Process and apparatus for the production of vinyl chloride

Abstract

The application relates to the technical field of wastewater treatment, in particular to a vinyl chloride production method and a production device. The vinyl chloride production method comprises the following steps: taking hydrogen chloride, oxygen and ethylene as main raw materials to generate high-temperature gas containing dichloroethane through an oxychlorination reaction; cooling the high-temperature gas by using a quenching medium, wherein the quenching medium does not contain alkaline substances; separating dichloroethane A from the cooled gas; adding lye into first wastewater; precipitating metal ions in second wastewater and adsorbing organic matters in the second wastewater; performing steam stripping on third wastewater to obtain fourth wastewater and dichloroethane B; generating vinyl chloride monomer by using dichloroethane, wherein the dichloroethane comprises the dichloroethane A and the dichloroethane B; mixing the fourth wastewater and an oxidizing agent to perform catalytic oxidation treatment. The application can solve the problem that wastewater treatment is difficult in VCM production, improve the plugging problem of a wastewater stripping tower and solve the problem that a difficult biochemical treatment system is unstable.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of wastewater treatment, in particular to a production method and production device of vinyl chloride. BACKGROUND

[0002] Vinyl chloride (VCM) is an important chemical raw material, most of which is used to produce polyvinyl chloride resin. Industrial VCM production mainly has the calcium carbide method and the ethylene oxychlorination method. The latter is more widely used because of its wide raw material sources and lower cost. The ethylene oxychlorination method uses hydrogen chloride, oxygen and ethylene as main raw materials to generate high-temperature gas through oxychlorination reaction in a fluidized bed reactor. The high-temperature gas includes dichloroethane (hereinafter abbreviated as EDC). The high-temperature gas enters a quench tower and exchanges heat with a quenching medium (usually alkaline) in the tower. At the same time, unreacted hydrogen chloride and catalyst powder are captured. The temperature is rapidly reduced. The cooled gas enters a decanter. In the decanter, EDC is separated from other components. The EDC separated from the decanter is refined and then enters a cracking furnace to crack to obtain VCM monomer for PVC polymerization production. In the above process, a large amount of wastewater is generated in the quench tower. This part of wastewater is mainly collected in a wastewater stripping tower to recover part of EDC. After being refined, the EDC collected from the decanter enters the cracking furnace to crack to obtain VCM monomer. A large amount of wastewater is also generated after stripping, which is about 31 t / h together with the wastewater generated by other devices. Because it contains a large amount of organic matter and salt, it is difficult to degrade by ordinary biochemical method and can only be sent to a difficult biochemical treatment system. The difficult biochemical treatment system uses traditional biochemical sludge to treat the wastewater. At present, the treatment of high-salt wastewater generated in the VCM production process is a big problem faced by VCM production. The following problems exist: (1) The wastewater stripping tower is prone to blockage. The blockage is cleaned about once every quarter, affecting the long-term stable operation of the device; (2) Because the salt content in the VCM wastewater is high and fluctuates greatly, the active bacteria in the biochemical sludge in the difficult biochemical system are easily impacted, leading to instability of the biochemical system and leading to TOC exceeding the standard of the effluent. SUMMARY

[0003] Based on this, the first aspect of the present application provides a production method of vinyl chloride, which aims to improve the problem of difficult wastewater treatment faced by VCM production, improve the blockage problem of the wastewater stripping tower, and solve the problem of instability of the difficult biochemical treatment system. The technical scheme is as follows:

[0004] A production method of vinyl chloride, comprising the following steps:

[0005] Using hydrogen chloride, oxygen and ethylene as main raw materials to generate high-temperature gas containing dichloroethane through oxychlorination reaction;

[0006] cooling the high-temperature gas by using a quenching medium to obtain a cooled gas and first waste water, wherein the quenching medium does not contain an alkaline substance;

[0007] separating dichloroethane A from the cooled gas;

[0008] adding lye to the first waste water to obtain second waste water;

[0009] precipitating metal ions in the second waste water and adsorbing organic substances in the second waste water to obtain third waste water;

[0010] stripping the third waste water to obtain fourth waste water and dichloroethane B;

[0011] generating chloroethylene monomer by using dichloroethane, wherein the dichloroethane includes the dichloroethane A and the dichloroethane B;

[0012] mixing the fourth waste water and an oxidizing agent to perform catalytic oxidation treatment.

[0013] Compared with the conventional scheme, the present application has the following beneficial effects:

[0014] In the conventional VCM production process, the high-salt waste water is mainly from the waste water at the bottom of the quenching tower. In the quenching tower, the quenching medium flowing from the top usually contains an alkaline substance, so that the unreacted hydrogen chloride and the entrained catalyst powder can be captured while being quenched. At this time, the waste water at the bottom of the quenching tower contains a high content of salt and a high content of organic substances. The present application finds that the high content of organic substances at the bottom of the quenching tower is related to the alkaline substance added in the quenching medium. The quenching tower usually contains fillers and trays to increase the gas-liquid contact area and improve the heat transfer efficiency. After the alkaline substance is added in the quenching medium, the alkaline substance will remain on the fillers and trays. Although the alkaline substance can capture the unreacted hydrogen chloride and the entrained catalyst powder, some side reactions will occur in the tower to generate refractory organic substances. Based on the above analysis, the applicant breaks the conventional thinking and cools the high-temperature gas after the oxychlorination reaction by using a quenching medium that does not contain an alkaline substance. At the same time, lye is added in the quenching waste water (i.e., the first waste water). By adjusting the addition position of the lye, the amount of the quenching medium can be reduced, thereby reducing the amount of the first waste water. In addition, most of the Cl -The concentrated alkali (about 76wt% to 85wt%) in the first wastewater can neutralize hydrochloric acid, prevent corrosion of equipment caused by increasing concentration of hydrochloric acid, and reduce production of refractory organic matter. Compared with the conventional method of adding alkali in the quenching medium, the application adjusts the position of adding alkali, so that the amount of quenching medium is reduced from about 12t / h to 4t / h to 8t / h, and the amount of wastewater produced by quenching is reduced from about 9t / h to 2t / h to 7t / h, and the amount of wastewater treatment is reduced by 22wt% to 78wt%; the organic matter in the wastewater is reduced by 25wt%, and the content of refractory organic matter is reduced from 190ppm to 220ppm to less than 10ppm, the content of formic acid, ethylene glycol, trichloroacetaldehyde and other refractory organic matter (DO) in the quenching wastewater is greatly reduced, and the total organic matter content (TOC) is reduced from 1.3g / L to 1.4g / L to 0.8g / L to 1.1g / L. On this basis, the second wastewater after adding alkali is precipitated, the metal ions are precipitated, and the metal in the catalyst captured by the quenching medium reacts with the alkali to generate hydroxide, which can adsorb part of the organic matter in the wastewater and further reduce the TOC. After the above treatment, the wastewater is subjected to stripping treatment, and the frequency of water vapor stripping tower plugging can be reduced from 1 time / quarter to 1 time / year. After stripping, the fourth wastewater can be catalytically oxidized under an oxidizing agent, and can be directly used as a raw material for brine electrolysis after reaching the standard, avoiding the problem of entering the difficult biochemical treatment system and causing system instability.

