CA2099222C

CA2099222C - Process and apparatus for working up pyrotechnical material

Info

Publication number: CA2099222C
Application number: CA002099222A
Authority: CA
Inventors: Hans E. Magenheimer; Roland Traute; Wolfgang Simon; Heinz Hebisch; Hans-Heinrich Brehmer; Norbert Goltz; Uwe Rothenstein
Original assignee: Buck Werke GmbH and Co
Current assignee: Buck Werke GmbH and Co
Priority date: 1992-06-29
Filing date: 1993-06-25
Publication date: 1998-11-24
Anticipated expiration: 2013-06-25
Also published as: TW239187B; EP0577046B1; DE59303937D1; ATE143486T1; TR27066A; CA2099222A1; EP0577046A1

Abstract

In order to work up pyrotechnical material, I.
the pyrotechnical material is burned in a controlled manner, the slag is optionally allowed to continue reacting and the crude gas formed is passed through a high-temperature region in which the gas is exposed to a temperature of at least 1200°C over a predetermined period in order to decompose organic substances still present; II. the crude gas formed during the combustion is cooled to a temperature below 400 C; III. the crude gas is purified under dry conditions by first feeding it into a preliminary separator, coarse particles being separated off, and then feeding the crude gas via fine dust filters in order to separate off finely divided solids and/or IV. the crude gas is optionally purified under wet conditions by first passing it through a rotary scrubber and then passing it via one or more absorption units and V. the purified gas is released as waste air.
In a variant of this process, pyrotechnical material A, where predominantly alkaline reaction products are formed, and pyrotechnical material B, where predominantly acidic reaction products are formed, are subjected to controlled combustion in the first stage.

Description

2~9~2~

Process and appar~tus for working up pyrotechnical material The invention relates to processes for working up pyrotechnical material and an apparatus suitable for this purpose.
Pyrotechnical munitions, such as illumination elements, flares, propellant charges, for example for rockets, which are no longer suitable for use owing to the expiry of their shelf life, must be disposed of.
0 Owing to the pyrotechnical potential and the high strength of the active material, safe mechanical separ-ation of the active materials is impossible or is poss-ible only at a disproportionately high expense.
Illumination elements consist, as a rule, of a container, which is usually made of metal, preferably of aluminium, a fuse and the active material. The active material is composed of a light metal powder as an energy source, an oxidising agent which csn eliminate oxygen, an organic binder for mechanical strengthening of the mixture and optionally colour intensifiers. As a rule, magnesium is used as the light metal powder since other suitable metals are either toxicologically unsafe or too expensive. As a rule, nitrates, in particular sodium nitrate, are used as oxidising agents, chlorates or perchlorates also being used in exceptional cases.
Polymers are used as organic binders. Halogen-containing compounds, in particular fluorine-containing or chlorine-containing metal salts, are present as colour inten-sifiers. When the illumination elements burn, predomi-nantly metal oxides, such as magnesium oxide, sodium oxide and aluminlum oxide, nitrogen and oxides of nitrogen and carbon oxides and optionally hydrogen halide are therefore formed. Propellant charges consist essentially of nitrogen cellulose.
The active materials of projectiles which are intended to release irritants contain a high proportion of chlorinated hydrocarbons in addition to aluminium or zinc in powder form or as grit and irritation-promoting .

