Porous ceramic fillters are the most promising devices for high temperature and high pressure dust removal processes. For making practical use of these devices one of the most important subjects is to evaluate long term durability of the filter element. In this paper we investigated an evaluation methos which predicted the duration time of the filter. In a long term use of the filter the baseline pressure loss in filter element, which was observed just after filter cleaning, increased gradually because of plugging of filter pores. As the additional pressure loss was proportional to the face velocity and gas viscosity, the apparent influence of these factors was eliminated by making use of an additional pressure loss coefficient. Experimental results showed that the cofficient was proportional to the number of filtration cycles on log-log coordinate. This fact enabled prediction of the baseline pressure loss increase and the change of cleaning interval, from which the duration term of the filter was estimated.
Effect of aerosol particle sedimentation on the growth rate of condensation (evaporation) and Brownian coagulation is theoretically discussed. Model calculation suggests that the rate of Brownian coagulation increases about 10 times owing to the aerosol particle sedimentation. Such effect is an important factor controlling global geochemical cycle of particulate matter and related gases in the atmosphere, such as reduction of the stratospheric volcanic clouds which are organized by sulphuric aerosols, ash particles, and gases.