Printing steaming waste gas treatment system and process

Abstract

The application discloses a printing steaming waste gas treatment system and process, relates to the technical field of waste gas treatment, and has the technical scheme as follows: the input end of the waste gas collecting unit is connected with the exhaust port of a steaming machine, and the output end is connected to a waste heat recovery unit; the heat medium outlet of the waste heat recovery unit is connected to a waste gas purification unit, the cold medium inlet is connected with a production process water pipeline, and the hot water outlet is connected with a production hot water storage tank; the gas inlet of the waste gas purification unit is connected with the heat medium outlet of the waste heat recovery unit, the bottom of the waste gas purification unit is provided with a circulating water tank, and the circulating water tank is connected with the spraying layer of a spraying tower through a circulating pipeline. The application realizes the step-by-step utilization of waste heat by recycling the heated process make-up water for the pretreatment water washing process and introducing the insufficiently recovered waste heat into the steam heating system of the steaming machine through a waste heat standby recovery branch; the water in the clean water storage tank is qualified and is recycled for the spraying tower make-up water; and the intelligent control unit is used to realize the full-automatic operation.

Description

Technical Field

[0001] This invention relates to the field of waste gas treatment technology, and more specifically, to a waste gas treatment system and process for printing steaming. Background Technology

[0002] In the production process of printed fabrics, steaming is a key step. The steaming machine uses high-temperature saturated steam to act on the printed fabric, so that the dye is fixed to the fiber.

[0003] During the evaporation process, a large amount of high-temperature and high-humidity waste gas is emitted. Existing treatment technologies such as spray washing, activated carbon adsorption, or catalytic combustion can purify the waste gas to a certain extent, but they ignore the large amount of heat energy contained in the waste gas. During the waste gas purification and emission process, the heat energy is directly lost. The spray washing process generates a certain amount of dyeing and printing wastewater. If this wastewater is discharged directly, the treatment cost is high. If it is simply treated and reused, it is easy to cause the spray system to be blocked or even cause secondary pollution. Activated carbon adsorption requires the activated carbon to be replaced regularly, generating solid waste. Moreover, the adsorption efficiency for VOCs is limited, making it difficult to meet increasingly stringent emission standards. Catalytic combustion has the problems of high energy consumption and high investment costs.

[0004] Therefore, a new solution is needed to address this problem. Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the purpose of this invention is to provide a printing steaming waste gas treatment system and process, which realizes the recovery and utilization of waste heat from waste gas, improves the waste gas purification effect, enables the resource reuse of spray wastewater, reduces treatment costs, and reduces the generation of solid waste through a new structural design.

[0006] The above-mentioned technical objective of the present invention is achieved through the following technical solution: a printing steaming waste gas treatment system, comprising a waste gas collection unit, a waste heat recovery unit, a waste gas purification unit and a wastewater treatment and reuse unit connected in sequence, and further comprising an intelligent control unit, wherein the intelligent control unit is electrically connected to the waste gas collection unit, the waste heat recovery unit, the waste gas purification unit and the wastewater treatment and reuse unit respectively, so as to realize full-process automated control; The input end of the exhaust gas collection unit is connected to the exhaust port of the steam generator, and its output end is connected to the waste heat recovery unit. The exhaust gas collection unit includes a gas collection hood, a guide pipe, and a pre-filter. The gas collection hood is made of high-temperature resistant and corrosion-resistant material and is sealed to the exhaust port of the steam generator. The guide pipe is equipped with a guide plate, and the pre-filter is filled with a metal filter screen to intercept fabric fiber debris in the exhaust gas and prevent fibers from entering subsequent units and causing blockage. The waste heat recovery unit is a gas-liquid heat exchanger. Its heat medium outlet is connected to the waste gas purification unit through an exhaust pipe. The exhaust pipe is equipped with an air volume regulating valve and a temperature sensor for real-time monitoring of waste gas flow and temperature. The cold medium inlet of the waste heat recovery unit is connected to the production process water pipeline, and its hot water outlet is connected to the production hot water storage tank. The production hot water storage tank is equipped with a temperature sensor and a liquid level sensor for storing the preheated process water and reusing it in the production process. A one-way valve is installed on the pipeline between the waste heat recovery unit and the production hot water storage tank to prevent hot water backflow. The exhaust gas purification unit is a spray tower, whose inlet is connected to the heat medium outlet of the waste heat recovery unit. The top of the spray tower is equipped with a demister to remove water mist from the purified exhaust gas. The bottom of the spray tower is equipped with a circulating water tank, which is connected to the spray layer at the top of the tower through a circulation pipeline to form a washing circulation loop. The circulation pipeline is equipped with a circulation pump and a flow regulating valve. The spray layer is equipped with multiple atomizing nozzles to atomize the washing water and increase the contact area between the exhaust gas and the washing water. The circulating water tank is equipped with an online pH monitor, an online COD monitor, and an automatic dosing device to monitor the pH value and COD concentration of the circulating water in real time and adjust them automatically. The wastewater treatment and reuse unit adopts a low-temperature vacuum evaporation system. Its wastewater input end is connected to the circulating water tank of the spray tower through a pipeline. The pipeline is equipped with a wastewater transfer pump and a solenoid valve. The distilled water output end of the low-temperature vacuum evaporation system is connected to a clean water storage tank. The outlet of the clean water storage tank is connected to the circulating water tank of the spray tower for replenishing water to the washing system. The clean water storage tank is equipped with a water quality monitoring sensor for monitoring the water quality of the distilled water. Its concentrated liquid output end is connected to an external collection device. The concentrated liquid output pipeline is equipped with a concentration sensor for monitoring the concentration of the concentrated liquid.

