Discussion on the calculation of solvent recovery rate — highly practical value

The original poster can look it up online

I’ve seen it, I’ve learned it!* Thank you, Lou:handshake

The original text of the plan may not have been uploaded in a proper format; I’m posting it here now: 1. Overview: The painting workshop emits large amounts of exhaust gas from the drying process of coatings, and this gas contains high concentrations of toluene. If such waste gas is released directly into the atmosphere without treatment, it will not only pollute the surrounding environment but also lead to significant consumption of raw materials; furthermore, it will have an adverse effect on the company’s reputation. Therefore, it must be treated. Based on on-site investigations and research analyses, Hangzhou Yida Environmental Protection Technology Consulting Co., Ltd. has developed feasible plans for the treatment and recovery of toluene in coating-related exhaust gases, intended for reference by enterprises and environmental protection authorities, to prepare for the formal implementation of such projects in the future. 2. Design basis 2.1 Types, concentrations, and temperature of pollutants in the exhaust gas: Type of pollutant: Toluene. Amount of pollutant emitted: 270 kg/h; volume of exhaust gas emitted: 33,000 m3/h. Temperature at the outlet of the oven: 70–80°C. Calculations show that the toluene concentration is 8,182 mg/m3, which classifies this situation as one with high concentrations and high flow rates of exhaust gas. 2.2 Design scale: Waste gas treatment capacity: 33,000 m3/h ； The toluene emission is 270 kg/h (maximum value). Note: This design is based on the maximum value. 2.3 Scope of design: From the outlet at the junction of the workshop exhaust pipes, through to the inlet of the unit and up to the outlet of the exhaust fan, including all process equipment, connection pipes, fittings, valves, fans, electrical installations, automatic control devices, etc. 2.4 Emission concentrations of treated gas: The exhaust emission standards shall comply with the secondary standards specified in GB16297-1996, \"Comprehensive Emission Standards for Air Pollutants\", as detailed in Table 1. Table 1: Secondary emission standards for toluene in GB16297-1996
Serial Number | Maximum allowable emission concentration, mg/m3 | Maximum allowable emission rate, kg/h | Height of exhaust stack, m
Secondary Standards | 1. Toluene | 40 | 15 | 3.12 | 20 | 5.23 | 30 | 18 | 2.5

Design references and regulatory standards:
“Safety Regulations for Painting Operations – Ventilation and Purification in Painting Processes”, GB 6515-86 **Standard Bureau, 1986**; “Ventilation and Dust Removal Technologies”; “Industrial Ventilation”; “Manual of Environmental Protection Equipment and Materials”; “Regulations on Environmental Protection Management for Construction Projects”, Decree No. 253 of the State Council of the People’s Republic of China, 1998.

2.6 Control system: An automatic control system based on programmable logic controllers (PLCs) is used to optimize the operation of the treatment system, reduce operating costs, and enhance the reliability of equipment operation. 3. Process Design 3.1 Design Principles 1. Strictly comply with **environmental protection regulations; in accordance with the specified emission standards, ensure that all parameters of the treated exhaust gas meet or exceed the standard values. 2. It adopts advanced, rational, mature, and reliable processing technologies, offering significant environmental, social, and economic benefits. 3. Process design and equipment selection allow for considerable flexibility and adjustment during production, ensuring compliance with emission standards. 4. During operation, it facilitates operational management and maintenance, while reducing power consumption and operating costs. 3.2 Selection of waste gas treatment methods At present, the main methods for treating organic waste gases include the following: (1) Combustion method, which includes high-temperature combustion and catalytic combustion. The former requires additional fuel for combustion; therefore, when using this method, it is necessary to consider the recovery and utilization of thermal energy ； Catalytic combustion has low energy consumption, but at the beginning of operation, electric heating is required to raise the exhaust gas to the ignition temperature; therefore, it is not suitable for applications involving frequent start-up and shutdown. Given that the heat recovered by high-temperature combustion exceeds the