AU4024099A - Anfo composition - Google Patents

Description

WO 99/61395 PCT/AU99/00390 -1 ANFO COMPOSITION The present invention relates to an explosive composition, in particular to an ammonium nitrate/fuel oil (ANFO) composition suited for blasting soft media such as overburden and 5 coal. The detonation of explosives compositions releases energy in a number of forms. Two of these types of energy release are particularly important in providing control over the blast to ensure that the size distribution and scatter of the burden is as desired, these are fragmentation 10 energy and heave energy. Fragmentation energy (often referred to as shock energy) determines the ability of the explosive composition to shatter the surrounding media. Blasting hard media, such as rock, requires explosive compositions with relatively high fragmentation energy. Heave energy (often referred to as bubble energy) determines the ability of the explosive composition to move its surrounds. When blasting soft media, such as overburden 15 or coal the use of explosive compositions with low fragmentation energy and relatively high heave energy is preferred. ANFO and ANFO-based explosives compositions are widely used in civilian applications such as in mining operations. ANFO is a substantially oxygen balanced blend of particulate 20 ammonium nitrate coated with a fuel oil. Typically, ANFO contains 94% (by weight) ammonium nitrate and 6% (by weight) fuel oil. The wide use of ANFO in civilian blasting operations is mainly due to its cost, ease of manufacture, ease of handling and loading, and its convenience and performance as a bulk system. Notwithstanding a lack of water resistance, ANFO and ANFO-based explosives compositions are still preferred for use in dry 25 blasts. ANFO and ANFO-based explosive compositions often provide too high a fragmentation energy when used in blasting soft media and therefore techniques such as air decking and the like have been used to reduce the fragmentation energy released on detonation. Other techniques for reducing or controlling the explosive energy include the dilution of the explosive composition with inert materials, bulking of the explosive 30 composition with low-density materials (either inert or fuels), and aerating or gassing the WO 99/61395 PCT/AU99/00390 -2 explosive composition using microballons or the like. The use of air decking and other techniques for reducing fragmentation energy also has the effect of reducing the heave energy. The reduction in heave energy is generally undesirable as it is desirable to maintain or at least minimise any loss of heave energy concomitant with a reduction in fragmentation energy so 5 that the explosive composition is capable of providing similar movement of the burden. In blast patterns for open cut mines or quarries, blastholes are generally spaced apart evenly across the bench, the separation distance assuming a consistent bench and determined by the amount of ANFO required for the blast. Each bench, however, may typically contain regions 10 of harder and softer materials. While softer regions may be provided for by the use of air decking and the like to reduce the fragmentation energy, the concomminant local reduction in heave energy results in an increased spread of the burden and increases the difficulty and cost of its collection. There is desired a means of varying the fragmentation energy of an ANFO or ANFO-based explosive composition which maintains heave energy or at least 15 minimises any reduction in heave energy. We have now found an ANFO explosive composition which is of reduced fragmentation energy yet retains a desirable level of heave energy. Advantageously, the explosive compositions of the present invention may be tailored to provide the desired balance of 20 fragmentation energy and heave energy and can be readily varied within and between blastholes in order to provide optimum blast performance. According to the present invention there is provided an explosive composition comprising particulate ammonium nitrate, fuel oil and a heave agent wherein said heave agent is selected 25 from the group consisting of inorganic ammonium compounds, organic ammonium compounds, amides, carbonates and nitrates with the proviso that the heave agent is not ammonium nitrate and wherein said heave agent is present in an amount of greater than 5% by weight. 30 The explosive compositions of the present invention comprise ammonium nitrate and fuel oil, WO 99/61395 PCT/AU99/00390 -3 blends of which are often referred to in the art as 'ANFO'. The explosive composition used in the present invention preferably contains sufficient fuel oil such that the explosive composition is essentially oxygen-balanced, taking into consideration the total oxidizing salts, fuel oil, sensitizers, and other additives present in the explosive. 'Essentially oxygen 5 balanced' means the blend has an oxygen balance more positive than about minus 25 % and, preferably, in the range of about minus 10% to plus 10%. If the explosive composition is to be used by itself, then the composition should be essentially oxygen-balanced. However, if an emulsion or other explosive agent is blended with the ANFO, then the final mixed explosive composition is essentially oxygen-balanced. 10 It is preferred that the fuel oil is present in an amount of from about 2% to about 10% by weight based upon the weight of the ammonium nitrate and the fuel oil. More preferably, the fuel oil is present in an amount of from about 3% to about 6% by weight. Advantageously, the use of the heave agent may reduce the fuel oil requirement of the 15 explosive composition. Preferably the weight ratio of ammonium nitrate to fuel oil is in the range of from 97:3 to 96:4. Particulate ammonium nitrates suitable for use in ANFO blasting explosives are known in the art. Suitable ammonium nitrate particles may be in the form of separate discrete particles 20 such as prills, granules, pellets and fines. Suitable low porosity ammonium nitrate particles which may be utilized in the explosives of this invention are taught in United Stated Patent No. 4,736,683. A relatively small portion of the ammonium nitrate component may be replaced by other 25 inorganic oxidizer salts known in the art including alkali metal nitrates and perchorates (such as sodium nitrate and potassium nitrate) or alkaline-earth metal nitrates and perchlorates (such as calcium, magnesium and barium nitrates). These additional components will generally be added in amounts up to about 20% by weight and, more typically up to about 15% by weight based upon the weight of the ammonium nitrate. 30 WO 99/61395 PCT/AU99/00390 -4 It is preferred that the ammonium nitrate is coated with an anti-caking agent. Ammonium nitrate coatings are known in the art. The ammonium nitrate may be coated with a conventional anti-caking agent such as clay (for example, bentonite), talc or metallic salts of aliphatic monocarboxylic acids of 6 to 24 carbon atoms. The metallic component of the salt 5 may be alkali or alkaline-earth metals such as sodium, zinc, copper, magnesium, potassium, calcium, barium and strontium. The fatty acid may be hexanoic acid, heptanoic acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid. oleic acid or tallic acid or the like. Preferably, the coating is magnesium stearate or a mixture of magnesium stearate and magnesium oxide. 