JP2003261324A - Method of producing granular ammonium nitrate and granular ammonium nitrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide granular ammonium nitrate which is hard in spite of its low bulk specific gravity, and exhibits powdering prevention effect. <P>SOLUTION: In the method of producing granular ammonium nitrate, sulfuric acid is incorporated into granular ammonium nitrate to obtain the granular ammonium nitrate which has increased hardness in spite of its low bulk specific gravity and is prevented from being powdered. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing granular ammonium nitrate, particularly porous granular ammonium nitrate (porous acrylic nitrate). More specifically, it relates to a method for producing granular ammonium nitrate, which can be suitably used as an explosive commonly used in industrial blasting operations such as tunnel excavation, quarrying, mining, and rock mining.

[0002]

2. Description of the Related Art Granular ammonium nitrate (ammonium nitrate salt), especially porous prill ammonium nitrate, is inexpensive and chemically stable. Therefore, it is an oxidizing agent for explosives such as ammonium nitrate oil explosive (hereinafter abbreviated as "ANFO"). Is widely used as. As a method for producing granular ammonium nitrate, a molten ammonium nitrate solution of about 94 to 96% by weight is usually added at a high temperature of about 140 to 160 ° C.
It is manufactured by granulation using an injection granulator such as a prilling granulator or prilling tower. Granular ammonium nitrate immediately after granulation usually contains about 2 to 4% by weight of water, so that it is dried, and if necessary, an anti-caking material or the like is sprayed to give a granular ammonium nitrate product. It should be noted that the molten ammonium sulfate is a molten ammonium nitrate and one containing a small amount of water (hydrous molten ammonium nitrate).

There are various methods for drying granular ammonium nitrate, such as one-step drying and two or more steps of drying including preliminary drying.
In the conventional method for producing granular ammonium nitrate, particularly porous prill ammonium nitrate, it is common to carry out drying at a relatively high temperature to obtain a product having a moisture content after drying of less than 0.1%. It was By adopting such a method,
This is because the porous performance is sufficient and it is possible to obtain porous prilled ammonium sulfate having a relatively large particle size. Porous prill ammonium nitrate obtained by such a method usually has an average particle size of about 1 to 2 mm and a bulk specific gravity of 0.7 to 0.8 g / c.
Since it was about c and the oil absorption rate was about 8 to 13%, it was preferable for ANFO.

ANFO is an explosive which is a mixture of porous granular ammonium nitrate and light oil. It can be easily manufactured with a simple device, and since it has excellent fluidity, it can be directly poured into the blast hole and loaded by an ANFO loader. Be possible,
Furthermore, it is widely used because it has low impact sensitivity, is safe, and is inexpensive.

[0005]

On the other hand, as a method for enhancing the power of ANFO, it has been performed to increase the voids inside porous prill ammonium nitrate to enhance the explosive reactivity. The adjustment of the bulk specific gravity of the porous granular ammonium nitrate is performed by adjusting the ammonium nitrate concentration in the molten ammonium nitrate used during the granulation.
That is, in order to reduce the bulk specific gravity of porous granular ammonium nitrate, it is performed by decreasing the ammonium nitrate concentration in molten ammonium nitrate during granulation (that is, increasing the water content).

The low bulk specific gravity porous granular ammonium nitrate produced in this manner reduces the concentration of ammonium nitrate in the molten ammonium nitrate during granulation, so that the void volume inside the obtained porous granular ammonium nitrate increases, A product having a reduced bulk specific gravity is obtained. Then, the oil absorption rate of the light oil increases and the power as an explosive increases, but there is a problem that the hardness becomes soft and the powder easily collapses and is easily pulverized.

This not only causes the problem of pulverization at the time of manufacturing the porous prill ammonium nitrate itself or at the time of loading with an ANFO loader, but when the pulverization becomes more violent, the fluidity of the porous prill ammonium nitrate itself is lowered. ,
In addition, the bulk specific gravity is increased to the contrary, the amount charged in the blast hole is increased, and the explosive cost is increased. Then, there is a problem in that the working environment is deteriorated due to the dust of ammonium sulfate that has been pulverized.

The present invention solves the conventional pulverization problem of low bulk specific gravity porous prill ammonium nitrate and has high power when used as an explosive,
In addition, it is intended to provide granular ammonium nitrate which is difficult to be pulverized.

