Thermal and exergetic approach to wet type rotary kiln process and evaluation of waste heat powered ORC (Organic Rankine Cycle)

Abstract

In this study, the energetic and exergetic performance analysis of a rotary kiln and cooling section in a cement factory using wet method was carried out based on the actual operational data. The energy and exergy efficiencies of the wet type rotary kiln are about 46% and 35%, respectively. The results showed that a great amount of heat energy of 30.5 MW is exhausted from the chimney of rotary kiln. In order to evaluate recovery capacity of exhausted gas, Organic Rankine Cycle (ORC) was considered and its energetic and exergetic performance were evaluated for isentropic and dry type fluids for different conditions. Isentropic fluid, R245fa shows the best performance while the dry fluid, R600a has the lowest performance. For condensation temperature of 303 K and evaporation pressure of 1500 kPa, the thermal and exergy efficiencies of R600a are 9.8% and 21.7% while the thermal and exergy efficiencies of R245fa are 13% and 29%, respectively. Isentropic fluids, R245fa, R142b can be used at high evaporator pressures and low condenser temperatures as R600 and R600a are not appropriate after a certain pressure since the efficiency remain stable. The exergy destruction rates in heat exchanger and evaporator are about 80% of the total exergy destruction. (C) 2016 Elsevier Ltd. All rights reserved.