|Title of Invention||
A PROCESS FOR THE PREPARATION OF CONTROLLED RELEASE UREA FERTIUSER WITH IMPROVED NITROGEN USE EFFICSENCY
|Abstract||A process for the preparation of coating composition usingaldehydes, preferably furtual, suitably acidified with a mineral and or an organic acid and mixed with a surface acting agent and method of coating on prilled urea fertiliser is described. The coated chemicals on the surface of prilled urea undergo a chemical reaction known as condensation with the formation of a thinfilm over prills. The moisture formed by the condensation reaction is removed by drying at about 80 c which simultaneously results in the curing of the coated area. rendering the formation of infusible resins on the coated surface. thereby reducing the rate of dissolution in water. The coated area shows better nitrogen efficiency than plain (uncoated) area prills. Further, urease-inhabitors and nltrification-inhabitors is optionally added to the coating solution to enhance the agronomic quality of coated area. The mole ratio of area to aldehyde is preferably maintained as 80.1, which is quite low as compared to previously patented disclosures that specify a ration of 1:1 to 5:1 thus, in addition to the savings in raw material, major cost reduction are envisaged due to the eliminations of various unit operations meant for the removal of aqueous phase from the solid product. The process does not generate any liquid effluent. PRICE: THIRTY RUPEES|
The agronomic efficiency of urea a straight nitrogenous fertilizer, had been demonstrated to be low due to leaching, luxury consumption and rapid biohydrolysis. Nitrogen losses may vary from 10% under best field conditions to about 70% under poorest conditions. Thus there is a tremendous potential for the conservation of fertilizer nitrogen by minimizing or eliminating these losses. According to the statistical compilations of the Fertilizer Association of India, consumption of urea in India is close to 15 million tons per annum in the recent years; a portion of this quantity is typically met by imports. By looking at the industrial and economic scenario regarding the production and consumption of urea, and its ultimate agronomic efficiency, it can be said that, improvement in the nitrogen efficiency of urea would provide major benefits to the Indian economy. For example, if plain urea is modified in such a way to release its nitrogen content in a controlled manner, the agronomic loss of urea-nitrogen would consequently be at a reduced level. Even if a mere 10% of applied urea could be saved in India, it would be 1.5 million tons of urea per annum, which amounts to approximately Rs.750 crores at prevailing urea prices. Since urea is utilized worldwide, any significant technology development to improve its nitrogen efficiency shall provide certain savings which may not, necessarily, be restricted to India, but would naturally be extended to the fertilizer industry and the farmers around the globe. In this context, it is the objective of this invention to modify the physicochemical properties of urea prills so as to improve the nitrogen efficiency.
In this regard, a few products/derivatives of urea (called as slow release urea) such as, urea-form or urea-formaldehyde resins, have been developed in Europe, US and Japan in the past four decades.
These nitrogenous fertilizer products are primarily the end products of the reaction of urea with the corresponding aldehyde, the reaction/processing scheme of urea with different aldehydes is generally similar, and the urea-formaldehyde resin is popular in this class. The basic strategy of preparation disclosed in various patents (US 2,766,283; Brit.789, 075; USSR 331,052; Ger.Offen.2, 422,238; Indian 137,253; Fr. Demande 2,270,221) so far, involves the reaction of urea with aqueous formaldehyde generally in the mole ratio ranging from 1:1 to 5:1 in the liquid phase. Since formaldehyde has essentially been marketed as an aqueous solution of approximately 37% strength, presence of a large quantity of water in the reaction step is inevitable. The insoluble product is known to settle at the end of the reaction, and this should be followed by filtration and/or centrifugation to remove the aqueous layer, and finally the moisture content of the product should be reduced by drying. The mole ratio of water to formaldehyde generally ranges from 20:1 to 80:1 (US patent 2,766,283); removal of large quantities of water is an energy-consuming process; for related reasons, the product tends to be expensive; consequently, urea-form did not attract large scale field applications. Similar fertilizer resins seem to have been developed by reacting urea with other aldehydes, such as acetaldehyde, crotonaldehyde, iso-propionaldehyde; furfural, and isobutyraldehyde, as well as with mixtures of aldehydes. Here again, the mole ratio of urea to aldehyde generally ranges (Japan patent 69 16,334; Fr. Demande 1,528,310; Ger. Offen 1,146,080; Ger. Offen. 2,024,770) from 3:1 to 1:1. However, the cost of the respective urea-aldehyde resins seem to be prohibitive for field applications due to the price of raw materials, and aqueous reaction conditions which warrants several unit operations for product separation from the mother liquor, even though the products had been demonstrated to be superior to plain urea in terms of nitrogen release and efficiency.
