CN1075045C - A process for manufacturing compound fertilizers - Google Patents
A process for manufacturing compound fertilizers Download PDFInfo
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- CN1075045C CN1075045C CN94102234A CN94102234A CN1075045C CN 1075045 C CN1075045 C CN 1075045C CN 94102234 A CN94102234 A CN 94102234A CN 94102234 A CN94102234 A CN 94102234A CN 1075045 C CN1075045 C CN 1075045C
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Abstract
The invention provides a method to produce particle fertilizer products with better performance and nitrogen, phosphorus and/or potassium contents. (a) The fine classified fertilizers with nitrogen, phosphorus and/or potassium contents are contacted with water to produce a wet mixture, (b) the mixture is granulated into fertilizer particles, and (c) through an optional further treatment, the fertilizer particles are made into particle fertilizer products. Step (a) includes three substeps: (i) the fine classified raw fertilizer are divided into at least two parts, and the first part has a weight of about 5-10 percent of the total, (ii) the first part is contacted with water to produce a slurry material with 5-30 percent of water contents, and (iii) the slurry is contacted with the remain part(s) of the raw fertilizer to produce a wet mixture with 1-5 percent of water contents.
Description
The present invention relates to a process for the preparation of a granular fertilizer product containing N and P and/or K, wherein:
(α) contacting the finely divided fertilizer material containing N and/or P and/or K with water to produce a wet mixture, and
(b) granulating the wet mixture into a granulated fertilizer, and optionally,
(c) further processing said fertilizer granules to obtain said granulated fertilizer product.
In nitrates containing NPK (N = nitrogen, P = phosphorus, K = potassium), several chemical reactions occur. These chemical reactions should be completed during the manufacturing process to avoid continuing the chemical reactions. These subsequent post-reactions lead to a number of undesirable phenomena, such as reduced crushing strength, surface cracking, increased caking tendency, dusting of the salt surface leading to dust generation during handling, and low abrasion.
The reaction between ammonium nitrate and potassium chloride results in the formation of potassium nitrate and ammonium chloride.
In principle, the reaction between ammonium nitrate and potassium chloride can be inhibited with non-reactive potassium chloride, but this method is not attractive in view of the non-reactive potassium chloride not being readily available. The reaction can also be stopped with slurries having a relatively low water content. However, in practice such stringent conditions may result in the process being a very sensitive process.
Another common method of completing the reaction between ammonium nitrate and commercial potassium chloride is to use an excess of ammonium nitrate or an excess of potassium chloride to allow complete conversion of either potassium chloride or ammonium nitrate. Complete conversion may also be achieved, for example, by premixing the ammonium nitrate and potassium chloride in a separate mixer before the granulator to increase the reaction time of the initial components. This type of process cannot be used in the case of molar excess of potassium chloride, since the mixture is too viscous to granulate.
Complete conversion can be achieved using finely divided potassium chloride or using preheated potassium chloride. However, these methods require high energy consumption and therefore lead to correspondingly high production costs.
Complete conversion of ammonium sulfate is generally required to prevent further post-reaction. To form double salts such as 2NH4NO3 *(NH4)2SO4,3NH4NO3 *-(NH4)2SO4Resulting in agglomeration and degradation of the particles. The completion of the reaction can be promoted by crushing the ammonium sulfate. Another possible approach is to use an anhydrous slurry in operation. The adsorbed moisture accelerates the completeness of the reaction during handling and storage. The double salt thus formed has greater solubility in water and also mobile ions are susceptible to salting out from the particles. This leads to a high caking tendency.
In the case of ammonium sulfate and potassium chloride, potassium sulfate is produced according to the following equation.
Thepotassium sulfate produced is almost free of unreacted and produces a series of solid solutions (NH)4,K)2SO4. In the case of finely divided ammonium sulfate and potassium chloride, the reaction is completed during storage. In the case of both components being larger crystals, the reaction proceeds at the crystal surface but if there is not enough water to accelerate the reaction, the reaction does not proceed further.
Ammonium double salts also form a series of solid solutions 2 (NH)4,K)NO3 *(NH4,K)2SO4. This series of solid solutions dissolves more readily in water than the initial components. Due to the higher solubility, mobile ions are present to accelerate further reactions. When such compounds are present in complex fertilizers, they cause serious quality problems associated with high caking properties.
The reaction between ammonium sulphate and ammonium or potassium nitrate may be carried out in a similar manner to that described above.
