RU2498972C1 - Method of moisture removal from pyro powders - Google Patents

Abstract

FIELD: weapons and ammunition.

SUBSTANCE: proposed method comprises two-step removal of moisture brought about by wetting from powder elements. First, moisture is displaced from powder elements by ethyl alcohol in concentration of 95-96% under centrifugal force in sprinkling of powder with alcohol in amount of 0.35-0.50 l/kg for fine powders and 0.50-1.00 l/kg for medium powders with simultaneous powder expression for 2-3 min and final expression for at least 10 min. Removal of residual amount of water-alcohol mix from powder to required magnitudes is performed by drying in table drier or dry-cure cabinets by air heated to 25-40°C for at least 1 hour with simultaneous forced discharge of used air or drying in 70 mmHg-vacuum for at least 1.5 h. Batch centrifuges are used for displacement.

EFFECT: fast and safe process, higher efficiency.

3 cl, 2 tbl

Description

This invention relates to the production of fine and medium-grained pyroxylin defects, namely, the removal of moisture from powder elements and can be used in the manufacture of gunpowder for artillery shots and cartridges for sports, hunting, pistol, rifle and other purposes.

In the scientific and technical literature, a periodic method is known for the manufacture of pyroxylin powders of various grades (Gorst A.G. “Gunpowder and explosives” - M .: Mashinostroenie, 1972, p.152-155), in which after removal of solvents (alcohol and ether) with the help of gunpowder in water, its final drying is carried out with warm air.

There is also known a method of manufacturing granular pyroxylin powders (Gindich V.I. "Technology of pyroxylin powders", v.2, Kazan, 1995, pp. 9-11, 19-59, 102-114, 226-234, etc.), according to to which the removal of alcohol-ether moisture from pyroxylin powders is carried out periodically by soaking in water, and the subsequent removal of aqueous moisture from the powder elements is provided by two-stage drying. This method is the closest to the proposed technical solution and therefore is selected by the authors as a prototype. According to the prototype, the method of removing aqueous moisture from the powder elements in the manufacture of granular pyroxylin powders is as follows.

Pyroxylin powder, after passing through a series of consecutive processing steps, enters the water pool to remove alcohol-ether moisture, where during the process of soaking with a gradual increase in water temperature from 20-25 ° to 40-45 ° C, alcohol is mainly removed, and the residual content volatile components (alcohol and ether) in the powder are adjusted to the required content of non-volatile volatiles. Then make drying and moisturizing gunpowder.

Granular powder is dried in table dryers by blowing heated air through a layer of raw powder. During the drying process, both free (surface) moisture and most of the bound moisture are removed from wet powder.

The gunpowder is dried in two steps. At the beginning, air heated to a temperature of 75 ° C is supplied to warm up and remove surface moisture (1st stage). After the powder warms up to a temperature of 50 ° C, the 2nd stage begins - the drying itself. At the same time, the temperature of the air supplied to the drying is reduced to 55 ° C and drying is continued at this temperature. Depending on the brand of gunpowder and the height of the layer of gunpowder loaded into the dryer, the drying and moistening time of the granular gunpowder in the table driers is, respectively, in the range from 20 to 130 hours and from 2 to 10 hours. After drying, the gunpowder with the content of removed volatiles within 0.2-0.7 wt.% Is cooled, then it is humidified to the required content of removed substances (from 0.7 to 1.8 wt.%), Unloaded from the dryer and subjected to mixing. This method of removing water moisture is currently used in the manufacture of all grades of pyroxylin powders.

A significant drawback of this method of removing water moisture by drying in the manufacture of granular powders is the presence in the manufacturing process of the drying stage, which is characterized in practice by the inhomogeneous drying of granular powders and the high fire and explosion hazard of the process. Both structural and technological disadvantages are the reason for the non-uniform drying of the powder elements and the non-uniform distribution of residual moisture in the dried powder: the design of the dryer is imperfect, since the hot air is blown through the raw powder layer (layer thickness of about 40 cm) only from the bottom up and therefore the lower layers gunpowder dried much faster than the top. This leads to large fluctuations in the content of volatile substances in the finished powder. In addition, inhomogeneous drying is also facilitated by the fact that the mixing of gunpowder during the drying process is strictly prohibited due to the possible occurrence of static electricity and, as a consequence, the appearance of a fire hazard and explosion of the dried products.

