Integrated water-saving process for coking methanol cogeneration enterprise

Abstract

The application discloses a kind of coking methanol co-production enterprise comprehensive water-saving process, it is related to coking, methanol technical field, the process includes the following specific flow: raw water pretreatment: raw water enters integrated pretreatment device, by accurate dosing flocculant and coagulant aid, and combining stirring mixing and sedimentation separation process, reduce the turbidity index of raw water, the innovation process of the present application by raw water pretreatment, condensate water recycling, waste heat wastewater and condensate comprehensive utilization, reclaimed water reuse control and desalted water concentrated water regeneration reuse, not only effectively reduce the turbidity of raw water, make it meet the requirements of subsequent processing procedure, also by accurate control and efficient processing, the condensate water, boiler blowdown, methanol conversion process condensate and reclaimed water etc. originally possibly wasted are converted into usable water resources, simultaneously by deep treatment sewage and recycling resource therein, further reduce the consumption of fresh water resources, significantly improve the water resource recycling rate of enterprise.

Description

Technical Field

[0001] This invention relates to the field of industrial water-saving technology, specifically a comprehensive water-saving process for coking and methanol co-production enterprises. Background Technology

[0002] In current industrial production, especially in coking and methanol co-production enterprises, the efficient utilization and scientific management of water resources have become an important cornerstone for sustainable development. These enterprises typically rely on surface water as their main water source. However, surface water quality fluctuates greatly and has high turbidity, posing a severe challenge to subsequent water treatment processes. To ensure the smooth operation of the production process, enterprises must pre-treat raw water to meet the specific water quality requirements of different production stages. This includes strictly controlling the concentration of calcium and magnesium ions in boiler water to prevent scaling, and considering the corrosiveness of water quality to equipment and the growth of microorganisms in circulating water systems. Therefore, how to improve water resource utilization and reduce treatment costs while ensuring water quality has become a pressing technical challenge for coking and methanol co-production enterprises.

[0003] However, traditional water use and water treatment processes in coking and methanol co-production enterprises are inadequate in the face of the above challenges. On the one hand, traditional pretreatment processes often struggle to effectively cope with the high-frequency fluctuations in raw water turbidity, leading to increased pressure on subsequent treatment stages and unsatisfactory treatment results. On the other hand, traditional condensate recovery systems lack efficient and accurate monitoring and control methods, resulting in low recycling rates of high-quality condensate, while low-quality condensate is often overlooked or misused, causing resource waste. In addition, traditional wastewater treatment processes also have many shortcomings in terms of treatment efficiency, resource recovery, and cost control. For example, boiler blowdown water and methanol conversion process condensate are often directly discharged or inefficiently utilized, while wastewater such as residual ammonia water from chemical production often fails to achieve ideal purification effects during treatment, resulting in large wastewater discharge volumes and ineffective recovery of the resources contained within them.

[0004] To address the aforementioned issues, it is necessary to optimize the existing integrated water-saving processes in coking and methanol co-production enterprises. By optimizing key aspects such as raw water pretreatment, condensate recovery and utilization, comprehensive utilization of waste heat and condensate, greywater reuse and regulation, demineralized water concentrate regeneration and reuse, and advanced wastewater treatment and resource recovery, the maximum utilization and efficient management of water resources are achieved. Therefore, developing an integrated water-saving process for coking and methanol co-production enterprises that can comprehensively achieve the above characteristics is of great significance. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a comprehensive water-saving process for coking and methanol co-production enterprises. This process efficiently treats raw water through an integrated pretreatment unit, effectively reducing its turbidity and providing stable influent conditions for subsequent treatment stages. Simultaneously, the process employs advanced technologies such as condensate recovery and utilization, comprehensive utilization of waste heat wastewater and condensate, greywater reuse regulation, and demineralized water concentrate regeneration and reuse, maximizing water resource utilization. Furthermore, for wastewater such as residual ammonia from chemical production, this invention also proposes a deep wastewater treatment and resource recovery process. Through advanced technologies such as ammonia stripping, biological treatment, membrane treatment, and evaporation salt extraction, it achieves efficient resource recovery and utilization from wastewater.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a comprehensive water-saving process for coking and methanol co-production enterprises, the process comprising the following specific steps:

[0007] Raw water pretreatment: Raw water is introduced into an integrated pretreatment device. By precisely adding flocculants and coagulants, and combining mixing and sedimentation separation processes, the turbidity index of the raw water is reduced to meet the influent requirements of the subsequent demineralized water preparation process.

[0008] Condensate recycling: including high-quality condensate reuse, low-quality condensate classification treatment, and deaerator exhaust steam condensate recycling and treatment;

[0009] For high-quality condensate reuse, the high-quality condensate generated by the steam turbine is directly transported to the boiler deaerator through the pipeline system. During the transportation process, flow sensors and online water quality monitors are installed to monitor the flow rate, temperature, conductivity and various ion concentration parameters of the condensate in real time, ensuring that the condensate can be efficiently and safely reused in the boiler feedwater system, thereby reducing the consumption of demineralized water.

[0010] For the graded treatment of low-quality condensate, there are two methods: condensate recovery for low-pressure boilers and condensate reuse using mixed-bed purification. For condensate recovery for low-pressure boilers, low-quality condensate is collected in a specific collection area. After water quality analysis and testing, condensate that meets the water quality standards for low-pressure boilers is pumped into the low-pressure boiler through a variable frequency speed control pump system and recycled as makeup water. For condensate reuse using mixed-bed purification, low-quality condensate with a high risk of pollution is introduced into a mixed-bed purification device. In the mixed bed, impurities and dissolved organic matter in the condensate are removed through the synergistic effect of anion and cation exchange resins, so that the treated condensate meets the demineralized water standard. The purified condensate is then transported to a demineralized water storage system as an alternative source of demineralized water.

[0011] For the recovery and treatment of deaerator exhaust steam condensate, an integrated equipment for deaerator exhaust steam condensate and heat recovery is adopted. The demineralized water and deaerator exhaust steam are used for heat exchange. During the heat exchange process, the exhaust steam is quickly condensed into water and recovered to the storage container. At the same time, the heat carried by the exhaust steam is fully absorbed by the demineralized water, and the oxygen in it is freely discharged into the atmosphere through the exhaust channel.

[0012] Comprehensive utilization of waste heat and condensate: including waste heat recovery and utilization of boiler blowdown and purification and reuse of condensate from methanol conversion process;

[0013] For the recovery and utilization of waste heat from boiler wastewater, the wastewater generated during boiler operation is collected into storage tanks and rapidly cooled by a high-efficiency plate cooler to reach the inlet water temperature requirement of the methanol evaporative air cooler. The cooled wastewater is then transported to the methanol evaporative air cooler through a pipeline system with controllable flow rate, replacing the cooling task of the demineralized water.

