Several problems should be paid attention to in compound fertilizer granulation
It is a little problematic and difficult in the NPK fertilizer production. When we produce compound fertilizer, we should pay attention to the following points, which can help you make better compound fertilizer granules.
First, the humidity problem: the optimum moisture content of urea ammonium phosphate material is about 3%, which is lower than that of other systems, and the granulation pass rate is only 30%, and the production capacity is low.
Second, the temperature problem: When the granulation temperature is high, the liquid phase amount of the system increases, because the inorganic salt increases with the increase of solubility, and the mutual dissolution and reaction form the amount of double salt increases, the degree of uniformity increases, and the liquid phase is added. The amount should be appropriately reduced, and the granulation moisture content should be adjusted as the solubility of the raw material changes.
Third, the problem of material solubility: In the high nitrogen ratio compound fertilizer, the amount of urea added exceeds 50%, and the solubility is large, so the liquid amount is high. It can be improved by adding powdered urea at lower operating temperatures. However, the urea dissolution and heat absorption operation reduces the granulation temperature and increases the difficulty of operation. The resulting low melting point mixture makes it more difficult to control the granulation.
The fourth point, the problem of returning material: Mainly affects the granulation temperature, the solubility of the humidity material and the granulation core. The temperature stability, particle size distribution, temperature and humidity of the return material are essential for granulation and must be strictly controlled.
Fifth, the ph problem of the material: ph is an important indicator of whether the compatibility of the material system is suitable. In the granulation system of ammonium phosphate, the pH value of the material is controlled between 6.0 and 6.5. When the material is acidic, the solubility of the material is large, and the reaction is violent, and the particles are bound to form a ball, which produces large particles. If it is alkaline, the ammonia loss is large, the material reactivity is poor, and the material is not easily granulated.
The sixth point is the melting point of the material. The melting point of the mixture is generally lower than the lowest melting point of each component. The eutectic point of urea, potassium chloride and monoammonium phosphate is about 115 degrees. This is the viscosity temperature. . The operating temperature inside the fertilizer granulator machine should be near this temperature. The urinary-based compound fertilizer has a decreasing viscous temperature as the water content increases, so the high-temperature, low-water granulation conditions can not only improve the granulation condition, but also facilitate the subsequent drying and sieving operations.
Others, such as reducing the temperature and humidity of the fertilizer granulator machine export material, or using two-stage dry low-temperature large-volume drying method, with increasing cost, but is safer and more reasonable for urea-based compound fertilizer.