CA1180559A - System for making a homogeneous aqueous slurry-type blasting composition - Google Patents
System for making a homogeneous aqueous slurry-type blasting compositionInfo
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- CA1180559A CA1180559A CA000379514A CA379514A CA1180559A CA 1180559 A CA1180559 A CA 1180559A CA 000379514 A CA000379514 A CA 000379514A CA 379514 A CA379514 A CA 379514A CA 1180559 A CA1180559 A CA 1180559A
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Abstract
SYSTEM FOR MAKING AN AQUEOUS
SLURRY-TYPE BLASTING COMPOSITION
Abstract A blasting composition, method and system for making such is disclosed. The blasting composition is a homogeneous slurry-type blasting agent containing a major amount of water and a relatively small amount of a particulate fuel, preferably a particulate metal fuel. The blasting composition is made by premixing the fuel with water and a gelling agent to form a stable suspension of fuel in the water, metering the suspension of fuel into a dry particulate mixture of an inorganic metal oxidizer and a gelling agent, and slowly tumbling the mixture a short time sufficient to obtain a uniform composition without desensitizing the composition to detonation.
SLURRY-TYPE BLASTING COMPOSITION
Abstract A blasting composition, method and system for making such is disclosed. The blasting composition is a homogeneous slurry-type blasting agent containing a major amount of water and a relatively small amount of a particulate fuel, preferably a particulate metal fuel. The blasting composition is made by premixing the fuel with water and a gelling agent to form a stable suspension of fuel in the water, metering the suspension of fuel into a dry particulate mixture of an inorganic metal oxidizer and a gelling agent, and slowly tumbling the mixture a short time sufficient to obtain a uniform composition without desensitizing the composition to detonation.
Description
'I
Desc_i~t_ n SYSTEM FOR MAKING AN A~UROUS
SLURRY-TYP _ LASTING COMPOSITION
Technical Field This invention relates to a homogeneous slurry-type blasting composition, and to a method and system for making such.
Backc~round Art Aqueous and oil-based inorganic nitrate slurry explosives are extensively used in strip mining oE coal and other construction usesO These slurry-type explosives gen-erally contain a major amount oE an inorganic nitrate and a fuel together with water or oil and a thickening or gelatin-izing agent. ~he most common way of making slurry-type explosive compositions has generally involved employing an aqueous solution of ammonium nitrate or alkali or alkaline earth metal nitrates to which the other components are added. Finely divided aluminum flakes are commonly used in such compositions; however, "dusting" of this particulate material during manufacture of blasting compositions pre-sents an extreme hazard. It is also difficult to obtain a homoqeneous mix of the metal nitrate and metal particles without segregation. If the components are not uniEortnly mixed, the explosive composition either does not detonate or performs unsatisEactorily.
~t has remalned a problem to develop a slurry-type exPlosive composition which can be manufactured quickly, without the need for special equipment, at reasonable cost, and with safety.
The following UOS. patents disclose slurry-t~lpe blasting compositions and methods of making them; however, none of them employ a method or composition as describec~ and claimed herein.
~, .JI.~ .D
U.S. Patent No. 3,Z94,601 discloses a slurry-type blasting composition oE ammonium nltrate as an oxidizerl hexamethylenetetramine as a fuel, water~ and a thickening or gelling agent. No particulate metal as a fllel is employed.
The blasting composition i5 formed by mixing the ammonium nitrate, gelling agent together in a steam-jacketed vessel to melt them and s]owly adding to the dry, hot melted mix-ture hexamethylenetetramine dissolved in boiling water, the mixture being blended until a cohesive mass is formed.
U.S. Patent No. 3,765,967 discloses a slurry explosive prepared by dissolving an inorganic metal per-chlorate in water toqether with a thickener and particulate pentaerythritol tetranitrate and adding finely divlded alumlnum to the aqueous slurry.
U.S. Patent No. 5,985,593 discloses a method of making a slurry explosive by solubilizing nitromethane in an aqueous gel oE sodium perchlorate which includes a solubil-i~ing agent for the nitromethane, such as ethylene glycol.
U.S. Patent No. 3,787,254 discloses a water-base slurry composition made by distributing a liquid hydrocarbon fuel in an emulsion-like form of a mixture of ammonium nitrate and calcium nitrate, and then adding a thickening or gelling agent. Aluminum metal is added as a secondary fuel for certain of the compositions.
