A high-carbon, low-hydrogen pressure swing adsorption purification process system and method

Abstract

This invention pertains to the field of hydrogen energy, specifically a high-carbon, low-hydrogen pressure swing adsorption (PSA) purification process system and method. The system, along the gas flow direction, sequentially includes a carbon-based conversion unit, a heat exchange-cooling-gas-liquid separation unit, a compressor, at least two switchable decarbonization and desulfurization towers, a fine desulfurization tower, a PSA unit, a desorbed gas buffer tank, a desorbed gas compressor, and a fuel gas tank. This invention increases the hydrogen fraction in the feed gas from 30-50% to 50-70% through carbon-based conversion, then removes total sulfur to ≤0.1ppm through multi-stage desulfurization and decarbonization, finally producing fuel cell-grade hydrogen with a purity of ≥99.97% via PSA. Simultaneously, the desorbed gas is pressurized, buffered, and then divided into two stages for reuse. This invention effectively improves hydrogen recovery rate and desorbed gas utilization rate, solving the problems of high energy consumption and adsorbent poisoning in the purification of high-carbon, low-hydrogen by-product gases. It is applicable to various feed gases such as coke oven gas, refinery gas, and methanol tail gas.

Description

Technical Field

[0001] This invention belongs to the field of hydrogen energy and relates to hydrogen production, particularly a high-carbon, low-hydrogen pressure swing adsorption purification process system and method. Background Technology

[0002] In my country's coal chemical and petrochemical industries, a large amount of by-product gases with high carbon and sulfur content and low hydrogen content are produced. Most of these by-product gases are used for combustion, resulting in a significant waste of valuable resources. Different by-product gases are produced using different processes, resulting in varying impurities in the hydrogen. These impurities mainly consist of methane, C2 organic matter, methanol, CO, coal tar, and sulfides. Specifically, the H2 volume fraction in coke oven gas does not exceed 60%, in refinery gas it is around 75%, and in methanol by-product gas it is around 70%.

[0003] Currently, purification technologies for high-carbon, low-hydrogen by-product gases (such as coke oven gas, refinery gas, and methanol tail gas) are mainly divided into two categories:

[0004] 1. Direct Purification Method: This method directly processes the feed gas using a single Pressure Swing Adsorption (PSA) unit. However, due to the low hydrogen concentration in the feed gas (typically <50%) and complex impurity composition (including CO2, H2S, CH4, N2, etc.), the adsorbent load is too high, the recovery rate is low, and the purity of the product hydrogen is difficult to meet the requirements of fuel cell grade (≥99.97%). Furthermore, the low hydrogen concentration in the feed gas and the hydrogen content in the desorbed gas being less than 30% result in high energy consumption per unit of hydrogen production. Alternatively, the desorbed gas may be directly emitted or used as low-value fuel, failing to achieve hydrogen cascade recovery and resulting in poor economic efficiency.

[0005] 2. Pretreatment + PSA method: Chemical methods (such as water-gas shift reaction) or physical methods (such as cryogenic separation) are used to pretreat the raw gas, but there are problems such as high energy consumption (such as water-gas shift requires high temperature and high pressure) and complex equipment (cryotherapy requires low temperature system), and the effect on removing polar impurities such as sulfides is limited. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a high-carbon, low-hydrogen pressure swing adsorption purification process system and method. Through carbon-based conversion pretreatment → multi-stage desulfurization and decarbonization → pressure swing adsorption coupled process, sulfur- and carbon-containing substances are converted into easily separable substances, and then removed by pressure swing adsorption device and discharged in stages. At the same time, it is conducive to carbon neutralization and comprehensive utilization of usable gas, improves the utilization rate of desorbed gas, achieves efficient recovery of high-purity hydrogen, and ensures the quality of hydrogen products.

