Investigation and Reduction of Radiation Heat Losses from a Rotary Kiln by Using Low-emissivity Paint

Abstract

Rotary kilns are thermal processing units used for processing solid materials at extremely high temperatures. In the cement industry, calcination takes place inside a rotary kiln and is a highly energy-intensive process. This paper investigates the reduction of radiative heat loss from the kiln surface by applying a low-emissivity coating and simulates the physical behavior inside the kiln using ANSYS. The study also considers the need for a practical emissivity value because decreasing surface emissivity reduces radiative heat loss but increases kiln-shell temperature. A detailed heat-transfer analysis was conducted to quantify the effect of surface emissivity on shell temperature. For the baseline case, the total surface heat loss was approximately 5.17 MW, with about 70% due to radiation and 30% due to convection. The analysis suggests an emissivity of 0.6, for which the shell temperature increases by approximately 45 °C while the total heat loss decreases by approximately 250 kW (4.8%). Using a net calorific value of 25.958 MJ/kg, this corresponds to an estimated coal saving of approximately 832 kg/day. The results indicate that a low-emissivity coating can reduce kiln heat loss, although the accompanying increase in shell temperature must also be considered.