[0014] For the purification and reuse of condensate from the methanol conversion process: The condensate generated by the methanol conversion process enters a high-efficiency stripping tower for stripping treatment. In the stripping tower, dissolved gases in the condensate are effectively removed through gas-liquid contact and precise temperature and pressure control. The condensate after stripping is transported to a methanol evaporative air cooler, where it shares the cooling task with the treated boiler wastewater.

[0015] Water reuse regulation: After preliminary treatment and with stable water quality, the treated water is introduced into the demineralized water preparation unit as a supplement to the raw water. During the process of the treated water entering the demineralized water preparation unit, the chloride ion content of the demineralized water concentrate is monitored in real time online by a chloride ion sensor. Based on the preset chloride ion content threshold, the flow rate and the proportion of the treated water are adjusted to ensure that the chloride ion content of the demineralized water concentrate is always within an acceptable range, so that it can be recycled as a qualified supplementary water source for the circulating water system.

[0016] Demineralized water concentrate regeneration and reuse: The concentrate produced by the demineralized water preparation unit is transported to a high-density tank for deep treatment. In the high-density tank, by adding chemical precipitants, using hydraulic stirring conditions, and precisely controlling the sedimentation time, the hardness index of the concentrate is effectively reduced, and calcium and magnesium ions and some dissolved solids are removed. After the concentrate is treated in the high-density tank, and after water quality testing confirms that its water quality meets the standard requirements for circulating water replenishment, it is reinjected into the circulating water system as a replenishment water source through a variable frequency constant pressure pumping system, thereby significantly reducing the circulating water system's demand for fresh water resources.

[0017] Advanced wastewater treatment and resource recovery: including ammonia nitrogen wastewater pretreatment, comprehensive wastewater treatment and reuse, and evaporation salt extraction and product refining;

[0018] For the pretreatment of ammonia nitrogen wastewater, the residual ammonia water generated during the chemical production process enters the ammonia stripping treatment device. In the ammonia stripping device, by controlling the steam heating temperature, pressure and residence time, ammonia nitrogen is efficiently separated in the form of ammonia gas, thereby significantly reducing the ammonia nitrogen content of the treated wastewater to within the influent requirements of the sewage treatment device. The treated wastewater is then transported to the subsequent sewage treatment device for further treatment through gravity pipelines.

[0019] For comprehensive wastewater treatment and reuse, the wastewater treatment device integrates a biological treatment unit, a reverse osmosis membrane treatment unit, a nanofiltration membrane treatment unit, and a STRO special membrane treatment unit. Wastewater from ammonia production and various types of wastewater generated by chemical plants enter the biological treatment unit, where organic pollutants are removed through the degradation of microorganisms. After biological treatment, the wastewater enters the reverse osmosis membrane treatment unit, the nanofiltration membrane treatment unit, and the STRO special membrane treatment unit. Through the synergistic effect of the membrane treatment processes, the wastewater is deeply separated into concentrated water that can be used for salt extraction and reclaimed water that can be recycled. The reclaimed water is recycled to the reclaimed water reuse system for recycling, while the concentrated water is transported to the evaporation and salt extraction unit for further salt extraction treatment.

[0020] For evaporation salt extraction and product refining, the evaporation salt extraction device uses a multi-effect evaporation process to extract salt from the concentrated water after wastewater treatment. During the multi-effect evaporation process, by precisely controlling the temperature, pressure, liquid level, and steam flow parameters of each evaporator, sodium chloride and sodium sulfate salts in the concentrated water are gradually crystallized and precipitated. After the precipitated salt crystals are processed by centrifugation, washing, and drying, sodium chloride and sodium sulfate products that meet national standards are obtained, realizing the efficient recovery and utilization of resources in wastewater.

[0021] Furthermore, in the raw water pretreatment step, polyaluminum chloride is selected as the flocculant, with a dosage of 10-100 mg / L, and polyacrylamide is selected as the coagulant aid, with a dosage of 0.1-10 mg / L. The stirring speed is set at 100-300 rpm, and the stirring time is 3-10 minutes. The sedimentation separation zone adopts an inclined plate sedimentation or sedimentation tank structure, and the sedimentation time is 30-120 minutes. Gravity is used to make the flocs settle to the bottom, and the supernatant flows out through overflow, thereby reducing the turbidity of the raw water to meet the influent requirements of the subsequent demineralized water preparation process.

[0022] Furthermore, in the condensate recycling step, within the mixed bed, impurity ions and dissolved organic matter in the condensate are removed through the synergistic effect of cation and anion exchange resins. Specifically, cation and anion exchange resins are loaded according to the size of the mixed bed and the required treatment volume. The cation exchange resin is a styrene-based strong acid cation exchange resin, and the anion exchange resin is a styrene-based strong base anion exchange resin. After loading, the resin is pretreated by rinsing it with clean water at a flow rate of 10-20 m / h until the effluent is clear and free of impurities. The cation exchange resin is then soaked in 4-6% hydrochloric acid for 8-12 hours to displace the impurity ions from the resin. For the anion exchange resin, it is soaked in 3-5% sodium hydroxide solution. The soaking time is 8-12 hours. After soaking, the resin is rinsed with clean water until the pH of the rinsing water is close to neutral. Low-quality condensate with a high risk of contamination is transported to the mixed bed purification device through corrosion-resistant pipes. The flow regulating valve on the pipe controls the flow rate of the condensate into the mixed bed at a rate of 10-30 m / h. When the condensate enters the mixed bed, it comes into contact with the cation exchange resin. On the surface of the cation exchange resin, calcium, magnesium, and iron ions in the water will exchange with hydrogen ions on the resin, thereby removing metal cations from the condensate. The water after cation exchange continues to flow downwards and comes into contact with the anion exchange resin. Chloride, sulfate, and carbonate ions in the water will exchange with hydroxide ions on the resin. After treatment by the anion and cation exchange resins, the purified condensate flows out from the mixed bed outlet.

[0023] Furthermore, in the comprehensive utilization step of waste heat wastewater and condensate, the wastewater generated during boiler operation is collected into storage tanks and rapidly cooled by a high-efficiency plate cooler. The cooler is made of stainless steel plates. By adjusting the cooling water flow rate and the number of plates, the wastewater temperature is precisely reduced to the inlet water temperature requirement of the methanol evaporative air cooler. The cooling water temperature difference of the plate cooler is 10-30℃, and the temperature of the wastewater after cooling is 30-50℃. The cooled wastewater is then transported to the methanol evaporative air cooler through a flow-controllable pipeline system. The wastewater flow rate is automatically adjusted according to the air cooler load requirements. The pipeline flow rate is 0.3-1.2m / s to ensure the stable operation of the replacement of part of the demineralized water cooling task.

