Claims: A process for preparing granules of sulphur, fertilizer having sulphur and bentonite comprising of

a. initial dry mixing and blending of the powdered comprising of sulphur bentonite mixture in a blender so that a uniform distribution of each ingredient through the mix is achieved, and
b. massing and granulation of dry primary powdered particles in a coating drum using a granulation fluid, which easily vaporizes and is non-toxic, the said granulation fluid wetting the powder in its initial stage thereby forming liquid films on their surface, which creates liquid bridges at the point of contact, further surface tension and negative capillary pressure in such bridges provide a cohesive force ensuring particle adhesion.

2. The process as claimed in claim 1, wherein the bentonite selected may be calcium bentonite.

3. The process as claimed in claim 1, wherein the bentonite selected may be sodium bentonite.

4. The process as claimed in claim 1, wherein the blender may be rotary blender.

5. The process as claimed in claim 1, wherein colouring is given to the mixture in the blender by spraying the colour solution

6. The process as claimed in claim 1, wherein the granulation of milled sulphur and bentonite is done in a rotating coating drum.

7. The process as claimed in claim 1, wherein the granulation fluid is hot water spray or steam condensate at 70°C.

8. The process as claimed in claim 7, wherein hot water spray is done by atomising the water with compressed air.

9. The process as claimed in claim 6, wherein the rotating speed of the coating drum shall be generally in the range of 8-12 rpm and more specifically in the range of 9-10 rpm.

10. The process as claimed in claim 6, wherein the inclination of the coating drum shall be in the range of 30-40° from the horizontal.

11. The process as claimed in claim 6 further includes a step in which wet granules collected from coating are first dried in sun shine to reduce the moisture content to about 5% and then dried in pan type dryer to reduce the moisture content to less than 1% by blowing hot air.

12. The process as claimed in claim 11, wherein the hot air blowing is done by using air compressor which can develop pressure upto 7 kg/cm2.

13. The process as claimed in claim 11, wherein the dried product is sieved to separate 1-2 mm size granules as product size and the oversize granules and fines are recycled.

14. The process as claimed in claim 1, wherein the 95% of prepared granules are in the size range between 1mm to 2mm
, Description:FIELD OF THE INVENTION

This invention relates to a process for the production of uniformly sized micro granules of bentonite sulphur and, more precisely, relates to a novel method for producing quickly and completely water dispersible form of sulphur fertilizer in the form of spherical micro granules from milled sulphur and bentonite clay powder mixture.

The present invention provides the manufacturing process for micro granulation of milled sulphur and Bentonite mixture with high dispersion properties.

BACKGROUND OF THE INVENTION:

This invention relates to a process for the manufacture of sulphur fertilizer in micro granular form of Bentonite sulphur.

Sulphur is mainly a secondary nutrient for plants following nitrogen, phosphorus, and potassium. And it is an essential plant nutrient. Sulphur is necessary for plant growth and nutrition.

It contributes to an increase in crop yields in three different ways:
• Sulphur provides a direct nutritive value
• Provides indirect nutrient value as soil amendments, especially for calcareous and saline alkali soils
• Improves the use efficiency of other essential plant nutrients, particularly nitrogen and phosphorus.

Oil crops, legumes, forages, and some vegetables require more sulphur than phosphorus for optimal yield and quality. Usual recommendations for correcting deficiency are 25 to 50 kg S/ha for oil crops, legume, sugarcane, and some vegetable crops and 15 to 30 kg S/ha for cereal crops and silage grass. A shortage of Sulphur can cause serious reductions in crop yield and quality.

Most of the sulphur nutrient is supplied through sulphate fertilizers and present generation sulphur-containing fertilizers are mostly phosphate type often involves the incorporation of Sulphates. A disadvantage of Sulphates is that they are very mobile in the soil and easily leach out of the root zone, effectively making the Sulphate nutrient unavailable to the plants. Elemental Sulphur is not leached out of the soil as readily as sulphates. Instead, micron-sized elemental sulphur particles (e.g. with size from 1 to 200 µm) are oxidized to sulphate sulphur, which is the form utilized by the plants, by soil bacteria during the cropping season. By considering above factors elemental sulphur can therefore be considered as a slow (timed) release form of plant nutrient sulphur that is less prone to leaching out of the crops root zone. Elemental sulphur offers some additional benefits in agriculture, including acting as a fungicide against certain microorganisms, acting as a pesticide against certain soil and plant pests, assisting the decomposition of plant residues and improving phosphorus and nitrogen nutrient utilization and reducing the pH of alkaline and calcareous soils.

