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An Experimental Method for Micro-Particle Ammonium Nitrate (MP-AN)_FINAL

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An Experimental Method for Producing a Micro-Particle Ammonium Nitrate (MP-AN) Christopher Jon Preston P.Eng. MCP, Consulting Engineer, North Bay, Ontario, Canada Abstract This paper describes a type of ammonium nitrate (AN) produced in a patented experimental atomization/aerodynamic process. This AN exhibits outstanding properties for use as a main ingredient to a new family of AN-based commercial explosives. Micro-particle ammonium nitrate (MP-AN) is produced by atomizing either an 83% or 85% AN solution which has been doped with a two component surfactant NSol 1000 (NSol). NSol imparts some water-resistance as well as provides a means of increasing density and bulk strength. Increased detonation velocities, well in the range of emulsion explosives, can be achieved. The maximum manufacturing temperature is less than 100°C. The methodology has the potential of being environmentally friendly since any effluent can be recycled back into a make-up tank to be re-used by the closed loop method. The process has a small footprint. The manufacturing process imparts high densities to MP-AN with a particle distribution spanning at least three orders of magnitude that facilitates close-packing. This type of distribution allows bulk strengths to have values that are typically attained with emulsion blend explosives. Adding fuel along with varying percentages of NSol to MP-AN produces an MP-ANFO explosive that can be made with two sensitivities, either booster or detonator sensitive. This versatility can be attained without any major changes in the manufacturing process. In addition, when mixed with fuel oil and binders, MP-ANFO has the potential of producing an energy variable explosive by altering the water content. MP-ANFO has water resistance similar to watergel explosives. Introduction This paper presents a description of a patented process used to produce a new type of AN for commercial explosives that has very different properties from those associated with normal porous AN prills. The development of the process is described along with properties of an explosive type called MP-ANFO. Field tests proved that doping AN solution (83/85%) with NSol can produce enhanced MP-AN feed for the manufacture of commercial explosives. Terms that are pertinent to the content outlined in this document are given in Table 1. Table 1. Definitions of Terms Used AN Ammonium nitrate FO Fuel oil CERL Canadian Explosive Research Laboratory ANFO Ammonium nitrate/fuel oil mixed in the ratio of 94% AN and 6% FO MP-AN Micro-particle ammonium nitrate containing 7% water not fueled MP-ANFO MP-ANFO 0.1 11 MP-AN (with 7% water) mixed with x% FO and binders fueled This code translates to MP-ANFO with 0.1% NSol 1000 with 11% water added NSol 1000 Two component crystal habit modifier (surfactant) used in the manufacture of MP-AN, NSol is also a contraction of NSol 1000 Binder 1 Non-complexing binder (non-crosslinking) Binder 2 Self-complexing binder (self-crosslinking) VOD Velocity of detonation
Transcript
Page 1: An Experimental Method for Micro-Particle Ammonium Nitrate (MP-AN)_FINAL

An Experimental Method for Producing a Micro-Particle Ammonium Nitrate (MP-AN)

Christopher Jon Preston P.Eng. MCP, Consulting Engineer, North Bay, Ontario, Canada

Abstract This paper describes a type of ammonium nitrate (AN) produced in a patented experimental

atomization/aerodynamic process. This AN exhibits outstanding properties for use as a main ingredient to

a new family of AN-based commercial explosives. Micro-particle ammonium nitrate (MP-AN) is

produced by atomizing either an 83% or 85% AN solution which has been doped with a two component

surfactant NSol 1000 (NSol). NSol imparts some water-resistance as well as provides a means of

increasing density and bulk strength. Increased detonation velocities, well in the range of emulsion

explosives, can be achieved. The maximum manufacturing temperature is less than 100°C. The

methodology has the potential of being environmentally friendly since any effluent can be recycled back

into a make-up tank to be re-used by the closed loop method. The process has a small footprint.

The manufacturing process imparts high densities to MP-AN with a particle distribution spanning at least

three orders of magnitude that facilitates close-packing. This type of distribution allows bulk strengths to

have values that are typically attained with emulsion blend explosives. Adding fuel along with varying

percentages of NSol to MP-AN produces an MP-ANFO explosive that can be made with two sensitivities,

either booster or detonator sensitive. This versatility can be attained without any major changes in the

manufacturing process. In addition, when mixed with fuel oil and binders, MP-ANFO has the potential of

producing an energy variable explosive by altering the water content. MP-ANFO has water resistance

similar to watergel explosives.

