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Description of the production process in PVC plants I. Acetylene workshop 1.1. Description of the production process at the raw material station: Calcium carbide in bags is transported to the jaw crusher using a trolley; the calcium carbide is then poured out of the bags and fed into the crusher for crushing, after which it is sent to the silo via a conveyor belt. 1.2. Description of the production process at the feeding station: In coordination with the raw material station, calcium carbide is transported to the silo and then fed into the measuring hopper. After purging a storage tank with nitrogen, open the valve to add calcium carbide into a storage tank. (Open the nitrogen valve during feeding to displace the air in the storage hopper and prevent combustion or explosion accidents during feeding.) 1.3. Description of the production process at this station: Calcium carbide from the two storage hoppers is continuously fed into the generator using electromagnetic vibratory conveyors. Calcium carbide reacts with water inside the generator, and the resulting crude acetylene gas escapes from the top of the generator, then passes through a slag trap, a positive water seal, and a cooling tower before entering the purification system and the gas holder. “Water is continuously added to the slurry catcher together with industrial water, spent sodium hydroxide, and calcium carbide supernatant, and then flows into the generator to maintain the generator temperature between 75°C and 90°C as well as to keep the liquid level inside the generator at an appropriate level ； The dilute carbide slurry resulting from the decomposition of calcium carbide continuously overflows through the overflow pipe, while the concentrated slurry and other impurities are swept to the bottom by the rake teeth inside the generator and removed periodically. When the generator pressure exceeds 10,000 Pa, acetylene gas is automatically vented through a safety water seal; when the generator pressure drops, acetylene gas enters the generator via an air tank and through an inverse water seal to maintain positive pressure in the generator ； After being initially cooled and washed in the slag drop catcher, the acetylene gas enters the positive water seal, and then proceeds to the spray cooling tower and the packed cooling tower, where its temperature is reduced to room temperature before it enters the purification system. 1.4. Description of the production process in the purification units: Acetylene gas exits from the top of the cooling tower and enters the water ring pump, where it is pressurized and sent to Tower No. 1 and Tower No. 2 for purification. Sodium hypochlorite solution is used for direct spraying, thereby oxidizing impurities such as PH3 and H2S present in crude acetylene into acidic substances like H3PO4 and H2SO4 ； It is then fed into a neutralization tower, where it comes into counter-current contact with an alkaline solution at a concentration of 5–13% that is sprayed from the top of the tower, thereby neutralizing the acidic substances in the crude acetylene gas. The acetylene gas (with a purity of >98.5%) exits the tower at the top and is sent to the synthesis workshop. The NaClO used in the cleaning tower is pumped from a NaClO storage tank to Tower 2 for use there. The NaClO that has been used in Tower 2 is then pumped to Tower 1 for use. The waste NaClO from Tower 1 is discharged into the wastewater tank for further utilization. 1.5. Description of the production process at the filtration station: After the calcium carbide slurry overflows from the generation station into the concentration tank, it is pumped to the programmable filter press using a slurry pump. Filtration results in the formation of a solid cake and a liquid phase. The program controls the processes of releasing the filter elements, removing them, and taking down the solid cake; finally, a forklift is used to load the cake and transport it to the storage area ； The clear liquid is first pumped to the cooling tower by a hot water pump; after being cooled, it is sent to the acetylene workshop using a cold water pump. II. Synthesis Workshop 2.1. Description of the production process for the hydrogen chloride production unit: Qualified H2 and Cl2 from the chlor-alkali plant pass through buffer tanks and flame arrestors before entering the graphite synthesis furnace in a specific molar ratio (Cl2:H2 = 1:1.05–1.10). There, they burn at the burner tip; the resulting HCl gas is discharged from the top of the graphite synthesis furnace. It is cooled by a graphite cooler located at the furnace’s top, which removes any acidic mist carried along with it, reducing the temperature to below 45°C. The resulting hydrogen chloride is then sent to the hydrogen chloride distribution station. The qualified hydrogen