By considering these benefits many inventions came up with a solution of Elemental sulphur granulation but most of them dealt with liquid sulphur, which involves spraying of liquid sulphur along with a mixture of bentonite on to a rotating granulator and forming globules or pellets and pastels, and cooling them to room temperature.

But they are having so many draw backs including:

• Bigger size of particle -difficult to disperse
• Irregular shape – very low surface are.
• Low dispersion rates, on time availability to plant requirements
• Slow action of microorganisms due to granule integrity, etc.

To overcome all these draw backs we have developed a granular sulphur product using milled sulphur in form of micro granules which are having more surface area, very quick disintegration to very fine particles (less than 40 microns) in to soil, availability to the plant throughout the season.

PRIOR ARTS

So many number of patents are available on Granular sulphur manufacturing process and equipments that have been developed. But all of them discussed either granulation of liquid sulphur solution and its solidification to globules or pellets are not the subjects of present invention.

Europe patent EP2081878 A2 by Zaklady Chemiczne, filed on 20st Aug 2007 and published on Jul 29, 2009, with the title “Sulphur fertilizer and granulated sulphur fertilizer manufacturing method” discusses sulphur fertilizer, in form of globular granules or pellets consists solidified mixture of liquid sulphur, bentonite and SLS. In its solidified mixture, the fertilizer contains 60-95% of sulphur, 4-20% of bentonite, and 1-8% of SLS. In this method mixture of liquid sulphur with bentonite and SLS is splashed into the granulator at 120-150° C to form droplets, it forms a curtain of falling granules and solidified by passing air through the curtain of granules. The present invention of producing micro granular sulphur fertilizer is different from the above because the present invention does not aim at liquid sulphur or its solidification mixture to produce granular sulphur fertilizer.

US patent US 4,394,150 Explains globular granules of sulphur-bentonite fertilizer having a mixture of 88-89% of sulphur and 11—12% of bentonite and in this process the granules are formed by mixing ground down bentonite with liquid sulphur and dropping liquid mixture passed through holes in the bottom of tank containing the mixture, while drops are solidified into granules in liquid manure salt solutions and dried. Here also our invention of producing micro granular sulphur fertilizer is different from the above because it does not aim at liquid sulphur or its mixture of bentonite to produce granular sulphur fertilizer.

US patent US6331193 B1by Robin Phinney, filed on 17 Apr 1998 and published on 18 Dec 2001, with the title “Wet granulation method generating sulfur granules” presents a method of wet granulation of sulfur powder having about 99.9% particle size of -150 mesh and a binder material to form a pre-moistened mixture with moisture content of between 4% and 8% by weight and feeding pre-moistened mixture to a pan granulator containing sulfur powder. Our invention different from the above mentioned patent because it doesn’t involves-150 mesh sulphur powder and use of pan granulator.

Canadian patent CA1054821 A1 by Bob L. Caldwell, Canadian Superior Oil Ltd., filed on Sep 17, 1975 and published on May 22, 1979 titled “Granular sulfur-bentonite mixture for fertilizer” elaborates a method for manufacture of a WDG solid suspension of elemental sulphur in bentonite clay, comprising addition of 1 to 3 parts bentonite to 7 to 9 parts of molten sulphur, and mixing at 240 and 300°F., pouring the uniform mixture onto a wet thermally conductive metal plate, and to cool to a thickness of 1/4 to 2 inches, reducing size and separating granules size of minus 4/plus 14 mesh on the U.S. Standard scale.

OBJECT OF THE INVENTION

The main objective of this invention is to a manufacture a Sulphur fertilizer in the form of micro granules and with quick and complete dispersion into the soil which cannot be achieved through liquid sulphur melt granulation methods.

The object is to disclose a manufacturing process by which High dispersible sulphur fertilizer product is achieved more than that can be achieved by the conventional molten sulphur granulation processes.

The second object of the invention is that such micro granular bentonite sulphur fertilizer shall have Elemental sulphur content of more than 90% on weight basis.

