AU702690B2 - Improved coating for ammonium nitrate prills - Google Patents
Improved coating for ammonium nitrate prills Download PDFInfo
- Publication number
- AU702690B2 AU702690B2 AU20309/95A AU2030995A AU702690B2 AU 702690 B2 AU702690 B2 AU 702690B2 AU 20309/95 A AU20309/95 A AU 20309/95A AU 2030995 A AU2030995 A AU 2030995A AU 702690 B2 AU702690 B2 AU 702690B2
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- AU
- Australia
- Prior art keywords
- coating
- prills
- ammonium nitrate
- coating according
- nitrate prills
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Classifications
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- C—CHEMISTRY; METALLURGY
- C06—EXPLOSIVES; MATCHES
- C06B—EXPLOSIVES OR THERMIC COMPOSITIONS; MANUFACTURE THEREOF; USE OF SINGLE SUBSTANCES AS EXPLOSIVES
- C06B45/00—Compositions or products which are defined by structure or arrangement of component of product
- C06B45/18—Compositions or products which are defined by structure or arrangement of component of product comprising a coated component
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- C—CHEMISTRY; METALLURGY
- C06—EXPLOSIVES; MATCHES
- C06B—EXPLOSIVES OR THERMIC COMPOSITIONS; MANUFACTURE THEREOF; USE OF SINGLE SUBSTANCES AS EXPLOSIVES
- C06B45/00—Compositions or products which are defined by structure or arrangement of component of product
- C06B45/18—Compositions or products which are defined by structure or arrangement of component of product comprising a coated component
- C06B45/30—Compositions or products which are defined by structure or arrangement of component of product comprising a coated component the component base containing an inorganic explosive or an inorganic thermic component
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- C—CHEMISTRY; METALLURGY
- C05—FERTILISERS; MANUFACTURE THEREOF
- C05C—NITROGENOUS FERTILISERS
- C05C1/00—Ammonium nitrate fertilisers
- C05C1/02—Granulation; Pelletisation; Stabilisation; Colouring
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- C—CHEMISTRY; METALLURGY
- C06—EXPLOSIVES; MATCHES
- C06B—EXPLOSIVES OR THERMIC COMPOSITIONS; MANUFACTURE THEREOF; USE OF SINGLE SUBSTANCES AS EXPLOSIVES
- C06B31/00—Compositions containing an inorganic nitrogen-oxygen salt
- C06B31/28—Compositions containing an inorganic nitrogen-oxygen salt the salt being ammonium nitrate
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- C—CHEMISTRY; METALLURGY
- C06—EXPLOSIVES; MATCHES
- C06B—EXPLOSIVES OR THERMIC COMPOSITIONS; MANUFACTURE THEREOF; USE OF SINGLE SUBSTANCES AS EXPLOSIVES
- C06B45/00—Compositions or products which are defined by structure or arrangement of component of product
- C06B45/18—Compositions or products which are defined by structure or arrangement of component of product comprising a coated component
- C06B45/30—Compositions or products which are defined by structure or arrangement of component of product comprising a coated component the component base containing an inorganic explosive or an inorganic thermic component
- C06B45/32—Compositions or products which are defined by structure or arrangement of component of product comprising a coated component the component base containing an inorganic explosive or an inorganic thermic component the coating containing an organic compound
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Crystallography & Structural Chemistry (AREA)
- Fertilizers (AREA)
- Lubricants (AREA)
- Paints Or Removers (AREA)
Description
P/00/011 Regulation 3.2
AUSTRALIA
Patents Act 1990
ORIGINAL
COMPLETE SPECIFICATION STANDARD PATENT Invention Title: "IMPROVED COATING FOR AMMONIUM NITRATE PRILLS" The following statement is a full description of this invention, including the best method of performing it known to me:o e sc o e se o i IMPROVED COATING FOR AMMONIUM NITRATE PRILLS The present invention is directed to an improved coating material for use on ammonium nitrate prills. This coating material improved the flowability of the prills and reduces the amount of fines that result from the transportation and/or storage of the prills.
