Rotary kiln simulation for energy recovery: The precalciner cement kiln case

Abstract

Cement production process is energy intensive both in terms of the thermal and electrical energy. In fact, energy demand accounts for about 40 % of operational costs. Significant heat losses are present even in modern plants, affecting negatively both on production costs and emissions. These losses are mainly due to the sensible heat in the hot flue gases and exhaust air streams used for cooling down the clinker (35 % of the process heat losses). Given the good quality of the available sensible heat in these streams (temperatures above 280 °C), a heat recovery system can be considered to increase the overall efficiency of the cement plant. The aim of this work is to create a simplified model of a cement rotary kiln to study the heat recovery optimization. Results were consistent with the temperature, pressure and flowrates ranges indicated in the literature. The model here proposed can be adapted to simulate other processes involving a rotary kiln. As a result of the study of the proposed case scenario, the plant was found to potentially generate 3.2 kWh/ton of clinker of electricity, equivalent to approximately 20 % of the total plant electrical consumption.