Coking production operation methods

Our facility uses the water-washing ammonia process; you can use this as a reference. Table of Contents: I. Desulfurization 3 1. Brief description of the process flow and flow diagram 3 2. Technical specifications and quality standards for raw materials and products 3 3. List of equipment 3 4. Process technical parameters for each position 4 5. Normal operation 5 6. Startup and shutdown procedures 6 7. Abnormal situations and their handling 7 8. Classification of process accidents and assignment of responsibilities 7 II. Procedures for final cooling, ammonia washing, and ammonia evaporation 9 1. Process flow and brief description 9 2. Technical specifications for raw materials and products 9 3. List of equipment 10 4. Process technical parameters for each position 11 5. Normal operation 11 6. Startup and shutdown procedures 12 7. Abnormal situations and their handling 13 8. Classification of process accidents and assignment of responsibilities 13 III. Procedures for benzene washing and crude benzene distillation 15 1. Brief description of the process flow 15 2. Technical specifications and quality standards for raw materials and products 16 3. List of equipment 17 4. Process technical parameters for each position 18 5. Normal operation 19 6. Startup and shutdown procedures 20 7. Abnormal situations and their handling 22 8. Classification of process accidents and assignment of responsibilities 23 IV. Purification of naphthalene 25 1. Brief description of the process flow and flow diagram 25 2. Technical specifications and quality standards for raw materials and products 25 3. List of equipment 25 4. Process technical parameters for each position 26 5. Normal operation 26 6. Startup and shutdown procedures 27 7. Operations in special situations 28 8. Classification of process accidents and assignment of responsibilities 29 9. Safety precautions 30 I. Desulfurization 1. Brief description of the process flow and flow diagram The gas sent from the blower unit, with a temperature of approximately 20–35°C and a pressure of 5–1.5 kPa, enters the desulfurization tower. The gas enters the bottom of the desulfurization tower, where it comes into counterflow contact with the desulfurization liquid sprayed from the top of the tower; after H2S and HCN are removed, the gas is discharged from the top of the tower and sent to the final cooling tower. The desulfurization liquid discharged from the bottom of the desulfurization tower enters the rich liquid tank through a liquid seal tank, and is then pumped by a desulfurization liquid circulation pump into the oxidation regeneration tank, where air is introduced to enable the desulfurization liquid to be regenerated within the tank. The regenerated desulfurization liquid flows back to the circulation tank through a level regulator at the top. The sulfur foam floating on the expanded area at the top of the regeneration tank flows automatically into the sulfur foam tank due to the difference in liquid levels; the sulfur foam is then pumped by a foam pump to a plate and frame filter press, where it is filtered into a filter cake that is packaged for export. The discharged desulfurization liquid enters an underground tank, from where it is pumped to a circulation tank for reuse. The alkali consumed during the desulfurization process is replenished by pumping the alkaline solution prepared in the alkali preparation tank into the circulation tank. The process flow diagram is attached below. 2. Technical specifications and quality standards for raw materials and products
2.1 Technical specifications for raw materials and products
Gas temperature entering the desulfurization tower: 20–35°C
H2S content in the gas entering the desulfurization tower: 4–8 g/m3
Low-pressure steam pressure from the preceding process unit: ≥0.4 MPa
2.2 Quality standards for products
H2S content in the gas after passing through the desulfurization tower: < 1 g/m3
Suspended sulfur content: ≤3.0 g/l
Desulfurization efficiency: >80–95%

3. List of equipment
| Serial No. | Equipment Name | Specification Model | Quantity |
|-------------|----------------|--------------------|----------|
| 1 | Desulfurization liquid circulation pump | Q=500 m3/h, H=60 m, EAP300K5-500 | 3 |
| 2 | Desulfurization tower | DN3200×32500 | 1 |
| 3 | Rich liquid tank | DN6000×15000, V=145 m3 | 1 |
| 4 | Regeneration tank | DN5000/6000/7000, H=6000 mm | 1 |
| 5 | Alkali preparation tank | – | 1 |
| 6 | Foam pump | – | 1 |
| 7 | Filtrate pump | Q=10.5 m3/h, H=42 m, CHZ25-200A | 8 |
| 8 | Foam tank | 2600×5000 | 1 |
| 9 | Underground vent tank | 2600×5000 | 1 |
| 10 | Level regulator | DN=800/600 | 1 |
| 11 | Plate and frame filter press | 30 m2 | 1 |
| 12 | Circulating liquid tank | DN6000×6000 | 1 |
| 13 | Sulfurization slurry tank | 1500×4000×1500 | 2 |

4. Process technical parameters for the operation unit
4.1 Temperature parameters
Gas temperature after the blower: ≤35°C
Gas temperature entering the desulfurization tower: 20–35°C
Temperature of the solution entering the desulfurization tower: 30–40°C
Temperature of the solution in the reaction tank: 30–40°C
4.2 Pressure parameters
Pressure of gas entering the desulfurization tower: 5–15 kPa
Pressure of gas exiting the desulfurization tower: 4.5–14.5 kPa
Pressure entering the regeneration injector: ≥0.4 MPa
Air pressure entering the injector: 0.4–0.6 MPa
4.3 Resistance and flow rate parameters
Resistance in the desulfurization tower: ≤1500 Pa
Flow rate of the solution entering the desulfurization tower: 350–450 m3/h
4.4 Quality parameters
pH value of the desulfurization liquid: 8.5–9.2
H2S content in the gas after passing through the desulfurization tower: < 1 g/m3
Suspended sulfur content: ≤3.0 g/l

5. Normal operation
5.1 Desulfurization unit
5.1.1 Responsibilities
5.1.1.1 Responsible for operating and adjusting the flow rates, pressures, and temperatures of the gas and circulating liquid, in accordance with the requirements of the process parameters ； Responsible for the recovery and preliminary processing of sulfur foam, closely monitoring the bubbling activity at the top of the regeneration tank, and properly adjusting the liquid level ； Reduce the content of suspended sulfur in the system in a timely manner, fully recover sulfur, produce sulfur and supply sulfur slurry, so as to meet the requirements of the process technical specifications. 5.1.1.2 Control the liquid level in the foam tank according to the process requirements. 5.1.1.3 Check the condition of the sulfur foam in the foam tank once per hour, and be responsible for starting up, stopping, and ensuring the proper operation of the plate and frame filter press. 5.1.1.4 Carry out chemical dosing in accordance with the workshop’s instructions to ensure that the components of the desulfurization solution meet the requirements of the desulfurization process. 