[0007] The technical solution of this invention is:

[0008] The first aspect of the present invention is to provide a high-carbon, low-hydrogen pressure swing adsorption purification process system, comprising, in sequence along the gas flow direction:

[0009] The carbon-based conversion unit is used to selectively hydrogenate unsaturated hydrocarbons and organic sulfur in the feed gas into H2 and H2S, increasing the hydrogen gas fraction from 30-50% to 50-70%.

[0010] The heat exchange-cooling-gas-liquid separation unit includes a raw gas heat exchanger, a water cooler, and a gas-liquid separator, which is used to cool the converted gas and remove liquid impurities.

[0011] A compressor is used to pressurize gas to the working pressure required for desulfurization and decarbonization.

[0012] At least two decarbonization and desulfurization towers that can be switched between, with decarbonization agent and desulfurization agent layered in the towers along the airflow direction;

[0013] The fine desulfurization tower is used for deep desulfurization of the gas outlet from the decarbonization and desulfurization tower, which can reduce the total sulfur to ≤0.2ppm;

[0014] The PSA unit is used to purify hydrogen from the gas after fine desulfurization. The hydrogen is sent into the hydrogen pipeline network and the desorbed gas is sent into the desorbed gas buffer tank.

[0015] The desorption gas buffer tank, desorption gas compressor, and fuel gas tank are connected in series to pressurize and buffer the desorption gas;

[0016] And a programmable valve assembly, used to achieve the following dual-path cascade reuse:

[0017] First route: The desorption gas containing ≥40% (vol) hydrogen in the fuel gas tank is used as backflush gas and introduced into the decarbonization and desulfurization tower in the regeneration stage through the fuel gas decarbonization and desulfurization tower regulating valve to replace the external purge gas;

[0018] The second route: The remaining desorbed gas is sent to the fuel gas pipeline through the fuel gas tank and the fuel gas pipeline regulating valve to achieve material recovery.

[0019] Furthermore, each decarbonization and desulfurization tower is equipped with three outlets at the bottom: an acid gas pipeline, a fuel gas pipeline, and a flare pipeline. The acid gas pipeline is used for the emission of high-concentration CO2 and H2S in the early stage of regeneration, the fuel gas pipeline is used for the recovery of hydrogen-containing gas in the later stage of backflushing, and the flare pipeline is used for the safe emission of low-pressure residual gas at the end. Each pipeline is equipped with an independent regulating valve to realize segmented control of the regeneration process.

[0020] Furthermore, the top pipeline of each decarbonization and desulfurization tower is divided into two lines: the first line connects to the fine desulfurization tower, and the second line connects to the fuel gas tank.

[0021] Furthermore, the desorbed gas compressor and the buffer tank pressure form a control loop to maintain the desorbed gas system pressure between 10-40 kPa.

[0022] Furthermore, the fuel gas tank to fuel gas pipeline regulating valve is interlocked with the fuel gas pipeline pressure, controlling the fuel gas pipeline pressure while ensuring the pressure of the purge gas in the decarbonization and desulfurization tower.

[0023] Furthermore, the outlet pipeline of the desorption gas buffer tank is equipped with a desorption gas buffer tank flare pressure regulating valve, which is interlocked with the desorption gas buffer tank to ensure that the pressure inside the desorption gas buffer tank does not exceed the limit.

[0024] A second aspect of the present invention is to provide a high-carbon, low-hydrogen pressure swing adsorption purification process based on the system, comprising, in sequence:

[0025] S1 carbon-based conversion: Under the action of a catalyst, the hydrogen gas fraction of the feed gas is increased from 30-50% to 50-70%;

[0026] S2 heat exchange-cooling-gas-liquid separation: cooling to 30-50℃ and removing liquid impurities;

[0027] S3 compression: pressurizes to the working pressure for desulfurization and decarbonization;

[0028] S4 multi-stage desulfurization / decarbonization: The gas passes through the decarbonization and desulfurization tower and the fine desulfurization tower in sequence, with total sulfur ≤0.2ppm;

[0029] S5 Pressure Swing Adsorption: Obtains fuel cell-grade hydrogen with a purity ≥99.97%, while simultaneously generating desorption gas;

[0030] S6 Dual-path recovery of desorbed gas: After being pressurized by the desorbed gas compressor, the desorbed gas enters the fuel gas tank. One path is used as backflushing gas and passes through the valve regeneration decarbonization and desulfurization tower. The other path passes through the fuel gas tank to the fuel gas pipeline regulating valve and is sent into the fuel gas pipeline network.

