A vacuum pressure swing adsorption apparatus

Abstract

The utility model discloses a kind of vacuum pressure swing adsorption devices, including pressure swing adsorption device, wherein containing vacuum pump and a group of parallelly arranged adsorbers, it is characterized in that, still include vacuum machine and a group of expanders;Desorption end of any the adsorber is connected with the vacuum machine and vacuum pump respectively, pressure equalization end of any the adsorber is connected with one the expander, any the expander is connected by shaft coupling with the vacuum machine.The device in VPSA pressure equalization step sequence, when high-pressure gas expands and depressurizes, provides mechanical energy to vacuum machine using expander, provides the negative pressure energy required for desorption, simultaneously, do work to gas internal energy, the temperature of process gas is greatly reduced, and then the equilibrium adsorption capacity of adsorbent is improved, and the operating efficiency of device is improved.

Description

Technical Field

[0001] This utility model belongs to the field of adsorption technology, and relates to an adsorption device, particularly a vacuum pressure swing adsorption device (VPSA). Background Technology

[0002] Pressure Swing Adsorption (PSA) is a gas separation technology that uses periodic pressure changes. It utilizes the selective adsorption characteristics of adsorbents on gas components and achieves continuous separation through cyclical operations of pressure adsorption and depressurization desorption. It features low operating temperature and no need for thermal regeneration, and is mainly used in fields such as air separation oxygen production and hydrogen purification.

[0003] Vacuum pressure swing adsorption (VPSA) is a gas separation technology that utilizes the difference in adsorption capacity of gases on solid adsorbents, primarily used in hydrogen purification. The entire process involves periodically changing the system pressure, causing impurities in the mixed gas to be captured by the adsorbent, while hydrogen passes through the adsorption bed into subsequent stages, ultimately producing high-purity hydrogen.

[0004] Compared to traditional pressure swing adsorption (PSA), VPSA employs vacuum technology in the desorption stage, significantly reducing the concentration of residual impurities and increasing hydrogen purity to over 99.99%. Compared to cryogenic separation, VPSA reduces equipment investment by approximately 40% and shortens start-up time from several hours to within 30 minutes, making it more suitable for production needs, but its unit energy consumption is higher. Summary of the Invention

[0005] The purpose of this invention is to provide a novel vacuum pressure swing adsorption (VPSA) device that solves the technical problem of high energy consumption during the desorption stage of VPSA. By utilizing the expansion of high-pressure gas during the VPSA process to output mechanical work, it provides the negative pressure energy required for desorption, while significantly reducing the temperature of the process gas, thereby increasing the equilibrium adsorption capacity of the molecular sieve and improving the operating efficiency of the device.

[0006] The present invention adopts the following technical solution: A vacuum pressure swing adsorption (PSA) device includes a vacuum pump and a set of adsorbers connected in parallel. The device is characterized by further including a vacuum compressor and a set of expanders. The desorption end of any of the adsorbers is connected to the vacuum compressor and the vacuum pump, respectively. The pressure equalization end of any of the adsorbers is connected to one of the expanders. Each expander is connected to the vacuum compressor via a coupling.

[0007] The device utilizes the expansion and depressurization of high-pressure gas during the VPSA equalization step to output mechanical work through the expander, driving the vacuum machine to operate and providing the negative pressure energy required for the desorption step. At the same time, the high-pressure gas undergoes adiabatic expansion in the expander, doing work and consuming the internal energy of the gas itself, thus significantly reducing the temperature of the process gas.

[0008] Furthermore, the vacuum pressure swing adsorption device also includes a desorption gas compressor, which is connected to the outlet of the vacuum machine and the vacuum pump. The desorption gas desorbed by the vacuum machine or the vacuum pump is sent to the desorption gas compressor. After being pressurized by the compressor, the desorption gas is sent to the downstream section to recover the desorption gas and reuse it, thereby maximizing the efficiency of the device.

[0009] Furthermore, the expander is a turbine expander, which has the characteristics of large flow rate, simple structure, small size, high efficiency and long operating cycle.

[0010] In the aforementioned device, the number of adsorbers corresponds to the number of expanders, and they are connected in parallel to continuously provide power to the vacuum pump. The vacuum pressure swing adsorption device is equipped with a vacuum pump; if the negative pressure generated by the vacuum pump cannot meet the desorption requirements of the device, the vacuum pump intervenes to ensure the qualified regeneration of the adsorption tower.

