DESC:FIELD OF INVENTION

The present invention relates to the manufacturing process of Potassium Nitrate (KNO3) based NPK customised fertilizers which are difficult to granulate in the conventional drum granulation process. The innovative steps involved are the selection of suitable materials for obtaining the NPK grade and for achieving good granulation, adopting a special granulation technique with the usage of pan granulator and maintaining the suitable and appropriate process parameters while granulating.

BACKGROUND OF THE INVENTION

Potassium nitrate is crystalline salt containing two primary nutrients viz Nitrogen and Potash. Normally NPK fertilisers manufacturing process use Muriate of potash (KCl) or Potassium sulphate (K2SO4) for achieving K2O content in the fertiliser. Both these salts contain only one primary nutrient viz K2O. But Potassium nitrate with two primary nutrients possesses high significance as fertiliser. It can be directly used as a fertiliser with N & K2O content. But the plants require another primary nutrient i.e. P2O5 also for proper growth and crop yield and hence if we want to use Potassium nitrate directly as a fertiliser, we need to apply another fertiliser that contains P2O5 to the plants. Two fertilisers physical mixing while applying is a tedious job to the farmers and the ratio of mixing is also a challenge to them. Hence it would be wise to formulate an NPK fertiliser with proper composition of N, P2O5 and K2O and to make integrated granules. This invention is giving us a way of making NPK customised fertiliser by using KNO3 as source for N & K2O and properly selected P fertiliser for incorporating P2O5 in it. Granulation of such two or more fertilisers mixture is a challenge with respect to getting round shaped, uniformly sized strengthy granules with uniform N, P2O5 and K2O contents. This innovation deals with the granulation of KNO3 based fertiliser with incorporation of P2O5 to make NPK fertiliser.

Most of the existing granulation process use the spray of Pre-Neutralized slurry of phosphoric acid reacted with ammonia on to the recycle bed of a mixture NPK fertiliser fines and other solid raw materials in the rotary drum granulator. Spray of hot slurry brings temperature and wetness to the material bed in the granulator thus making the granulation easy. But in the present case we are not using reaction & pre-neutralisation step between phosphoric acid and ammonia, we are considering to take ammonium phosphate fertiliser as one of the materials to get mixed with the Potassium Nitrate. Granulation of this physical mixture to form round shaped, uniformly sized strengthy granules with uniform N, P2O5 and K2O contents is a challenge and requires specialised equipment, selected granulation additives and specific process parameters that are favourable for the granulation.

DESCRIPTION OF THE PRIOR ART

Since long period granulation of NP/NPK fertilisers is known by ammoniation granulation methods by spraying ammonium phosphate slurry on the revolving bed of recycle material in the granulator. Prior arts are available for water granulation and steam granulation of various fertiliser mixtures but there is no evidence of sound process or proved process for granulation of KNO3 based NPK customised fertilisers in which KNO3 is one of the raw materials for source of K2O and N and other raw materials being for P2O5 source and additives to favour granulation.

US Patent US3993466 discloses a process for the production of a nitrogen-potassium, and phosphorus containing fertilizer having reduced chlorine and calcium content. Calcium- containing phosphate rock is first reacted with nitric acid to produce a mixture containing nitrogen, calcium, and phosphorus-containing solution. The mixture is then contacted with a potassium and ammonium ion-exchange resins so as to replace the Calcium ions in the mixture with potassium and ammonium ions. The calcium-soaked resin is separated from the solution containing potassium, nitrogen and phosphorus and the solution is worked to yield a fertilizer. This process is deferent from our innovation that their process involves no of stages from rock digestion to slurry contacting with ion exchange resins. Whereas our process is related to innovative steps like selection of materials viz MAP, Potassium nitrate, Urea, SSP, Kieserite, Micro nutrient substances, crushing & blending them at specific ratios with granulation additive and granulation in a specialised equipment viz pan granulator specific temperature & moisture conditions.

