Feasibility of Utilizing Boiler Blowdown Waste Heat for Operating an Absorption Refrigeration Chiller

This paper presents results of a study carried out to determine the feasibility of utilizing boiler blowdown heat for operating an absorption refrigeration chiller. In the study the coal power plant situated in Sri Lanka was used. This consists of three identical power plant units operated on “Rankine Reheat – Regenerative Steam Cycle. Each unit has 300MW rated capacity with an overall efficiency between 35%-40%. Continuous blowdown of the plant boiler is done at the rate of 10tons/hour. The temperature of the blow down water is at 97.5oC. The study aimed at investigating the possibility of utilizing heat recovered through boiler blowdown water to operate a vapor absorption refrigeration plant to supply required chill water for site air conditioning needs. The power plant at present has three central air conditioning units with cooling capacities of 900, 960 and 640kW operating on vapor compression refrigeration to produce chill water requirements. The amount of heat that could be extracted from the blowdown water (from one unit) was estimated as 496kW. Accordingly, an absorption chiller was selected to match the available heat and based on inlet and outlet temperatures recommended by the manufactures. All necessary auxiliary equipment for the installation of the selected the absorption chiller which replaces the present vapour compression refrigeration system was determined together with economic feasibility. The study demonstrated the possibility of successful utilization of boiler blowdown water for useful application, hence savings in energy.