Alkali washing system and method for removing residual additives in recycled vinyl chloride monomer
The double-tower alkaline washing system is used to perform primary and secondary washing on the recovered vinyl chloride monomer, which solves the problem of residual additives affecting polymerization reaction control and product quality, achieves efficient removal of residual additives, and improves the purity of the recovered monomer and the stability of equipment operation.
Patent Information
- Application Number
- CN202211606309.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2022-12-14
- Publication Date
- 2025-09-05
- Estimated Expiration
- 2042-12-14
AI Technical Summary
In the production of polyvinyl chloride, it is difficult to effectively remove the residual additives in the recovered vinyl chloride monomer, which leads to difficulties in controlling the polymerization reaction, reduced quality of PVC products and blockage of pipeline equipment.
A double-tower alkali washing system is used, including an upper alkali washing tower and a lower alkali washing tower. Residual additives are removed through reverse contact washing. The temperature and concentration of the alkali solution are controlled by a circulating pump and a cooler to achieve primary and secondary washing treatments.
It improves the purity of the recovered monomers, improves the whiteness of the PVC product, reduces the self-polymerization of pipeline equipment, and avoids the blockage of valves and distillation towers.
Smart Images
Figure CN116139794B_ABST
Abstract
Description
Technical Field
[0001] The invention relates to an alkali washing process in polyvinyl chloride production, in particular to an alkali washing system and an alkali washing method for removing residual additives in recycled vinyl chloride monomer, belonging to the field of chemical production. Background Art
[0002] In the polyvinyl chloride production process, after the reaction in the polymerization kettle is completed, 15% to 18% of the vinyl chloride monomer in the kettle has not participated in the reaction. The traditional method is to condense the unreacted gaseous monomer into liquid monomer through self-pressure and pressurized recovery and send it into the recovery monomer storage tank, and then enter the polymerization kettle together with fresh monomer for polymerization reaction and reuse.
[0003] However, the recovered monomer contains residual additives such as dispersants and initiators from the polymerization reaction, as well as impurities such as high-grade waste, acetaldehyde, and hydrogen chloride. When the recovered monomer containing residual additives is added to the polymerization kettle again to participate in the reaction, the polymerization reaction is difficult to control and has a great impact on the quality whiteness index of PVC products. Self-polymerization is also prone to occur in pipeline equipment, and the resulting self-polymers will clog valves, pipelines, and distillation towers.
[0004] At present, the residual additives in the recovered vinyl chloride monomer are generally removed by using alkaline washing. Generally, a single alkaline washing tower is set up or two alkaline washing towers are connected in series to remove the residual additives contained in the recovered vinyl chloride monomer, but the effect is not very ideal and the quality of the recovered monomer needs to be improved. Summary of the Invention
[0005] The present invention provides an alkali washing system and an alkali washing method for removing residual additives in recovered vinyl chloride monomer. The purpose is to solve the problems that the residual additives in the polymerization reaction of the recycled vinyl chloride monomer during polyvinyl chloride production affect the polymerization reaction, making the polymerization reaction difficult to control, affecting the quality and whiteness of PVC products, and causing self-polymerization of pipeline equipment, thereby clogging valves, pipelines and distillation towers.
[0006] To achieve the above object, the present invention provides the following technical solutions:
[0007] An alkali washing system for removing residual additives in recycled vinyl chloride monomer comprises an alkali washing tower, wherein the alkali washing tower comprises an alkali washing upper tower (1) and an alkali washing lower tower (2), the bottom of the alkali washing lower tower (2) is provided with a recovered monomer inlet pipe (3), the top of the alkali washing upper tower (1) is provided with a recovered monomer outlet pipe (4), the upper parts of the alkali washing upper tower (1) and the alkali washing lower tower (2) are respectively provided with an upper tower alkali liquid feed pipeline (5) and a lower tower alkali liquid feed pipeline (6), and the upper tower alkali liquid feed pipeline (5) and the lower tower alkali liquid feed pipeline (6) are respectively provided with a recovered monomer inlet pipe (3) and a recovered monomer outlet pipe (4). An alkali liquid circulation pipeline (7) is provided between the pipelines (6); an upper tower alkali liquid discharge pipeline (18) and a lower tower alkali liquid discharge pipeline (19) are provided at the bottoms of the upper alkali washing tower (1) and the lower alkali washing tower (2), respectively; an upper tower circulation pump (10) and an upper tower cooler (13) are provided between the upper tower alkali liquid feed pipeline (5) and the upper tower alkali liquid discharge pipeline (18); and a lower tower circulation pump (9) and a lower tower cooler (11) are provided between the lower tower alkali liquid feed pipeline (6) and the lower tower alkali liquid discharge pipeline (19).