10 The amount of anti-caking agent which may be used is preferably from about 0.1 to about 1 weight percent and, more preferably, from about 0.1% to about 0.2% by weight based on the weight of the inorganic oxidizer salt which is to be coated. When the coating is a metallic salt of a fatty acid, such as magnesium stearate, then lesser amounts of the anti-caking agent 15 are utilized. The fuel oil used in the explosive compositions of the present invention are known in the art as fuel oils suitable for ANFO's. Fuel oil, and particularly No. 2 fuel oil, as well as No. 2 diesel fuel, are typical (and preferred) fuels for compounding with ammonium nitrate to form 20 the explosive compositions of this invention. The specifications for No. 2 fuel oil are well known: a flash point above 38oC., a 90 % distillation point of 282 min. -338oC. max., and a maximum Saybolt Universal viscosity at 38oC. of 38 seconds (3.6 cSt) (ASTM D396-84 Standard Specifications for Fuel Oil). The specifications for No.2 diesel fuel are also well known (a flash point above 52 0 C.), and are set forth in ASTM D975 Standard Specification 25 for Diesel Fuel Oils. Petroleum cuts sometimes referred to as low or partially refined oils are also suitable fuel components. Various other types of commercially available liquid hydrocarbons can be used. In fact, any liquid hydrocarbon that can be mixed in liquid form is suitable for the formulation of such blasting agents. Fuel oil may be partially or wholly replaced with one or more other oxidizable materials such as other hydrocarbon fractions 30 derived from petroleum and similar fractions derived from other fossil fuels. These include WO 99/61395 PCT/AU99/00390 -5 heating oil, diesel fuel, jet fuel (particularly jet "A" fuel), oil, kerosene, lube oil, coal oil, kerogen extract (from shale oil) and the like. Oils derived from plant and animal origins and synthetic products such as alcohols (e.g. having a chain link of 6 to 18 carbons, or more), glycols, amines, esters, ketones and refined mineral oils (which are liquids at room 5 temperature and preferably have a flash point above 38 0 C.) may also be used instead of fuel oil. Supplementary fuels of the saturated fatty acid type which are suitable for use in the carbonaceous fuel component include octanoic acid, decanoic acid, lauric acid, palmetic acid, behenic acid and steric acid. Supplementary fuels of the higher alcohol type which are suitable for use in the carbonaceous fuel component include hexyl alcohol, nonyl alcohol, 10 lauryl alcohol, cetyl alcohol and stearyl alcohol. Other miscible, carbonaceous materials useful as supplementary fuels in the carbonaceous fuel component include the vegetable oils such as corn oil, cotton seed oil and soya bean oil. Carbohydrate materials exemplified by mannose, glucose, sucrose, fructose, maltose, and molasses may be added as supplemental fuels if desired. 15 Small amounts of high melting point waxes melting points of at least 38oC, generally < lwt% of the fuel, can also be used as a component of the carbonaceous fuel. Waxes which may be used in the carbonaceous fuel component include waxes derived from petroleum such as petrolatum wax, microcrystalline wax, and paraffin wax; mineral waxes such as ozocerite, 20 and montan wax; animal waxes such as spermaceti; and insect waxes such as beeswax, and Chinese wax. A petroleum oil of any desired kinematic viscosity may be used as a component of the carbonaceous fuel and may include oils having kinematic viscosities varying form a thin liquid 25 to those (in minor proportions) which are so thick that they do not flow at ordinary temperatures. Kinematic viscosities at 25oC for typical petroleum oils appear in the range of about 5 to about 4,000 cSt. Most preferably, the fuel oil (containing any such petroleum oil) possesses a kinematic 30 viscosity of less than about 200 cSt, and still more preferably of from about 2 to about WO 99/61395 PCT/AU99/00390 -6 100cSt, as determined at 25 0 C. The explosive compositions of this invention are substantially dry. Preferably, the explosive composition contains less than about 1% by weight water and, more preferably less than about 5 0.5% by weight water, and most preferably, less than about 0.2% by weight water. Various modifiers, densifiers and sensitizers which are conventionally used in the art may be incorporated into the explosive compositions of this invention. For example, energy increasers such as aluminium, magnesium, aluminium-magnesium alloys, ferrophosphorus, 10 ferrosilicon, lead and its salts and trinitrotoluene may be added. The ANFO compositions of the present invention may be sensitized with sensitizers such as those known to persons skilled in the art. Suitable sensitizers include polystyrene beads. Water blocking agents such as guar gum may be applied as a coating to the ammonium nitrate 15 as is taught in United States Patent No. 4,889,570. The explosive compositions of the present invention may be made by any continuous, semi continuous or batch process which is currently used to make ANFO explosive compositions. When the fuel source is a mixture of one or more oils, then these oils are preferably mixed 20 prior to their addition to the ammonium nitrate. The heave agent may be selected from the group consisting of inorganic ammonium compounds, organic ammonium compounds, amides, carbonates and nitrates with the proviso that the heave agent is not ammonium nitrate wherein the heave agent is present in an amount 25 of greater than 5% by weight. Inorganic ammonium compounds include ammonium salts, ammonium double salts and mixtures thereof. Preferred inorganic ammonium compounds include ammonium sulfate, ammonium chloride, ammonium carbonate, ammonium bicarbonate, ammonium thiosulphate, 30 ammonium thiocyanate, ammonium sulphonate, and ammonium phosphate. Preferred double WO 99/61395 PCT/AU99/00390 -7 salts include ammonium sulphate nitrate, ammonium phosphate nitrate and ammonium calcium nitrate. The preferred inorganic ammonium containing double salt is ammonium sulphate nitrate. We have found that fertilizer grade ammonium sulphate nitrate is particularly suited for use in the present invention. 5 Organic ammonium compounds suitable for use in the present invention include ammonium acetate, ammonium oxalate, ammonium tartrate and ammonium citrate. Carbonates suitable for use in the present invention include calcium carbonate and sodium 10 carbonate. Nitrates suitable for use in the present invention include calcium nitrate. Amides suitable for use in the present invention include urea and dicyandiamide. It is particularly preferred to use urea in the present invention in amounts from 20% to 30%. The use of such quantities of urea is particularly effective in reducing the velocity of detonation of the explosive composition whilst generating significant volumes of gas. Urea is a desired heave 15 agent also due to its cost effectiveness. The heave agents used in the explosive compositions of the present invention are present in an amount of greater than 5 % by weight. The heave agents may be readily used in amounts up to about 60% by weight. It is preferred that the heave agent be present in the explosive 20 composition in amount of from 20 to 40 by weight. We have generally found that the incorporation of a heave agent into an ANFO or ANFO based explosive composition reduces substantially the oxygen balance of the composition. As a result, the amount of fuel oil required to achieve an oxygen balanced explosive 25 composition is reduced. This reduction in fuel oil along with the reduction associated with the replacement of ANFO with heave agent results in a significant reduction of the fuel oil requirement for the explosives composition while the heave energy is substantially maintained. 30 The preferred particle size of the heave agent is in the range of from 1 to 10 mm in diameter.

