FIELD OF INVENTION
This invention relates to a sulphur fortified ammonium phosphate fertilizer. More particularly this invention relates to a process for manufacturing diammonium phosphate fertilizer fortified with sulphur.

PRIOR ART:
US 6544313 discloses a fertilizer composition that includes a plurality of particles in which the particles feature a plurality of sulfur platelets embedded within a fertilizer portion, and a method for preparing this composition in which fertilizer-containing particles are sprayed first with a molten sulfur spray, and then with a slurry containing fertilizer or a precursor thereof, followed by curing.

US 7470304 discloses a process for the manufacture of sulphur-containing fertilizers comprising the steps of: (a) mixing ammonia, phosphoric acid and water in a reactor unit to obtain an ammonium phosphate mixture; (b) introducing the mixture obtained in step (a) into a granulator unit to obtain granules, wherein a liquid phase comprising elemental sulphur is brought into contact with ammonia, phosphoric acid and water in the reactor unit in step (a) or is introduced in the granulator unit in step (b).
US 5152821 discloses a granular fertilizer prepared by coating particles of a base fertilizer, selected from orthophosphates of calcium ammonium and potassium and mixtures thereof, with: (a) a first layer comprising 1 to 5% (by weight of the total composition) of water or an aqueous solution of a salt selected from the group of sulphates and phosphates of ammonium or potassium and mixtures thereof; and (b) a second layer comprising (i) elemental sulphur and/or (ii) a supplemental micronutrient, and, if the first layer consists of water only, (iii) 0.1 to 10% (by weight of the total composition) of a salt selected from the group consisting of water-soluble sulphates and phosphates of ammonium or potassium, sulphates of metallic trace elements, and mixtures thereof.

US 3333939 discloses a process for preparing a fertilizer for use in alkaline soils comprising in combination the steps of: (a) reacting urea with phosphoric acid to form ureaphosphate; (b) mixing said ureaphosphate with ammonium phosphate to form discrete granules of the mixture; and (c) coating said discrete granules with sulfur.

US 4377406 disclose a process for the production of fluid fertilizers made from phosphoric acid, sulfuric acid, liquid anhydrous ammonia, and water.

US 4762546 discloses novel compositions and techniques for economically producing highly concentrated nitrogen-sulfur suspension fertilizers using cheap and readily available by-product ammonium sulfate or by-product sulfuric acid and ammonia in conjunction with solid, liquid, or suspension nitrogen fertilizers and suspending clay.

US 5653782 relates to a process for obtaining sulfur-containing fertilizers. According to the invention, a substrate containing fertilizer particles is heated to a temperature above the melting point of sulfur and subsequently by admixing with the sulfur, the latter is melted by the heat provided by said preheated fertilizer particles, producing a homogeneous coating on the fertilizer particles.

US5571303 discloses a particulate sulfur-based fertilizer and process of preparation thereof. The process comprises: (i) providing a first stream comprising ammonia; (ii) providing a second stream comprising a least one member selected from the group consisting of sulfuric acid, phosphoric acid and mixtures thereof; (iii) providing a third stream comprising an aqueous liquid; (iv) mixing the first stream, the second stream and the third stream to provide a liquid reaction mixture; (v) feeding the liquid reaction mixture to a mixer; (vi) feeding a fourth stream comprising molten sulfur to the mixer; (vii) maintaining a pressure drop across the mixer of at least about 200 kPa to form a homogenized melt of sulfur-based fertilizer; and (viii) solidifying the homogenized melt to produce the particulate sulfur-based fertilizer.

The sulphur institute website www.sulphurinstitute.org disclose the basic background of this art.

Sulphur is necessary for plant growth and nutrition. Following nitrogen, phosphorus, and potassium, sulphur is an essential plant nutrient. It contributes to an increase in crop yields in three different ways: 1) it provides a direct nutritive value; 2) it provides indirect nutritive value as soil amendments, especially for calcareous and saline alkali soils; and 3) it improves the use efficiency of other essential plant nutrients, particularly nitrogen and phosphorus.

