megalomania
June 25th, 2003, 05:21 PM
shady mutha
Frequent Poster
Posts: 149
From: australia
Registered: SEP 2000
posted March 12, 2001 05:32 PM
--------------------------------------------------------------------------------
Abel as early as 1874,Kast and T.Urbanski proved that the presence of water in high explosives increased the rate of detonation.This found limited practical application in the use of nitrocellulose with water in demolition cartridges.Streng and Kirshenbaum obtained a patent for an explosive composed of ammonium nitrate aqueous solution with aluminium powder.In the United States the "slurry explosives" developed by Cook and tested in the Iron Ore Co.,in Canada in 1957 was quickly accepted in open pit work.The original composition by Cook and Farnam was 25% coarse TNT,55% NH4NO3(35-45%)and NaNO3(10-20%)20%h2O with added guar gum as a thickening agent.The addition of the thickening agent was a considerable improvement as it prevented segregation of the ingredients.Guar gum is a polysaccharide:galacto-mannan.
Also another patent appeared at the same time by Hardel and Bjork who used aluminium powder as a sensitizer(instead of TNT)
It was soon recognized that the presence of tiny air bubbles in the slurry was a very good sensitizer.The bubbles adhere to TNT particles or Al powder and help detonation by creating hot spots by adiabatic compression.
Another kind of early slurry was that developed by Gehrig of Atlas Chemical Industries.It consisted of a saturated solution of ammonium nitrate in nitric acid of 60-70% HNO3 and some organic substances which are not attacked by nitric acid,for example,vinyl polymers.
The advantages of slurry explosives were summarized by Mahadevan.
(1)By dissolution,water brings the ingredients into close contact with each other.
(2)It provides a continuous medium through which a detonation wave passes.
(3)It desensitizes the explosive against fire,sparks,impact and friction.
(4)Water is believed to increase the energy of the explosive by taking part in the reaction at the time of explosion especially when Al is present.
(5)It affects the products of detonation and suppresses the formation of toxic gases:carbon monoxide and oxides of nitrogen
(6)It has a pronounced effect on the "coke oven"reaction 2 CO-->C+CO2 which is very important in preventing dissociation of energetic products of detonation such as H2O and CO2.
c0deblue
Frequent Poster
Posts: 229
From:
Registered: JAN 2001
posted March 12, 2001 09:43 PM
--------------------------------------------------------------------------------
Excellent information Shady. Don't know if anyone's said it, but you certainly provide an invaluable service in transcribing these excerpts. Wish these could be condensed into an e-book.
What continues to puzzle me about "wet" explosives is the seeming conflict between the need to maintain AN as dry as possible to insure detonation, versus the obvious advantages of wet mixtures or slurries as stated in (1) and (2) of the reference cited above.
It's well known that the absorption or admixture of water has a pronounced desensitizing effect on AN - even prolonged exposure to humid conditions can spell the difference between successful detonation and total failure. Item (3) of the Mahadevan summary remarks upon this desensitizing effect (although the "advantage" of desensitizing something as IN-sensitive as AN is unclear to me).
Two possibilities (and questions) occur:
(a) Assuming that AN slurries require a larger initiator/booster than the dry product, why is insuring "dryness" of AN always emphasized as critical? Why not simply specify a more powerful initiator/booster charge under all conditions and thereby compensate for ANY water that may be present?
(b) Assuming that AN slurries will only detonate under heavy confinement, wouldn't their use be limited to applications such as rockblasting where the borehole provides the necessary containment? And wouldn't this requirement render AN slurries useless for anything else?
Of further interest:
"(4) Water is believed to increase the energy of the explosive by taking part in the reaction at the time of explosion especially when Al is present."
I find this statement intriguing, as it goes to one of the questions posed in the "Brain-Drain Explosive System" thread. Again, what is the mechanism (as distinct from (1) and (2) above) by which water "increases the energy of the explosive", and to what extent (and at what level) does water "take part in the reaction"?
10fingers
Frequent Poster
Posts: 442
From: USA
Registered: SEP 2000
posted March 12, 2001 11:58 PM
--------------------------------------------------------------------------------
There is a formula in the book "expedient hand grenades" that is an ammonium nitrate based water gel. It is supposed to be equal to 75% dynamite.
[This message has been edited by 10fingers (edited March 19, 2001).]
Anthony
Moderator
Posts: 2321
From: England
Registered: SEP 2000
posted March 13, 2001 01:55 PM
--------------------------------------------------------------------------------
Sureky upon detonation, the water splits into H2 and 02 which combusts, probably releasing a large volume of gas? Then again I would have thought that the energy of the explosion used to split the water would be greater than that generated by combusting H2 and 02?
