A setting machine oil fume waste gas treatment system and process based on thermal energy gradient recovery and TO furnace

Abstract

The application discloses a setting machine oil fume waste gas treatment system and process based on thermal energy gradient recovery and TO furnace, and belongs to the field of textile printing and dyeing waste gas treatment and waste heat recovery technology. The setting machine oil fume waste gas treatment system and process based on thermal energy gradient recovery and TO furnace comprises a setting machine, a TO furnace, a plate heat exchanger, a spray tower and a tubular heat exchanger. Three subsystems are formed, namely, a waste gas shunting and treatment subsystem, a heat pump and latent heat recovery subsystem and an air preheating and blowing subsystem. The setting machine is divided into a front section, a middle section and a tail section along the fabric advancing direction, and the three sections respectively form oven sections. The setting machine oil fume waste gas treatment system and process realizes gradient recovery and utilization of different grade thermal energy from high-temperature incineration flue gas to low-temperature spray water, and simultaneously ensures that waste gas purification reaches a standard discharge and that the system is long-term stable.

Description

Technical Field

[0001] This invention belongs to the field of textile printing and dyeing waste gas treatment and waste heat recovery technology. More specifically, it relates to a stenter oil fume waste gas treatment system and process based on heat energy cascade recovery and TO furnace. Background Technology

[0002] Textile setting machines are the core equipment for fabric finishing. Their working principle is to stretch and set the fabric containing finishing agents in a high-temperature (170~230℃) oven. During the setting process, organic substances such as spinning oil and finishing auxiliaries on the fabric surface volatilize at high temperatures, generating a large amount of oily fumes. The main characteristics of this fumes are: high temperature, high moisture content, and the presence of oily components such as mineral oil and organosilicon, as well as fiber dust. It is a typical high-temperature, high-humidity, dusty, and oily industrial fumes.

[0003] Currently, the main methods for treating stenter oil fume exhaust gas include single processes or simple combinations thereof, such as electrostatic adsorption, spray washing, activated carbon adsorption, and biological methods. Electrostatic adsorption is prone to failure due to short circuits caused by oil buildup; spray washing has limited efficiency in removing fine oil mist and generates large amounts of wastewater; activated carbon adsorption has high operating costs and is difficult to regenerate; in terms of incineration, while sending stenter oil fume exhaust gas into a TO furnace for high-temperature incineration can achieve complete decomposition of organic matter, it also involves the consumption of high-grade heat energy; regarding heat recovery, the common practice in existing technologies is to use gas-to-gas heat exchangers to recover exhaust heat for preheating fresh air; however, the oil and dust content of stenter exhaust gas easily leads to scaling on the heat exchanger surface, increasing thermal resistance, drastically reducing heat exchange efficiency, and posing a fire hazard.

[0004] It is impossible to effectively recover the large amount of heat energy carried in the exhaust gas, and it is also impossible to achieve the tiered utilization of heat energy of different grades. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a stenter oil fume exhaust gas treatment system and process based on heat energy cascade recovery and TO furnace. It can realize the cascade recovery and utilization of heat energy of different grades from high-temperature incineration flue gas to low-temperature spray water, while ensuring that the exhaust gas is purified to meet emission standards and that the system operates stably for a long time.

[0006] The present invention discloses a stenter oil fume exhaust gas treatment system based on heat energy cascade recovery and TO furnace, which includes a stenter, TO furnace, plate heat exchanger, spray tower and tubular heat exchanger; forming three subsystems, namely an exhaust gas diversion and treatment subsystem, a heat pump and latent heat recovery subsystem and an air preheating and air supply subsystem; the stenter is divided into a front section, a middle section and a tail section along the fabric travel direction, which respectively form the drying oven section;

[0007] The exhaust gas diversion and treatment subsystem includes parallel front-end diversion branches, middle-end diversion branches, and rear-end diversion branches, used to independently treat the exhaust gas generated in each section of the stenter. In the front-end diversion branch, the exhaust gas from the front section is cooled by heat release through a plate heat exchanger before entering the spray tower for circulating water spraying and cooling. In the middle-end diversion branch, the exhaust gas from the middle section is led out and sent to the TO furnace for incineration to form combustion flue gas. In the rear-end diversion branch, the exhaust gas from the rear section directly enters the spray tower for spraying and cooling.

[0008] The heat pump and latent heat recovery subsystem includes an extraction loop and a recovery loop for heat recycling from the spray tower and tubular heat exchanger. The extraction loop extracts low-grade heat energy from the circulating water of the spray tower. The recovery loop collects the circulating water at the bottom of the spray tower, cools it down by heat exchange, and then sends it back to the top spray exhaust gas. The exhaust gas comes into contact with the spray water and mixes heat, thus cooling the exhaust gas.

[0009] The air preheating and air supply subsystem includes a mixing main circuit and air supply branch circuits, which are used to deliver preheated air to the corresponding oven sections according to the demand. Fresh air enters the cold side of the plate heat exchanger and is heated by the exhaust gas in the front section to form preheated air. The combustion flue gas in the middle section is mixed with the preheated air to obtain the air supply mixture. The air supply mixture is distributed into three streams according to the target temperature requirements of the front, middle and rear sections, and sent to the corresponding oven sections respectively.

[0010] As a further improvement of the present invention, the setting machine is a through-type oven with an airflow isolation device between adjacent sections; air inlets are provided on the sides of the front section, middle section and tail section, and the two ends of the setting machine are the fabric inlet and the fabric outlet, respectively. The fabric inlet is located on the left side of the setting machine and the fabric outlet is located on the right side of the setting machine.

