A vinyl chloride mixed gas cooler ice melting device

Abstract

The utility model relates to a chemical production technical field, concretely is a kind of vinyl chloride mixed gas cooler ice-melting device, including vinyl chloride mixed gas cooler, first tube-shell heat exchanger and be arranged between vinyl chloride mixed gas cooler and first tube-shell heat exchanger and act on the thawing system of vinyl chloride mixed gas cooler, still including the waste heat reuse system being arranged on thawing system;Waste heat reuse system and thawing system cooperate to use and realize the recycling of nitrogen waste heat circulation. The waste heat reuse system of second tube-shell heat exchanger, third tube-shell heat exchanger and relevant pipeline composition can recover the waste heat carried by nitrogen after thawing. First by second tube-shell heat exchanger preheating inlet pipe cold water, again by third tube-shell heat exchanger and steam cooperation heating, by first tube-shell heat exchanger heating circulating nitrogen;Hot water is conveyed to external production system reuse after heat exchange hot water back pipe, compared with the mode that existing technology heat is directly discharged, improve energy utilization, reduce chemical production energy consumption.

Description

Technical Field

[0001] This utility model relates to the technical field of vinyl chloride production equipment, specifically to a de-icing device for a vinyl chloride mixed gas cooler, used to solve the problem of production interruption caused by ice blockage inside the cooler during the cooling process of vinyl chloride mixed gas. Background Technology

[0002] In the vinyl chloride synthesis and distillation process, after the crude vinyl chloride mixture is washed with water and alkali to remove impurities, it needs to be condensed in a vinyl chloride mixture cooler using a low-temperature medium (such as brine at around -35°C) to recover vinyl chloride monomer from the gas phase. Since the mixture inevitably contains saturated water vapor, under low-temperature cooling, the water vapor liquefies and freezes on the shell side or inner wall of the tubes of the cooler, forming an ice layer that blocks the heat exchange channels. As the ice layer thickens, the cooler's heat exchange efficiency drops sharply, and the system resistance increases, eventually requiring shutdown for de-icing, severely impacting production continuity.

[0003] To address the condenser icing problem, existing technologies include de-icing devices, such as the tail gas condenser de-icing device disclosed in patent number CN220853277U. This device stores brine in a de-icing brine tank, directly heats the brine in the tank with low-pressure steam, and then a water pump drives the heated brine through a single-path inlet and outlet water pipe to circulate with the condenser, melting the ice layer and shortening the processing time compared to natural thawing. However, it has significant drawbacks in practical applications with vinyl chloride mixed gas coolers: Firstly, the use of single-path brine circulation and direct heating inside the storage tank results in uneven brine temperature distribution and difficulty in uniformly covering the multi-pass shell structure of the vinyl chloride mixture cooler, which easily leads to slow local ice melting and low overall de-icing efficiency. Secondly, simply installing temperature sensors on the de-icing brine storage tank makes it impossible to monitor the temperature of the circulating medium at the inlet and outlet of the cooler in real time. This results in poor temperature control accuracy and can easily lead to energy waste due to overheating or incomplete de-icing due to insufficient heating. Third, relying on a single water pump to provide circulation power, without setting up a pressure and flow regulation structure, when the internal blockage of the vinyl chloride mixture cooler causes fluctuations in system resistance, it is easy to experience a sudden drop in circulation flow and water pump overload, resulting in poor stability of the de-icing process. Fourth, the lack of a waste heat recovery structure means that the heat carried by the circulating medium after de-icing is directly emitted, resulting in energy waste and failing to meet the energy-saving requirements of chemical production.

[0004] The aforementioned defects make it difficult for the existing technology to meet the requirements of vinyl chloride mixed gas coolers for efficient, stable, and energy-saving de-icing, and a targeted optimization solution is urgently needed. Utility Model Content

[0005] The purpose of this invention is to provide a de-icing device for a vinyl chloride mixed gas cooler, which solves the problems mentioned in the prior art in the background section.

[0006] To achieve the above objectives, this utility model provides the following technical solution: a de-icing device for a vinyl chloride mixed gas cooler, comprising a vinyl chloride mixed gas cooler, a first shell-and-tube heat exchanger, and a de-icing system disposed between the vinyl chloride mixed gas cooler and the first shell-and-tube heat exchanger and acting on the vinyl chloride mixed gas cooler; further comprising a waste heat recovery system disposed on the de-icing system; the waste heat recovery system is used in conjunction with the de-icing system to realize the recycling of nitrogen waste heat.