[0007] Preferably, the waste heat recovery unit is a plate heat exchanger. Its exhaust gas inlet is connected to the pre-filter of the exhaust gas collection unit, and its exhaust gas outlet is connected to the spray tower. Its heat medium inlet is connected to the production process water pipeline, and its heat medium outlet is connected to the production hot water storage tank. The exhaust gas channel of the plate heat exchanger is equipped with baffles to enhance the contact between the exhaust gas and the heat exchange medium and improve the heat exchange efficiency. Through heat exchange, the ambient temperature tap water can be preheated to 65-75℃ for use in the pretreatment water washing process. The waste heat recovery unit is also equipped with a waste heat backup recovery branch. One end of the waste heat backup recovery branch is connected to the heat medium outlet of the waste heat recovery unit, and the other end is connected to the steam heating system of the steam generator. This branch is used to reuse the waste heat that has not been fully recovered for the preheating of the steam generator, further improving the waste heat recovery utilization rate.

[0008] Preferably, the spray tower is a vertical countercurrent scrubbing tower, with a spray layer at the top and a packing layer in the middle. The packing layer is made of modified polypropylene and has a hydrophobic coating on its surface to prevent dyes and slurries from adhering and reduce clogging. The height of the packing layer is 1.5-2.5m. A circulating water tank is provided at the bottom, with a drain outlet at the bottom for periodically discharging precipitated impurities. The circulating water tank is also equipped with a stirring device, which is electrically connected to an intelligent control unit to fully mix the added chemicals with the circulating water, improving the neutralization effect and washing efficiency, while preventing impurities from settling and clumping.

[0009] Preferably, the low-temperature vacuum evaporation system of the wastewater treatment and reuse unit includes a vacuum evaporation kettle, a condenser, a vacuum pump, and a heat pump unit. The vacuum evaporation kettle is connected to a circulating water tank via a pipeline for extracting sprayed wastewater. The heat pump unit is connected to both the vacuum evaporation kettle and the condenser, providing an evaporation heat source and a condensation cold source. The heat pump unit is an air source heat pump with an energy efficiency ratio of 4.5 or higher. The outlet of the condenser is connected to a clean water storage tank. The condenser contains condenser tubes made of corrosion-resistant material.

[0010] Preferably, the intelligent control unit includes a PLC controller, a touch screen, and a data acquisition module. The data acquisition module is electrically connected to a temperature sensor, a liquid level sensor, a pH online monitor, a COD online monitor, a concentration sensor, an air volume regulating valve, a circulating pump, a wastewater transfer pump, a solenoid valve, an automatic dosing device, a heat pump unit, and a vacuum pump, respectively. It is used to collect the operating parameters of each unit and transmit the parameters to the PLC controller. The PLC controller automatically adjusts the operating status of each device according to preset parameters. The touch screen is used to display operating parameters and perform manual operations.