[0009]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies in view of the above problems, and as a result, during the production of porous prill ammonium nitrate, dilute nitric acid under specific operating conditions, specifically, before ammonium nitrate reaction. By adding dilute sulfuric acid in it, or by adding ammonium sulfate in the ammonium nitrate melt before granulation, the hardness of the low bulk specific gravity porous prill ammonium nitrate can be made harder,
It was found that the pulverization prevention effect is improved. In other words, by adding a specific amount of sulfate to the ammonium nitrate reaction solution and granulating the ammonium nitrate melt to obtain granular ammonium nitrate, a double salt of ammonium nitrate and sulfuric acid is generated to change the crystal habit of ammonium nitrate crystals. And the present invention was completed.

That is, the gist of the present invention resides in a method for producing granular ammonium nitrate, which comprises granulating hydrous molten ammonium nitrate containing a specific amount of sulfate and having an ammonium nitrate concentration of 85 to 95% by weight. Preferably, water-containing molten ammonium nitrate is granulated to obtain granular ammonium nitrate having a water content of 4 to 10% by weight, and the granular ammonium nitrate is then matured at 40 to 70 ° C. The method for producing granular ammonium nitrate is characterized by drying under conditions below the transition temperature to

Another gist of the present invention is that the sulfate group content is 30 to 3000 ppm and the bulk specific gravity is 0.5 to 0.7.
It is present in granular ammonium nitrate having a content of [g / cm ³ ] and preferably has an oil absorption of 15 to 30%, more preferably a water content of 0.1 or more, and particularly a water content of 0.1 to 0.3. weight%
It is present in granular ammonium nitrate.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.
In the production method of the present invention, first, dilute sulfuric acid is added to dilute nitric acid or ammonium sulfate is added to the ammonium nitrate reaction solution to obtain an ammonium nitrate reaction solution containing a sulfate group. Either dilute sulfuric acid or ammonium sulfate may be added. The amount of dilute sulfuric acid to be added is 30 to 3000 ppm relative to ammonium nitrate, especially 60 to 3
It is preferably 00 ppm. If the added amount is too low, the effect of making the hardness hard cannot be obtained, and conversely, if the added amount is too large, the purity of ammonium nitrate is lowered, and the performance after the ANFO explosive is deteriorated.

Next, granular ammonium nitrate is granulated from the molten ammonium nitrate whose concentration has been adjusted. At this time, it is preferable that the concentration of ammonium nitrate in the molten ammonium sulfate is relatively low, generally 85 to 95% by weight, and particularly 88 to 95% by weight.
95% by weight, further 90 to 93% by weight, especially 90 to 92
It is preferably in the weight%. If the ammonium nitrate concentration is too high, the bulk specific gravity of the granular ammonium sulfate after granulation, drying and cooling will be high, and if it is too low, it will be low.
The molten ammonium sulfate used in the present invention means a molten ammonium nitrate and one containing a small amount of water (hydrous molten ammonium sulfate). The water content at this time is arbitrary, but is generally 5 to 15% by weight, preferably 8 to 10%.

As the granulation method, any conventionally known method may be used, and for example, it may be manufactured by granulating using an injection granulating device such as a prilling granulator or a prilling tower. The temperature of molten ammonium sulfate used for granulation may be appropriately selected within a range in which the molten ammonium sulfate maintains fluidity, and is generally 13
It may be 0 to 160 ° C. Although the water content of the obtained porous granular ammonium sulfate is arbitrary, it is usually 2 to 10% by weight, 4 to 10% by weight, and 5 to 8% by weight, respectively, and is granulated so as to undergo a subsequent drying step. The obtained porous granular ammonium nitrate is preferable because it can lower the bulk density and increase the hardness.

Next, the porous granular ammonium nitrate obtained by granulation is dried. The present invention is characterized in that the drying is performed in two stages of preliminary drying and subsequent drying. In the preliminary drying, the drying is performed at a relatively low drying temperature, specifically 40 to 70 ° C. The drying temperature is preferably 40 to 65 ° C, more preferably 45 to 60 ° C, and particularly preferably 50 to 55 ° C. The drying temperature may fluctuate within a certain range, and the fluctuation range is not particularly limited as long as the drying temperature is within the above range, but it is generally preferable to carry out within a range of 10 ° C. . The water content of granular ammonium nitrate used in this preliminary drying step is optional, but is generally 10% by weight or less, especially 8% by weight or less, further 4 to 8% by weight, and particularly 5 to 7% by weight. Is preferred. It is preferable that after drying to some extent in this way, further drying is performed in the subsequent drying step.

