Multi-objective Parameters Optimization And Economy Environment Evaluation For Organic Rankine Cycle

Effective control of the total energy consumption,effective implementation of energy conservation priority principle,is China's basic energy policy.Under the background of this policy,how to improve energy efficiency,especially in the energy consumption process of low grade waste heat resources into a convenient and flexible power has been become a widespread concern in the field of science and engineering.Organic Rankine cycle with low evaporation temperature of working fluid and low maintenance requirements is a better choice to solve a lot of problems of low temperature waste heat recovery.Based on organic Rankine cycle thermodynamic inverse problem,the thermal properties of ORC with eight working fluids had been studied.Considering the three aspects of thermodynamic cycle,economic and environment,a novelty multi-objective optimization model was established.The optimization design of ORC can improve the utilization rate of the combined energy system,and improve the performance of organic Rankine cycle and the cycle of applicability.On the basis of the optimization model,the ORC coupled heat source after optimization design was introduced into utilization of waste heat of cement industry in China.The application prospect of organic Rankine cycle in the field is explicit.The ORC is a good technology for energy saving in China's industry.In this paper,based on the thermodynamic model and calculation and the inverse problem of ORC,the performace of the ORCs with working fluid R114,R245 fa,R245ca,R123,R601,R11,R141 b and R113 is studied,respectively.This result found that the thermodynamic performances of the ORCs with different working fluids are different.The thermal efficiency of R123 is max.Under the constraints of the critical temperature of the working fluid and the narrow temperature difference of the evaporator,the maximum evaporation temperature of different working fluids is different.The cycle thermal efficiency increases with the increase of evaporation temperature.Increasing the condensation effect can improve the cycle thermal efficiency.The results are in good agreement with the experimental results of our laboratory,and the relationship between the critical temperature and the cycle thermal efficiency is further explained by the concept of integral temperat ure difference.In the aspect of model building,this paper fully absorbs the theory of environmental impact load from the cradle to grave.According to the heat source working conditions,the heat source is divided into two types: fixed parameter heat source and fluctuation parameter heat source.The objective functions are to maximize the net power output and exergy efficiency and to minimize the pay-back-period(PBP)and environment impact load(EIL).The evaporation and condensation temperatures are the control parameters.The optimization model includes sub-models of thermal,economic and environment impact.The certainty and the uncertainty optimization methods deal with the optimization problem.Two kinds of models are solved by genetic algorithm,the combination of neural network and genetic algorithm,and the results are compared and analyzed.The study found When the fluctuation of the heat source parameters is considered,the uncertainty optimization method yields more stable system performance th an the certainty optimization method.The uncertainty optimization decreases the requirement of the equipments.The uncertainty optimization method simplifies the optimization process because it does not need the sensitivity analysis after the optimal para meters are reached.Using the optimization model,the organic Rankine cycle was introduced into new dry cement production line of 4000 tons / day in China.The waste heat of the kiln cooler of the cement production line is taken as the heat source of 220?.Five organic fluids hexane,isohexane,R601,R123 and R245 fa is selected as the working fluids.The ORCs coupled heat source is design using the multi-objective optimization model.NPV and PBP were used to evaluate the economics of the application system.The environmental assessment of the application system is carried out by using the life cycle assessment.It showed that the waste heat of cement industry using ORC is feasible and efficient heat recovery can effectively improve the energy efficiency.The ORC with R601 as the working fluid had the best economic performance and apparently gas emission reductions among those with the five working fluids.The ORCs integrated with the cement production line could have good economic performance and reduce the gas emissions apparently.The economic performance of ORCs applied in the cement industry will be further improved when the application scale is increased.