A device and method for producing medium-pressure steam as a by-product of vinyl chloride synthesis system

Abstract

The invention discloses a device for producing medium-pressure steam as a by-product of a vinyl chloride synthesis system, wherein the water outlet of the synthesis reactor is connected to a flash tank, the water inlet of the synthesis reactor is connected to a booster pump, and the reaction gas outlet of the synthesis reactor is connected to a heat exchanger; the water outlet of the flash tank is respectively connected to a booster pump and a hot water pump, and the steam outlet of the flash tank is connected to a water vapor compressor; the water vapor compressor is connected to a steam user; the hot water pump is connected to a hot water user through a pipeline; one end of the pipeline heater is connected to a condensate pump, and the other end is connected to the booster pump through a first automatic regulating valve; a condensate storage tank is provided with a water replenishment valve, and the condensate storage tank is connected to the condensate pump; a fresh water valve is provided at the water inlet of the heat exchanger, and the water outlet of the heat exchanger is connected to the condensate storage tank through a pipeline. The device and method for producing medium-pressure steam as a by-product of a vinyl chloride synthesis system of the invention can simultaneously accurately control the temperature of the vinyl chloride synthesis reactor and the production of medium-pressure steam, thereby achieving increased product output and heat energy recovery and utilization.

Description

Technical Field

[0001] The invention relates to a device and method for producing medium-pressure steam as a by-product of a vinyl chloride synthesis system, belonging to the technical field of polyvinyl chloride by-products. Background Art

[0002] In the production process of polyvinyl chloride in my country, a large amount of acetylene gas and hydrogen chloride gas are needed to synthesize vinyl chloride gas, thereby producing polyvinyl chloride. A large amount of heat will be generated in the process of synthesizing vinyl chloride from acetylene gas and hydrogen chloride gas: CH≡CH+HCl→CH2=CHCl+124.8kJ / mol (29.8kcal / mol). Based on the annual production of 1 million tons of polyvinyl chloride, the coal consumption for boiler steam production is converted to 147,692 tons.

[0003] For the recovery and utilization of heat energy from vinyl chloride synthesis, the main treatment methods in China are: one is to use the temperature difference of cooling water as the power source, and the cooling water of each reactor is closed and self-circulated. This process easily causes the upper part of the reactor to be filled with water vapor, the reactor temperature is uneven and unadjustable, and the chemical reaction intensity on the reaction side is limited. In addition, the obtained water vapor is naturally vaporized and cannot be used by users at the lower end; the other is to install a circulating cooling water storage tank and a cooling water heat exchanger, and the cooling tower takes away the cooling water heat, which consumes a lot of energy. The main recycling methods in China are: one is to use the lithium bromide process, which has a large initial investment and poor industry response to the operation effect; the other is to directly use the naturally vaporized low-quality water vapor, which has few uses and low utilization rate. Summary of the invention

[0004] The object of the present invention is to provide a device and method for producing medium-pressure steam as a by-product of a vinyl chloride synthesis system in response to the above-mentioned problems. The present invention can simultaneously and accurately control the temperature of the vinyl chloride synthesis reactor and the production of medium-pressure steam, thereby increasing product output and recovering heat energy.

[0005] The technical solution adopted by the present invention is as follows:

[0006] A device for producing medium-pressure steam as a by-product of a vinyl chloride synthesis system, comprising a synthesis reactor, a flash tank, a water vapor compressor, a booster pump, a hot water pump, a pipeline heater, a cooling water replenishment system, a condensate storage tank, a condensate pump and a heat exchanger;

[0007] The water outlet of the synthesis reactor is connected to the flash tank, the water inlet of the synthesis reactor is connected to the booster pump, and the reaction gas outlet of the synthesis reactor is connected to the heat exchanger;

[0008] The water outlet of the flash tank is connected to the booster pump and the hot water pump respectively, and the steam outlet of the flash tank is connected to the water vapor compressor;

