A vinyl chloride synthesis replacement gas recovery and deep purification device

Abstract

This application discloses a device for recovering and deeply purifying vinyl chloride synthesis displacement gas, specifically relating to the field of chemical gas treatment technology. It includes two alkaline scrubbing towers connected in series, with each tower's outlet equipped with a gas-liquid separator. The end pipes of the two series-connected alkaline scrubbing towers are connected to a raw material gas buffer tank. The outlet of the raw material gas buffer tank is connected to an adsorption tower. The outlet of the adsorption tower's desorbed gas is connected to a vacuum pump. The top crude purified gas outlet of the adsorption tower is connected to a purified gas buffer tank. The outlet of the purified gas buffer tank is connected to a heater. A circulating fan for pressurization is installed between the purified gas buffer tank and the heater. The heater's outlet is connected to two dehydrocarbonization towers connected in series. The end pipes of the two series-connected dehydrocarbonization towers are connected to a cooler. Furthermore, the cooler and the adjacent dehydrocarbonization tower are connected by a circulating pipe leading to the inlet of the circulating fan. This application reduces pipeline corrosion and successfully recovers gases such as vinyl chloride and acetylene.

Description

Technical Field

[0001] This utility model belongs to the field of chemical gas treatment technology, specifically relating to a device for recovering and deeply purifying vinyl chloride synthesis displacement gas. Background Technology

[0002] Hydrogen chloride is a colorless, non-flammable gas with a pungent odor. It is highly soluble in water, forming hydrochloric acid, and is highly corrosive to the environment and equipment. High concentrations of hydrogen chloride are strongly irritating to the respiratory tract and eyes, and highly corrosive to the skin and mucous membranes. Vinyl chloride, also known as vinyl chloride, is an important monomer used in polymer chemicals. It is produced by reacting acetylene with hydrogen chloride and is a carcinogen. Long-term exposure may cause diseases such as liver cancer. When mixed with air, it easily forms an explosive gas mixture, and its release into the atmosphere damages the ozone layer.

[0003] In the calcium carbide process for polyvinyl chloride (PVC) production, the mercury-containing catalyst in the converter tubes of the vinyl chloride synthesis step needs to be extracted and refilled approximately every six months. During this process, the converter must first be blind-plate isolated, and nitrogen must be used to purge the hydrogen chloride and vinyl chloride content to ensure it meets standards. In conventional processing, the purged gas is transported to the gas holder, which leads to a gradual increase in the inert gas content, resulting in a series of adverse consequences, including decreased compressor efficiency and increased power consumption; increased operating pressure in the distillation system, poorer condensation effect, and greater product quality fluctuations; and increased load on the pressure swing adsorption (PSA) system, leading to decreased recovery efficiency. Some companies discharge the gas directly without treatment, causing not only environmental pollution but also significant safety risks. Untreated purge gas, or gas that has absorbed hydrogen chloride, directly entering the PSA system can cause corrosion of equipment and pipelines due to acid or water content, accelerating the adsorbent's failure rate.

[0004] As the operating time of a pressure swing adsorption (PSA) device increases, the adsorption capacity of its adsorbent gradually weakens. During the system's cyclic production process, some inert gases and non-methane hydrocarbons cannot be completely consumed. Long-term accumulation will exacerbate system deterioration, leading to fluctuations in gas emission indicators and potentially failing to meet environmental regulations.

[0005] Therefore, a new type of device for recovering and deeply purifying vinyl chloride synthesis gas is needed. Utility Model Content

[0006] To address the aforementioned problems, this utility model discloses a device for recovering and deeply purifying vinyl chloride synthesis displacement gas.