thermal energy required for production, it is not suitable. And adopting catalytic combustion directly requires too much investment. (2) Absorption method: This involves using an appropriate absorbent (such as diesel, kerosene, water, or other media) in an absorption tower to carry out the absorption process. Once the desired concentration is reached, the solvent is separated from the absorbed liquid; the solvent is recovered, while the absorbed liquid is reused or processed further. The key to this method lies in the selection of the absorbent. Its application is limited to some extent due to the difficulty in separating the solvent from the absorbent. (3) Activated carbon adsorption method: Porous activated carbon or activated carbon fibers are used to absorb organic waste gases; once saturated, they are regenerated using low-pressure steam. During regeneration, the solvent-containing waste gases are discharged and the solvent is recovered after condensation and water separation. This method is suitable for discontinuous treatment processes, and it is particularly effective for recovering solvents from organic waste gases with low concentrations. (4) Condensation method: It primarily uses a cold medium to treat high-temperature organic waste gas vapor, enabling effective recovery of solvents. The effectiveness of the treatment depends on the temperature of the refrigerant; its efficiency is relatively lower compared to other methods, making it suitable for treating high-concentration waste gases. Given the conditions of this project, the condensation-activated carbon adsorption method is more suitable. By combining these two methods to recover toluene from dried exhaust gas, the advantages of the condensation method – its suitability for treating exhaust gases with high concentrations – and those of the activated carbon adsorption method – its effective performance – are taken into account. Preliminary condensation allows for a reduction in the toluene concentration, thereby decreasing the load on the activated carbon and extending its regeneration cycle; this approach enables a balance between recovery efficiency and treatment costs. 3.3 System process flow: Based on the actual conditions of this plant, to improve the recovery efficiency of toluene, it is necessary to strengthen efforts in the following two areas: one is the collection of dried waste gas, so as to capture as much toluene as possible and send it to the solvent recovery unit ； Second, the collected exhaust gas is treated and recycled using appropriate methods. The process flow is shown in Figure 3-1:

Continuing: Dried exhaust gas, fan, exhaust blower, collection hood, shell-and-tube condenser 1, solvent-water separator, toluene storage tank 2, cooling water storage tank, water tank, filter flame arrester, activated carbon adsorber, exhaust gas emission, low-pressure steam, boiler room, shell-and-tube condenser 2, condensed water recovery tank, toluene storage tank 1. Figure 3-1: System process flow diagram. Process description: Since the concentration of toluene in the exhaust gas exiting the oven is high, it is first collected together and passed through a set of filter flame arresters to remove solid impurities from the exhaust gas; thereafter, it enters the shell-and-tube condenser, where the gaseous toluene is condensed into a liquid state. After condensation, the temperature is cooled below 24°C. Since the boiling point of toluene is about 110°C, most of the toluene can be recovered. The condensed exhaust gas is guided by an induced draft fan into an activated carbon adsorber for adsorption treatment. Two sets of adsorbers are provided and used alternately. The saturated activated carbon is regenerated using low-pressure steam, and the resulting gas phase is returned to the condenser for solvent recovery. The recovered solvent is separated using a water separator and then reused. 4. Description of the process system 4.1 Overview This process system can be divided into the following 3 systems: exhaust gas collection system, exhaust gas purification system, and exhaust ventilation system. The exhaust gas collection system mainly includes local exhaust hoods, air volume control valves, and ducts. The exhaust gas purification system mainly includes a dust collector, a condenser, and an activated carbon adsorption unit. The exhaust system mainly includes an exhaust fan, an air volume control valve, and a chimney. 