5.1.1.5 Responsible for the maintenance of the equipment assigned to this position as well as the cleaning of the equipment’s surrounding area. Participate in the testing and acceptance processes after repairs are carried out on devices such as circulation pumps. Regularly lubricate pumps and valve screws to ensure their proper operation. Check instruments frequently, and report any damage or malfunctions promptly. 5.2 Daily Operations 5.2.1 Items to be checked hourly 5.2.1.1 Pump outlet pressure, motor operating current, solution circulation rate, and gas pressure. 5.2.1.2 Check whether the temperatures of the front and rear bearings of the pump, as well as the temperature of the motor casing, are normal, and whether there are any abnormal noises. 5.2.1.3 Gas temperature and circulating liquid temperature. 5.2.2 Items to be checked every half hour 5.2.2.1 Liquid levels in underground tanks, waste liquid tanks, and other such tanks. 5.2.2.2 Make adjustments in coordination with the control room staff based on the situation of sulfur foam overflow. 5.2.3 Items to be checked every two hours: Check whether outdoor equipment is leaking air or fluid; increase frequent inspections in case of any abnormal conditions. 5.2.4 During each day shift, the operating crew shall clean the drain pipes of the gas pipelines. 5.2.5 Regulation of the overflow volume from the regeneration tank 5.2.5.1 Regularly check the overflow condition in the regeneration tank; generally, the overflow level of the level controller is adjusted to control the overflow volume, and in some cases, the solution circulation rate can also be adjusted for this purpose. 5.3 Filter Press 5.3.1 Responsibilities 5.3.1.1 This position is responsible for pumping the sulfur slurry from the sulfur foam tank to the filter press in order to carry out filtration and form sulfur cakes, which are then transported to the sulfur pooling area. 5.3.1.2 Be responsible for discharging materials according to the requirements of operational specifications; it is strictly prohibited to allow sulfur foam to be carried along with the liquid, and records must be kept. 5.3.1.3 Responsible for the maintenance of equipment, valves, instruments, etc. in this position, ensuring they remain in good condition with no leaks; timely lubrication of the oiling points on all screw valves, as well as proper maintenance and cleaning. 5.3.1.4 Responsible for the recovery of solutions and slag, as well as for the cleaning and maintenance of equipment and the premises. 6. Startup and shutdown procedures 6.1 Startup and shutdown of the desulfurization tower 6.1.1 Starting up the tower 6.1.1.1 Notify the electricians, fitters, and instrument technicians to check the associated equipment to ensure it is in good condition. 6.1.1.2 Prepare the desulfurization solution. 6.1.1.3 Notify relevant units such as the drum cooling team and the dispatch department. 6.1.1.4 Before starting operations in winter, all oil and water pipelines must be cleaned. 6.1.1.5 Check whether the manhole of the tower is properly sealed, whether the water seal and the bottom of the tower are filled with water to prevent gas from escaping, and open the vent valve at the top of the tower. 6.1.1.6 Open the steam purge valve to displace the air in the tower with steam, until a large amount of steam emerges from the vent pipe. 6.1.1.7 Start the desulfurization liquid circulation pump to enable the circulation liquid to be sprayed, and adjust the temperatures, pressures, and circulation rates at various locations to meet the technical specifications. 6.1.1.8 Slightly open the gas inlet valve to use gas to displace the vapor inside the tower; once a large amount of gas begins to emerge from the vent pipe at the top of the tower, indicating that the explosion test has been successful, close the gas vent pipe valve. After opening the outlet valve and the inlet valve, slowly close the bypass valve, while paying attention to changes in pressure behind the blower as well as the resistance in the desulfurization tower. 6.1.2 Shutdown of the tower 6.1.2.1 Stop the desulfurization liquid circulation pump, and close the inlet and outlet valves as well as the main valve of the regeneration tank’s injection pipeline. 6.1.2.2 Open the gas bypass valve. 6.1.2.3 Close the gas inlet and outlet valves of the desulfurization tower, and open the vent valve at the top of the tower. 6.1.2.4 To carry out work inside the tower, the gas inlet and outlet valves must be covered with blind flanges, and then the area should be cleaned using steam until steam begins to emerge from the vent pipes. Once the steam supply is turned off, the manholes on the tower should be opened for ventilation. Work can only begin inside the tower after safety inspections confirm that it is safe to do so. 6.1.2.5 In the event of a long-term shutdown of the tower, it is necessary to drain and clean the relevant equipment and pipelines. 6.2 Startup and shutdown of the desulfurization liquid circulation pump 6.2.1 Before starting, it is necessary to check that the pipes and valves are in normal condition prior to operation; moreover, the pump bearings must be filled with lubricating grease. The coupling should be turned by hand to ensure normal operation. 6.2.2 Before starting, slightly open the pump’s inlet valve, close the outlet valve, and open the pressure gauge valve. Then start the motor; once the pump is operating properly and the pressure gauge shows the correct pressure, gradually open the pump’s inlet and outlet valves until the flow rate is adjusted to the desired level. 6.2.3 When the pump stops operating, first reduce the flow rate by closing the pump’s outlet valve, then turn off the power supply. After the pump has stopped, close the inlet valve as well. In winter, when the pump is shut down, the water remaining inside it should be drained to prevent it from freezing and cracking. 7. Abnormal Conditions and Handling 7.1 Sudden Power Outage 7.1.1 If a fault occurs in the electrical circuit of a pump or related mechanical equipment, the backup equipment shall be activated. 7.1.2 In the event of a short-term power outage, close the pump outlet valve. 7.2 High resistance in the desulfurization tower 7.2.1 Contact the relevant departments. 7.2.2 Open the traffic pipe valve as instructed. 8. Classification and allocation of responsibility for process accidents: Any accident that occurs during the production process due to the operator failing to follow the prescribed procedures or acting carelessly during operation is considered a process accident. 8.1 Failure of the desulfurization liquid circulation pump: If the desulfurization liquid circulation pump fails to operate due to reasons such as an excessively low liquid level in the reaction tank or a sudden power outage, and the on-duty operator fails to detect this in time, resulting in disruptions to the normal desulfurization process, the on-duty operator shall be held responsible. 