Patent Application
20070107820
Not applicable.
This invention relates to material breaking or fracturing methods and compositions and systems useful therein. More specifically, it relates to gas-generating compositions, fracturing systems, and methods of using and making the foregoing.
Excavation of hard materials, such as rock and concrete, is a primary activity in underground mining, surface mining, open pits and quarries, earth moving and allied construction works, and in civil demolition projects. Explosive blasting has historically been used to break hard materials during excavation, but this technique is not suitable for all applications due to handling and safety concerns that accompany the use of high explosive materials. For instance, explosive blasting is known to produce noise, vibration and flyrock, and explosive materials are subject to strict handling and transportation restrictions. Alternative methods for fracturing or breaking hard material have become increasingly important in recent years for several reasons. For instance, in civil engineering and quarry operations, there is a growing need to reduce insurance costs, increase worker safety, lower the cost of safety, and achieve a lower total cost of fracturing the desired materials.
Mechanical impact breakers and other rock breaking and excavation tools, such as tunnel boring machines and roadheader machines, are alternatives to explosive blasting. However, these techniques require expensive and highly specialized tools. Moreover, repetitive breaking can result in wear and dulling of the machinery over time which can require sharpening or replacing expensive machine parts.
Additional breaking methods have been developed that employ a military-type cannon system. A propellant-based cartridge is fired into the cannon to discharge high-pressure gasses into a hole drilled into the material to initiate fracture. This is a relatively safe method, but also relies on sophisticated and expensive equipment that has a limited lifetime due to the degradation accompanying repeated firings.
In some applications, high explosives cannot be used due to regulatory restrictions and mechanical breaking means are impractical due to the material's location and/or high compressive strength. To this end, a variety of small charge breaking methods have been developed.
In U.S. Pat. No. 6,679,175, Gavrilovic teaches a propellant based small charge breaking system, including double-base propellants combined with ammonium nitrate that intend to solve the problems of fly-rock, noise, vibration, and the regulatory restrictions associated with high explosives. While this method offers a potential alternative to conventional means, it is not without drawbacks. The propellant formulas disclosed are known to be hygroscopic and have a high tendency to misfire, which is both costly and dangerous. In addition, the fracturing efficiencies disclosed, commonly expressed as the powder factor by those skilled in the art of the propellants, are relatively low, leading to higher drilling, boring, and cartridge costs.
In U.S. Pat. No. 6,145,933, Watson et al., describes the combined use of small high explosive charges and mechanical breaking means. This combined method provides improved efficiency over either method when used alone, but does not overcome the problems of regulatory restrictions and the high cost of transport and safety when using a high explosive material.
In GB 2,341,917 and GB 2,395,714, non-explosive compositions are disclosed for use in breaking systems, such as for breaking rock.
Deflagrating compositions used in small charge breaking applications are safer than high explosives, but can provide insufficient results due to the time required to produce enough gas to fracture the material. This delay in generating large quantities of gas inside a hole drilled into the material provides more opportunity for the gas that has been generated to escape by rifling and ejecting the stemming material instead of building up inside the hole. Thus, there continues to be a need for new safe and/or cost efficient and/or effective methods for breaking hard materials.
The present invention provides novel methods and compositions for breaking or fracturing hard materials that address one or more of the drawbacks present in alternate breaking systems and/or provides additional alternatives to conventional breaking methods. In particular, gas-generating compositions, fracturing systems and methods of using the foregoing are described.
Provided are compositions useful in fracturing a material such as rock or concrete and associated systems. The compositions when ignited have a burn rate that is less than the speed of sound in air at standard conditions. Systems typically include a composition within a cartridge which may have an igniter suitable to ignite the composition.
The composition typically exhibits at least two distinct values of change in burn rate with change in natural log of pressure. The composition typically burns at a lower rate when first ignited, and then burns at a much faster rate once combustion has proceeded and the combustion products produce a certain pressure in a hole in the material to be fractured.
The composition may comprise one or more of the following compositions (A), (B1), (C1), and/or D:
composition (A) comprises (a) at least one carbohydrate fuel; (b) at least one compound selected from the group consisting of potassium perchlorate, potassium nitrate, potassium chlorate, potassium sulfate and a perchlorate salt; (c) at least one substance selected from the group consisting of ferrosilicon, magnalium, aluminum metal and magnesium metal; and (d) less than 5 weight percent ammonium oxalate;
composition (B1) comprises (a) at least one carbohydrate fuel; (b) at least one compound selected from the group consisting of potassium perchlorate, potassium nitrate, potassium chlorate, potassium sulfate and a perchlorate salt; (c) at least one substance selected from the group consisting of ferrosilicon, magnalium, aluminum metal and magnesium metal; and (d) X weight percent ammonium oxalate, wherein X is less than 12 weight percent ammonium oxalate, and composition (B1) has a powder factor that is less than the powder factor of composition (B2), wherein composition (B2) is identical to composition (B1) with the exceptions composition (B2) comprises 12% ammonium oxalate and the sum of weight percentages of components (a), (b) and (c) in composition (B2) is reduced in total by 12−X;
composition (C1) comprises (a) at least one carbohydrate fuel; (b) at least one compound selected from the group consisting of potassium perchlorate, potassium nitrate, potassium chlorate, potassium sulfate and a perchlorate salt; (c) at least one substance selected from the group consisting of ferrosilicon, magnalium, aluminum metal and magnesium metal; and (d) X weight percent ammonium oxalate, wherein X is less than 12 weight percent ammonium oxalate, and composition (C1) has a powder factor that is less than the powder factor of composition (C2), wherein composition (C2) comprises 12 weight percent ammonium oxalate, about 37 weight percent potassium perchlorate, about 24 weight percent salicylic acid, about 26 weight percent ferrosilicon and about 1 weight percent borax; and
composition (D) comprises (a) at least one carbohydrate fuel; (b) at least one compound selected from the group consisting of potassium perchlorate, potassium nitrate, potassium chlorate, potassium sulfate and a perchlorate salt; (c) at least one substance selected from the group consisting of ferrosilicon, magnalium, aluminum metal and magnesium metal, wherein the ignited composition exhibits a first change in burn rate with change in ln(p) to a first pressure and a second change in burn rate with change in ln(p) at pressures greater than the first pressure, and wherein the second change in burn rate with change in ln(p) is greater than the first change in burn rate with change in ln(p).
Also disclosed is a method of fracturing a hard material such as rock or concrete, in which a composition as disclosed herein is inserted into a hole in the material, stemming material is placed over the composition, and the composition is ignited to produce gas, thus producing sufficient pressure to fracture the material.
