Indirect-fired Rotary Kiln


Indirect-fired rotary kiln has a combustion chamber on the peripheral barrel. The heat generated by the combustion of flue gas is transferred to the material through the cylinder. The material is calcined at high temperatures, and the calcined product is discharged from the discharge valve. The exhaust gas is treated or emptied or utilized. The indirect-fired rotary kiln is suitable for the production of various materials requiring indirect continuous heating.

Our indirect-fired rotary kiln can use different fuels for heating, in addition to traditional coal, oil, gas, it can also use electricity for heating. Among them, the electric heating rotary kiln is in huge demand and is highly praised by the market. One is because the heat source is clean and does not cause environmental pollution, and the other is because the power supply is more convenient and efficient.

Indirect-fired Rotary Kiln Application

Molecular sieve roasting and catalyst

When the indirect-fired rotary kiln is used to calcine the catalyst and molecular sieve. It can make s sure that the purity of the product. This is because the multi-zone temperature can be set coordinatedly in order to complete the reaction such as dehydration or unit cell shrinkage.

Sludge distillation and toxic waste incineration

The indirect-fired rotary kiln can recycle the condensed water, combustible gas, and biochar left by the calcined sludge. The indirect rotary kiln chemically reacts to sludge in a closed, anaerobic, non-combustible, and high-temperature state. Under the reaction of dry distillation and thermal decomposition, sludge goes through pyrolysis, dehydrogenation, thermal condensation, gasification, and carbonization, so that the water in the sludge becomes condensed water, and the organic matter in the sludge is converted into a combustible gas, which is then recycled.

Indirect fired rotary kiln burns toxic hazardous waste. The toxic waste is incinerated in a sealed space, and the generated toxic gas can be fully recycled.

structure of indirect-fired rotary kiln

Indirect-fired Rotary Kiln Advantages

  • Indirect-fired rotary kiln has high purity. Indirect way makes no contaminant and high purity of the product. The exhaust gas can be treated then discharged.
  • Indirect-fired rotary kiln is suitable for the processing of powdery and granular materials.
  • Indirect-fired rotary kiln’s calcination temperature is stable and easy to control. The cylinder is made of special stainless steel and the calcination temperature can reach 1150 °C. Moreover, the process parameters such as calcination temperature, calcination atmosphere, calcination time and calcination yield can be flexibly controlled.
  • Indirect-fired rotary kiln body’s inclination and cylinder speed can conveniently and flexibly adjust. Automatic control ensures continuous and stable production and effective protection of the cylinder.
  • The indirect-fired rotary kiln uses low operating costs. Waste heat can be fully utilized.
  • Indirect-fired rotary kiln has clean combustion to meet environmental emission standards. It can be heated by natural gas, liquefied gas, coke oven gas, generator gas, diesel oil, and electricity, or it can be equipped with fuel and gas dual-use system.
  • Indirect-fired rotary kiln has a wide range of applications. It is suitable for the combustion, roasting, incineration, decomposition, and drying of non-metallic minerals, metal mines, chemical products and agricultural products, such as coal kaolin, basic magnesium carbonate, magnesium hydroxide, magnesium chloride, 3A, 5A molecular sieve catalyst. , copper sulfate, barite, nickel oxide, titanium dioxide, zinc ore, sewage sediment, agricultural waste, and industrial waste.

Indirect-fired Rotary Kiln VS Direct-fired Rotary Kiln

Indirect-fired rotary kiln equipment has been widely recognized as the most suitable solid bulk material handling the machine in the past 100 years. The common type of rotary kiln equipment is the direct-fired rotary kiln. The direct-fired rotary kiln’s character is that the combusted materials are directly in contact with the raw material being processed. In traditional rotary kilns, pulverized coal is generally fed into the kiln and ignited by a burner, so that the mixed coal materials are burned and heated to the required temperature. Traditional rotary kilns can also use fuel gas, heavy oil, and other fuels as heat sources. But its shortcoming is also obvious, that is, it cannot handle flammable and explosive materials that cannot be heated by an open flame.

At this time, the advantages of an indirect heating rotary kiln are reflected.

Indirect combustion has received widespread attention in recent years. Indirect rotary kiln has become a more common commercial option in the past 25 years. Indirect rotary kiln differs from direct combustion in that all heat transferred to the processing material is radiated through the casing meanwhile the construction material can withstand higher temperatures.

The indirect rotary kiln is horizontal. You can preheat the surface of the rotary kiln by burning natural gas or fuel. Heat is transferred to many burners outside the barrel to avoid local overheating of the enclosure. The indirect heating rotary kiln is mainly used to process flammable, explosive, or chemically active substances, and it is not recommended to be applied to the production line of quicklime or cement.

Indirect-fired Rotary Kiln Prospect On Disposal Of Waste

Indirect-fired rotary kiln treatment of waste is a popular method of treating waste in recent years, but it is still rarely used in China. In fact, the use of indirect rotary kiln incineration to treat waste has been successfully practiced worldwide, showing great advantages in economics, prevention of secondary pollution, and thoroughness of waste innocuous treatment. Indirect-fired rotary kiln has so many advantages.

  • Firstly, the temperature in the indirect rotary kiln is higher. The temperature of the furnace tube is between 1200-1300 ° C, and the temperature of the material is less than 1150° C.
  • Secondly, the residence time of the flue gas in the indirect rotary kiln is longer, and the residence time is 4s at the temperature of the flue gas above 1100 ° C. Also, the material in the kiln is continuously suspended and tumbling, which is beneficial to the complete incineration of hazardous waste.
  • Thirdly, the flammable part of the hazardous waste can be decomposed into harmless gas after being fully burned. The harmful dust in the flue gas is collected by the rotary kiln and after the treatment, dust can achieve safe discharge standards; the indirect rotary kiln can fix most of the heavy metals in the waste in the clinker to avoid re-diffusion. The residue of the incineration waste is mixed into the cement clinker and enters the final cement product, no longer creating secondary harm to the environment. Therefore, the use of an indirect rotary kiln for the disposal of hazardous waste is a thorough and economical method.

Kiln Operation Parameters

ModelRated operating temperatureFurnace pipe sizeRated heating powerInstallation AngleCapacityPowerDimensionsWeight
RQ240 1100℃φ2.4×16.5m2500000kcal/h0.5~2.5°~3000kg/h380VAC
Main technical parameters of RQ series indirect gas heating rotary kiln