US Patent US6176892B1 (CN1204309A) relates to a method for making NK-fertilizers basically from calcium nitrate fertilizer and the potassium nitrate which are melted at 90-120° C. and then heated to the desired particulation temperature being 160-190° C for prilling, and 90-140° C for granulation. The components are mixed in ratios giving a melt or suspension comprising 40-14 weight % calcium nitrate, 55-85 weight % potassium nitrate, 0.5-6 weight % water, 0-4 weight % ammonium nitrate and 0-5 weight % magnesium nitrate. Our innovation is different from this process as we are not melting the raw materials. Our process is related to innovative steps like selection of materials viz MAP, Potassium nitrate, Urea, SSP, Kieserite, Micro nutrient substances, crushing & blending them at specific ratios with granulation additive and granulation in a specialised equipment viz pan granulator specific temperature & moisture conditions hence our invention is different from this patent.

Chinese patent CN104387156A proposed an improved process for producing spherical and granulated nitrogen-phosphorus-potassium mixed fertilizer based on a nitro phosphate fertilizer device comprises the following steps: firstly, mixing a calcium nitrate filter cake in a working procedure of calcium nitrate crystallization with potassium nitrate in proportion, drying, and crushing to obtain a potash-lime fertilizer; drying and crushing NP slurry in a working procedure of mother liquor evaporation to obtain a nitro phosphate fertilizer; feeding both of the potash-lime fertilizer and the nitro phosphate fertilizer in proportion into a stock bin at the top of a high tower, stirring and mixing in the stock bin, heating up and fusing through a smelt tank of the high tower, and finally, granulating by a granulation sprayer of the high tower to obtain the spherical and granulated nitrogen-phosphorus-potassium mixed fertilizer. Our process is completely different as we are not forming any melt of Potash lime fertilizer as well as NP slurry, and our process does not involve spray of the fused melt through tower to form spherical granules hence our invention is different from this patent.

WO2007117151A2 concerns a method for producing high N-NP or high N-NPK fertilizer preferably with N > 25 weight % having less than 70 weight % AN, from a melt comprising ammonium nitrate, ammonium phosphate, optionally also DAP, DCP and minor quantities of other components. Solid AS is mixed into an almost water free NP melt either alone or together with a potassium salt, where after the melt is particulates preferably by prilling. The water content of the melt is kept less than 2 weight %, preferable less than 1 weight %. The melt has N/P > 2.1 (equals N/P2O5 > 0.9) and Ca/P< 1, preferably 0.3-0.7. The potassium salt is KCl or K2SO4 or a mixture of these.AS is added as crystalline or crushed, having a particle size with d50 in the range of 0.10- 0.90 mm, preferably 0.40 -0.60 mm. In addition, 0.1 to 10 weight % reactive, preferably 0.2 - 1 weight %, finely divided MgO, CaO or other strongly water binding agent is added to the melt. The average particle size is preferably 0.2-3.0 mm. The total amount of salt mixed into the melt should be less than 52 weight %, preferably less than 45 weight %. But our innovation is specific about pan granulation of blend of Potassium Nitrate, Ammonium phosphates, with granulation additive. and does not require melting of any of the raw materials hence our invention is different from this patent.

Chinese Patent CN101333121B discloses an isomorphism-based calcium-potassium nitrate compound fertilizer, comprising solid solution crystal and mother liquor; the solid solution crystal is unequal compound calcium-potassium nitrate, with the following molecular expression: KNO3*xCa (NO3)2, wherein, x is 0.1-0.2. industrial potassium nitrate, calcium nitrate and water are measured, mixed and stirred; the potassium nitrate and the calcium nitrate are fully dissolved in water through heating; the solution is then cooled with cooling water to the crystallization temperature so as to release solid solution crystallization liquid after the solution forms a large number of crystals; through separation precipitation, the solid solution crystallized compound is achieved. Our process doesn’t involve usage of Calcium nitrate, solution preparation of KNO3 and Ca (NO)3 mixture and crystallization of liquid, our process is blend preparation of KNO3, MAP, Urea, Kieserite, SSP and micro nutrient substances and granulating them in a Pan granulator which is completely different form process mentioned in the patent hence our invention is different from this patent.