[0031] Furthermore, the hydrogen content of the backflushing gas in S6 is ≥40% (vol). During the regeneration process, the desorbed gas is discharged in stages through the acid gas pipeline, fuel gas pipeline and flare pipeline.

[0032] Furthermore, the adsorbent in the decarbonization and desulfurization tower is layered, with decarbonization occurring first and then desulfurization occurring, thus avoiding competitive adsorption of CO2.

[0033] Furthermore, the PSA unit rationally selects the adsorption process based on the actual gas volume, ensuring that the total sulfur at the outlet of the fine desulfurization tower is ≤0.2ppm, thus protecting the PSA adsorbent from sulfur poisoning.

[0034] The advantages and positive effects of this invention are:

[0035] 1. This invention selectively hydrogenates unsaturated hydrocarbons and organic sulfur in the feed gas into hydrogen and hydrogen sulfide through a carbon-based conversion device, significantly increasing the hydrogen concentration in the feed gas from 30%-50% to 50%-70%, and greatly improving the hydrogen yield.

[0036] 2. This invention recycles the pressure swing adsorption (PSA) desorbed gas after backflushing it through a fuel gas tank. The hydrogen content in the desorbed gas is increased from <30% in the traditional process to ≥40%, and the hydrogen recovery rate is increased from <60% in the traditional PSA unit to 80%, which greatly improves the resource utilization rate of hydrogen.

[0037] 3. The decarbonization and desulfurization tower of the present invention adopts layered packing of adsorbent, which removes impurities more thoroughly and avoids the problem of PSA adsorbent poisoning caused by polar impurities such as sulfides and halides in traditional processes, thus greatly improving the adsorbent life.

[0038] 4. In this invention, the desorbed gas is pressurized by a compressor and then used in two ways. One way is used as backflushing gas and returned to the decarbonization and desulfurization tower to participate in regeneration, which reduces the amount of purge gas used and improves the hydrogen recovery rate. The other way is entered into the fuel gas pipeline to recover heat and improve the utilization rate of the desorbed gas.

[0039] 5. The carbon-based conversion device of the present invention adopts catalyst formulation optimization and reaction temperature control, which can flexibly adapt to the compositional differences of various high-carbon and low-hydrogen feedstock gases such as coke oven gas, refinery gas, and methanol tail gas. It has strong process adaptability and can handle a variety of complex feedstock gases.

[0040] 6. The decarbonization and desulfurization tower of the present invention can be flexibly configured in 2-N units according to the working conditions. At the same time, a fine desulfurization tower is added after the tower, which improves the stability of the device and ensures product quality. Attached Figure Description

[0041] Figure 1 : A schematic diagram of the process of this invention.

