Another major heating method of indirect-fired rotary kiln is oil fuel heating, which we call oil fuel rotary kiln or oil-fired rotary kiln. The oil fuel rotary kiln is directly heated by an oil burner on the outer wall of the kiln pipe, and the material inside the kiln pipe is heated by heat conduction. So as to avoid the pollution of materials by burning volatiles. Oil fuel heating is the main heating method for cement rotary kilns and lime rotary kilns located in crude oil-producing areas.
According to the different types of fuel oil, the oil-fired rotary kiln can be divided into crude oil rotary kiln, diesel rotary kiln, and so on. Depending on the oil, the burner of the oil rotary kiln will also be different. In the form of oil mist, the fuel is ejected through the nozzle and ignited by the ignition device. The fuel oil is evenly distributed on one side of the heating kiln body in a straight line, and the open flame is directly sprayed on the outer surface of the kiln pipe.
Advantages of Oil-Fired Rotary Kiln
The oil fuel rotary kiln has many advantages. Among them, the oil mist combustion reaction is fast, and the heating process is fast, which is beneficial to shorten the cold heating process of the kiln and can effectively shorten the heating time. In addition, the oil rotary kiln has the following obvious advantages.
Reduce powder wall sticking and improve powder properties
In the pre-burning process of powder, the phenomenon of powder sticking to the wall often occurs. The reason why the powder sticks to the wall is that the mixture of the fine powder, water vapor, and PVA glue volatilized in the heating process is attached to the inner wall of the kiln pipe, which is in a static state relative to the kiln pipe. In the process of using, the mixture casting will accumulate and thicken, which will directly affect the pre burning temperature of the product. In order to reduce the sticky wall of the powder, the oil fuel rotary kiln has been improved in the following aspects.
- Increase the temperature of the kiln pipe inlet
- Increase ventilation intensity of the kiln
- Use a rapping hammer to disturb the powder in the kiln
Good product consistency
In the pre-burning process of the powder, the consistency of the product depends on the degree of adhesion of the powder to the wall of the kiln pipe. The problem of powder sticking to the wall is well solved in the oil-fired rotary kiln, and the consistency of powder produced is very good.
Oil-fired rotary kiln belongs to large rotary kiln equipment. The production capacity of an oil-fired rotary kiln can reach 500kg per hour and 3600 tons per year, which is equivalent to the production capacity of 2-3 electric heating rotary kiln. Moreover, the oil fuel rotary kiln saves the production of land and reduces the maintenance work.
Adjustable cooling speed
Some materials, such as a few soft ferrite powder materials, need to be processed by slow cooling. Slow oxidation allows the pre-fired powder to be fully oxidized, avoiding re-oxidation of the final fired product.
Taking soft ferrite powder as an example, the ideal sintering curve, temperature curve of electric heating rotary kiln, and oil fuel rotary kiln are shown in the figure below. We can see that the cooling rate of the pre-burned material is also required. Due to the short pipe of the electric heating rotary kiln, the powder is naturally cooled after exiting the tube, and the cooling rate cannot be controlled. The cooling pipe of the oil-fired rotary kiln can adjust the flow of cooling water to control the cooling speed of the powder, as close as possible to the ideal temperature curve, to ensure the performance of the powder.
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