RU2497792C1 - Method of spherical powder pre-drying - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to production of spherical powders for small arms. Method of spherical powder drying including spherical powder with graphite feed into air transport line and, via cyclone precipitator, to drier whereat powder with graphite at 50 to 100°C is fed via air transport line to preheater composed of two-stage tube. Spherical powder and air heated in vortex flow to 95-105°C are fed to the first stage while air heated in vortex flow to 95-105°C is fed to second stage. Dried spherical powder with moisture content of 8-10 wt % is fed to final drying.

EFFECT: complete removal of surface moisture, decreased moisture content from 18-22 wt % to 8-10 wt %, fast drying.

1 dwg, 1 tbl, 5 ex

Description

The invention relates to the field of production of spherical powders (TFP) for small arms.

In the literature [1] there are known methods of drying various materials, including bulk in boiling, flowing modes. However, the known drying methods are unacceptable for drying TFP due to the high sensitivity to temperature effects.

As a prototype [2], the authors chose a method for producing TFP, according to which a graphite suspension is introduced into the powder after squeezing from water, followed by the supply of gunpowder with graphite into a pneumatic conveying line under compressed air pressure, where during the TFP with graphite movement in a heated air stream in the mode boiling at a temperature of 80 ... 95 ° C, drying and graphitization of gunpowder takes place.

The disadvantage of this method is that during the movement of gunpowder through a pneumatic conveyor line, a slight removal of surface moisture occurs and the TFP coming to the drying has a total humidity of 18 to 22 wt.%.

The aim of the invention is the removal of surface moisture from spherical gunpowder in a stream of hot air before it is fed to the final drying.

The goal is achieved in a method for pre-drying spherical powder, including feeding spherical powder with graphite to the pneumatic conveyor line, and then through the cyclone precipitator for drying, in which spherical powder with a moisture content of 18 ... 22 wt.% With graphite at a temperature of from 50 to 100 ° C is fed through a pneumatic conveyor line to a pre-drying apparatus, which is a pipe with a diameter of 300 mm and a total working length of 10.4 meters, made of 2 steps, where 250 ... 300 kg / h are spherical from the pneumatic conveyor line powder and additionally in a vortex flow heated air to a temperature of 95 ... 105 ° C, with a flow rate of 4000 m ³ / h, with a pressure of 50 ... 100 mm of water. Art. and the speed of the air flow from 9 to 11 m / s, the second stage additionally serves in the vortex stream heated air to a temperature of 95 ... 105 ° C with a flow rate of 1000 m ³ / h, dried spherical powder with a moisture content of 8 to 10 wt.% served for final drying.

The pre-drying apparatus shown in the drawing is designed to remove free moisture from the TFP in a turbulent flow of hot air. The preliminary drying apparatus TFP works in conjunction with the main apparatus for drying gunpowder.

The pre-dryer consists of two stages. Hot air with a pressure of 50 ... 100 mm of water is supplied to the first stage through a pipe with axial spiral flows pos. 1. Art. and a speed of 9 ... 11 m / s. A suspension of gunpowder with air is fed tangentially from the pneumatic transport into the stream of swirling air flow. The dried gunpowder is captured by a stream of hot air and through the top position pos. 2 and the vertical liquefaction pipeline enters the second stage. In the second stage, through the inlet pipe pos. 3, hot air with a temperature of 95 ... 105 ° C is additionally supplied. The dried gunpowder from the 2nd stage enters through the cyclone precipitator into the final drying apparatus.

When air enters the 1st and 2nd stages of the preliminary drying apparatus under the influence of the hot air flow, its own weight and the vertical arrangement of the pipelines of the preliminary drying apparatus, intensive removal of surface moisture from the powder occurs, as well as its partial graphitization and polishing.

In order to ensure significant relative speeds of the powder and air, to improve the heat transfer conditions, the design of the preliminary drying apparatus provides for the tangential introduction of gunpowder, since the gunpowder in this case has no axial component, and under the influence of a stream of hot air swirling from swirls pos. 1, gunpowder makes 1 ... 1.5 turns in a spiral inside the apparatus and thereby increases the residence time of the powder inside the apparatus.

Hot air is supplied to the pre-dryer under pressure from 50 to 100 mm of water. Art. Reduced air pressure less than 50 mm of water. Art. leads to precipitation of the product in the apparatus, and an increase in air pressure of more than 100 mm of water. Art. reduces the time spent in the device. A decrease in the temperature of hot air below 95 ° C leads to incomplete removal of surface moisture from the TFP, and an increase in the temperature of the coolant above 105 ° C is associated with the danger of conducting the process of preliminary drying of gunpowder.

The productivity of the pre-drying apparatus is 250 ... 300 kg / h. The consumption of hot air for the first stage is 4000 m ³ / h, for the second stage 1000 m ³ / h.

The working length of the preliminary drying apparatus of the first stage is 4.6 m, the second stage is 5.8 m, the total working length of the preliminary drying apparatus is 10.4 m. TFP humidity: initial 18 ... 22 wt.%, Final 8 ... 10 wt. % The internal diameter of the pre-dryer is 300 mm. The performance of the pre-drying apparatus is calculated based on the performance of the main drying apparatus.

