DESC:FIELD

The present disclosure relates to a process for the preparation of a monohydrated calcium nitrate.

BACKGROUND

The background information herein below relates to the present disclosure but is not necessarily prior art.

Plant nutrients such as nitrogen (N), phosphorous (P) and potassium (K) and the like are applied to soil and crops either in a solid form or in a liquid form. Calcium nitrate is an excellent source of nitrogen as a primary nutrient and calcium as a secondary nutrient. Conventionally, calcium nitrate is prepared from various starting materials such as reacting gypsum (calcium sulphate hydrated), calcium carbonate, and the like with nitric acid. However, the excess acidity is left in the product after the reaction which is required to be neutralized. The use of ammonium hydroxide is used for neutralization. The use of ammonium hydroxide leads to production of ammonium nitrate. In an industrial set up, buildup of ammonium nitrate in a reactor is highly hazardous as it is an explosive. Further, commonly available forms of calcium nitrate such as calcium nitrate tetrahydrate and calcium nitrate dihydtrate, are hygroscopic and hence unstable. A remedy is to remove the water of crystallization, however, removing the water completely from such form is highly energy consuming.

Therefore, there is felt a need to provide a process for the preparation of a monohydrated calcium nitrate that mitigates the aforestated drawbacks mentioned herein above.

OBJECTS

Some of the objects of the present disclosure, which at least one embodiment herein satisfies, are as follows:

An object of the present disclosure is to ameliorate one or more problems of the prior art or to at least provide a useful alternative.

Another object of the present disclosure is to provide a process for the preparation of a monohydrated calcium nitrate.

Yet another object of the present disclosure is to provide a process for the preparation of a monohydrated calcium nitrate that is simple, cost-effective, requires less energy consumption and environment friendly.

Still another object of the present disclosure is to provide a monohydrated calcium nitrate that can used as a fertilizer and has enhanced shelf life.

Still another object of the present disclosure is to provide a process for the preparation of a crystalline monohydrated calcium nitrate.

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 the preparation of a monohydrated calcium nitrate. The process comprises: mixing a predetermined amount of calcium hydroxide in a predetermined amount of water to obtain a suspension. A predetermined amount of nitric acid is added slowly in the so obtained suspension and reacted with the nitric acid at a first predetermined temperature for a predetermined time period to obtain a reaction mixture that comprises calcium nitrate in a solution form and an un-reacted calcium hydroxide. The un-reacted calcium hydroxide is separated from the reaction mixture to obtain a product mixture comprising calcium nitrate and the product mixture is dried at a second predetermined temperature to obtain the monohydrated calcium nitrate in crystalline form.

BRIEF DESCRIPTION OF ACCOMPANYING DRAWING
The present disclosure will now be described with the help of the accompanying drawing, in which:

Figure 1: A graphical representation of tomato crop yield from the application of monohydrated calcium nitrate; and

Figure 2: A graphical representation of yield comparison of tomato crop with liquid calcium nitrate application.

DETAILED DESCRIPTION

Embodiments, of the present disclosure, will now be described with reference to the accompanying drawing.

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.

As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed elements.

The plants nutrients such as nitrogen, phosphorous and potassium are the essential nutrients which are added into the soil and applied to crops in a solid form or in water soluble form for better production of crop or better yield. Calcium nitrate is the greatest source of the nitrogen as a primary nutrient and calcium as a secondary nutrient. Typically, calcium nitrate is obtained from various raw materials such as calcium carbonate, gypsum by reacting with nitric acid. However, the calcium nitrate obtained via this process is hazadours to the soil and crops due to the presence of excess amount of acid in the product which need to be neutralized. In order to overcome this drawback, ammonium hydroxide is employed for neutralization of excess acid, however, addition of ammonium hydroxide further leads to production of ammonium nitrate which is highly explosive in an industrial set up. Furthermore, the commonly available forms of calcium nitrate such as calcium nitrate tetrahydrate and calcium nitrate dihydrate are hygroscopic, hence unstable on storage. A remedy is to remove the water of crystallization, however, removing the water completely from such form is highly energy consuming. Thus, there is a definite need of a process for the preparation of a monohydrated calcium nitrate that overcome all the above-mentioned drawbacks.