[0011] As a further improvement of the present invention, the plate spacing on the flue gas side of the plate heat exchanger is not less than 15 mm; a metal fiber filter is installed at the flue gas inlet to intercept fibers and larger particle size oil mist in the exhaust gas; and steam at 0.3~0.5 MPa is periodically introduced to clean the heat exchange plates.

[0012] As a further improvement of the present invention, a multi-layer spraying device is installed inside the spray tower. An external water source is supplied into the spray tower, and circulating water is sprayed evenly from the top of the tower, where it comes into countercurrent contact with the exhaust gas entering from the bottom of the tower for heat exchange. A heat exchange tube is installed in the middle of the spray tower as an evaporator, and the tube side of the tubular heat exchanger serves as a condenser. A compressor and a throttling valve are installed between the spray tower and the tubular heat exchanger. The heat pump working fluid absorbs heat from the spray circulating water on the evaporation side and evaporates into low-pressure steam. After being compressed and heated by the compressor, it enters the condensation side to release heat and condense, thus completing the extraction loop. After being depressurized by the throttling valve, it returns to the evaporation side to complete the cycle, thus completing the recovery loop.

[0013] As a further improvement of the present invention, it also includes an electrostatic precipitator; the spray exhaust gas from the spray tower enters the electrostatic precipitator, which is a wet electrostatic precipitator, using corrosion-resistant electrode materials and equipped with insulator anti-creep protection.

[0014] As a further improvement of the present invention, an oil-water separation and filtration device is provided at the bottom of the spray tower, and the liquid water generated by condensation is recycled for spray tower makeup water; the oil-water separation and filtration device includes an inclined plate oil-water separator and a multi-media filter.

[0015] As a further improvement of the present invention, the heat exchange tubes are made of stainless steel or titanium, and are arranged in a serpentine or spiral shape in the middle of the spray tower.

[0016] As a further improvement of the present invention, the temperatures of the three air streams in the air supply branch are respectively 210~220℃ in the front section, 220~230℃ in the middle section, and 210~230℃ in the tail section.

[0017] As a further improvement of the present invention, each section of the oven is equipped with an auxiliary heater on its pipeline. The auxiliary heater is a natural gas burner or an electric heater. When the air-fuel mixture enters the corresponding pipeline, if the actual temperature of a certain section is insufficient to meet the target temperature requirement of that section, the auxiliary heater installed on the corresponding pipeline will supplement the temperature to the target temperature.

[0018] A process for treating oil fume exhaust gas from a stenter based on heat energy cascade recovery and a TO furnace, which is implemented based on a stenter oil fume exhaust gas treatment system based on heat energy cascade recovery and a TO furnace, includes steps S1-S4.

[0019] Step S1: The high-concentration oily fume exhaust gas discharged from the middle section of the stenter is sent into the TO furnace at a flow rate of 2500~3500 Nm³ / h, and the furnace temperature is maintained at 780~820℃ using natural gas as fuel; the exhaust volume is adjusted by a variable frequency fan.

[0020] Step S2: The high-humidity, low-concentration oily fume exhaust gas with a temperature of 170~190℃ discharged from the front section of the stenter is sent to the hot side of the plate heat exchanger at a flow rate of 2500~3500 Nm³ / h to release heat and cool it to 90~110℃, and then sent to the spray tower with internal heat exchanger tubes; the low-concentration oily fume exhaust gas discharged from the tail section of the stenter is directly sent to the spray tower for spray cooling at a flow rate of 2500~3500 Nm³ / h; the exhaust volume of the front, middle and tail sections all include the natural air volume that seeps into the drying oven through the side air inlet and the fabric inlet and outlet at both ends. The seeping air is distributed to each drying oven section under the action of a slight negative pressure and is discharged in an organized manner with the exhaust of each section; the exhaust gas is sprayed and cooled to 40~50℃ by circulating water in the spray tower. During the spraying process, water vapor is condensed and released. The latent heat released by condensation is absorbed by the circulating water. After that, it is sent to the electrostatic precipitator to remove oil mist and form purified gas for discharge.

[0021] Step S3: Extract low-grade heat energy from the spray water at a temperature of 40~50℃ in the spray tower. The extracted heat includes the sensible heat of the waste gas and the latent heat of water vapor condensation. Heat 3000~5000 Nm³ / h of fresh air to 55~80℃, and then further heat it to 80~110℃ by the waste gas in the previous stage of step S2 on the cold side of the plate heat exchanger to form preheated air.

[0022] Step S4: Mix the flue gas discharged from the TO furnace with the preheated air from step S3 to obtain a supply air mixture with a flow rate of 5500~8500 Nm³ / h and a temperature of 280~420℃; the supply air mixture is divided into three streams according to the target temperature requirements of the front section, middle section and tail section: 210~220℃ for the front section, 220~230℃ for the middle section and 210~230℃ for the tail section, and sent to the corresponding oven sections respectively.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] 1. By setting up a waste gas diversion and treatment subsystem, the waste gas is treated separately according to the spatial distribution differences in the concentration and moisture content of the waste gas in the three-stage drying oven of the stenter. The high-concentration waste gas in the middle stage is sent to the TO furnace for incineration, and its calorific value is used to heat the air. The high-moisture waste gas in the front stage is sprayed after gas-to-gas heat exchange. The self-condensation rinsing effect cools the waste gas, causing some of the supersaturated water vapor in it to condense. The condensate droplets adhere to the surface of the heat exchange plate and flow down the plate surface, which produces an auxiliary wetting and partial scouring effect on the heat exchange surface, which can slow down the deposition rate of oil fume particles on the heat exchange surface to a certain extent. The low-concentration waste gas in the tail stage is directly sprayed to reduce the scaling load of the heat exchanger.