Also disclosed is a method of fracturing a material, in which the method involves oxidizing a compound at a first change in burn rate with change in ln pressure within a hole in the material to produce a gas; containing the gas generated in the oxidizing step to attain a sufficient pressure within the hole such that a second change in burn rate with change in ln pressure occurs; and producing an additional amount of gas such that the pressure increases and the material fractures.
Also disclosed herein is a method of making a composition comprising:
(a) providing at least one carbohydrate fuel;
(b) providing at least one compound selected from the group consisting of potassium perchlorate, potassium nitrate, potassium chlorate, potassium sulfate and a perchlorate salt;
(c) providing at least one compound selected from the group consisting of ferrosilicon, magnalium, aluminum metal or magnesium metal;
(d) combining the compounds provided in steps (a)-(c) in amounts and under conditions sufficient to produce a composition having a tap density of about 0.8 g/cc to about 1.5 g/cc.
A number of variations of the compositions, systems, and methods above are discussed herein, including in the appended claims which form a part of this specification.
Breaking hard material such as rock and concrete is accomplished by the methods, systems and compositions disclosed herein. The methods, systems and compositions can be used in a wide variety of applications, including demolition and excavation applications, and are particularly beneficial as alternatives to high explosive blasting and/or mechanical fracturing or when commercial propellant charges provide insufficient breaking results.
The gas-generating compositions disclosed herein comprise oxidizer and fuel components that upon ignition deflagrate and burn sub-sonically even at elevated pressures, including but not limited to pressures up to about 4,000 psig. In contrast, highly explosive materials detonate, producing supersonic shock waves at atmospheric pressure.
Various gas-generating compositions disclosed herein differ from commercial propellants known to the inventors in that they do not have a tendency to rifle or expel stemming material when used in material breaking. While not wishing to be bound by theory, it is believed that various compositions disclosed herein, when ignited, may exhibit two (dual) or more distinct changes in burn rate as a function of the natural log of pressure (ln(p)) over the compositions' burn lifetime. That is, the compositions are believed to exhibit a first change in burn rate as a function of ln(p) to a first pressure and a second change in burn rate as a function of ln(p) at pressures greater than the first pressure, wherein the second change in burn rate as a function of ln(p) is greater than the first change in burn rate as a function of ln(p). As will be understood to those of skill in the art, a composition exhibits a dual burn rate if, over the burn life of the composition or at least between pressures ranging from about 100 psig to about 4,000 or from about 100 psig to about 2,000 psig or from about 500 psig to about 4,000 psig or from about 500 psig to about 2,000 psig or from about 600 psig to about 1,000 psig, the composition exhibits a first change in burn rate as a function of ln(p) to a first pressure and a second change in burn rate as a function of ln(p) at pressures greater than the first pressure, wherein the second change in burn rate as a function of ln(p) is greater than the first change in burn rate as a function of ln(p). Except for the inflection point indicating the identity of the first pressure beyond which the second change in burn rate as a function of ln(p) begins, positive or negative undulations in burn rate as a function of ln(p) over small pressure ranges, for example over a pressure range of 50 psig or under, are not considered distinct burn rates for the purposes of establishing a dual or more burn rate. An example of a composition exhibiting a dual burn rate is found in Example 1 and a plot of the composition's burn rate as a function of ln(p) is shown in
In one variation, the gas-generating compositions exhibit dual changes in burn rate as a function of ln(p) where the second change in burn rate as a function of ln(p) is at least about twice as great as the first change in burn rate as a function of ln(p). In other variations, the gas-generating composition exhibits dual changes in burn rate as a function of ln(p) where the second change in burn rate as a function of ln(p) is at least about 2 or 3 or 4 or 5 or 6 or 7 or 8 or 9 or 10 or 20 or 25 or 30 or 40 or 50 or greater than about 10 or greater than about 25 or between about 10 and 15 or between about 10 and 45 or between about 20 and 45 or between about 25 and 35 times greater than the first change in burn rate as a function of ln(p). In another variation, the compositions disclosed herein burn sub-sonically at pressures of about 5,000 psig or at pressures of about 10,000 psig or at pressures of about 15,000 psig or at pressures of about 20,000 psig and the compositions exhibit a first change in burn rate as a function of ln(p) to a first pressure and a second change in burn rate as a function of ln(p) at pressures greater than the first pressure and the second change in burn rate as a function of ln(p) is at least about 2 or 3 or 4 or 5 or 6 or 7 or 8 or 9 or 10 or 20 or 25 or 30 or 40 or 50 or greater than about 10 or greater than about 25 or between about 10 and 15 or between about 10 and 45 or between about 20 and 45 or between about 25 and 35 times greater than the first change in burn rate as a function of ln(p). In one variation, the gas-generating compositions burns sub-sonically at pressures of about 5,000 psig or at pressures of about 10,000 psig or at pressures of about 15,000 psig or at pressures of about 20,000 psig and exhibits more than two changes in burn rate as a function of ln(p). In compositions exhibiting more than two changes in burn rate as a function of ln(p), a plot of burn rate as a function of ln(p) will have more than one inflection point and will thus identify at least two or three or more than three pressure ranges at which the composition undergoes a change in burn rate as a function of ln(p).
Any of the compositions disclosed herein may exhibit at least a dual burn rate where the second or greater changes in burn rates as a function of ln(p) can be any of the values specified herein above, such as 30 times as great or more than the first change in burn rate as a function of ln(p).
The compositions' dual or more change in burn rate as a function of ln(p) is believed to result in greater volumes of gas production over the same period of time when compared to propellants that do not exhibit a dual change in burn rate as a function of ln(p) or exhibit a lesser burn rate as a function of ln(p) when compared to a first and/or a second change in burn rate as a function of ln(p) exhibited by the compositions disclosed herein. Because the gas-generating compositions and propellants for use in fracturing material are generally ignited under confined conditions, such as in a hole in the material to be fractured and covered with stemming material, the gas-generating compositions having a dual burn rate are believed to build up more pressure in the form of gas during the same amount of time as compared to propellants lacking the dual burn rate mechanism burning under identical conditions. The present compositions' faster build-up of pressure with time is believed to be at least partly responsible for their decreased incidence of rifling and/or seepage of the gas through the stemming material, and in their ability to provide faster, more efficient breaking.
Various compositions disclosed herein generate a large volume of gas in a short time period as compared to compositions not exhibiting a dual or more burn rate. The compositions' generation of a large volume of gas over a small time period is believed to prevent the stemming material from rifling because the stemming material does not have the time or power to be displaced or ejected from the hole. Because the present compositions are not high explosives, the benefits of fast, efficient breaking are obtained without compromising safety and its associated costs.
