AU2017203167A1

AU2017203167A1 - Granular fertilizer and soil conditioning formulations

Info

Publication number: AU2017203167A1
Application number: AU2017203167A
Authority: AU
Inventors: Phillip Haldon Taylor
Original assignee: Midland Distributors Ltd
Current assignee: Midland Distributors Ltd
Priority date: 2016-05-13
Filing date: 2017-05-12
Publication date: 2017-11-30

Abstract

Abstract Disclosed are granular fertilizer and soil conditioning formulations, and methods for their preparation. The granules include a combination of a binder selected from the group of alkali earth (i.e. group 11 metals including magnesium, calcium etc.) oxides, alkali earth hydroxides and siliceous clays (e.g. a phyllosilicate clay), and a material selected from gypsum, calcium sulfate hemihydrate, dolomite, limestone or rock phosphate. The combination enables the production of the granules by means of compaction. 1- ~ r F f I j-4-± ~4211~t1T4 ~ ' YL Kmi 0- 1.. I-f ~~ ilK Figure 1

Description

Granular fertilizer and soil conditioning formulations Field

The invention relates to fertilizer and soil conditioning formulations and more specifically to granular fertilizer and soil conditioning formulations, and to methods for their preparation.

Background

Any discussion of the prior art throughout the specification should in no way be considered as an admission that such prior art is widely known or forms part of common general knowledge in the field.

The efficient dispersal of fertilizing agents and soil conditioning agents across land requires that the agents have suitable flow qualities to allow them to be distributed evenly and rapidly.

Some natural materials have compositions which could enhance plant growth, but cannot be efficiently dispersed because the natural state of the material does not flow smoothly, even when crushed or pulverised, making their use as commercial fertilizing or soil conditioning agents more difficult. The poor flow of such natural materials is generally attributed to irregular shape or surface characteristics of the material. Such materials may have a particularly cohesive or sticky nature, and prone to clumping. This makes these materials difficult to spread using conventional spreading techniques.

Examples of these materials include gypsum (calcium sulfate dihydrate), dolomite (calcium magnesium carbonate), phosphate rock (or rock phosphate, which comprises calcium phosphate minerals which can be approximated to tricalcium phosphate, and typically comprises between 7 and 16 % P, more typically 10 to 16%P) and limestone (calcium carbonate). Dolomite, gypsum and calcium carbonate are used as calcium-rich soil conditioning agents. Phosphate rock, in addition to comprising calcium, has high levels of P. However, these materials, in their raw form, have poor flow qualities making them difficult to be commercially used in their raw form. For example, application of these materials via aircraft is severely restricted due to the inability to quickly dump the material in an emergency.

In addition, calcium sulfate hemihydrate (e.g. including that recycled from building plasterboard), having the same calcium to sulfate ratio as gypsum, also has the potential to be used as a fertilizing or soil conditioning agent.

To improve handling of raw materials, they may be manufactured into granules or pellets. One method for doing so involves the use of compressive forces on the material to press the material into a particular shape. Another method involves the agglomeration of small particles into larger granules by a growth agitation process, commonly in a rotating drum (such as a pelletiser).

Gypsum, calcium sulfate hemihydrate, dolomite, rock phosphate and calcium carbonate are not able to be easily granulated by compaction alone - the material does not bind together and/or crumbles easily. Similarly, agglomeration techniques applied to these materials tend to produce granules which are undesirably soft, and create a large proportion of dust and fines. In addition, agglomeration techniques are energy intensive compared to compaction, particularly if the granules require additional drying.

Some natural materials are chemically treated to improve the nutrient availability for the plants. For example, rock phosphate is treated with acid to produce superphosphate fertilizers (also known as acidulated phosphate rock). Superphosphate can be environmentally damaging, in that excessive application of superphosphate leads to phosphate leaching from soils to waterways. In addition, over time superphosphate increases the phosphate retention (P retention) of soils, reducing the availability of phosphate to plants. In addition, superphosphate is reactive with some other fertilizing or soil conditioning agents (especially alkaline agents), which restricts the formulations which may be produced containing superphosphate.

Object of the invention

It is an object of the present invention to provide a soil conditioning agent or fertilizing agent granule and method for its production which addresses, overcomes or ameliorates at least one of the abovementioned disadvantages, or at least provides the public with a useful choice.

