The invention relates to a method for recycling 
high concentration ammonia nitrogen and making 
ammonia nitrogen into large granule high purity 
struvite. At first, a granulating main body is changed to a three-section tapered 
fluidized bed reactor. The reactor is composed of a 
feeding tube, a granulating tube, and a 
sediment tube; the connection part between the 
sediment tube and the granulating tube is in a truncated cone shape, the inclined angel theta of the 
generatrix of the connection part is 25 degree to 45 degree; the ratio of the external 
diameter of the big end of the granulating tube to the external 
diameter of the small end of the granulating tube is equal to 3:1; the ratio of the length of the granulating tube to the external 
diameter of the small end of the granulating tube is equal to 50:1; a 
pH probe is arranged in the granulating tube, the bottom of the granulating tube and the top of the 
feeding tube are both provided with a granulating tube valve; the bottom of the feeding 
pipe which is provided with five material inlets is provided with a discharging valve; and the length ratio of the 
sediment tube to the granulating tube to the 
feeding tube is equal to 2:5:1. 
High concentration nitrogen-
phosphor wastewater with a NH4<+>-N concentration of 1000 to 1600 mg / L and a 
magnesium chloride solution are simultaneously pumped into the granulating main body, at the same time the 
mole ratio of NH4<+>-N: PO4<3>-P:Mg<2+> is controlled at 1.5:1:1.1-1.5:1:1.3, the pH value is controlled at 6 to 7, the 
reflux ratio is controlled at 12 to 30, the diameter of the formed 
struvite particle is in a range of 3 to 8 mm, the purity of the 
struvite particle can reach 97.5% or more, and the 
hardness of the struvite particle is (20.3 + / - 1) kg / mm2. The method can used to prepare struvite from 
high concentration ammonia nitrogen industrial and poultry culture 
wastewater, garbage 
leachate, or 
sludge fermentation broth.