[0042] Among them: 1-Raw gas inlet valve, 2-Raw gas heat exchanger, 3-Carbon-based conversion device, 4-Conversion device to raw gas heat exchanger valve, 5-Conversion device to water cooler valve, 6-Raw gas heat exchanger to water cooler valve, 7-Water cooler, 8-Circulating water pipeline, 9-Gas-liquid separator, 10-Compressor, 11-Compressor outlet valve, 12-Decarbonization and desulfurization tower A inlet regulating valve, 13-Decarbonization and desulfurization tower B inlet regulating valve, 14-Decarbonization and desulfurization tower A, 15-Decarbonization and desulfurization tower B, 16-Decarbonization and desulfurization tower A to fine desulfurization tower shut-off valve, 17-Fuel gas tank to decarbonization and desulfurization tower A shut-off valve, 18-Decarbonization and desulfurization tower B to fine desulfurization tower shut-off valve, 19-Fuel gas tank to fine desulfurization tower A shut-off valve, 19-Fuel gas tank to fine desulfurization tower A shut-off valve, 10-Fuel gas tank to fine desulfurization tower A shut-off valve, 10-Fuel gas tank to fine desulfurization tower B ... 20 - Cut-off valve from feed gas tank to decarbonization and desulfurization tower B; 21 - Fine desulfurization tower; 22 - PSA unit; 23 - Desorption gas buffer tank; 24 - Pressure regulating valve from desorption gas buffer tank to flare; 25 - Desorption gas compressor; 26 - Fuel gas tank; 27 - Regulating valve from decarbonization and desulfurization tower B to flare; 28 - Regulating valve from decarbonization and desulfurization tower B to decarbonization and desulfurization pipeline; 29 - Cut-off valve from decarbonization and desulfurization tower B to fuel gas pipeline; 30 - Regulating valve from decarbonization and desulfurization tower A to flare; 31 - Regulating valve from decarbonization and desulfurization tower A to decarbonization and desulfurization pipeline; 32 - Cut-off valve from decarbonization and desulfurization tower A to fuel gas pipeline; 33 - Regulating valve from fuel gas tank to fuel gas pipeline. Detailed Implementation

[0043] The present invention will be further described in detail below through specific embodiments. The following embodiments are merely descriptive and not limiting, and should not be used to limit the scope of protection of the present invention.

[0044] This invention provides a high-carbon, low-hydrogen pressure swing adsorption purification system. The process flow is as follows: The raw gas, after being preheated by the raw gas inlet valve 1 and the raw gas heat exchanger 2, enters the carbon-based conversion device 3. Alkane and organic sulfur in the gas are converted into hydrogen, CO2, and H2S. The resulting high-temperature gas passes through the conversion device to the raw gas heat exchanger valve 4 and enters the raw gas heat exchanger 2 for heat exchange with the raw gas. After cooling, the high-temperature gas passes through the raw gas heat exchanger to the water cooler valve 6 and enters the water cooler 7 for further cooling. A conversion device to water cooler valve 5 is installed on the pipeline connecting the high-temperature gas to and from the raw gas heat exchanger 2. Its function is to allow raw gas that does not require carbon-based conversion to directly enter the water cooler and subsequent systems. The raw gas that has undergone high-temperature conversion passes through the water cooler 7, and the circulating water pipeline 8 provides cooling to the water cooler 7. The cooled gas passes through a gas-liquid separator 9 to separate the liquid before entering the compressor 10 for pressurization.

[0045] After being pressurized, the gas is split into two streams after passing through the compressor outlet valve 11. One stream enters the decarbonization and desulfurization tower A14 through the inlet regulating valve 12 of the decarbonization and desulfurization tower A, and the other stream enters the decarbonization and desulfurization tower B15 through the inlet regulating valve 13 of the decarbonization and desulfurization tower B. The bottom pipeline of the decarbonization and desulfurization tower A14 is divided into three paths: the first path connects to the flare network through the decarbonization and desulfurization tower A to flare regulating valve 30; the second path connects to the acid gas network through the decarbonization and desulfurization tower A to decarbonization and desulfurization pipeline regulating valve 31; and the third path connects to the fuel gas network through the decarbonization and desulfurization tower A to fuel gas network shut-off valve 32. Similarly, the bottom pipeline of the decarbonization and desulfurization tower B15 is divided into three paths: the first path connects to the flare network through the decarbonization and desulfurization tower B to flare regulating valve 27; the second path connects to the acid gas network through the decarbonization and desulfurization tower B to decarbonization and desulfurization pipeline regulating valve 28; and the third path connects to the fuel gas network through the decarbonization and desulfurization tower B to fuel gas network shut-off valve 29. At the top of the decarbonization and desulfurization tower A14, the pipeline is divided into two lines. The first line connects to the fine desulfurization tower 20 via the shut-off valve 16 from the decarbonization and desulfurization tower A to the fine desulfurization tower. The second line connects to the fuel gas tank 25 via the shut-off valve 17 from the fuel gas tank to the decarbonization and desulfurization tower A and the regulating valve 26 from the fuel gas tank to the decarbonization and desulfurization tower. Similarly, at the top of the decarbonization and desulfurization tower B15, the pipeline is divided into two lines. The first line connects to the fine desulfurization tower 20 via the shut-off valve 18 from the decarbonization and desulfurization tower B to the fine desulfurization tower. The second line connects to the fuel gas tank 25 via the shut-off valve 19 from the fuel gas tank to the decarbonization and desulfurization tower B and the regulating valve 26 from the fuel gas tank to the decarbonization and desulfurization tower.

