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Potassium recovery from the fly ash from a grate boiler firing agro‐residues: effects of unburnt carbon and calcination pretreatment
Author(s) -
Wang Shi Yong,
Xiao Xue,
Wang Xiao Qiang,
Dong Chang Qing,
Li Wen Yan,
Lu Qiang,
Wang Ti Peng
Publication year - 2017
Publication title -
journal of chemical technology and biotechnology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.64
H-Index - 117
eISSN - 1097-4660
pISSN - 0268-2575
DOI - 10.1002/jctb.5062
Subject(s) - fly ash , potassium , leaching (pedology) , calcination , chemistry , leachate , pulp and paper industry , waste management , toxicity characteristic leaching procedure , boiler (water heating) , coal , bottom ash , nutrient , environmental science , environmental chemistry , biochemistry , organic chemistry , soil science , engineering , soil water , catalysis , heavy metals
BACKGROUND The biomass‐fired power in China is mainly fueled by agro‐residue, and is suffering the bottlenecks of feedstock supply, super heater corrosion and nutrient cycle. How to recycle the ash nutrient to farmland is crucial for ecological sustainability. This work investigated potassium recovery from the fly ash of a grate boiler firing agro‐residue using leaching methods. RESULTS The studied ash contains a massive amount of fixed carbon (158.92 mg g −1 ) and little volatile matter (39.44 mg g −1 ). The unburnt carbon strongly decreases the concentration ( C K ) in the leachate and recovery percentage ( RP K ) of potassium nutrient by 17.6–24.1% and 9.0–18.8%, respectively. Calcination pretreatment in air at 500 °C for 30 min should be employed before leaching to remove the unburnt carbon. Mineralogy analysis shows that low‐temperature pre‐calcination (≤575 °C) does not affect potassium solubility. Under the optimal leaching of calcined ash in water with liquid‐to‐solid ratio 3 for 30 min at room temperature, C K in the leachate, dissolution percentage ( DP K ) and recovery percentage ( RP K ) of potassium element reached 17.21 g L −1 , 82.0%, and 62.6%, respectively. CONCLUSIONS The fly ash from grate boilers firing agro‐residue is much better than other marginal potash sources. This work is helpful to improve the technology of agro‐residue fired power. © 2016 Society of Chemical Industry