[0011] Preferably, the exhaust gas purification unit further includes an auxiliary purification component, which is disposed between the outlet of the spray tower and the chimney. The auxiliary purification component includes an activated carbon adsorption layer and a photocatalytic oxidation module. The activated carbon adsorption layer uses honeycomb activated carbon, and the photocatalytic oxidation module uses TiO2 photocatalyst. Through ultraviolet irradiation, the residual VOCs in the exhaust gas are oxidized and decomposed into harmless CO2 and H2O, further improving the exhaust gas purification effect.

[0012] A process for treating printing steaming waste gas, used to operate the aforementioned printing steaming waste gas treatment system, includes the following steps: S1: The exhaust gas emitted by the steamer at a temperature of 160-180℃ is collected by the gas collection hood of the exhaust gas collection unit and guided to the pre-filter through the guide pipe. The metal filter screen intercepts fabric fiber debris in the exhaust gas to prevent the fibers from entering the subsequent units and causing blockage. S2: The pre-treated waste gas is introduced into the plate heat exchanger of the waste heat recovery unit to exchange heat with the process makeup water at 20-25℃. The heat exchange effect is enhanced by the baffle plate. After the waste gas is cooled to 60-70℃, it enters the waste gas purification unit. After the process makeup water absorbs heat and is heated to 65-75℃, it is stored in the production hot water storage tank through a one-way valve for use in the pre-treatment washing process. The intelligent control unit monitors the temperature of waste gas and hot water in real time through temperature sensors and adjusts the flow rate of process makeup water to ensure stable heat exchange effect. When the heat exchange efficiency of the waste heat recovery unit is lower than 80%, the intelligent control unit issues an alarm signal. S3: The cooled exhaust gas enters from the bottom of the spray tower and comes into countercurrent contact with the washing water sprayed from the atomizing nozzles of the top spray layer. The gas reacts fully on the surface of the packing layer. The intelligent control unit monitors the pH value in the circulating water tank in real time through the pH online monitoring instrument and adds soda ash to adjust the pH value to 7.5-8.5 through the automatic dosing device to neutralize the acidic substances in the exhaust gas. The COD concentration of the circulating water is monitored in real time through the COD online monitoring instrument. When the COD concentration does not reach the preset value, the circulating water is recycled by the circulating pump. The particulate matter, slurry and some VOCs in the exhaust gas are captured by the washing water and fall into the circulating water tank at the bottom of the tower. The stirring device in the circulating water tank works continuously to ensure that the reagents and circulating water are fully mixed. After the purified exhaust gas passes through the top demister to remove water mist, it enters the auxiliary purification component. The residual VOCs are adsorbed by the activated carbon adsorption layer and then oxidized and decomposed by the photocatalytic oxidation module. Finally, it is discharged into the air through the chimney. S4: When the COD concentration of wastewater in the circulating water tank reaches 8000-12000 mg / L, the intelligent control unit automatically starts the wastewater treatment and reuse unit. The wastewater is pumped into the vacuum evaporator of the low-temperature vacuum evaporation system by the wastewater transfer pump. The vacuum pump draws the system pressure to -95 to -98 kPa. The heat pump unit provides the evaporation heat source for the vacuum evaporation kettle, maintaining the evaporation temperature at 35-45℃, and at the same time provides the condensation cold source for the condenser. The wastewater evaporates under vacuum, and the generated secondary steam is condensed by the condenser to form distilled water. After the distilled water passes the water quality monitoring sensor, it is stored in the clean water storage tank and used to replenish the circulating water tank of the spray tower. The concentrate in the evaporation kettle is monitored by the concentration sensor. When the concentrate is reduced to 8-10% of the original wastewater volume, it is transported to the external collection device or further dried through the concentrate output pipeline. S5: The intelligent control unit collects the operating parameters of each unit in real time through the data acquisition module and displays them on the touch screen. When the parameters exceed the preset range, it automatically issues an alarm signal and adjusts the operating status of the relevant equipment. It also periodically discharges the sedimented impurities through the drain outlet of the circulating water tank and periodically cleans the metal filter screen of the pre-filter, the atomizing nozzles of the spray layer, and the packing layer to ensure stable system operation.

