Continuous Extraction of Potassium and Phosphorus from Biomass Fuel Incineration Ash

Abstract

To utilize the incineration ashes of biomass fuels effectively, the recovery of potassium and phosphorus contained in them was examined. Through sequential iterative extraction of potassium and phosphorus from mixed ash (bamboo chips, cow dung pellets, sewage sludge pellets), potassium was selectively extracted without loss of phosphorus by using 0.01 mol･L −1 HCl. In addition, by adding 70% H2SO4 to the phosphoruscontaining extract that was used once for phosphorus extraction, the extract could be used again as an extractant. By repeating the phosphorus extraction three times, the phosphorus concentration in the extract was increased by as much as about 2.8 times. Therefore, it was possible to extract potassium and phosphorus continuously from the same mixed combustion ash. The water-soluble potassium content in the recovered potassium compound was 39.6%, and the content of citric-soluble phosphate in the recovered phosphorus compound was 15.7%. Both the recovered potassium compound and phosphorus compound can be used as raw materials for by-product fertilizers with high concentrations of fertilizer components.