DESC:FIELD
The present disclosure relates to a process for preparation of ammonium sulphate granules.
BACKGROUND
The background information herein below relates to the present disclosure but is not necessarily prior art.
Ammonium sulphate is widely used as a fertilizer having a source of plant nutrients such as nitrogen (N) and sulphur (S). Generally, the minimum requirement of N and S in ammonium sulphate fertilizer is 20.5 % and 23 %, respectively. Ammonium sulphate fertilizer is available in crystalline form, having a very fine particle size of ~1 mm.
Conventional application of crystalline ammonium sulphate on the plants/in the soil is associated with major drawbacks such as non-uniform distribution/spreading of the crystals in the soil, due to irregularity in crystal shape, smaller grain size, poor flow characteristics, agglomeration etc. Uniformity of grains plays a major role in the distribution of fertilizers during its application. Further, when applied to plants through broadcasting (distribution of fertilizers by hand), the crystals falling on the leaves of the plant will cause phytotoxicity, that burns the leaves. This leads to the agricultural production loss as well as the fertilizer wastage. Even further, during the application of such fine crystalline ammonium sulphate fertilizer on the plants, the problems associated with health are observed due to dusting and inhalation.
Attempts have been made to improve the crystal quality of ammonium sulphate like application of reverse flow crystallization, but were not cost effective and the crystals still had non-uniformity.
Therefore, there is felt a need to provide a process for preparing ammonium sulphate granules that overcomes the drawbacks mentioned herein above.
OBJECTS
Some of the objects of the present disclosure, which at least one embodiment herein satisfies, are as follows:
It is an object of the present disclosure to ameliorate one or more problems of the prior art or to at least provide a useful alternative.
An object of the present disclosure is to provide a process for preparation of ammonium sulphate granules.
Another object of the present disclosure is to provide a simple, safe, and efficient process for the preparation of ammonium sulphate granules.
Still another object of the present disclosure is to provide a fertilizer composition comprising ammonium sulphate granules.
Other objects and advantages of the present disclosure will be more apparent from the following description, which is not intended to limit the scope of the present disclosure.
SUMMARY
The present disclosure relates to a process for preparing ammonium sulphate granules. The process comprises grinding crystalline ammonium sulphate powder to obtain a ground ammonium sulphate. The ground crystalline ammonium sulphate powder is blended with at least one binder to obtain a mixture. The mixture is granulated by sprinkling a fluid medium to obtain a moist granules of ammonium sulphate. The moist granules are dried to obtain the ammonium sulphate granules having a particle size in the range of 0.5 mm to 6 mm.
The ammonium sulphate granules of the present disclosure are characterized by having a nitrogen content in the range of 18% to 21%, a particle size in the range of 0.5 mm to 6 mm and a crushing strength in the range of 0.5 kg to 5 kg per granule.
DETAILED DESCRIPTION
Embodiments are provided so as to thoroughly and fully convey the scope of the present disclosure to the person skilled in the art. Numerous details are set forth, relating to specific components, and methods, to provide a complete understanding of embodiments of the present disclosure. It will be apparent to the person skilled in the art that the details provided in the embodiments should not be construed to limit the scope of the present disclosure. In some embodiments, well-known processes, well-known apparatus structures, and well-known techniques are not described in detail.
The terminology used, in the present disclosure, is only for the purpose of explaining a particular embodiment and such terminology shall not be considered to limit the scope of the present disclosure. As used in the present disclosure, the forms "a", "an", and "the" may be intended to include the plural forms as well, unless the context clearly suggests otherwise. The terms "comprises," "comprising," "including", and "having", are open ended transitional phrases and therefore specify the presence of stated features, integers, steps, operations, elements, modules, units and/or components, but do not forbid the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. The particular order of steps disclosed in the method and process of the present disclosure is not to be construed as necessarily requiring their performance as described or illustrated. It is also to be understood that additional or alternative steps may be employed.
The terms first, second, third, etc., should not be construed to limit the scope of the present disclosure as the aforementioned terms may be only used to distinguish one element, component, region, layer or section from another component, region, layer or section. Terms such as first, second, third etc., when used herein do not imply a specific sequence or order unless clearly suggested by the present disclosure.
Conventional applications of the crystalline ammonium sulphate on the plants/in the soil are associated with major drawbacks such as non-uniform distribution/spreading of the crystals in the soil. This non-uniform distribution is due to the irregularity in crystal shape, smaller grain size, the poor flow characteristics, agglomeration etc. Uniformity of grains plays major role in the distribution of fertilizers during application. Further, when applied to plants through broadcasting (distribution of fertilizers by hand), the crystals falling on the leaves of the plant will cause phytotoxicity, that burns the leaves. This leads to the agricultural production loss as well as the fertilizer wastage.