WO 99/61395 PCT/AU99/00390 -8 The optimum particle size is dependent upon the size (diameter) of the charge. It is preferable to use larger diameter heave agents in large diameter boreholes such as those used for blasting overburden or coal (150 to 320 mm blastholes). The preferred particle size is about 1 to 2 mm. Ammonium sulphate nitrate (fertilizer grade) is a preferred heave agent and 5 is readily commercially available in a particle size of 85% in the range of 2 to 5 mm and a mean particle size from 2.8 to 3.5mm. The compositions of the present invention may be made by blending the heave agent with a premixed ammonium nitrate/fuel oil composition. Alternatively, the porous ammonium 10 nitrate prill may be blended with the heave agent and the blend subsequently combined with the fuel oil to produce the composition of the present invention. While not wishing to be bound by theory, the applicants have performed a number of theoretical calculations in order to assesses the likely performance of the explosive 15 compositions according to the present invention. Below in tables, 1 and 2 there is reproduced the results of the theoretical calculations using "Ideal Explosives Code" ("IDEX") to calculate the ideal explosives properties. TABLE ONE 20 ASN/ANFO(98/2) 0/100 20/80 30/70 40/60 50/50 60/40 02 Balance 12.89 7.87 5.35 2.84 0.33 -2.18 Density (g/cc) 0.82 0.86 0.89 0.91 0.94 0.96 Heat of Reaction 2.37 2.1 1.97 1.84 1.7 1.57 25 (MJI/kg) Ideal VoD (m/s) 4476 4481 4490 4506 4529 4550 CJ Temperature (K) 2307 2147 2068 1988 1905 1822 Gas Volume (1/kg) 1080 1050 1040 1020 1010 994 WO 99/61395 PCT/AU99/00390 -9 REE to 100MPa 68 62 59 56 53 49 (Standard) RBS to 100MPa 70 67 65 64 62 59 (Standard) 5 TABLE TWO ASN/ANFO(94/6) 0/100 20/80 30/70 I40/60 5050 60/40 02 Balance -1.32 -3.5 -4.59 -5.68 -6.77 -7.86 Density (g/cc) 0.82 0.86 0.89 0.91 0.94 0.96 10 Heat of Reaction 3.82 3.13 2.8 2.47 2.14 1.8 (MJ/kg) Particle Velocity 1288 1227 1197 1166 1133 1096 CJ Temperature 3041 2676 2499 2318 2131 1937 (K) 15 Gas Volume (1/kg) 1070 1050 1040 1020 1010 1000 REE to 100MPa 102 87 79 71 64 56 (Standard) RBS to 100MPa 105 94 87 81 75 68 (Standard) 20 Without wishing to be bound by theory it is believed that the heave agents play an important part in the process of detonation reactions. The main effect is on the rate of energy release, the degree of combustion, and the gas generation. 25 The rate of energy release is controlled by the detonation velocity and the reaction zone length. It is believed the addition of a heave agent has a retarding effect on the detonation velocity. The reduction in VOD allows more energy to be available for the rock breaking process heave energy.

