NZ617022B2 - Improvements in and relating to the manufacture of granular material - Google Patents

Abstract

grinding apparatus for finely grinding material and for granulating that material is disclosed. The apparatus includes a chamber (2), grinding means (3c) and pelletising means (4). The grinding means (3c) and pelletising means (4) are housed within the chamber (2). The grinding means (3c) are adapted to both grind the material to effect finely ground material particles and apply pressure to subsequently compress the finely ground material particles into granules via the pelletising means (4). One or both of the grinding means (3c) and the pelletising means (4) are configured to maximise the residence time of the material in contact with the grinding means (3c) to effect the finely ground material component to produce granules formed via the pelletising means in a single-pass, one operation grinding and pelleting process. The granules formed include a fine to superfine particle portion of fine particles in the range of less than 75 micron and less than 45 micron in size, respectively. Granules of material and a method of manufacturing granules of material are also disclosed. ted to both grind the material to effect finely ground material particles and apply pressure to subsequently compress the finely ground material particles into granules via the pelletising means (4). One or both of the grinding means (3c) and the pelletising means (4) are configured to maximise the residence time of the material in contact with the grinding means (3c) to effect the finely ground material component to produce granules formed via the pelletising means in a single-pass, one operation grinding and pelleting process. The granules formed include a fine to superfine particle portion of fine particles in the range of less than 75 micron and less than 45 micron in size, respectively. Granules of material and a method of manufacturing granules of material are also disclosed.

Description

Patents Form No. 5 Fee No. 4: $250.00 IPSPEC Ref: 125-4140NZ PATENTS ACT 1953 COMPLETE SPECIFICATION IMPROVEMENTS IN AND RELATING TO THE MANUFACTURE OF GRANULAR MATERIAL After NZ Patent Appln No. 603241 Dated: 25 October 2012 I ROBERT HAMILTON HALL, a New Zealand citizen, of 2155 State Highway 2, RD6, Te Puke, New Zealand, do hereby declare this invention to be described in the following statement: IMPROVEMENTS IN AND RELATING TO THE MANUFACTURE OF GRANULAR MATERIAL Technical Field This invention relates to improvements in and relating to the manufacture of granular material.

Particularly, the invention relates to the method and apparatus for finely grinding materials and for producing pellets for particular applications. An application used to example the apparatus and pellets produced, relates to the manufacture of soil treatments.

In relation to the application of manufacturing soil treatments, this invention is directed to providing a substantially improved apparatus for finely grinding soil treatment components to achieve very fine particles and increase the available surface area of selected soil treatment components when applied in to and on to the soil.

The apparatus enables selected soil treatment components to be either or both finely ground separately and in combination to achieve fertiliser compositions tailored to meet specific requirements of soils to which the compositions are applied. In addition, the apparatus enables selected soil treatment components to be finely ground such that fertiliser compositions produced include soil treatment components having a selected range of particle sizes and in preferred ratios tailored to meet specific requirements of soils to which the compositions are applied.

Further, the soil treatment composition is manufactured in a granular form for ease of handling, storage, transportation and application on to and in to the soil.

It is envisaged the invention will be applicable to any situation, for example agricultural, horticultural, forestry, commercial, industrial or domestic situations where materials are required to be finely ground and pelletised.

Therefore, the invention may have applications outside the field of soil treatment compositions in granular form. Accordingly, the grinding apparatus may be adapted for grinding/pelletising materials other than fertiliser components.

Background Art The production of granules from compressed material occurs in a number of industries and the end products may be used as animal foodstuffs, combustible materials and so forth.

Different methods of granule production use various apparata. One such method involves the production of granules by means of pelletising machines. There are various types of pelletising machines.

Die pellet mills (of the roller and die type) have been used for the production of granular products for many years. Such pelletising apparata are typically referred to as flat die pellet mills and ring die pellet mills. Typically, two types of rollers are employed in such mills.

These are known as flat and tapered rollers. The die itself may be a flat plate or an annular ring.

Via this method, the granules are produced by rollers rotating over a surface, or a surface rotating under rollers. The surface is perforated with apertures of a specific size and length.

The action of the rollers against the surface (die) "presses" the material to be granulated through the surface (die). The size of the apertures and the length equating to the compression zone, result in a granule of a particular size, length and crush strength.

Granular materials have a number of realisable advantages over powdered materials in that the former are easier to handle, store, transport and use/apply. These advantages are particularly relevant to fertiliser compositions in granular form.

However, in using such pelletising apparatus for the manufacture of fertiliser granules, it is to be noted that the fertiliser material is often simply pressed into the granular form. The original fertiliser composition may therefore be comprised of differently sized particles of the soil treatment components used in the fertilser composition.

As such, granules formed from such fertilser compositions are less likely to be tailor-made in respect of particle distribution, size and surface area, as may be required to suit the soils to which the fertilisers are applied. Further, whilst various applications may be tailored with respect to the dispersal as fast, slow, medium release products over time, they are typically less tailored in respect of particle distribution, size and surface area, in order to suit climatic conditions as required.

In any agricultural, horticultural, forestry, commercial, industrial or domestic situation where at least optimal growth of vegetation is required or desired a number of factors interplay. Not the least of such factors is soil type/structure and nutrient availability. Soil structure has a major influence on water and air movement, biological activity, root growth, seedling emergence and plant retention. Soil structure is determined by how individual soil granules clump and thus the arrangement of soil pores between them.

Soils also differ in nutrient profile. Accordingly, fertilisers are routinely applied to soils to achieve the nutrient profile desired to sustain plant growth for harvest and/or to provide nutrients to grazing stock animals.

However, whilst fertilisers may be applied to meet nutritional needs of plants and for addressing the nutrient profile of the soil, such applications can lead to the problem of over- fertilisation which is primarily associated with the use of artificial fertilisers and results from the massive quantities applied and the destructive nature of chemical fertilisers on soil nutrient holding structures. The high solubilities of chemical fertilisers also exacerbate their tendency to degrade ecosystems For these reasons, it is important to know the soil type, the nutrient content of the soil and nutrient requirements of the crop, so that desired outcomes may be carefully balanced with the application of soil conditioning and/or fertiliser products. By careful monitoring of soil, climatic conditions and crop requirements, wastage of expensive fertilisers and potential costs of cleaning up any pollution created can be avoided.

Many fertilisers produced do not balance out such considerations, particularly as regards particle size, particle surface area and particle distribution of the soil treatment components and how granular fertilisers may be tailor-made to respond to differing requirements in different soils in different regions across different countries.

There are also problems associated with storage and application of some soil treatment products and fertilisers. For example, fine elemental sulphur is both explosive and a health hazard.

Elemental sulphur is an important agronomic nutrient; although, fine elemental sulphur is required to be agglomerated in order to be applied. Similarly however, too much sulphur has less beneficial effects when, for example, it is in the form of soluble sulphate that ends up in runoff into waterways polluting local waterways and groundwater each year. The use of elemental sulphur means that the run-off from sulphate into waterways is able to be reduced by between 48-90%.

Nitrogen fertilisers in some weather or soil conditions can cause emissions of the greenhouse gas, nitrous oxide (N O). Ammonia gas (NH ) may be emitted following application of inorganic fertilisers, or manure or slurry; and ammonia can also increase soil acidity (lowering of soil pH). Excessive nitrogen fertiliser applications can also lead to pest problems by increasing the birth rate, longevity and overall fitness of certain pests. In addition, while nitrogen is an important agronomic nutrient, much of the unused nitrogen ends up in waterways.

Phosphorus is essential for the division of cells at the growth points of the plant roots underground, as well as at the growth points of plants above the ground. If the plants take up too little phosphorous, they grow slowly and remain small, and the ripening of especially grain seeds is slowed down. Too much phosphorous in the soil or too much of it added by way of fertiliser is not really harmful for plant growth, but it is a waste of money, as not only sulphate but also phosphate represents a significant economic loss for farmers and countries as a whole with both being applied to the extent that the lost nutrients in runoff ultimately pollute and damage the environment.

An alternative phosphate fertiliser to superphosphate is reactive rock phosphate (RPR). There are many grades of rock phosphate available around the world. The agronomic value of rock phosphate is dependent on the following parameters: total phosphorus pentoxide (P O ) content, particle size distribution, and solubility.

Fine grinding of fertiliser/soil treatment components is a way to maximise availability of the fertiliser/soil treatment components of a fertiliser composition for plants. For example, fine grinding has been used as a method to increase the reactivity of phosphate rock. Grinding provides ‘fresh’ particle surfaces, increases geometric surface area, and increases solubility measurements. The problem with finely ground rock phosphate is fine dust and the cost of fine grinding.

Further, frequently, fine grinding of the components is undertaken at a separate stage to the subsequent pelletising of the fertiliser compositions. This typically requires at least two separate processes and apparata; one, to grind the fertiliser soil treatment components and another, to produce the final fertiliser composition (from a mixture of ground soil treatment components) in to a granular form.

It would instead be preferable to have a single apparatus capable of: 1) Finely grinding soil treatment components to pre-determined particle sizes and having preferred surface areas, 2) Mixing the soil treatment components together in preferred ratios and to effect preferred particle distributions; and also 3) Producing pellets/granules of preferred sizes and crush strengths for application to particular soils.

While the present invention has a number of potentially realisable applications, it is in relation to problems associated with existing soil treatment and fertilising systems and the methods of manufacturing them, that the present invention was developed.

