Device for recycling and deeply purifying hydrogen in discharged tail gas

Abstract

The utility model provides a device for recycling and deeply purifying hydrogen in discharged tail gas. The device comprises a buffer tank I, a heat exchanger, a compressor, a buffer tank II and a purifying tower, a gas inlet is formed in the buffer tank I and is connected with a tail gas discharge pipe; the air outlet end of the buffer tank I is connected with the air inlet end of the heat exchanger I, the air outlet end of the heat exchanger I is connected with the air inlet of the buffer tank II through the compressor, and the air outlet of the buffer tank II is connected with the air inlet at the lower end of the purifying tower; a gas outlet in the upper end of the purifying tower is connected with a gas inlet of a buffer tank III through a vacuum pump; a gas outlet of the buffer tank III is connected with the deep purification device. The device is small in occupied area and low in investment, so that the damage of chemical enterprises to the environment is reduced, and meanwhile, hydrogen with economic value is recovered.

Description

Technical Field

[0001] This utility model relates to the field of chemical gas emissions, and in particular to a device for hydrogen recovery and deep purification in exhaust gas. Background Technology

[0002] In the calcium carbide-based PVC production process, the distillation system discharges tail gas containing components such as vinyl chloride, acetylene, hydrogen, nitrogen, and other non-methane hydrocarbons. A two-stage pressure swing adsorption (PSA) separation technology is typically used to separate and recover vinyl chloride, acetylene, and hydrogen from the tail gas. The first stage primarily recovers vinyl chloride and acetylene, while the second stage primarily recovers hydrogen. The desorbed gas from this process is the exhaust gas, mainly containing nitrogen, hydrogen, and trace amounts of non-methane hydrocarbons. Initially, the PSA unit's emission standards meet design and environmental requirements. However, with the application of ultra-low mercury catalysts and the increased operating time of the PSA unit, the content of vinyl chloride and acetylene in the distillation tail gas increases compared to design values, and the volume of distillation tail gas also increases significantly. Some non-methane hydrocarbons cannot be consumed during the system's circulating production process, leading to a long-term accumulation and an increase in non-methane hydrocarbon content, making emissions prone to exceeding standards. Therefore, some adsorption separation units can no longer meet the original design specifications and emission standards; thus, further advanced treatment of the exhaust gas from the original adsorption separation units is necessary. Because the exhaust gas contains a high amount of hydrogen, the catalytic reaction in the deep treatment process generates a lot of heat, posing certain safety hazards. Therefore, adding a hydrogen recovery device before the deep purification process can reduce the amount of hydrogen entering the deep treatment process and also has certain economic value. Summary of the Invention

[0003] To address the aforementioned problems, this invention discloses a hydrogen recovery and deep purification device for exhaust gases, which requires a small footprint and low investment, thereby reducing the environmental damage caused by chemical enterprises while recovering economically valuable hydrogen.

[0004] A device for hydrogen recovery and deep purification in exhaust gas includes a first buffer tank, a heat exchanger, a compressor, a second buffer tank, and a purification tower. The first buffer tank has an inlet connected to the exhaust gas pipe. The outlet of the first buffer tank is connected to the inlet of the first heat exchanger. The outlet of the first heat exchanger is connected to the inlet of the second buffer tank via the compressor. The outlet of the second buffer tank is connected to the inlet at the lower end of the purification tower. The outlet at the upper end of the purification tower is connected to the inlet of the third buffer tank via a vacuum pump. The outlet of the third buffer tank is connected to the deep purification device.

[0005] Furthermore, the deep purification device includes a primary fine stripping tower, a secondary fine stripping tower, and a heat exchanger. The outlet of the buffer tank is connected to the inlet of the primary fine stripping tower. The outlet of the primary fine stripping tower is connected to the inlet of the secondary fine stripping tower via a circulating fan. The outlet of the secondary fine stripping tower is connected to the heat exchanger via a flash evaporator. One end of the heat exchanger is connected to an exhaust pipe.

[0006] Furthermore, the exhaust pipe is equipped with an exhaust flow regulating valve.

[0007] Furthermore, a flow meter is installed on the pipe connecting the buffer tank 2 to the purification tower.

[0008] The working principle of this utility model is as follows:

[0009] 1. The exhaust gas from the distillation tail gas recovery system, i.e. the raw material gas, is buffered by buffer tank one, cooled by heat exchanger one, pressurized by compressor, buffered by buffer tank two, and then metered by flow meter before entering the purification tower as the raw material gas of the unit.

[0010] 2. The raw gas flows from bottom to top through the purification tower. During this process, most substances except hydrogen are adsorbed by the adsorbent. The hydrogen discharged from the top of the purification tower is returned as product gas to the inlet of the original hydrogen extraction unit for further purification and recovery. After adsorption, the adsorbed nitrogen, acetylene, ethane and other components are desorbed by depressurization and vacuum pump. After being buffered in the second buffer tank, they enter the deep purification unit for further treatment.

[0011] 3. The deep purification unit consists of two-stage fine stripping towers and related heat exchangers. The coarse purified gas enters the first-stage fine stripping tower, where a circulating fan pressurizes it to a specific pressure, and then it sequentially enters the second-stage fine stripping tower. During this process, components such as non-methane total hydrocarbons are catalytically converted, thereby achieving deep purification and ultimately obtaining qualified purified gas. After recovering some heat through a flash evaporator and a heat exchanger, the purified gas is cooled and then discharged outside the boundary area through a regulating valve.

