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Fertibon Products offers Granulating Aid in a free flowing liquid formulation pumpable at ambient temperature and it should be dosed directly into the Pre Neutralizer at a dosage of 0.1 to 0.15% by weight of final rate of production. It helps to increase the bonding and crushing strength of the final product. It also arrests the fines production and practically eliminates dusting in total.
Please note that though Granulating Aid gives improvement in crushing strength and reduction of fines in the fertilizer it also depends on other factors and process conditions. Granulating Aid does not in any way interfere with the chemical properties and the end use of fertilizer. Granulating Aid is non-toxic and easily bio-degradable. |
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Dosing of Granulating Aid |
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Granulation or Nodulization is a physical phenomenon which happens when particles agglomerate together due to repeated tumbling action. Depending on feed analysis, range of feed, tumbling action residence time and bonding property including moisture level, the granulation, size range and spherecity of granules formed varies. Desired granulation can be controlled by studying a number of parameters in a system. They can be broadly classified as follows: |
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| 1. |
Particle Size Gradation: In physically mixing and granulating a feed, the particle size gradation plays a vital role in porosity of the granules formed. |
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| 2. |
Moisture Level: Since granulation only by a tumbling action does not impart any compaction it is imperative that certain amount of moisture is a prerequisite for agglomeration. The moisture level can be fixed only by pilot plant studies, but since dying of the granules will be required thereafter minimum or optimum moisture level that could impart the necessary minimum strength to retain the granulometry while the granules are in motion is an important criterion since drying costs are prohibitive. |
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| 3. |
Granulator Design: There are three types of granulators. Pan type, Rotary Drum type and Blunger type. In a Rotary Drum type granulator which we have taken up specifically for studying the diameter, length, speed, angle, number of baffles, dimensions of the baffles, angle of the baffles, position, feed input nozzles/ hopper positioning, recycle ratio etc. Interplay in granulation of the product. Generally Rotary Drum granulators are designed much less than the critical speed and such speed take care of fluent tumbling action that would assure minimum abrasion and excessive fall. The details of granulator design are beyond the scope of this literature. |
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| 4. |
Feed Consistency: In a DAP/ NPK plant, the feed that has to offer the necessary moisture and proper crystallized graded particles is obtained from a pre neutralizer. The molar ratio, temperature, pH and the method of neutralization including any sulphuric acid that may be in the phosphoric acid or externally added will decide the crystallinity of the phosphatic precipitate. The moisture level adjustment depends on whether the final product is DAP or NPK depending on the extent of feed variation including fillers. Similarly, the concept of this product can be extended to ANP manufacture. |
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| 5. |
Fillers: While DAP has only fillers such as sand, urea, bantonite etc., NPK has also the additive of potash. The gradation of sieve analysis of sand and/ or potash makes a total impact at the granulation stage. |
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| 6. |
Plasticity and Binding properties of the Feed Material: DAP as crystallized has sufficient crystallinity and gradation of particle size to granulate well in a Rotary Drum granulator. But the physical addition of sand or any such inert fillers interferes to some extent in plasticity and binding properties of DAP. In spite of this DAP can be granulated reasonably well to the desired size range controlling the recycle ratio. In any case the plastic property of the slurry to the granulator is by itself insufficient if an NPK has to be granulated to give adequate granulometry with requisite properties such as spherecity, sieve analysis, crush strength, impact strength, abrasion resistance, etc. |
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| 7. |
Granulating Aid: A granulating aid is an ingredient which has the following functions. It is an optimum blend of crystal habit modifier which has a control on crystallization, flotation aid to keep particles in uniform suspension, binding aid which cotes each and every crystal uniformly for required adhesive properties and to provide bonding strength in the granulation due to superior plasticity of the slurry product. |
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| a. |
Optimizing Crystallization Aids: A Granulation Aid is ideally added to the pre-neutralizer, since it is the characteristics of the feed slurry that decides the extent of required granulation. The granulation aid participated in the neutralization by modifying the crystallinity to ideally suit for graded particle size. Also, the slurry consistency and its flowability get automatically tailored to the granulator requirements. |
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| b. |
Flotation Aid: This helps in keeping all the particles in uniform suspension for better flowability and mixing at the granulator. |
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