Responsibilities for the routine inspection of dry quenching coke processing equipment
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1. The main equipment for the management of the routine inspection tasks related to dry quenching coke machinery includes: traction devices, charging cranes, charging systems, discharging systems, gas circulation systems, boilers, dry quenching furnaces, pump room equipment, and other shared equipment. 2. To prevent harm to the environment during maintenance, it is generally not allowed to use air to blow away dust; in special cases, an application must be submitted to the higher-level management authorities, and approval must be obtained before such action can be taken. 3. The waste grease discharged or removed from operating equipment must be captured using appropriate measures, and collected promptly at the designated storage area for waste grease; it is then recovered and disposed of on a regular basis by the development company. 4. Spare parts for maintenance must be stored in designated locations and marked with prominent signs, with a dedicated person responsible for their management. 5. The use of cleaning agents, rust removers, and similar substances during maintenance work should be controlled as important environmental factors; cleaning agents must not be discharged casually into the drainage system, and proper recycling procedures must be followed. 6. Batteries used for routine inspections, as well as oily waste, should be recycled in accordance with regulations. 7. Strengthen regular inspections of dust collection pipes, dust collectors, and similar components such as those used for loading, discharging, and covering coke ovens; any leaks must be addressed promptly. 8. To prevent damage to the environment during maintenance, it is generally not allowed to use air to blow away dust; in special cases, an application must be submitted to the higher-level management authorities, and approval must be obtained before such action can be taken. 9. The waste grease discharged or removed from operating equipment must be captured using appropriate measures, and collected promptly at the designated storage area for waste grease; it is then recovered and disposed of on a regular basis by the development company. 10. Spare parts for maintenance must be stored in designated locations and marked with visible signs, with a dedicated person assigned to oversee them. 11. The use of cleaning agents, rust removers, and similar substances during maintenance work should be controlled as important environmental factors; cleaning agents must not be discharged casually into the drainage system, and proper recycling procedures must be followed. 12. Batteries used for routine inspections, as well as oily waste, should be recycled in accordance with regulations. 13. Regular inspections should be carried out on dust collection pipes, hoods, and similar components such as those used for loading, unloading, and covering the coke ovens; any leaks must be repaired promptly. When working in areas with gas, at least two people must be present, a CO detector should be used, attention should be paid to the wind direction, and an oxygen (air) respirator should be used if necessary. If a gas leak is detected, set up warning barriers, place hazard signs, and report it promptly. This post was last edited by ryn on 2009-2-19 20:05.]
Dry quenching of coke (English name: Coke Dry Quenching Equipment, abbreviated as C, D, Q) involves using inert gases circulated within a closed container to quench the red-hot coke, thereby effectively controlling various sources of pollution during this process. Its advantages include: (1) Significant energy savings in dry coke quenching. We know that during the coke extraction process from a coke oven, the heat carried away by the red coke accounts for approximately 40% of the total heat supplied to the oven; it represents the largest component in terms of the heat balance of the coke oven. Moreover, since the temperature of the red coke is around 1000°C, it has a high capacity to recover sensible heat, making it highly valuable for recovery and utilization. Therefore, the complete dry quenching plant is equipped with a waste heat recovery boiler and steam generation equipment; the steam produced by recovering the sensible heat of red coke is used for power generation, and it can also be supplied to the plant’s steam network for industrial use. (2) Dry quenching of coke can prevent pollution of the air and water bodies during the quenching process. Since dry quenching is carried out in a sealed container, no coke dust or gases containing harmful substances are released into the atmosphere. The dry quenching process does not require water, so it does not cause pollution to water bodies. (3) Dry quenching of coke can produce high-quality coke. Wet quenching of coke causes rapid cooling of the red coke, generating significant internal stresses that greatly affect the strength of the coke. Dry quenching of coke does not pose the problem of rapid cooling; it allows for the production of coke with higher strength and better thermal stability compared to wet quenching. Moreover, the particle size of the coke is uniform, and there is less coke dust. Therefore, dry-quenched coke can reduce the coke consumption per ton of pig iron by 2–3%, increasing the output of blast furnace pig iron by about 1%. (4) Dry quenching of coke features a high degree of automation and safe, reliable operation; although the investment is large, the returns are good and the investment can be recovered quickly. Our country is a major producer of coke; it is essential to control pollution and produce high-quality coke, and there are great prospects for promoting and developing dry quenching technology. At present, over 95% of the dry quenching equipment in our country is domestically produced, which has played a significant role in promoting the application and development of new dry quenching technologies