In the nitrate phosphate process phosphate rock is converted to the phosphorus form, which is useful for plants. This occurs when nitric acid reacts with the phosphate stone, where phosphorus is released as phosphoric acid. The acid mixture produced in the subsequent step is neutralized with ammonium to the desired extent. The calcium nitrate formed in these processes can be removed by crystallizing it as calcium nitrate tetrahydrate, but has the disadvantages of an expensive crystallization process step and a large amount of by-products. Calcium can also be precipitated with acids, such as phosphoric acid, in many ammonia reactors, which has the disadvantage that, for example, many reactors are required and the storage of the ammonium salt of the acid is required, which means high investment and complicated operation.
In the process for manufacturing a compound fertilizer by steam granulation, solid raw materials are crushed and mixed together, followed by a granulation stage, in which steam or water is added. In these processes, granulation is sensitive to granulation conditions such as moisture content, temperature, etc., and the physical properties of the final product are poor. In the manufacture of nitrate-containing products, ammonium nitrate is reacted with potassium chloride continuously for a relatively long time, with the result that strong crystal bridges are formed between the particles, indicating a strong tendency to caking.
In granulation in a TVA ammonium granulator, ammonia or ammoniated solution is reacted with sulfuric acid or phosphoric acid to produce a slurry. The disadvantage of this process is the need to supply liquid raw materials such as acid and ammonia.
Mechanically blended fertilizers or bulk blended fertilizers allow for production in various ratios with respect to their initial ingredient content. However, bulk blending is only a practical proposition as long as the fertilizer raw materials used in bulk blending fertilizer production are well granulated and the particle size distribution is not only close but also very similar. It is difficult to produce granules of urea, ammonium sulfate, potassium chloride, ammonium phosphate, diammonium phosphate having a narrow size range in a practical manner using conventional granulation equipment such as a drum or a tumbler or a cylinder blender. These factors affect the physical properties of the blended fertilizer, and especially when the blending components are granular urea, granular ammonium phosphate, dense potassium chloride and coarse crystalline ammonium sulfate, the different particle size distributions also cause non-uniform distribution patterns in the field.
In the compacting method, different raw materials are fed through a compactor and the raw material particles are compacted by pressure. The product properties are not good due to high abrasion, which leads to dust formation in the product handling.
It has now been found that a compound fertilizer with a simplified process scheme and good physical properties can be obtained by an improved manufacturing process. The invention relates to a method for producing a granular fertilizer product containing N and P and/or K, wherein
(a) Contacting finely divided fertilizer raw material containing N and/or P and/or K with water to produce a wet mixture, and
(b) granulating the wet mixture into fertilizer granules, and optionally
(c) Further processing said fertilizer granules to obtain said granulated fertilizer product,
it is essentially characterized by the contacting step:
(a) comprises the following steps:
dividing the finely divided fertilizer material into at least two portions, the first portion constituting from about 10% to about 50% by weight of the entire finely divided fertilizer material,
(ii) contacting a first portion of the finely divided fertiliser material with water and/or steam to obtain a slurry having a moisture content of from 5% to 30% by weight; and
(iii) contacting said slurry with the remainder of the finely divided fertiliser material to produce a wet mixture having a water content of from about 1% to 5% by weight.
It will thus be appreciated that the above-mentioned disadvantages of the prior art processes are avoided by a novel process for the preparation of a granular fertilizer comprising N and P and/or K, wherein afinely divided fertilizer material is divided into at least two portions, a first portion constituting from about 10% to about 50% by weight of the total finely divided fertilizer material, said first portion being contacted with water to obtain an aqueous slurry comprising from 5% to 30% by weight of water, said aqueous slurry being contacted with the remainder of the finely divided fertilizer material to obtain a wet mixture having a water content of from about 1% to 5% by weight.
Said wet mixture is then granulated into fertilizer granules, and optionally, the fertilizer granules are further processed to obtain said granular fertilizer product.
Solid commercial fertilizer materials may be used in the present invention. The fertilizer raw material is finely divided and, preferably, pulverized. Nitrate-containing NK and/or NP and/or NPK fertilizers are advantageous as the first part of the finely divided fertilizer raw material according to the invention. The first part, i.e. the part which is contacted with water to obtain an aqueous slurry, may also be an ammoniacal non-nitrate type NP and/or NPK fertilizer. According to a preferred embodiment of the invention, the NK or NP or NPK fertilizers comprise ammonium sulphate, potassium chloride, monoammonium phosphate and diammonium phosphate.