WO 99/61395 PCT/AU99/00390 - 10 The reduction in VOD is believed to be achieved through the chemical interaction with decomposition reactions for ammonium nitrate, following the adsorption of the heat released during decomposition of the competing reactions. The temperature of detonation is also reduced in compositions of the present invention. 5 The critical diameter of the charges on addition of the heave agents are believed to be a function of the reaction zone length. The reaction zone lengths are very short for the fast detonating explosives (2-10mm) and very long for the relatively slow detonating charges (35-37mm). We have observed an appreciable slowing down of the reactions within the 10 detonation front allows more energy to be available for the residual gas expansion behind the C-J plane. The addition of so called inert substances like, sodium chloride, to explosives compositions results in a decline in the VOD which, generally, is in direct proportion to 15 the quantities of material added. However, the main difference between the inert material and the heave agents is that inert materials will not contribute to the gas generation on detonation. In contradistinction to the present invention, the addition of inert materials will lead to reduction of the total gas volume per kg of the explosives composition. 20 We believe that the materials specified in the invention play an important part in the process of decomposition of ammonium nitrate explosives. The rate determining step in the combustion of ammonium nitrate is believed to be the dissociation reaction into ammonia and nitric acid; 25

NH

4 NO3 > NH 3 + HNO 3 endothermic (1) We believe that the heave agents inhibit or retard the process of above reaction (1) by: 30 WO 99/61395 PCT/AU99/00390 -11 (i) Generation of the excess ammonia through decomposition and substantially shift equilibrium of the dissociation to the left, for example (NH4) 2

C

2 04 > 2NH 3 + (COOH) 2 (2) 5 Ammonium Oxalate > Ammonia + Oxalic Acid (ii) Urea, dicyanamide or other reducing materials combining with nitric acid or the nitrogen oxides produced during ammonium nitrate decomposition in reaction (1). It is believed that the un-oxidised ammonia accumulates in the reaction zone 10 and the burning process in reaction (1) will be inhibited or retarded.

