Abstract
Volcanic ash erupted from Sakurajima Volcano variously influences on air-conditioning systems. Especially, it requires considerable maintenance for air filters. Therefore to develop the air filters suitable to eliminating volcanic ash and lowering the maintenance is very important for the districts around Sakurajima. In this paper, two kinds of trial air filters are produced and the performances of them are experimentally examined. First, a trial filter, designed on the theory of inertial dust collection, is produced. The filter is intended to be set at the upstream side of the finer filters to decrease their load. The ash collecting part is formed using curved eliminators with or without grooves set parallel to the direction of the ash-containing air flow. Ash collection coefficients are examined using volcanic ash collected from several places around Sakurajima. The overall ash collection coefficients are between 70% to 90% for eliminators with grooves, 65% to 85% for eliminators without grooves, when the air velocity is less than 4m/s. The partial ash collection coefficients, corresponding to the ash diameter regions 0〜75μm, 75〜125μm, 125〜250μm, 250〜500μm are 22%, 75%, 98% and 100%, respectively, when the air velocity is 3m/s. These values decrease to 9%, 40%, 89%, and 99%, respectively, when the air velocity is 4m/s. It is verified that the overall ash collection coefficients synthesized from the partial collection coefficients are similar to those by measurements. Next, the efficiency of a wet type ash filter is examined. Water circulating system together with an water spraying nozzle is attached at the upstream side. The ash collection coefficient by this filter is more than 97%. However, as wet ash gradually sticks on the eliminator with water spraying, which will eventually require the maintenance, it can only be recommended to be used in the restricted area where the influence of ash is serious.