4.2 Brief Description of the Functions of the Main Process Equipment 1. Dust Collector: Its primary function is to remove paint mist particles from organic waste gases, preventing these particles from sticking to the activated carbon fiber material in the adsorption bed and thus affecting the efficiency of adsorbing harmful gases. Secondly, it is to prevent the purification equipment from being affected in the event of a fire in the production equipment. 2. Condenser: The function of the condenser _1 is to condense gaseous toluene in organic waste gas into a liquid, thereby reducing the toluene content in the waste gas, improving the efficiency of activated carbon adsorption treatment, and simultaneously recovering some of the toluene. The function of the condenser_2 is to condense the toluene and water vapor obtained through desorption into liquids, thereby recovering the toluene obtained via desorption. 3. Activated carbon adsorption unit: The activated carbon adsorption unit is an important component of the purification system. Its purpose is to use adsorption to retain organic substances in exhaust gases, thereby further purifying those gases, and to recover some of the toluene through methods such as low-pressure steam stripping and condensation. 5. Design of main equipment 5.1 Main design parameters The main design parameters and the desired performance levels are shown in Table 5-1. Table 5-1: Main design parameters and requirements, treatment efficiency, process air volume (m3/h), toluene inlet concentration (mg/m3), concentration after treatment (mg/m3), recovery rate (kg/h), and recovery efficiency (%). Column-type condenser: 33,000; 818; 290; 424; 4.99%; 0.7%. Activated carbon adsorber: 9,044; 0; 24.09%; 5.65%; 5.2%. Main equipment: 1. Dust collector (Option 1): Based on the properties and volume of the waste gas, the XCX type cyclone dust collector with a diameter of Ф1300mm and four tubes has been selected for this project. In addition to its long-cone structure, the XCX type cyclone dust collector is equipped with an arc-shaped drag reducer in the exhaust pipe to reduce the dust collector’s drag coefficient. The specific parameters are as follows: Inlet wind speed: 24 m/s ； Air volume: 33,700 m3/h ； Pressure loss: 1039Pa ； Dust removal efficiency: It can remove dust particles larger than 5µm, with an efficiency of 95%–99%. (Solution 2) Based on the properties and volume of the exhaust gas, this project selects eleven SJ-type high-precision metal microporous filters (ten in use and one for cleaning as a spare). This air filter is made of micrometal material produced by sintering metal and alloy powders, and possesses excellent properties such as high temperature resistance, corrosion resistance, uniform pore size distribution, good air permeability, high mechanical strength, washability and regenerability, as well as weldability and machinability. The specific parameters of the SJ-type high-precision metal microporous filter are as follows: DN=250mm ； Import wind speed: 20 m/s ； Air volume: 3530 m3/h ； Shell material: SUS304L ； Filter element material: Sintered metal powder tube ； Filter precision: 0.5–120μm ； Working pressure: 0.6–1.6 Mpa. 2. Flame arrestors: Based on the properties of the exhaust gases and the volume of gas flow, ten ZHQ-B type pipeline explosion-proof wave N flame arrestors have been selected for this project; their specific parameters are: DN=250mm ； Import wind speed: 20m/s ； Shell material: carbon steel ； Core material: Stainless steel wave N strip. 3. Shell-and-tube condenser_1: Depending on the properties and volume of the waste gas, fixed-plate heat exchangers are used in this project to condense the waste gas and recover some toluene. To facilitate the removal of condensate, and considering that the exhaust gas is relatively clean after dust removal, the flow path is designed such that the exhaust gas flows through the tubes outside (i.e., in the shell side), while the cooling water flows through the tubes inside. Furthermore, in order to achieve a certain recovery efficiency while also taking into account the cost of cooling water, the inlet temperature of the cooling water was set at 20°C at room temperature, and the outlet temperature at 23°C. The inlet temperature of the drying exhaust gas is 80°C, and it drops below 24°C after condensation. The specific calculations are as follows: (1) Given conditions: the volume flow rate of the exhaust gas from drying is 33,000 m3/h; the inlet temperature is 80°C, the toluene concentration is 8,182 mg/m3, and the flow rate is 270 kg/h. The outlet temperature is 24°C, while the inlet temperature of the cooling water is 20°C and its outlet temperature is 23°C.

