BG63296B1 - Method and installation for the preparation of porous granulated ammonium nitrate - Google Patents

Abstract

The invention relates to a method for the production of porous granulated ammonium nitrate which is a raw material for making explosive and propulsion substances, such as naphtha-ammonium nitrate industrial explosives, as well as to a plant for its materialization. By the method, calcium and/or magnesium nitrate is added to an aqueous solution of ammonium nitrate with a concentration of 85-88 %, the mixture solution produced in being concentrated to 99.7-99.8 %, and a surfactant is added to it, selected from the group of anion sulphonate high-molecular surfactant. The mixture is homogenized and is fed for prill-granulation, compressed air being fed as a counter-flow to the falling granules, maintaining a pseudo-fluidized bed of the porous granules formed. The granule temperature in the upper part of the fluidized bed is maintained within 90 to 120 degree C, and from 35 to 50 degrees C in its downstream part, before its discharge; finally the cooled granules are covered by anti-sticking agent. The plant consists of an evaporator (1), connected across a buffer-collector (2) to the lower part of a high-speed aperture piezometric flow meter-mixer (3), to the top of which a tank (4) is connected across a valve adjuster. The mixer (3) is connected, on the other side, with a low-revolution acoustic granulator (5), mounted at a height not lower than 25 m from the level of the fluidized bed (6) formed in a granulation tower. To the lower part of the tower, a vertical tray mixer (7) by means of a conveyor, is connected, to which a tank (9) is connected. The granules produced have high mechanical strength and are physically stable, regardless of the storage temperature conditions and operation, having, at the same time, high porosity and fully meet with the user needs for their sorption and retention capacity. 5 claims, 1 figure

Description

(54) METHOD AND INSTALLATION FOR THE PREPARATION OF POROUS GRANNED AMMONIUM SEMITTER

Technical field

The invention relates to a process for the preparation of porous granular ammonium nitrate, which is a raw material for the production of explosive and propulsive substances, for example, petroleum nitrate industrial explosives, and to an installation for carrying out the method.

BACKGROUND OF THE INVENTION

The basic requirements for ammonium nitrate as a starting material for the production of explosive and permeable substances are the porosity, sorption and retention capacity, mechanical strength and stability under temperature changes. In order to achieve optimum performance, a number of methods have been developed for the production of porous granular ammonium nitrate, each of which aims to optimize at least one of these indicators, as well as to achieve technological improvements.

A method is known for the preparation of porous granular saltpeter BG 47389, in which water-soluble organic and inorganic salts and water-insoluble minerals such as sodium or ammonium salt of disulfonic acid and dinaftylmethanium, dinaftylmethane, dinaftylmethyl, are added in a solution or melt of ammonium nitrate. iron-P sulfate and chalk, or NF and ammonium sulfate, or NF and iron II sulfate and chalk. Ammonium sulphate is introduced in the form of an aqueous solution, the iron sulphate as an aqueous solution or in solid state, the chalk is introduced into the melt just before granulation in solid state, finely ground with a particle size below 0.063 mm, and the NF dispersant is introduced into the melt of ammonium nitrate immediately before granulation as aqueous solutions. Granules with increased sorption capacity and mechanical strength are obtained.

No. 2 063 929C1 discloses a process for the preparation of porous granular ammonium nitrate, according to which a melt of nitrate is first introduced into ferrous sulfate in the form of an aqueous solution and then a NF dispersant in a mixture with an aqueous slurry containing chalk. The resulting granules are non-sticky, waterproof and have a mechanical strength of 760 g / gran.

The disadvantages of both methods are the introduction of an insoluble component, which is unacceptable in the production of water-gel explosives where insoluble impurities up to a maximum of 0.002% are required. Consumers' requirements for water-soluble iron are a maximum of 5 ppm, for sulfates a maximum of 1.0 ppm, and those for oil retention in the order of 10%.

A similar method is described in RU N ° 94038400A1. This method involves the introduction into the melt of ammonium nitrate of an additive consisting of urea, potassium carbonate, dispersant NF.

