Thermodynamic Analysis of Waste Heat Recovery Systems in Large Waste Heat Generating Industries

Abstract

The accelerating growth of electricity demand necessitates looking for potential waste heat recovery solutions in production industries. Significant potential for efficient waste heat recovery is observed in the cement manufacturing industry. Based on the waste heat source temperatures in a cement plant, two potential candidates, the supercritical CO2 Brayton (S-CO2) cycle or the Organic Rankine cycle (ORC), promises low capital cost and enhanced thermodynamic performance. The current study focuses on modelling and optimization of the S-CO2 and ORC cycles for a 1 MTPA cement plant, with the raw-clinker preheater as the waste-heat source. The primary objective is to maximize the net-power output using genetic algorithms. A comparative performance analysis of the two ORCs with working fluids: R134a and Propane, the simply recuperated S-CO2 cycle (RC) and recompressed-recuperated S-CO2 cycle (RRC) configurations is presented with varying number of preheaters. For all cases, ORC-R134a yields more power than the ORC-Propane, RC, and RRC configurations. In terms of the waste heat recovered, ORC-Propane marginally outperforms ORC-R134a. The ORC configurations recover 32%–38% of the available heat, while the S-CO2 configurations recover, at maximum, 25%–30% of the available heat.