Study On Process Optimization And Industrialization Of Urea Sulfuric Acid Compound Fertilizer

Clean process of urea-sulfuric acid compound fertilizer technology can produce NPK fertilizers directly with low grade phosphate rock has great economic, social and environmental benefits due to its simple process, excellent performance and no "three wastes" discharge.In this paper, clean process of urea sulfuric acid compound fertilizer technology was systematically studied. Physical properties of urea-sulfuric acid, such as density and viscosity, were measured and related; The technology conditions of decomposing phosphate rock with urea sulfuric-acid were optimized; Urea-sulfuric acid compound fertilizer were prepared and the slow release properties of nitrogen were also studied.1 Determination and correlation of densities and viscosities of solutions with urea-sulfuric acid. Densities data of the solution (urea:sulfuric acid:water=X:1:Y; X=0.5,1,1.5,2,2.5,3,3.5,Y=1,2) were measured by Gay-Lussac type pycnometers at the temperature range of (283.15 to 363.15) K. Viscosities data of the solution (urea:sulfuric acid:water=X:1:Y; X=1,1.5,2,2.5,3,3.5,Y=1,2) were measured by rotational viscometer at the temperature range of (288.15 to 363.15) K.The results show that:When the composition of the solutions with urea-sulfuric acid is constant, the density decreases with increasing temperature. When the temperature is constant, the density of the solutions decreases with increasing mole fraction of urea and the mole fraction of water.It is found that the density (ρ/g·cm-3) of urea-sulfuric acid has the correlation with mole fraction of urea and temperature(T/K):When the composition of the solutions with urea-sulfuric acid is constant, the viscosity decreases with increasing temperature. The processs of viscosity can be divided into three phases:sharply decreasing phase, slowly decreasing phase, stable phase. When the temperature is constant, as the mole fraction of urea increases, the viscosity increases at first, but then decreases;The viscosity decreases with the increasing mole fraction of water. It is found that the viscosity (η/mPa·s) of urea-sulfuric acid has the correlation with temperature(T/K):2 The technology optimization of decomposition of low grade phosphate rock using urea-sulfuric acid. The influencing factors, such as reation time, reation temperature, stirring speed, consumption of urea-sulfuric acid, particle size of phosphorus rock, composition of acidolysis agent and consumption of active addition agent have been investigated in the acidification by urea sulfuric acid for low grade phosphate rock and the better process conditions have been obtained. Under the optimized process conditions, conversion rate can be up to 94% or so. Optimized process conditions provide a basis for the industrialization of producing compound fertilizer with urea-sulfuric acid.3 Preparation of urea-sulfuric acid compound fertilizer and determination on nitrogen slow release properties. Two standard urea-sulfuric acid compound fertilizers of different nutrient specifications, were prepared by disc granulation. In order to evaluate the nitrogen slow release effects of commercialized compound fertilizer and prepared urea-sulfuric acid compound fertilizer, water-immersion rate method was adopted. Results show that urea-sulfuric acid compound fertilizer has better slow release capability than commercialized compound fertilizer. Nitrogen in urea-sulfuric acid compound fertilizer is of two types:one is complex state and the other is non-complex state. Furthermore, the complex nitrogen, which has the ability of slow releasing, exists as CaSO4·XCO(NH2)2 in urea-sulfuric acid compound fertilizer.