Summary of the invention

It has surprisingly been found that the combination of a binder selected from the group of alkali earth (i.e. group II metals including magnesium, calcium etc.) oxides, alkali earth hydroxides and siliceous clays (e.g. a phyllosilicate clay), with a primary material selected from gypsum, calcium sulfate hemihydrate, dolomite, limestone or rock phosphate enables the production of granules by means of compaction. The granules produced by compaction require less energy to produce and are therefore more cost-effective and environmentally sustainable than granules produced by agglomeration techniques.

Preferred binders include calcium oxide, magnesium oxide, calcium hydroxide, magnesium hydroxide and bentonite clay. These may be selected based on their effect on binding the granule, and on the mineral nutrient profile of the granule desired by the user.

In one aspect, there is provided a method of making a fertilizing or soil conditioning granule including preparing a feed composition including a primary ingredient selected from the group consisting of gypsum, calcium sulfate hemihydrate, dolomite, phosphate rock, calcium carbonate and a combination thereof; a binder selected from the group consisting of siliceous clay, alkali metal oxides, alkali metal hydroxides, and a combination thereof; compacting the composition at compaction pressure of at least 2000 psi.

Preferably, the binder is 0.5 to 10 wt.% of the feed composition.

Preferably, the gypsum is naturally occurring gypsum, or otherwise industrially manufactured gypsum.

Preferably, the calcium sulfate hemihydrate is obtained from recycled plasterboard. Preferably, the siliceous clay is bentonite.

Preferably, the feed composition further includes water in an amount of 0 to 5 wt. %.

Preferably, the compacting is performed by counter rotating rollers.

Preferably, the surface of one or more rollers includes indentations.

Preferably, the rotation of the rollers is synchronised such that the indentations on each roller oppose one another at the nip region of the rollers.

Preferably, the method further includes sorting the compacted material by size.

In one embodiment, the feed composition further includes monoammonium phosphate.

In one embodiment, the method further includes the addition to the feed composition of one or more plant nutrients, pesticides, herbicides, or a combination thereof.

Preferably, the plant nutrients are selected from the group consisting of: elemental sulfur, potassium sulfate, magnesium carbonate, urea, ammonium sulfate, copper sulfate, zinc sulfate, manganese sulfate, boron compounds, cobalt sulfate, ferrous sulfate, potassium iodate, sodium selenite and sodium molybdate.

In one preferred embodiment, the feed composition includes: about 45 wt. % of gypsum; about 45 wt. % rock phosphate; and about 10 wt. % of a binder selected from the group consisting of siliceous clay, alkali metal oxides, alkali metal hydroxides, and a combination thereof.

In one embodiment, the feed composition includes about 45 wt. % of gypsum; about 45 wt. % rock phosphate; and about 10 wt. % of a binder selected from the group consisting of siliceous clay, alkali metal oxides, alkali metal hydroxides, and a combination thereof; and is adapted to be compacted to produce a fertilizer granule.

Preferably, the siliceous clay is bentonite.

In a further aspect, there is provided a soil conditioning or fertilizing granule including about 45 wt. % of gypsum; about 45 wt. % rock phosphate; and about 10 wt. % of a binder selected from the group consisting of siliceous clay, alkali metal oxides, alkali metal hydroxides, and a combination thereof.

Preferably, the siliceous clay is bentonite.

In a further aspect, there is provided a method of making a phosphate fertilizer granule including: preparing a feed composition including: 50 to 80 wt.% phosphate rock; 20 to 50 wt.% of a second ingredient selected from the group consisting of gypsum, calcium sulfate hemihydrate, dolomite, calcium carbonate and a combination thereof; compacting the composition at compaction pressure of at least 2000 psi.

Preferably, the phosphate rock is present in an amount of 65 wt.%.

Preferably, the second ingredient comprises gypsum in an amount of 30 wt.%.

Preferably, the granule further includes 1 to 10 wt.% elemental sulfur.

Preferably, the gypsum is naturally occurring gypsum or otherwise industrially manufactured gypsum.

Preferably, the calcium sulfate hemihydrate is obtained from recycled plasterboard.

Preferably, the compacting is performed by counter rotating rollers.

Preferably, the surface of one or more rollers includes indentations.

Preferably, the rotation of the rollers is synchronised such that the indentations on each roller oppose one another in the nip region of the rollers.

Preferably, the method further includes sorting the compacted material by size.

Preferably, the method further includes the addition of one or more plant nutrients, pesticides, herbicides, or a combination thereof.

In a further aspect, there is provided an apparatus for manufacturing a fertilizing or soil conditioning granule, the apparatus comprising a roller compactor.