[0009] The steam compressor is connected to the steam user, the steam user is connected to the steam trap, and the steam trap is connected to the condensate storage tank;

[0010] The hot water pump is connected to the hot water user through a pipeline, and the hot water user is connected to the condensate storage tank;

[0011] One end of the pipeline heater is connected to the condensate pump, the other end of the pipeline heater is connected to the water inlet of the booster pump through the first automatic regulating valve, and the pipeline heater is connected to the water vapor regulating valve through the temperature controller;

[0012] The condensate storage tank is provided with a water supply valve, and the water outlet of the condensate storage tank is connected to the condensate pump;

[0013] A fresh water valve is provided at the water inlet of the heat exchanger, and the water outlet of the heat exchanger is connected to the condensed water storage tank through a pipeline.

[0014] The present invention has the following features: 1. A cooling water circulation system: a booster pump is connected to a vinyl chloride synthesis reactor through a pipeline; a vinyl chloride synthesis reactor is connected to a flash tank through a pipeline; a flash tank is connected to a booster pump through a pipeline; 2. A water vapor system: a flash tank is connected to a water vapor compressor through a pipeline, a water vapor compressor is connected to a steam user through a pipeline; a steam user is connected to a steam trap through a pipeline, a steam trap is connected to a condensate storage tank through a pipeline, a condensate storage tank is connected to a condensate pump through a pipeline, a condensate pump is connected to a pipeline heater through a pipeline, a pipeline heater is connected to a first automatic regulating valve through a pipeline, the first automatic regulating valve is connected to the inlet of the booster pump through a regulating valve and a pipeline, and the booster pump is connected to the flash tank through a pipeline. 3. A hot water system: a flash tank is connected to a hot water pump through a pipeline, a hot water pump is connected to a hot water user through a pipeline, a hot water user is connected to a condensate storage tank through a pipeline, and is incorporated into a cooling water circulation system; 4. The water side of a heat exchanger is connected to a condensate storage tank through a pipeline, and is incorporated into a cooling water circulation system through a condensate pump, and the material side of the heat exchanger is connected to a synthesis reactor through a pipeline. The device and method for producing medium-pressure steam as a by-product of a vinyl chloride synthesis system of the present invention can recover the heat limit of the chemical reaction and transfer it to medium-pressure steam output, while accurately controlling the reaction temperature of the vinyl chloride synthesis reactor.

[0015] In the present invention, the reaction heat is removed from the synthesis reactor by a forced large flow of cooling water, the pressure in the flash tank is adjusted by a steam compressor, the tank pressure determines the cooling water vaporization intensity, the cooling water vaporization intensity determines the cooling water temperature, the cooling water temperature determines the synthesis reactor temperature, and at the same time, the outlet of the water vapor compressor produces medium-pressure water vapor as a byproduct. The water vapor compressor can adjust the pressure in the flash tank and pressurize the water vapor out to raise its temperature by 65-70°C.

[0016] Preferably, the synthesis reactor is a shell-and-tube heat exchanger type, where the synthesis reaction is carried out in the gas phase on one side of the tubes to release heat; and cooling water is used to transfer the reaction heat on the other side of the tubes.

[0017] Preferably, a baffle is provided on the cooling water side of the synthesis reactor to divide the cooling water side into three sections which are not connected to each other, and each section is provided with a water inlet and a water outlet.

[0018] In the above scheme, cooling water is introduced into the reaction system in three sections, which makes it easier to control the flow rate of cooling water and thus the reaction temperature.

[0019] Preferably, a wire mesh foam catcher is provided in the flash tank above the water inlet, and a manual drain valve, an automatic drain valve, a first pressure controller, a first liquid level controller and a temperature sensor are provided on the flash tank. The automatic drain valve is interlocked with the first pressure controller, the first pressure controller is interlocked with the water vapor compressor, and the first liquid level controller is interlocked with the automatic regulating valve.

