Oxychlorination reaction system and method based on a four-stage reactor

Abstract

The present invention provides an oxychlorination reaction system and method based on a four-stage reactor. The oxychlorination reaction system based on a four-stage reactor includes four oxychlorination reactors connected in series in sequence, an oxychlorination reaction unit based on a four-stage reactor, and a product post-treatment and ethylene recycling unit, wherein: each oxychlorination reactor is a fixed-bed reactor, each oxychlorination reactor is provided with a cooling mechanism, an oxygen pipeline is respectively connected to each oxychlorination reactor through an oxygen branch pipeline, and a hydrogen chloride pipeline and an ethylene pipeline are connected to the first-stage oxychlorination reactor at the head end. This system has low energy consumption and high safety factor.

Description

Technical Field

[0001] The present invention relates to the technical field of chemical engineering, and particularly to an oxychlorination reaction system and method based on a four-stage reactor. Background Art

[0002] The production of vinyl chloride is divided into ethylene method and acetylene method according to raw materials, and mainly includes calcium carbide or natural gas acetylene method, combined method, oxychlorination method and total balance oxychlorination method according to production processes. Among them, the ethylene oxychlorination process is currently recognized as an advanced and reasonable production route in the world. It directly synthesizes vinyl chloride from hydrogen chloride, oxygen and ethylene. The technical key of the oxychlorination unit is the type of reactor and the source of oxygen. There are two types of reactor forms: fluidized bed reactor and fixed bed reactor.

[0003] When operating with a fluidized bed reactor, ethylene, oxygen and hydrogen chloride are simultaneously added to the reactor in a certain proportion. There are internal cooling coils for heat removal in the fluidized bed reactor, and a cyclone separator is provided at the upper part of the reactor to collect the catalyst entrained in the material. In this reactor, not only the loss of the catalyst will occur, but also the catalyst is easily released into the wastewater, causing environmental pollution.

[0004] In the fixed bed reactor, the catalyst is fixed, and the environmental pollution is small. However, the single-unit production capacity of the fixed bed reactor is small. In the prior art, the production capacity is improved by connecting two fixed beds in series. For example, in the invention patent "Oxychlorination Reaction of Ethylene in Two-Stage Fixed Bed Reactors" with the authorization announcement number CN1067041C, dichloroethane is produced by connecting two reactors in series. In this reaction system, oxygen enters the two-stage fixed bed reactor in a ratio of 50%:50%, and the safety factor is low. At the same time, the minimum load of the two-stage reactor system is 30%, which cannot meet the needs of the plant for low-load operation. Summary of the Invention

[0005] The purpose of the present invention is to provide an oxychlorination reaction system based on a four-stage fixed bed reactor in combination to solve the problems of low safety factor and high operating load in the existing oxychlorination reaction system based on a four-stage reactor.

[0006] Another purpose of the present invention is to provide an oxychlorination reaction method.

[0007] An oxychlorination reaction unit based on a four-stage reactor includes four oxychlorination reactors connected in series in sequence, wherein:

[0008] Each oxychlorination reactor is a fixed bed reactor, and each oxychlorination reactor is provided with a cooling mechanism. The oxygen pipeline is respectively connected to each oxychlorination reactor through an oxygen branch pipeline, and the hydrogen chloride pipeline and the ethylene pipeline are connected to the first-stage oxychlorination reactor at the head end.

[0009] In the above technical solution, each oxychlorination reactor is a tubular fixed-bed reactor, and preheating mechanisms are provided on the oxygen pipeline, hydrogen chloride pipeline, and ethylene pipeline, and the cooling mechanism is a high-pressure steam heat removal mechanism.

[0010] In the above technical solution, the four oxychlorination reactors are respectively a primary oxychlorination reactor R-301, a secondary oxychlorination reactor R-302, a tertiary oxychlorination reactor R-303, and a quaternary oxychlorination reactor R-304. The hydrogen chloride pipeline and the ethylene pipeline are connected to the primary oxychlorination reactor R-301, and the oxygen pipeline is respectively connected to each oxychlorination reactor through an oxygen branch pipeline.