Preferably, the roller compactor includes counter rotating rollers, and the surface of one or more of the rollers includes indentations. The rotation of the rollers is synchronised such that the indentations on each roller oppose one another in the nip region of the rollers. The apparatus preferably includes a mechanism to sort the granules by size.

When alkali earth oxides and hydroxides are used in the method of the present invention, the heat produced during the compaction process contributes to the drying of the granule, which further increases the hardness of the material without the requirement for additional drying, thereby reducing the energy cost in production.

Granules produced in this way also have improved hardness and reduced the dust/fines of fertilizer granules, when compared to granules produced by agglomeration techniques.

The combination of rock phosphate with gypsum or dolomite and, optionally, alkali earth oxide and sulfur, provides a phosphate-containing fertilizer granule with reduced negative effects associated with superphosphate, such as reduced leaching and a reduced effect on phosphate retention in soils.

In some embodiments, the rock phosphate-containing granules may further include monoammonium phosphate.

Gypsum may be directly obtained from natural gypsum deposits, or obtained from industrial processes.

In addition, a soil conditioning/fertilizing granule may be prepared by compaction by combining gypsum with virgin or recycled plaster wallboard, wherein the plaster wallboard mostly comprises calcium sulfate hemihydrate. For example, the gypsum may be combined or fortified with recycled wall board and alkali earth oxide.

Brief description of the drawings

The invention will now be described by example only and with reference to the Figure, in which:

Figure 1 is a schematic of the granulating arrangement for preparing granules of the present invention.

Detailed description of the invention

Unless the context clearly requires otherwise, throughout the description, the words “comprise”, “comprising”, and the like, are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense, that is to say, in the sense of “including, but not limited to”.

The primary ingredient of the fertilizing or soil conditioning granule is selected from gypsum, dolomite, recycled calcium sulfate hemihydrate, rock phosphate, lime (calcium carbonate) and combinations thereof.

The primary ingredient is combined with a binder selected from the group consisting of siliceous clay (in particular, phyllosilicate clay), alkali metal oxides, alkali metal hydroxides, and a combination thereof. The use of these binders increases the hardness of the granule. Preferably, if clay is to be used, the clay is bentonite. Without being bound by theory, it is believed that the binders assist in the hardening of the granule by withdrawing moisture from the primary material. In the case of the alkali earth oxides and hydroxides, the withdrawal of moisture occurs as a result of a chemical reaction, and in the case of the siliceous clay the withdrawal occurs by intercalation/sequestration of the water between the clay layers, and possibly due to the presence of Mg, Na or K. Best results are achieved where the binder is present in amounts of between 0.5 and 10 wt.%.

In some cases, the feed composition may require the addition of water. This may be done to reduce the dustiness of the feed composition or to assist in the lubrication of the composition and assist its feed into the granulator. In some cases, up to 5% wt. water will be required to produce a feed composition suitable for use in the composition. However, water may not need to be added as the primary material may already contain sufficient residual water, either as water of crystallisation or bulk/surface water in the material.

In an alternative embodiment, rock phosphate may be combined with gypsum and elemental sulfur to form a granule having a N-P-K-S profile which is similar to that of superphosphate (advantageously having a reduced effect of P retention in soil and having reduced leaching).

Rock phosphate-containing granules may further include monoammonium phosphate. Monoammonium phosphate has a faster rate of phosphate release than rock phosphate on the paddock. Addition of monoammonium phosphate to rock phosphate-containing feed compositions can therefore result in a granule having a release profile closer to the release profile of superphosphate.

Granules according to the present invention are prepared from the feed composition described herein by means of compaction. Whilst different compaction techniques are known, including rams and rollers, for preparing granules, the feed composition of the present invention is preferably fed to a roller compactor comprising counter rotating rollers.

In a preferred embodiment, the rollers are indented with a pattern of dimples or cups and are synchronised such that each dimple directly opposes a dimple on the other roller at the nip region (compaction zone) of the rollers. It has been surprisingly found that the indents on the roller shaped in this way improves the ballistic properties of the granule and the uniformity of the granule shape, and reduces the production of flakes and other irregularly shaped granules, thereby reducing the need for reprocessing material. However, alternative embodiments are envisioned where the dimples are intentionally off-set at the nip region, or where only one of the rollers is dimpled and one is smooth, such that a dimple meets a smooth surface.

Using the indented rollers, the pressure of the compaction of the feed composition is preferably greater than 2000 psi.

