Dehydration system for recovering vinyl chloride monomer

Abstract

The utility model discloses a kind of recovery vinyl chloride monomer's dehydration systems, including vinyl chloride gas cabinet, compressor, vinyl chloride condenser and drying device, compressor is screw compressor unit, vinyl chloride gas cabinet is connected with screw compressor unit, screw compressor unit is connected with vinyl chloride condenser, vinyl chloride condenser is connected with crude monomer storage tank, crude monomer storage tank is connected with drying device, drying device is connected with rectification process.Compared with prior art, the utility model recovers vinyl chloride monomer's dehydration system, using screw compressor unit and molecular sieve dryer, overall operation is good, recovery vinyl chloride liquid monomer water content can reach 100ppm below, rectification process plugging condition is eliminated, equipment operation stable fault frequency is obviously reduced, system stable operation rate is greatly improved, monomer storage tank does not need to drain, labor intensity of staff is reduced, further reduce potential risk, production safety stability is effectively guaranteed.

Description

Technical Field

[0001] This utility model relates to the field of vinyl chloride monomer recovery technology, and in particular to a dehydration system for recovering vinyl chloride monomer. Background Technology

[0002] During the vinyl chloride recovery process, a high water content in the recovered monomers will cause many adverse effects. The presence of water in the monomers leads to the hydrolysis of vinyl chloride peroxides, generating acidic substances such as hydrogen chloride, formic acid, and formaldehyde, which causes corrosion of the distillation system equipment. The iron ions generated by the equipment corrosion will promote the formation of peroxides by oxygen and vinyl chloride in the system. Peroxides can trigger the polymerization of vinyl chloride, generating polyvinyl chloride with a low degree of polymerization, which seriously affects normal production.

[0003] In existing technology, chlor-alkali enterprises dry and dehydrate recovered liquid vinyl chloride in a solid alkali drying tower. Vinyl chloride gas from the gas holder is pressurized by a water ring compressor and sent to a vinyl chloride condenser to condense into crude monomer. The crude monomer stored in the crude monomer storage tank is then refined in a distillation tower to remove high-boiling impurities. Finally, purified monomer of acceptable purity is obtained from the solid alkali drying tower and stored in a refined monomer storage tank for later use. Because the recovered vinyl chloride has a high water content (approximately 2000-3000 ppm), the dehydration effect of the solid alkali drying tower is poor, causing blockages in the distillation tower trays and connected pipelines, with a blockage frequency as high as 6 times per year. Simultaneously, the monomer pump bearings and bushings wear, resulting in significant equipment losses, high maintenance costs, and disruption of production stability.

[0004] Furthermore, using solid alkali as a desiccant presents high safety risks and demanding workloads for employees during alkali replacement operations. Each replacement requires the entire solid alkali drying tower to be replaced, blind flanges to be installed on-site, and manual loading of the solid alkali into the tower, a process that carries a high risk of alkali burns. Solid alkali absorbs water and becomes liquid alkali, accumulating at the bottom of the solid alkali drying tower. Due to the high concentration and viscosity of the alkali solution, and the considerable distance between the solid alkali drying tower and the waste alkali discharge tank, especially in winter when temperatures are low, the alkali discharge pipeline is highly susceptible to blockage due to alkali solidification. Utility Model Content

[0005] To address the aforementioned technical problems, this invention provides a dehydration system for recovering vinyl chloride monomer, employing a screw compressor unit to avoid the introduction of external moisture and a molecular sieve dryer to improve dehydration efficiency.

[0006] To achieve this technical objective, the present invention adopts the following solution: A dehydration system for recovering vinyl chloride monomer includes a vinyl chloride gas holder, a compressor, a vinyl chloride condenser, and a drying device. The compressor is a screw compressor unit. The vinyl chloride gas holder is connected to the screw compressor unit. The screw compressor unit is connected to the vinyl chloride condenser. The vinyl chloride condenser is connected to a crude monomer storage tank. The crude monomer storage tank is connected to the drying device, and the drying device is connected to a distillation process.