Jhonbus
Frequent Poster
Posts: 347
From:
Registered: SEP 2000
posted March 13, 2001 02:33 PM
--------------------------------------------------------------------------------
The energy required to split water into its constituent elements in their standard states (ie. H2 and O2) is exactly the same as the energy released when H2 and O2 combine (in a 2:1 ratio of course) to form water. However water could react with aluminium to form aluminium hydroxide and hydrogen. I think this is probably the reaction implied in the excerpt.
[This message has been edited by Jhonbus (edited March 13, 2001).]
shady mutha
Frequent Poster
Posts: 149
From: australia
Registered: SEP 2000
posted March 13, 2001 04:57 PM
--------------------------------------------------------------------------------
Cross-linking Agents
One of the draw-backs of early compositions was the low viscosity of the solution and hence the ease of segregation and loss of air bubbles.A significant achievement consisted in increasing the viscosity of guar gum by adding borax and other boron compounds,antimony compounds e.g. ammonium pyroantimonate,potassium antimony tartrate followed by adding dichromate,that is oxidation of trivalent to pentavalent antimony was found to give an efficent cross linking agent.Semi-synthetic and synthetic polymers are also used as thickening agents.Such are carboxymethyl cellulose and polyacrylamide respectively.
Surface Active and Emulsifying Agents
Surface active agents(surfactants)improve the dispersion of ingredients and consistency of slurry.According to Hiroshi by adding small amounts of alkali metal salts of alkydiphenyl ether disulphonic acid a slurry explosive was obtained which can be initiated with a No 6 cap without adding sensitizers.Also alkali metal salts of sulfuric acid esters of higher aliphatic alcohol,of aromatic sulphonic acids are good surfactants and improve the detonability of slurry explosives.Sorbitol momooleate was recommended as the emulsifier.
Oxygen Carriers
In addition ammonium nitrate,sodium nitrate and calcium nitrate are added to slurry explosives.A mixture of calcium nitrate and sulfur seems to be particularly efficent.Calcium nitrate makes slurry more resistant to low temperature and can withstand the temperature of -12.c.Ammonium perchlorate can also be used.
Aluminum
The addition of aluminum powder in a form of foil,flakes or granules can make slurry without nitro compounds.The patent by Davis,Fassnacht,Kirst and Noran gives slurry explosives composed of ammonium and sodium nitrate,aluminum and water.An emulsifier is added to help the presence of air bubbles.Flakes and dust of aluminum posed handling problems as it resists wetting of aqueous medium.Mahadevan and Varadarajan solved the problem by wetting aluminum with ethylene glycol and adding such paste to the mixture.
Frequent Poster
Posts: 149
From: australia
Registered: SEP 2000
posted March 12, 2001 05:32 PM
--------------------------------------------------------------------------------
Abel as early as 1874,Kast and T.Urbanski proved that the presence of water in high explosives increased the rate of detonation.This found limited practical application in the use of nitrocellulose with water in demolition cartridges.Streng and Kirshenbaum obtained a patent for an explosive composed of ammonium nitrate aqueous solution with aluminium powder.In the United States the "slurry explosives" developed by Cook and tested in the Iron Ore Co.,in Canada in 1957 was quickly accepted in open pit work.The original composition by Cook and Farnam was 25% coarse TNT,55% NH4NO3(35-45%)and NaNO3(10-20%)20%h2O with added guar gum as a thickening agent.The addition of the thickening agent was a considerable improvement as it prevented segregation of the ingredients.Guar gum is a polysaccharide:galacto-mannan.
Also another patent appeared at the same time by Hardel and Bjork who used aluminium powder as a sensitizer(instead of TNT)
It was soon recognized that the presence of tiny air bubbles in the slurry was a very good sensitizer.The bubbles adhere to TNT particles or Al powder and help detonation by creating hot spots by adiabatic compression.
Another kind of early slurry was that developed by Gehrig of Atlas Chemical Industries.It consisted of a saturated solution of ammonium nitrate in nitric acid of 60-70% HNO3 and some organic substances which are not attacked by nitric acid,for example,vinyl polymers.
The advantages of slurry explosives were summarized by Mahadevan.
(1)By dissolution,water brings the ingredients into close contact with each other.
(2)It provides a continuous medium through which a detonation wave passes.
(3)It desensitizes the explosive against fire,sparks,impact and friction.
(4)Water is believed to increase the energy of the explosive by taking part in the reaction at the time of explosion especially when Al is present.
(5)It affects the products of detonation and suppresses the formation of toxic gases:carbon monoxide and oxides of nitrogen
(6)It has a pronounced effect on the "coke oven"reaction 2 CO-->C+CO2 which is very important in preventing dissociation of energetic products of detonation such as H2O and CO2.
c0deblue
Frequent Poster
Posts: 229
From:
Registered: JAN 2001
posted March 12, 2001 09:43 PM
--------------------------------------------------------------------------------
Excellent information Shady. Don't know if anyone's said it, but you certainly provide an invaluable service in transcribing these excerpts. Wish these could be condensed into an e-book.
