Experimental and theoretical analysis on the safety and efficiency of an ultra-supercritical pulverized coal-fired boiler with low mass flux vertical water wall

摘要

The heat transfer safety of low mass flux vertical water wall suitable for a high efficiency and wide-load ultra-supercritical coal-fired boiler is investigated experimentally. The pressure drop characteristics of supercritical water are discussed. The net thermal efficiency of an ultra-supercritical pulverized coal-fired power plant is analyzed theoretically by considering the power consumption of the feed water pump. The experimental results demonstrate the test water wall tube exhibits good heat transfer and low pressure drop characteristics at low mass flux and in the normal heat flux range. However, the self-compensation characteristic between parallel tubes can be destroyed at high test heat flux when the test pressure is near the critical value. In this case, the metal temperature and pressure drop of the water wall tube increase fast and abnormally. This phenomenon indicates the distributions of in-tube mass flux and furnace heat flux no longer match, which threatens the heat transfer safety of the water wall. Corresponding analysis demonstrates that on the premise of ensuring the heat transfer safety of the water wall, adopting the low mass flux technology can improve net thermal efficiency of the power plant.