European patent EP2994441A2 discloses a process for making NPK grade fertilisers f comprising nitrogen in the range of from 10 wt. % to 20 wt. %; P2O5 in the range of from 10 wt. % to 20 wt. %; K2O in the range of from 5 wt. % to 18 wt. %; and sulfate in the range of from 5 wt. % to 15 wt. % such as 15-15-15, 16-16-16, 12-12-17, 18-18-5 with MgO using reaction process as phosphoric acid, sulphuric acid, rock phosphate, ammonia, potassium nitrate as raw materials. This process is described as using the rotary drum granulator with the slurry granulation process. Our process is related to innovative steps like selection of materials viz MAP, Potassium nitrate, Urea, SSP, Kieserite, Micro nutrient substances, crushing & blending them at specific ratios with granulation additive and granulation in a specialised equipment viz pan granulator specific temperature & moisture conditions hence our invention is different from this patent.

The European patent EP 2032511A2 relates to an NPK fertilizer, comprising both nitrate and urea as the main nitrogen sources, thus attaining high nitrogen levels with ammonium nitrate concentrations falling below maximum limit values set by international legislation and classification, while at the same time explosion risks associated with the use of ammonium nitrate are avoided. The invention relates to a process for producing fertilizer granules of the above mentioned type having excellent resistance properties and high nitrogen content wherein said granules may be coated by methods typical in the art, if desired.2The process disclosed in this patent is reaction of biotite, phlogopite, muscovite, vermiculite, or another phyllosilicate containing potassium, magnesium and/or iron with nitric acid in presence of sulphuric acid and granulating the slurry in the rotary drum granulator where urea also is fed. Our process is related to innovative steps like selection of materials viz MAP, Potassium nitrate, Urea, SSP, Kieserite, Micro nutrient substances, crushing & blending them at specific ratios with granulation additive and granulation in a specialised equipment viz pan granulator specific temperature & moisture conditions hence our invention is different from this patent.

European patent EP2578557A1 discloses a process to manufacture water-soluble solid composition comprises nitrogen, phosphorus and potassium, where the composition is present in the form of homogeneous granules, which comprise an acid-base reaction product between phosphoric acid, nitric acid, potassium hydroxide and ammonia, and a mixture of ammonium-potassium nitrate salt. Our process is related to innovative steps like selection of materials viz MAP, Potassium nitrate, Urea, SSP, Kieserite, Micro nutrient substances, crushing & blending them at specific ratios with granulation additive and granulation in a specialised equipment viz pan granulator specific temperature & moisture conditions hence our invention is different from this patent.

OBJECTIVE OF THE INVENTION

The main objective of the present invention is to provide a process for manufacture of an NPK customised fertilizer using Potassium nitrate as a major raw material as it contains two primary nutrients and having significant importance among the many compound fertilisers that exist.
The second objective of the present invention is to manufacture an NPK customised fertiliser that is complete with secondary nutrients content and some micro nutrients content also.
Another objective of the invention is to manufacture the fertilisers mixture in a selected suitable granulator that favours the granulation instead of using conventional rotary drum granulator.
Another objective of the present invention is to choose the fertiliser materials containing secondary and micro nutrients such that they do not create hurdles in granulation rather they should help to improve granulation.
One more objective of the invention is to add a granulation additive to facilitate granulation of the fertiliser mixture to form uniform composition, uniform sized, round shaped, granules.
One more objective of the invention is to capture the right process parameters of the granulation namely the temperature, moisture, speed of the pan, angle of the pan, spray nozzles position and other conditions that work in favour of the granulation.

DETAILED DESCRIPTION OF THE DRAWINGS

Figure 1: Flow Chart for Potassium nitrate based NPK fertilizers through PAN granulator

Legend:
1. Raw Materials (KNO3, SSP& FeSO4)
2. Raw Materials (Urea, MAP, ZnSO4, Disodium Octa borate)
3. MgSO4.3H2O
4. RM Crusher 1
5. RM Crusher 2
6. Blending
7. PAN Granulation
8.Blower
9. Drying
10. Screening
11. Product Granules
12. Fines
13. Over Size material
14. Oversize Crusher
15. Cooling
16. Packing

