CN111943785B

CN111943785B - Method for preparing passivated NTO (nitrate-doped nitrate) by recycling waste fusion-cast explosive NTO

Info

Publication number: CN111943785B
Application number: CN202010717181.5A
Authority: CN
Inventors: 贾林; 蒋忠亮; 刘文亮; 张冬梅; 王芳芳; 王琼; 张林军; 陈智群; 顾妍
Original assignee: Xian Modern Chemistry Research Institute
Current assignee: Xian Modern Chemistry Research Institute
Priority date: 2020-07-23
Filing date: 2020-07-23
Publication date: 2021-10-01
Anticipated expiration: 2040-07-23
Also published as: CN111943785A

Abstract

The invention discloses a method for preparing passivated NTO (nitrate-doped nitrate-oxide) by recycling waste fusion-cast explosive NTO. Extracting the fusion-cast explosive with hot water, cooling, filtering, drying, washing with toluene, filtering and drying to obtain a crude NTO product; dissolving the NTO crude product in hot water, dropwise adding a sodium bicarbonate aqueous solution to neutralize residual acid, quickly cooling, stirring at a high speed, filtering and drying to obtain an NTO recrystallized product. Preparing the NTO recrystallized product by adopting a supercritical coating technology to obtain a passivated NTO semi-finished product, and circulating for 5 times at the temperature of 70-85-70 ℃ to obtain the passivated NTO. The purity of the NTO recovered by the method is more than 99 percent, the recovery rate is more than 82 percent, and the recovery process is simple and environment-friendly. The method improves the coating quality of the desensitizer to NTO crystals, not only increases the thermal safety, but also prevents NTO from corroding the metal shell of the warhead and oxidizing Al powder in the explosive, and is suitable for manufacturing the explosive containing Al.

Description

Method for preparing passivated NTO (nitrate-doped nitrate) by recycling waste fusion-cast explosive NTO

Technical Field

The invention belongs to the field of explosives and powders, and mainly relates to a method for recovering NTO (nitrate-nitrite oxide) in NTO-based waste fusion-cast explosives, and the research field of a manufacturing process of passivated NTO for producing aluminum-containing PBX (polymer bonded explosive).

Background

The explosives used for weapons and ammunition have certain storage and service life, and after being stored for a period of time, the safety and reliability of storage and use of the explosives can be changed greatly, so that the explosives become waste explosives. In addition, explosive production and upgrading of weapons systems also produce waste explosives. The general military countries accumulate about thousands to tens of thousands of tons of waste explosives and powders every year. The waste explosives and powders still have the characteristics of burning and explosion, and most of the explosives and powders have toxicity, so that the explosives and powders are seriously life-threatening and pollute the environment if not handled or not handled properly.

For the treatment of waste explosives and powders, various military countries begin various exploration researches as early as the 50 s of the 20 th century, and some research results are obtained. To summarize, there are mainly the following 3 treatment methods:

(1) the open sea dumping method comprises the following steps: the method comprises packaging the waste explosive, and pouring into open sea or deep sea. The method obviously causes pollution damage to the marine ecological environment and is an undesirable treatment method.

(2) Deep soil burying method: the waste explosives and powders are directly buried by soil, the method can pollute the environment as an open sea dumping method, and the explosives and powders buried for years still have explosive force and do not eliminate hidden dangers.

(3) An open-air combustion method: in destruction sites remote from cities and utilities. The method is simple to operate and low in treatment cost, is a treatment method commonly adopted in all countries in the world at present, but a large amount of high-concentration polluted waste gas and solid combustion residues generated in incineration can invade human and ecological environment along with air flow, rainwater and the like. In order to meet the strict environmental regulations and avoid environmental pollution caused by open-air incineration, controlled incineration technologies, i.e., incinerator incineration technologies, have been studied by organizations. The incinerator incineration method is to incinerate under controlled conditions to decompose and oxidize the waste explosives and powders sufficiently, so as to reduce the generation amount of pollutants to the minimum, but the method is high in cost and large in waste, and only a few developed countries adopt the method.

Under the requirements of environmental protection laws and regulations and elimination of potential safety hazards, the traditional method for treating waste explosives and powders is gradually abandoned and needs to be replaced by a method with less environmental pollution, less potential safety hazards and economy.

Because the waste explosives and powders are also a material with large energy content, the research of treating the waste explosives and powders in various countries not only aims at protecting the environment, but also recycles the waste explosives and powders as an available resource, thereby achieving two purposes. From the current data, aiming at the two points of environmental protection and resource recycling, people have researched various methods for treating waste explosives and powders, which can be classified into three categories in general: physical methods, chemical methods, biological methods. The physical method is that the insecurity of the waste explosives and powders is reduced by some physical means (such as mechanical crushing, mechanical calendering, solvent extraction and the like), and the waste explosives and powders are converted into raw materials or finished products which can be reused. The physical means include the following methods:

(1) solvent extraction method: useful substances in the waste explosives and powders can be recovered. As early as the early 50 s of the 20 th century, olympic corporation, usa, utilized a suitable solvent to extract and remove components other than Nitrocellulose (NC) from a mono-propellant, and recovered the NC. The purity of the recovered NC reaches 98-99.5%, and the recovery cost of the NC is estimated to be only one tenth of the cost required for manufacturing new NC. TPL company of America successfully recovers each explosive component from some mixed explosives by adopting a solvent extraction method, and is already industrially produced. The whole separation process is roughly divided into 3 steps: crushing the waste explosive; secondly, separating by using a solvent according to the solubility difference of each explosive component in the solvent; thirdly, refining the separated components by adopting a recrystallization method.

(2) A melting method: the components are separated by utilizing the difference of melting points of the components in the composition of the waste explosives and powders. An exemplary application of this method is the separation of a mixed explosive composition comprising TNT and RDX, wherein due to the relatively low melting point of TNT, the TNT in the mixed explosive is melted by a suitable heating method and then separated from the RDX which is still in a solid state. Thus not only the waste explosive is treated, but also the useful substances are recovered.

(3) Mechanical rolling method: the waste gunpowder can be made into qualified finished gunpowder products again by a mechanical calendering method after being softened by heating and soaking in a certain solvent. During the processing, a proper amount of stabilizer can be added to improve the stability of the gunpowder finished product.

(4) Preparing civil explosive: the explosive components separated from the waste explosives and powders or the crushed waste explosives and powders can be prepared into civil explosives (such as slurry explosives, emulsion explosives, powder explosives and the like) in various forms by adding necessary stabilizing agents and conditioning agents in a mechanical mixing mode. And certain retired explosives and powders with certain stability can be directly used in certain civil blasting occasions by adopting a proper detonation mode. The method for preparing the overdue explosives and explosives into the civil explosives is a good measure for changing waste into valuable.

