Compound fertilizer pellet manufacturing

Abstract

1. A method for producing a pelletized fertilizer product, comprising the steps of: producing a first mixture of phosphoric acid and ammonia; adding the first mixture and polyhalite powder to a pelletizer to produce a second mixture; and, while the pelletizer processes the second mixture to produce pellets, supplying ammonia to the second mixture to complete the formation of ammonium phosphate in the second mixture.

Description

[Technical Field]

[0001] The present invention relates to a method for producing fertilizer pellets and to fertilizer pellets. [Background technology]

[0002] A common method of supplementing plant-available nutrients is to treat seedbeds, fields, and other growing media with agglomerated pelleted fertilizer products. Pelleted products have the advantages of being highly stable, easy to spread with conventional horticultural and agricultural machinery, and easy to apply at the desired rate.

[0003] A wide variety of fertilizer compositions are available, and the effectiveness of a particular fertilizer composition will depend on factors such as the type of plant to which it is applied, the maturity of the plant, the condition of the growing medium, and environmental conditions.

[0004] Major plant nutrients include nitrogen, phosphorus, potassium, magnesium, calcium, and sulfur. Fertilizer compositions may incorporate these individual nutrient elements through inclusion in any of a number of chemical compounds. Even if different compounds contain the same basic nutrient elements, the bioavailability of the nutrient elements may vary depending on the mechanism by which the compound is broken down. Nutrient bioavailability may also vary as a result of other aspects of the fertilizer's chemical or mechanical formulation. For example, some fertilizer pellets incorporate slowly degrading coatings or binders to delay nutrient release. Some compounds rely on the microflora in the growing medium to release their nutrient elements. Some compositions make nutrients available in a chelated form to improve nutrient uptake.

[0005] To provide multiple nutrients, growers can apply multiple different fertilizer compositions or a single multi-nutrient fertilizer composition. For a multi-nutrient composition to be effective, its component compounds must be in a properly balanced ratio and able to function effectively in the presence of other components. This effectiveness may depend on factors other than the fertilizer's contents, such as environmental water, heat, and the presence of certain microflora. It is difficult to predict the effectiveness of a multi-nutrient fertilizer for plants, especially when it depends on environmental factors. However, if a multi-nutrient fertilizer composition is effective, it has the advantage of only needing to be sprayed on the crop once.

[0006] Certain minerals, especially evaporite minerals, can be used as sources of nutrients such as potassium, calcium, magnesium, and sulfur. For example, gypsum can be pelletized and used as a source of calcium and sulfur.

[0007] Polyhalite is an evaporite mineral. It is a complex hydrated sulfate of potassium, calcium, and magnesium with the general formula K2Ca2Mg(SO4)4·2H2O. Polyhalite deposits occur in Austria, China, Germany, India, Iran, Turkey, Ukraine, the United Kingdom, and the United States.

[0008] Polyhalite is valuable as a raw material for agricultural fertilizers. Several prior art methods have proposed decomposing natural polyhalite to extract specific nutrients. See, for example, WO 2013 / 074328, US 1,946,068, and US 4,246,019. However, intact polyhalite can also provide sulfur, potassium, calcium, and magnesium to soil and can be used as a fertilizer.

[0009] The mineral polyhalite can be applied in raw or crushed form. This minimizes processing costs but has many drawbacks. Once applied to the soil, the raw mineral takes time to decompose, delaying the bioavailability of its components. When applied in chip form, polyhalite tends to be irregularly shaped and sized, making it difficult to distribute evenly and potentially difficult to apply using certain agricultural spraying equipment. Powdered polyhalite is difficult to distribute evenly in agricultural applications, and because polyhalite powder is hygroscopic, its mechanical properties can change rapidly and radically over time when exposed to air. Summary of the Invention

[0010] Fertilizer products that are easy to apply and provide many nutrients in a way that is particularly beneficial to plants are desirable.

