RU2685662C1 - Method for cellulose nitrate grinding - Google Patents

Abstract

FIELD: technological processes.SUBSTANCE: invention relates to the technology of producing cellulose nitrates (CN) with nitrogen content of 209.0 ml NO/g and more, made from wood-based cellulose raw materials of the CA brand and cotton raw material of the CC brand, specifically to the technology of industrial grinding thereof on a disk mill MD-31 and subsequent fractionation of ground fibers on an industrial factionalist. Method involves preliminary condensation of the initial CN suspension to concentration of 3–9 wt% and subsequent grinding of the condensed mass of the CN continuously and in one step at the MD-31 mill, having thin knives and a working gap between the rotor and stator knives ranging from 0.07 up to 0.10 mm. Then the ground CN suspension is sent to sort the fibers along their length into the factionalist where the business, coarse and fine fractions of the product are separated, wherein business (main) fraction of crushed CN, having a narrow fraction composition throughout the length of the fiber in range of 0.20 to 0.60 mm, is fed into the lavatory for final stabilization and subsequent processing into pyroxylin powder, large fraction of product with fiber length of 0.60 mm and more is returned to production for additional milling, and fine fraction – with fiber length of less than 0.20 mm is recycled into production of pellet powder.EFFECT: method enables to obtain, under industrial conditions, qualitative and homogeneous pyroxylin No 1 according to fractional composition, which corresponds to required standards and suitable for subsequent processing thereof into different powders.4 cl, 1 dwg, 2 tbl

Description

The invention relates to the production of cellulose nitrates (NC) with a nitrogen content of 209.0 ml NO / g and more, in particular the manufacture of pyroxylin No. 1 from wood fiber pulp of the CA brand and cotton raw material of the HC brand in industrial conditions.

As is known, pyroxylin powders are made of pyroxylins No. 1 and No. 2, taken in a certain ratio, and pyroxylin No. 1 with a nitrogen content of 209.0-217.0 ml NO / g is predominantly made of wood (fibrous) cellulose of the CA brand, pyroxylin No. 2 with a nitrogen content of 193.7-199.3 ml of NO / g - from cotton cellulose of the KhTS brand by nitration with a nitrous acid mixture [1, pp. 150-151; 2, pp. 290-294]. Therefore, in the production of NTS, associated with the manufacture of pyroxylin and other types of powders, special attention is paid to the qualitative grinding of the initial cellulose nitrates - pyroxylins No. 1 and No. 2, since it ensures that the fibers of spent acids (HNO ₃ and H ₂₎ are completely removed from the capillaries. SO ₄ ), and the subsequent high processability of pyroxylin processing into gunpowder.

Known [3, p. 350; 4, pp. 318-324] the method of grinding NC, including pyroxylin No. 1 on conical mills RK-01 (Jordan) of continuous action. The pulverized cellulose nitrates in the form of an aqueous suspension pass through 3-5 successively connected mills RK-01, and thickening devices (thickeners) are installed between the individual devices, and the mass concentration of NTS in the aqueous suspension during grinding is usually maintained from 3.0 to 4, 5 wt. % The method provides a satisfactory quality of grinding, but it is very uneconomical and does not meet modern production requirements. The main disadvantages of the method are not sufficiently homogeneous crushed fibers NTS, as the residence time of the product in the mill, due to the reverse flow and transfer of the product mass, is different (1.5-5.0 s). In addition, the rotor and the stator of the mill have a complex typesetting headset, which requires considerable labor when replacing knives. The mills have, in addition, a large metal content.

The literature also describes another method of grinding pyroxylin No. 1 using the Kuzmin disk mill (DMK) [4, pp. 324-330], which performs the grinding process of the product in one pass. When using mills of the DMK type, there is also an insufficiently high uniformity of the ground fibers of cellulose nitrates and a small specific surface of the fiber. At the same time, with a relatively small mill productivity, a complex grinding headset is required.

Of the known, other methods of continuous grinding of cellulose nitrates, including pyroxylin No. 1, from wood pulp of the CA brand, as well as pyroxylin No. 2, and colloxylin "H", made from HZ brand cotton pulp, it is necessary to note the method using an installation consisting of two disk mills MD-31 [5, p. 267-269].

A similar method of grinding NTS, including pyroxylin No. 1, is given in another source [6, pp. 77-80], which also describes the method of grinding NTS in two successively operated MD-31 disk mills.