[0046] The decarbonized and desulfurized gas enters the fine desulfurization tower 20 through a pipeline for further fine desulfurization, reducing the sulfur content of the desulfurized gas to below 0.2 ppm. The desulfurized gas flows out from the top of the fine desulfurization tower 20 and is then connected to the PSA unit 21 for hydrogen purification via a pipeline. The purified hydrogen enters the hydrogen pipeline network. The desorbed gas is sent to the inlet of the desorbed gas buffer tank 22 through a pipeline. The outlet of the desorbed gas buffer tank 22 is connected to the inlet of the desorbed gas compressor 24 through a pipeline. The pipeline between the outlet of the desorbed gas buffer tank 22 and the inlet of the desorbed gas compressor 24 is connected to the flare network through the desorbed gas buffer tank to flare pressure regulating valve 23. After being compressed by the desorbed gas compressor 24, the desorbed gas enters the inlet of the fuel gas tank 25 through a pipeline. The outlet of the fuel gas tank 25 is sent to the fuel gas pipeline network through the fuel gas tank to fuel gas pipeline regulating valve 33.

[0047] After being pressurized by the desorbed gas compressor, the desorbed gas enters the fuel gas tank for storage. The fuel gas is controlled by the program to go to the decarbonization and desulfurization tower regulating valve 26, and the gas in the fuel gas tank is used to backflush the decarbonization and desulfurization tower. The fuel gas tank goes to the fuel gas pipeline regulating valve 33 to regulate the pressure and ensure the stability of the fuel gas tank.

[0048] The decarbonization and desulfurization towers, through program control, use either the regulating valve 28 of the decarbonization and desulfurization tower B to the decarbonization and desulfurization pipeline or the regulating valve 31 of the decarbonization and desulfurization tower A to discharge the adsorbed acidic substances and other polar substances in the early stage of desorption into the acid gas pipeline network. After backflushing, the desorbed gas in the fuel gas tank is controlled by the program to use the regulating valve 26 of the decarbonization and desulfurization tower, the shut-off valve 17 of the fuel gas tank to the decarbonization and desulfurization tower A, the shut-off valve 19 of the fuel gas tank to the decarbonization and desulfurization tower B, the regulating valve 30 of the decarbonization and desulfurization tower A to the flare, the regulating valve 27 of the decarbonization and desulfurization tower B to the flare, the shut-off valve 32 of the decarbonization and desulfurization tower A to the fuel gas pipeline network, and the shut-off valve 29 of the decarbonization and desulfurization tower B to the fuel gas pipeline network for backflushing and purging. When the pressure is high, the gas is discharged into the fuel gas pipeline network; when the pressure is low, the gas is discharged into the flare system.

[0049] The decarbonization and desulfurization adsorbent can be filled with different types and quantities of adsorbents according to the different types and concentrations of impurities in the raw gas, to ensure complete removal of acidic gases.

