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Abstract

Blow down water is the part of water that is purposely drained during the boiler operation to limit the level of impurities in boiler water to an acceptable level. So it is contains large quantity of heat energy. The aim of the present work is to improve energy efficiency of steam boilers in the south refineries company/Al-Basrah. This aim has been achieved through designed and manufactured of a heat exchanger consists of a shell and coiled tube unit to recover heat from surface blow down water and reducing indirect losses. The blow down water (hot fluid) is supplied to the heat exchanger at atmospheric pressure by passing it through the shell side and the feed water (cold fluid) in the coils tube side. These were done as counter flow. A flow control valve is used to control the flow rate of hot blow down water inside the heat exchanger. The experiments are done at the blow down water and feed water flow rates ranging between (0.06-0.14) m3/h with 0.02 m3/h interval, and between (0.1-0.5) m3/h with 0.1m3/h interval, respectively. The experimental results proved the effectiveness of the heat recovery system in improving the boiler efficiency where a percentage of 83.16% of the energy is lost with blow-down water that can be recovered using heat-recovery unit with an energy saving of 103411.8 MJ/day. Which will save a mass of fuel equals to 482.46 ton/ year. The heat recovery unit is proved to be a good solution for saving energy and reducing harmful emissions to the environment and it contributes to the maintenance of sewage pipes from damage caused by the heat of discharge water by cooling the water before discharging it into the sewer system.