石膏雨，是指燃煤电厂或钢厂排放烟气用石灰脱硫后，生成的硫酸钙随水蒸气大量逃逸，在空气冷却后变成石膏，或与其它逃逸物质聚团形成二次颗粒物或气溶胶的过程。
       空气清洗技术特别适合拦截或捕捉烟气中的超细颗粒物或气溶胶。2016年12月，我们用一台15万立方米的大型空气清洗机组对山西某燃煤电厂用双碱法喷淋处理后的排放烟气进行再次处理，成功拦截“石膏雨”。如下图片中可清晰看见两种排放烟气呈截然不同的颜色，经空气清洗处理过的烟气呈青色。
        Gypsum rain is referred as to the fine particle of calcine sulphate bought out largely by the brow of gas be cooled down and form new particles suspending in the air. In winter time, this wet particles drop down to the ground.
       Air cleaning technology is typically suitable for intercept the rain of gypsum. In Dec. 2016, a large air cleaner (150,000 m3/h) had successfully used in a power station who use coal. The following picture shows the two different color of the exit smoke from one after alkali washing treatment, and from the one after retreating by air cleaning. The releasing smoke from air cleaner is almost transparent.