These methods do not provide a good indication of the thermal stability of the resulting granules.

EP 0 850 878A1 describes a method and an installation for the production of porous granular ammonium nitrate. The method is as follows. Solid ammonium nitrate was introduced into a drum type fluidized bed granulator over which an ammonium nitrate solution of between 94 and 98% was injected and the granulation was carried out at 135 to 170 ° C. The removal of water from the solution is carried out at the expense of the heat from the crystallization of the nitrate and the heat of the supplied air stream under a fluidized bed, and the residual moisture is removed by drying at the outlet of the granulator. The solution may contain surfactants, as well as anti-abrasive additives, ammonium sulfate, magnesium nitrate, aluminum sulfate or other metal salts. The installation for carrying out this method includes a rotary drum type and fluidized bed granulator, a device for injecting ammonium nitrate solution into the granulator, devices for introducing into the granulator recycled solid ammonium nitrate, dryer, sieve, cooler and lubricating device commercial sieve, device for recycling part of the small particles leaving the sieve, crusher and second sieve for screening ammonium nitrate solids which can serve as pellet cores and apparatus means for transferring them to the granulator.

The method is technologically sophisticated and requires precise temperature control and expensive equipment.

The products obtained by this and the other methods mentioned have a temperature transition at 32.3 ° C, which causes problems in storage and use of the products at different temperatures and temperature changes due to changes in the crystal structure, accompanied by changes in volume, destruction of the granules and recrystallization processes.

A method is known for the preparation of stabilized ammonium nitrate (EP 0 786 434A1, which is used to produce a rocket charge. The method, which aims at suppressing the temperature transition at 32 ° C, provides for the addition of ammonium nitrate to 1 to 7% potassium nitrate by weight and 0.1 to 1% by weight organic dye containing at least one arylsulfonate group selected from the group of benzosulfonates and naphthalenesulfonates The product obtained is powdery, sufficiently dry and indestructible when stored.

The production of ammonium nitrate granules, which has both high porosity, high sorption and retention capacity, in particular with respect to diesel fuel, and sufficient mechanical strength related to the temperature transitions of nitrate, is still a serious technical problem.

SUMMARY OF THE INVENTION

The object of the invention is solved by a process for preparing porous granular ammonium nitrate, which is as follows. To an aqueous solution of ammonium nitrate at a concentration of 85-88% is added a 1.2-2.0% solution of dolomite or magnesite. The solution was concentrated to 99.7-99.8% and was dosed with 3-4 kg / t surfactant selected from the group of anionic sulfonate high molecular weight surfactants. The mixture was homogenized and fed for granulation. The granules having a temperature of 90-120 ° C reach an area of fluidized bed formed by the obtained granules by a counter-flowing air stream. At the outlet of the fluidized bed, the granules are at a temperature of 35-50 °. The cooled granules are coated with an anti-shatter agent and submitted for packaging.

The invention also relates to an installation for carrying out the method. It consists of a vaporizer connected via a buffer tank to the lower part of a high-speed piezometric flowmeter-mixer, to which a surfactant solution tank is connected through a regulator valve. The mixer is connected to a low-speed acoustic granulator mounted at a height of at least 25 m from the level of the fluidized bed created in the granulation tower. A vertical plate mixer is connected to the bottom of the granulation tower via a conveyor, to which an anti-shrinkage agent tank is connected.

The method according to the invention achieves a displacement of the polymorphic conversion point at temperatures above ordinary ambient temperatures, while at the same time the polymorphic conversion point at 84 ° C is absent; the stable crystalline form of the finished product is maintained at temperatures higher by about 20 ° C than analogues. The obtained pellets are of high mechanical strength and physically stable, regardless of the storage and use temperature conditions, have a high porosity and fully satisfy the consumer sorption and retention requirements. The intended temperature regime and the manner in which it is provided provides for a slow and uniform cooling of the granules and prevents sharp cooling, which would lead to radial cracks from the nucleus to the surface of the granules.

