Performance Investigation Of Heat Recovery From Flue Gas In A Coal-fired Boiler

Coal-fired power plants consume a lot of coal resources while providing electricity in China,boiler as one of the main equipment of the power plant,its efficiency will affect the overall economic performance,reducing the heat loss of the boiler can effectively improve the efficiency,and the heat loss of exhaust gas accounts for the largest proportion of the boiler heat loss,so it is an important energy-saving measures to recover waste heat from flue gas through the heat recovery system.Taking a 680 MW super critical unit as an example in China,six integrated schemes of series,parallel,cross-level parallel and series-parallel hybrid were established aiming at the different integration methods of low temperature economizer and regenerative system,and the optimal integration scheme was obtained;Based on the FLUENT software,the characteristics under variable operating conditions of fluorine plastic light tube low temperature economizer were studied,and the effects of tube arrangement,tube pitch and tube number on the flow heat transfer characteristics were analyzed,the heat transfer and resistance characteristics under different conditions were obtained,and the simulation results were compared with the empirical calculation values in the standard formula,which verified the correctness;According to the integrated optimal scheme,based on simulation,the low temperature economizer were designed from the structure type,the flow rate of the fluid inside and outside the tube,total heat transfer coefficient and pressure drop and economic analysis was carried out.The results showed that when the low temperature economizer is connected in parallel between the 6 low pressure heater and the 7 low pressure heater,the import and export water temperature is 53.37? and 120.50? and import and export of the smoke temperature is 143? and 85? respectively,the value of coal consumption rate is maximum and energy saving effect is best.After added low temperature economizer,the steam turbine swept volume and power supply coal consumption is reduced,comprehensive coal consumption rate decreased by 3.942g/(kW·h),recovery of the flue gas waste heat 57.09 MW,the heat loss rate is reduced by 102.27kJ/(kW·h),the thermal economy of the unit is improved by 1.36%,annual savings of 9650 tons and annual coal income of 4.825 million yuan.