More specifically, it was with regard to the issues of providing a method of grinding treatment components to specific particles sizes and having particular distribution profiles and surface areas within soil treatment compositions – preferably in granular form - so the treatment compositions are more appropriately tailored to specifically suit the specific application, soil conditions and climatic conditions, including temperature.

It was also developed with safety and health issues typically associated with such systems, along with addressing environmental concerns relevant to fertiliser applications that the present invention was developed.

Finally, it was having regard to the need to provide a treatment system that would easily disperse in the soil, provide the desired effect, had sufficient compressive strength to ensure that the product did not break-up during storage, transport and handling and that would minimise waste of product when applied.

It would be useful therefore, to have a process for manufacturing granular fertiliser products comprised of varying soil treatment components in relevant soil treatment compositions for application on to and/or in to soils that: 1. Could finely grind fertiliser components to preferred particle sizes, surface areas and quantities; 2. Could produce granular fertilisers tailor-made to specifically suit the specific application, soil conditions and climatic conditions including temperature; and 3. Considered and improved on safety and health issues of existing systems; and 4. Was effective at mobilising nutrients and/or soil enhancing components so that good plant growth could be achieved with lower nutrient densities; and . Effected less wastage of nutrients and/or soil enhancing components through run- off, air dispersal and so had regard to environmental concerns; and 6. Minimised the build-up of potentially toxic products in soils and plants; and 7. Released nutrients at a determined, more consistent rate, helping to avoid boom- and-bust patterns; and 8. Helped, where applicable, to retain soil moisture, reducing the stress to plants and soil structures due to temporary moisture stress; and 9. Contributed where appropriate to improving the soil structure; and . Minimised the possibility of "burning" plants with concentrated chemicals due to an over-supply of some nutrients, or nutrients in specific forms; and 11. Provided a more cost effective alternative to present systems employed; including costs of handling, transportation and application costs, and 12. Provided a consistent product, so that accurate application of nutrients to match soil type and plant production was possible.; and 13. Would be easy to use.

It would therefore be advantageous to have an invention that offered at least some, if not all, of the potential advantages of the above proposed means for manufacturing soil treatments. It is therefore an object of the present invention to consider the above problems and provide at least one solution which addresses a plurality of these problems.

It is another object of the present invention to at least provide the public with a useful choice or alternative system.

Further aspects and advantages of the present invention will become apparent from the ensuing description which is given by way of example only.

It should be appreciated that variations to the described embodiments are possible and would fall within the scope of the present invention. It is a therefore, a further object of the present invention that whilst the grinding apparatus is described with reference to grinding soil treatment components to produce granular fertilisers, the grinding apparatus is also relevant for use in a number of other applications where fine grinding of material is required and resultant products are preferably pressed into granular form.

Disclosure of Invention The present invention is directed to improved grinding and pelletising apparata for use with materials where it is preferable that the material is firstly ground to finer particles, particularly where a pre-determined proportion of the particles are very finely ground, prior to formation of the pellets/granules.

For the purpose of the present invention, the term “pelletising apparatus”, including the term “pellet mill” shall mean and include any apparatus adapted to grind any material as required for any pre-determined application, where the grinding aspect facilitates the production of material particles having a preferred size or sizes, surface areas and distribution; and the apparatus also includes means to form and/or compact into granules/pellets, such material to facilitate ease of handling, storage, transportation, application and subsequently dispersion of the contents of the pellet/granule when required. It should therefore be appreciated that the terms pelletising apparatus and pellet mill are not intended to limit the scope of the present invention.

Typically, a pellet mill, or pellet press, is used to create pellets or granules from powdered material. Pellet mills are typically used to combine small materials into a larger, homogeneous mass, rather than break large materials into smaller pieces. As such these pelletising machines include rollers that operate to press powdered material through a die to create the pellets or granules required.

However, the apparatus of the present invention is also configured to operate as a grinding mill, in that it breaks down the material into smaller, finely ground particle sizes with a resultant increase in overall surface area of the material particles. Where the materials being ground are soil treatment/fertiliser components, it may be the case that the higher the surface area of the fertiliser components, the greater the reactivity of the components when on or in the soil.

Surface area is generally proportional to fineness, but it is also related to the structure of the material.

The material particles are then combined together during the pressing action of the mill to form granules where the particle sizes are of a pre-determined size, having a pre-determined surface area and the particles are distributed throughout the granule in a preferred ratio.

A number of soil treatment components are produced as fertiliser granules by means of pelletising apparatus. Soil treatment components (such as elemental sulphur and Reactive Phosphate Rock) are also examples of materials whereby traditionally, the component is firstly ground and then subsequently compressed (often using a different apparatus) to form the granular fertilisers.

A die pellet mill is an example of a pelletising machine. However, in the present invention, the principles of a die pellet mill are expanded on, to provide improved means for grinding material to include a very fine particulate within the ground material; and, ultimately producing pellets/granules produced there from.

There are two types of rollers used with pelletising machines - flat and tapered. The roller surface is substantially hard. With a die pellet mill, there is also included a die. The surface of the die is also hard. The die surface also includes multiple apertures into which the ground material is pressed by the action of the rollers. The pressure applied results in compaction of the material and effects production of a granule or pellet. In the present invention, it is the action of the rollers that also contributes to grinding the material between the rollers and the die surface.

For the purpose of the present invention the term “die” shall mean and include any configuration of a plate, a mold, a perforated block or similar through which the material is compressed into or, is drawn or extruded, for shaping; or, an otherwise formed tool or device for imparting a desired shape, form, or finish to a the material or for impressing the material in order to form granules of a preferred shape, size, strength and so forth. It should however be appreciated that use of the term “die” is not intended to limit the scope of the present invention.

For the purpose of the present invention the term “roller” shall mean and include, any cylinder which is used to grind, press, shape, spread, or smooth the material. The cylinder or parts thereof may be typically adapted to revolve. For example, the roller may form part of a unit comprised of two or more rollers interconnected to each other. Depending on the configuration of the pelletising apparatus, the entire unit may rotate and/or only the individual rollers may rotate.

The term “material” shall be broadly interpreted to include any material able to be ground and compressed into pellets/granules through the operation of the pelletising apparatus.

Specifically however, for the purpose of describing one embodiment of the present invention, the term “material”, in describing the present invention includes soil treatment components and/or any additional agents or additives for inclusion with the soil treatment components in order to produce a fertiliser composition ultimately in a finished granular form.

It should however be appreciated that the present invention may be adapted for use with a range of other materials, for varying applications.

The present invention is based on using a unique grinding and compression technique to achieve finely ground soil component particles, along with other additives/agents as required, prior to compaction of a formed soil treatment composition into a granular form.

In relation to the ground material, the term “grinding” broadly means and includes any powdering or pulverising process as may be applied to many kinds of materials.

For the purpose of the present invention the term “granule” shall mean any small blocks of molded and/or compressed and/or otherwise formed material; and, shall include varyingly shaped and sized pellets, fragments, briquettes and so forth. The use of the term granule (or pellet) should therefore not be seen as limiting this invention. Granules may be formed subject to use of any appropriate technique.

Preferably, the granules of material are directed to a fertiliser produced using a soil treatment composition so formed from any one or more in combination of soil treatment components along with other additives/agents such as trace elements, binding agents, dispersing agents, fluids, organic materials, sugars; soil conditioners; suppressants or accelerants for timed delivery of a specific component and so forth, as required to provide benefits to the composition, and/or may be used to bind the various components in the composition together to contribute to the formation of the fertiliser in a granular form.

Binding agents/dispersing agents may include: bentonite, Muriate of Potash (MOP), sugars, waxes, oils and so forth. Even water can be used as an effective binder during compaction of RPR granules. Fluids added to component(s) mixes may include (other than water), other solvents, waxes, oils and so forth. Soil conditioners may include lime, bentonite, and so forth.

Active soil components may include lime, urea, organic nitrogen, Reactive Phosphate Rock, elemental sulphur and so forth. Trace elements may include any required for improved plant and/or animal health. The granules may include enzymes, sugars and so forth to enable boosted or immediate release of preferred components in to the soil. Alternatively, inhibitors such as urease and/or nitrate inhibitors and/or other components may be included to effect a delayed release of certain components. For example, 1% of vegetable oil may be used to slow down dispersion of reactive phosphate rock (RPR) granules.

Any variations to the percentages of the component/agent/additive contributions in the fertiliser composition on a percentage weight:weight basis are envisaged to reasonably fall within the scope of the present invention.

Preferably, the pelletising apparatus of the present invention is an adapted die pellet mill.

There are various forms of pellet mills in the prior art. These include flat die mills, ring (or annular) die mills, screw presses and hydraulic presses. For the purpose of the present invention the method of manufacture of soil treatment granules in the form of a fertiliser uses an improved die mill configuration.

Die pellet mills typically include a chamber into which material is fed. Within the chamber there is a plurality of rollers. At a preferred location relative to the chamber is a die. The die defines a point of exit for the material leaving the chamber and in conjunction defines the point at which pelletising of the material occurs. The die may be flat or configured as a ring.

Any one or more of the rollers, roller bearings, or the die, may be in communication with a shaft. The shaft drives the movement or rotation of the rollers or the die within the chamber, thereby resulting in movement of the material from the chamber to the die.

In such die mills, apertures of preferred configuration are arranged in the ring die or flat die.

The die, also known as a mold, receives the uncompressed material from the chamber into a shaped aperture that defines the final pellet shape. The die apertures may be tapered and counter-bored at the inlet and/or counter-bored and tapered at the outlet.

