RU2591947C1 - Method of porous granulated ammonium nitrate producing - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: method involves preparing ammonium nitrate solution, adding to obtained solution of first part of stabilising additive, represented by mixture of phosphoric and sulphuric acid ammonium salts or acids and their neutralisation with ammonia, evaporating obtained solution to state of melt, adding surfactant, porophore additive and second part of the stabilising additive to obtained melt, represented by magnesium nitrates, calcium or iron that is followed by granulation. First and second parts of stabilising additive ingredients, taken in stoichiometric ratio, in granulation form insoluble carrier and ammonium nitrate as a result of exchange reaction.

EFFECT: invention provides high static strength, low caking and residual moisture content, high stability of granules to thermal heating-cooling cycles.

1 cl, 3 tbl, 13 ex

Description

The invention relates to the field of creating special types of raw materials and technology for producing inorganic substances (salts) used in the production of industrial explosive materials, namely the production of porous granular ammonium nitrate.

Technical field

A known method of producing porous granular ammonium nitrate (patent RU 2230028 C1 [Open Joint-Stock Company "Azot"] 10.06.2004), including the neutralization of nitric acid with ammonia, evaporation of the solution to obtain concentrated melt, the introduction of hydrolyzed salts of trivalent metals into the melt, mixing with an aqueous suspension containing a pore-forming agent in the form of a carbonate salt of a metal, sodium or ammonium salt of naphthalene methyldisulfonic acid (dispersant NF) and sodium or potassium stearates, granulation of the mixture with the following treatment of granules with surface-active additives (water-soluble sodium or potassium carbonate and calcium carbonate suspended in its solution, the concentration of sodium or potassium carbonate being 5-15%, and the content of calcium carbonate 30-50% of the total weight of the suspension fed to the mixing )

The disadvantages of this method are:

- increased amount of water introduced with additives into the resulting granules of ammonium nitrate;

- the introduction of chalk (CaCO ₃ ), which partially turns into calcium nitrate, which reduces the quality of the granules, increasing their caking and reducing static strength;

- preparation and introduction into the melt of ammonium nitrate of a pore-forming additive in the form of a mixture of surfactants and pore-forming components leads to foaming of the prepared aqueous suspension, which complicates its preparation, pumping and dosing into the melt.

A known method of producing porous granular ammonium nitrate (patent RU 2101228 C1 [Open Joint-Stock Company Acron]] 01/10/1998) by introducing an additive in a highly concentrated melt of ammonium nitrate, in which an amount of aluminum-containing inorganic polymers is used as a hardening additive to ensure the content additives 0.4-1.45% of the mass. by weight of nitrate, and as a modifying additive, a solution of a mixture of ammonium salts and surfactants is used in an amount providing an additive content of 0.04-0.5% by weight of nitrate, followed by cooling and drying.

The disadvantages of this method are:

- increased water content in the resulting granules of porous ammonium nitrate from 0.5 to 2.5% of the mass, which dramatically reduces the static strength of the granules and increases their caking;

- the content in the melt of ammonium nitrate is 0.4-1.45% of the mass. the solid phase leads to complications with the organization of the process of dispersing such a melt into droplets with static and vibrostatic granulators;

- solid particles of aluminosilicate polymer do not provide a high rate of nucleation of crystallization centers in the molten ammonium nitrate, as they do not have chemical, physical and crystallographic affinity for it.

The closest technological solution is the method for producing porous granular ammonium nitrate (patent RU 2261842 C1 [Open Joint-Stock Company Acron] 10.10.2005), including the introduction of a pore-forming additive and dispersant NF into the melt, followed by granulation, characterized in that they obtain a solution of ammonium nitrate and injected into it a stabilizing additive of nitrates of magnesium and / or calcium up to 2.0% of the mass. in terms of an anhydrous product, the resulting solution is evaporated to obtain a melt; as a pore-forming additive, a highly concentrated solution of ammonium carbonate in ammonium nitrate with 28-37% of the mass is used. ammonium carbonate, 40-46% of the mass. ammonium nitrate and 20-25% of the mass. water with a temperature of 10-40 ° C in an amount of 0.05-0.35% of the mass. or a mixture of urea with a highly concentrated solution of ammonium carbonate in ammonium nitrate in the ratio (0.6 ÷ 0.7): 1 with 38-42% of the mass. urea, 17-23% of the mass. ammonium carbonate, 24-28% of the mass. ammonium nitrate and 14-16% of the mass. water with a temperature of 10-40 ° C in an amount of 0.1-0.55% wt., and the pore-forming additive is mixed with the dispersant NF in the melt or before introduction into the melt. This method is selected as a prototype.