[0013] Preferably, in step S2, the heat exchange efficiency of the waste heat recovery unit is ≥80%. When the temperature of the exhaust gas from the evaporator fluctuates, the intelligent control unit adjusts the opening of the air volume regulating valve to stabilize the exhaust gas flow and ensure the heat exchange effect. The waste heat backup recovery branch can be selectively opened according to the preheating requirements of the evaporator to reuse the unrecovered waste heat for the evaporator, further saving energy.

[0014] Preferably, in step S3, the liquid-to-gas ratio of the spray tower is controlled at 2-4 L / m³, the packing layer resistance is controlled at 800-1200 Pa, the flow rate of the circulating pump is adjusted by a flow regulating valve to ensure that the washing water and the exhaust gas are in full contact, the activated carbon adsorption layer in the auxiliary purification component is replaced regularly, with a replacement cycle of 3-6 months, and the ultraviolet lamps of the photocatalytic oxidation module are regularly inspected to ensure the oxidation and decomposition effect.

[0015] Preferably, in step S4, the heat pump efficiency ratio of the low-temperature vacuum evaporation system is above 4.5, the energy consumption is 80-120 kW·h per ton of wastewater evaporated, the COD concentration of the distilled water is controlled below 500 mg / L, and if the water quality test fails, the distilled water is sent back to the low-temperature vacuum evaporation system for further treatment to ensure that the recycled water quality meets the standards.

[0016] In summary, the present invention has the following beneficial effects: 1. By setting up a waste heat recovery unit, a plate heat exchanger is used to exchange heat between high-temperature steaming waste gas and low-temperature process water. The process water is heated and stored in a production hot water storage tank, which can be directly reused in the pretreatment water washing process. In addition, the waste heat backup recovery branch can introduce the waste heat that has not been fully recovered into the steam heating system of the steaming machine, so as to realize the cascade utilization of waste heat, reduce energy waste, and reduce the production cost of enterprises.

[0017] 2. The wastewater generated by the spraying is treated by a low-temperature vacuum evaporation system. The heat pump unit provides both evaporation heat source and condensation cold source, reducing energy consumption. After passing the water quality monitoring sensor in the clean water storage tank, the water is reused to make up for the spraying tower, realizing a closed-loop circulation of washing water. The volume of concentrated liquid is reduced to 8-10% of the original wastewater volume, reducing the amount of hazardous waste to be disposed of.

[0018] 3. The intelligent control unit integrates a PLC controller, touch screen, and data acquisition module to monitor key parameters such as temperature, liquid level, pH value, COD concentration, and concentrate concentration in real time. It also automatically adjusts the operating status of actuators such as air volume regulating valve, circulating pump, wastewater transfer pump, automatic dosing device, heat pump unit, and vacuum pump. The concentration sensor monitors the concentrate concentration in real time and automatically controls discharge when the set threshold is reached, achieving unattended fully automatic operation. When parameters exceed the preset range, the system automatically alarms and adjusts to ensure the stability and reliability of the entire treatment process. Attached Figure Description

[0019] Figure 1 This is a system diagram of the printing steaming waste gas treatment in this invention; Figure 2 This is a process diagram for treating printing steaming waste gas in this invention. Detailed Implementation

[0020] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0021] Example: A printing steaming waste gas treatment system, such as Figures 1-2 As shown, the system includes an exhaust gas collection unit, a waste heat recovery unit, an exhaust gas purification unit, a wastewater treatment and reuse unit, and an intelligent control unit. The intelligent control unit is electrically connected to each of the above units to achieve fully automated control of the entire process. The exhaust gas collection unit includes a gas collection hood, a guide pipe, and a pre-filter. The gas collection hood is made of high-temperature resistant and corrosion-resistant stainless steel and is sealed to the exhaust port of the evaporator to prevent exhaust gas leakage. The guide pipe is equipped with a guide plate to guide the exhaust gas to flow smoothly and reduce airflow resistance. The pre-filter is filled with a 300-mesh metal filter to intercept fabric fiber debris in the exhaust gas and prevent fibers from entering subsequent units and causing blockage. The metal filter is removable for easy cleaning and replacement. The waste heat recovery unit uses a gas-liquid plate heat exchanger. Its exhaust gas inlet is connected to the pre-filter, and its exhaust gas outlet is connected to the exhaust gas purification unit through an exhaust duct. The unit's spray tower is equipped with an airflow regulating valve and a temperature sensor in its exhaust duct to monitor the exhaust gas flow and temperature in real time. The plate heat exchanger's exhaust gas passage is equipped with baffles to enhance the contact between the exhaust gas and the heat exchange medium, improving heat exchange efficiency. Its cold medium inlet is connected to the production process water pipeline, which carries water at a temperature of 20-25℃. The hot water outlet is connected to a production hot water storage tank, which is equipped with a temperature sensor and a level sensor to monitor the hot water temperature and level. A one-way valve is installed on the pipeline between the production hot water storage tank and the plate heat exchanger to prevent hot water backflow. The waste heat recovery unit also has a waste heat backup recovery branch. One end of the waste heat backup recovery branch is connected to the heat medium outlet of the plate heat exchanger, and the other end is connected to the steam heating system of the steam generator, used to return insufficiently recovered waste heat to the steam generator for preheating.