[0007] Furthermore, the screw compressor unit is equipped with an organic precooler and a precooler at the inlet, and an organic postcooler and an aftercooler at the outlet.

[0008] Furthermore, the drying device includes a shielded pump, a molecular sieve dryer, and a buffer tank. The inlet of the shielded pump is connected to the crude monomer storage tank, the outlet of the shielded pump is connected to the monomer inlet of the molecular sieve dryer, the monomer outlet of the molecular sieve dryer is connected to the buffer tank, and the buffer tank is connected to the distillation process.

[0009] Furthermore, the drying device also includes an electric heater and a heat exchanger; the electric heater is connected to the unit outlet of the molecular sieve dryer, the heat exchanger is connected to the unit inlet of the molecular sieve dryer, and the heat exchanger is connected to the vinyl chloride gas holder.

[0010] Furthermore, two shielded pumps are installed, one in operation and one on standby; at least two molecular sieve dryers are installed, and multiple molecular sieve dryers are connected in parallel.

[0011] Furthermore, the screw compressor unit adopts a PLC programmable controller.

[0012] Compared with the prior art, the beneficial effects of this utility model are as follows: This utility model's dehydration system for recovering vinyl chloride monomer uses a screw compressor unit and a molecular sieve dryer. The system operates well overall, and the water content of the recovered liquid vinyl chloride monomer can reach below 100 ppm. The blockage in the distillation process is eliminated, the equipment operates stably, the frequency of failures is significantly reduced, the system's stable operation rate is greatly improved, there is no need to drain water from the monomer storage tank, the workload of employees is reduced, potential risks are further reduced, and production safety and stability are effectively guaranteed. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the dehydration system for recovering vinyl chloride monomer in an embodiment of this utility model.

[0014] Figure 2 This is a schematic diagram of the drying device in an embodiment of the present invention.

[0015] The following are labeled in the diagram: 1. Vinyl chloride gas holder; 2. Pre-cooler; 3. Pre-water distributor; 4. Screw compressor unit; 5. Post-oil separator; 6. Post-cooler; 7. Vinyl chloride condenser; 8. Crude monomer storage tank; 9. Drying device; 10. Buffer tank; 11. Shielded pump; 12. Molecular sieve dryer; 13. Electric heater; 14. Heat exchanger. Detailed Implementation

[0016] To fully understand the purpose, features and effects of this utility model, the following specific embodiments will be used to describe this utility model in detail, but this utility model is not limited thereto.

[0017] See Figure 1 and Figure 2 This utility model provides a dehydration system for recovering vinyl chloride monomer, including a vinyl chloride gas holder 1, a compressor, a vinyl chloride condenser 7, a crude monomer storage tank 8, and a drying device 9, wherein the compressor is a screw compressor unit 4. The vinyl chloride gas holder 1 is connected to the screw compressor unit 4, the screw compressor unit 4 is connected to the vinyl chloride condenser 7, the vinyl chloride condenser 7 is connected to the crude monomer storage tank 8, the crude monomer storage tank 8 is connected to the drying device 9, and the drying device 9 is connected to the distillation process.

[0018] In one specific embodiment, the screw compressor unit 4 is provided with an organic precooler 2 and a precooler 3 at the inlet, the precooler 2 is connected to the vinyl chloride gas holder 1, and the screw compressor unit 4 is provided with an organic post-oil separator 5 and a postcooler 6 at the outlet, the postcooler 6 is connected to the vinyl chloride condenser 7.

[0019] Screw compressor unit 4 is existing equipment. Its main working principle is that a pair of meshing male and female rotors within the compressor rotate at a certain transmission ratio, generating periodic volume changes to complete the intake, compression, and discharge of gas. The gas is compressed in the closed toothed volume. The lubricating oil injected into the compressor cavity contains almost no free water, and it is efficiently separated and recycled in the subsequent oil-gas separator. Therefore, using screw compressor unit 4 will not introduce additional moisture.

