JPH10291883A - Explosive composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an explosive compsn. less liable to cake even at high temp. and humidity and having superior antistatic performance by incorporating ammonium nitrate, fuel oil and starch or modified starch. SOLUTION: This explosive compsn. contains 70-97 wt.% ammonium nitrate, 2 5-25 wt.% fuel oil and 0.01-4.5 wt.% starch or modified starch. The ammonium nitrate is porous ammonium nitrate granule or a mixture of porous ammonium nitrate granule with its crushed product and has 5-24% rate of oil absorption, 0.5-2.5 mm average diameter and a hardness of 4-25. The fuel oil is, e.g. mineral oil, animal oil, alcohol, wax, a nitro compd. or a mixture of them. The starch is, e.g. wheat starch, cornstarch, rice starch or a mixture of them. The modified starch is, e.g. oxidized starch, acetyl starch, phosphated starch or a mixture of them. The average particle diameter of the starch or modified starch is 2-500 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to explosive compositions. More specifically, the present invention relates to an explosive composition that can be used for industrial blasting operations such as quarrying and mining, and in particular, blasting operations that are directly performed by pouring into a perforation or the like.

[0002]

2. Description of the Related Art As explosives used in industrial blasting operations, dynamite, hydrous explosives, nitrite explosives, explosives containing ammonium nitrate and fuel oil as main components (hereinafter referred to as ANFO explosives) and the like are well known. As an explosive for quarrying and mining, ANFO explosives are often used because they are inexpensive and can be directly poured into perforations.

[0003]

The main component of the ANFO explosive is porous and granular ammonium nitrate (hereinafter referred to as porous prill nitrate), which often accounts for 90% by weight or more of the entire explosive. The ANFO explosive is an explosive having a relatively simple structure in which a liquid fuel such as light oil is mixed with the porous prill nitrate.

[0004] Ammonium is about 12 g at 0 ° C for 100 g of water
It is a substance easily soluble in water that dissolves at 0 g or at about 950 g at 100 ° C., and has the property that its solubility in water rapidly increases at high temperatures.

[0005] Since the main component of the ANFO explosive is porous prill nitrate as described above, under high temperature storage conditions such as summertime, under high temperature storage conditions, the moisture in the air or the moisture contained in the packaging material reduces the amount of nitrate. When the surface partially dissolves and the temperature drops at night or the like, crystals precipitate from the dissolved ammonium nitrate surface,
At this time, the phenomenon that the adjacent ammonium nitrate particles adhere to each other repeatedly occurs, and a problem is observed that the entire ANFO explosive solidifies (also referred to as solidification or caking). In order to prevent this solidification, it is possible to prevent the temperature of the ANFO explosive from being raised, in other words, by taking measures such as air-conditioning the storage location.
This is often difficult due to cost or storage space. In order to prevent this problem, an anti-solidification agent is mixed into the porous prilled ammonium nitrate, which can prevent solidification to some extent. However, in the case of extremely high temperature and high humidity, solidification cannot be sufficiently prevented.

Further, when the ANFO explosive is sent at a high speed by a pneumatic conveying type loading machine for loading into a blast hole or when it is poured into a blast hole, friction between the explosive particles or the explosive particles and the hose wall surface, the destruction of the hose, A large amount of static electricity is generated by friction with the wall of an object. The generated static electricity is ANF
There is a danger that the O-explosive itself is charged and accumulated in a blast hole, a hose, a loading operator, etc., and causes an explosion accident due to discharge to an electric detonator.

As a general countermeasure against this, a method of incorporating a water-soluble antistatic agent into an ANFO explosive as an aqueous solution or a method of dissolving an oil-soluble antistatic agent in light oil and using the same has been practiced. The use of water-soluble substances absorbs water, and the use of oil-soluble substances does not sufficiently prevent water permeation at high temperatures.
The problem of explosive solidification has not been solved.

[0008]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventor has found that the use of starch or modified starch as an additive for ANFO explosives has led to
The present invention has been found to not only make it harder for the NFO explosive to solidify, but also to show an excellent antistatic effect, thereby completing the present invention.

That is, the present invention provides: (1) an explosive composition comprising ammonium nitrate, a fuel oil and starch or modified starch; and (2) a starch or modified starch with respect to the entire explosive composition. The explosive composition according to (1), wherein the explosive composition according to (1) is contained in an amount of 0.01 to 4.5% by weight. (3) The ammonium nitrate is a porous prill ammonium nitrate or a mixture of porous prill ammonium nitrate and a crushed product thereof. Composition.

