Research On Construction Of Supersaturated Vapor Environment By Cooling Method

Pollution of atmospheric particle matter in our country is in serious condition which brings lots of damage to people's life and health. Coal-fired power plants are one of the main pollution sources because the conventional dust collecting equipment has a very low efficiency to remove fine particles. Heterogeneous condensation is a very promising preprocessing technology to promote the enlargement of fine particles and it can significantly improve the efficiency of traditional particle collection devices. Combination of vapor heterogeneous condensation and wet flue gas desulfurization (WFGD) system can create supersaturated environment with low power consumption, which has huge practical value.An experimental apparatus is designed to build the supersaturated environment and also measure the supersaturation. What's more, the heat and mass transfer model is established to calculate the supersaturation. The high humidity gas of WFGD system is used to build the supersaturated vapor environment by cooling method in condensation chamber. Relations of constructing supersaturated environment with different operating parameters are deeply researched both in experimental and computational aspects. Results are showed as follow:(1) It's very easy to build a uniform supersaturated environment by cooling high humidity gas.(2) The increase of flue gas relative humidity and an appropriate increase of gas temperature will help to improve the vapor supersaturation; the cooling temperature of chamber wall has a very obvious impact on the supersaturated environment, the supersaturation will be higher with a lower cooling temperature; the polytetrafluoroethylene material condenser with low surface energy can restrain vapor condensation and effectively enhance the supersaturation.(3) The calculation results show that the supersaturated environment is first appeared and reach the maximum near the chamber wall when cooling saturated gas to build it; along the axial direction of the chamber, the temperature and pressure of airflow are tending to decrease to a stable level continually, while the supersaturation firstly increases and then decreases; when the temperature of inlet airflow is 323K and the cooling temperature decreases from 303K to 293K, the maximum supersaturation near the wall increases from 1.11 to 1.3; with the increase of airflow velocity or pressure, the peak of supersaturation do not change significantly, but the position of the maximum value goes backward towards the axial direction, moreover, the supersaturation is enhanced and become more uniform.(4) The comparison between experiment and calculation results shows that the experimental value is bigger than calculated value around 15%, but the method of measuring supersaturation is effective as a qualitative way to evaluate the effect of supersaturated environment.