The disadvantages of this method are:

- the use of urea in the pore-forming additive, which reduces the static strength of the granules, increases their hygroscopicity and caking;

- the use of unstable when heated above 30 ° C and decomposes into ammonia and carbon dioxide ammonium carbonate;

- mixing the NF dispersant with a solution of a pore-forming additive leads to the formation of foam and makes it difficult to pump and meter the solution of the additive, while their simultaneous mixing in ammonium nitrate melt reduces the positive effect of the NF dispersant (SAS) on the uniform distribution of gas bubbles in the melt.

SUMMARY OF THE INVENTION

The technical result of the present invention is to obtain granular porous ammonium nitrate with high static strength (up to 16 N / granule), reduced caking and residual moisture up to 0.32%, with an adjustable bulk density of granules (from 700 to 900 kg / m ³ ) and Absorbent (from 8.0 to 26.0%) and retention (from 5.6 to 13.0%) diesel pellet ability, as well as with increased resistance of pellets to thermal cycles of heating-cooling (-20-60 ° C up to 70 cycles) with a decrease in the static strength of the granules in 2 times, which both Sintered by a decrease in the quality indicators of granules during their transportation and storage.

The technical result is achieved by the fact that:

- an increase in the rate of nucleation of crystallization centers, a decrease in the size of crystalline grains and, therefore, the required strength of the crystalline structure of the granules is ensured by the introduction of a stabilizing additive into ammonium nitrate, consisting of components that, when chemically reacted, form molecules of an insoluble carrier and a molecule of the starting material that are not melting in the initial melt. The additive is introduced in an amount of 0.1-2.0% of the mass. in terms of dry matter. The components of the additive are administered separately in space and time. Preferably, the molecules of the resulting carrier are stable, including double salts, which bind excess water to crystalline hydrates and significantly slow down the rate of nucleation and growth of centers of modification transformations;

- the most uniform distribution of the additive components in the volume of the ammonium nitrate melt is achieved by introducing some of the components of the modifying additive, excluding deposition on the heating surfaces of the evaporators or making it difficult to evaporate, in the initial solution of ammonium nitrate with its subsequent evaporation to the state of melt and introducing the remaining parts of the additive that do not meet this requirement, in the melt immediately before granulation;

- creation of conditions for gas evolution that ensures pore formation in the granule at the time of formation of the melt droplets and their crystallization, is solved by advancing and separate in space and time by introducing into the melt the additive component containing surfactant, compared with the pore-forming component and the remaining parts of the stabilizing additive. The use of technical carbonates or mixtures thereof as pore-forming components provides a lower gas evolution rate compared to pure carbonates.

The process of obtaining granular porous ammonium nitrate according to the claimed method is as follows: by neutralizing nitric acid with gaseous ammonia, an 85-92% aqueous solution of ammonium nitrate is obtained, the first part of the components of the stabilizing additive is introduced into it, which is used as a mixture of ammonium salts of phosphoric and sulfuric acids or acids themselves while neutralizing them with ammonia, which upon evaporation do not cause deposits on the heating surfaces of evaporators and do not impede otsess evaporating the ammonium nitrate solution. Then the resulting solution is evaporated to a state of melt with a water content of 0.2% of the mass. Then a saturated aqueous solution of a surfactant (surfactant) is introduced into the melt at a boiling temperature in the amount of 0.02-0.1% by mass. in terms of dry matter (as a surfactant, in particular, a mixture of lauryl sulfate or sodium stearate with an NF dispersant is used). Then, a saturated aqueous solution of a mixture of technical carbonates of Na, K, ammonium, etc. or individual salts is introduced into the melt at a boiling point in the amount of 0.1-0.5% of the mass. in terms of dry matter. Immediately before granulation, the remainder of the components of the stabilizing additive is introduced, which are magnesium, calcium or iron nitrates, which are taken in stoichiometric proportion to the already introduced parts of the stabilizing additive, and form, as a result of the exchange reaction, insoluble carrier molecules and the starting material (ammonium nitrate). Due to its high dispersion, complete affinity for the crystalline phase, and the fact that the nuclei are not afraid of overheating of the melt, an ideal nucleating (structuring) additive is obtained. This sharply increases the rate of nucleation of crystallization centers in the cooled melt. The resulting melt is dispersed into droplets, crystallize them, cool the resulting granules and condition them.

The present invention is illustrated by the following examples.