[0050] The decarbonization and desulfurization towers can be set up in 2-N units depending on the actual situation.

[0051] The desorbed gas compressor 24 and the desorbed gas buffer tank pressure form a control loop. If the pressure in the desorbed gas buffer tank 22 is too high, the frequency converter of the desorbed gas compressor 24 is increased, and the load of the desorbed gas compressor 24 is increased.

[0052] The fuel gas tank to fuel gas pipeline regulating valve 33 is interlocked with the fuel gas pipeline pressure, controlling the fuel gas pipeline pressure while ensuring the pressure during the decarbonization and desulfurization tower purging process.

[0053] The pressure regulating valve 23 of the desorption gas buffer tank is interlocked with the desorption gas buffer tank 22 to ensure that the pressure inside the desorption gas buffer tank 22 does not exceed the pressure limit, and at the same time ensures that the pressure of the desorption gas system of the PSA device 21 is controlled at 10-40 kPa to prevent high pressure of the desorption gas system from affecting the desorption effect of the pressure swing adsorption device.

[0054] The working principle and specific operating steps of this invention are as follows:

[0055] Open the raw gas inlet valve 1. The raw gas, after preheating by exchanging heat with the high-temperature gas at the outlet of the carbon-based conversion unit 3 via the raw gas heat exchanger 2, enters the carbon-based conversion unit 3, where carbon-containing organic matter or organic sulfur is converted into hydrogen. The high-temperature gas at the outlet of the carbon-based conversion unit 3 passes through the conversion unit to the raw gas heat exchanger valve 4 and the raw gas heat exchanger 2, and then through the raw gas heat exchanger to the water cooler valve 6, entering the water cooler 7. The water cooler 7 uses circulating water for heat exchange. When the hydrogen content in the raw gas is high and the carbon-based conversion unit 3 is not in operation, the conversion unit to the water cooler valve 5 can be opened directly, and the conversion unit to the raw gas heat exchanger valve 4 and the raw gas heat exchanger to the water cooler valve 6 can be closed. The gas passing through the water cooler 7, after passing through the gas-liquid separator 9 to separate from the liquid, enters the compressor 10. After being pressurized, it passes through the compressor outlet valve 11. Depending on the actual operating conditions, multiple decarbonization and desulfurization towers can be connected. For ease of explanation, this example uses two decarbonization and desulfurization towers. One is in operation, and the other is being regenerated or on standby.

[0056] Taking the adsorption of decarbonization and desulfurization tower A14 as an example, the inlet regulating valve 12 of decarbonization and desulfurization tower A and the shut-off valve 16 of decarbonization and desulfurization tower A are opened by program control, so that the compressed gas enters the decarbonization and desulfurization tower A14 to remove acidic gases from the gas.

[0057] After adsorption is completed in decarbonization and desulfurization tower A14, the desorption process begins. Open the inlet regulating valve 13 of decarbonization and desulfurization tower B and the shut-off valve 18 of decarbonization and desulfurization tower B to put decarbonization and desulfurization tower B15 into operation. Close the inlet regulating valve 12 of decarbonization and desulfurization tower A and the shut-off valve 16 of decarbonization and desulfurization tower A, and open the regulating valve 31 of decarbonization and desulfurization tower A to decarbonization and desulfurization pipeline to discharge the desorbed gas into the acid gas pipeline network. When the discharge pressure no longer decreases, open the shut-off valve 17 of fuel gas tank to decarbonization and desulfurization tower A and the regulating valve 26 of fuel gas to decarbonization and desulfurization tower A, and open the shut-off valve 32 of decarbonization and desulfurization tower A to fuel gas pipeline network to introduce gas from fuel gas tank 25 for purging, which is then discharged into the fuel gas system. This fuel gas tank 25 can simultaneously purge multiple decarbonization and desulfurization towers. When the pressure inside the decarbonization and desulfurization tower A14 is lower than that of the fuel gas pipeline, close the shut-off valve 32 from the decarbonization and desulfurization tower A to the fuel gas pipeline, and then open the regulating valve 30 from the decarbonization and desulfurization tower A to the flare for further purging. The purging time can be set according to the actual working conditions. After purging, close the regulating valve 26 from the fuel gas to the decarbonization and desulfurization tower, the shut-off valve 17 from the fuel gas tank to the decarbonization and desulfurization tower A, and the regulating valve 30 from the decarbonization and desulfurization tower A to the flare. Gradually open the regulating valve 12 at the inlet of the decarbonization and desulfurization tower A to gradually increase the pressure of the decarbonization and desulfurization tower A14 to the compressor outlet pressure for backup.