The invention adopts the solvent extraction method in the method to extract NTO in the NTO-based waste fusion-cast explosive, and then prepares passivated NTO. The passivated NTO can be used for manufacturing aluminum-containing pressed explosive.

NTO (chemical name is 3-nitro-1, 2, 4-triazole-5-ketone) is a high-energy low-sensitivity elementary explosive with excellent comprehensive performance, the appearance of the elementary explosive is white or light yellow crystal particles, the thermal stability is better, the melting point is more than or equal to 260 ℃ (decomposition), the DSC decomposition peak temperature is more than or equal to 270 ℃, and the elementary explosive has certain acidity. The NTO is produced through nitrating TO (chemical name is 1,2, 4-triazole-5-ketone) with mixed nitric-sulfuric acid TO obtain crude NTO product, and re-crystallizing TO raise purity and improve crystal form. It can be seen that more waste acid is produced in the production of NTO, and the recovery of NTO from waste fusion cast explosives does not produce more waste acid, which is beneficial to environmental protection.

Currently, NTO-based explosive formulations are mainly classified into 3 types: fusion cast explosives, plastic bonded explosives (PBX) and molded explosives. Dozens of NTO-based explosive formulations have been developed in Fahrenheit, American, English, etc. (see tables 1,2, 3, 4).

TABLE 1 US and Switzerland NTO-based fusion cast explosive formulations

Name (R)	NTO	TNT	Additive agent	Adhesive agent
					TNTO	50	50	—	—
TNTO/D2	52	42	—	6(D2)
					TNTO/OD2	52	42	—	6(OD2)
TNTO 0	38	40	16 (aluminium)	6(D2)
					TNTO Ⅰ	42	34	19 (aluminium)	5(D2)
TNTO Ⅲ	42	30	19 (aluminium)	9(D2)
					AFX-645	48	32	12 (aluminium)	8(WP-660)
GD-1	65	35	—	—
					GD-2	35	35	30(HMX)	—

TABLE 2 French and American NTO-based PBX formulations

TABLE 3 England, Switzerland, Germany and Canada NTO-based PBX formulations

Name (R)	NTO	HMX	Additive agent	Energetic plasticizer	Adhesive agent
						CPX 412	50	30	—	10(K10)	10(PolyNIMMO)
CPX 450	40	20	20 (aluminium)	10(K10)	10(PolyNIMMO)
						CPX 458	30	30	20 (aluminium)	10(K10)	10(PolyNIMMO)
GD-3	72	12	—	—	16(HTPB)
						GD-5	40	43	—	10(BDNPA/F)	7(PGA)
HX 310	25	47	10(NG)	—	18(HTPB)
						CHN-037	76	—	—	—	24(GAP)

TABLE 4 NTO-based compression molded explosive formulations

Name (R)	NTO	HMX	BDNPA/F	Adhesive agent
					GD-9	47.5	47.5	2.5	2.5(Cariflex1101)
GD-11	48	48	—	4(Cariflex1101)
					GD-13	48	48	—	2/2(Hy Temp/DOA)
France 1	55.5	37	—	7/0.5 (Kelf/graphite)

From tables 1,2, 3, and 4, it can be seen that NTO can be used in 11 formulations of Al containing explosives, 6 of which are Al containing PBX press charges.

Al-containing explosives, also called high power explosives, are explosives prepared by adding Al powder into explosives in different proportions. Because Al powder emits high heat in the secondary reaction after the detonation wave front, the explosive can generate high detonation heat and high specific volume during detonation, thereby having higher work capacity, and still being an important series forming mixed explosives.

The Al-containing mixed explosive is used in some countries in the first world war, and during the second world war, Al-containing explosives are used in all warfare countries on a large scale to load underwater weapons and ammunitions, air weapons and air bombs. At present, many tactical missiles are filled with Al-containing mixed explosives. With the development of the cosmonautic industry, Al-containing heat-resistant explosives are also appeared and applied to an Apollo spacecraft system. The main explosive in the Al-containing mixed explosive is also greatly developed, and from the end of world war II to the present, the main explosive used in the Al-containing mixed explosive is not only various in variety, but also greatly improved in performance, and starts to appear as a heat-resistant or insensitive explosive. After the 70 s of the last century, Al-containing explosives with low vulnerability have been developed abroad, and are used for equipping navy, air force and tank troops.

The Al-containing explosive using heat-resistant explosive as main explosive is characterized by three high and one low (high density, high melting point, high explosion heat and low explosion speed). The main explosive has high melting point, low vapor pressure and no obvious physical and chemical change. The ammunition filled with the high-power explosive can bear the aerodynamic heating and space low-pressure action of the projectile, the warhead and the aircraft during high-speed flight, and can also bear the high-temperature action generated in a chamber during the continuous firing of a quick-firing weapon.

The function of Al powder in the mixed explosive is that the Al powder and the oxidation synthesis and the secondary reaction of the explosion product are carried out to generate Al₂O₃Thereby releasing a large amount of heat, thereby improving the explosion heat of the explosive. Some high-temperature and high-pressure reducing gas generated by the reaction of the Al powder and the explosion products is mixed with the surrounding air to generate secondary explosion, so that the duration of the explosion action is greatly prolonged. It can be seen that if the Al powder is largely deactivated, it is oxidized into Al in advance₂O₃The explosive detonation heat is reduced.

NTO is a typical high energy low sensitivity explosive with thermal stability and insensitivity to external stimuli. NTO is added into an explosive containing Al in French EURENCO, insensitive explosives containing Al XP3264 and PBXW-126 are developed, the performance and the insensitivity of the explosive are superior to those of a common explosive H-6, and the air explosion performance is obviously higher than that of PBXN-109.

Al powder reacts with water, so that it is stored and produced while being kept dry without contacting water, and Al-containing explosives are generally produced by a dry mixing method. The dry mixing method is to mix the insensitive explosive and Al powder, for example, the passivated RDX (A-IX-I) and the Al powder are mixed in an aluminum barrel, the rotation speed of the barrel is 30-40 r/min, and the mixture is mixed for 30 minutes to prepare the passivated black aluminum explosive (A-IX-II).

The quality of the coating of the desensitizer has an effect on the sensitivity of the passivated explosive. Because the occurrence of hot spots between explosive particles or between the explosive and contact materials under the mechanical action is the first step of initiating the explosive to rapidly react chemically, the probability of hot spots generated and propagated under the mechanical action is reduced, and the explosive reaction of the explosive is reduced.

