Simultaneous removal efficiencies of hydrophilic and hydrophobic gaseous pollutants are experimentally determined, and the macroscopic removal mechanism of pollutants in a dry scrubber is analyzed using the extended model of three phase equilibrium distribution of pollutant at high temperatures that can describe the different morphological conditions of adsorbent and water at varying relative humidities.
For the simplicity, the inside of spray dryer is divided into three regions of; (1) absorption, (2) 3-phase equilibrium, and (3) a-desorption, and the removal efficiencies of each pollutants at three regions are observed at different experimental conditions to see the effects of important parameters of dry scrubber.
The laboratory experiments simulate the three regions of spray dryer with the temperature control and thus evaporation rate of water from the slurry particle. SO2 as a hydrophilic gaseous pollutant and vinyl chloride as a hydrophobic toxic gas are selected for the future field application to solid waste incineration, and the two types of slurry are made of the two sorbents; 10%w Ca(OH)2, and 10%w NaOH.
Result of temperature effect shows the length of absorption plus 3-phase region is decreased as the operation temperature is increased, which results in the lower removal efficiency of SO2 but higher removal for vinyl chloride in the adsorption region of dry scrubber.
The removal efficiency of SO2 is higher in NaOH slurry than in Ca(OH)2 slurry due to the hygroscopic nature of NaOH, while the removal of vinyl chloride is higher in Ca(OH)2 case.
From the analysis of results using 3-phase equilibrium distribution model, the effective 2-phase partition coefficients can be obtained, and the possible extension in the application of the 3-phase equilibrium model in a dry scrubber design has been demonstrated.