[0007] To achieve the above objectives, the technical solution of this utility model is as follows:

[0008] A vinyl chloride synthesis displacement gas recovery and deep purification device includes two alkaline washing towers connected in series, with each alkaline washing tower having a gas-liquid separator at its outlet. The end pipes of the two alkaline washing towers connected in series are connected to a raw material gas buffer tank. The outlet of the raw material gas buffer tank is connected to an adsorption tower. The desorbed gas outlet of the adsorption tower is connected to a vacuum pump, and the outlet of the vacuum pump is connected to a vinyl chloride recovery gas holder. The top crude purified gas outlet of the adsorption tower is connected to a purified gas buffer tank, and the outlet of the purified gas buffer tank is connected to a heater. A circulating fan for pressurization is installed between the purified gas buffer tank and the heater. The outlet of the heater is connected to two dehydrocarbonization towers connected in series. The end pipes of the two dehydrocarbonization towers connected in series are connected to a cooler, and the pipeline between the cooler and the adjacent dehydrocarbonization tower is also connected to a circulating pipeline leading to the inlet of the circulating fan.

[0009] As a preferred embodiment of this utility model, each of the gas-liquid separators is further provided with an extraction fan at its outlet, and the outlets of the two extraction fans are respectively connected to the alkali washing tower and the raw material gas buffer tank.

[0010] As a preferred embodiment of this invention, a compressor is provided between the raw material gas buffer tank and the adsorption tower.

[0011] As a preferred embodiment of this invention, the adsorption tower is provided with multiple adsorption beds that adsorb different substances.

[0012] The beneficial effects of this utility model are as follows:

[0013] I. This application removes acid and water from the vinyl chloride synthesis replacement gas before adsorbing and desorbing gases such as vinyl chloride and acetylene and transporting them to the gas holder, which reduces the corrosion of pipelines and successfully recovers gases such as vinyl chloride and acetylene, thereby improving economic benefits.

[0014] 2. This application involves subjecting organic waste gas to a vigorous catalytic oxidation reaction within the catalytic layer to generate carbon dioxide and water, thereby obtaining purified gas that meets emission standards, reducing direct emissions of synthesis replacement gas, significantly improving the environmental quality of the work site, effectively reducing the content of non-methane total hydrocarbons in the emitted gas, eliminating environmental data exceeding standards, and preventing the accumulation of inert gases and non-methane total hydrocarbons in the device from affecting the treatment of subsequent gases.

[0015] Third, in the initial operation stage of the dehydrogenation tower, this application uses an electric heater to provide the required heat. Subsequently, the system can use the heat generated by itself to maintain operational balance, thereby reducing power consumption, reducing the operating load of the original unit's compressor, distillation, tail gas adsorption and other systems, and enhancing the stability of system operation. Attached Figure Description

[0016] Figure 1 This is a diagram showing the overall connection relationship of an embodiment of the present utility model.

[0017] List of identifiers in attached diagrams:

[0018] 1. Alkali washing tower; 2. Gas-liquid separator; 3. Exhaust fan; 4. Raw material gas buffer tank; 5. Compressor; 6. Adsorption tower; 7. Vacuum pump; 8. Purified gas buffer tank; 9. Circulating fan; 10. Heater; 11. Dehydrocarbonization tower; 12. Cooler. Detailed Implementation

[0019] The present invention will be further explained below with reference to the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention.

[0020] Please see Figure 1 A device for recovering and deeply purifying vinyl chloride synthesis displacement gas includes two alkaline scrubbing towers 1 connected in series, with a gas-liquid separator 2 installed at the outlet of each alkaline scrubbing tower 1. The alkaline scrubbing towers 1 and gas-liquid separators 2 constitute a pretreatment unit. This unit should be continuously protected with nitrogen to prevent air intake. The primary alkaline scrubbing tower 1 in the pretreatment unit must be kept alkaline, while the secondary alkaline scrubbing tower 1 serves as a safety tower; acidic gases are strictly prohibited from entering subsequent systems, as this would exacerbate corrosion of equipment pipelines and potentially reduce the processing capacity of the adsorption tower 6 or even cause the internal packing to collapse. The hydrogen chloride content in the mixed gas treated by the two alkaline scrubbing towers 1 is 0% wt. The main body (tower body and trays) of the alkaline scrubbing tower 1 is made of FRP, and the liquid distributor is made of rigid PVC. An internal remote thermometer is installed, and the operating temperature does not exceed 65℃. The gas-liquid separator 2 is lined with rubber and equipped with a wire mesh filter; the equipment operating pressure difference does not exceed 2 kPa.