The desensitizer is mainly made of materials with good plasticity, low hardness and easy deformation. When the explosive coated with the insensitive agent is subjected to mechanical action, the substances are easily filled among explosive crystal grains, and the substances have the functions of heat absorption and heat insulation and reduce bubbles among the explosive crystal grains, so that hot spots are reduced, and the detonation probability is reduced. Meanwhile, under the action of external force, the fillers can not make explosive grains directly contact with each other, so that the fillers play a role in buffering and lubricating, the phenomena of friction and stress concentration among the explosive grains are reduced, the probability of hot spots is reduced, and the mechanical sensitivity of the explosive is also reduced. If the coating of the insensitive agent on the surface of the explosive crystal is incomplete, the duration time of the hot spot is longer than the heat conduction time of the hot spot propagating through the insensitive agent layer, and the self-acceleration reaction of the explosive is easy to cause.

The conventional explosive charging method comprises the following steps: tamping, injection, press, screw, and plastic. The invention uses passivated NTO, which can be added with Al powder and pressed into Al-containing explosive column.

The explosive grain size ratio of the pressed explosive columns has strict requirements, so that the energy and density of a mixed explosive product can be improved, and the content of a main explosive can be improved as much as possible. In order to ensure that explosive particles are arranged tightly as much as possible, the main explosive of the shaped explosive in foreign countries adopts the particle grading technology, namely the solid explosive particles are matched in size properly, so that small particles can be filled in gaps among large particles, the particles can be arranged more tightly, and the requirement of improving the filling density of the product is met. Generally, when particle size distribution is used, large particles account for 3/4 and small particles account for 1/4. The particle grading can improve the pressed density and the compressive strength of the product.

According to the requirement of the grading of the grains of the pressed explosive columns, the produced NTO granular products are classified according to the grain size interval, NTO with the grain size of 30-60 meshes (250-600 mu m) belongs to the class I, and NTO with the grain size of 60-80 meshes (180-250 mu m) belongs to the class II.

Currently, most of the methods for manufacturing insensitive explosives by adopting a water suspension method process, for example, the manufacturing method of passivated RDX comprises the following steps: firstly, putting RDX into water, heating, then adding a desensitizer, adhering the desensitizer to the surface of the RDX in a molten state, and cooling to form a coating layer on the surface of the RDX to form passivated RDX.

The water suspension method is simple to operate, short in production period and easy for mass production. In the production process, water is used as a dispersion medium and a heat transfer medium, so that the production safety can be ensured. If the temperature, the vacuum degree and the stirring speed are well controlled, the particles with smooth and compact appearance and quite uniform size can be obtained. However, because NTO has strong solubility in hot water, a part of NTO is lost when the water suspension method is used for preparing the passivated NTO, and the loss amount is difficult to control.

The supercritical fluid coating (SCF) technology has been developed rapidly in recent years, and the main products include pharmaceuticals, foods, fertilizers and the like, so as to cover the unpleasant odor of the drugs, improve the stability of the products, facilitate application and storage and the like. The SCF coating technique has the characteristics of high diffusion coefficient of the gas phase and strong solvency of the liquid phase. The technique is adopted to coat and manufacture passivated NTO due to supercritical CO₂Has high-efficiency mass transfer and low surface tension, and can lead the insensitive agent to coat the NTO particles.

Mixing NTO with desensitizer solution at a certain proportion to form suspension, placing in a high-pressure autoclave heated in water bath, introducing CO from bottom of the autoclave₂Stirring the suspension until the temperature and pressure in the kettle reach a certain stable supercritical state (T)_C＝31℃，P_C7.39MPa), then the upper valve part of the kettle is opened, and the CO is continuously introduced into the lower part of the kettle₂Regulating upper valve to maintain constant pressure in reactor, supercritical CO₂Extracting organic solvent (ethyl acetate) in the suspension liquid, taking away residual solvent in the explosive, and finally quickly releasing to obtain the final product. By adopting super clinical practiceBoundary CO₂The preparation of the passivated NTO can avoid NTO loss due to no participation of water, and the processes of stirring, coating, drying and the like are completed at one time, so that the preparation method is time-saving, efficient and safe, and can meet the requirement of large-scale production.

The deficiency is supercritical CO₂Part of NTO crystals in the passivated NTO prepared by coating are debonded, which is caused by the final rapid pressure relief (the pressure is rapidly changed from 7.38MPa to the normal pressure). The analysis reason is as follows: the NTO crystal has defects in quality (the crystal quality refers to the neatness degree of the arrangement of crystal micro-regions, and the existence of structural defects such as micro-pores, micro-cracks, crystal dislocation, twin crystals and the like in the crystal can reduce the crystal quality), and the crystal is cracked from the defects through rapid pressure relief, and at the moment, the insensitive layer is cured and formed and cannot cover a newly generated crystal fracture surface; secondly, a plurality of NTO crystals are stacked together and coated, gaps exist among the crystals, the crystals are dispersed during rapid pressure relief, and new crystal surfaces appear, but the desensitizer is solidified, so that the new crystal surfaces cannot be coated.

When the Al-containing explosive column is manufactured by pressing and mounting the debonded NTO crystals, the debonded NTO crystals are in rigid contact under higher pressure, and are easy to become heat accumulation points due to friction, so that the debonded NTO crystals have higher potential safety hazard. In addition, the NTO crystals de-bond, reducing the tensile and compressive strength of the compacted charge, and environmental stresses can cause the charge to crack at the de-bonded crystal grains during subsequent shipping and storage. In use, the column cracks can also affect the detonation properties of the explosive.

In addition, NTO has certain acidity, and the pH value of an NTO aqueous solution with the concentration of 0.1mol/L at 20 ℃ is 2.67, so that the NTO aqueous solution has corrosiveness to metals under a damp and hot environment. If Al powder in the explosive is oxidized by NTO, the explosive power is reduced; if the warhead shell is oxidized and corroded, the use safety of the ammunition is affected.

In order to prepare the completely coated passivated NTO, a subject group is added with a temperature cycle process on the basis of coating by a supercritical method, so that the desensitizer is heated, softened and extended, thereby effectively coating the surface of the NTO crystal and improving the coating quality of the desensitizer.

In addition, the production mode of NTO is as follows: preparing an NTO crude product by nitrifying 1,2, 4-triazole-5-ketone (TO for short), then washing the NTO crude product with neutral water for many times TO remove residual acid (nitric acid) in the NTO crude product, recrystallizing NTO in an organic solvent TO improve the crystal form, and then applying the NTO. The water consumption for washing the residual acid is larger, and the NTO has larger solubility in water, so the NTO loss in the residual acid washing process is larger, and the generated wastewater amount is larger. The recrystallization process also produces a large amount of waste liquid. And the residual acid is removed first and then the crystal form is improved, so that the working procedures are more. Therefore, it is desirable for the project group to simplify the steps of washing residual acid and recrystallization and to reduce NTO loss and the amount of waste liquid.