Introduction

This paper presents a description of a patented process used to produce a new type of AN for commercial

explosives that has very different properties from those associated with normal porous AN prills. The

development of the process is described along with properties of an explosive type called MP-ANFO.

Field tests proved that doping AN solution (83/85%) with NSol can produce enhanced MP-AN feed for

the manufacture of commercial explosives. Terms that are pertinent to the content outlined in this

document are given in Table 1.

Table 1. Definitions of Terms Used

AN Ammonium nitrate

FO Fuel oil

CERL Canadian Explosive Research Laboratory

ANFO Ammonium nitrate/fuel oil mixed in the ratio of 94% AN and 6% FO

MP-AN Micro-particle ammonium nitrate containing 7% water – not fueled

MP-ANFO

MP-ANFO 0.1 11

MP-AN (with 7% water) mixed with x% FO and binders – fueled

This code translates to MP-ANFO with 0.1% NSol 1000 with 11% water added

NSol 1000 Two component crystal habit modifier (surfactant) used in the manufacture of

MP-AN, NSol is also a contraction of NSol 1000

Binder 1 Non-complexing binder (non-crosslinking)

Binder 2 Self-complexing binder (self-crosslinking)

VOD Velocity of detonation

Page 2: An Experimental Method for Micro-Particle Ammonium Nitrate (MP-AN)_FINAL

Typical properties of normal porous prilled ANFO are shown in Table 2. Two parameters that are always

of importance are “shock” and “heave.” Shock or brisance is a measure of the shattering action of the

detonation head which is supported by the chemical reaction preceding it. The greater the detonation

velocity of the shock front, the greater the brisance.

The chemical reaction following the shock front is formed by the reflection of release waves back into a

conical shaped detonation head where further reaction of ingredients takes place. This generates a gas

expansion zone of high pressure that pushes against the borehole wall. This zone is responsible for the

heave generated by commercial explosives.

Table 2. Properties of Porous Prilled ANFO

Density 0.83 – 0.85 g/cc bulk; prill density ρ = 1.3 g/cc

Ideal Detonation Velocity 4,500 m/sec at 0.85 g/cc in 300 mm charge diameter (confined)

Critical Diameter 50 mm (confined)

Shock (Brisance) Low

Gas Expansion (Heave) High

Energy 850 cal/g

Water resistance None

Consistency Prills, free flowing

Storage Poor (degrade due to temperature recycling and humidity)

Particle Size Range (- 8 + 16) Tyler (1.19 ≥ Ps ≤ 2.38 mm)

Testing Cooled Samples of AN Solution with the NSol 1000 Additive Two concentrations of NSol were used. The first involved mixing AN solution with 0.1% NSol in order

to get a quantity of MP-AN for testing. The second would raise the NSol content to 1.0% for comparison

to test sensitivity levels of MP-AN (NSol acts as a fuel). The most expedient method (first iteration)

involved using buckets and paddles in which small batches of 50 kg (110.2 lb) of AN solution containing

0.1% NSol were mixed and cooled slowly. This was repeated for 1.0% NSol.

First Iteration – Buckets and Paddles Figure 1 shows MP-AN at 0.1% NSol and 1.0% NSol respectively, cooled and dried to give resulting final

products shown below. No fuel oil has been added.

The appropriate quantity of 85% AN solution was weighed out in a stainless steel vat and heated NSOL

at 95°C was added to the AN solution. Ammonia was generated and vented. Slow stirring mixed the two

ingredients together. After a short period of time, the clear AN solution started to appear ‘milky’ and this

occurred at the temperature of 76.6°C (170°F) for 85% AN solution with 0.1% NSOL added. Cooling

continued down to about 20°C (68°F).

