Waste Heat Recovery From Industrial Processes:A Comparison Between Kalina And Organic Rankine Cycles

The abundant waste heat resources generated in the process systems have high value of deep utilization.In general,these heat sources are directly consumed by utilities,which brings a lot of negative impact on environment and energy saving.Hence,the work of improving energy efficiency by recovering waste heat from industrial processes can meet the urgent need of energy conservation and emission reduction.Kalina Cycle and Organic Rankine Cycle(ORC)have favorable application in the field of low temperature power generation.Kalina cycle could be matched with the low temperature waste heat resources,as its work fluid,ammonia water,is not an azeotrope and boiled at changing temperature.It can be applied to waste heat recovery which has a wide temperature range.ORC can be applied to multiple types of waste heat recovery projects,as a lot of organics with different properties can be selected as its working fluid.The operating parameters of a Kalina Cycle are analyzed in this thesis.It is found that the pressure and concentration of the working fluid are the key factors of a Kalina Cycle.The optimal operating pressure and concentration of the working fluid are related to the temperature distribution of the waste heat.The higher temperature distribution of waste heat can lead to the higher optimal operating pressure and the lower optimal concentration of the working fluid,and vice versa.According to the composite curves of waste heat,three types of waste heat: concave waste heat,convex waste heat and linear waste heat,are classified in this thesis.Based on the Energy Level —Enthalpy diagram,the different performances between a Kalina Cycle and an ORC for different types of waste heat recovery are conducted.It is found that,a Kalina Cycle is suitable for the concave and linear waste heat recovery,while an ORC is suitable for the convex waste heat recovery.The higher the proportion of low temperature waste heat in the whole heat source is,the lower the pressure of working fluid for an ORC is.This thesis can provide a reference for the selection of the waste heat recovery by power system and system’s parameters optimization.