EP0113617B1 - Inert nitrate-fuel type slurry, explosive obtained by incorporating air, and manufacturing processes - Google Patents

Description

The present invention relates to a nitrate-fuel type slurry, inert (or insensitive) during its manufacture, its transport and its storage, stable during the latter, and which can be easily transformed on the shooting site into a pumpable explosive, powerful and with interesting additional characteristics.

Nitrate-fuel combinations have been known for a very long time. There are also known "porridges" containing these elements and conventional additives.

There are two families of porridge. The first generation of products of this type contained explosive substances as a sensitizer.

Since a second generation, spray mixtures containing air have been developed as sensitizers.

It should be noted in this regard that it is, moreover, impossible to date to avoid incorporating air in a significant quantity in the slurries, during manufacture.

Thus, all known slurries contain an amount of air such that they are not inert, and this as soon as they are manufactured, which has obvious drawbacks, particularly in the field of security.

The object of the present invention is to preserve the known advantages of combinations of the nitrate-fuel type, which we currently know to manufacture only in solid and immediately explosive form, that is to say non-inert, but as a manufacturer on this base a slurry which is inert during manufacture, transport and storage, and which makes it possible to prepare on the firing site, as simply as possible, a powerful explosive which is itself pumpable and has a set of qualities interesting.

These objectives are achieved by the slurries according to the invention, the characteristic of which is that they do not contain air, or at least not in a sensitizing form.

Given current knowledge in this field and the products marketed, obtaining such a slurry free of air, free of explosive substances, and physically stable (no phase separation) for a very long period did not seem possible. to the skilled person, despite the major interest of such a product.

This result can however be achieved by using in a doubly original way (in terms of function and in terms of the quantity used) a product known and used for a long time in the technical sector considered.

According to the invention, an inert and stable slurry is provided, without any explosive element, used to produce an explosive, of the type containing water, ammonium nitrate alone or in admixture with certain soluble alkali (sodium) or alkaline nitrates. - earth (calcium), fuel, a system of hydration gums and a crosslinking agent, characterized in that the system of hydration gums consists of a mixture of a partially depolymerized base gum, of a bipolymerized gum the hydration of which is very rapid in water, but very slow in the solution of ammonium nitrate and of a polyacrylamide, and in that said crosslinking agent consists of a self-crosslinking gum used in a proportion of between 200 and 600 ppm, said slurry being pumpable, containing no air included or containing manufacturing area in a non-sensitizing form.

The invention is therefore based on the discovery that it was possible to obtain an inert and stable slurry, using a system of hydration gums as defined above in association with a self-crosslinking gum, known per se, as crosslinking agent. .

According to the invention, the self-crosslinking gum is used in very low doses and causes very slow crosslinking of the two gums contained in a system of hydration gums, a preferred embodiment of which will be indicated below.

Advantageously, the “GUARTEC 417” gum sold by the Mills Company will be used as self-crosslinking gum.

A second essential element of the invention lies in the incorporation of a combination of a surfactant and of a powerful solvent for this surfactant.

It was indicated above that the object of the invention was to obtain a slurry containing no sensitizing air.

However, another object of the invention is to obtain a slurry which can be reactivated easily on the site, for example by introducing fine air bubbles into the inert mass to sensitize it.

The inert slurry must also be stable on storage, so avoid separation of the aqueous phase from the fuel.

These contradictory requirements are satisfied according to the invention by the use in combination of a very foaming surfactant (which is paradoxical given the fact that one wishes to incorporate as little air as possible) and a powerful solvent type DMSO (dimethyl sulfoxide).

• - lors de la préparation de la bouillie, on parvient à stabiliser la dispersion de fuel tout en évitant le moussage, et cette stabilité se conserve au stockage;
• - lors de la sensibilisation (c'est-à-dire transformation de la bouillie inerte en un explosif sur le site) le tensio-actif présent dans la masse favorise l'invorporation de fines bulles d'air ou de gaz sensibilisateur (oxygène, etc.) dans la bouillie, si ce moyen de sensibilisation - qui est le plus simple - est employé.