The present disclosure provides a process for the preparation of a monohydrated calcium nitrate.

In an aspect of the present disclosure, there is provided with a process for the preparation of a monohydrated calcium nitrate. The process is described in detail as:

In the first step, a predetermined amount of calcium hydroxide is mixed in a predetermined amount of water to obtain a suspension.

In accordance with the present disclosure, the predetermined amount of calcium hydroxide is in the range of 5 wt% to 30 wt% with respect to the total weight of the raw material. In an exemplary embodiment, the predetermined amount of calcium hydroxide is 12 wt% with respect to the total weight of the raw material.

In accordance with the present disclosure, the predetermined amount of water is in the range of 10 wt% to 20 wt% with respect to the total weight of the raw material. In an exemplary embodiment, the predetermined amount of water is 12 wt% with respect to the total weight of the raw material.

In accordance with the present disclosure, the calcium hydroxide has a purity in the range of 85 to 95%. In an exemplary embodiment, the calcium hydroxide has purity of 90%.

The generally followed process of production of calcium nitrate involves reaction of calcium carbonate with nitric acid, which involves release of carbon dioxide in huge quantity. The importance of using calcium hydroxide instead of calcium carbonate is there is no formation of CO2 gas. No effervesces are formed while carrying out reaction with calcium hydroxide. Hence no greenhouse gas emission is occurring here.

In the second step, a predetermined amount of nitric acid is added slowly in the so obtained suspension followed by reacting with the nitric acid at a first predetermined temperature for a predetermined time period to obtain a reaction mixture comprises calcium nitrate in solution form and an un-reacted calcium hydroxide.

In accordance with the present disclosure, the predetermined amount of nitric acid is in the range of 70 wt% to 95 wt%. In an exemplary embodiment, the predetermined amount of nitric acid is 75 wt%.

In accordance with the present disclosure, the first predetermined temperature is in the range of ¬¬60 °C to 90 °C. In an exemplary embodiment, the first predetermined temperature is ¬¬80°C.

In accordance with the present disclosure, the predetermined time period is in the range of 3 hours to 5 hours. In an exemplary embodiment, the predetermined time period is 4 hours.

In an embodiment of the present disclosure, the nitric acid is a spent nitric acid.

In accordance with the present disclosure, the concentration of nitric acid is in the range of 15 to 65%. In an exemplary embodiment, the concentration of nitric acid is in the range of 17 to 20%. In another exemplary embodiment, the concentration of nitric acid is 60%.

In accordance with the present disclosure, the ratio of the calcium hydroxide to the nitric acid is in the range of 1:4: 1:8. In an exemplary embodiment, the ratio of the calcium hydroxide to the nitric acid is 1:6.25.

In accordance with the present disclosure, the slow addition of the nitric acid into the suspension is carried out for a time period in the range of 30 minutes to 189 minutes. In an exemplary embodiment, the slow addition of the nitric acid into the suspension is carried out for a time period of 60 minutes.

The addition of nitric acid into the suspension results in an exothermic reaction, hence the nitric acid is added slowly.

In the third step, the unreacted calcium hydroxide is separated via simple filtration or vacuum filtration technique by using filter having a pore size in the range of 20 to 25 microns, to obtain a product mixture comprising calcium nitrate. The filtrate (liquid) contains calcium nitrate whereas residue contains unreacted calcium hydroxide which is filtered out.

The unreacted calcium hydroxide is separately filtered out and further recycled for use.

In the fourth step, the product mixture is dried at a second predetermined temperature to obtain the monohydrated calcium nitrate in crystalline form.

In accordance with the present disclosure, the product mixture is dried either by spray drying in a spray drier or by rotary drying in a rotary dryer.