[0020] In the above scheme, the liquid level of the flash tank is controlled by the first liquid level controller; the pressure in the water vapor compressor tank is controlled by the first pressure controller; by setting an automatic drain valve, and the automatic drain valve is interlocked with the first pressure controller, when the pressure in the water vapor compressor tank exceeds the set value due to a failure, it can be emptied in time to prevent the cooling water temperature from rising rapidly and causing the catalyst in the synthesis reactor to sublime; by setting a wire mesh collector, droplets are prevented from being sucked into the water vapor compressor, and high-temperature corrosion inhibitor is prevented from entering the water vapor compressor, thereby extending the use time of the high-temperature corrosion inhibitor.

[0021] Preferably, the first automatic regulating valve is connected to the automatic reflux valve via a first liquid level controller, the automatic reflux valve is connected to the condensate storage tank, and the first automatic regulating valve and the automatic reflux valve have opposite switches.

[0022] In the above scheme, the liquid level height of the flash tank is controlled.

[0023] Preferably, the driving motor of the water vapor compressor is controlled by a frequency converter, a second pressure controller, a flow sensor and a temperature sensor are arranged at the outlet of the water vapor compressor, and the second pressure controller is interlocked with a second automatic regulating valve.

[0024] In the above scheme, the back pressure of the water vapor compressor is guaranteed and the reverse flow of system materials is prevented.

[0025] Preferably, a pressure sensor is provided at the outlet of the boost pump.

[0026] Preferably, the hot water user is vinyl chloride synthesis reaction material.

[0027] Preferably, a flow sensor is provided at the water outlet of the condensate pump, and the outlet is connected to the condensate storage tank via an automatic reflux valve.

[0028] Preferably, the condensate storage tank is normally in a closed state.

[0029] In the above scheme, the oxygen content of the circulating cooling water is reduced to slow down the corrosion rate of the reactor.

[0030] Preferably, the water replenishment valve is interlocked with a second liquid level controller arranged in the condensate storage tank.

[0031] In the above scheme, the circulating cooling water level is ensured to be stable to prevent the synthesis reactor from drying out due to lack of water.

[0032] Preferably, the equipment and pipelines in the device are insulated.

[0033] In the above scheme, by insulating the equipment and pipelines, the heat radiation loss and the damage to the building caused by heat radiation can be reduced.

[0034] A method for producing medium-pressure steam as a by-product in a vinyl chloride synthesis system comprises the following steps:

[0035] Step 1: Open the water supply valve to replenish cooling water to the condensate storage tank, and the water supply valve is interlocked with the second liquid level controller to control the liquid level of the condensate storage tank;

[0036] Step 2: Pump water from the condensate storage tank to the pipeline heater through the condensate pump;

[0037] Step 3: Start the water vapor regulating valve to heat the water in the pipeline heater. The water vapor regulating valve is interlocked with the temperature controller to control the water temperature. During normal operation, the water vapor regulating valve and the temperature controller are released from the interlock.

[0038] Step 4: Open the inlet and outlet valves of the booster pump and the inlet and outlet valves of the synthesis reactor, and the high-temperature water of the pipeline heater flows to the synthesis reactor through the first automatic regulating valve and the booster pump, and then flows to the flash tank, wherein the first automatic regulating valve, the automatic reflux valve and the first liquid level controller are interlocked to control the liquid level of the flash tank, and the first automatic regulating valve and the automatic reflux valve are switched in opposite directions;

[0039] Step 5: When the liquid level in the flash tank reaches the set value, start the booster pump;

[0040] Step 6: Start the hot water pump to deliver the high-temperature water in the flash tank to the hot water user to preheat the vinyl chloride synthesis reaction materials, and then return it to the condensate storage tank for circulation;

[0041] Step 7: Open the material valve of the synthesis reactor to release heat energy by vinyl chloride synthesis reaction, and the cooling water provided by the booster pump cools and exchanges heat with the heat energy, and the heat-exchanged water returns to the flash tank through the pipeline for circulation;

[0042] Step 8: When the pressure of the flash tank reaches the set value, the steam compressor is started to provide high-temperature steam to the steam user. After use, the steam is returned to the condensate storage tank for circulation through the steam trap. The steam compressor is interlocked with the pressure controller to control the pressure in the flash tank;

[0043] Step 9: Open the fresh water valve and introduce fresh soft water into the heat exchanger for heat exchange with vinyl chloride gas. The water after heat exchange enters the condensed water storage tank for circulation.