Most crops remove 15 to 30 kg for sulphur per hectare (S/ha). Oil crops, legumes, forages, and some vegetables require more sulphur than phosphorus for optimal yield and quality. Plants contain as much sulphur as phosphorus, with an average content of approximately 0.25%. Usual recommendations for correcting deficiency are 15 to 30 kg S/ha for cereal crops and silage grass; and 25 to 50 kg S/ha for oil crops, legume, sugarcane, and some vegetable crops.
Sulphur deficiency is becoming severe in agricultural production in recent years because of the following reasons

More sulphur is removed from the soil as a result of an increase in agricultural production using enhanced fertilizers, intensifying cropping systems, promoting high-yield crop varieties, and improving irrigation. Not only the sulphur is removed but less sulphur gets added to the soil due to the increasing proportions of sulphur-free fertilizers, such as urea, diammonium phosphate (DAP), and potassium chloride; and decreasing use of traditional organic manures and sulphur-containing fertilizers, such as single super phosphate and ammonium sulphate, and sulphur-containing pesticides. Further lower sulphur dioxide emissions are reducing atmospheric availability, one of the important historical sources of sulphur for agriculture around industrial areas.

Both the yield and quality of crops grown on sulphur-deficient soils are reduced. Sulphur fertilizer can increase crop yields and quality and result in significant economic returns to producers. Sulphur fertilization also improves overall fertilizer efficiency.

Most sulphur-containing fertilizer materials generally can be divided into two groups: 1) fertilizers containing sulphate, and 2) fertilizers containing elemental sulphur. Sulphate-containing fertilizers provide most of the fertilizer sulphur applied to soils. The most significant and popular sources are ammonium sulphate, single superphosphate (SSP), potassium sulphate, potassium magnesium sulphate, and gypsum. These materials have the advantages of supplying sulphur primarily as a component of multi-nutrient fertilizers in a sulphate form that is immediately available for plant uptake. A disadvantage of sulphate is that they are very mobile in soil and leachable, effectively making the sulphate nutrient unavailable to the plants.. Elemental sulphur-containing fertilizers are the most concentrated sulphur carriers. However elemental sulphur has to be oxidized into sulphate form such as granular sulphur-bentonite to improve the effectiveness of elemental sulphur. The advantage of using elemental sulphur is that it is not leached out of soil as are sulphates. Further elemental sulphur offers some additional benefits in fertilizers as it acts as a fungicide against certain micro organism, as a pesticide against certain soil and plant pests. It assits the decomposition of plant residue and it improves phosphorous and nitrogen utilization and reduces the pH of alkaline and calcareous soil. It is therefore more advantageous to have sulphur present as elemental sulphur in fertilizers.

The above cited patents and literature materials available openly disclose various process for the preparation of sulphur enhanced fertilizers by incorporation of sulphur into the fertilizers. The sulphur introduced in the fertilizers are either in sulphate form, or elemental sulphur in molten/liquid/powder form. The incorporation of sulphur as sulphate in to the fertilizer results in leaching of sulphate into the soil thereby effectively making the sulphate nutrient unavailable to the plants. Further the incorporation of molten/liquid elemental sulphur into the fertilizer is cumbersome and laborious process due to hazardous nature of molten/liquid elemental sulphur as it causes severe burns on improper handling, the Combustion product, SO2 is highly toxic, Degassing in storage creates explosive vapors, Degassing in storage creates toxic atmosphere, etc. Some of the prior arts discussed above deals with coating of sulphur onto the fertilizer which prevents a uniform distribution of ammonium sulphate and sulphur into the soil. Hence there exists a need to develop a process of preparing sulphur enhanced fertilizers devoid of above discussed drawbacks.

OBJECT OF INVENTION

The main object of the present invention is to overcome the problems encountered in the prior art by adopting powdered elemental sulphur safely in the process of preparation of sulphur fortified diammonium phosphate fertilizer without the problem of combustion and thereby overcoming the usage of hazardous molten/liquid elemental sulphur.