Flat die mills use a flat die (like a dinner plate) and the material is introduced to the top of the die and forced through it. The die is usually turned by a set of gears (ring and pinion). However in some cases, the rollers are driven and the die is stationary. Therefore, the rollers may rotate across the surface of the die, or the die may rotate under the rollers. Either option of a driven die or a driven roller variety is preferably able to be adapted in relation to the present invention, along with potential option whereby both the die and rollers rotate.

In accordance with the present invention, a flat die is preferably used instead of annular die.

Typically, flat die mills effect more friction/heat, are simpler to assemble and disassemble and tend to be cheaper to source parts. However, any suitable pelletising arrangement may be adapted for use with the present invention.

Preferably, the die may be stainless steel or any other suitable metal, adapted for a longer lifespan. Carbon steel may however be used, although such metal may have corrosion issues over time.

The compression of the material into and through the die apertures is effected by the action of the rollers against the die surface. The material may be formed into strands. Cutting means on the opposite side of the die typically cut the exposed pellet free from the die.

The pressure applied to material in the compression zone of the die contributes in part to determining the hardness or crush strength of the pellet or granule produced therein. Preferably, the pressure applied is pre-determined to effect granules having preferred crush strengths. The crush strength may also be determined by any one or more of the components used, the size of the component particles, the proportion of particles of particular sizes, fluids added to the component mixture, the drying temperature and/or drying time of the granules formed.

To achieve finely ground particles of the soil components used, the soil components are subjected to grinding. Preferably, in the present invention, the grinding means is achieved by the action of either or both a plurality of rollers and a surface, with the material there between.

Preferably, the surface is a portion of a die that is contacted by the rollers.

The rollers are preferably cylindrical. Preferably, where the rollers are adapted to rotate, the rollers rotate at predetermined speeds. The number of rollers may be at least two, or may be up to three or more.

The surface of the rollers may be adapted to preferably be substantially smooth, to effect uniform grinding of the material introduced into the mill to predetermined particle sizes.

However, the surface of the rollers may alternatively be configured to include projections to effect differential or improved grinding of the material across a range of preferred particle sizes. Accordingly, a portion of the material may be very finely ground, whilst a proportion of the material may be less finely ground.

Where the material being ground is a soil treatment component or a composition of two or more components, additives and/or agents, varyingly sized particles may be preferred for some soil types. However, in other soils having very finely ground components may be required per se, to enable the soil treatment components to be optimally available when the composition is applied on to or in to the soil.

Preferably, the grinding of the soil treatment components, agents and additives and so forth, is effected by the action of the grinding means on the component material. Said action is the effect of powdering or pulverizing the component material between the rollers and the contacted surface of the die.

A die pellet mill of the present invention preferably operates on the basis of a single-pass grinding resulting in high fineness particles.

Preferably, the die is a perforated surface with apertures of a pre-determined specific size and shape and depth. Preferably, the apertures are uniformly configured. However, in some embodiments the apertures may be varyingly configured and varyingly arranged across and throughout the die surface.

The surface area of the die may be increased or decreased by adapting the die in relation to the number, arrangement and configuration of the die apertures. The surface area of the die may also be increased or decreased depending on whether the die apertures are tapered and counter- bored at the inlet surface of the die.

While in preferred embodiments of the present invention, the grinding means also operate as pressing means, in other embodiments however, additional pressing means may be included to operate in conjunction with the rollers/die arrangement.

Preferably, the granules are produced by the rollers "pressing" the material to be granulated through a perforated die with apertures of a specific size to produce a particular granule size.

Heat, applied to the process or effected through the grinding and compression process, speeds up the time it takes to produce the pellet or granule and improves the overall structure of the pellet.

The present invention includes the use of rollers whereby the surface of the roller is oriented to lie substantially parallel to the die surface. As such, a substantial portion of the surface of the roller at any time during rotation movement of the rollers and/or die, contacts the material and applies pressure against the material and the die surface. For ease of reference when describing the rollers providing preferred results with the present invention,, the rollers being so described shall be referred to as “flat rollers” and “reversed tapered rollers”. However, use of these terms is not intended to limit the scope of the present invention.

The use of flat rollers has been compared with the use of traditional tapered rollers. Such traditional tapered rollers may be referred to as inward tapering rollers, meaning the smaller diameter tapered end of the roller is closer to the centre of the pelletising chamber, while the larger diameter portion of the roller is closer to the outside wall of the chamber. Tapered rollers are typically used to reduce the costs associated with pelletising. The tapered shape rollers reduce the friction which may be created between rollers and die and thereby save on energy consumption, as well as lengthening die and roller life. However, the speed and therefore a pressure differential between the inside and the outside of the tapered roller means there is a reduced grinding efficiency in the main grinding zone.

From testing undertaken, flat rollers have instead been found to produce a preferred grinding effect during the pelletising process. It has been noted that the inside face of the flat roller exerts more pressure in the grinding zone resulting in a greater grinding effect, than when traditional tapered rollers have been used.

While tapered rollers may reduce the abrasion/degradation problems from varying distances traversed by round roller over a flat die, such wear-and-tear problems with flat rollers may be eliminated almost entirely through proper engineering practices.

However, tapered rollers (where only a portion of the roller face along the length of the roller exerts pressure in the grinding zone), may be preferred for compositions required to have varying proportions of finely ground and coarsely ground material/component particles.

One potentially realisable advantage of the flat roller grinding method is that it results in an additional percentage of fine material of less than 100 micron in size.

However, preferably, the grinding effect is maximised by the use of either or both flat rollers and “reversed” tapered rollers. The use of “reversed” tapered rollers - meaning the rollers are tapered in substantially the opposite direction to the traditional inward tapered rollers - is not previously known.

Reversed tapered rollers have their larger diameter portion closer to the centre or inside of the pelletising chamber; while the smaller diameter portion of the roller is closer to the external wall of the chamber. This results in an increased rotational velocity and increased grinding force when compared with traditionally arranged tapered rollers. As a result of the profile and the surface speed differential created, the material in the pelletising chamber moves toward the grinding zone, so effectively enabling the material to be ultimately ground to even finer particle sizes.

The use of flat rollers provides at least 10% better grinding effect than is typically achievable with the use of traditionally tapered rollers. That is, there is at least 10% more fine particles below 75 micron in size when using flat rollers as compared with traditionally tapered rollers.

The use of reversed tapered rollers provides a further additional percentage improvement in grinding efficiency over and above the grinding effect achieved with flat rollers alone. It is estimated that this effect results in at least an additional 10% -12% again of material being ground to particle sizes of less than 75 micron.

Preferably, a wider than normal flat roller may also be used, to maximise the grinding effect through contact between the roller and the soil treatment component(s) and die. Flat die pellet mills are more able to accommodate wider rollers than ring die pellet mills. Ring die pellet mills are restricted by ring diameter, so the roller cannot be enlarged as may be required for application with the present invention. In addition, the roller bearing room is smaller, so the assembly bearing is not strong enough to withstand additional pressure, so leads to more frequent repair.

Preferably, either or both the outer and inner portions of the roller may be used for grinding.

Preferably, the configuration of grinding means also enables improved compaction for the manufacture of fertiliser pellets incorporating high fineness particles.

When the soil treatment component(s) has been ground, the ground product is then preferably swept towards and under the portion of the roller which in turn applies the pressure to the component(s) to press the ground particles through the die apertures.

Preferably, there is a pressure adjusting means included with the pelletising apparatus of the present invention. This is preferable so that the roller/die gap can be adjusted to accommodate different materials and/or achieve the preferred grinding action and/or to exert the preferred pressure required in the pelletising process.

An advantage of the compaction method following the fine grinding is that significant heat is produced during the grinding process. This results in the granules being at approximately 60 C - 70 C immediately after compaction.

Typically granules need warm air to dry aid with drying. With the use of flat rollers ambient air can be used as no further drying is required.

In addition, the temperature of the granules formed under high pressure means that for some components, the heat causes them to be smeared by the grinding process and they effectively form a coating around the granule surface. This coating may enable faster/boosted availability of that component in to the soil when the granule is applied; or, the coating effects a delayed availability of that or other granule components.

Further, the high pressure compaction results in granules with higher crush strengths.

Preferably, the grinding produces finely ground soil treatment components whereby the particles have increased surface area.

Single pass grinding and compaction is especially suited for the production of elemental sulphur granules. It is possible to produce elemental sulphur granules with sulphur particles where 90% of the particles are sized less than 75 microns. This can be achieved without classification.

Further, having regard to reactive phosphate rock, RPR reactivity is directly proportional to fineness. A relatively unreactive RPR which is finely ground can become sufficiently reactive so as to be useful as a fertiliser. By applying this process for grinding Reactive Phosphate Rock (RPR), it allows for lower grade RPR to be used, since increased particle fineness increases reactivity. An RPR granule with 95% of particles passing 45 micron gives a higher citric acid response.

RPR particle size distribution is also a critical factor determining whether a particular RPR can be used in given soil and climate conditions. This invention demonstrates that an RPR granule consisting of a large proportion of less than 45 micron material is able to be widely used in various conditions - for example, particularly with South Island soils and climate conditions.

Other advantages of using lower grade RPR can be lower cadmium levels. Such a process as described within the present invention does not appear to have been used in the production of granules including finely ground RPR.

A typical RPR fertiliser will take 3-5 years for the majority of particles to react releasing phosphate into the soil. Finely ground and granulated RPR (95% < 45 micron) will release a significant proportion of phosphate within one year while retaining the benefits of low surface run-off. Smaller granule sizes are more effective to achieving this outcome.

