JPS6210926B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention provides an improved method for producing ammonium nitrate prills and granules. There are two types of ammonium nitrate prills, which can be distinguished by free flow bulk density. High density (free flow bulk density>
0.85g/ml) is generally used as fertilizer. Low density (free flow bulk density <0.85g/ml)
are commonly used in explosive compositions. These two types of ammonium nitrate prills involve reacting nitric acid and ammonia to produce a hot liquid containing ammonium nitrate, spraying this hot liquid down a tower to form solid prills, and cooling these prills. It can be manufactured by a modification of the process. Low-density ammonium nitrate prills are produced by reacting nitric acid with ammonia in a neutralizer and evaporating most of the water from the resulting ammonium nitrate solution in an evaporator, typically containing 1-6% water. dropping the thermal concentrate from the top of the prilling tower and collecting the prills thus formed;
Produced by drying and cooling. High-density ammonium nitrate prill is made by reacting nitric acid with ammonia in a neutralizer and evaporating the resulting ammonium nitrate solution in an evaporator to reduce the water content of the ammonium nitrate solution to less than 1% to form a melt-like concentrate. It is produced by dropping the hot melt from the evaporator from the top of a prilling tower and collecting and cooling the dry prills thus formed. The word "dry" is H ₂ O
Means the content is less than 0.2%. Ammonium nitrate granules are produced by preparing a hot concentrate of ammonium nitrate in the manner described above for the production of low density ammonium nitrate prills. This hot concentrate is added to the recycled solid ammonium nitrate in a granulator where granules are produced by agglomeration of the recycled solid ammonium nitrate and solidification of the concentrate. These granules are dried and sieved.
Granules with dimensions outside the desired product dimensions are crushed, placed in a granulator, and recirculated.
Provides solid ammonium nitrate recycle. No. 3,639,643 discloses that the mechanical strength of ammonium nitrate prills and granules is increased by preparing them to contain colloidal aluminum hydroxide. Aluminum hydroxide is produced by adding aluminum sulfate to the ammonium nitrate concentrate after the evaporation step. The high mechanical strength of prills and granules provides high resistance to prill and granule breakage during handling, compaction and caking during storage, and decomposition during temperature changes near crystalline phase transition temperatures. Now, in the production of ammonium nitrate prills and granules containing aluminum compounds, in order to give high strength, it is necessary to add aluminum salts as a source of aluminum compounds to the reactants in the neutralizer, or at the latest before the concentrate is formed. It has been found that it is advantageous to do so. The drying properties of ammonium nitrate prills and granules produced by the process of adding aluminum salts in the neutralizer are better than those produced without the addition of aluminum salts and those produced by the process of adding aluminum salts after the evaporation stage. It was observed that it was excellent. Much gentler drying conditions are required. Although this advantage is more pronounced in the production of low density prills and granules, it also helps dry high density prills during the priming process. Gentler drying conditions mean less prill wear and less prilling tower smoke. Prilling tower smoke is a phenomenon of entrainment of extremely fine solid particles of ammonium nitrate entrained in the gas passing through the prilling tower. Another advantage lies in the better control of PH that can be achieved throughout the process. The neutralizer contains stoichiometric amounts of reactants, i.e. 1:1
ammonia (NH ₃ ) and nitric acid (HNO ₃ ) in the molar ratio of
(PH of this composition is
Ideally, it operates by titrating ammonia and nitric acid to produce an equivalence point of 3.9, which is referred to as the equivalence point. (Throughout this specification, PH, unless otherwise specified, refers to the PH of an aqueous solution derived from the composition diluted with or dissolved in water such that the resulting solution contains about 10% by weight ammonium nitrate; (This PH measurement is performed at room temperature using a regular PH meter.) However, because the ammonia-nitric acid neutralization curve is steep, the addition of reactants to the neutralizer must be controlled and the contents It is impossible to maintain at the equivalence point. For safety reasons, most neutralizers are operated with excess ammonia and therefore on the high PH side. Typically, the neutralizer has a content of 5.2
It is operated to have a PH of ~5.5, and below this PH range it is difficult to stably control the reaction. However, we have found that by adding aluminum salts to the reactants in the neutralizer, stable control can be achieved at lower pHs, such as as low as 4.6. One advantage of this is that the amount of ammonia emissions in the next evaporation stage is reduced. During the concentration of hot ammonium nitrate solution, ammonia is also removed from the solution along with water until the stoichiometric equivalence point is reached, and the PH of the concentrate is