What continues to puzzle me about "wet" explosives is the seeming conflict between the need to maintain AN as dry as possible to insure detonation, versus the obvious advantages of wet mixtures or slurries as stated in (1) and (2) of the reference cited above.
It's well known that the absorption or admixture of water has a pronounced desensitizing effect on AN - even prolonged exposure to humid conditions can spell the difference between successful detonation and total failure. Item (3) of the Mahadevan summary remarks upon this desensitizing effect (although the "advantage" of desensitizing something as IN-sensitive as AN is unclear to me).
Two possibilities (and questions) occur:
(a) Assuming that AN slurries require a larger initiator/booster than the dry product, why is insuring "dryness" of AN always emphasized as critical? Why not simply specify a more powerful initiator/booster charge under all conditions and thereby compensate for ANY water that may be present?
(b) Assuming that AN slurries will only detonate under heavy confinement, wouldn't their use be limited to applications such as rockblasting where the borehole provides the necessary containment? And wouldn't this requirement render AN slurries useless for anything else?
Of further interest:
"(4) Water is believed to increase the energy of the explosive by taking part in the reaction at the time of explosion especially when Al is present."
I find this statement intriguing, as it goes to one of the questions posed in the "Brain-Drain Explosive System" thread. Again, what is the mechanism (as distinct from (1) and (2) above) by which water "increases the energy of the explosive", and to what extent (and at what level) does water "take part in the reaction"?
10fingers
Frequent Poster
Posts: 442
From: USA
Registered: SEP 2000
posted March 12, 2001 11:58 PM
--------------------------------------------------------------------------------
There is a formula in the book "expedient hand grenades" that is an ammonium nitrate based water gel. It is supposed to be equal to 75% dynamite.
[This message has been edited by 10fingers (edited March 19, 2001).]
Anthony
Moderator
Posts: 2321
From: England
Registered: SEP 2000
posted March 13, 2001 01:55 PM
--------------------------------------------------------------------------------
Sureky upon detonation, the water splits into H2 and 02 which combusts, probably releasing a large volume of gas? Then again I would have thought that the energy of the explosion used to split the water would be greater than that generated by combusting H2 and 02?
Jhonbus
Frequent Poster
Posts: 347
From:
Registered: SEP 2000
posted March 13, 2001 02:33 PM
--------------------------------------------------------------------------------
The energy required to split water into its constituent elements in their standard states (ie. H2 and O2) is exactly the same as the energy released when H2 and O2 combine (in a 2:1 ratio of course) to form water. However water could react with aluminium to form aluminium hydroxide and hydrogen. I think this is probably the reaction implied in the excerpt.
[This message has been edited by Jhonbus (edited March 13, 2001).]
shady mutha
Frequent Poster
Posts: 149
From: australia
Registered: SEP 2000
posted March 13, 2001 04:57 PM
--------------------------------------------------------------------------------
Cross-linking Agents
One of the draw-backs of early compositions was the low viscosity of the solution and hence the ease of segregation and loss of air bubbles.A significant achievement consisted in increasing the viscosity of guar gum by adding borax and other boron compounds,antimony compounds e.g. ammonium pyroantimonate,potassium antimony tartrate followed by adding dichromate,that is oxidation of trivalent to pentavalent antimony was found to give an efficent cross linking agent.Semi-synthetic and synthetic polymers are also used as thickening agents.Such are carboxymethyl cellulose and polyacrylamide respectively.
Surface Active and Emulsifying Agents
Surface active agents(surfactants)improve the dispersion of ingredients and consistency of slurry.According to Hiroshi by adding small amounts of alkali metal salts of alkydiphenyl ether disulphonic acid a slurry explosive was obtained which can be initiated with a No 6 cap without adding sensitizers.Also alkali metal salts of sulfuric acid esters of higher aliphatic alcohol,of aromatic sulphonic acids are good surfactants and improve the detonability of slurry explosives.Sorbitol momooleate was recommended as the emulsifier.
Oxygen Carriers
In addition ammonium nitrate,sodium nitrate and calcium nitrate are added to slurry explosives.A mixture of calcium nitrate and sulfur seems to be particularly efficent.Calcium nitrate makes slurry more resistant to low temperature and can withstand the temperature of -12.c.Ammonium perchlorate can also be used.
Aluminum
The addition of aluminum powder in a form of foil,flakes or granules can make slurry without nitro compounds.The patent by Davis,Fassnacht,Kirst and Noran gives slurry explosives composed of ammonium and sodium nitrate,aluminum and water.An emulsifier is added to help the presence of air bubbles.Flakes and dust of aluminum posed handling problems as it resists wetting of aqueous medium.Mahadevan and Varadarajan solved the problem by wetting aluminum with ethylene glycol and adding such paste to the mixture.