[0011] A first aspect of the present invention is a method of producing a pelletized fertilizer product, the method comprising the steps of producing a first mixture comprising phosphoric acid and ammonia, adding the first mixture and polyhalite powder to a granulator to produce a second mixture, and, while the granulator processes the second mixture to produce pellets, supplying ammonia to the second mixture to complete the formation of ammonium phosphate in the second mixture.

[0012] The granulator can process the second mixture to produce pellets by mixing the second mixture while supplying ammonia. Producing a first mixture of phosphoric acid and ammonia may include mixing phosphoric acid while introducing ammonia into the phosphoric acid. The ammonia present in the first mixture may react with the phosphoric acid to produce ammonium phosphate, and the ammonia may be introduced in an amount insufficient to complete the production of ammonium phosphate in the first mixture. Supplying ammonia to the second mixture may include introducing ammonia gas into the second mixture. Supplying ammonia to the second mixture may include introducing liquid ammonia into the second mixture. The ammonia present in the second mixture may react with the phosphoric acid to produce ammonium phosphate, and the ammonia may be introduced in an amount sufficient to complete the production of ammonium phosphate in the second mixture. The predetermined ratio of ammonia to phosphoric acid may be one that completes the production of ammonium phosphate from the phosphoric acid, or an amount of ammonia less than the predetermined ratio may be introduced into the first mixture. The predetermined ratio of ammonia to phosphoric acid may be one that completes the production of ammonium phosphate from the phosphoric acid, and the ammonia may be introduced into the second mixture to substantially meet the predetermined ratio.

[0013] Producing the first mixture of phosphoric acid and ammonia may include adding a liquid to the first mixture. The liquid may be water. The liquid may be ammonia.

[0014] The powder may have a mass average particle size in the range of 50 to 500 μm. The pellets may contain a mixture of 80% by weight or more of polyhalite powder and ammonium phosphate. The amount of the first mixture added to the polyhalite powder may be such that the pellets consist of 20% to 80% by weight of ammonium phosphate. The amount of the first mixture added to the polyhalite powder may be such that the pellets consist of 20% to 80% by weight of polyhalite powder.

[0015] A second aspect of the present invention is a fertilizer pellet containing a mixture of polyhalite powder and ammonium phosphate as its main component.

[0016] The pellets may contain 60% to 80% by weight of ammonium phosphate. The pellets may contain 20% to 40% by weight of polyhalite powder. The pellets may contain 80% or more by weight of a mixture of polyhalite powder and ammonium phosphate.

[0017] A third aspect of the present invention is a fertilizer product comprising a plurality of pellets as described herein. A fourth aspect of the present invention is a pelleted fertilizer product, wherein at least 50% of the pellets are pellets as described herein. [Brief explanation of the drawings]

[0018] The invention will now be described, by way of example only, with reference to the accompanying drawings in which:

[0019] [Figure 1] FIG. 1 is a diagram showing a general overview of the fertilizer manufacturing process. DETAILED DESCRIPTION OF THE INVENTION

[0020] The following description is presented to enable any person skilled in the art to make and use the invention, and is provided in the context of a particular application. Various modifications to the disclosed embodiments will be apparent to those skilled in the art.

[0021] The general principles defined herein may be applied to other embodiments and applications without departing from the spirit and scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown, but is to be accorded the widest scope consistent with the principles and features disclosed herein.

[0022] The present invention relates to a method for producing a pelletized fertilizer product. The method includes producing a first mixture of phosphoric acid and ammonia and adding the first mixture and polyhalite powder to a granulator to produce a second mixture. The method further includes supplying ammonia to the second mixture to complete the formation of ammonium phosphate in the second mixture while the granulator processes the second mixture to produce pellets. The present invention also relates to fertilizer pellets based on a mixture of polyhalite powder and ammonium phosphate.

[0023] A general overview of the fertilizer manufacturing process is shown in Figure 1. The manufacturing process will be explained with reference to Figure 1.