[0011] On the other hand, an oxychlorination reaction system based on a quaternary reactor is characterized by including the above-mentioned oxychlorination reaction unit based on a quaternary reactor and a product post-treatment and ethylene recycling unit, wherein: the product post-treatment and ethylene recycling unit includes a gas-liquid separation tank for gas-liquid separation. The outlet of the quaternary oxychlorination reactor at the end is connected to the inlet of the gas-liquid separation tank. The liquid outlet of the gas-liquid separation tank is connected to an ethylene recovery tower through a pipeline to remove dissolved ethylene. There are fillers in the ethylene recovery tower. A steam inlet pipeline is provided at the lower part of the ethylene recovery tower. The bottom of the ethylene recovery tower is connected to an EDC water washing tank V-120 through a pipeline to collect dichloroethane.

[0012] In the above technical solution, there are two stages of the gas-liquid separation tank, which are respectively a primary oxychlorination separation tank V-300 and a secondary oxychlorination separation tank V-310.

[0013] In the above technical solution, the product post-treatment and ethylene recycling unit includes a primary oxychlorination separation tank V-300, a secondary oxychlorination separation tank V-310, and an ethylene recovery tower T-300. The outlet of the quaternary oxychlorination reactor R-304 is connected to the primary oxychlorination separation tank V-300 through an outlet pipeline for the first gas-liquid separation. The liquid outlet of the primary oxychlorination separation tank V-300 is respectively connected to the top of the ethylene recovery tower T-300 and the inlet pipeline of the quaternary oxychlorination reactor R-304 through an output pipeline provided with an oxychlorination reactor product pump P-300A / B. A condensate cooler E-304 is provided on the return pipeline between the oxychlorination reactor product pump P-300A / B and the top of the primary oxychlorination separation tank V-300. The top gas outlet of the ethylene recovery tower T-300 is connected to the pipeline between the quaternary oxychlorination reactor R-304 and the primary oxychlorination separation tank V-300. The bottom liquid outlet of the ethylene recovery tower T-300 is connected to the EDC water washing tank V-120 through a pipeline provided with a water-cooled heat exchanger E-312;

[0014] The gas outlet of the first-stage oxychlorination separation tank V-300 is connected to the inlet of the second-stage oxychlorination separation tank V-310 through a pipeline provided with a condenser E-310 (shell-and-tube graphite condenser) for the second gas-liquid separation. The liquid outlet of the second-stage oxychlorination separation tank V-310 is connected to the first-stage oxychlorination separation tank V-300. The gas outlet of the second-stage oxychlorination separation tank V-310 is connected to the first-stage oxychlorination reactor R-301 through a pipeline provided with an Oxy recycle compressor C-300 to transport the ethylene recycle gas. The outlet of the Oxy recycle compressor C-300 is also connected to a condensate tank V-311 through a pipeline provided with a gas condenser E-311. The top gas outlet of the condensate tank V-311 is connected to an Oxy purification dryer D-310A / B. The bottom liquid outlet of the condensate tank V-311 is connected to the first-stage oxychlorination separation tank V-300 through a pipeline. The Oxy purification dryers D-310A / B are respectively connected to the HDC reactor R-101 or the purified gas chlorination reactor R-102 through pipelines.

[0015] On the other hand, in the present invention, an oxychlorination reaction method is provided. After being preheated, hydrogen chloride is transported to the first-stage oxychlorination reactor. After being preheated, ethylene or a mixture of preheated ethylene and high-concentration ethylene recycle gas is transported to the first-stage oxychlorination reactor. Oxygen is preheated or fed into the first-stage oxychlorination reactor R-301, the second-stage oxychlorination reactor R-302, the third-stage oxychlorination reactor R-303, and the fourth-stage oxychlorination reactor R-304 according to a ratio of 30:30:30:10. The four oxychlorination reactors are all tubular fixed-bed reactors. Under the action of a copper chloride catalyst in each tubular fixed-bed reactor, hydrogen chloride, oxygen, and ethylene successively carry out oxychlorination reactions. The heat energy generated by the reaction in each oxychlorination reactor is removed by a cooling mechanism.