[0025] 2. By setting up a heat pump and latent heat recovery subsystem, high-grade flue gas is directly used to heat the supply air mixture, medium-grade front-end exhaust gas is preheated to fresh air through gas-to-gas heat exchange, and low-grade spray water heat energy is upgraded by the heat pump to heat fresh air; the latent heat of water vapor condensation is effectively recovered and utilized. In the spray tower, the exhaust gas is sprayed by circulating water to cool down to 40~50℃. During this process, the water vapor in the exhaust gas condenses and precipitates as the temperature drops below the dew point. The large amount of latent heat released by condensation is absorbed by the circulating water. At the same time, the spray water also plays a role in washing and removing residual oil mist and dust in the exhaust gas.

[0026] 3. By setting up an air preheating and air supply subsystem, the target air supply temperature of each section can be determined according to the fabric type and process requirements, making the air supply temperature more accurate. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the overall structure of the present invention;

[0028] Figure 2 This is a schematic diagram of the waste gas diversion and treatment subsystem of the present invention;

[0029] Figure 3 This is a schematic diagram of the structure of the heat pump and latent heat recovery subsystem of the present invention;

[0030] Figure 4 This is a schematic diagram of the air preheating and air supply subsystem of the present invention;

[0031] Figure 5 This is a schematic diagram of the process flow of the present invention.

[0032] Explanation of the labels in the diagram:

[0033] 1. Stenter 2. TO furnace 3. Plate heat exchanger 4. Spray tower 5. Electrostatic demister 6. Compressor 7. Tubular heat exchanger 8. Throttling valve 9. Front section 10. Middle section 11. Tail section 12. Air inlet 13. Fabric inlet 14. Fabric outlet 15. Heat exchange tube 16. Heat exchange tube 41. Detailed Implementation

[0034] Specific Implementation Example 1: Please refer to... Figures 1-4 A stenter oil fume exhaust gas treatment system based on heat energy cascade recovery and TO furnace, comprising a stenter 1, a TO furnace 2, a plate heat exchanger 3, a spray tower 4, an electrostatic demister 5, a compressor 6, a tubular heat exchanger 7, and a throttling valve 8.

[0035] Setting machine 1 is a through-type drying oven, along the fabric travel direction ( Figure 1 The oven is divided into three sections (from left to right): front section 11, middle section 12, and rear section 13, which together form the oven section. Airflow isolation devices, such as air curtains or partitions, are installed between adjacent sections to reduce cross-flow between sections.

[0036] Air inlets 14 are provided on the sides of the front section 11, middle section 12 and tail section 13 of the setting machine 1. The two ends of the setting machine 1 are the fabric inlet 15 and the fabric outlet 16, respectively. The fabric inlet 15 is located on the left side of the setting machine 1, and the fabric outlet 16 is located on the right side of the setting machine 1.

[0037] Preferably, during the operation of the stenter 1, some ambient temperature air (approximately 20-30°C) naturally infiltrates into the interior of the stenter 1 through the side air inlet 14 and the fabric inlets and outlets at both ends, participates in the hot air circulation of each section, and is then discharged through the exhaust system. The flow rate of this naturally infiltrated air is related to factors such as the fabric type, machine speed, and the internal and external pressure difference of the stenter 1, and the flow rate can be adjusted by the adjustable louvered damper of the air inlet 14. At the same time, air curtain devices are respectively installed at the front section 11 near the fabric inlet 15 and the tail section 13 near the fabric outlet 16, using high-speed airflow to form an air curtain barrier to reduce the amount of uncontrolled air infiltration at the fabric inlets and outlets.

[0038] It consists of three subsystems: a waste gas diversion and treatment subsystem, a heat pump and latent heat recovery subsystem, and an air preheating and supply subsystem. The waste gas diversion and treatment subsystem includes parallel front-end diversion branches, middle-end diversion branches, and rear-end diversion branches, which independently treat the waste gas generated in each section of the stenter 1.

[0039] The front-end branch is used to treat the exhaust gas generated in the front-end 11. The exhaust gas in the front-end 11 passes through the plate heat exchanger 3, where it is cooled and then enters the spray tower 4 for spray cooling. The front-end 11 is the area where the fabric just enters the stenter 1. Due to the evaporation of a large amount of moisture in the wet fabric, the exhaust gas in the front-end has a high moisture content (usually 150~250 g / kg dry air) and a temperature of about 170~190℃, while the oil fume concentration is low (usually 10~30 mg / Nm³). Therefore, the exhaust gas generated in the front-end 11 is high-humidity, low-oil-fume-concentration exhaust gas. The exhaust gas is first fed into the hot side of the plate heat exchanger 3 at a flow rate of 2500~3500 Nm³ / h, transferring heat to the fresh air on the cold side before its own temperature drops to 90~110℃. During the passage of the exhaust gas through the plate heat exchanger 3, its high moisture content has a positive effect: the cooling of the exhaust gas causes partial condensation of the supersaturated water vapor. The condensate droplets adhere to the surface of the heat exchange plates and flow down the plates, providing auxiliary wetting and partial scouring of the heat exchange surface, which can, to some extent, slow down the deposition rate of oil fume particles on the heat exchange surface. In this embodiment, the plate heat exchanger 3 is a gas-to-gas plate heat exchanger.

[0040] It should be noted that the mineral oil and silicone oil components in the fumes of the stenter 1 are hydrophobic, and the condensate tends to condense into beads when it comes into contact with oily dirt. The rinsing effect is affected by the surface hydrophilicity and the thickness of the oil stains. Preferably, the plate heat exchanger 3 has a large plate spacing and is equipped with a metal fiber filter in front, which can be periodically purged with steam to prevent scaling.