20~222 ~ additives. Propellant charge powders develop a hlgh proportion of oxides of nitrogen when they undergo combustion.
The disposal of this pyrotechnical material therefore presents problems owing to the high proportion of environmental pollutants, such as oxides of nitrogen and halohydrocarbons, which are formed during the combustion and must not escape into the environment. The working up of such a material and the separation of the pollutants is, as a rule, very expensive.
DE-B 41 06 615 discloses a process for working up smoke elements or smoke active materials containing chlorinated hydrocarbons. These active materials are processed in such a way that the zinc and aluminiun compounds contained therein can be recovered and reused.
This process relates to special working up steps for the chlorinated hydrocarbons contained in the active materials. Furthermore, DE-A 40 37 919 discloses a process for disposing of propellant charges from munitions, in which the propellant charges are comminuted with the addition of water and then burned using a special fluidised-bed furnace.
It is the object of the invention to provide a process by means of which pyrotechnical material, in particular illumination elements and propellant charges, can be disposed of, which can be carried out safely and in which no harmful substances are conveyed into the environment.
To achieve this ob~ect different process variants and apparatus for carrying out these proces~es are provided, which can be ad~usted optimally to the respect-ive material to be disposed of.
According to one aspect of the invention a process is provided for working up pyrotechnical material, which is characteri~ed in that I. the pyrotechnical material i8 burned in a controlled manner, the slag is optionally allowed to continue reacting and the crude gas formed is passed through a high-temperature region in which the gas is at a tempera-~9~

