Abstract: Abstract:Using national economic evaluation method, the internal revenue rates under differential investment of two cooling schames of a mine mouth power plant, which are reservoir composited cooling water supply (oncethrough cooling water supply and recirculating water cooling system) and cooling tower secondary circulation method, were compared. The comparison conclusion is that the scheme of reservoir composited cooling water supply is superior to the cooling tower secondary circulation method. The technical advancement and the economy of the scheme are as below. The water temperature of the reservoir, whch is locates in piedmont of high latitude area, is more lower. The back pressure of the steam turbine with final stage long blade is lower. The Rankine cycle efficiency of the unit is higher. The evaporation loss of the water resource is reduced as far as possible, so the water saving effect is excellent. The difficulty of the reservoir to melt ice in winter is solved, and the discharge is meets with the standard of thermal discharge of the reservoir. The scale of the project is larger, and the social effect is favourable. The coal mine, the thermal power generation, the hydropower generation and the reservoir were developed integratedly, which formed great intensive advantages and comprehensive development effects. The generating cost of the plant is lower. The reservoir composited cooling water supply scheme is an innovative application of the oncethrough water supply cooling system in arid region.

Key words: Keywords:mine mouth powe plant, oncethrough cooling water supply, composited cooling water supply；economic evaluation； internal revenue rate under differential investment