Thermo-economic Performance Analysis Of Kalina Cycle Based On Low Temperature Flue Gas Waste Heat Power Generation

This project mainly focused on analysed the thermo-economic p_erformance of the Kalina cycle driven by the low temp_erature flue gas waste heat.Taking the Kalina cycle as the research object,the thermo-economic p_erformance versus outlet temp_erature of flue gas were analyzed under variations of the pinch point temp_erature difference of evaporator??T_e?,evaporation pressure?p_e?and basic ammonia mass fraction?x?.Considering the corrosion of low temp_erature flue gas,the necessity and reasonability of limiting outlet temp_erature of flue gas at its minimum allowed discharge temp_erature were studied.Moreover,considering the thermodynamic and economic constraints simultaneously,the critical external heat source conditions available for Kalina syste m are clarified.The critical external heat source conditions include the maximum allowed heat source temp_erature T_gi,max,the minimum allowed heat source temp_erature T_gi,min and the minimum allowed heat source mass flow rate mg,min.Results show that the system exists optimal outlet temp_erature of flue gas(T_go,opt)and evaporation pressure(p_e,opt)for levelized energy cost?LEC?,while the optimal outlet temp_erature of flue gas(T_go,opt)is associated with the pinch point temp_erature difference of evaporator?? T_e?,evaporation pressure?p_e?and basic ammonia mass fraction?x?.For net work?Wnet?and exergy efficiency??e x?,it only exists optimal evaporation pressure(p_e,opt).The economic factors affect directly the optimal op_eration parameters of the system.The economic factors and low temp_erature flue gas corrosion problem should be considered comprehensively to choose the appropriate op_eration parameters in view of different heat source conditions.In addition,the maximum allowed heat source temp_erature T_gi,max and the minimum allowed heat source temp_erature T_gi,min gradually decrease with the increasing of ammonia mass fraction under the fixed evaporating pressure p_e.And the greater the ammonia mass fraction,the narrower the temp_erature range of heat source that can be used.The flue gas mass flow rate mg has significant impact on the minimum allowed heat source temp_erature T_gi,min.Along with the flue gas mass flow rate mg increases,the minimum allowed heat source temp_erature T_gi,min becomes lower.When the ammonia mass fraction is in a certain condition,the maximum allowed heat source temp_erature T_gi,max increases with the increasing of the evaporating pressure p_e while the minimum allowed heat source temp_erature T_gi,min and the minimum allowed heat source mass flow rate mg,min firstly fall down,then rise up with the increasing of evaporating pressure p_e.And the minimum allowed heat source mass flow rate mg,min reduces sharply with the increase of heat source temp_erature T_gi.For the comparative between Kalina cycle and sub-ORC under different heat source conditions,the appropriate zeotropic mixtures and ammonia ratio were selected based on p_erformance optimization in the first place,then compared the thermo-economic p_erformance between the Kalina cycle and subcritical organic Rankine cycle.The results show that,the distribution ratio of the working fluids doesn't exist when the thermodynamic p_erformance and economic p_erformance of the the subcritical ORC cycle system are both optimal.When LEC is used as the economic evaluation index,the economic p_erformance of the pure refrigerant is better than that of the zeotropic mixtures;but the thermal p_erformance of the pure refrigerant is worse than that of the zeotropic mixtures when choose Wnet as the thermal evaluation index.In the range of Tgo,the thermal p_erformance of subcritical ORC cycle is better than that of Kalina cycle,and the Kalina cycle economic p_erformance is bet ter than that of ORC.The highest proportion of exergy loss of Kalina cycle and subcritical ORC cycle is the condenser and evaporator,the turbine is the second,so as for the optimization of syste m components,evaporator,condenser and turbine are the key to the improve Kalina cycle and subcritical ORC.In the range of T_gi,there exists critical T_gi(T_gi,cr).If T_gi is higher than T_gi,cr,the thermal p_erformance of the subcritical ORC cycle is prior,on the contrary,the Kalina cycle is preferential.But the economic p_erformance of Kalina cycle is always better than that of subcritical ORC cycle.