(1) Calculation of toluene recovery rate: The Antoine constants for toluene are A=16.0137, B=3096.52, C=53.67. According to the Antoine equation (where p is the saturated vapor pressure at temperature T, in mmHg), at 80°C, p = 291.21 mmHg ； At 24°C, p = 27.00 mmHg. Therefore, the recovery rate when the temperature is reduced from 80°C to 24°C is 90.7%. Thus, the amount of toluene that condenses at 24°C is 270 × 90.7% = 244.90 kg/h, and the remaining flow rate is 270 – 244.9 = 25.1 kg/h. At 24°C, the total volume of the waste gas is approximately , and the concentration of toluene remaining in the waste gas after condensation is (3) To calculate the area A of the heat exchanger, at 80°C the mass flow rate of toluene is 270 kg/h; therefore, the volume of toluene discharged per hour is V. The total volume flow rate of the waste gas is 33,000 m3/h, with an average molecular weight of the waste gas of approximately 28. At 80°C, the mass flow rate of exhaust gas = kg/h; the mass flow rate of air in the exhaust gas is 31908 – 270 = 31638 kg/h. The exhaust gas temperature drops from 80°C (T1) to 24°C (T2), while the cold water temperature rises from 20°C (t1) to 23°C (t2). The heat load Q1 = heat transfer for cooling toluene + heat transfer for cooling air = 270 × 1.7 × (80 – 24) + 31638 × 1.005 × (80 – 24) = 1.8×10^6 kJ/h. The amount of cooling water required is W = 143 t/h. Considering a single-pass configuration first: the logarithmic mean temperature difference is 19.95 K. By referring to the temperature correction coefficient chart using the values of R and P, the temperature difference correction factor is 0.89, which is greater than 0.8; hence, a single-pass configuration is appropriate. Therefore, the effective temperature difference is 17.8 K. Assuming that the overall heat transfer coefficient of the heat exchanger is known, the required heat transfer area is 216 m2. (4) Calculation of the basic parameters for the main process and structure: Steel pipes with dimensions Φ25×2.5 mm are used, made of grade 20 steel. Taking the flow rate of the cooling water inside the pipes as 0.5 m/s, the number of pipes is 253, and the length of each pipe is 10.9 m. Therefore, with 2 tubes in each bank, the total number of pipes becomes 253×2=506. The nominal diameter of the shell is DN=800 mm, and the nominal pressure is 10 kgf/cm2. The heat exchange tubes are arranged in an equilateral triangle pattern, and the tubes are connected to the tube sheet by welding. In summary, the main parameters of the tubular condenser _1 are as follows: 506 steel tubes with a length of 6m and a diameter of Φ25×2.5mm (made of grade 20 steel) are used ； Shell diameter 800mm ； Heat exchange area: 216 m2 ； The cooling water consumption is 143 t/h ； The toluene recovery rate is 90.7% ； The exhaust gas temperature drops from 80°C to 24°C, while the cooling water temperature rises from 20°C to 23°C. 3. Shell-and-tube condenser_2: Based on the properties of the waste gas and its volume, fixed-plate heat exchangers are used in this project to condense toluene and water vapor, thereby recovering the toluene obtained through desorption. To facilitate the drainage of condensate, the flow path is designed such that toluene and water vapor flow between the tubes (i.e., in the shell side), while cooling water flows inside the tubes. Furthermore, to achieve a certain recovery efficiency while taking into account the costs of cooling water, the inlet temperature of the cooling water was set at 20°C and the outlet temperature at 25°C; the inlet temperature of the steam was set at 120°C, and it drops below 30°C after condensation. The specific calculations are as follows: (1) Determine the required amount of steam. The toluene recovery rate during desorption = 95.6%. The amount