In addition to the primary ingredient and binder, the feed composition may also comprise additional plant nutrients selected from the group consisting of: elemental sulfur, calcium carbonate (lime), potassium sulfate, magnesium carbonate, urea, ammonium sulfate, copper sulfate, zinc sulfate, manganese sulfate, boron compounds, cobalt sulfate, ferrous sulfate, potassium iodate, sodium selenite and sodium molybdate.

In addition, it has been surprisingly found that a feed composition comprising gypsum, magnesium oxide and phosphate rock produces a granule with desirable physical properties, as well as a good nutrient profile for use as a fertilizer or soil conditioning agent (see Table 7).

With reference to Figure 1, granules were produced from feed formulations shown in Tables 1 to 7 according to the following method:

The raw materials were combined in intake hopper 1 and combined in Infeed Tip Hopper 1. Optimal particle size for the raw material is between 0.5mm and 1 mm diameter, but particles sizes greater than 6mm have been used successfully. Additional water may be added (up to 5 wt.%) depending on the moisture content of the raw materials and the ambient humidity.

Where calcium sulfate hemihydrate, in the form of recycled wall board, is used, the recycled wallboard was crushed to particle size of <5mm, and blended with raw natural gypsum. The paper covering the wallboard may also be incorporated. No additional moisture is required. With reference to Table 1, the blend of gypsum and recycled wall board comprises roughly equal amounts of each component, by weight.

For all compositions described in Tables 1 to 7, the feed formulation is transported via metering screw conveyor 2 to feed distributor 3 which distributes the admixture to one of two granulators 4, 5. The granulators include counter rotating roller compactors, each roller having indentations (dimples) on their surface and being synchronised such that the indentations on each roller oppose each other at the nip region of the rollers. The granulators produce granules having dimensions that correlate to the size of the dimples on the roller surface.

It has been found that the use of dimpled rollers reduces the production of flakes (which tend to be irregular in shape), and exerts compaction force on the admixture so as to produce a granule having a regular, preferably spheroidal, shape.

The feed composition is compacted by the rollers at a pressure of at least 2000 psi, so as to produce granules having average diameter of 3 to 5 mm, depending on the specification of the indentations on the rollers. The granules are transported by belt conveyor 7 to rotary screen 8, which separates the granules from the fines and oversize pieces. The rotary screen 8 is a trommel type rotary screen which removes rough edges and break co joined granules and give the granules a final form and improved shape. The fines are returned to feed distributor 3 by screw conveyor 9 and the granules are transported, e.g. for packaging, drying or storage, by “Z” pattern bucket elevator 10.

With reference to the feed formulation of Table 6 and 7, a granule is produced using rock phosphate having a P value of typically 15-16%P. Some of the rock phosphate may be substituted with monoammonium phosphate. The rock phosphate-containing granules of the present invention have several advantages over superphosphate compositions. Primarily, rock phosphate has reduced leaching and a greater resistance to a change of pH once it is spread on the ground when compared to superphosphate, thereby being more environmentally friendly. Further, the rock phosphate feed compositions are generally more stable and can be blended with other products more reliably. For example, superphosphate, having acidic properties, causes undesirable effects in alkaline blends. Moreover, the rock-phosphate granules produced according to the present invention have a lower manufacturing cost and a lower capital requirement (in that the preparation does not require an acid plant to produce superphosphate). In addition, the use of rock phosphate instead of superphosphate in this formulation means that the phosphorus is not subject to P retention as superphosphate. Therefore there is more phosphorus available to the environment.

In addition to the finding that the siliceous clay functions as a binder in the granules of the present invention, it has also been found that the incorporation of a siliceous clay increases the rate at which the granule breaks down on the paddock. It is also envisioned that alternative additives may be used in the feed composition for the granule to increase the rate of on-paddock break down.

Although this invention has been described by way of example and with reference to possible embodiments thereof, it is to be understood that modifications or improvements may be made thereto without departing from the scope of the invention. The invention may also be said broadly to consist in the parts, elements and features referred to or indicated in the specification of the application, individually or collectively, in any or all combinations of two or more of said parts, elements or features. Furthermore, where reference has been made to specific components or integers of the invention having known equivalents, then such equivalents are herein incorporated as if individually set forth.