7 Introduction to the Inspection and Maintenance System for Dry Quenching of Coke 1 Selection of Equipment Maintenance Modes The dry quenching coke system requires significant capital investment; its stable operation helps to reduce energy consumption, improve the quality of coke, and contribute to environmental protection. It is therefore important to determine the appropriate maintenance mode for its daily upkeep in order to maintain optimal operational conditions. Currently, there are generally two modes for the routine maintenance of equipment: repairing it before a failure occurs – that is, preventive maintenance – and repairing it after a failure has taken place – that is, corrective maintenance. Post-maintenance repairs make it impossible to control the duration of equipment failures and the extent of damage, whereas pre-maintenance repairs allow for the prior planning of the repair time, the areas that need repair, and the degree of repair, thereby enabling the prevention and control of equipment failures. Since preventive maintenance has clear advantages over corrective maintenance, it is being given more and more attention and adopted by businesses. To properly implement preventive maintenance, it is necessary to have an accurate understanding of the equipment’s operating conditions, thereby avoiding both over-maintenance and under-maintenance of the equipment. To monitor the operating status of equipment, instruments can be used for surveillance, or manual inspections at appropriate times can also be employed. Given the current level of economic and technical capabilities, employing manual monitoring at appropriate times and formulating reasonable maintenance plans based on the results of such monitoring to carry out repairs on equipment is the preferred maintenance approach for companies aiming to conduct preventive maintenance; this is known as the routine inspection and maintenance system. “The \"inspection and maintenance system\" is a equipment maintenance management system in which production operators conduct routine visual inspections of the equipment; at the same time, specialized technical personnel (referred to as inspection officers) are assigned to monitor the condition of the equipment. Based on the results of these monitoring efforts, regular maintenance plans are formulated, and professional equipment maintenance technicians carry out the maintenance work according to these plans. The quality of the maintenance is verified by the inspection officers. The production process of the dry quenching system requires a high degree of continuity, which necessitates the prevention and control of equipment failures as well as scheduled maintenance. The preventive maintenance system can meet this requirement effectively; it is recommended that your company adopt this maintenance management approach for the dry quenching system being constructed.
Issues such as the emission of waste gases and dust during the coking process, as well as heat loss, are major problems that hinder the improvement of competitiveness among steel companies around the world. To overcome a series of challenges, industrially advanced countries around the world have made great efforts to promote the use of dry quenching technology for coke. This is because the dry quenching technology features significant environmental protection and energy-saving benefits; it can improve the quality of coke, reduce the coke ratio fed into the furnace, enhance the production capacity of blast furnaces, and recover thermal energy from red coke to generate steam and electricity, thereby yielding notable advantages. In recent years, China’s key steel enterprises have actively adopted and drawn on the latest foreign technologies, showing courage in exploration and practice, which has enabled them to achieve results that place them at the forefront both internationally and domestically. At the technical appraisal meeting for MaSteel’s dry quenching process, which was held recently under the auspices of the Anhui Provincial Department of Science and Technology as commissioned by the Ministry of Science and Technology, experts concluded that the design of the equipment used in MaSteel’s coke oven dry quenching process is reasonable, and its operation is stable and reliable. It fully meets the safety and technical requirements for coke oven operations, filling a gap in China’s capabilities in this area. On par with WuSteel’s systems, it represents a leading level in China and even reaches international advanced standards. Thanks to the advanced