Page 3: An Experimental Method for Micro-Particle Ammonium Nitrate (MP-AN)_FINAL

Figure 1. MP-AN (left) made from 85% AN solution and 0.1% NSol which appears dusty and

soapy. On the right, MP-AN made with 85% AN solution and 1.0% NSol appears waxy. The testing that would be conducted included initial safety testing:

Heat stability for the purpose of testing the reactivity of ingredients;

Bullet and shot shell (projectile) sensitivity – equipment safety;

DOT test standard – transportation safety;

Environmental parameters – temperature and pressure (hydrostatic head);

Handling and storage – seasonal; and

Physical properties and VOD curve.

Heat Stability Testing Heat stability testing involved screening individual ingredients for exothermic events using a simple, hot

oil bath arrangement shown in Figure 2 along with a chart recorder.

Projectile Impact for Testing Mechanical Energy Input Projectile impact testing involved the use of a facility dedicated for conducting the impact energy work.

This facility is shown in Figure 3. It had an above ground bombproof shelter and a shielded shot

containment tube made from military grade steel.

Figure 2. Hot oil bath and test tube contents for ingredient testing along with a chart recorder.

Page 4: An Experimental Method for Micro-Particle Ammonium Nitrate (MP-AN)_FINAL

Figure 3. Rifle stand arrangement so that muzzle velocity could be determined with a time

interval counter (left) and the sample setup within an armoured tube for containing any blast

event. A steel backdrop is setup to deflect projectiles safely.

DOT Donor/Receptor (Explosive/Lead Cylinder) Test for Sensitivity This test used a 15 gr detonator placed in a 100 g sample of test explosive with the sample (donor) placed

on a lead cylinder (receptor) with dimensions 64 mm (2.52 in) diameter by 100 mm (3.94 in) long. The

goal was to detect any deformation in the lead cylinder. Figure 4 shows the test setup to determine the

sensitivity of the different MP-AN sample formulations using NSol.

Characterization Tests – Temperature and Pressure Standard detonation profiling tests were completed for both temperature and pressure effects. Again,

testing was done for both 0.1% NSol and 1.0% NSol formulations. These tests were completed in schedule

40 steel pipe using 0.5 kg (1.1 lb) primers and monitored with either time interval or continuous velocity

methods. The pressure container was fabricated using a flange locking assembly that allowed pressures of

724 kPa (105 psi) to be applied without any leaking. Typical charge testing arrangements (confined) are

shown in Figure 5. For these tests, the MP-AN samples were made up from the spray process that is

discussed later in this document. Densities were much higher than the cooling process generated due to

close-packing of the bead-like particulate along with the density of the AN particles which were at the

crystal density of AN.

Figure 4. Test result for a detonated DOT sample that has deformed the lead cylinder receptor

indicating a failure. This defines the classification for transporting this material.

Page 5: An Experimental Method for Micro-Particle Ammonium Nitrate (MP-AN)_FINAL

The velocity-diameter data in Figure 6 was obtained using the first iteration method. Table 3 shows sample

temperature effects on VOD data and Table 4 lists some test results of static pressure effects on detonation

velocity using the spray generated MP-AN. Water content was 11%. No binder was used for any of these

characterization tests and samples came from the same batch.

Table 3. Detonation Velocity vs. Temperature for MP-ANFO (Spray Generated MP-AN)

(Confined – No Binder – Water Content 11%)

Test

Number

Diameter

(mm)

Density

(g/cc)

Primer

(kg)

Temperature

(°C)

Detonation Velocity

(m/sec)

#1 152 1.23 0.5 -15 5,140

#2 100 1.25 0.5 -20 4,800

#3 100 1.25 0.5 -10 4,895

Figure 5. Confined VOD shot (left) and a confined pressure shot (right).

Figure 6. Detonation velocity vs. charge diameter curves for both 0.1% and 1.0% NSOL MP-

AN mixed with fuel oil. Water content was around 11%. Density varied from 1.08-1.12 g/cc for

the 0.1% MP-MANFO and 0.98-1.06 for the 1.0% MP-ANFO. No binder was used.