SUMMARY OF THE INVENTION

The present invention relates to the manufacturing process of Potassium Nitrate (KNO3) based NPK customised fertilizers which are difficult to granulate in the conventional drum granulation process. The innovative steps involved are the selection of suitable materials for obtaining the NPK grade and for achieving good granulation, adopting a special granulation technique with the usage of pan granulator and maintaining the suitable and appropriate process parameters while granulating. This process for making Potassium Nitrate based NPK grade customised fertiliser containing Potassium Nitrate as a base raw material and other fertilisers Mono Ammonium Phosphate powder (as a source for P2O5), Single Super Phosphate powder (to supplement P2O5 and also as a source for CaO & Sulphate sulphur content0,Urea pills (to supplement Nitrogen content in the form of amide), Kieserite powder (as a source for MgO content and also as granulating additive), Zinc sulphate mono hydrate crystals (as a source for Zinc content),Ferrous sulphate hepta hydrate crystals (as a source for Iron content), Di Sodium Octa Borate Tetra hydrate(as a source for Boron) mixing them in two groups except Kieserite powder, Crushing up to 100 mesh size and blending them along with Kieserite powder and granulating the mixture in pan granulator with the addition of LP steam as source of heat and moisture and drying the green granules in a rotary heated surface dryer and separating the product size granules in the screens, cooling the product size granules to obtain round shaped, uniformly sized, uniform composition in N, P2O5, K2O and other secondary and micro nutrient contents, enough crushing strength of desired composition of NPK and secondary and micro nutrients.

DETAILED DESCRIPTION OF THE INVENTION

According to the present invention, Potassium nitrate based NPK customised fertilizers can be produced by direct mixing of some choosen fertiliser materials and a granulation additive and by granulating them in an inclined pan granulator positioned at a selected angle that is arrived by pilot experiments and by operating at an appropriate speed with addition of LP steam to give heat and moisture content.

Choosing the raw materials for the Task: Choosing the right raw materials for this task is an innovative step because they not only contain nutrients like N, P2O5, K2O, Secondary or micro nutrients but also behave in a way to granulation either favourable or unfavourable. As said in one of the objectives Potassium nitrate is one of the raw materials for the process. All the raw materials that are required for the process are mentioned below.
1. Potassium Nitrate pills: As a source for N & K2O,
2. Mono Ammonium Phosphate powder: As a source for P2O5
3. Single Super Phosphate powder: To supplement P2O5 and also as a source for CaO & Sulphate sulphur content.
4. Urea pills: To supplement Nitrogen content in the form of amide.
5. Kieserite powder: As a source for MgO content and also as granulating additive
6. Zinc sulphate mono hydrate crystals: As a source for Zinc content
7. Ferrous sulphate hepta hydrate crystals: As a source for Iron content
8. Di Sodium Octa Borate Tetra hydrate: As a source for Boron

If desired customised fertiliser should contain other micro nutrients such as Manganese, Copper, Chlorine, Molybdenum we can chose the compounds containing these micro nutrients and make the formulation. In addition, we can also add growth promoting agents like amino, Humic, fulvic acid components, Organic carbon containing components also in the formulation.

Crushing the Raw materials before granulation: The second innovative step of the manufacturing process of Potassium nitrate based NPK customised fertiliser is crushing the raw materials to an appropriate size to favour the granulation. above raw materials are not of uniform size hence they need to be brought to uniform size before they are granulated. Potassium nitrate and Urea are in the form of pills, Mono ammonium phosphate, SSP, kieserite is in the form of powder and zinc sulphate, Ferrous sulphate and Di sodium Tetra Borate are in the form of crystals. These raw materials are divided into two groups as mentioned below with respect compatibility of while crushing.

1. Group1: Potassium nitrate, SSP and Ferrous sulphate
2. Group2: MAP, Urea, Zinc sulphate and Disodium Octa borate
Kieserite is already a fine powder hence it need not be crushed.

The above grouping is done to control moisture absorption during crushing and to avoid caking or scale formation in the crusher. If other raw materials with other micro nutrients are to be added they can be added in to either group1 or grou2 based on the hydrated molecules and free moisture in each of them so as to balance the moisture content such that moisture is not very high in any group. The desirable size after crushing is 90% passing through 100 mesh. Crushing is done in batches with appropriate quantity of each material to match with the final grade of the customised fertiliser grade. For example, each substance of Group 1 materials (legend 1 in fig1) are taken in quantity as per the formulation required per ton of the final product are crushed in crusher (4) of fig 1. In the same way each substance of group 2 materials (legend 2 of fig1) is crushed in the crusher (5).

