RU2188817C2 - Liquid nitric acid esters production process and installation for implementation of process - Google Patents

Abstract

FIELD: explosives. SUBSTANCE: invention relates to production of nitric acid esters used in manufacture of ballistite powders, industrial explosives, and liquid monofuels. Liquid nitric acid esters are prepared by nitration of ethanol in a small-reaction volume nitrator followed by cooling reaction mixture in flow cooler, separating nitro emulsion, and washing nitric acid ester. Nitration is conducted in two steps involving complete withdrawal of exhausted acid from the process and intermediate cooling of first-step nitration mixture. First-step nitrator receives 50-60% and second-step nitrator 50-40% of required amount of alcohol to be nitrated. Weight ratio of nitration mixture to alcohol is selected such as to exclude achievement of nitric acid ester decomposition temperature. EFFECT: expanded operation possibilities by reducing productivity according to existing needs and widened stock-list of nitric acid esters. 4 cl, 3 dwg, 1 tbl

Description

 The invention relates to the production of nitric acid esters used in the production of ballistic powders, industrial explosives, liquid unitary fuels, as a medicine (nitroglycerin). These are nitric acid esters of glycerol, ethylene glycol, di- and triethylene glycol, propylene glycol, and mixtures thereof.

There are various batch and continuous plants for producing liquid nitroesters. Any installation involves the following process steps:
- preparation of nitrating mixtures (mixtures of nitric and sulfuric acids);
- preparation of the starting alcohols and their mixtures;
- preparation of washing liquids (warm and cold water, soda solution);
- nitration of alcohols;
- separation of acid nitroester from spent acid;
- washing acid nitroester with washing liquids;
- processing of waste acids;
- neutralization of wash water from nitrofair.

 The equipment of the main stages: nitration, separation and washing is located in a separate bunded building or in reinforced concrete cabins. The remaining stages can be located in other buildings and, in essence, they are independent productions.

 In batch plants, nitration and washing are carried out in air-stirred reactors, separation is carried out either directly in the nitrator or in a special separator-settler (Naum A. Nitroglycerin and nitroglycerin explosives. - M .: Goskhimizdat, 1934, p. 44-79).

 At existing continuous foreign Biation and Schmidt-Meisner plants and at domestic separation plants, nitration is carried out in reactors with a mechanical stirrer, coil or tubing for cooling. The nitromass from the nitrator enters a static separator (a container with a sight glass for monitoring the level of phase separation), from which flows of spent acid and acid nitroether are continuously withdrawn. The latter is washed in a system of several apparatuses with mechanical mixers and labyrinth type separators. It is washed first with cold water, then with a soda solution and warm water. Instead of apparatus with mechanical stirring, air-mixed columns are also used.

 Until now, domestic non-separation plants have been preserved, which are distinguished by the fact that the nitromass in a special apparatus is diluted with water and then sent for separation and the separated nitro-ether for washing.

 The main disadvantages of these installations are the large load (300-1000 kg) of the building with an explosive product and the long stages of starting and stopping the process (up to 4 hours). As a rule, accidents on them end with the complete destruction of the building and equipment, and human casualties are not uncommon.

 Continuous injection plants operating in a number of countries and in Russia are more perfect, in which the nitration of alcohols is carried out in the injector, and the separation of the nitroester from the spent acid in a centrifuge. To remove the heat of reaction, a cooled nitrating mixture is fed into the injector, into which spent acid is added in order to increase the volume of heat-removing liquids (Swedish patents 165427, US 2217903, 3111538, Great Britain 808103, 735888, 822870; A.M. Pennie, Explisivstoffe, 1962, t .10, p. 213-219). Acidic nitroesters are washed in the same equipment as in other continuous plants.

 Closest to the proposed invention relating to a method for producing nitroesters is the method described in German patent 1058039 "Method for producing nitric esters of aliphatic alcohols."