In accordance with the present disclosure, the second predetermined temperature is in the range of ¬¬110°C to 140°C. In an exemplary embodiment, the second predetermined temperature is ¬¬130°C.
In accordance with the present disclosure, the so obtained crystals of monohydrated calcium nitrate are processed into an extruder-granulator to obtain monohydrated calcium nitrate in granular form.
In accordance with the present disclosure, the granulation is done via extruder granulation, and drums granulation or pan granulation.
In accordance with the present disclosure, the granules of monohydrated calcium nitrate are characterized to evaluate the total nitrogen content, nitrate nitrogen content, water soluble calcium, an insoluble matter, and crushing strength respectively.
In accordance with the present disclosure, the monohydrated calcium nitrate has nitrogen content in an amount in the range of 10 wt% to 20 wt%. In an exemplary embodiment, the nitrogen content is 16.19 wt%. In another exemplary embodiment, the nitrogen content is 16.24 wt%.
In accordance with the present disclosure, the monohydrated calcium nitrate has nitrate nitrogen content in an amount in the range of 10 wt% to 20 wt%. In an exemplary embodiment, the nitrate nitrogen is 15.88 wt%. In another exemplary embodiment, the nitrate nitrogen is 16.06 wt%.
In accordance with the present disclosure, the monohydrated calcium nitrate has water soluble calcium in an amount in the range of 15 wt% to 30 wt%. In an exemplary embodiment, the water soluble calcium is 22.68 wt%. In another exemplary embodiment, the water soluble calcium is 22.82 wt%.
In accordance with the present disclosure, the monohydrated calcium nitrate has insoluble matter in an amount in the range of 0 wt% to 0.2 wt%. In an exemplary embodiment, the insoluble matter is 0.1 wt%. In another exemplary embodiment, the insoluble matter is zero.
In accordance with the present disclosure, the monohydrated calcium nitrate has a crushing strength is in the range of 1 kg/granule to 5 kg/granule. In an exemplary embodiment, the crushing strength of the monohydrated calcium nitrate is 3 kg/granule.
In accordance with the present disclosure, the monohydrated calcium nitrate is used as a fertilizer.
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: Preparation of a monohydrated calcium nitrate in accordance with the process of the present disclosure:

Example 1
80 gm of calcium hydroxide (90% pure) was added in 80 gm water to obtain a suspension of calcium hydroxide. 500 gm of nitric acid having a concentration of 17-20% was added slowly to the suspension over a period of 1 hour followed by reacting at 80 °C for 4 hours to obtain a reaction mixture comprising calcium nitrate in a solution form and an un-reacted calcium hydroxide. The reaction mixture was filtered to remove the un-reacted calcium hydroxide to obtain a product mixture comprising calcium nitrate in a solution form. The separated un-reacted calcium hydroxide was reused further. The product mixture comprising the calcium nitrate solution was spray dried at 130 °C to obtain the monohydrated calcium nitrate in a crystalline form. This calcium nitrate monohydrated powder already containing one water molecule of crystallization was processed to an extruder-granulator to obtain a granulated monohydrated calcium nitrate.

The granulated monohydrated calcium nitrate was further analysed and the results obtained are provided in table 1.
Table 1
Parameters Results
Total nitrogen content (%, w/w) 16.19
Nitrate nitrogen content (%, w/w) 15.88
Water soluble calcium (%, w/w) 22.68
Insoluble matter (%, w/w) 0.1
Crushing strength (kg/granule) 3

