The effect of thermal insulation of the lining on the heat exchange of rotating apparatuses

Abstract

Rotary kilns are used in many industries to process bulk raw materials. In the building materials industry, rotary kilns are widely used for heat treatment. However, the fuel utilization factor in rotary kilns is extremely low. Thus, the bulk of cement clinker is fired in furnaces, the thermal efficiency of which does not exceed 55-60%. Therefore, the task of increasing the efficiency of such units is extremely relevant. In operating furnaces, heat losses to the environment only through the furnace body reach 20-25% of the total heat of combustion. In this case, one of the main factors determining the thermal efficiency of furnace operation is the value of thermal resistance of lining. The aim of the work is to study the evolution and temperature changes in the rotary kiln lining made of shaped refractory to reduce heat losses to the environment and improve the efficiency by increasing the thermal resistance of the lining. The increase in thermal resistance is achieved by changing the shape of the refractory by creating appropriate cells and introducing additional fibrous insulating material into them. A mathematical model and software have been developed and numerical calculations have been carried out to determine non-stationary temperature fields in the lining with a thermal insulating element and to substantiate the choice of an appropriate thermal insulating fibrous material. Analyzing the calculation results, it is possible to conclude about the expediency of using a lining with increased thermal resistance. The use of this technical solution makes it possible to reduce heat losses through the housing by 18-24%, to increase the amount of transferred material in the working zone by 1.5-8% due to the creation of an appropriate temperature field in the working volume, and to reduce the mass of the lining and the furnace as a whole. and increase the energy efficiency of the thermal unit. The presence of cells with additional thermal insulation contributes to the emergence of thermal pulsations having oscillatory character and affecting the intensification of heat and mass exchange processes, which in general contributes to the performance of the thermal unit. A significant advantage of this method is also the fact that increasing the energy efficiency of the furnace does not require additional fuel consumption, increasing the temperature or increasing the enthalpy of the combustion products.