In at least one preferred embodiment of the present invention, the effective grinding surface of the grinding means is adapted to be increased. To increase the grinding surface it is possible to reduce the outside diameter of the counter-bore, being the entry point of the finely ground particles into the compression zone of the die plate of the grinding means – during the formation of the granules. While this adjustment may result in a decrease in efficiency in terms of granule production, any such decrease is countered by the increase in the amount of preferred fine material (<75 micron) that is able to be produced.

Testing based on such adjustments to quantify the effect of adjusting the counter-bore will be relevant to achieving preferred granules comprised of soil treatment components of preferred particle sizes.

In addition, preferably the compression zone of the die is able to be pre-determined. The ability to accurately size the compression zone enables the compaction of the granule made by this method to be very accurately controlled. Controlling the compaction of the soil treatment components means that the resultant granule will include preferred particle sizes, surface areas and particle distribution as required for the soil treatment to be effected.

For example, having less compression zone area produces granules with a lower compressive strength and a shorter dispersion time, when compared with granules formed under a higher compression area which would demonstrate a higher compressive strength and longer dispersion time.

This enables a vital balance to be struck between product strength and dispersion of the product on to and in to the soil. The ability to predetermine granule strength and rate of dispersion will also depend on the soil treatment components of the granules. The benefits include an ability to manufacture specific granules to suit various soils in varying regions and countries – having regard to at least the soil structure, plant nutrient requirements and climatic and environmental conditions.

For example, in some colder climates – such as in the South Island of New Zealand- in order to be effective during the first year after application sulphur fertilisers must contain sulphur particles less than 75 micron in size. Assuming the cost of a sulphur application at $500 (not including cartage and spreading charges), each 10% increase in the production of these fine sulphur particles effectively adds as extra $50 of sulphur value for that year.

This method of manufacture is especially suited for fertiliser granules containing elemental sulphur. Traditionally, elemental sulphur fertilisers are dangerous to produce. This method provides a potentially realisable advantage in that it enables grinding and compaction of the elemental sulphur to occur without the risk of explosion. The ability to add further moisture also enhances this safety aspect of handling fine sulphur.

Elemental sulphur, as with any of the preferred soil treatment components, is preferably finely ground to improve its “availability” to plants. In addition, the elemental sulphur, again as with any of the preferred soil treatment components, may be combined with at least one other agent.

In various embodiments of the present invention, the soil treatment components of any preferred soil treatment composition, may be finely ground separately and produced into granular form; or, may be ground separately and then combined prior to being compressed in to granular form; or, may be intermixed and ground together and formed in to granular form.

In accordance with another aspect of the present invention, one or more component or additive/agent may optionally be dispersed in a fluid and then added to dry components prior to pelletising. This step may be employed where it may be preferable that particles of one component or agent/additive are fully interspersed with and between the particles of other/the soil treatment component(s) and the addition of a component mixed with a fluid better achieves this interspersion.

The variations possible within the present invention enable the soil treatment components to be tailored in terms of a preferred profile of particle sizes, surface areas and quantity, for application alone, or in conjunction with other soil treatment components having the same, or different, profiles – as may be needed to suit specific requirements.

The final granule is dependent on the method of producing the granules. For example, the finer the grind of the components, the easier it may be to form the granules. However, there may need to be consideration of other aspects to ensure the desired granule crush strength and rate at which the granule dissolves, is achieved. The coarseness of the grind may improve the strength of the granule, but may not be desirable for some soils. So, the granules are preferably formed taking into account the soils, the climate, the period of time the components are desired to be released, and so forth. Therefore a number of variations are possible within the ambit of the present invention.

Preferably, the granule or pellet size for the granular form of the composition is 2 - 8 millimeters.

Preferably the granule or pellet size for the granular form of the fertiliser composition is 6 millimeter.

In accordance with another aspect of the present invention, the preferred components in the preferred compositions are finely ground to particles sizes which benefit the predetermined and desired availability of the soil treatment components in the composition when the granular form is applied to soils.

The pressure applied in the formation of the granule may be pre-determined, as required to produce stable, dust free granules having preferred dispersion characteristics. Having stable, and dust free granules is advantageous when storing, transporting and applying the fertiliser granules. The method of manufacture of the granules is relevant to achieving this. However, the method of preparation of the granule will also pre-determine the crush strength as required for any particular application.

The prepared granules are preferably dried or cooled to improve the hardness of the granules/pellets. Using high pressure techniques contributes to producing harder pellets/granules which are drier. Granules formed by high pressure need only ambient air cooling for hardening to occur due the temperature at which the pellets leave the press (at approximately 60 C).

Certain agents/components of the granule may assist in the production of high strength granules. For example, Muriate of Potash (MOP) is a salt and re-crystallises when it dries.

This characteristic imparts strength to the fertiliser granule.

Other components, agents, additives may be highly water-soluble and so enables the granule to rapidly dissolve when coming into contact with moisture. This characteristic imparts excellent dispersing ability to the granules when applied.

As will be appreciated, this invention is directed to provide an improved method for manufacturing soil treatment compositions in granular form. As such the present invention is directed to an improved pelletising apparatus, which includes both grinding and pelletising means. The soil treatment composition so produced via the improved pelletising apparatus is preferably directed to improving soil condition and/or soil-nutrient availability for plants.

The term “treatment” as used in this specification will typically involve a knowledge of the condition of the soil (preferably via prior analysis) and involve administration to the soil, via one or a regimen of applications, a particular preferred composition which aids in improving at least the soil condition (including structure) and/or soil nutrient content.

Preferably, the soil treatment composition is provided in granule form for application to soils.

The granular product includes one or more of the following features: a) Is a controlled release granule formulated for a specific soil type. b) Is comprised of components having one or more of a preferred particle size, preferred particle distribution, preferred particle surface area. c) Includes component(s) directed to a specific treatment, specific soil type, specific climatic conditions. d) Includes a component that facilitates dispersal of the granule in water. e) Includes a component contributing to the binding of the components. f) Includes a component that facilitates rapid release of at least one other component from the granule. g) Is uniform in size. h) Is dust free for improved handling, spreading, transportation and safety. i) Is colour coded to ensure correct formulation application to particular soil types. j) Is an improvement on products prone to leaching. k) Granules are not easily separated during a mix. l) Fast acting for rapid results – such as rapid plant availability of nutrients. m) A product which is adapted to address some environmental concerns existing as a result of the use of traditional chemical fertilisers.

Preferably, the granule is able to be adapted to be specifically tailor-made in respect of the particle distribution of its components to suit various applications, soil and climatic conditions (including temperature) as required.

The granule may have varying composition depending on the components of the granule and the application it is designed for.

Preferably, the granule is able to be adapted to be specifically tailor-made in respect of particle size and/or surface area of its components to suit various applications, soil and climatic conditions (including temperature) as required. The granule may have varying particle sizes within its composition depending on the components of the granule and the application it is designed for.

Preferably, the particle size is optimised by fine-grinding to suit differing soil conditions and the purpose for which it is being used.

Preferably, the granule components are such that the granule components are selected to be able to be tailor made to suit specific soil types in particular countries and for particular soil types in particular regions within said countries.

Preferably, the granule, following application, is required to make the components of the granule available within or on the soil. To achieve this, the granule preferably disperses at a preferred rate. The rate of dispersion is pre-determined by the soil components, agents and additives, but also by the grinding and pressing method of the present invention.

Preferably the dispersion of the granule enables the components of the granule to be available.

However, the individual components of the granule may vary in the rate at which each will be directly available for the specific need. For example one component may be immediately available for use – whether as a nutrient or soil conditioner; whilst others may be released in the soil over time, or at different rates, or with the onset of particular climatic or soil temperature/conditions as required.

In addition, the granule form avoids the limitations of traditional mixed fertilisers which are in powdered or loose form. Such fertilisers are typically transported at some stage. The vibrations generated during transportation can cause the different component nutrients to separate out due to their varying densities. When the fertiliser is then applied there is the potential for uneven distribution of the components of the fertiliser and so some areas may remain or may result in being more deficient in a particular component when compared to another.

It will therefore be appreciated that the invention broadly consists in the parts, elements and features described in this specification, and is deemed to include any equivalents known in the art which, if substituted for the prescribed integers, would not materially alter the substance of the invention.

Variations to the invention may be desirable depending on the applications with which it is to be used. Regard would of course be had to effecting the desired particle size(s) of the fertiliser/soil treatment components and so forth, dependent on the grinding effect of the rollers employed, the die and the roller-to-die separation.

In addition, the pressing of the components into granular form will pre-determine rates of delivery of the soil components and so forth dispersing into and on to the soil.

Concentrations or volume to volume ratios of the components of the granule, the various components of the granules, the dimensions of the granule, the dissolution rates, the method of application of the granules and so forth may all be varied as required to effect the desired outcome.

Whilst some varying embodiments of the present invention have been described above and are to be yet exampled, it should further be appreciated different embodiments, uses, and applications of the present invention also exist. Further embodiments of the present invention will now be given by way of example only, to help better describe and define the present invention. However, describing the specified embodiments should not be seen as limiting the scope of this invention.