Another object of the present invention is to develop a process for manufacturing di ammonium phosphate fertilizer fortified with sulphur using a scrubber, reactor and a granulator.

Another object of the present invention is to incorporate either elemental sulphur or sulphur bentonite in diammonium phosphate to form sulphur fortified ammonium phosphate fertilizer.

Another object of the invention is to grind the elemental sulphur into phosphoric acid in a scrubber unit in a step prior to the step of introducing ammonia thereby eliminating the problem of dust and risk of explosion due to combustion of sulphur in air and thereafter granulating the mixtures.

Another object of the invention is to add ground elemental sulphur into phosphoric acid in a scrubber unit in a step prior to the step of introducing ammonia thereby eliminating the problem of dust and risk of explosion due to combustion of sulphur in air and thereafter granulating the mixtures.

Another object of the invention is to introduce the sulphur as sulphur bentonite and contacting the sulphur bentonite with ammonium phosphate in a granulator to obtain granules of ammonium phosphate fortified with sulphur.

Another object of the invention is to avoid the use of molten sulphur in the process as is known in the prior art. Molten sulphur is more difficult to handle.

Another object of the present invention is also an attempt to limit the use of water in the manufacturing process but simultaneously overcome the disadvantage of formation of solid ammonium phosphate generally suffered in processes using lesser amounts of water,

Another object of the invention is to eliminate the use of liquid sulphur or molten sulphur in the process.
Another object of the present invention is to develop a safe and eco friendly process utilizing elemental sulphur.

Yet another object of the present invention is to utilize the developed fertilizer for agricultural purpose.

SUMMARY OF THE INVENTION

The invention relates to a method of preparing sulphur fortified diammonium Phosphate (DAP) fertilizer. The method comprises of embedding solid sulphur in elemental form into diammonium phosphate. The embedding of sulphur is by contacting sulphur bentonite with ammonium phosphate in a granulator to form sulphur fortified diammonium phosphate. The embedding can also be carried out by grinding plurality of elemental sulphur in phosphoric acid to form a slurry in a scrubber and thereafter contacting ammonia with the slurry to form fortified diammonium phosphate or by adding ground elemental sulphur in phosphoric acid to form a slurry in a scrubber and thereafter contacting ammonia with the slurry to form fortified diammonium phosphate. The composition of the sulphur fortified diammonium phosphate fertilizer comprises of 18% nitrogen, 46% P2O5 and 4% sulphur i.e., 18-46-0-4.

DESCRIPTION OF INVENTION
The invention relates to a process for producing sulphur fortified diammonium Phosphate (DAP) fertilizer. The three primary nutrients essential for crop growth are Nitrogen (N), Phosphorus (P) and Potassium (K). Diammonium Phosphate (DAP) is
a phosphatic fertiliser that is used widely in India. The composition of DAP is 18-46-0 which implies that it contains 18% N and 46% P205. It is reported that the Indian soils are deficient in sulphur (S) which is fourth most important nutrient for crops after N.P, and K. The present invention aims to add elemental sulphur (ES) to DAP without altering its basic composition with respect to N and P in order to improve the performance of DAP in sulphur deficient soils. The formulation of the product is 18-46-0-4 which implies that it is 18-46-0 DAP with 4% S. The product formulation was determined by available scope for adding elemental sulphur in the place of inert filler used in the typical DAP process so as to not alter the N and P205 percentages. Since typically 40 kg of filler is used per ton of DAP, the upper limit ES in the product is 4% S.

The typical DAP process as shown in Figure 1 involves the reaction of ammonia and phosphoric acid in a pipe reactor. The resulting slurry is sprayed inside the granulator on a rolling bed of crushed DAP granules which get converted to larger size granules through coating and agglomeration. The granules leaving the granulator are dried in the dryer and then screened to obtain the product fraction. The oversize fraction is crushed and recycled to the granulator along with the fines for use as seed material for further granulation with the pipe reactor slurry. The product is cooled and sent for packing. The gases from the granulator, dryer and cooler are sent to the scrubbers for trapping dust and ammonia before being released into the atmosphere.