It drops to 3.9. Therefore, the lower the PH at which the neutralizer is operated, the less ammonia will be discharged from the evaporator and the less ammonia will have to be removed from the effluent and recycled. However, the method of the present invention can be practiced with any desired PH distribution throughout the process, including those commonly used. Conveniently, the PH of the solution in the neutralizer
may be in the range 4.2 to 5.5 without significantly affecting the aforementioned advantages that accrue in the drying operation when the method of the invention is used. Another advantage of adding the aluminum salt before the evaporation stage rather than at the end of the process is that the PH of the concentrate from the evaporator is not affected. For example, if aluminum sulfate is added to the concentrate from the evaporator, the PH of the concentrate may be lower than 3.0. This is done to raise the PH to the desired level for prilling or granulation, typically 4.0-5.0 for low-density prills and granules and 5.0-6.0 for high-density prills. This means that extra ammonia must be added. Therefore, when producing a prilled or granulated material containing ammonium nitrate, ammonia and nitric acid are reacted in a neutralizer to produce a solution of ammonium nitrate, and this solution is evaporated to the required concentration. and subjecting the resulting concentrate to a prilling or granulation process to form prills or granules, optionally drying and cooling the same, the method comprising: It is characterized in that at least one water-soluble aluminum salt is added to the solution of ammonium nitrate before the completion of the concentration step. The process can be carried out batchwise or continuously or semi-continuously. It is difficult to identify the actual aluminum compounds present in ammonium nitrate solutions, concentrates, prills or granules, depending on the stage of the process. However, it has been found that the advantages already mentioned as afforded by the present invention can be achieved by adding a water-soluble aluminum salt to a solution of ammonium nitrate. However, aluminum halides are specifically excluded from the present invention since the presence of halides, even in small amounts, in the ammonium nitrate manufacturing process is undesirable. Suitable water-soluble aluminum salts are selected from sulfates such as aluminum sulfate and sodium aluminum sulfate, with aluminum sulfate being preferably used. Aluminum nitrate is also suitable. Preferably, the water-soluble aluminum salt is added as an aqueous solution. For example, a convenient form of solution for use is one commonly used in water treatment, i.e. 7.5% aluminum sulfate (as Al ₂ O ₃ ) and 0.5% free sulfuric acid content.
% H ₂ SO ₄ (both % by weight) in water. The process of the invention includes the addition of a water-soluble aluminum salt such that the final product prill contains at least 100 parts by weight (as Al ₂ O ₃ ) of aluminum compound per million parts by weight of ammonium nitrate. The level of addition is 800 parts per million parts by weight of ammonium nitrate.
~2000 parts by weight is preferred. In the process according to the invention, it is preferred that only a portion of the desired content of aluminum compounds in the prilled or granulated material is obtained by adding aluminum salts to the solution of ammonium nitrate before evaporation. The remaining amount necessary to provide the desired content of aluminum compounds in the prilled or granulated product can be added at any suitable stage of the process stream after the evaporation stage. Preferably, at least 20% by weight of the total weight of added aluminum is added to the process reactant stream before the concentrate is formed. Therefore, in a preferred embodiment of the invention, in a first addition at least one water-soluble aluminum salt is added to the solution of ammonium nitrate before the concentrate is formed, and in a second addition at least one water-soluble aluminum salt is added to the solution of ammonium nitrate before the concentrate is formed. A method of making prilled or granulated ammonium nitrate is provided, wherein a water-soluble aluminum salt of 100% is added to the process stream after the concentrate is formed. Conveniently, the water-soluble aluminum salt added in the second addition is selected from the group below. Aluminum sulfate Aluminum nitrate Aluminum double salts such as ammonium aluminum sulfate, sodium aluminum sulfate, potassium aluminum sulfate Aluminates such as sodium aluminate,
Potassium aluminate The use of aluminates does not lower the PH of the concentrate when they are added to the concentrate and therefore the use of potassium aluminate in the concentrate to adjust the PH to the desired value for the prilling or granulation process. This is preferred because it reduces the amount of ammonia that must be added to the product. Although it is generally more convenient to add the aluminum salts as an aqueous solution in the second addition, in some situations, such as in the manufacture of high density prills, these salts are added as solids due to the small amount of additional water introduced. is more preferable. The method of the present invention is based on the pH of ammonium nitrate solution produced by the reaction of ammonia and nitric acid.
