Performance improvement of 500 MW coal power plant at low temperature steam condition by suitable operation practice

摘要

This paper proposes a novel operational technique to produce electricity efficiently and environmentally at very low main steam (MS) and hot reheat (HRH) temperature steam conditions of a 500 MW Subcritical coal-fired power plant which is modelled in the computer-based thermodynamic modelling software 'Cycle-Tempo' at different plant operating conditions. Result shows that the combined effect of lower operating pressure with partial withdrawal of top high-pressure feed water heater#6 (HPH#6) from service improve the plant performance during low-temperature steam condition and this operational strategy can be continued until arising the condition of super heater/re-heater spray water requirement or low flue gas exit temperature. In the present case, the improvement in net plant energy efficiency is found of about 0.57% point at the optimum operating point. This improvement is due to increase in MS and HRH steam temperatures by about 3℃ and 62℃ , respectively. Individual approach for reduction of high-pressure turbine inlet pressure from 165 to 145 bar improves the net plant energy efficiency by about 0.31%. In the present case, partial withdrawal of high-pressure feed water heater #5 (2nd feed water heater from top) from service deteriorates the plant performance by increasing the extraction steam flow rate in the top heater (HPH#6). Hence, there is an opportunity for saving the coal of about 5.20 t/h and CO_2 reduction of about 5.56 t/h by the proposed best operation practise at optimum operating point in 500 MW coal power plant.