8.2 If the resistance in the desulfurization tower is high, or if this leads to gas release from the coke oven, the control room should monitor the pressure behind the fan and instruct the operators on duty to adjust the desulfurization valve promptly. In the event that delays in adjustment or handling result in an increase in the resistance of the desulfurization tower, thereby causing excessive pressure behind the fan that cannot be adjusted and forcing gas to be released, the operator on duty shall be held responsible, in accordance with the principle that those who operate the equipment are accountable for any issues that arise. 8.3 Product quality incidents: Any cases in which the product quality at this workstation is substandard due to careless operation, inadequate control over the quality of raw materials, or failure to make adjustments in accordance with technical specifications are the responsibility of the operator on duty. 8.4 Operational accidents resulting from imperfect process technical specifications are the responsibility of both technical managers and operators. II. Operating procedures for final cooling and ammonia evaporation 1. Process flow and brief description: Final cooling of gas – The gas coming from the desulfurization tower enters at the top of the final cooling tower; after being cooled twice, first with circulating water at 35°C and then with cold water at 15–20°C, the temperature of the gas drops below 30°C, after which it proceeds to the next stage of the process. The condensate generated during the gas cooling process is discharged through the outlet at the bottom of the final cooling tower. Ammonia washing and ammonia distillation: The gas coming from the final cooling unit enters the ammonia washing tower at its bottom; the ammonia washing solution enters the tower from the middle, while soft water enters from the top and comes into contact with the gas in the opposite direction. As the NH3 in the gas is absorbed by the ammonia washing solution, the gas is discharged from the top of the tower. The ammonia washing solution and the soft water, having absorbed ammonia, mix together at the bottom of the tower to form an ammonia-rich solution, which is then discharged to the ammonia-rich solution tank. The ammonia-rich water is pumped to the top reducer of the ammonia distillation tower, where it exchanges heat with ammonia vapor to reach a temperature of around 50º–60ºC. It then goes to the ammonia-rich water-wastewater heat exchanger, where it exchanges heat with the ammonia distillation wastewater to reach a temperature of around 90ºC before entering the ammonia distillation tower. Direct steam enters from the bottom of the tower, carrying the ammonia present in the ammonia-rich water to the top of the tower. At the same time, a large amount of water vapor is also sent to the condenser at the top; there, the majority of the water vapor and a small amount of ammonia condense into liquid and flow back directly, thereby keeping the temperature at the top of the tower around 97°C. Meanwhile, the ammonia vapor, after being concentrated, is discharged from the top and enters the incinerator where it is broken down into N2 and H2. The H2 gas then burns to form H2O, which is released into the atmosphere along with N2. The ammonia-enriched water from which ammonia has been vaporized is converted into ammonia-vaporization wastewater and flows out at the bottom of the tower. After passing through a heat exchanger, it enters the circulating ammonia water tank, where it is pumped out by a circulating ammonia water pump; part of this water is sent to the coking quenching tank, while another portion is sent to a wastewater cooler before being used for spraying at the top of the ammonia washing tower. (The sum of the added soft water volume and steam consumption constitutes the wastewater volume sent to the coking quench tank, which is approximately 10–12 t/h). 2. Technical specifications for raw materials and products
2.1 Raw materials
2.1.1 Gas: Temperature < 30°C, Pressure > 20 kPa, Flow rate > 5000–20000 Nm3/h
2.1.2 Ammonia washing water: Temperature 30–33°C, Flow rate 15–20 Nm3/h, Pressure > 0.5 Mpa
2.1.3 Soft water: Temperature ≤ 25°C, Pressure ≥ 0.4 Mpa, Flow rate 8–10 Nm3/h
2.2 Finished products
2.2.1 Ammonia gas: Flow rate 0.5–0.7 t/h, Concentration 18.0%
2.2.2 Ammonia-rich water: Ammonia content 6–8 g/L
2.2.3 Ammonia-evaporation wastewater: Flow rate 20–25 Nm3/h, Concentration < 0.03%
2.2.4 Gas after ammonia washing: Ammonia content < 0.05 g/m3, Temperature < 30°C
3. List of equipment
| Serial No. | Equipment name | Specification model | Unit | Quantity | Weight (kg) | Remarks |
|------------|----------------|--------------------|------|----------|-------------|---------|
| 1 | Ammonia washing tower | Ф3200×31500 (H) | Unit | 1 | 41000 | Fasteners are made of stainless steel |
| 2 | Ammonia-evaporation tower | Ф1400×14910 (H) | Unit | 1 | 18075 | Fasteners are made of stainless steel |
| 3 | Soft water tank | Ф3600×3600 | Unit | 1 | 3000 | |
| 4 | Ammonia-rich water tank | Ф4000×4000 | Unit | 1 | 4200 | |
| 5 | Circulating ammonia water tank | Ф4000×4000 | Unit | 1 | 4200 | |
| 6 | Ammonia water reflux tank | Ф2000×2000 | Unit | 1 | 500 | |
| 7 | Pressure vessel | | Unit | 1 | | |
| 8 | Ammonia-rich wastewater heat exchanger | | Unit | 2 | | |
| 9 | Ammonia condenser | 30 m2 | Unit | 1 | 1000 | |
| 10 | Wastewater cooler | 100 m2 | Unit | 1 | 4000 | |
| 11 | Ammonia incinerator | Ф2000×6577 (L) | Unit | 1 | 30975 | |
| 12 | Soft water pump | LYA32-160 | Unit | 2 | | |
| 13 | Ammonia-rich water pump | ANS80×40×200 | Unit | 1 | 1000 | |
| 14 | Circulating ammonia water pump | ANS80×40×200 | Unit | 2 | 1000 | |
| 15 | Underground vent tank | Φ2600×5000 (L) | Unit | 1 | 2600 | |
| 16 | Submersible pump | LYA40-200 | Unit | 1 | | |
| 17 | Chimney | | Unit | 1 | | |
| 18 | Final cooling tower | FN1400 m2 | Unit | 1 | 73906 | |
4. Process technical parameters for each operation stage
4.1 Temperature:
- Temperature at the top of the tower: 95º–97°C
- Temperature at the bottom of the tower: 105°C
- Temperature of ammonia-rich water entering the tower: > 90°C
- Steam temperature: > 250°C
4.2 Pressure:
- Steam pressure: > 0.8 Mpa
- Pressure at the top of the ammonia-evaporation tower: 0.01 Mpa
- Pressure at the bottom of the ammonia-evaporation tower: 0.03 Mpa
4.3 Flow rate:
- Steam flow rate: > 4.5 t/h
- Flow rate of ammonia-rich water: 20–25 Nm3/h
4.4 Liquid level: 30–80%
4.5 Normal operation