[0058] The gas after fine desulfurization is purified by the PSA unit 21 to complete the hydrogen purification. The product gas is sent to the hydrogen pipeline network. The generated desorbed gas enters the desorbed gas buffer tank 22 and then enters the desorbed gas compressor 24. If the desorbed gas compressor pumping volume decreases, the pressure regulating valve 23 of the desorbed gas buffer tank is used to control the pressure and maintain the pressure in the desorbed gas buffer tank 22 at 10-40 kPa to ensure the desorption effect of the pressure swing adsorption unit.

[0059] After passing through the desorbed gas compressor 24, the desorbed gas enters the fuel gas tank and is divided into two paths. One path controls the fuel gas tank to the fuel gas pipeline regulating valve 33 to send the desorbed gas to the fuel gas pipeline, ensuring that the fuel gas pipeline pressure is between 0.02-0.1 MPa. The other path passes through the fuel gas to the decarbonization and desulfurization tower regulating valve 26 and enters the decarbonization and desulfurization tower system for backflushing.

[0060] The desorbed gas compressor 24 and the desorbed gas buffer tank pressure form a control loop. If the pressure inside the desorbed gas buffer tank 22 is too high, the frequency converter of the desorbed gas compressor 24 is increased, thereby increasing the load on the desorbed gas compressor 24. The fuel gas tank to fuel gas pipeline regulating valve 33 is interlocked with the fuel gas pipeline pressure, controlling the fuel gas pipeline pressure while ensuring the pressure during the decarbonization and desulfurization tower purging process. The desorbed gas buffer tank to flare pressure regulating valve 23 is interlocked with the desorbed gas buffer tank 22, ensuring that the pressure inside the desorbed gas buffer tank 22 does not exceed the pressure limit, while ensuring that the desorbed gas system pressure of the PSA unit 21 is controlled within 10-40 kPa to prevent high desorbed gas system pressure from affecting the desorption effect of the pressure swing adsorption unit.

[0061] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several modifications and improvements can be made without departing from the inventive concept, and these all fall within the protection scope of the present invention.

Claims

1. A high-carbon, low-hydrogen pressure swing adsorption purification process system, characterized in that, Along the airflow direction, the following are included in sequence: The carbon-based conversion unit (3) is used to selectively hydrogenate unsaturated hydrocarbons and organic sulfur in the feed gas into H2 and H2S, thereby increasing the hydrogen gas fraction from 30-50% to 50-70%. The heat exchange-cooling-gas-liquid separation unit includes a raw gas heat exchanger (2), a water cooler (7), and a gas-liquid separator (9), which are used to cool the converted gas and remove liquid impurities. Compressor (10) is used to pressurize the gas to the working pressure for desulfurization and decarbonization; At least two decarbonization and desulfurization towers that can be switched between are used. The decarbonization agent and desulfurization agent are layered in the towers along the airflow direction, which can reduce the total sulfur to ≤0.1ppm. Fine desulfurization tower (20) is used for deep desulfurization of the gas outlet from the decarbonization and desulfurization tower; The PSA unit (21) is used to purify hydrogen from the gas after fine desulfurization. The hydrogen is sent into the hydrogen pipeline network, and the desorbed gas is sent into the desorbed gas buffer tank (22). The desorption gas buffer tank (22), the desorption gas compressor (24), and the fuel gas tank (25) are connected in series to pressurize and buffer the desorption gas; And a programmable valve assembly, used to achieve the following dual-path cascade reuse: First route: The desorption gas containing ≥40% hydrogen in the fuel gas tank (25) is used as backflush gas and introduced into the decarbonization and desulfurization tower in the regeneration stage through the fuel gas decarbonization and desulfurization tower regulating valve (26) to replace the external purge gas; The second route: The remaining desorbed gas is sent to the fuel gas pipeline through the fuel gas tank to the fuel gas pipeline regulating valve (33) to realize material recovery.