Several attempts have been made to improve crystal quality of ammonium sulphate like application of reverse flow crystallization. However, the conventional processes are not cost effective, and the crystals still had the non-uniformity.
Therefore, the present disclosure provides a process for preparation of ammonium sulphate granules. The process of the present disclosure is simple, safe and environmental friendly which provides ammonium sulphate granules having a nitrogen content in the range of 18% to 21%, a particle size in the range of 0.5 mm to 6 mm and a crushing strength in the range of 0.5 kg to 5 kg per granule.
In one aspect, the present disclosure provides a process for preparation of ammonium sulphate granules. The process is described in detail as given below.
The process comprises a step of grinding crystalline ammonium sulphate to obtain ammonium sulphate powder.
Typically, the step of grinding produces ammonium sulphate powder having a particle size in the range of 50 µm to 250 µm. In an exemplary embodiment, the ammonium sulphate powder has a particle size of 150 µm.
The step of grinding is carried out by using a milling technique selected from the group consisting of ball mill, hammer mill, pulveriser and a grinding disc. In an exemplary embodiment, the grinding is carried out by using a pulveriser.
In an exemplary embodiment, ammonium sulphate crystals having minimum 21 % nitrogen is ground in a pulveriser to obtain the ammonium sulphate powder having a particle size of 150 µm.
In the next step of the process, the ammonium sulphate powder is blended with at least one binder to obtain a mixture.
Typically, the step of blending is carried out by using a mixing device selected from a drum type homogenizer mixer and a disc type homogenizer mixer.
The binder is at least one selected from the group consisting of clay, bentonite, zeolite, dolomite, alkali metal salt of lignosulphonic acid, ammonium salts of lignosulphonic acid, polyvinyl pyrrolidone, polyethylene glycol, calcium oxide, magnesium sulphate, starch, starch extracts, starch derivatives, wheat flour, rice flour, guar gum and refined wheat flour. In an exemplary embodiment, the binder is polyvinyl pyrrolidone. In an another embodiment, the binder is refined wheat flour. In still another embodiment, the binder is a mixture of polyvinyl pyrrolidones and refined wheat flour. In yet another embodiment, the binder is calcium bentonite.
The amount of binder used during the step of blending is in the range of 0.1 wt.% to 5 wt.%. In an exemplary embodiment, the amount of the binder used during the blending is 0.7 wt.%
The mixture of ammonium sulphate powder and binder is granulated by sprinking a fluid medium to obtain a moist granules of ammonium sulphate.
In an embodiment, the step of granulation is carried out by using a granulator selected from a pan granulator and a drum granulator. In an exemplary embodiment, the step of granulation is carried out by using the pan granulator.
In another embodiment of the present disclosure, the step of granulation is carried out by using rotating granulator. The speed of rotation of granulator is in the range of 20 rpm to 30 rpm. In an embodiment, the speed of rotating granulator is 30 rpm.
In an exemplary embodiment, the step of granulation is carried by using a rotating pan granulator having a rotating speed of 30 rpm.
The fluid medium is selected from water and aqueous ammonium hydroxide. In an exemplary embodiment, the fluid medium is water. In an another embodiment, the fluid medium is aqueous ammonium hydroxide having a concentration in the range of 20 wt.% to 30 wt. %. In an exemplary embodiment, the fluid medium is aqueous ammonium hydroxide having a concentration of 24 wt.%
The sprinkling of fluid medium is adapted in order to control formation of oversized granules. If the fluid medium droplets of larger size falls in the granulating mix, quick agglomeration of particles may occur leading to the formation of larger granules.
The spraying of aqueous ammonium hydroxide solution provides a source of ammonical nitrogen to the granules. During the drying, when ammonium sulphate heated to 100°C, partial degradation of the product leads to release of the ammonia. However, when ammonium hydroxide solution is sprinkled during the granulation, the loss of nitrogen from granular ammonium sulphate product while drying is negligible at that temperature. Further, at elevated temperature, faster drying is achieved without loss of nitrogen content from the ammonium sulphate granules.