In summary, the project group found that the current NTO production and the use of supercritical methods to produce passivated NTO can be improved:

(1) concentrated nitric acid is produced in the nitration production of NTO, more waste acid is produced, and the NTO can be recovered by considering a green process;

(2) residual acid is washed by NTO crude product, the crystal form improving process is complex, the loss of NTO is large, and the amount of waste liquid is large;

(3) the passivated NTO prepared by the supercritical method has the phenomenon of NTO crystal 'debonding', so that the danger of the subsequent press fitting process is increased; the contact of the 'debonded' NTO crystals reduces the tensile strength and the compressive strength of the pressed explosive column, cracks are easy to generate under the environmental stress, and the detonation performance of the explosive is influenced;

(4) bare NTO is acidic and will corrode the metal shell of the warhead on the one hand, and if this passivated NTO is used in Al containing explosives on the other hand, part of the Al powder is oxidized to Al by NTO₂O₃And the explosive power is reduced.

Disclosure of Invention

The specific technical solution of the present invention is summarized as follows.

The method for manufacturing passivated NTO by recycling waste fusion cast explosive NTO is characterized by comprising the following steps:

(1) weighing waste NTO-based fusion cast explosive to be recycled, mixing the waste NTO-based fusion cast explosive with deionized water, wherein the mass ratio of the waste NTO-based fusion cast explosive to the deionized water is 10g NTO to 60g deionized water, and crushing the NTO-based fusion cast explosive in the deionized water to prepare a medicine block with the diameter not more than 5 mm;

(2) adding deionized water into the medicine block prepared in the step (1), adding 30g of deionized water into the medicine block according to the mass ratio of 10g of NTO, heating to dissolve the medicine block, standing for 1 hour, filtering, and introducing into a pre-cooled ice bath kettle for cooling, wherein the filtering and introducing processes need to be completed within 10 minutes, the solution in the ice bath kettle is stirred to be in a turbulent flow state all the time, and NTO solid is separated out; when the temperature of the solution is reduced to 5 ℃, continuously stirring for 2 hours at the temperature, filtering and drying to obtain NTO impurities;

(3) soaking and washing the NTO mixture in the second step by using toluene at the temperature of 50-70 ℃, wherein the single washing dosage is 10g of NTO mixture, and filtering and removing the toluene by using 0.5-1 mL of toluene; soaking, washing and filtering for 3-5 times, and then drying to obtain a crude NTO product;

(4) mixing the NTO crude product obtained in the step (3) with deionized water, wherein the mass ratio of the NTO crude product to the deionized water is 10g, namely 80g of deionized water is heated and dissolved, a sodium bicarbonate aqueous solution with the mass concentration of 1% is dripped, when the pH value of the solution is 2.3, the dripping is stopped, the solution is introduced into a precooled ice bath kettle to cool, the introduction process needs to be completed within 10 minutes, the solution in the ice bath kettle is stirred to be always in a turbulent flow state, and NTO solid is separated out; when the temperature of the solution is reduced to 5 ℃, continuing stirring for 2 hours at the temperature, filtering and drying to obtain an NTO recrystallized product;

(5) sieving the NTO recrystallized product obtained in the step (4) to obtain an NTO recrystallized product with two granularity ranges of 30-60 meshes and 60-80 meshes, and mixing the NTO recrystallized products with the two granularity ranges of 30-60 meshes and 60-80 meshes according to the mass ratio of 3:1 to obtain an NTO recrystallized product with mixed granularity; preparing a desensitizer from polyvinyl acetate and purified ozokerite in a mass ratio of 1:1, and adding ethyl acetate into the desensitizer to prepare a desensitizer solution with the concentration of 20% g/ml; adding the mixed particle size NTO recrystallized product into a desensitizer solution according to the mass ratio of 95g to 5g of the mixed particle size NTO recrystallized product to the desensitizer solution to form a suspension, and placing the suspension into a high-pressure kettle heated in a water bath at the temperature of 50-60 ℃; introducing CO from the bottom of the kettle₂Gas, stirring the suspension until the temperature and the pressure in the kettle reach a supercritical state, wherein the supercritical state is T_C＝31.1℃、P_CAfter 7.39MPa, the upper valve of the kettle is partially opened and the lower valve is openedContinuously introducing CO₂Gas, adjusting an upper valve to keep the pressure in the kettle constant, and stopping introducing CO after 1 hour₂Gas is filled in the reactor and a valve at the upper part of the reactor is completely opened, thus obtaining a passivated NTO semi-finished product;

(6) preserving the heat of the passivated NTO semi-finished product obtained in the step (5) for 1 hour at 70 ℃, then heating to 85 ℃ at the heating rate of 20 ℃/hour, and then cooling to 70 ℃ at the cooling rate of 20 ℃/hour to finish 1 time of temperature cycle; and 5 times of circulation is carried out totally, then the temperature is reduced to the room temperature at the rate of 20 ℃/hour, and the passivation NTO semi-finished product is stirred once every 0.5 hour in the whole temperature treatment process, so that the passivation NTO is finally obtained.

According to the method for preparing the passivated NTO by recycling the waste fusion cast explosive NTO, the purity of the NTO recrystallized product is more than 99.0 percent, the mass content of nitric acid is less than 0.05 percent, the mass content of water is less than 0.10 percent, and the recovery rate is more than 82 percent.

The method for preparing passivated NTO by recycling waste fusion cast explosive NTO is characterized in that toluene after washing NTO impurities can be recycled by using a rotary evaporation technology, and the recycled toluene can be used for washing NTO impurities of other batches.

The method of the invention has the following advantages:

(1) the recovery of NTO is green and environment-friendly, the process is simple, and the popularization rate of the used equipment is high; compared with the nitration production method, the method for recovering NTO does not produce waste acid and is economical; the resulting TNT-containing toluene can be used after a simple treatment. The purity of NTO is more than 99 percent, the content of nitric acid is less than 0.05 percent, the content of water is less than 0.10 percent, and the recovery rate is more than 82 percent;

(2) residual acid is washed by NTO crude product, recrystallization is carried out to improve the merging and simplification of crystal form procedures, the process is green and pollution-free, and the loss amount and the waste liquid amount of NTO are reduced;

(3) the problem of incomplete coating of a supercritical method is solved, the coating quality of the NTO crystal by the insensitive agent is improved, and the safety of a subsequent press-fitting process is improved; the tensile strength and the compressive strength of the pressed explosive columns are increased, cracks are reduced, and the detonation performance of the explosive is not influenced;

(4) the coating quality of the desensitizer on NTO crystals is improved, the corrosivity of the exposed NTO on a metal shell of a fighting bucket and the oxidation of Al powder in Al-containing explosive are reduced, and the method is an effective method for ensuring the explosive power.

