Process for Making Granules and Agglomerates from Powders

Abstract

A method of processing a powder, comprising (a) contacting the powder with (i) a 2-40% by weight solution of a sulphur- or phosphorous-containing mineral acid or a mixture thereof, or (ii) one or more alkaline earth metal oxides, carbonates or hydroxides, or a mixture thereof; (b) combining the product of (a)(i) with one or more alkaline earth metal oxides, carbonates or hydroxides, or a mixture thereof; or combining the product of (a)(ii) with a 2-40% by weight solution of a sulphur- or phosphorous-containing mineral acid or a mixture thereof and optionally with further of the alkaline earth metal oxides, carbonates or hydroxides, or a mixture thereof; and (c) granulating the combination of (b) to form granules.

Phosphate- and potassium-containing fertilisers are made using the granules.

Claims

1. A method of processing a powder, comprising (a) contacting the powder with (i) a 2%-40% by weight solution of a sulphur- or phosphorous-containing mineral acid or a mixture thereof, or (ii) one or more alkaline earth metal oxides, carbonates or hydroxides, or a mixture thereof; (b) combining the product of (a)(i) with one or more alkaline earth metal oxides, carbonates or hydroxides, or a mixture thereof; or combining the product of (a)(ii) with a 2%-40% by weight solution of a sulphur- or phosphorous-containing mineral acid or a mixture thereof and optionally with further of the alkaline earth metal oxides, carbonates or hydroxides, or a mixture thereof; and (c) granulating the combination of (b) to form granules.

2. (canceled)

3. A method according to claim 1, wherein step (b) comprises forming granules of mass median diameter (MMD) from 2 mm to 10 mm.

4. A method according to claim 1, wherein the powder comprises ash e.g. from combustion of one or more of bone meal, biomass, animal litter, poultry litter, paper, straw, offal and crematorium residues.

5. A method according to claim 1, wherein the powder comprises dust e.g. industrial dust, industrial waste dust, dust abatement residues, cement kiln dust and industrial flue dust.

6. A method according to claim 4, wherein 90% or more by weight of the powder consists of ash.

7. A method according to claim 1, wherein the powder has a MMD of up to 1 mm.

8. (canceled)

9. A method according to claim 1 comprising contacting the powder with a 3%-30% by weight solution of the acid.

10. A method according to claim 1 wherein the acid comprises sulphuric acid, phosphoric acid or mixtures thereof.

11. A method according to claim 1 comprising combining the product of (a) with an oxide or hydroxide of calcium or magnesium, or mixtures thereof.

12. A method according to claim 1 comprising combining the powder with the acid at a weight ratio of from 1:1 to 10:1 powder:acid.

13. A method of processing an ash, said ash comprising one or more alkaline earth metal oxides, carbonates or hydroxides, the method comprising (a) combining the ash with 2%-40% by weight solution of a sulphur- or phosphorous-containing mineral acid or a mixture thereof, (b) granulating the combination of (a) to form granules.

14. (canceled)

15. A method according to claim 13, wherein step (b) comprises forming granules of mass median diameter (MMD) from 2 mm to 10 mm.

16. (canceled)

17. A method according to claim 13, wherein the ash comprises 2% or more of the alkaline earth metal oxide, carbonate or hydroxide or a mixture thereof.

18. A method according to claim 13, wherein the powder has a MMD of up to 1 mm.

19. A method according to claim 13 comprising combining the ash with a 3%-30% by weight solution of the acid.

20. A method according to claim 13, wherein the acid comprises sulphuric acid, phosphoric acid or mixtures thereof.

21. (canceled)

22. A method according to claim 13 comprising combining the powder with the acid at a weight ratio of from 1:1 to 10:1 powder:acid.

23-25. (canceled)

26. A method of making a fertiliser, the method comprising processing ash comprising meat and bone meal ash, straw ash, poultry litter ash and mixtures thereof, the processing comprising (a) mixing the ash with an aqueous solution of from 5% to 30% sulphuric acid by weight in a weight ratio of 10 parts ash:1-5 parts solution; (b) combining the product of (a) with calcium (II) oxide at a ratio of 20 parts ash:1-5 parts calcium (II) oxide, agitating the combination and allowing it to cure; and (c) granulating the combination of (b) to form granules of MMD 2 mm-5 mm.