In one variation, the compositions for use in the systems and methods described herein comprise a fuel, an oxidizer and a metal or alloy, provided that the composition comprises less than about 10 weight percent or less than about 8 weight percent or less than about 6 weight percent or less than about 5 weight percent or less than about 4 weigh percent or less than about 3 weight percent or less than about 2 weight percent or less than about 1 weight percent or is substantially free of or is essentially free of or is completely free of ammonium oxalate or other low-energy nitrogen containing fuel such as oxamide or guanadine nitrate. In another variation, the compositions for use in the systems and methods described herein generally comprise a fuel, an oxidizer and a metal or alloy, provided that the composition comprises less than 12 weight percent ammonium oxalate or other low-energy nitrogen containing fuel such as oxamide or guanadine nitrate and the ignited composition generates gas sufficient to fracture hard material. In another variation, the compositions for use in the systems and methods described herein generally comprise a fuel, an oxidizer and a metal or alloy, provided that the ignited composition exhibits a first change in burn rate as a function of ln(p) to a first pressure and a second change in burn rate as a function of ln(p) at pressures greater than the first pressure, and wherein the second change in burn rate as a function of ln(p) is greater than the first change in burn rate as a function of ln(p). In another variation, the compositions for use in the systems and methods described herein exhibit at least a dual burn rate when ignited and generally comprise a fuel, an oxidizer and a metal or alloy, provided that the composition comprises less than about 10 weight percent or less than about 8 weight percent or less than about 6 weight percent or less than about 5 weight percent or less than about 4 weigh percent or less than about 3 weight percent or less than about 2 weight percent or less than about 1 weight percent or is substantially free of or is completely free of ammonium oxalate or other low-energy nitrogen containing fuel such as oxamide or guanadine nitrate. In another variation, the compositions for use in the systems and methods described herein exhibit at least a dual burn rate when ignited and generally comprise a fuel, an oxidizer and a metal or alloy, provided that the composition comprises less than 12 weight percent ammonium oxalate or other low-energy nitrogen containing fuel such as oxamide or guanadine nitrate and the ignited composition generates gas sufficient to fracture hard material.
Optional additional components may be added to the gas-generating compositions, including substances known to modify the burn rate of a gas-generating composition, such as substances known to increase the burn rate. The gas-generating composition may comprise oxidizer and fuel components selected for their low cost and/or low hygroscopicity and/or long shelf life and/or favorable burn rate and/or gas generation properties. In one variation, the gas-generating composition comprises oxidizer and fuel components that are selected for their low cost and low hygroscopicity and long shelf life and favorable burn rate and gas generation properties. By selecting materials having a low hygroscopicity, the misfires common in certain existing compositions are reduced. Misfires are often costly due to the loss of cartridges, and dangerous due to the risks associated with live cartridge extraction.
Oxidizers and/or fuels and/or additional components having a hygroscopicity point greater than 90% are known to have lower chances of absorbing water during manufacture and storage. Water and moisture in a gas-generating composition can cause a reduction in burn rate and a greater chance of misfires. In addition, low hygroscopicity is believed to contribute to the long shelf life of the gas-generating compositions, which can be stored for at least up to several years. This stability over time is beneficial, especially when compared to alternative formulations for fracturing material, such as those consisting of ammonium nitrate and nitrocellulose, which are known to be hygroscopic and exhibit a relatively short shelf-life.
Oxidizer
An oxidizer having one or more or all of the following properties may be used in the gas-generating composition: high oxygen content and/or high reactivity and/or low hygroscopicity which leads to a long shelf life. Such oxidizers include, but are not limited to, inorganic perchlorate, chlorate, nitrate and sulfate salts. For instance, potassium perchlorate, potassium chlorate, potassium nitrate, and potassium sulfate may be used in the gas-generating compositions. Salts composed of sodium ions and ammonium ions are known to be hygroscopic and are not preferred, though if the gas-generating composition is contained in a cartridge that is suitably sealed against water ingress and/or egress, they can be made to perform suitably and may be used in the gas-generating composition. Other oxidizers known to those of skill in the art can be used, provided that the resulting gas-generating composition exhibits the gas-generating properties disclosed herein, such as a dual burn rate. In one variation, an oxidizer such as potassium perchlorate is used as the oxidizer due to its high oxygen content and high reactivity and low hygroscopicity which leads to a long shelf life.
Fuel
The gas-generating composition will generally employ a fuel having one or more or all of the following properties: low hygroscopicity and/or low cost and/or suitable reactivity with the selected oxidizer components. In one variation, a fuel such as lactose is used as the fuel component due to its low hygroscopicity and low cost, and suitable reactivity with the selected oxidizer components. Fuels that may be used in the gas-generating compositions include, but are not limited to, carbohydrate fuels, including monosaccharides, oligosaccharides and polysaccharides as well as substances derived from monosaccharides by reduction of the carbonyl group (alditols), by oxidation of one or more terminal groups to carboxylic acids, or by replacement of one or more hydroxy group(s) by a hydrogen atom, an amino group, a thiol group or similar heteroatomic groups or any hydrate of any of the foregoing or listed anywhere herein, such as a monohydrate or dehydrate thereof. The carbohydrate fuel can be a sugar, such as a monosaccharide or oligosaccharide, including an aldose, dialdose, aldoketose, ketose and diketose, as well as deoxy sugars and amino sugars, and their derivatives. The carbohydrate fuel can be an oligosaccharide, including a trisaccharide, tetrasaccharide, pentasaccharide, or a polysacharide including homopolysaccharide or heteropolysaccharide, including any hydrate thereof, such as a monohydrate. Other suitable fuels include carbohydrates and starches such as lactose, sucrose, glucose, fructose, ascorbic and erythroscorbic acids, and wheat and potato starches. Carbohydrate fuels also include derivatives of any of the forgoing compounds, meaning compounds that are derivable from carbohydrate starting materials.
In one variation, the carbohydrate fuel is used with a perchlorate oxidizer, such as potassium perchlorate. The carbohydrate fuel and perchlorate oxidizer can be any of the fuels and perchlorates disclosed herein, such as a composition including a saccharide fuel and perchlorate oxidizer, a monosaccharide fuel and perchlorate oxidizer or a lactose, sucrose, glucose or fructose fuel and a perchlorate oxidizer. In one variation, lactose or a hydrate thereof, such as lactose monohydrate, is used with the oxidizer potassium perchlorate.
Various other components described in the section below entitled ‘Additional Components’ may also act as fuels and will be readily recognizable as such by those of skill in the art.