ture of at least 1200-C over a predetermined period in order to decompose organic substances still present;
II. the crude gas formed during the combustion is cooled to a temperature below 400 C;
III. the crude gas is purified under dry conditions by first feeding it into a preliminary separator, coarse particles being separated off, and then feeding it via fine dust filters in order to separate off finely divided solids, and/or IV. the crude gas is purified under wet conditions by first passing it through a rotary scrubber and feeding it via one or more absorption units, and V. the pure gas is released as waste air.
With the process according to the invention, it is possible to reduce to a very small level the harmful components, such as oxides of nitrogen and halogen compounds, which are formed during the combustion of the pyrotechnical material and to minimise the cost of the gas purification. In addition, reusable substances are obtained and the heat generated during the combustion can be effectively used. For the purposes of the invention, pyrotechnical material is understood as meaning pyrotechnical articles or pyrotechnical charges.
In the first stage of this embodiment of the process according to the invention, the pyrotechnical material is burned in a controlled manner. Combustion may take place continuously or batchwise, in the continuous procedure the material supplled preferably being ignited in each case by the material already present in the reactor, whereas in the batchwise process a batch is always burned and thereafter the next batch is fed in and ignited. The throughput and residence time are dependent on the material to be burned, the type of process and the reactor used. In general, the residence time is in the range from 10 seconds to 1 minute.
Combustion is effected in one or more combustion chambers. The combustion chamber used is a reactor which can withstand the h;gh temperatures generated during the combustion and can be loaded in a suitable manner. Either - :
-, 2~9~222 B tube reactor or a reactor having a brlck llning i5 preferably used. A vertlcally arranged apparatus whlch consists of steel resistant to hlgh temperatures and ls cooled internally with gas is preferably used as the tube reactor. For this purpose, air is introduced via tangen-tial nozzles and is passed over tangential plates in such a way that it flows along the wall of the tube reactor and hence cools the steel jacket. This ensures that the reactor jacket is at a temperature of no more than 400-C, which it withstands without damage. By feeding the air via tangential nozzles, the high temperature zone is limited in a defined manner to a certain region. This ensures on the one hand that organic pollutants are virtually completely degraded directly on formation by the combustion of the pyrotechnical elements and, on the other hand, that caking of material or abrasion at the internal wall is prevented.
In another embodiment, a reactor having a brick linlng is used. This reactor constitutes a closed pres-sure-tight space which is lined on the inside with refractory material and is preferably a trough reactor or rotary kiln. Since the refractory material withstands temperatures of from above 1500 to 2000 C, it need not be cooled. In a preferred embodiment of the reactor having a brick lining, a mobile trough which receives melting material and falllng slag and can be emptied batchwise is provided below the combustion chamber.
one or more identical or different reactors can be simultaneously used for the process according to the invention. A tube reactor ls preferably used for worklng up pyrotechnlcal materlal where predomlnantly alkallne compounds escape lnto the crude gas, whereas a trough reactor i8 used for working up pyrotechnical materlal which releases predominantly acldic vapours.
After the controlled combustion of the pyrotechnical material, the crude gas formed is passed through a high-temperature reglon in which it is kept at a temperature of at least 1200 C over a predetermined perlod in order to decompose any organlc substances still - 5 ~99222 BU 46/47 present. If the crude gas has reached a temperature of over 1200-C as a result of combustion, it is sufficient to keep the crude gas in the reaction region over the predetermined period without additional heating. In an embodiment, this is effected, for example, by ensuring that the reactor has a sufficient height so that the residence time of the ascending crude gas is sufficient for complete reaction in the high-temperature region. In another embodiment, in which the air is blown in tangen-tially, the crude gas (reaction gas) is passed spirallyupwards and thus remains for a sufficiently long time in the high-temperature region. If the crude gas is not hot enough, an external heating source is provided in order to heat the crude gas to the desired temperature. The period of subsequent heating depends on the proportion of organic compounds and can be easily determined by one skilled in the art. As a rule, a period of 2 to 10 seconds is ~ufficient. A temperature of at least 1200-C, preferably at least 1500 C, is required in order to decompose the organic compounds.
The crude gas which leaves the high-temperature region contains virtually only inorganic compounds, which are partly ln gaseous form and partly in the form of very small particles. Dependlng on the composition of the crude gas, dry purification and/or wet purification are carried out. The wet purification can be carried out before or after the dry purification. Preferably, the crude gas is flrst purified under dry conditions and then optionally sub~ected to a wet purification, depending on reguirements. Since the gas which emerges from the high-temperature region has a very high temperature, lt is cooled to a temperature of below 400 C, the heat simulta-neously possibly being used. In various applications, cold air can be mixed with the hot gas in the proce~ for cooling. In addition, heat can be utilised by using known heat recovery techniques. An example of this i8 the connection to the heat circulation of a heating station.
The crude gas is cooled to temperatures below 400 C or, preferably, below 200 C, depending on the subsequent .:
., .
.
-.
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treatment.
The crude gas is purified under dry and/or wet conditions. For the dry purification, the gas should be cooled preferably to below 200 C in order thus effec-tively to prevent de novo syntheses of organic pollu-tants. Furthermore, the filters usually used for the purification cannot as a rule withstand higher tempera-tures without damage.
For the dry separation, the crude gas is first fed into a preliminary separator in which coarse particles are separated off. Coar~e particles are desig-nated as particles which have a size of at least 10 ym.
The separation of the coarse particles can be effected in a manner known per se. A multicyclone is preferably used for the separation. The type of particles separated off in the multicyclone is dependent on the pyrotechnical material worked up. If, for example, flare active materials or illumination elements are burnt, the coarse particles which are separated off in the multicyclone consist predominantly of magnesium oxide and/or aluminium oxide. The oxides separated off in the multicyclone can be reused.
The crude gas which has been freed from the coarse partlcles and has been sufficiently cooled by the pretreatment can then be fed via a fine dust filter to separate off small solid particles, i.e. particles having a dlameter of less than 10 ~m. Woven fabric fllters are preferably used as fine dust filters. In a preferred embodiment, a system having several filters is used, one part of the filters being loaded simultaneously and the other part of the filters being cleaned to remove the deposited solids mixture. With the fine dust filters, the crude gas can be purified to a solids content of S 10 mg/m3. The gas emerging from the fine dust filters is now at a temperature of about 100 C and, if it no longer contains any gaseous lmpurities, can be released directly as waste air. If the gas still has gaseous impurities, in particular halogen-containing compounds or oxides of nitrogen, it is ~ub~ected to a wet purification ~.
. :
.