5.1 Check the operating condition of each pump; ensure that the temperature of motors and bearings is below 70°C℃ ； The machine vibration is less than 0.06 mm, with no abnormal noises. 5.2 Ensure relatively stable liquid levels in each tank and tower. 5.3 Adjust each feed temperature to meet the technical specifications. 5.4 Adjust the feed and return flow rates to stabilize the operating parameters of the ammonia evaporation tower and ensure they meet the specified requirements. 5.5 Conduct regular inspections of the operational status of on-site equipment, as well as temperature, pressure, and liquid level levels, once every hour; in case of any issues, address them promptly by contacting the relevant personnel. 5.6 Work in conjunction with the laboratory technician to promptly carry out sampling and testing of raw materials, intermediate products, and finished products, and make adjustments based on the test results. 5.7 Maintain the cleanliness of the equipment and the surrounding environment, and ensure proper lubrication of the operating equipment and valve stems. 5.8 Keep proper records that are complete, accurate, and neat. 6. Startup and shutdown procedures: 6.1 Preparations before startup: 6.1.1 Carefully inspect the valves of all equipment to ensure they are functional and in a ready state for use. 6.1.2 Notify the instruments to ensure they are functioning properly and prepare for calibration. 6.1.3 Notify the electrician to inspect the electrical appliances; once everything is confirmed to be in order, power should be supplied to the appliances. 6.1.4 Notify the steam supply department and water supply pump room to supply low- and medium-temperature water, soft water, and steam. 6.1.5 Open the top vent pipe and introduce steam into the tower and the gas outlet pipeline to displace air, until a large amount of steam emerges from the vent pipe. 6.2 Commencement of operation: 6.2.1 Upon receiving the order to start operation, notify all relevant personnel to supply water for the cold circulation. 6.2.2 When the liquid level in the soft water tank reaches 30%, start the soft water pump and adjust the feed rate to 15 t/h. 6.2.3 Sequentially open the gas outlet valve and inlet valve of the ammonia washing tower, and close the bypass valve; once a large amount of gas begins to emerge from the vent pipe at the top of the tower, close the vent pipe. 6.2.4 When the liquid level in the ammonia-rich water tank reaches 30%, start the ammonia-rich water pump. 6.2.5 Once a liquid level is observed at the bottom of the ammonia vaporization tower, open the direct steam inlet valve and adjust it as specified. 6.2.6 Notify the environmental protection department, start the wastewater pump to discharge the wastewater, and at the same time turn on the circulating water for the wastewater cooler. 6.2.7 Adjust various temperatures, pressures, and liquid levels to ensure they are within the acceptable range. 6.2.8 Further adjust the temperature, pressure, and liquid level parameters at various locations to ensure they remain within acceptable ranges. 6.2.9 Sample and test concentrated ammonia solution as well as wastewater for ammonia content, and make further adjustments based on the test results until the product quality meets the standards. 6.2.10 Notify the incinerator to prepare for burning NH3 vapor. 6.2.11 Notify the coking plant regarding the wastewater to be sent outside. 6.2.12 When the new system is put into operation, pilot production should be carried out using fresh water, following the same steps as above. 6.3 Shutdown: 6.3.1 Sequentially open the gas traffic valves of the ammonia washing tower, close the inlet and outlet gas valves, and open the vent pipe. 6.3.2 Stop the soft water pump. 7.3. Stop the 3 ammonia water pumps. 6.3.4 Stop the wastewater pump. 6.3.5 Shut off medium and low-temperature water at all locations. 6.3.5 After cleaning the top of the ammonia vaporization tower with steam, stop the air supply. 6.3.6 During prolonged shutdowns in winter, all equipment and pipelines shall be vented. 6.4 Pump starting operation: 6.4.1 Check whether the motor and pump are in normal condition. 6.4.2 Power supply to be restored after the turning gear operates smoothly (idle operation should be normal with no abnormal noises). 6.4.3 Open the pump inlet valve; after starting the pump, open the pump outlet valve once the outlet pressure rises. 6.4.4 When it is necessary to stop the pump, the power supply should be cut off first, followed by closing the inlet and outlet valves of the pump. 7. Abnormal situations and handling: 7.1 Sudden power outage or interruption of medium/low temperature water supply: 7.1.1 Immediately close the inlet and outlet valves of all pumps. 7.1.2 Close the medium and low-temperature water valves everywhere. 7.1.3 Notify the relevant units. 7.1.4 Wait for power supply to be restored before starting work. 8. Classification of process accidents and assignment of responsibilities: Any accident that occurs during the production process due to the operator failing to follow the operating procedures or acting carelessly during operation is considered a process accident. A The overflow of wastewater is caused by the tanks being full. After a power or water outage, no action was taken, resulting in increased system pressure and an explosion. 9. This process is a new one, and these procedures are provisional. Any issues with their applicability should be reported promptly so that appropriate adjustments can be made to improve the procedures. III. Operating Procedures for Benzene Washing and Crude Benzene Distillation 1. Brief description of the process flow (1) Benzene washing: The coke oven gas supplied from the coking plant is cooled in an ultimate cooling tower and then passed through an ammonia washing tower, as a result of which the gas temperature drops below 30°C and the ammonia content in the gas is reduced to 0.05 g/m3. The gas then enters the benzene washing tower from its bottom; after being washed, it exits the tower at the top and is sent either to a unit for further naphthalene removal or back to the coking plant. The benzene washing process takes place in a benzene washing tower, and the solvent used for washing gas of benzene is tar wash oil or recycled oil (oil-poor). The purchased tar wash oil is fed into the new wash oil tank (circulation oil tank), where it is pumped out by a circulation oil pump and sent to the top of the benzene washing tower to be sprayed inside the tower. The lean oil flows from the top of the tower to the bottom, while the gas flows from the bottom to the top. Under the action of the packing in the benzene washing tower, the rising gas mixes thoroughly with the descending lean oil, allowing for mass and heat transfer; the benzene compounds in the gas are absorbed by the lean oil. As a result, the benzene content in the gas after washing drops to 2–4 g/m3. Meanwhile, rich oil containing benzene is obtained at the bottom of the benzene washing tower. (2) Benzene distillation: The benzene distillation process takes place in a benzene distillation tower. The steam benzene tower has a total of 30 trays: 15 of them are feed trays, the top 30 trays serve as reflux trays, and 29 trays are used for oil-water outlet. The oil-rich liquid at