chloride is used as a raw material – one portion is supplied to the conversion unit, while another portion is sent to a packed tower where it is absorbed by pure water to produce high-purity acid. Unqualified hydrogen chloride gas generated during initial operation or when production is not operating properly is absorbed using a two-stage graphite falling film absorber; once the hydrogen chloride content in the exhaust gas falls below 5×10-6 (5 ppm), it is released, while the resulting waste acid is produced for sale. 2.2. Description of the production process in the conversion unit: The refined acetylene gas supplied from the acetylene workshop (after preliminary cooling and dehydration in an acetylene pre-cooler) and the hydrogen chloride supplied from the hydrogen chloride unit (after preliminary cooling to remove some water in a pre-cooler) enter the mixer respectively through orifice flow meters, in a molar ratio of C2H2/HCl = 1/1.05–1.1, where they are thoroughly mixed. Subsequently, they pass through a graphite condenser and are indirectly cooled to -12°C to -16°C using -35°C ice brine. Part of the water contained in the mixed gas in the graphite condenser condenses to form hydrochloric acid at about 40% concentration, which is discharged directly from the bottom of the graphite condenser. The other part remains in the gas in mist form; as this gas passes through two acid mist filters connected in series, the acid mist is captured and separated by glass wool impregnated with silicone oil. The mixed gas after freeze-drying enters a preheater, where it is heated to 70°C–80°C using hot water. It then proceeds to a series of converters arranged in sequence; within the tubes of these converters, there are mercury catalysts adsorbed on activated carbon, which facilitate an addition reaction between acetylene and hydrogen chloride. In the first set of converters, 20–30% of the acetylene remains unconverted, so it moves on to the subsequent converters to continue the reaction, ensuring that the amount of unconverted acetylene at the outlet is kept below 3%. Crude vinyl chloride with a purity of ≥90% is produced, and the heat generated during the synthesis reaction is removed by circulating hot water at around 90°C to 98°C pumped from the heating unit. 2.3. Description of the purification process: The crude vinyl chloride exits the converter and passes through a mercury removal unit filled with activated carbon, which adsorbs and removes sublimated substances such as mercury chloride produced by the catalyst at high temperatures. After that, it goes through a vinyl chloride cooler; the cooled crude vinyl chloride gas then enters the primary foam tower and the secondary foam tower. Dilute acid pumped in from the hydrochloric acid desorption unit is sprayed from the top of the secondary foam tower to absorb any excess hydrogen chloride gas in the crude monomer. The concentrated hydrochloric acid, after being cooled by a hydrochloric acid cooler, continues to flow into the secondary foam washing tower to absorb more hydrogen chloride. This acid then moves to the hydrochloric acid intermediate tank via gravity; the approximately 31% concentrated hydrochloric acid in this tank is pumped using a concentrated acid pump for use in the desorption cycle. The gas emerging from the foam tower enters the packed-bed wash tower, where the dilute acid sprayed from the top of the tower absorbs the remaining small amount of hydrogen chloride gas. The resulting hydrochloric acid with increased concentration is fed into the circulation acid tank via an acid seal. The dilute acid in the circulating acid tank is pumped by an acid pump; a small portion is sent to the foam tower as an absorbent to produce concentrated acid, while most of it is sent back to the packed tower to be reused as an absorbent. A valve for adding industrial water is installed at the circulating acid tank to replenish the acid lost due to its transfer to the foam tower for acid concentration, thereby maintaining a stable liquid level in the circulating acid tank. Additionally, the dilute acid stream sent from the hydrochloric acid desorption unit is sent to the acetylene pressure filtration clarifier in order to maintain the acid concentration in the circulating acid tank at 6%–8%. The gas exiting the top of the packed tower is sent to the alkali scrubber, where residual trace amounts of hydrogen chloride and a small amount of carbon dioxide are removed using an alkaline solution with a concentration of about 5% to 15%. The purified crude VC gas is then sent for compression and stored in a VC gas tank. The deionized water supplied by the utility department is added to the hot water circulation tank, and an appropriate amount of steam is introduced to heat it to 85°C–95°C for use in the conversion and distillation units. When it is needed, the centrifugal pump is started to pump the hot water to these units. 