This method consists in nitration of alcohol in a nitrator with a small reaction volume, cooling the reaction mixture in a flow cooler, separating the nitroemulsion and washing the nitroester. The disadvantages of this method, for the implementation of which an injector-nitrator is used, are limited by the pressure of the working nitro mixture supplied through the nozzle (it must be at least 0.4 MPa), clogging of the injector nozzle with acid sludge, which occurs at a productivity below 100 kg / h, and also (due to the fact that the injector-nitrator does not have cooling surfaces), the need for special techniques for the removal of reaction heat is necessary: previously, the nitrating acid mixture is cooled to the lowest possible temperature, based on Physically nitrosmesi properties (viscosity, freezing point) not lower than -10 ^o C; the amount of the nitrating mixture of acids is increased by a factor of 2–3, so that after mixing with nitrated alcohol and releasing all the reaction heat, the temperature of the reaction mass does not exceed the permissible limits for safety reasons. An increase in the amount of nitro mixture is achieved by adding to the fresh nitro mixture, which is involved directly in the nitration process, the spent acid, which is, as it were, an inert solvent, the heating of which consumes excess heat of reaction. In addition, the reaction mass after the nitrator is immediately cooled in a flow-through refrigerator; further operations with it are carried out at safe temperatures, in the sense of decomposition of nitroesters. Thus, the return to the process of spent acid with nitroesters dissolved in it increases the volume of acid mixtures supplied to the nitrator by a factor of 2–3, accordingly, the load on the separation equipment increases and auxiliary acid farming becomes more complicated. Along with this, regardless of whether the nitration process is ongoing or not, it is necessary to periodically turn on refrigerators to cool the nitro mixture. It is especially difficult to prevent the decomposition of nitroesters dissolved in the working nitro mixture when producing nitro esters such as dinitrates of di- and triethylene glycols, 1,2-propylene glycol. Those. The known method has limitations on the nomenclature of the obtained nitroesters and on productivity in the direction of reduction and, therefore, has reduced operational capabilities.

 The same patent describes a plant for producing nitroesters, which is closest to the proposed one.

 Stage nitration and separation of such a plant is illustrated in figure 1. The washing stage is carried out in a centrifugal extractor (not figuratively shown in FIG. 1, since it remains unchanged in the claimed solution).

 From the description of the patent it follows that the known installation includes auxiliary equipment that does not affect the essence of the invention and not conditionally shown in the scheme given in the patent. These are means for transporting and heating nitrated alcohol, means for transporting and cooling the working nitrating mixture of acids in a supply tank, a container and a pump for storing and transporting fresh nitrating mixture, a control separator for separating nitroester from spent acid in case of a centrifuge malfunction. Since the inventive method allows to exclude the use of part of the auxiliary equipment, it is advisable to bring in figure 1 the above equipment.

 The known installation has a tank for nitrated alcohol 1 with a pump 2 and a heater 3, a tank with a constant level of alcohol 4, a tank for a working nitro mixture 5 with pumps 6 and 7 and a refrigerator 8 and a tank for fresh nitro mixture 9 with a pump 10, a refrigerator for a working nitro mixture 11, injector-nitrator 12 with valves for supplying alcohol 13 and regulating vacuum 14, refrigerator nitroemulsion 15, centrifuge 16, control separator 17, conveying injectors 18 and junction box 19.

The working nitro mixture is a mixture of fresh anhydrous nitro mixture (a mixture of nitric and sulfuric acids) and waste acid, which contains water and dissolved nitroesters. The mass ratio between them depends on the nitrated alcohol and is usually in the range from 1: 1 to 1: 2. Typically, two containers for a working nitro mixture are installed (Fig. 1 shows one, item 5). From one tank, the working nitro mixture is consumed during the nitration process, and waste acid is taken into another tank, which is mixed with the fresh nitro mixture supplied by the pump 10 from the tank 9. The mixing of these acids is carried out by circulating the acids by the pump 7 through the refrigerator 8. This refrigerator is also used to cool the working nitro-mixtures in the summer to prevent the decomposition of nitroesters dissolved in acid (for a number of nitroesters such as di- and triethylene glycols dinitrates, propylene glycol dinitrates and other maxi the maximum permissible temperature during storage of the working nitro mixture is 15 ^o С).