In the case of urea containing nitrogen, phosphorus, and potassium, it is also preferred that the remainder of the finely divided fertiliser feedstock comprises urea.
In the method according to the invention, the finely divided fertilizer material is divided into at least two portions, the first portion constituting about 10% to 50% by weight of the entire finely divided fertilizer material. The first portion is then contacted with water to produce an aqueous slurry containing from 5% to 30% by weight water. In this step, the finely divided fertilizer raw material is brought into good contact with water at 50 to 150 ℃, preferably in an additional dissolution vessel equipped with a heater and a stirrer. According to a particular embodiment of the invention, the first part of the finely divided fertiliser raw material is contacted with water in two sub-steps, preferably in separate vessels. At this stage, the chemical reactions described above are reduced due to the low reaction potential of the slurry produced. Most of the ammonium nitrate in the slurry has reacted and no further reaction takes place during storage and handling of the fertilizer.
After the slurry is formed, it is contacted with the remainder of the finely divided fertilizer material to produce a moist mixture having a water content of about 1% to 5% by weight. This is followed by a granulation step of the moist mixture. The slurry is introduced into a granulator such as a tumbler, cylinder blender or the like. It is advantageous to carry out the contacting of the aqueous slurry with the remaining part of the finely divided fertilizer raw material and said granulation stage in the same granulator. According to one embodiment of the invention, the granulation step is carried out in a granulator at a temperature of 50 to 100 ℃ to coagulate the finely divided fertilizer raw material into granules. Can be used in the present inventionTypical d50The granulation is carried out with slightly crushed raw materials having values ranging from 50 to 800 μm.
Further processing is carried out after the granulation step to obtain the granular fertilizer product of the present invention. Further processing may include a drying step to reduce moisture from the fertilizer granules, preferably to about 0.2% to 0.5% by weight. A cooling step may also be included to reduce the temperature of the fertilizer granules to about 30 to 55 c. Preferably, the further treatment may also include a classification step, such as sieving the granulated fertilizer. The fractionation step separates out a commercially suitable product having a size range from 1 to 10mm, preferably a size range from 2 to 5 mm. In this case it is particularly preferred to return the insufficiently sized fertilizer particles to the step of contact between the water slurry and the remaining part of the finely divided fertilizer material. The classification step may also include returning oversized fertilizer particles that have been crushed to a small particle size to said contacting step.
The invention is further illustrated in the examples set out below. These examples are intended to be illustrative only and not limiting.
Example 1: NPK fertilizer containing nitrate
225kg/t NP30-10 and 100kg/t diammonium phosphate were fed continuously by a belt feeder into a reactor equipped with a mixer. The temperature of the reaction vessel was maintained at 120 ℃ and the moisture content was adjusted to about 10%.
The slightly non-viscous liquid mixture is passed through a cylindrical blender granulator at a temperature of about 60-75 c. Other raw materials, such as 236kg/t ammonium sulfate crushed (to about 750 μm), 255kg/t potassium chloride, 163kg/t crushed monoammonium phosphate and 14kg/t filler were likewise fed continuously to the granulator.
The resulting granules, having an exit temperature of about 60 c, were dried to a moisture content of about 0.4%, sieved into a fraction smaller than 2mm, a product fraction of 2-5mm and a fraction larger than 5mm, the latter fraction being crushed again. The less than 2mm portion and the crushed portion are returned to the granulator as solid recycle material.
Even stored for several weeksProduct granules (N-P) stored after storage2O5-K2O15-15-15) showed no tendency to cake. The crush strength of the resulting product was about 35N.
The above product was produced by the following procedure using NK as a raw material. Continuously supplying 253kg/t of NK (N-K) by a belt conveyer2O24-13) and 290kg/t of monoammonium phosphate into a mixing vessel equipped with a mixer. The temperature of the reaction vessel was maintained at 74 ℃ and a moisture content of about 9% by the addition of steam.
The slightly viscous slurry was passed into a drum granulator at a temperature of about 68 ℃. 290kg/t of crushed ammonium sulfate and 197kg/t of potassium chloride were also continuously supplied to this granulator.
The resulting granules were dried to a moisture content of about 0.4% and sieved to a fraction of less than 2mm, a product fraction of 2-5mm, and a fraction greater than 5mm, the latter fraction being crushed again, the fraction less than 2mm and the crushed fraction being returned to the granulator as solid recycle material.