[0016] In the above technical solution, the product discharged from the fourth-stage oxychlorination reactor R-304 enters the first-stage oxychlorination separation tank V-300 for the first gas-liquid separation. After the gas is separated from the condensed EDC and water, it then enters the second-stage oxychlorination separation tank V-310 for the second gas-liquid separation. The separated liquid is returned to the first-stage oxychlorination separation tank V-300. Part of the gas is compressed by the oxychlorination recycle compressor C-300 and sent to the first-stage oxychlorination reactor R-301 for utilization as ethylene recycle gas. Part of the gas is condensed by the gas condenser E-311 and enters the condensate tank V-311. The liquid generated by the condensation in the condensate tank V-311 enters the first-stage oxychlorination separation tank V-300. The uncondensed gas in the condensate tank V-311 is dried by the Oxy purification dryers D-310A / B and then sent to the HDC reactor R-101 or the purified gas chlorination reactor R-102;

[0017] The liquid stream discharged from the oxychlorination primary separation tank V-300 consists of EDC-rich and water, and a large amount of dissolved ethylene still remains in the aqueous phase. Part of it is pumped to the ethylene recovery column T-300 by the oxychlorination reactor product pumps P-300A / B, and part enters the oxychlorination primary separation tank V-300 after being condensed by the condensate cooler E-304.

[0018] The residual water in the gas phase leaving the oxychlorination secondary separation tank V-310 will be removed in the Oxy purification and drying units D-310A / B. The liquid from the oxychlorination primary separation tank V-300 is pumped to the top of the ethylene recovery column T-300. Medium-pressure steam is injected into the bottom of the ethylene recovery column T-300. The vapor at the top of the column is sent to the primary oxychlorination reactor R-301. The liquid level at the bottom of the ethylene recovery column T-300 is controlled by the water-cooled heat exchanger E-312 and then sent to the EDC water wash tank V-120.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0020] 1. Low environmental impact: The present invention adopts a fixed-bed process. Compared with a fluidized-bed catalyst, there is basically no loss, and thus the catalyst will not be discharged into the wastewater, reducing the copper pollution to a minimum. A large amount of wastewater is not generated, and the dioxin related to the catalyst used in the oxychlorination process is reduced to the lowest limit.

[0021] 2. High selectivity and safe operation: The ethylene concentration is the main driving factor for the selective formation of EDC in the reaction. The ethylene concentration that can be controlled by the fixed-bed process of the present invention is greater than 90%. Through the series operation of four oxychlorination reactors and the oxygen split of 30%:30%:30%:10%, the reaction conversion rate of hydrogen chloride (HCl) is greater than 99.8% (while the conversion rate of the two-stage fixed bed is 99.7%), so the selectivity for EDC can be as high as over 98.5%. The organic phase recovered from the oxychlorination unit needs to be sent to the EDC refining acid-base washing process to neutralize the HCl in the organic phase with alkali. Through this process operation, the HCl content in the recovered organic phase can be effectively reduced, thereby reducing the consumption of NaOH in the EDC refining acid-base washing unit. At the same time, since oxygen is added step by step at 30%:30%:30%:10%, compared with the ratio of 50%:50% in the two-stage reactor, the equipment operation is safer.

[0022] 3. Low catalyst consumption: The loss of the fixed-bed catalyst is basically zero, so there is no need to continuously add the catalyst, thus avoiding the need for continuous treatment of solid (waste) materials. Since the load of a single reactor is relatively low, the average service life of the catalyst in the four-stage reactor is generally more than 4 years, which is 2 - 4 months longer than that of the two-stage reactor.

[0023] 4. Reduction of waste gas emissions: Before entering the scrubber, the oxychlorination unit is not designed with an exhaust (opening) to the atmosphere. The tail gas from the oxychlorination unit will be sent to the high-temperature chlorination reactor R-101 or enter the purified gas chlorination reactor R-102. During startup and shutdown, the oxychlorination unit will not exhaust to the atmosphere.