The main challenge faced for manufacturing DAP with 4% S is the addition of ES into the typical DAP production process in a safe manner as the main hazards associated with handling of ES are dust explosions and fires. Earlier patents are devoted to production of Ammonium Phosphates (AP) containing ES wherein the grade of product is different from DAP with 4% S.

The present invention relates to a process for producing diammonium Phosphate (DAP) fertilizer incorporating maximum of 4% sulphur in elemental form. The basic principle behind the process is as follows. There is scope to add around 40 kg of inert material called filler per ton of DAP (which is equivalent to 4% by weight) to achieve the desired grade of 18% Nitrogen and 46% P205 viz. 18-46-0. This filler material can be sand, clay, fly ash, gypsum etc. In some cases the phosphoric acid used for the manufacture of DAP itself contains a high level of inert solids (mainly gypsum) which fulfills the stoichiometric requirement of filler and therefore no external addition is required. Keeping this in mind, it is attempted to produce a grade of DAP using elemental sulphur in place of filler. The elemental sulphur is also an inert material and therefore can be considered to be a type of filler.

The present invention relates to a process for manufacturing diammonium ' phosphate fertilizer fortified with sulphur obtained from either elemental sulphur or sulphur bentonite using a scrubber, reactor and a granulator.

In the process for manufacturing diammonium phosphate fertilizer fortified with sulphur, the use of powdered elemental sulphur even though safer than molten/liquid elemental sulphur, leads to dust and risk of explosion due to combustion of sulphur. But in the present invention, powdered elemental sulphur is safely used without the problem of combustion by grinding the elemental sulphur with phosphoric acid or adding ground elemental sulphur with phosphoric acid in a scrubber unit as sulphur gets completely binded with phosphoric acid without leaving any dust to the environment thereby eliminating the risk of combustion.

As per the invention, there has been envisaged more than one way of introducing the elemental sulphur to embed sulphur into diammonium phosphate. The Sulphur may be added in the system, used in preparing the fertilizer product in two different ways. The system generally as known in prior art involves reactor and a granulator. The conventional system may be used for the processes as envisaged in the invention. The reference of the word "reactor", "granulator" will be understood by the skilled person in the art knowing the preparation of fertilizer products more specifically the preparation with ammonium phosphates.

1. The sulphur may be introduced, in the scrubber portion, as ground or unground solid sulphur to the scrubber liquor, which is fed to the reactor. As such the first method adopts the introduction of sulphur in the reactor.

2. Alternatively the sulphur may also be introduced in the granulator, as ground or unground solid sulphur to recycle belt transferring material, i.e., the recycled ammonium phosphate fed to granulator for the purpose of granulating. The introduction at this stage involves the step of granulating the introduced sulphur with the ammonium phosphate entering from the reactor into the granulator.

The two modes of addition of elemental sulphur are depicted in Figure 1 The numerals are given below for understanding the figure 1. The figure 1 depicts the two flowpaths, one of which may be selected as described in the above two methods. It is very clear from figure 1 that conventional system can be used for working the invention with the two methods as described in the previous para.

Reference numerals in Figure 1.
1. Sulphuric acid.
2. Phosphoric acid
3. Sulphur Granule
4. S-Bentonite
5. Sump Effluent
6. Pre Scrubber
7. Sump Effluent tank
8. Sulphur Mixing tank
9. Pipe reactor feed tank
10. Dust and fumes to pre scrubber
11. Granulator
12. Pulveriser
13. Conveyor
14. Dust and Fumes to scrubber
15. Dryer
16. Screen
17. Pulveriser
18. Dust and fumes to scrubber
19. Cooler
20. Product

In one of the preferred embodiment the process for manufacture of diammonium phosphate fertilizer fortified with sulphur comprises of grinding the elemental sulphur or adding ground elemental sulphur in phosphoric acid to obtain homogeneous slurry containing micro particles of sulphur equally dispersed in phosphoric acid. The obtained slurry is then mixed with ammonia in a reactor, preferably a pipe reactor, but not limited to pipe reactor, to obtain sulphur fortified diammonium phosphate fertilizer. The dispersed sulphur does not precipitate easily as it is in the micronized form and thereby available homogenously distributed in the prepared ammonium phosphate based fertilizers.