Hereinafter, the present invention will be described in detail. The starches or modified starches used in the explosive composition of the present invention include various shapes such as a circle, an ellipse, and a polygon depending on the source plant, and any of them can be used. Specific examples of starches that can be used include soluble starch, wheat starch, corn starch, potato starch, rice starch, sweetened starch, tapioca starch, and the like.Examples of modified starch that can be used include α-starch. , Oxidized starch, acetyl starch, phosphate starch, etherified starch (hydroxyethyl starch, hydroxymethyl starch, sodium starch glycolate, etc.), starch-acrylic acid graft polymer and the like. Used as a mixture of more than one species. As the average particle size,
Usually, it is 2 to 500 μm, preferably 10 to 100 μm. As the starch or modified starch used in the explosive composition of the present invention, any of the above-mentioned substances is effective, but wheat starch in particular exhibits an excellent effect.

If the amount of starch or modified starch used in the explosive composition of the present invention is too small, the effect is not sufficient. If the amount is too large, the performance as an explosive may be reduced. Preferably 0.01
To 4.5% by weight, more preferably 0.2 to 3% by weight.

The ammonium nitrate used in the explosive composition of the present invention is:
Porous prill nitrate (unground product) having an oil absorption of 5 to 24%, an average particle size of 0.5 to 2.5 mm, and a hardness of 4 to 25 is preferable. The ammonium nitrate used in the present invention may be porous prill nitrate or a mixture of porous prill nitrate and its pulverized product, and the amount used is usually in the range of 70 to 97% by weight based on the entire explosive composition. , Preferably in the range of 90 to 95% by weight.

The oil absorption rate of ammonium nitrate is calculated by immersing a predetermined amount of sample nitric acid in light oil for a certain period of time, performing suction filtration, and calculating the oil adsorption from the weight difference before and after the test. For example, 50 g of sample nitric acid is placed in a glass filter (11G-1) having a diameter of 40 mm and a depth of 50 mm, weighed with an upper direct balance, and set in a vacuum device. Next, 40 ml of light oil is injected into the glass filter, and the mixture is thoroughly stirred with a thin rod to achieve mixed contact between ammonium nitrate and light oil. After standing for 5 minutes, open the lower cock attached to the glass filter and let light oil flow naturally for 2 minutes. Subsequently, after suctioning with a vacuum pump for 5 minutes (at a flow rate of about 30 ml / min), the glass filter containing the sample ammonium adsorbed with light oil is weighed with an upper plate direct balance. The increase is the light oil adsorption. Original sample nitrate 50
The ratio (%) of the light oil adsorption (g) to g is indicated as the oil absorption (%). The calculation formula is as shown in the following formula (1).
The above is based on the method defined by the Industrial Explosives Association.

Oil absorption rate (%) = gas oil adsorption (g) / sample 50 (g) × 100 (1)

The oil absorption rate of ammonium nitrate depends mainly on the pore volume and effective diameter (minimum diameter of pores through which light oil can penetrate) distributed inside the grains. For example, if the pore volume is large, Since the space capable of holding the light oil inside the grains is large, the oil absorption rate is large.

The so-called porous prill nitrate having many pores inside the particles is usually granulated by passing an aqueous solution of a high-temperature nitrate solution having a controlled concentration through an injection granulator (a pre-ring granulator or a pre-ring tower). It is manufactured through a subsequent drying step, cooling step, and the like. The pore volume, effective pore diameter, etc. of porous prill ammonium nitrate are largely governed by raw material conditions such as ammonium nitrate concentration and solution temperature in the granulation process, granulation equipment, and manufacturing processes such as operating conditions of the drying equipment. By adjusting these manufacturing processes, a product having a desired oil absorption can be obtained.

The average particle size of ammonium nitrate is calculated from a weight distribution obtained by passing a certain amount of ammonium nitrate through various sieves having different sieves and obtaining the weight of each sieve. The calculation formula is as shown in the following formula (2).