[0024] As mentioned above, polyhalite is a complex hydrated sulfate of potassium, calcium, and magnesium, with the general formula K2Ca2Mg(SO4)4·2H2O. Polyhalite has a Mohs hardness of approximately 2.5 to 3.5. Polyhalite can be extracted from natural deposits by mining. Mined polyhalite may be intimately bound to other minerals, forming impurities in the polyhalite. These other minerals are preferably present in low proportions (e.g., less than 10% or even less than 5% in high-quality ore). Mined polyhalite can be crushed into blocks or chips of a size suitable for transportation and processing. For example, as-mined rock may be fed into a crusher, such as a jaw crusher and / or a cone crusher, to obtain chip material of approximately uniform size. Chips with a maximum dimension of approximately 20 mm or less and / or an average dimension of 5–10 mm have proven convenient for transportation from mines. The chips can be transported by conveyor, truck, or other convenient mechanism.

[0025] Polyhalite chips are fed into a first hopper 1 as shown by an arrow 2. The polyhalite chips are discharged from the first hopper and processed into a powder.

[0026] The raw or chipped polyhalite is processed to produce a powder consisting essentially of polyhalite. This may be preferably done using a high-pressure grinding roller (HPGR) device 3, or a ball mill (e.g., a continuous "Harding" ball mill) or an attritor mill. The average particle size of the powder depends on various process parameters, such as the residence time of the feedstock in the powderizer and the configuration of the powderizer. Oversized particles discharged from the powderizer may be returned to the device for further processing. The desired powder size depends on the nature of the subsequent processing steps, but good results have been found by screening the powderizer product through a 500 μm sieve and accepting the sieved material for further processing. Oversized particles discharged from the powderizer that do not pass through the sieve can be returned to the powderizer for further processing. Suitable levels of powder for the next step are as follows: 100% passing through a 500 μm sieve and 80% (by mass) passing through a 200 μm sieve. Preferably, at least 50% of the powder mass, more preferably at least 70%, is made up of particles having a particle size, i.e., maximum or mean diameter, in the range 50-500 μm, more preferably 100-250 μm, as measured by a Malvern Mastersizer 3000 or by a sieve shaker.

[0027] Impurities in the mined rock may be separated out before the mined rock is powdered, or if the impurities are in a reasonably low proportion to the desired minerals, they may be retained and powdered. Thus, the powdered polyhalite may also contain other minerals.

[0028] The powdered polyhalite passes through air cyclone 4, which separates the powdered polyhalite into particles of a desired size, while oversized particles descend through air cyclone 4 for recycling. The output from air cyclone 4 is placed into second hopper 5, which outputs to a device that both mixes and pelletizes. Thus, as shown in FIG. 1, second hopper 5 may output to granulator 6.

[0029] The granulator 6 is also supplied with liquid from a pre-neutralizer 7 and a first storage tank 8. The first storage tank 8 stores liquid ammonia or ammonia gas. In some cases, both liquid ammonia and ammonia gas are used in the process. In this case, separate storage tanks for liquid ammonia and ammonia gas may be provided. When referring to either liquid ammonia or ammonia gas, it will be understood that reference may be to a proportion of each or a proportion of one followed by the other. Alternatively, only liquid ammonia or ammonia gas may be used in the process.

[0030] The second storage tank 9 stores phosphoric acid. The first storage tank 8 and the second storage tank 9 are connected to the pre-neutralizer 7. The pre-neutralizer 7 is supplied with phosphoric acid from the second storage tank 9 and ammonia liquid / gas from the first storage tank 8. Phosphoric acid may be introduced into the pre-neutralizer 7, and ammonia liquid / gas may be tubed into the phosphoric acid so that the ammonia liquid / gas bubbles through the phosphoric acid and reacts with the acid. The pre-neutralizer 7 may include a mixing paddle 10 for mixing the liquid present in the pre-neutralizer 7. The combination of the phosphoric acid and ammonia liquid / gas in the pre-neutralizer 7 produces a first mixture consisting of phosphoric acid and ammonia. The first mixture may be in the form of a slurry.