It has been discovered that this combination allows the surfactant to perform two different essential functions:

• - During the preparation of the slurry, we manage to stabilize the dispersion of fuel while avoiding foaming, and this stability is preserved during storage;
• - during the sensitization (that is to say transformation of the inert slurry into an explosive on the site) the surfactant present in the mass promotes the incorporation of fine air bubbles or sensitizing gas (oxygen, etc.) in porridge, if this means of awareness - which is the simplest - is used.

It should be noted that not all surfactants are suitable. This is particularly the case with surfactants the most common, such as, for example, alkylarylsulfonates. With lauryl sulfate, in particular, the diesel phase separates in a few weeks. Products with an epoxy bridge will also be avoided.

The best results have been obtained with a combination: betaine derivative + DMSO.

It has been specified above that the inert slurry obtained according to the invention is pumpable, which represents an essential advantage.

It can therefore be sensitized in a very simple way by incorporation of air on the site, or of a different sensitizing gas, incorporation made particularly effective thanks to the special choice of surfactant and of its solvent.

Of course, on the site, the sensitized porridge can be carted for transport to the actual shooting location.

Alternatively, it is also possible to sensitize the inert slurry by incorporating, in a known manner, hollow glass beads, bakelite and similar materials and making a cartridge.

• - bien que pompable, elle est cependant assez visqueuse pour bien résister à l'eau (ce qui est important car il arrive fréquemment sur les chantiers de rencontrer de l'eau au fond des trous de tir); l'homme du métieur sait que, à partir du type de composants décrits plus haut, ce compromis entre la pompabilité et la résistance à l'eau, qui sont deux caractéristiques contradictoires, est extrêmement difficile à réaliser: l'invention y parvient, probablement en raison des propriétés spéciales et inattendues de réticulation de la gomme GUARTEC utilisée à cette fin.
• - la durée de vie de l'explosif (de l'ordre de 100h), c'est-à-dire de la bouillie après sa sensibilisation, est suffisamment longue pour permettre un tir retardé, ce qui arrive fréquement sur les chantiers, mais suffisamment courte pour que, assez rapidement, l'explosif redevienne inerte (probablement par coalescence des bulles d'air introduites). Ainsi en cas de perte, d'oubli, de vol de l'explosif, celui-ci cesse très rapidement d'être dangereux.

At this stage, the activated porridge has two additional advantages:

• - although pumpable, it is however viscous enough to resist water well (which is important because it frequently happens on construction sites to meet water at the bottom of shooting holes); those skilled in the art know that, from the type of components described above, this compromise between pumpability and water resistance, which are two contradictory characteristics, is extremely difficult to achieve: the invention achieves this, probably due to the special and unexpected crosslinking properties of the GUARTEC gum used for this purpose.
• - the life of the explosive (of the order of 100 hours), that is to say of the porridge after being sensitized, is long enough to allow a delayed firing, which often happens on construction sites, but short enough for the explosive to become inert fairly quickly (probably by coalescence of the air bubbles introduced). So in case of loss, forgetfulness, theft of the explosive, it quickly ceases to be dangerous.

Of course, this lifetime of the explosive (of the order of 100 hours) should not be confused with the lifetime of the storage of the inert slurry, which is very long: of the order of one year.

According to the invention, the "hydration gum" used in fact is an original combination of two gums and a polyacrylamide.

• a) gomme de base partiellement dépolymérisée,
• b) gomme bipolymérisée, dont l'hydratation est très rapide dans l'eau mais très lente dans la solution de nitrate d'ammonium de départ,
• c) polyacrylamide dont la fonction est double:

• i) hydratation,
• ii) formation d'un gel à caractère filandreux.

This combination is as follows:

• a) partially depolymerized base gum,
• b) bipolymerized gum, the hydration of which is very rapid in water but very slow in the starting ammonium nitrate solution,
• c) polyacrylamide whose function is twofold:

• i) hydration,
• ii) formation of a stringy gel.