[0011] Furthermore, the expander is provided with a bypass connecting both ends. Preferably, an expander outlet control valve is provided at the expander outlet, and an expander bypass control valve is provided on the bypass to keep the expander always running in the forward direction. When the airflow flows in the reverse direction, the bypass control valve is activated to avoid mechanical power loss.

[0012] Furthermore, the device includes a set of programmable valves to control the sequence of operations. Each of the adsorbers includes a feed gas inlet programmable valve, a product gas outlet programmable valve, a desorption gas programmable valve, and a pressure equalization programmable valve. The reverse release and desorption sequences are controlled separately by their respective programmable valves and operate independently without interference.

[0013] Beneficial effects: The vacuum pressure swing adsorption device of this invention can utilize the process gas depressurization process during the pressure equalization step of the PSA device in daily operation. When the process gas expands and depressurizes in the expander, it outputs mechanical work to drive the vacuum machine to complete the vacuum desorption of the regenerator. At the same time, the high-pressure gas undergoes adiabatic expansion in the expander to do work and consume the internal energy of the gas itself, which greatly reduces the temperature of the process gas, thereby increasing the equilibrium adsorption capacity of the molecular sieve. This device not only improves the operating efficiency of the device, but also reduces the operating cost. Attached Figure Description

[0014] Figure 1 A schematic diagram of the structure of the vacuum pressure swing adsorption (VPSA) device of this invention.

[0015] Among them, 1 (A~F), adsorption tower; 2 (A~F), turbine expander; 3, vacuum machine; 4, desorption gas compressor; 5, vacuum pump; 6 (A~F), raw material gas inlet control valve; 7 (A~F), product gas outlet control valve; 8 (A~F), desorption gas control valve; 9 (A~F), pressure equalization control valve; 10 (A~F), turbine expander outlet control valve; 11 (A~F), turbine expander bypass control valve; 12, vacuum gauge; 13, 14, desorption gas switching control valve; 15, vacuum machine switching control valve; 16, vacuum pump switching control valve. Detailed Implementation

[0016] The specific embodiments of the present invention will be described in detail below. However, it should be noted that the scope of protection of the present invention is not limited to these specific embodiments, but is determined by the claims.

[0017] like Figure 1 A vacuum pressure swing adsorption (PSA) device for hydrogen purification includes six adsorbers 1A-1F connected in parallel. The desorption ends of adsorbers 1A-1F are connected to a vacuum compressor 3 and a vacuum pump 5, respectively, with a vacuum compressor switching control valve 15 and a vacuum pump switching control valve 16 installed on the connecting pipelines. The outlets of the vacuum compressor 3 and vacuum pump 5 are connected to a desorption gas compressor 4 for recovering the desorbed gas. Each adsorber 1A-1F is connected to a turbine expander 2A-2F at its pressure equalization end, and the turbine expander 2A-2F is connected to the vacuum compressor 3 by a coupling. Each turbine expander 2A-2F has a bypass connecting its two ends, and a bypass valve is installed on the bypass.

[0018] The adsorbers 1A to 1F contain an adsorbent, such as a molecular sieve bed, which can be an adsorption tower, adsorption tank, or other forms.

[0019] See Figure 1 Each of the adsorbers 1A to 1F includes a set of programmable valves, including raw material gas inlet programmable valves 6A to 6F, product gas outlet programmable valves 7A to 7F, desorption gas programmable valves 8A to 8F, pressure balance programmable valves 9A to 9F, turbine expander outlet programmable valves 10A to 10F, and expander bypass programmable valves 11A to 11F.

[0020] The downstream pipelines of the turbine expander 2A to 2F are equipped with cold insulation material to prevent personnel injury caused by low pipeline temperatures.

[0021] In the PSA process, a single adsorption tower mainly involves cycles of adsorption, depressurization, regeneration, pressurization, and re-adsorption. A traditional PSA process with six adsorption towers, operating in a (6-2-3 / P) mode, involves each tower sequentially undergoing the following steps in one cycle of the main process: adsorption A, first-stage pressure equalization depressurization E1D, second-stage pressure equalization depressurization E2D, third-stage pressure equalization depressurization E3D, forward discharge, reverse discharge, rinsing, third-stage pressure equalization pressurization E3R, second-stage pressure equalization pressurization E2R, first-stage pressure equalization pressurization E1R, and final pressurization FR. The switching between these steps is automatically achieved through programmable control valves on several adsorption towers according to a specific control program.