In an embodiment, at least one pigment and a fluid medium is added to the mixture of ammonium sulphate powder and binder to form an admixture prior to granulation. The admixture is extruded in an extruder to obtain extrudates. In one embodiment, the extrudates are in the form of pellets. Further, the extrudated pellets are introduced into a granulator to obtain spherical (granular) ammonium sulphate granules. In an exemplary embodiment, the saffron color pigment is used.
In an embodiment, the moist ammonium sulphate granules of the size 2.5 mm to 4 mm are separated before subjecting to the step of drying. In an exemplary embodiment, separation is carried out using vibro- screen.
The moist granules are dried to obtain ammonium sulphate granules.
Typically, the step of drying is carried out at the temperature in the range of 60 °C to 100 °C. In an exemplary embodiment, the step of drying is carried out at a 70 °C. In another exemplary embodiment, the step of drying is carried out in a rotating drum dryer at 70 oC. In still another exemplary embodiment, the step of drying is carried out at 100 °C when ammonium hydroxide is sprinked during the step of granulation.
The drying is carried out for a time period in the range of 20-40 minutes when the fluid medium is aqueous ammonium hydroxide and the drying is carried out for a time period in the range of 45-70 minutes when the fluid medium is water.
In an exemplary embodiment, the ammonium sulphate granules have a nitrogen content in the range of 20% to 21%, a particle size in the range of 0.5 mm to 6 mm and a crushing strength of ammonium sulphate granules is in the range of 1.5 kg to 2.5 kg per granule.
The present disclosure provides the ammonium sulphate granules having a nitrogen content in the range of 18% to 21%, a particle size in the range of 0.5 mm to 6 mm and a crushing strength in the range of 0.5 kg to 5 kg per granule by the process which is simple, safe and environmental friendly.
The foregoing description of the embodiments has been provided for purposes of illustration and not intended to limit the scope of the present disclosure. Individual components of a particular embodiment are generally not limited to that particular embodiment, but, are interchangeable. Such variations are not to be regarded as a departure from the present disclosure, and all such modifications are considered to be within the scope of the present disclosure.
The present disclosure is further described in light of the following experiments which are set forth for illustration purpose only and not to be construed for limiting the scope of the disclosure. The following experiments can be scaled up to industrial/commercial scale and the results obtained can be extrapolated to industrial scale.
EXPERIMENTAL DETAILS
Experiment 1
Ammonium sulphate crystals having 21 % nitrogen and crystal size range 0.01 – 1 mm was ground in a pulveriser to obtain a fine powder of ammonium sulphate having a particle size 150 µm. To 992 g of ammonium sulphate powder, 8 g of polyvinyl pyrrolidone was added to obtain a mixture. The mixture was introduced to a rotating pan granulator at a rotation speed of 30 rpm. Water (~100 ml) was sprinkled slowly to the rotating mix for 10 minutes to form granules. The granules thus formed were sieved using a vibro screen separator and the size fraction of 2.5 – 4 mm was collected for drying. The undersized and oversized fraction of granules after crushing to smaller size was recycled with the next batch. The separated fraction of granules was introduced to a rotating drum dryer rotating at speed of 7 rpm facilitated with hot air blow of contact temperature 70 °C. The dried granules were analyzed and the analysis data is given in table 1.
Experiment 2
The procedure as given in Experiment 1 was repeated except that the 990 g of ammonium sulphate powder, 8 g of Maida and 2 g of saffron color (as pigment) were mixed to obtain a mixture. The dried granules were then analyzed and the analysis data is given in table 1.
Experiment 3
Ammonium sulphate crystals having 21 % nitrogen content and crystal size range 0.01 – 1 mm was ground a pulveriser to obtain a fine powder of ammonium sulphate having a particle size 150 µm. To 20 kg of ammonium sulphate powder, 120 g of Maida, 40 g polyvinyl pyrrolidone and 40 g of saffron color (as pigment) were added and mixed to obtain a homogeneous mixture. In the same mixer, water was sprayed to make the mixture to a thick paste. The thick paste was introduced into an extruder to produce pellets of 2.5 – 4 mm size. These pellets were then introduced to a rotating pan granulator at a rotating speed of 30 rpm to convert the pellets to spherical granules. The granules thus formed were sieved and the size fraction of 2.5 – 4 mm was separated. The separated fraction of granules was introduced to a rotating drum dryer rotating at a rotating speed of 7 rpm facilitated with hot air blow of contact temperature 70 °C. The dried granules were then analyzed and the analyzed data is given in table 1.
