A comprehensive approach for designing, modeling and optimizing of waste heat recovery cycle and power generation system in a cement plant: A thermo-economic and environmental assessment

Abstract

Mazandaran cement plant in Iran is to be retrofitted for decreasing energy consumption and increasing energy efficiency. This project came up with designing heat recovery from grate coolers (Air Quenching Cooler or AQC boiler) and heat recovery from cyclones’ exhaust gases (Suspension Preheater or SP boiler). The procedures of modeling (in energy, exergy, economic and environmental aspects) and optimum design of waste heat recovery and power generation (WHRPG) systems for two parallel lines of cement production which are new and specific to our studied cement plant are reported here. The objective functions were exergy destruction (which was minimized) and relative annual benefit (which was maximized). Results for our case study for Rankine (Organic Rankine) cycle showed that using water (toluene) as working fluid provided 9.14 (6.56) MW power output with exergy destruction ratio of 47.9% (53.5%). Furthermore, the amount of fuel for producing steam and providing the equal value of power output was estimated to be 2.38 × 107 (1.7 × 107) m3 natural gas and its corresponding cost was 2.1 × 106 $/year (1.46 × 106 $/year), with 5.36 × 104 ton/year (3.81 × 104 ton/year) lower CO2 production. The payback period for equipment installed was 3.4 (5.1) years for water (toluene) as the working fluid.