A Mathematical Modelling and Simulation for Reduction in Thermal Losses by Painting DRI Kiln

Abstract

Rotary Kilns has been widely used for processing minerals, producing cement, calcining of rotary kilns consume energy intensively. Therefore it is desired to assess the thermal losses from the kiln surface and find a way to reduce the energy losses. The paper gives an insight in the mathematical modelling of rotary kiln of a DRI Plant to investigate the savings by painting the kiln outer surface with low-emissivity paint. However, it must be carefully evaluated the insulation effect of the paint because good insulation will increase the metal shell temperature. Too much temperature increase could result in structural problems induced by differential thermal expansion between the shell metal and the refractory bricks. In this paper, heat transfer analysis is conducted to help make a decision concerning paint selection and the potential consequence of painting the kiln surface. The paint emissivity has a significant effect on the kiln surface heat transfer. Lower emissivity paint decreases thermal losses but increases the kiln surface temperature. A commercial available paint with the emissivity of 0.65 is selected to achieve the optimum result of an energy saving of 369 kW without imposing detrimental destruction to the refractory brick's integrity inside the kiln. The amount of saving can increase if around emissivity of 0.5 can be selected but the availability of the quality of paint is another concern. Moreover with this emissivity, the reduction in coal consumption is around 3000 kg/day with an energy saving of 668kW.