Phase-stabilized ammonium nitrate explosive

Abstract

A phase-stabilized ammonium nitrate (PSAN) explosive is provided, comprising PSAN prills and a fuel. The PSAN prills contain ammonium nitrate, a potassium salt, and an inorganic porosity enhancer.

Description

Technical Field

[0001] Cross - reference to related applications This application claims priority to Australian Provisional Patent Application No. 2020 / 902693, entitled PHASE - STABILIZED AMMONIUM NITRATE EXPLOSIVES, filed on July 31, 2020, the entire contents of which are incorporated herein by reference.

Background Art

[0002] This disclosure generally relates to explosives. More specifically, this disclosure relates to phase - stabilized ammonium nitrate (PSAN) explosives.

Brief Description of the Drawings

[0003] The embodiments disclosed herein will become more fully apparent from the following description and the appended claims, taken in conjunction with the accompanying drawings.

[0004] [Figure 1] A graph showing the crushing strength versus thermal cycle of ammonium nitrate fuel oil (ANFO) made from conventional ammonium nitrate (AN) prills and ANFO made from exemplary PSAN prills. [Figure 2] A graph showing the temperature of PSAN prills compared to conventional LDAN prills when cycled in an oven. [Figure 3] A graph showing the time taken to heat PSAN prills to 50 °C compared to conventional LDAN prills. [Figure 4] A graph showing the time taken to cool PSAN prills from 50 °C compared to conventional LDAN prills. [Figure 5] A graph showing the DSC of conventional LDAN prills. [Figure 6] A graph showing the DSC of PSAN prills.

Modes for Carrying Out the Invention

[0005] Phase-stabilized ammonium nitrate (PSAN) explosives, along with related methods, are disclosed herein. PSAN prills containing inorganic porosity enhancers such as aluminum sulfate have been found to be thermally stable even in the presence of fuel.

[0006] Thermal cycling of ammonium nitrate (AN) at temperatures approximately 32°C above and below results in crystalline phase changes. Thermal cycling of AN prill leads to expansion and contraction of AN prill, each accompanied by a related crystalline phase change. As shown in Table 1, crystalline phase changes of AN also occur at other temperatures. [Table 1]

[0007] The expansion and contraction mechanisms of AN prill can adversely affect its integrity and / or stability. For example, expansion and contraction can lead to i) weakening of AN prill, ii) increased AN fine powder formation (e.g., AN prill may disintegrate), iii) increased fragility of AN prill, and / or iv) increased moisture penetration into AN prill. These properties or effects can contribute to caking of AN prill, which can result in processing and handling problems, loss of free-flow behavior, and / or substandard products. This also applies to AN prill mixed with liquid fuels, such as fuel oil No. 2.

[0008] Any method disclosed herein includes one or more steps or actions for carrying out the described method. The method steps and / or actions may be interchangeable with one another. In other words, the order and / or use of any particular steps and / or actions may be modified unless a particular order of steps or actions is required for the proper operation of the embodiment. Also, a subroutine or only a portion of a method described herein may be a separate method within the scope of this disclosure. In other words, some methods may include only a portion of the steps described in a more detailed method.

[0009] Throughout this specification, any reference to “a particular embodiment” or “that embodiment” means that a particular feature, structure, or characteristic described in relation to that embodiment is included in at least one embodiment. Therefore, not all quotations or variations thereof listed throughout this specification necessarily refer to the same embodiment.

[0010] As reflected in the following claims, aspects of the present invention are in fewer combinations than all the features of any single embodiment disclosed above. Thus, the claims following this detailed description are explicitly incorporated into this detailed description, and each claim stands independently as a distinct embodiment. This disclosure includes all permutations of independent claims with their dependent claims.

[0011] The enumeration of the term “first” in the claims with respect to features or elements does not necessarily imply the presence of a second or additional such feature or element. It will be apparent to those skilled in the art that details of the embodiments described herein can be modified without departing from the underlying principles of this disclosure.

[0012] The PSAN explosives provided herein may exhibit a significantly increased shelf life compared to conventional or standard low-density ammonium nitrate (LDAN) prill-based explosives, for example, during the summer months when temperatures can frequently cycle above and below 32°C. Therefore, PSAN explosives may be shipped to or used in tropical regions and may have an increased shelf life compared to conventional LDAN ANFO. PSAN explosives may significantly reduce the health, safety, and / or environmental risks associated with caked and / or blocky ANFO. PSAN explosives may eliminate the need for temperature-controlled storage infrastructure (e.g., air-conditioned ANFO storage facilities). PSAN explosives may increase the flexibility of ANFO supply plans to customers. PSAN explosives may reduce or eliminate bottlenecks in product shipments. Furthermore, PSAN explosives may be used in multiple markets (e.g., Asia Pacific and North America).

[0013] PSAN explosives, as well as PSAN prills and methods for preparing the explosives, are disclosed herein. It will be readily apparent that the components of the embodiments generally described below can be arranged and designed in a wide variety of different configurations. Therefore, the following more detailed descriptions of the various embodiments described below and illustrated in the figures are not intended to limit the scope of this disclosure, but merely represent various embodiments.