A problem that has plagued the Bulk Explosive Art for some time is the interaction of ammonium nitrate prills with each other or the environment once the prill has been manufactured. Generally, the prill is made in what is known as a prilling tower, bagged or placed in large bins for storage. Eventually the prills are shipped in bulk to their final destination for use, either as explosives or as fertilizer depending upon the density of the prill. The problem is simply that moisture in the air, friction due to 20 normal transportation, and the environmental factors associated with transportation and storage of bulk materials has a dispositive effect on the integrity of the prilled material. This results in an ammonium nitrate prill that becomes less effective as the final product with the 25 production of fines and becomes less handleable due to caking.
Much of the prior art that deals with the coating of *ammonium nitrate prills is directed to coating to protect the prill from the invasive effects of solvents often used as a 30 carrier for the prills when loaded in a borehole. In particular, U.S. patents 4,615,751, 4,404,050, and 4,555,278 are directed to different means and process whereby the ammonium nitrate prill is protected for some shelf life time period from the admixed solvents.
Attempts have been made to extend the storage life of prills with the addition of a coating for dry storage. U.S.
patent 3,834,955 discloses coating ammonium nitrate with a hydrophobic coating comprised of fatty acids, aluminum, talc, 4 and zinc stearate. Japanese patent 49,047,300 discloses the use of salts of metals, except magnesium, in combination with stearate and prill. U.S. patent 4,220,965 discloses the use of alkylamines and mineral oil with ammonium nitrate prills.
Some of the explosives coatings in the following references are directed to coating for transportation and storage purposes.
The present invention differs from that art in that the primary interest is in protecting the ammonium nitrate prill during the fragile stage of dry storage and transportation without affecting and in some cases improving its performance characteristics in the field. The invention is found useful for coating dense and porous ammonium nitrate prills for use Sin explosives and fertilizers.
15 SUMMARY OF THE INVENTION A coating for ammonium nitrate prills comprising a stearic salt formed from metal ions selected from the group consisting of alkali metal ions, alkaline earth metal ions, aluminium ions, 'zinc ions or some combination thereof, combined with a stearic 20 acid wherein said coating further comprises a dispersing agent comprised of fatty amides and wherein said salt comprises from about 1 to 80 weight percent of said coating.
Preferably the stearate salt is present from 20 to 60 weight percent. Most preferably the stearate salt is present from 30 to 40 weight percent The alkali metal ions are preferably selected from sodium and potassium, most preferably sodium. The alkaline earth metal ions are preferably magnesium and calcium and most preferably magnesium.
Examples of fatty amides compatible with this coating are comprised of branched, saturated and/or unsaturated linear hydrocarbons of carbon number ranging between C12 to The most preferred fatty amides are steramides, disteramides and combinations thereof.
kry~e~c~sl~ IIU~ The metal ions associate with the stearic acid to form the stearate salt, generally, one metal ion to each stearate.
The stearate then combines with the dispersant, the fatty amides, to form an admixture which is homogeneously dispersed as a coating.
The ammonium nitrate prill may be formed so that the density of the prill has both open and closed porosity. The porosity of the ammonium nitrate affects performance of the end product use whether the use is to be as a fertilizer or as an explosive. Generally, more porous ammonium nitrate prills are used as explosives. For the purpose of the present invention, whether open or closed porosity is present has little effect upon the coatability of the inventive coating.
15 For example, open porosity means that pores extend into the interstices of the prill. This additional porosity has no effect on the coating since the coating does not need to close the open porosity for the coating to be effective for the purposes of transportation and storage. The coating is hydrophobic and produces a pronounced hydrophobic effect upon the ammonium nitrate prill. As a result, it has been observed that water does not easily penetrate the coating even though the open porosity remains uncoated. It is believed that because of this effect, fewer fines are creaLed 25 since there is less interaction between ambient water vapor and the prill.
As an additional benefit, the coating offers itself as a lubricant to the normal frictional forces observed in batches of prills. The lubricating aspect of the coating also aids in the reduction of fines since there is a correlation between increased fines and increased abrasion.
