Several Processes in Current Compound (Mixed) Fertilizer Manufacturing
At present, there are the following processes in the manufacture of compound (mixed) fertilizers in my country:
- Slurry production process technology,
- High-tower granulation production technology of urea-based compound fertilizer,
- Melt granulation production process technology,
- Dry powder physical agglomerate method production technology,
- Production technology of blending method.
Blending production technology
This process is the simplest compound fertilizer production process in my country.
The compound fertilizer manufactured by this process or method is called blended fertilizer or BB fertilizer. Its characteristic is that the process is simple and the ratio of raw material fertilizers is flexible and the raw material fertilizer remains intact, which is relatively intuitive, and the nutrient ratio is easy to adjust. But its disadvantages are: fertilizer is easy to produce nitrogen, phosphorus and potassium separation during transportation and application, and fertilizer is easy to absorb moisture and agglomerate. At present, most BB fertilizer formulas on the market are high-nitrogen, high-potassium, high-concentration type, and lack middle and trace elements.
Production technology of dry powder physical agglomerate method
The dry powder physical agglomerate granulation technology is to select several kinds of fertilizer raw material dry powder to measure and mix according to the needs, and use the binder as the binding agent to granulate in the granulator. The granulation of dry powder mixture requires heating and adding water or steam to increase the amount of liquid phase, and then agglomerate into compound fertilizer particles of a certain size in a disc or drum under rolling conditions. At present, the addition of acid (especially the addition of phosphoric acid) and ammonia is usually used in this type of process to increase the amount of wave phase, and the chemical reaction that occurs is used to provide heat. point. The materials in the granulator should be controlled at the best temperature (50 ~ 80 ℃) and the best water content (2.5% ~ 7.5%) to achieve suitable granulation conditions. The compound fertilizer manufactured by this process will have no substantial difference from the above-mentioned BB fertilizer in terms of the composition of nitrogen, phosphorus and potassium of the fertilizer. It just unites the smaller particles (powder) into particles. Therefore, it can also be said that the compound fertilizer manufactured by this process is a deep-processed BB fertilizer.
Slurry production process technology
The slurry process is the reaction product of sulfuric acid, nitric acid, phosphoric acid or some mixed acids and ammonia (sometimes the product of the reaction of acid and phosphate rock powder) is nitrogen and phosphorus slurry. Then add potassium salt to the slurry or directly add the potassium salt to the granulator, and then spray the nitrogen and phosphorus slurry into the granulator, and then react with the potassium salt at high temperature to prepare the nitrogen, phosphorus and potassium ternary compound fertilizer. The nutrient content in the compound fertilizer manufactured by this process is very uniform, and the nutrient content and ratio in the chemical fertilizers of large and small grains are exactly the same. The physical and chemical properties of the particles are first-rate. The forms of nitrogen in fertilizers include ammonium nitrogen and nitrate nitrogen, so the fertilizer efficiency is better than single urea or single ammonium nitrogen, phosphorus and potassium fertilizers.
High-tower granulation production technology of urea-based compound fertilizer
This process is a new process that has appeared in the production of compound fertilizers in recent years, that is, the high-tower urea-based compound fertilizer process. It actually melts the urea, the molten urine wave is metered and then sent to the mixer machine with a melting pump, and then the heated powdered monoammonium phosphate, potassium helium and additives (auxiliary materials) are metered and added to the heater for heating , The pre-heated auxiliary material is sent to the mixer and the molten urine is mixed and fully mixed to form an addition compound slurry with high solubility and certain fluidity. Then, it flows into the rotating nozzle at the top of the tower by its own gravity and then sprays into droplets. The droplets descend from the top of the tower and contact the rising cold air to transfer heat in the opposite direction, crystallize, solidify and cool in the air into finished particles. The large particles sieved out are crushed by the crusher and used with the fine powder as the returned material and re-added to the heater for recycling.
The advantages of high tower urea-based compound fertilizer are
- The physical properties of the fertilizer are very good. The particles are round with small holes, which are not easy to be imitated. The surface of the fertilizer is smooth and not easy to compact.
- The production and operation environmental conditions are good, all the discharged dust is recycled as return material for recycling, and there is no three wastes discharge.
- The whole process makes full use of the hot cutting energy of molten urine and the heat of reaction between urea solution and ammonium phosphate or potassium chloride to evaporate water and make the water content in the material extremely low. There is no need to do drying treatment, thereby reducing energy consumption and production costs.
However, the melt granulation method also has certain limitations, mainly in the following aspects.
- Since the solid solution mixture is required to form a flowable melt during the production process, the specifications of the finished product are subject to some restrictions.
- The range of product particle adjustment is very small.
- In the production process, the control requirements for temperature, material ratio, mixing time, and particle size are relatively strict.
- To ensure the smooth progress of the granulation process and product quality, the granulation tower must have a certain height.