[0022] like Figures 1-2As shown, the exhaust gas purification unit includes a spray tower, a circulating pump, an induced draft fan, a chimney, and auxiliary purification components. The spray tower is a vertical counter-current scrubbing tower with a spray layer at the top. Multiple atomizing nozzles within the spray layer atomize the scrubbing water, increasing the contact area between the exhaust gas and the scrubbing water. The middle section of the spray tower is filled with a 2.0m high layer of modified polypropylene packing material. The packing material surface has a hydrophobic coating to prevent dyes and slurries from adhering and reduce clogging. A circulating water tank is located at the bottom of the tower, with a drain outlet at the bottom for periodically discharging settled impurities. The circulating water tank is equipped with an online pH monitor and an online COD monitor. The system includes an instrument, an automatic dosing device, and a stirring device. The stirring device is electrically connected to the intelligent control unit to fully mix the agent with circulating water. The circulating water tank is connected to the spray layer via a circulating pump. A flow regulating valve is installed on the circulating pipeline to form a washing circulation loop. A demister is installed at the top of the spray tower to remove water mist from the purified exhaust gas. The auxiliary purification components are located between the outlet of the spray tower and the chimney, including an activated carbon adsorption layer and a photocatalytic oxidation module. The activated carbon adsorption layer uses honeycomb activated carbon, and the photocatalytic oxidation module uses TiO2 photocatalyst to oxidize and decompose residual VOCs in the exhaust gas through ultraviolet irradiation.

[0023] like Figures 1-2 As shown, the wastewater treatment and reuse unit includes a vacuum evaporator, a condenser, a vacuum pump, a heat pump unit, and a clean water storage tank. The vacuum evaporator is connected to a circulating water tank via a pipeline with a solenoid valve. A wastewater transfer pump is installed on the pipeline. The heat pump unit is an air source heat pump, connected to both the vacuum evaporator and the condenser, providing evaporation heat source and condensation cold source. The heat pump has an efficiency ratio of 4.5 or higher. The condenser is equipped with corrosion-resistant stainless steel condenser tubes. The outlet of the condenser is connected to the clean water storage tank. The clean water storage tank is equipped with a water quality monitoring sensor to monitor the quality of the distilled water. The clean water storage tank is connected to the circulating water tank of the spray tower via a water replenishment pump. The concentrated liquid output end of the vacuum evaporator is connected to an external collection device, which may be a concentrated liquid storage tank, a hazardous waste ton container, or a waste collection tank. A concentration sensor is installed on the concentrated liquid output pipeline to monitor the concentrated liquid concentration in real time and control the discharge of concentrated liquid when the concentration reaches a set upper limit threshold.

