Energy, environmental, and economic analysis of a new configuration multi-stage flash distillation unit coupled with steam power plant

Abstract

This study focuses on the utilization of three waste streams from a power plant for the provision of cooling water and required steam for heating purposes in a multi-stage flash desalination (MSF) unit. The mathematical model for a new configuration of MSF desalination is presented. In conventional MSF desalination unit, a stream of salt water is used for desalination and system coolant. A new structure for the desired desalination process, proportional to the salt concentration of the feed streams and based-on un-mixing of the target streams has been proposed. The proposed system required 18 m2 of cross-sectional area and also 87 m2/(kg/s) of specific heat transfer area in the power plant with seven stages. The optimal value of top brine temperature (TBT) has 110 °C and the capacity of the proposed MSF desalination unit is 92.43 m3 of fresh water/day. The gain output ratio (GOR), energy intensity and water cost of the system are calculated to be 3.12, 706.8 kJ/kg, and 0.69 $/m3, respectively. By application of proposed MSF desalination, the annual emission of 1167.5 tons CO2 into the atmosphere can be obviated and the cost savings resulting from equal fuel consumption amount to $116,315.5 per year.