[0022] As can be seen from the aforementioned traditional pressure swing adsorption (PSA) unit process, during the regeneration step, product hydrogen is used as the regeneration purge gas. This greatly reduces the product hydrogen recovery rate and increases the amount of gas to be drawn in. Consequently, the installed capacity and exhaust volume of the gas to be drawn in the purge gas compressor are increased, resulting in a significant increase in energy consumption.

[0023] The vacuum pressure swing adsorption (VPSA) device utilizes the process gas depressurization process during the first stage pressure equalization drop (E1D), the second stage pressure equalization drop (E2D), and the third stage pressure equalization drop (E3D) (equilibrium drop: residual gas in the tower is transferred to other adsorption towers to recover effective components). When the process gas expands and depressurizes through the turbine expander, it outputs mechanical work to drive the vacuum machine to operate and complete the vacuum desorption of the regeneration adsorption tower.

[0024] Taking cycle one as an example: Adsorbers 1A and 1F perform the adsorption step, adsorbers 1B and 1E perform the pressure equalization step (pressure increases in 1B, pressure decreases in 1E), adsorber 1D performs the vacuum regeneration step, and adsorber 1C performs the reverse discharge step. Other cycle steps are omitted. The feed gas enters adsorbers 1A and 1F via feed gas inlet control valves 6A and 6F, where impurities are adsorbed. The product gas is then discharged from the device via product gas outlet control valves 7A and 7F. Simultaneously, adsorbers 1B and 1E open equalization control valves 9B and 9E based on pressure, turbine expander outlet control valves 10B and 10E close, and turbine expander bypass control valves 11B and 11E close, performing the pressure equalization step between adsorbers 1B and 1E. During the depressurization process of adsorber 1E, turbine expander 2E starts operating, and then transmits kinetic energy to vacuum pump 3 via coupling. Simultaneously, the desorption gas control valve 8D and switching valve of adsorber 1D, along with vacuum pump 16, open to initiate the vacuuming and regeneration process for adsorber 1D. Desorption gas pipeline pressure gauge 12 detects the vacuum level. If the vacuum level does not reach the set value, vacuum pump 5 starts, completing the regeneration of adsorber 1D. Desorption gas control valve 8C and switching valve 13 of adsorber 1C open to initiate the reverse discharge process.

[0025] The aforementioned vacuum pressure swing adsorption (PSA) device is used to purify hydrogen. The raw gas from the previous stage enters the vacuum pressure swing adsorption (PSA) stage. After removing a large number of impurities such as N2, CH4, CO, and CO2, hydrogen with a hydrogen content greater than 99.99% is obtained.

[0026] The aforementioned vacuum pressure swing adsorption (VPSA) device utilizes the mechanical work output by the high-pressure gas during the pressure equalization step of the VPSA unit as it expands and depressurizes, driving the vacuum pump to provide the vacuum pressure required for the desorption step. If the vacuum pressure is insufficient, a backup vacuum pump intervenes to regenerate the adsorber. Simultaneously, the high-pressure gas undergoes adiabatic expansion within the expander, consuming its internal energy and significantly reducing the temperature of the process gas. This, in turn, increases the equilibrium adsorption capacity of the molecular sieve and improves the operating efficiency of the device.

Claims

1. A vacuum pressure swing adsorption (PSA) device, comprising a PSA unit including a vacuum pump and a set of adsorbers connected in parallel, characterized in that, It also includes a vacuum machine and a set of expanders; the desorption end of any of the adsorbers is connected to the vacuum machine and the vacuum pump respectively, the pressure equalization end of any of the adsorbers is connected to one of the expanders, and any of the expanders is connected to the vacuum machine by a coupling.

2. The vacuum pressure swing adsorption device according to claim 1, characterized in that, The expander is a turbine expander.

3. The vacuum pressure swing adsorption device according to claim 1, characterized in that, The vacuum pressure swing adsorption device further includes a desorption gas compressor, which is connected to the outlet of the vacuum machine and the vacuum pump.

4. The vacuum pressure swing adsorption device according to claim 1, characterized in that, The expander is equipped with a bypass connecting both ends.

5. The vacuum pressure swing adsorption device according to claim 4, characterized in that, An expander outlet control valve is provided at the expander outlet, and an expander bypass control valve is provided on the bypass.

6. The vacuum pressure swing adsorption device according to claim 1, characterized in that, The adsorber includes a feed gas inlet control valve, a product gas outlet control valve, a desorption gas control valve, and a pressure equalization control valve.

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