 Nitrated alcohol is prepared in a container 1 and preheated by circulation of a pump 2 through a heater 3, after which it enters the tank 4.

Installation works continuously. The nitro mixture by the metering pump 6 is fed through the refrigerator 11, where it is cooled to a temperature of minus 5 ^o C to minus 10 ^o C, into the injector nitrator 12. Due to the vacuum created by the acid stream from the tank 4 through the valve 13, alcohol is sucked into the injector chamber and mixes up with nitro mixture. The vacuum value is regulated by valve 14. The resulting emulsion of the nitroester in spent acid with a temperature of 40-55 ^o C (heated by the heat of reaction) is cooled in the refrigerator 15 and separated in a centrifuge 16. The spent acid further passes through a static control separator 17 and in the junction box 19 split into two streams. One stream is mixed with fresh nitro mixture, the second stream is sent to the stage of decomposition of nitroesters dissolved in acid and then for disposal. Nitroesters from the centrifuge 16 and the control separator 17 with the injectors 18 are passed to the washing stage.

 The known installation, in comparison with other continuously operating installations, in which conventional capacitive reactors with mixers and cooling surfaces are used for nitration, compares favorably with the use of a jet mixer (injector) as a nitrating apparatus. An injector-nitrator reduces the nitration time to the kinetically possible (1 s) and eliminates high loads of nitration equipment with explosive and unstable nitroesters mixed with acids.

 The prototype plant is used to produce nitroglycerin, ethylene glycol dinitrate and mixtures of nitroglycerin with diethylene glycol dinitrate. The productivity of such plants is 160-1600 kg / h. With a decrease in productivity to 50 kg / h, insurmountable obstacles arise. The diameter of the nozzle of the injector used as a nitrator in this case should not exceed 0.6-0.7 mm. The sludge always present in acids often clogs such a nozzle and the nitration process does not just stop, but is also accompanied by the throwing of the nitro mixture in the communication for nitrated alcohol and its rapid decomposition. T. about. , the known installation has limited operational capabilities. It is possible to obtain on it only those nitrophyres which are sufficiently stable in a mixture with acids, and only with a plant productivity of at least not less than 100 kg / h.

 The objective of the present invention is to develop a method for producing liquid nitroesters and installation for its implementation, which allows to expand operational capabilities by reducing productivity in accordance with the existing need and expanding the range of obtained nitroesters, including nitro esters with low stability when in contact with mixtures of nitric and sulfuric acids while maintaining dignity nitrator with a short residence time of reagents (not more than 1 s) and the exclusion of addition from worked acid into a nitrating acid mixture.

 The problem is solved by the proposed method for producing liquid nitroesters and installation for its implementation.

 To obtain the above technical result in the claimed method for producing liquid nitroesters by nitration of alcohol in a nitrator with a small reaction volume, cooling the reaction mixture in a flow cooler, separating the nitroemulsion and washing the nitroester, the peculiarity is that the nitration is carried out in two stages in different nitrators only with fresh nitro-mixtures with the complete withdrawal of spent acid from the process with intermediate cooling of nitromass after the first stage, moreover, in the nitrator of the first stage odayut 50-60%, and in the second nitrator stage 50-40% of the required amount nitruemogo alcohol, the weight ratio and an alcohol selected nitrosmesi precluding the achievement of nitroesters decomposition temperature.

 Distinctive features of the proposed method from the prototype are the nitration in two stages in different nitrators, the use of only fresh nitro mixtures, the complete withdrawal of spent acid from the process, which allows us to consider the proposed method as meeting the criterion of "novelty."

 Comparison of the proposed method with the prototype and other methods for producing nitroesters, identified in the prior art, showed that it is not known the technical solution to the problem in which the proposed combination of features would take place.

Only the proposed combination of distinctive features from the prototype with the remaining essential features of the proposed method allows not only to preserve the advantages of a nitrator with a short residence time of reagents (not more than 1 s), as in the prototype, but also to eliminate the addition of spent acid to the nitrating mixture of acids with subsequent storage of the resulting nitrosmesi working with the system maintaining the temperature not higher than 15 ^o C, and therefore it becomes possible to securely obtain nitroesters including a bottom nitrofeiry oh stability in the medium of nitric and sulfuric acids, i.e., to achieve the expansion of the range of obtained nitroesters, as well as to reduce the productivity margin in accordance with the existing need, and ultimately ensure the expansion of operational capabilities.

