COAL FUEL ROTARY KILN For Sale

Coal Fuel Rotary Kiln Introduction

Coal-fueled rotary kiln, also called coal-fired rotary kiln, is a rotary high-temperature calcining equipment with coal as the main fuel. The fuel types of rotary kiln include gas (gas rotary kiln), liquid (fuel oil rotary kiln) and solid or powder.
Compared with other fuels, coal is the cheapest fuel, so coal-fired rotary kiln is widely used in cement, lime, metallurgy, chemical industry and other industries. Its core feature is to utilize the high temperature generated by coal combustion (usually 1200~1600℃), so that the material in the rotary kiln to complete the physicochemical reaction, such as carbonate decomposition, mineral sintering and so on.

Coal Fuel Rotary Kiln Working Principle

Coal powder is sprayed into the kiln head through the burner, mixed with the primary air and burned, forming a high temperature flame (1200~1600℃). Raw material enters from the kiln tail and moves to the kiln head with the rotation of the kiln body, experiencing:

• Preheating section (200~800℃): water evaporation, clay dehydration.
• Decomposition section (800~1100℃): Calcium carbonate (CaCO₃) decomposes into calcium oxide (CaO) + CO₂.
• Sintering section (1300~1450℃): the minerals melt and form cement clinker minerals such as tricalcium silicate (C₃S).

After that, the high-temperature clinker enters the cooler and cools rapidly to below 100°C, recovering the waste heat for combustion. Exhaust gas from the kiln end is discharged after preheater and dust removal.

Quality requirements of coal-fueled rotary kiln combustion coal

In coal fuel rotary kiln, the quality of coal directly affects the calcining efficiency, clinker quality, equipment life and environmental emissions. For the quality of coal, first consider its calorific value. The greater the calorific value of coal, the better, and the lower the ash content, the better. Secondly, the volatile matter content is required to be within a certain range. The following is the quality requirement and impact analysis of coal fuel rotary kiln on coal:

1. Heat generation (calorific value)
   When the calorific value ≥ 23 MJ/kg (5500 kcal/kg) is the most ideal calorific value. When the calorific value <20 MJ/kg is too low state, will lead to insufficient combustion temperature, low calorific value of coal will increase the unit heat consumption of calcined cement clinker, reduce the unit output of rotary kiln, clinker minerals are not fully formed.
2. Ash
   Ash content of coal is the main indicator of coal combustion and decomposition used in coal-fired rotary kiln and calciner. Ash content should be ≤ 26% in general, and the ash content of high-quality coal is suggested to be <15%. Excessive ash will reduce the effective calorific value and increase the risk of skinning and ringing in the kiln. Al₂O₃, SiO₂, etc. in ash may enter clinker and change the proportion of cement composition.
3. Volatile matter
   When the volatile matter is between 20% and 33%, the bituminous coal is the best, the flame is longer and the calcination is more uniform. If the volatile fraction is too low (such as anthracite), it will lead to difficulty in catching fire, poor flame stability, the kiln will appear long black flame, high temperature area is more concentrated; if the volatile fraction is too high, it will lead to too fast combustion, which may lead to high temperature in the local area, and damage the refractory material.
4. Sulfur
   It is generally recommended that the sulfur content ≤ 2%, sulfur content <1% is the ideal value. Sulfur combustion will generate SO₂, easy to react with alkali metals in the kiln to form a crust, clogging the preheater. High-sulfur coal needs to be equipped with desulfurization equipment, otherwise the pollution emission exceeds the standard.
5. Fineness
   The fineness of coal powder in coal-fired rotary kiln should be controlled at 88 μm, and the sieve residue should be less than 15%.
6. Moisture
   It is generally recommended that the moisture of pulverized coal is ≤1%~2%, and it is better to control it between 0.5% and 1%. Excessive moisture will reduce the combustion temperature, increase heat consumption, and lead to clogging of pulverized coal transportation.

Bituminous Coal

Anthracite

Bituminous Coal and Anthracite are two types of coal often used in coal-fueled rotary kilns.
Anthracite has high fixed carbon content, low volatile matter, high density, high hardness, high ignition point, no smoke when burning, and is the coal with the highest degree of coalization. Bituminous Coal is the coal with the deeper degree of coalification, burns with a longer flame, has a flame, and has a higher volatile fraction than anthracite.

Coal Fuel Rotary Kiln Technical Parameters

Why do cement plants use anthracite coal?

Cement plants choose anthracite as rotary kiln fuel, mainly based on the high calorific value, low sulfur and ash, long flame characteristics and some of the kiln type of process demand is highly matched. Bituminous coal is the most deeply coalized coal with the highest carbon content, low ash, low moisture, and high calorific value of up to 25,000~32,500kJ/kg, which can keep the temperature in the cement rotary kiln at 1450℃.

However, with the popularization of new dry process kilns (precalciner kilns), bituminous coal or blending technology is gradually becoming mainstream.