Preparation of a nano-scale ceramic membrane and its application in the medium-pressure boiler with phosphate treatment

•High compressive strength substrate was prepared by clay and modified fly ash.•Attapulgite powder was sintered into a membrane.•Rejection of PO43– resulted from Donnan exclusion and dielectric effect.•Boilers reused the water treated by a filter based on attapulgite membrane.•Reusing the treated water reduced the blowdown rate to less than 1%.

An attapulgite nano-scale (NS) membrane was prepared on the clay-fly ash ceramic substrate. Based on this NS membrane, a membrane filter was developed for the problem of energy waste, thermal and phosphorus pollution resulting from the high blowdown rate of medium-pressure boilers. Mounting this membrane filter on the boiler blowdown pipe, it could separate both particles and ions, which are larger or smaller than the membrane pore size. The quality of treated water met the requirements of feed water standards in medium-pressure boilers. Recycling treated water to the feed water system could reduce the boiler blowdown rate to less than 1%.