[0044] In the present invention, the cooling water after flash evaporation is circulated to cool the synthesis reactor through a booster pump and / or a thermal siphon effect.

[0045] Preferably, in step three, the high-temperature cooling water is supplied at a pressure of 0.3-0.4 MPa, a temperature of 88-90°C, and a flow rate of 12-15 m3 / h to ensure that the water level can reach 45-55% of the flash tank level to ensure that the material reaction is preheated to the required temperature.

[0046] Preferably, in step five, the temperature of the cooling water during the initial operation is 88-90°C to preheat the synthesis reactor and activate the catalyst, and the circulating cooling water flow rate is greater than 40m3 / h to ensure that the reaction heat is removed in time.

[0047] Preferably, in step five, the temperature of the cooling water is 100°C to 102°C during normal operation to prevent the catalyst on the reaction side of the synthesis reactor from sublimating and failing, and the circulating cooling water flow rate should be greater than 40m3 / h to ensure that the reaction heat is removed in time.

[0048] Preferably, in step five, the lift of the booster pump should be between 11 and 15 m to ensure that the cooling water can circulate.

[0049] Preferably, in step eight, the vaporization area of ​​the flash tank is 1.2 to 1.5 times the calculated area to ensure economical operation of the water vapor compressor.

[0050] Preferably, in step eight, the pressure in the flash tank is maintained at 2-5 KPa to achieve an evaporation intensity when the flash area is certain, ensuring that the heat in the circulating cooling water is taken away in time; the liquid level in the flash tank is maintained at 50%-60% to prevent the unstable flow of circulating cooling water from causing the temperature of the synthesis reactor to be uncontrolled.

[0051] Preferably, in step eight, the water vapor compressor has a 70% to 100% energy level automatic adjustment function to ensure that the pressure in the flash tank can be changed as required, thereby controlling the cooling water temperature and further achieving the optimal reaction temperature of the vinyl chloride synthesis reactor.

[0052] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0053] 1. The temperature of the synthesis reactor can be accurately controlled to optimize the efficiency of the synthesis reaction;

[0054] 2. It can transfer the reaction heat to low-quality steam to the maximum extent, and at the same time, it can pressurize the low-quality steam to improve the efficiency of the steam compressor;

[0055] 3. The pressurized steam can be directly delivered to the back-end steam users, replacing the existing boiler to produce steam and reducing carbon emissions. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] The present invention will now be described by way of example with reference to the accompanying drawings, in which:

[0057] Figure 1 It is the process flow diagram of the device;

[0058] Figure 2 is a schematic diagram of the synthesis reactor.

[0059] Markings in the figure: R01-synthesis reactor, P01-boosting pump, P02-hot water pump, P03-condensate pump, E01-flash tank, E02-steam user, E03-hot water user, E04-heat exchanger, B01-steam heater, C01-steam compressor, V01-condensate storage tank, 1-wire mesh foam collector, 2-automatic drain valve, 3-first pressure controller, 4-first liquid level controller, 5-second pressure controller, 6-second automatic regulating valve, 7-water supply valve, 8-second liquid level controller, 9-first automatic regulating valve, 10-automatic reflux valve, 11-fresh water valve, 12-steam regulating valve, 13-temperature controller, 14-baffle, 15-water inlet of synthesis reactor, 16-water outlet of synthesis reactor. DETAILED DESCRIPTION

[0060] All features disclosed in this specification, or steps in all methods or processes disclosed, except mutually exclusive features and / or steps, can be combined in any manner.

