Coal fuel rotary kiln or coal-fired rotary kiln is a kind of rotary kiln equipment that uses coal as fuel. The fuel types of rotary kiln include gas (gas-fired rotary kiln), liquid (oil-fired rotary kiln), and solid or powder. Because coal is the cheapest fuel compared with other fuels, coal-fired rotary kiln is widely used in the world.
Quality Requirements for Coal-fired in Coal Fuel Rotary Kilns
For the quality of coal used in coal fuel rotary kilns, the calorific value should be considered first. The larger the calorific value of coal, the better, and the lower the ash content, the better, which will help achieve the flame temperature required for calcination in a coal-fired rotary kiln. Secondly, the volatile content is required to be within a certain range.
- Calorific value
For the calorific value of burning coal, the higher the better, which can increase the heat generation capacity and the calcination temperature. Coal with a lower calorific value increases the unit heat consumption of calcined cement clinker and reduces the unit output of the rotary kiln. Under normal circumstances, it is required that the low calorific value of coal should be greater than 21772kJ/kg.
Coal with low volatile content is not easy to catch fire. Long black flames will appear in the kiln, and the high-temperature zone is more concentrated. In order to make the flame of the coal-fired rotary kiln longer and the calcination more uniform, the volatile content of coal is generally required to be between 22% and 32%.
The ash content of coal is the main indicator of coal used in coal fuel rotary kilns and calciners for firing and decomposition. Combined with the process equipment and control conditions of the cement industry, it is generally required that the ash content of coal powder should be less than 27% for the outside pre decomposition calciner.
The moisture content should generally be less than 2%, and it is best to control it between 0.5% and 1%.
The fineness of pulverized coal in the coal-fired rotary kiln is best controlled at 88 μm, and the sieve residue is less than 15%.
The types of coal used in coal fuel rotary kiln generally include bituminous coal and anthracite. The main difference is that the volatile matter of anthracite is lower than that of bituminous coal.
Bituminous coal is a coal with a deep coalification degree, and when it burns, the flame is longer and has flames.
Anthracite is the coal with the highest degree of coalification. It has high fixed carbon content, low volatile yield, high density, high hardness, high ignition point, and no smoke during combustion.
Why do Cement Plants Use Anthracite?
Cement production has high requirements for the calorific value of coal. The calorific value directly affects the temperature in the cement kiln and then affects the production of C3S. In order to ensure that the temperature in the cement rotary kiln is maintained at 1450℃, the coal is required to have a higher calorific value. Anthracite is the coal with the deepest degree of coalification, with the most carbon content, less ash, less moisture, and high calorific value, up to 25000 ~ 32500kJ/kg, so it is the best fuel for cement rotary kiln in cement plant.
Latest Design of AGICO Coal Fuel Rotary Kiln to Prevent Ring Formation
Many cement plants have encountered ring formation in coal-fired rotary kiln. The formation of ring formation greatly reduces the output of clinker, seriously affects the quality of clinker, increases coal consumption, power consumption and other costs. In order to reduce the occurrence of ring formation in the production process of coal fuel rotary kiln, combined with the data analysis of rotary kiln for many years, our technical research and development engineers have made the latest improvement design for the coal fuel rotary kiln.
- Raise the temperature of the kiln pipe feed inlet
Increasing the temperature at the inlet of the kiln pipe can accelerate the heating rate of the powder. The faster heating rate makes the lattice defects formed by phase transformation of raw materials too late to correct, which is conducive to the solid-state reaction and shortens the pre sintering time.
- Increase the ventilation intensity
The high-temperature zone of the coal fuel rotary kiln is as long as 6m, and most of the PVA glue is burned. The two ends of the kiln pipe are designed into a fully sealed structure, and the residual PVA glue, water vapor, and a small amount of fine powder are thickened into the dust collector by strong air extraction, and then recycled at the same time. This method can reduce the conditions for the formation of powder sticking problems.
- Use a vibration hammer
The coal-fired rotary kiln uses a vibrating hammer to strengthen the disturbance of the powder in the kiln pipe. The kiln pipe is vibrated once every 90 ° rotation, and the powder in the pipe wall slides down randomly, which can further reduce the powder sticking to the wall.
Specification Parameters of Coal Fuel Rotary Kiln
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