Comparative environmental impacts and emission reductions of introducing the novel organic Rankine & Kalina cycles to recover waste heat for a roller kiln

Abstract

Abstract In order to simultaneously utilize the flue gas and cooling gas of a roller kiln, the novel organic Rankine (ORC) & Kalina cycles (KC) with parallel double-evaporator (PD) including PD-BORC, PD-RORC, PD-KC11 and PD-KC34 are introduced for the waste heat recovery. To evaluate the environmental influences performance for the recommended thermodynamic cycles, environment impact loads and emission reductions analysis are employed from the life-cycle perspective. Also, to select a more environmentally friendly model, the system environmental influences based on thermodynamic, economic, environmental and watery criteria are investigated. Results show that under the four criteria, the pump contribute mostly to GWP (global warming potential), AP (acidification potential), EP (eutrophication potential) and HTP (human toxicity potential), evaporation unit is dominant in POCP (photochemical ozone creation potential) and SWP (solid waste potential), and both evaporation unit and pump have the main influence on SAP (soot and dust potential). Meanwhile, operation phase makes the greatest contribution to GWP, AP and HTP, construction phase has the greatest influence on POCP and SWP, and construction and operation phases account for the largest proportion of EP and SAP. It can also be concluded that SAP has the most serious impact on the environment while POCP is the least significant factor. Besides, from the perspective of environment impact load, PD-BORC is the best selection, and the system design based on environmental criterion has the minimum value. Also, in terms of the emission reduction, PD-KC34 is the priority selection, and the maximum emission reduction can be achieved under thermodynamic criterion. Furthermore, the reduction ratio of environment impact load can be increased with increasing the evaporator inlet temperature, decreasing the condenser outlet temperature, increasing the superheat degree (PD-ORCs) and decreasing the superheat degree (PD-KCs), and decreasing the ammonia concentration (PD-KCs).