US3558749A - Method for the production of the ammonium nitrate component of an nh4no3-containing explosive of high detonation speed - Google Patents

Abstract

THE AMMONIUM NITRATE COMPONENT OF AN OIL- AND NH4N03-CONTAINING EXPLOSIVE OF HIGH DETONATION SPEED IS MANUFACTURED FROM AN INADEQUATELY POROUS COMMERCIAL FORM OF AMMONIUM NITRATE BY GRINDING THE LATTER, SEPARATING FROM THE GROUND MATERIAL THE FRACTION HAVING A PARTICLE SIZE OF FROM 0.05 TO 0.125 MM., COMPRESSING THIS FRACTION INTO A MASS HAVING AN "OPEN POROSITY" OF AT LEAST 10% BY WEIGHT, COMMINUTING THE RESULTANT POROUS MASS, AND SEPARATING OUT THE FRACTION HAVING A PARTICLE SIZE OF FROM 0.5 TO 2MM. THE LATTER IS SUBSEQUENTLY HALFFILLED BY IMPREGNATION WITH OIL SUCH AS DIESEL OIL OR SPINDLE OIL.

Description

United States Patent 3,558,749 METHOD FOR THE PRODUCTION OF THE AMMONIUM NITRATE COMPONENT OF AN NH NO -CONTAININ G EXPLOSIVE OF HIGH DETONATION SPEED Viktor Rank, Linz (Danube), Hans Tentschert, Leonding, near Linz (Danube), and Harald Junker and Kurt Allgeuer, Linz (Danube), Austria, assiguors to Osterreicbische Stickstofiwerke Aktiengesellschaft, Linz, Austria N0 Drawing. Original application Jan. 30, 1967, Ser. No. 7 612,308. Divided and this application July 5, 1968, Ser.

No. 742,703 Claims priority, application Austria, Feb. 2, 1966, A 927/66 Int. Cl. C06b 1/04 US. Cl. 2643 1 Claim ABSTRACT OF THE DISCLOSURE The ammonium nitrate component of an oiland NH NO -containing explosive of high detonation speed is manufactured from an inadequately porous commercial form of ammonium nitrate by grinding the latter, separating from the ground material the fraction having a particle size of from 0.05 to 0.125 mm., compressing this fraction into a mass having an open porosity of at least 10% by weight, comminuting the resultant porous mass, and separating out the fraction having a particle size of from 0.5 to 2 mm. The latter is subsequently halffilled by impregnation with oil such as diesel oil or spindle oil.

The present application is a division of copending application, Ser. No. 612,308, filed Jan. 30, 1967, now abandoned.

The invention relates to a method for the manufacture of the NH NO -containing component of an ammonium nitrate-containing explosive of high detonation speed.

It is known to manufacture explosives for industrial application, especially rock explosives, by admixing solid and/ or liquid carbon carriers with solid ammonium nitrate, and at the same time it is possible to affect the se nsitivity and detonation speed or explosive power of such mixtures by certain pre-treatments of the ammonium nitrate and/or by further additives. Thus for example attempts have been made to impart higher porosity to the cheaper, non-porous, dense prill, before or after adding carbon-containing admixture or impregnating substances, by grinding, compressing and subsequent breaking-up, in order to improve the absorptive capacity for the liquid additives. Iun this way it has already proved possible to achieve relatively good detonation speeds. A temperature fluctuation treatment of the ammonium nitrate is also supposed to improve the absorptive capacity for liquid carbon carriers by loosening the lattice as a result of changing its structure.

Though several of the methods indicated have achieved good success, it has now been found that they can be still further significantly improved by following the procedure described hereinafter. What has been found is that by suitably selecting the particle size of the starting material which has been comminuted by grinding or crushing, such as crystalline or prilled ammonium nitrate, an increase in the absorptive capacity for liquid carbonaceous fillers beyond the extent hitherto attained can be achieved, without the impregnation oil seeping out on storage.

According to the present invention the fraction of the ground material having a particle size from 0.05 to 0.125 mm. is sieved out for the above purpose. This fraction Patented Jan. 26, 1971 is condensed by pressure, in any desired manner, into a mass having a porosity, expressed as the oil uptake without leaving a residue, of at least 10% by Weight, and the material is then comminuted into particles having a size of 0.5 to 2 mm. and impregnated with a liquid carbonaceous filler, for example, spindle oil or diesel oil.

Thus in accordance with the present invention there is provided an ammonium nitrate-containing explosive of high detonation speed which comprises ammonium nitrate having an open porosity, as hereinbefore defined, of at least 10% by weight, impregnated with a nonexplosive, liquid carbonaceous filler in an amount which stoichiometrically corresponds to the desired oxygen balance in the explosive.