[0014] One aspect of this disclosure relates to phase-stabilized ammonium nitrate (PSAN) explosives. PSAN explosives may include PSAN prills and fuel. In some embodiments, PSAN prills may contain 0.5 mol% to 5 mol% potassium ions of a potassium salt based on the ammonium ions of ammonium nitrate. In various embodiments, the mol% of potassium ions based on the ammonium ions may be 2 mol% to 5 mol%, 2 mol% to 4 mol%, 2.1 mol% to 4.0 mol%, or about 3 mol%. In contrast, conventional or standard low-density ammonium nitrate (LDAN) prills or LDAN prill-based explosives may refer to LDAN prills or LDAN prill-based explosives lacking potassium salts or ions. PSAN prills may be explosive grade. In certain embodiments, PSAN prills may be low-density ("low-density" prills have a bulk density of 0.84 kg / L or less).

[0015] "Explosive-grade" AN prills have a minimum porosity of at least 5.7 FOR %. Explosive-grade, low-density AN (LDAN) prills are generally manufactured to contain available and unavailable porosity, such as by incorporating a suitable porosity-forming agent into a concentrated ammonium nitrate solution before prilling. Explosive-grade prills are generally manufactured to contain available and unavailable porosity that allows for sufficient absorption of fuel oil so that the material can effectively explode. The ability of the prill to absorb diesel fuel oil is used to determine if the porosity is suitable for manufacturing explosives. Functional determination of porosity can be performed using a fuel oil retention test, in which a measured amount of AN prill is added to a measured amount of fuel oil and mixed for a specific time. Excess fuel oil is removed using absorbent tissue paper, the total mass of the formed ANFO product is recorded, and the percentage increase in mass is calculated. The porosity of PSAN prill, determined by the fuel oil retention percentage (FOR%), can be 6 FOR% to 15 FOR%, 6 FOR% to 12 FOR%, or 5.5 FOR% to 9 FOR%. In many cases, the porosity is preferably such that the fuel oil absorption level is at least 5.7 FOR%, so that an acceptable oxygen balance is achieved when sufficient fuel oil is added to the PSAN prill to produce ANFO. The calculation of total porosity, including unavailable porosity, can be determined in a suitable fluid medium.

[0016] To measure FOR% which correlates with the porosity of ammonium nitrate prillated, the following method may be used. The method measures the increase in mass of a selected sample of prill after complete immersion in diesel fuel oil (DFO) and removal of excess DFO using a paper towel. The method may be a quality check used in product raw material evaluation. First, a 40 g (±0.05 g) sample of AN prill (with fine powder removed) is weighed and placed in a labeled and weighed 250 mL screw-top sample vial. This is recorded as the "initial weight". Next, 6.5 mL of DFO can be added and distributed uniformly throughout the sample. The lid can be tightly closed and shaken vigorously for 30 seconds. Then, the sample vial can be placed on a bottle roller and the apparatus can be operated at 40 rpm for 20 minutes. After 20 minutes, the vial can be lightly tapped on a bench to remove any prill adhering to the lid. Two strips of blotting paper can be placed: one loosely wrapped along the side of the bottle, and the second tightly wrapped and inserted into the center of the first strip of blotting paper. The lid can be replaced, and the bottle is then manually shaken for 3 minutes. The prill should roll freely inside the bottle. The sample bottle can be placed on a bottle roller and the apparatus can be operated at 40 rpm for 15 minutes. The prill should spread evenly along the length of the bottle, and the roller can be adjusted to achieve this. The blotting paper strips can then be carefully removed, taking care not to remove the prill from the bottle. The prill can be transferred to a weighed 100 mL beaker and weighed in 0.05 g increments. This is recorded as the "final weight". The fuel oil retention (FOR)% can be calculated as follows: FOR(%)=((Final weight - Initial weight) / Final weight)x100

[0017] PSAN prill also includes an inorganic porosity enhancer. The inorganic porosity enhancer may include an interface surface modifier and / or a pore-forming agent. The interface surface modifier may also be a crystal habit modifier. Examples of inorganic porosity enhancers include aluminum sulfate, iron sulfate, magnesium oxide, or any polyvalent sulfate, either anhydrous or in hydrate form. The inorganic porosity enhancer may also include additives. In certain embodiments, the inorganic porosity enhancer does not contain iron sulfate, magnesium oxide, or any of the compounds thereof. In certain embodiments, the inorganic porosity enhancer contains aluminum sulfate.

[0018] In certain embodiments, the concentration of the inorganic porosity enhancer may be 400 ppm to 4,000 ppm, for example, 400 ppm to 1,000 ppm, 500 ppm to 900 ppm, 600 ppm to 800 ppm, or 700 ppm, or for example, 2,000 ppm to 4,000 ppm, 2,500 ppm to 3,900 ppm, 3,000 ppm to 3,700 ppm, or about 3,500 ppm.