[0008] Furthermore, a waste alkali solution discharge pipeline (16) is provided between the lower tower circulation pump (9) and the lower tower cooler (11).
[0009] Furthermore, the device further comprises a start-up preheater (12), wherein the start-up preheater (12) is arranged in parallel with the upper tower cooler (13). When the device is started, the start-up preheater (12) is first opened, and the upper tower cooler (13) is closed. The alkali solution is circulated and heated through the start-up preheater (12). When the alkali solution temperature rises to the target value and the liquid levels of the alkali washing upper tower (1) and the alkali washing lower tower (2) both reach the target values, the upper tower cooler (13) is opened, and the start-up preheater (12) is closed.
[0010] Furthermore, the start-up preheater (12) is provided with a steam pipeline (17), and the alkali solution is heated by using the steam pipeline (10).
[0011] Furthermore, a new alkali solution replenishing pipeline (15) is provided on the pipeline between the upper tower circulation pump (10) and the upper tower cooler (13), and fresh alkali solution in the alkali tank is replenished to the alkali washing upper tower (1) through the new alkali solution replenishing pipeline (15).
[0012] Furthermore, a regulating valve (8) is provided on the alkali liquid circulation pipeline (7). When the alkali liquid in the alkali washing upper tower (1) needs to be pumped into the alkali washing lower tower (2), the regulating valve (8) is opened to circulate the alkali liquid in the alkali washing upper tower (1) into the alkali washing lower tower (2) through the alkali liquid circulation pipeline (7).
[0013] Furthermore, the upper tower cooler (13) and the lower tower cooler (11) are both provided with a circulating water pipeline (14). The function of the circulating water pipeline (14) is to circulate cooling water to the upper tower cooler (13) and the lower tower cooler (11), thereby lowering the temperature of the upper and lower coolers and ensuring that the temperature of the circulating alkali solution meets the system requirements.
[0014] An alkali washing method for removing residual additives in recycled vinyl chloride monomer, using the above-mentioned alkali washing system for removing residual additives in recycled vinyl chloride monomer, mainly comprises the following steps:
[0015] (1) The gas phase recovered vinyl chloride monomer enters the alkali washing tower from the recovery monomer inlet pipe (3) at the bottom of the alkali washing lower tower (2), flows from bottom to top in the alkali washing tower, and passes through the alkali washing lower tower (2) and the alkali washing upper tower (1) in sequence. At the same time, alkali liquor with a concentration of 8-15% enters the alkali washing lower tower (2) and the alkali washing upper tower (1) from the upper tower alkali liquor feed pipeline (5) and the lower tower alkali liquor feed pipeline (6) at the top of the alkali washing upper tower (1) and the alkali washing lower tower (2) respectively. The alkali liquor flows from top to bottom in the alkali washing upper tower (1) and the alkali washing lower tower (2) and contacts and washes the gas phase recovered vinyl chloride monomer in the reverse direction. The gas phase recovered vinyl chloride monomer undergoes the primary treatment of the alkali washing lower tower (2) and the secondary treatment of the alkali washing upper tower (1), and then passes through the alkali washing upper tower (1 ) The recovered monomer outlet pipe (4) at the top sends the vinyl chloride gas after alkali washing out of the alkali washing tower to the next step, and the alkali liquor for washing the gas phase to recover vinyl chloride monomer is discharged through the upper tower alkali liquor outlet pipeline (18) and the lower tower alkali liquor outlet pipeline (19) respectively, and is transported to the upper part of the alkali washing upper tower (1) and the alkali washing lower tower (2) by the upper tower circulation pump (10) and the lower tower circulation pump (9) for recycling. The circulating alkali liquor is cooled by the cooler to make the temperature of the alkali washing tower 30-40°C;
[0016] (2) When the alkali solution concentration in the alkali washing lower tower (2) is less than 8% for NaOH and greater than 8% for Na2CO3, the alkali solution in the alkali washing lower tower (2) is discharged through the waste alkali solution discharge pipeline (16), and then the alkali solution in the alkali washing upper tower (1) is introduced into the alkali washing lower tower (2) through the alkali solution circulation pipeline (7) provided between the upper tower alkali solution feed pipeline (5) and the lower tower alkali solution feed pipeline (6), and fresh alkali solution is added to the alkali washing upper tower (1).