[0007] Furthermore, the defrosting system includes a nitrogen inlet pipe and a nitrogen booster; the shell-side outlet of the vinyl chloride mixture cooler is connected to the tube-side inlet of the first shell-and-tube heat exchanger via a heat exchanger inlet pipe, the tube-side outlet of the first shell-and-tube heat exchanger is connected to the nitrogen booster inlet via a booster inlet pipe, the nitrogen booster outlet is connected to the shell-side inlet of the vinyl chloride mixture cooler via a booster outlet pipe, and the nitrogen inlet pipe is connected to the heat exchanger inlet pipe.

[0008] Furthermore, the waste heat recovery system includes a second shell-and-tube heat exchanger and a third shell-and-tube heat exchanger; the shell-side inlet and outlet of the second shell-and-tube heat exchanger are connected in series on the heat exchanger inlet pipe, a water inlet pipe is connected to the tube-side inlet of the second shell-and-tube heat exchanger, the tube-side outlet of the second shell-and-tube heat exchanger is connected to the shell-side inlet of the third shell-and-tube heat exchanger, the shell-side inlet of the first shell-and-tube heat exchanger and the shell-side outlet of the third shell-and-tube heat exchanger are connected by a hot water outlet pipe, a steam inlet pipe and a steam return pipe are respectively connected to the tube-side inlet and outlet of the third shell-and-tube heat exchanger, and a hot water return pipe is connected to the shell-side outlet of the first shell-and-tube heat exchanger.

[0009] Furthermore, regulating valves are provided on the nitrogen inlet pipe, the booster outlet pipe, and the hot water outlet pipe.

[0010] Furthermore, the nitrogen inlet pipe is characterized by being equipped with a pressure gauge.

[0011] Furthermore, the feature is that a flow meter is also provided on the air outlet pipe of the booster.

[0012] Furthermore, the feature is that a thermometer is also provided on the hot water outlet pipe.

[0013] Furthermore, the regulating valve, pressure gauge, flow meter, nitrogen booster, thermometer, and third shell-and-tube heat exchanger are all connected to the PLC controller.

[0014] The de-icing device for the vinyl chloride mixed gas cooler of this utility model, through optimized structural design, can specifically solve the problems of low de-icing efficiency, poor control precision, unstable circulation, and energy waste existing in the prior art (CN220853277U). The specific beneficial effects are as follows: 1. Improved uniformity and efficiency of defrosting: The defrosting system of this invention adopts a closed-loop nitrogen circulation design. Nitrogen is pressurized to 2.0-2.5MPa by a nitrogen booster and then delivered to the shell side of the vinyl chloride mixture cooler. The high-pressure nitrogen can flow evenly through all heat exchange channels in the shell side of the cooler, avoiding the problem of uneven coverage caused by single-path brine circulation in the prior art. At the same time, a first shell-and-tube heat exchanger is connected in series in the nitrogen circulation path to preheat the circulating nitrogen, further ensuring the stability of the nitrogen temperature, realizing rapid and uniform melting of the ice layer in the cooler, and shortening the defrosting time.

[0015] 2. Improved Parameter Control Accuracy: This utility model is equipped with multiple monitoring components such as regulating valves, pressure gauges, flow meters, and thermometers, all of which are connected to a PLC controller. The pressure gauge monitors the nitrogen inlet pressure in real time, the flow meter monitors the nitrogen flow rate at the booster outlet, and the thermometer monitors the hot water outlet temperature. The PLC controller can dynamically adjust the nitrogen booster speed and the opening of each pipeline regulating valve based on the monitoring data. Compared with the existing technology that only relies on the temperature of the storage tank for control, this achieves precise control of nitrogen pressure, flow rate, and hot water temperature, avoiding overheating or underheating and improving the de-icing accuracy.

