PERFORMANCE OF FILTERS WHEN LOADED WITH NaCL AND KCL PARTICLES IN LOW RELATIVE HUMIDITY ENVIRONMENTS

摘要

In this study two low efficiency cellulose filters were loaded with sodium chloride(NaCI)and potassium chloride(KCI)particles of super-micron sizes in low relative humidity(RH)environments(RH < 30%).As NaCI and KCI particles have similar material properties,such as density and crystal structure,it was believed that no difference would be observed in the filter loading curves(pressure drop vs.the loaded particle mass/volume)of particles of the same size in such low RH environments.It is shown that at 30% RH the initial penetration and the loading curves of filters loaded with NaCI and KCI particles are nearly the same.However,as the RH decreased to 15% so the loading curve of NaCI particles deviated from that of KCI.The curve of NaCI particles moved to the right of the KCI curves.In other words,with the same pressure drop,the filter can be loaded with a greater volume of NaCI particles than KCI particles.Furthermore,the influence of filter structure and particle size on the shifting of the loading curve was investigated by performing the same loading test with two different particle sizes.It was found that the observed RH effect on the loading curve was more significant for low efficiency filters loaded with large super-micron particles.SEM examination showed that the morphology of the test particles is different when RH is varied.It was concluded that a possible reason for the dissimilarity of the NaCI particle loading curve at 15% RH is the difference in the particle morphology.