[0019] The potassium salt can be any potassium salt, such that it is selected from at least one of potassium hydroxide, potassium nitrate, potassium sulfate, potassium bisulfate, potassium carbonate, and potassium bicarbonate. In some embodiments, potassium may be selected from at least one of potassium hydroxide, potassium nitrate, and potassium sulfate.

[0020] In some embodiments, the PSAN prill may contain 0.5 mol% to 5 mol% potassium ions of potassium hydroxide based on the ammonium ions of ammonium nitrate (which corresponds to 0.4 wt% to 4 wt% by weight of potassium hydroxide based on ammonium nitrate). In various embodiments, the mol% of potassium ions based on ammonium ions may be 2 mol% to 5 mol% (about 1.5 wt% to 4 wt% potassium hydroxide), 2 mol% to 4 mol% (about 1.5 wt% to 3 wt% potassium hydroxide), 2.1 mol% to 4.0 mol% (about 1.5 wt% to 3 wt% potassium hydroxide), or about 3 mol% (about 2 wt% potassium hydroxide).

[0021] In certain embodiments, the PSAN prill may contain 0.5 mol% to 5 mol% potassium ions of potassium nitrate based on the ammonium ions of AN (1 wt% to 6 wt% potassium nitrate based on AN). In various embodiments, the mol% of potassium ions based on ammonium ions may be 2 mol% to 5 mol% (about 3 wt% to 6 wt% potassium nitrate), 2 mol% to 4 mol% (about 3 wt% to 5 wt% potassium nitrate), 2.1 mol% to 4.0 mol% (about 3 wt% to 5 wt% potassium nitrate), or about 3 mol% (about 4 wt% potassium nitrate).

[0022] In various embodiments, the PSAN prill may contain 0.5 mol% to 5 mol% potassium ions of potassium sulfate based on the ammonium ions of ammonium nitrate (1 wt% to 10 wt% potassium sulfate based on ammonium nitrate). In various embodiments, the mol% of potassium ions based on ammonium ions may be 2 mol% to 5 mol% (about 5 wt% to 10 wt% potassium sulfate), 2 mol% to 4 mol% (about 5 wt% to 8 wt% potassium sulfate), 2.1 mol% to 4.0 mol% (about 5 wt% to 8 wt% potassium sulfate), or about 3 mol% (about 6 wt% potassium sulfate).

[0023] In some embodiments, the bulk density of the PSAN prill can be less than 0.9 kg / L. Further, the PSAN prill may lack or substantially lack a 32°C crystalline phase change. Alternatively, the 32°C crystalline phase change can be shifted to a temperature higher than 50°C. The PSAN prill may lack or substantially lack an 84°C crystalline phase change. Alternatively, the 84°C crystalline phase change can be shifted to a temperature higher than 90°C or 95°C. In certain embodiments, the presence of the 32°C crystalline phase change and / or the 84°C crystalline phase change can be determined by thermal analysis and / or X-ray diffraction measurements. For example, the thermal analysis can include differential scanning calorimetry (DSC) and / or thermogravimetric analysis (TGA) analysis. The "substantial absence" of the 32°C phase change can correspond to a sufficient removal of the phase change such that the PSAN prill can remain within customer specifications, such as the specifications listed in Table 2, when the PSAN prill is thermally cycled 50 times.

[0024] In various embodiments, when the PSAN explosive is thermally cycled 50 times, the thermally cycled PSAN explosive can have an average crushing strength greater than 0.4 kg, such as 0.4 kg to 2.0 kg, 0.5 kg to 1.5 kg, 0.6 kg to 1.0 kg, or 0.7 kg to 0.9 kg. One cycle can include exposing the PSAN explosive to 15°C for 4 hours, followed by exposing it to 45°C for 4 hours.

[0025] In some embodiments, when the PSAN explosive is thermally cycled 20 times ("test PSAN explosive"), the average crushing strength of the thermally cycled PSAN explosive can be greater than the average crushing strength of a non-thermally cycled control PSAN explosive. One cycle includes exposing the PSAN explosive to 15°C for 4 hours, followed by exposing it to 45°C for 4 hours. The test PSAN explosive and the control PSAN explosive contain the same components, but the test PSAN explosive is subjected to thermal cycling and the control PSAN explosive is not subjected to thermal cycling.

[0026] The average crush strength of a thermally cycled PSAN explosive may be 5–100% greater than that of a non-thermally cycled control PSAN explosive. In other embodiments, the average crush strength of a thermally cycled PSAN explosive may be 25–100% greater than that of a non-thermally cycled control PSAN explosive. In specific embodiments, the average crush strength of a thermally cycled PSAN explosive may be 10–80%, 20–60%, or 25–40% greater than that of a non-thermally cycled control PSAN explosive. In other embodiments, the average crush strength of a thermally cycled PSAN explosive may be 35–90%, 45–80%, or 55–70% greater than that of a non-thermally cycled control PSAN explosive. Thus, thermal cycling can be used to increase the hardness of PSAN explosives.