Example 1

In an apparatus suitable for evaporating an aqueous solution of ammonium nitrate:

(1) - flooded 85% of the mass. an aqueous solution of ammonium nitrate, the concentration of which was controlled by a hydrometer by its density, at a temperature of 120 ° C;

(2) - the first part of the components of the stabilizing additive was introduced into it, which do not impede the evaporation process and are not deposited on the heating surfaces of the evaporators in the form of a mixture of ammonium salts of phosphoric and sulfuric acids or the acids themselves while neutralizing them with ammonia to pH = 6.0 ÷ 6.8 with a constant positive result in the amount of 0.06 and 0.02% of the mass. in terms of P ₂ O ₅ and ammonium sulfate, respectively, with continuous stirring;

(3) - the solution of ammonium nitrate was evaporated (and dried) to a state of melt with a water content of not more than 0.2% of the mass. (according to Fisher);

(4) - then a saturated aqueous solution of a mixture of surface-active substances (SAS) was introduced into the melt obtained after evaporation: sodium stearate with an NF dispersant (grade A is the sodium salt of naphthalene methyldisulfonic acid that meets the requirements of GOST 6848-73) in a 1: 1 ratio in the amount of 0.02% of the mass. in terms of dry matter;

(5) - then a saturated aqueous solution of a mixture of industrial potash and soda in a ratio of 1: 1 in an amount of 0.1% of the mass was gradually introduced into the obtained melt. in terms of dry matter at its boiling point with continuous stirring of the melt;

(6) - then the remainder of the stabilizing additive was gradually introduced in the form of 0.02% by weight of an aqueous solution of magnesium nitrate or AKB caustic magnesite. in terms of MgO, providing a stoichiometric ratio of the first and second parts of the components of the stabilizing additive, with continuous mixing and dispersion of the melt, with gas bubbles emitted from the smelter in the form of a polydisperse mixture of melt drops in ascending at a speed of 0.5 m / s at a temperature of 25 ° With the air flow in a glass column with a diameter of 100 mm, consisting of 6 tsars 1 m long and having a rotating flanged plate in the lower part with a glass wool laid on it, filled with easily evaporating liquid, t mperatura which boil below the Leidenfrost temperature on the surface of the granules. In this case, the crystallizing drop of the melt “hovers” in the vapor flowing around it of an easily evaporating liquid, simulating the process of crystallization of the drops of melt when they fall in the granulation tower. The adequacy of this method to the real process in the granulation tower is confirmed and further confirmed by reproducing the results given in the prototype (see table. 1).

(7) - the resulting mixture of polydisperse granules was cooled on a rotating plate or in a fluidized bed with atmospheric air to 50 ° C, conditioned with various types of conditioning additives (see paragraph 4 of Table 1), as well as with NF dispersant, “lilamine” in an amount of 0 , 05% of the mass.

(8) - the obtained granules of ammonium nitrate were subjected to the tests listed in table. 1 according to standard methods TU 2143-635-00209023-99.

Example 2

The implementation of the method according to example 1. The difference is that in (2) the stabilizing additive was introduced in the form of a mixture of ammonium salts of phosphoric and sulfuric acids or the acids themselves while neutralizing them with ammonia to pH = 6.0 ÷ 6.8 with the same positive result in the amount of 0.3 and 0.1% of the mass. in terms of P ₂ O ₅ and ammonium sulfate and, respectively; in (4), a saturated aqueous solution of surfactants lauryl sulfate with a dispersant NF (grade A) was introduced in a ratio of 1: 1 in an amount of 0.05% of the mass. in terms of dry matter; in (5), a saturated aqueous solution of a mixture of industrial potash and soda was introduced in a ratio of 1: 1 in an amount of 0.3% of the mass. in terms of dry matter; in (6), an aqueous solution of magnesium nitrate or AKV caustic magnesite, saturated at boiling point, was introduced in an amount of 0.072% by mass. in terms of MgO, providing a stoichiometric ratio of the components of the stabilizing additive.

Example 3

The implementation of the method according to example 1. The difference is that in (2) the stabilizing additive was introduced in the form of a mixture of ammonium salts of phosphoric and sulfuric acids or the acids themselves while neutralizing them with ammonia to pH = 6.0 ÷ 6.8 with the same positive result in the amount of 1.2 and 0.4% of the mass. in terms of P ₂ About ₅ and ammonium sulfate, respectively; in (4), a saturated aqueous solution of surfactants was introduced: sodium stearate with a dispersant NF (grade A) in a ratio of 1: 1 in an amount of 0.1% of the mass. in terms of dry matter; in (5), a saturated aqueous solution of a mixture of industrial potash and soda was introduced in a ratio of 1: 1 in an amount of 0.5% of the mass. in terms of dry matter; in (6), an aqueous solution of magnesium nitrate or AKV caustic magnesite saturated in boiling point was introduced in an amount of 0.4% by mass. in terms of MgO, providing a stoichiometric ratio of the components of the stabilizing additive.