2. The system according to claim 1, characterized in that, Each decarbonization and desulfurization tower has three outlets at the bottom: an acid gas pipeline, a fuel gas pipeline, and a flare pipeline. The acid gas pipeline is used for the emission of high-concentration CO2 and H2S in the early stage of regeneration, the fuel gas pipeline is used for the recovery of hydrogen-containing gas in the later stage of backflushing, and the flare pipeline is used for the safe emission of low-pressure residual gas at the end. Each pipeline is equipped with an independent regulating valve to realize segmented control of the regeneration process.

3. The system according to claim 1, characterized in that, The top pipeline of each decarbonization and desulfurization tower is divided into two lines. The first line is connected to the fine desulfurization tower (20), and the second line is connected to the fuel gas tank (25).

4. The system according to claim 1, characterized in that, The desorbed gas compressor (24) and the desorbed gas buffer tank (22) form a control loop to maintain the desorbed gas system pressure between 10-40 kPa.

5. The system according to claim 1, characterized in that, The fuel gas tank to fuel gas pipeline regulating valve (33) is interlocked with the fuel gas pipeline pressure, controlling the fuel gas pipeline pressure while ensuring the pressure of the purging gas of the decarbonization and desulfurization tower.

6. The system according to claim 1, characterized in that, The outlet pipeline of the desorption gas buffer tank (22) is equipped with a desorption gas buffer tank flare pressure regulating valve (23). The desorption gas buffer tank flare pressure regulating valve (23) is interlocked with the desorption gas buffer tank (22) to ensure that the pressure inside the desorption gas buffer tank (22) does not exceed the pressure limit.

7. A high-carbon, low-hydrogen pressure swing adsorption purification process according to any one of claims 1-6, characterized in that, In order, they include: S1 carbon-based conversion: Under the action of a catalyst, the hydrogen gas fraction of the feed gas is increased from 30-50% to 50-70%; S2 heat exchange-cooling-gas-liquid separation: cooling to 30-50℃ and removing liquid impurities; S3 compression: pressurizes to the working pressure for desulfurization and decarbonization; S4 multi-stage desulfurization / decarbonization: The gas passes through the decarbonization and desulfurization tower and the fine desulfurization tower in sequence, with total sulfur ≤0.1ppm; S5 Pressure Swing Adsorption: Obtains fuel cell-grade hydrogen with a purity ≥99.97%, while simultaneously generating desorption gas; S6 Dual-path reuse of desorbed gas: After being pressurized by the desorbed gas compressor (24), the desorbed gas enters the fuel gas tank (25). One path is used as backflushing gas and passes through the fuel gas to the decarbonization and desulfurization tower regulating valve (26) to regenerate the decarbonization and desulfurization tower. The other path passes through the fuel gas tank to the fuel gas pipeline regulating valve (33) and is sent into the fuel gas pipeline.

8. The process method according to claim 7, characterized in that, In S6, the backflushing gas contains ≥40% hydrogen. During the regeneration process, the desorbed gas is discharged in stages through the acid gas pipeline, fuel gas pipeline, and flare pipeline.

9. The process method according to claim 7, characterized in that, The adsorbent in the decarbonization and desulfurization tower is layered, with decarbonization occurring first and then desulfurization.

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