METHOD FOR PRODUCING PHOSPHOROUS FERTILIZER

摘要

[Problem] To collect phosphorous and produce a high-quality phosphorous fertilizer from sewage water at low cost. [Solution] A method for producing a phosphorous fertilizer, which comprises bringing septage (S1) in a sewage-treatment plant into contact with a calcium-containing collecting material (A1) to collect phosphorous from the septage (S1) and burning a collected phosphorous product (AP), sludge (S9) generated in the sewage-treatment plant and a calcium source that serves as composition-adjusting agent (A2). The burning of the collected phosphorous product (AP) and others may be carried out at a burning temperature of 1150 to 1350°C inclusive. The calcium oxide content in the phosphorous fertilizer may be 30 to 55 mass% inclusive. It becomes possible to produce a high-quality phosphorous fertilizer having a phosphoric acid solubility in an aqueous citric acid solution of 60% or more and/or a silicic acid solubility of 40% or more. Besides the calcium source, a magnesium source and/or a silica source may be added as the composition-adjusting agent. The resultant burned product (B1) may be pulverized and then granulated together with a granulation aid (A3) using a granulating/molding machine(17).