[0061] Any feature disclosed in this specification, unless otherwise stated, can be replaced by other equivalent or alternative features with similar purposes. That is, unless otherwise stated, each feature is only an example of a series of equivalent or similar features.

[0062] like Figure 1-2 As shown, a device for producing medium-pressure steam as a by-product of a vinyl chloride synthesis system in this embodiment includes a synthesis reactor R01, a flash tank E01, a water vapor compressor C01, a booster pump P01, a hot water pump P02, a pipeline heater, a cooling water replenishment system, a condensate storage tank V01, a condensate pump P03 and a heat exchanger E04;

[0063] The synthesis reactor R01 is a shell-and-tube heat exchanger E04 type, and the gas phase on one side of the shell-and-tube performs synthesis reaction and releases heat; a baffle 14 is provided on the other side of the shell-and-tube to divide the cooling water side into three sections that are not connected to each other, and each section is provided with a water inlet and a water outlet; the water outlet 16 of the synthesis reactor is connected to the flash tank E01, the water inlet 15 of the synthesis reactor is connected to the booster pump P01, the reaction gas outlet of the synthesis reactor R01 is connected to the heat exchanger E04, and the water outlet 16 of the synthesis reactor is provided with a temperature sensor and a flow sensor;

[0064] A wire mesh foam trap 1 is provided above the water inlet in the flash tank E01, and a manual drain valve, an automatic drain valve 2, a first pressure controller 3, a first liquid level controller 4 and a temperature sensor are provided on the flash tank E01. The automatic drain valve 2 is interlocked with the first pressure controller 3, the first pressure controller 3 is interlocked with the water vapor compressor C01, and the first liquid level controller 4 is interlocked with the automatic regulating valve; the water outlet of the flash tank E01 is respectively connected to the booster pump P01 and the hot water pump P02, and the steam outlet of the flash tank E01 is connected to the water vapor compressor C01;

[0065] The driving motor of the water vapor compressor C01 is controlled by a frequency converter. A second pressure controller 5, a flow sensor and a temperature sensor are arranged at the outlet of the water vapor compressor C01. The second pressure controller 5 is interlocked with a second automatic regulating valve 6. The water vapor compressor C01 is connected to the steam user E02, the steam user E02 is connected to the steam trap, and the steam trap is connected to the condensate storage tank V01. The water vapor compressor C01 is interlocked with the pressure controller to control the pressure in the flash tank E01.

[0066] The hot water pump P02 is connected to the hot water user E03 through a pipeline. A temperature sensor and a flow sensor are set at the outlet of the hot water pump P02. The hot water user E03 is connected to the condensed water storage tank V01. The hot water pump P02 is directly connected to the condensed water storage tank V01 through another pipeline, and directly returns water to the condensed water storage tank V01 when needed. The hot water pump P02 is high-lift, small-flow, and high-temperature resistant, and provides the heat demand for the hot water user E03. When the liquid level of the cooling water system is high but high-temperature water must be supplemented, the liquid level of the flash tank E01 can be adjusted;

[0067] The condensate storage tank V01 is in a closed state. A water replenishment valve 7 is provided on the condensate storage tank V01. The water replenishment valve 7 is interlocked with a second liquid level controller 8 provided on the condensate storage tank V01. The condensate storage tank V01 collects condensate and can also be used to add high-temperature corrosion inhibitors. The outlet of the condensate storage tank V01 is connected to the condensate pump P03. The condensate storage tank V01 is high-lift and medium-flow and high-temperature resistant. A flow sensor is provided at the outlet of the condensate pump P03, which is connected to the condensate storage tank V01 through an automatic reflux valve 10.