Hence, an objective of this invention is to reduce quantity of aldehyde required as raw material, reduce the number of unit operations involved, and conduct the reaction without any addition of water as reaction medium.
Further, it shall be noted that, if the urea-aldehyde reaction is conducted in an aqueous medium, then an aqueous stream containing aldehydes, urea, and derivatives of urea-aldehyde has to be filtered off from the water-insoluble urea-aldehyde fertilizer. The effect is more pronounced if formaldehyde is used as the aldehyde of choice. Formaldehyde is traditionally available in the market as a 30 -50% aqueous solution and is seldom available as a pure material; hence after the urea-formaldehyde reaction, the product has to be separated, and the aqueous medium has to be disposed off as an effluent. Invariably, the aqueous medium would contain unreacted urea, unreacted formaldehyde, and derivatives of ureaformaldehyde. Thus effluent treatment becomes inevitable. These unit operations for water removal, viz., filtration/centrifugation, and then drying, form part of the production process. Each of these unit operations naturally contribute certain operating costs which should be incorporated in the product cost; moreover, effluent treatment cost should be added up. In view of these factors, an objective of this invention is to eliminate the use of water as the reaction medium. In other words, this invention does not employ any fluid medium for the urea-aldehyde reaction. Elimination of the aqueous reaction medium would naturally eliminate the filtration/centrifugation steps and the related operating costs. Moreover, the process described in this invention does not generate any liquid effluent and so it is a clean technology. By practice of this invention, the need for an effluent treatment scheme and the related operating costs are totally eliminated.
DESCRIPTION OF THE INVENTION
A spray of a suitable aldehyde may alter the surface of the urea particles. Furfural ma/ preferably be used, although other aldehydes, or any combination of aldehydes, with suitable physical properties (such as melting point, boiling point, viscosity, etc.,) at the reacting conditions may be chosen. Earlier patents emphasized that urea should be reacted with the aldehyde to the maximum possible extent. To facilitate this, all of the urea for chemical reaction was required to be in the liquid (solution) state for complete mixing with the solution containing aldehydes, and for ease of reaction; unlike such disclosures, the present invention aims to convert only the surface of the urea particle and leave the inner portion of the particle unaltered. Accordingly, this invention requires a reduced quantity of aldehydes only to be applied on the surface of urea particles. The mole ratio of urea to aldehyde may be in the ratio 40:1 to 90:1, preferably 80:1; when compared with the disclosures In earlier patents (for the preparation of ureaformaldehyde fertilizers), the aldehyde requirement is reduced by 8 to 80 times approximately. Needless to say, decrease in aldehyde requirement would decrease raw material cost, and hence product cost.
Since, only the surface reaction of urea particles is desired, water is not used as the reaction medium and effectively no solvent medium is required. Furfural, an aldehyde almost free of water, is the aldehyde preferred for the reaction, although other aldehydes or a mixture of aldehydes is also used. While choosing a solution of aldehydes, the following points may be noted: the aldehyde shall have a low melting point and a high boiling point, remain as a liquid at ambient temperatures thus provide a sufficient range of temperature to conduct the reaction. Furfural has such a convenient range of working temperature and it reacts readily with urea at ambient temperature under appropriate conditions; by way of examples without limitations,
acetaldehyde, propionaldehyde, butyraldehyde, isobutyraldehyde or benzaldehyde is used. Hence the requirement of any heating device for the chemical reaction is dispensed with. The aldehyde, as sprayed and coated on the urea particles, effects the chemical conversion. Thus, an aldehyde or a combination of two or more aldehydes from the following list is used.:
furfural, formaldehyde, acetaldehyde, propionadehyde, butyraldehyde, isobutyraldehyde, benzaldehyde
Another chemical property of such aldehyde that is most desirable for its selection for reaction with urea is that, the reaction product with urea should be insoluble in water. One of the objectives of this invention is to reduce the losses of fertilizer nitrogen by leaching; hence, it is important that the chosen aldehyde should form water-insoluble products on reaction with urea. It is preferable that the aldehyde liquid is acidified using a mineral acid/or an organic acid in the ratio of 2.0-15 kg per ton of urea for rapid reaction . The mineral/organic acid is one of the following:
Concentrated sulphuric acid; Concentrated hydrochloric acid, acetic acid,
benzoic acid, terephthalic acid and phthalic acid. Acidic reaction conditions, with pH preferably less than 4, promotes acid catalysed condensation reaction on the surface of urea particles forming water insoluble thin film coating.
