EP2480519B1

EP2480519B1 - Process for the production of an explosive

Info

Publication number: EP2480519B1
Application number: EP10765500.3A
Authority: EP
Inventors: Laurence Justin Pienaar Wilson; André Pienaar; Charl Vermaak
Original assignee: AEL Mining Services Ltd
Current assignee: AEL Mining Services Ltd
Priority date: 2009-09-23
Filing date: 2010-09-16
Publication date: 2013-10-23
Anticipated expiration: 2030-09-16
Also published as: DK2480519T3; AP2012006175A0; PT2480519E; MA33684B1; AR081511A1; WO2011036611A1; CA2774606A1; ES2436189T3; AP3055A; AU2010299537A1; CL2012000712A1; PE20110378A1; EP2480519A1; HRP20131099T1; ZA201006760B; PL2480519T3; AU2010299537B2

Description

THIS INVENTION relates, broadly, to ammonium nitrate/fuel oil explosives, also known as ANFO or ANFEX explosives, and hereinafter also referred to as ANFO explosives. More particularly, the invention relates to a process for producing an ANFO explosive, and to an ANFO explosive when produced by the process.
Water and oil emulsion components, such as those used in the production of ANFO explosives, are known to be unstable in that separation of the oil and water phases after mixing thereof occurs readily. Such separation is particularly problematic when the emulsion is pre-mixed and then transported to an ANFO explosive manufacturing site or operation, since re-mixing of the emulsion is required before it can be used in manufacture of the ANFO explosive. Conventional approaches to overcoming or inhibiting this instability include adding surfactants to the emulsion and continuous stirring of the emulsion. Continuous stirring of the emulsion is, however, a cumbersome exercise. The use of surfactants is a viable alternative, but surfactants are expensive and in bulk operations, such as the manufacturing of large quantities of ANFO explosive, the use of large quantities of surfactants is thus not an economically attractive option.
It is thus an object of the present invention to provide a cost-effective process for the production of an ANFO explosive, which addresses, in particular, the separation of water and oil components of a water/oil emulsion used in the production of a fuel oil for the ANFO explosive production.
According to the invention, there is provided a process for producing an ammonium nitrate/fuel oil explosive, the process including:

admixing an oil with water to form a fuel comprising an emulsion;
introducing ozone into the emulsion, thereby to obtain an ozonated emulsion; and
admixing the ozonated emulsion with solid particulate ammonium nitrate to absorb the emulsion into the ammonium nitrate, thereby to form an ammonium nitrate/fuel oil explosive.

The introduction of the ozone into the emulsion may include bubbling ozone or an ozone-containing gas through the emulsion. Bubbling the ozone or the ozone-containing gas through the emulsion may be conducted at a sufficiently high rate such as to cause ozonation of the emulsion.
The introduction of the ozone into the emulsion causes the viscosity of the emulsion to increase. The introduction of ozone into the emulsion may therefore be conducted for a sufficient treatment period so as to obtain an emulsion of desired viscosity. More particularly, the introduction of ozone into the emulsion may be continued for a treatment period of from about 1 hour to about 24 hours, e.g. for about 3 hours. On becoming ozonated, the emulsion typically attains a black or milky black appearance, and the bubbling of the ozone through the emulsion will therefore typically continue until such an appearance has been attained. It is expected that, in becoming ozonated, the viscosity of the emulsion will increase above that of the oil used in emulsification. The extent to which the viscosity increases is understood also to be dependent on the quantity of water used to form the emulsion.
Typically, the ozone is obtained by passing compressed air, oxygen, nitrogen, or mixtures thereof through an ozone generator. The product gas from the ozone generator typically contains 3% to 6%, by volume, ozone; this product gas can then be bubbled through the emulsion.
The introduction of the ozone, or ozone-containing gas, into the emulsion may be conducted simultaneously with the admixing of the oil and the water.
It will be appreciated that, depending on, amongst others, the relative proportions of oil and water used, the emulsion may thus be either a water-in-oil emulsion or an oil-in-water emulsion.
Sufficient of the oil and the water may be used such that the oil forms 50%-98% by mass of the emulsion, with the balance thus being water. Preferably, sufficient of the oil and the water is used such that the oil forms 72%-89% by mass of the emulsion, e.g. about 75% by mass thereof. Thus, when the oil forms 75% by mass of the emulsion, the water will form 25% by mass thereof.
The oil may, in particular, be used lubricating oil. Still more particularly, the lubricating oil may be of the type employed, or rather previously employed, for the lubrication of motor vehicle parts. The motor vehicle parts may, in particular, be those of utility vehicles of the kind used in mines or similar machinery, which require lubrication. The use of reclaimed motor lubricating oils in blasting compositions is known from U.S. Patent 4 111 727 .
The admixing of the oil and the water may be effected by means of high-shear mixing. This may be achieved by using a high-shear mixer or another emulsification method or means.
The admixing of the oil and the water may be effected in the presence of an emulsifier/surfactant, hereinafter referred to as a surfactant. When used, the surfactant may typically form 0.2%-1.0% by mass of the emulsion. Preferably, the surfactant, when used, forms 0.3%-0.8%, e.g. about 0.5% of the emulsion.
At least a portion of the surfactant used may be provided by the oil. In this regard it will be appreciated that used lubricating oil normally contains some surfactants, and these surfactants can thus constitute at least part of the surfactant as discussed above. It is envisaged that, normally, it will typically not be necessary to use any additional or external surfactant.
The relative proportions of emulsion and ammonium nitrate employed in producing the ammonium nitrate/fuel oil (ANFO) explosive will be more or less conventional. More particularly, sufficient of the emulsion and the ammonium nitrate may be used in producing the ANFO explosive such that the oil forms 2.5%-22% by mass of the ANFO explosive. More preferably, sufficient of the emulsion and the ammonium nitrate may be used such that the oil forms 5%-7% by mass of the ANFO explosive, e.g. about 6% by mass thereof.
The particulate ammonium nitrate may be in the form of porous ammonium nitrate prills, i.e. porous prilled ammonium nitrate. Typically, the porous prilled ammonium nitrate (PPAN) will be of the type conventionally used in the manufacture of ANFO explosives. The PPAN prills may be employed in a mass ratio to the fuel of 98:2 - 78:22. Preferably, the PPAN is employed in a mass ratio to the fuel of 94:6 - 91:9, e.g. about 94:6.
Admixing the ozonated emulsion with the porous prilled ammonium nitrate may be conducted in conventional fashion by pumping the emulsion from a source tank and spraying it by means of a nozzle onto the ammonium nitrate which is moved along by the flutes of an auger. It is expected that moving the ammonium nitrate in such a fashion will provide additional mixing. Alternatively, and typically for preparing the ANFO explosive on a batch scale, a concrete mixer or the like may be used.
The invention extends to an ANFO explosive when produced in accordance with the process described herein.
The invention will now be described, by way of example, with reference to the accompanying non-limiting illustrative worked Example.