27. A method according to claim 1 comprising granulating the combination while it is curing.

28. A method according to claim 1, wherein the method is a method of making a fertiliser.

29-33. (canceled)

Description

[0066] The invention is now illustrated in specific examples, with reference to the accompanying drawings in which:

[0067] FIG. 1 shows mean height of plants tested in growing trials using fertilisers of the invention; and

[0068] FIG. 2 shows mean cumulative leaf chlorophyll score of plants tested in growing trials using fertilisers of the invention.

EXAMPLES

Example 1

Meat and Bone Meal Ash

[0069] 200 g of a 10% solution of sulphuric acid was added to 500 g of finely divided meat and bone meal ash. The mixture was vigorously mixed until a homogeneous slurry was achieved, this taking about 8-10 minutes. To this was added 50 g of finely divided lime (CaO) and the slurry was continually mixed until a stiff paste was formed, again taking about 10 minutes. The paste was then broken up and granulated with the aid of a granulator giving granules of approximate size 3-4 mm diameter.

[0070] A sample of granules were removed and dusted with further bone ash powder to prevent agglomeration.

[0071] The resultant granules, although reasonably hard, continued to cool and harden over the following 2-3 hours. The granules were then ready for spreading as fertiliser.

Example 2

Straw Ash

[0072] 200 g of a 5% solution of sulphuric acid was added to 500 g of finely divided, pale white straw ash. The mixture was then thoroughly mixed over about 6 minutes until a homogeneous paste was achieved. To this was added 36 g of finely divided lime (CaO) and continually mixed until a stiff paste was formed. The paste was then broken up through a suitable mesh, with the resultant being placed in a pan granulator for granulation.

[0073] The resultant granules produced were dark, almost black in colour, firm and continued to harden over time (about 4 hours).

Example 3

Chicken Litter Ash

[0074] 100 g of a 20% solution of sulphuric acid was added to 500 g of finely divided chicken litter ash. The mixture was then thoroughly mixed until a homogeneous paste was achieved. To this was then added 50 g of finely divided lime (CaO) and continually mixed until a stiff paste was formed. The paste was then broken up through a mesh, with the resultant particles being placed in a pan granulator for granulation. The granules were then dusted with further chicken litter ash powder to prevent agglomeration prior to allowing to cure.

[0075] The resultant granules were firm and continued to harden over time.

Example 4

Meat and Bone Meal Ash (Combined Mixer/Granulator)

[0076] 500 g of finely divided meat and bone meal ash was added to a high intensity mixer/granulator apparatus. 200 g of a 10% solution of sulphuric acid was added to mixer/granulator. The mixture was vigorously mixed until a homogeneous slurry was achieved, this taking about 8-10 minutes. To this was added 50 g of finely divided lime (CaO). The resultant slurry was continually mixed until the ashes agglomerated giving granules of approximate size 3-4 mm diameter.

[0077] A sample of granules were removed and dusted with further bone ash powder to prevent agglomeration.

[0078] The resultant granules, although reasonably hard, continued to cool and harden over the following 2-3 hours. The granules were then ready for spreading as fertiliser.

Example 5

Granule Analysis

[0079] The nitrogen, phosphorous and potassium content of each of the granules formed in Examples 1 to 3 were analysed and are shown in Table 1.

TABLE-US-00001 TABLE 1 Nitrogen Phosphorous Potassium Content (%) Content (%) Content (%) Example 1 0 20.6 0 Example 2 0 0 41.5 Example 3 0 16 12

Example 6

Growing Trials

[0080] Materials and Methods

[0081] Formulations based on Examples 1 and 3 were tested in growing trials.

[0082] Broad beans (var Aquadulce Claudia) were established at commercial sowing rates in 5 L pots containing vermiculite plus sufficient nitrogen content to artificially create a medium soil with a soil nitrogen supply (SNS) of 1. In order to create this medium soil nitrogen was added as urea at a standard rate of 0.1 g per 5 L pot, based on a pot diameter of 22.5 cm, and superphosphate and potassium sulphate were added at the same rate as P.sub.2O.sub.5 and K.sub.2O, respectively. This artificial medium soil created a baseline for crop growth, as previously shown to be effective in STC study E954, and served as the negative control treatment. Inoculum (Legume Fix, Legume Technology Ltd.) was also added to this substrate in order to ensure presence of beneficial bacteria for nitrogen fixation.