functionality of these technologies, a 1×125t/h dry quenching unit can recover 52,019 tons of standard coal in terms of energy each year, which is equivalent to a reduction of 56.7 kg of standard coal per ton of coke produced. It is understood that the dry quenching upgrades of coke ovens No. 7 and 8 carried out by Wuhan Iron and Steel during the Ninth Five-Year Plan period, as well as those of coke ovens No. 5 and 6 implemented by Maanshan Iron and Steel during the Tenth Five-Year Plan period, were designed to produce 1 million tons of coke per year, with a processing capacity of 1×125 t/h. The red coke transportation systems used in these projects are equipped with automatic alignment devices, which enable motor cars and coke tank cars to transfer coke at designated locations. In terms of cooling, the use of rotating coke drums, a charging bell, a water preheater, and vibrating feeders has improved the uniformity of coke particle size within the coke oven, thereby enhancing the cooling efficiency of the dry quenching furnace. Meanwhile, the top of the dry quenching furnace is equipped with an annular water seal seat at the coke hole location, which allows the lifting seal cover of the coke loading funnel to be inserted into the water seal seat accurately during coke loading, thereby effectively preventing dust from escaping. Based on the financial evaluation results of Maanshan Iron and Steel’s No. 5 and No. 6, as well as Wuhan Iron and Steel’s No. 7 and No. 8 dry quenching units, it can be seen that once this project is put into operation, the internal rate of return on total investment (after taxes) will be around 13%, which is higher than the benchmark rate of 7%. These financial indicators represent the best values in the steel coking industry. Based on the results of this application, it is evident that the adoption of this new technology by China’s key steel enterprises will yield significant social and economic benefits. Baosteel was the first in China to adopt the dry quenching technology for coke. After years of operational experience, its coke quality parameters show a moisture content of <1% ； M40 is 80%, M10 is 6.5%, and the ash content is 11.32%. It shows advantages such as 80% recovery of the sensible heat of red coke, suppression of erosion by dust and harmful gases, improvement in coke quality, and a reduction in the coke ratio required for furnace operation. However, compared with world-leading technologies, although Baosteel has managed to address issues such as energy waste and dust pollution to a considerable extent, the limited technology provided by Japan has led to problems such as a low designed vaporization rate, resulting in energy-saving and environmental protection benefits that do not meet the desired levels. Jigang introduced a dry quenching system from Ukraine in the 1990s; although it achieved certain energy-saving effects, it still fell short when compared to the world’s leading dry quenching technologies. Experts in the domestic coking industry suggest that China’s steel enterprises should always take the industrially advanced countries around the world as a model, accelerate the development of larger-scale dry quenching equipment, focus on improving technical parameters, work to reduce the temperature of the circulating gas, and lower the gas-to-material ratio. In addition, attention should also be paid to the management of automation control technology; only in this way can the dry quenching technology in China’s coking industry continue to improve steadily.
9.3.1 Daily maintenance of the ash conveying system: The devices used for the daily maintenance of the dry quenching dust collector include scraper conveyors, bucket elevators, ash storage tanks, and suction devices. 1. Scraper conveyor maintenance technology: Scraper conveyor maintenance includes the replacement of the head wheel, tail wheel, scraper chain, and the entire conveyor unit. ⑴ The initial maintenance is further divided into mechanical and electrical parts. Mechanical part: First, remove the bolts using gas cutting or a wrench, then remove the scraper chain ； Use a securely reliable chain hoist attached to a peg to remove the head wheel assembly ； Replace the front wheel, replace the main drive sprocket ； Reinstall the head wheel assembly, reinstall the scraper chain ； Reinstall the main drive chain. The installation of the first-stage wheel assembly must ensure precision in its central positioning. For the electrical section, first remove the foot bolts and inspect the motor; if it is damaged, disconnect its power cable first and replace the motor. ⑵ Tail wheel maintenance: Remove the bearing housing bolts and take out the tail wheel assembly ； Replace the tail wheel ； Ensure the centerline of the tail wheel. ⑶ Scraper chain replacement: Remove the scraper chain; after assembling a new one, reinstall it using steel wire ropes and a chain block. ⑷ Complete unit replacement: Assemble the scraper machine frame on the ground, locate the lifting points to attach the slings, remove the base bolts, then use gas cutting to disassemble the entire horizontal scraper machine before lifting it down ； Reinstall the new scraper conveyor, fit the main drive chain, adjust the scraper conveyor so that it does not scrape the casing; ensure that the scraper chain and the drive chain are at an appropriate tension, then power on it for a test run. Technical requirements: The center symmetry of the front and rear wheels must be 8 mm; the minimum distance between the chain and the grooves in the machine unit should be 10 mm; there should be a misalignment of 2 mm at the inner edge of the machine groove flanges. Levelness shall not exceed 0.4 mm, and straightness shall be 0.3/1000. 