Blending of the crushed materials with Kieserite: The crushed materials from the above are mixed with the Kieserite (3) in a quantity that is required per ton of final customised grade product in a blender (6) in batches. This blending is to achieve two things, the first one being to achieve uniform mixing of all the substances including micro nutrient substances to obtain uniform composition of nutrients and the second one is to distribute the moisture of the substances equally to all the mixture so as to avoid cake/scale/lumps formation during granulation.

Granulation: The mixture coming out of blender (6) is fed in to a pan granulator (7) for the next step of manufacturing process. The equipment selected for the granulation of this mixture is considered as innovative thinking because this material mixture is difficult to granulate in the conventional drum granulator, hence specialised equipment is required. Pan granulator is a specialised granulation equipment positioned at prefixed angle. The angle can be changed as per the behaviour of the material at which the material gets granulated to the desired size. The speed of the pan also can be changed as it is driven by a Variable frequency drive motor. On the pan granulator recycle fine and crushed over size material also comes along with the fresh raw material powder mixture. LP steam is sprayed on the rotating material to give heat and add moisture to it to favour the granulation. The temperature and moisture of the material bed are important parameters which are to be maintained for achieving the good granulation. These parameters are captured by conducting several experiments for these materials and concluded that the suitable parameters are 60-70 deg C and 7-8% moisture. These parameters are applicable to any composition of material mixture involving potassium nitrate as one of the raw materials but not applicable when potassium nitrate is not there as raw material.

Drying: The green granules from the granulator are dried in a specialised dryer (9) in which the delicate wet granules are not broken but dried to desired moisture content. The selection of suitable dryer is also an innovative step because such a dryer can handle the granules up to 10% moisture content, where-as the conventional hot air blow drying process can handle up to 4% moisture content. The dryer selected for this process is heated surface rotary drum. The shell of the rotary drum is heated by electric coils around it and the heat is passed to the material revolving inside. Because of the continuous rotation of the material inside and removal of moisture by the forced ambient air supplied by the blower(8) i.e. ( the blower sucks the ambient air by regulate the damper and converts into forced air to the dryer) that is blown through the material inside the dryer, the material receives the heat uniformly and the received heat is utilised for evaporation of moisture from the surface of the granule and the same evaporated moisture is driven away by the forced ambient air blown through it. At the outlet of the dryer the material contains 1% moisture and gains strength.

Screening and cooling: The material from the dryer is screened in a vibrating/gyratory screens (10) and the over size and fines separated from the product. The oversize granules (13) are crushed in the crusher (14) that is provided in the recycle loop and sent back to the pan granulator along with the fines (12) coming out from bottom of the screens. This step is a regular art process as available in the many granulation plants.

The product size granules (11) from the screens are cooled in a rotary drum cooler (15) with counter current flow of ambient air. After cooling the granules get hardened due to the absence of plasticity of the granule and also due to further loss of moisture. Thus, the product granules (16) in this process are more strengthy and they are eligible to undergo for packing stage.

The product that is produced through this process is uniform in size, spherical in shape and hard in integrity, and some other physical properties like moisture holding capacity, Critical relative humidity etc., are also considerably increased by this formulation which and reduces the urea requirement for ton of product.

Examples
Two products, compositions mentioned below are produced in the process as described above.
1. Product1: NPK 10-25-10-2.5% CaO-1.5% MgO-2.5%S-0.5%Zn-0.3% Fe
2. Product2: NPK 12-06-24-1.0% CaO-4.0% MgO-3.5%-S-0.3%Zn-0.3%Fe-0.2%B.