Additional Components
Additional components may optionally be added to the gas-generating composition, for example, to increase the burn rate or to act as oxidizers in certain instances, which may improve the fracturing efficiency of the proposed system. Other additional components may act as catalysts which tend to increase the rate of gas generation. Such catalysts include but are not limited to metal oxides such as iron oxide and copper oxide, and organometalics such as ferrocene. A composition with a high fracturing efficiency will tend to reach a greater peak pressure within the drill hole before initiating fracture. By more rapidly building up pressure, the stemming material is less likely to be ejected, and the available energy in the form of pressure that can be used to fracture and move the material is greater
Additional components that may be added to the gas-generating composition may be components known to increase the rate of gas generation. Such additional components include, but are not limited to, metal benzoate, nitrobenzoate, and gluconate salts, including sodium benzoate, sodium nitrobenzoate, sodium gluconate, and the analogous salts of potassium ions. Such additional components have been found to increase the burn rate while at the same time serving as fuel components that are able to contribute to the total volume of gas generated.
Additional components that may be added to the gas-generating composition may be components that are not known to increase the gas generation but may, for instance, burn exothermically and increase the heat of the reaction when the composition is ignited. Such additional components have been found to function suitably as burn rate enhancers, but add only heat to the reaction and do not increase the volume of gas generated. By adding heat to the reaction, the burn rate and therefore gas generation rate is increased. Additionally, the heat functions to expand the available gas, thereby increasing the pressure and improving the fracturing efficiency.
Such additional components include, but are not limited to, alkali metals or salts thereof, alkaline earth metals or salts thereof, transition metals or salts thereof, other metals or salts thereof or mixtures or alloys of the same that are known by those of skill in the art to be relatively safe to handle. For instance, ferrosilicon, magnalium, aluminum, and magnesium and the like are relatively safe to handle whereas lithium metal is known to be highly flammable and explosive when exposed to air.
Ferrosilicon is believed to act as a reducing agent in the gas-generating compositions. Ferrosilicon, in the presence of an oxidizer such as perchlorate, is believed to receive an oxygen from the perchlorate oxidizer, resulting in an exothermic reaction which gives off a great quantity of heat that increases the burn rate of the composition.
Metal alloys for use in the gas-generating compositions as additional components include any alloys having the properties discussed above. Alloys comprising elements or metals selected from iron, silicon, aluminum, magnesium, titanium and zirconium are intended as additional components, such as components that achieve the desired burn rate characteristics disclosed herein. Metal alloys include single alloys or composites or two or more alloys. Examples of suitable metal alloys include magnalium and alloys created from iron, silicon, aluminum, magnesium, titanium and zirconium. Ferroalloys, including but not limited to ferrosilicon, ferromanganese, magnesium ferrosilicon, ferrochromium, ferromagnesium, ferrotitanium, ferroboron and ferrophosphorous are also metal alloys acceptable for use as additional components. Metal alloys may be present in the gas-generating composition as any alloy composition. For instance, ferrosilicon can be used in the gas-generating composition as an alloy of 50/50 iron/silicon or as other ratios such as 15, 45, 75 or 90% silicon. In one variation, the gas-generating composition comprises ferrosilicon as about a 50/50 iron/silicon alloy.
A single gas-generating composition may comprise more than one additional component described herein. For instance, the gas-generating composition may comprise at least two metal alloys or at least one metal salt and at least one metal alloy. For instance, a gas-generating composition may comprise both an alkaline earth metal or other metal alloy, such as magnalium, and a transition metal alloy, including a ferroalloy, such as ferrosilicon. In one variation, the gas-generating composition may comprise both an alkaline earth metal or other metal alloy and a transition metal alloy, such as a gas generating composition comprising both ferrosilicon and magnalium.
Because of the high temperatures and pressures achieved within the drill hole, which is discussed in more detail under the heading ‘hole’ below, ferrosilicon and magnalium have been found to be a useful combination in the gas-generating composition. While not wishing to be bound by any theory, it is believed that magnalium is reduced in the presence of ferrosilicon at high temperature and pressure, thus acting as an oxidizing agent, and then later oxidized again to liberate heat when the thermodynamic conditions permit. Theory aside, the inventors have found this combination to have a high fracturing efficiency in the gas-generation composition and fracturing system.
Gas generating compositions comprising at least one metal powder have been found to be powerful gas-generating compositions. The more powerful gas generating compositions, including compositions comprising at least one metal powder such as compositions comprising aluminum and/or magnesium powder, are suitable for applications where the material to be fractured is difficult to break. Such materials include embedded material or material having only one free face. These materials can require significantly more power, such as about five times or more power, to effect fracturing. Therefore, compositions with increasing amounts of metals, including high energy metals like aluminum and magnesium, find use in breaking or fracturing hard materials such as embedded rock for mass excavation applications.
In general, a gas-generating composition can be prepared by selecting at least one fuel, at least one oxidizer and at least one additional component disclosed herein. By selecting the disclosed fuel, oxidizer and additional components for the gas-generating composition, an improvement over existing gas-generating compositions can be achieved. In particular, the gas-generating compositions disclosed herein may have improved fracturing efficiencies and/or longer shelf life and/or a reduced tendency to misfire. In one variation, the gas generating composition exhibits improved fracturing efficiency and a longer shelf life and a reduced tendency to misfire.
Gas-generating composition components can be present in the gas-generating composition in any amount, so long as the composition retains its ability to act as a gas-generator with a sufficient burn rate, such as any of the particular burn rates and mechanisms disclosed herein.
A fuel component may be present in the gas-generating composition in an amount ranging from 5% to 45%, from 5% to 40%, from 5% to 35%, from 5% to 30%, from 5% to 25%, from 5% to 20%, from 5% to 15%, from 5% to 10%, from 10% to 45%, from 15% to 45%, from 20% to 45%, from 25% to 45%, from 30% to 45%, from 35% to 45%, from 40% to 45%, from 10% to 45%, from 10% to 40%, from 10% to 35%, from 10% to 30%, from 10% to 25%, from 10% to 20%, from 10% to 15%, from 15% to 45%, from 15% to 35%, from 15% to 30%, from 15% to 25%, from 15% to 20%, from 20% to 45%, from 20% to 30%, from 25% to 35%, and from 20% to 25% by weight.
An oxidizer may be present in the gas-generating composition in an amount ranging from 30% to 85%, from 30% to 80%, from 30% to 75%, from 30% to 65%, from 30% to 60%, from 30% to 55%, from 30% to 50%, from 30% to 45%, from 30% to 40%, from 30% to 35%, from 35% to 80%, from 35% to 75%, from 35% to 70%, from 35% to 65%, from 35% to 60%, from 35% to 55%, from 35% to 50%, from 35% to 45%, from 35% to 40%, from 35% to 35%, from 40% to 80%, from 40% to 75%, from 40% to 70%, from 40% to 65%, from 40% to 60%, from 40% to 55%, from 40% to 50%, from 40% to 45%, from 45% to 80%, from 45% to 75%, from 45% to 70%, from 45% to 65%, from 45% to 60%, from 45% to 55%, from 45% to 50%, from 50% to 80%, from 50% to 75%, from 50% to 70%, from 50% to 65%, from 50% to 60%, from 50% to 55%, from 55% to 80%, from 55% to 75%, from 55% to 65%, from 55% to 60%, from 60% to 80%, from 60% to 75%, from 60% to 70%, from 60% to 65%, from 65% to 80%, from 65% to 75%, from 65% to 70%, from 70%-80%, and from 70% to 75% by weight.