[0016] 3. Enhanced cycle stability: The nitrogen booster in this thawing system has a rated exhaust pressure of 2.5 MPa and an exhaust volume of 18 m³ / s. 3 The screw-type booster compressor with a speed of / min can adapt to system resistance fluctuations; at the same time, regulating valves are installed on the nitrogen inlet pipe and the booster compressor outlet pipe to compensate for pressure changes caused by cooler blockage in real time, avoiding the problems of overload and flow interruption caused by the single water pump circulation in the existing technology, ensuring continuous and stable nitrogen circulation, and reducing the interruption rate in the de-icing process.

[0017] 4. Achieving waste heat recycling and energy saving: This utility model adds a waste heat recovery system consisting of a second shell-and-tube heat exchanger, a third shell-and-tube heat exchanger, and related pipelines, which can recover the waste heat carried by nitrogen after thawing. First, the cold water in the inlet pipe is preheated through the second shell-and-tube heat exchanger, then heated to 80-90℃ by steam in conjunction with the third shell-and-tube heat exchanger, and finally heated by circulating nitrogen through the first shell-and-tube heat exchanger. Simultaneously, the cooled hot water after heat exchange is transported to an external production system (such as a heat tracing pipeline) for reuse via a hot water return pipe. Compared to the existing technology of directly discharging heat, this improves energy utilization and reduces energy consumption in chemical production.

[0018] 5. Strong adaptability and wide range of applications: The vinyl chloride mixed gas cooler of this utility model adopts a horizontal shell and tube structure made of 304 stainless steel. The first, second and third shell and tube heat exchangers are of the same model and are adapted to the heat exchange requirements of nitrogen and hot water. The pipelines are all made of 304 stainless steel tubes that can withstand high pressure and high temperature. The overall structure is designed for the multi-pass shell-side characteristics of vinyl chloride mixed gas coolers. Compared with the existing technology that is only adapted to the structure of conventional tail gas condensers, it can accurately match the de-icing requirements of coolers in vinyl chloride production of different scales, and has stronger adaptability and practicality. Attached Figure Description

[0019] Figure 1 This is a process flow diagram of the present invention; Figure 2 This is a system block diagram of the present invention.

[0020] In the diagram: 1. Vinyl chloride mixed gas cooler; 2. First shell-and-tube heat exchanger; 3. Nitrogen inlet pipe; 4. Nitrogen booster compressor; 5. Heat exchanger inlet pipe; 6. Booster compressor inlet pipe; 7. Booster compressor outlet pipe; 8. Second shell-and-tube heat exchanger; 9. Third shell-and-tube heat exchanger; 10. Water inlet pipe; 11. Hot water outlet pipe; 12. Steam inlet pipe; 13. Steam return pipe; 14. Hot water return pipe; 15. Regulating valve; 16. Pressure gauge; 17. Flow meter; 18. Thermometer. Detailed Implementation

[0021] To make the objectives, technical solutions, and beneficial effects of this utility model clearer, the following detailed description is provided in conjunction with the accompanying drawings and specific embodiments. Figure 1-2 As shown, this utility model discloses a vinyl chloride mixed gas cooler de-icing device, which is used in chemical production scenarios to achieve efficient de-icing and waste heat recycling, while meeting the requirements of stability, safety, and economy. The core of this device consists of a vinyl chloride mixed gas cooler 1, three sets of shell-and-tube heat exchangers, a de-icing system, a waste heat recovery system, and intelligent control components, as detailed below: The vinyl chloride mixture cooler 1 is a horizontal shell-and-tube cooler of model BEM-800-2.5. Both the shell and tube sides are made of 304 stainless steel to withstand the corrosiveness of the vinyl chloride mixture. The heat exchange area of ​​the cooler is set at 50㎡, and the design pressure is 1.6MPa. It is suitable for the medium-scale mixed gas cooling needs in chemical production. Its core function is to cool the vinyl chloride mixture and, at the same time, to thaw the frozen gas under the action of the defrosting system.

[0022] The three shell-and-tube heat exchangers include a first shell-and-tube heat exchanger 2, a second shell-and-tube heat exchanger 8, and a third shell-and-tube heat exchanger 9. All three are model BEM-600-1.6, made of 304 stainless steel, with a heat exchange area of ​​30㎡ and a design pressure of 1.0MPa. The first shell-and-tube heat exchanger 2 is mainly used for heat exchange with the gas at the shell-side outlet of the vinyl chloride mixture cooler, recovering heat from the gas. The second shell-and-tube heat exchanger 8 is used for heat exchange with the cold water introduced through the inlet pipe, initially raising the water temperature. The third shell-and-tube heat exchanger 9 further heats the cold water through steam heating, providing a hot water heat source for the first shell-and-tube heat exchanger 2.