[0015] Optionally, the quenching medium is selected from one or more of PVC centrifugal mother liquor, decanting backwater without alkali, and industrial PW water.

[0016] Optionally, the amount of alkali satisfies that the concentration of HCl in the second wastewater is 0.7wt% to 1.7wt%. Preferably, the concentration of HCl in the second wastewater is 0.9wt% to 1.5wt%.

[0017] Optionally, the alkali in the alkali solution includes one or more of sodium hydroxide, sodium carbonate and sodium bicarbonate.

[0018] Optionally, the concentration of alkali in the alkali solution is 10wt% to 25wt%. Preferably, the concentration of alkali in the alkali solution is 10wt% to 25wt%.

[0019] Optionally, the pH of the second wastewater is adjusted to precipitate metal ions in the second wastewater, and to adsorb organic matters in the second wastewater, the metal ions including one or more of Fe ions, Cu ions and Al ions. By adjusting the pH to precipitate the metal ions in the second wastewater, the addition of a flocculant for sedimentation can be avoided, and the metal in the catalyst captured by the quenching medium reacts with the base in the second wastewater to generate hydroxides, which can adsorb part of the organic matters in the second wastewater to further reduce the TOC. By precipitating the metal ions, the plugging frequency of the original wastewater stripping tower can be reduced from once per quarter to once per year.

[0020] Optionally, the concentrations of the Al ions, Cu ions and Fe ions in the third wastewater are all less than 0.1 ppm, and the TOC is 0.6 g / L to 0.8 g / L.

[0021] Optionally, the metal ions in the second wastewater are precipitated, and the organic matters in the second wastewater are adsorbed to obtain the third wastewater, including the following steps:

[0022] The pH of the second wastewater is controlled to be 6 to 8 to cause a first precipitation to obtain a first suspension and a first supernatant. Preferably, the pH of the second wastewater is controlled to be 6.5 to 7.5.

[0023] The pH of the first supernatant is controlled to be 11 to 13 to cause a second precipitation to obtain a second suspension and a second supernatant, the second supernatant being the third wastewater. Preferably, the pH of the first supernatant is controlled to be 11.5 to 12.5.

[0024] Optionally, the second suspension is subjected to a centrifugal treatment to obtain a centrifugal liquid and a wet residue.

[0025] Optionally, the centrifugal liquid is subjected to a stripping treatment to obtain a fourth wastewater and dichloroethane C, the dichloroethane including the dichloroethane C, and the fourth wastewater and the oxidizing agent are mixed for a catalytic oxidation treatment.

[0026] Optionally, the wet residue is subjected to a metal recovery. The wet residue contains a large amount of Fe, Cu and Al, and can be used for metal recovery. In some examples, the content of Cu in the wet residue can be 13 wt% to 32 wt%, and the content of Al can be 15 wt% to 35 wt%.

[0027] It can be understood that the third wastewater and the centrifugal liquid can be simultaneously subjected to stripping, or can be separately subjected to stripping, and the process conditions are the same in the two cases. The fourth wastewater and the fifth wastewater can be simultaneously subjected to a catalytic oxidation treatment, or can be separately subjected to a catalytic oxidation treatment, and the process conditions are the same in the two cases.

[0028] Optionally, the TOC in the fourth wastewater after stripping is 0.3 g / L to 0.5 g / L.

[0029] Optionally, the process conditions for stripping the third wastewater include a stripping ratio of 1:(20-30), preferably 1:(24-26).

[0030] Optionally, the process conditions for stripping the third wastewater include a stripping temperature of 100°C to 105°C, preferably 102°C to 103°C.

[0031] After stripping, dichloroethane B can be recovered through a dichloroethane recovery system. At the same time, dichloroethane A separated from the cooling gas can also be collected using the dichloroethane recovery system. The dichloroethane including dichloroethane A and dichloroethane B is subjected to a refining treatment and a cracking treatment, and vinyl chloride monomer can be obtained.

[0032] The fourth wastewater produced after stripping is mixed with an oxidizing agent and subjected to catalytic oxidation treatment to further remove TOC.

[0033] Optionally, the oxidizing agent is provided by incineration wastewater containing available chlorine, which is obtained from the flue gas after incineration of waste gas and waste liquid in the production process of vinyl chloride, followed by condensation, acid absorption, and alkali washing. The waste gas and waste liquid in the production process of vinyl chloride can be incinerated at high temperature in an incinerator to convert into flue gas containing CO2, H2O, HCl, and a small amount of free chlorine. The flue gas is condensed, acid absorbed, and alkali washed to obtain incineration wastewater. It can be understood that the waste gas and waste liquid in the production process of vinyl chloride are waste gas and waste liquid in the production process of vinyl chloride that are not specifically mentioned in this article.

[0034] After mixing the quenching wastewater with the incineration wastewater, the catalytic oxidation is carried out separately, which not only reduces the cost of oxidizing agents such as sodium hypochlorite, but also combines the two high-salinity wastewaters (incineration wastewater is high-salinity wastewater) in the production process of vinyl chloride for treatment, achieving the purpose of treating waste with waste and relieving the pressure on the subsequent system.

[0035] Optionally, the content of available chlorine in the incineration wastewater containing available chlorine is 0.8wt% to 1.0wt%. At this time, the amount of incineration wastewater is 2.1 t / h to 2.9 t / h.

[0036] Optionally, the pH value of the catalytic oxidation treatment is 11 to 13.

[0037] Optionally, the n(TOC):n(available chlorine) of the catalytic oxidation treatment is 1:(2-3). Wherein, n(TOC):n(available chlorine) represents the molar ratio of TOC and available chlorine in the fourth wastewater.

[0038] Optionally, after the catalytic oxidation treatment, exhaust gas and exhaust water are obtained, the exhaust gas is directly discharged, and the exhaust water is neutralized to reach the standard after being adsorbed by a resin, and is used as a raw material for brine electrolysis to avoid entering a difficult biochemical treatment system.

[0039] Optionally, the exhaust water contains 5wt%-10wt% NaCl, and the TOC is reduced to within 10mg / L.

[0040] Optionally, low-salt wastewater in the production of vinyl chloride is collected, and sixth wastewater and dichloroethane D are obtained by stripping, the sixth wastewater is sent to a general biochemical system for treatment, and the dichloroethane includes the dichloroethane D, wherein the low-salt wastewater includes wastewater generated in oxygen-chlorination reaction, EDC recovery system, EDC refining, EDC cracking, etc. For example, it includes washing water of an alkali washing tank of the EDC recovery system, and decanting water of an EDC refining light removal tower, etc.

