The Design And Analysis Of Flue Gas And Cycling Water Waste Heat Utilization System In Thermal Power Plant

At present, the contradiction between energy supply and demand has becomeincreasingly worldwide prominent. Environmental pollution is threatening the livingand development of human. Therefore, the sustainable development among theenvironment, energy and economy became an imminent strategic issue in this situation.All the countries around the world have increased emphasis on the development andutilization of renewable energy and waste heat. We all know that, thermal power plantsgenerate electricity throgh thermal power conversion on the basis of Rankine cycle.There exists large heat loss in this process.And the main heat loss in power plant iscaused by turbine cold source loss and the exhaust gas loss of boiler flue gas. So, it willmake a significant contribution to energy saving of the whole community,that if we canrecycle and reuse waste heat more effctively.In reccent years, as the theoretical and technical level developing, some new wasteheat recovery methods come into our view. Especially the development and applicationof the low temperature-corrosion resistant materials and heat pump technology，make iteasier for us to recover and reuse waste heat in power plant. This article will focus onthe features of the condensing steam thermal power plant in the northern region withthis new methods. And, with combination of the1000MW condensing steam indirect aircooling unit thermal system configuration, this article will analyze the the feasibilityand economy of recycling the flue gas heat and intercooling cycle water waste heat withthe low-temperature economizer and heat pump technology respectively.After analyzing and comparing many plans, we found that the economic benefit ofthe two-stage low-temperature economizer heating boiler inlet air plan is the best. Theplan makes use of desulfurization to absorb the temperature at the tower entrance of thesecond low-temperature economizer to heat the aqueous medium, which then heats theinlet air in the air preheater, the efficiency of the boiler increases by about0.72%. Thataqueous medium heats the inlet air in the air preheater results in the increase of theexhaust gas temperature of the air preheater. The first stage low-temperature economizerat the exit of the air preheater can heat the high-temperature-part condensated water,pushing the relatively high extraction steam back to the turbine to work. Thus theeffeciency of waste heat utilization increases, the heat consumption of turbine decreasesby about54kJ/kWh, the cost can be recovered in about4.4years. According to the analysis of cycling water waste heat in thermal power plant, theconclusion can be made as follow: If heating loads are stable and reliable,absorptionheat pump can be utilized for its better economic benefits.However, to the purecondensation units,duing to its low heating loads,the scale of using absorption heatpump is too small and the economic benefits of energy saving is unsignificant.With theinitial investment of4.6millon yuan, the annual profit is only2.43million yuan,whichcannot cover the investment balance during the limited years for economic operation.