[0021] The end pipes of the two alkaline washing towers 1 connected in series are connected to a raw material gas buffer tank 4, and the outlet of the raw material gas buffer tank 4 is connected to an adsorption tower 6. The outlet of the desorbed gas from the adsorption tower 6 is connected to a vacuum pump 7, and the outlet of the vacuum pump 7 is connected to a vinyl chloride recovery gas holder. The top crude purified gas outlet of the adsorption tower 6 is connected to a purified gas buffer tank 8, and the outlet of the purified gas buffer tank 8 is connected to a heater 10. The outlet of the heater 10 is connected to two dehydrocarbon removal towers 11 connected in series. The end pipes of the two dehydrocarbon removal towers 11 connected in series are connected to a cooler 12, and the pipeline between the cooler 12 and the adjacent dehydrocarbon removal tower 11 is also connected to a circulation pipeline leading to the inlet of the circulating fan 9.

[0022] Each gas-liquid separator 2 is also equipped with an extraction fan 3 at its outlet, and the outlets of the two extraction fans 3 are respectively connected to the alkaline washing tower 1 and the raw material gas buffer tank 4 to maintain a slight negative pressure at the bottom outlet of the alkaline washing tower 1.

[0023] A compressor 5 is installed between the raw material gas buffer tank 4 and the adsorption tower 6. The compressor 5 is used to increase the adsorption pressure of the adsorption tower 6.

[0024] The adsorption tower 6 is equipped with multiple adsorption beds that adsorb different substances to efficiently adsorb various gas components. While adsorbing and desorbing vinyl chloride, the adsorption tower 6 also adsorbs and desorbs components such as acetylene. The crude purified gas, mainly composed of nitrogen, is discharged from the top of the adsorption tower 6 and sent to the non-methane total hydrocarbon deep purification unit for further treatment. A circulating fan 9 for pressurization is installed between the purified gas buffer tank 8 and the heater 10. The non-methane total hydrocarbon deep purification unit consists of the circulating fan 9, the heater 10, the hydrocarbon removal tower 11, and the cooler 12. The crude purified gas is pressurized to 50 kPa by the circulating fan 9 and heated to 300°C by the heater 10, before sequentially entering the two hydrocarbon removal towers 11 for treatment. Trace amounts of acetylene, hydrogen, carbon monoxide, and other components are catalytically converted into water and carbon dioxide, thereby achieving deep purification and releasing non-methane total hydrocarbons in the air with a concentration ≤20 mg / m³. 3 This will also reduce the number of times the on-site toxic gas alarms go off.

[0025] The synthesis displacement gas recovery technology of adsorption tower 6 utilizes the selectivity of the adsorbent for the adsorbed substances and the difference in adsorption capacity with pressure. Under high pressure, heavy components in the raw material, such as vinyl chloride and acetylene, are adsorbed, and under low pressure, these components are desorbed, allowing the adsorbent to regenerate. Acetylene and vinyl chloride are desorbed and recovered to the gas holder, while the crude purified gas, mainly nitrogen, enters the purified gas buffer tank 8 and is used as the circulating gas for dehydrocarbon removal tower 11.

[0026] Working principle:

[0027] During operation, the vinyl chloride synthesis replacement gas passes through two alkaline scrubbing towers 1 sequentially to absorb hydrogen chloride. The second alkaline scrubbing tower 1 is a safety tower to prevent acidic gases from entering subsequent systems and corroding equipment pipelines. Gas-liquid separators 2 are installed at the outlets of alkaline scrubbing towers 1 to ensure that only gas can enter the subsequent processing flow. Then, the mixed gas with the acidic gases removed enters the raw material gas buffer tank 4 for uniform mixing. After that, the mixed gas with the acidic gases removed enters the adsorption tower 6. The adsorption tower 6 adsorbs and desorbs components such as vinyl chloride and acetylene. The desorbed gas enters the recovery gas holder through the vacuum pump 7. The crude purified gas, mainly composed of nitrogen, is discharged from the top of the adsorption tower 6 after processing. It first enters the purified gas buffer tank 8 for uniform mixing and then is sent to the non-methane total hydrocarbon deep purification device for further processing.