Drawings

FIG. 1 is a graph of the solubility of NTO in different solvents at 20 ℃ versus the polarity of the solvent.

Fig. 2 is a graph of the solubility of NTO in water at different temperatures.

The present invention will be described in further detail with reference to the following drawings and examples.

Detailed Description

Example 1

In order to recover the NTO in the fusion-cast explosive and manufacture passivated NTO, the present example performs research works of establishing a method, recovering the quality characterization of an NTO recrystallized product, and passivating the quality characterization of the passivated NTO. The results of the study of the examples are finally summarized: from these test results, it can be shown that the method of this patent can recover qualified NTO recrystallized product from waste molten cast explosive and can produce passivated NTO with high coating quality.

The following is a detailed description of the recovery of passivated NTO from a sample of waste cast explosive (TNT/NTO/binder 52/42/6 components and amounts).

Method for establishing

1.1 solvent selection for NTO recovery

The patent adopts a solvent extraction method to recover NTO in the fusion-cast explosive. The key technology of solvent extraction is to select a suitable solvent so that the component to be recovered is separated from the other components. The solvent used for NTO recovery can be determined by solubility testing.

A glass vial with a stopper was charged with 15g of NTO and 30mL of solvent, screwed down and placed in a chamber at 20 ℃ for at least 3 days with occasional shaking of the sample vial to produce a supersaturated solution of NTO. Accurately sucking 20mL of the upper clear NTO saturated solution in the glass bottle into a small beaker (the small beaker is subjected to constant weight at 70 ℃), putting the small beaker on a water bath at 70 ℃ to evaporate the solvent, and separating out NTO solid. The small beaker containing the NTO solids was then placed in a 70 ℃ oven at constant weight. The mass of NTO per 100mL of the solvent, i.e., the solubility Ω of NTO in the solvent, was calculated according to formula (1). The results of the different solvent tests are shown in Table 5, and the polarity of each solvent is also shown in Table 5. FIG. 1 is a graph of the solubility of NTO in different solvents at 20 ℃ versus the polarity of the solvent.

Ω＝m÷(20－m/1.93)×100……………………………………..(1)

In the formula: omega-NTO solubility, g/100 mL;

m-mass of NTO in the small beaker, g;

20-volume of saturated solution of NTO aspirated, mL;

1.93-density of NTO, g/cm³。

TABLE 5 solubility test results of NTO in various solvents (20 ℃ C.)

Name of solvent	Polarity of solvent	Ω，g/100mL	Name of solvent	Polarity of solvent	Ω，g/100mL
						Dimethyl formamide	6.4	36.42	Ethyl acetate	4.4	0.29
Tetrahydrofuran (THF)	4.2	5.15	Ether (A)	2.9	0.09
						Ethanol	4.3	1.94	Methylene dichloride	3.1	0.02
Acetone (II)	5.4	1.51	Toluene	2.4	0.01
						Water (W)	10.2	1.37	N-hexane	0.06	0.00

As can be seen from table 5 and fig. 1, the solvent with strong polarity has relatively large capability of dissolving the NTO at 20 ℃, but the solubility and the polarity of the solvent are not completely and positively correlated.

The NTO has a chemical structure of

With C-NO₂And C ═ O groups, and therefore polar and/or containing-OH, -NH₂The solvent of the radical dissolves NTO well. Dimethylformamide is an aprotic polar solvent, has an influence on NTO molecules,produces a solvating effect and has the strongest solubility to NTO.

And (3) recovering NTO from the waste molten and cast explosive, wherein a solvent which has strong NTO solubility and does not dissolve TNT and the adhesive is selected. The solubility of TNT in some organic solvents (20 ℃) was also determined by the same method, and the results are shown in Table 6.

TABLE 6 solubility test results of TNT in various solvents (20 ℃ C.)

From tables 5 and 6 it can be seen that water is the most desirable solvent.

The solubility Ω of NTO in water increases with increasing temperature T (see fig. 2), Ω ═ 0.0008T²+0.0087T+0.7493(R²0.9994), it was calculated that 9.6g of NTO was dissolved in 100mL of water at 100 ℃ and 8.8g of NTO was precipitated when the temperature was lowered to 5 ℃. Therefore, the NTO is determined to be dissolved out from the fused cast explosive by hot water, and then the temperature is reduced to 5 ℃ to separate out the NTO. And (3) keeping high-speed stirring in the process of separating out the NTO solid to ensure that the crystallization liquid is always in a turbulent flow state, so that the separated NTO recrystallized product is non-rod-shaped and meets the requirement of granularity (30-80 meshes).

Because 9.6g NTO is dissolved in 100mL of water at 100 ℃, during actual recovery operation, NTO is dissolved according to the proportion of 10g NTO and 90g of water, an NTO supersaturated solution can be formed, and a part of separated NTO solid becomes crystal nucleus, which is beneficial to the separation of NTO when the solution is cooled.

Some TNT will dissolve in the hot water (see Table 7), so the NTO precipitated by cooling will contain a small amount of TNT. As can be seen from Table 7, 0.147g of TNT was dissolved in 100mL of water at 100 ℃ and 0.137g of TNT was precipitated by cooling to 5 ℃.

TABLE 7 solubility of TNT in Water at different temperatures

Temperature, C	TNT solubility, g/100mL	Temperature, C	TNT solubility, g/100mL
				5	0.010	35	0.022
15	0.012	50	0.047
				20	0.013	60	0.067
25	0.015	70	0.087
				30	0.017	100	0.147

Therefore, NTO and TNT are saturated in 100mL of water at 100 ℃, and when the temperature is reduced to 5 ℃, the NTO and the TNT in the precipitated solid are 9.6g and 0.137g at most respectively, and the content of the TNT in 10g of NTO impurities can reach 0.14g through calculation. Toluene dissolution TNT does not dissolve NTO, TNT can be removed by washing with a small amount of hot toluene, increasing the purity of the NTO.