[0027] Crushing strength can be determined by the following method. All equipment, including gloves, must be dry, and samples must be sealed in airtight containers when stored. Samples are prepared by first weighing a 250g sample of the final ANFO product and transferring it to the top of a sieve stack consisting of a 2.36mm sieve, a 2.00mm sieve, and a collection pan. The sample and sieve stack are placed in a sieve shaker for 10 minutes at an amplitude setting of 60. Fine particles in the collection pan and oversized particles in the 2.36mm sieve are discarded. A portion of the sample is taken from the 2.00mm sieve and used for the crushing test. For the crushing test, 20 individual ANFO particles (AN prill + fuel oil) are randomly selected from the 2.00mm sieve. The values ​​are recorded in KgF units using a crushing test apparatus including a force gauge meter (e.g., Model M5-5) and a test stand stage (e.g., electric test stand ESM301L). Place the particle in the center of the test stand stage. Zero out the force gauge meter. Lower the force gauge piston to crush the test particle. After the force gauge is fully extended, record the applied force as the crushing resistance. This process is performed for each of the 20 particles. The crushing resistance is calculated as the average crushing resistance of the 20 particles.

[0028] The shelf life of PSAN explosives provided herein may be at least 6 months. For example, PSAN explosives may have a shelf life of up to 6 months or more (at least 2 months, at least 4 months, or at least 6 months, etc.) when stored during a hot summer with an average daytime ambient temperature of 30°C to 50°C and an average nighttime temperature of 10°C to 30°C. In contrast, the shelf life of conventional LDAN ANFO would be much shorter without the aid of temperature-controlled storage.

[0029] The PSAN prill of PSAN explosive may have denser and more uniform crystalline domains than the potassium-free explosive-grade ammonium nitrate prill. Without being constrained by theory, the denser crystalline domains of PSAN prill may contribute to the improved hardness of PSAN prill compared to conventional LDAN prill. Without being constrained by theory, it is thought that the combination of potassium and a porosity enhancer may contribute to the denser and more uniform crystalline domains of PSAN prill. Therefore, the combination of potassium and a porosity enhancer may contribute to the remarkably increased crush strength of PSAN prill while maintaining all of the prill's porosity and low density. The crystalline domains can be determined by scanning electron microscopy and energy-dispersive spectroscopy (SEM-EDS).

[0030] PSAN prills may have potassium uniformly distributed throughout the prill. If the PSAN prill contains an interfacial surface modifier containing an alkyl group (such as part of a polymer), the PSAN prill may have carbon uniformly distributed throughout the prill.

[0031] Examples of fuels that can be used with PSAN Prill include, but are not limited to, liquid fuels such as fuel oil, diesel oil, distillates, furnace oil, kerosene, gasoline, and naphtha; waxes such as microcrystalline wax, paraffin wax, and slack wax; paraffin oil; benzene, toluene, and xylene oil; asphalt materials; polymer oils, such as low molecular weight polymers of olefins; animal oils, such as fish oil; and other mineral, hydrocarbon, and fatty oils, as well as mixtures thereof. Any fuel typically used for or with ANFO may be used.

[0032] The weight ratio of PSAN prill to fuel is 80:20–97:3, 85:15–96:4, 90:10–95:5, or 94:6. In certain embodiments, the fuel is not ammonium nitrate emulsion but the same fuel as conventional ANFO.

[0033] Any combination of components and their amounts or concentrations described with reference to the PSAN prill or PSAN explosive provided above may also be incorporated into a method for preparing the PSAN prill or PSAN explosive. Furthermore, any of the properties or measurements of the PSAN prill or PSAN explosive provided above (e.g., bulk density, mean crush strength, and shelf life) may be applicable to the PSAN prill or PSAN explosive prepared by the disclosed method.

[0034] Another aspect of this disclosure relates to a method for increasing the hardness (e.g., mean crush strength) of a PSAN explosive. Furthermore, any of the properties or measurements of the PSAN explosive provided above may be applicable to a PSAN explosive prepared by a method for increasing the hardness of a PSAN explosive. The method may include providing the PSAN prill discussed above and thermal cycling the PSAN prill multiple times (e.g., at least 10 times or at least 20 times). After cycling, the mean crush strength of the thermally cycled PSAN explosive may be greater than that of a control PSAN explosive that has not been thermally cycled. One cycle may include exposing the PSAN explosive to 15°C for 4 hours, followed by 45°C for 4 hours.

[0035] Another aspect of this disclosure relates to a method for preparing PSAN prills and / or PSAN explosives. The method may include forming a PSAN solution containing a potassium salt and ammonium nitrate, and crystallizing the PSAN solution to form PSAN prills. The PSAN prills may be explosive grade and low density. The method may further include combining a porosity enhancer (e.g., aluminum sulfate) with the PSAN solution. Forming a PSAN solution may include mixing a potassium salt (solution) with water (or process condensate), and reacting the mixture with nitric acid and ammonia, for example, in a neutralizing agent, to form a PSAN solution.