[0041] Vinyl chloride is produced by the method of the present application, and Cl - sources are sorted out from the source, the high-salt quenching wastewater is treated separately, the amount of discharge water generated in the production of vinyl chloride is reduced from about 31t / h to 15t / h-22t / h, the content of Cl - is reduced from 1.1wt% to below 100ppm, and the low-salt wastewater can be directly sent to a general biochemical system for treatment after stripping to avoid entering a difficult biochemical treatment system and to alleviate the pressure on the subsequent biochemical system.

[0042] The wastewater treatment cost of the traditional VCM production method is high, accounting for about 60% of the total income, while the VCM production method of the present application can reduce the VCM wastewater treatment cost by about 10-12 million yuan / year, and improve the long-period stable operation capability of the device, which has good economic benefits and industrial application prospects.

[0043] The second aspect of the present application provides a vinyl chloride production device, which is used for the production of the above-mentioned vinyl chloride, and the technical scheme is as follows:

[0044] A vinyl chloride production device, comprising:

[0045] A fluidized bed reactor for hydrogen chloride, oxygen and ethylene to occur oxygen-chlorination reaction to generate high-temperature gas containing dichloroethane;

[0046] A quenching tower connected with the fluidized bed reactor, for flowing in a quenching medium containing no alkaline substance to cool the high-temperature gas into cooled gas and generate first wastewater;

[0047] A decanter connected with the top of the quenching tower, for separating dichloroethane A from the cooled gas;

[0048] An alkali solution delivery pipeline, an input end of the alkali solution delivery pipeline is located outside the quench tower, and an output end of the alkali solution delivery pipeline is located inside the quench tower, and the alkali solution delivery pipeline is used for delivering alkali solution to the first wastewater to generate second wastewater;

[0049] A sedimentation tank, which is connected to a bottom of the quench tower, is used for precipitating metal ions in the second wastewater and adsorbing organic substances in the second wastewater to obtain third wastewater;

[0050] A first wastewater stripping tower, which is connected to the sedimentation tank, is used for stripping the third wastewater to obtain fourth wastewater and dichloroethane B;

[0051] A chemical oxidation tower, which is connected to the first wastewater stripping tower, is used for catalytically oxidizing a mixture of the fourth wastewater and an oxidizing agent.

[0052] It can be understood that the quenching medium without the alkaline substance flows into the top of the quench tower, and the first wastewater is generated at the bottom of the quench tower, and the acid concentration in the tower bottom wastewater is increased, in order to avoid equipment corrosion, the alkali solution delivery pipeline is arranged inside the quench tower, the acid concentration is controlled, and the alkali solution is added to the first wastewater instead of being added to the quenching medium, so that the amount of the quenching medium can be reduced, and then the amount of the first wastewater can be reduced, and the content of the organic substances in the first wastewater, especially the content of the refractory organic substances, can be reduced.

[0053] Optionally, the vinyl chloride production device further comprises a spray head, and the spray head is connected to the output end of the alkali solution delivery pipeline. The spray head can make the alkali solution quickly disperse, and avoid local alkali concentration being too high.

[0054] Optionally, the sedimentation tank comprises a first sedimentation tank and a second sedimentation tank, one end of the first sedimentation tank is connected to the bottom of the quench tower, the other end of the first sedimentation tank is connected to the second sedimentation tank, and the second sedimentation tank is connected to the first wastewater stripping tower.

[0055] The first sedimentation tank is used for causing the second wastewater to undergo first precipitation to obtain first suspension and first supernatant; the second sedimentation tank is used for causing the first supernatant to undergo second precipitation to obtain second suspension and second supernatant, and the second supernatant is the third wastewater.

[0056] Optionally, the vinyl chloride production device further comprises a pump, and the first supernatant can be discharged into the second sedimentation tank through the pump. The second supernatant can also enter the first wastewater stripping tower through the pump.

[0057] Optionally, the vinyl chloride production device further comprises a centrifuge, one end of the centrifuge is connected to the second sedimentation tank, and the other end of the centrifuge is connected to the first wastewater stripping tower, and the centrifuge is used for centrifuging the second suspension. After the second suspension enters the first wastewater stripping tower, the first wastewater stripping tower performs stripping on the second suspension to obtain fifth wastewater and dichloroethane C.

[0058] It can be understood that the centrifuge is selected as a horizontal screw centrifuge, and the suspension at the bottom of the second sedimentation tank can enter a drum through a feed pipeline of the horizontal screw centrifuge, and after centrifugation, wet residue is discharged from a residue port.

[0059] Optionally, the vinyl chloride production device further comprises a incinerator connected with the device for generating waste gas and waste liquid in the production process of the vinyl chloride, for incinerating the waste gas and waste liquid.

[0060] Optionally, the vinyl chloride production device further comprises a second waste water stripping tower connected with the device for generating low-salt waste water in the production process of the vinyl chloride, for stripping the low-salt waste water to obtain sixth waste water and dichloroethane D.

[0061] Optionally, the process conditions for stripping the low-salt waste water include a stripping ratio of 1:(20-30), preferably 1:(24-26).

[0062] Optionally, the process conditions for stripping the low-salt waste water include a stripping temperature of 100-105°C, preferably 102-103°C.

[0063] Optionally, the vinyl chloride production device further comprises a dichloroethane recovery system, a refined light component removal tower, a refined heavy component removal tower and a cracking furnace, the dichloroethane recovery system is connected with the decanter and the first waste water stripping tower respectively, the refined light component removal tower is connected with the dichloroethane recovery system, the refined heavy component removal tower is connected with the refined light component removal tower, the cracking furnace is connected with the refined heavy component removal tower, the dichloroethane recovery system is used for collecting the dichloroethane A and the dichloroethane B, the refined light component removal tower is used for removing water and light components in the dichloroethane, the refined heavy component removal tower is used for removing heavy components in the dichloroethane, and the cracking furnace is used for cracking the dichloroethane to generate vinyl chloride.

[0064] Optionally, the dichloroethane recovery system is also used for collecting the dichloroethane C.

[0065] Optionally, the dichloroethane recovery system is also connected with the second waste water stripping tower, for collecting the dichloroethane D.

[0066] Optionally, the dichloroethane recovery system comprises connected alkali washing tanks and water washing tanks, wherein the alkali washing tanks are mainly used for removing acid, aldehyde and other impurities, and the water washing tanks are mainly used for removing alkali.

[0067] The vinyl chloride production device of the present application can reduce and improve the problem of difficult waste water treatment faced by VCM production, improve the plugging problem of the first waste water stripping tower, and solve the problem of unstable difficult biochemical treatment system while producing vinyl chloride. BRIEF DESCRIPTION OF DRAWINGS

[0068] In order to more clearly illustrate the technical solutions in the embodiments of the present application, more completely understand the present application and its beneficial effects, the following will briefly introduce the drawings needed to be used in the embodiments. Obviously, the drawings in the following description only some embodiments of the present application, and for those skilled in the art, on the premise of not creating labor, can also obtain other drawings according to these drawings.

[0069] Figure 1 The schematic diagram of the vinyl chloride production device for Comparative Example 1 is shown in the figure.