The selected elements of the installation ensure optimum implementation of the process steps with minimal energy consumption and elemental maintenance.

Explanation of the annexed figures

Figure 1 is a diagram of an installation for producing porous granular ammonium nitrate according to the invention.

An exemplary embodiment of the invention

The installation shown in FIG. 1 consists of an evaporator 1, a buffer box 2, a high-speed split piezometer mixer 3, a reservoir 4 connected via a valve-regulator to the mixer 3, which is connected to a low-speed acoustic granulator 5 located in the upper part of the granulation tower in which the fluidized bed is maintained 6. The outlet of the tower at its bottom is connected through a conveyor with a vertical static dish mixer 7 to which a tank 8 is also connected.

The method is as follows.

To a solution of ammonium nitrate at a concentration of 85-88% is added a 1.0-2.0% solution of dolomite or a solution of magnesite. The resulting solution was concentrated to 99.7 99.8% in evaporator 1, then fed into buffer collector 2, from which it was fed into the mixer 3. In it, depending on the amount of ammonium nitrate, via a valve regulator from collector 4, 3 - 4kg / t of a 25% surfactant solution is dosed, for example, a commercially available SKFERT product, homogenized in one mixer chamber and granulated at a temperature of 172-185 ° C using the acoustic granulator 5. The granulator is mounted at the top of a granulation tower at a height of 40.5t above the level of the fluidized bed. The granules reach the zone of fluidized bed 6 at a temperature of 90-120 ° C, where the air flow supporting the fluidized bed is cooled to a temperature of 35-50 ° C, maintaining the temperature in this interval by adjusting the amount of air supplied to the fluidized bed and the amount of flue gas sucked out by the axial fans (not shown in the figure) from the granulation tower. The cooled product is passed through a vertical static plate mixer 7, providing 98-100% even coverage of the product with an anti-shrinkage agent supplied by tank 8.

The product thus obtained is packed in packages of 40 and 50 kg, as well as in large bags of 500-1000 kg.

The finished product has the following characteristics: terrorists: Ammonium nitrate %, min - 98.7 Nitrogen %, min - 34,5 Moisture %, max - 0.5 Insoluble in water impurities %, max - 0.02 Water soluble iron ppm, max - 3 Chlorides ppm, max - 5

Sulphates %, max -0.2 Organic compounds, general C. %, max -0.2 MgO (CaO + MgO) %, max - 0,5 pH of 10% aqueous solution min -4.0 Bulk density kg / m ³ - 700-850 Oil content %, min - 9

Pellet strength kgc / gran. - 0.65- 0.75

Granulometry from 1 - 4 mm%, min - 95 under 1 mm%, max - 5

Examples of specific embodiments of the invention

Example 1. To the melt ammonium nitrate obtained after the third stage of evaporation, at a concentration of 99.8% by weight. a 25% surfactant solution (commercial product SKFERT) is introduced and the same is pelleted in an acoustic granulator.

Experiments have been carried out with different amounts of surfactant.

Example 1. 1: With 2 kg / l surfactant, the nitrate has an oil content of 5.5-6%, a moisture content of 0.30-0.32%, a static strength of 0.356-0.382 kgc / gran.

Example 1.2: C3 kg / t PAH nitrate has an oil content of 7.3-8.2%, moisture content of 0.34 - 0.38%, static strength of 0.311 - 0.332 kgc / gran.

Example 1.3: With 4 kg / t the nitrate has an oil content of 8.6 - 11.8%, a moisture content of 0.42 - 0.48%, a static strength of 0.258-0.283 kgf / gran.

Example 2. A stainless steel vessel of 50 l volume was filled with a melt containing 0.33 0.50% MgO [1.20-1.90% Mg (NO ₃ ) ₂ ]. The vessel is equipped with a stirrer and an electronic temperature controller maintains a temperature of 180-182 ° C. To the melt was added 25% surfactant solution in an amount of 0.075-0.1% by weight, as a 100% substance. The mixture is homogenized and allowed to flow through a static granulator with 50 holes with a diameter of 1.00 mm in a granulation tower with a height of 40.5 t. The obtained granules have an oil content of 7.2-12%, a moisture content of 0.40-0.45% , static quality 0,650-0,756 kgf / pellet.