An additional component, such as a component that adds heat to the ensuing reaction of the gas-generating composition or acts as an oxidizer, may be present in the gas-generating composition in a range from 0% to 30%, from 0% to 25%, from 0% to 20%, from 0% to 15%, from 0% to 10%, from 0% to 5%, from 5% to 30%, from 5% to 25%, from 5% to 20%, from 5% to 15%, from 5% to 10%, from 10% to 30%, from 10% to 25%, from 10% to 20%, from 10% to 15%, from 15% to 30%, from 15% to 25%, from 15% to 20%, from 20% to 30%, and from 20% to 25% by weight.
In general, when the fuel, oxidizer and additional component(s) chosen for a given composition are combined, the total weight percentages of the fuel, oxidizer and additional component(s) will be a value of about 100 total weight percent. As known to those of skill in the art, additional components may be added to the composition, including but not limited to flow agents or binders, such as a flow agent or binder in an amount that is less than about 5 weight % or less than about 3 weight % or about 1 weight % of the total weight of the composition.
In one variation, the oxidizer and fuel combination is potassium perchlorate and lactose, respectively. Alternative oxidizer and fuel combinations may be employed in the gas-generating composition in order to achieve similar, though sometimes slightly less effective, results.
The following Table 1 lists gas-generating compositions. The compositions below may optionally comprise a second or more additional component. For instance, it is intended that every composition listed in Table 1 can further comprise at least one of ferrosilicon, magnalium, aluminum, magnesium, sodium benzoate, sodium nitrobenzoate, sodium gluconate, potassium benzoate, potassium nitrobenzoate, potassium gluconate or iron oxide, the same as if each combination were individually and separately listed. By way of example, the compositions may comprise two additional components, such as a composition comprising both ferrosilicon and magnalium, or any other combination of more than one additional component. In addition, the compositions below may optionally comprise other components, such as a flow agent, for example, Neosil. All such additional gas-generating compositions are described herein to the same extent as if each and every possible combination is individually and separately listed.
Any of the compositions in Table 1 or elsewhere may be present in a gas-generating composition in any weight percentage, such as the weight percentages described above. The total weight percentage of a composition is generally about 100. Accordingly, components of a composition are generally chosen in weight percentages such that the total weight percentage of a given composition is about 100. For instance, the gas-generating composition can contain a fuel, oxidizer and additional components in the weight percentage ranges shown in Table 2, and may contain further components, such as less than 5 weight percent or about 1 weight percent flow agent such as Neosil, provided that the total sum of weight percentages of all components of the composition is 100 or about 100%.
Weight percentages are generally measured by the weight of a commercially available chemical composition, with no drying steps or extra precautions being taken during storage or weighing to guard against absorption of moisture, such as from moisture in the air. In this way, the dry weight percentage of a given component in a composition may vary slightly according to small changes in moisture content of the commercially available component.
Table 2 lists representative examples of fuel, oxidizer and additional components, although it is recognized that all fuel, oxidizers and additional agents disclosed herein may be used in the gas-generating compositions in the ranges indicated.
Additional examples of gas-generating compositions are listed below in Table 3 as gas-generating compositions A-H. In one variation, each of the weight percentages listed in Table 3 can be increased or decreased by about 30% or by about 25% or by about 20% or by about 15% or by about 10% or by about 5% of the values listed. For instance, in one variation, a composition can comprise 56 weight %±10% potassium perchlorate such that potassium perchlorate may be present in the composition in about 50 weight % or about 62 weight %. In another variation, each of the weight percentages listed in Table 3 can be increased or decreased by between about 5-10% or between about 5-20% or between about 5-30% or between about 10-20% or between about 10-30% or between about 15-25% or between about 15-30% or between about 20-40% or between about 30-40% of the values listed. In yet another variation, each of the weight percentages listed in Table 3 can be increased or decreased by less than 30% or less than 25% or less than 20% or less than 15% or less than 10% or less than 5% or less than 3% of the values listed.
Composition Preparation
The gas-generating compositions may be prepared in any suitable mixing apparatus known to those of skill in the art, such as an apparatus comprising a rotating stainless steel drum with no mixing fins, or any powder mixing apparatus of suitable size that is commonly known to those skilled in the art. The compositions are generally in the form of a powder, which can be loose, loosely packed or packed to at least a density that allows shaping of the powder composition into a desirable shape, such as a bar or tapered shape such as a cone.
The gas-generating composition can be made in any batch size, such as about a 10 or 20 or 30 or 40 or 50 or 60 or 70 or 80 or 90 or 100 pound or more batch size. In preparing the gas-generating compositions, it was found that increasing the batch size in the mixing apparatus from 40 lb to 100 lb, corresponding to the total weight of the mixture, had the effect of increasing the powder density by as much as 40%. Therefore, a larger mixing batch is preferred. It is believed that a higher density of powder serves to increase the burn rate and reduce the gas volume available in the cartridge, thereby increasing the fracturing efficiency of the cartridge. By scaling up the mixing apparatus to larger batch sizes, it is expected that the powder density may increase further, and the beneficial properties obtained therein may be further improved.
In one variation, the composition is made such that at least a portion of the composition exhibits a tap density of about 0.5 g/cc or about 0.6 g/cc or about 0.7 g/cc or about 0.8 g/cc or about 0.9 g/cc or about 1.0 g/cc or about 1.03 g/cc or about 1.5 g/cc or greater than about 1.5 g/cc or greater than about 1.0 g/cc or between about 0.06 g/cc and about 1.8 g/cc or between about 0.08 g/cc and about 1.6 g/cc or between about 1.0 g/cc and about 1.4 g/cc or between about 1.1 g/cc and about 1.3 g/cc or between about 1.2 g/cc and about 1.8 g/cc or between about 1.2 g/cc and about 1.6 g/cc or between about 1.0 g/cc and about 2.0 g/cc or between about 1.0 g/cc and about 3.0 g/cc or less than about 2.0 g/cc or less than about 1.8 g/cc or less than about 1.5 g/cc.
A method of making a composition is also described wherein the method comprises the steps of providing at least one fuel, such as a carbohydrate fuel, providing at least oxidizer, such as potassium perchlorate, potassium nitrate, potassium chlorate, potassium sulfate or a perchlorate salt, providing at least one additional component, such as of ferrosilicon and/or magnalium and combining the compounds in amounts and under conditions sufficient to produce a composition having a tap density according to any of the values described herein, such as a tap density greater than about 1.2 g/cc.