the bottom of the tower flows automatically into the oil-rich tank. The rich oil in the rich oil tank is pumped out using a rich oil pump and sent successively to the gas-oil heat exchanger at the top of the benzene distillation tower, the rich-poor oil heat exchanger at the bottom of the tower, and then heated in a tubular furnace before entering the benzene distillation tower from its middle section. Direct steam is introduced into the bottom of the tower for heating. The steam rising inside the benzene distillation tower flows from the bottom to the top of the tower, while the oil-rich mixture flows from the middle of the tower toward the bottom. Under the action of the steam, the benzene compounds in the oil-rich mixture are vaporized and continue to flow upward along the tower. The oil that has had its benzene removed by the steam flows back to the bottom of the tower. The lean oil at the bottom of the tower flows by gravity, entering successively the lean-ric oil heat exchanger and the lean oil cooler, before reaching the circulating oil tank. The lean oil in this tank is pumped out using a circulating oil pump and then sent to the top of the benzene washing tower for benzene removal. The benzene-containing rich oil and the benzene-free lean oil circulate during the benzene washing process as well as the benzene distillation process. The benzene compounds vaporized by steam in the benzene vaporization tower continue to flow upward toward the top of the tower, where they come into full contact with the reflux liquid moving downward, allowing for mass and heat transfer; ultimately, benzene vapor of acceptable purity is obtained at the top of the tower. The benzene vapor at the top of the tower enters the overhead oil-gas heat exchanger and then the overhead condenser, where it is condensed into a liquid. This liquid then goes into the crude benzene oil-water separator; the water separated out flows into a control separator for further separation. The water is subsequently sent to the ammonia vaporization cycle’s ammonia water tank, where it is used for ammonia washing ； The separated crude benzene enters the reflux tank. Some of the crude benzene in this tank is pumped out using a crude benzene reflux pump and sent to the top of the distillation tower, where it enters the tower through the reflux inlet as the reflux liquid for the distillation tower. The remaining crude benzene in the reflux tank flows into an intermediate tank; once it has passed quality checks, it is pumped into a large storage tank on a scheduled basis to be sold as a product. (3) Regeneration: To remove moisture from the benzene distillation tower and prevent water accumulation inside the tower, which could disrupt its equilibrium, an oil-water mixture is drawn off at the 29th level of the tower. After separation, the water enters the crude benzene control separator at the top of the tower, while the separated oil returns to the inlet at the 28th level to re-enter the tower. To remove polymers from the circulating oil and maintain its high benzene-washing capacity, it is necessary to regenerate the circulating oil. For this purpose, a portion of the oil-rich stream (2–3%) coming out of the tubular furnace is sent to the regenerator. Superheated steam heated by the tubular furnace is introduced at the bottom of the regenerator; under the action of this steam, the oil-rich stream is regenerated. The regenerated oil vapor returns to the benzene distillation tower, while the residue at the bottom of the regenerator is placed in an underground tank where it is cooled with water. The residue in the tank is removed periodically and either sold or processed further. 2. Raw Materials, Product Technical Requirements and Quality Standards
2.1 Raw Materials
Gas flow rate: 20,000 m3/h; Temperature: less than 30°C. Benzene content in the gas before entering the tower: 33–36 g/m3. Flow rate of lean oil entering the tower: 30–35 t/h; Temperature of lean oil: less than 30°C. Flow rate of rich oil: 30–35 t/h; Benzene content in rich oil: 1.6–2.5%. Steam pressure at the inlet: ≥0.5 Mpa; Gas pressure at the inlet: ≥1500 Pa.
2.2 Products
Benzene content in lean oil: ≤0.5%. Crude benzene: Density ≤0.878 g/cm3; Initial boiling point: 90°C; Dry point: ≤180°C. Benzene content after passing through the gas tower: less than 2–4 g/m3.
3. List of Equipment
| Serial No. | Equipment Name | Specification Model | Quantity |
|-------------|----------------|--------------------|----------|
| 1 | Cylindrical Tube Furnace | 170x104 Kcal/h, with chimney and fan | 1 unit |
| 2 | 30-Stage Bubble Column Debenzination Tower | H=27700 mm, Ф1600 mm | 1 unit |
| 3 | Regenerator | Ф1600 mm, H=9000 mm | 1 unit |
| 4 | Rich Oil Tank | Vg=50 m3, H=4250 mm, Dg=4400 mm | 1 unit |
| 5 | Lean Oil Tank | Vg=50 m3, H=4250 mm, Dg=4400 mm | 1 unit |
| 6 | Fresh Wash Oil Tank | Vg=50 m3, H=4250 mm, Dg=4400 mm | 1 unit |
| 7 | Crude Benzene Storage Tank | Vg=200 m3, H=6000 mm, Dg=7000 mm | 1 unit |
| 8 | Underground Drainage Oil Tank | Vg=25 m3, H=6500 mm, Dg=2400 mm, with submersible pump LYA32-160 | 1 unit |
| 9 | Crude Benzene Oil-Water Separator | Dg=1000 m3, H=3600 mm | 1 unit |
| 10 | Crude Benzene Control Separator | Dg=1000 m3, H=3600 mm | 1 unit |
| 11 | Crude Benzene Reflux Tank | Dg=1000 m3, H=3600 mm | 1 unit |
| 12 | Oil-Water Separator at the Top of the Debenzination Tower | Dg=1000 m3, H=1500 mm | 1 unit |
| 13 | Circulation Oil Pumps | ANS80x40x200 | 2 units |
| 14 | Rich Oil Pumps | ANS80x40x330 | 2 units |
| 15 | Crude Benzene Reflux Pumps | ESH25-200 | 2 units |
| 16 | Crude Benzene Product Pumps | ANS40x25x160 | 1 unit |
| 17 | Heat Exchangers for Lean and Rich Oil at the Bottom of the Distillation Tower | Diameter: 600 mm, Length: 7000 mm; Heat exchange area: 180 m2 | 2 units |
| 18 | Coolers for Lean Oil at the Bottom of the Distillation Tower | Diameter: 600 mm, Length: 7000 mm; Heat exchange area: 180 m2 | 3 units |
| 19 | Oil-Gas Heat Exchanger at the Top of the Distillation Tower | Diameter: 700 mm, Length: 7100 mm; Heat exchange area: 220 m2 | 1 unit |
| 20 | Condenser for Crude Benzene at the Top of the Distillation Tower | Diameter: 700 mm, Length: 7100 mm; Heat exchange area: 220 m2 | 1 unit |
4. Process Technical Parameters
4.1 Temperature Parameters
Temperature of gas entering the benzenation tower: less than 30°C. Temperature of lean oil sprayed: 2–3°C higher than the temperature of the gas entering the tower (to prevent water in the gas from entering the oil). Temperature of rich oil entering the tower: 180–190°C. Temperature of superheated steam: >300–320°C. Temperature at the top of the regenerator: ≥180°C. Temperature at the top of the debenzination tower: 90°C. Temperature of the side water line: 100°C. Temperatures of oil-gas heat exchangers and condensers: [values not specified]. Temperature of hot lean oil at the bottom of the tower: [values not specified].