D = Σ (R × X / 100) (2) where D = average particle size (mm) R = residual weight on each sieve mesh (%) X = average mesh size of sieve mesh (mm)

The hardness of granular ammonium nitrate is calculated by mechanically crushing a fixed amount of sample nitric acid by a hardness measuring device under certain conditions, and using the measured value of the crushed amount. The device used is a pan (200 m diameter) that rotates with a horizontally fixed rotation axis on a vertical rotation axis that rotates through a speed reducer.
m) and a non-rotating grind plate (diameter 190 mm, weight 1715 g) which is dropped onto the tray. 50 g of sample nitrate is placed in a tray of a hardness measuring device, spread evenly over the entire surface of the plate, and a grinding plate is placed on top of this to start the device. After a certain period of time, the apparatus is stopped, and after the standstill, the pan is taken out, the sample inside is put into a predetermined sieve, and shaken for 1 minute using a shaker. Then, a crushed product passed through a sieve is collected, weighed, and the ratio (%) of the crushed amount (g) to 50 g of the original sample nitrate is indicated as hardness. The calculation formula is as shown in the following formula (3). The above is based on the method defined in the Industrial Explosives Association Law.

Hardness (%) = Amount of crush (g) / Sample 50 (g) × 100 (3)

The ammonium nitrate used in the explosive composition of the present invention is:
A pulverized product of porous prill nitrate may be used. Such a pulverized product is a general pulverization method of pulverizing porous prill nitrate having an oil absorption of 5 to 24% into a powdery form of a solid material such as a ball mill and an edge runner. The average particle size is usually 0.01 to 0.5 mm,
Preferably it is 0.01 to 0.3 mm.

In the explosive composition of the present invention, it is preferable to use a mixture of porous prill nitrate and its pulverized product, and the ratio is arbitrary.

The fuel oil used in the explosive composition of the present invention is preferably an oil which is liquid at the time of mixing. Specific examples of usable fuel oils include mineral oils such as No. 2 light oil and kerosene, and animal oils. Further, depending on the application, alcohols,
Waxes, nitro compounds and the like can be used alone or as a mixture as a fuel oil. It is not necessary to heat the fuel oil if it is liquid at normal temperature, but it is preferable that the fuel oil having a high melting point is heated to be liquid and mixed with the porous prill nitrate at a temperature higher than the temperature at which it becomes liquid.

The amount of fuel oil used in the explosive composition of the present invention is usually 2.5 to 25% by weight of the entire explosive composition,
Preferably it is in the range of 4 to 10% by weight.

The explosive composition of the present invention may contain, if necessary, an oxidizing agent other than porous prill nitrate and / or its pulverized product, for example, potassium nitrate and perchlorate, and other powdered fuels such as wood powder and Al powder. Additives can be added.

The explosive composition of the present invention is obtained by using a mixer such as a kneader or a rotary mixer to mix porous prill nitrate or a mixture of porous prill nitrate and its pulverized product, fuel oil and starch or modified starch. Manufactured by It is preferable to add starch or modified starch after mixing fuel oil with porous prill nitrate or a mixture of porous prill nitrate and its pulverized product. In addition, other mixers can be used as long as they have stirring and mixing functions. When a fuel oil having a high melting point is used, it is preferable to use a mixer equipped with a heating and warming device. It is preferable that the mixing is performed with stirring, mixing speed and time in which the particles of the porous prill nitrate are not so crushed,
Normally at a rotation speed of about 20 rpm to 120 rpm for 2 minutes to 2
Mixing may be performed for about 0 minutes. When separately adding and mixing the fuel oil, starch or modified starch, the mixture of the porous prill nitrate or the mixture of the porous prill nitrate and the pulverized product and the fuel oil, 20 rpm to 120 r
about 2 minutes to 20 minutes at a rotation speed of about pm, and further add starches or modified starch to the mixture and add 20 to 120 rpm.
The mixing may be performed at a rotation speed of about pm for about 1 to 20 minutes.

Since the explosive composition of the present invention contains a starch or a modified starch which functions as an anti-solidification agent and an antistatic agent, it has an excellent antistatic effect and is extremely hard to solidify even at high temperature and high humidity. It shows the characteristic that.

[0028]

EXAMPLES The present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. In the examples, parts mean parts by weight. % Is% by weight.

Example 1 93.5 parts of porous prill nitrate having an oil absorption of 12%, an average particle diameter of 1 mm and a hardness of 12 were transferred to a horizontal kneader equipped with a sigma blade at room temperature, and 6 parts of No. 2 light oil was added. Mix for 5 minutes. Thereafter, 0.5 parts of wheat starch having an average particle size of about 20 μm was added and mixed at the same rotation speed for 1 minute to obtain an explosive composition of the present invention.