Brief Description of Drawings Further aspects of the present invention will become apparent from the following description, given by way of example only and with reference to the accompanying drawings in which: Figure 1 is a diagrammatic representation of an embodiment of a flat die pelletising apparatus where the rollers are tapered, in accordance with one embodiment of the present invention; and Figure 2 is a diagrammatic representation of an embodiment of a flat die pelletising apparatus where the rollers are flat, in accordance with another embodiment of the present invention; and Figure 3 is a diagrammatic representation of an embodiment of a flat die pelletising apparatus where the rollers are flat, but wide, in accordance with another embodiment of the present invention; and Figure 4 is a table illustrating the improved effective grinding of material using flat rollers versus tapered rollers, in accordance with another embodiment of the present invention; and Figure 5 is a diagrammatic representation of an embodiment of a flat die pelletising apparatus where the rollers are reversed tapered, in accordance with one embodiment of the present invention; and Figure 6 is a diagrammatic representation of an embodiment of an elevation view of a typical pellet die showing: the compression zone (effective thickness), counter- bore and a one–step relief, in accordance with one embodiment of the present invention; and Figure 7 is a table illustrating the differences between the tested strength and dispersion rate of pellets produced where only the compression zone length is varied, in accordance with one embodiment of the present invention; and Figure 8 is a further table summarising the effect on the strength and dispersion rate of pellets produced where the compression zone length is varied, in accordance with the embodiment of Figure 7 of the present invention; and Figure 9 is a diagrammatic representation illustrating an adjustment to the outside diameter of the counter-bore of the die apertures in order to increase the grinding surface, in accordance with one embodiment of the present invention; Figure 10 is a table illustrating the relative percentage of particle sizes of ground reactive rock phosphate (RPR) in pellets both before and after a single pass grinding and compaction pelletising process using the improved pelletising apparatus, in accordance with one embodiment of the present invention; and Figure 11 is a photographic representation illustrating a three “tapered roller” configuration for use with a die pellet mill, to illustrate embodiments applicable to the present invention; and Figure 12 is a photographic representation illustrating a two “flat roller” configuration for use with a flat die pellet mill, along with the flat die plate showing die apertures, to illustrate embodiments applicable to the present invention.

Best Modes for Carrying Out the Invention With reference to the present invention by example only, there is provided an improved method and apparatus for the manufacture of granular material. To example the method, the description refers to the manufacture of fertiliser granules used for soil treatments. The granules are adapted to include various components desirable in the conditioning or treatment of soils.

The present invention includes an improved pelletising apparatus generally illustrated by arrow 1. The pelletising apparatus is an improved die pellet mill (1). Various embodiments of pelletising mills are diagrammatically represented in cross-section in Figures 1-3 and in Figure . However, Figure 5 illustrates one embodiment of the present invention.

The improved pellet mill provides a single-pass, one operation grinding and pelleting process whereby the grinding aspect results in very finely ground material particles which are then compressed into pellets/granules having preferred particle surface areas and sizes, particle distributions, along with granule size and shape, crush strength and dispersion time.

Typically, the grinding of material in die pellet mills, such as relevant to the present invention, is achieved by the action of either or both a plurality of rollers and a surface, with the material there between. Accordingly, die pellet mills, such as relevant to the present invention, include a chamber 2, grinding means rollers 3 (being a plurality of rollers) and a grinding means pelletising surface 4.

The chamber 2 operates as a hopper in that it accommodates and delivers the material to be ground and pelletised to the area where the grinding means 3 and pelletising 4 means are located. However, the chamber 2 is also configured such that it either or both contains and encloses the grinding means 3 and the pelletising means 4.

Separate hopper means (not shown) may also be specifically used with the pellet mill of the present invention for the bulk storage of the material prior to it being delivered into the chamber 2.

Typically with standard pellet mills, the materials/soil treatment components are put into the chamber where pressure is applied to the material by the rollers, and the material is pushed into the pelletising means portion, to form the pellets/granules.

The method of manufacture of the granular material/pellets of the present invention is however, further determined by improved grinding means (as generally indicated by arrow 3, as exampled in Figure 1). The grinding means 3 is configured as a roller. The figures illustrate a plurality of rollers used with the pelletising apparatus, for grinding the soil treatment components and so forth. The grinding means are preferably reversed tapered rollers 3a, as illustrated in Figure 5. Flat rollers 3b may also be used alone (as shown in Figures 2 and 12) or, be used in conjunction with reversed tapered rollers. Alternatively, the flat rollers may be wide flat rollers 3c, as illustrated in Figure 3. In other embodiments of pellet mills, the rollers may be traditionally tapered 3d, as represented in Figure 1 and as shown in a photographic representation in Figure 11.

The rollers are interlinked/joined (to form a combined roller unit arrangement) via interconnection means 7. The interconnection means may be determined by the number of rollers employed in the pelletising apparatus.

For example, where two rollers are interlinked, as illustrated in Figures 1-3, 5 and 12, the rollers may be connected via an appropriately configured, substantially elongate, rod 7a or similar, with each roller being located diametrically opposite the other.

Where more than two rollers are interlinked and/or where the rollers are traditionally tapered or reversed tapered rollers, a central hub interconnection means 7b may be used. Figure 11 illustrates such a configuration.

The operation and configuration of the roller interconnection means will also be determined by whether the entire roller unit is required to rotate within the interior of the chamber relative to stationary pressing means; or, alternatively, whether the roller unit is substantially static (with only the rollers themselves rotating on the spot) and the pressing means rotates; or whether the roller unit, the rollers and the pressing means are required to rotate relative to each other.

Movement of the roller unit will typically be associated with a drive shaft, including drive means, bearings and gears to drive rotation of the roller unit and/or rotation of the rollers. The interconnection means will accommodate such a shaft. Where only the pelletising means rotates, the drive shaft will be primarily associated with the pelletising means. In embodiments where both the roller unit and the rollers and the pelletising means are required to rotate, single or multiple drive shaft(s) may be associated with either or both the roller units, rollers and the pelletising means.

It may be appreciated that any interconnecting means may be used, or adapted for use, as required with the present invention.

Typically, pelletising apparata have been used primarily for effecting production of pellets due to the action of the rollers pressing the material into the pellestising means. While some grinding is evident, the primary purpose of the pelletising apparatus is not for effecting grinding of the material into fine or superfine particles. Figure 4 is a table illustrating a 12.1% increase in material particles of less than 75 micron when using flat rollers as compared with traditional tapered rollers. However, in the present invention, the grinding means specifically grinds material placed into the chamber 2, between the rollers 3a and the surface 4a of the pelletising means 4.

The use of the reversed tapered rollers 3a, further effects a substantially greater proportion (by at least an additional 10%) of fine and superfine particles in the material ground between the reversed tapered rollers 3a and the surface 4a of the pelletising means 4, than would otherwise exist if the rollers were simply or primarily operating to apply pressure to push the material into the pelletising means, or if flat rollers were used. Figure 10 illustrates the increase in the fine particle portion (less than 75 micron) of reactive phosphate rock following use of the pelletising apparatus of the present invention, compared with the much lower fine particulate portion present prior to grinding and pelletising of the RPR via the present invention.

The grinding means applies pressure to the ground soil treatment components and effects accumulation of the ground particles into the pelletising means.

The pelletising means includes a die 4. The die surface 4a of the pellisting means may be substantially flat or be configured as an annular ring. The die surface 4a of the pelletising means of the present invention, as illustrated in Figures 1-3, 5 and 11, is in the form of a substantially flat plate.

The die 4 includes multiple apertures 6 of pre-determined size/width and depth/length and spatial arrangement. The number and arrangement of the apertures 6, defines the number of granules/pellets produced. The size/width of the apertures defines the shape and size/width of the granules/pellets produced.

Figures 6 and 7 illustrate the die apertures 6 in cross-section. The die apertures include an entry point 6a, and an exit point 6b. Either or both the entry and exit point may be tapered/counterbored (as at 8) or, be otherwise configured as a stepped relief (as at 10). The depth/length of the apertures through the die defines a substantially elongate compression zone 9, where the material/soil components are compressed.

Granules of varying thickness and length may be formed as desired, by varying the aperture size/diameter and the length of compression zone. The length of the granules/pellets is defined by either or both the material/soil components compressed into strands determined by the compression zone 9 length and/or the length the compressed material strand is as it exits the compression zone of the die.

Cutters may be employed to cut the length of compressed material to effect pellets/granules of substantially uniform lengths as the compressed material exits the compression zone of the die.

Alternatively, the material may break free from the die as the material is pushed through the apertures and, thereby form pellets/granules of random length(s), or a range of preferred lengths.

In order to increase the effective grinding surface 4a of the die 4, the tapered counterbored entry point 8 of the die aperture 6, may be adjusted. Figure 7, represents an option where the dotted line represents such an adjustment, thereby effectively increasing the surface area 4a of the die able to be used in the grinding process.

The grinding action of the rollers 3a against the surface 4a of the pelletising means is adapted to be adjusted to grind the material to pre-determined particle sizes from coarse, to very finely ground material. The adjustable distance between the rollers and the surface of the die, is in the vicinity of area 11.

Within the pellet mill the grinding fineness may be adjusted by any one or more of: 1. The pressure set between the rollers and the surface of the pelletising means/plate. 2. The angle of the rollers. 3. The speed of rotation of the rollers 4. The size of the apertures in the die.

. The location within the chamber where the feed enters the mill. For example, if more material is fed in to the centre of the chamber, the further it has to spread out, so the more rolled it is and finer it gets.

The extent of compression, including the length of the compression zone, defines the crush strength of the granules and the dispersion time for the material/soil treatment components to be made available on to and/or into the soil.

Figures 8 and 9 represent data from tests where the length of compression zone was adjusted.

As can be seen from the results, where the compression zone is lengthened, the crush strength of the granule is increased, but the granule also takes longer to disperse.