System
In general, a gas-generating system comprises a gas-generating composition within a container, such as cartridge. The system can also include a material to be fractured such that the gas-generating system comprises a container, a gas-generating composition within the container and a material to be fractured. In addition, the system can also include a stemming material such that the gas-generating system comprises a container, a gas-generating composition within the container, a material to be fractured and a stemming material.
The gas-generating composition system may comprise several component parts, each of which is discussed in turn below. Examples of the system are found in
Referring to
Material
The gas-generating compositions may be used in the systems and methods disclosed herein to fracture a material. The material can be any material for which fractioning is desired. The material to be fractured includes any hard material such as solid or semi-fractured rock, concrete, granite, marble, hard clay, sandstone, limestone, dolomite, basalt, mineral deposits, diamond, gold or silver, precious or semi-precious stone and quartz. The compositions are useful in certain applications, including but not limited to, excavation of hard materials in such applications as surface mining, open pits and quarries, earth moving and allied construction works, and in civil demolition projects. The compressive strengths of the material can be greater than 20 MPa, and often greater than 100 MPa. When the compressive strengths exceed 100 MPa, mechanical breaking such as by impact hammers becomes impractical and costly, making the proposed system a more desirable choice. The concrete materials may include foundations, piers, and reinforced structural concrete as found in bridges or other structures.
Charging Material with Gas-Generating Composition:
In one variation, the material to be fractured is charged with a gas-generating composition by positioning the gas-generating composition in a hole present in the material. The gas-generating composition may be contained within a cartridge, which is described in more detail below under the section entitled ‘cartridge’. Positioning the gas-generating cartridge allows control over factors such as orienting the igniter, such as at the bottom of the hole, keeping moisture out of the composition, and preventing mixing between the stemming material and the powder. However, the gas-generating compositions can be used as a loose powder and/or shaped powder, including a bar of powder. A bar of powder can be made with a mold as known to those of skill in the art. Generally a very small amount of moisture is added to the gas-generating composition to allow it to clump or bind in a mold. After the moistened powder is pressed into a mold and the desired shape is obtained, the shaped powder can be baked to dryness to ensure that moisture has been driven from the powder prior to use.
Hole
The material to be fractured can be charged with the gas-generating composition by placing the composition in a hole present or made in the material. The hole may be created by any methods known to those skilled in the art, such as drilling using a pneumatic or impact drill equipped with a steel drill. The depth of the hole from the surface of the material may be any depth that allows a desired volume of the material to be fractured. In one variation, the hole is at least about 2 feet deep from the surface of the material to provide sufficient length for the stemming material, and may be deeper to allow for a greater volume of material to be fractured. In one variation, the hole length is greater than 10 or about 10 or about 8 or about 6 or about 4 or about 3 or about 1 times the length of the cartridge.
The length of the cartridge can vary, and can hold varying amount of gas-generating composition, depending on both the length and diameter of the cartridge. For instance, a cartridge can be about 1½″ or about 2″ or about 2¼″ or about 5″ or about 10″ or about 12″ or about 15″ or about 18″ or more in length. A cartridge with a longer length may contain the same amount of material as a cartridge of shorter length, provided that the diameter of the cartridge is smaller in the longer cartridge than in the shorter cartridge. For instance, a 2¼″ in length cartridge may contain about 50 g of gas-generating composition, a 15″ in length cartridge may contain about 600 g of gas-generating composition, and an 18″ in length composition may contain about 300 g of gas-generating composition. In this example, the 18″ cartridge has a diameter that is smaller than the diameter of the 15″ in length cartridge.
In order for gas-generating system to be optimized, care is usually taken to minimize the available volume within the cartridge and drill hole. By reducing the free volume of air, the expanding gas is able to perform more work on the surrounding rock by achieving a higher total pressure before a fracture occurs, which releases the gas.
To this end, the diameter of the drill hole that will contain the gas-generating composition or cartridge may be a diameter that minimizes the available volume with in the drill hole. In one variation, the drill hole will not exceed 0.75″ more than the outer diameter of the cartridge, preferably less than 0.5″ more, and more preferably less the 0.25″ more than the outer diameter of the cartridge housing. In one variation, a hole is created having a diameter of about 1¼″ and in another variation, a hole is created having a diameter of about 2″. In yet another variation, the drill hole is no greater than about 2″. In one variation, a cartridge of diameter of about 1⅛″ is used in connection with a drill hole having a diameter of about 1¼″. In another variation, a cartridge having a diameter of about 1¾″ is used in connection with a drill hole having a diameter of about 1⅞″. In yet another variation, the ratio of cartridge diameter to drill hole diameter is about 0.5 to about 0.9.
The depth of the drill hole can be any depth that is required to fracture the material. The depth of the drill from the surface of the material to be fractured can be, for example, about two or about three times the length of the cartridge containing the gas-generating composition. The depth of the hole is generally a depth that is sufficiently deep that, e.g., the stemming material effectively seals the hole over the short time period required for the composition to ignite and generate a large volume of gas to fracture or break the material.
More than one cartridge can be place in a single hole and multiple holes may be created for a single cartridge. When multiple holes are created for use with a single cartridge, one of the holes will contain the cartridge and the remaining holes act as weak spots. For instance, a series of holes can be created in a material to be fractured, where every other hole in the series contains a cartridge. In this way, fracturing or breaking occurs toward the weak spots formed by the holes that are not charged with cartridges, allowing the user to control the breakage and create a straight line split along the line of drill holes. If multiple cartridges are used in a single hole, a stemming material can be placed between the charges. As known to one of skill in the art, placing a stemming material between multiple charges tends to distribute the gas pressure evenly along the length of the hole, leading to improved fracturing efficiency in longer holes. If the energy is concentrated at the bottom of the hole for example, large un-fractured chunks of material to be fractured could remain unbroken near the surface of the material. Multiple charges include two or three or four or five or six or more charges for use in a single hole.
In one variation, a hole is created in the material to be fractured such that the “free volume” or total volume of the hole minus the volume taken up by the gas-generating carrier, such as a cartridge, is less than about 55% of the total volume. In one variation the free volume inside the hole less than about 65% or less than about 50% or less than about 40% or less than about 30% of the total volume. The free volume is generally filled with stemming material.
Cartridge
The gas-generating composition may be contained in any suitable way, such as in a cartridge, which aids in the ease of transporting and/or storing and/or charging and/or igniting the gas-generating composition. In one variation, the gas-generating composition may be contained in a cartridge, which aids in the ease of transporting and storing and charging and igniting the gas-generating composition. In one variation, the cartridge is constructed such that the cartridge does not break in the conditions in the hole until the pressure inside the cartridge reaches the first pressure indicating a change in burn rate as a function of ln(p).