U.S. Patent No. 3,886,n10 discloses a water-base slurry composition made by incorporating a small amount of a thickener to an aqueous oxidizing solution of ammonium ni~
trate and thereafter adding a dry mix of a particulate solid fuel, such as finely divided aluminum, to the solution by stirring and mixincl, the dry mix including a supplemental thickening agent and a cross-linking agent.
U.S. Patent No. 3,378,415 discloses an explosive slurry made by melting together the li~uefiable component of the composition, i.e., ammonium nitrate and sodium nitrate, and then mixing in a dough~type mixer the mixture of the metal nitrates and a carbonaceous fuel, such as starch or woodmeal; a particulate metal, such as aluminum powder or flake; water; and a thickening agent, if needed. It is esserltial to melt the LiqueEiable incJredients ~irst ~nd then add the fuel an~ other inq~ec3ients to avoid spontaneous ignition thereof.
UOS. Patent No. 3,235,425 discloses a sequence o steps for mixing a slurry-type blasting composition by mix-ing together a dry mixtllre of ammonium nitrate and a gelling agent, then adding the resulting dry mix to water, and thereafter mixing in a smokeless powder.
None of the patenks disclose a sequence oE mixing steps to avoid dusting of particulate metal such as aluminum used as a fuel in the production of blasting compositions nor a method which avoids desensitizinc~ the composition during manufacture.
Disclosure of Inventio Ik is a primary object of this invention to pro-vide a method of quickly formulating an aqueous, slurry-type blasting agent safely and economically.
It is a further object of this invention to pro-vide a method of formulating a homogeneous, aqueous, slurry~type blasting agent using flaked aluminum, with little or no dusting of the aluminum.
It is a further object oE this invention to pro-vide an aqueous, slurry-type blasting composition wherein the two components of the hlasting composition can be sepa-rately packaged and mixed together quickly and safely with-out the need for sophisticated equipment and without desen-sitizing the composition.
It is a Eurther object oE this invention to pro-vide an aqueous, slurry-type blasting agent employing no toxic ingredients and which can be handled in an open plant~
It is a further object oE this invention to pro-vide an aqueous, slurry-type blasting agent employing a high proportion oE water and a relatively small amount oE parti-culate aluminum and still obtain a blasting compositionhaving good blasting characteristics.
It is a further object oE this invention to provide a two-component aqueous slurr~-type blastinq agent 3q.'~
employing dry, particulate ammonium nit-rate, the endothermic reaction occurring when the dry amrnonium nltrate is mixed with the aqueous fuel suspension providing greater thermal stabiliy and insensitivity.
These and other objects are accomplished by premixing a fuel with water and a gelling agent to Eorm a stable suspension of the fuel in the water, mixing together (in dry Eorm) a particulate nitrate oxidizer together with a gelling agent, and blending the suspension and dry mixture by subjecting them to a slow tumbling action -for a brie period of time. The blasting composition comprises 50-80 percent by weight ammonium nitrate, 0~5-10 percent uel, preferably flaked aluminumin an amount ranginy from 1-4 per-cent, 15-35 percent by weight water, 0.5~10 percent gelling 15 a~ent, preferably 1--2 percent, 0.02-0.5 percent of a cross-linking agent and, optionally, 0~05-1 percent o-E a glycol, such as ethylene or propylene glycol.
Brief Description of the Drawinqs The drawing illustrates a schematic diagram of a batch mixing system for formulation of an aqueous, slurry-type blasting composition of the type disclosed herein.
Best Mode for Carr~ing Out the Invention The inorganic nitrate which is preferably employed as the nitrate component of the explosive composition of this invention is ammonium nitrate; however, other inorganic nitrates can be employed alone or in admixture with the ammonium nitrate, such as the alkali or alkaline earth metal nitrates; e.g., sodium nitrate, potassium nitrate, calcium nitrate. IE a mixture is used, it should generally contain a predominant amount of ammonium nitrate in preEerence to the other nitratQs. The nitrate used can be in an~ form;
i.e., crushed, prill or a combination of the two, reasonably oil- and water-free. Fertilizer-grade ammonium nitrate is suitable. The particulate nitrate is usually processed through a hammermill or other means to grind it to a uniform particulate size before being blended with the other compo-nents in the explosive compoC3ition. ~lthollclh a clr~ ge1:LincJor thickening agent may be added to the oxidizer, it is preferable to adcl the gelling agent and cross-linking a~ent to the aqueous suspension to avoid any problems of (1) pre-mature cross linkinq, should the ammonium nitrate becomedamp, or (2) toxicity, which is a problem with certain of the cross-linking compounds. rrhe thickening agents may be any of the conventional thickening agents employed in the preparation of slurry explosives, such as guar gum, starches and synthetic polymers, such as the polyacrylamides. Cross-linking agents may also be added for the thickening agent.