The closest analogue of the claimed invention is the method of grinding NTS on two disk mills MD-31, given in the above source [5, pp. 267-269, 272], which was chosen by the authors as a prototype. In accordance with the prototype, the grinding of pyroxylin No. 1 (from wood pulp of the CA brand) is carried out at an installation consisting of two successively connected MD-31 disk mills. Water suspension of the crushed product with a mass fraction from 4.0 to 5.0% from the mixer mass pump is fed into the grinding chamber of the first disk mill, then goes to the grinding discs. Moving further into the gap between the disks and the working surfaces of the knife set, the fibers are crushed by cutting, grinding (hydrodynamic amorphization effect).

At the first mill, an inter-blade gap is set from 0.10 to 0.12 mm, and at the second mill - a gap from 0.07 to 0.08 mm. In order to cut the fibers more intensively, headsets with thin knives are used.

If we take into account that the degree of grinding is estimated by sieve analysis, which is based on the fractionation of the mass according to the maximum permissible fiber length, then the more intense the shortening (cutting) of the fibers occurs, the more efficiently the mills work. Considering the different requirements for the quality of grinding of pyroxylins No. 1, No. 2 and colloxylin “H”, it is necessary for each of them to choose their own grinding headset.

Significant disadvantages of this method (prototype) of pyroxylin No. 1 grinding from wood pulp of the CA brand are the use of two 500-millimeter-sized mills for grinding, which requires a very large power consumption. In addition, the installation has a high metal content, as well as the fact that the NTS mass crushed in this installation has a significant non-uniformity along the length of the fibers - i.e. large spread of fractions along the length of the fibers (from 0.15 mm or less to 1.0-3.0 mm). As is known, a large variation in the length of the crushed NTS fibers influences both the technology of their subsequent processing into gunpowder and the quality of the various types of gunpowder made from them.

The present invention is to eliminate or reduce the above disadvantages, namely the creation of a more perfect and economical method of grinding pyroxylin No. 1 from wood pulp of the CA brand and cotton raw material of the KhT brand, which provides, on the basis of the one MD-31 mill used, in obtaining crushed fibers with a narrow fractional composition along the fiber length, for example, in the range from 0.20 to 0.60 mm and their subsequent high-quality processing into all brands of pyroxylin and other types of powders.

The technical result is achieved by the fact that the grinding of cellulose nitrates with a nitrogen content of 209.0 ml NO / r and more (pyroxylin No. 1, made of wood pulp of the CA brand and cotton raw materials of the KhT brand) is carried out continuously, in the form of an aqueous suspension with a concentration from 3, 0 to 9.0 wt. % and in one step on the disk mill MD-31, containing on the working surfaces of the disks thin knives and having a working gap between the blades of the rotor and stator in the range from 0.07 to 0.10 mm. Then the suspension of crushed pyroxylin No. 1 fibers is passed through a sieve fractionator for subsequent sorting with the final release of the business, large and small fractions of the product, and the business (main) narrow fraction of pyroxylin No. 1 (with a fiber length from 0.20 to 0.60 mm) is sent in the laver for final stabilization and subsequent processing into gunpowder, a large fraction NTS with a fiber length of 0.60 mm and more is returned to production for re-grinding, and a fine fraction with a fiber length of less than 0.20 mm is subjected to subsequent scrap The analysis of the composition of the processed pyroxylin No. 1 in the production of spherical powder (1 PL)

At the same time, the required concentration of the condensed (water) suspension of cellulose nitrates for grinding is provided as a preliminary upholding of the initial suspension in the mixer and followed by siphoning from it (discharging through special pipes) excess clarified water - to create a suspension with a concentration from 3.0 to 5.0 wt. %, and using to obtain a suspension of crushed NTS with a concentration in the range from 5.0 to 9.0 wt. % of a typical continuous drum thickener installed above the mill at a height of at least 3.0 m (to ensure a continuous and stable supply of the concentrated mass to the mill due to the corresponding pressure created at the same time). Moreover, to obtain a condensed suspension NTS with a concentration of from 3.0 to 5.0 wt. % and feed it continuously to the mill, the condensation of the NC suspension is carried out simultaneously in several mixers (up to 4 pcs.).

The quality of grinding of cellulose nitrates in the MD-31 mill is controlled on samples of the ground product (from the business fraction) using standard methods (screen and volume methods) and determining the fiber length interval using the Metso FS5 fiber properties analyzer (manufactured by Metso, Finland).

For fine and coarse screening of crushed NTS fibers (i.e., separation of the main, business fraction, as well as coarse and fine fractions), a pressure head, multistage sieve fractionator with slit-like openings and operating at an operating pressure of at least 0.40 MPa is used. its performance is equal to or greater than the performance of the MD-31 mill. In the process of operation of the fractionator, the regulation of the consistency of the suspension of the NC is carried out, if necessary, by partially diluting it with the process water supplied to the apparatus.

