Problems and Countermeasures in the Operation of Rotary Kiln

时间:2021-11-05 作者 :超级管理员

As the bituminous coal calcined by a plant needs to be purchased, it undoubtedly increases the investment cost. In order to reduce the production cost, the plant considers adopting the local anthracite calcination method. Because anthracite has many incompatibilities in the application of rotary kiln in the plant, a series of improvement measures have been taken in the later stage of the plant to make the rotary kiln run stably and smoothly.

1、 Problems in trial production

During trial production, the following problems were found in the system:

1. Often unburned pulverized coal enters the kiln through the decomposing furnace, rising flue and preheater c-tube, and a "blue flame" is generated on the surface of the material, indicating that the incomplete combustion of pulverized coal is serious.

2. The temperature at the inlet and outlet of C ₄ cylinder is "upside down". The temperature of the rising flue at the kiln tail is high (up to 1100 ℃), and the materials in the rising flue, C ₄, C ₃ and even C ₃ cylinder are sticky and crusted from time to time, which is very easy to block the flue with narrow space, resulting in poor ventilation of the kiln system, turbulent thermal system and difficult feeding of the preheater, affecting the normal operation of the firing system.

3. The flexible movable metal connecting hose between the fixed air duct of the first section of the cooler grate bed and the movable charging beam has the defects of insufficient fatigue strength and easy to break and leak air, resulting in insufficient cooling air pressure in the charging beam, unable to adjust the air supply of the first section of the grate bed, the phenomenon of "Red River" and "black hole" in clinker, and the grate bed is easy to leak fine powder.

4. The material at the coal air inlet of the pulverized coal burner is not wear-resistant, and the outer wall and inner air pipe wall of the coal air pipe are worn through, resulting in coal gushing from the outer wall and pulverized coal channeling into the inner air pipe to abrade the cyclone, and the working efficiency of the burner decreases.

2、 Improvement measures

1. Expansion of ascending flue volume of calciner and kiln tail

According to the characteristics of high fixed carbon content, low volatile content and long burn out time of anthracite, in order to prolong the residence time of pulverized coal in the boiler and improve the burn out rate of pulverized coal, the company raised the calciner by 9m again and increased the volume of the calciner by 104.23m on the basis of the previous transformation ³。 In addition to the top technical transformation, the furnace capacity was increased by 138.97m twice ³。 The diameter of the furnace bottom nozzle is reduced by 10cm, the speed of the tertiary air into the furnace is increased, the spouting effect is enhanced, and the chance of "material collapse" of the decomposition furnace is reduced. On this basis, the diameter of the rising flue at the kiln tail is moderately expanded, and the flue volume is increased by 45.74m ³, Make the flue become the "secondary combustion chamber" of the system. Due to the setting of this combustion chamber, the unburned fixed carbon particles in the furnace gas can be further burned in the "secondary combustion chamber" with the help of the high temperature of the flue gas at the kiln tail. At the same time, 20% ~ 30% of the raw material of C ₃ cylinder can be fed into the "secondary combustion chamber" through the distribution valve to reduce the proportion of raw material distributed into the calciner, reduce the heat absorption of raw material in the furnace and increase the combustion temperature, change the situation that the rising flue is easy to crust due to narrow pipe and high gas temperature, and ensure the stability of ventilation of rotary kiln and calciner, The decomposition rate of CaCO ₃ of raw material into the kiln is stabilized at 85% ~ 90%.

2. Increase the combustion space of pulverized coal at the furnace bottom

In the decomposition furnace dominated by chemical combustion, the space atmosphere of initial ignition of pulverized coal is very important. In order to make the pulverized coal ignite quickly after entering the boiler, the spreading table in the furnace will be moved up by 200mm to make it close to the spreading port. In this way, the spreading surface is increased, the spreading uniformity is enhanced, and the combustion space of pulverized coal at the bottom of the furnace is increased. At the same time, the coal injection pipe is changed from horizontal bidirectional injection in the middle of the lower cone of the furnace to downward inclined 15 ° bidirectional injection to the neck of the furnace bottom. The increased combustion space in the cone can prolong the residence time of pulverized coal combustion. The injected pulverized coal is strongly mixed with the high-temperature tertiary air injected into the furnace at the speed of 30m / s, resulting in eddy current effect, rapid combustion and heat release, increasing the initial temperature of the feeding point, promoting the combustion of pulverized coal and the decomposition of raw meal CaCO ₃.

3. Improvement of cooling machine

The flexible deflection device is adopted to replace the six flexible movable metal connecting hoses between the fixed air duct under the first section of the grate bed and the movable inflation longitudinal beam of the cooler. After replacement, the effect is good, ensuring the air supply and air volume in different areas of the first section of the grate bed. At the same time, a sealing compartment is added under the grate, and a high-pressure fan is added in the top room to enhance the sealing of the grate bed and effectively solve the problem of fine powder of red hot clinker penetrating under the grate. Measures have also been taken or replaced one by one in the transformation for the cooling machine parts with quality problems. After rectification, the operation efficiency of the cooler is improved, the operation requirements of thick material layer and small air volume are met, the "Red River" and "black hole" phenomena of clinker on the grate bed are eliminated, and the supply of secondary and tertiary air is effectively guaranteed.

4. Treatment of easily worn parts of pulverized coal burner

By adding a wear-resistant protective layer at the coal air inlet of the easily worn part of the pulverized coal burner, the wear-resistant ability of the place is effectively enhanced and the operation of the pulverized coal burner is ensured.

After the above improvements, the calcination system of the rotary kiln tends to be stable and normal, anthracite has been better applied in the rotary kiln, and the production cost has been significantly reduced. Due to the full use of local anthracite resources, it also promotes the development of local related industries.