[0017] An alkali washing method for removing residual additives in recycled vinyl chloride monomer, using the alkali washing system for removing residual additives in recycled vinyl chloride monomer as described above, is characterized in that it mainly comprises the following steps:
[0018] (1) Alkali is pumped into the alkali washing upper tower (1) through the new alkali liquid replenishing pipeline (15), the upper tower circulation pump (10) is started, the alkali liquid circulation flow rate is adjusted to 100-130m3 / h, the circulating alkali liquid is heated through the start-up preheater (12), the alkali liquid of the upper tower with the adjusted temperature is passed into the alkali washing lower tower (2) through the alkali liquid circulation pipeline (7), the lower tower circulation pump (9) is started, the alkali liquid circulation flow rate is adjusted to 100-130m3 / h, the liquid level of the alkali washing lower tower (2) is controlled to 2-2.5m, fresh alkali liquid is continuously passed into the alkali washing upper tower (1), the alkali liquid is heated through the start-up preheater (12), and the liquid level of the alkali washing upper tower (1) is controlled to 1-1.5m. When the alkali liquid temperature in the alkali washing tower is 30-40℃, the start-up preheater (12) is closed;
[0019] (2) The gas phase recovered vinyl chloride monomer enters the alkali washing tower from the recovery monomer inlet pipe (3) at the bottom of the alkali washing lower tower (2), flows from bottom to top in the alkali washing tower, and passes through the alkali washing lower tower (2) and the alkali washing upper tower (1) in sequence. At the same time, alkali liquor with a concentration of 8-15% enters the alkali washing lower tower (2) and the alkali washing upper tower (1) from the upper tower alkali liquor feed pipeline (5) and the lower tower alkali liquor feed pipeline (6) at the upper part of the alkali washing upper tower (1) and the alkali washing lower tower (2) respectively. The alkali liquor flows from top to bottom in the alkali washing upper tower (1) and the alkali washing lower tower (2) and contacts and washes the gas phase recovered vinyl chloride monomer in the reverse direction. The gas phase recovered vinyl chloride monomer undergoes the primary treatment of the alkali washing lower tower (2) and the secondary treatment of the alkali washing upper tower (1), and then passes through the alkali washing upper tower (1 ) The recovered monomer outlet pipe (4) at the top sends the vinyl chloride gas after alkali washing out of the alkali washing tower to the next step, and the alkali liquor for washing the gas phase to recover vinyl chloride monomer is discharged through the upper tower alkali liquor outlet pipeline (18) and the lower tower alkali liquor outlet pipeline (19) respectively, and is transported to the upper part of the alkali washing upper tower (1) and the alkali washing lower tower (2) by the upper tower circulation pump (10) and the lower tower circulation pump (9) for recycling. The circulating alkali liquor is cooled by the cooler to make the temperature of the alkali washing tower 30-40°C;
[0020] (3) When the alkali solution concentration in the alkali washing lower tower (2) is less than 8% for NaOH and greater than 8% for Na2CO3, the alkali solution in the alkali washing lower tower (2) is discharged through the waste alkali solution discharge pipeline (16), and then the alkali solution in the alkali washing upper tower (1) is introduced into the alkali washing lower tower (2) through the alkali solution circulation pipeline (7) provided between the upper tower alkali solution feed pipeline (5) and the lower tower alkali solution feed pipeline (6), and fresh alkali solution is added to the alkali washing upper tower (1).