On reaction with aldehydes, the urea particles tend to stick together. In order to minimize such an agglomeration of particles, a surface-active agent is preferably added at a concentration of 0.6 - 10.0 kg. per ton of urea. By way of examples without limitations, one of the following surface-active agents is employed.
Stearic acid, oleic acid, palmitic acid, propyleneglycol monostearate, propylene glycol monopalmitate, propylene glycol monolaurate, propylene glycol monooleate, propyleneglycol monomyristate.
In the absence of a surface-acting agent, the urea particles are found to agglomerate during the reaction step; in order to break down the agglomerates after the reaction step to the desired particle size, a pulverizer or any other size reduction equipment is used; further, such a size reduction equipment traditionally generates lot of dust and hence cyclones or some other devices for particle capture must be used. Incorporation of an inert surface-acting agent in the aldehyde for reaction, dispenses the need for size reduction equipment and other related devices.
It is also found that this coating formulation is suitable enough to incorporate various additives such as urease-inhibitors, microbially-toxic agents, micronutrients, nitrification-inhibitors. These additives are used either alone or as admixtures thereof. By way of examples without limitations, neem leaf powder, neem cake, neem oil, zinc dust, gypsum copper chloride, borax, boric acid and sodium azide are used as urease-inhibitors for controlling the hydrolysis of urea in soil. It is well known that substances such as, zinc dust, copper chloride, gypsum and borax function as micronutrients for the crops, and as biochemical inhibitors in the soil. In addition, boric acid and sodium azide are also used as urease-inhibitors to avoid unwanted hydrolysis of urea by the ureaseenzyme. These micronutrients/urease inhibitors either above or in combination of two or more of them are added to the urea in the ratio of 1.8 to 5 kg per ton of urea.
Hence, in this invention a small volume of aldehyde, preferably furfural, is acidified, added with a surface active substance, optionally added with urease-inhibitor and coated on prilled urea. Thus the coating composition comprising furfuraldehyde.
concentrated sulphuric acid and oleic acid is prepared by mixing them in the specified ratio. Additives such as urease-inhibitor cum micronutrients were mixed with this coating composition using suitable stirrer. This formulation was sprayed over urea prills with continuous mixing either manually or in a coating device, which is generally available in granulation laboratories. On coating, the acid catalysed condensation reaction slowly takes place on the surface of urea prills and the reaction is completed in about 4 hours at room temperature. The temperature of prills is kept at any temperature between 40 and 110°C, preferably between 40 and 80°C for five minutes. When the reaction temperature is increased upto 110°C directly, the rate of condensation reaction is accelerated and the reaction time is reduced from 4 hours to 1 hour. The temperature limit is indicated to prevent melting of urea and the vapourization of the aldehyde. If urea particles tend to melt, and solidify thereafter, it would then involve a size reduction step to comminute the fertilizer to the required particle size; such a size reduction step would increase the product cost. Thus, limiting the temperature below the melting of urea, eliminates the size reduction step.