[0024] Furthermore, in the comprehensive utilization step of waste heat wastewater and condensate, dissolved gases in the condensate are effectively removed within the stripping tower through gas-liquid contact and precise temperature and pressure control. Specifically, the methanol conversion process condensate enters the stripping tower from the top or middle inlet. The feed rate is adjusted according to the processing capacity of the stripping tower and the flow rate of the condensate, ranging from 5-20 m / h. Simultaneously, a flow meter and regulating valve are installed on the feed pipe to precisely control the feed rate. Nitrogen gas is introduced at the bottom of the stripping tower, with a flow rate controlled at 10-100 m / h. Based on the composition of the condensate and the nature of the impurities to be removed, the stripping temperature is set between 50-90℃, and the pressure between 0.1-0.5 MPa. When the condensate enters the stripping tower, it flows downwards along the packing surface under gravity, forming a liquid film. Simultaneously, the gas introduced from the bottom flows upwards through the gaps in the packing, fully contacting the liquid film. The large gas-liquid contact area... The contact time is determined to be 30-120 seconds based on the height of the stripping tower and the liquid flow rate. During the contact process, volatile impurities and dissolved gases, due to their higher partial pressure in the gas phase than in the liquid phase, will transfer from the liquid phase to the gas phase. The condensate flows downward from the downcomer of the tower plate, while the gas flows upward from the openings of the tower plate, forming a bubble layer on the tower plate. The gas and liquid are fully mixed on the tower plate. The contact time per plate is 10-30 seconds, and the total contact time is adjusted by the number of tower plates, ranging from 30-300 seconds. During the bubbling process, dissolved gases escape from the liquid phase and enter the gas phase. After sufficient gas-liquid contact, the gas containing dissolved gases is discharged from the top of the stripping tower. The discharged gas is transported through pipelines to subsequent processing equipment for further treatment to prevent pollutants from being released into the atmosphere. The condensate after stripping and purification flows out from the bottom of the stripping tower and is transported through pipelines to the methanol evaporative air cooler, where it shares the cooling task with the treated boiler wastewater.

[0025] Furthermore, in the demineralized water concentrate regeneration and reuse step, in the high-density tank, a chemical precipitant is added, hydraulic stirring is employed, and the sedimentation time is precisely controlled. Sodium carbonate is selected as the chemical precipitant, and the dosage is determined based on the hardness of the concentrate, with an excess of 12%-25%. The stirring speed is 60-120 rpm, which reacts with calcium and magnesium ions in the concentrate to form precipitates. The sedimentation time is 80-150 minutes, promoting the growth and settling of the precipitate particles. The precipitated sludge is periodically discharged through a sludge discharge system, and the supernatant from the high-density tank flows out through a pipeline. The outflowing supernatant is tested by a strict water quality testing system, including tests for hardness, dissolved solids, and pH. When the water quality meets the requirements of the circulating water makeup water standard, it is reinjected into the circulating water system through a variable frequency constant pressure pumping system with a pressure adjustment range of 0.25-0.55 MPa and a flow accuracy of ±2.5%. The pumping system automatically adjusts the flow rate according to the pressure and water level requirements of the circulating water system. Check valves and filters are installed on the pipeline to prevent backflow and impurities from entering the circulating water system.

[0026] Furthermore, in the wastewater deep treatment and resource recovery step, in the ammonia stripping device, by controlling the steam heating temperature, pressure, and residence time, ammonia nitrogen is efficiently separated in the form of ammonia gas. The steam heating temperature is 102-115℃, the pressure is controlled at 0.25-0.45MPa, and the residence time of ammonia water in the device is controlled at 40-100 minutes, so that ammonia nitrogen is efficiently separated in the form of ammonia gas.

[0027] Furthermore, in the advanced wastewater treatment and resource recovery steps, the wastewater treatment device integrates multiple advanced treatment processes, including a biological treatment unit, a reverse osmosis membrane treatment unit, a nanofiltration membrane treatment unit, and a STRO special membrane treatment unit. Specifically, ammonia stripping wastewater from chemical production and various wastewaters generated by chemical plants first flow into the equalization tank of the biological treatment unit. After 6-10 hours of stirring and mixing, adjusting the pH to 7-8 and the temperature to 25-30℃, it is pumped into the activated sludge aeration tank at a flow rate of 15-25 m³ / h by a lift pump. Activated sludge is added to the aeration tank, with an MLSS of 3000-5000 mg / L, an aeration intensity of 0.8-1.2 m³ / (m²・min), a dissolved oxygen level of 4-5 mg / L, and a retention time of 20-30 hours. Microorganisms decompose macromolecular organic matter. The treated wastewater then flows into the secondary sedimentation tank for sludge-water separation, with a surface loading of 1-1.2 m³ / (m²・h) and a reflux ratio set at 40%-60%. The supernatant enters the reverse osmosis membrane treatment tank. The wastewater is filtered by a security filter and then pressurized to 2-3 MPa by a high-pressure pump before being fed into a polyamide composite membrane spiral wound module. The recovery rate is set at 65%-70%. Operation is ensured by monitoring influent and effluent parameters. When the flux decreases, the wastewater is cleaned in stages with citric acid and sodium hydroxide, with a cycle of 1.5-2 months. The freshwater is reused as greywater. The concentrate enters the nanofiltration membrane treatment unit. The nanofiltration concentrate is pressurized to 1-2 MPa by a high-pressure pump and fed into a hollow fiber module with a specific molecular weight cutoff of 200-800 Da. The recovery rate is set at 55%-65%. Chemical cleaning is performed when the flux decreases. If the nanofiltration concentrate does not meet the requirements for evaporation and salt extraction, it enters the STRO special membrane treatment unit. After precision filtration, the concentrate is pressurized to 3-5 MPa by a high-pressure pump and fed into a disc tube module. The recovery rate is 45%-55%. Operation is ensured by monitoring parameters. Finally, the concentrate is sent to the evaporation and salt extraction unit. The freshwater is reused or further treated depending on the water quality. All units work together to achieve wastewater resource utilization and zero discharge, while reducing costs and pollution risks.

[0028] Furthermore, in the wastewater deep treatment and resource recovery step, the evaporation and salt extraction device adopts a multi-effect evaporation process. Each effect evaporator adopts a falling film evaporator or forced circulation evaporator structure. The first effect temperature of each effect evaporator is controlled at 85-110℃, the last effect temperature at 35-55℃, the first effect pressure at 0.05-0.15MPa, the last effect pressure at 0.01-0.05MPa, and the steam flow rate at 2-8t / h. This allows sodium chloride and sodium sulfate and other salts in the concentrated water to gradually crystallize and precipitate. The precipitated salt crystals are then separated into solid and liquid by a centrifugal separation device at a speed of 1500-4000 rpm. The separated salt crystals enter a washing and drying system, where impurities are removed by countercurrent washing. The sodium chloride and sodium sulfate products that meet national standards are obtained by vacuum drying at a temperature of 60-120℃. The condensate generated during the evaporation process is recycled to a greywater reuse system or other treatment units.