[0036] In some embodiments, the use of a PSAN solution containing potassium salt and ammonium nitrate offers manufacturing advantages in the formation of PSAN prills compared to conventional AN solutions used in the formation of conventional LDAN prills lacking potassium salt. These manufacturing advantages can provide opportunities to eliminate bottlenecks in the plant manufacturing process. For example, conventional LDAN prill production often requires reducing the prilling rate in hotter and more humid months to ensure prill formation within appropriate specifications, due to i) the prill temperature observed at the bottom of the prill column and / or ii) the prill temperature observed when exiting the cooling mechanism (e.g., a fluidized bed cooler). With the PSAN solution disclosed herein, such a reduction in the prilling rate is not required.

[0037] When crystallizing a PSAN solution to form PSAN prills, droplets of the prill solution are dropped into a prill column. As the droplets fall, they cool and solidify to form individual prills. After further drying in a pre-dryer and drying drum, and screening to remove oversized and undersized material, the prills are then transferred to a cooling mechanism (e.g., a fluidized bed cooler) for further cooling, after which the prills may be further processed (e.g., coated), stored, and / or packaged. Typically, the temperature limit for conventional LDAN prills upon reaching the bottom of the prill column is 78°C to 82°C. This temperature limit ensures that conventional LDAN prills have completed the crystalline phase transition from phase II to phase III at approximately 84°C before reaching the bottom of the prill column. Conventional LDAN prills exceeding this temperature limit at the bottom of the prill column may still be undergoing phase transition, causing clamping / caking and / or other problems downstream in the manufacturing process. Furthermore, having conventional LDAN prills exceeding this temperature limit at the bottom of the prillation column is a common problem during prill production, especially in high-temperature and high-humidity environments (e.g., environments with ambient temperatures of 35°C to 45°C).

[0038] The temperature of conventional LDAN prill exiting a cooling mechanism (e.g., a fluidized bed cooler) is typically required to be below 30°C. This temperature ensures that the conventional LDAN prill has completed its crystalline phase transition from phase III to phase IV at approximately 32°C before the application of a coating (e.g., an anti-caking coating). Conventional LDAN prill exiting a cooling mechanism (e.g., a fluidized bed cooler) above this temperature may still be undergoing phase transition, causing clamping / caking and / or otherwise loss of free flow of the prill in the silo or post-coating drum. This can further cause problems when attempting to remove the prill from the silo or post-coating drum and place it into a transport container, bulk dump truck, etc. Having conventional LDAN prill exiting a cooling mechanism (e.g., a fluidized bed cooler) above this temperature is a common problem during prill production, especially in high-temperature and high-humidity environments (e.g., environments with ambient temperatures of 35°C to 45°C). To address these issues, conventional manufacturing techniques reduce the prilling rate from a maximum of approximately 40 tons per hour (T / h) to less than 35 T / h, less than 33 T / h, less than 30 T / h, or less than 27 T / h, especially in high-temperature and high-humidity environments (e.g., environments with ambient temperatures of 35°C to 45°C). In other words, conventional manufacturing techniques reduce the prilling rate to 25 T / h to 35 T / h, or 25 T / h to 30 T / h, especially in high-temperature and high-humidity environments (e.g., environments with ambient temperatures of 35°C to 45°C). To put it another way, conventional manufacturing techniques reduce the prilling rate from 100% of the designed maximum rate to less than 90%, less than 80%, or less than 70% of the designed maximum rate, or to 60% to 90%, 60% to 80%, or 60% to 70% of the designed maximum rate, especially in high-temperature and high-humidity environments (for example, environments with ambient temperatures of 35°C to 45°C).

[0039] Higher prillation rates can be achieved in high-temperature and high-humidity environments with the PSAN solutions disclosed herein. As previously mentioned, the 32°C phase shift is minimized and / or eliminated, and the 84°C phase shift is shifted to higher temperatures with the PSAN solutions disclosed herein. For example, the 84°C phase shift can be shifted (or increased) by about 5°C to about 25°C, or about 10°C to about 20°C. In certain embodiments, the 84°C phase is shifted to 95°C to 105°C.

[0040] Because the phase change temperature has increased to 84°C, the temperature limit at the bottom of the prillation column can also be increased without causing manufacturing problems. For example, the temperature limit of PSAN prill at the bottom of the prillation column can be increased to at least 85°C, at least 86°C, at least 87°C, at least 88°C, at least 89°C, or at least 90°C, even in high-temperature and high-humidity environments (e.g., environments with ambient temperatures of 35°C to 45°C). In other words, the upper temperature limit of PSAN prill at the bottom of the prillation column can be increased to 85°C to 95°C, or 85°C to 90°C, even in high-temperature and high-humidity environments (e.g., environments with ambient temperatures of 35°C to 45°C).

