Treatment system capable of recycling VOCs waste gas discharged by low-temperature methanol washing carbon dioxide

Abstract

The utility model relates to a treatment system capable of recycling VOCs (volatile organic compounds) waste gas discharged by low-temperature methanol washing carbon dioxide, which aims at solving the technical problem that the VOCs waste gas cannot be recycled after being burnt at present, and adopts the technical scheme that firstly, the maximum proportion of carbon dioxide is recycled by adopting the processes of compressing, purifying, liquefying and rectifying carbon dioxide; an industrial-grade or food-grade liquid carbon dioxide product is prepared at low cost, low-gas-volume and high-concentration VOCs waste gas such as regenerated gas and non-condensable gas in the system is purified by adopting a pressure swing adsorption process, up-to-standard emission is realized, and meanwhile, a fuel gas product with a high calorific value is obtained. According to the low-temperature methanol washing carbon dioxide emission VOCs waste gas recycling device, effective components in low-temperature methanol washing carbon dioxide emission VOCs waste gas can be reasonably recycled, industrial-grade / food-grade liquid carbon dioxide products can be produced, high-calorific-value fuel gas products can be obtained, and social benefits and economic benefits are remarkable.

Description

Technical Field

[0001] The utility model belongs to the technical field of recycling VOCs waste gas emitted by low-temperature methanol washing with carbon dioxide, and specifically relates to a processing system capable of recycling VOCs waste gas emitted by low-temperature methanol washing with carbon dioxide. Background Art

[0002] In the field of coal chemical industry, low-temperature methanol washing technology is widely used in the purification process of coal-to-synthetic ammonia and synthetic methanol due to its many advantages such as high purification degree, good selectivity and easy regeneration. In the carbon dioxide VOCs waste gas emitted in the low-temperature methanol washing purification process, carbon dioxide usually accounts for 80%-90%. In addition to carbon dioxide gas, it also contains saturated water and certain concentrations of hydrogen, carbon monoxide, methanol, methane and other VOCs components. If the carbon dioxide VOCs waste gas emitted by low-temperature methanol washing is directly discharged into the atmosphere, it will not only pollute the environment, but also cause a waste of precious resources.

[0003] However, the above-mentioned treatment process not only has the problems of high equipment investment cost and high system operating cost, but also simply burns the gas directly without recycling the largest proportion of carbon dioxide and does not fully consider the resource characteristics of VOCs components. Utility Model Content

[0004] The purpose of the utility model is to solve the above problems and provide a processing system for VOCs waste gas emitted by low-temperature methanol washing with carbon dioxide that can be recycled.

[0005] In order to solve the above technical problems, the technical solution adopted by the utility model is:

[0006] A treatment system for VOCs waste gas emitted by low-temperature methanol washing with carbon dioxide that can be recycled, including a gas-liquid buffer tank, a compressor, a purification unit, a liquefaction unit, an ice machine, a distillation tower, an industrial-grade / food-grade liquid CO2 product storage tank, and a pressure swing adsorption unit;

[0007] The VOCs waste gas emitted by the carbon dioxide from the low-temperature methanol washing device enters the gas-liquid buffer tank, the outlet of the gas-liquid buffer tank is connected to the inlet of the compressor, the outlet of the compressor is connected to the inlet of the purification unit, the outlet of the purification unit is connected to the inlet of the liquefaction unit, the ice machine is connected to the liquefaction unit, the outlet of the liquefaction unit is connected to the inlet of the distillation tower, the outlet of the distillation tower is connected to the liquid CO2 product storage tank, the exhaust port of the liquid CO2 product storage tank is connected to the adsorption tower of the purification unit through the gas phase carbon dioxide pipeline, the outlet of the liquid CO2 product storage tank is input into the tank truck through a pump, the exhaust ports of the purification unit and the liquefaction unit are both connected to the air inlet of the pressure swing adsorption unit, and the analysis gas discharge port of the pressure swing adsorption unit is connected to the downstream for sale or self-use.

[0008] Furthermore, the purification unit comprises two parallel adsorption towers, and the adsorption towers are filled with molecular sieves, activated carbon and alumina.

[0009] Furthermore, the refrigerant medium in the liquefaction unit is liquid ammonia or green Freon.

[0010] Furthermore, the liquid CO2 product storage tank includes an industrial-grade liquid CO2 product storage tank and a food-grade liquid CO2 product storage tank.