[0021] Furthermore, the pressure of the alkali washing tower is less than 0.4 MPa.
[0022] Compared with the prior art, the present invention performs primary and secondary washing treatments on the recovered vinyl chloride monomer containing polymerization aids through an alkali washing upper tower and an alkali washing lower tower, thereby effectively removing residues in the recovered monomer, improving the purity of the recovered monomer, reducing the difficulty in controlling the recovered monomer when participating in the polymerization reaction, improving the whiteness of the PVC product, and significantly reducing the self-polymerization of pipeline equipment, thereby avoiding blockage of valves, pipelines and distillation towers. BRIEF DESCRIPTION OF THE DRAWINGS
[0023] Figure 1 It is a structural diagram of the invention.
[0024] As shown in the figure: 1 is the alkali washing upper tower, 2 is the alkali washing lower tower, 3 is the recovery monomer inlet pipe, 4 is the recovery monomer outlet pipe, 5 is the upper tower alkali solution feed pipeline, 6 is the lower tower alkali solution feed pipeline, 7 is the alkali solution circulation pipeline, 8 is the regulating valve, 9 is the lower tower circulation pump, 10 is the upper tower circulation pump, 11 is the lower tower cooler, 12 is the start-up preheater, 13 is the upper tower cooler, 14 is the circulating water pipeline, 15 is the new alkali solution replenishment pipeline, 16 is the waste alkali solution discharge pipeline, 17 is the steam pipeline, 18 is the upper tower alkali solution discharge pipeline, and 19 is the lower tower alkali solution discharge pipeline. DETAILED DESCRIPTION
[0025] Reference Figure 1 , the preferred embodiments of the present invention are described in detail below.
[0026] Example 1: An alkali washing system for removing residual additives in recycled vinyl chloride monomer, comprising an alkali washing tower, the alkali washing tower comprising an alkali washing upper tower 1 and an alkali washing lower tower 2, the bottom of the alkali washing lower tower 2 is provided with a monomer recovery air inlet pipe 3, the top of the alkali washing upper tower 1 is provided with a monomer recovery air outlet pipe 4, the upper parts of the alkali washing upper tower 1 and the alkali washing lower tower 2 are respectively provided with an upper tower alkali liquid feed pipeline 5 and a lower tower alkali liquid feed pipeline 6, and an alkali liquid circulation pipeline 7 is provided between the upper tower alkali liquid feed pipeline 5 and the lower tower alkali liquid feed pipeline 6, and a regulating valve 8 is provided on the alkali liquid circulation pipeline 7. When the alkali liquid in the alkali washing upper tower 1 needs to be pumped into the alkali washing lower tower 2, the regulating valve 8 is opened, and the alkali liquid in the alkali washing upper tower 1 is circulated to the alkali washing lower tower 2 through the alkali liquid circulation pipeline 7.
[0027] An upper tower alkali solution discharge pipeline 18 and a lower tower alkali solution discharge pipeline 19 are respectively provided at the bottom of the upper alkali washing tower 1 and the lower alkali washing tower 2. An upper tower circulation pump 10 and an upper tower cooler 13 are provided between the upper tower alkali solution feed pipeline 5 and the upper tower alkali solution discharge pipeline 18. A new alkali solution replenishment pipeline 15 is provided on the pipeline between the upper tower circulation pump 10 and the upper tower cooler 13. Fresh alkali solution in the alkali tank is replenished to the upper alkali washing tower 1 through the new alkali solution replenishment pipeline 15.
[0028] A lower tower circulation pump 9 and a lower tower cooler 11 are provided between the lower tower alkali solution feed pipeline 6 and the lower tower alkali solution discharge pipeline 19 , and a waste alkali solution discharge pipeline 16 is provided between the lower tower circulation pump 9 and the lower tower cooler 11 .
[0029] The upper tower cooler 13 and the lower tower cooler 11 are both provided with a circulating water pipeline 14. The function of the circulating water pipeline 14 is to circulate cooling water to the upper tower cooler 13 and the lower tower cooler 11, so as to reduce the temperature of the upper and lower coolers and ensure that the temperature of the circulating alkali solution meets the system requirements.