The predrying time may be appropriately selected in consideration of the production equipment and the time required for production, but generally 5 to 6
0 minutes, especially 5 to 45 minutes, further 5 to 30 minutes, especially 10
It is preferably -20 minutes. If the predrying time is too long, the hardness of the ammonium nitrate after drying and cooling may become soft, and if it is too short, the moisture content of the ammonium nitrate may increase.

After the preliminary drying, the drying is carried out under a higher drying temperature condition.
It is important to keep the temperature below the transition temperature to the I phase. Specifically, after preliminary drying, the temperature is raised to perform drying.
The temperature is less than 85 ° C. This temperature may be less than 85 ° C, but is particularly 70 to 84 ° C, especially 70 to 80 ° C.
It is preferable to carry out drying. The time required for this drying may be appropriately selected, but is generally 30 to 60 minutes, and preferably 40 to 50 minutes. If the drying time is too long, the moisture content of ammonium nitrate decreases and the hardness becomes soft, while if it is too short, the moisture content of ammonium nitrate may increase.

If necessary, a drying accelerator or the like may be applied to the surface of the porous granular ammonium sulfate after preliminary drying by spraying or the like. Specific examples of the drying accelerator include aliphatic alkylamines and salts thereof. Above all, it is preferable to use an alkylamine nitrate, particularly an alkylamine nitrate having 10 or more carbon atoms. The method of application may be spraying using such a drying accelerator as an aqueous solution or dispersion. The concentration of the drying accelerator in the aqueous solution or dispersion used is arbitrary, but generally the concentration of the drying accelerator is 0.1.
-10 wt%, especially 0.5-8 wt%, especially 0.5-
It is preferably 5% by weight. The amount of the porous granular ammonium nitrate to be sprayed is also optional, and is generally 1 × 10 ^-2 to 1% by weight, preferably 5 × 10 ^-2.
˜3 × 10 ⁻¹ wt%.

The drying temperature in the present invention refers to the temperature of the dry atmosphere of porous granular ammonium nitrate used for drying, and is usually the temperature of a heat source such as dry air used for drying. In the present invention, as described above, by performing the drying in two stages, it is possible to obtain a porous granular ammonium nitrate having a low hardness and a low hardness. The mechanism is not clear, but in the preliminary drying, part of the water in the porous granular ammonium nitrate is removed to cover the crystalline surface of the porous granular ammonium nitrate with a hard film, and in the next drying process, it is gently dried. It is considered that this is because the generation of cracks in ammonium nitrate can be suppressed.

As the drying method / apparatus used in the manufacturing method of the present invention, any conventionally known method / apparatus may be used. For example, there is a method of using a jet tank using dry heated air batchwise or continuously. In addition, continuously feeding porous granular ammonium sulfate to a drying device adjusted to a constant temperature, providing a weir at the outlet of the device, changing the height of the weir, so that the porous granular ammonium sulfate stays in the drying device for a predetermined time. A drying device may be used.

The production method of the present invention is suitable for the production of porous granular ammonium nitrate having any desired properties, and is particularly suitable for the production of porous granular ammonium nitrate having a low bulk specific gravity. Above all, the bulk specific gravity is 0.5 to 0.
7 [g / cc], further 0.5 to 0.68 [g / cc],
It is particularly suitable for the production of porous granular ammonium nitrate having a concentration of 0.5 to 0.65 [g / cc]. At this time, the water content of the porous granular ammonium nitrate is arbitrary, but is 0.1% by weight or more, and particularly 0.1.
It is suitable for the production of porous granular ammonium nitrate which is 1 to 0.3% by weight.

Further, although the oil absorption rate of the porous granular ammonium sulfate produced in the present invention is arbitrary, the oil absorption amount is generally 8 to 30% by weight, particularly 15 to 30% by weight, and further 15% based on the weight of porous granular ammonium sulfate. ~ 25% by weight, especially 18-23% by weight
It is suitable for the production of porous granular ammonium nitrate. The hardness is preferably 3% to 10%, more preferably 4% to 7%. Among them, the production method of the present invention is suitable for production of the granular ammonium sulfate of the present invention, that is, the granular ammonium sulfate having a sulfate group content of 30 to 3000 ppm and a bulk specific gravity of 0.5 to 0.7 [g / cc]. The granular ammonium nitrate of the present invention has a sulfate content of 30.
-3000 ppm, bulk specific gravity is 0.5-0.7 [g / c
c], especially 0.5 to 0.68 [g / cc], especially 0.
It is preferably 5 to 0.65 [g / cc]. The oil absorption rate of granular ammonium nitrate is 15 to 30% by weight, more preferably 15 to 25% by weight, and especially 18 to 23% by weight based on the weight of granular ammonium sulfate.
Is preferred. More preferably, the moisture content of granular ammonium nitrate is 0.1% by weight or more, and 0.1 to 0.3% by weight is particularly preferable.