[0031] When ammonia liquid / gas is introduced into the phosphoric acid, it reacts with the phosphoric acid. This reaction produces ammonium phosphate. The introduction of ammonia liquid / gas lowers the pH of the first mixture. The amount of ammonia liquid / gas introduced can be selected so that the pH of the first mixture drops to about 5-6. Depending on the amount of ammonia liquid / gas introduced into the phosphoric acid, monoammonium phosphate (MAP), diammonium phosphate (DAP), or a combination of the two may be produced in the first mixture in the pre-neutralizer. The amount of ammonia liquid / gas introduced into the first mixture is less than the amount required to complete the production of ammonium phosphate (the desired form, whether MAP or DAP). This means that substantially no phosphoric acid remains in the mixture when ammonium phosphate production is complete.

[0032] There is a predetermined ratio of ammonia to phosphoric acid that completes the production of ammonium phosphate from phosphoric acid. This predetermined ratio may be a target ratio. The predetermined ratio differs depending on whether MAP or DAP is being produced. The predetermined ratio for MAP is 1:1, and the predetermined ratio for DAP is 2:1.

[0033] Water may also be introduced into the pre-neutralizer to aid in mixing the phosphoric acid and ammonia.

[0034] The pre-neutralizer 7 is connected to the granulator 6 so that the pre-neutralizer 7 can supply a first mixture of phosphoric acid and ammonia to the granulator 6. The first storage tank is further connected to the granulator 6 so that the first storage tank can supply ammonia liquid / gas directly to the granulator 6.

[0035] An example of such a granulator is the Intensive Mixer / Granulator available from Maschinenfabrik Gustav Eirich GmbH. The granulator can be configured to discharge the material during operation, allowing for continuous operation. Alternatively, the granulator can operate in batch mode, where the material is processed according to a set program and then discharged all at once.

[0036] The polyhalite powder is passed from a second hopper 5 to a granulator 6. The first mixture is also passed from a pre-neutralizer 7 to the granulator 6. The amounts of polyhalite powder and the first mixture passed to the granulator 6 are selected depending on the desired ratio of polyhalite to ammonium phosphate in the final pellets. Once the polyhalite powder and the first mixture are added, they are mixed by the granulator 6 to produce a second mixture.

[0037] Ammonia liquid / gas is injected into the granulator from the first storage tank 8. The ammonia liquid / gas is then injected into the second mixture. The amount of ammonia liquid / gas injected is selected to complete the production of ammonium phosphate in the second mixture. The second mixture can be tested to determine when the pH of the second mixture reaches about 7, which indicates the completion of the production of ammonium phosphate within the second mixture. The ammonium phosphate in the second mixture can be in the form of DAP or MAP, depending on the amount of ammonium introduced into the pre-neutralizer 7 and the granulator 6.

[0038] The introduction of liquid from the pre-neutralizer 7 also has the effect of causing agglomeration of the polyhalite powder and thus agglomeration and pelletization of the second mixture in the granulator 6 .

[0039] The amounts of the first mixture and ammonium introduced into the polyhalite powder in the granulator can be selected according to the desired ratio of polyhalite powder to ammonium phosphate in the pellets, which generally include weight ratios of 1:10, 1:5, 3:10, 2:5, 1:2, 3:5, 7:10, 4:5, 9:10, 1:1, 10:9, 5:4, 10:7, 5:3, 2:1, 5:2, 10:3, 5:1, and 10:1.

[0040] The pellets may contain 20% or more by weight polyhalite, 30% or more by weight polyhalite, 40% or more by weight polyhalite, 50% or more by weight polyhalite, 60% or more by weight polyhalite, 70% or more by weight polyhalite, or 80% or more by weight polyhalite. Preferably, the fertilizer product contains less than 80% by weight polyhalite, more preferably less than 60% by weight polyhalite, more preferably 20% to 40% by weight polyhalite, more preferably 20% to 35% by weight polyhalite.