The raw materials and their quantities used for these two products are given in the below table. All quantities are mentioned in Kgs/ton of product

Raw material For product 1 For product 2
Potassium Nitrate, 13-0-45 grade 225 535
Low grade MAP, 10-45-0 grade 530 125
SSP, 16% P2O5 100 38
Urea, 46% N 40 83
Kieserite, MgSO4.3H2O 65 174
ZnSO4.H2O 15 9
FeSO4.7H2O 15 16
Di Sodium Octa Borate Tetra hydrae 0 10

The essential features of the inventions are: -
1. A process for making Potassium Nitrate based NPK grade customised fertiliser containing Potassium Nitrate as a base raw material and other fertilisers Mono Ammonium Phosphate powder (as a source for P2O5), Single Super Phosphate powder (to supplement P2O5 and also as a source for CaO & Sulphate sulphur content0,Urea pills (to supplement Nitrogen content in the form of amide), Kieserite powder (as a source for MgO content and also as granulating additive), Zinc sulphate mono hydrate crystals (as a source for Zinc content),Ferrous sulphate hepta hydrate crystals (as a source for Iron content), Di Sodium Octa Borate Tetra hydrate(as a source for Boron) mixing them in two groups except Kieserite powder,
Crushing up to 100 mesh size and blending them along with Kieserite powder and granulating the mixture in pan granulator with the addition of LP steam as source of heat and moisture and drying the green granules in a rotary heated surface dryer and separating the product size granules in the screens, cooling the product size granules to obtain round shaped, uniformly sized, uniform composition in N, P2O5, K2O and other secondary and micro nutrient contents, enough crushing strength of desired composition of NPK and secondary and micro nutrients.

2. The fertiliser manufactured as detailed above contains primary nutrients N, P2O5, K2O and the secondary nutrients Ca, Mg & S and the micro nutrients such as Zinc, Fe, Boron etc as desired and dosed accordingly in the mixture.

3. The process for the manufacture of fertiliser as detailed above consists of the process in which crushing of the raw materials is done in two groups in the required proportion as per the grade of the final fertiliser grade desire, group1 being Potassium nitrate, SSP and Ferrous sulphate and group2 being MAP, Urea, Zinc sulphate and Disodium Octa borate so as to balance the moisture contents and hygroscopic properties to avoid the caking and scaling formation during crushing.

4. The process for the manufacture of fertiliser as detailed above consists of blending of the crushed materials along with the Kieserite which is already in powder form and which acts as granulation add in a blender to get uniform composition of mixture and to distribute the moisture content uniformly to all the components of the mixture.

5. The process for the manufacture of fertiliser as detailed above consists of Granulation of the mixture along with the recycle fines in specialised granulation equipment that is a pan granulator where LP steam is sprayed upon the feed material and due to the temperature of material at 60-70 degC and moisture content of 7-8% in it the mixture gets granulated in to round granules of uniform size and uniform composition.

6. The process for the manufacture of fertiliser as detailed above consists of drying of the green granules coming out of pan granulator in a specialised rotary dryer where the shell surface of the rotary dryer is heated with the surrounding heating coils by radiation and the heat from the shell is dissipated to the rotating granules in the dryer. Due to heat the moisture content in the granules is evaporated and the moisture thus evaporated is driven away by co-current ambient air flow through the dryer.

7. The process for the manufacture of fertiliser as detailed above consists of screening for separating the oversize and fine, the oversize material is crushed and sent back to the pan granulator along with the fines from the screens as recycle material.

8. The fertiliser manufactured as per the process as detailed above possesses good crushing strength, round shape, uniformity in size and uniform composition.

9. The process for the manufacture of fertiliser as detailed above is applicable to any NPK customised fertiliser that is desired to be made with potassium nitrate as one of the raw materials even when the composition of N, P2O5, K2O and secondary and micro nutrients vary even though the examples in the patent application are shown for two grades only viz 1) 10-25-10-2.5% CaO-1.5% MgO-2.5%S-0.5%Zn-0.3%Fe and 2) 12-06-24-1.0%CaO-4.0%MgO-3.5%S-0.3%Zn-0.3%Fe-0.2%B.

In one aspect the invention discloses a process for preparing Potassium Nitrate based NPK grade fertiliser composition which involves selecting Potassium Nitrate of a specific grade as a base raw material, mixing with at least one or more source ingredient selected from the group which are P2O5 source – Phosphorus Pentoxide, a CaO source – Calcium Oxide, a SO42 source – Sulphate Sulphur, a N2 source – Nitrogen, a MgO source – Magnesium Oxide, a ZnO Source – Zinc Oxide, a Fe source – Iron source and a B source – Boron source. This composition is unique.