No Binder Added

Page 6: An Experimental Method for Micro-Particle Ammonium Nitrate (MP-AN)_FINAL

Table 4. Test Results for MP-ANFO (Spray Generated) Applied Static Pressure Testing in

Schedule 40 Steel Pipe – 724 kPa (105 psi)

(Confined – No Binder – Water Content 11%)

Test

Number

Diameter

(mm)

Duration

(days)

Density

(g/cc)

Detonation Velocity

(m/sec)

#1 203 1 1.25 3,629

#2 203 8 1.27 3,735

#3 203 21 1.23 3,432

Second Iteration – Basic Concept for a Simple Spray Dry Process Instead of using the slow methodology of cooling along with the attendant small needles problem, a spray

nozzle configuration was assembled. This allowed a more rapid cooling effect to be attained and a

distribution of fine particles that generated a range of particle sizes (0.8 ≥ Ps ≤ 250 microns).

This generated a close-packed configuration for MP-AN and densities up to 1.44 g/cc were achieved. A

standard off-the-shelf water nozzle manufactured by Spray Systems of Wheaton, IL, USA, was used to

generate the MP-AN particles. The design took the form of the process shown in Figure 7. However the

experimental setup used, shown in Figure 9, was even more primitive.

Figure 7. Spray method of rapid cooling 85% AN solution doped with 0.1% NSol. Note the

direction of airflow; particles were pulled through the system by the vacuum blower.

Two types of nozzles were eventually tried. External mix nozzles were prone to give larger droplets of

spray but had a range of operating flow rates. Internal mix nozzles give a much finer spray but operate at

a fixed flow rate. Each flow rate for each internal mix nozzle created a “signature” droplet distribution.

This external mix nozzle was chosen - 1/4JBCJS+SU4S - to explore droplet size and production rate. Both

nozzle types are shown in Figure 8 below.

Page 7: An Experimental Method for Micro-Particle Ammonium Nitrate (MP-AN)_FINAL

Figure 8. The internal mix nozzle (left) and the external mix (right).

The actual configuration of the spray setup is presented in Figure 9.

Figure 9. The heated tank with the attached nozzle (left). The spray chamber is shown in the

middle photo and a capture of the actual spray is rendered last (right). Gravity feed was used.

The particles were collected using a very crude cyclone collector. The difference in the shapes of the MP-

AN particulate using the buckets and paddles cooling method compared to the spray method are shown in

Figure 10.

It was found by experiment that the external mix nozzle chosen would work for outputs up to a rate of 45

kg/hr (99.2 lb/hr). This nozzle produced droplet distributions centered at 400 microns. Any rates higher

than 45 kg/hr (99.2 lb/hr) produced clogging in the tubing and collector. The system was designed so the

MP-AN particles would be “pulled” – not pushed - through the tube section and the crude cyclone

assembly. The flow into the nozzle was by gravity feeding the doped AN solution.

A small 3,000 kg (6,614 lb) field trial at a limestone quarry was conducted using MP-ANFO (0.1% NSol

with 11% water). Densities of the MP-ANFO ranged from 1.25-1.44 g/cc loaded into holes 16 m (52.5 ft)

deep and 185 mm (7.28 in) in diameter. Detonation velocities exceeded 6,000 m/s (19,685 ft/s) and were

measured with an MREL MicroTrap® data logger. There were no problems loading the MP-ANFO

explosive packaged in 55 kg (121.25 lb) bags.

Page 8: An Experimental Method for Micro-Particle Ammonium Nitrate (MP-AN)_FINAL

Figure 10. Indication of the differences between cooling MP-AN slowly versus the spray method.

Needles about 1 mm long are produced by slow cooling and the spherical particles are producd

by spraying are roughly 0.5 mm in diameter (optical microscope).

Third Iteration – Larger Scale Spray Method The spray evaporation setup shown in Figure 11 was intended to produce larger quantities of MP-AN

particles at a higher rate using a larger nozzle - 1/2JBCJ-SS+SU70-SS. However the rate of production

did not exceed 100 kg/hr (220.5 lb/hr) because of clogging and build up issues. These problems were

extensive and this particular plant configuration never reached its designed output of 346 kg (762.8 lb)

MP-AN at 7% water. In spite of the problems associated with water spray nozzles, enough MP-AN

material was laboriously collected to make about 25,000 kg (55,116 lb) of MP-ANFO averaging a density

of 1.25 g/cc. This was produced to conduct some field trials at an underground mine in Northern Ontario.