The drying process of granular powder is carried out periodically in table dryers. In addition, drying in them lasts a very long time (up to 20-130 hours for various brands), so it has a small capacity (from 50 to 150 kg per hour on 1 table). The drying process in this way is also accompanied by significant specific consumption of thermal energy and high labor costs associated with manual loading and unloading of gunpowder. In addition, during manual operations of unloading and moving dried products, there is also a high likelihood of static electricity in the gunpowder, and therefore carrying out these works can lead to the risk of fire and explosion.

The objective of the invention is the creation of a high-performance and economical technology for the manufacture of small and medium-grained pyroxylin powders, which also provide high quality products and fire and explosion safety of the production.

The technical result is achieved by the fact that in the manufacture of fine and medium-grained powders, the displacement of water moisture acquired in the process of soaking of the powder elements (in an amount of up to 15-20 wt.%) Is carried out with ethanol with a volume concentration of 95-96% under the action of centrifugal force in the following mode: irrigation of gunpowder with alcohol at its dosage (dosage coefficient) in the range 0.35-0.50 l / kg - for fine-grained gunpowder (with a burning arch thickness from 0.20 to 0.35 mm) and 0.50-1.00 l / kg - for medium-grained powder (with arch thickness from 0.40 to 0.60 mm ) with simultaneous extraction of gunpowder for 2-3 minutes and its final extraction for at least 10 minutes, moreover, displacement of water moisture from the powder with alcohol is carried out in batch centrifuges (for example, VG-1000 × 400, NM-4, etc.) at a working speed of rotation of its rotor of at least 1000 rpm

In this case, the values of the residual content of the removed and non-removable volatile components may not meet the requirements of technological documentation, i.e. there may be an overestimated moisture content in the powder discharged from the centrifuge, therefore, to eliminate this phenomenon in the manufacture of gunpowder by this method, the latter is subjected to additional drying (in one stage) with air heated to 25-40 ° C for at least 1 hour in a drying or sowing machine with simultaneous forced removal of exhaust air from the apparatus or drying in vacuum with a vacuum of at least 70 mm Hg for at least 1.5 hours.

In the process of irrigation of gunpowder with rectified alcohol and simultaneous action on the powder elements with centrifugal force, they achieve the replacement of water in the inner layers of the powder elements with alcohol and its displacement to the surface of the powder (that is, they absorb hygroscopic moisture to surface). After the final extraction of gunpowder, the content of residual moisture in it mainly approaches the requirements of normative and technical documentation. If, after displacement by alcohol, the powder has an overestimated moisture content, then it is brought by drying with heated air to the required standards or by treatment in a vacuum.

The positive effect of the proposed method for the manufacture of fine and medium-grained pyroxylin powder is that during its manufacturing the stage of two-stage drying (i.e., removal of volatiles to the accepted standards) and humidification of the powder are replaced by the operation of displacing the alcohol acquired during the soaking of water moisture - rectification under the influence of centrifugal forces and, if necessary, subsequent short-term drying of the powder with heated air or processing in a vacuum. At the same time, replacing the drying stage with accelerated removal of water moisture reduces the production time by 35–40% and increases the overall productivity of the production line by approximately the same amount.

At the same time, displacement of water moisture from the powder by alcohol under the action of centrifugal forces and its subsequent drying provide the required degree of displacement of water-alcohol moisture and a more uniform content of residual non-removable substances in the powder elements and, therefore, a stable quality of the released powder, and elimination of the manufacturing process of the fire and explosive stage of the drying of gunpowder significantly increases the overall safety of the powder production.