[0070] Figure 2 The schematic diagram of the vinyl chloride production device for Comparative Example 1 is shown in the figure. DETAILED DESCRIPTION

[0071] The present application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, the purpose of providing these embodiments is to make the disclosure of the present application more thorough and comprehensive.

[0072] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application belongs. The terminology used in the description of the present application herein only for the purpose of describing specific embodiments of the present application, and is not intended to limit the present application.

[0073] The term

[0074] Unless otherwise stated or contradictory, the terms or phrases used herein have the following meanings:

[0075] In the present application, the terms "a plurality of", "a plurality of", "a plurality of", "a plurality of" and the like, unless otherwise specified, refer to more than two or equal to two in quantity. For example, "one or more" means one or more than two.

[0076] In the present application, the terms "optionally", "optional" and "optional" mean optional, that is, selected from "have" or "no" two parallel schemes. If there are multiple "optional" in a technical solution, unless otherwise specified, and there is no contradictory or mutual restrictive relationship, each "optional" is independent.

[0077] In the present application, the terms "first", "second", "third", "fourth" and the like in the "first aspect", "second aspect", "third aspect", "fourth aspect" and the like are only for the purpose of description, and cannot be understood as indicating or implying relative importance or quantity, nor can it be understood as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "first", "second", "third", "fourth" and the like only serve the purpose of non-exhaustive enumeration description, and should be understood as not constituting a closed limitation on the quantity.

[0078] In the present application, with respect to the numerical interval (i.e. numerical range), if no special instructions are given, the optional numerical distribution within the above numerical interval is considered to be continuous, and includes the two numerical end points (i.e. the minimum value and the maximum value) of the numerical range, as well as every numerical value between the two numerical end points.

[0079] In the present application, the temperature parameter, if not specifically limited, allows both constant temperature treatment and variation within a certain temperature range. It should be understood that the constant temperature treatment allows the temperature to fluctuate within the accuracy range controlled by the instrument. It is allowed to fluctuate within the range of, for example, ±5℃, ±4℃, ±3℃, ±2℃, ±1℃.

[0080] In the present application, % (w / w) and wt% both represent weight percentage, % (v / v) refers to volume percentage, and % (w / v) refers to mass volume percentage.

[0081] The following is further illustrated in combination with specific examples and comparative examples. The raw materials involved in the following specific examples and comparative examples, if not specifically stated, can be sourced from the market. The instruments used, if not specifically stated, can be sourced from the market. The processes involved, if not specifically stated, are routine choices for those skilled in the art.

[0082] Comparative Example 1

[0083] This comparative example provides a production method and production device for VCM, as follows:

[0084] The structural diagram of the VCM production device 100 is as follows: Figure 1As shown, it comprises a fluidized bed reactor 11, a quench tower 12, a decanter 13, a light-removing refining tower 14, a heavy-removing refining tower 15, a cracking furnace 16, a wastewater stripping tower 17 and a difficultly biodegradable system 18, wherein the quench tower 12 is connected to the fluidized bed reactor 11, the decanter 13 is connected to the top of the quench tower 12, the light-removing refining tower 14 is connected to the decanter 13 through an EDC recovery system (not shown in the figure), one end of the heavy-removing refining tower 15 is connected to the light-removing refining tower 14, and the other end is connected to the cracking furnace 16, the wastewater stripping tower 17 is connected to the bottom of the quench tower 12, the top of the wastewater stripping tower 17 is connected to the light-removing refining tower 14 through the EDC recovery system (not shown in the figure), and the bottom of the wastewater stripping tower 17 is connected to the difficultly biodegradable system 18.

[0085] The production method of VCM is as follows: in the fluidized bed reactor, hydrogen chloride, oxygen and ethylene are used as main raw materials to generate high-temperature gas containing dichloroethane through oxychlorination reaction, the high-temperature gas enters the quench tower, 12t / h of the decanter backwater after being alkali-added is used as quenching medium, the quenching medium flows down from the top of the quench tower to cool the high-temperature gas into cooled gas, the cooled gas enters the decanter from the top of the quench tower, the decanter is alkali-added at 117kg / h, the first wastewater of 9t / h is generated at the bottom of the quench tower, the TOC of the first wastewater is 1469mg / L, the contents of formic acid, ethylene glycol and trichloroacetaldehyde are 2560ppm, 52ppm and 2902ppm respectively, and in particular, it also contains 218ppm of difficultly degradable substances, the Cl - content is 1.8wt%. The first wastewater enters the wastewater stripping tower, the light components EDC are recovered in the wastewater stripping tower, mixed with the separated EDC in the decanter, enters the light-removing refining tower and the heavy-removing refining tower for refining treatment, and then enters the cracking furnace for cracking treatment to obtain VCM monomer, the water at the bottom of the wastewater stripping tower is the second wastewater, the second wastewater is mixed with the low-salt wastewater generated by the EDC recovery alkali washing water and the EDC light-removing refining tower decanter water, the total wastewater production is 31t / h, the TOC is 635mg / L, the Cl - content is 1.1wt%, and due to the high salt and high organic matter, it is all sent to the difficultly biodegradable water system for treatment. At this time, the high-salt and high-organic matter wastewater is easy to impact the active bacteria in the biological sludge of the difficultly biodegradable system, resulting in instability of the biological system, high frequency of TOC exceeding the standard of the effluent, and great difficulty in wastewater treatment. In addition, the wastewater stripping tower is easy to be blocked, and needs to be cleaned once every quarter.

[0086] Example 1

[0087] The embodiment provides a production method and a production device of VCM, and specifically as follows:

[0088] The structural schematic diagram of the production device 200 of VCM is as shown in Figure 2As shown, it comprises a fluidized bed reactor 201, a quench tower 202, a decanter 203, a light-removing tower 204, a heavy-removing tower 205, a cracking furnace 206, an alkali delivery pipeline 207, a first sedimentation tank 208, a second sedimentation tank 209, a horizontal screw centrifuge 210, a first waste water stripping tower 211, an incinerator 212, a chemical oxidation tower 213, a second waste water stripping tower 214 and a general biochemical system 215. The quench tower 202 is connected to the fluidized bed reactor 201, the decanter 203 is connected to the top of the quench tower 202, the light-removing tower 204 is connected to the decanter 203 through an EDC recovery system (not shown in the figure), one end of the heavy-removing tower 205 is connected to the light-removing tower 204 and the other end is connected to the cracking furnace 206, the input end of the alkali delivery pipeline 207 is located outside the quench tower 202 and the output end is located inside the quench tower 202, the first sedimentation tank 208 is connected to the bottom of the quench tower 202, the second sedimentation tank 209 is connected to the first sedimentation tank 208, the first waste water stripping tower 211 is connected to the second sedimentation tank 209, one end of the horizontal screw centrifuge 210 is connected to the bottom of the second sedimentation tank 209 and the other end is connected to the first waste water stripping tower 211, the top of the first waste water stripping tower 211 is connected to the light-removing tower 204 through an EDC recovery system (not shown in the figure), the bottom is connected to the chemical oxidation tower 213, and the incinerator 212 is connected to the chemical oxidation tower 213. The top of the second waste water stripping tower 214 is connected to the light-removing tower 204 through an EDC recovery system (not shown in the figure), and the bottom is connected to the general biochemical system 215.

