Thermodynamic and technoeconomic comparative justification of a waste heat recovery process with integration of multifluid and indirect evaporative cooler

Abstract

For a well-developed, efficient and feasible system, it is necessary to produce power generation enormously with a reduction in harmful emissions like Carbon dioxide (CO2), Carbon monoxide (CO), Nitrogen (N), Nitrogen oxide (NOx), and Sulphur dioxide (SO2). Waste heat gases emit directly into an environment, it has many adverse effects on the environment including global warming, environmental pollution, and effect on human health as well. Researchers believe that a thermally efficient system could be achieved by converting waste heat gases into net power output. From this system, the efficiency obtained is 5% to 8% unable to meet the space and cost demands of this waste heat recovery (WHR) system. For waste heat recovery, the most typical cycles used for this are the Rankine cycle and Brayton cycle. Even though these are the best cycles but their efficiency is not as such maximum. By observing all these aspects, there is a different way of recovering waste heat and that is an indirect evaporative cooler (IDE). An indirect evaporative cooler is beneficial in terms of enormous power generation, getting maximum efficiency, low operating cost, and acquiring a sustainable system. The focus of current research was to recover industrial waste heat gases exhausted from SP boilers in the cement industry. ASPEN HYSYS software is used for generating a waste heat recovery model that further operates on the Maisotsenko cycle (M cycle). The topping cycle and bottoming cycle are used in this model. Both the working fluid air and binary mixture CO2-C7H8 operated in a model. By manipulating the model with working fluid air, this system generated a net power output of 68.53 MW with 35.44% thermal efficiency. Integrating the model with a binary mixture of CO2-C7H8 permits 48.59 MW output power with a 38.57% efficiency value. Comparison analysis is performed for extracting the best optimal parameters with extreme power generation and the greatest efficiency value. The industrial operating parameters of the Bestway cement industry operated in this developed model present 38.04 MW and 30.63 MW of power generation with 27.78% and 27.77% efficiency by executing both fluids air and CO2-C7H8 mixture. A techno-economic analysis (TEA) is performed for this entire waste heat recovery system which exhibits a cost of $30/MWh along 3 years payback period.