HNO

3 + CO (NH) > CO(NH) 2

HNO

3 (3) Nitric Acid + Urea > Urea Nitrate 15 Thus it is believed that the heave agents act as the retarding agents in the ammonium nitrate decomposition reactions. The reactions (2) and (3) shift the equilibrium of the reaction (1) to the left and thus are believed to control the rate of energy release. 20 The interaction of the heave agents with the ammonium nitrate blasting agents allows the following reaction to proceed to completion:

NH

4

NO

3 > 2H, 2 0 + 0.5 02 + N 2 exothermic (4) 25 Driving of the reaction (4) towards the release of the exothermic heat is believed to be possibly due to elimination of the excess of oxygen through reaction with ammonia, which is generated from the decomposition of the retarding agent in reaction (2) 2 NH 3 +1.5 02 > N 2 + 3 H 2 0 exothermic (5) 30 WO 99/61395 PCT/AU99/00390 - 12 Even small amounts of combustible substances influence exothermic decomposition to proceed with the release of appreciable quantities of exothermic heat energies. Decomposition into gaseous constituents is believed to be facilitated by the use of weaker acid ammonium salts, ie ammonium salts with lower disassociation temperatures (vis 2). 5 Ammonium nitrate is an oxygen positive molecule containing one atom of oxygen per molecule in excess what is required for the complete combustion of its hydrogen (vis 4). When heat is present, then the excess of oxygen is available for the oxidation of the 10 hydrogen of the ammonia group in the ammonium salt added (vis5). The oxidation of ammonia (in the ammonium salt) generates heat, which is then further demanded for the conversion of the acid residues (in the ammonium salt) into gaseous products.

(COOH)

2 + Heat > H+ 2 + 2 COO- endothermic (6) 15 In addition to above, there is at the same time demand for thermal energy for the preceding disassociation of ammonium nitrate into ammonia and the nitric acid.

NH

4

NO

3 + Heat > NH 3 + HNO 3 endothermic (1) 20 The addition of heave agents in accordance with the present invention to ANFO based blasting agents appears to have a retarding and slightly desensitising effect on the explosive decomposition process. Furthermore, the heave agents appear to provide a thermal energy surplus due to oxidation of the ammonia group (shown in reaction (5) 25 below) and a thermal energy deficit due to the disassociation reaction of the acid radical (6). It is believed that the heave agents have significant impact on chemical reactions and thermochemistry. The rate of the chemical energy release is extremely important in 30 performance of explosives to break the rock. The partition of the energy into WO 99/61395 PCT/AU99/00390 - 13 fragmentation and heave determines the ability of the explosives to move its surrounds. The agents of the invention effectively control delivery of the heave energy through slowing down the chemical reactions in the detonation front as shown by both, reduction 5 of VOD values and extension of the reaction zone length (critical diameter). Furthermore, the compositions deliver large gas volumes and hence is advantageous in efficient blasting in soft overburden and coal applications. The heave agents, through reactions with the ammonium nitrate prill, are believed to 10 produce large volumes of gaseous molecules as a result of the detonation process. The direct oxidation of the fuel oil by the ammonium nitrate prill produces large volumes of gas which is extremely hot and thus tends to have very high energy. 15 Advantageously, the present invention provides a readily variable explosive composition which permits the rate of energy release to be controlled whilst maintaining the generation of high volumes of gas. The composition of the present invention permits a predrilled pattern of boreholes to be loaded with explosive compositions having an energy release rate specifically selected for each borehole and even regions within each borehole. The 20 use of variable energy explosives according to the present invention permits greater control in the placing of broken overburden and may reduce or eliminate back break. Advantageously, the compositions of the present invention may be provided with variable energy profiles and rates of energy release by varying the proportion of heave agent 25 incorporated into the explosive composition during manufacture and auguring of the explosive composition into the borehole. ANFO-based explosive compositions are often manufactured by mixing the ammonium nitrate particles with fuel oil on site using bulk trucks. The onsite manufacture of ANFO-based explosive compositions may be readily adapted for the manufacture of the explosive compositions of the present invention. The 30 ammonium nitrate particulate material and the heave agent may be premixed and the WO 99/61395 PCT/AU99/00390 -14 explosive composition of the present invention manufactured in the usual way. Advantageously, an additional storage facility may be incorporated into the mobile explosive manufacturing unit, thereby allowing the control of the amount of heave agent 5 to be readily varied by controlling the rate at which the heave agent is metered into the explosive manufacturing process. This will allow the composition of the explosive to be readily varied from blasthole to blasthole and also to be readily varied within any particular blasthole. Local variations in geology may be readily taken into account by providing appropriate energy releases even within a blast hole. 10 The heave agent may be incorporated into the ANFO-based explosive composition either by blending with the ammonium nitrate particles prior to the incorporation of the fuel oil or the heave agent may be incorporated into an already blended ANFO composition. 15 Advantageously, the compositions of the present invention permit a reduction in the generation of coal fines, reduce the back over break, improve the formation and placement of rock overburden thereby providing increased drag line and shovel efficiency and may eliminate bullying of the ground. 20 We have also found that the incorporation of the heave agent may permit a reduction in the amount of fuel oil present in the explosive composition. Typically, ammonium nitrate fuel oil compositions are oxygen balanced and have 94% by weight porous ammonium nitrate prill and 6% by weight fuel oil. The fuel oil is the most expensive component and advantageously, by incorporating the gas generating agent in accordance with the present 25 invention the amount of fuel oil required may be reduced. For example, it is believed that an effective blast may be obtained using a 97:3 ANFO composition combined with the heave agent. In fact, we have found that the selection of heave agents such as urea and other reducing agents permit the total elimination of the need for fuel oil in the blasting agent. 30 WO 99/61395 PCT/AU99/00390 - 15 While the ANFO explosive compositions of the instant invention may be used by themselves, these explosives may also be blended with emulsion explosives or water gel explosives as is known in the art. 5 Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" and "comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps. 10 The present invention will now be further described with reference to the following non limiting examples. Examples 1 to 3 Comparative Examples CE1 and CE2 15 The ammonium sulfate nitrate, if any, was blended with an ANFO blasting agent prepared from ammonium nitrate prill and fuel oil in the proportions specified in Table 3. The density of the blasting agent is shown in Table 3. Examples 1 to 3 have a ratio of AN:FO of 96:4, as does Example CE2. 20 TABLE THREE Example No. CE1 CE2 1 2 3 Ammonium 94 96 67.2(96) 57.6(96) 48.0(96) 25 Nitrate Prill Fuel Oil 6 4 2.8(4) 2.4(4) 2.0(4) Ammonium

