Feasibility study of the energy and economic gain that can be achieved by driving the boiler feedwater pump with a backpressure steam turbine

Abstract

The low-pressure steam requirement in the iron and steel production plant is obtained through pressure reduction stations with unrestrained expansion. In this study, the feasibility of obtaining the low-pressure steam that is needed in the plant in a backpressure turbine instead of pressure reduction stations has been studied. In this way, it is foreseen that a significant amount of wasted energy during the unrestrained expansion in pressure reduction stations, can be recovered as shaft work during the expansion process performed in the turbine. The obtained shaft work is planned to be used in the boiler feedwater pump drive. It is aimed to increase the efficiency of the system by the deactivation of boiler feedwater pump electric motors and as well as bringing the energy that is lost during the unrestrained expansion of the superheated steam to the system through the pump drive. The estimated size of energy saving of the system could be reached to 33.74%. The annual size of achievable saving has been determined by approximately 8,094,810 kWh and economically $509,973. The payback period of the estimated $683,079 investment is 1.34 years. A determined amount of saving is also equivalent to the reduction of 7,285,329 kg CO₂ emission, annually.