Cross-linXing agents are especially useful where the stabil-ity or integrity of the composition needs to be maintained.
The cross-linking agents are generally metal salts, such as ferric nitrate, sodium dichromate, ammonium, antimony salts, etc. The inorganic nitrate, with or without the gelling agent and cross-linking agent, in dry form, Eorms one compo-nent of the two--component explosive composition.
The second component of the explosive composition ~o is comprised of a fuel, preferably a finely divided metal, such as aluminum, which is premixed with water and a gelling or thickening agent which suspends and causes the aluminum to be absorbed by the water. Preferred is de-dusted alumi-num flake which includes a coating of a polyfluorocarbon and/or a metal stearate to prevent reaction with water.
Alcoa 1651, manufactured by the Aluminum Company of America, is suitable, as are other commercially available aluminum flake products. This particulate aluminum is susceptible to dus-ting i~ diskurbed, or example~ by vibration, and is extr~mely hazardous to use if dusting cannot be prevented durlng mixing of the explosive composition. It was found that premixing the aluminum particles with water and a ge3l-ing agent substantially eliminated dusting. The gelling or thickening agent employed can be the same as that blended with the dry inorganic oxidizer. Preferred is one oE the guar gums, preferably used without a cross-linking agent~
It is also desirable to add a small amount of a glycol, such as propylene glycol, to the suspension to aid in dispersing the yel]inq agent. ~rhe amollnk 0~ wa~e~ blendetl with the particulate aluminum an~ ~elLing aclerlt shollld be only enouqh to form a concerltrate of aluminum suspende(J in an aqueous system. An impeller, vortex mixer is preEerred for prepara-tion of the concentrate This concentrate can be packagedin suitable cartridges and shipped to the intended blending site for blending with the first component. ~t the use site, the two components of the explosive composition are blended together with additional water to produce an aque-ous, slurry-type blasting agent which can be used with safety.
Reference is made to the drawing illustrating a schematic diagram of the equipment used for blending the explosive composition. The particulate ammonium nitrate or other inorganic nitrate or mixture thereof is delivered into a bin 10 by an ~uger 12 coming from a bulk facility holding the nitrate. The inorganic nitrate drops into a hammermill 14 which grinds the inorganic oxidizer to a uni~orm particle size. The ground inorganic nitrate exits Erom the hammer-mill and is conveyed by auger 16 -to a mixer 18, similar to a conventional mortar mixer. A dry gelling agen-t may be added to the oxidizer in the mixer. The mixer incorporates mixing blades within it which slowly tumble the dry, particulate mixture. The mixer i5 pivotally mounted at pivot point 19 to frame members 20 for dumping the mixture, aEter blending of the second component, into a bin and auger packer 22 as illustraked. A scale 24 is included beneath hopper 10 for measuring a predetermined weight oE the dry particulate oxidizer to be fed into the mixer 18. When formulating the explosive composition, a predetermined weight of the dry particulate oxidizer, as weighed by the bag scale 2~, is fed into the hammermill 14 and into the mortar mixer 18.
The second component oE the explosive composition (the concentrate o~ particulate aluminum suspended in an aqueous slurry) is poured into the mortar mixer simultane-ously with or prior to the addition of a predetermined amount of additional water. Once the second component is added to the dry particulate mixture in the mixer, the mixer 5~
i9 act:ivated to ~lowly tumble the Inixlur~ or1ly ~or: a sho~k perio~ of tirne, gene~ally 2 to 3() seconds. C~ the ~ixture is mixed too rapidly, the sensitivity oE the explosive corn-pOSitiOIl is destroyed. IE mixed too slowly, a non-uniform composition is obtained~ If the mixture is mixed too rapid-ly, the aluminum will dust. After the short mixing time of the two components, the mixture, having a molasses-like con-sistencv, is dumped into the auger pacXer 24, where it is packed in polyethylene or other plastic packages or car-tridges. The mixer 18 is provided with an interlock mechan-ism which prevents mixing until the proper amounts oE the two components have been added to the mixer. The final explosive composition should have a composition consisting essentially of 50-80 percent by weight ammonium nitrate or other inorganic nitrate or mixtures thereof, 0 n 5-10 percent particulate aluminum, preferably 1-4 percent, l5-35 percent water, 0.5-10 percent gelling agent, 0.02-0.5 percent cross-linking agent and 0.05-1.0 percent oE a glycol, such as ethylene or propylene glycol.