Experiment 4
The procedure as given in Experiment 1 was repeated except that the 1000 g of powdered ammonium sulphate having nitrogen content 21%, 6 g of Maida, 2 g polyvinyl pyrrolidone and 2 g of saffron color (as pigment) were mixed to obtain a mixture. The dried granules were then analyzed and the Analysis data is given in table 1.
Experiment 5
The procedure as given in Experiment 1 was repeated except that the 1000 g of ammonium sulphate powder, 50 g of powdered calcium bentonite clay was added and mixed in a rotating mixer to obtain a homogenous mixture. 24% NH4OH was sprinkled during the granulation. The dried granules were then analyzed and the analysis data is given in table 1.

Table 1: Analysis of ammonium sulphate granules
Parameter Expt 1 Expt 2 Expt 3 Expt 4 Expt 5
Granule size 2.5 to 4 mm 2.5 to 4 mm 2.5 to 4 mm 2.5 to 4 mm 2.5 to 4 mm
Yield 49 % 45 % 65 % 32 % 25 %
Crushing Strength (Average of 20 granules) 2.4
kg/granule 2.6
kg/granule 2.1 kg/granule 2.6 kg/granule 1.5 kg/granule
Moisture 0.22 % 0.32 % 0.36 % 0.15 % 0.32 %
Nitrogen 20.8% 20.7 % 20.56 % 20.55 % 20.05%
Sulphur 23.8 % 24.3 % 24.4 % 24.5 % 22.9 %
Free Acidity NIL 0.01 % 0.007 % 0.01 % NIL

Results depicted in table 1 show that the ammonium sulphate granules obtained by the process of the present disclosure have the nitrogen content (20-21%) and sulphur content (22-25%) in the maximum range which is required by plants. The implication is that, the amount of binder material plays a major role in controlling the nitrogen and sulphur content in ammonium sulphate granules. This is more evident from example 5, where the quantity of binder used is ~5 wt%, it has been attempted to add more nitrogen to the granules by use of ammonium hydroxide, but the results of nitrogen and sulphur are marginally lower than the results obtained in other experiments.
It is also evident from experiment 3 that when granulation is attempted using bulk quantity, yield increases considerably, showing the potential for upscaling the process to industrial level. Recycling of the undersized and oversized fraction will lead to a yield of 100 % in all the cases.
Experiment 6
Ammonium sulphate crystals having 21 % N, negligible free acidity and crystal size range 0 – 1 mm was ground to fine powder of size ~150 µm in a pulveriser. To 992 g of ammonium sulphate powder, 6 g of Maida and 2 g of pigment of saffron colour were added and mixed to homogeneity in a rotating pan granulator to obtain a mixture. 21% of Ammonium hydroxide solution was sprayed to the mixture in a rotating pan granulator to form spherical granules of size up to 4 mm. The rotation speed of pan granulator was 30 rpm. Hot air of contact temperature up to 100°C was applied to the granules in rotating pan dryer rotating at 7 rpm.
With the use of the higher temperature, quick drying was achieved. Use of ammonium hydroxide prevented any loss of ammonical nitrogen from the granular product while draying at elevated temperature.
Experiment 7
Crystalline ammonium sulphate (21 % N, negligible free acidity and crystal size range 0 – 1 mm) was ground to fine powder of size ~150 µm. To 992 g of ammonium sulphate powder, 6 g of Maida and 2 g of saffron pigment were added and mixed to homogeneity in a rotating pan granulator to obtain a mixture. To the mixture in the rotating pan granulator, water was sprayed to form spherical granules of size up to 4 mm. The rotation speed of pan granulator was 30 rpm. Hot air of contact temperature up to 100°C was applied to the granules in rotating pan dryer rotating at 7 rpm. Samples were drawn and analyzed. Analysis results are given in table 2.
Table 2: Comparative analysis of ammonium sulphate granules prepared by sprinking water and ammonium hydroxide solution
Parameter Expt 6 Expt 7
Fluid medium Ammonium Hydroxide Water
Drying temperature 100°C 100°C
Granule size 2.5 to 4 mm 2.5 to 4 mm
Yield 70 % 65 %
Crushing Strength (Average of 20 granules) 2 kg/granule 1.8 kg/granule
Moisture 0.15 % 0.3
Nitrogen 21. 9 % 20.44
Sulphur 24.08 % 24.39
Free Acidity Nil 0.011 %
Time to dry down to 1 % moisture 25 min. 58 min.
