The Research On Granulation Of Superphosphate And Diammonium Phosphate Powders

Fertilizer powder was pelletized by pan granulation, which not only improved nutrient efficiency, but also conveniently fertilized. Fertilizer particle was to achieve a certain amount of particle strength and dispersion. This paper studied the granulation technologies of superphosphate and diammonium phosphate powders by pan granulator. Owing to powder viscosity, large intensity and poor dispersibility of particle, granulation technologies of superphosphate were systematically investigated. Granulation technologies of high magnesium superphosphate and diammonium phosphate were improved to enhance the particle intensity because of their high dispersion and poor intensity. The main results were as follows:The intensity of superphosphate particles using water as binder were increased as the drying temperature increasing, while disintegration and drop rates were decreased. Superphosphate particles rapidly disintegrated and dropped through sieve pore as drying temperature below 90℃, the rates reduced when the temperature was 92.5℃, the drop rate was close to 0 as the drying temperature above 95℃.Superphosphate particle dispersibility increased with sodium docecyl benzene sulfonate(SDBS) concentration increasing while it was used as binder. When concentrations of SDBS, Span 80 were 0.8% and 0.016%, the particle was greatly dispersible, and the intensity, disintegration rate and drop rate was 68.7 N, 100% and 62%, respectively. When concentrations of SDBS, Tween 80 were 0.8% and 0.016%, the particle was greatly dispersible, too, the intensity was 47.9 N, disintegration rate was 100% with 2 min of the culture time, and drop rate was 44% with 10 min of the culture time.A scheme of orthogonal test, which included 3 factors and 3 levels, was designed to evaluate the effect of mixed binder of SDBS, Span 80 and Tween 80 on forming superphosphate particle by pan granulation. Range analysis of drop rate showed that the sequence of factors was SDBS > Span 80 > Tween 80. The optimized concentration of SDBS, Span 80 and Tween 80 was 0.8%, 0.008%, and 0.008%, respectively, and superphosphate intensity in the treatment was 53.2 N, while the disintegration rate and drop rate was 100%, 68%.On the base of superphosphate granulation technology, ammonium chloride(NH4Cl) was used as binder to explore the granulation process of high-magnesium superphosphate. The results showed that the particle intensity gradually increased with the increasing of binder concentration. When ammonium chloride concentration was 25%, the particle intensity was greater, and the average was 45.2 N.Phosphorus efficiency was directly influenced by dissolution mechanism of superphosphate granules and the nutrient release. The granule dissolution process was investigated in water at the temperature of 20, 25, 30, 35 and 40℃, respectively. The results showed the dissolution process ofsuperphosphate granules conformed to shrinking core model.Control step successively fellinto internal diffusion control, and interface-external diffusion control. Model equations were significant linear correlation at 5% level, and diffusion control switch was done gradually.Conclusions had scientific significances on promoting single superphosphate application and increasing fertilizer efficiency.Because diammonium phosphate(DAP) contained impurities, the particle intensity was unstable. After a series of research, sodium carboxymethyl cellulose(CMC-Na) was used as binder to explore the granulation technology of DAP. Results showed that the DAP particle intensity increased with CMC-Na concentration increasing. When the concentration of CMC-Na was 1%, the particle intensity was 42.7 N.