[0041] When the 32°C phase change is minimized and / or eliminated, there will be little to no PSAN prill that experience the 32°C phase change after leaving the cooling mechanism (fluidized bed cooler) and / or during the coating process. As a result, the temperature limit of the PSAN prill leaving the cooling mechanism (e.g., fluidized bed cooler) can be increased. In some embodiments, the temperature limit is increased to at least 35°C, at least 36°C, at least 37°C, at least 38°C, at least 39°C, or at least 40°C, even in high-temperature and high-humidity environments (e.g., environments with ambient temperatures of 35°C to 45°C). In other words, the temperature limit is increased to 30°C to 40°C, 32°C to 40°C, or 35°C to 40°C, even in high-temperature and high-humidity environments (e.g., environments with ambient temperatures of 35°C to 45°C). Furthermore, when the 32°C phase change is minimized and / or eliminated, less thermal energy is released by the PSAN prill due to the absence of the phase change, so the PSAN prill also exits the cooling mechanism (e.g., fluidized bed cooler) at a lower temperature than a conventional LDAN. For example, in some embodiments, the PSAN prill exits the cooling mechanism (e.g., fluidized bed cooler) at a temperature 2°C to 5°C, or 3°C to 4°C, lower than a conventional LDAN under the same manufacturing conditions, even in high-temperature and high-humidity environments (e.g., environments with ambient temperatures of 35°C to 45°C).

[0042] i) the increased temperature limit of PSAN prill at the bottom of the prillation column, and ii) the minimized 32°C phase change temperature, one or more of these also enable the manufacturing process to maintain the plant design maximum prillation rate, or a higher prillation rate, e.g., above 35 T / h, 36 T / h, 37 T / h, 38 T / h, 39 T / h, or 40 T / h, even in high-temperature and high-humidity environments (e.g., environments with ambient temperatures of 35°C to 45°C). In other words, the prillation rate of the PSAN prill solution disclosed herein may be 35 T / h to 42 T / h, or 38 T / h to 41 T / h, even in high-temperature and high-humidity environments (e.g., environments with ambient temperatures of 35°C to 45°C). To put it another way, even in high-temperature and high-humidity environments (for example, environments with ambient temperatures of 35°C to 45°C), the maximum prillation rate of the PSAN prill solution disclosed herein may be at least 10%, at least 20%, at least 30%, at least 40%, or at least 50% higher than the maximum prillation rate obtained with conventional LDAN prill solutions, or the maximum prillation rate of the PSAN prill solution disclosed herein may be 10% to 60%, 10% to 50%, 10% to 40%, 10% to 30%, or 10% to 20% higher than the maximum prillation rate obtained with conventional LDAN prill solutions. [Examples]

[0043] The following examples illustrate the disclosed methods and compositions. Those skilled in the art will recognize that variations of these and other examples of the disclosed methods and compositions are possible without excessive experimentation.

[0044] Example 1 - Generation of preloids for analysis The following method was used to generate the pre-loids: 2.8 mm diameter holes were drilled into the top of a 5 mm thick TEFLON® plate to a depth of approximately 3 mm. 0.9 mm diameter drainage holes were then drilled into these holes. AN solution was then added to the plate to fill the 2.8 mm holes. As the pre-loids cooled, they were extruded through the drainage holes from the 2.8 mm holes in the TEFLON® plate.

[0045] Example 2 - Analysis of potassium salts In addition to AN and potassium salts in the initial solution, a preloid containing aluminum sulfate (either aluminum sulfate solution from Ixom Chemicals or aluminum sulfate from Merck BDH) was prepared. The following samples were prepared for analysis: 1) ANFO alone (94:6), 2) AN (94:6) combined with 0.07% AI2SO4 (700 ppm) and 3.5 mol% KNO3 in combination with a dye-containing fuel oil, 3) AN (94:6) combined with 0.07% AI2SO4 and 2.5 mol% KNO3 in combination with a dye-containing fuel oil, and 4) AN (94:6) combined with 3,500 ppm AI2SO4 and 2.5 mol% KNO3 in combination with a dye-containing fuel oil.

[0046] The samples were placed in a cycling oven (PANASONIC® MIR-254 Cooled Incubator). The cycling oven was designed to mimic thermal cycling that occurs in the field. The oven was set so that one cycle consisted of a 4-hour period at 15°C followed by a 4-hour period at 45°C. The samples were cycled a total of 140 times (Table 2 and Figure 1). [Table 2]

[0047] Throughout the cycling process, the condition and potential degradation of the sample were visually observed. Furthermore, crushing tests were performed at various points to demonstrate the potential changes in sample hardness throughout the cycling process (using a Mark-10 ESM303 Motorized Test Stand and a Mark-10 Digital Force Gauge M5-20).

[0048] The samples were tested for crush strength (hardness) throughout the thermal cycling process. Crushing tests were performed at the points shown in Figure 1. These data demonstrate that the extended shelf life demonstrated in phase-stabilized AN can be replicated in ANFO produced in PSAN using aluminum sulfate as an internal additive.

[0049] Example 3 - Production of PSAN prills in a plant and comparison with LDAN prills The following samples were prepared via the Kaltenbach Thuring process: PSAN sample 1-AN and PSAN prill containing 2.5 mol% KOH (49% KOH solution), and PSAN sample 2-AN and PSAN prill containing 3.5 mol% KOH (49% KOH solution).