of toluene that needs to be stripped is 25.1 × 95.6% = 24.0 kg/h. Generally, the steam volume is determined as follows: Desorption solvent volume = (4–10):1; thus, the steam volume is set at 150 kg/h. (2) Calculation of the recovery rate of condensed toluene: The Antoine constants for toluene are A=16.0137, B=3096.52, C=53.67. According to Antoine’s equation (where p is the saturated vapor pressure at temperature T, in mmHg), at 120°C, p = 984.7 mmHg ； At 30°C, p = 36.67 mmHg. Therefore, the recovery rate when cooling from 80°C to 30°C is 97.3%, meaning that virtually all of the toluene is condensed. (3) Calculate the area A of the heat exchanger: at 120°C, the mass flow rate of toluene is 24 kg/h, and the mass flow rate of steam is 150 kg/h. The steam temperature drops from 120°C to 30°C, while the cooling water temperature rises from 20°C to 25°C. The heat load Q1 = heat transfer for cooling toluene + heat transfer due to steam + latent heat of steam condensation = 24 × 1.7 × (120 – 30) + 150 × 4.2 × (120 – 30) + 150 × 2232 = 0.395×106 kJ/h. The amount of cooling water required is W = 18.8 t/h. Assuming a single-pass configuration, the logarithmic mean temperature difference is 37.76 K. By referring to the temperature correction coefficient chart using the values of R and P, the temperature difference correction factor is 0.93, which is greater than 0.8; hence, a single-pass design is appropriate. Therefore, the effective temperature difference is 35 K. Assuming that the overall heat transfer coefficient of the heat exchanger is known, the required heat transfer area is 9 m2. (4) Calculation of basic parameters for the main process and structure: Steel pipes with dimensions Φ25×2.5 mm are used, made of grade 20 steel. With the flow rate of the cooling water inside the tubes set at 0.5 m/s, the number of tubes is 34, and the length of each tube is 3.4 m. Therefore, the number of tubes in the heat exchanger’s tube side is 2, the length of each such tube is 2 m, and the total number of tubes is 34×2=68. The nominal diameter of the shell is DN=400 mm, and the nominal pressure is 16 kgf/cm2. The heat exchange tubes are arranged in an equilateral triangle pattern, and the tubes are connected to the tube sheet by welding. In summary, the main parameters of the tube-type condenser _2 are as follows: 68 steel tubes with a length of 2m and dimensions of Φ25×2.5mm (made of grade 20 steel) are used ； Heat exchange area: 9 m2 ；

Shell diameter 400mm； The cooling water consumption is 18.8 t/h ； The steam temperature drops from 120°C to 30°C, while the cooling water temperature rises from 20°C to 25°C. 4. Activated carbon adsorption unit and auxiliary equipment: (1) Depending on the properties and volume of the waste gas, this project utilizes a fixed-bed activated carbon adsorption system regenerated with low-pressure steam to further recover toluene from the waste gas. The volume of exhaust gas is 33,000 m3/h, with a temperature of 24°C. The exhaust gas contains 904 mg/m3 of toluene, and the desired concentration of toluene at the outlet is 40 mg/m3, which means a purification efficiency of 95.6%. (2) Calculation of the saturated adsorption capacity of activated carbon for toluene: The parameters for a certain type of activated carbon are as follows: bulk density = 450 kg/m3, particle size = 5 mm, and porosity = 0.40. The adsorption isotherm equation for toluene on this activated carbon is given by: where a is the equilibrium adsorption amount at a gas phase concentration of, in kg/kgAC ； – Concentration of toluene in the gas phase, g/m3. Based on a toluene concentration of 0.904 g/m3 in the exhaust gas, the static saturated adsorption capacity of activated carbon for toluene, a, is 0.330 kg/kgAC. (3) Calculation of key parameters for