In another aspect this process for preparing Potassium Nitrate based composition as described above involves a method after selecting Potassium Nitrate of 13-0-45 grade with an amount 225 kgs and adding this to a mixture of Low grade MAP, 10-45-0 grade amount 530 kgs, SSP, 16% P2O5 amount 100 kgs, Urea, 46% N amount 40 kgs, Kieserite, MgSO4.3H2O amount 65 kgs, ZnSO4.H2O amount 15 kgs and FeSO4.7H2O amount 15 kgs to prepare one ton of fertiliser composition.

In third aspect the process further discloses preparing Potassium Nitrate based composition as described above, wherein the method includes the step of selecting Potassium Nitrate 13-0-45 grade 535 kgs and adding this to a mixture of Low grade MAP, 10-45-0 grade amount 125 kgs, SSP, 16% P2O5 amount 38 kgs, Urea, 46% N amount 83 kgs, Kieserite, MgSO4.3H2O amount 174 kgs, ZnSO4.H2O amount 9 kgs, FeSO4.7H2O amount 16 kgs and Di Sodium Octa Borate Tetra hydrae amount 10 kgs to prepare one ton of fertiliser composition.

In fourth aspect, the invention discloses the process for preparing Potassium Nitrate based composition as described above, wherein the step of mixing further includes crushing Potassium Nitrate along with all selected source ingredients except Kieserite powder up to 100 mesh size to prepare crushed mixed powder, blending the crushed mixed powder with Kieserite powder to form a mixture, granulating the mixture of step (b) in a pan granulator using LP steam as source of heat and moisture to form green granules, drying green granules in a rotary heated surface dryer to form dry granules screening the dry granules for desired size, and cooling the screened dry granules which exhibit round shape, uniform size and uniform composition.

In fifth aspect the invention discloses the process for preparing Potassium Nitrate based composition as described above, the step of crushing includes crushing the selected source ingredients in two groups based on the desired grade of the prepared fertilizer composition, wherein Group I being Potassium Nitrate, SSP and Ferrous Sulphate and Group II being MAP, Urea, Zinc Sulphate and Disodium Octa Borate.

In sixth aspect the invention discloses the process for preparing Potassium Nitrate based composition as described above, wherein the step of granulation including maintaining the feed material temperature at around 60-70°C and moisture content of 7-8% during LP steam spraying which achieves granulation with round granules of uniform size and uniform composition.

In seventh aspect the invention discloses the process for preparing Potassium Nitrate based composition as described above, wherein the step of drying green granules in rotary dryer includes having a rotary dryer which has a shell surface heated with surrounded with heating coils whereby the heat from the shell is dissipated to the rotating granules within and the moisture content in the green granules is evaporated and driven away by co-current ambient air flow through the dryer.

In eighth aspect the invention discloses the process for preparing Potassium Nitrate based composition as described above, wherein step of drying includes evaporation to an extent that at the outlet of the dryer the material contains 1% moisture.

In nineth aspect the invention discloses a unique composition which is a Potassium Nitrate based NPK grade fertiliser composition prepared as per the method described above and which composition has a specific grade which is NPK 10-25-10, 2.5% CaO, 1.5% MgO, 2.5%S, 0.5%Zn and 0.3% Fe.

In another aspect the invention also discloses another unique composition which is a Potassium Nitrate based NPK based fertiliser composition prepared by the methods described above and having a specific grade which is NPK 12-06-24, 1.0% CaO, 4.0% MgO, 3.5%-S, 0.3%Zn, 0.3%Fe and 0.2%B.

The applicant relies upon the provisional specification filed in this application and shall be considered as part and parcel of complete specification.