[0089] The production method of VCM is as follows: in the fluidized bed reactor, hydrogen chloride, oxygen and ethylene are used as main raw materials to generate high-temperature gas containing dichloroethane by oxychlorination reaction, the high-temperature gas enters the quench tower, 8 t / h of decanting backwater without alkali is used as quenching medium, the quenching medium flows down from the top of the quench tower to cool the high-temperature gas into cooled gas, the cooled gas enters the decanter from the top of the quench tower, no alkali is added in the decanter, the first waste water 4.7 t / h is generated at the bottom of the quench tower, alkali is added into the first waste water through the alkali delivery pipeline, the concentration of HCl in the obtained second waste water is 1 wt%, the TOC in the second waste water is 897 mg / L, the contents of formic acid, ethylene glycol and chloral are 661 ppm, 165 ppm and 1809 ppm respectively, in particular, the content of refractory substances is reduced to 3 ppm, the Cl -The content of the second wastewater is 2.8 wt%, and the contents of metal ions Fe, Cu and Al are 5 ppm, 49 ppm and 379 ppm respectively. The second wastewater is discharged into the first sedimentation tank with a pH value of 7.2, and a first suspension and a first supernatant are obtained in the first sedimentation tank. The first supernatant is discharged into the second sedimentation tank with a pH value of 11.8, and a second suspension and a second supernatant are obtained in the second sedimentation tank. The second suspension is subjected to centrifugal treatment by a horizontal screw centrifuge to obtain a centrifugal liquid and wet residue. The centrifugal liquid is subjected to stripping in the first wastewater stripping tower, and the wet residue contains a large amount of Fe, Cu and Al and is used for metal recovery. The second supernatant is the third wastewater, and the TOC in the third wastewater is reduced to 742 mg / L, and the contents of metal ions Al, Cu and Fe are all less than 0.1 ppm. The third wastewater is discharged into the first wastewater stripping tower, and the stripping ratio is set to 1:26, and the temperature is 103°C. Light components EDC are recovered in the first wastewater stripping tower, and the water at the bottom of the first wastewater stripping tower is the fourth wastewater and the fifth wastewater, and the TOC in the fourth wastewater and the fifth wastewater is 586 mg / L. The fourth wastewater and the fifth wastewater are mixed with incineration wastewater (containing effective chlorine 0.96 wt%) generated by a 2.5 t / h incinerator, and are discharged into the chemical oxidation tower. The generated exhaust gas is directly discharged, and the TOC of the water at the bottom of the chemical oxidation tower is 6 mg / L. After being adsorbed by a resin and neutralized, the water contains 5 wt% NaCl, and is sent to a chlor-alkali device for use as raw material for brine electrolysis. Low-salt wastewater generated by EDC recovery alkali washing tanks and EDC refining and light removal towers is mixed, and the total wastewater generation is 15 t / h, the TOC is 692 mg / L, and the Cl - The content of the second wastewater is 2.8 wt%, and the contents of metal ions Fe, Cu and Al are 5 ppm, 49 ppm and 379 ppm respectively. The second wastewater is discharged into the first sedimentation tank with a pH value of 7.2, and a first suspension and a first supernatant are obtained in the first sedimentation tank. The first supernatant is discharged into the second sedimentation tank with a pH value of 11.8, and a second suspension and a second supernatant are obtained in the second sedimentation tank. The second suspension is subjected to centrifugal treatment by a horizontal screw centrifuge to obtain a centrifugal liquid and wet residue. The centrifugal liquid is subjected to stripping in the first wastewater stripping tower, and the wet residue contains a large amount of Fe, Cu and Al and is used for metal recovery. The second supernatant is the third wastewater, and the TOC in the third wastewater is reduced to 742 mg / L, and the contents of metal ions Al, Cu and Fe are all less than 0.1 ppm. The third wastewater is discharged into the first wastewater stripping tower, and the stripping ratio is set to 1:26, and the temperature is 103°C. Light components EDC are recovered in the first wastewater stripping tower, and the water at the bottom of the first wastewater stripping tower is the fourth wastewater and the fifth wastewater, and the TOC in the fourth wastewater and the fifth wastewater is 586 mg / L. The fourth wastewater and the fifth wastewater are mixed with incineration wastewater (containing effective chlorine 0.96 wt%) generated by a 2.5 t / h incinerator, and are discharged into the chemical oxidation tower. The generated exhaust gas is directly discharged, and the TOC of the water at the bottom of the chemical oxidation tower is 6 mg / L. After being adsorbed by a resin and neutralized, the water contains 5 wt% NaCl, and is sent to a chlor-alkali device for use as raw material for brine electrolysis. Low-salt wastewater generated by EDC recovery alkali washing tanks and EDC refining and light removal towers is mixed, and the total wastewater generation is 15 t / h, the TOC is 692 mg / L, and the Cl

[0090] Example 2

[0091] The present embodiment provides a production method and a production device for VCM, which are specifically as follows:

[0092] The structure diagram of the production device for VCM is shown in Figure 2 which is the same as that in Example 1.

