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Renovation and application of type 80 coke oven clean coal drying system Zhou Bendong (Henan Pingdingshan University, Pingdingshan 467021) Liang Jianbo Zhang Zhili Lu Fengli (Pingmei Tianhong Coking Company, Pingdingshan 467021) The washed lump clean coal and fine coal from the coal washing plant of Tianhong Coking Company are mixed through dehydration screens and centrifuges, and then transported to the clean coal yard via belts for natural dehydration. After coal blending, they are supplied to the Type 80 coke oven. Due to the expansion and renovation of the Type 80 coke oven, the output increased from 560,000 tons to 800,000 tons. The natural dehydration and drying time of the clean coal in the coal yard was short, so it was directly supplied to the coke oven. Therefore, the moisture content was above 20%, which caused great difficulties in coal blending production and coke oven charging. The Type 80 coke oven clean coal drying system was put into use after the coke oven was expanded and renovated. The moisture content of the coal entering the oven was reduced from 20% to about 10%. The process flow is shown in Figure 1. The entire drying system consists of a feeding part, a drying system, a dust removal system and a discharging system. Figure 1 Process flow chart of the clean coal drying system 1. The clean coal on the No. 9 belt of the feeding system falls to the No. 901 belt through the plow separator, and then is transported by the No. 902 and 903 belts, and enters the drum dryer through the feeding scraper and chute. 1.1 Problems The plow-type coal unloading and material distribution system consists of an electric push rod, a coal separator, and a chute. The coal separator is made of steel frame structure and a layer of transport tape. The following problems exist in actual production. (1) Due to the short dehydration time of coal in the coal yard, the coal is wet and sticky and difficult to separate, and often adheres to the coal separator, causing unfavorable coal separation, resulting in less coal separation and low drying output. (2) The uneven force on the belt causes the belt to often deviate and wear, seriously affecting the service life of the belt. (3) The unloading chute is often blocked, which increases the labor intensity of workers. 1.2 Modification measures (1) Add a 1.2m×1.5m steel plate with a thickness of 6mm under the plow coal separator of the No. 9 belt to make it evenly contact with the belt, which solves the problem of belt deviation and wear and extends the service life of the belt. (2) Add a 400mm × 1200mm stainless steel plate to the outside of the plow coal separator belt, and use the wear resistance of stainless steel to basically separate the coal on the belt and smoothly enter the chute, increasing the output of drying clean coal. (3) Change the unloading plate of the chute to stainless steel and increase the slope of the chute, which solves the problem of chute blockage and shed materials, and reduces the labor intensity of workers. 2 Drum dryer 2.1 Working performance The 80 type coke oven clean coal drying system uses the JNG3420 energy-saving drum dryer, which has the following characteristics: (1) The optimized design of the guide plate reduces the entrainment phenomenon in the coal guide plate. (2) The machine is equipped with a new lifting device, which strengthens heat exchange, improves evaporation intensity and drying efficiency. (3) The machine is equipped with a cleaning device to improve the uniformity and drying efficiency of the dried products. 2.2 Problems In actual production, the fire retaining wall and furnace roof often collapse, causing the gas flame to directly burn into the unloading chute and the drum dryer blocking plate, causing the steel plate to be in direct contact with the flame. The steel plate material is Q235, and the refractory service temperature is 425°C, while the furnace temperature is as high as 1000°C, causing the steel plate to deform, burn, and oxidize and peel. When the production task is heavy, the chute will be scrapped in less than one month, requiring frequent maintenance. The maintenance work environment is harsh and the maintenance cost is extremely high, reaching more than 300,000 yuan in 2005 alone. 2.3 Modification measures (1) Improve the structure of the blocking plate to avoid direct contact between the flame and the weld, slow down the oxidation and burning rate of the weld, and increase the service life of the blocking plate from 3 months to about 1 year. (2) Double-layer blocking boards are used, filled with lightweight refractory materials, and the blocking board reinforcement plates are increased from 4 to 12, which slows down the rate of burning and deformation of the blocking boards. (3) The material of the chute is 1Cr18Ni9Ti. The service life of the equipment has been increased from 3 months to 2 years, which not only ensures the supply of coal for the coke oven, but also reduces the labor intensity of maintenance and reduces equipment maintenance costs. 