2 ~

- 7 - B~ 46/47 after the dry purification. In the working up of flares and illumination elements, the gas i8 as a rule so pure that wet purification is no longer necessary.
Instead of the dry purification of the gas, wet purification can be carried out. This is useful if the gas contains predominantly gaseous impurities, such as halogen compounds and oxides of nitrogen, and a smaller amount of alkali metal and alkaline earth metal oxides.
The wet purification may also be carried out before or, preferably, after the dry purification.
If the wet purification of the crude gas is carried out as a first purification step, the crude gas is preferably first cooled to a temperature of below 140 C in a heat exchanger unit. The crude gas cooled in the heat exchanger or the crude gas purified ~nder dry conditions is then passed into a scrubbing apparatus for scrubbing the crude gas. Apparatuses of this type are known to those skilled in the art. For scrubbing, the crude gas is preferably first fed through a Venturi unit in order to cool the gas to such an extent that its temperature is below the boiling point of water. It is then passed into a rotary scrubber. After the rotary scrubbing unit, gas scrubbing is carried out in a known manner usinq one or more absorption units. Packed or tray columns which are loaded with suitable wash liguids depending on the loading of the gas are preferably used for this purpose. Further filter units which are equip-ped, for example, with cataly8ts or carbon absorption filters may be connected to these columns lf necessary.
The very pure gas emerging from the absorption unit or units is removed as waste air.
To ensure that, during the entire process, no crude gas which has not been completely purified can escape into the environment, the entire plant is operated under reduced pressure. Thls ls effected in a manner known per se, for example by using an extraction fan.
~ he process accordlng to the inventlon can be adjusted in a variable manner to the conditions which arise during the combustion of different pyrotechnical - -', ' .

2~2~

- 8 - BU 46t47 materials. Thus, the individual stages of the process can be connected in series depending on requirements. If, for example, flare and illumination materials which form predominantly particulate oxides are burnt, the crude gas is preferably passed via preliminary ~eparators and fine dust filters after cooling and is then sufficiently pure to be released into the environment. If pyrotechnical elements in which a high proportion of gaseous impurities are formed are worked up, the crude gas is preferably purified by scrubbing and passage through absorption units. If the gas furthermore contains solid components, it can be fed through preliminary separators and fine dust filters prior to scrubbing. In every case, the process is carried out Ln such a way that the gas contains only amounts of solids and gaseous compounds which are so small that it fulfils existing emission limits when released into the environment.
According to a further aspect of the present invention another process for working up pyrotechnical material is provided, which is characterised in that I. a pyrotechnical material A, where predominantly alkaline reaction products are formed, and a pyro-technical material B, where predominantly acidic reaction products are formed, are sub~ected to controlled combus-t~on, II. the combined crude gases formed during the combustionare cooled to a temperature below 400'C, III. the combined crude gases are purified under dry conditions by first feeding them into a preliminary separator, coarse particles belng separated off, and then feeding them via fine dust filters in order to separate off finely divided solids, and/or IV. the combined crude gases are purified under wet conditions by first passing them through a rotary scrubber and feeding them via one or more absorption unit(s), and V. the pure gas is released as waste air.
In the first stage of thi~ embodiment according to the invention, pyrotechnical material A, where pre---' 2~9922~

dominantly alkaline reaction products are formed, and pyrotec~nical material B, where predominantly acidic reaction products are formed, are subjected to controlled combustion. The combustion can be carried out con-tinuously or batchwise, in the continuous procedure thematerial supplied preferably being ignited in each case by the material already present in the reactor, while in the batchwise process one batch is always burned and thereafter the next batch is fed in and ignited. The throughput and residence time of the material are depen-dent on the material to be burned, the type of process and the reactor used. In general, the residence time is in the range from lO seconds to 1 minute.
According to the invention, two va~iants are provided for the combustion of the pyrotechnical material. In a first variant, pyrotechnical material A
and pyrotechnical B are burned separately in two reactors and the crude gases are then combined by, for example, feeding the crude gas formed during the combustion of the pyrotechnical material A into the reactor in which the pyrotechnical material B is burned. In a second variant, pyrotechnical material A and pyrotechnical material B in a suitable ratio are burned simultaneously in one reactor. An essential feature of the invention is that predominantly alkaline reaction products are formed during the combustion of the pyrotechnical material A
whereas predominantly acidic reaction products are formed during the combustion of the pyrotechnical materlal B.
For example, flare actlve materlals, lllumination elements and thermite-llke mlxtures are u~ed as pyrotechnlcal material A. For example, propellant charge powders, smoke and irritant active materials and coloured smoke~ may be mentioned as pyrotechnical material B. The alkaline products formed during the combustion of the pyrotechnical material A are predominantly alkali metal and alkaline earth metal oxide~, while the acidic reac-tion products formed during combustion of the pyro-technical material B are, as a rule, halogen compounds and oxides of nitrogen.