4.2 Pressure Parameters
Resistance in the benzenation tower: less than 2500 Pa. Pressure at the bottom of the debenzination tower: ≤0.04 MPa. Pressure at the top of the debenzination tower: ≤0.01 MPa. Steam pressure at the inlet: ≥0.5 MPa. Gas pressure entering the tubular furnace: 2000 Pa–6000 Pa.
4.3 Flow Rate Parameters
Flow rate of rich oil entering the benzenation tower: 30–35 m3/h. Flow rate of steam: 0.5–1 t/h. Reflux ratio: 3–5.
4.4 Quality Parameters
Benzene content in lean oil: ≤0.05%. Ammonia content in the separated water: ≤0.06%. Density of light benzene: ≤0.878 g/m3. Initial boiling point: 90°C. Dry point: ≤180°C. Amount of wash oil used: 50–100 kilograms per ton of crude benzene.
4.5 Liquid Levels
Liquid levels in all tanks and towers should be maintained at 1/3 to 2/3 of their capacity. 5. Normal operation 5.1 Key operating points 5.1.1 Regularly check the temperature, pressure, and flow rates at various locations to ensure they are within specified limits. In particular, it is important to check whether the gas combustion in the tubular furnace is operating normally; once extinguishment is detected, re-ignition must be carried out in accordance with the tubular furnace ignition procedures. 5.1.2 It is necessary to regularly monitor the resistance in the ammonia scrubber and benzene scrubber; when the resistance exceeds the specified value, adjustments and cleaning should be carried out promptly. 5.1.3 Pay attention to the changes in the temperature of the washing oil and the gas; generally, it should be maintained such that the temperature of the washing oil is 2–7°C higher than that of the gas. 5.1.4 Regularly check and adjust the levels of the oil-rich tank, oil-poor tank, etc., keeping them at 1/2–1/3 of their capacity to prevent overfilling or emptying. Fuel should be added when the liquid level is low; under no circumstances should the fuel inlet valve of the regenerator be closed to maintain the liquid level. 5.1.5 Control the interface of the oil-water separator to prevent separated water from entering crude benzene. 5.1.6 The regenerator should discharge slag at regular intervals; in case of special circumstances, slag should be discharged promptly, and the pipes should be cleaned after disposal. 5.1.7 It is necessary to regularly analyze the quality of the recycled washing oil, determine appropriately the amount of washing oil to be regenerated, and replenish it with qualified new washing oil according to actual conditions. 5.1.8 Accurately measure the production volume of crude benzene by monitoring the liquid level in the crude benzene storage tank. 5.1.9 The amount of direct steam supplied to the benzene removal tower has a significant impact on product quality as well as the benzene content in the rich and lean oils; when too much steam is used, black oil may emerge from the top of the tower, so it should be controlled appropriately. 5.1.10 Regularly check equipment and pipelines for any leaks, and address any issues found promptly. 5.1.11 The oil drained underground should be pumped away promptly; full-flow discharge is strictly prohibited. 5.1.12 As specified, record the operational metrics for the position once per hour. 5.1.13 Contact the laboratory to take samples in a timely manner for various tests (mainly benzene content in gas before the tower, benzene content in gas after the tower, benzene content in rich oil, benzene content in lean oil, and the quality of crude benzene). Record the results of these tests, and make adjustments promptly based on those results to ensure that the quality of all products meets the required standards. 5.1.14 Regularly inspect the equipment; turn the standby equipment over once per shift. 5.1.15 Strictly follow the routine of lubricating the pump’s bearing housings on Fridays, maintaining the oil level at 2/3. 5.1.16 Conduct equipment and environmental cleaning once per shift to ensure that the equipment is clean, the environment is tidy, and there is no oil contamination on the equipment. 6. Startup and shutdown procedures 6.1 Preparations before startup 6.1.1 Carefully inspect the valves of all equipment to ensure they are functional and in a ready state for use. 6.1.2 Notify the instruments to ensure they are functioning properly, and carry out calibration and measurement control for the systems. 6.1.3 Notify the electrician to inspect the electrical appliances; once everything is confirmed to be in order, power should be supplied to the appliances. 6.1.4 Sufficient purchased washing oil shall be supplied to the new washing oil tank for use. 6.1.5 Direct steam is supplied either from the regenerator or from the bottom of the benzene removal tower to purge the oil system and ensure its smooth operation. The flow path is as follows: regenerator → benzene removal tower → crude benzene gas-oil heat exchanger → crude benzene condenser → crude benzene oil-water separator → crude benzene control separator → crude benzene reflux column. Steam is also used to purge the rich-oil/lean-oil heat exchanger, the lean-oil cooler, and the pipelines for rich and lean oil, in order to keep them unobstructed; steam supply is stopped after purging is complete. 6.1.6 The oil-water separators at the top of each tower, the oil-water separator for crude benzene, the control separator, and the crude benzene reflux column are filled with water. 6.1.7 Open the vent valve at the top of the benzene washing tower, and purge it with sufficient steam for half an hour. Then open the gas inlet valve of the tower to supply gas; after sampling at the gas sampling valve at the top of the tower and confirming that the gas explosion test is successful, close the vent valve and open the bottom drain valve to discharge the condensed steam from the bottom of the tower, after which wait to start up the operation. 6.1.8 Prepare the tubular furnace for ignition; purge the gas pipeline with steam. After the gas is supplied and the gas explosion test is successful, close the gas valve and wait to start operation. (The startup of a new tubular furnace must follow the heating curve provided by the manufacturer in order to ensure the strength of the refractory materials in the furnace walls.) This work must be carried out in advance for new installations.) 6.1.9 Before starting operations in winter, the oil and water pipelines need to be cleaned. 6.2 Commencement of work 6.2.1 After receiving notification from the foreman, make contact with the previous process as well as the coking plant to get everything ready for commencement of work. 6.2.2 Before starting up, the desulfurization and ammonia washing systems must be operating properly. Especially for the first commissioning, the installation and pressure testing of all equipment, pipelines, valves, instruments, etc. have been completed successfully. Especially because the products are flammable, explosive, and toxic, it is necessary to carry out all necessary safety and fire prevention measures. 6.2.3 Start the circulation oil pump to convey the lean oil (newly washed oil) to the top of the benzene washing tower. Once the liquid level of the rich oil at the bottom of the benzene washing tower reaches 2/3, start the rich oil pump. The rich oil passes through the gas-oil heat exchanger at the top of the benzene distillation tower, the lean-rich oil heat exchanger, and the tubular furnace, before finally entering the benzene distillation tower. The lean oil at the bottom of the tower flows, driven by gravity, through the lean-rich oil heat exchanger and the lean oil cooler, before ultimately reaching the circulation oil tank. Once the low and high oil systems begin to circulate, it is important to regularly check for any leaks or abnormalities, and to report any issues found promptly for handling. 