[0023] The defrosting system includes a nitrogen inlet pipe 3, a nitrogen booster pipe 4, a heat exchanger inlet pipe 5, a booster pipe 6, and a booster outlet pipe 7. The nitrogen inlet pipe 3, heat exchanger inlet pipe 5, booster pipe 6, and booster outlet pipe 7 are all made of DN80 304 stainless steel tubing, with a pressure resistance of 2.0 MPa, to prevent pipeline damage due to pressure fluctuations during nitrogen delivery. The nitrogen booster pipe 4 is a VFC-180 screw-type booster compressor with a rated discharge pressure of 2.5 MPa and a discharge capacity of 18 m³ / s. 3 The pressure can be increased to a level that meets the thawing requirements, providing high-pressure nitrogen to the shell side of the vinyl chloride mixture cooler to achieve thawing.

[0024] The waste heat recovery system includes an inlet pipe 10, a hot water outlet pipe 11, a steam inlet pipe 12, a steam return pipe 13, and a hot water return pipe 14. All of these pipes are made of DN65 304 stainless steel, capable of withstanding temperatures up to 300℃ and pressures up to 1.6MPa, suitable for hot water and steam transport conditions. The cold water temperature introduced through the inlet pipe 10 is controlled at 20-25℃, and the steam pressure introduced through the steam inlet pipe 12 is 0.8MPa with a temperature of 180℃, ensuring that the cold water can be heated to 80-90℃ through the third shell-and-tube heat exchanger 9 before being transported to the shell side of the first shell-and-tube heat exchanger 2 for heat exchange.

[0025] The control and monitoring components include a regulating valve 15, a pressure gauge 16, a flow meter 17, and a thermometer 18. The regulating valve 15 is a ZJHP-16C pneumatic diaphragm single-seat regulating valve, with a nominal diameter matching the corresponding pipeline (the regulating valves on the nitrogen inlet pipe, booster outlet pipe, and hot water outlet pipe are DN80, DN80, and DN65 respectively), with an adjustment accuracy of ±1%, used to control the flow rate of nitrogen and hot water. The pressure gauge 16 is a Y-100 type stainless steel pressure gauge with a range of 0-4.0 MPa and an accuracy class of 1.6, used to monitor the pressure in the nitrogen inlet pipe in real time. The flow meter 17 is an LWGY-80 type turbine flow meter with a measurement range of 0-50 m³ / h. 3 / h, accuracy class 0.5, monitors the flow rate of nitrogen in the outlet pipe of the booster; thermometer 18 is a WZP-230 platinum resistance thermometer, measuring range 0-200℃, accuracy class A, detects the temperature of hot water in the hot water outlet pipe; the PLC controller is a Siemens S7-1200 series CPU 1214C, with analog and digital input / output functions, which can realize centralized control and data acquisition of various components.

[0026] The shell-side outlet of the vinyl chloride mixture cooler 1 in the defrosting system is connected to one end of the heat exchanger inlet pipe 5 via a flange, and the other end of the heat exchanger inlet pipe 5 is connected to the tube-side inlet flange of the first shell-and-tube heat exchanger 2. The tube-side outlet of the first shell-and-tube heat exchanger 2 is connected to the inlet flange of the nitrogen booster 4 via the booster inlet pipe 6, and the outlet of the nitrogen booster 4 is connected to the shell-side inlet flange of the vinyl chloride mixture cooler 1 via the booster outlet pipe 7. The nitrogen inlet pipe 3 is welded to the middle of the heat exchanger inlet pipe 5 via a tee joint to achieve supplementary nitrogen delivery into the heat exchanger inlet pipe.