[0041] The pellets may comprise 20% or more ammonium phosphate by weight, 30% or more ammonium phosphate by weight, 40% or more ammonium phosphate by weight, 50% or more ammonium phosphate by weight, 60% or more ammonium phosphate by weight, 70% or more ammonium phosphate by weight, 80% or more ammonium phosphate by weight. Preferably, the fertilizer product may comprise 20% or more ammonium phosphate by weight, more preferably 40% or more ammonium phosphate by weight, more preferably 60% to 80% ammonium phosphate by weight, more preferably 65% ​​to 80% ammonium phosphate by weight.

[0042] The pellets may be primarily composed by weight of a mixture of polyhalite powder and ammonium phosphate. The pellets may also include a mixture of 80% by weight or more of polyhalite powder and ammonium phosphate, 85% by weight of polyhalite powder and ammonium phosphate, 90% by weight of polyhalite powder and ammonium phosphate, 95% by weight of polyhalite powder and ammonium phosphate, 96% by weight of polyhalite powder and ammonium phosphate, 97% by weight of polyhalite powder and ammonium phosphate, 98% by weight of polyhalite powder and ammonium phosphate, 99% by weight of polyhalite powder and ammonium phosphate, or 99.5% by weight of polyhalite powder and ammonium phosphate.

[0043] After the pelleting process is complete, the pellets are discharged from the granulator 6 into the dryer 14, which may be a drying conveyor. The pellets contain ammonium phosphate and polyhalite. A holding time of approximately 3 minutes in the dryer 14, which can heat the pellets to a temperature of approximately 150°C, has been found to be sufficient to sufficiently dry the pellets. This allows the pellets to harden. Pellets produced using polyhalite powder, phosphoric acid, and ammonia can have a crush strength in the range of 2.2 kgf. This is equivalent to the generally accepted lower limit of 2.2 kgf for agricultural pellets. Moisture can be removed from the dryer using a reverse-jet air filter. The operating temperature and holding time of the dryer can be selected to provide pellets of the required strength for subsequent handling. A rotary dryer can also be used to dry the pellets.

[0044] The dried material discharged from dryer 14 can be screened to separate undersized and / or oversized pellets from pellets in the desired size range. The desired size range can be, for example, pellets that pass through a 4 mm sieve but not through a 2 mm sieve. Alternatively, other sizes can be selected as appropriate depending on the desired application.

[0045] The dried pellets may be passed through a first size screener 12 to separate oversized pellets from pellets having the desired larger size. The oversized pellets are re-ground, preferably using a high pressure grinding roller (HPGR) device 16, or a ball mill (e.g., a continuous "Harding" ball mill) or an attritor mill. The re-ground pellets are fed to a second hopper 5 and recycled through the process again. The dried pellets may be passed through a second size screener 13 to separate undersized pellets from pellets having the desired smaller size. The undersized pellets are returned to the second hopper 5 and re-introduced to the granulator 6 and recycled through the process again.

[0046] Finally, the sized pellets (as indicated by arrow 17) can be cooled and packaged, for example, in 600 kg sacks or 25 kg bags (15), or shipped in bulk for use elsewhere or further processing. The pellets can be supplied for agricultural use. Finally, they can be spread on fields or other agricultural and horticultural substrates to act as fertilizer. The composite pellets can also be used for purposes other than fertilization.

[0047] The pellets may also contain other additives, such as one or more of the following, in any combination: - ingredients that have the effect of chemically and / or mechanically stabilizing and / or preserving the pellets: for example those that increase their shelf life, reduce their susceptibility to environmental pollutants or reduce the likelihood of the pellets being destroyed during application (e.g. pH buffers); - ingredients having the effect of enhancing the fertilizer effect of polyhalite and / or ammonium phosphate, for example by accelerating or retarding the decomposition of polyhalite in the field; - ingredients that have the effect of protecting or promoting the growth of crops by means other than fertilization: for example, herbicides, fungicides, insecticides, rodenticides, hormones, plant stimulants, mycorrhizal fungi or spores; -Seeds: seeds of angiosperms, gymnosperms, and / or crop species (e.g. cereals such as wheat, corn, rice, millet, barley, oats, rye, etc.); - Further fertilizer compositions that, in addition to polyhalite and ammonium phosphate, provide macro- or micronutrients; -pigments; - Substances that have the effect of changing the soil pH: lime, sulfur, etc. Such ingredients can be added at any suitable stage in the process. For example, they can be combined with the polyhalite powder before or during the sizing step, or with the polyhalite / phosphoric acid / ammonia mixture, or with the phosphoric acid / ammonia mixture. They can also be sprayed or otherwise coated onto the pellets before or after drying.