the fixed-bed adsorber: The gas flow rate in the adsorber was set at 0.4 m/s; under these conditions, the length of the adsorption zone is 0.3 m. The dynamic adsorption capacity of the activated carbon in this adsorption zone is taken to be 35% of its static saturated adsorption capacity. Therefore, the amount of toluene adsorbed by the activated carbon in the adsorption zone is 0.116 kg/kg. Assuming that the adsorption capacity of the activated carbon, which has already reached dynamic saturation outside the adsorption band, is 90% of its static saturated adsorption capacity, the amount of toluene adsorbed by the activated carbon after saturation is 0.297 kg/kg. The diameter of the adsorber is . The amount of activated carbon contained in the adsorption cartridge is . The amount of toluene that can be adsorbed by the activated carbon in the cartridge is . Assuming an adsorption cycle duration of 2 days (16 hours), the amount of substance adsorbed per cycle is . The amount of activated carbon required outside the adsorption cartridge is . The total height of the adsorber is . The total amount of activated carbon used is . The formula for estimating the pressure drop as air flows through the fixed-bed layer is: Where: – Pressure drop, Pa ； – Porosity, m3 of void space per m3 of adsorption bed ； – Adsorbent particle diameter, m ； －Gas density, kg/m3 ； G – gas apparent mass flux, ； D – Bed depth, m ； – Gas viscosity, . At 30°C, the gas density is , the viscosity is , and . Therefore, the calculated pressure drop is , which represents the theoretical power consumption. Assuming a fan efficiency of 0.70, the actual power consumption is . In light of this, two fixed-bed activated carbon adsorbers are used alternately; their key parameters are: an activated carbon bulk density of 450 kg/m3, a particle size of 5 mm, and a porosity of 0.40 ； The total amount of activated carbon used was 7.77 m3 ； The total height of the adsorber is 0.339 m, with a diameter of 5.4 m ； The adsorption working cycle is 2 days (16 hours) ； Purification efficiency > 95.6% ； The actual power consumption is 3.876 kW. (4) At the inlet main pipe of the activated carbon adsorber unit, a B4-72 type explosion-proof centrifugal ventilator is installed; its air volume is Q=33,000 m3/h, air pressure is 671 Pa, and the motor power is 35 kW. (5) Solvent-water separator: The vapor consumption is 150 kg/h (i.e., 150 m3/h) for water vapor, and 24 kg/h (i.e., 7 m3/h) for toluene. Desorption is carried out once every two days, for two hours each time; therefore, the volume of the solvent-water separator is set at 350 m3. A safety vent pipe is installed on this solvent-water separator, which is emptied every two days. (6) Toluene storage tank 2: Since the toluene desorption rate is 24 kg/h (i.e., 7 m3/h), and desorption occurs once every two days, each time…

With two hours added, 14 m3 of toluene is produced in two days. Therefore, a storage tank with a diameter of 3m and a height of 2m can be used for storage. A safety vent pipe should be installed on the storage tank. (7) Liquid pump: An explosion-proof pipeline pump of the 50SGB10-8 type is used to separate toluene from the solvent-water separator. Its main parameters are a diameter of 50 mm, a rated flow rate of 10 m3/h, a head of 8 m, a rotation speed of 2900 r.p.m., and a power output of 7.5 kW. Two 4B15A centrifugal water pumps are used to separate the condensate water from the solvent-water separator. Their main parameters are a rated flow rate of 86 m3/h, a head of 8.5 m, a rotational speed of 2900 r.p.m., and a power output of 2.78 kW. 5.3 Others 1. Electrical and automatic control systems: The total installed capacity of the processing system is 36.9 kW, and it is controlled by centrally installed electrical