[0023]

EXAMPLES The present invention will be described more concretely with reference to the following examples. The present invention is not limited to the following examples unless it exceeds the gist. In addition, unless otherwise specified, "part" and "%" used in the examples are
Parts by weight and% by weight are shown. Further, in the examples shown below, the bulk specific gravity, hardness and oil absorption of porous granular ammonium nitrate were determined as follows. (1) A hopper having an upper end diameter of 93 mm, a lower end diameter of 15.5 mm, and a height of 120 mm, which is provided with a damper at the lower end of the bulk specific gravity, has an inner diameter of 40 mm.
mm, depth 80 mm, volume 100 cm ^{3 on} a container,
Arrange so that the distance between the upper end of the container and the lower end of the hopper is 36.5 mm.

Next, 120 cm ³ of porous granular sodium nitrate was charged into the hopper, the damper was pulled out, and the mixture was allowed to naturally flow into the container. Scrape off the granular ammonium nitrate that has risen from the top of the container with a ruler, and measure the weight of the granular ammonium sulfate in the container with a balance. After weighing, the weight W (g) of granular ammonium nitrate in the container,
Using the container volume (100 cm ³ ) V, the bulk specific gravity is W / V
It was calculated as (g / cm ³ ). (2) A certain amount of porous granular ammonium nitrate was crushed mechanically by a hardness measuring device under certain conditions, and the crushed amount was measured to measure the hardness. The device used for the measurement is a pan (diameter 200 mm) that rotates together with a rotary shaft that is horizontally fixed on a rotary shaft that rotates through a reduction gear, and a non-rotating grinding pan (diameter 190 mm, weight) that is dropped onto this pan. 171
5g).

As a sample, 50 g of porous granular ammonium nitrate was put in a pan of a hardness measuring device, spread evenly over the entire surface of the plate, and a grinding plate was placed on the pan to start the device. After rotating for 15 seconds with the rotation speed of the rotating dish set to 40 [rpm], the rotation was stopped, and after resting, the receiving tray was taken out and the sample inside was subjected to a predetermined sieve (mesh sieve through which non-crushed particles do not pass). put in,
Shake for 1 minute using a shaker. Next, the crushed product that passed through the sieve was collected, weighed, and the original sample granular ammonium nitrate 50 g
Ratio (%) of crush amount (g) to:
Sample 50 (g) x 100) was defined as the hardness. The smaller this value is, the harder the porous granular ammonium nitrate is. (3) Oil Absorption Rate After immersing a certain amount of porous granular ammonium nitrate in light oil (No. 2 light oil) for 5 minutes, suction filtration was performed, and the oil adsorption amount of light oil was measured from the weight difference before and after the test to obtain the oil absorption amount. Specifically, the ratio (%) of the light oil adsorption component (g) to the porous granular ammonium nitrate 50g: (gas oil adsorption component (g) / porous granular ammonium nitrate 50)
(G) × 100) was taken as the oil absorption rate, and the method for measuring this oil absorption rate was in accordance with the Industrial Explosives Association Law. Example 1 100 ppm of dilute sulfuric acid was added to the raw material dilute nitric acid and reacted with ammonia to prepare a ammonium nitrate reaction solution. Porous granular ammonium nitrate (water content: 6.2%, ammonium nitrate temperature: 65 ° C) obtained by spraying a molten ammonium nitrate solution adjusted to have an ammonium nitrate concentration of 92.6% from the top of the granulation tower was dried at an air temperature of 55 ° C. Pre-dried for 10 minutes.