[0027] The shell-side inlet and outlet of the second shell-and-tube heat exchanger 8 in the waste heat recovery system are connected in series via flanges to two sections of the heat exchanger inlet pipe 5, forming a passage for gas to flow through the shell side of the second shell-and-tube heat exchanger. The tube-side inlet of the second shell-and-tube heat exchanger 8 is connected to the water inlet pipe 10 via a flange, and the tube-side outlet is connected to the shell-side inlet of the third shell-and-tube heat exchanger 9 via a flange. The shell-side outlet of the third shell-and-tube heat exchanger 9 is connected to the shell-side inlet flange of the first shell-and-tube heat exchanger 2 via a hot water outlet pipe 11, and the shell-side outlet of the first shell-and-tube heat exchanger 2 is connected to the external hot water recovery system via a hot water return pipe 14. The tube-side inlet of the third shell-and-tube heat exchanger 9 is connected to the steam inlet pipe 12 via a flange, and the tube-side outlet is connected to the steam return pipe 13 via a flange, forming a steam heating circuit.

[0028] The regulating valve 15 and pressure gauge 16 on the nitrogen inlet pipe 3 of the control and monitoring components are both installed on the pipeline via flanges or threads, with the pressure gauge located downstream of the regulating valve for easy monitoring of the regulated nitrogen pressure; the regulating valve 15 and flow meter 17 on the booster outlet pipe 7 are installed via flanges, with the flow meter located downstream of the regulating valve to ensure that the regulated nitrogen flow rate is measured; the regulating valve 15 and thermometer 18 on the hot water outlet pipe 11 are installed via flanges, with the thermometer located downstream of the regulating valve to detect the regulated hot water temperature; the regulating valve 15, pressure gauge 16, flow meter 17, nitrogen booster 4, thermometer 18, and steam inlet valve of the third shell-and-tube heat exchanger 9 are all connected to the input / output interface of the PLC controller via signal lines to realize signal transmission and control command issuance.

[0029] The working process of this utility model device mainly realizes the dual functions of defrosting cycle and waste heat recovery. It achieves fully automatic parameter control through a PLC controller, ensuring efficient defrosting of the vinyl chloride mixed gas cooler while maximizing the recovery of nitrogen waste heat. The specific work is divided into three parts: preparation stage, defrosting and waste heat recovery stage, and control stage, as detailed below: I. Preparation Stage 1. Before starting, confirm the status of each component through the PLC controller: The regulating valves 15 on the nitrogen inlet pipe 3, the booster outlet pipe 7, and the hot water outlet pipe 11 are all in the fully closed state; the steam inlet valves of the nitrogen booster 4 and the third shell-and-tube heat exchanger 9 are in the off state; the pipelines of the water inlet pipe 10, the hot water return pipe 14, and the steam return pipe 13 are not blocked, and the pressure gauge 16, the flow meter 17, and the thermometer 18 are all calibrated normally and have a stable signal connection with the PLC controller.

[0030] 2. Open the inlet valve 10 and introduce 20-25℃ cold water into the tube side of the second shell-and-tube heat exchanger 8. After the tube side is full of water (confirmed by pipeline pressure feedback), start the control valve of the steam inlet valve 12 to introduce 0.8MPa, 180℃ steam into the tube side of the third shell-and-tube heat exchanger 9 to heat the cold water in the shell side until the thermometer 18 detects that the water temperature in the hot water outlet valve 11 has risen to 80-90℃ (set target value). Then close the steam valve to temporarily store the hot water.

[0031] Start the nitrogen booster 4 and wait for it to run stably under no-load. Then, slowly open the regulating valve 15 of the nitrogen inlet pipe 3 to add nitrogen into the heat exchanger inlet pipe 5. Monitor the pipeline pressure through the pressure gauge 16 until the pressure stabilizes at 1.2-1.5 MPa (to meet the requirement of 1.6 MPa pressure resistance for the shell side of the vinyl chloride mixed gas cooler 1).

[0032] II. Thawing and Waste Heat Recovery Stage 1. Nitrogen circulation process of the defrosting system The PLC controller issues a command to open the regulating valve 15 of the booster compressor outlet pipe 7. The nitrogen booster compressor 4 further pressurizes the nitrogen gas (pressure 1.2-1.5MPa) in the heat exchanger inlet pipe 5 to 2.0-2.5MPa, and then delivers it to the shell-side inlet of the vinyl chloride mixture cooler 1 through the booster compressor outlet pipe 7. The high-pressure nitrogen gas flows in the shell side of the cooler 1, directly exchanging heat with the ice layer on the shell wall, absorbing the heat of the melting ice layer (the ice layer temperature is below 0℃, and the nitrogen gas temperature gradually rises to 30-40℃ due to preheating and circulation), achieving rapid thawing of the ice layer. The melted water is discharged through the drain valve (standard equipment) at the bottom of the cooler 1.