The solubility of TNT in hot toluene at 50, 60 and 70 ℃ was 208, 367 and 826g/100mL, respectively, and the solubility of TNT in 10g of NTO mixture at 50, 60 and 70 ℃ was 0.07, 0.04 and 0.02mL, respectively. For the sake of safety, determining that' soaking and washing NTO mixed materials by toluene at 50-70 ℃, using 0.5-1 mL toluene for 10g NTO mixed materials in a single washing, and removing the toluene by suction filtration; and (3) soaking, washing and filtering for 3-5 times, and then drying to obtain an NTO crude product. The toluene after washing the NTO impurities is recovered by a rotary evaporation technology (the toluene and the TNT are separated), the TNT content in the recovered toluene is about 0.02g/100mL, and the toluene can be continuously used for washing the TNT in other batches of NTO impurities.

The fused cast explosive also contains 6% of the binder, so it should also be noted whether the binder is also extracted. Therefore, the NTO recrystallized product extracted by the method is washed by hot gasoline, filtered, dried and weighed. The adhesive is a non-polar organic matter, the hot gasoline is a good solvent for the adhesive, and if the NTO recrystallized product contains the adhesive, the quality of the NTO recrystallized product after washing by the hot gasoline is reduced. The quality of the NTO recrystallization products is not reduced by respectively detecting 5 parts, which shows that the operation method of the patent can not extract the adhesive.

1.2 driving off the residual acid content in the recovered NTO

The waste NTO-based fusion cast explosive often contains a certain amount of residual acid (nitric acid) generated by thermal decomposition, and the residual acid has a catalytic effect on the decomposition of NTO, so the content of the residual acid in the recovered NTO is strictly controlled. In the NTO recrystallization step, 1% sodium bicarbonate water solution is dripped into the NTO crude product water solution to neutralize the residual acid. This method of adding the aqueous solution of the salt of meta-base to the aqueous solution of NTO avoids the possibility of decomposition of NTO (which would generate nitric acid and would increase the risk of decomposition) due to the violent exothermic heat during the reaction of high concentration of acid and base, because of the low concentrations of acid and base.

However, the more alkaline environment also accelerates the decomposition of NTO, so sodium bicarbonate cannot be added too much. The NTO itself is slightly acidic, the acidity of the aqueous solution is also strong, and the pH value of the aqueous NTO solution with the purity of 99.0 percent is 2.67 (0.1M aqueous solution at 20 ℃). Through tests, when sodium bicarbonate is dripped into a hot water solution of a NTO crude product and the pH value is 2.2-2.4, the NTO recrystallized product obtained by cooling, filtering and drying can meet the requirements that the purity is more than or equal to 99.0% and the residual acid is less than or equal to 0.05%, and the purity and the residual acid content are unchanged after the NTO recrystallized product is stored for 127 days at 70 ℃. The pH of a 0.1M aqueous NTO solution prepared from the NTO recrystallized product was 2.67 at 20 ℃. Therefore, in the dropping of sodium hydrogencarbonate, "when the pH of the solution was 2.3, the dropping was stopped" was determined.

1.3 determination of the holding temperature of the passivated NTO semi-finished product

The desensitizer consists of polyvinyl acetate and purified ceresin in a mass ratio of 1: 1. The purified ceresin is pure ceresin which is obtained by processing and refining factice obtained by vacuum residuum through asphalt crude oil and mainly consists of various hydrocarbons. The melting point of the purified ceresin wax is 68-78 ℃. The polyvinyl acetate has the molecular weight of 1-6 ten thousand, the glass transition temperature of 29 ℃ and the softening point of 45-90 ℃.

According to the characteristics of the desensitizer, the temperature determination principle of the passivation NTO semi-finished product in the heat preservation stage is as follows:

(1) the temperature is raised to soften the desensitizer in a semi-flow softened state, which is beneficial to improving the coating quality of NTO crystals; the higher the temperature, the shorter the time required for the binder to soften;

(2) the temperature should not be too high, and the high temperature will accelerate the chemical decomposition of NTO because NTO contains C-NO₂Radical, C-NO at elevated temperature₂Bond cleavage to produce NO_XAnd NO_XBut also can self-catalyze and decompose NTO, even burn after decomposing to a certain degree;

(3) too high a temperature may also deteriorate the quality of the NTO crystal to generate new defects (physical changes);

(4) the temperature cannot be too high, the oil permeability of the purified ceresin can be improved only to a certain extent by the polytetrafluoroethylene ester, and the purified ceresin can still have obvious liquefaction and oil permeability when the temperature is too high;

(5) preferably, the part with lower thermal deformation temperature in the desensitizer is softened firstly, and then the temperature is continuously raised, so that the molecular chain of the part with higher polymerization degree of polyvinyl acetate is fully extended from the curling state, and the extension of the ordered molecular chain is more beneficial to obtaining the high-quality coating effect;

(6) the cooling speed is not too fast, so as to prevent the generation of a new debonding interface caused by large difference between the thermal expansion and cold contraction of the desensitizer coating layer and the NTO crystal.

According to the principle and the effect of the actual sample after heat preservation, the operation conditions of the heat preservation process are finally determined as follows: preserving the heat of the passivated NTO semi-finished product for 1 hour at 70 ℃, then heating to 85 ℃ at the heating rate of 20 ℃/hour, and then cooling to 70 ℃ at the cooling rate of 20 ℃/hour to finish 1 time of temperature cycle; and 5 times of circulation is carried out, then the temperature is reduced to the room temperature at the rate of 20 ℃/hour, and the passivation NTO semi-finished product is stirred once every 0.5 hour in the whole temperature treatment process to prevent the desensitizer from concentrating downwards under the action of gravity. The stirring is carried out by paying attention to the force without causing mechanical friction of the passivated NTO, thereby generating a new debonding crystal face.

Second, quality characterization of recovered NTO recrystallized product

2.1 moisture content

And detecting the recovered NTO recrystallized product by using an oven method, wherein the water content is 0.07 percent by mass.

2.2 purity and residual acid content

Detecting by using a high performance liquid chromatography: the mobile phase is acetonitrile/mixed phosphate water solution which is 5/95 (volume ratio), and the detection wavelength is 220nm, and the C18 chromatographic column is adopted. Dissolving the sample with water, injecting the solution into liquid chromatograph for detection, wherein the retention time of nitric acid is 0.7min, and the retention time of NTO is 3.2 min. The detection result by adopting an external standard method is that the purity of NTO is 99.1 percent, and the mass content of residual acid (nitric acid) is 0.04 percent.

2.3 recovery rate

Preparing fused cast explosive columns with the same component content, and dividing into 5 parts for respectively recycling NTO according to the invention to obtain NTO recrystallized products. The recovery rate is obtained by dividing the mass of the recovered NTO recrystallized product by the theoretical mass of NTO, and is 82.2-85.5%.