[0024] 5. High reliability: Since (the oxychlorination reactor) is made of the best materials, the average overhaul period is more than 2.5 years, which is about 6 months longer than that of the second-stage reactor.

[0025] 6. Low maintenance cost: The maintenance cost is extremely low. During normal shutdown for overhaul, regular maintenance of the oxychlorination reactor is not required. Moreover, compared with the second-stage reactor, the amount of oxygen introduced into the first-stage reactor is reduced, the carbonization of organic matter is significantly improved, and the reactor pressure drop (coke adhering to the upper porcelain rings) is controlled. Basically, no coke removal work is required within the catalyst life cycle. While for the second-stage reactor, within the catalyst life cycle (3 - 4 years), 1 to 2 overhaul works are inevitable. Therefore, even when the circulating liquid in the oxychlorination recycle compressor contains high concentrations of organic matter and water (H2O) at the top of the first oxychlorination reactor, excessive carbon deposition will not occur, reducing the workload of maintenance.

[0026] 7. Large load adjustment range and easy control: The minimum load of the second-stage reactor system is about 30%, and the minimum load of the fourth-stage reactor can reach 20%, meeting the needs of the plant for low-load operation, which can be achieved through automatic control.

[0027] 8. Convenient operation: When the fourth-stage reactor system shuts down, no further operation is required. When starting from 0 to full load operation, it can be achieved in less than 30 minutes. Description of the Drawings

[0028] Figure 1 The shown process flow diagram of the oxychlorination reaction. Detailed Embodiments

[0029] The following further describes the present invention in detail with specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0030] Embodiment 1

[0031] An oxychlorination reaction unit based on a four-stage reactor, including four oxychlorination reactors connected in series in sequence, wherein:

[0032] Each oxychlorination reactor is a fixed-bed reactor, and each oxychlorination reactor is provided with a cooling mechanism. The oxygen pipeline is respectively connected to each oxychlorination reactor through an oxygen branch pipeline, and the hydrogen chloride pipeline and the ethylene pipeline are connected to the first-stage oxychlorination reactor at the head end.

[0033] Preferably, each oxychlorination reactor is a tubular fixed-bed reactor, and preheating mechanisms are provided on the oxygen pipeline, the hydrogen chloride pipeline, and the ethylene pipeline. The cooling mechanism is a high-pressure steam heat removal mechanism. An ethylene preheater E-300 is provided on the ethylene pipeline, an HCL preheater E-301 is provided on the hydrogen chloride pipeline, and an oxygen preheater E-302 is provided on the oxygen pipeline.

[0034] The four oxychlorination reactors are respectively a primary oxychlorination reactor R-301, a secondary oxychlorination reactor R-302, a tertiary oxychlorination reactor R-303, and a quaternary oxychlorination reactor R-304. The hydrogen chloride pipeline and the ethylene pipeline are connected to the primary oxychlorination reactor R-301. The oxygen pipeline is respectively connected to each oxychlorination reactor through an oxygen branch pipeline to introduce oxygen into the four oxychlorination reactors R-301, R-302, R-303, and R-304 in a predetermined proportion, and the oxygen concentration is maintained below the flammable limit.

[0035] Example 2

[0036] An oxychlorination reaction system based on a quaternary reactor includes an oxychlorination reaction unit based on a quaternary reactor and a product post-treatment and ethylene recycling unit as described in Example 1, wherein: The product post-treatment and ethylene recycling unit includes a gas-liquid separation tank for gas-liquid separation. The outlet of the quaternary oxychlorination reactor at the end is connected to the inlet of the gas-liquid separation tank. The liquid outlet of the gas-liquid separation tank is connected to an ethylene recovery tower through a pipeline to remove dissolved ethylene. There is packing in the ethylene recovery tower. A steam inlet pipeline is provided at the lower part of the ethylene recovery tower. The bottom of the ethylene recovery tower is connected to an EDC water washing tank V-120 through a pipeline to collect dichloroethane.