[0083] A negative control (i.e. no additional fertiliser) was tested alongside seven further treatments arranged within a climate controlled glasshouse. A positive control was used containing standard phosphate (P.sub.2O.sub.5) and Potash (K.sub.2O) at a rate of 150 kg/ha each, following consultation with recommendations in Fertiliser Manual RB209 (Defra) for fertiliser application to broad beans grown on low fertile medium soils. Six commercial fertiliser treatments were also tested in which the P or K element was replaced by granules of Examples 1 or 3 at high, medium and low rates, where the medium rate was set to be comparable to the amount of nutrient available in the positive control. Irrigation was ad libitum and provided using mains water. Each treatment was replicated five times in a randomised block design. Treatment details are provided in Table 2. Fertilisers incorporating granules of Examples 1 and 3 above were used as specified in the Table.

TABLE-US-00002 TABLE 2 Treatment details, assuming an evidenced P content in P21 of 21.7% and an evidenced K content in straw ash of 35.2%, and correcting for K present in P21 (3.18%) and P present in straw ash (1.81%). P content of superphosphate = 18%; K content of potash = 42%. Amount per 5 L pot.sup.NB Treatment Nutrients Granules of Granules of Label added P/K content Superphosphate Example 1 Potash Example 3 Control NPK Baseline Commercial PK 150/150 kg/ha 3.33 1.43 PK (C PK) P21 high PK.sup.a 300/150 kg/ha 5.53 1.33 (H P21) P21 med* PK.sup.a 150/150 kg/ha 2.76 1.39 (M P21) P21 low PK.sup.a 75/150 kg/ha 1.38 1.40 (L P21) Straw ash PK.sup.b 150/300 kg/ha 3.22 3.41 high (H SA) Straw ash PK.sup.b 150/150 kg/ha 3.28 1.70 med** (M SA) Straw ash PK.sup.b 150/75 kg/ha 3.31 0.85 low (L SA) *where P added should be equivalent to the commercial PK control; **where K added should be equivalent to the commercial PK control; .sup.aP added via P21, K uniform; .sup.bK added via Straw ash, P uniform. .sup.NBThe amount of P and K per pot has been corrected for field sowing rates, where in an equivalent field area only 0.10 of a bean plant would be grown.

[0084] A single product application was undertaken, with Mg also added evenly across all pots (0.1 g/pot) post-emergence. Products were applied immediately prior to sowing on the 08.02.16 as a surface treatment and lightly incorporated into the surface of the substrate. Five beans were initially sown per pot, though thinned to one post-emergence (to increase establishment per pot and provide data on germination).

[0085] Regular agronomic assessments were done throughout the trial period, looking for appropriate indicators of crop quality and yield (i.e. plant height, leaf chlorophyll content). At the end of the study period root and above-ground plant mass was determined and an assessment of bean yield made.

[0086] Prior to commencing the study 5 sub-samples of clean vermiculite were taken and combined as a single sample for chemical analysis by NRM. At the end of the trial samples were taken from all pots and combined into a single sample per treatment prior to sending for the same analysis. This was done to allow comment to be made on remaining nutrient in treated pots vs both baseline levels and untreated vermiculite. This element of the work was included through sub-contract, with the projects nine samples analysed by NRM analysis package H001 (which is appropriate for vermiculite according to NRM). This entailed extraction according to BSEN13040 2000 [1:5] and was expected to produce data on Dry Matter, Bulk Density, Dry Density, pH, Conductivity, Nitrate-N and Ammonium-N with calculated soluble N, Chloride, Sulphate, Potassium, Phosphorous, Magnesium, Calcium, Sodium, Iron, Manganese, Zinc, Copper and Boron.

[0087] Regular observations were undertaken to record the pest and disease levels that occurred. The crops were treated, as with the standard comparison crop, with the fungicide (Signum) to control chocolate spot on the 07.04.16. No further diseases or pests were observed throughout the trial period.

[0088] At the end of the trial all remaining product provided by the funder was collected for return to the funder. This included any growing media used in the trial that was exposed to treatment with product, as well as any remaining product returned post-analysis from NRM.