2.4. Description of the compression process: The gas coming out of the purification system enters the vinyl chloride gas tank. The vinyl chloride in the tank is cooled to 5℃–15℃ using a pre-compressor cooler with water at +5℃. After the condensate water is separated off via a water separator, it is pressurized to 0.55±0.03 MPa (gauge) by a screw compressor. It is then cooled to 45℃–50℃ by an after-compressor cooler and sent directly to the distillation unit. 2.5. Description of the production process in the distillation unit: The crude vinyl chloride gas with a pressure of 0.5 ±0.03 MPa (gauge pressure) from the compression system is first sent to the total condenser ； Indirect cooling with +5℃ water is used to condense and liquefy most of the vinyl chloride gas; after water removal in the low-boiling tower feed tank, it enters the low-boiling tower ； The non-condensed gas enters the exhaust gas condenser, where it is further condensed using chilled brine at –35°C. The resulting condensate goes into the feed tank of the low-boiling-point tower; after water is removed, it enters the tower. The material at the bottom of the tower is indirectly heated by hot water from the purification unit using a reboiler within the tower, which vaporizes the low-boiling substances present in the liquid flowing downward along the tower trays. This vapor is then condensed in the top condenser (using cooled water at +5°C) to form the top reflux stream. The non-condensed gas exits the tower through the top and enters the exhaust gas condenser for further condensation. The vinyl chloride, from which low-boiling compounds have been removed in the bottom of the low-boiling tower, is continuously fed into the high-boiling tower via a pneumatic valve under pressure difference. The liquid flowing downward in the high-boiling tower is heated by the reboiler in that tower, causing the vinyl chloride to vaporize; it is then separated through distillation in the high-boiling tower. The pure vinyl chloride gas discharged from the top of the tower is partially condensed in the top condenser (using cooling water at +5°C) to form reflux liquid for the tower; most of this gas enters the product condenser, where it is indirectly cooled by water at +5°C to condense the vinyl chloride into a liquid, which is then stored in the monomer product tank. As needed, the purified vinyl chloride is pumped to the polymerization plant using a monomer pump. The high-boiling substances discharged from the bottom of the high-boiling tower are sent to the residue storage tank, and periodically forced into the evaporation tank (twice per shift, for 5 minutes each time); the vinyl chloride gas evolved through heating with hot water is recovered and stored in a gas holder. The remaining high-boiling substances are pressed into the dichloroethane storage tank. 2.6. Description of the production process at the exhaust gas unit: The uncondensed gases emitted from the exhaust gas condenser enter at the bottom of the tubular adsorber; the vinyl chloride component in the exhaust gas is then adsorbed by the adsorbent. The heat generated during this adsorption process is removed by cooling water at a temperature of +5°C between the tubes. The hydrogen and nitrogen that are not adsorbed exit from the top of the adsorber and are vented through the exhaust gas control valve. When the amount of vinyl chloride and acetylene adsorbed in the adsorbent reaches saturation, the exhaust gas is directed to another adsorber. At this point, the pressure in the low-boiling tower system decreases, and hot water is introduced into the tubes of the first adsorber. A vacuum pump is then used to draw air in, so that the desorbed vinyl chloride gas can be freed from impurities such as carbon powder through a vacuum tank; part of this gas is sent to the second stage of conversion, while another part is sent to the compression unit for further compression before being sent to distillation. 2.7. Description of the process flow for the hydrochloric acid desorption unit: Concentrated hydrochloric acid is pumped from the storage tank to the desorption tower, where it is sprayed from the top of the tower. There, it meets the hot, dilute acid gas-liquid mixture coming from the reboiler, allowing for heat and mass transfer, thereby enabling the desorption of hydrogen chloride gas. The hydrogen chloride gas containing water vapor exits from the top of the tower; after passing through a graphite cooler, it is fed into the outer tube. The separated hydrogen chloride gas is then sent to the vinyl chloride synthesis process for use. The separated concentrated hydrochloric acid is sent to the acid storage tank, from where it is periodically discharged into the concentrated acid storage tank. The dilute acid obtained at the bottom of the tower is partially fed into a reboiler to produce a gas-liquid mixture of dilute acid, while another portion is sent to a chiller for cooling before being fed into a dilute acid storage tank. There it is used again to wash the foam tower; the resulting acid has a concentration of around 31%, and it is then used in the desorption tower. 