Method for Preparing N-P Compound Fertilizer from Incinerated Sewage Sludge Ash (ISSA)
AssigneeSichuan University
InventorsMin LIU, Ying CHEN, He HONG
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Abstract
The present disclosure provides a method for preparing an N-P compound fertilizer from incinerated sewage sludge ash (ISSA), and relates to the technical field of compound fertilizer production. In the present disclosure, the ISSA is used as a main raw material, and a phosphorus-rich supernatant is obtained using high-concentration nitric acid at a low liquid-to-solid ratio. The phosphorus-rich supernatant and aqueous ammonia are mixed to obtain a white precipitate. The white precipitate is dried and pulverized to obtain a high-grade N-P compound fertilizer. The present disclosure realizes the resource utilization of excess sludge in sewage treatment plants.
Claims18
A method for preparing an N-P compound fertilizer from incinerated sewage sludge ash (ISSA), comprising the following steps:
- (1) weighing the ISSA, drying to a constant weight, and cooling in an airtight environment;
- (2) heating and mixing a nitric acid solution with the ISSA to obtain a mixed solution;
- (3) subjecting the mixed solution to a reaction by fully stirring in a constant-temperature stirring device, and conducting centrifugation on an obtained reacted mixed solution to avoid formation of colloids, thereby obtaining a phosphorus-rich supernatant and an ISSA residue;
- (4) adjusting the phosphorus-rich supernatant to a pH value of 6 to 8 using aqueous ammonia with a mass fraction of 15% to 25%, conducting a reaction fully under stirring to obtain a white turbid liquid, and conducting centrifugation on the white turbid liquid to avoid formation of colloids, thereby obtaining a white precipitate;
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- (5) subjecting the white precipitate to drying, pulverizing, and sieving by a 100-mesh sieve to obtain the N-P compound fertilizer.
Dependencies are inferred from the claim text.