[0041] Furthermore, the plate spacing on the flue gas side (exhaust gas side of the front section 11) of the plate heat exchanger 3 is not less than 15 mm (significantly greater than the conventional 6~10 mm plate spacing); a metal fiber filter (filtration accuracy 50~100μm) is installed at the flue gas side inlet to intercept fibers and larger particle size oil mist in the exhaust gas; steam at 0.3~0.5 MPa can be periodically introduced to clean the heat exchange plates.

[0042] The middle section branch is used to treat the waste gas generated in the middle section 12. The waste gas in the middle section 12 is led out through the middle section 12 and sent to the TO furnace 2 for incineration to form incineration flue gas. The exhaust volume of the middle section can be adjusted by a variable frequency fan according to the process requirements.

[0043] Section 12 is the area where the fabric heats up most intensely and oil volatilizes most readily within the setting machine 1. It produces the highest concentration of oil fumes in its exhaust gas (typically 50-200 mg / Nm³) at a moderate temperature (170-190℃). This exhaust gas is separately drawn out through the section's exhaust duct and, driven by a variable frequency fan, fed into the TO furnace 2 at a flow rate of 2500-3500 Nm³ / h for high-temperature combustion. The TO furnace 2 receives natural gas from the outside and uses it as auxiliary fuel to maintain the furnace temperature at 780-820℃ (natural gas consumption is 15-30 Nm³ / h, based on the lower calorific value of natural gas 35.9 MJ / Nm³). Under high-temperature, aerobic conditions, the organic matter in the oil fumes is completely oxidized and decomposed into CO2 and H2O. Because the oil mist components in the fumes have a certain calorific value, they can partially replace natural gas consumption after combustion. The combustion flue gas temperature is 780-820℃.

[0044] The tail section branch is used to treat the exhaust gas generated in the tail section 13; the exhaust gas in the tail section 13 directly enters the spray tower 4 of the internal heat exchanger 41 for spray cooling, and the exhaust gas in the tail section 11 bypasses the plate heat exchanger 3 to reduce its flue gas side flow and scaling tendency.

[0045] The fabric in the tail section 13 has basically completed drying and setting. The oil fume concentration in the exhaust gas in this section is relatively low (usually 5~15 mg / Nm³), and the temperature is about 130~160℃. The exhaust gas in this section is directly sent to the spray tower 4 with internal heat exchange tubes at a flow rate of 2500~3500 Nm³ / h for spray cooling, without passing through the plate heat exchanger 3. This reduces the overall flow rate on the flue gas side of the plate heat exchanger 3 and lowers the fouling rate on the heat exchange surface. At the same time, the exhaust gas in the tail section 11 has a relatively low moisture content and is not suitable as a high-humidity gas source required for self-condensation rinsing in the plate heat exchanger 3.

[0046] The exhaust volumes of the aforementioned front section 11, middle section 12, and rear section 13 all include the natural air intake volume that seeps into the setting machine 1 through the side air inlet 14 and the fabric inlets and outlets at both ends. The infiltrated air is distributed to each drying section under a slight negative pressure and is discharged with each section. The sensible heat absorbed by this part of the air as it is heated from room temperature (20~30℃) to exhaust temperature (130~190℃) enters the heat pump and latent heat recovery subsystem with the exhaust air.

[0047] The spray exhaust gas from the spray tower 4 enters the electrostatic precipitator 5, which is a wet electrostatic precipitator. It uses corrosion-resistant electrode materials and is equipped with insulator anti-creep protection. After removing oil mist and water droplets, it forms purified gas that is discharged into the air.

[0048] The spray tower 4 is equipped with a multi-layer spray system. An external water source is supplied to the spray tower 4, and the circulating water is sprayed evenly from the top of the tower, interacting counter-currently with the exhaust gas entering from the bottom of the tower for heat exchange. The exhaust gas is cooled to 40~50℃ by the circulating water spray. During this process, the water vapor in the exhaust gas (mainly from the high moisture content of the exhaust gas in the preceding stage) condenses and precipitates as the temperature drops below the dew point. The large amount of latent heat released by condensation is absorbed by the circulating water. At the same time, the spray water also washes and removes residual oil mist and dust in the exhaust gas. The sprayed exhaust gas (temperature 40~50℃, close to saturation) is discharged from the top of the tower and enters the wet electrostatic precipitator 5.

[0049] The wet electrostatic precipitator 5 uses corrosion-resistant electrode materials (such as 316L stainless steel or conductive glass fiber reinforced plastic) and is equipped with hot air protection or electric heating protection devices in the insulator area to prevent condensation and creepage on the insulator surface in a saturated humid environment. Under the action of high-voltage electrostatics, fine oil mist droplets and water mist droplets in the exhaust gas are efficiently captured, and the purified gas is discharged into the atmosphere through the exhaust stack after meeting the emission standards.

[0050] The heat pump and latent heat recovery subsystem includes an extraction loop and a recovery loop, which circulate and recover heat from the spray tower 4 and the tubular heat exchanger 7. The heat exchange tube 41 located in the middle of the spray tower 4 serves as the evaporator (heat absorption side) of this subsystem, and the tube side of the tubular heat exchanger 7 serves as the condenser (heat release side) of the subsystem. The heat pump working fluid (such as medium- and high-temperature heat pump working fluids such as R134a, R245fa, or R1233zd(E)) absorbs heat from the spray circulating water on the evaporation side and evaporates into low-pressure vapor. After being compressed and heated by the compressor 6, it enters the condensation side to release heat and condense, thus completing the extraction loop. After being depressurized by the throttling valve 8, it returns to the evaporation side to complete the cycle, thus completing the recovery loop.