A total of five small blasts were conducted at the mine using MP-ANFO with 0.1% NSol and with a water

content averaging 11%. Binders were added to give a marshmallow consistency to the bagged explosive

MP-ANFO so that there would be an attempt to provide 100% coupling to the borehole wall. The hole

diameters for open stope slot and slash were at 165 mm (6.5 in), but the bag diameter was far less – 140

mm (5.5 in). Bagging the MP-ANFO was a convenient way of packaging this experimental explosive.

The loading conditions were not good, the blast patterns contained many decked charges. The explosive

was removed from the bags and dropped down holes and coupling ratios anywhere from 95% to 110%

were achieved. In some cases the explosive was spongy enough to migrate into scabs formed at the

borehole wall due to stresses. The MP-ANFO had enough inherent strength from the binders that

prevented stemming material, used to separate decks, from passing into the explosive. There was one stiff

batch of MP-ANFO manufactured creating an undesirable loading and handling issue; too much of the

self-complexing binder was added. The fragmentation was equivalent to emulsion explosives and the

“marshmallow” consistency was favoured by the blasting crews.

Note for coupling ratios larger than an assumed diameter of a blasthole:

In underground mining, drilling holes through highly stressed volumes of ore can lead to scabbing of

the borehole wall with the result that explosives that are loaded into the stressed hole may actually

bleed into cracks and open scabs. This giving a standard explosive column rise a value that suggests the

coupling ratio is over 100%. This happens because there is more explosive in the hole than anticipated

with the bit diameter that had been used in the calculation.

Scale: 1mm numbered

Page 9: An Experimental Method for Micro-Particle Ammonium Nitrate (MP-AN)_FINAL

Figure 11. Severe clogging (left) and spray chamber (middle). The spray nozzle (right) is in action.

A very poor rate of production that never exceeded 90 kg/hr (198 lb/hr) was the result of this

particular configuration. Humidity was a key issue. A short spray tube did not provide enough

time for particles to release water.

Figure 12 shows one of the stopes where test blasts were set up. The direction of blast motion was to the

free face with very little back-break. Fragmentation was equivalent to that produced by emulsion

explosives according to the scooptram operators. Each blast was monitored with detonation velocity probes

and seismometers. Detonation velocities were monitored using continuous velocity-resistance wire

methodology. In those holes that were monitored, detonation velocities measured over five separate blasts

ranged from 4,880 to 5,614 m/sec (16,011 to 18,419 ft/s). MiniTrap II’s were used to get the continuous

velocity records.

Figure 12. An open hole in front of next ring to be loaded with not much damage to floor (left).

Note that the back is undamaged from blasting with the screen and bolting still intact (right).

Samples of the detonation velocity results are given in Figure 13. The seismometers were situated close

to the blasting for the purpose of getting better resolution records in order to delineate deck vibration

readings to determine maximum charge weight/scaled distance values. However it was noted that

maximum vibration levels did not exceed the mine guidelines.

Page 10: An Experimental Method for Micro-Particle Ammonium Nitrate (MP-AN)_FINAL

Figure 13. Detonation velocity results from in-hole monitoring of MP-ANFO 0.1% NSOL.

Samples of the MP-AN particulate were taken for testing at the Willet Green Center in Sudbury, ON, in

order to determine the particle distribution obtained by the specific nozzle used for the field trial. An

electron microscope was used with particle sizing and distribution equipment that used laser diffraction

for measuring distribution shown in Figures 14 and 15 respectively.

Figure 14. Particles at a magnification scale of 100 and 20 microns respectively for an internal

mix nozzle.

Figure 15. Particle distribution for an internal mix nozzle is on the left with a distribution for an

external mix nozzle on the right. Particle density was found to be 1.71 g/cc.

Page 11: An Experimental Method for Micro-Particle Ammonium Nitrate (MP-AN)_FINAL

Some interesting consistencies of MP-ANFO are shown below in Figure 16. The range of consistencies

for the MP-ANFO is remarkable especially considering the types of loading equipment that are available.

MP-ANFO can be pumped, augered and extruded and packaged in bags or cartridges providing the right

combination of binders is used (in conjunction with a fixed percentage of water).