[0033] After the defrosting operation, the nitrogen gas (temperature dropped to 15-25℃, still carrying some residual heat) is discharged from the shell-side outlet of cooler 1, flows through the heat exchanger inlet pipe 5, sequentially through the shell side of the second shell-and-tube heat exchanger 8 and the tube side of the first shell-and-tube heat exchanger 2, and finally flows back to the inlet of nitrogen booster 4 through the booster inlet pipe 6, forming a closed loop. During this period, a small amount of nitrogen is continuously supplemented through the regulating valve 15 of nitrogen inlet pipe 3 (to compensate for minor leaks in the pipeline) to maintain the pressure stability of the circulation system.

[0034] 2. Energy exchange process of waste heat recovery system First-stage waste heat recovery (nitrogen → cold water preheating) When the circulating nitrogen gas (discharged from cooler 1, temperature 15-25℃) in the heat exchanger inlet pipe 5 flows through the shell side of the second shell-and-tube heat exchanger 8, it transfers its own waste heat to the 20-25℃ cold water in the tube side, raising the temperature of the cold water to 35-45℃, thus achieving the initial recovery of nitrogen waste heat; the preheated cold water is discharged from the tube side outlet of the second shell-and-tube heat exchanger 8 and enters the shell side of the third shell-and-tube heat exchanger 9.

[0035] Second-stage waste heat enhancement (steam → cold water heating) Steam at 0.8 MPa and 180°C is introduced into the tube side of the third shell-and-tube heat exchanger 9 to further heat the preheated cold water (35-45°C) in the shell side to 80-90°C. The heated hot water is then transported to the shell side of the first shell-and-tube heat exchanger 2 through the hot water outlet pipe 11.

[0036] The third-stage waste heat utilization (hot water → nitrogen reheating) involves introducing 80-90°C hot water into the shell side of the first shell-and-tube heat exchanger 2, where it exchanges heat with circulating nitrogen (discharged from the second shell-and-tube heat exchanger 8, with its temperature reduced to 10-15°C) in the tube side, raising the nitrogen temperature to 25-30°C before sending it to the nitrogen booster 4. The hot water, with its temperature reduced to 50-60°C after heat exchange, is then transported to an external hot water recovery system (such as a heat tracing pipeline in chemical production) through the hot water return pipe 14, realizing the full-chain utilization of waste heat.

[0037] III. Parameter Dynamic Adjustment Stage 1. The PLC controller collects signals from various monitoring components in real time and automatically adjusts equipment operating parameters according to preset thresholds to ensure system stability and efficiency. If pressure gauge 16 detects that the pressure in nitrogen inlet pipe 3 is lower than 1.2 MPa, the PLC controls the opening of regulating valve 15 in nitrogen inlet pipe 3 to increase and replenish nitrogen; if the pressure is higher than 1.5 MPa, the opening is reduced.

[0038] If the flow meter 17 detects that the nitrogen flow rate at the booster compressor outlet pipe 7 is less than 10 m³ / h... 3 / h (minimum thawing requirement), the PLC increases the speed of nitrogen booster 4 to increase the exhaust volume; if the flow rate is higher than 30m3 If the speed is reduced to / h (to avoid energy waste), then the rotation speed is reduced.

[0039] If the thermometer 18 detects that the water temperature at the hot water outlet pipe 11 is below 80℃, the PLC opens the steam inlet valve of the third shell-and-tube heat exchanger 9 to supplement 180℃ steam to heat the cold water; if the water temperature is above 90℃, the steam valve is closed to maintain the temperature using the residual heat of the pipeline.

[0040] 2. The thawing endpoint is determined by indirect parameter feedback indicating thawing completion: When the nitrogen temperature at the outlet of the shell side of the vinyl chloride mixed gas cooler (which can be monitored by adding a temperature sensor) stabilizes at 5-40℃ (after the ice layer has completely melted, the nitrogen has no heat loss and the temperature rises), and remains stable for 10 minutes without fluctuation, the PLC determines that the defrosting is complete and enters the standby shutdown state.

