| Allam cycle using supercritical CO2 as working fluid is a disruptive power generation technology which is expected to overcome the bottleneck of the existing thermal power cycle effectively and solve the problems of emissions from thermal power generation.Organic Rankine cycle is a low temperature waste heat recovery technology which can be widely used in the recovery of industrial waste heat,solar power,geothermal sources,biomass combustion and other fields.In view of these two kinds of power generation technology with great potential.Thermodynamic analysis,process simulation and performance optimization of the two technologies with huge potential are performed on the gPROMS platform and studies of core equipment and the key problem of heat transfer process are presented in this paper.Firstly,a detailed process model of Allam cycle has been developed and comprehensive parametric sensitivity analysis of vital design and operating parameters has been conducted,including the turbine inlet temperature,inlet pressure,pressure ratio and outlet temperature of coolers and so on.The possible coupling configurations with other cycles have been studied as well.Secondly,a thermodynamic model of organic Rankine cycle driven by low-temperature hot water has been also developed and the influence of some vital parameters on the system performance has been examined under two conditions of fixed heat exchanger pinch point temperature and fixed total heat absorption of system.On this basis,parametric optimization has been conducted considering different system performance evaluation indexes.Besides,the influence of the pinch point temperature difference of heat exchangers and the heat source temperature on the optimal operation parameters of the system have been explored as well.The design of evaporator and condenser under optimal conditions has been conducted,moreover,the influence of the heat exchanger size parameters including plate spacing,plate length,plate width on the performance of heat exchangers are also presented.In addition,based on the modeling and analysis of subcritical organic Rankine cycle,supercritical organic Rankine cycle system driven by the same heat source with suitable working fluid has also been modelled and studied.It is of great importance to evaluate pinch point temperature difference caused by the unique properties of supercritical fluids,furthermore,the effects of turbine inlet temperature and pressure on the system performance has been examined as well.Evaporator design of the supercritical organic Rankine cycle has been conducted and the effect of thermodynamic properties of working fluid near critical point on the heat transfer process has also been explored.The integrated process model established in this paper can realize the performance simulation and analysis on system level,which can help to reveal general performance characteristics of organic Rankine cycle and Allam cycle and the optimization criterion of key parameters can provide theoretical guidance and reference for optimization design and control of similar power cycles. |