Figure 16. Illustrates “marshmallow” consistency (left) and putty consistency (right).

From testing and trials conducted to date using the spray method, a summary of the detonation velocity

vs. charge diameter characteristics are shown in Figure 17. These curves were generated from MP-AN

samples that were mixed with fuel oil and binders and packed into schedule 40 steel pipe about 1 m (3.28

ft) long in a range of charge diameters and detonated. Both continuous velocity probes and time interval

targets were used to plot the curves presented in Figure 17. Primers used were 0.5 kg (1.1 lb) initiated by

50 gr reinforced primacord.

Figure 17. Detonation characteristics in different diameters of charge for ANFO and MP-

ANFO at 0.1% and 1.0% NSol 1000. MP-ANFO was made with binders.

Table 4 summaries the properties for only the 0.1% NSol formulated MP-ANFO containing 11[CP1]%

Page 12: An Experimental Method for Micro-Particle Ammonium Nitrate (MP-AN)_FINAL

water. This table can be directly compared to Table 1 for porous prilled ANFO properties.

Table 4. Properties of MP-ANFO at 0.1% NSol and 11% water with Binders

Density 0.70 – 1.44 g/cc bulk; prill density ρ = 1.71 g/cc

Detonation Velocity Range 3,500 – 6,500 m/sec at ranged density above – ideal at 7000

m/sec

Critical Diameter 36 mm (confined) – not detonator sensitive

Shock (Brisance) high

Gas Expansion (Heave) high

Energy 640 - 850 cal/g dependent on % water

Water resistance Same as slurries and/or watergels

Consistency Plastic, putty, rubber, marshmallow, C4

Storage Excellent if container is intact

Particle Size Range (- 400) Tyler (0.8 ≥ Ps ≤ 250 microns)

Fourth Iteration – Patented Flight Tube Technology Iterations to date had shortcomings not only with production rate but also moisture content due to the

inability to control humidity. CFD software Fluent® was used to gain more insight into the fluid dynamics

using humidity controlled air flow to bleed off moisture from MP-AN droplets. A “flight tube” was

designed from the simulations and was conceptualized in Figure 18.

Figure 18. Example for the “flight tube”

configuration at a specific spray

concentration. The flow is laminar (not

turbulent).

A mock-up of a design using a flow rate of 250 kg/hr (551.2 lb/hr) for MP-AN at 0.1% NSol and 7%

water is shown in Figure 19 below. The velocity of the airflow measured at different points across the

Page 13: An Experimental Method for Micro-Particle Ammonium Nitrate (MP-AN)_FINAL

diameter of the tubing by a pitot tube, was constant. The calculations obtained by Fluent® CFD were

employed.

Figure 19. Flight tube sections bolted together (top left) along with a wet filter (top right).

Each acrylic section was 1.5 m (4.9 ft) long and 1 m (3.28 ft) diameter with the injector inserted at the air

intake. A wet filter was used to trap any MP-AN particles or droplets after exiting the cyclone assembly.

Any effluent trapped by the wet filter was dumped directly back into a make-up tank (not shown).

Humidity control was accomplished by controlling room temperature but this proved to be far from

adequate. A plenum chamber would be used in future iterations to provide humidity control. The

experimental plant was designed for 250 kg/hr (551.2 lb/hr) and was successful in producing this rate of

MP-AN as long as the relative humidity was kept at 20% or below. Enough MP-AN at 0.1% NSol was

collected for additional testing and shipping samples. It was found that even this simple test arrangement

produced consistent MP-AN with a moisture content at 7% ± 0.5% water. The particle size distributions

were very consistent with the three orders of magnitude spread previously obtained and measured.

Since this configuration held promise, a small scale production plant was conceptualized using PLC

control for humidity control in the process, moisture content in the MP-AN product, as well as monitoring

laminar airstream flow. Process temperature along with NSol addition would be PLC controlled as well.

A suitable nozzle for better atomization and flow rate has been modeled and is being tested. This nozzle

is a variant that does not use water spray configurations associated with nozzles designed as water spray

utility devices. A Laval (convergent/divergent) nozzle will be used.

The economic savings achieved by replacing the stainless steel that would have been required for

construction of the flight tube was considerable. There is also the advantage of seeing and visualizing the

material being made via the transparent process.