2. Maintenance of bucket elevators: The maintenance of bucket elevators includes the inspection of the head pulley, tail pulley, and belt. ⑴ First-round maintenance: Open the top, inspection holes, and transmission components ； Remove the head wheel bearing housing cover, left and right tension wheels, etc ； Check for wear, lack of oil, and meshing conditions in all areas ； If there is a malfunction, resolve it promptly ； Replace, reinstall, repair, adjust, and replenish lubricant. ⑵ Tail wheel maintenance: Open the rear inspection hole to remove accumulated dust ； Remove the pressing wheel, and adjust the roller, tail wheel, tail wheel shaft, and middle roller ； Check for wear, lack of oil, and assembly conditions in all areas ； If there is a malfunction, resolve it promptly ； Return to maintenance, adjust and replace, add lubricant. ⑶ Chain belt inspection: Open the inspection holes at the head, middle, and tail sections ； Inspect the chain belt, as well as the wear, deformation, and aging of the ash hopper; check for any wear or defects in the ash hopper, and carry out repairs or replacements as necessary ； Adjust the front and rear wheels, then resume testing ； Ensures no scraping and no abnormal noises. ⑷ For the complete replacement of a bucket elevator, check the equipment’s dimensions and model specifications. First, assemble the bucket chain and ash hopper on the ground, and then install the maintenance platform on the elevator’s casing as required ； Remove the connections related to the old conveyor; use a crane to lift out the conveyor’s outer casing, idler wheel, and chain. Install the new conveyor, adjust the operation system and the verticality of the housing, then weld and reinstall the ash discharge pipe, adjust the motor, restore the manhole cover, and conduct a trial run. Technical requirements: Horizontal deviation of the spindle is 0.3/1000, vertical deviation between the upper and lower spindles is 4 mm, and vertical deviation is 7 mm. (Measure and adjust the deformation of the machine body as well as the levelness of the drive wheel spindle; measure the linear deformation of the housing – for housings under 10 meters in length, the deformation amount is ±8 mm, and for those over 20 meters in length, it is ±15 mm; the levelness of the spindle should be 0.5°.) The main tools used are: 300mm, with a precision of 0.02mm; inspections are carried out using a level, steel tape measure, and a magnetic plumb bob). ⑸ Maintenance procedures for elevator motors: Position the crane, remove the existing equipment (such as drive chains), as well as the motors, cable trays (decide whether removal is necessary based on specific circumstances), pipes, etc., and place them in designated locations ； Install new pipes, tray systems, and motors, and ensure that the alignment of the motor sprocket with the conveyor belt sprocket meets the standards; attach the drive chain; connect the power supply ； After inspection and production confirmation, remove the power outage sign and restore power supply ； Conduct a trial run; check whether the motor is operating properly, and clean up any debris around it. Technical requirements: Cable trays and pipes must be installed horizontally and vertically; there should be no joints in the cables inside the pipes, the welding of cable pipes must be secure, and jumpers must be properly installed ； The motor should have a reliable grounding ； The bolts must be tightened firmly; there should be no looseness. The motor’s wiring terminals should be sealed to prevent water infiltration. 3. Ash storage tank maintenance ⑴ Filter unit maintenance: Open the manhole and check whether the tension of the filter bags is appropriate; replace them if necessary ； Inspect and adjust the mechanism, and repair it; ensure that the mechanism is flexible and secure ； Close the manhole. ⑵ Level gauge maintenance: Inspection and repair of the probe, proper installation of the probe, and sensitive response ； If necessary, replace it entirely to restore it. ⑶ Vibration motor maintenance: Remove and inspect the vibration pendulum blades, repair them; ensure proper installation of the pendulum blades; inspect and repair the electrical components ； The motor is firmly installed. ⑷ Ash hopper maintenance: Remove accumulated ash, open the manhole, clean away any remaining ash promptly, check for damage to the hopper itself, and ensure there are no leaks. Seal any defects if present. 4. Inspection of the suction device: Ensure that there is no ash blockage in the ash suction pipe, identify and resolve any faults, guarantee smooth operation, keep all driving bearings clean and lubricated, and ensure that the valve plates rotate smoothly ； Sealed properly, bolts tightened ； Adjust the drive chain, restore electrical adjustments, and conduct a trial run.