Product granules (N-P) stored even after 8 weeks storage2O5-K2O15-15-15) showed no caking tendency. Slight moisture is introduced into the product and does not increase the tendency to cake. The crushing strength of the granules was about 60N.
Example 2: nitrate-free NPK fertilizer
200kg/t of diammonium phosphate and 133kg/t of monoammonium phosphate were continuously fed into a mixing vessel equipped with a mixer. The raw material is continuously fed by a belt conveyor. The temperature in the reaction vessel was maintained at 100 ℃ and the moisture content was adjusted to about 12.5%.
The slightly viscous liquid mixture is passed through a drum granulator at a temperature of about 50-60 c. The remaining part, consisting of 79kg/t crushed monoammonium phosphate, 489kg/t crushed (about 750 μm) ammonium sulfate and 99kg/t filler, was also fed continuously to the granulator.
The resulting granules, having an exit temperature of about 60 c, were dried to a moisture content of about 0.3% and sieved to a fraction of less than 2mm, a product fraction of 2-5mm and a fraction of more than 5mm, the latter fraction being crushed again. The fraction smaller than 2mm and the crushed fraction are returned to the granulator as solid recycle.
Stored product particles (N-P) even after several weeks of storage2O5-K2O16-20-0) showed no tendency to cake. The crushing strength of the resulting granules was about 30N.
Another substance not containing nitrate (N-P)2O5-K2O16-16-8) was prepared by the following procedure. 350kg/t of diammonium phosphate was continuously fed by a belt conveyor into a mixing vessel equipped with a mixer. And the temperature was maintained at 57 ℃ with steam and the moisture content was adjusted to about 18.5%.
The slightly viscous slurry was passed through a drum granulator at a temperature of about 50 ℃. 137kg/t of potassium chloride and 494kg/t of slightly crushed ammonium sulfate were also continuously supplied to this granulator.
The granules formed are dried to a moisture content of about 0.5 to 0.8% and sieved off in a fraction of less than 2mm, a product fraction of 2-5mm and a fraction of more than 5mm, the latter fraction being crushed. The fraction smaller than 2mm and the crushed fraction are returned to the granulator as solid recycle.
Product granules (N-P) which are stored even after storage for several weeks2O5-K2O16-16-8) showed no caking tendency. The crushing strength was about 45N.
Example 3: urea-containing NPK fertilizer
150kg/t of diammonium phosphate and 258kg/t of monoammonium phosphate were continuously supplied by a belt conveyor to a mixing vessel equipped with a mixer. The temperature of the reaction vessel was maintained at 98 ℃ and the moisture content was adjusted to about 15%.
The slightly viscous liquid mixture is passed into a drum granulator at a temperature of 50-60 ℃. 55kg/t of urea, 106kg/t of crushed ammonium sulfate, 404kg/t of potassium sulfate and 20kg/t of magnesium sulfate were continuously supplied to the granulator.
The resulting granules, having an exit temperature of about 50 c, were dried to a moisture content of about 0.3% and sieved to a fraction of less than 2mm, a product fraction of 2-5mm and a fraction of more than 5mm, the latter fraction being crushed. The fraction smaller than 2mm and the crushed fraction are returned to the granulator as solid recycle.
The stored product particles show no caking tendency even after several weeks of storage. The crushing strength of the resulting granules was about 38N.
Example 4: NPK fertilizer using nitrate containing NPK as raw material
200kg/t of diammonium phosphate and 275kg/t of NPK (26-7-4) were continuously fed by a belt conveyor into a mixing vessel equipped with a mixer. The temperature in the reaction vessel was maintained at 125 ℃ and the moisture content was maintained at about 12%.
The slightly viscous liquid mixture was passed into the granulator of a cylindrical blender at a temperature of about 60-65 c. 275kg/t of crushed ammonium sulfate, 215kg/t of potassium chloride and 40kg/t of a filler were continuously supplied to the granulator in the same manner.
The resulting granules were dried to a moisture content of about 0.3% and sieved to give a fraction of less than 2mm, a product fraction of 2-5mm, and a fraction of more than 5mm, the latter fraction being crushed. The fraction smaller than 2mm and the crushed fraction are returned to the granulator as solid recycle.
Stored product particles (N-P) even after several weeks of storage2O5-K2O16-11-14) showed no caking tendency. The crushing strength of the resulting granules was about 50N.
