Design of ORC-RO system for utilizing waste heat from flue gases of coal-fired thermal power plant

Abstract

Waste heat recovery is an efficient tool to reuse waste energy to provide useful energy products. This method addresses the practical solution for sustainable products, which reduces CO2 emissions. The organic Rankine cycle is the most desirable option for waste heat recovery systems as it operates with low heat source temperature, which is auspicious in designing flexible and compact systems. This paper aims to design an organic Rankine cycle coupled with reverse osmosis to drive RO system by utilizing waste heat from flue gases of the thermal power plant. The boiler feed (make-up) water has been treated using the RO system, and the concentrate from the RO system can be used to suppress coal fly ash. The recycling reverse osmosis system is designed according to the boiler feedwater input for achieving more than 80 % recovery. The RO feed water is pre-heated by condensing vapor from the ORC expander, which reduces the specific energy consumption of the RO system. Also, the flue gas characteristics are discussed, which can be utilized at above dew-point temperature to avoid corrosion. This concept design is developed for the 2 MW coal-fired thermal power plant.