Claims

What is claimed is:

1. A method of making a fertilizing or soil conditioning granule including preparing a feed composition including a primary ingredient selected from the group consisting of gypsum, calcium sulfate hemihydrate, dolomite, phosphate rock, calcium carbonate and a combination thereof; a binder selected from the group consisting of siliceous clay, alkali metal oxides, alkali metal hydroxides, and a combination thereof; compacting the composition at compaction pressure of at least 2000 psi.
2. The method of claim 1, wherein the binder is 0.5 to 10 wt.% of the feed composition.
3. The method of claim 1 or 2, wherein the gypsum is naturally occurring gypsum or otherwise industrially manufactured gypsum.
4. The method of any one of the preceding claims, wherein the calcium sulfate hemihydrate is obtained from recycled plasterboard.
5. The method of any one of the preceding claims, wherein the siliceous clay is bentonite.
6. The method of any one of the preceding claims, wherein the feed composition further includes water in an amount of 0 to 5 wt. %.
7. The method of any one of the preceding claims, wherein the compacting is performed by counter rotating rollers.
8. The method of claim 7, wherein the surface of one or more rollers includes indentations.
9. The method of claim 8, wherein the rotation of the rollers is synchronised such that the indentations on each roller oppose one another at the nip region of the rollers.
10. The method of any one of the preceding claims, further including sorting the compacted material by size.
11. The method of any one of the preceding claims, further including the addition to the feed composition of one or more plant nutrients, pesticides, herbicides, or a combination thereof.
12. The method of claim 11, wherein the plant nutrients are selected from the group consisting of; elemental sulfur, potassium sulfate, magnesium carbonate, urea, ammonium sulfate, copper sulfate, zinc sulfate, manganese sulfate, boron compounds, cobalt sulfate, ferrous sulfate, potassium iodate, sodium selenite and sodium molybdate.
13. The method of any one of the preceding claims, wherein the feed composition includes: about 45 wt. % of gypsum; about 45 wt. % rock phosphate; and about 10 wt. % of a binder selected from the group consisting of siliceous clay, alkali metal oxides, alkali metal hydroxides, and a combination thereof.
14. A feed composition for use in the method of claim 1, including about 45 wt. % of gypsum; about 45 wt. % rock phosphate; and about 10 wt. % of a binder selected from the group consisting of siliceous clay, alkali metal oxides, alkali metal hydroxides, and a combination thereof; the feed composition being adapted for being compacted to produce a fertilizer granule.
15. The feed composition of claim 14, wherein the siliceous clay is bentonite.
16. A soil conditioning or fertilizing granule including about 45 wt. % of gypsum; about 45 wt. % rock phosphate; and about 10 wt. % of a binder selected from the group consisting of siliceous clay, alkali metal oxides, alkali metal hydroxides, and a combination thereof.
17. The soil conditioning or fertilizing granule of claim 16, wherein the siliceous clay is bentonite.
18. A method of making a phosphate fertilizer granule including: preparing a feed composition including: 50 to 80 wt.% phosphate rock; 20 to 50 wt.% of a second ingredient selected from the group consisting of gypsum, calcium sulfate hemihydrate, dolomite, calcium carbonate and a combination thereof; compacting the composition at compaction pressure of at least 2000 psi.
19. The method of claim 18, wherein the phosphate rock is present in an amount of about 65 wt.%.
20. The method of claim 18 or 19, wherein the second ingredient comprises gypsum in an amount of about 30 wt.%
21. The method of any one of claims 18 to 20, further including 1 to 10 wt.% elemental sulfur.
22. The method of any one of claim 18 to 21, wherein the gypsum is naturally occurring gypsum or otherwise industrially manufactured gypsum.
23. The method of any one of claims 18 to 22, wherein the calcium sulfate hemihydrate is obtained from recycled plasterboard.
24. The method of any one of claims 18 to 23, wherein the feed composition further includes water in an amount of 0 to 5 wt. %.
25. The method of any one of claims 18 to 24, wherein the compacting is performed by counter rotating rollers.
26. The method of claim 25, wherein the surface of one or more rollers includes indentations.
27. The method of claim 26, wherein the rotation of the rollers is synchronised such that the indentations on each roller oppose one another at the nip region of the rollers.
28. The method of any one of claims 18 to 27, further including sorting the compacted material by size.
29. The method of any one of claims 18 to 28, further including the addition of one or more plant nutrients, pesticides, herbicides, or a combination thereof.
30. The method of claim 29, wherein the plant nutrients are selected from the group consisting of: elemental sulfur, potassium sulfate, magnesium carbonate, urea, ammonium sulfate, copper sulfate, zinc sulfate, manganese sulfate, boron compounds, cobalt sulfate, ferrous sulfate, potassium iodate, sodium selenite and sodium molybdate.