[0037] Preferably, there are two gas-liquid separation tanks, namely a primary oxychlorination separation tank V-300 and a secondary oxychlorination separation tank V-310. Both gas-liquid separation tanks can be vertical carbon steel containers lined with PTFE.

[0038] The post-treatment of the product and the ethylene recycling unit include the first-stage oxychlorination separation tank V-300, the second-stage oxychlorination separation tank V-310, and the ethylene recovery tower T-300. The discharge port of the four-stage oxychlorination reactor R-304 is connected to the first-stage oxychlorination separation tank V-300 through a discharge pipeline for the first gas-liquid separation. The liquid outlet of the first-stage oxychlorination separation tank V-300 is respectively connected to the top of the ethylene recovery tower T-300 and the inlet pipeline of the first-stage oxychlorination separation tank V-300 through the output pipelines provided with the oxychlorination reactor product pumps P-300A / B. A condensate cooler E-304 is provided on the reflux pipeline between the oxychlorination reactor product pumps P-300A / B and the top of the first-stage oxychlorination separation tank V-300. The top gas outlet of the ethylene recovery tower T-300 is connected to the pipeline between the four-stage oxychlorination reactor R-304 and the first-stage oxychlorination separation tank V-300. The bottom liquid outlet of the ethylene recovery tower T-300 is connected to the EDC water washing tank V-120 through a pipeline provided with a water-cooled heat exchanger E-312;

[0039] The gas outlet of the first-stage oxychlorination separation tank V-300 is connected to the inlet of the second-stage oxychlorination separation tank V-310 through a pipeline provided with a condenser E-310 (shell-and-tube graphite condenser) for the second gas-liquid separation. The liquid outlet of the second-stage oxychlorination separation tank V-310 is connected to the first-stage oxychlorination separation tank V-300. The gas outlet of the second-stage oxychlorination separation tank V-310 is connected to the first-stage oxychlorination reactor R-301 through a pipeline provided with an Oxy recycle compressor C-300 to transport the ethylene recycle gas. The outlet of the Oxy recycle compressor C-300 is also connected to a condensate tank V-311 through a pipeline provided with a gas condenser E-311. The top gas outlet of the condensate tank V-311 is connected to the Oxy purification dryer D-310A / B. The bottom liquid outlet of the condensate tank V-311 is connected to the first-stage oxychlorination separation tank V-300 through a pipeline. The Oxy purification dryers D-310A / B are respectively connected to the HDC reactor R-101 or the purified gas chlorination reactor R-102 through pipelines.

[0040] Example 3

[0041] The oxychlorination reaction system based on a four-stage reactor is a gas-phase reaction of ethylene (C2H4), anhydrous hydrogen chloride (HCl), and oxygen (O2) using a copper chloride (CuCl2) catalyst to produce dichloroethane (EDC: C2H4Cl2) and water (H2O). The reaction process is carried out in series in four tubular fixed-bed reactors. A large excess of ethylene is used to help control the reaction temperature and keep the oxygen concentration below the flammability limit. The unreacted ethylene is separated from the EDC and water, compressed, and then recycled back to the reactor system.

[0042] Total reaction process on the catalyst bed;

[0043] C2H4 (gas) + 2HCl (gas) + 1 / 2O2 (gas) → C2H4Cl2 (liquid) + H2O (liquid)

[0044] The oxychlorination reaction method includes the following steps:

[0045] Step 1, Hydrogen chloride is preheated to about 155°C and transported to the first-stage oxychlorination reactor. Ethylene preheated to about 155°C is mixed with high-concentration ethylene recycle gas and then transported to the first-stage oxychlorination reactor. Oxygen is preheated to 152 - 157°C, preferably about 155°C, and is fed into the first-stage oxychlorination reactor, the second-stage oxychlorination reactor, the third-stage oxychlorination reactor, and the fourth-stage oxychlorination reactor respectively according to the ratio of 30:30:30:10. The four oxychlorination reactors are all tubular fixed-bed reactors. Under the action of cupric chloride catalyst in each tubular fixed-bed reactor, hydrogen chloride, oxygen, and ethylene successively carry out oxychlorination reactions, and the heat energy generated by the reaction in each oxychlorination reactor is removed by the cooling mechanism.