[0030] Example 2: Compared with Example 1, the difference of this embodiment is that it also includes a start-up preheater 12, which is provided with a steam pipeline 17. The start-up preheater 12 is arranged in parallel with the upper tower cooler 13. When the device is started, the start-up preheater 12 is first opened and the upper tower cooler 13 is closed. The alkali solution circulates in the alkali washing upper tower 1, the start-up preheater 12 and the import and export pipelines through the upper tower circulation pump 10 and the alkali solution in the start-up preheater 12 is heated by using the steam pipeline 17. When the alkali solution temperature in the alkali washing upper tower 1 rises to the target value and the liquid levels of the alkali washing upper tower 1 and the alkali washing lower tower 2 reach the target value, the upper tower cooler 13 is opened and the start-up preheater 12 is closed. The gas phase with unreacted residual additives sent by the compressor is introduced into the alkali washing tower to recover vinyl chloride monomer, and is reversely contacted and washed with the alkali solution in the tower.
[0031] Example 3: An alkaline washing method for removing residual additives in recycled vinyl chloride monomer, mainly comprising the following steps:
[0032] (1) The gas phase recovery of vinyl chloride monomer enters the alkali washing tower from the recovery monomer inlet pipe 3 at the bottom of the alkali washing lower tower 2, flows from bottom to top in the alkali washing tower, and passes through the alkali washing lower tower 2 and the alkali washing upper tower 1 in turn. At the same time, the concentration is 8-15%. The alkali liquor enters the alkali washing lower tower 2 and the alkali washing upper tower 1 from the upper tower alkali liquor feed pipeline 5 and the lower tower alkali liquor feed pipeline 6 at the upper parts of the alkali washing upper tower 1 and the alkali washing lower tower 2 respectively. The alkali liquor flows from top to bottom in the alkali washing upper tower 1 and the alkali washing lower tower 2, contacts with the gas-phase recovered vinyl chloride monomer in reverse and washes. The gas-phase recovered vinyl chloride monomer undergoes the primary treatment of the alkali washing lower tower 2 and the secondary treatment of the alkali washing upper tower 1 respectively, and the alkali-washed vinyl chloride gas is sent out of the alkali washing tower to the next step through the recovered monomer outlet pipe 4 at the top of the alkali washing upper tower 1. The alkali liquor washed with the gas-phase recovered vinyl chloride monomer is discharged through the upper tower alkali liquor discharge pipeline 18 and the lower tower alkali liquor discharge pipeline 19 respectively, and is transported to the upper part of the alkali washing upper tower 1 and the alkali washing lower tower 2 by the upper tower circulation pump 10 and the lower tower circulation pump 9 for recycling. The circulating alkali liquor is cooled by the cooler to make the temperature of the alkali washing tower 30-40°C;
[0033] (2) When the alkali solution concentration in the alkali washing lower tower 2 is: NaOH is less than 8% and Na2CO3 is greater than 8%, the alkali solution in the alkali washing lower tower 2 is discharged through the waste alkali solution discharge pipeline 16, and then the alkali solution in the alkali washing upper tower 1 is introduced into the alkali washing lower tower 2 through the alkali solution circulation pipeline 7 provided between the upper tower alkali solution feed pipeline 5 and the lower tower alkali solution feed pipeline 6, and fresh alkali solution is added to the alkali washing upper tower 1.