-

-

30.0 40.0 50.0 Sulphate Nitrate' 30 Density (g/cc) 0.80 0.82 0.86 0.88 0.89 WO 99/61395 PCT/AU99/00390 - 16 1. Ammonium Nitrate Prill:

NITROPRIL

TM

- Explosive grade prilled ammonium nitrate ex Orica Australia Pty Ltd 2. Fuel Oil:- Number 2 fuel oil 5 WO 99/61395 PCT/AU99/00390 - 17 3. Ammonium Sulfate Nitrate : ex BASF 60% Ammonium Sulfate 40% Ammonium Nitrate 5 The dry blasting agents were then tested to measure velocities of detonation. Two lengths of optical fibre with clean cut ends are inserted into the explosive in a cardboard tube under test a known distance apart (typically 100mm). The other ends of the fibres are connected to the terminals of an electronic timer which is capable of timing the light 10 pulses from a start and stop signal. The optical fibre which is located in the charge closest to the detonator is the start signal for the timer and should be connected to terminal 0. The second optical fibre stops the timer and should be connected to terminal 1. The timer times the light pulse from the detonation front as it passes the start and stop 15 optical fibres and displays this time in milliseconds. The velocity of detonation is calculated from the time taken for the detonation front to pass from the first to the second fibre. Charges of explosive in different diameter cardboard tubes were detonated. The critical 20 diameter was determined by the smallest charge diameter at which 100% detonation of the charges was obtained. Available relative effective energy, available relative bulk energy and gas volume were calculated. 25 The results of these tests are shown in Table 4.

WO 99/61395 PCT/AU99/00390 -18 TABLE FOUR Example. C CE2 1 2 3 VOD(km/s) 5 Unconfined Charge Diameter 120mm 3.3 2.7 1.9 Fail Fail 152mm 3.6 3.0 2.4 1.6 1.3 185mm 3.9 3.2 2.6 2.2 1.5 10 200mn 4.3 3.3 E 2.8 2.4 2.1 250mm 4.5 / 3.1 / 2.4 Critical Diameter > 100 > 100 > 120 > 150 > 150 (mm) Available Energy: 15 Relative Effective 100 87 71 66 60 (ANFO) Relative Bulk 100 89 76 73 67 (ANFO) Gas Volume 1080 1070 1040 1020 1010 20 (Lit/kg) Examples 4 to 8 Comparative Example CE3 25 Dry ANFO blasting agents where prepared from the components listed in Table 5 in accordance with the procedure described in Example 1.

