Optimization of rotary lime kiln in Henan Province


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Over burning of lime in rotary kiln and optimization measures

Limestone calcination is the decomposition reaction of material accumulation heat. In the process of calcination, the uniformity and permeability of fire are very important. stay Rotary kiln After preheating, calcining, cooling and decomposing, Cao is precipitated to form fine grains full of voids. Because the calcination is not good, it is easy to appear the intercalation phenomenon that the limestone is not completely decomposed. If Cao is in the high temperature zone for a long time, its grain size will grow up gradually, its volume will shrink, its porosity will decrease, and it will become "over burnt lime", its activity will be reduced and it will be difficult to hydration. In this paper, through raw material management, gas fuel management and equipment management measures to optimize the production of lime.

 Rotary kiln

1. Raw material management

(1) The particle size of raw materials plays an important role in the over burning of lime products. The ideal particle size range of raw material is 40 ~ 80mm, and the particle size ratio (material to small material ratio) is generally 2 ~ 2.5, which is less than 3. It is also an important condition for high yield and low consumption. Some raw materials have larger particle size, with the particle size of 150 mm or even 200 mm. Some of them are irregular in shape and flat in shape, which are easy to cause internal entrapment of finished products. If the particle size is too small, it is easy to cause over burning. If the granularity of raw materials is not up to standard, communicate with the company to improve the granularity of raw materials.

(2) There are more raw materials in the sediment. Because there is no water washing system in the raw material section of rotary kiln, the excessive sediment in raw material directly affects the calcination of finished products. The raw material vibrating screen is easy to block the screen gap due to excessive wet sediment, and the screening efficiency will be lost if it is not cleaned in time. The sediment directly enters the kiln, affecting the air permeability of the kiln, resulting in the increase of kiln pressure, unstable calcination, stable gas transmission and distribution, and reduction of lime products. The impurities in the sediment are mainly composed of SiO2, Al2O3, Fe2O3, etc. at high temperature, it is easy to form low melting point and adhesive compound with calcium oxide in lime, which penetrates into Cao crystal, blocks the pores of lime and reduces the activity of lime. In order to effectively control the entry of impurities, it is necessary to strengthen screening and optimize raw material acceptance management in the daily production management process. In sunny days, the stock yard should be used to store clean raw materials to ensure the supply of high-quality raw materials. At the same time, it is required to clean the raw materials twice per shift to ensure the screening of raw materials.

2. Gas and fuel management

(1) As the fuel of calcining metallurgical lime in rotary kiln, converter gas is an important factor affecting lime production. The change of gas calorific value directly causes the temperature fluctuation of calcination zone in the kiln, which affects the products. When the converter gas is relatively high, less air can be used to ensure the full combustion of gas, the amount of flue gas generated in the combustion process is relatively stable, and the kiln pressure is relatively low, which is also conducive to the decomposition and precipitation of lime and promote the full decomposition of lime. However, when the calorific value of gas is low, in order to ensure the heat consumption required for lime decomposition under the same output, the gas consumption should be increased, the combustion air should also be increased, and the kiln pressure would be increased, which would have a negative impact on the lime decomposition. Moreover, a large amount of flue gas will directly lead to the high temperature of the waste gas, which will lead to the reduction of the service life of the sealing ring on the kiln top and the flange gasket of the spray gun, and the vicious circulation will affect the lime products. Therefore, in the daily production and operation process, communicate with the smelting unit and production scheduling, when the heat value of converter gas is lower than 6000kj · M-3, and the gas inlet pressure is lower than 8KPa, timely feedback shall be made to do a good job of regulation.

(2) The insufficient capacity of gas holder leads to frequent start-up and shutdown of the kiln. The monthly average gas tank capacity is short of nearly 100 hours, and the sudden start-up and shutdown of the kiln is not conducive to the stable production of furnace conditions. In terms of operation, it is required to formulate the matters needing attention in the production organization and management of rotary kiln. It is required to pay close attention to the gas tank capacity. If the tank capacity is low, timely communicate with the outside, reduce the production and limit the production, extend the production time and reduce the shutdown time.

3. Strengthen equipment management and maintain stable production

(1) Through the "two week regular repair" of the kiln, some equipment faults existing in the production process of the kiln are eliminated to ensure the stable production.

(2) The diameter of the hydraulic buffer cylinder at the head of the kiln is increased frequently, and the hydraulic cylinder at the head of the kiln is broken frequently, and the hydraulic cylinder at the head of the hydraulic cylinder is changed to extend the service life of the hydraulic cylinder.

(3) The service life of seal ring of discharge valve is prolonged. Through the observation of the damage of the sealing ring of the discharge valve, it is found that the damage comes from two aspects: one is that some materials are stuck between the sealing ring and the gate valve during the lime discharging, or the material level of the small lime silo at the kiln bottom is on the high side, the material surface is inclined, and the material level switch is not in good contact, which causes the finished product to be blocked at the sealing ring of the discharge port and is mechanically crushed by the gate valve; the other is that the particle size of the stone is too large When the ash temperature is not properly controlled, it will cause damage. The material level switch is transformed from "touch type" to "limit switch type" to improve alarm accuracy. And adjust the speed of the hydraulic cylinder to extend the closing time of the hydraulic cylinder. In the process control, select the ore spot with appropriate particle size and control the ash temperature. The service life of the seal ring is increased from 3 to 6.

(4) Strengthen the maintenance of the air gun to ensure that the middle passage is clean. The passage of rotary kiln is the premise of "parallel flow heat storage". When the rotary kiln changes direction and releases the kiln pressure, the dust in the kiln will stagnate and deposit on the surface of refractory brick in the middle passage, blocking the channel. Therefore, it is necessary to ensure reliable purging of air gun and smooth passage in daily management.

Through the optimized transformation and management of rotary kiln, the average monthly burning of metallurgical lime in rotary kiln is reduced, and the gas consumption is also reduced to a certain extent. The lime product is effectively improved and the steel-making production is better served.

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