Technology of complex fertilizers with ammonizer-granulator

JSC NIUIF is the leading organization in Russia and the CIS countries in complex NP, NPS and NPK fertilizer manufacture technology with ammonizer-granulator. The main advantages of this technology are:

  1. High production capacity of one process line;
  2. A wide range of manufactured fertilizer grades;
  3. Low energy consumption;
  4. The possibility of rapid transition between different types of product;
  5. High quality of final product.

Ammonizer-Granulator

Ammonizer-granulator (AG) is a drum-type apparatus that combines the processes of ammoniation and granulation. Due to the heat generated by the interaction of ammonia with acids, the material is also dried in AG. This allows to reduce energy consumption per unit, as well as duration of the process cycle and number of necessary equipment in the process line compared to other methods. The use of AG is the most effective in the manufacture of granular fertilizers on the basis of concentrated WPA.

AG is a rotating drum with handling rings, with which the drum rests on trunnion rollers. The material for ammoniation and granulation enters through the inlet chute, located in the head of the apparatus. AG is installed at an angle of 1÷3° to the horizon, as a result, the material moves through the granulator to the discharge, located in the tail part of the apparatus. Discharge seal rings are installed at the ends of the drum, they provide the necessary level of drum filling. In the inner part of the drum there is a scraper, which cleans scaling from inner surface, ammonia distributor, ammonia, water and pulp supply pipes and lifting device. AG vary in size and interior design.

AG have a fairly high production capacity. The process line including AG is highly productive. Combining the processes of mixing, ammoniation and granulation in one unit allows to reduce energy consumption and improve the quality of mineral fertilizers.

The dimensions (diameter and length) of the granulator are determined by the process line production capacity, as well as the system recycle. The most commonly used ammonizer-granulators (DxL):

  • 2.2x5 m for 30-40 t/h production capacity;
  • 4x8 m for 70-120 t/h production capacity;
  • 4.5x9 m for 100-140 t/h production capacity;
  • 5x10 m for 110-160 t/h production capacity.

Necessary requirement for ammonizer-granulator technology is to mostly use concentrated WPA.

For extraction of phosphoric acid, that has a high content of impurities, and therefore is difficult to evaporate, it is advisable to implement the production process with the use of diluted WPA, but with intermediate evaporation of partially ammoniated slurry.

Fertilizer manufacture flowsheet with Ammonizer-Granulator

Complex fertilizer manufacture flowsheet with AG is shown in Figures 1 and 2. It includes ammoniation of a mixture of sulphuric and phosphoric acids in pipe reactor, granulation and pre-ammoniation in AG, drying of granules in drying drum, the classification of granules with the recycle of crushed oversize and small fraction, and also parts of commercial fraction in AG, in the form of recycle. 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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Pipe reactor plants   

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Figure 1. Complex fertilizers manufacture flowsheet with ammonizer-granulator and pipe reactors

Technology with AG allows the 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. To increase nitrogen ratio and expand the range of products, it is possible to use urea or ammonium nitrate as one of the nitrogen-containing components. This allows the manufacture of such fertilizers as 16:16:16, 17:17:17, 22:11:11, 19:9:19, 27:6:6, 20:10:10 and a number of others.

In some cases, it is advisable to implement a phosphorus and sulphuric (nitric) acids two-stage neutralization unit: the first stage in the pre-neutralizer (PN reactor or a high-speed ammonizer-evaporator), the second stage - in pipe reactors (PR).

The implementation of the two-stage ammoniation allows you to:

  • increase the ammoniated slurry load, hence, increase the ratio of W:T at the granulation stage, which is necessary for grades with low phosphorus content: 15-15-15; 16-16-8; 20-20-0 + 14S;
  • make it possible to increase the consumption of sulphuric acid for ammoniation and thereby replace part of the crystalline ammonium sulphate;
  • partially use non-concentrated WPA.

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Figure 2. Complex fertilizers manufacture flowsheet with ammonizer-granulator and two-stage neutralization of acids

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PN reactor and high-speed ammonizer-evaporator 

Proven and reliable AG-DD technology provides a high unit capacity, versatility and flexibility of production due to the following improvements:

  • two-stage sequential ammoniation process in PN reactor and in 2-3 pipe reactors;
  • optimal space configuration in AG and design of the nozzles at the outlet of the pipelines;
  • improved design of the inner lifting flights of the drying drum;
  • easy to manage recycle with minimum equipment units and at the same time reliable and with high production capacity;
  • efficient cooling system: fluid bed cooler and heat exchanger;
  • innovative improvement technology for quality parameters of final products through the use of modifying additives;
  • efficient wet scrubbing system: Venturi scrubber - scrubber tower - high-speed foam scrubber; that provides low pollutant emissions and low power consumption.

Nitrate-containing complex fertilizers manufacture

The use of ammonium nitrate in the complex fertilizers manufacture increases fire and explosion safety. To reduce the risk of fire and explosion during manufacture of these types of fertilizers, JSC NIUIF presented and patented (RF Patent 2 541 641 C1) a method of joint neutralization of nitric and phosphoric acids (Figure 3). It is also advisable to preliminary mix a part of the ammoniated slurry and potassium chloride for a higher degree of chemical processes conversion and reduce the caking of the final product.

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Figure 3. Nitrate-containing complex fertilizers manufacture flowsheet (RF Patent 2 541 641 C1)

To improve the quality of the final product, the obtained granules are coated with a coating oil in a coater drum before entering the storage. Coating of the product reduces its hygroscopicity, caking and dustiness. JSC NIUIF presented and patented a method of fertilizer granules coating (RF patent 2 307 115 C1).

Use of magnesium additives

To further reduce the caking and dustiness of complex fertilizers, JSC NIUIF presented and patented (RF Patent 2 417 756 C1) a method for using magnesium-containing additives (magnesite, brucite). This method, shown in Figure 3, involves mixing a magnesium-containing additive with phosphoric acid and then feeding it to ammoniation. This method can also be used to supply micronutrients and other micro-additives.

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Figure 3. Magnesium-containing additives injection method (RF Patent 2 417 756 C1)

Pipe reactors (PR)

To improve AG production capacity, ammoniation of phosphoric acid must first be carried out in PR. Figures 4 and 5 show drawings of PR presented and patented by JSC NIUIF (respectively, RF patents 2 360 729 C1 and 2 533 713 C1). These reactor designs make it possible to minimize the possibility of slurry sticking to the inner lifting flights and shell and reduce the metal intensity and improve reactor operating conditions.

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Figure 4. Pipe reactor (RF patent 2 360 729 C1):

1 - shell; 2 - nozzle; 3 – nozzle pipe; 4 - covers; 5 – ammonia inlet nozzle; 6 - ammonia distributor.

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Figure 5. Pipe reactor (RF patent 2 533 713 C1):

1 - acid inlet; 2 - flanges with gaskets; 3 - shell; 4 - ammonia inlet; 5 - product outlet; 6 - thin-walled reaction pipe; 7 - ammonia nozzles.

Taking into account the design data and customer requirements, JSC NIUIF specialists are ready to develop the technology and instrumentation for NP/NPS/NPK-fertilizer production with a unit capacity of 200 up to 1200 thousand tons of per year.