[0029] Compared with existing technologies, this integrated water-saving process for coking and methanol co-production enterprises has the following beneficial effects:

[0030] I. This invention utilizes innovative processes including raw water pretreatment, condensate recycling, comprehensive utilization of waste heat wastewater and condensate, greywater reuse regulation, and demineralized water concentrate regeneration and reuse. This not only effectively reduces the turbidity of raw water to meet the requirements of subsequent treatment processes, but also, through precise control and efficient treatment, transforms potentially wasted condensate, boiler blowdown, methanol conversion process condensate, and greywater into usable water resources. Furthermore, by deeply treating wastewater and recovering its resources, it further reduces the consumption of fresh water resources, significantly improving the enterprise's water resource recycling rate, reducing dependence on external fresh water resources, thereby reducing water resource costs and related treatment costs, and improving the enterprise's economic benefits.

[0031] Second, this invention helps reduce the environmental burden on enterprises by reducing the consumption of fresh water resources and the discharge of wastewater. In particular, through evaporation and salt extraction and product refining processes, the salt in wastewater is converted into valuable sodium chloride and sodium sulfate products, realizing the recycling of resources and the reduction of solid waste. In addition, this invention also adopts intelligent water quality monitoring equipment to ensure the efficient, stable and reliable operation of the entire process.

[0032] Other advantages, objectives and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination or study, or may be learned from the practice of the invention. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0034] Figure 1 A flowchart of a comprehensive water-saving process for a coking methanol co-production enterprise;

[0035] Figure 2 This is a schematic diagram of a comprehensive water-saving process for a coking and methanol co-production enterprise. Detailed Implementation

[0036] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with the accompanying drawings and preferred embodiments, is provided below. Example

[0037] In a large coking and methanol co-production enterprise, the raw water is taken from a nearby surface water source. The water quality has obvious fluctuation characteristics, with turbidity often at a high level and chemical composition unstable.

[0038] In the raw water pretreatment stage, the raw water first enters the integrated pretreatment device. Based on the real-time water quality monitoring data of the raw water, flocculant (polyaluminum chloride, dosage 50 mg / L) and coagulant aid (polyacrylamide, dosage 3 mg / L) are automatically and accurately added. In the mixing device, it is stirred at a speed of 180 rpm for 6 minutes, and then settled in the sedimentation separation zone for 70 minutes. After this treatment, the turbidity of the raw water is reduced from the initial 20 NTU to 3 NTU, which meets the influent requirements of the subsequent demineralized water preparation process. The treated raw water is stably transported to the demineralized water preparation system through the pipeline at a flow rate of 0.9 m / s. The flow monitoring and preliminary water quality testing devices on the pipeline ensure that there are no abnormalities in the transportation process.

[0039] In the condensate recycling process, high-quality condensate generated by the steam turbine is directly piped to the boiler deaerator. High-precision electromagnetic flow sensors and multi-parameter online water quality monitors on the pipelines monitor various parameters of the condensate in real time, such as flow rate, temperature, conductivity, and the concentration of various ions. The central control system automatically adjusts the delivery process based on this data to ensure the efficient reuse of high-quality condensate in the boiler feedwater system. Low-quality condensate is collected, centrally tested, and then precisely pumped to the low-pressure boiler as makeup water by a variable frequency speed control pump system. For low-quality condensate with a high risk of contamination, it enters a mixed-bed purification device at a flow rate of 18 m / h. The mixed bed is filled with a specific ratio of cation and anion exchange resins. The cation exchange resin is a styrene-based strong acidic cation exchange resin, and the anion exchange resin is a styrene-based strong base anion exchange resin. The regeneration cycle of the ion exchange resin is 20 hours, with a regenerant concentration of 4% hydrochloric acid and 3% sodium hydroxide, calculated at twice the resin volume. After purification by the mixed bed, the condensate meets the demineralized water standard and is transported to the demineralized water storage system.

[0040] Regarding the recovery and utilization of deaerator exhaust steam condensate, the deaerator exhaust steam is treated by an integrated deaerator exhaust steam condensate and heat recovery device. The heat exchanger inside the device uses copper tubes, with demineralized water flowing inside and exhaust steam outside. The exhaust steam and demineralized water exchange heat in a counter-current manner. Precise control of parameters such as heat exchange area and water flow velocity ensures rapid condensation of the exhaust steam into water for recovery. The recovered condensate meets oxygen content standards and is then transported to the demineralized water preparation system. During the comprehensive utilization of waste heat and condensate, boiler blowdown water is collected in an insulated storage tank and then treated by a plate cooler with a cooling water temperature difference of 18℃. After the blowdown water is cooled to 38℃, it is then cooled at a rate of 0.8... A flow rate of m / s is delivered to the methanol evaporative air cooler through a flow-controlled pipeline. An electric regulating valve automatically adjusts the flow rate according to the air cooler load, replacing part of the demineralized water cooling task. The methanol conversion process condensate enters a high-efficiency stripping tower. The stripping tower adopts a packed tower structure, filled with stainless steel Pall ring packing. Air is introduced at the bottom with a gas flow rate of 50 m³ / h, a temperature controlled at 70℃, and a pressure of 0.25 MPa. After stripping, the dissolved gases in the condensate are effectively removed. Then, together with the treated boiler wastewater, it undertakes the cooling task in the methanol evaporative air cooler, reducing the demineralized water consumption per ton of methanol production to 2.5.

[0041] During the reclaimed water reuse control process, a portion of the treated reclaimed water is connected to the raw water inlet of the demineralized water preparation unit. Chloride ion sensors and intelligent flow regulating valves are installed on the reclaimed water pipeline, while conductivity sensors and chloride ion sensors are installed on the concentrated water outlet pipeline of the demineralized water preparation unit. Based on the preset chloride ion content threshold and water quality relationship model, the intelligent control system automatically adjusts the opening of the reclaimed water flow regulating valve within a 5-second response time, precisely controlling the reclaimed water flow and inflow ratio to ensure that the chloride ion content of the demineralized water concentrate is within an acceptable range, making it a qualified supplementary water source for the circulating water system. The intelligent control system also has data storage and analysis functions, and can continuously optimize the control strategy based on historical data.

[0042] In the demineralized water concentrate regeneration and reuse stage, the concentrate generated by the demineralized water preparation unit enters the high-density tank deep treatment system through pipelines at a flow rate of 0.6 m / s. Sodium carbonate precipitant is added to the high-density tank (the dosage is calculated based on the hardness of the concentrate, with an excess of 18%). The stirring speed is 90 rpm, and the sedimentation time is 120 minutes. The sludge after sedimentation is discharged periodically. The supernatant undergoes strict water quality testing. When the hardness, dissolved solids, and pH indicators meet the requirements of the circulating water makeup water standard, it is reinjected into the circulating water system by a variable frequency constant pressure pumping system (pressure adjustment range 0.35-0.45 MPa, flow accuracy within ±2.5%). The pumping system automatically adjusts the flow rate according to the pressure and water level requirements of the circulating water system. Check valves and filters on the pipelines prevent backflow and impurities from entering.