The equipment needed to formulate the explosive composition is unsophisticated and the components, particu-larly the aluminum-containing component, can be packaged as a gel in concentrated form for transport to the formu]ation site. The ammonium nicrate or other inorganic nitrate can be acquired from any suitable source. The composition can be formulated quickly with no dusting problems and with safety. The Einal composition uses a relatively small amount of particulate aluminum. No other fuel is needed. A
relativ~ly high proportion of water is used in contrast to other commercially used slurry-type explosive compositions.
The aluminum content may be varied to vary the sensitivity of the explosive composition. Above about 3 percent alumi num the explosive composition is cap-sensitive. Below about 3 percent, a booster i5 necessary. It is important that the aqueous suspension of aluminum be added to the dry particu-late mixture to avoid dusting of the particulate aluminum and to insure a uniform, homogeneous composition which does not segregate.
Fxample 1 The exploslve composition described is generally prepared in batches weighing from 200 to 400 pounds each.
In a given day 20,000 pounds of the composition may be pre-parecl. To formu1ate 20,000 pounds of the explosive composi-tion requires 13,750 pounds of particulate prilled ammonium nitrate and 358 pounds of guar gum.
A batch amount of the ammonium nitrate was fed by auger into bin 1 n from a bulk facility and then fed through a hammermill which crushed the prills. The crushed ammonium nitrate was then fed by auger 16 into mixer 18 and mixed with a batch amount of guar gum~ The dry mixture was tum-bled slowly to orm a uniform mixture of the oxidizer and dry gelling agent.
An aqueous slurry concentrate of particulate aluminum was prepared by blending together with an impeller, vortex mixer 358 pounds of a de~dusted flake aluminum (Alcoa 1651), 1,076 pounds water, about 10 pounds of a gelling agent (MP 11, hydroxypropyl guar), and 20 pounds oE propy-lene glycol.
The concentrate of the gelatinous mixture of aluminum suspended in the aqueous gel was prepacka~ed in 300 pound polyethylene cartridges~ each cartridge weighing about 15 pounds, and shipped to the use site. ~t the use site the packages were slit and added to the batch quantity of the c]ry particuLate mixture of ammonium nitrate in the mixer with slow tumbling. ~Simul~aneously with addition of the aluminum concentrate (or separately), an additional batch amount o~ water was added to the composition (4,428 pounds water per 20,000 pounds oxiclizer). The mixture was blended after introduction of the water and concentrate Eor a time less than 5 seconds and was then fed into an auyer pac]cer which packed it into polyethylene cartric19es. The set-up time of the composition ranged from 24 to 48 hours. The blended and formulated explosive composition incorporated the following:
_ercenk Ammonium nitrate 68.75 Guar gum 1.79 Water --(1) Present in the aluminum-containing concentrate 5.33
Desc_i~t_ n SYSTEM FOR MAKING AN A~UROUS
SLURRY-TYP _ LASTING COMPOSITION
Technical Field This invention relates to a homogeneous slurry-type blasting composition, and to a method and system for making such.
Backc~round Art Aqueous and oil-based inorganic nitrate slurry explosives are extensively used in strip mining oE coal and other construction usesO These slurry-type explosives gen-erally contain a major amount oE an inorganic nitrate and a fuel together with water or oil and a thickening or gelatin-izing agent. ~he most common way of making slurry-type explosive compositions has generally involved employing an aqueous solution of ammonium nitrate or alkali or alkaline earth metal nitrates to which the other components are added. Finely divided aluminum flakes are commonly used in such compositions; however, "dusting" of this particulate material during manufacture of blasting compositions pre-sents an extreme hazard. It is also difficult to obtain a homoqeneous mix of the metal nitrate and metal particles without segregation. If the components are not uniEortnly mixed, the explosive composition either does not detonate or performs unsatisEactorily.
~t has remalned a problem to develop a slurry-type exPlosive composition which can be manufactured quickly, without the need for special equipment, at reasonable cost, and with safety.