This manufacturing method applies only to the production of fine- and medium-grained pyroxylin powders, in which, due to the denser packing of small powder elements in the layer of the product loaded into the centrifuge, water moisture is displaced by alcohol more efficiently than in coarse-grained powders. In this case, in contrast to coarse-grained powders, in fine- and medium-grained defects during their processing, free breakthrough of alcohol between the powder elements without the displacement of moisture does not occur.

The method of removing water moisture from the powder elements in the manufacture of fine and medium-grained pyroxylin powders according to the invention is carried out as follows:

After extraction from the pool, the soaked powder with a moisture content in the range of 15-20 wt.% Is loaded into a batch centrifuge, where during its operation the removal of water moisture from the powder is carried out by displacing it with alcohol under the following technological conditions:

1. Upon reaching the working speed of the centrifuge rotor (for example, 1000 rpm), the powder is irrigated with alcohol with a dosage of finely

-green powders in the range of 0.35-0.50 l per 1 kg of products and for medium-grained powders in the range of 0.50-1.00 l per 1 kg of products and the simultaneous squeezing of the powder for 2-3 minutes until the residual moisture is removed approximately to the level of 2.8-4.0 wt.%.

2. At a working speed of rotation of the rotor for at least 10 minutes, the final extraction of the powder is carried out until the content of non-removable (water-alcohol moisture) is 1.9-2.2 wt.% Or more. In the process of this extraction under the action of centrifugal force, water-alcohol moisture is displaced both from the volume between the powder elements and from inside them. At the same time, the average duration of the operation of displacing water moisture from gunpowders does not exceed 0.5 hours.

The gunpowder discharged from the centrifuge is then sent for additional short-term drying with air heated to 25-40 ° C to an apparatus, which can be used as a sieve or dryer, which can be placed in a room heated to the required temperature, for example, in a dining room a dryer, where for at least 1 hour the free (between the powder elements) and partially bound (inside the elements) alcohol-water moisture is removed and ultimately the residual water moisture content in the powder is usual to required standards (no more than 1.6 wt.% to melkozernenyh and not more than 1.8 wt.% to srednezernenyh powders). To increase the efficiency of the process, drying is carried out with the simultaneous forced removal of the exhausted (heated) air containing water and alcohol vapors from the processing unit or at a vacuum of at least 70 mm Hg. and processing time of at least 1.5 hours. After displacement of moisture with alcohol and subsequent additional drying of the gunpowder with air or under vacuum at least 70 mm Hg (within 1.5 hours or more) finely and medium-grained gunpowder in terms of residual removal is fully consistent with the required standards of the finished product and then they are transferred for further processing according to accepted serial technology.

The main distinguishing features of the new method of removing water moisture from the powder elements in the manufacture of fine and medium-grained powders from the prototype are:

1. Use after soaking to remove water moisture from the powder, instead of drying, the operation of displacement of ethyl alcohol-rectified volume concentration of 95-96%, ie the complete exclusion of the stage of two-stage drying of gunpowder.

2. The operation of displacing moisture from gunpowder, under the action of centrifugal force, in batch centrifuges used in serial production for dehydration of pyroxylins and colloxylins at operating rotor speeds (not less than 1000 rpm).

3. The operation of displacement in centrifuges according to the regime: irrigation of gunpowder with alcohol at dosages of 0.35-0.50 l / kg - for fine-grained and 0.50-1.00 l / kg - for medium-grained gunpowder, with the simultaneous extraction of gunpowder during working centrifuge rotor rotational speeds for 2-3 minutes and the final extraction of gunpowder for at least 10 minutes

4. Subsequent implementation of additional short-term (for at least 1 hour) drying of gunpowder with air heated to 25-40 ° C (with simultaneous forced removal of it from the treated apparatus) or drying in vacuum at a value of at least 70 mm Hg and with a processing time of at least 1.5 hours.

When testing technological modes of moisture removal, samples of gunpowder prepared according to the proposed method were prepared. Examples confirming the possibility of manufacturing some grades of fine and medium-grained powders by this method are shown in Tables 1 and 2. Their drying with heated air was carried out in an industrial table dryer.