[0028] During the deep purification of non-methane total hydrocarbons, the crude purified gas is pressurized to 50 kPa by the circulating fan 9 and heated to 300°C by the heater 10. It then sequentially enters two dehydrocarbon removal towers 11 for further processing. In the dehydrocarbon removal towers 11, trace amounts of acetylene, hydrogen, carbon monoxide, and other components are catalytically converted into water and carbon dioxide, thus achieving deep purification. A portion of the deeply purified gas is cooled and discharged from the cooler 12, while another portion is returned to the inlet of the circulating fan 9 through the circulation pipeline, maintaining a circulating gas volume of 3300 m³ / s. 3At approximately / h, the heat generated by the gas catalytic conversion is used to maintain heat balance, and heater 10 stops heating, thereby reducing power consumption.

[0029] The volume of replacement gas in vinyl chloride synthesis is uneven. To effectively protect the stable operation of the equipment, a raw material gas buffer tank 4 and a purified gas buffer tank 8 are respectively installed before the inlet of compressor 5 and circulating fan 9 to buffer and mix the gas evenly.

[0030] To address the potential for large fluctuations in the flow rate and composition of the upstream system, which could lead to excessive levels of non-methane total hydrocarbons in the exhaust gas, two sets of dehydrocarbon removal towers 11 connected in series were installed.

[0031] Once the unit is operating stably, it reduces the total non-methane hydrocarbon content while decreasing nitrogen enrichment, effectively reducing the operating load of the original unit's compressor, distillation, and tail gas adsorption systems, and enhancing the stability of the system operation.

[0032] It should be noted that the above content merely illustrates the technical concept of this utility model and cannot be used to limit the scope of protection of this utility model. For those skilled in the art, several improvements and modifications can be made without departing from the principle of this utility model, and all such improvements and modifications fall within the scope of protection of the claims of this utility model.

Claims

1. A chloroethylene synthesis displacement gas recovery and deep purification apparatus comprising two caustic wash columns (1), characterized in that, Two alkaline washing towers (1) are connected in series, and each alkaline washing tower (1) is equipped with a gas-liquid separator (2) at its outlet. The end pipes of the two alkaline washing towers (1) connected in series are connected to a raw material gas buffer tank (4). The outlet of the raw material gas buffer tank (4) is connected to an adsorption tower (6). The desorption gas outlet of the adsorption tower (6) is connected to a vacuum pump (7), and the outlet of the vacuum pump (7) is connected to a vinyl chloride recovery gas holder. The top crude purified gas outlet of the adsorption tower (6) is connected to a purified gas buffer tank (8). The outlet of the purified gas buffer tank (8) is connected to a heater (10). A circulating fan (9) for pressurization is provided between the purified gas buffer tank (8) and the heater (10). The outlet of the heater (10) is connected to two dehydrogenation towers (11) connected in series. The end pipes of the two dehydrogenation towers (11) connected in series are connected to a cooler (12). The pipeline between the cooler (12) and the adjacent dehydrogenation tower (11) is also connected to a circulating pipeline leading to the inlet of the circulating fan (9).

2. A vinyl chloride synthesis displacement recovery and deep purification device according to claim 1, characterized in that, Each of the gas-liquid separators (2) is also equipped with an extraction fan (3) at its outlet, and the outlets of the two extraction fans (3) are respectively connected to the alkaline washing tower (1) and the raw material gas buffer tank (4).

3. A vinyl chloride synthesis replacement gas recovery and deep purification device according to claim 1, characterized in that, A compressor (5) is installed between the raw material gas buffer tank (4) and the adsorption tower (6).

4. A vinyl chloride synthesis displacement recovery and deep purification device according to claim 1, characterized in that, The adsorption tower (6) is equipped with multiple adsorption beds that adsorb different substances.

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