WO 99/61395 PCT/AU99/00390 - 19 TABLE FIVE EampleNo. CE3 4 5 6 7 8 Ammonium Nitrate 94 67.2 79.2 57.6 73.6 82.2 5 Prill i (96) (97) (96) (97) (97) Fuel oil 2 6 2.8(4) 2.8(3) 2.4(4) 2.4(3) 2.8(3) Ammonium Sulfate / 30.0 / 40.0 / / Nitrate Ammonium / / 18.0 / 24.0 / 10 Sulphate 4 Ammonium / / / / 15.0 Bicarbonate' Density (g/cc) 0.80 0.87 0.88 0.88 0.89 0.88 1. Ammonium Nitrate Prill: 15

NITROPRIL

M

- Explosive grade prilled ammonium nitrate ex Orica Australia Pty Ltd 2. Fuel Oil:- Number 2 fuel oil 3. Ammonium Sulfate Nitrate : ex BASF 20 60% Ammonium Sulfate 40% Ammonium Nitrate 4. Ammonium Sulfate:-ex Incitec Industrial Chemicals 5. Ammonium Bicarbonate:-ex Spectrum Distributors 25 The dry blasting agents were substantially oxygen balanced and were tested in accordance with the procedures described in Example 1 and the results shown in Table 6.

WO 99/61395 PCT/AU99/00390 - 20 TABLE SIX Example No. CE3 1 4 I 5 I 6 7 8 VOD(km/s) Unconfined 5 Charge Diameter 2 120mm 3.3 F F / / 2.8 150mm 3.6 2.1 1.6 F F 3.2 185mm 3.9 2.6 2.3 1.6 1.5 3.1 Critical > 100 > 120 > 120 > 150 > 150 > 200 10 Diameter (nmm) Available Energy: Relative 100 71 72 66 67 Effective 15 (ANFO) Relative Bulk 100 76 77 73 74 / (ANFO) Gas Volume 1080 1040 1040 1020 1040 960 (Lit/kg) 20 Examples 9 to 11 Comparative Example CAE4 and CE5 25 Dry ANFO blasting agents where prepared from the components listed in Table 7 in accordance with the procedure described in Example 1.

WO 99/61395 PCT/AU99/00390 -21 TABLE SEVEN Example No. CE4 CE5 9 10 I 11 Anmonium 94.0 96.0 67.2(96) 48.0(96) 80.0 Nitrate Prill' 5 Fuel oil' 6.0 4.0 2.8(4) 2.0(4) / Ammonium / / 24.0* 40.0* / Nitrate 6 Urea 7 I / 6.0* 10.0* 20.0 Density (g/cc) 0.80 0.82 0.80 0.78 0.79 10 1. Ammonium Nitrate Prill:

NITROPRIL

M

- Explosive grade prilled ammonium nitrate ex Orica Australia Pty Ltd 2. Fuel Oil:- Number 2 fuel oil 3. Ammonium Sulfate Nitrate : 15 ex BASF 60% Ammonium Sulfate 40%Ammonium Nitrate 6. Ammonium Nitrate:-ex Incitec Industrial Chemicals 7. Urea:-ex Incitec Industrial Chemicals 20 The dry blasting agents were tested in accordance with the procedures described in Example 1 and the results shown in Table 8.

WO 99/61395 PCT/AU99/00390 - 22 TABLE EIGHT EExampme No. CE4 CE5 9 10 11 VOD(g/cc) Unconfimed 5 charge diameter 90mm F F 2.3 1.8 100mm / / 2.5 / 120mm 3.3 2.7 2.9 2.6 152mm 3.6 3.0 3.2 2.9 10 185mm 3.9 3.2 3.3 2.9 F 200mm 4.3 3.3 3.2 / 2.1 250mm 4.5 / 3.5 3.3 2.8 Critical > 100 > 100 > 60 >80 > 200 Diameter (mm) 15 Gas Volume 1080 1070 1070 1070 1070 (Lit/kg)

Claims (16)

1. An explosive composition comprising particulate ammonium nitrate, fuel oil and a heave agent wherein said heave agent is selected from the group consisting of inorganic 5 ammonium compounds, organic ammonium compounds, amides, carbonates and nitrates with the proviso that the heave agent is not ammonium nitrate and wherein said heave agent is present in an amount of greater than 5% by weight.

2. An explosive composition according to claim 1 wherein the heave agent is an 10 inorganic ammonium compound selected from the group consisting of ammonium sulfate, ammonium chloride, ammonium carbonate, ammonium bicarbonate, ammonium thiosulphate, ammonium thiocyanate, ammonium sulphonate, and ammonium phosphate.

3. An explosive composition according to either claim 1 or claim 2 wherein the heave 15 agent is an inorganic ammonium compound selected from the group consisting of ammonium sulphate nitrate, ammonium phosphate nitrate and ammonium calcium nitrate.