[0034] Example 4: An alkali washing method for removing residual additives in recycled vinyl chloride monomer, mainly comprising the following steps:
[0035] (1) Start the alkali tank's alkali pump, and pump the fresh alkali solution with a concentration of 8-15% configured in the alkali tank into the alkali washing upper tower 1 through the new alkali solution replenishing pipeline 15. When the liquid level of the alkali washing upper tower 1 is greater than 1m, start the upper tower circulation pump 10 to circulate the alkali solution in the alkali washing upper tower 1, the start-up preheater 12, the upper tower alkali solution feeding pipeline 5 and the upper tower alkali solution discharge pipeline 18. Adjust the alkali solution circulation flow rate to 100-130m3 / h, and control the upper tower liquid level at 1-1.5m. By adjusting the steam regulating valve on the steam pipeline 10, heat the alkali solution in the start-up preheater 12 and control the temperature to 30-40℃. Pass the alkali solution of the upper tower with adjusted temperature into the alkali washing lower tower 2 through the alkali solution circulation pipeline 7. Specifically, open the regulating valve 8 set on the alkali solution circulation pipeline 7, and the alkali solution in the alkali washing upper tower 1 is discharged from the upper tower alkali solution discharge pipeline 18. Discharge, through the start-up preheater 12, into the alkali washing lower tower 2 via the alkali solution circulation pipeline 7; when the liquid level of the alkali washing lower tower 2 is greater than 1m, start the lower tower circulation pump 9, circulate the alkali solution through the lower tower cooler 11, and adjust the alkali solution circulation flow rate to 100-130m3 / h. At this time, the regulating valve of the circulating water pipeline 14 on the lower tower cooler 11 is in a closed state, and the liquid level of the alkali washing lower tower 2 is controlled to be 2-2.5m. Close the regulating valve 8, continue to introduce fresh alkali solution into the alkali washing upper tower 1, heat the alkali solution through the start-up preheater 12, and control the liquid level of the alkali washing upper tower 1 to be 1-1.5m, and turn off the alkali adding pump; determine that when the liquid level of the alkali washing upper tower 1 is 1-1.5m, the liquid level of the alkali washing lower tower 2 is 2-2.5m, and the alkali solution temperature in the alkali washing tower is 30-40°C, open the upper tower cooler 13 and turn off the start-up preheater 12;
[0036] (2) Then the gaseous phase recovered vinyl chloride monomer with unreacted residual additives sent by the compressor is passed into the alkali washing tower from the recovery monomer inlet pipe 3 at the bottom of the alkali washing lower tower 2, and flows from bottom to top in the alkali washing tower, passing through the alkali washing lower tower 2 and the alkali washing upper tower 1 in turn. At the same time, the concentration is 8-15%. The alkali liquor enters the alkali washing lower tower 2 and the alkali washing upper tower 1 from the upper tower alkali liquor feed pipeline 5 and the lower tower alkali liquor feed pipeline 6 at the upper parts of the alkali washing upper tower 1 and the alkali washing lower tower 2 respectively. The alkali liquor is evenly distributed in the alkali washing upper tower 1 and the alkali washing lower tower 2 through the filler, and flows from top to bottom to contact and wash the gas-phase recovered vinyl chloride monomer in reverse. The gas-phase recovered vinyl chloride monomer first undergoes the primary treatment of the alkali washing lower tower 2 and then enters the alkali washing upper tower 1 for secondary treatment. Then, the alkali-washed vinyl chloride gas is sent out of the alkali washing tower to the next step through the recovered monomer outlet pipe 4 at the top of the alkali washing upper tower 1. The alkali liquor washed with the gas-phase recovered vinyl chloride monomer is discharged through the upper tower alkali liquor discharge pipeline 18 and the lower tower alkali liquor discharge pipeline 19 respectively, and is transported to the upper part of the alkali washing upper tower 1 and the alkali washing lower tower 2 by the upper tower circulation pump 10 and the lower tower circulation pump 9 for recycling. The circulating alkali liquor is cooled by the cooler so that the temperature of the alkali washing tower is 30-40°C.
[0037] (3) When it is detected that the concentration of the alkali liquid in the alkali washing lower tower 2 is unqualified: when the NaOH concentration is less than 8% and the Na2CO3 concentration is greater than 8%, the alkali liquid in the alkali washing lower tower 2 is discharged to the waste alkali liquid treatment process through the waste alkali liquid discharge pipeline 16, and then the alkali liquid in the alkali washing upper tower 1 is introduced into the alkali washing lower tower 2 through the alkali liquid circulation pipeline 7 provided between the upper tower alkali liquid feed pipeline 5 and the lower tower alkali liquid feed pipeline 6. Specifically, the regulating valve 8 provided on the alkali liquid circulation pipeline 7 is opened, and the alkali liquid in the alkali washing upper tower 1 is discharged from the upper tower alkali liquid discharge pipeline 18, passes through the upper tower cooler 13, and enters the alkali washing lower tower 2 through the alkali liquid circulation pipeline 7. Fresh alkali liquid is replenished in the alkali washing upper tower 1, and the pressure of the alkali washing tower is less than 0.4MPa.