[0024] like Figures 1-2As shown, the intelligent control unit includes a PLC controller, a touch screen, and a data acquisition module. The data acquisition module is electrically connected to a temperature sensor, a level sensor, a pH online monitor, a COD online monitor, a concentration sensor, an airflow regulating valve, a circulating pump, a wastewater transfer pump, a solenoid valve, an automatic dosing device, a heat pump unit, a vacuum pump, and a stirring device. The temperature sensor monitors the exhaust gas temperature and water temperature; the level sensor monitors the liquid level in the production hot water storage tank and the circulating water tank; the pH online monitor monitors the pH value in the spray tower's circulating water tank; the COD online monitor monitors the COD concentration in the spray tower's circulating water tank; and the concentration sensor monitors the concentration of the concentrated liquid in the wastewater treatment and reuse unit. The temperature and air volume regulating valves are used to regulate the exhaust gas flow rate; the circulating pump is used for the spray tower circulating water system; the wastewater transfer pump is used to transport wastewater from the circulating water tank to the wastewater treatment unit; the solenoid valve is used to control the on / off of each pipeline; the automatic dosing device is used to automatically add chemicals to the circulating water tank; the heat pump unit is used for heating and cooling the low-temperature vacuum evaporation system; the vacuum pump is used to maintain the vacuum level of the vacuum evaporation system; the stirring device is used to mix the chemical solution in the circulating water tank; the PLC controller is used to collect the operating parameters of each unit and transmit the parameters to the PLC controller. The PLC controller automatically adjusts the operating status of each device according to the preset parameters; the touch screen is used to display the operating parameters and perform manual operation. When the parameters exceed the preset range, an alarm signal is automatically issued.

[0025] A process for treating printing steaming waste gas, such as Figures 1-2 As shown, the specific process steps for operating the above-mentioned printing steaming waste gas treatment system are as follows: S1: The exhaust gas temperature of the steaming machine in the printing workshop is 160-180℃, and the air volume is 8000-10000m³ / h. The exhaust gas contains dye particles, paste, VOCs, fabric fiber debris and a small amount of acidic volatiles. After the exhaust gas is collected by the gas collection hood of the exhaust gas collection unit, it is guided to the pre-filter through the guide pipe. The fabric fiber debris in the exhaust gas is intercepted by a 300-mesh metal filter screen. The interception efficiency must reach more than 98% to prevent the fibers from entering the subsequent units and causing blockage. The intercepted fibers are cleaned regularly and can be recycled and reused. S2: The pre-treated waste gas is introduced into the plate heat exchanger of the waste heat recovery unit, where it exchanges heat with process soft water at a temperature of 20-25℃. The baffles inside the plate heat exchanger enhance the contact between the waste gas and the soft water, improving the heat exchange effect. After heat exchange, the waste gas temperature drops to 60℃ and enters the subsequent spray tower. The soft water is heated to 65-75℃ and stored in a 30m³ production hot water storage tank via a one-way valve, directly used in the pre-treatment flat washing machine's washing section. The annual heat recovery is equivalent to more than 700 tons of steam, resulting in significant energy savings. The intelligent control unit monitors the temperature of the waste gas and hot water in real time through temperature sensors and adjusts the flow rate of the process water to ensure… The heat exchange efficiency is stable at over 80%. When the exhaust gas temperature of the steamer fluctuates, the opening of the air volume regulating valve is adjusted to stabilize the exhaust gas flow. One end of the waste heat backup recovery branch is connected to the heat medium outlet of the waste heat recovery unit, and the other end is connected to the steam heating system of the steamer through a three-way regulating valve. According to the feedback from the internal temperature sensor of the steamer, the intelligent control unit automatically opens the waste heat backup recovery branch when the temperature of the steamer is lower than the set preheating threshold, and introduces the cooled exhaust gas into the steam heating system of the steamer for preheating. After the steamer reaches the working temperature, the branch is closed, thereby realizing the cascade utilization of waste heat, reducing steam consumption, and further saving energy. S3: The cooled exhaust gas enters from the bottom of the spray tower and comes into countercurrent contact with the washing water sprayed through atomizing nozzles in the spray layer. The gas reacts fully on the surface of the packing layer. The intelligent control unit monitors the pH value in the circulating water tank in real time using an online pH monitor. An automatic dosing device adds soda ash to adjust the pH value to approximately 7.5-8.5, neutralizing the acidic substances in the exhaust gas. The stirring device in the circulating water tank continuously operates to ensure thorough mixing of the soda ash and circulating water, enhancing the neutralization effect. An online COD monitor tracks the COD concentration of the circulating water in real time. When the COD concentration does not reach the preset value, the circulating water is recycled using a circulating pump. The flow rate of the circulating pump is adjusted by a flow regulating valve, controlling the liquid-to-gas ratio at 2-4 L / m³ and the packing layer resistance at 8. At approximately 00-1200 Pa, lint, dye particles, slurry, and some VOCs in the exhaust gas are captured by the washing water and fall into the circulating water tank at the bottom of the tower. After the purified exhaust gas passes through the demister at the top of the tower to remove water mist, it enters the auxiliary purification component. The residual VOCs are adsorbed by the activated carbon adsorption layer, and then oxidized and decomposed into harmless CO2 and H2O by the photocatalytic oxidation module. Finally, it is sent into the chimney by the induced draft fan for emission. The emission concentration must meet the requirements of the "Emission Standard of Air Pollutants for Textile Dyeing and Finishing Industry" (DB33 / 962-2015) (particulate matter ≤10mg / m³, non-methane total hydrocarbons ≤20mg / m³). The activated carbon adsorption layer is replaced every 3-6 months, and the ultraviolet lamps of the photocatalytic oxidation module are inspected every 6 months to ensure the oxidation and decomposition effect.