[0020] A pre-cooler 2 and a pre-water separator 3 are added at the inlet of the screw compressor unit 4, and an after-oil separator 5 and an after-cooler 6 are added at the outlet. The recovered vinyl chloride gas from the vinyl chloride gas holder 1 enters the screw compressor unit 4 after the moisture content is reduced by the pre-cooler 2 and the pre-water separator 3. After being filtered by the intake filter, it enters the compressor. The screw compressor pressurizes the gas, and the compressed high-temperature and high-pressure gas enters the oil separator and the high-efficiency oil separator to remove the lubricating oil. Then it enters the after-oil separator 5 to separate the oil from the compressed gas. The vinyl chloride gas then enters the after-cooler 6 to further cool the moisture in the vinyl chloride gas, and then it is sent to the vinyl chloride condenser 7 to be condensed into crude monomer.

[0021] The screw compressor unit 4 adopts a PLC programmable controller, enabling automatic control and offering multiple operating modes including "local automatic," "remote automatic," and "debugging mode." When remote control is selected via communication, the unit performs start-up, shutdown, and energy regulation operations based on signals from the host computer. In any operating mode, the compressor can adjust in real time according to the set parameters of suction and discharge pressure and current, achieving a high degree of automation. The compressor is also equipped with multiple protection devices, including those for high / low suction pressure, high / low suction temperature, high / low discharge pressure, high / low discharge temperature, low oil supply pressure, high oil supply temperature, and motor overload protection. After prolonged operation, the compressor runs smoothly with minimal vibration, is simple and convenient to use, and receives positive overall user feedback.

[0022] In one specific embodiment, the drying device 9 includes a shielded pump 11, a molecular sieve dryer 12, a buffer tank 10, an electric heater 13, and a heat exchanger 14. Two shielded pumps 11 are provided, one in operation and one on standby. At least two molecular sieve dryers 12 are provided, with multiple molecular sieve dryers 12 connected in parallel. The molecular sieve dryers 12 are used for adsorption, desorption, regeneration, or standby according to actual operating conditions to ensure continuous production. The inlet of the shielded pump 11 is connected to the crude monomer storage tank 8, and the outlet of the shielded pump 11 is connected to the monomer inlet of the molecular sieve dryer 12. The monomer outlet of the molecular sieve dryer 12 is connected to the buffer tank 10, which is connected to the distillation process. The electric heater 13 is connected to the monomer outlet of the molecular sieve dryer 12 and is connected to a nitrogen pipeline. The heat exchanger 14 is connected to the monomer inlet of the molecular sieve dryer 12 and is connected to the vinyl chloride gas holder 1. Each component of the drying device 9 is equipped with a programmable valve and a regulating valve on its connecting pipelines, which are connected to the automatic control system.

[0023] The working principle of the drying unit 9 is as follows: Each molecular sieve dryer 12 undergoes adsorption (A), reverse release (D), displacement (RP), hot blowing (H), and cold blowing (C) processes in one cycle. The vinyl chloride raw material liquid from the crude monomer storage tank 8 is pressurized to 0.5~0.6MPa by the shielded pump 11 and flows from bottom to top through the molecular sieve dryer 12 at a flow rate of 1~2t / h. At this time, the device temperature is at room temperature. Under the adsorption pressure, most of the water in the vinyl chloride liquid is selectively adsorbed by the desiccant. The product liquid, after the water has been removed, flows out from the top of the molecular sieve dryer 12 and enters the buffer tank 10. After the desiccant adsorption is saturated, the adsorption step stops. The residual vinyl chloride in the tower is controlled by the reverse release regulating valve to release it into the vinyl chloride gas holder 1. After the reverse release step stops, the nitrogen gas connected to the top of the molecular sieve dryer 12 is turned on to replace the remaining VCM (vinyl chloride) in the molecular sieve dryer 12. Then, the electric heater 13 is turned on, and nitrogen gas is heated by the electric heater 13. The heated nitrogen gas enters from the top of the molecular sieve dryer 12 to heat and regenerate the bed of the molecular sieve dryer 12. The regenerated desorbed gas leaves the molecular sieve dryer 12 and enters the heat exchanger 14. The heat exchanger 14 lowers the temperature of the regenerated desorbed gas and sends it to the vinyl chloride gas holder 1. After the hot blowing is completed, the desiccant is completely regenerated. At this time, the electric heater 13 stops heating, and the molecular sieve dryer 12 is cold-blown with nitrogen gas. When the temperature of the bed of the molecular sieve dryer 12 approaches the set temperature, the molecular sieve dryer 12 reaches the conditions for re-adsorption and enters the next adsorption and drying cycle.