The gums a) and b) will be chosen so as to be crosslinked with the GUARTEC gum used according to the invention as a crosslinking agent. The polyacrylamide will of course not be crosslinked.

This mixture participates in obtaining the properties of the inert slurry according to the invention, due to the fact that it is sufficiently fluid but nevertheless has a "stringy" character giving it a consistency similar to that of chewing gum.

In particular, also taking into account the presence in the inert slurry of a very foaming surfactant, as indicated above, it is possible to create, by simple aeration of the slurry on the site, a very fine very sensitizing network of air bubbles or sensitizing gas.

The manufacturing method which is recommended according to the invention must be such that it introduces as little air as possible into the slurry, which is extremely difficult with known slurries and methods.

The method used according to the invention comprises four main stages.

1 Part of the nitrate (representing approximately 30% by weight of the total mixture) is dissolved in water and the rest of the nitrate is added to this solution, which constitutes the first step.

Furthermore, a mixture consisting of part of the fuel or of diesel, the crosslinker according to the invention, is prepared separately ("GUARTEC" gum), and the first hydration gum (a) described above. The mixing time is approximately one hour. The addition of this mixture to solution (1) constitutes step (II).

• - le reste du fuel (ou de gazole)
• - la deuxième gomme d'hydratation (b) décrite ci-dessus
• - le polyacrylamide (c).

III Step (III) consists in then adding a mixture consisting of:

• - the rest of the fuel (or diesel)
• - the second hydration gum (b) described above
• - polyacrylamide (c).

IV The fourth step consists in adding the surfactant and its solvent.

The amount of air introduced can be controlled by density measurements and calculations.

The theoretical density (that is to say total absence of air) of the inert slurry according to the invention is 1.38-1.39.

When operating in a non-industrial manner, that is to say by taking precautions (manual mixing, etc.) incompatible with an acceptable cost, the density obtained is approximately 1.37, value very slightly lower at theoretical density.

The advantage of the invention is that, even when operating industrially, and even very quickly since it is recommended to use for the different stages a rapid mixer, for example with soc "Lôdige" type, the density generally does not drop below about 1.35, which indicates the weakness of the quantity of air introduced.

• l secondes
• Il 5 secondes
• III 10 secondes
• IV 5 secondes
• Ces valeurs sont importantes et ont été longues à déterminer.

With a coulter, laboratory mixer, the mixing times for the four stages are approximately:

• l seconds
• It 5 seconds
• III 10 seconds
• IV 5 seconds
• These values are important and have taken a long time to determine.

It will be noted that if a poorly adapted mixer is used, for example a ruben mixer for powders, the density of the slurry drops to about 1.30.

It should also be noted that, taking into account the starting materials used according to the invention, and the density of approximately 1.35 obtained according to an industrial technique, the skilled person considered that the porridge obtained should have the characteristics of an explosive.

However, if it is subjected to a very severe detonability test by the EEC [Annex II of the Official Journal of the European Communities No. 1250 of September 23, 1980] it turns out to be inert.

Without wishing to be limited by a theory, the applicant considers that this behavior contrary to what could be expected is due to a particularly slow kinetics of the crosslinking caused by the "GUARTEC" gum, kinetics which could not have been predicted since this gum does not had never been used, either as a crosslinking agent, or at a comparable dose. This very slow hydration-crosslinking would allow most of the air included to escape.

The following examples illustrate the invention without, however, limiting its scope.

Example 1 Preparation of an inert porridge Overall composition

• - water 10-14.5 (% by weight)
• - ammonium nitrate 84.75-79.65
• - fuel 4.00-4.39
• - gums 0.51-1.13, i.e.:

• (a) Viscogum FP 200 0.55-0.22
• (b) GUARTEC LV 0.11-0.28
• (c) BOZEFLOC NC 0.18-0.33

• - crosslinking 0.02-0.06 (200-600 ppm)
• - surfactant 0.22-0.44
• - dimethyl sulfoxide 0.11-0.22

Detailed composition

• - nitrate solution
• ammonium: water 12 (% by weight)
• NA 30
• - ammonium nitrate
• solid 52.57
• -1 ° fuel fraction 1.1
• - 2nd fuel fraction 3.03

• (a) -VISCOGUM FP 200 0.39
• (b) - GUARTEC LV 0.22
• (c) - BOZEFLOC NC 0.22

• - GUARTEC 417 320 ppm
• - INTRAPHOR 171 0.33
• - Dimethyl sulfoxide 0.11

Description of the elements: A) Ammonium nitrate

Element found in the boil in two forms: one in aqueous solution and the other in solid form.