Utilized small fraction NTS after fractionator in the form of an aqueous suspension with a concentration of from 2.0 to 4.0 wt. % is passed through a vacuum filter and then collected in the technological collection in the form of homogeneous products for the manufacture of spherical powder.

The main distinctive features of the claimed invention from the prototype are:

1) carrying out the grinding process NTS continuously and only in one step on the MD-31 mill, equipped with thin knives and working when the worker between the blades of the rotor and stator in the range from 0.07 to 0.10 mm;

2) carrying out the grinding process NTS on a thickened suspension in a wide range of concentrations (from 3.0 to 9.0 wt.%), And the prototype - in the form of a suspension with a concentration of NC from 4.0 to 5.0 wt. %, and the concentration of the suspension NTS to a concentration of from 3.0 to 5.0 wt. % is produced in the mixer (or mixers) by sedimentation of the suspension and siphoning of excess water, and for greater concentration (from 5.0 to 9.0 wt.%) - use a drum thickener located above the mill at a height of at least 3 m;

3) sorting the crushed product along the fiber length and separating the business, coarse and fine fractions from it and using for this purpose a multi-stage pressure sieve fractionator with slotted holes (with a capacity exceeding the performance of the MD-31 mill) and operating at an operating pressure of at least 0.40 MPa;

4) the ability to control the consistency of the sorted suspension NTS in the fractionator by feeding it, if necessary, to dilute the sorted mass of additional process water;

5) obtaining, after fractionation, crushed NTS of the main (business) fraction of the product corresponding to a narrow interval along the fiber length (from 0.20 to 0.60 mm) and using the NTS of this fraction during their subsequent processing into pyroxylin powders;

6) return to production for regrinding of the large fraction of NTS obtained after sorting in a fractionator and having a fiber length of 0.60 mm or more;

7) utilization of the fine fraction (with a fiber length of less than 0.20 mm) of crushed cellulose nitrates in the production of spherical powder;

8) operational quality control of grinding NTS on the MD-31 mill is carried out on samples of the ground product from the composition of the business fraction by determining the fiber length interval on the Metso FS5 fiber properties analyzer;

9) separation of the suspension of the utilized small fraction of the product (with a fiber length of less than 0.20 mm) after sorting in a fractionator on a vacuum filter and collecting it in the technological collection in the form of a homogeneous product.

The above essential features of this invention together provide a positive technical result.

In accordance with this invention, the method of grinding cellulose nitrates with a nitrogen content of 209.0 ml NO / g or more (pyroxylin No. 1) made from wood pulp of the CA brand or cotton raw material of the KhT brand under industrial conditions is as follows (Fig.).

In several mixers (1), at the same time, for the grinding of the MD-31 mill (3), a condensed suspension of NC with a concentration of from 3.0 to 5.0 wt. % due to sedimentation of the original suspension and subsequent siphoning (removal) of excess clarified water through special pipes in the mixer, and to obtain a suspension with a concentration of from 5.0 to 9.0 wt. % used continuous drum thickener (2), installed above the mill at a height of not less than 3 m and which ensures the continuous flow of a thickened mass from the drum thickener into the MD-31 mill for grinding due to the generated head.

The process of grinding cellulose nitrates with the required concentration of the product in an aqueous suspension (ranging from 3.0 to 9.0 wt.%) Is carried out continuously and in one step on an MD-31 disk mill containing thin knives on the working surfaces of the disks the gap between the rotor blades and the stator in the range from 0.07 to 0.10 mm (the corresponding gap is set in advance).

Then, the suspension of crushed cellulose nitrates for subsequent sorting (by fiber length) is sent from the mill to a pressure, multi-stage sieve (with slit-like holes) fractionator (4) for example, MultiSTage Screen brand (Valmet, Finland), with operating pressure from 0 , 40 to 0.50 MPa, where the separation of the suspension NTS with the release of business (main), large and small fractions of the crushed product. The business fraction of cellulose nitrates with a fiber length from 0.20 to 0.60 mm is sent further to laver (6), for final stabilization and subsequent processing into gunpowder, a large fraction of cellulose nitrates, with a fiber length from 0.60 to 1.0 mm and more is returned to production for regrinding (by adding to the suspension the initial comminuted product), and the fine fraction NC with fiber length of less than 0.20 mm is subjected to subsequent utilization in the production of spherical powder.

