Advanced Exergy Analysis And Its Application On Typical Chemical Engineering Process

In this thesis,starting from the process mechanism,advanced exergy analysis model of the " transport phenomena and reaction " typical units process in the chemical engineering process was established.The exergy destruction under the operation parameter that each process was close to the minimum thermodynamic equilibrium state was defined as the unavoidable exergy destruction of the process unit.Such as the minimum reflux ratio of the distillation column,the minimum liquid-gas ratio of the absorption column,and the minimum internal reflux of the complex fractionator,the minimum Gibbs energy of the reaction,the minimum fuel utilization coefficient of the furnace,the extreme efficiency of the pump and the compressor,the minimum temperature difference of the heat exchanger,the minimum pressure drop of the flash tank,mixer,and splitter,etc.The endogenous exergy destruction of the unit was calculated by the engineering method,and the energy saving evaluation index based on endogenous/exogenous exergy destruction was proposed.Compared with the energy saving evaluation index based on avoidable/unavoidable exergy destruction,it was more reasonable in quantifying the potential for energy saving.Compared with conventional exergy analysis,advanced exergy analysis was performed on typical chemical engineering processes to calculate unavoidable/avoidable,endogenous/exogenous exergy destruction,and Based on the evaluation index of advanced exergy analysis,quantified potential for the energy saving and indicated the order of improvement of the unit.In the new delayed coking process with dry cooling,the avoidable exergy destruction of waste heat boiler was the largest,which is 11.13 MW,accounting for 92.97% of the total avoidable exergy destruction in the process,of which the avoidable/ endogenous exergy destruction was 17.25 MW,and the avoidable/exogenous exergy destruction was 10.74 MW.The largest unavoidable/endogenous exergy destruction in the coke tower was 82.34 MW,accounting for 98.82% of total exergy destruction in the unit.In the atmospheric distillation process,the exergy efficiency of distillation column changed the most before and after the efficiency modification,increasing by 21.73%.In the acetone recovery process,the exergy destruction coefficient of each unit was small,all less than0.05%,and the exergy destruction ratio was ranked here in a descending order: heat exchanger,distillation column,absorption column,and pump,among which the least exergy destruction ratio was pump,less than 0.01%.In the process of chlorination of propylene to dichloropropane,the exergy efficiency of the mixer was higher than that of the reactor.Based on the energy saving evaluation index of exogenous exergy destruction,the largest exergy loss efficiency units of the above processes were: splitter(0.8143),flash tank(0.8158),heat exchanger(0.8320),mixer(0.5706);based on the energy saving evaluation index of endogenous/exogenous exergy destruction,the largest exergy loss efficiency units of the above processes were: splitter(0.6513),complex fractionator(0.6205),absorption column(0.6495),mixer(0.4661).