[0050] Using thermocouples and data loggers, the temperatures of conventional LDAN and PSAN samples 1 and 2 were measured over eight thermal cycles. For each thermal cycle, the samples were subjected to 45°C for 4 hours, followed by 15°C for 4 hours. Under these conditions, PSAN samples 1 and 2 readily reached high and low temperatures in the oven, while the conventional LDAN did not actually reach 45°C within 4 hours. This is shown in Figure 2. The temperature profiles shown in Figure 2 also exhibit the endothermic and exothermic behavior of the conventional LDAN (related to the known 32°C phase change). Since PSAN samples 1 and 2 do not have a phase change at 32°C, this was not observed in their temperature profiles.

[0051] Next, the heating and cooling times of PSAN prills were compared with those of conventional LDAN prills. For both conventional LDAN and PSAN prill samples, a thermocouple and data logger were placed in a 50°C oven, and the time it took for each sample to reach 50°C was determined (Figure 3). The samples were left in the oven overnight, and then transferred to ambient conditions to determine the time it took for the samples to cool to ambient temperature (Figure 4). Blank control samples (empty bottles) were also used. As shown in Figures 3 and 4, PSAN prills heat and cool more rapidly than conventional LDAN prills. This is due to the absence of a 32°C phase change in PSAN prills.

[0052] Example 4 - Production of PSAN prill in a plant and comparison with LDAN prill The following samples were prepared via the Kaltenbach Thuring process: PSAN prills containing AN and 2.5 mol% KOH (49% KOH solution). The PSAN prills were also coated with 700 ppm GALORYL® ATH 626M. Figures 5 and 6 show DSC data from conventional LDAN prills (Figure 5) and PSAN prills (Figure 6). As shown therein, the 84°C phase shift in the PSAN prills shifted to approximately 95°C–105°C, with 32°C being minimized.

[0053] The prilling rate was set to 40 T / h, with six prill heads online. The mean ambient temperature was approximately 38°C. Due to the 84°C phase shift to a higher temperature, the temperature limit at the bottom of the tower was set to 90°C. The PSAN prill temperature at the bottom of the tower was also measured and is shown in Table 3 below: [Table 3]

[0054] As shown in Table 3, the temperature of the PSAN prill at the bottom of the tower (82°C to 86°C) exceeded the temperature range achievable with conventional LDAN prill production (78°C to 82°C).

[0055] As a result of minimizing the 32°C phase change, the temperature of the PSAN prill exiting the cooling mechanism (e.g., fluidized bed cooler) was set to 35°C. The temperature of the PSAN prill was also observed when it exited the cooling mechanism (e.g., fluidized bed cooler (FBC)). This temperature is shown in Table 4 below: [Table 4]

[0056] Typically, the temperatures observed for conventional LDAN prills are in the range of 29°C to 30°C when the ambient temperature exceeds 35°C, which would necessitate a reduction in the prilling rate. However, PSAN prills, due to the absence of a 32°C phase change, exited the cooling mechanism (e.g., a fluidized bed cooler) at lower temperatures (24°C to 27°C).

[0057] For comparison, the following manufacturing parameters were achieved with PSAN prill versus conventional LDAN prill: [Table 5] [Table 6]

[0058] Without further detail, those skilled in the art will likely be able to make the most of this disclosure using the description provided herein. The examples and embodiments disclosed herein should be construed as merely illustrative and not in any way limiting the scope of this disclosure. It will be apparent to those skilled in the art and interested in this disclosure that the details of the embodiments described above can be modified without departing from the underlying principles of the disclosure herein.

Claims

1. A PSAN explosive comprising phase-stabilized ammonium nitrate (PSAN) prill and fuel, PSAN Prill, Ammonium nitrate and A potassium salt in which PSAN prill contains potassium ions in a potassium salt of 2.1 mol% to 5 mol% based on the ammonium ions of ammonium nitrate, However, the potassium salt is selected from the group consisting of potassium hydroxide, potassium nitrate, potassium sulfate, potassium bisulfate, potassium carbonate, and potassium bicarbonate. An inorganic porosity enhancer comprising aluminum sulfate, iron sulfate, magnesium oxide, or any polyvalent sulfate (polyvalent sulfate) in either anhydrous or hydrated form, Includes, PSAN Prill has a fuel oil retention percentage (FOR%) of at least 5.7%, PSAN prill has a bulk density of less than 0.9 kg / L. A PSAN explosive in which, when subjected to 20 thermal cycles, each cycle includes 4 hours at 15°C followed by 4 hours at 45°C, the average crush strength of the thermally cycled PSAN explosive is greater than the average crush strength of a control PSAN explosive that has not been thermally cycled.

2. The PSAN explosive according to claim 1, wherein the mol% of potassium ions based on ammonium ions is 2.1 mol% to 4 mol%.

3. The PSAN explosive according to claim 1 or 2, wherein the fuel comprises liquid fuels including fuel oil, diesel oil, distillates, furnace oil, kerosene, gasoline, or naphtha; waxes including microcrystalline wax, paraffin wax, or slack wax; paraffin oil, benzene, toluene, or xylene oil; asphalt materials, polymer oils, animal oils, or other mineral, hydrocarbon, or fatty oils; and mixtures thereof.