[0048] The composite pellets are preferably substantially free of voids, for example containing no more than 1%, no more than 2% or no more than 5% air by volume.

[0049] Although the characteristics are detailed for a single pellet, the standard may be applied to bulk pelleted fertilizer as (i) the average value for the entire bulk, (ii) the median value for the entire bulk, or (iii) as having 50% or more or 80% or more of the pellets in the bulk fertilizer having the required characteristics.

[0050] In three examples, phosphoric acid and ammonia gas were mixed to a pH of 5-6 to create a DAP preneutralizer slurry. Polyhalite powder was weighed and added to a sieving mixer. The polyhalite powder was mixed in the sieving mixer, and the slurry was added to the polyhalite powder by pouring. Ammonia gas was then injected into the mixture. Once the pH of the slurry-powder mixture reached approximately 7, the mixture was heated to dry it, and sieving began. Granules were produced and screened using Tyler 5-9 sieves to obtain the desired 2-4 mm particle size.

[0051] In the first example, 3.36 kg of phosphoric acid was added to a pre-neutralizer and mixed with bubbling ammonia gas until the pH reached approximately 6. 1550 mL of water was added throughout the process to help the mixture pass through the insoluble phase as it passed through the pH range of 1.6 to 5. 1 kg of polyhalite was added to a sieving mixer, and the slurry was introduced. Ammonia gas was bubbled through until the pH reached approximately 7, and the mixture was sieved to produce pellets. The resulting pellets were sieved to the desired particle size of 2-4 mm. The hardness of the resulting pellets was 2.3 kgf. The resulting pellets had a weight ratio of 80% DAP to 20% polyhalite powder.

[0052] In a second example, 2.73 kg of phosphoric acid was added to the pre-neutralizer and mixed with bubbling ammonia gas until the pH reached approximately 6. 1,250 mL of water was added throughout the process to aid in passing the insoluble phase as the mixture passed through the pH range of 1.6 to 5. 1.75 kg of polyhalite was added to the sieving mixer, and the slurry was introduced. Ammonia gas was bubbled through until the pH reached approximately 7, and the mixture was sieved to produce pellets. The resulting pellets were sieved to the desired particle size of 2-4 mm. The hardness of the resulting pellets was 2.1 kgf. The resulting pellets had a weight ratio of 65% DAP to 35% polyhalite powder.

[0053] In the third example, 1.68 kg of phosphoric acid was added to a pre-neutralizer and mixed with bubbling ammonia gas until the pH reached approximately 6. 1000 mL of water was added throughout the process to aid in passing the insoluble phase as the mixture passed through the pH range of 1.6 to 5. 3 kg of polyhalite was added to a sieving mixer, and the slurry was introduced. Ammonia gas was bubbled through until the pH reached approximately 7, and the mixture was sieved to produce pellets. The resulting pellets were sieved to the desired particle size of 2-4 mm. The hardness of the resulting pellets was 2.1 kgf / cm2. The resulting pellets had a weight ratio of 60% polyhalite powder to 40% DAP.

[0054] The applicant discloses each individual feature described herein and combinations of two or more such features independently, regardless of whether such feature or combination solves the problems disclosed herein, and to the extent that it is operable based on the specification as a whole in light of the general knowledge of those skilled in the art, without limiting the scope of the claims. The applicant indicates that aspects of the present invention may consist of any such individual feature or combination of features. In view of the foregoing description, it will be apparent to those skilled in the art that various modifications may be made within the scope of the present invention.