[0068] One end of the pipeline heater is connected to the condensate pump P03, and the other end of the pipeline heater is connected to the water inlet of the booster pump P01 through the first automatic regulating valve 9. The pipeline heater is connected to the water vapor regulating valve 12 through the temperature controller 13. The first automatic regulating valve 9 is connected to the automatic reflux valve 10 through the first liquid level controller 4. The automatic reflux valve 10 is connected to the condensate storage tank V01. The first automatic regulating valve 9 and the automatic reflux valve 10 have opposite switches.

[0069] Booster pump P01 is low head, large flow and high temperature resistant, ensuring cooling water circulation and timely taking away the reaction heat in synthesis reactor R01. A pressure sensor is installed at the outlet.

[0070] A fresh water valve 11 is provided at the water inlet of the heat exchanger E04, and a water outlet of the heat exchanger E04 is connected to the condensed water storage tank V01 through a pipeline.

[0071] A method for producing medium-pressure steam as a by-product in a vinyl chloride synthesis system comprises the following steps:

[0072] Step 1: Open the water replenishment valve 7 to replenish 10-15% of the liquid level cooling water for the condensed water storage tank V01. The water replenishment valve 7 is interlocked with the second liquid level controller to control the liquid level of the condensed water storage tank V01;

[0073] Step 2: Pump water from the condensate storage tank V01 to the pipeline heater through the condensate pump P03 to replenish circulating water for the circulating cooling water system;

[0074] Step 3: Start the water vapor regulating valve to heat the water in the pipeline heater. The water vapor regulating valve is interlocked with the temperature controller 13 to control the water temperature. The water temperature is controlled at 88-90°C. If the water temperature still cannot be raised to 88-90°C when the water vapor valve is fully opened, the amount of supplementary water is reduced through the outlet manual valve of the condensate pump P03. In normal operation, the water vapor regulating valve is interlocked with the temperature controller 13;

[0075] Step 4: Open the inlet and outlet valves of the booster pump P01 and the inlet and outlet valves of the synthesis reactor R01, and the high-temperature water of the pipeline heater flows to the synthesis reactor R01 through the first automatic regulating valve 9 and the booster pump P01, and then flows to the flash tank E01, wherein the first automatic regulating valve 9, the automatic reflux valve 10 and the first liquid level controller 4 are interlocked to control the liquid level of the flash tank E01, and the first automatic regulating valve 9 and the automatic reflux valve 10 are switched in opposite directions;

[0076] Step 5: When the liquid level of the flash tank E01 reaches 45-55% of the set value, start the booster pump P01;

[0077] Step 6: Start the hot water pump P02 to transport the high-temperature water in the flash tank E01 to the hot water user E03 to preheat the vinyl chloride synthesis reaction materials, and then return to the condensate storage tank V01 for circulation;

[0078] Step 7: Open the material valve of the synthesis reactor R01 to release heat energy by the vinyl chloride synthesis reaction. The cooling water provided by the booster pump P01 cools and exchanges heat with the heat. The heat-exchanged water returns to the flash tank E01 through the pipeline for circulation;

[0079] Step 8: When the pressure of the flash tank E01 reaches the set value of 2-5KPa, the water vapor compressor C01 is started to provide high-temperature steam for the steam user E02, and after use, it returns to the condensate storage tank V01 for circulation through the steam trap, and the water vapor compressor C01 is interlocked with the pressure controller to control the pressure in the flash tank E01;

[0080] Step nine: Open the fresh water valve 11, and introduce fresh soft water into the heat exchanger E04 for heat exchange with vinyl chloride gas. The water after heat exchange enters the condensed water storage tank V01 for circulation.

[0081] In the present invention, the cooling water after flash evaporation is circulated and cooled to the synthesis reactor R01 through the booster pump P01 and / or the thermal siphon effect.

[0082] Preferably, in step 3, the pressure of the supplementary high-temperature cooling water is 0.3-0.4 MPa, the temperature is 88-90°C, and the flow rate is 12-15 m 3 / h to ensure that the water level can reach the E0145~55% level of the flash tank to ensure that the material reaction is preheated to the required temperature.