4. The PSAN explosive according to any one of claims 1 to 3, wherein the weight ratio of PSAN prill to fuel is 80:20 to 97:

3.

5. A PSAN explosive according to any one of claims 1 to 4, wherein the fuel is not an emulsion.

6. The PSAN explosive according to any one of claims 1 to 5, wherein the inorganic porosity enhancer comprises aluminum sulfate.

7. The PSAN explosive according to any one of claims 1 to 6, wherein the concentration of the inorganic porosity enhancer in the prill is 400 ppm to 4,000 ppm.

8. The PSAN explosive according to any one of claims 1 to 7, wherein the potassium salt comprises at least one of potassium hydroxide, potassium nitrate, or potassium sulfate.

9. The PSAN explosive according to any one of claims 1 to 8, wherein the PSAN prill has a bulk density of less than 0.84 kg / L.

10. The PSAN explosive according to any one of claims 1 to 9, wherein the PSAN prill substantially lacks a 32°C crystalline phase change.

11. The PSAN explosive according to any one of claims 1 to 10, wherein the PSAN prill substantially lacks an 84°C crystalline phase change.

12. The PSAN explosive according to claim 10 or 11, wherein the presence of a 32°C or 84°C crystalline phase change is determined by thermal analysis or X-ray diffraction measurement.

13. The PSAN explosive according to claim 12, wherein the thermal analysis includes differential scanning calorimeter and thermogravimetric analysis.

14. A PSAN explosive according to any one of claims 1 to 13, wherein when the PSAN explosive is thermally cycled 50 times, one cycle comprises 4 hours at 15°C followed by 4 hours at 45°C, and the thermally cycled PSAN explosive has an average crush strength greater than 0.4 kg.

15. The PSAN explosive according to claim 14, wherein the average crush strength of the thermally cycled PSAN explosive is 5% to 100% greater than the average crush strength of the uncycled control PSAN explosive.

16. The PSAN explosive according to any one of claims 1 to 15, wherein the storage life of the PSAN explosive is at least two months at an average daytime ambient temperature of 30°C to 50°C and an average nighttime temperature of 10°C to 30°C.

17. A method for increasing the hardness of phase-stabilized ammonium nitrate (PSAN) explosive, A method comprising preparing a PSAN explosive according to any one of claims 1 to 16, and thermally cycling the PSAN explosive 20 or more times.

18. The method according to claim 17, wherein the average crush strength of a thermally cycled PSAN explosive is increased by at least 5% compared to the average crush strength of a control PSAN explosive that has not been thermally cycled.

19. A method for producing a phase-stabilized ammonium nitrate (PSAN) explosive according to any one of claims 1 to 16, potassium salts, An inorganic porosity enhancer comprising aluminum sulfate, iron sulfate, magnesium oxide, or any polyvalent sulfate, either in anhydrous or hydrated form, and Ammonium nitrate Forming a PSAN solution containing, The PSAN solution is crystallized by dropping droplets of the PSAN solution into a prill tower to form PSAN prills, Combining PSAN prill and fuel to form PSAN explosives. Includes, The temperature limit of PSAN prill at the bottom of the prill tower is at least 85°C. PSAN Prill has a fuel oil retention percentage (FOR%) of at least 5.7%, PSAN prill has a bulk density of less than 0.9 kg / L. A method in which a PSAN explosive is thermally cycled 20 times, with each cycle consisting of 4 hours at 15°C followed by 4 hours at 45°C, and the average crush strength of the thermally cycled PSAN explosive is greater than the average crush strength of a control PSAN explosive that is not thermally cycled.

20. The method according to claim 19, wherein the temperature limit of PSAN prill at the bottom of the prill tower is at least 86°C.

21. The method according to claim 20, wherein the temperature limit of PSAN prill at the bottom of the prill tower is 85°C to 95°C.

22. The method according to any one of claims 19 to 21, further comprising transferring the PSAN prill to a cooling mechanism.

23. The method according to claim 22, wherein the cooling mechanism includes a fluidized bed cooler.

24. The method according to claim 22 or 23, wherein the temperature limit of the PSAN prill exiting the cooling mechanism is at least 35°C.

25. The method according to claim 22 or 23, wherein the temperature limit of the PSAN prill exiting the cooling mechanism is 30°C to 40°C.

26. The method according to any one of claims 19 to 25, wherein the prillation rate is greater than 35 t / hour (tons / hour).

27. The method according to any one of claims 19 to 25, wherein the prilling rate is 35 t / hour to 42 t / hour.

28. The method according to any one of claims 19 to 25, wherein the prillation rate is at least 10% higher than the prillation rate obtained with a conventional LDAN prill solution.

29. The method according to any one of claims 19 to 25, wherein the prillation rate is 10% to 60% higher than the prillation rate obtained with a conventional LDAN prillation solution.

30. The method according to any one of claims 26 to 29, wherein the ambient temperature is 35°C to 45°C.

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