Inference: The calcium nitrate granules prepared in accordance with the present disclosure is in monohydrate form AND NOT di-hydrate or tri-hydrate form as known in the art. The calcium content of the monohydrate calcium nitrate granules of the present disclosure is more than 22.5% w/w which is greater than the calcium content present in the conventional calcium nitrate granules (18.5% w/w).
Example 2
800 gm of calcium hydroxide (90% pure) was added in 800 gm water to obtain a suspension of calcium hydroxide. 5000 gm of nitric acid having a concentration of 60% was added slowly to the suspension over a period of 1 hour followed by reacting at 80 °C for 4 hours to obtain a reaction mixture comprising calcium nitrate in a solution form and an un-reacted calcium hydroxide. The reaction mixture was filtered to remove the un-reacted calcium hydroxide to obtain a product mixture comprising calcium nitrate in a solution form. The separated un-reacted calcium hydroxide was reused further. The product mixture comprising the calcium nitrate solution was spray dried at 130 °C to obtain the monohydrated calcium nitrate in a crystalline form. This calcium nitrate monohydrated powder already containing one water molecule of crystallization was processed to an extruder-granulator to obtain a granulated monohydrated calcium nitrate.

The granulated monohydrated calcium nitrate was further analysed and the results obtained are provided in table 2.
Table 2
Parameters Results
Total nitrogen content (%, w/w) 16.24
Nitrate nitrogen content (%, w/w) 16.06
Water soluble calcium (%, w/w) 22.82
Insoluble matter (%, w/w) Prac. Nil
Crushing Strength (kg/granule) 3

The total weight of the materials used in example 2 was modified to get more volume of products to use in the field trials.

Experiment 2: Efficacy study of the monohydrated calcium nitrate as a fertilizer for Tomato crop:
Example A:
The so obtained monohydrated calcium nitrate granules of the example 2 were applied directly on tomato plant through soil application.
Increased growth and yield were observed with the application of the granular monohydrated calcium nitrate fertilizer on Tomatoes when compared to the results of application of a commercially available product. Fig 1. and Fig.2 indicates the plot size (i.e. 12 square meter), T1 to T13 represents the treatment or the application of the fertilizer on tomato crop. Treatment T1 to T7 relates to the composition of the present disclosure and T8 to T13 relates to the commercially available products. (fig. 1 and 2). Tomato crop was treated at different doses levels (T1 to T7) after the transplantation with the composition (granular monohydrated calcium nitrate fertilizer) of the present disclosure and the growth and yield were evaluated. It was observed that application of the granular monohydrated calcium nitrate fertilizer on tomato crop at a dose rate of 90 kg/ha at 40, 80 and 120 DATP (days after transplantation) suited for farmers as it gave the highest tomato fruit yield (fig. 1) which shows the enhanced yield of tomatoes obtained per plot by application of calcium nitrate granules of the present disclosure in comparison with the commercially available as well as control fertilizers (T8 to T13).

Example B: Application of monohydrated calcium nitrate as a fertilizer in liquid form:
A 50 % concentration solution of the monohydrated calcium nitrate of the present disclosure (before drying and granulation) was used to prepare dilute solutions of various concentrations (0.4 %, 0.6 % etc.) and applied to tomato through foliar spray.
It was observed that the application of 0.4 % concentration of the monohydrated calcium nitrate at flowering stage through spray provided the maximum plant height at 60 days after transplanting, and also observed the number of fruits per cluster, average fresh five fruit weight, fruit length and yield (fig. 2) which shows the enhanced yield of tomatoes obtained per plot by application of calcium nitrate prepared in accordance with the present disclosure in a liquid form when compared with commercially available as well as control fertilizers.

TECHNICAL ADVANCEMENTS

The present disclosure described herein above has several technical advantages including, but not limited to, the realization of a process for the preparation of a monohydrated calcium nitrate that:
• is safe;
• does not produce greenhouse emissions (carbon dioxide is not produced) and hence environment friendly;
• the reactants are recyclable and hence, the process is cost-effective;
• produces the monohydrated calcium nitrate having enhanced shelf life; and
• is less energy consuming and hence economic.

The embodiments herein and the various features and advantageous details thereof are explained with reference to the non-limiting embodiments in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.

The foregoing description of the specific embodiments so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.

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 disclosure to achieve one or more of the desired objects or results.