[0083] Preferably, in step 5, the temperature of the cooling water during the initial operation is 88-90°C, which is used to preheat the synthesis reactor R01 and activate the catalyst. The circulating cooling water flow rate is greater than 40m 3 / h, ensuring that the reaction heat is removed in time.

[0084] Preferably, in step 5, the temperature of the cooling water is 100°C to 102°C during normal operation to prevent the catalyst on the reaction side of the synthesis reactor R01 from sublimating and failing, and the circulating cooling water flow rate should be greater than 40m 3 / h, ensuring that the reaction heat is removed in time.

[0085] Preferably, in step five, the lift of the booster pump P01 should be between 11 and 15 m to ensure that the cooling water can circulate.

[0086] Preferably, in step eight, the vaporization area of ​​the flash tank E01 is 1.2 to 1.5 times the calculated area to ensure economical operation of the water vapor compressor C01.

[0087] Preferably, in step eight, the pressure in the flash tank E01 is maintained at 2-5 KPa to achieve an evaporation intensity when the flash area is certain, ensuring that the heat in the circulating cooling water is taken away in time; the liquid level in the flash tank E01 is maintained at 50%-60% to prevent the unstable flow of circulating cooling water from causing the temperature of the synthesis reactor R01 to be uncontrolled.

[0088] Preferably, in step eight, the water vapor compressor C01 has an automatic adjustment function of 70% to 100% energy level, ensuring that the pressure in the flash tank E01 can be changed as required, thereby controlling the cooling water temperature and further achieving the optimal reaction temperature of the vinyl chloride synthesis reactor R01.

[0089] The present invention is not limited to the above-mentioned specific embodiments, but extends to any new features or any new combination disclosed in this specification, as well as any new method or process steps or any new combination disclosed.

Claims

1. A device for producing medium-pressure steam as a by-product of a vinyl chloride synthesis system, characterized in that: Includes synthesis reactor, flash tank, steam compressor, booster pump, hot water pump, pipeline heater, cooling water make-up system, condensate storage tank, condensate pump and heat exchanger; The water outlet of the synthesis reactor is connected to the flash tank, the water inlet of the synthesis reactor is connected to the booster pump, and the reaction gas outlet of the synthesis reactor is connected to the heat exchanger; The water outlet of the flash tank is connected to the booster pump and the hot water pump respectively, and the steam outlet of the flash tank is connected to the water vapor compressor; The steam compressor is connected to the steam user, the steam user is connected to the steam trap, and the steam trap is connected to the condensate storage tank; The hot water pump is connected to the hot water user through a pipeline, and the hot water user is connected to the condensate storage tank; One end of the pipeline heater is connected to the condensate pump, the other end of the pipeline heater is connected to the water inlet of the booster pump through the first automatic regulating valve, and the pipeline heater is connected to the water vapor regulating valve through the temperature controller; The condensate storage tank is provided with a water supply valve, and the water outlet of the condensate storage tank is connected to the condensate pump; A fresh water valve is provided at the water inlet of the heat exchanger, and the water outlet of the heat exchanger is connected to the condensed water storage tank through a pipeline; A wire mesh foam catcher is arranged above the water inlet in the flash tank, and a manual drain valve, an automatic drain valve, a first pressure controller, a first liquid level controller and a temperature sensor are arranged on the flash tank, the automatic drain valve is interlocked with the first pressure controller, the first pressure controller is interlocked with the water vapor compressor, and the first liquid level controller is interlocked with the automatic regulating valve; The first automatic regulating valve is connected to the automatic reflux valve through a first liquid level controller, the automatic reflux valve is connected to the condensate storage tank, and the first automatic regulating valve and the automatic reflux valve have opposite switches; The driving motor of the water vapor compressor is controlled by a frequency converter, a second pressure controller, a flow sensor and a temperature sensor are arranged at the outlet of the water vapor compressor, and the second pressure controller is interlocked with a second automatic regulating valve; The water replenishment valve is interlocked with a second liquid level controller arranged in the condensed water storage tank.