[0043] In the advanced wastewater treatment and resource recovery step, the residual ammonia water from chemical production enters the ammonia stripping treatment unit. By precisely controlling the steam heating temperature to 108℃, the pressure to 0.35MPa, and the residence time of the ammonia water in the unit to 60 minutes, ammonia nitrogen is efficiently separated into ammonia gas. The ammonia gas is discharged from the top of the tower for treatment. The treated wastewater flows out from the bottom and is transported to the wastewater treatment unit through a pipeline at a flow rate of 0.6m / s. In the wastewater treatment unit, the biological treatment unit adopts an activated sludge aeration tank, where specific microbial strains are introduced and the aeration intensity is controlled. With dissolved oxygen concentration of 4 mg / L and water temperature of 28℃, most organic pollutants in the wastewater are degraded. The biologically treated wastewater then sequentially enters a reverse osmosis membrane treatment unit (using a polyamide composite membrane, operating pressure 2.5 MPa, recovery rate 68%), a nanofiltration membrane treatment unit (using membrane material with a molecular weight cutoff of 500 Da, operating pressure 1.5 MPa), and a STRO special membrane treatment unit (activated only when the nanofiltration concentrate does not meet the requirements for evaporation and salt extraction). Each membrane treatment unit precisely controls operating parameters such as pressure, flow rate, and recovery rate. The system separates wastewater into concentrated water suitable for salt extraction and recycled water. The recycled water is piped back to a reuse system, while the concentrated water is transported to an evaporation and salt extraction unit. Each pipeline has a flow velocity of 0.5 m / s and is equipped with flow and water quality monitoring devices. The evaporation and salt extraction unit employs a multi-effect evaporation process, with each effect using a falling film evaporator structure. The first-effect temperature is 95℃, and the last-effect temperature is 45℃. The pressure is 0.08 MPa (absolute pressure) for the first effect and 0.02 MPa (absolute pressure) for the last effect. The steam flow rate is 5 t / h. By precisely controlling these key parameters, sodium chloride and sodium sulfate, among other salts, gradually crystallize out of the concentrated water. The precipitated salt crystals are then separated into solid and liquid components by a centrifugal separator (centrifugal speed 2500 rpm) and enter a washing and drying system. Impurities are removed by countercurrent washing, and the product is then dried with hot air at 90°C to obtain sodium chloride and sodium sulfate products that meet national standards. The condensate generated during the evaporation process is recycled to a greywater reuse system. The entire evaporation, salt extraction, and product refining process is monitored and operated by an automated control system to ensure efficient and stable operation.

[0044] By implementing this comprehensive water-saving technology, the company has achieved remarkable results in water resource utilization. The consumption of demineralized water per ton of methanol production has been reduced by about 20%, the amount of circulating water replenishment has been reduced by about 25%, and the cost of sewage treatment has been reduced by about 30%. This has effectively reduced water consumption and sewage discharge, greatly improved the company's economic and environmental benefits, and laid a solid foundation for the company's sustainable development. Example

[0045] In a medium-sized coking and methanol co-production enterprise, the raw water source is surface water in the surrounding area that is slightly affected by industrial activities. The water quality has certain fluctuation characteristics and contains a variety of complex components.

[0046] Raw water enters the integrated pretreatment unit. Based on real-time water quality monitoring results, the unit adds flocculant polyaluminum chloride at a dosage of 30 mg / L and coagulant aid polyacrylamide at a dosage of 1 mg / L. The mixture is thoroughly mixed by stirring at a speed of 150 rpm for 5 minutes. After that, the water settles in the sedimentation zone for 50 minutes. After treatment, the turbidity of the raw water is reduced from the initial 15 NTU to 2 NTU, meeting the influent standard for subsequent demineralized water preparation. The raw water is then transported to the demineralized water preparation system through pipelines at a flow rate of 0.7 m / s. The flow rate and water quality monitoring devices on the pipelines ensure a stable supply of raw water and that the water quality meets the standards.

[0047] High-quality condensate from the steam turbine is transported to the boiler deaerator via a dedicated, insulated pipeline with a flow rate of 1.5 m / s. The pipeline is equipped with a high-precision electromagnetic flow sensor and a multi-parameter online water quality monitor to monitor condensate parameters in real time and control them via a central control system, ensuring efficient condensate reuse. Low-quality condensate is collected and tested for water quality every two days. When the condensate hardness is detected to be 0.3 mmol / L, meeting the low-pressure boiler water standard, it is pumped to the low-pressure boiler via a variable frequency speed-regulating pump system. The pumping system automatically adjusts the flow rate based on the boiler water level and water demand. For low-quality condensate with a higher risk of contamination, it enters a mixed-bed purification device at a flow rate of 15 m / h. The mixed bed is filled with a specific ratio of anion and cation exchange resins. Styrene-based strong acid cation exchange resin and styrene-based strong base anion exchange resin are selected. The regeneration cycle of the ion exchange resin is 18 hours. The concentration of the regenerant hydrochloric acid is 3.5% and the concentration of sodium hydroxide is 2.5%, calculated based on 1.5 times the resin volume. After the purified condensate meets the demineralized water standard, it is transported to the demineralized water storage system. Water quality monitoring points are set on the pipeline to ensure that the water quality meets the standard. The exhaust steam of the deaerator is treated through an integrated recovery device. The heat exchanger is made of copper tubes. The demineralized water inside the tubes and the exhaust steam outside the tubes exchange heat countercurrently. Through precise control of parameters, the exhaust steam condenses into water and is recovered to the storage container. The liquid level monitoring is linked with the drain pump to transport the condensate to the demineralized water preparation system. The exhaust channel ensures that the oxygen content of the recovered exhaust steam condensate is qualified.

[0048] Boiler wastewater is collected in an insulated storage tank and treated by a plate cooler. With a temperature difference of 15℃, the wastewater is cooled to 35℃ and then sent to a methanol evaporative air cooler at a flow rate of 0.6 m / s through a flow-controlled pipeline. An electric regulating valve adjusts the flow rate according to the air cooler load, partially replacing the cooling task of the demineralized water. The methanol conversion process condensate enters a packed tower structure with stainless steel Pall ring packing. Air is introduced at the bottom at a flow rate of 30 m / h, a temperature of 60℃, and a pressure of 0.2 MPa. After air stripping, impurities in the condensate are removed. Then, together with the treated boiler wastewater, it undertakes the cooling task in the methanol evaporative air cooler, reducing the demineralized water consumption per ton of methanol production to 2.6.

[0049] Partially treated reclaimed water is connected to the raw water inlet of the demineralized water preparation unit. Chloride ion sensors and intelligent flow regulating valves are installed on the reclaimed water pipeline, and conductivity sensors and chloride ion sensors are installed on the concentrated water outlet pipeline of the demineralized water preparation unit. Based on preset thresholds and water quality relationship models, the intelligent control system automatically adjusts the opening of the reclaimed water flow regulating valve within a 6-second response time to precisely control the reclaimed water flow and inflow ratio, ensuring that the chloride ion content of the demineralized water concentrate is acceptable and can be recycled as a supplementary water source for the circulating water system. The intelligent control system can also optimize the control strategy based on historical data.