Example 4

The implementation of the method according to example 1 with the changes recorded in example 2. The difference is that in (2) the stabilizing additive was introduced in the form of ammonium salts of phosphoric acid (the acid itself) or sulfuric acid (the acid itself) while neutralizing them with ammonia to pH = 6.0 ÷ 6.8 with the same positive result in the amount of 0.5 or 0.24% of the mass. in terms of P ₂ O ₅ and ammonium sulfate, respectively.

Example 5

The implementation of the method according to example 1 with the changes recorded in example 2. The difference is that in (5) was introduced a saturated aqueous solution of technical soda in an amount of 0.3% wt. In terms of dry substance; in (6), an aqueous solution of magnesium nitrate and iron (III) nitrate saturated at boiling point was introduced in a ratio of 1: 5 mass, in terms of MgO and Fe ₂ O _3, respectively, in an amount of 0.5% mass. in terms of dry matter, providing a stoichiometric ratio of the components of the stabilizing additive.

Example 6

The implementation of the method according to example 1 with the changes recorded in example 2. The difference is that in (5), an aqueous solution of technical ammonium carbonate and urea was saturated at 40 ° C in a ratio of 1: 2 in an amount of 0.3% by weight. in terms of solids; in (6), an aqueous solution of aluminum nitrate saturated at boiling point was introduced in an amount of 0.1% of the mass. based on Al ₂ O _3, providing a stoichiometric ratio of the stabilizing additive components.

Example 7

The implementation of the method according to example 1 with the changes recorded in example 2. The difference is that in (5) was introduced a saturated aqueous solution of technical potash in the amount of 0.3% of the mass. in terms of dry matter; in (6), a saturated aqueous solution of calcium nitrate was introduced at a boiling point in the amount of 0.15% of the mass. in terms of CaO, providing a stoichiometric ratio of the components of the stabilizing additive.

Example 8

The implementation of the method according to example 1 with the changes recorded in example 2. The difference is that in (4) was introduced a saturated aqueous solution of a surfactant - sodium stearate in an amount of 0.05% of the mass. in terms of dry matter.

Example 9

The implementation of the method according to example 1 with the changes recorded in example 2. The difference is that in (4) a saturated aqueous solution of surfactants was introduced in the form of a mixture: sodium stearate with a dispersant NF (grade A) in a ratio of 1: 1 in the amount of 0.05% of the mass. in terms of dry matter.

Example 10

The implementation of the method according to example 1 with the changes recorded in example 2. The difference is that in (4) was introduced a saturated aqueous solution of a surfactant - dispersant NF (grade A) in the amount of 0.05% of the mass. in terms of dry matter.

Example 11

The implementation of the method according to example 1 with the changes recorded in example 2. The difference is that in (4) was introduced a saturated aqueous solution of a surfactant - lauryl sulfate in an amount of 0.05% of the mass. in terms of dry matter.

Example 12

The implementation of the method according to example 1 with the changes recorded in example 2. The difference is that in (4) was introduced a saturated aqueous solution of surfactants in the form of a mixture of monoalkylphenolpolyglycol ether (OP-7) with a dispersant NF (grade A) in the ratio 1: 1 in an amount of 0.05% of the mass. in terms of dry matter.

Example 13

The implementation of the method according to example 1 with the changes recorded in example 3. The difference is that in (4) a saturated aqueous solution of surfactants was introduced in the form of a mixture: dialkylphenolpolyglycol ether (OP-10) with a dispersant NF (grade A) in the ratio 1: 1 in an amount of 0.05% of the mass. in terms of dry matter.

Claims (2)

1. A method of obtaining a porous granular ammonium nitrate, including obtaining a solution of ammonium nitrate, introducing into the resulting solution the first part of a stabilizing additive, which is used as a mixture of ammonium salts of phosphoric and sulfuric acids or the acids themselves while neutralizing them with ammonia, evaporating the resulting solution to a melt state , the introduction of the resulting melt surfactant, pore-forming additives and the second part of the stabilizing additives, which use nitrate magnesium, calcium or iron, followed by granulation, characterized in that the first and second part of the components of the stabilizing additive are taken in a stoichiometric ratio and, during the granulation process, form an insoluble carrier and ammonium nitrate as a result of the exchange reaction. 2. The method according to p. 1, characterized in that the stabilizing additive is introduced in an amount of 0.1-2.0 wt.% In terms of dry matter.