2. The device for producing medium-pressure steam as a by-product of vinyl chloride synthesis system according to claim 1, characterized in that: A baffle is arranged on the cooling water side of the synthesis reactor to divide the cooling water side into three sections which are not connected to each other, and each section is provided with a water inlet and a water outlet.

3. A method for producing medium-pressure steam as a by-product in a vinyl chloride synthesis system, characterized in that: The device for producing medium-pressure steam as a by-product of a vinyl chloride synthesis system using any one of claims 1 to 2 comprises the following steps: Step 1: Open the water supply valve to replenish cooling water to the condensate storage tank, and the water supply valve is interlocked with the second liquid level controller to control the liquid level of the condensate storage tank; Step 2: Pump water from the condensate storage tank to the pipeline heater through the condensate pump; Step 3: Start the water vapor regulating valve to heat the water in the pipeline heater. The water vapor regulating valve is interlocked with the temperature controller to control the water temperature. During normal operation, the water vapor regulating valve and the temperature controller are released from the interlock. Step 4: Open the inlet and outlet valves of the booster pump and the inlet and outlet valves of the synthesis reactor, and the high-temperature water of the pipeline heater flows to the synthesis reactor through the first automatic regulating valve and the booster pump, and then flows to the flash tank, wherein the first automatic regulating valve, the automatic reflux valve and the first liquid level controller are interlocked to control the liquid level of the flash tank, and the first automatic regulating valve and the automatic reflux valve are switched in opposite directions; Step 5: When the liquid level in the flash tank reaches the set value, start the booster pump; Step 6: Start the hot water pump to deliver the high-temperature water in the flash tank to the hot water user to preheat the vinyl chloride synthesis reaction materials, and then return it to the condensate storage tank for circulation; Step 7: Open the material valve of the synthesis reactor to release heat energy by vinyl chloride synthesis reaction, and the cooling water provided by the booster pump cools and exchanges heat with the heat energy, and the heat-exchanged water returns to the flash tank through the pipeline for circulation; Step 8: When the pressure of the flash tank reaches the set value, the steam compressor is started to provide high-temperature steam to the steam user. After use, the steam is returned to the condensate storage tank for circulation through the steam trap. The steam compressor is interlocked with the pressure controller to control the pressure in the flash tank; Step 9: Open the fresh water valve and introduce fresh soft water into the heat exchanger for heat exchange with vinyl chloride gas. The water after heat exchange enters the condensed water storage tank for circulation.

4. The method for producing medium-pressure steam as a by-product in a vinyl chloride synthesis system as claimed in claim 3, characterized in that: In step 5, the temperature of the cooling water during the initial operation is 88-90°C, which is used to preheat the synthesis reactor and activate the catalyst. The circulating cooling water flow rate is greater than 40m³ / h to ensure that the reaction heat is removed in time.

5. The method for producing medium-pressure steam as a by-product in a vinyl chloride synthesis system as claimed in claim 3, characterized in that: In step 5, the temperature of the cooling water is 100°C to 102°C during normal operation to prevent the catalyst on the reaction side of the synthesis reactor from sublimating and failing. The circulating cooling water flow rate should be greater than 40m³ / h to ensure that the reaction heat is removed in time.

6. The method for producing medium-pressure steam as a by-product in a vinyl chloride synthesis system as claimed in claim 3, characterized in that: In step eight, the pressure in the flash tank is maintained at 2-5 KPa to achieve an evaporation intensity when the flash area is certain, ensuring that the heat in the circulating cooling water is taken away in time; the liquid level in the flash tank is maintained at 50%-60% to prevent the unstable flow of circulating cooling water from causing the temperature of the synthesis reactor to be uncontrolled.

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