A decrease in the consumption of hot air in the first stage of less than 4000 m ³ / h will lead to a decrease in the internal diameter of the apparatus, and an increase in air flow over 4000 m ³ / h will lead to an increase in the diameter of the apparatus.

A decrease in the working length of the apparatus of less than 10.4 m does not ensure complete removal of surface moisture, and an increase in the working length of the apparatus for pre-drying gunpowder of more than 10.4 m is impractical. Also for the second stage, a decrease in air flow rate of less than 1000 m ³ / h is associated with a decrease in the internal diameter of the preliminary drying apparatus, and an increase in hot air flow rate of more than 1000 m ³ / h is associated with an increase in the diameter of the apparatus.

The preliminary drying apparatus allows you to remove surface moisture, while internal moisture during the final drying of the TFP is removed 1 ... 1.5 hours to a moisture content of 0.3 ... 0.9 wt.%. Without the use of a preliminary drying apparatus, the final drying of the powder was carried out for 2.5 ... 3.5 hours.

Technological modes and physico-chemical characteristics of the powder according to the method developed by the authors for preliminary drying of spherical powder within the boundary conditions (examples 1 ... 3) and outside the boundary conditions (examples 4, 5) are given in the table.

Table Technological modes and physico-chemical characteristics of spherical powder Name of indicator Example (Ex. No. 1) Etc. Number 2 Etc. Number 3 Etc. Number 4 Etc. Number 5 The moisture content of the TFP fed to the drying, wt.% eighteen twenty 22 eighteen thirty Air temperature in the pneumatic conveying line, ° С fifty 80 one hundred 40 105 The total drying time of the powder in the dryer without preliminary drying, hour - - - 2,5 3,5 Diameter of pre-drying apparatus, mm 300 300 300 300 300 Length of 1 step, m 4.6 4.6 4.6 4.6 4.6 Length 2 steps, m 5.8 5.8 5.8 5.8 5.8 The total length of the pre-dryer, m 10,4 10,4 10,4 10,4 10,4 Pre-Dryer Capacity 250 270 300 230 330 The temperature of the heated air supplied to the pre-dryer, ° C 95 one hundred 105 80 105 Air consumption in the first stage, m ³ / hour 4000 4000 4000 4000 4000 Air consumption in the second stage, m ³ / hour 1000 1000 1000 1000 1000 Air pressure in the dryer, mm water fifty 70 one hundred 40 110 The speed of the flow, m / s 9 10 eleven 8 12 The humidity of the spherical powder after the preliminary drying apparatus, wt.% 10 9 8 12 eleven The drying time of the powder in the main dryer, hours 1,5 1,2 1,0 1,6 1.8 The moisture content of the powder after the final drying, wt.% 0.9 0.6 0.3 1,0 1,2 Chemical resistance TFP, mmHg 40 41 43 42 41

From the above table data it is seen that according to the method developed by the authors for the preliminary drying of the TFP within the boundary conditions (examples 1 ... 3), the surface moisture is completely removed. In the powder, internal moisture remains within 8 ... 10 wt.%, Which is removed during basic drying 1 ... 1.5 hours to a moisture content of 0.3 ... 0.9 wt.%. While during the drying of gunpowder without preliminary drying, the time of general drying of spherical gunpowder is 2.5 ... 3.5 hours. In the process of preliminary drying, additional graphitization and polishing of the TFP occurs. Outside the boundary conditions (examples 4, 5), the drying cycle of gunpowder lengthens.

Pre-drying of the TFP does not reduce the chemical resistance of the powder.

Therefore, the method of preliminary drying of TFP developed by the authors allows:

- completely remove surface moisture;

- reduce the overall drying cycle of gunpowder to 1 ... 1.5 hours;

- reduce the humidity of the spherical powder during the preliminary drying from 18 ... 22 wt.% to 8 ... 10 wt.%.

Literature

1. Kasatkin A.G. Basic processes and apparatuses of chemical technology. - M .: Chemistry, 1973. - 750 p.

2. "Method for producing spherical powder", patent RU 2183604, C06B 21/00, publ. 06/20/20002, 6 s.

Claims (1)

A method for pre-drying spherical powder, including feeding spherical powder with graphite to a pneumatic conveyor line, and then through a precipitating cyclone for drying, characterized in that spherical powder with a moisture content of 18-22 wt.% With graphite is supplied at a temperature of from 50 to 100 ° C through a pneumatic conveyor line to a pre-drying apparatus, which is a pipe with a diameter of 300 mm and a total working length of 10.4 m, made of 2 steps, where 250-300 kg / h of spherical gunpowder is supplied to the first step from the pneumatic conveyor line and, in addition, to hrevom stream of heated air to a temperature of 95-105 ° C, at a rate of 4000 m ³ / h, with a pressure of 50-100 mm of water. Art. and a speed of air flow from 9 to 11 m / s, in the second stage, heated air is additionally supplied in a vortex stream to a temperature of 95-105 ° C with a flow rate of 1000 m ³ / h, dried spherical powder with a moisture content of 8 to 10 wt.% served for final drying.

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