Experiment Study On The Evaporation Of Multicomponent Droplet In Airflow

Spray evaporation is a high efficient and environmental way to treat the FGD waste water. By using the atomizing nozzle, the waste water is sprayed into flue gas duct between air preheater and electrostatic precipitator, through technique of evaporation by flue gas, solid particles can be dried from waste water and achieved zero-emission. But it has many difficult problems to use this method in the project, the droplet evaporation in flue gas is complicated and can't be observed directly. Studying the characteristics of droplet evaporation is of great significance.In this paper, studying a suspend single droplet evaporation in airflow, design and build test bench based on similarity theory. Researching different kinds of droplet in external environment condition and droplet physical properties. The experimental results indicate that:(1) Droplet evaporation rate is increased first then decreased in the evaporation process. For single-component droplet, the higher the boiling point is, the smaller the average evaporation coefficient, thermal conductivity is also a key factor in evaporation, droplet's survival time is decreased by the rise of thermal conductivity.(2) For evaporation process of alkalescency droplet?salt droplet and water droplet, it is found that bi-component droplet's evaporation rate decrease dramatically and no longer meet the D2-t law at the end of evaporation. The evaporation process of the droplet meet the D2-t3 law. Vapour pressure of bi-component droplet is lower than water droplet, sodium hydroxide solution droplet's vapour pressure is also lower than magnesium chloride solution droplet, and the thermal capacity of sodium hydroxide solution is higher than magnesium chloride solution. In the same condition, the sequence of evaporation from biggest to smallest is water droplet?salt droplet and alkalescency droplet. Both increase of airflow temperature and velocity can promote droplet's evaporation rate, but the effect that temperature increase is better than velocity increase, particularly in water droplet evaporation. Established droplet evaporation model, deduced the relationship between square of droplet and time, calculated water droplet's evaporate constant and compared with experimental results. Deviation between theoretical values and experimental results is small and the theoretical value error decrease with increase of airflow temperature and velocity.(3) For FGD waste water, both the increase of airflow temperature and velocity can promote droplet's evaporation rate dramatically, the droplet's survival time is increase with the concentration of waste water. The thermal conductivity and vapour pressure of FGD waste water droplet is lower than bi-component droplet, In the same condition, the sequence of evaporation from smallest to biggest is FGD waste water droplet?alkalescency droplet and salt droplet?water droplet.