottom of the adsorption tower or from the top of the adsorption tower (preferably from the bottom of the tower); adsorption tower D is in the vacuum desorption state, and the adsorbed CO2 and trace amounts of CH4 in the adsorption tower are desorbed to obtain a by-product CO2 gas, and the gas concentration can reach more than 98%. The states of adsorption towers A to D in each cycle are as follows:

[0040]

[0041] To verify the carbon dioxide recovery rate and methanol consumption in the system of the present utility model, the following embodiments are adopted.

[0042] Embodiment 1

[0043] For a 1000-cubic-meter methanol-to-hydrogen system, a one-stage pressure swing adsorption purification and a two-stage atmospheric pressure vacuum decarbonization process are adopted. Methanol and the recovered condensate from the scrubbing tower are mixed to form a 50-54% methanol aqueous solution, which then enters the heat recovery heat exchanger and then enters the vaporization and superheating unit. The vaporized gas is mixed with the compressed and recovered gas and then enters the converter in the methanol conversion unit to obtain the converted gas of the reaction. The converted gas undergoes heat recovery in the low-temperature conversion unit and the heat exchange unit and is cooled and condensed to 35°C and then enters the scrubbing tower for liquid separation to recover the unreacted methanol. The scrubbed converted gas enters the first-stage pressure swing adsorption hydrogen production unit to obtain product hydrogen; the desorbed gas enters the second-stage atmospheric pressure pressure swing adsorption decarbonization unit for recovery, and vacuum desorption is adopted to obtain a carbon dioxide mixed gas of more than 97%. The overhead recovered gas enters the converted gas inlet of the converter in the methanol conversion unit through the compression unit to convert the unreacted CO into hydrogen and carbon dioxide, and after another pressure swing adsorption, hydrogen and carbon dioxide are recovered. The consumption of raw materials at each stage in the methanol cracking hydrogen production process in this embodiment, as well as the content of the converted gas and the recovered gas, are shown in the following table:

[0044]

[0045] As can be seen from the above table, by adopting the system of the present utility model, hydrogen of more than 99.99% can be obtained, and at the same time, carbon dioxide of more than 97% can be obtained. The carbon dioxide is 100% recovered, and the methanol consumption per cubic meter of hydrogen is reduced to 0.48 kg / Nm 3 ·H2. Using the existing technology, the methanol consumption per cubic meter of hydrogen is 0.58 - 0.64 kg / Nm 3 ·H2. By adopting the system of the present utility model, while recovering high-concentration carbon dioxide, the methanol consumption is effectively reduced, and the production cost is reduced.

[0046] Embodiment 2

[0047] A 5000-cubic-meter methanol-to-hydrogen system adopts a one-stage pressure swing adsorption purification and a two-stage atmospheric pressure vacuum decarbonization process. Methanol is mixed with the recovered condensate from the washing tower to form a methanol aqueous solution with a ratio of 50-54%, and then enters the heat recovery heat exchanger and then enters the vaporization and superheating unit. The vaporized gas is mixed with the compressed and recovered gas and then enters the converter in the methanol conversion unit to obtain the converted gas of the reaction. The converted gas passes through the low-temperature conversion unit and the heat exchange unit for heat recovery and is cooled and condensed to 35°C and then enters the washing tower for liquid separation to recover and utilize the unreacted methanol. The washed converted gas enters the first-stage pressure swing adsorption to produce hydrogen to obtain the product hydrogen; the desorbed gas enters the second-stage atmospheric pressure pressure swing adsorption for carbon recovery, and vacuum desorption is used to obtain a carbon dioxide mixed gas with more than 97%. The top recycled gas enters the converted gas inlet through a compressor to convert the unreacted CO into hydrogen and recover hydrogen while recovering carbon dioxide. Through this process, hydrogen with a purity of more than 99.99% can be obtained, and carbon dioxide with a purity of more than 96% can be obtained at the same time, and the methanol consumption per cubic meter of hydrogen is reduced to 0.49 kg. The consumption of raw materials at each stage in the methanol cracking to hydrogen process in this implementation, as well as the content of the converted gas and the recycled gas, are shown in the following table:

[0048]

[0049] As can be seen from the above table, by adopting the system of the present invention, hydrogen with a purity of more than 99.99% can be obtained, and carbon dioxide with a purity of more than 96% can be obtained at the same time. The carbon dioxide is 100% recovered, and the methanol consumption per cubic meter of hydrogen is reduced to 0.486 kg.

Claims

1. A system for hydrogen production by methanol conversion and recovery of high-concentration carbon dioxide, comprising a raw material unit, a vaporization and superheating unit, a methanol conversion unit, a heat exchange unit, a condensation and liquid separation unit, and a pressure swing adsorption unit that are connected in sequence through pipelines; characterized in that: It further includes a compression unit. The inlet of the compression unit is connected to the outlet of the pressure swing adsorption unit through a pipeline, and the outlet of the compression unit is respectively connected to the inlet of the vaporization and superheating unit, the inlet of the methanol conversion unit, and the outlet of the methanol conversion unit through pipelines.

2. The system for methanol conversion to hydrogen and recovery of high-concentration carbon dioxide according to claim 1, characterized in that: The pressure swing adsorption unit includes a pressure swing adsorption hydrogen extraction unit and a pressure swing adsorption decarbonization unit; the inlet of the compression unit is connected to the outlet of the pressure swing adsorption decarbonization unit of the pressure swing adsorption unit through a pipeline.

3. A system for methanol conversion to hydrogen and recovery of high-concentration carbon dioxide according to claim 1, characterized in that: A low-temperature conversion unit is further connected between the methanol conversion unit and the heat exchange unit, and the position where the outlet of the compression unit is connected to the outlet of the methanol conversion unit is located at the inlet of the low-temperature conversion unit.

4. A system for methanol conversion to hydrogen and recovery of high-concentration carbon dioxide according to claim 1 or 2, characterized in that: The pressure swing adsorption unit includes N adsorption towers connected in series and parallel, where N≥4, and the series and parallel connection means that the gas outlet end of the previous adsorption tower is connected to the gas inlet end of the subsequent adsorption tower through a pipeline.

5. A system for methanol conversion to hydrogen and recovery of high-concentration carbon dioxide according to claim 4, characterized in that: The pressure swing adsorption unit further includes a hydrogen extraction desorbed gas device, a recycled gas recovery device, and a carbon dioxide recovery device. The hydrogen extraction desorbed gas device is respectively connected to the inlet ends of the N adsorption towers, and the outlet ends of the N adsorption towers are respectively connected to the recycled gas recovery device and the carbon dioxide recovery device through pipelines.

6. The system for methanol conversion to hydrogen and recovery of high-concentration carbon dioxide according to claim 1, wherein: A gas compressor is further connected between the pressure swing adsorption hydrogen extraction unit and the pressure swing adsorption decarbonization unit.

7. A system for methanol conversion to hydrogen and recovery of high-concentration carbon dioxide according to claim 1, characterized in that: The raw material unit includes a desalted water addition unit and a methanol addition unit.

8. A system for methanol conversion to hydrogen and recovery of high-concentration carbon dioxide according to claim 1, characterized in that: The gas outlet end of the condensation and liquid separation unit is also connected to the gas inlet end of the vaporization and superheating unit.

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