can be carried out such that it is in the range of 4.2 to 5.5. Preferably this is in the range 4.6-5.0. In another preferred embodiment of the invention, the ammonium nitrate prills or granules are produced by a continuous process. That is, a solution of ammonium nitrate is produced continuously by the reaction of ammonia and nitric acid in a previously produced solution of ammonium nitrate, and the water-soluble aluminum salt is produced before the ammonium nitrate solution is concentrated to an extent suitable for prilling or granulation. It is added continuously to the ammonium nitrate solution. In this preferred embodiment involving a continuous process, the amounts of ammonia and nitric acid added are such that the pH of the ammonium nitrate solution ranges from 4.2 to 5.5, preferably from 4.6 to 5.5.
It is controlled to be kept within the range of 5.0. The term "continuous" and related terms herein refer to a mode of operation as distinguished from "batch mode." Although the addition of aluminum at any stage before the formation of a concentrate, i.e., a solution or melt containing no more than 6% water by weight, may provide drying advantages, these advantages described above do not apply to addition. It will only be fully reaped if it is done during the reaction stage. Therefore, a preferred feature of the invention is that the addition of the aluminum compound before the evaporator is made to the neutralizer where it is being reacted with the ammonia nitrate. This addition is preferably made to the neutralizer such that the aluminum compound is introduced into the reactant medium at a pH of 4.2 to 5.5, in particular 4.6 to 5.0. When the process of the invention is carried out in the preferred continuous manner, the water-soluble aluminum salt can be added to the neutralizer continuously at the same time as the addition of nitric acid and ammonia. Aluminum salt is a solution of ammonium nitrate.This solution contains ammonium nitrate 100
to the previously produced solution of ammonium nitrate in such an amount that it will have an aluminum compound content in an amount ranging from 100 to 2000 parts by weight (as Al ₂ O ₃ ) per 10,000 parts by weight (as NH ₄ NO ₃ ). Preferably, it is added directly. In some cases, especially in the production of composites where many different products are being produced from a common stream of ammonium nitrate solution, the addition of aluminum salts to a storage tank of ammonium nitrate for use in the process of this invention may be useful. is more convenient. The following examples are provided to further illustrate the invention and are not meant to limit the invention thereto. In the examples, "parts" and "%" are expressed by weight unless otherwise specified. Example 1 This example illustrates the method of the present invention used to produce low density prills. Nitric acid and gaseous ammonia were successively added to the previously produced ammonium nitrate solution to produce an ammonium nitrate solution containing about 85% ammonium nitrate in a neutralizer. At the same time, 50 parts water to 50 parts
Aluminum sulfate in the form of an aqueous solution prepared by dissolving Al ₂ (SO ₄ ) _{3.18H 2} O is added to an ammonium nitrate solution in a neutralizer, and sulfuric acid is added per million parts by weight of ammonium nitrate (as NH ₄ NO ₃ ) produced. aluminum
It was added in an amount _of 280 parts (as _Al2O3 ). Adjust the ammonia addition level so that the pH of the solution in the neutralizer is 5.2~
Controlled to maintain it at 5.4. The solution from the neutralizer was concentrated in a falling film evaporator to a concentrate containing 95% ammonium nitrate. The PH of the solution drops to 3.9 during this evaporation process and gaseous ammonia is added to lower the PH of the concentrate.
Adjusted to 4.2-4.6. The concentrate was then prilled in a conventional prilling tower. The prills were then dried and measured using the standard Karl Fischer test.