The cartridge can be any shape, including a bar, a rod, a cone, a sphere, a trapezoid or any rectangular, square or tapered shape having any number of sides.
In one variation, the cartridge has at least one closable end. The cartridge can include a housing, such as in the shape of a tube, made of or coated by any material, including water-proof or water-repellant materials such as high-density polyethylene (HDPE). The wall thickness of the cartridge can be any thickness, and will vary according to the cartridge material. For example, a HDPE or other polymer-based cartridge can have a wall thickness of approximately 0.05″. It is desirable for the cartridge to have sufficient strength so as to be durable during transport and loading, but not so strong as to allow high-pressure gasses to build-up in the case of an accidental ignition outside the drill hole. The wall thickness may be less than 0.2″, less than 0.1″, or less than 0.05″. It is intended for the cartridge to pass the UN classification of 1.4S or 1.4C, meaning there is no significant danger for explosion while the cartridge is being transported. By limiting the strength of the cartridge, the tendency of creating an explosion is reduced and the beneficial classification of 1.4 can be obtained.
In one variation, the cartridge can be a tube having at least one closable end, which can be permanently closed, such as when a tube is manufactured as a single unit with at least one closed end, or removably closed, such as when a hollow tube can be closed by one or more end caps that can be put on or taken off of the open ends of the tube. The end caps can be inserted into the inner hollow portion of a cartridge tube to create a seal or can be fitted over the housing body. If the cartridge has removable ends, any closable end can be employed, including friction or other suitable end caps that screw or clamp or glue into place. In one variation, the cartridge is closed with end caps that are also comprised of HDPE, and which may have 1 or 2 or more friction ribs to hold the caps in place and create a seal.
When an igniter wire is used, a hole can be created in an end cap, such as punched or drilled into one cap to allow an igniter wire, which is discussed in more detail below, to pass through. The hole is typically just large enough to allow the thickness of the wire to pass through. Once the igniter wire is in place, a bead of hot glue, silicone, or epoxy may be applied to the area to seal the hole against the passage of moist air and water. The glue may be allowed to seep into the hole and create a tight seal up into and around the top portion of the cartridge. Care is often taken to minimize the available volume within the cartridge and drill hole. By reducing the free volume of air, the expanding gas is able to perform more work on the surrounding rock by achieving a higher total pressure before a fracture occurs, releasing the gas.
The gas-generating composition can be inserted into the cartridge in loose powder form or can be shaped, for instance, into a bar. When the cartridges are filled with powder gas-generating compositions, the free space left in the cartridge is generally less than about 5 or less than about 10%, but can be as much as about 20%.
For a cartridge containing a loose powder form of the gas-generating compositions, the igniter, ignition wire and black powder wick may be inserted into the loose powder. Generally, the ignition wire and igniter are inserted into the cartridge via a hole in an end cap. The igniter can then be attached to the wick, such as a black powder wick, via a tie wrap, a string, an adhesive or any other material that allows the wick to stay in proximity to the igniter. The wick can be, e.g., about 1-5 inches in length, or about 2 or about 3 or about 4 inches in length. While not wishing to be bound by theory, it is believed that the igniter generally ignites both the wick and the gas-generating composition. However, a close proximity of the wick to the igniter decreases the incidence of misfires in that even if the gas-generating composition powder were to move away from the igniter, such as could happen during movement involved in transport, the wick when ignited by the igniter will ensure ignition of the composition.
Igniter Wire
The wire extending from the electric igniter out of the cartridge through the end cap is preferably 22 gauge or thicker to prevent breakage during loading of the cartridge and the compression of the stemming material. The igniter wire can be extended as far as necessary to provide for a safe distance to ignite the gas-generating formula, typically a few hundred feet. In general, a cartridge includes about 10 or about 15 feet of igniter wire extending from the cartridge, enabling a cartridge placed into a drill hole to have at least some igniter wire exposed outside of the hole. In one variation, multiple cartridges are linked together via their extension wires. The ignition wires are generally connected to a power source or interlinked with each other by stripping at least a portion of an outer coating of a wire and contacting the wire to the power source or another ignition wire, such as by twisting two wires together. However, the ignition wires may also comprise a quick fit connector or plug/socket connection to connect the ignition wire to a power source or to another ignition wire.
Sealing
An optional bead of hot glue, epoxy, or silicone, or similar material may be used to seal the cartridge from water egress. The entire cartridge can be dipped into a rubber-like substance, or encased in a plastic bag before loading into the hole to seal out any standing water which may be present at the bottom of the hole or elsewhere.
Stemming
Once the material to be fractured is charged with the gas-generating composition, e.g., by placing the sealed cartridge equipped with a wire into a hole of the material as described above, the hole is covered using stemming material, such as aggregate stone or other composition commonly known to those skilled in the art. The stemming material contains the gases from the ignited gas-generating composition in the hole for a time sufficient to cause fracturing of the rock.
The stemming material can be any material that is stable under the conditions present in the hole during ignition and deflagration. Examples of suitable stemming material include resin, water-based gel, cementitious material, grout, concrete, metal or composite bar, clay, gravel, sand, and dirt. One variation of the stemming includes coarse damp sand composition having grit ranging from 15 to 25. Other stemming compositions may include a rubber plug filled with sand, or fly ash in combination with aggregate stone. When using unconsolidated stemming material such as wet gravel, sand or dirt, a firm compaction of the stemming composition by hand during the loading process using a wooden or steel rod can help prevent the stemming composition from rifling out of the hole, as known to those skilled in the art. Due to the ability of the gas-generating compositions to generate gas sufficient to fracture material in a shorter time than is known for other deflagrating materials, wet sand is generally a sufficient stemming material and does not experience a high incidence of rifling. A blast mat known to those of skill in the art can be placed over the stemmed hole.
Igniter
Ignition of the gas-generating composition may occur by methods known in the art. An igniter for use in the system can be of any suitable design, and can be electronic, electric or non-electric and can ignite a material in any way, such as electrically, thermally or by generating a spark. The igniter can include a timer that can control ignition time and delay ignition until a pre-programmed time and can also include a microprocessor and/or memory. In one variation, the igniter is used in connection with ignition wires. In another variation, the igniter is remotely activated and does not require use of ignition wires.
In one variation, the igniter is an electric igniter, such as an electric igniter of a pyrotechnic composition. Ignition of the gas-generating composition using an electric igniter allows ignition at a safe distance from the material to be fractured, generally several hundred feet or more.