2.8. Description of the production process at the freezing station: The prepared calcium chloride solution is stored in a salt water tank, from where it is pumped to the refrigeration unit by a salt water pump. Liquid ammonia absorbs heat and turns into ammonia gas; this gas is then compressed by a compression unit, and after that it condenses in an evaporation condenser, returning to its liquid state and being stored in an ammonia storage tank. Meanwhile, the salt water loses heat and its temperature drops, resulting in salt water at the desired temperature, which is then sent to the synthesis and mixing freezing processes as well as the distillation process. 2.9. Description of the production process for the lithium bromide unit: The cold water returning from the return water tank (at around 12°C) is pumped by a return water pump into the lithium bromide chiller. There, through heat exchange, water at 7°C is produced and sent to the storage tank. This water is then pumped by a cold water supply pump to the acetylene processing unit, as well as to the synthesis and distillation processes in the caustic soda plant; in the storage tank, this 7°C water mixes with water at 5°C produced by the Freon-based chiller. Cold water undergoes heat exchange during the aforementioned process, absorbing heat and raising the water temperature to 12°C. Water at 12℃ returns to the return water tank in the lithium bromide chiller process, where it then enters the refrigeration cycle. 2.10. Description of the production process for the circulating water system: The hot water from the lithium bromide and hydrogen chloride production units in the 100,000-ton/year PVC plant flows directly into the cooling tower; after being cooled, it goes into the cooling water tank. Circulating water pumps then transport the water from this tank to the various processes mentioned above, where it is reused. When the temperature of the cooling water is ≥35°C, the cooling water in the tank is sent back to the cooling tower for cooling using a control pump. III. Polymerization Workshop 3.1. Description of the production process in the polymerization area: After the polymerization reactors (R3101A-H) are coated, their bottom valves are inspected, and their manhole covers are checked, and after vacuuming is completed successfully, the water used for polymerization is sent from the deionized water preparation unit to the deionized water storage tank. From there, it is pumped into the polymerization reactors using water feed pumps (P3102A/B), after passing through deionized water filters (F3101A/B), or it is pumped into the reactors using injection pumps (P3111A/B). The dispersant and pH regulator are metered using flow meters, while the initiator is weighed, and all of these are added to the polymerization reactor along with deionized water. Fresh monomer and recycled monomer are added to the polymerization reactor in a certain ratio, after being filtered through fresh monomer filters (F3102A/B) and recycled monomer filter (F3302) as well as measured by flow meters. Finally, the molecular weight regulator is added to the polymerization reactor after being metered by a metering pump. After confirming that the safety production requirements are met, initiate pre-mixing. After pre-mixing, the circulating water is pumped into the jacket of the polymerization reactor by the circulating water pump (P3110A-L), and the heating injector (X3102A-H) is activated to raise the temperature of the material to the specified level. Thereafter, the automated control system takes over to regulate the polymerization temperature using circulating cooling water, until the reaction is complete. Start the slurry transfer pumps (P3112A/B) to press the suspended slurry into the slurry discharge tanks (V3118A/B). The unreacted monomer gas in the reactor is captured by the foam trap (V3119) together with the resin powder, and then recovered by the compression and condensation unit. The captured resin powder is pumped back to the slurry discharge tank (V3118A/B) by the recovery slurry pump. 3.2. Description of the production process in the stripping unit: The slurry coming out of the slurry discharge tanks (V3118A/B) is filtered through the slurry filters (F3201A/B), and then pumped via the stripping tower feed pumps (P3201A/B) into the spiral plate heat exchanger (E3201), where it is preheated by the hot slurry coming from the bottom of the stripping tower. After being heated by the spiral plate heat exchanger, the slurry