A product with a moisture content ranging from 0.10 to 0.15% _H2O was obtained. The drying process was carried out in a conventional drying apparatus comprising a series of three rotating drying drums. The residence time in the dryer was 58 minutes and the amount of drying air used was 4.1 Kg per 1.0 Kg of product in the form of prilled ammonium nitrate. Example 2 This example illustrates another process of the invention used to produce low density ammonium nitrate prills. aluminum sulfate in the form of an aqueous aluminum sulfate solution containing 7.5% (as Al ₂ O ₃ ) aluminum sulfate and a free sulfuric acid content of 0.5% H ₂ SO ₄ (both expressed on a weight basis) to ammonium nitrate in a neutralizer; 85% ammonium nitrate was added in the same manner as in Example 1, except that 600 parts of aluminum sulfate (as Al ₂ O ₃ ) were added per million parts of ammonium nitrate (as NH ₄ NO ₃ ) produced. A solution was prepared containing: Ammonia was added so that the pH of the ammonium nitrate solution in the neutralizer was in the range of 4.7 to 4.9. The solution was evaporated as in Example 1 to a concentrate containing 95% ammonium nitrate, and 600 parts of aluminum sulfate (as Al ₂ O ₃ ) per million parts of ammonium nitrate present were added to the neutralizer. was added to the concentrate as a solution of aluminum sulfate at the same concentration. Prior to the addition of aluminum sulfate, gaseous ammonia was added to the concentrate such that the PH of the concentrate after addition of the aluminum salt was at least 4.2. The concentrate was then prilled in a conventional prilling tower and the product prills were dried to a moisture content of 0.09-0.13% _H2O as determined by Karl Fischer test. The drying equipment used was the same as in Example 1. The residence time in the dryer was 58 minutes, and the amount of drying air used was 3.9 kg per 1.0 kg of product. Example 3 This example describes, for comparison, a process for producing low density ammonium nitrate prills containing aluminum compounds by adding aluminum salts only to the concentrate. A solution containing 83% ammonium nitrate was prepared similar to the procedure used in Example 1, but without the addition of aluminum sulfate. The minimum level of gaseous ammonia addition to obtain stable PH control was such as to produce a solution with a PH in the range of 5.2-5.4. The solution was concentrated to obtain a concentrate containing 95% ammonium nitrate and a pH of 3.9. Addition of 1000 parts of aluminum sulfate (as Al ₂ O ₃ ) per million parts of ammonium nitrate (as NH ₄ NO ₃ ) in the concentrate brought the PH below 2.0. Prior to prilling under normal prilling conditions, gaseous ammonia was added to increase the PH of the concentrate to a suitable value. The fact that it is difficult to dry the prills produced by the above method, which is different from the method of the present invention, can be seen from the following facts. That is, the product prills were prepared using the same drying equipment used in Examples 1 and 2, with the highest amount available;
In other words, even when using 4.5 kg of dry air per 1.0 kg of product, the
It was not possible to dry at a moisture content lower than 0.16-0.30% _H2O . Example 4 This example describes a process for making low density ammonium nitrate prills without the addition of aluminum as a comparison. The steps of neutralization, evaporation, prilling and drying described in Example 1 were repeated without adding the aluminum compound at any stage. The pH at various stages was as follows. Stable PH on neutralization 5.1-5.3 PH after evaporation 3.9-4.1 PH on prilling 4.5-4.7 The same drying equipment used in Examples 1-3 was used except that the residence time of the prills in the drying equipment was 84 minutes and The operating conditions were varied such that the amount of drying air was 6.2 Kg per 1.0 Kg of product, yielding product prills containing 0.11-0.13% _H2O as determined by Karl Fischer method. Samples of prills produced by the process described in Examples 1-4 were tested to determine their quality as follows. The hardness of the prills was compared using the friability test described below. It should be understood that hardness varies inversely to friability, ie, highly friable materials have lower hardness. Airflow from an 11 psig air supply was expanded through a 2.5 mm orifice into a 13 mm ID tube opening into a standard 25 mm ID cast iron pipe elbow. The prills left behind by the No. 16 BSS sieve were dropped into the air stream 184 mm upstream from the elbow. After impacting the elbow, these prills were collected and the weight percent passed through the No. 16 BSS sieve was determined. A temperature cycle test was conducted as follows. The polyethylene sample bag containing some of the prills remaining on the No. 16 BSS sieve was placed in an oven with suitable heating and cooling mechanisms to obtain the predetermined temperature pattern and heated between 15°C and 45°C within 6 hours. was temperature cycled. Prill has this transition temperature of 32℃ by 8
This cycle was repeated four times. Bulk density is the weight per unit volume of a container of prills filled and homogenized without being pressurized or shaken. Moisture in the prills was determined by a conventional Karl Fischer test. The results of these tests for the products of Examples 1-4 are shown in Table 1.