[0011] Furthermore, the adsorption tower of the pressure swing adsorption unit is filled with molecular sieves, activated carbon and alumina.

[0012] Compared with the prior art, the beneficial effects of the utility model are:

[0013] 1. The utility model adopts the process of carbon dioxide compression, purification, liquefaction and distillation to recover the largest proportion of carbon dioxide, and prepares industrial-grade or food-grade liquid carbon dioxide products at low cost;

[0014] 2. The utility model uses a pressure swing adsorption process to purify low-volume, high-concentration VOCs waste gas such as regenerated gas and non-condensable gas in the system to achieve standard emissions and obtain high calorific value gas products;

[0015] 3. The utility model can rationally recycle the effective components in the VOCs waste gas emitted by low-temperature methanol washing of carbon dioxide, and can not only produce industrial-grade / food-grade liquid carbon dioxide products, but also obtain high calorific value gas products, with significant social and economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic diagram of the structure of the utility model;

[0017] In the figure: 1. Gas-liquid buffer tank; 2. Compressor; 3. Purification unit; 4. Liquefaction unit; 5. Ice machine; 6. Distillation tower; 7. Industrial grade / food grade liquid CO2 product storage tank; 8. Gaseous carbon dioxide pipeline; 9. Pressure swing adsorption unit. DETAILED DESCRIPTION

[0018] The utility model is further described below in conjunction with the accompanying drawings and embodiments. Example

[0019] like Figure 1 As shown, a treatment system for VOCs waste gas emitted by low-temperature methanol washing with carbon dioxide can be recycled, comprising a gas-liquid buffer tank 1, a compressor 2, a purification unit 3, a liquefaction unit 4, an ice machine 5, a distillation tower 6, an industrial-grade / food-grade liquid CO2 product storage tank 7 and a pressure swing adsorption unit 9;

[0020] The VOCs waste gas emitted by the carbon dioxide from the low-temperature methanol washing device enters the gas-liquid buffer tank 1, the outlet of the gas-liquid buffer tank 1 is connected to the inlet of the compressor 2, the outlet of the compressor 2 is connected to the inlet of the purification unit 3, the purification unit 3 contains two parallel adsorption towers, the adsorption towers are equipped with molecular sieves, activated carbon, and alumina, the outlet of the purification unit 3 is connected to the inlet of the liquefaction unit 4, the ice machine 5 is connected to the liquefaction unit 4, the refrigerant medium is liquid ammonia, the outlet of the liquefaction unit 4 is connected to the inlet of the distillation tower 6, the outlet of the distillation tower 6 is connected to the liquid CO2 product storage tank 7, including industrial-grade liquid CO2 product storage tanks and food-grade liquid CO2 product storage tanks, and according to the demand for liquid carbon dioxide products in the surrounding market, the production of industrial-grade liquid carbon dioxide products or food-grade liquid carbon dioxide products can be selected by the user;

[0021] The exhaust port of the liquid CO2 product storage tank 7 is connected to the adsorption tower of the purification unit 3 through the gas phase carbon dioxide pipeline 8, and the outlet of the liquid CO2 product storage tank 7 is input into the tank truck through a pump, and the exhaust ports of the purification unit 3 and the liquefaction unit 4 are both connected to the air inlet of the pressure swing adsorption unit 9. The adsorption tower of the pressure swing adsorption unit 9 is equipped with molecular sieves, activated carbon and alumina, and the exhaust port of the analyzed gas is connected to the downstream for sale or self-use.

[0022] The refrigerant medium in the liquefaction unit 4 may also be green Freon.

[0023] The working process of this utility model:

[0024] The carbon dioxide emission VOCs waste gas from the low-temperature methanol washing device enters the gas-liquid buffer tank 1, and the supersaturated water carried in the low-temperature methanol washing carbon dioxide emission VOCs waste gas is separated. The separated low-temperature methanol washing carbon dioxide emission VOCs waste gas enters the compressor 2 and is pressurized to 2.5-3.0MPaG and then sent to the downstream purification unit 3. The purification unit 3 contains two parallel adsorption towers, which are equipped with molecular sieves, activated carbon, and alumina. The two parallel adsorption towers in the purification unit 3 take turns to adsorb and purify the compressed low-temperature methanol washing carbon dioxide emission VOCs waste gas. When one of the adsorption towers is saturated with adsorption, the gaseous CO2 evaporated in the industrial-grade / food-grade liquid CO2 product storage 7 is heated and then enters the adsorption tower of the purification unit 3 along the gaseous carbon dioxide pipeline 8 for desorption and regeneration. The regenerated gas is sent to the subsequent pressure swing adsorption unit 9. The pressurized low-temperature methanol carbon dioxide is washed and the VOCs waste gas is sent to the downstream liquefaction unit 4 after the water and high-boiling point VOCs components are removed by the purification unit 3. In the liquefaction unit 4, the exhaust gas is evaporated by the refrigerant medium liquid nitrogen to condense the gaseous CO2 into liquid CO2 and sent to the downstream distillation unit 6 for distillation and purification. Liquid nitrogen is vaporized into gaseous state, and the liquid nitrogen is recycled after being processed by ice machine 5. In the distillation unit 6, non-condensable gases such as nitrogen, methane, carbon monoxide are released through the pressure control valve at the top of the distillation tower and sent to the subsequent pressure swing adsorption unit 9. The liquid carbon dioxide after distillation and purification is sent to the industrial grade / food grade liquid CO2 product storage tank 7, and is pumped into the tank truck through the industrial grade / food grade liquid carbon dioxide product pipeline for export or use. According to the demand for liquid carbon dioxide products in the surrounding market, coal chemical enterprises can choose to produce industrial grade or food grade carbon dioxide products. The grade liquid carbon dioxide product is in the pressure swing adsorption unit 9, and the adsorption tower is equipped with molecular sieves, activated carbon, and alumina. The regenerated gas and non-condensable gas from the purification unit 3 and the distillation unit 6 are both low-volume, high-concentration VOCs gases, which are sent to the subsequent pressure swing adsorption unit 9 for adsorption purification and then achieved standard emission through the purified gas pipeline. The analyzed gas obtained by the analysis treatment of the pressure swing adsorption unit 9 is a low-volume, high-concentration VOCs gas, which is a high calorific value gas product and can be sold through a high calorific value gas pipeline or used by coal chemical enterprises.

Claims

1. A treatment system for recycling VOCs waste gas emitted by washing carbon dioxide with low-temperature methanol, characterized in that: It includes a gas-liquid buffer tank (1), a compressor (2), a purification unit (3), a liquefaction unit (4), an ice machine (5), a distillation tower (6), an industrial-grade / food-grade liquid CO2 product storage tank (7) and a pressure swing adsorption unit (9); The VOCs waste gas emitted by the carbon dioxide from the low-temperature methanol washing device enters the gas-liquid buffer tank (1), the outlet of the gas-liquid buffer tank (1) is connected to the inlet of the compressor (2), the outlet of the compressor (2) is connected to the inlet of the purification unit (3), the outlet of the purification unit (3) is connected to the inlet of the liquefaction unit (4), the ice machine (5) is connected to the liquefaction unit (4), the outlet of the liquefaction unit (4) is connected to the inlet of the distillation tower (6), the outlet of the distillation tower (6) is connected to the liquid CO2 product storage tank (7), the exhaust port of the liquid CO2 product storage tank (7) is connected to the adsorption tower of the purification unit (3) through the gas phase carbon dioxide pipeline (8), the outlet of the liquid CO2 product storage tank (7) is input into the tank truck through the pump, the exhaust ports of the purification unit (3) and the liquefaction unit (4) are both connected to the air inlet of the pressure swing adsorption unit (9), and the analytical gas discharge port of the pressure swing adsorption unit (9) is connected to the downstream for external sale or self-use.

2. According to claim 1, a system for recycling VOCs waste gas emitted by washing carbon dioxide with low-temperature methanol, characterized in that: The purification unit (3) comprises two adsorption towers connected in parallel, and the adsorption towers are filled with molecular sieves, activated carbon and alumina.

3. According to claim 1, a treatment system for recycling VOCs waste gas emitted by washing carbon dioxide with low-temperature methanol is characterized in that: The refrigerant medium in the liquefaction unit (4) is liquid ammonia or green Freon.

4. According to claim 1, a treatment system for recycling VOCs waste gas emitted by washing carbon dioxide with low-temperature methanol is characterized in that: The liquid CO2 product storage tank (7) includes an industrial-grade liquid CO2 product storage tank and a food-grade liquid CO2 product storage tank.

5. According to claim 1, a treatment system for recycling VOCs waste gas emitted by washing carbon dioxide with low-temperature methanol is characterized in that: The adsorption tower of the pressure swing adsorption unit (9) is filled with molecular sieve, activated carbon and alumina.

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