reaches a temperature of approximately 95°C and enters the top of the stripping tower (T3201). It flows downward through the small holes in the sieve plates inside the tower, where it comes into countercurrent contact with the steam entering from the bottom of the tower – steam that has been filtered by the steam filter (F3202) before entering the bottom of the stripping tower. This contact facilitates heat and mass transfer, and the resin as well as the residual monomers in the aqueous phase are stripped away by the rising water vapor. The monomer vapor containing saturated water vapor escapes from the top of the stripping tower and enters the top condenser of the stripping tower (E3202). Most of this water vapor is condensed and enters the stripping tower condensate gas-liquid separator (V3201). The uncondensed monomer gas is sent to the compression and condensation unit. Some of the condensate water in the stripper condensate gas-liquid separator (V3201) is pumped to the top of the stripper using the stripper return pump (P3203) for spraying. The stripped slurry is discharged from the bottom of the stripping tower, fed to the spiral plate heat exchanger (E3201) via the centrifugal buffer tank feed pump (P3202A.B), and then sent to the centrifugal buffer tank in the drying section. 3.3. Compression condensation: The unreacted GVCM polymer is collected from the foam catcher (V3119), filtered through the VCM gas filter (F3301), and then sent to the vinyl chloride distribution station (V3302). When the pressure of VCM gas is > 0.25 MPa, GVCM goes directly from the vinyl chloride distribution station to the primary condenser (E3301A/B/C) ； When 0.05MPa ≤ GVCM pressure ≤ 0.25MPa, GVCM is provided by the vinyl chloride distribution station’s water-ring compressor units (C3301A/B) ； When the pressure of GVCM is < 0.05 MPa, GVCM returns directly from the vinyl chloride distribution station to the gas holder. The LVCM condensed in the primary condenser enters the monomer gas-liquid separator (V3304), and finally reaches the recovered monomer storage tank (V3303). The GVCM that has not been condensed in the primary condenser is condensed in the secondary condenser (E3302) before entering the recovered monomer tank (V3303). The uncondensed gas goes to the exhaust seal tank in the polymerization process. The water containing VCM in the recycled monomer tank is separated by a water-liquid separator (V3305); the GVCM is sent back to the gas holder, while the water is discharged into the drain ； The LVCM in the recycled monomer tank is pumped by the recycled monomer feed pumps (P3301A/B), filtered through the recycled monomer filter (V3304), and then added to the polymerization reactor. 3.4. The centrifugally dried PVC slurry is pumped from the stripping unit’s centrifugal mixing tank via pump P3302A/B to the drying unit’s centrifugal mixing tank V3405. The PVC slurry is kept in a suspended state through stirring, and is evenly fed into the centrifuges M3401A/B by the centrifuge feed pumps P3401A/B. Through centrifugation, the separated mother liquor enters the mother liquor sedimentation tanks V3404A/B; after centrifugation, a wet PVC material with a water content of about 20%-25% is obtained, which is then sent to the air-flow drying tower T3401 via the first and second screw conveyors L3401 and L3402. The air is filtered through filter X3401 to remove dust, pressurized by blower C3401, and then heated to around 150°C by air heater E3401 before being fed into the inlet at the bottom of T3401 ； In T3401, the air flow carries the PVC wet material fed by the secondary screw conveyor L3402 upward at high speed, enabling rapid mass and heat transfer; the surface moisture in the wet material particles vaporizes quickly and is carried away by the hot air flow, with the temperature of this hot air flow dropping to around 70°C. The airflow carries the material at high speed in a tangential direction into the pulse cyclone dryer E3402. Inside the dryer, the material particles and the airflow undergo multiple cycles of separation and mixing under the action of centrifugal force and the central hole, allowing for prolonged mass and heat transfer. As a result, the particles lose their internal bound water, meeting the drying requirements and becoming qualified products. The airflow carries the dried finished product into the cyclone separator V3401 for gas-solid separation. The PVC particles pass through the primary vibrating screens M3402A/B/C and the secondary vibrating screens M3403 to have the coarse (residual) material removed; the qualified products then enter the intermediate silos V3402A/B/C, from where they are sent to the large silos V3501A/B via the transfer tanks V3403A/B/C before being packaged and shipped out. The exhaust gas is discharged into the atmosphere via exhaust fan C3402 and silencer V3406.