[0024] After the dehydration system for recovering vinyl chloride monomer of this invention was put into production, it operated well overall. The water content of the recovered liquid vinyl chloride monomer (vinyl chloride monomer in buffer tank 10) could reach below 100 ppm (see Table 1). Compared with the original process using a water ring compressor and a solid alkali drying tower, the water content of liquid vinyl chloride decreased by about 97%. After the dehydration system for recovering vinyl chloride monomer of this invention was put into production, the blockage in the distillation process was eliminated, the frequency of equipment failures was significantly reduced, the system's stable operation rate was greatly improved, there was no need to drain water from the monomer storage tank, the workload of employees was reduced, potential risks were further reduced, and production safety and stability were effectively guaranteed.

[0025] Table 1. Analysis results of vinyl chloride water content after system commissioning 1 55 2 37 3 62 4 43 Finally, it should be noted that the above-listed embodiments are merely preferred embodiments of the present invention. Of course, those skilled in the art can make modifications and variations to the present invention. If such modifications and variations fall within the scope of the claims of the present invention and their equivalents, they should be considered as being within the protection scope of the present invention.

Claims

1. A dehydration system for recovering vinyl chloride monomer, comprising a vinyl chloride gas holder (1), a compressor, a vinyl chloride condenser (7), and a drying device (9), characterized in that, The compressor is a screw compressor unit (4). The vinyl chloride gas holder (1) is connected to the screw compressor unit (4). The screw compressor unit (4) is connected to the vinyl chloride condenser (7). The vinyl chloride condenser (7) is connected to the crude monomer storage tank (8). The crude monomer storage tank (8) is connected to the drying device (9). The drying device (9) is connected to the distillation process.

2. The dehydrating system for recovering chloroethylene monomer according to claim 1, wherein The screw compressor unit (4) is equipped with an organic precooler (2) and a precooler (3) at the inlet, and an organic postcooler (5) and a postcooler (6) at the outlet.

3. The dehydrating system for recovering vinyl chloride monomer according to claim 1, wherein The drying device (9) includes a shielded pump (11), a molecular sieve dryer (12) and a buffer tank (10). The inlet of the shielded pump (11) is connected to the crude monomer storage tank (8), the outlet of the shielded pump (11) is connected to the monomer inlet of the molecular sieve dryer (12), the monomer outlet of the molecular sieve dryer (12) is connected to the buffer tank (10), and the buffer tank (10) is connected to the distillation process.

4. The dehydrating system for recovering chloroethylene monomer according to claim 3, wherein The drying device (9) also includes an electric heater (13) and a heat exchanger (14); the electric heater (13) is connected to the monomer outlet of the molecular sieve dryer (12), the heat exchanger (14) is connected to the monomer inlet of the molecular sieve dryer (12), and the heat exchanger (14) is connected to the vinyl chloride gas holder (1).

5. The dehydrating system for recovering vinyl chloride monomer according to claim 3 or 4, characterized by, Two shielded pumps (11) are set up, one in operation and one on standby; at least two molecular sieve dryers (12) are set up, and multiple molecular sieve dryers (12) are set up in parallel.

6. The dehydrating system for recovering chloroethylene monomer according to claim 1, wherein The screw compressor unit (4) adopts a PLC programmable controller.

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