As can be seen from the data presented in table 1, the efficiency of the process of displacing aqueous moisture from gunpowder depends on the amount (dosage) of alcohol supplied for displacement: its optimal dosage for fine-grained powders is 0.35-0.50 l / kg and for medium-grained 0.50 -1.00 l / kg, and at a lower dosage (less than 0.35 l / kg), the displacement of fine-grained powders (examples Nos. 1 and 2) of the moisture is not carried out fully (the residual moisture content after drying is 2.10-2, 20 wt.%), And with a larger dosage (more than 0.50 l / kg, examples Nos. 13 and 14) - significant There is no significant increase in the required degree of displacement even after drying with heated air. At the same time, with a dosage of alcohol in the range of 0.35-0.50 l / kg, the required humidity values are achieved after additional drying with air (examples Nos. 5, 6 and 9, 10). The same regularity of the effect of dosage on the degree of displacement is observed in medium-grained powders (with a burning arch thickness of 0.50-0.55 mm): the optimal alcohol dosage for displacing aqueous moisture in these powders is in the range 0.50-1.00 l / kg (examples 7, 8 and 11, 12). And in porous powders, due to their specific structure and by analogy with the capillary-porous structure of cellulose nitrates, the displacement of moisture from them by alcohol in a new way should be even more efficient.

The increase in the time of the final spin from 10 to 30 min or more to achieve the desired moisture content of the samples of gunpowder (table 1, examples 13-16, table 2, examples 19-24) has little effect. At the same time, with an increase in the spin time to 30 min, a sharp decrease in the moisture content of the powder samples also does not occur. Therefore, the final extraction of gunpowder must be done for at least 10 minutes.

At the same time, a centrifugal force sufficient to displace moisture with alcohol is provided at rotor speeds used in serial production for the dehydration of pyroxylins and colloxylins of batch centrifuges (type VG - 1000 × 4000, NM-4, etc.) in the range of 1000-1200 rpm (table 2). At a lower rotation speed (<1000 rpm, for example, 700 rpm), the displacement effect is negligible (Table 1), with an increase to 1200 rpm, and higher centrifugal force (separation factor) increases and the effect of moisture displacement will be increase. Therefore, with increasing centrifugal force, the effect of moisture displacement by alcohol increases. However, in the domestic industry, batch centrifuges are produced only with a rotor speed of not more than 1200 rpm.

From the experimental data given in tables 1 and 2, it also follows that additional short-term drying of the powder allows it to reduce the residual moisture content in it to 1.2-1.6 wt.%, I.e. to the required limit values of humidity obtained by serial technology after drying and moistening of fine and medium-grained pyroxylin powders. At the same time, the residual moisture content in the gunpowders is in a rather narrow range of values and, therefore, gunpowder is homogeneous in terms of water-alcohol moisture content.

The proposed method for the manufacture of fine and medium-grained pyroxylin powders, compared with the prototype, allows:

1. Get homogeneous in the content of water-alcohol moisture pyroxylin powder.

2. To reduce the duration of moisture removal from gunpowder from 20-130 hours to 1.5-2.0 hours.

3. To reduce the duration of the manufacture of fine and medium-grained pyroxylin powders by 35-40% and to increase the productivity of the technological line for their production.

4. To significantly reduce the specific consumption of thermal energy.

5. By replacing the drying stage with less hazardous operations, significantly reduce the fire and explosion hazard of the production of fine and medium-grained pyroxylin powders.

Based on the proposed method, it is possible to create modern, high-performance, economical, and fire- and explosion-proof industrial technologies for the manufacture of small and medium-grained pyroxylin powders of a wide assortment, including for hunting and sports cartridges.