[0089] Results

[0090] Plant Height

[0091] The height of each plant was measured at 7 intervals prior to harvest. The mean height for each treatment group can been seen in FIG. 1 (n=5).

[0092] Chlorophyll Content

[0093] The mean cumulative leaf chlorophyll score was measured at 3 intervals over the course of the study period for each treatment. This is shown in FIG. 2 (n=5).

[0094] Above-Ground Plant Biomass

[0095] The above-ground plant biomass and below-ground plant biomass at harvest was measured for each treatment. The mean values and standard errors are shown in Table 3 below.

TABLE-US-00003 TABLE 3 Mean Above- Mean Below- Ground Ground Treatment Biomass (g) Biomass (g) Control 8.1 1.5 27.79 2.55 C PK 21.9 6.4 30.58 6.53 H P21 17.1 3.0 30.78 0.87 M P21 17.0 3.4 39.73 4.06 L P21 10.9 2.9 27.79 4.04 H SA 22.4 6.5 52.85 10.86 M SA 26.1 6.8 50.61 12.71 L SA 16.0 5.0 34.44 11.11

[0096] Harvest Parameters

[0097] Following harvest, the number of pods, the pod weight and bean weights were measured for each treatment group. The mean values and standard errors are shown in Table 4 below:

TABLE-US-00004 TABLE 4 Mean pod Mean pod Mean bean Treatment number weight (g) weight (g) Control 1.2 0.2 10.4 4.3 4.2 1.9 C PK 1.0 0.4 24.2 9.8 9.1 3.8 H P21 0.4 0.2 21.3 0.5 8.6 0.4 M P21 0.8 0.4 15.5 5.3 4.4 1.8 L P21 1.0 0.3 7.8 2.2 3.5 0.3 H SA 1.4 0.5 39.9 15.6 15.8 7.4 M SA 2.0 0.8 27.7 10.7 7.9 3.7 L SA 1.0 0.3 22.9 12.7 10.2 4.5

[0098] Chemical analysis of substrate revealed little variation between P21 and SA treatments vs the PK control (C PK) for most parameters. However, a notable exception to this pattern was seen for chloride, which appeared elevated by SA. It was clear from observations on plant growth and vigour that the increases seen had no negative impact on plants grown under the SA treatments, and could potentially be seen as beneficial given the key role of chloride as a plant micro-nutrient.

[0099] Data generally demonstrated improved performance of broad beans under the positive control treatment (with added PK) vs the negative control, as expected. This was notable for all measured above-ground growth parameters, with the exception of leaf number. Similarly improved performance of bean plants was consistently observed under experimental treatments when P21 was applied at a high rate and when SA was applied at either a high or medium rate, with low SA application also matching the positive control, particularly in terms of yield parameters. SA also appeared to have a stronger positive effect on below-ground growth parameters, with high and medium rates of SA being the only treatments that appeared to increase root fresh weight over the control, with the possible exception of P21 at a medium rate, albeit non-significantly according to the statistical analysis run. In no instance did application of either experimental treatment result in negative effects on broad beans.

[0100] Chemical analysis showed that for the majority of compounds assessed, treatment with P21 and SA had no observable effect. Nevertheless, results also suggested that use of SA may have elevated chloride concentrations within the substrate, though not at any detriment to crop growth.

[0101] The results supported that SA (using Example 3 product) offers particular potential as a K fertiliser in legume production, with benefits of SA use evidenced at all rates tested, including the lowest rate used. The added benefit might be derived from fertilising broad beans with SA as opposed to potash, where SA had apparently comparable benefits to potash, even when the SA was applied at a lower rate. As an essential micro-nutrient, increased chloride may have even contributed to the generally positive effect of SA on bean growth.

[0102] Benefits of P21 (using Example 1 product) were less apparent in the current study, where at a comparable (i.e. medium) rate to superphosphate, P21 was typically out-performed in terms of its ability to promote plant growth and yield. Nevertheless, at an increased rate the benefits of P21 fertilisation appeared similar to superphosphate, supporting its use as a fertiliser (and especially given the lower cost of P21 production and its micronutrient content).

[0103] In no instance were any negative effects on broad bean performance observed, supporting crop safety of the products used at the rates tested.

[0104] The invention hence provides methods for processing powders, e.g. ashes, to form granules that are useful in or as fertilisers.