control cabinets. To improve the recovery rate and reduce energy consumption, the operation of the equipment is under automated control. Parameter setting and monitoring are carried out by the upper-level industrial computer, while the operation of the equipment is controlled by the PLC. The PLC is installed in the electrical control cabinet, and together with the industrial computer, it is placed in an explosion-proof isolated control room that facilitates operation. Parameters such as the temperature, pressure, and pipeline static electricity of the entire system are collected by sensors and transmitted to the centralized control room for automated control. 2. Steam supply: To reduce equipment investment and costs, low-pressure steam is used for the regeneration of saturated activated carbon, which is supplied directly by the plant’s boiler. The boiler outlet pressure is 0.2 Mpa, and the steam temperature is approximately 120°C. Based on engineering experience, the ratio of steam to the amount of solute adsorbed is approximately 4–10, requiring a total of 150 kg/h of steam. The gas supply cycle is 2 days. 3. Water supply: Based on the calculations for the two shell-and-tube condensers, the amount of water required for circulation is 143 + 18.8 = 161.8 tons/h, or 161.8 m3/h; this water is pumped to the condensers for reuse. The circulating water pump for condenser_1 uses two 4B15A type centrifugal clean water pumps, with design parameters of Q = 72 m3/h, H = 11 m, speed = 2900 r.p.m., and power of 2.87 kW. The circulating water pump for condenser_2 is a 2B19B type centrifugal clean water pump, with design parameters of Q = 20 m3/h, H = 10.3 m, speed = 2900 r.p.m., and power of 2.41 kW. Due to losses caused by evaporation, the circulating water needs to be replenished regularly, at a rate of approximately 8 m3 per day. 5.4 List of Main Equipment The main equipment is listed in Table 5-3. Table 5-3 List of Major Equipment
Serial Number | Equipment Name | Model or Specification | Quantity | Power (kW) | Remarks
--- | --- | --- | --- | --- | ---
Condensation System | 1. Dust Collector | XCX type, Ф1300mm, 4 tubes | 1 | — |
| 2. Flame Arrester | ZHQ-B type, Φ250, 10 | 1.5 | — |
| 3. Tubular Condenser_1 | Single-shell, double-pass, shell diameter Ф800; heat exchange area: 216 m² | 1 | — |
| 4. Tubular Condenser_2 | Single-shell, double-pass, shell diameter Ф400; heat exchange area: 9 m² | 1 | — |
Mixed Solvent Stratifier | 350 m³ capacity | 1 | — |
Cooling Water Circulation Pumps | 1: Q=72 m³/h, H=11 m; power: 2.87 kW | 1 | — |
| 2: Q=20 m³/h, H=10.3 m; power: 1.241 kW | 1 | — |
Toluene Condensation Pump | Q=10 m³/h, H=8 m; power: 7.5 kW | 1 | — |
Explosion-Proof Pipeline Pump | — | — | — | 1 |
Condensate Water Pump | Q=86 m³/h, H=8.5 m; power: 2.78 kW | 1 | — |
Activated Carbon Adsorption System | 10. Exhaust Fan | Q=33,000 m³/h | 1 | 35 kW |
| 11. Activated Carbon Adsorption Tanks | Φ5400*339 | 2 | 3.88 kW |
Temperature Measurement System | 6 | — | — | — |
Pressure Measurement System | 9 | — | — | — |
Fire Alarm System | 3 | — | — | — |
Pipes and Valves | 1 set | — | — | — |
Electrical Control Cabinet | 1, including PLC and high-voltage components | — | — | — |
Upper-Level Industrial Computer | 1 | — | — | — |
Other Auxiliary Materials | 6 | — | — | — |
Labor Force Requirement: 1 person per shift for equipment operation; 4 people in total for 4 shifts ； 1 part-time laboratory technician ； There is 1 part-time management staff member. A total of 4 people. 7. The investment estimate is shown in Table 7-1. Table 7-1 Investment Estimation Table

| Serial No. | Equipment Name | Main Technical Parameters | Quantity (sets) | Price (10,000 CNY) | Total Price (10,000 CNY) | Remarks |
| --- | --- | --- | --- | --- | --- | --- |
