The Design And Analysis Of Cogeneration Heating System Based On Waste Heat Recvery

With the rapid economic development, people’s living standards improve, whichcauses that the energy consumption is growing increasingly. The shortage tof theenergy prompts that researchers, experts and scholars of various countries have beendedicated to investigating all efficient energy saving mode. Thermal power plant’s coalconsumption is large, but the overall thermal efficiency is at low level to be only about37%. The large part energy is lost through the smoke and exhaust energy, and themaximum heat loss is the exhaust of the cold source. Aiming to improve the efficiencyof power plant, this text has designed two kinds of combined heat and powersystem based on thermoelectric exhaust steam waste heat recovery, and analyzedthe energy balance and exergy of the effective exhaust steam waste heat utilization, inorder to find an efficient way of exhaust steam waste heat utilization.Firstly, according to the thermodynamic parameters of condensable style units andthe heating needs of some areas, this text calculates the heat load, steam extractionvolume, exhaust volume, at rated conditions of high heat and backpressure andabsorption heat pump heating, and annotation the calculated parameters on the heatingenergy flow diagram of the system, furthermore draws the two primary heating systemprinciples thermodynamic system diagram, which lays the foundation of the energyanalysis and exergy analysis basis.Secondly, using of the energy consumption analysis way of energy balancealgorithm to calculate the two heating systems: change to the unit acting ability,changes in fan power consumption, the speed loss and heat exhaust unused has beencalculated after the exhaust steam pressure increase for the high back pressure heatingsystem, accordingly the total energy consumption model for the high back pressureheating system has been obtained; power generation’s decrease due to the reduced amount of extraction steam, changes in fan power consumption, as well as the internalenergy consumption has been calculated for the absorption heat pump system, draw thetotal energy consumption model of heat pump heating system, at last, the comparison ofenergy consumption has carried on between the two kinds of heating ways, and verifiedby using matlab program, draw a conclusion that heating by high back pressure has lessenergy.Thirdly, quality utilization has been analyzed for the two heating systems byexergy analysis method. A gray box model was established at first,which was linked tothe exergy, then the black box model was created，which was used to calculatethermodynamics consummating degree，exergy efficiency, exergy loss rate, and theexergy loss coefficient to each device of two heating systems. Then the calculationresults were analyzed.Through the comparison of energy consumption and energy quality of two kinds ofheating system, a conclusion can be draw that the energy consumption of high backpressure is small, and the rate of exergy loss and exergy loss coefficient is smallalso. But the irreversible loss of two kinds of heating methods for the air-cooledcondensers is maximum. So we should select appropriate units parameter according tothe parameters of unit load and heating needs while we use exhaust steam, toprevent cold source heat loss increased.