[0050] The concentrated water produced by the demineralized water preparation unit enters the high-density tank deep treatment system at a flow rate of 0.4 m / s. Sodium carbonate precipitant is added to the high-density tank (the amount added is calculated based on the hardness of the concentrated water, with an excess of 15%). The stirring speed is 70 rpm, and the sedimentation time is 100 minutes. The sludge after sedimentation is discharged periodically. The supernatant undergoes strict water quality testing. When the hardness, dissolved solids, and pH indicators meet the requirements of the circulating water makeup water standard, it is reinjected into the circulating water system by a variable frequency constant pressure pumping system (pressure adjustment range 0.3-0.5 MPa, flow accuracy within ±3%). The pumping system automatically adjusts the flow rate according to the pressure and water level requirements of the circulating water system. Check valves and filters on the pipeline prevent backflow and impurities from entering.

[0051] The residual ammonia water from the chemical production enters the ammonia stripping treatment unit. By precisely controlling the steam heating temperature to 105℃, the pressure to 0.3MPa, and the residence time of the ammonia water in the unit to 50 minutes, ammonia nitrogen is efficiently separated into ammonia gas. The ammonia gas is discharged from the top of the tower for treatment. The treated wastewater flows out from the bottom and is transported to the wastewater treatment unit through a pipeline at a flow rate of 0.4m / s. In the wastewater treatment unit, the biological treatment unit uses a biological contact oxidation tank with a biofilm method. Specific microbial strains are introduced, and parameters such as dissolved oxygen concentration of 3.5mg / L and water temperature of 25℃ are controlled to degrade most of the organic pollutants in the wastewater. The biologically treated wastewater then sequentially enters the reverse osmosis membrane treatment unit (using a polyamide composite membrane, operating pressure 2MPa, recovery rate 65%), the nanofiltration membrane treatment unit (using membrane material with a molecular weight cutoff of 300Da, operating pressure 1.2MPa), and the STRO special membrane treatment unit (only activated when the nanofiltration concentrate does not meet the requirements for evaporation and salt extraction). Each membrane treatment unit precisely controls operating parameters such as pressure, flow rate, and recovery rate to separate the wastewater into usable... The system consists of two parts: concentrated water from salt extraction and reclaimed water that can be recycled. The reclaimed water is piped back to the reclaimed water reuse system, while the concentrated water is transported to the evaporation and salt extraction unit. Each pipeline has a flow velocity of 0.3 m / s and is equipped with flow and water quality monitoring devices. The evaporation and salt extraction unit employs a multi-effect evaporation process, with each effect using a forced circulation evaporator structure. The first-effect temperature is 90℃, and the last-effect temperature is 40℃. The pressure is 0.06 MPa (absolute pressure) for the first effect and 0.015 MPa (absolute pressure) for the last effect. The steam flow rate is 3 t / h. This process is precisely controlled... These key parameters allow sodium chloride and sodium sulfate to gradually crystallize out of the concentrated water. The precipitated salt crystals are then separated into solid and liquid components by a centrifugal separator (centrifugal speed 2000 rpm) and enter a washing and drying system. Impurities are removed by countercurrent washing, and then the product is dried at 80°C under vacuum to obtain sodium chloride and sodium sulfate products that meet national standards. The condensate generated during the evaporation process is recycled to a greywater reuse system. The entire evaporation, salt extraction, and product refining process is monitored and operated by an automated control system to ensure efficient and stable operation.

[0052] By implementing this comprehensive water-saving process, the company reduced its demineralized water consumption per ton of methanol production by approximately 15%, its circulating water replenishment by approximately 20%, and its wastewater treatment costs by approximately 25%. This has yielded significant results in water resource utilization and cost control, and has strongly promoted the company's green and sustainable development.

