Fertilizers with micronutrients

A special role in plants growth play micronutrients - boron, manganese, copper, molybdenum, cobalt, zinc, and iron. The most popular way of using micronutrients is to mix them with nutrients in the form of granular complex fertilizers. Usually, the number of micronutrient types in a certain grade of fertilizers varies from one to four, the total micronutrients concentration ranges from 0.1 to 1% recalculated to active material. 

JSC NIUIF together with JSC Voskresensky NIUIF is developing and improving the technology of complex fertilizers with micronutrients, including in chelated form.

During development of a new complex fertilizers’ technology with micronutrients and adaptation of the existing process line for the manufacture of fertilizers with micronutrients, the following factors should be taken into account:

  • type of used raw materials and in what form the active substance is presented in the feedstock;
  • possibility of elements (micronutrients) in raw materials to enter into various reactions with the main components of fertilizers at different stages of the production process;
  • implemented fertilizer technology;
  • optimal parameters of the manufacture process taking into account the micronutrients used (mainly granulation, drying).

The supply of micronutrients in the manufacture process is carried out in two ways: dry and wet.

In the “dry” method, the micronutrients in their original form are fed to the recycle conveyor and then to the granulation stage. This method is commonly used for technology with ammonizer-granulator, provided that micronutrients in raw materials are in a fully available form.

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Figure 1. Micronutrients dry feed method

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Figure 2. Micronutrients wet feed method

The "wet" method involves pre-dissolution of micronutrients with phosphoric acid and subsequent feeding for ammoniation. The mixing tank is equipped with high-speed rotating device (agitator) to improve the micronutrients dissolving process. The “wet” method is commonly used for process lines with a drum granulator-dryer or when micronutrients feedstock is required to be converted into a soluble and available form.

Complex fertilizers technology with ammonizer-granulator with micronutrients feed to recycle conveyor

Complex fertilizers manufacture flowsheet with AG is shown in Figure 3. It includes ammoniation of sulphuric and phosphoric acids mixture in PR, granulation and pre-ammoniation in AG, drying of granules in a drum dryer, classification of granules with recycle of crushed oversize and fine fractions, and also part of commercial fraction in AG in the form of recycle through recycle process. The final product is cooled, coated with a coating oil to improve consumer properties and sent to the final product storage.

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            Figure 3. Complex fertilizers manufacture flowsheet with ammonizer-granulator (RF patent 2 455 228 C1)

Technology with AG allows manufacture of such fertilizers as monoammonium phosphate (MAP), diammonium phosphate (DAP), various types of NPK-fertilizers (9:25:25, 10:26:26, 13:19:19, 15:15:15, 16:16:8 and a number of others), various types of NPS-fertilizers (14:34:0-12S, 20:20:0-14S and a number of others), as well as fertilizers with micronutrients and other types of additives.

Complex fertilizers technology with drum granulator-dryer with micronutrients feed through dissolution

Complex fertilizers manufacture flowsheet with DGD is shown in Figure 4. It includes neutralization of sulphuric and phosphoric acids mixture with ammonia in pre-neutralizer, pre-ammoniation in PR, granulation and drying in DGD, classification of granules with recycle of crushed oversize and fine fractions, and also a part of commercial fraction in DGD in the form of recycle through recycle process. The final product is cooled, coated with a coating oil to improve consumer properties and sent to the final product storage.

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Figure 4. Flexible manufacture flowsheet of phosphate-containing fertilizers with DGD:

1 - neutralizer; 2 - bunkers; 3 - acid tank; 4 - tank mixing pulp with potassium chloride; 5 - pipe reactor; 6 - furnace-burner; 7 - DGD; 8 - elevators; 9 - screen; 10 - mill; 11 - “fluid bed” cooler; 12 - Solex cooler; 13 – coating drum.

Technology with DGD allows manufacture of such fertilizers as monoammonium phosphate (MAP), diammonium phosphate (DAP), various types of NPS-fertilizers (14:34:0-12S, 20:20:0-14S and several others), NPK-fertilizers based on calcium phosphates (0-20-20; 5-30-15; 10-15-15, etc.) with micronutrients.

Technology of liquid complex fertilizers (LCF) with micronutrients in chelate form

Manufacture flowsheet of 10:34 grade with micronutrients in chelated form (MN) is presented in Figure 5. The flowsheet includes a storage of chelated micronutrients, from which the solution is fed into the mixing tank, where it is mixed with LCF grade 11:37. After LCF grade 10:34 with micronutrients is fed to the storage, from where it can later be sent to railway tanks.

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Figure 5. Manufacture flowsheet of LCF with micronutrients in chelate form:

1 - mixing tank; 2 - MN storage with heat exchanger; 3 - tank truck; 4 – LCF storage with MN and heat exchanger; 5 - railway tank; 6 - pumps; 7 – LCF metering unit; 8 – MN metering unit.

Micronutrients in LCF are stored fully in available form, which ensures high efficiency of such fertilizers.