The aqueous solution is a solution whose crystallization temperature is preferably 32 ° C., but this example does not eliminate the use of solutions more or less loaded with ammonium nitrate.

The solid ammonium nitrate is preferably nitrate originating from the grinding of ammonium nitrate in "prill".

B) Fuel

Conventional fuel element called domestic fuel, with a density greater than 0.8 and whose flash point is above 55 ° C.

C) Hydration gums

• (a) VISGOGUM FP 200: gum from the CECA company, the origin of which is an extract from the endosperm of guar seed, named Cyamopsis tetragonolobus. By more or less marked depolymerization of this original gum, it is possible to use a series of gums in particular VISCOGUM FP 200, the aqueous solutions of which have a rheological character well suited to the problem posed. (see notice titled "GUAR VISCOGUM TECHNIQUES GUMS" (10.74) and notice FTC 0100 entitled "Measurement of viscosities of Viscogum Techniques" (02.76)).
• (b) GUARTEC LV: Gum from the General Mills Company (Henkel), modified to obtain a gel with relatively low viscosity.
  GUARTEC LV reinforces the activity of VISCOGUM FP 200 in their essential function of constituting with the aqueous solution a viscosity phase allowing pumping.
  Gelling gums obtained from starchy products, such as the product "SOLVITEX Cp" marketed by the company Paul DOITTAU, can advantageously replace GUARTEC LV gum.
• (c) BOZEFLOC N 26: Synthetic polymer from the company HOECHST: polyacrylamide with very high molecular weight (6 x 10 ⁶ ) non-ionic.

This polymer also gels aqueous solutions of ammonium nitrate, but does not crosslink with the crosslinker used. It modifies the kinetics of hydration and crosslinking of the two previous gums. The main purpose of this effect is to maintain, for a sufficient period of time, a minimum viscosity of the assembly in order to allow coalescence of the air bubbles introduced during manufacture and trapped in the mass, coalescence which prevents air. included mass awareness.

D) GUARTEC 417

Self-crosslinking gum used as a gelling agent, in the profession, at rates close to, in most cases, 1%. This gum could not be used as a hydration gum, according to the invention, the viscosities being too high.

On the other hand, in infinitely smaller proportions (200-600 ppm), it surprisingly has all the qualities of a crosslinker and causes crosslinking of the two gums (a) and (b) used.

The implementation requires a specific protocol.

Physical contact is made between the Guar 417 and the VISCOGUM FP 200 within a hydrophobic element, such as fuel oil, by intense mixing.

This operation facilitates a probable adsorption of Guar 417 gum on the VISCOGUM and causes very slow crosslinking.

The hydration-crosslinking phenomenon of the system finds its optimum achievement in a pH range between 5 and 6.

Note that this gum is self-crosslinking, that is to say has its own crosslinking elements, in very small quantities, and that nothing suggested that it even, in minimal proportions, would be able to act as crosslinking.

E) Surfactant

The dispersion of fuel oil in a hydrophilic composition also charged with ionic element (ammonium nitrate), the maintenance of this dispersion over time are facilitated by the use of a surfactant, INTROPHOR 171, from the company DIAMOND SHAMROCK, from the family of alkylamido-betaines.

By adding a powerful solvent such as dimethyl sulfoxide (DMSO) to the surfactant, its diffusion is improved within the mass, which makes it possible to reduce the stirring time and therefore to avoid introducing too much air bubbles despite the foaming nature of the surfactant, which is surprising.