Table 1 Examples confirming the feasibility of the method of removing moisture from fine and medium-grained powders No. of examples The initial moisture content of the sample, wt.% The thickness of the burning arch of gunpowder, mm Dosage of alcohol, l / kg The moisture content in the powder, wt.% Alcohol irrigation and spin (n = 1000 rpm) Processing time, min 1,5 2.0 3.0 3,5 one 10,2 0.22 0.28 6.20 * - - - 2 11.0 0.34 0.28 6.00 * - - - 3 10.3 0.55 0.45 6.23 * - - - four 12.1 0.50 0.45 6.80 * - - - 5 9.95 0.22 0.35 - 3.52 - - 6 11.80 0.34 0.35 - 3.23 - - 7 10.0 0.55 0.50 - 3.68 - - 8 11.88 0.50 0.50 - 3.82 - - 9 11.22 0.22 0.50 - - 2.87 - 10 9.40 0.34 0.50 - - 2.95 - eleven 11.88 0.55 1.00 - - 2.90 - 12 12.10 0.50 1.00 - - 3.00 - 13 11.10 0.22 0.60 - - - 4.00 fourteen 9.80 0.34 0.60 - - - 3,55 fifteen 11.25 0.55 1.15 - - - 3.80 16 12.00 0.50 1.15 - - - 3.95 17 prototype 9.75 0.25 The total duration of drying and moisturizing of the powders is 93 and 72 hours, with a final moisture content of 1.43 wt.% And 1.70 wt.%, Respectively 18 prototype 10.93 0.55 Note: 1. The examples marked * are performed at a rotational speed of the centrifuge rotor of 700 rpm. 2. The average duration of the displacement of aqueous moisture from powder elements with alcohol and their drying in examples 1-16 is 1.5 hours. 3. Gunpowder with a burning arch thickness of 0.2-0.35 mm refers to fine-grained gunpowder, and with a thickness of 0.40-0.56 mm it is considered to be medium-grained gunpowder

Table 1 (continued) No. of examples The thickness of the burning arch of gunpowder, mm The moisture content, wt.% Final spin (n = 1000 rpm) Air-borne (t = 35 ° C) Processing time, min 8.0 10.0 20,0 30,0 60.0 one 0.22 3,50 - - - 2.10 2 0.34 3.80 - - - 2.20 3 0.55 3.65 - - - 2.43 four 0.50 4.10 - - - 2,39 5 0.22 - 2.20 - - 1.40 6 0.34 - 2.10 - - 1.45 7 0.55 - 195 - - 1.28 8 0.50 - 2.00 - - 1.35 9 0.22 - - 2.00 - 1.13 10 0.34 - - 1.96 - 1,04 eleven 0.55 - - 1.90 - 1.10 12 0.50 - - 1.92 - 1.40 13 0.22 - - - 2.05 1.90 fourteen 0.34 - - - 1.90 1,60 fifteen 0.55 - - - 1.85 1.75 16 0.50 - - - 1.80 1.70 17 (prototype) 0.25 The total duration of drying and humidification is 93 hours, with a final moisture content of 1.43 wt.% 18 (prototype) 0.55 The total duration of drying and humidification is 72 hours, with a final humidity of 1.70 wt.% .

Claims (3)

1. The method of removing moisture from pyroxylin powder elements in the manufacture of fine and medium-grained powders, comprising the step of displacing moisture from the powder elements by drying, characterized in that the moisture acquired during the soaking of the powder elements is displaced by ethanol displacement by volume concentration of 95-96% under the action of centrifugal force by irrigation of gunpowder with alcohol at its dosages for fine-grained powders - 0.35-0.50 l / kg and medium-grained powders - 0.50-1.00 l / kg with simultaneous extraction of gunpowder for 2 -3 min and its final extraction for at least 10 min, and the subsequent removal from the powder of the residual water-alcohol moisture content to the required values is carried out in one stage by drying with air heated to 25-40 ° C for at least 1 hour with simultaneous forced removal exhaust air or drying gunpowder for at least 1.5 hours at the same temperature and vacuum with a vacuum of at least 70 mm Hg 2. The method according to claim 1, characterized in that the displacement of moisture by alcohol is carried out under the action of centrifugal force in batch centrifuges at a working rotor speed of at least 1000 rpm. 3. The method according to claim 1, characterized in that the drying of the gunpowder is carried out in table dryers or wire racks located in a room heated to the required temperature.