The quality of grinding of cellulose nitrates in the MD-31 mill is controlled by determining on samples of ground product (from the composition of the business fraction) the allowable fiber length interval (ranging from 0.20 to 0.60 mm) performed on the Metso FS5 fiber properties analyzer.

The volumetric capacity of the fractionator, at the same time, must be greater than the productivity of the MD-31 disk mill used. In this case, the adjustment of the consistency of the suspension of the product in the process of sorting in the fractionator, if necessary, is made by partial dilution of the suspension, which is additionally supplied with process water.

The residual fine fraction of the NC after the fractionator is passed in the form of an aqueous suspension through a vacuum filter (5) and is obtained in the technological collection in the form of a concentrated and homogeneous product, which is then sent for the manufacture of spherical powder.

Tables 1 and 2 give examples of the method for grinding cellulose nitrates under industrial conditions. From the above examples, it follows that when grinding NTS on a single MD-31 mill (Table 1), the content of coarse fraction (more than 0.60 mm) is slightly higher than the analogous indicator of the prototype (11.1-17.7 wt.% Versus 8.8 -11.7 wt.%) And the quality of grinding NTS according to the results of sieve analysis is also on the limit of permissible (examples No. 4-9).

Note: 1. The fractional composition of samples of crushed NTS in examples No. 1-9 was determined on the analyzer of the properties of the fiber Metso FS5.

2. Analysis of residues on sieve No. 016 and 063 of crushed NTS was carried out according to GOST B 5765-75, according to which for crushed pyroxylin No. 1, residue on sieve No. 0.06 and 063, respectively, should not exceed 7.0 wt. % and 0.09 wt. %

3. For examples Nos. 6, 7 and 8, the drum thickener of the suspension of the NC was located above the MD-31 mill at a height of 3.0 m, 4.0 m and 3.5 m, respectively.

4. In column 4 of table 1, the fraction means: numerator - the gap at the 1st mill, the denominator - the gap at the 2nd mill.

Note: 1. In examples No. 10-15, samples were taken from a fractionator during continuous operation of the installation (1 MD-31 mill and fractionator), after 2 hours from the beginning of their joint operation.

2. The fractional composition of the samples was analyzed on the Metso FS5 fiber properties analyzer, and the residue on the sieve Nos. 016 and 063 was measured in accordance with the method of GOST B 5765-75.

3. For the samples in examples No. 11, 13 and 14, the drum thickener of the NC suspension was located above the MD-31 mill at a height of 3.0 m.

4. The results of screen analysis, marked with *, refer to the product of the business fraction.

At the same time, the samples of the selected business fraction of the NC (examples Nos. 10-15) (Table 2) that have passed through the fractionator are crushed in the fractionation mill (examples Nos. 10-15) (Table 2) along the fiber are already in a much narrower and required fractional interval (from 0, 20 to 0.60 mm) and thus have good uniformity.

It should also be noted that the quality of grinding of these samples NTS (pyroxylin No. 1) on one MD-31 mill with their subsequent fractionation, both according to the results of sieve analysis, and on the fractional composition, with a margin met the required standards and therefore all of them (Table. 2) further processed by standard technology into pyroxylin powders of various grades.

Presented in tables 1 and 2, the results show a clear advantage of the proposed method of grinding cellulose nitrates in comparison with the prototype.

Thus, the proposed method of grinding cellulose nitrates, in comparison with the prototype, has the following advantages:

1) as a result of the developed invention, a more perfect method of continuous grinding of industrially produced cellulose nitrates - pyroxylin No. 1, made of wood pulp of the CA brand, cotton raw material of the HT brand and being the main component in the manufacture of pyroxylin and other types of gunpowder, has been created;

2) the method of grinding cellulose nitrates, in practical implementation, through the use of a single MD-31 disk mill (with thin knives) and with its integrated work with a fractionator ensures industrial production of high-quality and uniform fractional composition (from 0.20 to 0.60 mm) pyroxylin No. 1, which meets the required standards and is suitable for subsequent processing into various types of powders;

3) the proposed method, in comparison with the prototype, is highly economical, since there is a release of one MD-31 disk mill (with a capacity of 500 kW), and the power consumption of the pressure fractioner is only about 20 kW;

4) the method provides a full return of the unused coarse fraction of the product (fiber length more than 0.60 mm) in production for re-grinding as part of the initial suspension NTS;

5) at the same time, formed during grinding in an MD-31 mill and subsequent sorting, the small fraction of pyroxylin No. 1 (with a fiber length of less than 0.20 mm) in an amount of from 20.0 to 25.0 wt. % is also utilized by the direction in the production of spherical powder;