Manufacturing method

• 1 - Mouillage du nitrate d'ammonium solide par la solution aqueuse de nitrate d'ammonium.
• Il - Introduction de la première fraction fuel accompagnée du VISCOGUM FP 200 et GUARTEC 417.
• lll - Introduction de la deuxième fraction fuel accompagnée du GUARTEC LV et BOZEFLOC N 26. IV - Introduction du mélange (tension-actif + DMSO).

The manufacturing process can be divided into four stages.

• 1 - Wetting the solid ammonium nitrate with the aqueous ammonium nitrate solution.
• II - Introduction of the first fuel fraction accompanied by the VISCOGUM FP 200 and GUARTEC 417.
• lll - Introduction of the second fuel fraction accompanied by GUARTEC LV and BOZEFLOC N 26. IV - Introduction of the mixture (voltage-active + DMSO).

Depending on the dynamic mixer or kneader adopted, the mixing time for each of these stages is variable. The mixing process used is subject to the imperative of a final density as high as possible. Manual mixing, with the maximum of precautions, gives a final density of 1.37.

With a belt mixer (powder mixer), after 15 minutes to 20 minutes, we obtain a density of 1.30.

With a Lôdige type projection and swirl mixer, the overall mixing time is 25 seconds to reach a density of 1.35. Of course, this list of different types of mixers is not exhaustive.

Example 2 Use of porridge for explosive use.

According to the explosion criteria described in the standard described above of the Council of the European Communities (Test load placed in a tube fixed on five lead bearings. At the entrance of the tube, a Boostex is detonated. then the degree of crushing of each level. The less the levels distant from the Boostex are crushed, the less the explosion has spread and therefore the more the test load is inert), the slurry described above is comparable to an inert material. To activate this material, a physical means of dispersing very fine gas bubbles must be used to create an explosive with a density of less than 1.20.

On the operating site, a pump can be used, such as a sparrow pump, force-fed by a worm screw. Downstream of this pump, a static type mixer is placed to uniformly gasify the solid phase. The gas phase is introduced upstream of the static mixer. On leaving the static mixer, the slurry has all the characteristics of an explosive.

As gas, air can be used in particular.

In the case of sensitization by aeration, the invention makes it possible, thanks to aeration on the site, to vary the density of the explosive from the bottom of the hole to its orifice, according to the energy required , for example from d = 1.29 to d = 1.10, which is impossible with conventional pumpable explosives. In the case of explosives according to the invention, it suffices to vary the flow rate of aeration gas.

Explosive characteristics:

We made shots in steel tube with a diameter of 80 mm and a length of 600 mm, with priming by a Dynamite Booster type F 15 with a diameter (that is to say, whose length equals the diameter of the tube).

The results (average detonation velocity values) were as follows:

These values make it possible to classify the explosives according to the invention in the category of rapid explosives.

Power coefficient (practical use coefficient, UPC): about 1.

• diamètre 50 mm: d = 1,17
• diamètre 80 mm: d, = 1,27
• La figure unique annexée représente l'essai CEE décrit plus haut appliqué:
• - au sable (courbe a), produit inerte par excellence;
• - à la bouillie inerte selon l'invention (courbe b)
• - au nitrate d'ammonium agricole pur type Ammonitrate (courbe c)
• - au nitrate d'ammonium industriel pur type B3 (courbe d).

Limit densities (values above which there is no longer an explosion):

• diameter 50 mm: d = 1.17
• diameter 80 mm: d, = 1.27
• The single appended figure represents the EEC test described above applied:
• - sand (curve a), inert product par excellence;
• - inert slurry according to the invention (curve b)
• - with pure agricultural ammonium nitrate Ammonitrate type (curve c)
• - with pure industrial ammonium nitrate type B3 (curve d).

The test was carried out in a steel tube with a diameter of 100 mm, with priming by a Dynamite booster type F 15 of 1.5 kg (length 1 = 15 cm).

The curve obtained highlights the great inertia of the slurry according to the invention, before sensitization on the site.