[0051] In the extraction loop, the heat pump system extracts low-grade heat energy from the circulating water at a temperature of 40~50℃ in the spray tower 4. The extracted heat includes the sensible heat released by the cooling of waste gas and the latent heat released by the condensation of water vapor. The extracted heat is heated to 55~80℃ by the tubular heat exchanger 7, and the fresh air enters from one side of the tubular heat exchanger 7.

[0052] In the recovery loop, circulating water collects at the bottom of the spray tower 4 and is pumped back to the top of the spray tower 4 for spraying. The spray liquid first exchanges heat with the heat exchange tube 41 to cool down to 35~40℃ before falling and contacting the incoming waste gas for heat exchange, cooling the waste gas and causing the water vapor in the waste gas entering the spray tower 4 to condense and precipitate. The sensible heat released by the cooling of the waste gas and the latent heat released by the condensation of water vapor are both absorbed by the circulating water and transferred to the heat pump system. Preferably, the bottom of the spray tower 4 is equipped with an oil-water separator and filter device, and the liquid water generated by condensation is recycled for the makeup water of the spray tower 4. At the same time, a periodic drain outlet is provided to discharge the accumulated pollutants.

[0053] Specifically, the oil-water separation and filtration device includes an inclined plate oil-water separator and a multi-media filter (such as a dual-layer filter media of quartz sand and activated carbon). Before returning to the spraying process, the circulating water first passes through the inclined plate oil-water separator to remove floating and dispersed oil, and then passes through the multi-media filter to remove suspended solids and some dissolved organic matter. The oil content of the treated circulating water is less than 5 mg / L. Excess liquid water generated during the spraying process due to the condensation of water vapor in the exhaust gas is treated in the same way and reused as makeup water for the spraying tower, achieving near-zero water discharge. Preferably, to address the long-term accumulation of dissolved organic matter and salts in the circulating water, the spraying tower 4 is equipped with a periodic sewage discharge pipeline, with a sewage discharge cycle of 8~24 hours / time (adjusted according to water quality monitoring results), and the sewage discharge volume is approximately 1%~3% of the total circulating water volume.

[0054] It should be noted that the circulating water temperature at the bottom of the spray tower 4 is 40~50℃, which is only 10~30℃ higher than the ambient temperature of 20~30℃. This is typical low-grade heat energy, which is difficult to utilize directly without heat pump upgrading. The heat pump system consumes a small amount of electricity to drive the compressor 6, effectively extracting heat from this low-grade heat source. The extracted heat and the heat converted from the electrical work of the compressor 6 are released together on the condenser side to heat the fresh air flowing through the air side of the tubular heat exchanger 7. In this embodiment, the tubular heat exchanger 7 is a finned tube heat exchanger.

[0055] Preferably, the heat exchange tube 41 is made of stainless steel (304 or 316L) or titanium, either as a smooth tube or a finned tube, and is arranged in a serpentine or spiral shape in the middle of the spray tower 4. The heat pump working fluid flows inside the heat exchange tube 41, and its outer surface is continuously washed by the spray water from top to bottom during the operation of the spray tower 4. Therefore, compared with traditional immersion heat exchangers, the externally sprayed heat exchange tube 41 of this invention is less prone to accumulating oil and dirt on its surface, and its heat transfer performance can remain stable over a long period. Simultaneously, the spray liquid is first cooled to 35-40°C after passing through the heat exchange tube 41 section, and then falls into the lower gas-liquid contact section to transfer heat and mass with the exhaust gas. This increases the temperature difference between the spray liquid and the exhaust gas, improving heat transfer and condensation efficiency.

[0056] For example, under heat pump design conditions, the evaporation temperature is approximately 30~40℃, the condensation temperature is approximately 65~85℃, and the heating COP reaches 4.0~5.5 (i.e., consuming 1 unit of electrical work yields 4.0~5.5 units of heat). Taking an intermediate operating condition (heating 3000~5000 Nm³ / h of fresh air from 20℃ to 70℃), the heat pump system can recover approximately 120~180 kW of low-temperature waste heat from the spray water, with the compressor power consumption being approximately 25~40 kW.

[0057] For example, the condensate balance of the spray tower is calculated. The initial exhaust gas flow rate is 1000 Nm³ / h, with a moisture content of 200 g / kg dry air (approximately 1290 kg dry air / h). The final exhaust gas flow rate is 1250 Nm³ / h, with a moisture content of approximately 60 g / kg dry air (approximately 1615 kg dry air / h). The total amount of dry air entering the spray tower is approximately 2905 kg / h, and the amount of water vapor introduced is approximately 355 kg / h. The exhaust gas is cooled to 45℃ (near saturation, with a saturated moisture content of approximately 65 g / kg dry air) inside the spray tower. The amount of water vapor carried by the exhaust gas exiting the tower is approximately 2905 × 0.065 ≈ 189 kg / h. The amount of liquid water condensed is approximately 355 - 189 = 166 kg / h. When the moisture content of the exhaust gas fluctuates due to changes in fabric type or machine speed, the amount of condensate changes accordingly. The system automatically adjusts this through a liquid level sensor and a water supply valve.

[0058] The air preheating and air supply subsystem includes a mixing main circuit and air supply branch circuits, which are used to deliver preheated air into the corresponding oven sections according to demand.