[0038] The above description is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this field, several changes and improvements can be made without departing from the creative concept of the present invention, which all fall within the scope of protection of the present invention.
Claims
1. An alkali washing system for removing residual additives in recycled vinyl chloride monomer, comprising an alkali washing tower, characterized in that: The alkali washing tower comprises an upper alkali washing tower and a lower alkali washing tower, the bottom of the lower alkali washing tower is provided with a monomer recovery air inlet pipe, the top of the upper alkali washing tower is provided with a monomer recovery air outlet pipe, the upper parts of the upper alkali washing tower and the lower alkali washing tower are respectively provided with an upper tower alkali liquid feed pipeline and a lower tower alkali liquid feed pipeline, and an alkali liquid circulation pipeline is provided between the upper tower alkali liquid feed pipeline and the lower tower alkali liquid feed pipeline, the bottoms of the upper alkali washing tower and the lower alkali washing tower are respectively provided with an upper tower alkali liquid discharge pipeline and a lower tower alkali liquid discharge pipeline, an upper tower circulation pump and an upper tower cooler are provided between the upper tower alkali liquid feed pipeline and the upper tower alkali liquid discharge pipeline, and a lower tower circulation pump and a lower tower cooler are provided between the lower tower alkali liquid feed pipeline and the lower tower alkali liquid discharge pipeline.
2. The alkali washing system for removing residual additives in recycled vinyl chloride monomer according to claim 1, characterized in that: A waste alkali liquid discharge pipeline is provided between the lower tower circulation pump and the lower tower cooler.
3. The alkali washing system for removing residual additives in recycled vinyl chloride monomer according to claim 1, characterized in that: It also includes a start-up preheater, which is arranged in parallel with the upper tower cooler.
4. The alkali washing system for removing residual additives in recycled vinyl chloride monomer according to claim 3, characterized in that: The start-up preheater is provided with a steam pipeline.
5. The alkali washing system for removing residual additives in recycled vinyl chloride monomer according to claim 1, characterized in that: A new alkali solution replenishing pipeline is provided on the pipeline between the upper tower circulation pump and the upper tower cooler.
6. The alkali washing system for removing residual additives in recycled vinyl chloride monomer according to claim 1, characterized in that: A regulating valve is provided on the alkali solution circulation pipeline.
7. The alkali washing system for removing residual additives in recycled vinyl chloride monomer according to claim 1, characterized in that: The upper tower cooler and the lower tower cooler are both provided with circulating water pipelines.
8. An alkali washing method for removing residual additives in recycled vinyl chloride monomer, using the alkali washing system for removing residual additives in recycled vinyl chloride monomer according to claim 2, characterized in that: The main steps include: The gas phase recovered vinyl chloride monomer enters the alkali washing tower from the recovery monomer inlet pipe at the bottom of the alkali washing lower tower, flows from bottom to top in the alkali washing tower, and passes through the alkali washing lower tower and the alkali washing upper tower in turn. At the same time, alkali liquor with a concentration of 8-15% enters the alkali washing lower tower and the alkali washing upper tower from the upper tower alkali liquor feed pipeline and the lower tower alkali liquor feed pipeline at the top of the alkali washing upper tower and the alkali washing lower tower respectively. The alkali liquor flows from top to bottom in the alkali washing upper tower and the alkali washing lower tower, contacts with the gas phase recovered vinyl chloride monomer in the reverse direction and washes. The gas phase recovered vinyl chloride monomer After the primary treatment in the lower alkali washing tower and the secondary treatment in the upper alkali washing tower, the vinyl chloride gas after alkali washing is sent out of the alkali washing tower to the next process through the monomer recovery outlet pipe at the top of the upper alkali washing tower, and the alkali liquor for washing the gas phase to recover vinyl chloride monomer is discharged through the alkali liquor discharge pipeline of the upper tower and the alkali liquor discharge pipeline of the lower tower respectively, and transported to the upper part of the upper alkali washing tower and the lower alkali washing tower by the upper tower circulation pump and the lower tower circulation pump for recycling. The circulating alkali liquor is cooled by the cooler to make the temperature of the alkali washing tower 30-40℃; When the alkali liquor concentration in the alkali washing lower tower is: NaOH is less than 8%, and Na2CO3 is greater than 8%, the alkali liquor in the alkali washing lower tower is discharged through the waste alkali liquor discharge pipeline, and then the alkali liquor in the alkali washing upper tower is introduced into the alkali washing lower tower through the alkali liquor circulation pipeline provided between the alkali liquor feed pipeline of the upper tower and the alkali liquor feed pipeline of the lower tower, and fresh alkali liquor is added to the alkali washing upper tower.