[0053] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A comprehensive water-saving process for a coking and methanol co-production enterprise, characterized in that, The process includes the following specific steps: Raw water pretreatment: Raw water is introduced into an integrated pretreatment device. By precisely adding flocculants and coagulants, and combining mixing and sedimentation separation processes, the turbidity index of the raw water is reduced to meet the influent requirements of the subsequent demineralized water preparation process. Condensate recycling: including high-quality condensate reuse, low-quality condensate classification treatment, and deaerator exhaust steam condensate recycling and treatment; For high-quality condensate reuse, the high-quality condensate generated by the steam turbine is directly transported to the boiler deaerator through the pipeline system. During the transportation process, flow sensors and online water quality monitors are installed to monitor the flow rate, temperature, conductivity and various ion concentration parameters of the condensate in real time, ensuring that the condensate can be efficiently and safely reused in the boiler feedwater system, thereby reducing the consumption of demineralized water. For the graded treatment of low-quality condensate, there are two methods: condensate recovery for low-pressure boilers and condensate reuse using mixed-bed purification. For condensate recovery for low-pressure boilers, low-quality condensate is collected in a specific collection area. After water quality analysis and testing, condensate that meets the water quality standards for low-pressure boilers is pumped into the low-pressure boiler through a variable frequency speed control pump system and recycled as makeup water. For condensate reuse using mixed-bed purification, low-quality condensate with a high risk of pollution is introduced into a mixed-bed purification device. In the mixed bed, impurities and dissolved organic matter in the condensate are removed through the synergistic effect of anion and cation exchange resins, so that the treated condensate meets the demineralized water standard. The purified condensate is then transported to a demineralized water storage system as an alternative source of demineralized water. For the recovery and treatment of deaerator exhaust steam condensate, an integrated equipment for deaerator exhaust steam condensate and heat recovery is adopted. The demineralized water and deaerator exhaust steam are used for heat exchange. During the heat exchange process, the exhaust steam is quickly condensed into water and recovered to the storage container. At the same time, the heat carried by the exhaust steam is fully absorbed by the demineralized water, and the oxygen in it is freely discharged into the atmosphere through the exhaust channel. Comprehensive utilization of waste heat and condensate: including waste heat recovery and utilization of boiler blowdown and purification and reuse of condensate from methanol conversion process; For the recovery and utilization of waste heat from boiler wastewater, the wastewater generated during boiler operation is collected into storage tanks and rapidly cooled by a high-efficiency plate cooler to reach the inlet water temperature requirement of the methanol evaporative air cooler. The cooled wastewater is then transported to the methanol evaporative air cooler through a pipeline system with controllable flow rate, replacing the cooling task of the demineralized water. For the purification and reuse of condensate from the methanol conversion process: The condensate generated by the methanol conversion process enters a high-efficiency stripping tower for stripping treatment. In the stripping tower, dissolved gases in the condensate are effectively removed through gas-liquid contact and precise temperature and pressure control. The condensate after stripping is transported to a methanol evaporative air cooler, where it shares the cooling task with the treated boiler wastewater. Water reuse regulation: After preliminary treatment and with stable water quality, the treated water is introduced into the demineralized water preparation unit as a supplement to the raw water. During the process of the treated water entering the demineralized water preparation unit, the chloride ion content of the demineralized water concentrate is monitored in real time online by a chloride ion sensor. Based on the preset chloride ion content threshold, the flow rate and the proportion of the treated water are adjusted to ensure that the chloride ion content of the demineralized water concentrate is always within an acceptable range, so that it can be recycled as a qualified supplementary water source for the circulating water system. Demineralized water concentrate regeneration and reuse: The concentrate produced by the demineralized water preparation unit is transported to a high-density tank for deep treatment. In the high-density tank, by adding chemical precipitants, using hydraulic stirring conditions, and precisely controlling the sedimentation time, the hardness index of the concentrate is effectively reduced, and calcium and magnesium ions and some dissolved solids are removed. After the concentrate is treated in the high-density tank, and after water quality testing confirms that its water quality meets the standard requirements for circulating water replenishment, it is reinjected into the circulating water system as a replenishment water source through a variable frequency constant pressure pumping system, thereby significantly reducing the circulating water system's demand for fresh water resources. Advanced wastewater treatment and resource recovery: including ammonia nitrogen wastewater pretreatment, comprehensive wastewater treatment and reuse, and evaporation salt extraction and product refining; For the pretreatment of ammonia nitrogen wastewater, the residual ammonia water generated during the chemical production process enters the ammonia stripping treatment device. In the ammonia stripping device, by controlling the steam heating temperature, pressure and residence time, ammonia nitrogen is efficiently separated in the form of ammonia gas, thereby significantly reducing the ammonia nitrogen content of the treated wastewater to within the influent requirements of the sewage treatment device. The treated wastewater is then transported to the subsequent sewage treatment device for further treatment through gravity pipelines. For comprehensive wastewater treatment and reuse, the wastewater treatment device integrates a biological treatment unit, a reverse osmosis membrane treatment unit, a nanofiltration membrane treatment unit, and a STRO special membrane treatment unit. Wastewater from ammonia production and various types of wastewater generated by chemical plants enter the biological treatment unit, where organic pollutants are removed through the degradation of microorganisms. After biological treatment, the wastewater enters the reverse osmosis membrane treatment unit, the nanofiltration membrane treatment unit, and the STRO special membrane treatment unit. Through the synergistic effect of the membrane treatment processes, the wastewater is deeply separated into concentrated water that can be used for salt extraction and reclaimed water that can be recycled. The reclaimed water is recycled to the reclaimed water reuse system for recycling, while the concentrated water is transported to the evaporation and salt extraction unit for further salt extraction treatment. For evaporation salt extraction and product refining, the evaporation salt extraction device uses a multi-effect evaporation process to extract salt from the concentrated water after wastewater treatment. During the multi-effect evaporation process, by precisely controlling the temperature, pressure, liquid level, and steam flow parameters of each evaporator, sodium chloride and sodium sulfate salts in the concentrated water are gradually crystallized and precipitated. After the precipitated salt crystals are processed by centrifugation, washing, and drying, sodium chloride and sodium sulfate products that meet national standards are obtained, realizing the efficient recovery and utilization of resources in wastewater.

2. The comprehensive water-saving process for a coking and methanol co-production enterprise according to claim 1, characterized in that, In the raw water pretreatment step, polyaluminum chloride is selected as the flocculant, with a dosage of 10-100 mg / L, and polyacrylamide is selected as the coagulant aid, with a dosage of 0.1-10 mg / L. The stirring speed is set at 100-300 rpm, and the stirring time is 3-10 minutes. The sedimentation separation zone adopts an inclined plate sedimentation or sedimentation tank structure, and the sedimentation time is 30-120 minutes. Gravity is used to make the flocs settle to the bottom, and the supernatant flows out through overflow, thereby reducing the turbidity of the raw water to meet the influent requirements of the subsequent demineralized water preparation process.

3. The comprehensive water-saving process for a coking and methanol co-production enterprise according to claim 1, characterized in that, In the condensate recycling step, within the mixed bed, impurity ions and dissolved organic matter in the condensate are removed through the synergistic effect of cation and anion exchange resins. Specifically, cation and anion exchange resins are loaded according to the size of the mixed bed and the required treatment volume. The cation exchange resin is a styrene-based strong acid cation exchange resin, and the anion exchange resin is a styrene-based strong base anion exchange resin. After loading, the resins are pretreated by rinsing them with clean water at a flow rate of 10-20 m / h until the effluent is clear and free of impurities. The cation exchange resins are then soaked in 4-6% hydrochloric acid for 8-12 hours to displace the impurity ions. For the anion exchange resins, they are soaked in 3-5% sodium hydroxide solution. The soaking time is 8-12 hours. After soaking, the resin is rinsed with clean water until the pH of the rinsing water is close to neutral. Low-quality condensate with a high risk of contamination is transported to the mixed bed purification device through corrosion-resistant pipes. The flow regulating valve on the pipes controls the flow rate of the condensate into the mixed bed at a rate of 10-30 m / h. When the condensate enters the mixed bed, it comes into contact with the cation exchange resin. On the surface of the cation exchange resin, calcium, magnesium, and iron ions in the water will exchange with hydrogen ions on the resin, thereby removing metal cations from the condensate. The water after cation exchange continues to flow downwards and comes into contact with the anion exchange resin. Chloride, sulfate, and carbonate ions in the water will exchange with hydroxide ions on the resin. After treatment by the anion and cation exchange resins, the purified condensate flows out from the mixed bed outlet.

4. The comprehensive water-saving process for a coking and methanol co-production enterprise according to claim 1, characterized in that, In the comprehensive utilization step of waste heat and condensate, the wastewater generated during boiler operation is collected into storage tanks and rapidly cooled by a high-efficiency plate cooler. The cooler is made of stainless steel plates. By adjusting the cooling water flow rate and the number of plates, the wastewater temperature is precisely reduced to the inlet water temperature requirement of the methanol evaporative air cooler. The cooling water temperature difference of the plate cooler is 10-30℃, and the temperature of the wastewater after cooling is 30-50℃. The cooled wastewater is then transported to the methanol evaporative air cooler through a pipeline system with controllable flow. The wastewater flow rate is automatically adjusted according to the air cooler load requirements. The pipeline flow rate is 0.3-1.2m / s to ensure the stable operation of the replacement of part of the demineralized water cooling task.