 This gives reason to consider the proposed method as inventive.

The method is carried out using an installation containing a nitrator with a small reaction volume, containers for nitro mixture and nitrated alcohol, means for cooling and heating them, means for supplying them to the nitrator, a nitroemulsion refrigerator and a centrifuge, a feature is that between the nitroemulsion refrigerator and the centrifuge they are installed in series the second nitrator and the second emulsion refrigerator in such a way that the input of the nitro mixture of the second nitrator is connected by a pipe to the exit of the nitroemulsion from the first refrigerator, and the output is not The emulsions from the second refrigerator are connected by a pipeline to a centrifuge, each nitrator is connected by a pipe with a means for supplying alcohol to it, each nitrator is a plate open on top of a vertical shaft with bent upwards curved upwardly forming a toroidal cavity enclosed in a casing and introduced into the torus space a mixing tube, the end of which is directed towards the rotation of the plate and is located with the smallest possible clearance relative to the surface of the plate, the supply pipe nitro mixture in the center of the plate and the pipe for supplying alcohol with its placement from the intake end of the mixing tube at a distance corresponding to the angle of rotation of the plate around its axis by 100-180 ^o .

 In addition, a disk is fixed to the plates by means of radial partitions.

 It is advisable to perform the intake end of the mixing tube with pointed edges.

 The analysis of the prior art shows that the proposed installation for implementing the method for producing liquid nitroesters differs from the prototype in the other structural embodiment of the nitrator in the form of a plate (in the prototype, an injector), the presence of a second nitrator and a second emulsion refrigerator installed in a certain sequence.

 T.O. The claimed installation meets the criterion of "novelty."

 Comparison of the proposed installation with the prototype and other technical solutions showed that the installation is not known in which the proposed combination of features would take place.

 But it is precisely the combination of features that are distinctive from the prototype with other essential features of the proposed solution that made it possible to expand the operational capabilities of the installation by reducing its performance in accordance with the existing need and expanding the range of liquid nitroesters obtained while preserving the dignity of a nitrator with a small reaction volume and the complete removal of spent acid from process.

 That allows us to consider the proposed installation for implementing the method of producing liquid nitroesters with an inventive step.

 In addition, the fastening of the disk to the plates by means of radial partitions prevents the liquids supplied to the plate from slipping over the surface of the plate, so that the liquid at the periphery of the plate in its torus space acquires the same peripheral speed as the plate.

 It should be noted that to reduce local resistances at the entrance to the mixing tube, it is advisable to carry out its intake end with pointed edges.

The proposed installation for implementing the method for producing liquid nitroesters contains (Fig. 2) a container 1 for nitrated alcohol with a pump 2 and a heater 3, a container 9 for fresh nitro mixture with a metering pump 10, a refrigerator 11 for a fresh nitro mixture, a nitrator 12 'and a refrigerator 15' 1 -th nitration stage, nitrator 12 and refrigerator 15, 2nd nitration stage, centrifuge 16, control separator 17, injectors transporting nitroesters 18 and alcohol metering pumps 20. Nitrators 12 and 12 'of the 1st and 2nd stages are ( Fig. 3) enclosed in a rotating body in the vertical cantilever shaft, a plate 21 open at the top with curved toroidal sides bent upward and introduced into the torus space, a mixing tube 25, the end of which with pointed edges is directed towards the rotation of the plate 21 and is located with the smallest possible clearance relative to the surface of the plate 21, the tube 23 for feeding the nitro mixture in the center plates 21 and a pipe 24 for supplying alcohol with its placement from the intake end of the mixing tube 25 at a distance corresponding to the angle of rotation of the plate 21 around its axis by 100-180 ^o . A disk 22 with radial partitions 27 is fixed on the plate 21. In the lower part of the plate 21 there are channels 26 for releasing it from residual liquids after the rotation stops.