Example 2. 1 Worked as described in example 2, but instead of magnesite, the melt contains calcium and magnesium nitrate in a 2: 1 ratio. The obtained granules have an oil content of 8.3-10.8%, a moisture content of 0.43 0> 49%, a static strength of 0.471 - 0.522 kgf / gran. 5 In the annexed Table 1 we present the results of the analytical control of two samples of porous ammonium nitrate obtained by the method according to the invention, compared with BDS for ANT (technical ammonium nitrate) and user-required properties for PAN (porous ammonium nitrate).

No Indicators Dimension ONT norms Standards of the PAN Sample 133 A. Sample 133 B. 1. Ammonium nitrate (NH ₄ NO ₃ ) %, min 98.7 98.72 98.75 2. Nitrogen, N %, min 34.5 34.5 34.64 34.69 3. Moisture %, man 0.25 0.5 0.60 0.48 4. Water insoluble impurities %, max 0,005 0.02 0.08 0.002 5. Water soluble iron ppm, max 3 0.8 0.4 6. Chloride content ppm, max 5 1.13 1.09 7. Sulphate content %, max ο, ι 0.2 0.09 0.03 8. Organic compounds total carbon %, max it is not allowed 0.2 0,136 th most common 0.050 9. MgO, CaO %, max it is not allowed 0.5 0.396 0.396 10. pH of 10% aqueous solution Ph - min 4.5 4 6.94 6.62 11. Bulk density kg / m ³ 700- 850 817not. 888Up. 816No. 878Up. 12. 13. Granulometry %, min 9 8.28 8.38 - 1-4 mm % min 95 90 98 99 14. - <1mm Granule strength % max kgf / grand. 5 10 2 0.65 1 0.75

Claims (5)

Claims A process for the preparation of porous granular ammonium nitrate, characterized in that an aqueous solution of calcium and / or magnesium nitrate is added to an aqueous solution of ammonium nitrate at a concentration of 85-88%, the resulting solution is concentrated to 99 , 7-99,8% and a surfactant selected from the group of anionic sulfonate macromolecular surfactants is dosed thereto, the mixture is homogenized and fed for granulation, with compressed air being supplied in the opposite direction to the falling bundles. supports ps euphony layer of the formed porous granules, whereby the temperature of the granules in the upper part of the fluidized bed is maintained in the range of 90-120 ° C, and in the lower part at its exit - 35-50 ° C, and finally the cooled granules are covered with antifouling agent. A method according to claim 1, characterized in that in aqueous ammonium nitrate at a concentration of 82-88%, a 50-55% aqueous solution of a mixture of calcium nitrate and magnesium nitrate is preferably introduced, preferably in a ratio of 2: 1, in case of dolomite in an amount of 1.2 to 1.9%. Method according to claim 1, characterized in that a 38-42% aqueous solution of magnesium nitrate, optionally obtained from magnesite, is introduced into the 82-88% solution of ammonium nitrate in the amount of 1.2 -1.9%. A method according to claim 1, characterized in that a 25% solution of anionic sulfonate polymer is added to the concentrated to 99.7-99.8% solution of ammonium nitrate in an amount of 0.025-0.1% by weight as 100% active substance. 5. Installation for producing porous granulated nitrate, characterized in that it consists of an evaporator (1) connected via a buffer tank (2) to the bottom of a high-speed piezometric flowmeter (3), to the top of which is through a valve regulator a reservoir (4) is connected, the mixer (3) being connected in turn to a low-speed acoustic granulator (5), which is mounted at a height of not less than 25 m from the level of the fluidized bed (6) created in a granulation tower to which a vertical bar is connected to the bottom by a conveyor faucet mixer (7) to which tank (8) is connected.