Black Powder
An electric igniter has been found to be sufficient to ignite the gas-generating pyrotechnic formula within the cartridge. However, the presence of a wick, such as a black powder wick connected to the igniter has been found to reduce the tendency for misfires, which can be a dangerous and costly situation given the time required for extraction and the expense of a lost cartridge. The black powder wick is typically rolled paper containing black powder, approximately 2″ to 4″ long. While not wishing to be bound by any theory, it is believed that the relatively fast burn rate of the black powder wick rapidly ignites the first several inches of the gas-generating composition after ignition, allowing the heat and pressure in the cartridge to rise more rapidly than by the electric ignition alone, which in turn increases the burn rate of the remaining gas-generating composition. By achieving this small improvement in the time to peak pressure, it is believed that the fracturing efficiency is thus improved. Furthermore, in cases where the electric igniter would not otherwise be in contact with the gas-generating composition due to settling, manufacturing defects or improper orientation of the cartridge in the hole (upside down), the extended black powder wick serves to ensure proper ignition.
The wick can be made of other materials, including any of the black powder substitutes known to those of skill in the arts, such as Pyrodex®, Triple Seven®, Cordite, Ballistite or any material having the desired characteristics of a fast burn-rate at atmospheric pressure and a low ignition temperature (<500 C).
The systems disclosed can be used in a method of breaking or fracturing hard materials. While not wishing to be bound by theory, the gas-generating systems disclosed herein are believed to break or fracture hard material by creating or enhancing structural discontinuities or other weak spots within the material, resulting in material breaks and fractures. The forces created by the gas-generating compositions within the material create, disturb or otherwise act on weak spots within the material.
In one variation, a method for fracturing material involves creating a hole in the material, inserting a cartridge with a gas-generating composition within the cartridge into the hole, at least partially filling the hole with stemming material and igniting the composition. The gas-generating compositions for use in the methods can be any composition described herein, including a composition that comprises (a) at least one fuel, such as a carbohydrate; (b) at least one oxidizer, such as a compound selected from the group consisting of potassium perchlorate, potassium nitrate, potassium chlorate, potassium sulfate and a perchlorate salt; (c) at least one additional component, such as a compound selected from the group consisting of ferrosilicon, magnalium, aluminum metal and magnesium metal and (d) less than 5 weight percent ammonium oxalate. The gas-generating compositions for use in the methods can also be a composition comprising (a) at least one fuel, such as a carbohydrate; (b) at least one oxidizer, such as a compound selected from the group consisting of potassium perchlorate, potassium nitrate, potassium chlorate, potassium sulfate and a perchlorate salt; (c) at least one additional component, such as a compound selected from the group consisting of ferrosilicon, magnalium, aluminum metal and magnesium metal and (d) less than 12 weight percent ammonium oxalate, wherein the ignited composition generates gas sufficient to fracture the material. The gas-generating compositions for use in the methods can also be a composition that, when ignited, exhibits a first change in burn rate as a function of ln(p) to a first pressure and a second change in burn rate as a function of ln(p) at pressures greater than the first pressure, and wherein the second change in burn rate as a function of ln(p) is greater than the first change in burn rate as a function of ln(p).
In one variation, the method comprises the steps of charging a material to be fractured with a gas-generating composition and igniting the gas-generating composition. The method may comprise the steps of placing a cartridge filled with gas-generating composition into a hole located in the material to be fractured, and igniting the gas-generation composition. Any one or more additional steps may be employed, such as the steps of filling a cartridge with the gas-generating material, placing end caps on the cartridge, puncturing a hole into the end cap of the cartridge, placing an igniter wire into the gas-generation composition via the hole in the end cap, contacting the igniter wire with an electric igniter, and igniting the gas-generating composition.
The amount of gas-generating composition used in the systems and methods will vary depending on the application, as one skilled in the art will readily recognize. In one variation, the amount of gas-generating composition utilized to fracture material is the amount of gas-generating composition known as the powder factor. The powder factor is the weight of powder required to break a given volume of material, a value that is known to be dependant on factors such as the strength of the material to be fractured and/or the degree of confinement of the material and/or the amount of fracturing required in the given application. However, those of skill in the art will recognize and appreciate that the powder factor required to fracture material can change from one application to the next. For instance, a free-standing boulder may require a powder factor of only about 20 percent of the powder factor needed for use in fracturing a solid rock face or embedded material. In one variation, the gas-generating composition powder factor is about 100 g of gas-generating composition per cubic yard of material to be fractured. In one variation, the powder factor is more than about 100 g of gas-generating composition per cubic yard of material to be fractured. In one variation, the powder factor is less than about 100 g of gas-generating composition per cubic yard of material to be fractured.
A test can be conducted prior to first-time use of the disclosed systems and compositions to enable the operator to categorize the type of breakage desired for the particular type of application. In one application, the material to be fractured is a free standing boulder and the amount of gas-generating composition for use in fracturing the material is about 50 or about 60 or about 40 or between about 40-60 or more than 50 or less than 80 grams per cubic yard. In another application, the material to be fractured is an imbedded material with at least one free face and the amount of gas-generating composition for fracturing the material is about 100 or about 80 or about 110 or about 120 or more than about 100 or more than about 120 or less than about 160 or less than about 125 grams per cubic yard.
A closed bomb burn rate test was performed on a gas-generating composition. The burn rate test was conducted by Safety Management Services, Inc. In the test, a composition comprising lactose, ferrosilicon and potassium perchlorate was provided to Safety Management Services, Inc. as sticks of brittle white powder that fractured easily. For comparison, a commercially available propellant, Triple Seven pyrotechnic mixture manufactured by Hodgdon Powder Co., Inc., was also supplied for testing.
A sample of the tested composition was coated with Krylon™ UV-resistant clear acrylic coating to inhibit the flame from flashing down the sides of the sample, encouraging a linear burn. The sample was loaded into a vessel held at an isothermal temperature, after which the vessel was closed and sealed. Inert nitrogen gas was used to pressurize the vessel. The sample was ignited using a hot wire or small torch at one end. Pressure sensors were used to record the pressure increase per time. Burn rate was calculated by dividing the sample length by the measured burn time.
A test of the composition comprising lactose, ferrosilicon and potassium perchlorate was performed at 25° C., varying the pressure from 62 psig to 4,000 psig. Testing was concluded at 4,000 psig since the reaction was proceeding quicker than the instrumentation and data acquisition system could effectively measure. A plot of the burn rate data against the natural log of pressure (ln(p)) for this sample is included as
A test of the comparison propellant was performed at 25° C., varying the pressure from 250 psig to 7,000 psig. Testing was concluded at 7,000 psig since the sample showed a consistent trend in the burn rate. A plot of the burn rate data as a function of the natural log of pressure (ln(p)) for this sample is included as
All references, publications, patents and patent applications disclosed herein are hereby orated by reference in their entirety.
This application claims the benefit of U.S. Provisional Application No. 60/649,992, filed Feb. 4, 2005, which is incorporated by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 60649992 | Feb 2005 | US |