Ammonium sulphate when heated near to 100°C tend to release ammonia due to the degradation. Table 2 shows that spraying of aqueous ammonium hydroxide solution over water provides source of ammonical nitrogen to the granules. When ammonium hydroxide solution is sprinked during the granulation, the loss of nitrogen from granular ammonium sulphate product during the step of drying is negligible at elevated temperature. Further, at elevated temperature, faster drying is achieved without loss of nitrogen content from the ammonium sulphate granules. It can be seen from the Table 2 that, the drying time is significantly reduced when 21% of ammonium hydroxide solution was used as a sprinkling medium as compared to the water is used as a sprinkling medium.
The present disclosure provides a simple, faster, safe and environmental friendly process for the preparation for ammonium sulphate granules having a nitrogen content in the range of 18% to 21%, a particle size in the range of 0.5 mm to 6 mm and a crushing strength in the range of 0.5 kg to 5 kg per granule. The use of the binder as disclosed in present disclosure allows handle in tuning the nitrogen content in the ammonium sulphate granules.
TECHNICAL ADVANCEMENTS
The present disclosure described herein above has several technical advantages including, but not limited to, the realization of a process of preparation of granular ammonium phosphate:
• that is fast, simple, safe, and environment friendly.
Throughout this specification the word “comprise”, or variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.
The use of the expression “at least” or “at least one” suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the invention to achieve one or more of the desired objects or results. While certain embodiments of the inventions have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Variations or modifications to the formulation of this invention, within the scope of the invention, may occur to those skilled in the art upon reviewing the disclosure herein. Such variations or modifications are well within the spirit of this invention.
The numerical values given for various physical parameters, dimensions and quantities are only approximate values and it is envisaged that the values higher than the numerical value assigned to the physical parameters, dimensions and quantities fall within the scope of the invention unless there is a statement in the specification to the contrary.
While considerable emphasis has been placed herein on the specific features of the preferred embodiment, it will be appreciated that many additional features can be added and that many changes can be made in the preferred embodiment without departing from the principles of the disclosure. These and other changes in the preferred embodiment of the disclosure will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the disclosure and not as a limitation.
,CLAIMS:WE CLAIM:
1. A process for preparation of ammonium sulphate granules, said process comprising the following steps:
(i) grinding a crystalline ammonium sulphate to obtain ammonium sulphate powder having a particle size in the range of 50 µm to 250 µm;
(ii) blending the ammonium sulphate powder with at least one binder to obtain a mixture;
(iii) granulating the mixture by sprinkling a fluid medium to obtain a moist granules of ammonium sulphate; and
(iv) drying said moist granules to obtain the ammonium sulphate granules having a particle size in the range of 0.5 mm to 6 mm.
2. The process as claimed in claim 1, wherein said grinding is carried out by using a milling technique selected from the group consisting of a ball mill, a hammer mill, and a grinding disc.
3. The process as claimed in claim 1, wherein said blending is carried out by using a mixing device selected from a drum type homogenizer mixer and a disc type homogenizer mixer.
4. The process as claimed in claim 1, wherein said binder is at least one selected from the group consisting of clay, bentonite, zeolite, dolomite, alkali metal salt of lignosulphonic acid, ammonium salts of lignosulphonic acid, polyvinyl pyrrolidone, polyethylene glycol, calcium oxide, magnesium sulphate, starch, starch extracts, starch derivatives, wheat flour, rice flour, guar gum and refined wheat flour.
5. The process as claimed in claim 1, wherein the amount of said binder is in the range of 0.1 wt.% to 5 wt.% with respect to the total weight of said crystalline ammonium sulphate powder.
6. The process as claimed in claim 1, wherein said granulation is carried out by using a granulator selected from a pan granulator and a drum granulator, wherein said granulator has a rotating speed in the range of 20 rpm to 30 rpm.
7. The process as claimed in claim 1, wherein said fluid medium is selected from water and aqueous ammonium hydroxide having a concentration of ammonium hydroxide in the range of 20 wt.% to 30 wt. %..
8. The process as claimed in claim 1, wherein said drying is carried out at a temperature in the range of 60 °C to 100 °C.
9. The process as claimed in claim 8, wherein said drying is carried out for a time period in the range of 20-40 minutes when said fluid medium is aqueous ammonium hydroxide and wherein said drying is carried out for a time period in the range of 45-70 minutes when said fluid medium is water.
10. Ammonium sulphate granules, characterized by having a nitrogen content in the range of 18% to 21%, a particle size in the range of 0.5 mm to 6 mm and a crushing strength in the range of 0.5 kg to 5 kg per granule.