[0093] The production method of VCM is as follows: in a fluidized bed reactor, hydrogen chloride, oxygen and ethylene are used as main raw materials to generate high-temperature gas containing dichloroethane by oxychlorination reaction, the high-temperature gas enters a quench tower, 7 t / h of PVC centrifugal mother liquor is used as quenching medium, the quenching medium flows down from the top of the quench tower to cool the high-temperature gas into cooled gas, the cooled gas enters a decanter from the top of the quench tower, no alkali is added in the decanter, and the first wastewater 3.5 t / h is generated at the bottom of the quench tower. Alkali is added to the first wastewater through an alkali delivery pipeline, the concentration of HCl in the obtained second wastewater is 1.2 wt%, the TOC in the second wastewater is 863 mg / L, the contents of formic acid, ethylene glycol and trichloroacetaldehyde are 681 ppm, 182 ppm and 1878 ppm respectively, in particular, the content of refractory substances is reduced to 4 ppm, the content of Cl - The content of Cl is 3.6%, and the contents of metal ions Fe, Cu and Al are 5 ppm, 49 ppm and 447 ppm respectively. The second wastewater is discharged to a first sedimentation tank, the pH value of the first sedimentation tank is 6.9, a first suspension and a first supernatant are obtained in the first sedimentation tank, the first supernatant is discharged to a second sedimentation tank, the pH value of the second sedimentation tank is 11.6, a second suspension and a second supernatant are obtained in the second sedimentation tank, the second suspension is subjected to centrifugal treatment by a horizontal screw centrifuge to obtain a centrifugal liquid and wet residue, the centrifugal liquid enters a first wastewater stripping tower for stripping, and the wet residue contains a large amount of Fe, Cu and Al and is used for metal recovery. The second supernatant is the third wastewater, the TOC in the third wastewater is reduced to 693 mg / L, and the contents of metal ions Al, Cu and Fe are all less than 0.1 ppm. The third wastewater is discharged to the first wastewater stripping tower, the stripping ratio is set to 1:28, the temperature is 103°C, the light components EDC in the first wastewater stripping tower are recovered, and the water at the bottom of the first wastewater stripping tower is the fourth wastewater and the fifth wastewater, and the TOC in the fourth wastewater and the fifth wastewater is 398 mg / L. The fourth wastewater and the fifth wastewater are mixed with 2.4 t / h of incineration wastewater (containing effective chlorine 0.89 wt%) generated by an incinerator, and are discharged to a chemical oxidation tower for catalytic oxidation treatment, the generated exhaust gas is directly discharged, the TOC of the water at the bottom of the chemical oxidation tower is 5 mg / L, the water after resin adsorption and neutralization contains 6 wt% of NaCl, and is sent to a chlor-alkali device for salt water electrolysis raw material. The low-salt wastewater generated by washing water of an EDC recovery alkali washing tank and decanting water of an EDC refining light removal tower is mixed, and the total wastewater production is 17 t / h, the TOC is 699 mg / L, and the content of Cl -The content of 56 ppm, the low salt wastewater is discharged to the second wastewater stripping tower, the light component EDC in the second wastewater stripping tower is recovered, mixed with the separated and recovered EDC in the decanter, the EDC recovered in the first wastewater stripping tower, and then enters the refining light removal tower and the refining heavy removal tower for refining treatment, and then enters the cracking furnace and cracking treatment to obtain VCM monomer. The wastewater at the bottom of the second wastewater stripping tower is sent to the system general biochemical treatment. The cleaning frequency of the first wastewater stripping tower is reduced from 1 time / quarter to 1 time / year, and the cleaning frequency of the second wastewater stripping tower is 1 time / year.

[0094] Example 3

[0095] The embodiment provides a VCM production method and a production device, and specifically as follows:

[0096] The structure diagram of the VCM production device is shown in Figure 2 which is the same as that in example 1.

[0097] The VCM production method is as follows: in the fluidized bed reactor, hydrogen chloride, oxygen and ethylene are used as main raw materials to generate high-temperature gas containing dichloroethane through oxychlorination reaction. The high-temperature gas enters the quenching tower, and the non-alkali decanting water 6.5 t / h is used as the quenching medium. The quenching medium flows down from the top of the quenching tower to cool the high-temperature gas into cooled gas. The cooled gas enters the decanter from the top of the quenching tower. No alkali is added in the decanter. The first wastewater 3.1 t / h is generated at the bottom of the quenching tower. Alkali liquor is added to the first wastewater through the alkali liquor conveying pipeline. The concentration of HCl in the obtained second wastewater is 1.1 wt%, the TOC in the second wastewater is 934 mg / L, the contents of formic acid, ethylene glycol and trichloroacetaldehyde in the second wastewater are 736 ppm, 158 ppm and 2085 ppm respectively, and in particular, the content of the refractory substance is reduced to 5 ppm, the Cl -The content was 4.1%, with metal ion contents of Fe, Cu, and Al at 8 ppm, 75 ppm, and 496 ppm, respectively. The second wastewater was discharged into the first settling tank, where the pH was 7.3. The first suspension and first supernatant were obtained in the first settling tank. The first supernatant was discharged into the second settling tank, where the pH was 12.0. The second suspension and second supernatant were obtained in the second settling tank. The second suspension was centrifuged using a horizontal screw centrifuge to obtain centrifuged liquid and wet sludge. The centrifuged liquid was then fed into a first wastewater stripping tower for stripping. The wet sludge contained large amounts of Fe, Cu, and Al, which were used for metal recovery. The second supernatant became the third wastewater, with the TOC reduced to 674 mg / L, and the contents of metal ions Al, Cu, and Fe all less than 0.1 ppm. The third wastewater is discharged into the first wastewater stripping tower, with a stripping ratio of 1:29 and a temperature of 103℃. Light components are recovered by EDC in the first wastewater stripping tower. The effluent from the bottom of the first wastewater stripping tower is the fourth and fifth wastewater, with a TOC of 421 mg / L. The fourth and fifth wastewaters are mixed with 2.5 t / h incineration wastewater (containing 0.92 wt% available chlorine) from the incinerator and discharged into a chemical oxidation tower. The effluent from the catalytic oxidation treatment is directly discharged. The effluent from the bottom of the chemical oxidation tower has a TOC of 7 mg / L, and after resin adsorption and neutralization, it contains 6.2 wt% NaCl, which is sent to the chlor-alkali unit for use as feedstock for brine electrolysis. Low-salt wastewater generated from EDC recovery alkali washing tank wash water and EDC refining light component removal tower decantation water is mixed, resulting in a total wastewater generation of 18 t / h with a TOC of 692 mg / L and a NaCl concentration of 7 mg / L. - With a content of 47 ppm, low-salinity wastewater is discharged into the second wastewater stripping tower. Light component EDC is recovered in the second wastewater stripping tower and mixed with EDC recovered in the decanter and the first wastewater stripping tower. This mixture is then sent to a refining tower for removing light and heavy components, followed by pyrolysis in a cracking furnace to obtain VCM monomers. The wastewater at the bottom of the second wastewater stripping tower is sent to the system's general biological treatment. The cleaning frequency of the first wastewater stripping tower has decreased from once per quarter to once per year, while the cleaning frequency of the second wastewater stripping tower is once per year.

[0098] Example 4

[0099] This embodiment provides a method and apparatus for producing VCM, as detailed below:

[0100] A schematic diagram of the VCM production unit is shown below. Figure 2 As shown, it is the same as in Example 1.