Third, characterization of passivation NTO quality

3.1 Effect of the coating Process on NTO Crystal quality

The passivation NTO is prepared by adopting a supercritical heat preservation method, and whether the stress generated in the high-pressure and high-pressure decompression stage and the heat preservation stage of the supercritical method has a destructive effect (physical change) on the quality of the NTO crystal needs to be examined. The crystal quality of the NTO can be characterized by using a micro-Raman spectroscopy technology. Because the desensitizer influences the detection result, the NTO recrystallized product is singly coated by a supercritical heat preservation method in a simulated mode (without adding the desensitizer), and then the detection is carried out by a Raman spectroscopy.

The detection principle of the Raman spectrum is as follows: the micro-nano defects of the NTO crystal can widen the Raman spectrum peak, and the randomness of the defect distribution can increase the relative experimental standard deviation RSD. The raman spectrometer parameter settings are shown in table 8.

Table 8 raman spectrometer parameter settings

During the measurement, due to the fluctuation of the signal of the instrument, even if the same point of the same sample is detected, the detection data has certain dispersion, which is caused by the fluctuation of the instrument (equivalent to "baseline noise"), and the dispersion can exaggerate the difference between crystals, so the influence of the fluctuation of the instrument is required to be removed. Taking part of NTO recrystallized product to recrystallize twice as standard product, selecting one crystal from the standard product, repeating the test at fixed point for 12 times, with interval of 1 min, eliminating the influence of thermal stress generated by detection on NTO crystal, and measuring 1104cm in Raman spectrum^-1Peak width value (unit cm) of peak^-1) 10.131, 10.123, 10.188, 10.078, 10.117, 10.089, 10.078, 10.103, 10.144, 10.132, 10.094, 10.167, respectively, and RSD (0.34% (n-12) is calculated, which explainsRSD caused by signal fluctuation of measuring instrument_{Instrument for measuring the position of a moving object}＝0.33％(n＝12)。

Respectively and randomly selecting 10 crystal particles for each NTO sample, randomly selecting 2-3 points for testing for each NTO sample, and reading 1104cm^-1The width W of the half height peak of the characteristic peak_iCalculating the relative standard deviation RSD of all the detection results of 10 particles_NTO. Randomly selecting 10 NTO particles from NTO recrystallization products which are not coated with the desensitizer in the same batch, randomly selecting 2-3 points for testing each NTO particle, and reading 1104cm^-1The width W of the half height peak of the characteristic peak_iCalculating the experimental relative standard deviation RSD 'of all detection results of 10 particles'_NTO. When RSD_NTO－RSD’_NTO≤3RSD_{Instrument for measuring the position of a moving object}In this case, it is considered that the NTO crystal quality is not deteriorated by the pressure and thermal stress at the time of covering with the desensitizer. The results are shown in Table 9.

TABLE 9 NTO Crystal quality test results

From Table 9, RSD_NTO＝0.81％、RSD’_NTO0.53%, and 3RSD_{Instrument for measuring the position of a moving object}RSD when 0.33% × 3% is 0.99%_NTO－RSD’_NTO≤3RSD_{Instrument for measuring the position of a moving object}. It is shown that the pressure and thermal stress during the supercritical thermal insulation coating described in this patent do not deteriorate the quality of the NTO crystal.

3.2 Change in NTO purity and residual acid (nitric acid) content by coating Process

Whether the NTO is chemically changed or not can be represented by detecting the purity of the NTO after the supercritical heat preservation and the content of residual acid (nitric acid).

NTO contains C-NO₂The group, at low temperature, has proton transfer and intramolecular rotation superior to C-NO₂At high temperature, C-NO₂All of the keysCracking into the main path, so NTO is likely to decompose under large stress, and residual acid, nitric acid, is generated, and the purity of the nitric acid is also reduced.

The high performance liquid chromatography can detect the crystal purity and the residual acid content of NTO, and the detection result of NTO is influenced when the desensitizer for passivating the surface of the NTO crystal is dissolved and removed (the solvent for dissolving may also remove the residual acid or impurities in the NTO at the same time), so the NTO recrystallization product is simulated and coated by a supercritical heat preservation method (without adding the desensitizer). If the purity and the residual acid content of the NTO after the simulated coating are consistent with those of the NTO recrystallized product, the supercritical heat-preservation coating method is considered to not enable the NTO to generate chemical change. The assay data are listed in Table 10.

TABLE 10 purity and free acid test results before and after NTO sample coating incubation

The result of the detection	NTO recrystallized product	Simulated post-coating NTO
			NTO purity/%)	99.1	99.1
Residual acid (nitric acid)/%)	0.04	0.05

As can be seen from the data in Table 10, the purity and residual acid (nitric acid) of the NTO sample after the simulated coating are not substantially changed, which indicates that the pressure and thermal stress of the supercritical heat preservation method for coating described in this patent do not cause chemical decomposition of NTO.

3.3 coating quality characterization

A small amount of sudan red was added to the desensitizer solution to allow a clearer observation of the degree of coating of the desensitizer. The passivation NTO after heat preservation is observed by eyes, no debonded NTO particles exist, and the crystal face of the passivation NTO particles which are not coated by the desensitizer can be seen in the passivation NTO semi-finished product before heat preservation.

NTO has strong acidity and certain corrosivity to metal, and after coated by the desensitizer, the aqueous solution of the passivated NTO becomes neutral along with the improvement of the coating quality. Preparing aqueous solution with concentration of 0.1mol/L from NTO and passivated NTO respectively, wherein the pH values are 2.67 and 7.2 at 20 ℃, which indicates that NTO in the passivated NTO is completely coated by the desensitizer.

The coating quality of the desensitizer on NTO crystals in a longer time can also be characterized by passivating the corrosivity of NTO on metal in a damp and hot environment.

The metal test piece is 3 kinds of aluminum sheet, copper sheet and stainless steel sheet, and the oxide layer on two sides of the metal test piece is ground with No. 240 fine gauze.

10.0 +/-0.1 g NTO recrystallized product and passivated NTO are respectively weighed, half of the materials are poured into a glass container, 1 polished metal test piece is placed into the glass container, and the other half of the materials are poured into the glass container. A total of 6 glass containers were moved into the desiccator, which was covered with a lid. The lower part of the dryer was filled with saturated solution of sodium sulfate. The whole dryer is put into an oven at 60 ℃, and the humidity of the upper space of the liquid surface of the saturated solution of sodium sulfate is (85 +/-1)%.