9. An alkali washing method for removing residual additives in recycled vinyl chloride monomer, using the alkali washing system for removing residual additives in recycled vinyl chloride monomer according to claims 3-7, characterized in that: The main steps include: (1) Pump the alkali solution into the alkali washing upper tower through the new alkali solution replenishment pipeline, start the upper tower circulation pump, and adjust the alkali solution circulation flow rate to 100-130m 3 / h, start the preheater to heat the circulating alkali solution, pass the alkali solution of the upper tower with adjusted temperature into the lower alkali washing tower through the alkali solution circulation pipeline, start the lower tower circulation pump, and adjust the alkali solution circulation flow rate to 100-130m 3 / h, control the liquid level of the lower tower of the alkali washing tower to 2-2.5m, continue to introduce fresh alkali solution into the upper tower of the alkali washing tower and heat the alkali solution through the start-up preheater, and control the liquid level of the upper tower of the alkali washing tower to 1-1.5m, and when the alkali solution temperature in the alkali washing tower is 30-40℃, turn off the start-up preheater; (2) The gas phase recovery of vinyl chloride monomer enters the alkali washing tower from the recovery monomer inlet pipe at the bottom of the alkali washing tower, flows from bottom to top in the alkali washing tower, and passes through the alkali washing tower and the alkali washing tower in turn. At the same time, the concentration is 8-15%. The alkali liquor enters the alkali washing lower tower and the alkali washing upper tower from the upper tower alkali liquor feed pipeline and the lower tower alkali liquor feed pipeline at the upper part of the alkali washing upper tower and the alkali washing lower tower respectively. The alkali liquor flows from top to bottom in the alkali washing upper tower and the alkali washing lower tower, contacts with the gas-phase recovered vinyl chloride monomer in reverse and washes. The gas-phase recovered vinyl chloride monomer undergoes the primary treatment of the alkali washing lower tower and the secondary treatment of the alkali washing upper tower respectively, and the alkali-washed vinyl chloride gas is sent out of the alkali washing tower to the next process through the recovered monomer outlet pipe at the top of the alkali washing upper tower, and the alkali liquor washed with the gas-phase recovered vinyl chloride monomer is discharged through the upper tower alkali liquor discharge pipeline and the lower tower alkali liquor discharge pipeline respectively, and is transported to the upper part of the alkali washing upper tower and the alkali washing lower tower by the upper tower circulation pump and the lower tower circulation pump for recycling. The circulating alkali liquor is cooled by the cooler to make the temperature of the alkali washing tower 30-40°C; (3) When the alkali concentration in the lower alkali washing tower is less than 8% for NaOH and greater than 8% for Na2CO3, the alkali liquid in the lower alkali washing tower is discharged through the waste alkali liquid discharge pipeline, and then the alkali liquid in the upper alkali washing tower is introduced into the lower alkali washing tower through the alkali liquid circulation pipeline provided between the alkali liquid feed pipeline of the upper tower and the alkali liquid feed pipeline of the lower tower, and fresh alkali liquid is added to the upper alkali washing tower.
10. The alkali washing method for removing residual additives in recycled vinyl chloride monomer according to claim 8 or 9, characterized in that: The alkali washing tower pressure is less than 0.4 MPa.
Citation Information
Patent Citations
Alkali washing system for removing and recovering residual auxiliary agent in vinyl chloride monomer
CN218945043U