[0101] The production method of VCM is as follows: in a fluidized bed reactor, hydrogen chloride, oxygen and ethylene are used as main raw materials to generate high-temperature gas containing dichloroethane by oxychlorination reaction, the high-temperature gas enters a quenching tower, 6 t / h of backwater without alkali is used as quenching medium, the quenching medium flows down from the top of the quenching tower to cool the high-temperature gas into cooled gas, the cooled gas enters a decanter from the top of the quenching tower, no alkali is added in the decanter, and the first wastewater 2.5 t / h is generated at the bottom of the quenching tower. Alkali is added to the first wastewater through an alkali delivery pipeline, the concentration of HCl in the obtained second wastewater is 1.5 wt%, the TOC in the second wastewater is 956 mg / L, the contents of formic acid, ethylene glycol and trichloroacetaldehyde are 912 ppm, 156 ppm and 1483 ppm respectively, in particular, the content of refractory compounds is reduced to 4 ppm, the content of Cl - The content of Cl is 5.4%, and the contents of metal ions Fe, Cu and Al are 12 ppm, 135 ppm and 689 ppm respectively. The second wastewater is discharged to a first sedimentation tank, the pH value of the first sedimentation tank is 7.2, a first suspension and a first supernatant are obtained in the first sedimentation tank, the first supernatant is discharged to a second sedimentation tank, the pH value of the second sedimentation tank is 12.2, a second suspension and a second supernatant are obtained in the second sedimentation tank, the second suspension is treated by centrifugation through a horizontal screw centrifuge to obtain a centrifugal liquid and wet residue, the centrifugal liquid enters a first wastewater stripping tower for stripping, and the wet residue contains a large amount of Fe, Cu and Al and is used for metal recovery. The second supernatant is the third wastewater, the TOC in the third wastewater is reduced to 709 mg / L, and the contents of metal ions Al, Cu and Fe are all less than 0.1 ppm. The third wastewater is discharged to the first wastewater stripping tower, the stripping ratio is set to 1:30, the temperature is 102°C, the light components EDC are recovered in the first wastewater stripping tower, and the water at the bottom of the first wastewater stripping tower is the fourth wastewater and the fifth wastewater, and the TOC in the fourth wastewater and the fifth wastewater is 465 mg / L. The fourth wastewater and the fifth wastewater are mixed with 2.4 t / h of incineration wastewater (containing effective chlorine 0.84 wt%) generated by an incinerator, discharged to a chemical oxidation tower, and treated by catalytic oxidation to generate exhaust gas which is directly discharged, and the TOC of the water at the bottom of the chemical oxidation tower is 7 mg / L, which is adsorbed by resin and neutralized to contain 7.4 wt% of NaCl, and sent to a chlor-alkali device for raw material of brine electrolysis. The low-salt wastewater generated by washing water of EDC recovery alkali washing tank, decanting water of EDC refining light removal tower and the like is mixed, and the total wastewater generation is 19 t / h, the TOC is 687 mg / L, and the content of Cl -The content of 69ppm, the low salt wastewater is discharged to the second wastewater stripping tower, the light component EDC is recovered in the second wastewater stripping tower, mixed with the separated and recovered EDC in the decanter, the EDC recovered in the first wastewater stripping tower, and then enters the refining light removal tower and the refining heavy removal tower for refining treatment, and then enters the cracking furnace and cracking treatment to obtain VCM monomer. The wastewater at the bottom of the second wastewater stripping tower is sent to the system for general biochemical treatment. The cleaning frequency of the first wastewater stripping tower is reduced from 1 time / quarter to 1 time / year, and the cleaning frequency of the second wastewater stripping tower is 1 time / year.

[0102] Example 5

[0103] The embodiment provides a VCM production method and a production device, and specifically as follows:

[0104] The structure diagram of the VCM production device is shown in Figure 2 which is the same as that in example 1.

[0105] The VCM production method is as follows: in the fluidized bed reactor, hydrogen chloride, oxygen and ethylene are used as main raw materials to generate high-temperature gas containing dichloroethane through oxychlorination reaction. The high-temperature gas enters the quenching tower, and the non-alkali decanting water 4.5t / h is used as the quenching medium. The quenching medium flows down from the top of the quenching tower to cool the high-temperature gas into cooled gas. The cooled gas enters the decanter from the top of the quenching tower. No alkali is added in the decanter. The first wastewater 2.5t / h is generated at the bottom of the quenching tower. Alkali liquor is added to the first wastewater through the alkali liquor conveying pipeline. The concentration of HCl in the obtained second wastewater is 0.9wt%, the TOC in the second wastewater is 989mg / L, the contents of formic acid, ethylene glycol and trichloroacetaldehyde in the second wastewater are 937ppm, 201ppm and 1536ppm respectively, and in particular, the content of the refractory substance is reduced to 4ppm, the Cl -The content was 13.2%, with Fe, Cu, and Al ion contents of 23 ppm, 252 ppm, and 1612 ppm, respectively. The second wastewater was discharged into the first settling tank, where the pH was 7.0. A first suspension and a first supernatant were obtained in the first settling tank. The first supernatant was discharged into the second settling tank, where the pH was 12.2. A second suspension and a second supernatant were obtained in the second settling tank. The second suspension was centrifuged using a horizontal screw centrifuge to obtain centrifuged liquid and wet sludge. The centrifuged liquid was then fed into a first wastewater stripping tower for stripping. The wet sludge contained large amounts of Fe, Cu, and Al, which were used for metal recovery. The second supernatant became the third wastewater, with the TOC reduced to 709 mg / L, and the contents of Al, Cu, and Fe ions all less than 0.1 ppm. The third wastewater is discharged into the first wastewater stripping tower, with a stripping ratio of 1:30 and a temperature of 102℃. Light components are recovered by EDC in the first wastewater stripping tower. The effluent from the bottom of the first wastewater stripping tower is the fourth and fifth wastewater, with a TOC of 465 mg / L. The fourth and fifth wastewaters are mixed with incineration wastewater (containing 0.86 wt% available chlorine) from a 2.6 t / h incinerator and discharged into a chemical oxidation tower. The effluent from the catalytic oxidation treatment is directly discharged. The TOC of the effluent from the bottom of the chemical oxidation tower is 7 mg / L. After resin adsorption and neutralization, it contains 5 wt% NaCl and is sent to the chlor-alkali unit for use as feedstock for brine electrolysis. Low-salt wastewater generated from EDC recovery alkali washing tank wash water and EDC refining light component removal tower decantation water is mixed, resulting in a total wastewater generation of 22 t / h with a TOC of 692 mg / L and a Cl content of [missing information]. - With a content of 84 ppm, low-salinity wastewater is discharged into the second wastewater stripping tower. Light component EDC is recovered in the second wastewater stripping tower and mixed with EDC recovered in the decanter and the first wastewater stripping tower. This mixture is then sent to a refining tower for removing light and heavy components, followed by pyrolysis in a cracking furnace to obtain VCM monomers. The wastewater at the bottom of the second wastewater stripping tower is sent to the system's general biological treatment facility. The cleaning frequency of the first wastewater stripping tower has decreased from once per quarter to once per year, while the cleaning frequency of the second wastewater stripping tower is once per year.

[0106] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0107] The above-described embodiments are merely illustrative of several embodiments of the present application, which are described in more detail and in a specific manner, but should not be construed as limiting the scope of the patent. It should be noted that for those skilled in the art, several modifications and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims.

Claims

1. A method for producing vinyl chloride, characterized in that, Includes the following steps: Using hydrogen chloride, oxygen, and ethylene as the main raw materials, an oxychlorination reaction occurs to produce a high-temperature gas containing dichloroethane. The high-temperature gas is cooled using a quenching medium to obtain cooling gas and first wastewater, wherein the quenching medium does not contain alkaline substances; Dichloroethane A was obtained by separating from the cooling gas; Adding an alkaline solution to the first wastewater yields the second wastewater; The metal ions in the second wastewater are precipitated, and the organic matter in the second wastewater is adsorbed to obtain the third wastewater; The third wastewater was stripped to obtain a fourth wastewater and dichloroethane B; The dichloroethane is used to generate vinyl chloride monomer, wherein the dichloroethane includes dichloroethane A and dichloroethane B; The fourth wastewater and oxidant are mixed and subjected to catalytic oxidation treatment.