EXAMPLE 5 This example illustrates the process according to the invention used for the production of high density prills. 83-85% ammonium nitrate as described in Example 2, except that the addition level of aluminum sulfate was 1000 parts (as Al ₂ O ₃ ) per million parts of ammonium nitrate (as NH ₄ NO ₃ ). A solution containing . by adding ammonia
Provided stable PH control in the range of 4.6-5.0. The solution was melted by evaporation so that the water content was less than 0.08% _H2O . ammonium nitrate
200 parts per million (as Al ₂ O ₃ ) of aluminum sulfate was added to the melt. By adding gaseous ammonia to the melt,
The PH of the 10% solution was adjusted to a range of 4.4-4.8. The melt was then prilled in a conventional prilling tower and cooled by a conventional cooling process. The bulk density of the product measured by the above test is 0.9Kg/
, its PH was 5.0, friability was 0.4%, and water content was 0.12-0.18% _H2O . Example 6 For comparison, the production of high-density prills by a process different from that of the present invention will be described. A solution containing 83-85% ammonium nitrate was prepared as described in Example 3. Again, the lowest stable PH obtained in the neutralizer ranged from 5.2 to 5.4. The solution was melted, prilled, and cooled as described in Example 5, except that 500 parts (as Al ₂ O ₃ ) of aluminum sulfate per million parts of ammonium nitrate were added to the melt. The bulk density of the product determined by the above test was 0.95 Kg/, its pH 5.0, friability 0.9%, and moisture content 0.22-0.26% _H2O . Example 7 For comparison, a process for producing high density ammonium nitrate prills without the addition of aluminum is described. High density prills were made by repeating the procedure of Example 6, except that no aluminum sulfate was added. The product had a bulk density of 0.95 Kg/, a pH of 5.6, a friability of 3.5%, and a moisture content of 0.08-0.12% _H2O , as determined by the above-mentioned test. Samples of the products of Examples 5, 6 and 7 were subjected to the temperature cycling test described above. The results are shown in Table 2.

EXAMPLE 8 An ammonium nitrate concentrate was prepared as described in Example 2 to illustrate an embodiment of the process of the invention in which sodium aluminate is added in the second addition. Sodium aluminate in concentrate, ammonium nitrate in concentrate 100
Sufficient amounts were added to provide 1200 parts by weight (as Al ₂ O ₃ ) of aluminum compound per 10,000 parts by weight (as NH ₄ NO ₃ ). The PH of the concentrate increased to 4.0-5.0 upon addition of sodium aluminate, which made it unnecessary to add ammonia to the concentrate before prilling. EXAMPLE 9 This example illustrates the application of the method of the invention to the production of composites in which several ammonium nitrate-containing products are produced from a common process stream produced by the reaction of ammonia and nitric acid. be. An ammonium nitrate solution was prepared according to the procedure of Example 3 in the production of low density prills of ammonium nitrate containing 1200 parts by weight (as Al ₂ O ₃ ) of aluminum compound per million parts by weight of ammonium nitrate product. A portion of this solution was subjected to a preconcentration process involving evaporation to a concentration of 92% by weight ammonium nitrate. The partially concentrated solution was stored at elevated temperature to prevent crystallization. PH is
Ammonia was added so that it did not fall below 4.5. PH varied within the range of 4.5-7.0. The partially concentrated solution was transferred to a weighing tank. During this time, adjust the pH to 4.5 by adding nitric acid if necessary.
An aqueous aluminum sulfate solution was added to the solution in the metering tank as described in Example 1, resulting in 720 parts by weight of aluminum compound (as NH ₄ NO ₃ ) per million parts by weight of ammonium nitrate (as NH 4 NO 3 ) in a partially concentrated solution. (as Al ₂ O ₃ ). The pH of the solution in the metering tank was maintained at 5.2-5.7 by addition of ammonia. The solution from the metering tank was then concentrated by evaporation to obtain a concentrate with a fudge point of 118°C, corresponding to a concentration of 94.8% ammonium nitrate. Aluminum sulfate solution as described in Example 1 was added to the concentrate to determine the total content of aluminum compounds.
The desired level of 1200ppm was achieved. This concentrate was then prilled into the desired product.