6.2.4 Open the gas outlet valve of the benzene washing tower to send the gas to the next process step. 6.2.5 Once the circulation of lean and rich oil is operating normally, follow the ignition procedures for the tubular furnace: first, purge the furnace with air for 15–25 minutes, then insert a torch or a pre-ignited ignition tube into the furnace. After that, open the valve for the gas supplied to the furnace, ignite the gas there, and adjust the amounts of gas and air supplied to carry out temperature raising and dehydration of the rich oil. The temperature of the tubular furnace should be increased gradually; the increase should not exceed 100°C during the first 2 hours, and after 4 hours, it can be raised to the specified value. 6.2.6 When the oil-rich liquid temperature reaches 120°C, direct steam is introduced into the bottom of the benzene distillation tower for heating. 6.2.7 Open the cooling water for a section of the lean oil cooler according to the lean oil temperature, and adjust it to meet the technical requirements. 6.2.8 Feed water for the condenser at the top of the benzene distillation tower; control the interface in the water-organic separation unit at the top of the tower, as well as the interface in the separator used for crude benzene separation, and also monitor the liquid level in the crude benzene reflux tank. 6.2.9 When the liquid level in the crude benzene reflux tank reaches 2/3, start the reflux pump to send reflux to the top of the tower; also open the oil-water outlet and oil return valve located at the 29th tray at the top of the tower, in order to ensure proper reflux flow and maintain a normal temperature at the tower top. Control the interface of the oil-water separator at the top of the tower to prevent oil from entering the wastewater tank of the ammonia vaporization system. 6.2.10 Thoroughly check the pressure and temperature to ensure they meet technical specifications, and keep records of startup. 6.2.11 Further adjust the temperatures and flow rates at various locations based on the operation conditions and test results, to ensure that the crude benzene product meets the required standards. 6.2.12 Part of the oil-rich stream from behind the tubular furnace is fed into the regenerator, where it is heated by superheated steam that has been heated in the tubular furnace; this process enables the oil-rich stream to be regenerated. The amount of regenerated oil-rich stream is approximately 3% of the total amount of oil circulating in the system. The regenerated oil and gas are returned to the bottom of the benzene distillation tower, while the regeneration slag is discharged into an underground tank where it is cooled with water. Regularly clean the residues in the underground tank, and either sell them or dispose of them elsewhere. 6.3 Shutdown 6.3.1 After receiving notification from the foreman, contact the relevant parties and make preparations for the shutdown. 6.3.2 When stopping the oil supply to the regenerator and slag discharge is required, slag discharge should be carried out first. 6.3.3 Gradually reduce the gas flow and air flow to the tubular furnace, eventually close the gas valve of the tubular furnace, and then stop the operation of the fan. (In the event of a prolonged shutdown, a blind flange must be installed at the flange behind the gas valve to prevent gas from leaking into the tubular furnace and the surrounding area.) 6.3.4 Close the steam inlet valve of the tubular furnace to stop the superheated steam. 6.3.5 Stop feeding oil into the regenerator. 6.3.6 Close the direct steam valve at the bottom of the benzene distillation tower. 6.3.7 Stop the recirculation pump and close the inlet and outlet valves of the pump at the same time. 6.3.8 Once the temperature of the rich oil drops to 120°C, stop the circulating oil pump and the rich oil pump, and close the inlet and outlet valves of the pumps. 6.3.9 During prolonged shutdowns, the oil inside the pipes and equipment shall be drained into underground drainage tanks. 6.3.10 Add water to the oil-water separator to displace all the oil, then drain the water. 6.3.11 Close the inlet and outlet valves for the warm water and cold water in each cooler, thereby stopping the flow of warm water and cold water within those coolers. During prolonged shutdowns in winter, drain any water accumulated in the equipment and pipelines to prevent damage to them due to freezing. Additionally, use steam to clean the top of the benzene distillation tower as well as the oil pipelines at the bottom of the tower, ensuring that the equipment and pipelines in the oil circulation system remain unobstructed. 6.3.12 When shutting down the benzene washing tower, open the gas bypass pipe of the tower, close the gas inlet and outlet valves of the tower, and open the vent pipe at the top of the tower. 6.4 Ignition of the tubular furnace: Two conditions must be met for igniting the tubular furnace: ① Oil and steam must already be flowing inside the furnace. ②The gas pressure is sufficient. 6.4.1 First, check whether all the gas valves are airtight. 6.4.2 Turn on the blower and use air to blow for 15–25 minutes. 6.4.3 Open the main gas valve as well as the drain pipe to release the condensate, then close the drain valve. 6.4.4 Light the gas ignition tube. 6.4.5 Place the open-flame gas ignition tube on the gas nozzle of the burner, then open the gas valve to ignite the gas supplied to the furnace. At the same time, check whether the gas combustion is normal; if extinguishment occurs, ignition must be performed again in accordance with the ignition procedures. 7. Abnormal Conditions and Handling 7.1 Sudden Power Outage 7.1.1 Immediately close the gas valve of the tubular furnace. Open the steam fire suppression pipe of the tubular furnace and cool it down to 150°C to prevent the furnace tubes from being damaged. 7.1.2 Immediately close the direct steam valves of all equipment, as well as the valve at the outlet of the rich oil from the bottom of the benzene washing tower and any valve on the pipeline carrying the lean oil from the bottom of the benzene distillation tower, in order to prevent the rich oil tank and the lean oil tank from overflowing. 7.1.3 Close the outlet valves of each pump. 7.1.4 Cut off the power supply to each pump and the fan. 7.1.5 Contact the shift supervisor, electrician, and the workshop to find out the cause of the power outage and its duration. If the outage lasts for a long time, organize the operators to carry out shutdown procedures; if it is short-lived, arrange for the operators to prepare for resuming operations once power is restored. 7.2 Sudden shutdown of steam supply 7.2.1 Immediately close the gas valve of the tubular furnace to stop heating, and introduce fire-fighting steam to reduce the temperature to 150°C in order to prevent damage to the steam pipes inside the furnace. 7.2.2 Appropriately close any one of the lean oil valves on the outlet pipeline at the bottom of the benzene distillation tower, to prevent the lean oil inside the tower from rushing back into the circulation oil tank and causing it to overflow. 