A Review on the Applications of Rotary Kiln in Various Industries

Abstract:
This paper briefly discusses the various industrial application of the rotary kiln in various sectors considering the vital factors. A Rotary kiln is a cylinder which rotates around its cylindrical axis and acts as a device to exchange the heat. The operational efficiency of the kiln is based on various parameters like inclination angle, temperature, rotation speed, material flow rate and discharge rate. The construction, position and alignment of kiln are an essential factor for the smooth operation. Slight inclination with the horizontal axis makes the movement of solid bed towards the discharge head.
Keywords:Rotary kiln, Incinerator, Heat treatment, Cement, Pyrolyser, Dryer
I.Introduction
The rotary kiln is a horizontal circular cylinder lined with refractory material supported by support stations and driven via a girth gear and drive train. The drive train consists of DC electrical motors and gear boxes with hydraulic packs which are clearly shown in figure.1 The kiln cylinder is located at an angle to the horizon and rotates at low revolutions around its longitudinal axis and operates essentially as a heat exchanger, dryer, calcinator and incinerator. The inclination of cylinder makes an axial displacement of the solid bed, which moves towards the discharge end. The rotating cylinder acts simultaneously as a conveying device and stirrer by the use of internal fins which helps to mix and rotate the material in radial direction, from outside the kiln looks like a normal cylinder without any fins. Inclination angle of the cylinder, operating temperature, rotating speed, material flow rate and discharge rate are the vital parameters for the performance of the kiln. Kiln control is one of the most vital parts and the kiln is very sensitive for operation. Control of the kiln during its operation the assemblage of various components and process parameters is essential one in the rapid fast developing environment. Kiln is generally used for the processes like activated coal regeneration, lignite degasification, municipal waste disposal, scrap tire recycling, sewage sludge disposal, soil cleaning, waste wood recycling. Indirect heated rotary kilns are used for pyrolysis and thermo analysis processes due to the advantages of continuous process, very good blending of the product unlike batch processing and simple plant layouts.
A rotary kiln is a cylinder that rotates around its cylindrical axis and essentially operates as a device to exchange heat. The direct heated rotary kiln is broadly used for physical activation. Construction and position alignment of the kiln is very important for all the process. In thermal processing of residual materials with a various origin and predominantly for fire treatment of hazardous wastes rotary kiln are employed. In metallurgy they serve for heating of solid particles like, oxide ores reduction, limestone calcination, cleaning of swarfs from machine oil. Furthermore, these units find a large application in the silicate, chemical and pharmaceutical industry also used as an incinerator and pyrolyser in minerals, metallurgical, cement, sugar and food industries. In these sectors they are used mainly for heating and drying of bulk materials with different dimension. Rotary kilns are well established devices for numerous industrial applications in the field of waste lime recovery, proppent manufacture, activated carbon manufacture, sugar industry, food processing, pulp and paper industry, clays, thermal desorption of organic/hazardous wastes, mineral roasting, specialty ceramics, plastic processing, gypsum calcining, Tire pyrolysis, bauxite calcining, pigments, catalysts, phosphate production. The fig 2 shows some of various industrial applications of kiln which are explained in this paper in detail.