Another object of the invention is to manufacture micro granular sulphur fertilizer using 40 micron or lesser micron sized milled sulphur. A further object of the invention is not to use any conventional dispersion agents and binding materials other than bentonite clay powder and hot water

One more object of the invention is to provide such micro granular bentonite sulphur fertilizer in spherical and uniformly distributed micro granular form i.e. (1mm to 2mm) so that it would be comfortable to the end user for handling and transportation as well as in field application.

One important object of the invention is that the micro granular bentonite sulphur fertilizer shall contain elemental sulphur content minimum 90%, remaining is bentonite clay powder which is an essential material that enhances the dispersion property of the granule as well as reduces the scope for catching fire.

Another object is to achieve a process which does not suggest usage of filler as the objective is to maintain higher Elemental content in the product.

The final object of the invention is to provide the micro granular bentonite sulphur fertilizer granules with a lower moisture content i.e., 1.0% moisture content.

DESCRIPTION OF THE INVENTION

The granulation process uses hot water or steam condensate at 70°C as binder instead of traditional binder solutions as granulation liquid. Atomised spray of Hot water at 70°C provides a uniform distribution and also higher diffusion rate into the powder enabling production of spherical granules of higher surface area at shorter process time. It also has a more favorable thermal balance during the drying step. Hot water forms a hot thin film on the powder particles, requiring only a small amount of extra energy for its elimination as it evaporates very easily. The first advantage of using hot water for granulation is it is an eco-friendly process and eliminates use of organic solvents. The other advantage of such hot water granulation process is higher dissolution grade due to increased surface area of the prepared granules by this method compared to conventional wet granulation process. The novel feature of this invention is manufacture of micro granular bentonite sulphur fertilizer in granular form does not involves the addition any other foreign chemical dispersion agents, binding agents except bentonite which results in trimming the purity of fertilizer as well as alteration of the soil properties. An additional important feature of this invention there won’t be any non-degradable residual accumulation in soil after nutrients take up by plants.

Thus the primary feature of the present invention is to provide a process for continuously producing bentonite sulphur fertilizer in the form of spherical micro granules without using liquid sulphur spray or its solidification which involves heavy steam consumption and operational expenditure.

Another feature of the present invention is usage 40 micron sulphur powder as feed stock which can be easily converted into sulphate form by solubilizing bacteria and availability of nutrients throughout the plant growth period.

One more feature of the present invention is that micro size of the granular fertilizer which provides more surface area which enhances availability of nutrients and quicker and complete dispersion of nutrients into soil.

This invention provides a process for manufacturing micro granular sulphur fertilizer with inventive aspects which are
1. Sulphur has been milled to 40 microns size whereas other products have micronized sulphur (1-2 microns). 40 microns is more desirable from the point of view of matching the oxidation rate of sulphur with the uptake rate by plant. Sulphur particle size when pastilles of sulphur bentonite are applied typically is around 150 microns.
2. The apparatus used is a granulating equipment that is used in the pharma industry for production of microgranules of technicals. This equipment has been used for production of sulphur bentonite microgranules. Traditionally, sulphur bentonite products are being produced by forming molten sulphur bentonite mixtures in pastilles using a rotoformer. Some of the producers are using the spray drying route. However, the particle size is 0.2-0.5 mm which is not ideal for soil application as the product is normally mixed with other granular fertilisers and then spread on the soil.
3. Sulphur, though being a hydrophobic substance, has been found to granulate in the presence of moisture/steam and bentonite. This in itself as a technological breakthrough.
4. There is wide flexibility with respect to the particle size distribution desired for the product. PSD can be varied from 0.5-1.0 mm to 3-4 mm. This is not possible with other modes of manufacture.
5. The product offers a balanced combination of optimum sulphur particle size, quick dispersion, easy-to-apply granule size, agronomic efficiency as oxidation rate matches uptake rate.

Process steps

The process is a novel process for the manufacture of Micro granular sulphur fertilizer from blended mixture of 40 micron size ground sulphur powder of 99.99% purity, and Calcium or sodium bentonite powder and steam condensate a liquid media. It does not involve liquefying sulphur powder and its solidification. It contains 90 percent of nutrient that is fully available to plant without any additional impurities. Granulation process does not require any binder solution or chemical additives for imparting binding properties to powder material to form granules. And recyclable material is very less and involves few operational steps. Final product contains round spherical granules which are easy to handle as well as field application and having reasonable crushing strength and moisture less than 1.0%. And it does not involve any reaction steps and emission of Sox or any flue gasses.