[0012] The beneficial effects of this utility model are: the gas being processed is buffered by the buffer tank and automatically stabilized to maintain the continuous and stable operation of the raw material gas intake. Attached Figure Description

[0013] Figure 1 A diagram of the device of this utility model.

[0014] List of reference numerals in the attached diagram:

[0015] Wherein: 1-Buffer tank one; 2-Heat exchanger one; 3-Compressor; 4-Buffer tank two; 5-Purification tower; 6-Emission tail gas pipe; 7-Compressor; 8-Buffer tank three; 9-First-stage purification tower; 10-Second-stage purification tower; 11-Heat exchanger three; 12-Circulating fan; 13-Flash evaporator; 14-Exhaust pipe; 15-Exhaust flow regulating valve; 16-Flow meter. Detailed Implementation

[0016] The present invention will be further illustrated below with reference to the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. It should be noted that the terms "front," "rear," "left," "right," "up," and "down" used in the following description refer to directions in the accompanying drawings, and the terms "inner" and "outer" refer to directions toward or away from the geometric center of a specific component, respectively.

[0017] like Figure 1 As shown, this embodiment of a hydrogen recovery and deep purification device for exhaust gas includes a buffer tank 1, a heat exchanger 2, a compressor 3, a second buffer tank 4, and a purification tower 5. The buffer tank 1 has an inlet connected to the exhaust gas pipe 6. The outlet of the buffer tank 1 is connected to the inlet of the heat exchanger 2, and the outlet of the heat exchanger 2 is connected to the inlet of the second buffer tank 4 via the compressor 7. The outlet of the second buffer tank 4 is connected to the inlet at the lower end of the purification tower 5. The outlet at the upper end of the purification tower 5 is connected to the inlet of the third buffer tank 8 via a vacuum pump 6. The outlet of the third buffer tank 8 is connected to the deep purification device. A flow meter 16 is installed on the pipe connecting the second buffer tank 4 and the purification tower 5.

[0018] The deep purification device includes a primary fine stripping tower 9, a secondary fine stripping tower 10, and a heat exchanger 3 11; the outlet of the buffer tank 3 8 is connected to the inlet of the primary fine stripping tower 9; the outlet of the primary fine stripping tower 9 is connected to the inlet of the secondary fine stripping tower 10 via a circulating fan 12; the outlet of the secondary fine stripping tower 10 is connected to the heat exchanger 3 11 via a flash evaporator 13; one end of the heat exchanger 3 11 is connected to an exhaust pipe 14. An exhaust flow regulating valve 15 is installed on the exhaust pipe 14.

[0019] In this embodiment, the exhaust gas from the distillation tail gas recovery system, i.e., the feed gas, is buffered in buffer tank one, cooled by heat exchanger one, pressurized by compressor, buffered in buffer tank two, and then metered by flow meter before entering the purification tower as the feed gas for the unit. The feed gas flows from bottom to top through the purification tower. During this process, most substances except hydrogen are adsorbed by the adsorbent. The hydrogen discharged from the top of the purification tower is returned as product gas to the inlet of the original hydrogen extraction unit for further purification and recovery. After adsorption, the adsorbed nitrogen, acetylene, ethane, and other components are desorbed by depressurization and vacuum pumping, buffered in buffer tank two, and then enter the deep purification unit for further treatment. The deep purification unit consists of two-stage fine desorption towers and related heat exchangers. The crude purified gas enters the first-stage fine desorption tower, is pressurized to a specific pressure by a circulating fan, and then enters the second-stage fine desorption tower. During this process, components such as non-methane total hydrocarbons are catalytically converted, thereby achieving deep purification and finally obtaining qualified purified gas. The purified gas is cooled after recovering some heat through a flash evaporator and heat exchanger three, and then discharged outside the boundary through a regulating valve.

[0020] This embodiment ensures that the new national emission standards are met after deep treatment, thereby reducing the environmental damage caused by chemical enterprises and recovering economically valuable hydrogen.

[0021] The technical means disclosed in this invention are not limited to those disclosed in the above embodiments, but also include technical solutions composed of any combination of the above technical features.

Claims

1. A device for hydrogen recovery and deep purification in exhaust gas, characterized in that: It includes a buffer tank 1, a heat exchanger, a compressor, a buffer tank 2, and a purification tower; the buffer tank 1 is equipped with an air inlet connected to the exhaust pipe; the air outlet of the buffer tank 1 is connected to the air inlet of the heat exchanger 1, the air outlet of the heat exchanger 1 is connected to the air inlet of the buffer tank 2 through the compressor, the air outlet of the buffer tank 2 is connected to the air inlet at the lower end of the purification tower; the air outlet at the upper end of the purification tower is connected to the air inlet of the buffer tank 3 through a vacuum pump; the air outlet of the buffer tank 3 is connected to a deep purification device.

2. The hydrogen recovery and deep purification device for exhaust gas according to claim 1, characterized in that: The deep purification device includes a primary fine stripping tower, a secondary fine stripping tower, and a heat exchanger. The outlet of the buffer tank is connected to the inlet of the primary fine stripping tower. The outlet of the primary fine stripping tower is connected to the inlet of the secondary fine stripping tower via a circulating fan. The outlet of the secondary fine stripping tower is connected to the heat exchanger via a flash evaporator. One end of the heat exchanger is connected to the exhaust pipe.

3. The hydrogen recovery and deep purification device for exhaust gas according to claim 2, characterized in that: The exhaust pipe is equipped with an exhaust flow regulating valve.

4. The hydrogen recovery and deep purification device for exhaust gas according to claim 1, characterized in that: A flow meter is installed on the pipeline connecting the buffer tank 2 to the purification tower.

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