Research On The Composite System Of Reverse Osmosis Desalination Driven By Organic Rankine Cycle

Reverse osmosis(RO)desalination driven by organic rankine cycle(ORC)can solve the problems of water shortage and energy waste.In this paper,the experimental research and theoretical research on ORC-RO are presented.In experiment,firstly,an ORC machine with rated power of 5kW was set up and developed.The monitoring system and method of isolated network operation are put forward.For unstable heat source and cold resource,the automatic control system has good adaptability which can automatically adjust the operating conditions when the electric load was given.It is helpful for the output power and speed of expander to track the change of load quickly.In addition,when the ORC equipment and the automatic control system fail,the system can automatically take measures to protect the equipment from damage.Then,an ORC-RO system was set up and developed and the strategy of start and stop is proposed.The paper studied the influence of the outlet pressure of high pressure pump and the speed of high pressure pump on water production characteristics.The results show that the composite system can produce pure water stably,and the water quality can meet the relevant requirements with unable heat resource,which lays an important experimental foundation for the further study.In theory,firstly,a model of reverse osmosis(RO)desalination driven by Organic Rankine cycle(ORC)was designed.The seawater entered the condenser cooling from the organic fluid out of the expander which can improve the recovery rate of desalination.The paper analysed effects of ratio of mixture components,seawater inlet temperature and seawater flow rate on the cycle performance.The results show the water production of the system that seawater is heated by the condenser is 80%higher than the system that is not preheated.Then fresh water production of zeotropic mixtures is greater than pure fluid because of the temperature slip.Aiming at water production function,R134a/R245fa(0.5/0.5)is the best working fluid.In the operation of the system,when the high-pressure pump seawater inlet temperature less than 40?,the water flow depends on the power of high-pressure pump.When the water temperature exceeds the working temperature of the reverse osmosis membrane,the system need to open the drain valve and increase the water flow of the condenser and the excess water discharged from the drain valve.At the same time,the advantage of zeotropic mixtures is better than pure working fluid.Then,using R600a/R601a as organic working fluid,the performance of organic Rankine cycle-reverse osmosis desalination with different energy recovery methods were compared.The results show that the best mass fraction of R600a for the no energy recovery system,PWT energy recovery system,PES energy recovery system are respectively 0.7,0.8,0.9.The fresh water production of the BASIC system is 5.04kg/s and it is increased by 38.69%and 130.36%respectively by using the PWT system and PES system respectively.In the same power consumption,the fresh water production of three system is increased by 80.96%,39.44%and 19.57%respectively compared with the traditional reverse osmosis desalination driven by electricity.