Study On Heat And Mass Transfer Performance And Fly-ash Migration In Tray Column Applied In Evaporation Hot Water Tower

In this thesis, the performance characteristics of heat and mass transfer and fly-ash migration in dual-flow trays column were investigated. The result of this paper can be a theoretical guidance for evaporating hot water tower design and operating.The direct contact condensation efficiency of dual-flow trays column was studied on different gas-liquid operating conditions and tray geometry. A novel mathematical model based on steam and water countercurrent contact process was developed to predict the heat transfer efficiency. The relationship between flow parameters (FP) and number of transfer unit (NTU) was established and has a good agreement with the experiment data. The result indicated that the heat transfer efficiency decreased with a larger liquid-gas ratio and trays with larger hole diameter, less open area and larger fixed valve height have a better transfer performance.The effect of non-condensable gas and fly ash on the direct contact transfer process in the tower was discussed. The particle characteristics including particle size distribution, surface morphology and element composition in different phase were observed by Malvern particle size analyzer, SEM and EDS. The particles remove efficiency on different operating conditions and tray geometry was investigated. The result showed that the heat transfer efficiency decreased with the adding of fly ash particle. The fly ash particles in the vapor phase were mainly in irregular shape and rich in organic elements, while the particles captured by liquid phase were in spherical shape and rich in mineral element. The fly ash particles remove efficiency decreased with the increase of liquid vapor ratio and particle velocity and trays with less hole area, larger overflow weir height have a better particles remove performance.