In another preferred embodiment the process of manufacturing of diammonium phosphate fertilizer fortified with sulphur comprises of adding sulphur bentonite to the recycle stream transferring material to the granulator so that the sulphur bentonite particles get incorporated in the DAP granules during the granulation process in the granulator.

The first method for preparing a fertilizer product of di ammonium phosphate embedded with elemental sulphur comprises the step of grinding a plurality of elemental sulphur in phosphoric acid or adding ground elemental sulphur in phosphoric acid to form a slurry which will be introduced in the scrubber unit. This will be carried with the scrubber liquor into the reactor unit. In the reactor unit ammonia is made to contact with the said slurry so introduced into the reactor, allowing the elemental sulphur to disperse and embed itself into the ammonium phosphate thereby forming fortified di ammonium phosphate in the reactor. This is then further introduced into a granulator to form granules of fortified di ammonium phosphate. The granulator performs a role of conventional granulator for the purpose of sizing, shaping etc. The scrubber unit used in method 1 may be any device as is known in conventional system. The reactor unit used in method 1 may be any device known in conventional system wherein the ammonia is reacted with the slurry comprising elemental sulphur ground into phosphoric acid. The reactor unit is preferred to be a pipe reactor.

In the second method, the introduction of elemental sulphur comprises the step of, contacting the sulphur bentonite with ammonium phosphate at a stage where the process is reaching the granulator unit to obtain the fortified granules of di ammonium phosphate.

The granulator unit used in method 1 or 2 is any device to obtain granules of mixtures introduced into the device to form the granules as desired of the mixed product, the desired fertilizer product of the granule size so demanded.

The invention aims to prepare sulphur containing di-ammonium phosphate fertilizer granules enriched with elemental sulphur and as per the invention a maximum of 4 % of sulphur in elemental form is incorporated in diammonium phosphate.

As per the invention the composition of diammonium phosphate fortified with sulphur is 18% Nitrogen and 46% P205 and 4% sulphur viz. 18-46-0-4

The novelty of the invention lies in using the solid form of sulphur, ground or unground safely in the process of manufacturing ammonium phosphate based fertilizer, thereby achieving the desired available level of sulphur in the end prepared product but not using either molten sulphur or sulphur slurry in water as is known or practiced in the prior art. This is one of the novel aspects exhibited in the process disclosed in the invention. The other novelty lies in adding the elemental sulphur into phosphoric acid in the scrubbing unit of the system prior to introducing into reactor, thereby eliminating spraying of molten sulphur or sulphur slurry into granulator which contains ammonium phosphate/water mixture as is known and practiced in prior art.

The invention also differs from all of the prior art, in the sense that the prior art liquid sulphur slurry or molten sulphur is added directly to the reactor containing ammonia, phosphoric acid and water. This step is eliminated in the invention.
The invention also differs from the prior art in one another way in that in prior art the liquid sulphur slurry or molten sulphur is added directly to the granulator containing ammonium phosphate. It is not done so in the invention.

As such the invention does not practice any of the teaching or methods as described in any of the previous art but instead has achieved an novel but simple method of introducing the elemental sulphur in ground or unground form into phosphoric acid in the scrubbing section of the reactor itself. In this manner the issues relating to handling of solid sulphur is well within control and the method 1 as described herein is unique and novel. Alternatively the invention also describes another method wherein sulphur bentonite is introduced into granulator unit containing di ammonium phosphate. Either way the method 1 or method 2 herein above described are substantially different from all of the prior art, and may be though simpler than prior art, which means that the invention not only discloses a new process it is further advantageous as being a simpler process.