The following UOS. patents disclose slurry-t~lpe blasting compositions and methods of making them; however, none of them employ a method or composition as describec~ and claimed herein.
~, .JI.~ .D
U.S. Patent No. 3,Z94,601 discloses a slurry-type blasting composition oE ammonium nltrate as an oxidizerl hexamethylenetetramine as a fuel, water~ and a thickening or gelling agent. No particulate metal as a fllel is employed.
The blasting composition i5 formed by mixing the ammonium nitrate, gelling agent together in a steam-jacketed vessel to melt them and s]owly adding to the dry, hot melted mix-ture hexamethylenetetramine dissolved in boiling water, the mixture being blended until a cohesive mass is formed.
U.S. Patent No. 3,765,967 discloses a slurry explosive prepared by dissolving an inorganic metal per-chlorate in water toqether with a thickener and particulate pentaerythritol tetranitrate and adding finely divlded alumlnum to the aqueous slurry.
U.S. Patent No. 5,985,593 discloses a method of making a slurry explosive by solubilizing nitromethane in an aqueous gel oE sodium perchlorate which includes a solubil-i~ing agent for the nitromethane, such as ethylene glycol.
U.S. Patent No. 3,787,254 discloses a water-base slurry composition made by distributing a liquid hydrocarbon fuel in an emulsion-like form of a mixture of ammonium nitrate and calcium nitrate, and then adding a thickening or gelling agent. Aluminum metal is added as a secondary fuel for certain of the compositions.
U.S. Patent No. 3,886,n10 discloses a water-base slurry composition made by incorporating a small amount of a thickener to an aqueous oxidizing solution of ammonium ni~
trate and thereafter adding a dry mix of a particulate solid fuel, such as finely divided aluminum, to the solution by stirring and mixincl, the dry mix including a supplemental thickening agent and a cross-linking agent.
U.S. Patent No. 3,378,415 discloses an explosive slurry made by melting together the li~uefiable component of the composition, i.e., ammonium nitrate and sodium nitrate, and then mixing in a dough~type mixer the mixture of the metal nitrates and a carbonaceous fuel, such as starch or woodmeal; a particulate metal, such as aluminum powder or flake; water; and a thickening agent, if needed. It is esserltial to melt the LiqueEiable incJredients ~irst ~nd then add the fuel an~ other inq~ec3ients to avoid spontaneous ignition thereof.
UOS. Patent No. 3,235,425 discloses a sequence o steps for mixing a slurry-type blasting composition by mix-ing together a dry mixtllre of ammonium nitrate and a gelling agent, then adding the resulting dry mix to water, and thereafter mixing in a smokeless powder.
None of the patenks disclose a sequence oE mixing steps to avoid dusting of particulate metal such as aluminum used as a fuel in the production of blasting compositions nor a method which avoids desensitizinc~ the composition during manufacture.
Disclosure of Inventio Ik is a primary object of this invention to pro-vide a method of quickly formulating an aqueous, slurry-type blasting agent safely and economically.
It is a further object of this invention to pro-vide a method of formulating a homogeneous, aqueous, slurry~type blasting agent using flaked aluminum, with little or no dusting of the aluminum.
It is a further object oE this invention to pro-vide an aqueous, slurry-type blasting composition wherein the two components of the hlasting composition can be sepa-rately packaged and mixed together quickly and safely with-out the need for sophisticated equipment and without desen-sitizing the composition.
It is a Eurther object oE this invention to pro-vide an aqueous, slurry-type blasting agent employing no toxic ingredients and which can be handled in an open plant~
It is a further object oE this invention to pro-vide an aqueous, slurry-type blasting agent employing a high proportion oE water and a relatively small amount oE parti-culate aluminum and still obtain a blasting compositionhaving good blasting characteristics.
It is a further object oE this invention to provide a two-component aqueous slurr~-type blastinq agent 3q.'~
employing dry, particulate ammonium nit-rate, the endothermic reaction occurring when the dry amrnonium nltrate is mixed with the aqueous fuel suspension providing greater thermal stabiliy and insensitivity.