Installation works as follows. Fresh nitro mixture from the supply tank 9 is fed by the metering pump 10 through the refrigerator 11 to the nitrator 12 of the 1st stage through the tube 23. The nitro mixture in the refrigerator 11 is cooled to a temperature of minus 5 to minus 10 ^o C. Preheated to 35-60 ^o C of the supply tank 1 by circulation of the pump 2 through the heater 3, nitrated alcohol by one of the metering pumps 20 is supplied to the 1st stage nitrator through the tube 24. The ratio between the nitro mixture and the alcohol is chosen so that the nitration temperature does not exceed the permissible values, for example, when glycerol is nitrated 55 ^o C, diethylene glycol 41 ^o C. Getting on the surface of the rotating plate 21 of the nitrator 12, the nitro mixture in the gap between the disk 22 and the surface of the plate 21 is thrown to its periphery in the torus space. The nitrated alcohol is supplied there. Both liquids at a speed corresponding to the circumferential speed of rotation of the plate 21 are driven into the mixing tube 25 in the form of a turbulently mixed thin layer, which gradually increases as it brakes near the walls of the tube. In addition to liquids, a stream of air trapped by the rotating plate is driven into the mixing tube 25. Saturated with air, the reaction mixture is heated to a predetermined temperature, passes through the coil of the refrigerator 15 and is cooled to 0-5 ^o With brine supplied from the refrigeration machine (not shown in figure 2). The cooled reaction mixture enters the plate 21 'of the nitrator 12' of the 2nd stage. There, another metering pump 20 measures the second part of the nitrated alcohol in an amount also corresponding to the allowable nitration temperature. The mass ratio between the nitro mixture and the nitrated alcohol (nitration modulus) after the 2nd nitration step is for glycerol (5-5.5): 1, for diethylene glycol (2.8-3.2): 1, which is several times lower, than with nitration in the injector.

After the refrigerator of the 2nd stage 15 ', where the nitroemulsion is cooled to 16-18 ^o C, it enters the centrifuge 16, the spent acid separated from the nitroester passes through the control separator 17 and is removed from the process to the decomposition stage of the nitrotel dissolved in it. Nitroesters from the centrifuge 16 and the control separator 17 by the injectors 18 are transferred to the washing stage.

Nitration of alcohols in two stages with intermediate cooling of the reaction mixture eliminates the operation of returning the spent acid to the process and the corresponding equipment for mixing it with fresh nitro mixture, for storing the resulting nitro mixture with a temperature maintenance system of no higher than 15 ^o C. This makes it possible to safely obtain nitroesters with low stability in the environment of nitric and sulfuric acids.

 The use of the described design as a nitrator of a rotating plate (plate nitrator) allows vigorous mixing of the nitro mixture with nitrated alcohol when both liquids are supplied without pressure with a flow rate that has no downward restrictions. Experiments on models showed that at the outlet of the mixing tube (fluid velocity at the inlet 20 m / s) an emulsion forms with a droplet size of a dispersed phase of 5-6 μm, whereas in an injector-type nitrator when the working fluid is supplied under a pressure of 0.4-0 , 5 MPa, the average droplet size of the dispersed phase was 17-22 μm, and in a mixer such as a volume reactor with a propeller stirrer, 40-60 μm. The possibility of supplying the nitro mixture to the nitrator without pressure made it possible to carry out the second stage of nitration in the same nitrator when instead of the nitro mixture, the reaction mixture was fed with the residual amount of nitric acid contained in the fresh nitro mixture that did not react to the first stage.

 And at the same time, a disc-shaped nitrator retains the main advantage of an injector type nitrator. This is actually a complete absence of reaction volume. The nitration process occurs during the movement of fluids through the mixing tube. Alcohol enters the surface of the nitro mixture before the mixing tube and immediately enters the mixing tube, where it is intensively mixed with the nitro mixture and nitrated.