Summary

From the tests and trials to date, the following highlights are summarized:

Test Results

MP-AN can be made with a broad particle distribution to allow close-packing as a means of increasing

density

Page 14: An Experimental Method for Micro-Particle Ammonium Nitrate (MP-AN)_FINAL

MP-AN particle density is at the crystal density of AN (1.71 g/cc)

MP-AN appears to have excellent storage characteristics since it is made hydrophobic with the

addition of at least 0.1% NSol to 83% or 85% AN solution

MP-AN will dry out when exposed to air going through a stage called “cauliflowering”

MP-AN can be made by a simple process using a “flight tube” for evaporating moisture during the

spray process with a small footprint providing the rate is less than 250 kg/hr (551.2 lb/hr)

MP-ANFO has a high detonation velocity (VOD) and can be produced as a high density explosive

exhibiting high shock (brisance) and high gas (heave)

MP-ANFO supports up to 15% water in the formula

MP-ANFO at 0.1% NSol and 7% water will give a range of detonation velocities so that for every 1%

water added to the base formula, the detonation velocity will drop 500 m/sec up to a water content of

15% with the critical diameter increasing as additional water is added

MP-ANFO may be an energy variable product when additional water is added affecting the detonation

velocity

MP-ANFO can be made with different consistencies including rubber, marshmallow, putty, bread

dough and plastic

MP-ANFO exhibits high shear strength in the rubber consistency form

MP-ANFO can be delivered to the hole using simple ANFO bulk trucks with augers as a means of

conveyance

MP-ANFO made with an NSol concentration of 0.1% is not detonator sensitive

MP-ANFO made with an NSol concentration of 1.0% is detonator sensitive

Booster sensitive MP-ANFO and detonator sensitive MP-ANFO can be made using the same low

temperature process (less than 100°C (212°F))

As an end-use product (external from this paper)

All safety tests have been completed for MP-ANFO at 0.1% and 1.0% NSol 1000

Long term storage tests completed – covering at least 8 seasons

MSDS compliance for NSol 1000, MP-AN and MP-ANFO (alternate trade name)

Patents granted – Canada, USA, Mexico, Australia, South Africa, China, India, Indonesia, South

Korea, Russia

Patents pending – EU, Norway, Hong Kong

Challenges

MP-ANFO ingredient cost of production is driven by the price of AN solution and possibly fuel oil

This project needs investment to completely develop as well as more research and development

especially from the CFD standpoint and nozzle design

The perception is that this type of AN production would appear to be very disruptive to the

explosives industry as a whole (resistance to change, paradigm shift, not as cheap as prills)

Recommendations for Future Work Top priority is to explore the development of a spray nozzle that will allow MP-AN to be made in high

volumes typically at rates of 5,000 kg/hr (11,023 lb.hr). Standard spray equipment that can atomize

particles centered in the range of 50-100 microns is not available that can evaporate moisture from an high

Page 15: An Experimental Method for Micro-Particle Ammonium Nitrate (MP-AN)_FINAL

speed AN solution stream in the volume required. Propriety work has been done for volume rates of

airflow along with the introduction of doped AN solution into volumes of air and this work will continue.

References Nexco Binder Summary 2008 – Experiments Using NSOL Additive with 85% AN solution, Design of

Flight Tube Using Acrylic – 2009.

Personal Manual Covering Testing for MP-AN – Christopher Jon Preston, P.Eng. 2008

Nexco Inc – CFD Project Angle Tilt Study, Wojciech Kalata, Kathleen Brown, Spray Analysis and

Research Services, Spraying Systems Co.®, Wheaton, Ill, 2009.

Nexco Inc – Divergent Duct Study, Wojciech Kalata, Kathleen Brown, Spray Analysis and Research

Services, Spraying Systems Co.®, Wheaton, Ill 2009.

New Spray Dry Process using Divergent/Convergent Laval Nozzles, Internal Nexco Document, Chris

Preston, Robert Squirrell, North Bay, ON, Canada, 2009.

Fluent® CPD is a copyright software program, trademarked by ANSYS, Inc Southpointe, 275 Technology

Drive, Canonsburg, PA 15317, USA.


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