The ability to accurately size the compression zone of the die also enables the compaction of the granule made by this method to be very accurately controlled. Less compression area equates to the production of a granule/pellet having lower compressive strength and a shorter dispersion time.

A higher compression area equates to the production of a granule having higher compressive strength and a longer dispersion time. This enables a vital balance to be struck between product strength and the dispersion of the final granular product when applied on to and/or in to the soil.

The crush strength and dispersion time are also affected by the water content of the granule.

The use of the improved pellet mill to grind and pellet soil treatment components also includes a potentially realisable advantage in that the material is heated by and during the process, to reduce water content in the pellet, in one operation.

The amount of heat generated during the pelletising process may be controlled by: 1) The diameter of the hole in the die, 2) The compression area of the die. 3) Where the product is fed to the rollers.

Therefore, not only may the length of the compression zone be adjusted, but also the amount of water in the material may be adjusted as required to achieve preferred granule crush strength and dispersion rate.

The granule is preferably able to easily disperse over preferred time periods when applied to the soil and yet have sufficient compressive strength to ensure that the granule does not break-up during handling, storage, transport and application.

The Rollers The rollers used to effect grinding of the material in relation to the present invention, are crucial to achieving preferred and pre-determined particles sizes subsequently required within the pelletised material.

Fertiliser granules produced by means of the improved die pelletising machine may be produced by the roller unit/rollers rotating over a stationary die or, a die rotating under rollers.

Both of the above options effect a grinding action on the material introduced into the chamber of the pelletising apparatus, and both effect the "pressing" of the material to be granulated through the perforated die with apertures of a specific size to produce a particular granule size and with compression zones of a particular length to produce a granule of particular length and strength.

The use of the improved die pellet mills has identified and quantified the grinding effect – especially as it relates to the manufacture of high-surface area fertilisers. This grinding effect is maximised by use of the stated rollers - against the die surface.

The present invention uses either or both flat rollers and “reversed” tapered rollers. The use of reverse tapered rollers is substantially unique in such a process as grinding materials – such as soil treatment components – and pelletising the fine particles.

Tapered Rollers Traditional tapered rollers, as illustrated in Figures 1 and 11, are used to reduce energy costs associated with pelletising. There is a speed and therefore a pressure differential between the narrow diameter inside and the wider diameter outside of the tapered roller. This pressure differential however, effects a reduced grinding efficiency in the main grinding zone.

Flat Rollers Flat rollers, as illustrated in Figures 2 and 12, have been found to produce an improved grinding effect, as compared to the use of the traditionally tapered rollers used. The inside of the roller exerts more pressure in the grinding zone resulting in a greater grinding effect than achieved with the tapered rollers discussed above.

Where a wider than normal roller may be used, as illustrated in Figure 3, the outer or inner portion of the roller may be used for grinding. The ground product is then swept to under the portion of the roller which is pressing the material through the die apertures.

Experimental Results of Tapered Rollers versus Flat Rollers The grinding effect from using flat rollers results in at least an additional 10%-12% of fine material of less than 75 micron in size, than that possible through the use of inward tapered rollers.

Figure 4 is a table demonstrating some experimental results of grinding material using tapered rollers and flat rollers. Using RPR as the material being ground, the results demonstrate a 12.1% increase in material being ground to particle sizes of less than 75 micron when using flat rollers as compared with tapered rollers.

Drying Air Typically granules need warm air to dry aid with drying. With the use of flat rollers ambient air can be used as no further drying is required. This is another potentially realisable advantage of this compaction method in that significant heat is produced during the grinding process.

This results in the granules being at approximately 60 C - 70 C immediately after compaction and therefore not needing additional drying.

“Reversed” Tapered Rollers Unlike the traditionally configured tapered rollers as illustrated in Figures 1 and 11, for “reversed” tapered rollers, as illustrated in Figure 5, the larger diameter portion of the roller is on the inside of the roller arrangement, while the narrow diameter portion is on the outside of the roller arrangement. This larger diameter portion of the roller on the inside of the roller arrangement results in an increased rotational velocity and an increased grinding force in the grinding zone.

The use of “reversed” tapered rollers as illustrated in Figure 5 provides an additional percentage improvement in grinding efficiency. It has been estimated that using the reversed roller configuration of the present invention an even further additional 10% of material is ground to particle sizes of less than 75 micron being.

Counterbore Adjustment In order to increase the effective grinding surface within the apparatus, it is possible to reduce the outside diameter of the counterbore.

Figure 6 is a diagram illustrating a cross-sectional view of a single aperture in a typical pellet die showing one possible configuration of the:  Compression zone (9) (effective thickness).

 Counterbore (8).

 One–step relief (10).

Figure 7 illustrates one possible alternative cross-sectional view of the said single aperture in a pellet die showing a configuration where the counterbore portion/region is adjusted/modified (the dotted line 8a indicates the counterbore adjustment), such that the:  Compression zone effective length is increased as shown at “A”.

 Counterbore diameter/depth is reduced (new width is now “B”, so the counterbore is no longer existing in this view).

 One–step relief remains the same.

Whilst a decrease in efficiency may be noted in terms of grinding time and so forth, the increase grinding surface effects an increase the amount of finely ground material (of <75 micron) that can be produced. Further testing will further quantify the effect of adjusting the counterbore.

Pellet Formation and Affect of Adjusting the Compression Zone Using said typical pellet die, experimental results for pellets formed therein, where the material includes a soil treatment composition comprised of soil treatment components/additives/agents such as - elemental sulphur, inverted sugar and bentonite, the pellets are formed using the following die dimensions.  4mm diameter die apertures.

 Relief diameter: 6mm  Total die length: 20mm  Counterbore length: 5mm Figure 8 is a table illustrating the effect on the crush strength and dispersion time of pellets/granules formed when the compression zone length is adjusted. As is evident from the results, by increasing the length of the compression zone from 7mm to 15mm, the crush strength of the pellet/granule is increased, but so too is the time it takes for the material/particles to disperse from the pellet/granule.

Figure 9 descriptively explains the effect on the pellet/granule strength and dispersion properties where the length of the compression zone is varied.

The ideal pellet in terms of strength and dispersion will be found between the two results illustrated in the above referenced tables.

High pressure compaction High pressure compaction results in granules with higher crush strengths. Testing will enable further quantification of the effect of the pressure of compaction and the compression zone length on the strength and dispersion of pellets.

In addition, the components/additives/agents also used in the pellet creation, will affect the pellet/granule strength and dispersion properties.

Sulphur Pellets/Granules Further advantages arise depending on the material(s) being ground. This method of manufacture is especially suited for fertiliser pellets containing elemental sulphur.

Traditionally, sulphur fertilisers are dangerous to produce. Further, grinding elemental sulphur is expensive, dangerous and difficult. This method enables grinding and compaction of elemental sulphur to occur without the risk of explosion. The present invention enables effective grinding of elemental sulphur in a one pass operation that is safer (less than 30% elemental sulphur in a material mixture being ground is accepted not to explode).

The ability to add further moisture also enhances this safety aspect of handling finely ground elemental sulphur.

In addition, the fine elemental sulphur in the granules provides a form of faster acting sulphur that is readily plant available without the accompanying sulphate leaching problems associated with sulphate based fertilisers. The elemental sulphur is not easily leached or susceptible to run- off from the soil, giving considerable environmental benefits in the use of the granular fertiliser of the present invention.

In order to get a very fast sulphur response a minus 20 micron component may be included in the sulphur. The elemental sulphur may also include an even superfine component (of <10 micron).

Single pass grinding and compaction is especially suited for the production of elemental sulphur granules. It is possible to produce elemental sulphur granules with sulphur particles where 90% of the particles are less than 75 micron in size. This can be achieved without classification.

From an economic perspective, it should be appreciated that, in some colder climates - such as in the South Island of New Zealand - in order to be effective during the first year after application sulphur fertilisers must contain sulphur particles of less than 75 micron in size.

As previously explained, assuming there is a $500 sulphur cost (not including cartage and spreading charges), each 10% increase in the production of fine elemental sulphur particles in the granular product effectively adds an extra $50 of sulphur value for that year.

RPR Pellets/Granules As previously mentioned, the present invention is also suited to the production of fertiliser pellets containing reactive phosphate rock. This is first time this process has been used for grinding RPR. Figure 10 is a table illustrating the results of quantified particle sizes in ground RPR both before and after use of the present invention.

In relation to the finer grinding of the RPR by the flat and/or reversed tapered rollers of the present invention and the single-pass grinding and compaction in the manufacture of fertiliser pellets incorporating high fineness particles, the present invention produces ground RPR where a greater proportion of the particles have a size of less than 75 micron.

Further, the pelletising, grinding and heating occurring with the present invention means RPR of lower reactivity may be used because, increasing fineness increases the RPR reactivity. This has the potentially realisable advantage of being able to purchase and use lower reactive RPR at a cheaper cost.

Another advantage of the invention is also related to the ability to use lower grade RPR. Fine grinding of RPR also enables more effective removal of cadmium from reactive phosphate rock, providing an additional potentially realisable benefit having regard to reducing negative environmental impacts of using fertilisers including RPR with a high cadmium content.

Elemental Sulphur and RPR Pellets/Granules The effective, safe and fine grinding of the elemental sulphur in a one pass operation enables the elemental sulphur to also be combined with another material, such that the two products are able to be simultaneously ground and pelletised to produce a granule comprised of multiple components.