The examples and embodiments are provided only for the purpose of understanding and none of them shall limit the scope of the invention. All variants and modifications as will be envisaged by skilled person are within the spirit and scope of the invention. ,CLAIMS:WE CLAIM:

1. A process for preparing Potassium Nitrate based NPK grade fertiliser composition
a. selecting Potassium Nitrate of a specific grade as a base raw material,
b. mixing with at least one or more source ingredient selected from the group which are: -
- a P2O5 source – Phosphorus Pentoxide
- a CaO source – Calcium Oxide
- a SO42 source – Sulphate Sulphur
- a N2 source – Nitrogen
- a MgO source – Magnesium Oxide
- a ZnO Source – Zinc Oxide
- a Fe source – Iron source
- a B source – Boron source

2. The process for preparing Potassium Nitrate based composition as claimed in claim 1, wherein the method includes the step of selecting Potassium Nitrate of 13-0-45 grade with an amount 225 kgs and adding this to a mixture of
a. Low grade MAP, 10-45-0 grade amount 530 kgs
b. SSP, 16% P2O5 amount 100 kgs
c. Urea, 46% N amount 40 kgs
d. Kieserite, MgSO4.3H2O amount 65 kgs
e. ZnSO4.H2O amount 15 kgs
f. FeSO4.7H2O amount 15 kgs
to prepare one ton of fertiliser composition which composition has NPK 10-25-10, 2.5% CaO, 1.5% MgO, 2.5%S, 0.5%Zn and 0.3% Fe.

3. The process for preparing Potassium Nitrate based composition as claimed in claim 1, wherein the method includes the step of selecting Potassium Nitrate 13-0-45 grade 535 kgs and adding this to a mixture of
a. Low grade MAP, 10-45-0 grade amount 125 kgs
b. SSP, 16% P2O5 amount 38 kgs
c. Urea, 46% N amount 83 kgs
d. Kieserite, MgSO4.3H2O amount 174 kgs
e. ZnSO4.H2O amount 9 kgs
f. FeSO4.7H2O amount 16 kgs and
g. Di Sodium Octa Borate Tetra hydrate amount 10 kgs
to prepare one ton of fertiliser composition which composition has NPK 12-06-24, 1.0% CaO, 4.0% MgO, 3.5%-S, 0.3%Zn, 0.3%Fe and 0.2%B.
.

4. The process for preparing Potassium Nitrate based composition as claimed in claim 1, wherein the step of mixing further includes
a. crushing Potassium Nitrate along with all selected source ingredients except Kieserite powder up to 100 mesh size to prepare crushed mixed powder,
b. blending the crushed mixed powder with Kieserite powder to form a mixture,
c. granulating the mixture of step (b) in a pan granulator using LP steam as source of heat and moisture to form green granules,
d. drying green granules in a rotary heated surface dryer to form dry granules with the help of a blower
e. screening the dry granules for desired size, and
f. cooling the screened dry granules which exhibit round shape, uniform size and uniform composition.

5. The process for preparing Potassium Nitrate based composition as claimed in claim 1 and claim 4, the step of crushing includes crushing the selected source ingredients in two groups based on the desired grade of the prepared fertilizer composition, wherein Group I being Potassium Nitrate, SSP and Ferrous Sulphate and Group II being MAP, Urea, Zinc Sulphate and Disodium Octa Borate Tetra hydrate.

6. The process for preparing Potassium Nitrate based composition as claimed in claim 1 and claim 4, wherein the step of granulation including maintaining the feed material temperature at around 60-70°C and moisture content of 7-8% during LP steam spraying which achieves granulation with round granules of uniform size and uniform composition.

7. The process for preparing Potassium Nitrate based composition as claimed in claim 1 and claim 4, wherein the step of drying green granules in rotary dryer includes having a rotary dryer which has a shell surface heated with surrounded with heating coils whereby the heat from the shell is dissipated to the rotating granules within and the moisture content in the green granules is evaporated and driven away by co-current ambient air flow through the dryer.

8. The process for preparing Potassium Nitrate based composition as claimed in claim 1 and claim 4, wherein step of drying includes evaporation to an extent that at the outlet of the dryer the material contains 1% moisture.

9. A Potassium Nitrate based NPK grade fertiliser composition prepared as claimed in claim 1 has a grade which is
NPK 10-25-10
2.5% CaO
1.5% MgO
2.5%S
0.5%Zn
0.3% Fe

10. A Potassium Nitrate based NPK based fertiliser composition prepared as claimed in claim 1 having a grade which is
NPK 12-06-24
1.0% CaO
4.0% MgO
3.5%-S
0.3%Zn
0.3%Fe
0.2%B.