| 1 | Dust collector, XCX type, Ф1300mm | | 1 | 77.00 | 77.00 | |
| 2 | Flame arrester, ZHQ-B type, Φ250 | | 1 | 100.88 | 100.88 | |
| 3 | Tubular condenser_1, single-shell double-pass shell, Ф800 | | 1 | 11.20 | 8.00 | Heat exchange area: 216 m² |
| 4 | Tubular condenser_2, single-shell double-pass shell, Ф400 | | 1 | 11.20 | 5.00 | Heat exchange area: 9 m² |
| 5 | Explosion-proof fan, 3,300 m³/h | | 1 | 14.80 | 1.80 | Includes silencer and vibration damping base |
| 6 | Activated carbon adsorber, φ1400*3800 | | 1 | 281 | 16.00 | Includes activated carbon and accessories |
| 7 | Mixed solvent stratifier, 350 m³ | | 1 | 11.65 | 1.65 | |
| 8 | Circulation water pump_1, 72 m³/h | | 1 | 20.50 | 1.00 | |
| 9 | Circulation water pump_2, 20 m³/h | | 1 | 10.50 | 0.50 | |
| 10 | Condensed toluene pump, Q=10 m³/h | | 1 | 10.60 | 0.60 | Used for pneumatic valves and activated carbon regeneration |
| 11 | Condensation water pump, Q=86 m³/h | | 1 | 20.5 | 1.00 | Used for pneumatic valves and activated carbon regeneration |
| 12 | Pipes and valves of various specifications | | | 18.00 | 8.00 | Includes exhaust gas pipes, automatic valves, cooling water pipes and valves |
| 13 | Automatic control system | | | 112.00 | 12.00 | Includes PLC, industrial computer, instruments |
| 14 | Other auxiliary materials | | | 12.00 | 2.00 | |
| I. Direct equipment cost | | | | | 57.55 | |
| II. Other costs | | | | | | |
| 1. Design cost | | | | 8.52 | 8.52 × 10% | |
| 2. Installation cost | | | | 4.26 | 4.26 × 5% | |
| 3. Commissioning cost | | | | 4.26 | 4.26 × 5% | |
| 4. Management cost | | | | 2.56 | 2.56 × 3% | |
| III. Total project cost | | | | | 92.15 | |

8. Benefit estimation 8.1 Environmental benefits: Based on a production capacity of 300 days per year with 24 hours of operation per day, it is estimated that after treatment, the exhaust gases will result in a reduction of 1,944 tons of organic substances being released into the atmosphere each year, yielding significant environmental benefits. 8.2 Economic benefits: Assuming a consumption of 360 t/a of toluene in coating enterprises, more than 90% of this toluene ends up in the waste gases during drying. With a toluene recovery rate of over 99%, the total amount of toluene recovered each year is: 360 × 0.9 × 0.99 = 320.8 t/a. The price of toluene is calculated at 6,000 yuan per ton (price as of December 2004). The economic benefit resulting from recycling is: 320.8 tons/year × 6,000 yuan/ton = 1.9248 million yuan/year. 8.2 Operating costs: These mainly include costs for water and electricity, steam consumption, labor costs, and equipment depreciation. The calculations for each cost are as follows: 1. Water cost: Assuming that the circulating water is replaced once a month, with an additional 8 m3 of water added per day, the water cost is (161.8 m3 × 12 + 8 m3/day × 300 days) × 1.50 yuan/ton = 0.65 million yuan/year ； 2. Electricity cost: 40kW × 24h × 300d × 0.80 yuan/kWh × 0.75 = 172,800 yuan/year ； 3. Steam consumption cost: Steam consumption of 150 kg/h × 24 h × 300 × 120 yuan/t = 130,000 yuan/year. 4. Labor cost: With a salary of 15,000 yuan per year, the total amount is 60,000 yuan/year ； 5. Activated carbon consumption cost (service life: half a year); annual consumption cost is 92,400 yuan per year ； 6. Equipment depreciation: The useful life of major equipment is assumed to be 10 years, with an annual depreciation cost of around 100,000 yuan per year ； 7. Maintenance cost: 3% of the equipment cost, approximately 30,000 yuan per year ； The total cost of all the above items is 591,700 yuan per year. After deducting costs, the annual economic benefit amounts to 1.3331 million yuan, with an investment payback period of 0.75 years. All plans are as above; discussions are welcome, and experts are sought.