3 Hot blast stove The hot blast stove is the key equipment of the clean coal drying system, and the furnace temperature is around 1000°C. The hot blast stove is composed of a stove top, a stove wall, a combustion chamber and a fire retaining wall. There is a dryer unloading slot on the stove top. 3.1 Problems (1) The furnace roof is made of wedge-shaped refractory bricks with a lower trough entrance. There is no supporting structure around the refractory bricks, causing the furnace roof to often collapse. The flames directly burn to the concrete beams of the factory building and the iron tiles of the drying shed, causing the concrete to peel off and the power supply cable to burn. (2) After the furnace roof collapsed, it was built with wedge-shaped refractory bricks and poured with concrete. The service life was less than 2 months, and the repairs were frequent and expensive. In 2006 alone, the maintenance cost of the new drying hot blast furnace was as high as 200,000 yuan. (3) The fire retaining wall often collapses, causing the gas flame to burn directly to the unloading trough and the roller blocking plate, causing the steel plate to burn, carbonize, deform, burn, and oxidize and peel. The service life of the unloading trough and the roller blocking plate is extremely short. (4) The flamethrower is often burned out and damaged, causing flames to backfire and escape. (5) Since the emergency repair is carried out in the furnace, the furnace temperature is high, the dust is large, and the labor intensity of the workers is high. 3.2 Modification measures (1) The collapse of the fire retaining wall is due to inconsistent heating of the front and rear sides of the fire retaining wall. When the flame side of the fire retaining wall expands, it is subject to resistance from the rear, so the fire retaining wall often collapses toward the flame side. Change the fire retaining wall from a straight wall to a stepped wall, and add phosphoric acid to the refractory clay formula so that the fire retaining wall can be sintered together after being sprayed with flames. (2) Use new refractory casting materials to repair the furnace roof, and use vibrating rods to vibrate during the construction process to make the density reach 2400~2600kg/m3. Add tie bars, perform heat-resistant treatment on the steel bars, and rationally design expansion joints to increase the stiffness of the structure. (3) Develop a reasonable and feasible oven plan so that the moisture content of the refractory castable reaches the specified requirements and the refractory castable is sintered to the strength specified in the design. Since the refractory castable has good high-temperature strength after sintering, the service life is extended. (4) Modify the flamethrower and change the material from stainless steel to refractory casting material. 4. Dust removal system: The hot air from the combustion chamber enters the dryer to dry the clean coal. During this process, part of the fine-grained clean coal loses moisture and becomes lighter. The flue gas and vaporized water vapor are discharged into the atmosphere through the dust collector, flue, induced draft fan, and chimney under the action of the induced draft fan. The Type 80 coke oven clean coal drying system uses wet and dry combined dust removal equipment. The process flow is shown in Figure 2. Figure 2 Dust removal system process flow chart. The dry dust collector in the clean coal drying and dust removal system uses a multi-tube cyclone dust collector. The cyclone dust collector has a simple structure and is easy to maintain. It can handle various gases with dust concentrations in the range of 0.01 to 500 mg/m3. It is often used as a pre-dust collector in a multi-stage dust removal system. The wet dust collector in the clean coal drying dust removal system is an SFC type composite water mist dust collector, which is a high-efficiency dust collector matched with the coal drying system. The working process of the dust collector includes three dust removals: water bath, mist filter, and screen filter. It can effectively remove dust in the flue gas. Its performance parameters are as follows: Processing air volume: 10～20m3/h dust removal efficiency: 90%～98% resistance: 1～2 kPa water consumption: 1.5～3.0 t/h emission concentration: ≤75mg/m3 dry and wet combined dust removal equipment operates well, and the dust concentration of the exhaust gas can reach * * It complies with specified standards, has a simple structure and is easy to operate and maintain. However, in production practice, the cooling water of the original designed induced draft fan flows directly into the ditch without considering reuse, while the consumption of circulating water for fan cooling is 8 to 12t/h. It has been determined that the water pressure and water volume of the induced draft fan can be supplied to the dust collector. Therefore, the cooling water of the induced draft fan has been modified, which can save nearly 100,000 tons of water every year. 5 Transformation effects (1) The startup rate and usage efficiency of the equipment are improved, the labor intensity of coke oven coaling operators is reduced, the coking turnover time is shortened, the coke output is increased from 150 holes/d to 162 holes/d, the average coke production is increased by nearly 50,000 t/a, and the economic benefits are relatively significant. (2) Due to the reduction of the moisture content of the coal entering the furnace, the bulk density of the coal entering the furnace is increased and the coke quality is improved. The coke strength M40 is increased from 80% to 82%, and M10 is reduced to about 6%. (3) Extends the service life of the equipment and reduces the labor intensity of maintenance workers. The service life of the drum blocking plate has been increased from an average of 3 months to 1 year, the service life of the chute has been increased from an average of 3 months to 2 years, and the drying furnace top is still intact. (4) The maintenance cost of the equipment is reduced. It can save nearly 100,000 yuan in repair costs and material costs every year, save 100,000 tons of clean water, and reduce 100,000 tons of external sewage discharge. It has good economic and environmental benefits.