Experiments on aerosol removal by high-pressure water spray

Abstract

An experimental research was managed in the framework of the PASSAM European Project to measure the efficiency of high-pressure sprays in capturing aerosols when applied to a filtered containment venting system in case of severe accident.The campaign was carried out in a purposely built facility composed by a scrubbing chamber 0.5×1.0m and 1.5m high, with transparent walls to permit the complete view of the aerosol removal process, where the aerosol was injected to form a cloud of specific particle concentration. The chamber was equipped with a high pressure water spray system with a single nozzle placed on its top.The test matrix consisted in the combination of water pressure injections, in the range 50–130bar, on a cloud of monodispersed SiO2 particles with sizes 0.5 or 1.0μm and initial concentration ranging between 2 and 99mg/m3. The spray was kept running for 2 min and the efficiency of the removal was evaluated, along the test time, using an optical particle sizer.With respect to low-pressure sprays, the removal efficiency turned out much more significant: the half-life for 1μm particles with a removal high-pressure spray system is orders of magnitude shorter than that with a low-pressure spray system.The highest removal rate was detected with 1μm particles at the highest water injection pressure, mainly because of the high concentration of droplets with high velocity, while lower removal was measured for 0.5μm particles. No influence of the initial aerosol concentration was observed for both particle sizes.