This lubricating property also provides assistance in the anticaking result which is observed when the prills have been coated and stored. Often, without the inventive aY -I w coating, stored prills slowly become a single mass or transformed into a powdered mass. As a consequence, the prill loses its particle identity and becomes difficult to handle and less acceptable for its use in such final form.
The present inventive coating maintains the integrity of the particle identity. This is important since the shelf life, transportability, and usability are all enhanced.
Interestingly, the use of the stearate provides additional oxygen to the prill for use as an explosive. In the use of ammonium nitrate prills for explosives, the prills are often mixed with a fuel oil, making ANFO, to add fuel and oxidizer to enhance the explosive character of the prill.
The present invention easily lends itself to use in ANFO as a fuel with higher oxygen content. This can be advantageous dependent upon the needs of the explosive design.
Yet another advantage of this coating is its apparent chemical inertness to ammonium nitrate. Coatings often must bind with their substrates in order to coat effectively. In this instance, although the mechanism is not entirely clear, the coating coats without any substantial physico-chemical interaction. Since there is no substantial physico-chemical interaction the integrity of the prill surface is left intact. It is believed that the dominant interplay forces are physical and due to forces related to surface energies.
r Yet another advantage of this coating is its compatibility with explosive emulsion formulations. In general, an additional chemical agent often has the potential to cause a breakdown in the interaction of the various emulsion components in a formulation. Emulsion formulations are the outgrowth of volumes of experimentations wherein the final formulation becomes sensitive to the inclusion of additional chemical species. The AN prills coated with the inventive coating after being blended with emulsions exhibited similar properties to those of the blends based on uncoated prills. Therefore, it has been concluded to date 1 -~1111 that the inventive coating enhances the dry portion of the storage and handling of prills and does not interfere with the business end of the ammonium nitrate, explosions.
A preferred embodiment of the present invention is to dilute the coating with a diluent such as oils and waxes from about 10 to 80 percent by weight, most preferably 30 to weight percent. Oils found useful as a diluent are glycerides, paraffinic oil, mineral oils and combinations thereof. Waxes found useful are paraffinic waxes, beeswax, slackwax, and combinations thereof. In its most preferred embodiment the oil of choice is paraffinic oil and the wax of preference is slackwax.
In the application of the coating to the prill, it may be applied by any method known by those skilled in this art 5 for coating prills with a liquid coating. Generally, the coating is a liquid above 75 degrees centigrade and condenses to a solid below 65 degrees centigrade. The most preferred method of coating the present invention is to spray coat the prills on line after prill formation. The spray coat is applied in a coating drum. The coating drum has a controlled environment wherein the temperature and rate of feed of the prills is controlled. Coating integrity is assured by the reduction of temperature from a spray temperature of approximately 80 degrees centigrade which is subsequently 25 reduced to about prill temperature or about 30 degrees centigrade. The prill is subsequently stored to be shipped to its final destination.
DESCRIPTION OF THE EMBODIMENTS The following description is given to further illustrate the advantages provided by the present invention and are not intended to limit the scope of the invention. Generally, the prills for the following examples were manufactured by the same process. Any coating applied was applied to similarly made ammonium nitrate prills.
c I The coating of the present invention was made as follows. 5 parts of stearic acid (obtained from AKZO Chemicals) is reacted with 4.5 parts of octadecyl amine (obtained from AKZO Chemicals) at 120 degrees centigrade.
The reaction was continued until the formation of the stearamide was completed. 4 parts of magnesium stearate (obtained from Witco Chemical Company, Toronto, Canada) was mixed with 9 parts of paraffin oil as a slurry and slowly added to the hot amide solution in a stirred vessel. The admixtures slowly disperse into the amide making a clear solution. Then this clear solution is sprayed onto the prills by means of a spray nozzle connected with a metering pump in order to deliver the coating of a desired quantity.
Five comparative examples were made by a similar kind of process. The coatings of the comparative examples were as follows: Comparative Example 1 coating was Lilamine 81L (obtained from Berol Nobel, Sweden), Comparative Example 2 S. was Lilamine 88L (obtained from Berol Nobel), Comparative Example 3 was Galoryl ATH626 (obtained from Lobeko, US), 20 Comparative Example 4 was Carseland Regular with a coating of PetroAG/Talc in 0.05/.35 weight percent (obtained from Lobeko, US) and Comparative Example 5 was an uncoated prill.