" 209~222 - 10 - BU 46~47 For this embodiment, too, the combustion may be carried out in one of the above described combustion chambers.
A tube reactor is preferably used for w~rking up pyrotechnical material A, whereas a reactor having a brick lining is used for working up pyrotechnical material B.
After the controlled combustion of pyrotechnical material A and B, the crude gases formed are optionally combined, if the combustion was carried out in separate reactors, by passing the crude gas formed during com-bustion of one type of pyrotechnical material into the other reactor. The crude gas formed in each case during the combustion, or the combined crude gases, is or are passed through a high-temperature region in which they are kept at a temperature of at least 1200-C, preferably up to 1500~C, over a predetermined period in order to decompose any organic substances still present. If the crude gas has a temperature of more than 1200-C as a result of the combustion, it is sufficient to keep the crude gas in the reaction region over the predetermined period without additional heating. This is effected in one embodiment, for example, by ensuring that the reactor has a xufficient height so that the residence time of the ascending crude gas is adequate for complete reaction in the high-temperature region. In another embodiment, in which the air iB blown in tangentially, the crude gas (reaction gas) is passed spirally upwards and thus remains for a sufficiently long time in the high-temperature region. If the crude gas is not sufficientlyhot, an external heating ~ource i8 provided in order to heat the crude gas to the desired temperature. The perlod of subsequent heating depends on the proportion of organic compounds and can be readily determined by one skilled in the art. As a rule, a period of 2 to 10 seconds is sufficient. In order to decompose the organic compounds, a temperature of at least 1200-C, preferably at least 1500-C, is required.
The combined crude gase~ which leave the high-. ~

~ BU 46/47 temperature region contain virtually only ~norganiccompounds, which are partly gaseous ~nd partly in the form of very small particles. Depending on the com-position of the crude gas, dry purification and/or wet purification are carried out. The wet purification can be carried out before or after the dry purification. Prefer-ably, the crude gas is first purified under dry con-ditions and then optionally subjected to wet purifica-tion, depending on requirements. Since the gas which emerges from the high-temperature region has a very high temperature, it is cooled to a temperature of below 4~0 C, it being possible at the same time to utilise the heat. In various applications, cold air can be mixed with the hot gas for cooling in the course of the process. In addition, heat may be utilised by using known heat recovery techniques. An example of this is the connection to the heat circulation of a heating station. The crude gas is cooled to temperatures below 400 C or preferably below 200 C, depending on the subsequent treatment.
After thiC cooling stage, the crude gas is sub~ected to dry and/or wet purification. As a rule, a - dry purification is carried out since the compounds formed by reaction of the components of the combined crude gases are present in finely divided form. Where the gas contains a high proportion of gaseous impurities, the cooling can be followed directly by the wet purification.
However, this variant is less preferable. In the pre-ferred embodiment, the gas is passed to a dry purifica-tion stage. In this zone in which the gaB c0018 further, the compounds present in the crude gas react with one another. The alkaline compounds, in particular alkali metal and alkaline earth metal oxides, and the acidic compounds, in particular oxides of nitrogen, chlorides, fluorides and oxides of ~ulphur ( S~2 ~ S~3 ), can react to give salts, which can then be readily separated off under dry conditions. Thus, nitrate and especially nitrite salts are formed from the gaseous oxides of nitrogen, while the gaseous chlorides and fluorides are converted into chloride and fluoride salts, respectively. Dry ~ ~9~