Claims (1)

[Claims] 1. When producing a prilled or granulated material containing ammonium nitrate, ammonia and nitric acid are reacted in a neutralizer to produce a solution of ammonium nitrate, and this solution is prilled or granulated by evaporation. Concentrating to the concentration required for granulation, and subjecting the resulting concentrate to a prilling or granulation process to form prills or granules, optionally drying it;
A method comprising cooling, characterized in that at least one water-soluble aluminum salt is added to the solution of ammonium nitrate before the completion of the concentration step. 2. The method according to claim 1, wherein the water-soluble aluminum salt is aluminum sulfate. 3. The method according to claim 1, wherein the water-soluble aluminum salt is a double salt of aluminum sulfate. 4. The method of claim 3, wherein the double salt of aluminum sulfate is selected from the group consisting of ammonium aluminum sulfate, sodium aluminum sulfate, potassium aluminum sulfate, and mixtures thereof. 5. The method according to claim 1, wherein the water-soluble aluminum salt is aluminum nitrate. 6. The method of claim 1, wherein the water-soluble aluminum salt is added as an aqueous solution to the ammonium nitrate solution. 7. A patent claim in which the water-soluble aluminum salt is added to the ammonium nitrate solution in an amount greater than 100 parts by weight (as Al ₂ O ₃ ) per 1 million parts by weight of ammonium nitrate (as NH ₄ NO ₃ ) contained in the solution. The method described in item 1. 8 The water-soluble aluminum salt is present in the prilled or granulated material in an amount of 100 to 2000 parts by weight (as Al ₂ O ₃ ) per million parts by weight of ammonium nitrate (as NH ₄ NO ₃ ) in the material.
8. The method of claim 7, wherein the ammonium nitrate solution is added to the solution of ammonium nitrate in an amount sufficient to provide an amount of aluminum compound in the range (as). 9 The amount of the water-soluble aluminum salt added is in the range of 800 to 2000 parts by weight (as Al _{2 O 3 ) per 1 million parts by weight of ammonium nitrate (as NH 4 NO 3 ) in} the prilled material. 9. The method of claim 8, wherein the amount of aluminum compound is sufficient to provide an amount of aluminum compound. 10 In a first addition, at least one water-soluble aluminum salt is added to the solution of ammonium nitrate before the concentrate is formed, and in a second addition, at least one water-soluble aluminum salt is added to the solution of the ammonium nitrate before the concentrate is formed. 2. The method of claim 1, wherein the process stream is added to the process stream after the product has been formed. 11. The method of claim 10, wherein the water-soluble aluminum salt used in the second addition is aluminum sulfate. 12. The method according to claim 10, wherein the water-soluble aluminum salt used in the second addition is a double salt of aluminum sulfate. 13. Claim 12, wherein the double salt of aluminum sulfate is selected from the group consisting of ammonium aluminum sulfate, sodium aluminum sulfate, potassium aluminum sulfate, and mixtures thereof.
The method described in section. 14. The method of claim 10, wherein the water-soluble aluminum salt used in the second addition is aluminum nitrate. 15. The method according to claim 10, wherein the water-soluble aluminum salt used in the second addition is an aluminate. 16. The method of claim 15, wherein the aluminate is selected from the group consisting of sodium aluminate, potassium aluminate, and mixtures thereof. 17. The method of claim 10, wherein the water-soluble aluminum salt used in the second addition is added to the process stream as an aqueous solution. 18. Claims in which the water-soluble aluminum salt added in the first addition provides at least 20% by weight (as Al ₂ O ₃ ) of the total amount of aluminum compounds in the prilled or granulated material The method according to item 10. 19. Claim 1, wherein the ammonium nitrate solution produced by the reaction of ammonia and nitric acid has a pH in the range of 4.2 to 5.5 (inclusive).
The method described in section. 20 The above PH range is 4.6 to 5.0 (including both extreme values)
20. The method according to claim 19. 21. Claim 1, wherein the process is a continuous process and the ammonium nitrate solution is produced by continuously adding ammonia and nitric acid to a previously formed solution of ammonium nitrate in a neutralizer. The method described in section. 22. The method of claim 21, wherein the previously formed solution of ammonium nitrate has a pH in the range of 4.2 to 5.5, inclusive. 23. The method of claim 22, wherein the previously formed solution of ammonium nitrate has a pH in the range of 4.6 to 5.0, inclusive. 24. The method of claim 1, wherein the water-soluble aluminum salt is added to the neutralizer. 25. The method of claim 21, wherein the pre-formed ammonium nitrate solution comprises an aluminum compound, and at least one water-soluble aluminum salt is continuously added to the pre-formed ammonium nitrate solution. Method. 26 100 to 2000 parts by weight of ammonium nitrate (as NH ₄ NO ₃ ) in the solution of ammonium nitrate in which the aluminum compound was previously formed.
25. The method of claim 24 _, wherein the amount is in the range of parts by weight (as _Al2O3 ). 27. The water-soluble aluminum salt is dissolved in a solution of ammonium nitrate after the solution is removed from the neutralizer and before it is concentrated to the extent necessary to make it suitable for prilling or granulation.
The method of claim 1 as appended hereto.