Condensation reaction on the surface of urea results in the formation of a small quantity of moisture on the particles. This moisture content is removed during the heating process at 80°C -110°C. While the application of heat is primarily aimed at moisture removal, it simultaneously results in curing of the urea particles and makes the surface resins (urea-furfural derivatives) infusible and insoluble in water. The formation of such infusible resins on the surface of urea particles seems to retard its dissolution in water and promote slow availability of the constituent nitrogen to the crops by way of microbial decomposition, thus having a positive impact on the fertilizer. The following examples illustrate the practice of the process:
2.0 g of furfural, 0.2 g of the surface-active agent, oleic acid and 0.6g of the mineral acid, sulphuric (98%) acid were mixed together to obtain the coating composition. It was then mixed manually with 96.8 g of prilled urea at ambient temperature. The white urea particles which slowly turned black in colour, with the formation of a thin film on the surface due to the reaction between urea and aldehydes was heated preferably at temperature between 40° and 110°C, most preferably between 80°C and 90°C for 1 hour. This heating was done in a drier. Alternatively, it was more conveniently done in a granulator with heating provision..
1 kg of prilled urea was mixed with a coating composition comprising 22 gm of furfural, 14.8g of concentrated sulphuric acid, 1.8 g of oleic acid and 1.8 g of powdered neem leaves. The urea particles slowly turned brown in colour. After 4 hours, the coated urea was dried at 80°C in a fluid bed dryer for 5 minutes to reduce surface moisture to 0.5%. Twenty five percent of the nitrogen content of the coated urea thus prepared was found to be insoluble in cold water.
1 kg of prilled urea was mixed with a coating composition comprising 25g of furfural, 15g of concentrated sulphuric acid, 5g of oleic acid and 4g of neem cake powder to get brown coloured coated urea fertilizer. After 4 hours, it was dried at 80°C in a fluid bed dryer for 5 minutes to reduce the moisture to 0.5%.
20 g of powdered neem cake mixed with 14 ml of sulphuric acid (98%), 100 g of furfural and 3.0 g of oleic acid to obtain a paste. The paste was then mixed with 5 kg of prilled urea. The product, which turned black in colour was dried as In described in example 2 to get controlled release urea fertilizer.
A coating paste composition containing 5 g of terephthalic acid, 5 g of benzoic acid, 5 g of powdered neem leaves, 2 g of sulphuric acid (98%), 20 g of furfural and 1 g of oleic acid were mixed thoroughly with 1 kg of prilled urea to form a slow release urea fertilizer. It was further treated by heating as described in Example 2.
The efficacy of coated urea prepared as above was evaluated by comparison with uncoated urea in field trials with paddy. The plot size was 18 ft x 8.5 ft at Muthiahpuram in Tuticorin, Tamilnadu. The paddy variety was ASD-16. It was transplanted in November 1995 and harvested in February 1996. There were three treatments as shown below, and there were three replications. The three treatments are:
(A) control (raw urea) - applications of plain , uncoated, prilled urea at standard
dosage level of nitrogen recommended for paddy.
(B) Coated urea -100% - application of coated urea (prepared as described
above) at the same dosage level of (A) control, and,
(C) Coated urea - 80% - application of coated urea (prepared as described
above) at 80% of the dosage level of (A) control
It should be noted that (B) and (C) were prepared from the same brand and same batch of fertilizer grade (prilled) urea as that of (A). All of (A), and raw urea to prepare (B) and (C), were drawn from the same bag of fertilizer urea, and so the entire quantity of urea used in this field trial was uniform in all aspects before coating. (B) and (C) were coated and used. At the end of the field trial, the following yield (in kilograms) was obtained.
3 treatments (A) (B) (C)
Straw weight 57.24 63.82 54.78
Grain weight 24.66 26.28 24.34
It is noticeable that (B) had given 6% more yield than control. (C) and (A) gave almost equivalent yield, indicating that about 20% of applied urea can be saved, if fertilizer urea is applied as coated urea instead of plain urea.
100 g of prilled urea was mixed with a coating composition containing 0.5 g of powdered neem leaves, 0.5 g of terephthallc acid, 0.5 g of benzoic acid, 0.2 g of concentrated sulphuric acid, 2 g of furfural, 1 g of oleic acid. The coated urea particles became black and was processed as described in Example 2. The efficacy of coated urea thus prepared was evaluated against uncoated urea in a pot trial with maize.