[0059] First, fresh air is heated to 55~80℃ by the tubular heat exchanger 7 and then enters the cold side of the plate heat exchanger 3. It is further heated to 80~110℃ by the high humidity exhaust gas in the front section 11 of the stenter 1 to form preheated air. Second, the combustion flue gas (780~820℃) discharged from the TO furnace 2 is mixed with the preheated air and cooled to form a supply air mixture, which constitutes the general mixing path. Finally, the supply air mixture is divided into three streams and, by adjusting the air volume, is sent to the corresponding oven sections according to the target temperature requirements of the front section 11, the middle section 12 and the tail section 13, so as to form supply air branches.

[0060] The air supply path (280~420℃) is divided into three streams, which are respectively supplied to the front section 11, middle section 12, and rear section 13 of the stenter. Specifically, the air volume distribution of each stream is achieved through regulating air valves installed on each air supply branch pipe. The target air supply temperature for each section depends on the fabric type and process requirements; typically, it is 210~220℃ for the front section, 220~230℃ for the middle section, and 210~230℃ for the rear section.

[0061] Specifically, fresh outside air (approximately 20-30°C, 3000-5000 Nm³ / h) first flows through the air side of the finned tube heat exchanger 7 and is heated to 55-80°C by the condenser side of the heat pump system (primary preheating). Subsequently, the preheated air enters the cold side channel of the plate heat exchanger 3 and undergoes air-to-air heat exchange with the high-temperature exhaust gas (170-190°C) from the front section 11 of the stenter, and is further heated to 80-110°C (secondary preheating), forming preheated air. This two-stage preheating process achieves a gradient temperature increase from low-grade heat pump heat energy to medium-grade sensible heat from the exhaust gas.

[0062] For example, after mixing 1800 Nm³ / h of incineration flue gas (800℃) with 3600 Nm³ / h of preheated air (at a 1:2 ratio, 100℃), the mass-weighted method (considering the difference in specific heat capacity of air at different temperatures) is used for calculation: the mass flow rate of incineration flue gas is approximately 1800 × 1.293 ≈ 2327 kg / h, and the mass flow rate of preheated air is approximately 3600 × 1.293 ≈ 4655 kg / h; taking the isobaric specific heat capacity of air at 800℃ as approximately 1.14 kJ / (kg·K) and the isobaric specific heat capacity of air at 100℃ as approximately 1.01 kJ / (kg·K), the mixing temperature is approximately... (2327×1.14×800+4655×1.01×100) / (2327×1.14+4655×1.01)≈353℃;

[0063] If a 1:2.5 mixing ratio is used (1600 Nm³ / h of incineration flue gas and 4000 Nm³ / h of preheated air at 100℃), the calculated mixing temperature using the same method is approximately 318℃, falling within the range of 280~420℃. This temperature range is higher than the target temperatures of each section of the oven, providing a temperature margin for dilution and cooling by infiltrating ambient temperature air, while maximizing the utilization of the thermal energy of the high-grade incineration flue gas.

[0064] Preferably, each section of the setting machine 1 oven is equipped with a circulating fan. The fresh supply air mixed with the existing circulating hot air in the oven mixes to form a circulating airflow much larger than the fresh air volume. This airflow is then blown at high speed through upper and lower nozzles to both sides of the fabric for convective heat transfer. Only a portion of the exhaust air in each section is extracted from the circulating airflow (typically 15-30% of the circulating air volume in that section) to remove evaporated moisture and volatile oil components from the fabric. The remaining hot air continues to circulate within the oven. Therefore, the total air intake of the oven (supply air mixture plus natural infiltration air) is greater than the sum of the organized exhaust volumes of the three sections; the difference is the circulating air volume inside the oven.

[0065] It should be noted that the ambient air and the supply air mix in different sections of the oven. The dilution effect of the ambient air and the heat absorption effect of fabric heating and moisture evaporation result in the actual temperature inside the oven being lower than the temperature of the supply air mixture. When the infiltration air volume is insufficient or the fabric has low heat absorption, leading to a higher actual temperature inside the oven, the natural infiltration air volume is increased by increasing the opening of the louvered dampers, or fresh air is introduced for bypass cooling to lower the temperature. Similarly, when the actual temperature of a certain section is insufficient to meet the target temperature requirement for that section, the temperature is supplemented to the target temperature by an auxiliary heater installed on the corresponding pipeline. The auxiliary heater is a natural gas burner or an electric heater.

[0066] The first oven of the setting machine maintains a slight negative pressure operation, and all the naturally infiltrated air is discharged in an organized manner with the exhaust air. The heat it carries is then recycled with the exhaust air to achieve full-process cascade recovery of heat energy.

[0067] Specific Implementation Example 2: The similarities to Specific Implementation Example 1 will not be repeated here. The difference lies in the addition of a Selective Catalytic Reduction (SCR) denitrification device on the exhaust pipe of TO furnace 2. Before mixing with preheated air, the combustion flue gas passes through the SCR reactor. Under the promotion of the catalyst, ammonia or urea solution is injected into the flue gas as a reducing agent to remove NO from the flue gas. X (Mainly thermal NO) X The nitrogen is reduced to N2 and H2O. The SCR reaction temperature window is 300~400℃. The flue gas temperature is adjusted from 780~820℃ to the suitable temperature range of 300~400℃ for the SCR catalyst through a flue gas cooler or a cold air bypass. The sensible heat of the flue gas lost in this process can be partially recovered and reused by heating boiler feedwater or preheating combustion air. The clean flue gas after denitrification then enters the mixing section and mixes with the preheated air.

[0068] Specific Implementation Example 3: Please refer to Figure 5 A process for treating oil fume exhaust gas from a stenter based on cascaded heat recovery and a TO furnace includes steps S1-S4.

