The Research Of An Anti-caking Agent For Water-soluble Powder Fertilizer

Fertilizer plays an important role in the growth of crops,and the yield and quality of crops are directly affected by the quality of fertilizer.Water-soluble fertilizer,a multivariate compound fertilizer,can be completely dissolved in water.However,due to its small particle size,water-soluble fertilizer is facing more serious caking problems.Therefore,the study of an anti-caking agent for water-soluble fertilizer has an important practical significance.In this paper,the influencing factors of water-soluble fertilizer caking were investigated by the fast method of pressing packs-throwing packs-screening.If fertilizer components are not compatible with each other,the blocking degree of the fertilizer will be increased significantly;there is a critical value of the moisture content,and when the moisture content is higher than the critical value,the fertilizer caking rate increases rapidly;within the scope of the critical relative humidity,the higher relative humidity of the air easily bring about fertilizer agglomerating;fertilizer caking rate increases with higher temperature,higher pressure and larger duration.Agglomeration process mainly concentrates in the top 25 days,and it is not suitable for storage of water-soluble fertilizer with the pressure of exceeding 3000 N/m~2.The powder anti-caking agent of nitro-soluble fertilizer has been developed by using surfactants,polymers and inorganic salts as raw materials.It was denoted as Nitro-1,which formulation was the ratio S1/N1/P1/K1=2:4:1:14.A processing route was optimized,and the optimization condition of added amount and Nitro-1 size was 1.5%and 150～200mesh respectively.The practical application of Nitro-1 was also evaluated:raw material of Nitro-1 cost 38 yuan per ton of fertilizer,and Nitro-1 can reduce the caking rate of nitro water soluble fertilizer into 8.0%,which is advantage over industrial anticaking agents.The powder anti-caking agent of urea-soluble fertilizer has been developed by using surfactants and inorganic salts as raw materials.It was denoted as Urea-1,which formulation was the ratio S1/S2/K2/N1=4:3:3:6.A processing route was optimized,and the optimization condition of added amount and Urea-1 size was 0.8%and 150～200 mesh respectively.The practical application of Urea-1 was also evaluated:raw material of Urea-1 cost 25 yuan per ton of fertilizer,and Urea-1 can reduce the caking rate of urea water soluble fertilizer into 9.1%,which is advantage over industrial anticaking agents.The anti-caking mechanism of agents has been carried on the preliminary discussion:SEM relealed that the anti-caking agents may prevent the formation of gully holes and pore structures on the surface of fertilizer and make samples looser and smoother,and the agglomeration phenomenon has been alleviated;DSC results indicated that the anti-caking agents can move the phase transition backwards,and reduce the enthalpy value.When the phase change does not occur easily or phase transition occurs in case of fertilizer smaller changes,anti-caking effect will be alleviated;hygroscopic test results show that the anti-caking agents lead to the critical relative humidity of fertilizer increasing,the rate of absorption slower and crystallization more difficult to be formed;according to wettability test results,anti-caking agents could make the slop of fitting line smaller,equivalent to the hygroscopicity of fertilizer,then the adsorption of the particles by capillary action become smaller.In this case,the fertilizer caking degree will be reducing.