For example, the process may be used to simultaneously grind elemental sulphur and reactive phosphate rock (RPR). It is anticipated that such fine grinding and pelletising of two components, such as RPR and elemental sulphur in a one pass operation using pelletising means such as described in the present invention, has never been done before.

During the grinding process, the heat generated assists in increasing reactivity between the elemental sulphur, the RPR and water added to the mixture. The increased reactivity results in improved solubility of the RPR.

The smearing action of the grinding rollers against the die surface further increases the intimate contact between the water, elemental sulphur and RPR in such a combination of components Intimate particle contact When components such as elemental sulphur are inter-ground (under pressure) with another active, there is greater intimate contact between the particles. This results in a “bonding” together of the particles. As the inter-grinding takes place the granule is also being compacted and this produces heat between 60 C and 100 C.

Where elemental sulphur is concerned, the sulphur mobilises at around 80 C and will possibly mobilise at a lower temperature under the high pressures used to form this granule. The mobilised sulfur effectively smears the finely ground particles of other actives, thereby forming an extremely intimate contact.

The smearing effect of the sulphur not only serves to create intimate contact between the elemental sulphur and the other actives, but also can be utilised to effect at least one of reduced problems normally associated with the explosive nature of fine sulphur particles, increased surface area of the sulphur increasing its potential availability in or on the soil, a coating of the other actives with the sulphur enabling desired release profiles of the components of the granules to be achieved, and so forth.

In addition, biological oxidation of elemental sulphur (S) mixed and applied with other actives will increase and improve its effectiveness as a fertiliser.

Organic Fertiliser Options A range of organic fertiliser options are also possible using the present invention. For example, not only may fertilser products be produced using what are considered to be more environmentally appropriate natural organic elements; but also, the fine grinding option may enable various organic plant and animal materials to be included in the pellets/granules as may be required or preferred for some applications.

Customised granules As may be appreciated, the above examples illustrate how pellets/granules produced as soil treatment fertilisers using the present invention may be tailor-made, having regard to the components/additives/agents used and the desired crush strength and dispersion time of the pellets, in order to produce pellets/granules having potentially realisable benefits in terms of meeting the specific requirements of soils on to pr in to which the pellets/granules are applied.

The present invention enables a wide range of fertiliser options to be created in terms of: - components used (as required by plants and subsequently feeding animals - in different soils, different regions, different countries); and - pellet physical properties (including, size, crush strength, dispersion time, and so forth); whilst also having regard to other considerations such as - cost effectiveness, required applications, reducing environmental impacts and so forth.

The amounts of soil treatment components and any additional actives/agents/additives, soil conditioners and/or trace elements, in the granule, may be varied to suit the particular application.

The granules may also be tailored to suit specific regions in terms of the particle size and reactivity. The ability to customise the granules for use in different soils, in different countries and in different regions within a country, may also be effected.

Therefore, by varying any one or more of: a) The percentage of the soil treatment components in the treatment composition/granule; b) The percentage of any additional actives, and/or other macro or micronutrients, soil conditioners, beneficial bacteria or other plant beneficial organisms and/or trace elements in the treatment composition/granule; c) The percentage of fluid in the treatment composition/granule; d) What the fluid in the treatment composition/granule is; e) The size of the particles of the soil treatment component(s) and/or any additional actives and/or other macro or micronutrients and/or any soil conditioners, including lime and/or any trace elements in the treatment composition/granule; f) The proportion of particle sizes in the mixture – superfine, fine, coarse, etc. g) How the components are mixed – inter-ground, ground separately and then mixed, one being mixed with the fluid and then added to the remaining component(s); h) How the granules are prepared – using high or low pressure techniques - including the specific preparation technique itself and variations to that technique; i) How the granules are dried; j) The length of the compression zone in the formation of the granules/pellets; and so forth, the treatment composition and/or the granules prepared, may be customised as required for specific treatments.

When referring to the description of the present invention, it should also be understood that the term “comprise” where used herein is not to be considered to be used in a limiting sense.

Accordingly, ‘comprise’ does not represent nor define an exclusive set of items, but includes the possibility of other components and items being added to the list.

This specification is also based on the understanding of the inventor regarding the prior art.

The prior art description should not be regarded as being an authoritative disclosure of the true state of the prior art but rather as referring to considerations in and brought to the mind and attention of the inventor when developing this invention.

When referring to the description of the present invention, it should also be understood that the term “comprise” where used herein is not to be considered to be used in a limiting sense.

Accordingly, ‘comprise’ does not represent nor define an exclusive set of items, but includes the possibility of other components and items being added to the list.

This specification is also based on the understanding of the inventor regarding the prior art.

The prior art description should not be regarded as being an authoritative disclosure of the true state of the prior art but rather as referring to considerations in and brought to the mind and attention of the inventor when developing this invention.

Aspects of the present invention have been described by way of example only and it should be appreciated that modifications and additions may be made thereto without departing from the scope thereof, as defined in the appended claims.

THE

Claims (47)

CLAIMS DEFINING THE INVENTION ARE:

1. Grinding apparatus for finely grinding material and for producing said material in granular form, said grinding apparatus including a chamber, grinding means and pelletising means, said chamber configured to receive said material into the centre of the chamber, said grinding means including a surface, said surface being oriented substantially parallel to the pelletising means and being defined by either or both the dimensions and profile of the grinding means, and whereby a substantial portion of the surface at any time contacts the material and applies pressure against the material and the pelletising means to effect a grinding zone in the vicinity of introduction of the material into the chamber, and said pressure being pre-determined, to create a grinding force enabling the introduced material within the grinding zone to be finely ground to a material component including material particles of predetermined sizes, quantities and surface areas tailored for specific requirements, and to accumulate the finely ground material in the vicinity of the pelletising means, wherein the pressure applied by the grinding means subsequently directs the finely ground material component through the pelletising means, said pelletising means including a compression zone for compression of the finely ground material component into granules having predetermined characteristics defined thereby, and wherein the material is finely ground and compressed into granules in a single operation grinding and pelleting process within the chamber.

2. Grinding apparatus as claimed in Claim 1 wherein the chamber is configured to receive materials to be ground and accommodate the grinding means and the pelletising means.

3. Grinding apparatus as claimed in Claim 2 wherein the grinding means includes multiple rollers.

4. Grinding apparatus as claimed in Claim 3 wherein the multiple rollers are connected via interconnection means to create a roller unit.

5. Grinding apparatus as claimed in Claim 4 wherein the interconnection means determines whether: a) the entire roller unit rotates within the chamber relative to stationary pressing means; b) the roller unit remains substantially static with the rollers rotating on the spot on the pressing means rotates; or c) the roller unit, the rollers and the pelletising means rotate relative to each other.

6. Grinding apparatus as claimed in Claim 5 wherein the rollers include at least one of: a) Flat rollers – including wide flat rollers for applying a greater grinding surface against the material introduced to the chamber; b) Reversed tapered rollers where only a portion of the roller surface exerts grinding pressure to effect varying proportions of finely ground and coarsely ground material particles; or c) Flat rollers and reversed tapered rollers in combination or in sequence.

7. Grinding apparatus as claimed in Claim 6 wherein use of flat rollers results in at least an additional 10% of the finely ground material component having fine particles of less than 75 micron in size when using flat rollers as compared with traditionally inward tapered rollers.

8. Grinding apparatus as claimed in Claim 7 wherein reversed tapered rollers are configured to exert more pressure to powder or pulverizing the material in the grinding zone between the rollers and the contacted surface of the pelletising means which provides a further 10% -12% of the finely ground material component having particle sizes of less than 75 micron over and above the grinding effect achieved with flat rollers alone.

9. Grinding apparatus as claimed in Claim 8 wherein the grinding means also operates as pressing means by the rollers "pressing" the materials to be granulated through the pelletising means.

10. Grinding apparatus as claimed in Claim 9 wherein the pelletising means includes a die perforated with apertures having a predetermined configuration to produce a particular granule size.

11. Grinding apparatus as claimed in Claim 10 wherein the die apertures include an entry point and an exit point.

12. Grinding apparatus as claimed in Claim 11 wherein the apertures are uniformly configured and uniformly arranged across and throughout the die surface.

13. Grinding apparatus as claimed in Claim 11 wherein the apertures are varyingly configured and varyingly arranged across and throughout the die surface.

14. Grinding apparatus as claimed in Claim 12 or Claim 13 wherein the surface area of the die is increased or decreased by adapting the die in relation to the number, arrangement and configuration of the die apertures.

15. Grinding apparatus as claimed in Claim 14 wherein the surface area of the die is increased or decreased depending on whether the die apertures are any one of tapered, counter-bored, include a stepped-relief at the inlet surface of the die.

16. Grinding apparatus as claimed in Claim 14 wherein the apertures are provided across and throughout die surface in the number and arrangement as determined to produce the number of granules/pellets required and the final granule shape required having regard to the extent and speed with which the granule breaks down.

17. Grinding apparatus as claimed in Claim 15 wherein the apertures are configured across and throughout die surface in terms of size/width, as determined to produce granules/pellets with the particle fineness and granule compaction required having regard to the extent and speed with which the granule breaks down.

18. Grinding apparatus as claimed in Claim 17 wherein where one or a combination of two or more of: a) The roller unit, b) The individual rollers, and c) The pelletising means are required to rotate, the grinding apparatus includes single or multiple drive shaft(s) powered by drive means, bearings and gears to drive rotation of the roller unit and/or rotation of individual rollers and/or rotation of the die of the pelletising means.