The invention relates to a fertilizer product which is fortified with maximum of 4% elemental sulphur thereby rendering the fertilizer product as a safe and eco friendly product. With the elemental sulphur used in the invention there is no opportunity of leaching of sulphates into the soil thereby lessening the acidity of the soil so the fertilizer product as envisaged and prepared as per the invention will not only benefit the yield productivity immediately during the use of the product in the soil but due to the existence of sulphur only in the elemental form, the product will render safe maintenance of nutrient level in the used site also, even if the fortified product is used repeatedly for enhancing yield time and again in the same site over a long term. The invention is not limited to the percentage of the mentioned sulphur and ought to be understood as is known to skilled persons in the art. The invention ought not be restricted to the percentage disclosed herein which is made for the purpose of understanding only. The invention lies in the process and not in the percentage so disclosed for the scope of the invention. The invention uniquely exhibits the character of supplying the demanded need of nutrient of the soil for bettering the yield, by providing the required sulphur to the soil for the purpose of achieving better yield and simultaneously not leaching to acidify and deteriorating the soil in the site of use. As such the invention is useful for improving the yield which may be used with minimum adverse effect on the biodiversity as the soil is not deteriorating due to the product used in the soil.

The invention as such is for fertilizer product which is ammonium phosphate based fertilizers fortified with elemental sulphur, which uniquely improves the yield but does not deteriorate the soil.

In one aspect of the process, crushed sulphur bentonite containing 90% S and 10% bentonite was added to the recycle stream transferring material in a typical DAP process to the granulator so that the sulphur bentonite particles get incorporated in the DAP granules during the granulation process. The novelty of this process arises from the use of sulphur bentonite as a source of elemental sulphur rather than the pure solid sulphur used by others.

In another aspect of the process, sulphur mixed with bentonite powder was crushed and added to the recycle stream transferring material in a typical DAP process to the granulator so that the sulphur particles get incorporated in the DAP granules during the granulation process. Bentonite is an inert material and novelty of the process arises from the use of bentonite to suppress the explosive nature of sulphur dust during crushing and handling.

In another aspect of the process, crushed sulphur powder was added to the pipe reactor tank of a typical DAP process to form a slurry with the phosphoric acid/scrubber liquor and this slurry was then reacted with ammonia in a pipe reactor as in a typical DAP process to obtain diammonium phosphate granules in the granulator fortified with sulphur. The novelty of the process arises from the addition of 40 kg of sulphur per ton of DAP through the pipe reactor tank.

In another aspect of the process, solid sulphur was added in a continuous manner to a tank containing phosphoric acid/scrubber liquor and ground in situ using a high shear mixer. The slurry produced through wet grinding of sulphur was added continuously to the pipe reactor tank and the resulting slurry from the pipe reactor tank was reacted with ammonia in a pipe reactor as in a typical DAP process to obtain diammonium phosphate granules in the granulator fortified with sulphur. The novelty of the process arises from grinding of sulphur in a liquid medium using a single high shear mixer in a continuous process and addition of 40 kg of sulphur per ton of DAP through the pipe reactor tank.

In one of the preferred embodiment the present invention shall disclose a method of preparing sulphur fortified diammonium phosphate granules comprising embedding sulphur in elemental form into diammonium phosphate characterized in that the
sulphur is in solid form. As per the invention the embedding means contacting sulphur bentonite with ammonium phosphate in a granulator to form sulphur fortified diammonium phosphate. In accordance with the invention the embedding means adding ground elemental sulphur in phosphoric acid to form a slurry in a scrubber and thereafter contacting ammonia with the slurry to form fortified diammonium phosphate. According to the invention the embedding means grinding plurality of elemental sulphur in phosphoric acid to form a slurry in a scrubber and thereafter contacting ammonia with the slurry to form fortified diammonium phosphate.