Pot cultures were started in September 1995 and the seeds of maize were of a local variety. There were three treatments as in Example 5, viz., (A) control with uncoated urea.
(B) coated urea with urea dosage being the same as control, and
(C) coated urea with urea dosage equal to 80% of control.
There were five replications and harvest was done in December 1995. The height of the plant, the number of leaves and the length of the single longest leaf were noted in course of time to assess any variation in growth pattern:
Plant height (in cm) on 11*^ October 1995:
12 3 4
A 25 42 48 30
B 55 56 53 42
C 40 50 50 54
Conclusion: Plants fed with coated urea (both B and C) had grown significantly higher than the plants fed with uncoated urea (A). The difference between B and C seems to be insignificant.
Number of leaves (in cm) on 11*" October 1995:
12 3 4
A 9 9 10 7
8 9 10 8 7
C 10 8 9 8
Conclusion: The difference in the average number of leaves between A, B and C were insignificant.
Length of the single longest leaf (In cm) on 19"^ October 1995:
12 3 4 5 Average
A 60 73 73 58 75 67.8
B 75 70 69 79 81 74.8
C 71 82 75 73 80 76.2
Conclusion: The average length of the single longest leaf is significantly higher for plants for B and C in reference to control (A). Longer leaves generally indicate more area for photosynthesis; noticeably, plants with higher leaf-length (B and C) had also grown higher in comparison with control (A), indicating that more metabolic activity had taken place in the plants fed with coated urea. Higher metabolic activity should be attributed to better availability of urea-nitrogen. Yield:
Number of cobs Total weight Total number Total weigl
with grains of cobs (g) of grains of grains ((
A 4 640 970 343
B 5 875 1325 502
C 6 960 1152 447
Conclusion: The yield (total weight of grains) of B was higher than the control by 46%. The yield of 0 was higher than the control by 30%. Higher yield of plants fed with coated urea, shows that the coated urea has better nitrogen efficiency than uncoated urea.
Although several examples of the invention have been given, it will be appreciated that changes and modifications thereof may be made without departing frprri the
scope of the invention. Therefore, the invention shall not be limited to the specific examples and embodiments of the process shown and described herein, but shall be defined in scope by the following claims:
1) A process for the preparation of controlled release urea fertilizer with
improved nitrogen use efficiency by coating specially developed
composition, wherein the said composition
a) comprising an aldehydic substance like furfural, acetaldehyde, propionaldehyde, butyraldehyde isobutyraldehyde and benzaldehyde.
b) an acid catalyst like concentrated sulphuric acid, concentrated hydrochloric acid, acetic acid, benzoic acid, phthalic acid and terephthalic acid
c) a surface active substance like stearic acid, oleic acid, palmitic acid, propyleneglycol monolaurate, propyleneglycol monooleate and propyleneglycol mono myristate
d) an urease inhibitor like neem leaf powder, neevn cake, neem oil, zinc dust, copper chloride and borax is thoroughly mixed at room temperature and
e) the said composition is coated over urea prills with continuous mixing at room temperature and then heated at temperature between 40° and 110°C.
2) A process for the controlled release urea fertilizer as per claim 1 wherein the mole ratio of aldehyde to urea is between 1:40 to 1:90.
3) A process as per claim 1, wherein the acid catalyst like concentrated sulphuric acid or other acid from the group is taken in the ratio of 2.0-15 kg per ton of urea used.
4) A process as per claim 1, wherein the surface active substance from the
group is taken at 0.6 to 10 kg per ton of urea.
5) A process as claim 1, wherein the urease inhibitor from the group, neem
leaf powder, neem cake, neem oil, borax, boric acid, copper chloride, zinc
dust, sodium azide, gypsum either one or more as combination is added
|Indian Patent Application Number||1177/MAS/1996|
|PG Journal Number||30/2009|
|Date of Filing||04-Jul-1996|
|Name of Patentee||SOUTHERN PETROCHEMICAL INDUSTRIES CORPORATION LTD,|
|Applicant Address||97 MOUNT ROAD, MADRAS 32|
|PCT International Classification Number||C07C273/02|
|PCT International Application Number||N/A|
|PCT International Filing date|