These and other objects are accomplished by premixing a fuel with water and a gelling agent to Eorm a stable suspension of the fuel in the water, mixing together (in dry Eorm) a particulate nitrate oxidizer together with a gelling agent, and blending the suspension and dry mixture by subjecting them to a slow tumbling action -for a brie period of time. The blasting composition comprises 50-80 percent by weight ammonium nitrate, 0~5-10 percent uel, preferably flaked aluminumin an amount ranginy from 1-4 per-cent, 15-35 percent by weight water, 0.5~10 percent gelling 15 a~ent, preferably 1--2 percent, 0.02-0.5 percent of a cross-linking agent and, optionally, 0~05-1 percent o-E a glycol, such as ethylene or propylene glycol.
Brief Description of the Drawinqs The drawing illustrates a schematic diagram of a batch mixing system for formulation of an aqueous, slurry-type blasting composition of the type disclosed herein.
Best Mode for Carr~ing Out the Invention The inorganic nitrate which is preferably employed as the nitrate component of the explosive composition of this invention is ammonium nitrate; however, other inorganic nitrates can be employed alone or in admixture with the ammonium nitrate, such as the alkali or alkaline earth metal nitrates; e.g., sodium nitrate, potassium nitrate, calcium nitrate. IE a mixture is used, it should generally contain a predominant amount of ammonium nitrate in preEerence to the other nitratQs. The nitrate used can be in an~ form;
i.e., crushed, prill or a combination of the two, reasonably oil- and water-free. Fertilizer-grade ammonium nitrate is suitable. The particulate nitrate is usually processed through a hammermill or other means to grind it to a uniform particulate size before being blended with the other compo-nents in the explosive compoC3ition. ~lthollclh a clr~ ge1:LincJor thickening agent may be added to the oxidizer, it is preferable to adcl the gelling agent and cross-linking a~ent to the aqueous suspension to avoid any problems of (1) pre-mature cross linkinq, should the ammonium nitrate becomedamp, or (2) toxicity, which is a problem with certain of the cross-linking compounds. rrhe thickening agents may be any of the conventional thickening agents employed in the preparation of slurry explosives, such as guar gum, starches and synthetic polymers, such as the polyacrylamides. Cross-linking agents may also be added for the thickening agent.
Cross-linXing agents are especially useful where the stabil-ity or integrity of the composition needs to be maintained.
The cross-linking agents are generally metal salts, such as ferric nitrate, sodium dichromate, ammonium, antimony salts, etc. The inorganic nitrate, with or without the gelling agent and cross-linking agent, in dry form, Eorms one compo-nent of the two--component explosive composition.
The second component of the explosive composition ~o is comprised of a fuel, preferably a finely divided metal, such as aluminum, which is premixed with water and a gelling or thickening agent which suspends and causes the aluminum to be absorbed by the water. Preferred is de-dusted alumi-num flake which includes a coating of a polyfluorocarbon and/or a metal stearate to prevent reaction with water.
Alcoa 1651, manufactured by the Aluminum Company of America, is suitable, as are other commercially available aluminum flake products. This particulate aluminum is susceptible to dus-ting i~ diskurbed, or example~ by vibration, and is extr~mely hazardous to use if dusting cannot be prevented durlng mixing of the explosive composition. It was found that premixing the aluminum particles with water and a ge3l-ing agent substantially eliminated dusting. The gelling or thickening agent employed can be the same as that blended with the dry inorganic oxidizer. Preferred is one oE the guar gums, preferably used without a cross-linking agent~
It is also desirable to add a small amount of a glycol, such as propylene glycol, to the suspension to aid in dispersing the yel]inq agent. ~rhe amollnk 0~ wa~e~ blendetl with the particulate aluminum an~ ~elLing aclerlt shollld be only enouqh to form a concerltrate of aluminum suspende(J in an aqueous system. An impeller, vortex mixer is preEerred for prepara-tion of the concentrate This concentrate can be packagedin suitable cartridges and shipped to the intended blending site for blending with the first component. ~t the use site, the two components of the explosive composition are blended together with additional water to produce an aque-ous, slurry-type blasting agent which can be used with safety.
Reference is made to the drawing illustrating a schematic diagram of the equipment used for blending the explosive composition. The particulate ammonium nitrate or other inorganic nitrate or mixture thereof is delivered into a bin 10 by an ~uger 12 coming from a bulk facility holding the nitrate. The inorganic nitrate drops into a hammermill 14 which grinds the inorganic oxidizer to a uni~orm particle size. The ground inorganic nitrate exits Erom the hammer-mill and is conveyed by auger 16 -to a mixer 18, similar to a conventional mortar mixer. A dry gelling agen-t may be added to the oxidizer in the mixer. The mixer incorporates mixing blades within it which slowly tumble the dry, particulate mixture. The mixer i5 pivotally mounted at pivot point 19 to frame members 20 for dumping the mixture, aEter blending of the second component, into a bin and auger packer 22 as illustraked. A scale 24 is included beneath hopper 10 for measuring a predetermined weight oE the dry particulate oxidizer to be fed into the mixer 18. When formulating the explosive composition, a predetermined weight of the dry particulate oxidizer, as weighed by the bag scale 2~, is fed into the hammermill 14 and into the mortar mixer 18.