Example 2 93.1 parts of the same porous prill ammonium nitrate as in Example 1 was transferred to a rotary mixer (concrete mixer) at room temperature, 5.9 parts of No. 2 light oil was added, and the mixture was mixed at 70 rpm for 3 minutes. 1.0 part of sodium starch glycolate having a diameter of about 200 μm was added and mixed at the same rotation speed for another 5 minutes to obtain an explosive composition of the present invention.

Example 3 50 parts of the same porous prill nitrate as in Example 1 and 43.1 parts of its pulverized product (average particle size: 0.1 mm) were transferred to a horizontal kneader equipped with sigma blades at room temperature. .9 parts were added and mixed at 80 rpm for 2 minutes. Thereafter, 1.0 part of wheat starch having an average particle size of about 20 μm was added, and the mixture was further mixed at the same rotation speed for 3 minutes to obtain an explosive composition of the present invention.

Comparative Example 1 94 parts of the same porous prill nitrate as in Example 1 was transferred to a horizontal kneader equipped with a sigma wing at room temperature, 6 parts of No. 2 light oil was added, and mixed at 80 rpm for 5 minutes to prepare a comparative explosive composition. I got

For each of the explosive compositions obtained in Examples and Comparative Examples, the degree of solidification, electrostatic potential and explosion velocity were measured.

The sample used for measuring the degree of solidification has an inner diameter of 50 m.
m, 300 g of each explosive composition in a cylindrical container made of PVC having a height of 300 mm, heated at a temperature of 40 ° C. for 8 hours while applying a load of 2.7 kg thereon, and then heated at 20 ° C. for 16 hours.
Obtained by repeating the time cooling cycle twice.

The degree of solidification is measured by using bolts and nuts so that the rod moves only vertically in a column installed on a stand that does not move even if a load is applied to the end of the rod having a length of 500 mm. The above-described sample was placed at a position 100 mm from the end, a load was gradually applied to the side opposite to the fixed end, and the load was measured by reading the load at which the shape of the sample collapsed. Therefore, it is evaluated that the larger the measured value is, the more solidified it is.

The electrostatic potential was measured at a temperature of 10 ° C. and an absolute humidity of 5 g · H ₂ O / kg · air. A current collector in which 500 g of each explosive composition was poured out from the attached hopper at 100 g / sec, and a sensor was fixed at a distance of 100 mm vertically to the back surface of the spout through a hole with a diameter of 60 mm provided at a position 700 mm from the upper end of the spout. The measurement was carried out by reading the electrostatic potential generated in the policy using a potentiometer (KS-525, manufactured by Kasuga Electric).
The above is the standard (ES-81) defined by the Pharmacopoeia
It is based on.

The measurement of the explosion velocity is based on the standard (ES-41 (1)) defined by the Pharmaceutical Society of Japan, and 150 g of each explosive composition has an inner diameter of 35 mm and a specific gravity of 0.88.
The sample was placed in a steel tube having a thickness of 3 mm and a length of 230 mm, and was subjected to a Dortolish method using 15 g of a pentolite as a booster.

Table 1 shows the measurement test results of the solidification degree, electrostatic potential and explosion speed of each explosive composition.

[0039]

Table 1 Solidification degree (kg) Electrostatic potential (-kV) Explosion velocity (m / sec) Example 1 0.1 10 2880 Example 2 0.5 30 2850 Example 3 0.1 10 2980 Comparative example 1 13.62 100 2850

As can be seen from Table 1, regarding the degree of solidification,
Comparative Example 1 is very strongly solidified, while Example 1
No. to No. 3 cannot be said to be solidified, and it is clear that the antistatic effect in Examples 1 to 3 is also superior with respect to the electrostatic potential in Comparative Examples. In addition, regarding the explosion speed, as is clear from Examples 1 to 3, it was found that there was no decrease in the explosion speed due to the addition of wheat starch and sodium starch glycolate.

[0041]

The explosive composition of the present invention has an excellent antistatic effect and is hardly solidified even at high temperature and high humidity.

Claims (3)

[Claims] 1. An explosive composition comprising ammonium nitrate, fuel oil and starch or modified starch. 2. The explosive composition according to claim 1, wherein the starch or the modified starch is contained in an amount of 0.01 to 4.5% by weight based on the whole explosive composition. 3. The explosive composition according to claim 1, wherein the ammonium nitrate is porous prill ammonium nitrate or a mixture of porous prill ammonium nitrate and a crushed product thereof.