The five comparative examples and the inventive example were subjected to a caking test to determine the effect of 25 the inventive coating. 135 grams of prill of each example was poured into the mold. The mold was gently vibrated to allow the prills to settle to provide a uniform distribution of pressure throughout the sample. The height of the sample was measured and entered into the program parameters of the computer program which calculates the force required to break the caked prills. The mold was placed between the compression plates an Instron press and the prills compressed at a stress rate of 1 mm/min until the compression force of 4500N was reached. The sample was left under compression for a period of 10 minutes. The height of the caked sample was recorded. The program was preset to break the cake formed r -p 13~ 1 -II due to compression. The force required to break the cake was determined by computer analysis. The higher the force, the stronger the cake. The percent moisture was measured by Karl-Fisher titration technique, known by those skilled in this art. Table 1 shows the results of these tests.
TABLE 1 Example Coating Moisture Breaking Added by Strength Weight Strength Weight 1 0.10 0.12 2918 2 0.08 0.11 3287 3 0.10 0.12 1986 4 0.05/.35 0.12 2787 0 0.12 4600 inventive 0.06 0.10 1325 coating 15 The smaller the breaking strength the less caking occurred for the purposes of the caking test which has been interpreted to mean that less caking will occur during storage. It is noted that the inventive coating produced a 50% improvement over the closest comparative example, 20 Comparative Example 2. An additional inventive example was subjected to the caking test and found to have a breaking strength of 1024 N. This inventive example had a polysulfonate additive, in this case sodium polystyrene sulfonate combined with the prill first, then the inventive coating added. The polysulfonate additive is described in Australian Patent Application 36747/93 herein incorporated by reference.
Samples of the same examples in Table 1 were subjected to a temperature cycling test to determine the amount of fines which would be produced through hot and cold cyclic Sstorage tests. The coated prills were combined with 6% oil II I to form ANFO. The samples were cycled through a temperature range of 35 to minus 35 degrees centigrade, being held at ambient temperature (AMB), 20 degrees centigrade, for some periods. A measure of the integrity of the prills after such environmental tests is the amount of fines measured. Fines are defined as the particulate produced during storage with an average diameter of less than 1.18 mm. Table II gives the results, in grams, of fines recovered from each example.
More fines recovered indicates less shelf life.
TABLE II Example AMB 35C -35C 35C/35C 1 0.5 3.2 42.5 3.2 71.0 86.9 2 0.8 2.9 40.9 3.5 71.0 82.3 3 0.5 0.5 28 0.8 64.3 80.4 15 5 0.5 2.2 24.7 1.8 31.0 58.0 inventive 0.5 0.5 13.7 0.5 48.6 67.0 coating SIt is noted that of the coated samples, the inventive sample was the least invasive and at certain conditions showed much better results than all examples.
PII II
Claims (21)
1. A coating for ammonium nitrate prills comprising a stearic salt formed from metal ions selected from the group consisting of alkali metal ions, alkaline earth metal ions, aluminium ions, zinc ions or some combination thereof, combined with a stearic acid wherein said coating further comprises a dispersing agent comprised of fatty amides and wherein said salt comprises from about 1 to 80 weight percent of said coating.
2. A coating according to claim 1 wherein said metal ions are comprised of magnesium ions.
3. A coating according to either claim 1 or claim 2 wherein said stearate salt comprises from about 20 to 60 percent of said coating.
4. A coating according to any one of claims 1 to 3 wherein 2 said stearate salt comprises from about 30 to 40 percent of said coating.
5. A coating according to any one of cla:.ms 1 to 4 wherein said fatty amide is steramide, disteramide or a combination thereof.
6. A coating according to any one of claims 1 to 5 wherein the combination of stearate salt and fatty amide is homogeneously dispersed.
