Problems encountered in granulation of compound fertilizer equipment

2021/02/10

NPK fertilizer production equipment will encounter the following problems in the process of granulation; remind users to pay attention to when producing compound fertilizer.

First. Humidity issues: The best moisture content of urea ammonium phosphate materials is about 3%, which is lower than other systems, and the granulation qualification rate is only 30%, and the production capacity is low.

Second. Temperature problem: When the granulation temperature is high, the amount of liquid phase in the system increases, because the inorganic salt increases with the increase in solubility, and the amount of mutual dissolution and reaction to produce double salts increases, the uniformity improves, and the addition of liquid phase The amount should be appropriately reduced, and the granulation moisture content should be adjusted according to the solubility of the raw materials in the NPK fertilizer manufacturing process. For example, when the granulation temperature of the urea ammonium phosphate system is changed from 60 degrees to 90 degrees, the material moisture content should be reduced from 3.2% to 1.2%. In addition, the liquid viscosity and the surface tension are reduced, so that stronger particles are obtained under the action of mechanical external force.

Third. The problem of material solubility: In high-nitrogen compound fertilizer, the amount of urea added is more than 50%, and the solubility is large, so the amount of liquid phase is very high. It can be improved by adding powdered urea at lower operating temperatures but the urea dissolving endothermic operation reduces the granulation temperature and increases the difficulty of the operation. In addition, the low melting point mixture produced makes it more difficult to control the granulation.

Fourth. The problem of material return in the NPK fertilizer production line equipment. It mainly affects the granulation temperature, humidity, material solubility, and the core of the granulation. The temperature stability of the returned material, particle size distribution and temperature, and humidity are important for granulation and must be strictly controlled.

Fifth. The ph problem of the material. The ph is an important indicator of the compatibility of the material system. In the ammonium phosphate granulation system, it is more appropriate to control the pH value of the material between 6.0-6.5. When the material is acidic, the material solubility is large and the reaction severely it is easy to cause particles to bond into balls and produce large particles. Alkalescency will cause large ammonia loss, poor material reactivity, and material divergence is not easy to granulate. Adjust the pH value by adding ammonium bicarbonate, calcium magnesium phosphate, etc., which can be added by adjustment factories A small amount of gas ammonia and granulation steam mixed into the material layer can neutralize MAP, and the heat of reaction can increase the granulation temperature at the same time.