EXAMPLE

A water-in-oil emulsion, comprising, by mass, 25% water and 75% oil, was prepared by mixing appropriate quantities of water and used lubricating oil in a high-shear mixing vessel.
Ozonated air, i.e. a gas obtained by passing compressed air through an ozone generator and containing 3% to 6% ozone, by volume, was bubbled through the mixture for a treatment period of 3 hours, during which the viscosity of the emulsion increased above that of the oil used and the emulsion attained a black appearance. It will be appreciated that, in accordance with the other embodiments of invention, any other suitable gas may be used instead of compressed air to generate an ozone-containing gas which is then bubbled through the mixture or emulsion of water and used lubricating oil.
At the end of the treatment period, bubbling of the ozone through the emulsion was ceased. A stabilized water-in-oil emulsion was obtained.
An ANFO explosive was then prepared by admixing the stabilized emulsion or fuel with porous prilled ammonium nitrate (PPAN) in a mass ratio of PPAN: stabilized emulsion (fuel) of 94:6. The admixing was effected by pumping the emulsion from a source tank and spraying it by means of a nozzle on to the ammonium nitrate prills.
The Applicant believes that the present invention provides a viable and cost-effective process for the production of ANFO explosive which addresses, in particular, the difficulties associated with the separation of water and oil components of a water/oil emulsion.
The use of ozone in the formation of the oil/water emulsion, in accordance with the invention, serves to stabilize the emulsion so that separation of the emulsion into separate oil and water phases does not readily occur. When used lubricating oil is used as the oil, or as at least a component of the oil, then surfactants already present in the used lubricating oil serve to stabilize the emulsion even further, typically to the extent that it is not necessary to use any additional, i.e. external or additional, surfactant.
The stabilized ozonated emulsion provided by this process is thus economically attractive, as the need for large quantities of expensive additional surfactants to stabilize the emulsion is reduced or even eliminated. The stabilized emulsion was found to be stable for long periods of time, being particularly advantageous when the emulsion needs to be transported in premixed form to an ANFO explosive production site or operation.

Claims

A process for producing an ammonium nitrate/fuel oil explosive, the process including:
admixing an oil with water to form a fuel comprising an emulsion;

introducing ozone into the emulsion, thereby to obtain an ozonated emulsion; and

admixing the ozonated emulsion with solid particulate ammonium nitrate to absorb the emulsion into the ammonium nitrate, thereby to form an ammonium nitrate/fuel oil explosive.
The process according to Claim 1, wherein the introduction of the ozone into the emulsion includes bubbling ozone or an ozone-containing gas through the emulsion.
The process according to Claim 1 or Claim 2, wherein the introduction of the ozone into the emulsion is for a treatment period of from 1 hour to 24 hours.
The process according to any one of the preceding claims, wherein the introduction of the ozone into the emulsion takes place simultaneously with the admixing of the oil and the water.
The process according to any one of the preceding claims, wherein sufficient oil is used so that the oil constitutes 50% to 98% by mass of the emulsion.
The process according to any one of the preceding claims, wherein the oil is used lubricating oil.
The process according to Claim 6, wherein the admixing of the oil and the water is effected in the presence of a surfactant, with the surfactant forming from 0.2% to 1.0% by mass of the emulsion.
The process according to Claim 7, wherein at least a portion of the surfactant is provided by the oil.
The process according to any one of the preceding claims, wherein the relative proportions of the emulsion and the ammonium nitrate used are such that the oil forms from 2.5% to 22% by mass of the explosive.
The process according to any one of the preceding claims, wherein the particulate ammonium nitrate is in the form of porous prilled ammonium nitrate.
The process according to Claim 10, wherein the porous prilled ammonium nitrate is employed in a ratio to the fuel of 98:2 to 78:22 by mass.
The process according to Claim 10 or Claim 11, wherein the admixing of the ozonated emulsion with the porous prilled ammonium nitrate is effected by spraying the emulsion on to the ammonium nitrate while moving the ammonium nitrate along by means of the flutes of an auger.
The process according to Claim 10 or Claim 11, wherein the admixing of the stabilized emulsion with the porous prilled ammonium nitrate is effected in a concrete mixer.