7.2.3 Close the direct and indirect steam valves at all locations leading into the equipment, to prevent steam from entering the equipment suddenly, which could cause an increase in pressure and lead to an explosion. 7.2.4 Close the regenerator feed valve. 7.2.5 Contact the shift supervisor, the boiler room, and the workshop to find out the reason for the steam shutdown and the time it will occur. If the time is short, once steam is available, restart the tubular furnace, adjust the steam volume, and resume production; if the time is long, follow the shutdown procedures. 7.3 Sudden water supply interruption 7.3.1 Immediately reduce the heat and steam output, and adjust the return flow rate. 7.3.2 Contact the shift supervisor, the water pump room, and the workshop to find out the reason for and duration of the water outage. If the outage lasts for a long time, arrange for operators to carry out shutdown procedures; if it is short-lived, maintain the current status and resume production once water supply is restored. 7.4 Handling of Common Accidents 7.4.1 Flood in the Debenzene Tower Phenomenon: The pressure at the bottom of the tower gradually increases, the temperature downstream of the tower decreases, and the liquid level in the oil-poor tank gradually drops. Reason: The lean fuel system is clogged or a valve has failed, resulting in an excessively high rich fuel flow. Solution: Adjust the rich fuel flow and lean fuel system; if the problem is severe, stop operations for maintenance. 7.4.2 High resistance in the tubular furnace: The temperature of the rich oil increases, and the rich oil inside the furnace tubes burns up (the pressure at the outlet of the rich oil pump rises). Reason: Reduce the gas flow and air flow in the tubular furnace, as well as lower the temperature of the rich oil ； Inspect the furnace tubes. Solution: Increase the oil supply to adjust the amount of oil in the branch lines and continue production; if the situation is severe, stop production and replace the furnace tubes. 7.4.3 Oil leakage and fire in the rich oil line of a tubular furnace: Black smoke emanates from the chimney. Cause: Corrosion and perforation of the furnace tubes. Solution: Immediately close the gas valve, open the steam valve for extinguishing the fire; at the same time, stop the rich oil pump, lower the temperature of the furnace, and then investigate the cause to take appropriate action. 8. Classification and allocation of responsibility for process accidents: Any accident that occurs during the production process due to the operator failing to follow the prescribed procedures or acting carelessly during operation is considered a process accident. 8.1 Coking in the tubular furnace: Accidents resulting from tubular furnace coking, which affects production, occur due to a low flow rate of rich oil or a high flame intensity in the tubular furnace, leading to excessively high temperatures of the rich oil; failure to make timely adjustments is responsible for such incidents, and the on-duty operator is accountable for this. 8.2 Oil leakage and fire in tubular furnaces: If oil leakage leads to a fire in a tubular furnace, and a larger accident occurs due to delayed detection or failure to take emergency action, the operator on duty is held responsible. 8.3 Full or empty tanks due to overflow/evacuation: Any accidents resulting in overflow or evacuation of storage tanks caused by delayed adjustments, inadequate inspections, or failure to properly check the output shall be the responsibility of the operator, in accordance with the principle that those who carry out the operations are accountable. 8.4 Product quality incidents: Any cases in which the products produced are of substandard quality due to careless operation or failure to adjust them in accordance with technical specifications are the responsibility of the operator on duty. 8.5 Operational accidents resulting from imperfect process technical specifications are the responsibility of both technical managers and operators. IV. Purification of naphthalene 1. Brief description of the process flow and flow diagram: The gas obtained after benzene purification enters the naphthalene purification tower from its lower part, while light diesel is pumped to the top of the tower and sprayed in two stages. The gas and diesel flow in opposite directions within the tower, allowing for thorough contact between them; this facilitates the transfer of naphthalene-containing organic compounds from the gas to the diesel. Diesel is circulated and sprayed inside the tower; once the naphthalene content in the light diesel reaches a certain concentration and the quality of the gas exiting the tower approaches the specified limits, new diesel is added or replaced. The waste oil is pumped out using a waste diesel pump, while the gas free of naphthalene passes through the mist capture layer at the top of the tower before being sent to the gas storage tank. The flow diagram is provided below. 2. Technical requirements and quality standards for raw materials and products 2.1 Raw materials: Gas temperature before naphthalene washing: 30°C – 40℃ ； Naphthalene content in the air after benzene absorption: 600 mg/m3 in summer (April to October), 400 mg/m3 in winter (November to March) ； Cyclic spraying volume: 10–15 t/h ； Second-stage circulation spraying rate: 20-25t/h ； 2.2 Quality of purified coke oven gas: The gas at the outlet of the naphthalene washing tower contains less than 50 mg/m3 of naphthalene, and the tar content is:

Please check the post: Haichuan Chemical Industry Forum » Production Technology Exchange Area » Production Technology (Member-Only Area) » Guidelines for Coking Recovery Processes. Detailed descriptions can be found there: Attachment, 2007-5-27 03:49, Number of downloads: 16 – Crude benzene processing section operation standards.doc (92 KB); 2007-5-27 03:49, Number of downloads: 15 – Operating procedures for electric tar collectors.doc (73.5 KB); 2007-5-27 03:49, Number of downloads: 14 – Process technology operation standards for drum cooling sections.doc (90 KB); 2007-5-27 03:49, Number of downloads: 15 – Work standards for environmental testing positions.doc (108.5 KB); 2007-5-27 03:49, Number of downloads: 18 – Process technology operation standards for ammonium sulfate production sections.doc (69 KB); 2007-5-27 03:49, Number of downloads: 13 – Work standards for reagent preparation sections.doc (47.5 KB); 2007-5-27 03:49, Number of downloads: 14 – Operation standards for desulfurization sections.doc (74.5 KB); 2007-5-27 03:49, Number of downloads: 13 – Process details for wastewater treatment stations.doc (44.5 KB); 2007-5-27 03:49, Number of downloads: 14 – Technical regulations for circulating water sections.doc (44 KB); 2007-5-27 03:49, Number of downloads: 11 – Operating procedures for ammonia vaporization sections.doc (40.5 KB)

Thank you so much! ! Especially the procedures provided by friend ydq9197 are extremely useful to me! !

Thank you for the information you provided; it’s been very helpful to me.

Thank you for the information, OP; it’s been extremely useful to me. Thank you so much for your effort

Thank you to the original poster and the person from the third floor for sharing! ! ! ! ! ! ! !

Why can’t I download it? Could someone on the third floor send me a copy? Looking forward to a reply

Thanks for sharing! I’m a newcomer; this is exactly what I need

Why can’t such good materials be downloaded?

I can’t download the attachment! Thank you!

I can’t download the attachment! Thank you!