The second component oE the explosive composition (the concentrate o~ particulate aluminum suspended in an aqueous slurry) is poured into the mortar mixer simultane-ously with or prior to the addition of a predetermined amount of additional water. Once the second component is added to the dry particulate mixture in the mixer, the mixer 5~
i9 act:ivated to ~lowly tumble the Inixlur~ or1ly ~or: a sho~k perio~ of tirne, gene~ally 2 to 3() seconds. C~ the ~ixture is mixed too rapidly, the sensitivity oE the explosive corn-pOSitiOIl is destroyed. IE mixed too slowly, a non-uniform composition is obtained~ If the mixture is mixed too rapid-ly, the aluminum will dust. After the short mixing time of the two components, the mixture, having a molasses-like con-sistencv, is dumped into the auger pacXer 24, where it is packed in polyethylene or other plastic packages or car-tridges. The mixer 18 is provided with an interlock mechan-ism which prevents mixing until the proper amounts oE the two components have been added to the mixer. The final explosive composition should have a composition consisting essentially of 50-80 percent by weight ammonium nitrate or other inorganic nitrate or mixtures thereof, 0 n 5-10 percent particulate aluminum, preferably 1-4 percent, l5-35 percent water, 0.5-10 percent gelling agent, 0.02-0.5 percent cross-linking agent and 0.05-1.0 percent oE a glycol, such as ethylene or propylene glycol.
The equipment needed to formulate the explosive composition is unsophisticated and the components, particu-larly the aluminum-containing component, can be packaged as a gel in concentrated form for transport to the formu]ation site. The ammonium nicrate or other inorganic nitrate can be acquired from any suitable source. The composition can be formulated quickly with no dusting problems and with safety. The Einal composition uses a relatively small amount of particulate aluminum. No other fuel is needed. A
relativ~ly high proportion of water is used in contrast to other commercially used slurry-type explosive compositions.
The aluminum content may be varied to vary the sensitivity of the explosive composition. Above about 3 percent alumi num the explosive composition is cap-sensitive. Below about 3 percent, a booster i5 necessary. It is important that the aqueous suspension of aluminum be added to the dry particu-late mixture to avoid dusting of the particulate aluminum and to insure a uniform, homogeneous composition which does not segregate.
Fxample 1 The exploslve composition described is generally prepared in batches weighing from 200 to 400 pounds each.
In a given day 20,000 pounds of the composition may be pre-parecl. To formu1ate 20,000 pounds of the explosive composi-tion requires 13,750 pounds of particulate prilled ammonium nitrate and 358 pounds of guar gum.
A batch amount of the ammonium nitrate was fed by auger into bin 1 n from a bulk facility and then fed through a hammermill which crushed the prills. The crushed ammonium nitrate was then fed by auger 16 into mixer 18 and mixed with a batch amount of guar gum~ The dry mixture was tum-bled slowly to orm a uniform mixture of the oxidizer and dry gelling agent.
An aqueous slurry concentrate of particulate aluminum was prepared by blending together with an impeller, vortex mixer 358 pounds of a de~dusted flake aluminum (Alcoa 1651), 1,076 pounds water, about 10 pounds of a gelling agent (MP 11, hydroxypropyl guar), and 20 pounds oE propy-lene glycol.