As per the invention the addition of eiementaf suiphur into phosphoric acid is done continuously thereby achieving a continuous process as envisaged in the invention. The process of preparing sulphur fortified diammonium phosphate fertilizer in the present invention by continuous process achieves higher yield, consistent product quality, less intervention and thereby reduced efforts, cost and waste. As per the invention the sulphur bentonite used for the method of preparing sulphur fortified diammonium phosphate granules may be crushed sulphur bentonite containing 90% S and 10% bentonite or mixture of crushed sulphur and crushed bentonite powder.

In another preferred embodiment the present invention shall discloses an ammonium phosphate fertilizer granules with diammonium phosphate enriched with elemental sulphur, wherein the composition has of maximum 4% sulphur. As per the invention the diammonium phosphate composition further comprises 18% nitrogen, 46% P2O5 and 4% sulphur i.e., 18-46-0-4.

Example 1
DAP fortified with ES was produced in the pilot plant on 14th May 2009 by adding bentonite sulphur to the recycle stream. The analysis of the product was as follows: 18.1% N, 47.1% P205, and 4.1% ES. Mole ratio of the product was 1.95 and the crushing strength 1.5 kg/granule. The size fraction between 1 mm and 4 mm was 88.2%. 0.4 ton of product was collected.

Example 2

DAP fortified with ES was produced in the pilot plant on 23rd May 2009 by crushing a mixture of sulphur and bentonite and adding to the recycle stream. The analysis of the product was as follows: 18% N, 46.2% P205, and 4.08% ES. Mole ratio of the product was 1.98 and the crushing strength 1.7 kg/granule. The size fraction between 1 mm and 4 mm was 96.7%. 8 ton of product was collected.

Example 3
DAP fortified with ES was produced in the pilot plant on 5th June 2009 by adding crushed sulphur to the pipe reactor tank. The analysis of the product was as follows: 18.2% N, 46.9% P205, and 4.6% ES. Mole ratio of the product was 1.97 and the crushing strength was 2.0 kg/granule. The size fraction between 1 mm and 4 mm was 92.8%. 1.7 ton of product was collected.

Example 4
DAP fortified with ES was produced in the pilot plant on 5th November 2009 by grinding solid sulphur in scrubber liquor with a high shear mixer and adding the slurry continuously to the pipe reactor tank. The analysis of the product as was follows: 18.6% N, 45.9 % P205, and 6.72% ES. Mole ratio of the product was 1.91 and the crushing strength 2.1 kg/granule. 2.0 ton of product was collected.

WE CLAIM:

1. A method of preparing sulphur fortified diammonium phosphate granules comprising embedding sulphur in elemental form into diammonium phosphate characterized in that the sulphur is in solid form.

2. The method as claimed in claim 1 wherein embedding means contacting sulphur bentonite with ammonium phosphate in a granulator to form sulphur fortified diammonium phosphate.

3. The method as claimed in claim 1 wherein embedding means grinding plurality of elemental sulphur in phosphoric acid to form a slurry in a scrubber and thereafter contacting ammonia with the slurry to form fortified diammonium phosphate.

4. The method as claimed in claim 1 wherein embedding means adding ground elemental sulphur in phosphoric acid to form a slurry in a scrubber and thereafter contacting ammonia with the slurry to form fortified diammonium phosphate.

5. The method as claimed in claim 2 wherein the said sulphur bentonite is crushed sulphur bentonite containing 90% S and 10% bentonite

6. The method as claimed in claim 2 wherein the said sulphur bentonite is a mixture of crushed sulphur and crushed bentonite powder

7. An ammonium phosphate fertilizer granules with diammonium phosphate enriched with elemental sulphur, wherein the composition has of maximum 4% sulphur.

8. The fertilizer as claimed in claim 7, wherein the diammonium phosphate composition further comprises 18% nitrogen, 46% P205 and 4% sulphur i.e., 18-46-0-4.