Any discussion of documents, acts, materials, devices, articles or the like that has been included in this specification is solely for the purpose of providing a context for the disclosure. It is not to be taken as an admission that any or all of these matters form a part of the prior art base or were common general knowledge in the field relevant to the disclosure as it existed anywhere before the priority date of this application.

The numerical values mentioned for the various physical parameters, dimensions or quantities are only approximations and it is envisaged that the values higher/lower than the numerical values assigned to the parameters, dimensions or quantities fall within the scope of the disclosure, unless there is a statement in the specification specific to the contrary.

While considerable emphasis has been placed herein on the components and component parts of the preferred embodiments, it will be appreciated that many embodiments can be made and that many changes can be made in the preferred embodiments without departing from the principles of the disclosure. These and other changes in the preferred embodiment as well as other embodiments 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 the preparation of a monohydrated calcium nitrate, said process comprising the following steps:
a) mixing a predetermined amount of calcium hydroxide in a predetermined amount of water to obtain a suspension;
b) adding slowly a predetermined amount of nitric acid to said suspension and reacting said suspension with said nitric acid at a first predetermined temperature for a predetermined time period to obtain a reaction mixture comprising calcium nitrate in a solution form and an un-reacted calcium hydroxide;
c) separating said unreacted calcium hydroxide to obtain a product mixture comprising calcium nitrate; and
d) drying said product mixture at a second predetermined temperature to obtain said monohydrated calcium nitrate in a crystalline form.

2. The process as claimed in claim 1, wherein said monohydrated calcium nitrate in a crystalline form is granulated into an extruder-granulator to obtain a granulated monohydrated calcium nitrate.

3. The process as claimed in claim 1, wherein said calcium hydroxide has a purity in the range of 85 to 95%.

4. The process as claimed in claim 1, wherein a said nitric acid is a spent nitric acid.

5. The process as claimed in claim 1, wherein a concentration of said nitric acid is in the range of 15 to 65%.

6. The process as claimed in claim 1, wherein said predetermined amount of calcium hydroxide is in the range of 5 wt% to 30 wt% with respect to the total weight of the raw material, said predetermined amount of water is in the range of 10 wt% to 20 wt% with respect to the total weight of the raw material and predetermined amount of nitric acid is in the range of 70 wt% to 95 wt% with respect to the total weight of the raw material.

7. The process as claimed in claim 1, wherein a ratio of the calcium hydroxide to the nitric acid is in the range of 1:4 to 1:8.

8. The process as claimed in claim 1, wherein said first predetermined temperature is in the range of ¬¬60 °C to 90 °C and said second predetermined temperature is in the range of 110 °C to 140 °C.

9. The process as claimed in claim 1, wherein said slow addition of the nitric acid into said suspension is carried out for a time period in the range of 30 minutes to 180 minutes.

10. The process as claimed in claim 1, wherein said predetermined time period is in the range of ¬¬3 hours to 5 hours.

11. The process as claimed in claim 1, wherein said drying in step d) is carried out by using a spray dryer or rotary dryer.

12. The process as claimed in claim 1, wherein said monohydrated calcium nitrate is characterized by having:
• a total nitrogen content in an amount in the range of 10 wt% to 20 wt%,
• a nitrate nitrogen content in an amount in the range of 10 wt% to 20 wt%,
• a water soluble calcium in an amount in the range of 15 wt% to 30 wt%; and
• an insoluble matter in an amount in the range of 0 wt% to 0.2 wt%.

13. The process as claimed in claim 1, wherein said monohydrated calcium nitrate has a crushing strength in the range of 1 kg/granule to 5 kg/granule.

14. The process as claimed in claim 1, wherein said monohydrated calcium nitrate is used as a fertilizer.

Dated this 6th day of October, 2021

_______________________________
MOHAN RAJKUMAR DEWAN, IN/PA – 25
of R.K.DEWAN & CO.
Authorized Agent of Applicant

TO,
THE CONTROLLER OF PATENTS
THE PATENT OFFICE, AT MUMBAI