Claims

1. A method for producing pelleted fertilizer products, producing a first mixture comprising phosphoric acid and ammonia; adding the first mixture and polyhalite powder to a granulator to produce a second mixture; supplying ammonia to the second mixture to complete the formation of ammonium phosphate within the second mixture while the pelletizer is processing the second mixture to produce pellets; A manufacturing method comprising:

2. 10. The method of claim 1, wherein the pelletizer processes the second mixture to produce pellets by mixing the second mixture while supplying the ammonia.

3. 3. The method of claim 1 or 2, wherein producing the first mixture of phosphoric acid and ammonia comprises mixing the phosphoric acid while introducing the ammonia into the phosphoric acid.

4. 4. The method of producing a pelletized fertilizer product of any one of claims 1 to 3, wherein the ammonia present in the first mixture reacts with the phosphoric acid to produce ammonium phosphate, and the ammonia is introduced in an amount insufficient to complete the production of ammonium phosphate within the first mixture.

5. 5. The method for producing a pelletized fertilizer product of claim 1, wherein providing the ammonia to the second mixture comprises introducing ammonia gas into the second mixture.

6. 6. The method of producing a pelletized fertilizer product of claim 1, wherein providing the ammonia to the second mixture comprises introducing liquid ammonia to the second mixture.

7. 7. The method of producing a pelletized fertilizer product of any one of claims 1 to 6, wherein the ammonia present in the second mixture reacts with the phosphoric acid to produce ammonium phosphate, and the ammonia is introduced in an amount sufficient to complete the production of ammonium phosphate within the second mixture.

8. 8. The method of claim 1, wherein a predetermined ratio of ammonia to phosphoric acid completes the production of ammonium phosphate from phosphoric acid, and an amount of ammonia introduced into the first mixture is less than the predetermined ratio.

9. 9. The method for producing a pelletized fertilizer product according to any one of claims 1 to 8, wherein a predetermined ratio of ammonia to phosphoric acid completes the production of ammonium phosphate from phosphoric acid, and the ammonia is introduced into the second mixture to substantially satisfy the predetermined ratio.

10. 10. The method of producing a pelletized fertilizer product of any one of claims 1 to 9, wherein producing a first mixture of phosphoric acid and ammonia comprises adding a liquid to the first mixture.

11. 11. The method of claim 10, wherein the liquid is water.

12. 11. The method of producing a pelletized fertilizer product of claim 10, wherein the liquid is ammonia.

13. A method for producing a pelletized fertilizer product according to any one of claims 1 to 12, wherein the powder has a mass median particle size in the range of 50 to 500 μm.

14. The method for producing a pelletized fertilizer product according to any one of claims 1 to 13, wherein the pellets comprise at least 80% by weight of a mixture of polyhalite powder and ammonium phosphate.

15. 15. The method for producing a pelletized fertilizer product according to any one of claims 1 to 14, wherein the amount of the first mixture added to the polyhalite powder is such that the pellets consist of 20% to 80% ammonium phosphate by weight.

16. 16. The method for producing a pelletized fertilizer product according to any one of claims 1 to 15, wherein the amount of the first mixture added to the polyhalite powder is such that the pellets consist of 20% to 80% by weight of polyhalite powder.

17. The fertilizer pellets are mainly composed of a mixture of polyhalite powder and ammonium phosphate, and contain 50% to 80% by weight of ammonium phosphate.

18. 18. The fertilizer pellets of claim 17, wherein the pellets comprise 60% to 80% by weight of ammonium phosphate.

19. 19. The fertilizer pellet of claim 17 or 18, wherein the pellet comprises 20% to 40% by weight of polyhalite powder.

20. The fertilizer pellet according to any one of claims 17 to 19, wherein the pellet contains 80% by weight or more of a mixture of polyhalite powder and ammonium phosphate.

21. A fertilizer product comprising a plurality of pellets according to any one of claims 17 to 18.

22. A pelleted fertilizer product, wherein at least 50% of the pellets are pellets according to any one of claims 17 to 21.

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