[0026] S4: As the spray tower operates continuously, the COD concentration of the wastewater in the circulating water tank gradually increases. When the COD concentration reaches 8000-12000 mg / L, the intelligent control unit automatically starts the wastewater treatment and reuse unit. The wastewater is pumped into the vacuum evaporator of the low-temperature vacuum evaporation system via a wastewater transfer pump. The vacuum pump reduces the system pressure to -95 to -98 kPa. The heat pump unit provides the evaporation heat source for the vacuum evaporator, maintaining the evaporation temperature at around 35-45°C, while simultaneously providing the condenser with a cooling source. The wastewater evaporates under vacuum, and the resulting water vapor enters the condenser, where it is condensed into distillate by the condenser tubes. The COD removal rate of the water is ≥95%. The COD concentration of the distilled water is detected by a water quality monitoring sensor to be around 180-220 mg / L, which meets the reuse standard. After entering the clean water storage tank, it is recycled to the circulating water tank of the spray tower through a water replenishment pump, achieving near-zero wastewater discharge. The concentrate in the evaporation kettle is monitored by a concentration sensor. When the concentrate volume is reduced to 8-10% of the original wastewater volume, it is transported to an external collection device through the concentrate output pipeline and entrusted to a qualified unit for treatment. The heat pump energy efficiency ratio of the low temperature vacuum evaporation system is ≥4.5, and the energy consumption is 80-120 kW·h per ton of wastewater evaporated, which is low energy consumption.

[0027] S5: The intelligent control unit collects the operating parameters of each unit in real time through the data acquisition module, including temperature, liquid level, pH value, COD concentration, air volume, flow rate, etc., and displays them on the touch screen. Operators can monitor the system's operating status in real time. When parameters exceed the preset range, an alarm signal is automatically issued, and the operating status of related equipment is adjusted. For example, when the liquid level in the circulating water tank is too low, the water replenishment pump is automatically started to replenish water. The settled impurities are discharged through the drain outlet of the circulating water tank every month, and the metal filter screen of the pre-filter, the atomizing nozzles of the spray layer, and the packing layer are cleaned every two months to ensure stable system operation.

[0028] The above description is merely a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A printing steaming waste gas treatment system, comprising a waste gas collection unit, a waste heat recovery unit, a waste gas purification unit, a wastewater treatment and reuse unit, and an intelligent control unit electrically connected to each unit, characterized in that: The input end of the waste gas collection unit is connected to the exhaust port of the steam generator, and the output end is connected to the waste heat recovery unit. The waste heat recovery unit is a gas-liquid heat exchanger. The heat medium outlet of the waste heat recovery unit is connected to the waste gas purification unit, the cold medium inlet is connected to the production process water pipeline, and the hot water outlet is connected to the production hot water storage tank. The exhaust gas purification unit is a spray tower, whose air inlet is connected to the heat medium outlet of the waste heat recovery unit. The bottom of the exhaust gas purification unit is equipped with a circulating water tank, which is connected to the spray layer of the spray tower through a circulation pipeline. The wastewater treatment and reuse unit is a low-temperature vacuum evaporation system. The wastewater input end of the wastewater treatment and reuse unit is connected to a circulating water tank through a pipeline, and the distilled water output end is connected to a clean water storage tank. The outlet of the clean water storage tank is connected to the circulating water tank. The output end of the wastewater treatment and reuse unit is connected to an external collection device, which is used to temporarily store the high-concentration waste liquid remaining after evaporation of the wastewater treatment and reuse unit.