[0069] Step S1: The high-concentration oily fume exhaust gas discharged from the middle section 12 of the stenter 1 is fed into the TO furnace 2 at a flow rate of 2500~3500 Nm³ / h, and the furnace temperature is maintained at 780~820℃ using natural gas as fuel (natural gas consumption is 15~30 Nm³ / h, based on the lower calorific value of natural gas 35.9 MJ / Nm³); the exhaust volume is adjusted by a variable frequency fan.

[0070] Step S2: The high-humidity, low-concentration oily fume exhaust gas with a temperature of 170~190℃ discharged from the front section 11 of the stenter 1 is sent to the hot side of the plate heat exchanger 3 at a flow rate of 2500~3500 Nm³ / h for heat release and cooling to 90~110℃, and then sent to the spray tower 4 with internal heat exchanger tubes 41; the low-concentration oily fume exhaust gas discharged from the tail section 13 of the stenter 1 is sent to the hot side of the plate heat exchanger 3 at a flow rate of 2500~3500 Nm³ / h for heat release and cooling to 90~110℃, and then sent to the spray tower 4 with internal heat exchanger tubes 41; The flow rate of Nm³ / h directly enters the spray tower 4 for spray cooling; the exhaust volume of the front section 11, middle section 12 and tail section 13 all include the natural air volume that seeps into the drying oven through the side air inlet 14 and the fabric inlet and outlet at both ends. The infiltrated air is distributed to each drying oven section under the action of slight negative pressure and is discharged in an organized manner with the exhaust of each section; the exhaust gas is sprayed and cooled to 40~50℃ in the spray tower 4 by circulating water. During the spraying process, water vapor is condensed and released. The latent heat released by condensation is absorbed by the circulating water, and then sent to the wet electrostatic precipitator 5 to remove oil mist and form purified gas for discharge.

[0071] Step S3: Extract low-grade heat energy from the spray water at a temperature of 40~50℃ in the spray tower 4. The extracted heat includes the sensible heat of the waste gas and the latent heat of water vapor condensation. Heat the fresh air of 3000~5000 Nm³ / h to 55~80℃, and then further heat it to 80~110℃ by the waste gas in the front section 11 of step S2 on the cold side of the plate heat exchanger 3 to form preheated air.

[0072] Step S4: Mix the combustion flue gas discharged from TO furnace 2 with the preheated air from step S3 to obtain a supply air mixture with a flow rate of 5500~8500 Nm³ / h and a temperature of 280~420℃; the supply air mixture is divided into three streams according to the target temperature requirements of each section 11, 12 and 13, namely 210~220℃ for the front section, 220~230℃ for the middle section and 210~230℃ for the tail section, and sent to the corresponding oven sections respectively.

[0073] In each section of the oven, the supply air mixture mixes with ambient air that naturally infiltrates through the side air inlets and the fabric inlets and outlets at both ends. Due to the dilution effect of the ambient air and the heat absorption effect of fabric heating and moisture evaporation, the actual temperature inside the oven is lower than the temperature of the supply air mixture. When the actual temperature of a certain supply air mixture after dilution by the naturally infiltrated air is insufficient to meet the target temperature requirement of that section, the temperature is supplemented to the target temperature by an auxiliary heater installed on the corresponding pipeline.

Claims

1. A stenter oil fume treatment system based on heat energy cascade recovery and TO furnace, characterized in that: It includes a stenter (1), a TO furnace (2), a plate heat exchanger (3), a spray tower (4), and a tubular heat exchanger (7); forming three subsystems, namely, a waste gas diversion and treatment subsystem, a heat pump and latent heat recovery subsystem, and an air preheating and air supply subsystem; the stenter (1) is divided into a front section (11), a middle section (12), and a tail section (13) along the fabric travel direction, which respectively form the drying oven section; The waste gas diversion and treatment subsystem includes parallel front diversion branches, middle diversion branches and tail diversion branches, used to independently treat the waste gas generated in each section of the stenter (1); in the front diversion branch, the waste gas in the front section (11) is cooled by heat release through the plate heat exchanger (3) and then enters the spray tower (4) for circulating water spraying and cooling; in the middle diversion branch, the waste gas in the middle section (12) is drawn out and sent to the TO furnace (2) for combustion to form combustion flue gas; in the tail diversion branch, the waste gas in the tail section (13) directly enters the spray tower (4) for spraying and cooling. The heat pump and latent heat recovery subsystem includes an extraction loop and a recovery loop to circulate and recover heat from the spray tower (4) and the tubular heat exchanger (7); the extraction loop extracts low-grade heat energy from the circulating water of the spray tower (4); the recovery loop collects the circulating water at the bottom of the spray tower (4), cools it down after heat exchange, and sends it back to the top spray exhaust gas, where the exhaust gas comes into contact with the spray water and mixes heat, thus cooling the exhaust gas. The air preheating and air supply subsystem includes a mixing main path and an air supply branch path, which are used to send preheated air into the corresponding oven sections according to the demand. Fresh air enters the cold side of the plate heat exchanger (3) and is heated by the exhaust gas of the front section (11) to form preheated air. The combustion flue gas of the middle section (11) is mixed with the preheated air to obtain the air supply mixture. The air supply mixture is divided into three streams according to the target temperature requirements of the front section (11), the middle section (12) and the tail section (13), and sent into the corresponding oven sections respectively.

2. The stenter oil fume treatment system based on heat energy cascade recovery and TO furnace according to claim 1, characterized in that: The setting machine (1) is a through-type oven with airflow isolation devices between adjacent sections; air inlets (14) are provided on the sides of the front section (11), middle section (12) and tail section (13); the two ends of the setting machine (1) are the fabric inlet (15) and the fabric outlet (16), respectively; the fabric inlet (15) is located on the left side of the setting machine (1) and the fabric outlet (16) is located on the right side of the setting machine (1).