5. The comprehensive water-saving process for a coking and methanol co-production enterprise according to claim 1, characterized in that, In the comprehensive utilization step of waste heat wastewater and condensate, dissolved gases in the condensate are effectively removed through gas-liquid contact and precise temperature and pressure control within the stripping tower. Specifically, the methanol conversion process condensate enters the stripping tower from the top or middle inlet. The feed rate is adjusted according to the processing capacity of the stripping tower and the flow rate of the condensate, ranging from 5-20 m / h. A flow meter and regulating valve are installed on the feed pipe to precisely control the feed rate. Nitrogen gas is introduced at the bottom of the stripping tower, with a flow rate controlled at 10-100 m / h. The stripping temperature is set between 50-90℃ and the pressure between 0.1-0.5 MPa, depending on the composition of the condensate and the nature of the impurities to be removed. After entering the stripping tower, the condensate flows downwards along the packing surface under gravity, forming a liquid film. Simultaneously, the gas introduced from the bottom flows upwards through the gaps in the packing, fully contacting the liquid film. The gas-liquid contact area is large, and the contact time is relatively short. The contact time is determined to be 30-120 seconds based on the height of the stripping tower and the liquid flow rate. During the contact process, volatile impurities and dissolved gases, due to their higher partial pressure in the gas phase than in the liquid phase, will transfer from the liquid phase to the gas phase. The condensate flows downward from the downcomer of the tower plate, while the gas flows upward from the openings of the tower plate, forming a bubble layer on the tower plate. The gas and liquid are fully mixed on the tower plate, with a contact time of 10-30 seconds per plate. The total contact time is adjusted by the number of tower plates, ranging from 30-300 seconds. During the bubbling process, dissolved gases escape from the liquid phase and enter the gas phase. After sufficient gas-liquid contact, the gas containing dissolved gases is discharged from the top of the stripping tower. The discharged gas is transported through pipelines to subsequent processing equipment for further treatment to prevent pollutants from being released into the atmosphere. The condensate after stripping and purification flows out from the bottom of the stripping tower and is transported through pipelines to the methanol evaporative air cooler, where it shares the cooling task with the treated boiler wastewater.

6. The comprehensive water-saving process for a coking and methanol co-production enterprise according to claim 1, characterized in that, In the demineralized water concentrate regeneration and reuse step, in the high-density tank, a chemical precipitant is added, hydraulic stirring is employed, and the sedimentation time is precisely controlled. Sodium carbonate is selected as the chemical precipitant, and the dosage is determined based on the hardness of the concentrate, with an excess of 12%-25%. The stirring speed is 60-120 rpm. The precipitant reacts with calcium and magnesium ions in the concentrate to form precipitates. The sedimentation time is 80-150 minutes, promoting the growth and settling of the precipitate particles. The precipitated sludge is periodically discharged through a sludge discharge system. The supernatant from the high-density tank flows out through pipelines and is tested by a strict water quality testing system. The test items include hardness, dissolved solids, and pH. When the water quality meets the requirements of the circulating water makeup water standard, it is reinjected into the circulating water system through a variable frequency constant pressure pumping system with a pressure adjustment range of 0.25-0.55 MPa and a flow accuracy of ±2.5%. The pumping system automatically adjusts the flow rate according to the pressure and water level requirements of the circulating water system. Check valves and filters are installed on the pipelines to prevent backflow and impurities from entering the circulating water system.

7. The comprehensive water-saving process for a coking and methanol co-production enterprise according to claim 1, characterized in that, In the aforementioned wastewater deep treatment and resource recovery step, in the ammonia stripping device, ammonia nitrogen is efficiently separated into ammonia gas by controlling the steam heating temperature, pressure, and residence time. The steam heating temperature is 102-115℃, the pressure is controlled at 0.25-0.45MPa, and the residence time of ammonia water in the device is controlled at 40-100 minutes, so that ammonia nitrogen is efficiently separated into ammonia gas.

8. The comprehensive water-saving process for a coking and methanol co-production enterprise according to claim 1, characterized in that, In the advanced wastewater treatment and resource recovery steps, the wastewater treatment device integrates multiple advanced treatment processes, including a biological treatment unit, a reverse osmosis membrane treatment unit, a nanofiltration membrane treatment unit, and a STRO special membrane treatment unit. Specifically, ammonia stripping wastewater from chemical production and various wastewaters from chemical plants first flow into the equalization tank of the biological treatment unit. After 6-10 hours of stirring and mixing, adjusting the pH to 7-8 and the temperature to 25-30℃, it is pumped into the activated sludge aeration tank at a flow rate of 15-25 m³ / h by a lift pump. Activated sludge is added to the aeration tank, with an MLSS of 3000-5000 mg / L, an aeration intensity of 0.8-1.2 m³ / (m²・min), a dissolved oxygen level of 4-5 mg / L, and a retention time of 20-30 hours. Microorganisms decompose macromolecular organic matter. The treated wastewater then flows into the secondary sedimentation tank for sludge-water separation, with a surface loading of 1-1.2 m³ / (m²・h) and a reflux ratio set at 40%-60%. The supernatant then enters the reverse osmosis membrane treatment unit. After being filtered by a security filter, the wastewater is pressurized to 2-3 MPa by a high-pressure pump and fed into a polyamide composite membrane spiral wound module. The recovery rate is set at 65%-70%. Operation is ensured by monitoring influent and effluent parameters. When the flux decreases, the wastewater is cleaned in stages with citric acid and sodium hydroxide, with a cycle of 1.5-2 months. The freshwater is reused as greywater. The concentrate enters the nanofiltration membrane treatment unit. The nanofiltration concentrate is pressurized to 1-2 MPa by a high-pressure pump and fed into a hollow fiber module with a specific molecular weight cutoff of 200-800 Da. The recovery rate is set at 55%-65%. Chemical cleaning is performed when the flux decreases. If the nanofiltration concentrate does not meet the requirements for evaporation and salt extraction, it enters the STRO special membrane treatment unit. After precision filtration, it is pressurized to 3-5 MPa by a high-pressure pump and fed into a disc tube module. The recovery rate is 45%-55%. Operation is ensured by monitoring parameters. Finally, the concentrate is sent to the evaporation and salt extraction device. The freshwater is reused or further treated depending on the water quality. All units work together to achieve wastewater resource utilization and zero discharge, while reducing costs and pollution risks.

9. The comprehensive water-saving process for a coking and methanol co-production enterprise according to claim 1, characterized in that, In the wastewater deep treatment and resource recovery step, the evaporation and salt extraction device adopts a multi-effect evaporation process. Each effect evaporator adopts a falling film evaporator or forced circulation evaporator structure. The first effect temperature of each effect evaporator is controlled at 85-110℃, the last effect temperature at 35-55℃, the first effect pressure at 0.05-0.15MPa, the last effect pressure at 0.01-0.05MPa, and the steam flow rate at 2-8t / h. This allows sodium chloride and sodium sulfate salts in the concentrated water to gradually crystallize and precipitate. The precipitated salt crystals are then separated into solid and liquid by a centrifugal separation device at a speed of 1500-4000 rpm. The separated salt crystals enter a washing and drying system, where impurities are removed by countercurrent washing. The sodium chloride and sodium sulfate products that meet national standards are obtained by vacuum drying at a temperature of 60-120℃. The condensate generated during the evaporation process is recycled to a greywater reuse system or other treatment units.

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