After the constant temperature and humidity were continuously maintained for 30 days, the test piece was taken out. The aluminum sheet, copper sheet and stainless steel sheet contacting with the NTO recrystallized product and 3 kinds of metal test pieces contacting with the passivated NTO were put together and observed under natural light. It can be seen that the 3 metal test pieces contacting NTO recrystallized product are dark in color, have corrosion spots of different degrees, have rough edges of corroded areas, and are adhered to corroded edges after a small amount of NTO absorbs moisture. The 3 kinds of metal test pieces contacted with the passivated NTO are not corroded, and the color, the smoothness and the like are not changed compared with those before the test.

It can be seen that under the hot and humid environment, NTO is corrosive to metals (aluminum, copper, stainless steel) due to its acidity. The desensitizer completely coats NTO crystals, the passivated NTO is neutral, and metals (aluminum, copper and stainless steel) cannot be corroded and Al in Al-containing explosive cannot be oxidized in a damp and hot environment.

3.4 thermal safety characterization

And (3) calculating apparent activation energy by adopting an explosion point test of a 5-second delay period, and representing the thermal safety of the passivated NTO. The results of the calculation of the apparent activation energy of the NTO recrystallized product, the passivated NTO semi-finished product and the passivated NTO are 89625, 93616 and 99327J/mol respectively. It can be seen that the apparent activation energy increases after passivation, since more thermal energy is required to explode after encapsulation, so a higher apparent activation energy indicates better thermal safety. The verification test shows that the thermal safety is passivated NTO, a passivated NTO semi-finished product and a recrystallized product from high to low in sequence.

Fourth, conclusion

The method for preparing the passivated NTO by recycling the waste fusion-cast explosive NTO is established, and research results of examples show that the recycled NTO recrystallized product has the purity of 99.1 percent, the mass content of residual acid (nitric acid) of 0.04 percent, the mass content of water of 0.07 percent, the recovery rate of 82.2 to 85.5 percent, the recycling process is simple, and the method is green and economic. The obtained NTO recrystallized product is recycled, so that the manufactured insensitive NTO is completely coated, the physical and chemical quality of NTO crystals is not influenced by the coating process, the safety of the subsequent press mounting process is improved, the tensile strength and the compressive strength of the explosive column are increased, the corrosivity of acid NTO on a metal shell of a fighting part and the oxidization of Al powder in the explosive are reduced, and the method is suitable for manufacturing the explosive containing Al.

Claims

1. The method for manufacturing passivated NTO by recycling waste fusion cast explosive NTO is characterized by comprising the following steps:

weighing waste NTO-based cast explosive to be recycled, mixing the waste NTO-based cast explosive with deionized water, wherein the mass ratio of the waste NTO-based cast explosive to the deionized water is 10g NTO to 60g deionized water, and crushing the NTO-based cast explosive in the deionized water to prepare a medicine block with the diameter not more than 5 mm;

step two, adding deionized water into the medicine block prepared in the step one, adding 30g of deionized water according to the mass ratio of 10g NTO, heating to dissolve the medicine block, standing for 1 hour, filtering, and introducing into a pre-cooled ice bath kettle for cooling, wherein the filtering and introducing processes need to be completed within 10 minutes, the solution in the ice bath kettle is stirred to be in a turbulent flow state all the time, and NTO solid is separated out; when the temperature of the solution is reduced to 5 ℃, continuously stirring for 2 hours at the temperature, filtering and drying to obtain NTO impurities;

soaking and washing the NTO mixture in the second step by using toluene at the temperature of 50-70 ℃, wherein the single washing dosage is 10g of NTO mixture, and filtering and removing the toluene by using 0.5-1 mL of toluene; soaking, washing and filtering for 3-5 times, and then drying to obtain a crude NTO product;

step four, mixing the NTO crude product obtained in the step three with deionized water, wherein the mass ratio of the NTO crude product to the deionized water is 10g, 80g of deionized water is heated and dissolved, a sodium bicarbonate water solution with the mass concentration of 1% is dripped, when the pH value of the solution is 2.3, the dripping is stopped, the solution is introduced into a precooled ice bath kettle to cool the solution, the introduction process needs to be completed within 10 minutes, the solution in the ice bath kettle is stirred to be in a turbulent flow state all the time, and NTO solid is separated out; when the temperature of the solution is reduced to 5 ℃, continuing stirring for 2 hours at the temperature, filtering and drying to obtain an NTO recrystallized product;

screening the NTO recrystallized product obtained in the fourth step to obtain an NTO recrystallized product with two granularity ranges of 30-60 meshes and 60-80 meshes, and mixing the NTO recrystallized products with the two granularity ranges of 30-60 meshes and 60-80 meshes according to the mass ratio of 3:1 to obtain an NTO recrystallized product with mixed granularity; preparing a desensitizer from polyvinyl acetate and purified ozokerite in a mass ratio of 1:1, and adding ethyl acetate into the desensitizer to prepare a desensitizer solution with the concentration of 20% g/ml; adding the mixed particle size NTO recrystallized product into a desensitizer solution according to the mass ratio of 95g to 5g of the mixed particle size NTO recrystallized product to the desensitizer solution to form a suspension, and placing the suspension into a high-pressure kettle heated in a water bath at the temperature of 50-60 ℃; introducing CO from the bottom of the kettle₂Gas, stirring the suspension until the temperature and the pressure in the kettle reach a supercritical state, wherein the supercritical state is T_C＝31.1℃、P_CThen the upper valve of the reactor is partially opened and the lower part is continuously filled with CO₂Gas, adjusting an upper valve to keep the pressure in the kettle constant, and stopping introducing CO after 1 hour₂Gas and completeOpening a valve at the upper part of the kettle to obtain a passivated NTO semi-finished product;

step six, preserving the heat of the passivated NTO semi-finished product obtained in the step five for 1 hour at 70 ℃, then heating to 85 ℃ at the heating rate of 20 ℃/hour, and then cooling to 70 ℃ at the cooling rate of 20 ℃/hour to finish 1 time of temperature cycle; and 5 times of circulation is carried out totally, then the temperature is reduced to the room temperature at the rate of 20 ℃/hour, and the passivation NTO semi-finished product is stirred once every 0.5 hour in the whole temperature treatment process, so that the passivation NTO is finally obtained.

2. The method for manufacturing passivated NTO by recycling waste cast explosive NTO as claimed in claim 1, wherein purity of NTO recrystallized product is more than 99.0%, mass content of nitric acid in NTO recrystallization is less than 0.05%, mass content of water is less than 0.10%, and recovery rate of NTO recrystallized product is more than 82%.

3. The method for manufacturing passivated NTO by recycling waste molten cast explosive NTO as claimed in claim 1, wherein the toluene after washing the NTO impurities is recycled by rotary evaporation technique, and the recycled toluene is used for washing other NTO impurities.