Study On Influencing Factors Of Gas-liquid Separation Performance Of Spray Flash Evaporation System

In recent years,the China's energy consumption increases year by year with the rapid development of industrialization and urbanization.The industrial energy consumption accounts for 70% of total energy consumption in China.In the industrial section,a great deal of wastewater is featured by high viscosity and strong corrosivity,which would seriously damage the waste heat recovery equipment,and thus threaten operation safety of both industrial process and waste heat recovery process.Thus,recovering these industrial waste heat becomes difficult.To resolve above problem,a waste heat recovery process based on spray flash evaporation is adopted.As for the adopted waste heat recovery process,firstly,the superheat wastewater is sprayed in the vacuum condition,and then some steam is produced.Secondly,the produced steam is separated from the wastewater droplets by using steam-liquid separator,and go into steam condenser.Lastly,the separated steam is cooled by cooling water,and thus it is condensed.In such way,the waste heat and water are recovered.For optimizing design of the waste heat recovery process,the steam-liquid process is a key point,and it is very difficult due to shortage of theory support.In view of this demand,the research related to steam-liquid process was carried out.Firstly,mechanics of steam-liquid separation was analyzed,and its mathematical model was established.Secondly,the experimental rig of the steam-liquid separation and size measurement of sprayed droplets were set up.The distribution of sprayed droplets and characteristics of flash evaporation were studied by using the methods of experiment and numerical simulation.The main influencing factors on the gas-liquid separation performance were analyzed,and then their influencing regularity were revealed.The results show that the diameter distribution of sprayed droplets is normal,the radium of sprayed droplets becomes smaller with the increase of injection pressure of nozzle.The droplets with the diameter ranging from 400um to 800um accounts for 60-70%of total sprayed droplets.Increasing flashing evaporation and concentration of solution could result in lower flash evaporation rate.The flash evaporation rate can become higher by rising temperature of sprayed solution.The conductivity of Na₂CO₃ solution increases rapidly with the increase of temperature and mass concentration when mass concentration of Na₂CO₃ is lower than 20%.Otherwise,it is reversed.When diameter of droplets is higher than 52.5um,the steam-liquid separation efficiency is higher than 95%,and the influence of steam speed on steam-liquid separation efficiency becomes weak under this condition.When the diameter of droplets is smaller than15um,the steam-liquid separation efficiency is much lower.The major influencing factors of steam-liquid separation comprise solution temperature,solution mass concentration,injection pressure of nozzle,flashing evaporation pressure and height difference between nozzle outlet and solution level of flash evaporation chamber.Increasing solution temperature and injection pressure of nozzle would result in lower steam-liquid separation efficiency,but reducing height difference between nozzle outlet and solution level of flash evaporation chamber contributes to improve steam-liquid separation efficiency.Among these influencing factors,the influence of solution temperature on steam-liquid separation efficiency is the greatest.The studied results would contribute to guiding optimization design of steam-liquid separation process,and promote the development of waste heat recovery process based on spray flash evaporation.