The present invention of manufacturing of micro granular sulphur fertilizer involves granulation sulphur fertilizer in form of fine round spherical granules.

Process system consists of A coating drum type granulator with hot air blower to heat up the material and a fine spray nozzle setup for spraying binder solution if any on to the powder sulphur-bentonite mixer that is blended using a blender.
Finely ground sulphur powder with size of 40 microns of 90-92 percent by weight is mixed thoroughly with 8-10 % of sodium or calcium bentonite powder by weight in blender and on to the above mixture diluted color in water solution is sprayed if any coloration to product is required.

Blended material is then fed to the rotating coating drum and Hot water or steam condensate is sprayed on to the rotating powder material inside the drum. After starting the spray, over a period of 15 to 20 minutes powder material starts forming granules, once the required size product is obtained then stop the liquid spray and collect the product. Otherwise once granules formation is observed we can simultaneously feed the powder mixture and collect product granules from top layer continuously from the coating drum. Collected product is spread in trays and kept for sun drying.

Once the moisture in the sun dried product is reduced to below 5% then the granular material is fed to Pan type drier that is designed in-house by Coromandal and is dried to moisture less than 1.0% by blowing hot air through the wet granules. The dried material is then sieved using shifter for product size of -2mm to 1 mm. Rejects recycled in the next batch of granulation.

The figure 1 illustrates the block diagram of the invention

PART NUMBER PART NAME
1 COLOR SOLUTION SPRAY
2 MILLED SULPHER
3 BENTONITE
4 RIBBON BLENDER
5 HOT WATER SPRAY
6 COATING DRUM
7 GRANULAR PRODUCT FOR SUN DRYING
8 SUN DRIED PRODUCT
9 OVER SIZE CRUSHER
10 PAN TYPE DRIER
11 DRIED GRANULAR PRODUCT
12 HOT AIR COMPRESSOR
13 SHIFTER
14 FINAL PRODUCT FOR PACKING
15 FINES RECYCLE TO COATING DRUM

The purpose of the invention is to develop a composition of sulphur fertilizer, in form of globular granules or pellets, which would contain solidified mixture of liquid sulphur and bentonite, and disperse in contact with soil moisture into sulphur molecules of much smaller size than that is in case of known fertilizers of this type.

Salient Features of the process us referred herein :-

1) Sulphur fertilizer in form of uniform spherical micro granules constituting blended mixture of Elemental sulphur and bentonite, and steam condensate, and it contains: 90-92% of milled sulphur, 8-10% of bentonite, and 1-% of moisture, or any other fortified micro nutrients. 0.01 to 0.1% of Food Color can be added to the blended material if any special color appearance is required.
2) Sulphur Fertilizer is characterized in that it contains Milled sulphur of 30 microns to 40 microns particle size.
3) Sulphur Fertilizer is characterized in that it contains calcium bentonite.
4) Sulphur Fertilizer is characterized in that it can contain sodium bentonite also.
5) Sulphur Fertilizer is characterized in that it contains bentonite in powder form.
6) Sulphur Fertilizer is characterized in that it is produced by using steam condensate or hot water as a binding medium.
7) Sulphur Fertilizer is characterized in that it we can add any additional micro nutrients or additives as per our wish..
8) Sulphur Fertilizer is characterized in that we can add any required food grade coloring agents. .
9) Sulphur Fertilizer is characterized in that it final product should contain 95% product between 1mm to 2mm only.
10) Method developed to produce micro granular sulphur fertilizer, in which milled sulphur powder is mixed thoroughly with bentonite clay powder and any additional micro nutrients and the mixture is granulated in coating drum granulator with spray nozzle set up for addition of binder solution and granules are formed. Air heater provided to maintain the material at temperature between 50-60 Deg.C
11) Coating drum is to be rotated at a specified RPM generally 8-12 and specifically in the range of 9-10 and in a particular inclination specifically 30-40 deg from horizontal.
12) Method of manufacturing is characterized in that the air blower with heating coils at the discharge will help to maintain the temperature of the material in the coating drum..

The examples, embodiments and numerals etc are given for purpose of easy understanding. All variations and modifications are within the scope and sprit of the invention