The high open porosity of the ammonium nitrate produced in the manner described above is the prerequisite for achieving a detonation speed which is significantly increased relative to the normal standard, inasmuch as according to a further characteristic of the invention the sieved and comminuted compressed material is not completely impregnated with oil, i.e. until the open pore space is entirely filled, but rather it is only impregnated with such a quantity of a liquid, non-explosive carbonaceous filler, such as diesel oil or spindle oil as stoichiometrically corresponds to the desired oxygen balance of the explosive. Preferably an amount of 5.5 to 6% by weight of the carbonaceous filler, e.g. oil, suffices for this purpose. A larger or smaller amount of oil would, in use, result in an undesired excessive evolution of carbon monoxide or of nitrogen oxide. As a result of the ditfer ence between the open pore space and the oil-filled pore space there remains, after impregnation, a certain proportion of pores filled with air which is decisive for the particularly rapid propagation of the reaction wave in the explosive column.

If these two features of the invention, explained above, are observed, namely producing a certain above-normal open porosity in the ammonium nitrate granules and a partial oil impregnation, detonation speeds of at least 3000 m./ sec. are achieved, which can even be increased up to 3500 m./sec. In order to achieve this high detonation speed it is not necessary either to add absorptive substances or other explosives.

The ammonium nitrate-oil explosive of high detonation speed of the invention is thus primarily characterized by consisting of ammonium nitrate of open porosity of approximately 10% by weight and above and only such quantity of a liquid, non-explosive, carbonaceous carrier, such as diesel oil or spindle oil as is necessary to set up the desired oxygen balance of the explosive, preferably 5.5 to 6% by weight. The high open porosity of the ammonium nitrate component which according to the invention is required for such an explosive is obtained from inadequately porous commercial forms of ammonium nitrate by grinding, compressing, comminution and sieving.

Thus, a characteristic feature of the invention is the process for the manufacture of the ammonium nitrate component of the above-described explosive which comprises grinding, compressing and comminuting the starting ammonium nitrate, sieving from the resulting ground ammonium nitrate the fraction having a particle size from 0.05 to 0.125 mm., condensing this fraction into a mass having a porosity of at least 10% by weight, comminuting the said mass and sieving out from the comminuted material the fraction having a particle size from 0.5 to 2 mm.

The following examples illustrate the invention:

EXAMPLE 1 Dense ammonium nitrate prill containing 0.14% by weight of water and having an oil absorptive capacity which after immersing the prill in diesel oil and allowing it to drain for 6 hours proves to be 3.4% by weight, and

having a bulk density of 0.95 kg./l., was ground in a laboratory mill. The fraction having a particle size from 0.05 to 0.125 mm. was sieved out and compressed in a tablet press, at a pressure of around 200 kg./cm. into tablets of approximately 1.5 to 2 mm. thickness. These tablets were subsequently broken into fragments of size between 0.5 to 2 mm. The ammonium nitrate granules so obtained had high storage stability and abrasion resistance. They had an oil absorption capacity of 11.2% by weight in the pores. This oil absorption capacity was determined by pouring oil over the granules in vacuo, separating them from the oil after releasing the vacuum, and cleaning externally adhering oil off the granules by means of absorptive paper.

110 g. of spindle oil was sprayed over 2 kg. of these granules and thoroughly admixed therewith, and the product was then placed in an iron tube (1 m. long, cm; internal diameter, 5 mm. wall thickness, with a screw cap at one end) and caused to detonate by means of a primer charge (1 cartridge of gelatine-Donarit). The detonation speed was measured by the DAutriche method and proved to be 2,900 m./sec. at a distance of 20 cm. from the primer charge and 3,300 m./sec. at a distance of 80 cm.

EXAMPLE 2 Dense ammonium nitrate prills were ground as in EX- ample 1. The sieve fraction having a particle size from 0.05 to 0.125 mm. was fed into a roller press and compressed into sheets at such a high roller pressure as to result in an internal porosity (determined by oil absorp- I of this ammonium nitrate-oil mixture were introduced into a 3 m. long iron tube of 5 cm. internal diameter and 5 cm. wall thickness and detonated with a gelatine- Donarit cartridge. The detonation speeds measured at 20, and 280 cm. distance were 2,850, 3,350 and 3,400 m./sec., respectively.

What is claimed is: t

1. A method for the manufacture of the ammonium nitrate component of an ammonium nitrate and oil containing explosive of high detonation speed, said explosive containing 5.5 to 6% by weight of oil, from an inadequately porous commercial form of ammonium nitrate which comprises grinding the said commercial ammonium nitrate, sieving from the resulting ground ammonium nitrate the fraction having a particle size from 0.05 to 0.125 mm., compressing this fraction into a mass having a porosity of at least 10% by weight, comminuting the said porous mass and sieving out from the comminuted material the fraction having a particle size from 0.5 to 2 mm.

References Cited UNITED STATES PATENTS 2,499,321 2/1950 Lyte 149112X 3,061,488 10/1962 Scott 149112X 3,095,335 6/1963 McCloud et a1. 149-112X 3,111,437 11/1963 Hino et al 149112X 3,305,414 2/1967 Hodgson 14946 3,453,155 7/1969 Sheeran et a1. 149--112X BENJAMIN R. PADGETT, Primary Examiner S. I. LECHERT, ]R., Assistant Examiner US. Cl. X.R.