2. The printing steaming waste gas treatment system according to claim 1, characterized in that: The exhaust gas collection unit includes an exhaust hood, a flow guide pipe, and a pre-filter with a built-in metal filter screen. The waste heat recovery unit is a plate heat exchanger with a baffle plate in its exhaust gas channel. The waste heat recovery unit has a waste heat backup recovery branch, one end of which is connected to the heat medium outlet of the waste heat recovery unit and the other end is connected to the steam heating system of the steam generator.

3. The printing steaming waste gas treatment system according to claim 1, characterized in that: The spray tower is a vertical countercurrent scrubbing tower, with a modified polypropylene packing layer with a hydrophobic coating in the middle and a demister at the top. The circulating water tank is equipped with an online pH monitor, an online COD monitor, an automatic dosing device, and a stirring device electrically connected to the intelligent control unit. The bottom of the circulating water tank is equipped with a drain outlet.

4. The printing steaming waste gas treatment system according to claim 1, characterized in that: The exhaust gas purification unit also includes an auxiliary purification component disposed between the outlet of the spray tower and the chimney, the auxiliary purification component including an activated carbon adsorption layer and a photocatalytic oxidation module.

5. The printing steaming waste gas treatment system according to claim 1, characterized in that: The wastewater treatment and reuse unit includes a vacuum evaporator, a condenser, a vacuum pump, and a heat pump unit, with the heat pump unit connected to the vacuum evaporator and the condenser, respectively.

6. The printing steaming waste gas treatment system according to claim 1, characterized in that: The clean water storage tank is equipped with a water quality monitoring sensor, and the concentrated liquid output pipeline of the wastewater treatment and reuse unit is equipped with a concentration sensor. The intelligent control unit includes a PLC controller, a touch screen and a data acquisition module, and the data acquisition module is electrically connected to the sensors and actuators of each unit.

7. A process for treating printing steaming waste gas, used to operate the printing steaming waste gas treatment system according to any one of claims 1-6, characterized in that, Includes the following steps: S1: The exhaust gas at 160-180℃ discharged from the steamer is collected by the exhaust gas collection unit, and the fabric fiber debris in the exhaust gas is intercepted by the pre-filter. S2: The pretreated waste gas is introduced into the waste heat recovery unit and exchanged with the 20-25℃ process water output from the production process water pipeline to reduce the waste gas temperature to 60-70℃. After the process water is heated to 65-75℃, it is stored in the production hot water storage tank for reuse. S3: The cooled exhaust gas enters the spray tower and comes into countercurrent contact with the washing water. The pH value of the circulating water in the spray tower is adjusted to 7.5-8.5 by the automatic dosing device. The purified exhaust gas is discharged after demisting and auxiliary purification. S4: When the COD concentration of wastewater in the circulating water tank reaches 8000-12000 mg / L, the wastewater treatment and reuse unit is started. Evaporation is carried out under vacuum conditions of -95 to -98 KPa and temperature of 35-45℃. The resulting distilled water is used for spray replenishment, and the concentrated liquid is temporarily stored in an external collection device. S5: The intelligent control unit monitors and automatically adjusts the operating parameters of each unit in real time.

8. The printing steaming waste gas treatment process according to claim 7, characterized in that: In step S2, the process water flow and waste gas flow are adjusted by the intelligent control unit, the heat exchange efficiency is ≥80%, and the waste heat backup recovery branch can be selectively opened to reuse the waste heat for preheating of the steaming machine.

9. The printing steaming waste gas treatment process according to claim 7, characterized in that: In step S3, the liquid-to-gas ratio of the spray tower is controlled at 2-4 L / m³, the packing layer resistance is controlled at 800-1200 Pa, and the VOCs removal rate is ≥90%.

10. The printing steaming waste gas treatment process according to claim 7, characterized in that: In step S4, the heat pump energy efficiency ratio (COP) reaches 4.5 or higher, the energy consumption is 80-120 kW·h per ton of wastewater evaporated, the COD removal rate of distilled water is ≥95%, the volume of concentrated liquid is reduced to 8-10% of the original wastewater volume, and the distilled water is reused after passing water quality testing; otherwise, it is reprocessed.

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