Claims (18)
1. A process for the preparation of a granular fertilizer product containing N and P and/or K, wherein
(a) Contacting finely divided fertilizer raw material containing N and/or P and/or K with water to produce a wet mixture, and
(b) granulating the wet mixture into fertilizer granules, and optionally
(c) Further processing said fertilizer granules to obtain said granulated fertilizer product,
characterized in that the contacting step (a) comprises the following sub-steps:
dividing the finely divided fertiliser material into at least two fractions, the first fraction constituting from 10% to 50% by weight of the total finely divided fertiliser material,
(ii) contacting a first portion of the finely divided fertiliser feedstock with water and/or steam to obtain a slurry comprising from 5% to 30% by weight water;
(iii) contacting the slurry with the remainder of the finely divided fertiliser material to obtain a wet mixture having a water content of from 1% to 5% by weight.
2. A method according to claim 1, characterised in that the first part of the finely divided fertilizer raw material is a NK and/or NP and/or NPK fertilizer containing nitrates.
3. A method according to claim 1, characterized in that said first portion of finely divided fertilizer material is an ammonia-containing non-nitrate NP and/or NPK fertilizer.
4. A process according to claim 1,2 or 3, characterized in that the remainder of the finely divided NK or NP or NPK fertilizer raw material comprises ammonium sulphate, potassium chloride, monoammonium phosphate and diammonium phosphate.
5. A method according to claim 1,2 or 3, characterized in that the remaining part of the finely divided fertilizer raw material comprises urea.
6. A method according to claim 1,2 or 3, characterised in that the first portion of finely divided fertiliser raw material is contacted with water in sub-step (ii) at a temperature of 50 to 150 ℃.
7. The process according to claim 6, characterized in that the contacting is carried out in a further dissolution vessel equipped with a heater and a stirrer.
8. A method according to claim 1,2 or 3, characterised in that the first portion of finely divided fertiliser material is contacted with water in two stages in sub-step (ii).
9. The method according to claim 8, characterized in that the contacting is carried out in a further vessel.
10. A process accordingto claim 1,2 or 3, characterized in that the granulation step (b) is carried out in a granulator at a temperature of from 50 to 100 ℃ to coagulate finely divided fertilizer material into granules.
11. A process according to claim 1,2 or 3, characterised in that the granulation step (c) and the sub-step (iii) of contacting the slurry with the remainder of the finely divided fertiliser material are carried out in the same granulator.
12. A process according to claim 1,2 or 3 characterised in that step (c) includes a drying step to reduce the moisture content of the granular fertilizer to 0.2 to 0.5% by weight.
13. A process according to claim 1,2 or 3 characterised in that step (c) includes a cooling step to reduce the temperature of the granular fertilizer to between 30 and 55 ℃.
14. A process according to claim 1,2 or 3, characterized in that step (c) comprises a fractionation step, the resulting products being recovered in a size range from 1 to 10 mm.
15. A method according to claim 14, characterized in that said size ranges from 2 to 5 mm.
16. The method of claim 13, wherein the classification step comprises recycling undersized fertilizer particles to said contacting sub-step (iii).
17. A method according to claim 13, characterized in that oversized fertilizer granules that have been crushed to smaller granule sizes are recycled to said secondary step (iii).
18. A method according to claim 14, characterized in that oversized fertilizer granules that have been crushed to smaller granule sizes are recycled to said secondary step (iii).
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| TH019482 | 1993-07-08 | ||
| TH019482 | 1993-07-08 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN1097185A CN1097185A (en) | 1995-01-11 |
| CN1075045C true CN1075045C (en) | 2001-11-21 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN94102234A Expired - Fee Related CN1075045C (en) | 1993-07-08 | 1994-03-07 | A process for manufacturing compound fertilizers |
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| Country | Link |
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| CN (1) | CN1075045C (en) |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1032777A (en) * | 1987-10-24 | 1989-05-10 | 沈阳化工综合利用研究所 | A kind of method of making potassium phosphate urea |
| CN1056298A (en) * | 1990-11-29 | 1991-11-20 | 辽河化肥厂 | A kind of manufacturing process of urine-base boron fertilizer |
-
1994
- 1994-03-07 CN CN94102234A patent/CN1075045C/en not_active Expired - Fee Related
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1032777A (en) * | 1987-10-24 | 1989-05-10 | 沈阳化工综合利用研究所 | A kind of method of making potassium phosphate urea |
| CN1056298A (en) * | 1990-11-29 | 1991-11-20 | 辽河化肥厂 | A kind of manufacturing process of urine-base boron fertilizer |
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| Publication number | Publication date |
|---|---|
| CN1097185A (en) | 1995-01-11 |
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