The concentrate of the gelatinous mixture of aluminum suspended in the aqueous gel was prepacka~ed in 300 pound polyethylene cartridges~ each cartridge weighing about 15 pounds, and shipped to the use site. ~t the use site the packages were slit and added to the batch quantity of the c]ry particuLate mixture of ammonium nitrate in the mixer with slow tumbling. ~Simul~aneously with addition of the aluminum concentrate (or separately), an additional batch amount o~ water was added to the composition (4,428 pounds water per 20,000 pounds oxiclizer). The mixture was blended after introduction of the water and concentrate Eor a time less than 5 seconds and was then fed into an auyer pac]cer which packed it into polyethylene cartric19es. The set-up time of the composition ranged from 24 to 48 hours. The blended and formulated explosive composition incorporated the following:
_ercenk Ammonium nitrate 68.75 Guar gum 1.79 Water --(1) Present in the aluminum-containing concentrate 5.33
(2) Added at the time of formulation 22.14 Gelling agent Jaguar HP~11 (Stein-Hall, a division of Celanese Corporation) 0.05 Propylene glycol 0.10 Flake alumimum (Alcoa 1651) 1.79 The explosive composition, on plate dent tests, detonated completely and gave plate dents comparable to other slurry explosives.
Claims (7)
1. A method for making a homogeneous, aqueous slurry-type blasting composition containing a particulate inorganic nitrate oxidizer and a finely divided metal fuel comprising:
premixing the finely divided metal fuel with water and a gelling agent to form a stable suspension of the finely divided metal fuel in the water;
mixing the aqueous suspension of finely divided metal fuel with the particulate nitrate oxidizer and an addi-tional amount of water; and slowly tumbling the mixture for a brief time suffi-cient to uniformly mix the components.
premixing the finely divided metal fuel with water and a gelling agent to form a stable suspension of the finely divided metal fuel in the water;
mixing the aqueous suspension of finely divided metal fuel with the particulate nitrate oxidizer and an addi-tional amount of water; and slowly tumbling the mixture for a brief time suffi-cient to uniformly mix the components.
2. The method of claim 1, wherein the nitrate oxidizer is mixed with a gelling agent.
3. The method of claim 2, wherein the composition consists essentially of 50-80 percent by weight particulate inorganic nitrate, 0.5 to 10 percent by weight finely divided alumimum flake, 0.5 to 10 percent by weight gelling agent and 15 to 35 percent water.
4. The method of claim 2 wherein the mixing time ranges from 2 to 30 seconds, the inorganic nitrate is ammonium nitrate and wherein mixing of the aqueous suspension of finely divided fuel with the ammonium nitrate results in an endo-thermic reaction providing thermal stability and insensitivity to detonation.
5. A system for making a homogeneous, aqueous, slurry-type blasting composition which contains a particulate nitrate oxidizer, a finely divided metal fuel, and a gelling agent, the system comprising:
grinding means for grinding the particulate nitrate to a uniform particle size;
means for feeding the particulate oxidizer to a mixer having tumbling blades therein which subjects the mixture to a slow tumbling action;
means for feeding into the mixer a gelatinous concen-trate consisting essentially of finely divided aluminum in a stable suspension with water and a gelling agent; and means for packing the formulated explosive composi-tion in cartridges.
grinding means for grinding the particulate nitrate to a uniform particle size;
means for feeding the particulate oxidizer to a mixer having tumbling blades therein which subjects the mixture to a slow tumbling action;
means for feeding into the mixer a gelatinous concen-trate consisting essentially of finely divided aluminum in a stable suspension with water and a gelling agent; and means for packing the formulated explosive composi-tion in cartridges.
6. The method of claim 3, wherein the composition consists essentially of 50 to 80 percent by weight nitrate oxidizer, 1 to 4 percent by weight finely divided aluminum, 15 to 35 percent by weight water and 0.5 to 10 percent by weight gelling agent.
7. The system of claim 5, wherein the means for pack-ing is an auger packer.
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000379514A CA1180559A (en) | 1981-06-11 | 1981-06-11 | System for making a homogeneous aqueous slurry-type blasting composition |
| IN640/CAL/81A IN154683B (en) | 1981-06-11 | 1981-06-12 |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000379514A CA1180559A (en) | 1981-06-11 | 1981-06-11 | System for making a homogeneous aqueous slurry-type blasting composition |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1180559A true CA1180559A (en) | 1985-01-08 |
Family
ID=4120206
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000379514A Expired CA1180559A (en) | 1981-06-11 | 1981-06-11 | System for making a homogeneous aqueous slurry-type blasting composition |
Country Status (2)
| Country | Link |
|---|---|
| CA (1) | CA1180559A (en) |
| IN (1) | IN154683B (en) |
-
1981
- 1981-06-11 CA CA000379514A patent/CA1180559A/en not_active Expired
- 1981-06-12 IN IN640/CAL/81A patent/IN154683B/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| IN154683B (en) | 1984-12-08 |
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