[0046] Specifically, in order to avoid dew point corrosion, the raw materials hydrogen chloride (HCl), ethylene (C2H4), and oxygen (O2) are preheated to 152 - 157°C, preferably about 155°C, and then start to feed into the first-stage oxychlorination reactor R-301. Hydrogen chloride (HCL) and ethylene (C2H4) are transported to the first-stage oxychlorination reactor R-301, while oxygen (O2) is fed into the four oxychlorination reactors R-301, R-302, R-303, and R-304 respectively according to the ratio of 30:30:30:10. Pure ethylene (C2H4) is mixed with high-concentration ethylene (C2H4) recycle gas and then fed into the first-stage oxychlorination reactor R-301.

[0047] The reaction mechanisms of the four oxychlorination reactors are as follows:

[0048] The total preheated HCl and ethylene (C2H4) and the total oxygen (O2) designed according to the 30% feed ratio are fed into the first-stage oxychlorination reactor R-301. In this reactor, dichloroethane (EDC: C2H4Cl2) and water (H2O) vapor are generated at an expected oxychlorination unit reaction rate of 30%. The reaction occurs on the cupric chloride catalyst supported by an aluminum support base inside the reactor tube. The reaction process generates heat energy, and the heat energy is removed in the form of high-pressure steam with a pressure of about 1.50 - 1.95MPaG, preferably 1.85MPaG.

[0049] The gas leaving the first-stage oxychlorination reactor R-301 combines with oxygen (O2) and is then sent to the second-stage oxychlorination reactor R-302. The amount of oxygen (O2) added to the second-stage oxychlorination reactor R-302 is provided at about 30% of the requirement of the oxychlorination unit. The raw materials react to produce more dichloroethane (EDC: C2H4Cl2) and water (H2O) vapor. The reaction heat is removed by generating high-pressure steam at about 1.50 - 1.95 MPaG, preferably 1.85 MPaG.

[0050] The gas leaving the second-stage oxychlorination reactor R-302 combines with oxygen (O2) and enters the third-stage oxychlorination reactor (R-303). The amount of oxygen (O2) added to the third-stage oxychlorination reactor R-302 is provided at about 30% of the requirement of the oxychlorination unit. The raw materials react again to produce more dichloroethane (EDC: C2H4Cl2) and water (H2O) vapor. The reaction heat is removed by generating high-pressure steam at about 1.50 - 1.95 MPaG, preferably 1.85 MPaG.

[0051] The gas leaving the third-stage oxychlorination reactor R-303 combines with the remaining oxygen (O2) and enters the fourth-stage oxychlorination reactor R-304. The remaining oxygen (O2) required for the oxychlorination unit is sent to the fourth-stage oxychlorination reactor R-304 at a ratio of 10%. The raw materials react to produce more dichloroethane (EDC: C2H4Cl2)) and water (H2O) vapor. The reaction heat is removed by generating high-pressure steam at about 1.50 - 1.95 MPaG, preferably 1.85 MPaG.

[0052] When the gas leaves the fourth-stage oxychlorination reactor R-304, almost all of the oxygen (O2) and more than 99.8% of the hydrogen chloride (HCl) have reacted. All of the oxychlorination reactors (R-301, R-302, R-303, R-304) operate in the fuel-rich (oxygen-lean) range because a large amount of excess ethylene is used in this process to ensure that the oxygen (O2) concentration is below the flammable limit range.

[0053] By moderately adjusting the steam drum pressure on each stage of the oxychlorination reactor and the flow rate of the ethylene recycle gas going to the first-stage oxychlorination reactor R-301, the reaction temperature in each oxychlorination reactor can be controlled to a certain extent. The maximum temperature inside the tubes in the oxychlorination reactors R-302, R-303, R-304 should be maintained at 265 - 270 °C. It is necessary to ensure the total feed rate of ethylene / hydrogen chloride, and the hot spot temperature of the first-stage oxychlorination reactor R-301 will reach 280 °C.