 The possibility of nitration of alcohols in a plate nitrator is confirmed in direct experiments on nitration of cyclohexanol. This alcohol is extremely easily oxidized upon contact with nitrosolutions under conditions of insufficiently intensive mixing. We used a nitrator with a plate diameter of 80 mm, with an internal diameter of the mixing tube of 6 mm, and a plate rotation frequency of 3000 rpm.

The consumption of nitro mixture of 150 ml / min, temperature minus 14 ^o C;
cyclohezanol consumption 12 ml / min; temperature 27 ^° C;
nitration temperature 7-10 ^o C.

The nitroemulsion from the nitrator was taken into a cooled flask with water. Cyclohexyl nitrate was separated from the aqueous layer, washed and the yield was determined. It amounted to 89.6% of theoretical, which corresponds to the usually achieved yield in the nitration process at low temperatures from minus 20 to minus 25 ^o C, when cyclohexanol is not oxidized.

The nitration of glycerol in such a nitrator was carried out at 55-58 ^o C. Since glycerin is resistant to oxidation under such conditions, the process of nitration takes place without complications. The nitromass was cooled in a coil refrigerator, the coil of which is a continuation of the mixing tube of the nitrator. Then the acid nitroglycerin was separated and washed. The yield of nitroglycerin was 96% of theoretical.

 The table shows the recommended modes of two-step nitration of some alcohols.

According to the prototype, the nitration module of glycerol and ethylene glycol is 10-11, propylene glycol 10.5, diethylene glycol 8.0. If you nitrate these alcohols in a prototype installation using the nitro-mixtures indicated in the table with the same nitration modules, the nitration temperature of glycerol will be 110 ^o С, ethylene glycol 100 ^o С, diethylene glycol 95 ^o С, propylene glycol-1.2 98 ^o С. Naturally, such temperatures unacceptable, since the nitromass will rapidly decompose in the nitrating apparatus.

 Thus, the proposed installation design and two-stage nitration of alcohols on it is practically feasible. The need for such plants, especially of low productivity (up to 50 kg / h), for the implementation of the method for producing liquid nitroesters, is undeniable, which is confirmed by the practice of the Altai Federal Scientific Production Center and similar research and production organizations both in Russia and a number of other countries (China , India). And, therefore, the claimed invention has industrial applicability.

Claims (4)

 1. The method of producing liquid nitroesters by nitration of alcohol in a nitrator with a small reaction volume, cooling the reaction mixture in a flow cooler, separating the nitroemulsion and washing the nitroester, characterized in that the nitration is carried out in two stages with the complete removal of the spent acid from the process with intermediate cooling of the nitromass after the first stage, moreover, 50-60% are supplied to the nitrator of the first stage, and 50-40% of the required amount of nitrated alcohol to the second stage nitrator, while the mass ratio of the nitro mixture an alcohol selected precluding the achievement of nitroesters decomposition temperature. 2. Installation for producing liquid nitroesters containing a nitrator with a small reaction volume, containers for nitro mixtures and nitrated alcohol, means for cooling and heating them, means for supplying them to the nitrator, a nitroemulsion refrigerator and a centrifuge, characterized in that the nitroemulsion refrigerator and the centrifuge are installed in series the second nitrator and the second emulsion refrigerator in such a way that the input of the nitro mixture of the second nitrator is connected by a pipe to the exit of the nitroemulsion from the first refrigerator, and the output of the nitroemulsion these from the second refrigerator are connected by a pipeline to a centrifuge, each nitrator is connected by a pipe with a means for supplying alcohol to it, each nitrator is a plate enclosed in a casing and rotating on a vertical shaft with the sides curved upward, forming a toroidal cavity, and introduced into the torus the space of the mixing tube, the end of which is directed towards the rotation of the plate and is located with the smallest possible clearance relative to the surface of the plate, a tube for feeding nitro impurity at the center of a plate and a tube for supplying alcohol to locate it from the intake end of the mixing tube at a distance corresponding to the rotation angle of a plate around its axis by 100-180 ^o.  3. Installation according to claim 2, characterized in that a disk is fixed to the plates by means of radial partitions.  4. Installation according to claim 2, characterized in that the intake end of the mixing tube is made with pointed edges.

Images