3. The stenter oil fume exhaust gas treatment system based on heat energy cascade recovery and TO furnace according to claim 1, characterized in that: The plate spacing on the flue gas side of the plate heat exchanger (3) is not less than 15mm; a metal fiber filter is installed at the flue gas inlet to intercept fibers and larger particle size oil mist in the exhaust gas; 0.3~0.5 MPa steam is periodically introduced to clean the heat exchange plates.

4. The stenter oil fume exhaust gas treatment system based on heat energy cascade recovery and TO furnace according to claim 1, characterized in that: The spray tower (4) is equipped with a multi-layer spray device. External water source is supplied into the spray tower (4). The circulating water is sprayed down evenly from the top of the tower and comes into countercurrent contact with the exhaust gas entering from the bottom of the tower for heat exchange. A heat exchange tube (41) is installed in the middle of the spray tower (4) as an evaporator, and the tube side of the tubular heat exchanger (7) is used as a condenser. A compressor (6) and a throttling valve (8) are installed between the spray tower (4) and the tubular heat exchanger (7). The heat pump working fluid absorbs heat from the spray circulating water on the evaporation side and evaporates into low-pressure steam. After being compressed and heated by the compressor (6), it enters the condensation side to release heat and condense, so as to complete the extraction circuit. After being depressurized by the throttling valve (8), it returns to the evaporation side to complete the circulation, so as to complete the recovery circuit.

5. The stenter oil fume treatment system based on heat energy cascade recovery and TO furnace according to claim 1, characterized in that: It also includes an electrostatic precipitator (5); the spray exhaust gas from the spray tower (4) enters the electrostatic precipitator (5), which is a wet electrostatic precipitator, using corrosion-resistant electrode materials and equipped with insulator anti-creep protection.

6. The stenter oil fume treatment system based on heat energy cascade recovery and TO furnace according to claim 1, characterized in that: The bottom of the spray tower (4) is equipped with an oil-water separation and filtration device. The liquid water generated by condensation is recycled for water replenishment of the spray tower (4). The oil-water separation and filtration device includes an inclined plate oil-water separator and a multi-media filter.

7. The stenter oil fume exhaust gas treatment system based on heat energy cascade recovery and TO furnace according to claim 4, characterized in that: The heat exchange tubes (41) are made of stainless steel or titanium, and are arranged in a serpentine or spiral shape in the middle of the spray tower (4).

8. The stenter oil fume exhaust gas treatment system based on heat energy cascade recovery and TO furnace according to claim 1, characterized in that: The temperatures of the three air streams in the air supply branch are 210~220℃ for the front section, 220~230℃ for the middle section, and 210~230℃ for the rear section, respectively.

9. The stenter oil fume exhaust gas treatment system based on heat energy cascade recovery and TO furnace according to claim 1, characterized in that: Each section of the oven is equipped with an auxiliary heater on its pipeline. The auxiliary heater is either a natural gas burner or an electric heater. When the air-fuel mixture enters the corresponding pipeline, if the actual temperature of a certain section is insufficient to meet the target temperature requirement of that section, the auxiliary heater installed on the corresponding pipeline will supplement the temperature to the target temperature.

10. A process for treating oil fume exhaust gas from a stenter based on cascaded heat energy recovery and a TO furnace, characterized in that: It is implemented based on a stenter oil fume exhaust gas treatment system based on thermal energy cascade recovery and TO furnace as described in any one of claims 1-9, which includes steps S1-S4; Step S1: The high-concentration oily fume exhaust gas discharged from the middle section (12) of the stenter (1) is sent into the TO furnace (2) at a flow rate of 2500~3500 Nm³ / h, and the furnace temperature is maintained at 780~820℃ using natural gas as fuel; the exhaust volume is adjusted by a variable frequency fan; Step S2: The high humidity and low concentration oil fume exhaust gas with a temperature of 170~190℃ discharged from the front section (11) of the stenter (1) is sent to the hot side of the plate heat exchanger (3) at a flow rate of 2500~3500 Nm³ / h to release heat and cool it to 90~110℃, and then sent to the spray tower (4) with the internal heat exchanger tube (41); the low concentration oil fume exhaust gas discharged from the tail section (13) of the stenter (1) is directly sent to the spray tower (4) at a flow rate of 2500~3500 Nm³ / h for spray cooling; the exhaust gas is sprayed and cooled to 40~50℃ by circulating water in the spray tower (4), and water vapor is condensed and released during the spraying process. The latent heat released by the condensation is absorbed by the circulating water, and then sent to the electrostatic precipitator (5) to remove oil mist and form purified gas for discharge. Step S3: Extract low-grade heat energy from the spray water at a temperature of 40~50℃ in the spray tower (4). The extracted heat includes the sensible heat of the waste gas and the latent heat of water vapor condensation. Heat the fresh air of 3000~5000 Nm³ / h to 55~80℃, and then further heat it to 80~110℃ by the waste gas in the front section (11) of step S2 through the cold side of the plate heat exchanger (3) to form preheated air. Step S4: Mix the flue gas discharged from the TO furnace (2) with the preheated air from step S3 to obtain a supply air mixture with a flow rate of 5500~8500 Nm³ / h and a temperature of 280~420℃; the supply air mixture is divided into three streams according to the target temperature requirements of each section (11), (12) and (13): 210~220℃ for the front section, 220~230℃ for the middle section and 210~230℃ for the tail section, and sent to the corresponding oven sections respectively.

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