Next, porous granular ammonium nitrate was added to an aqueous solution of a drying accelerator (octadecylamine nitrate) (concentration 4% by weight).
Was sprayed and added so that the weight of the aqueous solution was 0.03% by weight with respect to 1 part by weight of porous granular ammonium nitrate, followed by drying at 70 to 75 ° C. for 45 minutes and then cooling at 18 ° C. for 45 minutes. . The physical properties of the obtained porous granular ammonium nitrate were water content 0.13%, bulk specific gravity 0.647 g / cm ³ , oil absorption rate 18.0%, and hardness 5.0%. (Example 2) 60 ppm of dilute sulfuric acid was added to the raw material dilute nitric acid and reacted with ammonia to prepare a ammonium nitrate reaction solution. Example 1 except that the concentration of ammonium nitrate was adjusted to 92.6%, and the obtained granular ammonium nitrate (water content: 5.4%, ammonium nitrate temperature: 80 ° C.) was pre-dried at a dry air temperature of 55 ° C. for 15 minutes. I went in the same way.

The physical properties of the obtained porous granular ammonium nitrate depend on the water content.
Content 0.15%, bulk specific gravity 0.669 g / cm³, Oil absorption
The rate was 16.6% and the hardness was 6.2%. (Comparative Example 1) An ammonium nitrate concentration without addition of dilute sulfuric acid: 95.4
% Of molten ammonium nitrate solution sprayed from the top of the granulation tower
Dried granular ammonium nitrate (water content 3.1%, ammonium nitrate temperature 73 ° C)
It was pre-dried at a dry air temperature of 65 ° C. for 45 minutes. At this time
The weir at the exit of the fluidized dryer had a height of 250 mm. Next
And an aqueous solution of an aliphatic alkylamine salt as a drying accelerator.
After adding (octadecylamine nitrate aqueous solution), dry
Air dried at 80-85 ° C for 45 minutes, cooling air temperature 18 ° C
For 45 minutes. The physical properties of the obtained granular ammonium nitrate depend on the water content.
Content 0.03%, bulk specific gravity 0.731 g / cm ³, Oil absorption
The rate was 13.6% and the hardness was 14.5%. (Comparative Example 2) An ammonium nitrate concentration of 95.6 without the addition of dilute sulfuric acid.
% Of molten ammonium nitrate solution sprayed from the top of the granulation tower
Dried granular ammonium nitrate (water content 3.4%, ammonium nitrate temperature 84 ° C)
It was pre-dried at a dry air temperature of 65 ° C. for 45 minutes. At this time
The weir at the exit of the fluidized dryer had a height of 150 mm. Next
And an aqueous solution of an aliphatic alkylamine salt as a drying accelerator.
After adding (octadecylamine nitrate aqueous solution), dry
Air dried at 80-85 ° C for 45 minutes, cooling air temperature 18 ° C
For 45 minutes. The physical properties of the obtained granular ammonium nitrate depend on the water content.
Content 0.03%, bulk specific gravity 0.736 g / cm ³, Oil absorption
The rate was 14.4% and the hardness was 14.4%.

[0028]

[Table 1]

[0029]

EFFECTS OF THE INVENTION According to the present invention, it is possible to obtain granular ammonium nitrate which retains high power when used as an explosive, and which significantly suppresses pulverization prevention due to hardness reduction due to low bulk specific gravity.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Toshikazu Yano             2-5-3 Marunouchi 2-chome, Chiyoda-ku, Tokyo             Ryo Chemical Co., Ltd.

Claims (6)

[Claims] 1. A method for producing granular ammonium sulfate, which comprises granulating hydrous molten ammonium nitrate having a sulfate content of 30 to 3000 ppm and an ammonium nitrate concentration of 85 to 95% by weight. 2. A hydrated molten ammonium nitrate having a sulfate group content of 30 to 3
The production method according to claim 1, which is obtained by reacting ammonia with a nitric acid aqueous solution of 000 ppm. 3. A water-containing molten ammonium nitrate is granulated to obtain a water content of 4 to
10% by weight of granular ammonium nitrate was obtained, and then this granular ammonium nitrate was added to 4
The method according to claim 1 or 2, wherein the maturation is performed at a temperature of 0 to 70 ° C, and then the nitrite is dried at a temperature lower than the transition temperature from the phase III to the phase II. 4. A sulfate group content of 30 to 3000 ppm,
Granular ammonium nitrate having a bulk specific gravity of 0.5 to 0.7 [g / cc]. 5. The granular ammonium nitrate according to claim 4, which has an oil absorption of 15 to 30%. 6. The granular ammonium nitrate according to claim 4, having a hardness of 3% to 10%.