6) the possibility of implementation at this grinding installation grinding process NTS in a wide range of concentrations (from 3.0 to 9.0 wt.%), Obtained as using the method using a drum thickener, disposable (to create pressure) above the MD-31 mill at a height of at least 3.0 m;

7) quality control of the grinding of cellulose nitrates of the main business fraction is performed on samples by the method of determining the fiber length interval (fraction) on the Metso FS5 fiber properties analyzer;

8) high-quality and continuous operation of the pressure fractioner is also ensured by regulating the consistency of the sorted mass due to the additional supply of process water to the fractionator.

On the basis of the present invention, a new industrial technology of grinding cellulose nitrates (pyroxylin No. 1) has been developed at the enterprise, followed by its development at the enterprises of the industry.

Literature

1. Horst A.G. Gunpowder and explosives. - M .: Mashinostroenie, 1972, - 208 p.

2. Orlova E.Yu. Chemistry and technology of high explosives: A textbook for universities, - 3rd ed., Pererab. -L. Chemistry, 1981, - 312 p.

3. Zakoshchikov A.P. Nitrocellulose. State publishing house of the defense industry, -M., 1950, - 370 p.

4. Gindich V.I. Technology of pyroxylin powders, vol. 1, Production of cellulose nitrates and acid regeneration. Kazan, ed. GosNIIKhP, 1995, - 554 p.

5. Gindich V.I., Zabelin L.V., Marchenko G.N. Production of cellulose nitrates. Technology and equipment. CNIINTI and TEI, 1984, - 355 p.

6. Dementieva D.I. Introduction to the technology of energy-saturated materials: a tutorial / D.I. Dementieva, I.S. Kononov, R.G. Malyshev, V.A. Kharitonov, Alt.Gos.Tech.un-t: BTI, - Biysk: Publishing House Alt.Gos.Tehn.un-ta, 2009, - 254 p.

Claims (4)

1. The method of grinding cellulose nitrates with a nitrogen content of 209.0 ml NO / g or more, made from wood pulp raw materials of the CA brand and cotton raw materials of the HC brand, including preliminary thickening of the aqueous suspension of the product, grinding it in the form of a suspension on a disk mill and feeding the suspension crushed cellulose nitrates for final stabilization, characterized in that the grinding of cellulose nitrates in the form of an aqueous suspension with a concentration of from 3.0 to 9.0 wt.% is carried out continuously and in one step in the MD-31 mill, containing On the working surfaces of the disks, thin knives and a rotor and a stator having a working gap between the knives range from 0.07 to 0.10 mm, after which the suspension of ground fibers of cellulose nitrates is passed through a sieve pressure fractioner for subsequent sorting, where the final separation of the business, coarse and fine fractions of the product, and the business fraction of the crushed cellulose nitrates, having a narrow fractional composition along the fiber in the range from 0.20 to 0.60 mm, is sent to the laver for final stabilization and after processing in pyroxylin and other types of powders, a large fraction of cellulose nitrates with a fiber length of 0.60 mm and more is returned to production for re-grinding, and a fine fraction with a fiber length of less than 0.20 mm and content in suspension ranging from 2, 0 to 4.0 wt.% Is subjected to subsequent disposal by adding it to the composition of the processed pyroxylin No. 1 in the production of spherical powder. 2. The method of grinding cellulose nitrates according to claim 1, characterized in that for thickening the aqueous suspension of cellulose nitrates to a concentration of from 3 to 5 wt.% Use preliminary settling of the initial suspension in the mixer, followed by siphoning an excess of clarified water from it, and for thickening the suspension to a concentration of from 5 to 9 wt.% apply continuous drum thickener, installed above the MD-31 mill at a height of not less than 3 m. 3. The method of grinding cellulose nitrates according to claim 1, characterized in that the quality of grinding cellulose nitrates in the MD-31 mill is continuously monitored on samples of the ground product from the composition of the business fraction by determining the fiber length interval using a Metso FS5 fiber properties analyzer. 4. The method of grinding cellulose nitrates according to claim 1, characterized in that for sorting the crushed fibers of cellulose nitrates use a pressure multistage sieve fractionator with slit-like holes and a volumetric capacity equal to or greater than the performance of the MD-31 disk mill, operating at a minimum working pressure 0.40 MPa, and the regulation of the consistency of the suspension of the product in the fractionator during sorting is carried out by partial dilution of the process water that is additionally supplied to the apparatus.

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