7. A coating according to any one of claims 1 t-.o r wherein said coating is hydrophobic.
8. A coating according to any one of claims 1 to 7 wherein Ssaid coating is combined with a diluent from about 1i0 to Mi II IL P OPIPl MLA 2I'K9 95 15 24:12 9 weight percent.
9. A coating according to any one of claims 1 to 8 wherein said coating is combined with a diluent from about 30 to weight percent.
A coating according to claim 8 wherein said diluent is an oil.
11. A coating according to claim 8 wherein said diluent is wax.
12. A coating according to claim 10 wherein said oil is o 0 selected from the group consisting of glycerides, paraffinic 15 oil, mineral oils or some combination thereof.
13. A coating according to claim 11 wherein said wax is selected from the group consisting of paraffinic wax, beeswax, Oe slackwax, or some combination thereof. S"
14. A coating according to any one of claims 1 to 13 wherein said coating is compatible with emulsion explosive formulations.
Ammonium nitrate prills comprising a coatinq according t:, any one of claims 1 to 14.
16. Ammonium nitrate prills according to claim I1 wherein sail prills further comprise sodium polystyrene sultonate.
17. Ammonium nitrate prills according to either claim 15 ir claim 16 wherein said prills further comprise a fuel oil.
18. An explosive composition comprising ammoniun nitrate prill: \coated with a coating composition according to any ione cf claimn I 171~1~C 11 I' f)PIhIMNIlA ()309 y 5. 24 12 9 -11- 1 to 14. J r cc r r D e o
19. An explosive composition comprising ammonium nitrate prills according to any one of claims 15 to 17 inclusive.
A coating according to any one of claims 1 to 14 substantially as herein described with reference to the examples, excluding the comparative examples.
21. Ammonium nitrate prills according to any one of claims to 17 substantially as herein described with reference to the examples, excluding the comparative examples. DATED this 24th Day of December, 1998 ICI CANADA INC by DAVIES COLLISON CAVE Patent Attorneys for the Applicant(s) II ABSTRACT The present invention is directed to a coating for amnnonium nitrate prills which enhances the storage life and facilitates the transportation of said prills. The coating is derived from stearic acid and is hydrophobic. *e t 0 eC e PP-~ rC Is
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US08/248,643 US5567910A (en) | 1994-05-25 | 1994-05-25 | Coating for ammonium nitrate prills |
| US08/248643 | 1994-05-25 |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| AU2030995A AU2030995A (en) | 1995-11-30 |
| AU702690B2 true AU702690B2 (en) | 1999-03-04 |
| AU702690C AU702690C (en) | 2000-07-20 |
Family
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Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3249474A (en) * | 1964-08-03 | 1966-05-03 | Robert B Clay | Explosive composition containing inorganic salts and coated metal |
| US3816191A (en) * | 1970-05-04 | 1974-06-11 | Dow Chemical Co | Method of making calcium nitrate explosive composition |
| US3834955A (en) * | 1972-03-10 | 1974-09-10 | Ici Australia Ltd | Coated ammonium nitrate |
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3249474A (en) * | 1964-08-03 | 1966-05-03 | Robert B Clay | Explosive composition containing inorganic salts and coated metal |
| US3816191A (en) * | 1970-05-04 | 1974-06-11 | Dow Chemical Co | Method of making calcium nitrate explosive composition |
| US3834955A (en) * | 1972-03-10 | 1974-09-10 | Ici Australia Ltd | Coated ammonium nitrate |
Also Published As
| Publication number | Publication date |
|---|---|
| AU2030995A (en) | 1995-11-30 |
| KR950032019A (en) | 1995-12-20 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| DA2 | Applications for amendment section 104 | ||
| DA3 | Amendments made section 104 |
Free format text: FT="THE" NATURE OF THE AMENDMENT IS AS WAS NOTIFIED IN THE OFFICIAL JOURNAL DATED 20000106 |
|
| PC | Assignment registered |
Owner name: ORICA EXPLOSIVES TECHNOLOGY PTY LTD Free format text: FORMER OWNER WAS: ICI CANADA INC. |
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| MK14 | Patent ceased section 143(a) (annual fees not paid) or expired |