Thermodynamic and economic investigation of a waste heat recovery system with thermoelectric generators in the cement industry
Panagiotis Lykas, Evangelos Bellos, Konstantinos Atsonios, Grigorios Itskos, Nikolaos Nikolopoulos
Abstract
• Thermoelectric generators are suggested to recover the cement kiln heat losses. • Thermodynamic, and economic analyses are performed. • A design power output of 115.19 kW, and an annual yield of 943.65 MWh are defined. • 371.8 tn CO2-eq are saved due to the electricity generation. • The payback period is 9.05 years, and the net present value at 1,338,698 €. The cement industry is among the largest consumers of primary energy in the industrial sector. However, a substantial portion of the waste heat generated by cement plants remains largely untapped. Thermoelectric generators (TEGs) represent a promising technology for waste heat recovery and are currently under development. The present paper analyses under both steady and unsteady conditions a TEG installation in a cement plant, aiming to recover the radiation heat losses of the rotary kiln through a heat exchanger placed on a secondary shell around the kiln. The proposed configuration is investigated thermodynamically, and economically. It is revealed that the number of installed thermoelectric modules strongly affects the overall performance, showing the need to optimize this value for each kiln section. For the specific pilot plant investigated, at the design point, the produced power output is equal to 115.19 kW el , with the yearly achievable annual electricity estimated to be 943.65 MWh el , with an annual TEG efficiency of 6.00 %, and an annual overall system efficiency of 2.17 %. Moreover, electricity production leads to a carbon emissions reduction of 371.80 tn CO2-eq per annum. Finally, the payback period of the system is computed at 9.05 years, and the net present value is found at 1,338,698€, while a sensitivity analysis enhances the economic evaluation.