19. Grinding apparatus as claimed in Claim 18 wherein the grinding apparatus is used to grind and pelletise material including soil treatment components for use as fertilisers.

20. Grinding apparatus as claimed in Claim 19 wherein the rotation of the rollers applies pressure to the material such that the material both accumulates and is then pushed into the pelletising means to produce the material in granular form.

21. Grinding apparatus as claimed in Claim 19 wherein the pressure applied by the grinding action of the rollers against the surface of the pelletising means is adapted to be adjusted to grind the material to pre-determined particle sizes from coarse, to very finely ground material.

22. Grinding apparatus as claimed in Claim 21 wherein the pressure applied to grind the material to pre-determined particle sizes from coarse to very finely ground material is adapted to be adjusted by any one or a combination of two or more of: a) The pressure set between the rollers and the surface of the pelletising means b) The angle of the rollers. c) The speed of rotation of the rollers d) The size of the apertures in the die. e) The location within the chamber where the feed material enters the grinding apparatus. f) The amount of material fed in to the centre of the chamber, as the further it spreads out and the more rolled it is the finer it gets.

23. Grinding apparatus as claimed in Claim 22 wherein the rotation of the rollers applies pressure to push the material through the apertures in the die and through a compression zone of the die to form strands of material that exit the compression zone of the die, with the length of the compressed material strand defining the granule size as it exits the compression zone of the die.

24. Grinding apparatus as claimed in Claim 23 wherein the length of compressed material is determined by cutters cutting the material as it is pushed through the apertures and exits the compression zone of the die, thereby forming pellets/granules of substantially uniform lengths.

25. Grinding apparatus as claimed in Claim 23 wherein the rotation of the rollers applies pressure to push the material through the apertures in the die and through a compression zone of the die to form strands of material that exit the compression zone of the die, and are broken off to form pellets/granules of random length(s) or having a range of lengths.

26. Grinding apparatus as claimed in Claim 24 or Claim 25 wherein the length of the compression zone, including the extent of compression, defines the crush strength of the granules and the dispersion time for the material to be made available as required.

27. Grinding apparatus as claimed in Claim 26 wherein the length of the compression zone of the die, including the extent of compression resulting from the pressure applied by the rollers effects high pressure compaction that is pre-determinable to enable production of granules having high crush strengths.

28. Grinding apparatus as claimed in Claim 27 wherein to effect production of granules via the grinding apparatus any one or more of the component material(s) used, the size of the component particles, the proportion of particles of particular sizes, fluids added to the component mixture, the drying temperature and/or drying time of the granules formed, also determine the crush strength of granules produced.

29. Grinding apparatus as claimed in Claim 28 wherein heat generated during either or both the grinding and pelletising process, or applied within the process determines the crush strength of the granule.

30. Grinding apparatus as claimed in Claim 29 wherein heat generated during either or both the grinding and pelletising process is controlled by: a) The diameter of the apertures in the die, b) The compression area of the die. c) Where the material is fed to the rollers.

31. Grinding apparatus as claimed in Claim 30 wherein heat generated during the grinding process is effected via the use of flat rollers resulting in granules of finely ground material produced during the pelletising process being at approximately 60˚C - 70˚C immediately after compaction, thereby avoiding the need for additional drying.

32. Grinding apparatus as claimed in Claim 31 wherein material used with the grinding and pelletising apparatus to produce granules of finely ground material includes elemental sulphur in which 90% of the particles are able to be ground to less than 75 micron in size.

33. Grinding apparatus as claimed in Claim 31 wherein material used with the grinding and pelletising apparatus to produce granules of finely ground material includes RPR (Reactive Phosphate Rock) where the material is able to be ground to particles of less than 75 micron in size, enabling RPR of lower reactivity to be used where increased fineness increases the RPR reactivity and enables removal of cadmium from the Reactive Phosphate Rock,

34. Grinding apparatus as claimed in Claim 33 wherein the grinding and pelletising apparatus is adapted to produce granules of finely ground material via the simultaneous fine grinding and pelletising of two component materials to effect intimate contact between the particles of each component.

35. Grinding apparatus as claimed in Claim 34 wherein the grinding and pelletising apparatus is adapted to produce granules comprised of elemental sulphur simultaneously finely interground with reactive phosphate rock (RPR).

36. Grinding apparatus as claimed in Claim 35 wherein the grinding and pelletising apparatus during the inter-grinding and compression process generates heat that assists the reactivity between the elemental sulphur, the RPR and water when added to the mixture.

37. Grinding apparatus as claimed in Claim 36 wherein the grinding and pelletising apparatus during the inter-grinding and compression process of the elemental sulphur, the RPR and water generates heat between 60˚C and 100˚C.

38. Grinding apparatus as claimed in Claim 37 wherein the grinding and pelletising apparatus during the inter-grinding and compression process generates heat that enables elemental sulphur particles to mobilise at around 80˚C and effectively smear the finely ground particles of the RPR and any other included actives.

39. Grinding apparatus as claimed in Claim 38 wherein the grinding and pelletising apparatus during the inter-grinding and compression process effects smearing of the elemental sulphur that results in intimate contact with other actives, reduces the explosive nature of fine sulphur particles, increases the surface area of the sulphur increasing its potential availability in or on the soil, enables pre-determined release profiles of the components of the granules to be achieved, and enables the biological oxidation of elemental sulphur (S) mixed and applied with other actives to increase its effectiveness as a fertiliser.

40. Grinding apparatus as claimed in Claim 39 wherein when using the grinding and pelletising apparatus for inter-grinding treatment compositions/materials and preparation of granules therefrom, the process is adapted to be customised by varying any one or more of: a) The percentage of the soil treatment components in the treatment composition/granule; b) The percentage of any additional actives, and/or other macro or micronutrients, soil conditioners, beneficial bacteria or other plant beneficial organisms and/or trace elements in the treatment composition/granule; c) The percentage of fluid in the treatment composition/granule; d) What the fluid in the treatment composition/granule is; e) The size of the particles of the soil treatment component(s) and/or any additional actives and/or other macro or micronutrients and/or any soil conditioners, including lime and/or any trace elements in the treatment composition/granule; f) The proportion of particle sizes in the mixture – superfine, fine, coarse; g) How the components are mixed – inter-ground, ground separately and then mixed, one being mixed with the fluid and then added to the remaining component(s); h) How the granules are prepared – using high or low pressure techniques - including the specific preparation technique itself and variations to that technique; i) How the granules are dried; j) The length of the compression zone in the formation of the granules/pellets.

41. Granules of material for use as soil treatment fertiliser compositions produced by the grinding apparatus for finely grinding material and for producing said material in granular form as claimed in Claim 1.

42. Granules of material for use as soil treatment fertiliser compositions as claimed in Claim 41 wherein the size of the granule of the material is 2 - 8 millimeters.

43. Granules of material for use as soil treatment fertiliser compositions as claimed in Claim 42 wherein the size of the granule of the material is 6 millimeters.

44. A method of manufacturing granules of material said granules including soil treatment material and said granules produced by means of the grinding apparatus for finely grinding material and for producing said material in granular form as claimed in Claim 1, said method including the steps of: a) Pre-determining the percentage of soil treatment components in the treatment composition/granule; b) Pre-determining the percentage of any additional actives, and/or other macro or micronutrients, soil conditioners, beneficial bacteria or other plant beneficial organisms and/or trace elements in the treatment composition/granule; c) Pre-determining the percentage of fluid in the treatment composition/granule; d) Pre-determining what the fluid in the treatment composition/granule is to be; e) Pre-determining the size of the particles of the soil treatment component(s) and/or any additional actives and/or other macro or micronutrients and/or any soil conditioners, including lime and/or any trace elements in the treatment composition/granule; f) Pre-determining the proportion of particle sizes in the mixture – superfine, fine, coarse; g) Pre-determining how the components are mixed – inter-ground, ground separately and then mixed, one being mixed with the fluid and then added to the remaining component(s); h) Pre-determining the high or low pressure technique to be used; i) Pre-determining the grinding means roller configuration to be used; j) Pre-determining the configuration of the pelletising means surface as regards arrangement, number , shape and size of the apertures of the pelletising surface and the length of the compression zone therein as required in the formation of the granules/pellets; k) Pre-determining if and how the formed granules are dried; and l) Preparing the granules by means of the grinding apparatus by introducing the pre- determined soil treatment material into the chamber of the grinding apparatus, and grinding said material and applying pressure thereto via the action of the grinding means in conjunction with the surface of the pelletising means, said grinding means adapted to effect the pre-determined finely ground material particles and to apply pressure to compress said finely ground particles into granules via said pelletising means, said grinding apparatus further distinguished by effecting granules having predetermined particle distributions, granule size and shape, crush strength and dispersion time, such that the treatment composition and/or the granules prepared are further customised as required for specific treatments.

45. Granules of material for use as soil treatment fertiliser compositions as claimed in any one of Claims 41 to 43, produced by means of grinding apparatus for finely grinding said material, as claimed in any one of Claims 1 to 40, and as further described herein with reference to the included examples and attached figures.

46. A method of manufacturing granules of material as claimed in Claim 44, said granules including soil treatment material and said granules produced by means of grinding apparatus for finely grinding said material, as claimed in any one of Claims 1 to 40, and as further described herein with reference to the included examples and attached figures.

47. Grinding apparatus for finely grinding material and for producing said material in granular form, as claimed in any one of Claims 1 to 40, and as further described herein with reference to the relevant included examples and attached figures. ROBERT HAMILTON HALL By his attorneys IPSPEC (NZ) LIMITED