In the present work, an alternative method to investigate the irreversibility in thermal systems was presented by applying in a cement plant. The method developed can also be applied to other thermal systems. Energy and exergy balances were calculated for whole system and its sub-units, which consist of clinker cooling, rotary kiln, calciner and preheater cyclone units. In the analyses, irreversibility sources are considered as combustion, chemical reaction, and heat transfer to raw material during mixing in the system, and heat transfer between the system and its environment. In cement plant, considering the whole system and sub-units, the equations for each type of irreversibility were derived and calculated results were given in the tabulated forms. Irreversibility sources and their effects on energy and exergy efficiency were investigated. A code was developed for the new approach considering the adiabatic conditions and used to calculate the irreversibility arisen from heat transfer to raw material during mixing in the system and heat transfer from the system to environment. First and second law efficiencies are calculated as 54 and 32%, respectively. Total exergy loss of the system is about 68%.
Key words: Energy analysis, exergy analysis, irreversibility, precalciner, parallel flow preheater cyclone, cement plant.
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