2. The method for producing vinyl chloride according to claim 1, characterized in that, The quenching medium is selected from one or more of the following: PVC centrifugal mother liquor, decanting return water without alkali, and industrial PW water.

3. The method for producing vinyl chloride according to claim 1, characterized in that, Includes at least one of the following features: (1) The amount of alkaline solution is such that the concentration of HCl in the second wastewater is 0.7wt% to 1.7wt%. (2) The alkali in the alkaline solution includes one or more of sodium hydroxide, sodium carbonate and sodium bicarbonate; (3) The concentration of alkali in the alkaline solution is 10wt% to 25wt%.

4. The method for producing vinyl chloride according to claim 1, characterized in that, The pH value of the second wastewater is adjusted to precipitate metal ions in the second wastewater and adsorb organic matter in the second wastewater. The metal ions include one or more of Fe ions, Cu ions and Al ions.

5. The method for producing vinyl chloride according to claim 4, characterized in that, The concentrations of Al, Cu, and Fe ions in the third wastewater were all less than 0.1 ppm, and the TOC was 0.6 g / L to 0.8 g / L.

6. The method for producing vinyl chloride according to claim 4, characterized in that, The process of precipitating metal ions from the second wastewater and adsorbing organic matter from the second wastewater to obtain the third wastewater includes the following steps: The pH of the second wastewater is controlled to be 6-8, resulting in the first precipitation and the first suspension and the first supernatant. The pH of the first supernatant is controlled to be 11-13, resulting in a second precipitation and yielding a second suspension and the third wastewater.

7. The method for producing vinyl chloride according to claim 6, characterized in that, The second suspension is centrifuged to obtain centrifuged liquid and wet residue.

8. The method for producing vinyl chloride according to claim 7, characterized in that, The centrifuged liquid is stripped to obtain a fifth wastewater and dichloroethane C, wherein the dichloroethane includes dichloroethane C. The fifth wastewater and the oxidant are then mixed and subjected to catalytic oxidation treatment.

9. The method for producing vinyl chloride according to claim 7, characterized in that, Metal recovery is performed on the wet slag.

10. The method for producing vinyl chloride according to any one of claims 1 to 9, characterized in that, The TOC in the fourth wastewater is 0.3 g / L to 0.5 g / L.

11. The method for producing vinyl chloride according to claim 10, characterized in that, The process conditions for stripping the third wastewater include at least one of the following conditions: (1) a stripping ratio of 1:(20-30); (2) a stripping temperature of 100℃-105℃.

12. The method for producing vinyl chloride according to any one of claims 1 to 9, characterized in that, The oxidant is provided by incineration wastewater containing available chlorine, which is derived from the waste gas and waste liquid in the production process of vinyl chloride after incineration, followed by condensation, acid absorption, and alkali washing.

13. The method for producing vinyl chloride according to claim 12, characterized in that, The process conditions for the catalytic oxidation treatment include at least one of the following conditions: (1) pH value is 11 to 13; (2) n(TOC):n(available chlorine) is 1:(2 to 3), where n(TOC):n(available chlorine) represents the molar ratio of TOC and available chlorine in the fourth wastewater.

14. The method for producing vinyl chloride according to claim 12, characterized in that, After catalytic oxidation treatment, gas and water are obtained. The gas is discharged directly, and the water is used as raw material for brine electrolysis after being adsorbed and neutralized by resin.

15. The method for producing vinyl chloride according to any one of claims 1 to 9, characterized in that, The low-salt wastewater from the vinyl chloride production process is collected, stripped, and then used to obtain sixth wastewater and dichloroethane D. The sixth wastewater is sent to a general biochemical system for treatment, and the dichloroethane includes dichloroethane D.

16. A vinyl chloride production apparatus, characterized in that, include: Fluidized bed reactor, used for the oxychlorination reaction of hydrogen chloride, oxygen and ethylene to produce a high-temperature gas containing dichloroethane; A quench tower, connected to the fluidized bed reactor, is used to allow the inflow of a quench medium free of alkaline substances to cool the high-temperature gas into a cooling gas and generate the first wastewater. A decanter, connected to the top of the quench tower, is used to separate dichloroethane A from the cooling gas; An alkali solution delivery pipeline, wherein the input end of the alkali solution delivery pipeline is located outside the quench tower and the output end is located inside the quench tower, is used to deliver alkali solution to the first wastewater to generate a second wastewater; A settling tank, connected to the bottom of the quench tower, is used to precipitate metal ions in the second wastewater and adsorb organic matter in the second wastewater to obtain the third wastewater; The first wastewater stripping tower, connected to the settling tank, is used for stripping the third wastewater to obtain the fourth wastewater and dichloroethane B. A chemical oxidation tower, connected to the first wastewater stripping tower, is used to catalytically oxidize the mixture of the fourth wastewater and the oxidant. It also includes a dichloroethane recovery system, a refining light component removal tower, a refining heavy component removal tower, and a cracking furnace. The dichloroethane recovery system is connected to the decanter and the first wastewater stripping tower, respectively. The refining light component removal tower is connected to the dichloroethane recovery system. The refining heavy component removal tower is connected to the refining light component removal tower. The cracking furnace is connected to the refining heavy component removal tower. The dichloroethane recovery system is used to collect dichloroethane A and dichloroethane B. The refining light component removal tower is used to remove water and light components from dichloroethane. The refining heavy component removal tower is used to remove heavy components from dichloroethane. The cracking furnace is used to crack dichloroethane to produce vinyl chloride.

17. The vinyl chloride production apparatus according to claim 16, characterized in that, Includes at least one of the following features: (1) It also includes a spray head, which is connected to the output end of the alkaline solution delivery pipeline; (2) The settling tank includes a first settling tank and a second settling tank. One end of the first settling tank is connected to the bottom of the quench tower, and the other end is connected to the second settling tank. The second settling tank is connected to the first wastewater stripping tower. The first settling tank is used to cause the second wastewater to undergo a first sedimentation, resulting in a first suspension and a first supernatant; the second settling tank is used to cause the first supernatant to undergo a second sedimentation, resulting in a second suspension and the third wastewater. (3) It also includes a centrifuge, one end of which is connected to the second sedimentation tank and the other end of which is connected to the first wastewater stripping tower, for centrifuging the second suspension; (4) It also includes an incinerator, which is connected to a device for incinerating the waste gas and waste liquid in the production process of vinyl chloride; (5) It also includes a second wastewater stripping tower, which is connected to the device that generates low-salt wastewater in the production process of vinyl chloride, for stripping the low-salt wastewater to obtain a sixth wastewater and dichloroethane D; (6) The dichloroethane recovery system is also used to collect the dichloroethane C.

18. The vinyl chloride production apparatus according to claim 17, characterized in that, The dichloroethane recovery system is also connected to the second wastewater stripping tower for collecting dichloroethane D.

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