RU2310635C1 - Process of preparing micronized ammonium perchlorate - Google Patents

Abstract

FIELD: mixed solid fuels.

SUBSTANCE: invention provides micronized ammonium perchlorate for mixed propellant comprising preparation of lecithin solution in dispersion liquid, preparation of ammonium perchlorate slurry in this solution, and reduction of slurry in bead mill in presence of glass beads. Solution of lecithin in dispersion liquid is prepared via dissolution of lecithin in 2.7-15.0% of the total amount of dispersion liquid, filtration of resulting solution, addition thereof to the rest of dispersion liquid, and stirring. As dispersion liquid, fluorodichloroethane is utilized. Reduction of slurry in bead mill is carried out at temperature not exceeding 25°C.

EFFECT: reduced particle size of ammonium perchlorate slurry to two and less microns.

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Description

The invention relates to the field of grinding of solid materials, including ammonium perchlorate, to obtain particles with a size of 2 or less microns, used in the manufacture of mixed solid rocket fuel. A known method of producing ammonium perchlorate with the indicated particle sizes [RF Patent No. 2246472 IPC С06В 21/00, 29/22, 45/30, С06D 5/00, which the authors adopted as a prototype]. According to this patent, ammonium perchlorate is ground in a bead mill in the form of a suspension in the presence of glass beads, while trifluorotrichloroethane (HFC-113) or methylene chloride are used as dispersion liquid, and the surfactant lecithin is introduced. Then the dispersion liquid is removed by temperature and vacuum distillation.

However, the method of producing ammonium perchlorate prototype has certain disadvantages. In 1999-2000 domestic producers of trifluorotrichloroethane as an ozone-hazardous substance were discontinued and its reserve has now been exhausted. No preliminary preparation of the surfactant lecithin is provided. The admissible temperature of the suspension is not set during the grinding process, which leads to the loss of part of the dispersion liquid with a change in the concentration of ammonium perchlorate in the suspension and thereby violates the established regimes in the technological process.

The technical task of this invention is to obtain ammonium perchlorate with a particle size of two or less microns in a new dispersion liquid, the introduction of preparatory operations of lecithin and limiting the upper limit of the temperature of the suspension during grinding to reduce the loss of dispersion liquid.

The technical result in a method for producing crushed ammonium perchlorate for mixed solid rocket fuel, including preparing a solution of lecithin in a dispersion liquid, preparing a suspension of ammonium perchlorate in this solution, grinding the suspension in a bead mill in the presence of glass beads, is achieved due to the fact that the solution of lecithin in dispersion liquids are prepared by dissolving lecithin in a 2.7-15.0% dispersion liquid, filtering the resulting solution, introducing it to the rest of the dispersion mass liquid and stirring, while fluorine-dichloroethane is used as the dispersion liquid, the suspension is ground in a bead mill at a temperature of no more than 25 ° С.

Of the currently produced dispersion liquids, fluorodichloroethane (chladone-141b) is the most suitable for ammonium perchlorate in terms of the basic physicochemical, fire and toxic characteristics close to trifluorotrichloroethane. The possibility of its use for the production of ground ammonium perchlorate with a particle size of two or less microns was established by the manufacture of its samples in laboratory and semi-factory installations with a bead mill.

Table 1 shows the data obtained by grinding ammonium perchlorate in suspension with a dispersion liquid Freon-141b in a two-rotor bead mill.

Table 1 The dependence of the mass-average particle size of ammonium perchlorate on the duration of grinding Duration of grinding, h Mass average particle size, microns, when used freon-113 Freon-141b 2 0.95 0.8 one 1,0 0.9 0.75 1,1 1,0 0.5 1.3 1,2 0.3 - 2.0