[0041] IV. System Shutdown Phase The PLC gradually cuts off the energy input. First, it shuts down the nitrogen booster 4. After it stops completely, it sequentially closes the regulating valves 15 of the nitrogen inlet pipe 3 and the booster outlet pipe 7. Then, it closes the valve of the steam inlet pipe 12 to stop the steam supply.

[0042] Medium purging and pipeline cleaning: Open the main valve of hot water return pipe 14 to purge the residual hot water in the shell side of the first shell-and-tube heat exchanger 2 and the third shell-and-tube heat exchanger 9; open the flushing valve of inlet pipe 10 and flush the tube side / shell side of the second and third shell-and-tube heat exchangers with 20-25℃ cold water to remove any possible residual impurities (such as vinyl chloride mixture condensate); after flushing, close all pipeline valves.

[0043] The equipment power failure and status recording function shuts down the power supply to the PLC controller and each device, automatically saves the current operation data (such as defrosting time, nitrogen consumption, and hot water recovery), and generates an operation report to facilitate subsequent maintenance and optimization.

Claims

1. A de-icing device for a vinyl chloride mixed gas cooler, comprising a vinyl chloride mixed gas cooler (1), a first shell-and-tube heat exchanger (2), and a de-icing system disposed between the vinyl chloride mixed gas cooler (1) and the first shell-and-tube heat exchanger (2) and acting on the vinyl chloride mixed gas cooler (1), characterized in that, It also includes a waste heat recovery system installed on the defrosting system; the waste heat recovery system is used in conjunction with the defrosting system to realize the recycling of nitrogen waste heat.

2. The de-icing device as described in claim 1, characterized in that, The defrosting system includes a nitrogen inlet pipe (3) and a nitrogen booster (4); the shell-side outlet of the vinyl chloride mixed gas cooler (1) is connected to the tube-side inlet of the first shell-and-tube heat exchanger (2) through the heat exchanger inlet pipe (5), the tube-side outlet of the first shell-and-tube heat exchanger (2) is connected to the inlet of the nitrogen booster (4) through the booster inlet pipe (6), the outlet of the nitrogen booster (4) is connected to the shell-side inlet of the vinyl chloride mixed gas cooler (1) through the booster outlet pipe (7), and the nitrogen inlet pipe (3) is connected to the heat exchanger inlet pipe (5).

3. The de-icing device as described in claim 2, characterized in that, The waste heat recovery system includes a second shell-and-tube heat exchanger (8) and a third shell-and-tube heat exchanger (9); the shell-side inlet and outlet of the second shell-and-tube heat exchanger (8) are connected in series to the heat exchanger inlet pipe (5), the inlet of the second shell-and-tube heat exchanger (8) is connected to a water inlet pipe (10), the outlet of the second shell-and-tube heat exchanger (8) is connected to the inlet of the third shell-and-tube heat exchanger (9), the inlet of the first shell-and-tube heat exchanger (2) and the outlet of the third shell-and-tube heat exchanger (9) are connected through a hot water outlet pipe (11), the inlet and outlet of the third shell-and-tube heat exchanger (9) are respectively connected to a steam inlet pipe (12) and a steam return pipe (13), and the outlet of the first shell-and-tube heat exchanger (2) is connected to a hot water return pipe (14).

4. The de-icing device as described in claim 3, characterized in that, The nitrogen inlet pipe (3), the booster outlet pipe (7), and the hot water outlet pipe (11) are all equipped with regulating valves (15).

5. The de-icing device as described in claim 4, characterized in that, A pressure gauge (16) is also provided on the nitrogen inlet pipe (3).

6. The de-icing device as described in claim 4, characterized in that, A flow meter (17) is also installed on the air outlet pipe (7) of the booster.

7. The de-icing device as described in claim 4, characterized in that, A thermometer (18) is also provided on the hot water outlet pipe (11).

8. The de-icing device as described in claim 7, characterized in that, The regulating valve (15), pressure gauge (16), flow meter (17), nitrogen booster (4), thermometer (18), and third shell-and-tube heat exchanger (9) are all connected to the PLC controller.

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