[0054] Step 2: The products discharged from the quaternary oxychlorination reactor R-304 enter the primary oxychlorination separation tank V-300 for the first gas-liquid separation. After the gas is separated from the condensed EDC and water, it then enters the secondary oxychlorination separation tank V-310 for secondary gas-liquid separation. The separated liquid is returned to the primary oxychlorination separation tank V-300. Part of the gas is compressed by the oxychlorination recycle compressor C-300 and sent to the primary oxychlorination reactor R-301 for use as ethylene recycle gas. Part of the gas is condensed by the gas condenser E-311 and then enters the condensate tank V-311. The liquid produced by the condensation in the condensate tank V-311 enters the primary oxychlorination separation tank V-300. The uncondensed gas in the condensate tank V-311 is dried by the Oxy purification dryer D-310A / B and then sent to the HDC reactor R-101 or the purified gas chlorination reactor R-102;

[0055] The liquid stream discharged from the primary oxychlorination separation tank V-300 consists of EDC-rich and water, and the aqueous phase still contains a large amount of dissolved ethylene. Part of it is pumped to the ethylene recovery column T-300 by the oxychlorination reactor product pumps P-300A / B, and part of it is cooled by the condensate cooler E-304 and then enters the primary oxychlorination separation tank V-300.

[0056] The primary oxychlorination separation tank V-300 and the secondary oxychlorination separation tank V-310 are both vertical carbon steel containers lined with PTFE.

[0057] The residual water in the gas phase leaving the secondary oxychlorination separation tank V-310 is removed in the Oxy purification dryer D-310A / B. Acid-resistant molecular sieves are installed in the Oxy purification dryer D-310A / B. The water content of the dried purified gas is continuously analyzed and then sent to the HDC reactor R-101 or the purified gas chlorination reactor R-102.

[0058] Step 3: In the ethylene recovery column T-300, the dissolved ethylene in the liquid products from the primary oxychlorination separation tank V-300 and the secondary separation tank V-310 is separated using medium-pressure steam (0.95 MpaG). The ethylene gas at the top of the ethylene recovery column is transported to the primary oxychlorination separation tank V-300, and the liquid at the bottom of the column is sent to the EDC water wash tank for washing to obtain EDC.

[0059] The liquid from the primary oxychlorination separation tank V-300 is pumped to the top of the ethylene recovery column T-300, and random packing is stacked at the top of the column. Under flow control, medium-pressure steam is injected into the bottom of the ethylene recovery column T-300. Before quenching, the top vapor mainly composed of EDC, water, and the recovered ethylene is sent to the primary oxychlorination separation tank V-300. The bottom flow of the ethylene recovery column T-300 is controlled by the water-cooled heat exchanger E-312 and then sent to the EDC water wash tank V-120.

[0060] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for oxychlorination reaction, characterized in that, The oxychlorination reaction method comprises the following steps: After being preheated, hydrogen chloride is transported to the first-stage oxychlorination reactor. After being preheated, ethylene or a mixture of preheated ethylene and high-concentration ethylene recycle gas is transported to the first-stage oxychlorination reactor. Oxygen is preheated and fed into the first-stage oxychlorination reactor, the second-stage oxychlorination reactor, the third-stage oxychlorination reactor, and the fourth-stage oxychlorination reactor respectively according to the ratio of 30:30:30:

10. The four oxychlorination reactors are all tubular fixed-bed reactors. Under the action of a copper chloride catalyst, hydrogen chloride, oxygen, and ethylene successively carry out oxychlorination reactions in each tubular fixed-bed reactor. The heat energy generated by the reaction in each oxychlorination reactor is removed by a cooling mechanism; The oxychlorination reaction method further comprises a product post-treatment and ethylene recycle method: The product discharged from the fourth-stage oxychlorination reactor enters an oxychlorination primary separation tank for the first gas-liquid separation. After the gas is separated from the condensed EDC and water and then condensed, it enters the oxychlorination secondary separation tank for secondary gas-liquid separation. The separated liquid is sent back to the oxychlorination primary separation tank. Part of the separated gas is compressed by an oxychlorination recycle compressor and sent to the first-stage oxychlorination reactor for utilization as ethylene recycle gas. Part of the separated gas is condensed by a gas condenser and then enters a condensate tank. The liquid generated by the condensation in the condensate tank enters the oxychlorination secondary separation tank. The uncondensed gas in the condensate tank is dried by an Oxy purification dryer and then sent to an HDC reactor or a purified gas chlorination reactor; The liquid stream discharged from the oxychlorination primary separation tank consists of EDC-rich and water, and a large amount of dissolved ethylene remains in the aqueous phase. Part of the liquid is pumped to an ethylene recovery tower by an oxychlorination reactor product pump, and part of the liquid is cooled and then sent back to the oxychlorination primary separation tank; In the ethylene recovery tower, the dissolved ethylene in the liquid-phase products from the oxychlorination primary separation tank and the secondary separation tank is separated. The ethylene gas at the top of the ethylene recovery tower is transported to the oxychlorination primary separation tank, and the liquid at the bottom of the tower is transported to an EDC water washing tank for water washing to obtain EDC; The above oxychlorination reaction method is carried out in an oxychlorination reaction system. The oxychlorination reaction system comprises an oxychlorination reaction unit and a product post-treatment and ethylene recycle unit, wherein: The oxychlorination reaction unit comprises four oxychlorination reactors connected in series. A cooling mechanism is provided on each oxychlorination reactor. The oxygen pipeline is respectively connected to each oxychlorination reactor through an oxygen branch pipeline. The hydrogen chloride pipeline and the ethylene pipeline are connected to the first-stage oxychlorination reactor at the head end. The highest temperature in the tubes of the second-stage oxychlorination reactor, the third-stage oxychlorination reactor, and the fourth-stage oxychlorination reactor is maintained at 265-270 °C, and the hot spot temperature of the first-stage oxychlorination reactor reaches 280 °C.

2. The method for oxychlorination reaction according to claim 1, characterized in that, The product post-treatment and ethylene recycling unit includes an oxychlorination primary separation tank, an oxychlorination secondary separation tank, and an ethylene recovery tower. The outlet of the four-stage oxychlorination reactor is connected to the oxychlorination primary separation tank through a discharge pipeline for the first gas-liquid separation. The liquid outlet of the oxychlorination primary separation tank is respectively connected to the top of the ethylene recovery tower and the inlet pipeline of the oxychlorination primary separation tank through an output pipeline provided with an oxychlorination reactor product pump. A condensate cooler is provided on the reflux pipeline between the oxychlorination reactor product pump and the top of the oxychlorination primary separation tank. The top gas outlet of the ethylene recovery tower is connected to the pipeline between the four-stage oxychlorination reactor and the oxychlorination primary separation tank. The bottom liquid outlet of the ethylene recovery tower is connected to the EDC water washing tank through a pipeline provided with a water-cooled heat exchanger; The gas outlet of the oxychlorination primary separation tank is connected to the inlet of the oxychlorination secondary separation tank through a pipeline provided with a condenser for the second gas-liquid separation. The liquid outlet of the oxychlorination secondary separation tank is connected to the oxychlorination primary separation tank. The gas outlet of the oxychlorination secondary separation tank is connected to the first-stage oxychlorination reactor through a pipeline provided with an oxychlorination recycle compressor to transport ethylene recycle gas. The outlet of the oxychlorination recycle compressor is also connected to a condensate tank through a pipeline provided with a gas condenser. The top gas outlet of the condensate tank is connected to an Oxy purification dryer. The bottom liquid outlet of the condensate tank is connected to the oxychlorination secondary separation tank through a pipeline. The Oxy purification dryer is respectively connected to the HDC reactor or the purified gas chlorination reactor through pipelines.

3. The method for oxychlorination reaction according to claim 1, characterized in that, Preheating mechanisms are provided on the oxygen pipeline, hydrogen chloride pipeline, and ethylene pipeline.

4. The method for oxychlorination reaction according to claim 1, characterized in that, The cooling mechanism is a high-pressure steam heat removal mechanism.

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