From the data of table 1 it can be seen that when freon-141b is used as a dispersion liquid, ammonium perchlorate is crushed to sizes of 2 microns or less. Used as a surfactant, lecithin is a paste or waxy mass. To fully fulfill the surface-active role, lecithin must be dissolved in a dispersion liquid. When it is dissolved during the preparation of the suspension and grinding in the first period, namely, until the lecithin is completely dissolved, its activity will not be fully manifested and the technological cycle of grinding ammonium perchlorate will be extended. In addition, lecithin is a complex substance - an ester of the amino alcohol of choline and diglyceride phosphoric (phosphatidic) acids. When lecithin is dissolved in Freon-141b, a small portion of insoluble matter floats to the surface, and some precipitates. Therefore, it becomes necessary to separate them by filtration after dissolving lecithin in Freon-141b. However, performing these operations on a factory scale with a large volume of dispersion liquid will lead to a lengthening of the technological cycle with a decrease in productivity or requires the installation of additional equipment. It seems possible to solve this problem by pre-dissolving a portion of lecithin in a small part of the dispersion liquid, followed by filtering from insoluble substances. Carrying out these operations to prepare a lecithin solution and filtering for a subsequent portion in the process of grinding the next portion will not lead to a lengthening of the technological cycle, that is, to a decrease in productivity. The calculation of the minimum required amount of dispersion liquid for the preparation of a lecithin solution is presented. The minimum dosage of lecithin is 1.1% of a portion of ammonium perchlorate. The dispersion liquid is taken in the ratio of ammonium perchlorate: dispersion medium = 1: (3-4). The minimum required amount of dispersion liquid for dissolution in relation to the total mass will be at a ratio of ammonium perchlorate and dispersion liquid 1: 4. With this ratio, the concentration of lecithin in the dispersion liquid will be 1.1: 4 = 0.275%. With a sufficiently rapid dissolution of lecithin in a dispersion liquid to a concentration of 10%, its required amount will be 10: 0.275 = 36.4 times less than the total amount. If we take the total amount of dispersion liquid as 100%, then the minimum amount for dispersion of a lecithin solution will be only 100: 36.4 = 2.7%. According to the experience in the manufacture of ammonium perchlorate in laboratory conditions and at a semi-factory plant with a relatively small amount of ground product and, accordingly, dispersion liquid, it is advisable to take a portion of it up to 15% of the total amount to dissolve lecithin in chladone-141b. Thus, for the dissolution of lecithin, the amount of dispersion liquid will be (2.7-15.0)% of its total volume.

For vessels operating without pressure, its maximum value should be no more than 0.7 kgf / cm ² (0.07 MPa). This pressure level corresponds to the vapor pressure of Freon-141b at a temperature of 25 ° C. In the process of intensive grinding, heat is generated and the temperature of the suspension in the bead mill increases. To cool the suspension, a coolant is fed into the jacket of the bead mill. In view of the foregoing, when grinding ammonium perchlorate in suspension, cooling is necessary to ensure that its temperature is not higher than 25 ° C.

The preparation of ground ammonium perchlorate, taking into account the proposed method of the invention, is as follows. A sample of lecithin is taken, which is dissolved in (2.7 ÷ 15.0)% dispersion liquid (Freon-141b). The proportion of the dispersion liquid within the specified limits is selected depending on the amount of the product to be ground and, accordingly, the dispersion liquid. The solution is filtered through a fabric filter. After filtration, the solution is introduced to the bulk of the dispersion liquid and mixed. To a solution of lecithin in a dispersion liquid with continuous stirring, a sample of ammonium perchlorate is introduced, then the suspension is circulated through a centrifugal pump. In the above manner, a prepared suspension of ammonium perchlorate in HFC141b is circulated through a bead mill into which glass beads are preloaded. During the passage of the suspension through the bead mill, grinding of crystals of ammonium perchlorate occurs. The circulation of the suspension according to the scheme mixer-pump-bead mill-mixer is continued until the desired particle size is determined by the grinding time. The crushed suspension is poured into a mobile container and sent to the drying phase. At this phase, the dispersion liquid is distilled off with the release of dry powdered ammonium perchlorate, which is used for the manufacture of mixed solid rocket fuel.

Below are the distinguishing features of the invention in comparison with the prototype.

table 2 Distinctive features of the invention from the prototype Name Prototype Proposed invention Dispersion fluid Trifluorotrichloroethane Fluorodichloroethane Preparation of lecithin solution a) dissolution In full dispersion liquid In 2.7-15.0% of the total dispersion liquid b) filtering Absent Filtration c) mixing In the process of dissolving lecithin The introduction of a solution of lecithin to the bulk of the dispersion liquid and mixing The temperature of the suspension during grinding Not regulated No more than 25 ° C

Claims (1)

A method of producing ground ammonium perchlorate for a mixed solid rocket fuel, comprising preparing a solution of lecithin in a dispersion liquid, preparing a suspension of ammonium perchlorate in this solution, grinding the suspension in a bead mill in the presence of glass beads, characterized in that a solution of lecithin in a dispersion liquid is prepared by dissolving lecithin in 2.7 ÷ 15.0% dispersion liquid, filtering the resulting solution, introducing it to the rest of the dispersion liquid and mixing, When this dispersion liquid as used ftordihloretan, milling the slurry in the bead mill is performed at a temperature not exceeding 25 ° C.