4. An explosive composition according to any one of claims 1 to 3 wherein the heave agent is an ammonium sulphate nitrate. 20

5. An explosive composition according to claim 1 to wherein the heave agent is a organic ammonium compound selected from the group consisting of ammonium acetate, ammonium oxalate, ammonium tartrate and ammonium citrate. 25

6. An explosive composition according to claim 1 wherein the heave agent is a carbonate selected from the group consisting of calcium carbonate and sodium carbonate.

7. An explosive composition according to claim 1 wherein the heave agent is calcium nitrate in an amount of greater than 20% by weight of the explosive composition. 30 WO 99/61395 PCT/AU99/00390 - 24

8. An explosive composition according to claim 1 wherein the heave agent is an amide selected from the group consisting of urea and dicyandiamide.

9. An explosive composition according to claim 8 wherein the heave agent is urea. 5

10. An explosive composition according to any one of claims 1 to 9 wherein the heave agent is present in the explosive composition in amount of from 20 to 40 by weight.

11. An explosive composition according to any one of claims 1 to 10 wherein the 10 heave agent has a particle size in the range of from 1 to 10 mm in diameter.

12. An explosive composition according to claim 11 wherein the particle size is in the range of from 1 to 2 mm. 15

13. An explosive composition according to any one of claims 1 to 12 wherein based upon the weight of the ammonium nitrate and the fuel oil. More preferably, the fuel oil is present in an amount of from about 3% to about 6% by weight.

14. An explosive composition according to any one of claims 1 to 2 wherein the weight 20 ratio of ammonium nitrate to fuel oil is in the range of from 97:3 to 96:4.

15. An explosive composition according to any one of claims 1 to 14 wherein the fuel oil is selected from the group consisting of No. 2 diesel fuel. 25

16. An explosive composition substantially as hereinbefore described with reference to the drawings and/or examples. WO 99/61395 -25- PCT/AU99/00390 AMENDED CLAIMS [received by the International Bureau on 22 September 1999 (22.09.99); original claims 1-16 replaced by amended claims 1-14 (2 pages)] CLAIMS 1. An explosive composition comprising particulate ammonium nitrate, fuel oil and a heave agent wherein said heave agent is selected from the group consisting of inorganic 5 ammonium compounds, organic ammonium compounds, amides, carbonates and nitrates with the proviso that the heave agent is not ammonium nitrate and wherein said heave agent is present in an amount of greater than 5% by weight. 2. An explosive composition according to claim 1 wherein the heave agent is an 10 inorganic ammonium compound selected from the group consisting of ammonium sulfate, ammonium chloride, ammonium carbonate, ammonium bicarbonate, ammomum thiosulphate, ammonium thiocyanate, ammonium sulphonate, and ammonium phosphate. 3. An explosive composition according to claim 1 wherein the heave agent is an 15 inorganic ammonium compound selected from the group consisting of ammonium sulphate nitrate, ammonium phosphate nitrate and ammonium calcium nitrate. 4. An explosive composition according to claim 1 wherein the heave agent is an ammonium sulphate nitrate. 20 5. An explosive composition according to claim 1 to wherein the heave agent is a organic ammonium compound selected from the group consisting of ammonium acetate, ammonium oxalate, ammonium tartrate and ammonium citrate. 25 6. An explosive composition according to claim 1 wherein the heave agent is a carbonate selected from the group consisting of calcium carbonate and sodium carbonate. 7. An explosive composition according to claim 1 wherein the heave agent is an amide selected from the group consisting of urea and dicyandiamide. 30 8 An explosive composition according to claim 7 wherein the heave agent is urea. AMENDED SHEET (ARTICLE 19) WO 99/61395 -26- PCT/AU99/00390 9. An explosive composition according to any one of claims 1 to 8 wherein the heave agent is present in the explosive composition in amount of from 20 to 40 by weight. 10. An explosive composition according to any one of claims 1 to 9 wherein the heave 5 agent has a particle size in the range of from 1 to 10 mm in diameter. 11. An explosive composition according to claim 10 wherein the particle size is in the range of from 1 to 2 mm. 10 12. An explosive composition according to any one of claims 1 to 11 wherein the fuel oil is present in an amount of from about 3 % to about 6% by weight based upon the weight of the ammonium nitrate and the fuel oil 13. An explosive composition according to any one of claims 1 to 11 wherein the 15 weight ratio of ammonium nitrate to fuel oil is in the range of from 97:3 to 96:4. 14. An explosive composition according to any one of claims 1 to 13 wherein the fuel oil is No. 2 diesel fuel. AMENDED SHEET (ARTICLE 19)