Claims (12)

1. Inert and stable slurry, without explosive elements, is provided for producing an explosive of the type containing water, ammonium nitrate on its own or in admixture with certain soluble alkaline (sodium) or alkaline-earth (calcium) nitrates, fuel, a system of hydrating gums and a crosslinking agent, charcterized in that the system of hydrating gums consists in a mixtue of a partly depolymerized basic gum, of a bipolymerized gum of which the hydration is very fast in water, but very slow in the solution of ammonium nitrate and of a polyacrylamide, and in that said cross-linking agent consists in a self-cross-linking gum used in a proporation varying between 200 and 600 ppm, said slurry being pumpable, and containing no included air, or else containing air of manufacture in non-sensitizing form.

2. Slurry according to claim 1, characterized in that it contains: (% by weight)

- water 10-14.5

- ammonium nitrate 84.75-79.65

- fuel 4.00-4.39

- hydration gums 0.51-1.13

- cross-linking agent self

cross-linking gum) 0.02-0.06 (200-600 ppm)

- surface-active agent 0.22-0.44

- solvent for the surface-active agent 0.11-0.22

3. Slurry according to claim 2, characterized in that it contains: (% by weight)

- water 12

- ammonium nitrate 82.57

-fuel 4.13

- hydration gums 0.83

- cross-linking agent

(self cross-linking gum) 0.03 (or 320 ppm)

-surface-active agent 0.33

- solvent for the surface-active agent 0.11

4. Slurry according to claim 2 or 3, charcterized in that it contains as surface-active agent a betaine derivative, particularly an alkyl-amidobetaine, and as associated solvent a powerful solvent like DMSO.

5. Slurry according to one of claims 1 to 4, characterized in that it contains as hydrating gum system a synergistic mixture of two gums:

- the first coming from extract of endosperm of guar grain of Cyamopsis tetragonolobus, and being partly depolymerized (0.39% by weight) ("VISCOGUM FP 200"),

- the second being a gum forming a gel with relatively low viscosity (0.22% by weight) ("GUARTEC LV") and of a non-ionic polyacrylamide of very high molecular weight.

6. Pumpable explosive obtained by sensitizing the inert slurry according to any one of claims 1 to 5, for example by aeration on the firing site by air or a sensitizing gas.

7. Pumpable or encapsulatable explosive obtained by sensitizing the inert slurry according to any one of claims 1 to 5, by the incorporation of hollow beads, particularly in glass or bakelite.

8. Process for the preparation of inert slurry according to any one of claims 1 to 5, characterized in that it comprises the four following steps:

I A portion of the nitrate (representing about 30% weight of the total mixture) is dissolved in water and to this solution is added the rest of the nitrate;

II A mixture is prepared separately which consists of a part of the fuel or gasoil, the cross-linking agent according to the invention, and the aforesaid first hydrating gum for about one hour, the resulting mixture being then added to the solution obtained in step (I);

III Then to the mixture obtained in Step (II) is added the rest of fuel or of the gasoil, the second hydrating gum described above; and the polyacrylamide; and

IV finally the surface-active agent and its.solvent.

9. Process according to claim 8, characterized in that a rapid mixer, such as of the blade type is used for each step.

10. Process for the manufacture, possibly on the site of use, of a pumpable explosive, characterized in that air or a sensitizing gas is incorporated into an inert slurry such as defined in any one of claims 1 to 5, or such as prepared by the process according to claim 8 or 9.

11. Use of a self-crosslinking gum in quantity ranging between 200 and 600 ppm, as crosslinking agent in a system comprising a partly depolymerized basic gum, a bipolymerized gum, of which the hydration is very fast in water, but very slow in the solution of ammonium nitrate and a polyacrylamide contained in a slurry of water-nitrate-fuel type.

12. Use of a self-crosslinking gum in quantity varying between 200 and 600 ppm, as crosslinking agent in a system comprising a partly depolymerized basic gum, a bipolymerized gum, of which the hydration is very fast in water, but very slow in the solution of ammonium nitrate and a polyacrylamide contained in a slurry of water-nitrate-fuel type, in combination with a surface-active foaming agent and solvent for the surfactant.

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