purification of the crude gas is therefore preferably carried out first, having the ad~antage that no wash waters which have to be worked up are produced and that the resulting solids can be directly reused.
The dry separation of the coarse particles in a preliminary separator and of the finely divided solids via fine dust filters may be carried out as in the first embodiment of the present invention as described above.
Depending on the composition of the pyrotechnical material A and B, after the fine separation the gas can be purified to such an extent that the proportions of particulate material and gaseous compounds are below the emission limits. It can then be released directly as waste air. If the gas still contains gaseous impurities, in particular halogen-containing compounds or oxides of nitrogen, it is sub~ected to a wet purification after the dry purification. As a rule, however, wet purification is no longer necessary if the material to be burned is suitably chosen.
In case, it is necessary to carry out a wet purification, this can be done as described above for the first embodiment of the process of the present invention.
The process according to this second embodiment of the invention can be ad~usted in a variable manner to the conditions which prevail dùring the combustion of different p~rotechnical materials. To carry out the process as effectively as possible, the type and amount of the pyrotechnical materials A and B are chosen so that as high a proportion as possible of the substances escaping in the crude gas react with one another to give salts, which are deposited under dry conditions. Thus, for example, it is advantageous to burn propellant charge powders which give 10 to 50% of oxides of nitrogen (based on nitro groups present) during the combustion with illumination active materials which form a high propor-tion of magnesium oxide, it being possible to reduce the proportion of oxides of nitrogen in the crude gas to the range of 10 to 100 ppm after the dry separation. It is al~o preferable to burn smoke or irritant materials which 2 ~

have a high content of organic halogen compounds with illumination active materials or thermite-like mixtures which contain magnesium. ~he ratios are chosen in each case so that complete binding of the hydrogen halides by alkali metal and alkaline earth metal elements is schieved.
When only one type of pyrotechnical material is available for disposal, a second additional component which replaces the other group of materials can be simultaneously burned. If, for example, only pyro-technical material A is present, ammonia or amines for binding nitrite and nitrate salts can be added to this material during the combustion as a replacement for pyrotechnical material B. If, on the other hand, only pyrotechnical material B has to be disposed of, magnesium, aluminium or iron powder can be added as pyrotechnical material A during the combustion, in order once again to promote salt formation.
The invention furthermore relates to an apparatus for working up pyrotechnical material, which is characterised by (A) one or more reactor(s) for the controlled combustion of pyrotechnical material; (B) a heat exchanger unit for cooling the crude gas to a temperature of below 400-C; (C) a preliminary separator for separating off coarse particles; and (D) one or more fine dust filters.
Optionally the apparatus of the present invention can additionally include (E) a scrubbing apparatus for scrubbing the crude gas and (F) one or more ab~orption unlt(s), the individual components (A) to (F) being capable of being connected to one another in any manner, depending on requirements.
Owing to the modular concept, the apparatus according to the invention is sultable for working up ; 35 various types of pyrotechnical material, such as, for example, signal and illumination pyrotechnics, propellant charge~, rocket propellant charges, smoke active materials, coloured smoke and irritant~. Depending on the type and state of aggregation of the compounds formed 2 ~ !9 ~ ~ ~ 2 during the controlled combustion, individual components or all components of the apparatus according to the invention can be connected to one another in succession.
In a preferred embodiment, as is suitable in particular for working up signal and illumination pyrotechnics, the components (A), (B), (C) and (D) are connected in series.
In another preferred embodiment, as is suitable in particular for working up smoke ac~ive materials, propel-lant charges and rocket propellant charges, the components (A), (B), (E) and (F) are connected in series.
If controlled combustion results in a very heterogeneous system which contains both gaseous impurities and very small particles, the components (A) to (F) are preferably connected in series. ~or very economical working up, component (B) is used in all cases since in this way the energy formed during the combustion can be recovered and put to a sensible use.
The apparatus according to the invention is now described in detail with reference to Figures 1 to 3.
Figure 1 shows an apparatus which is particularly suitable for working up signal and illumination pyro-technics. It has a tube reactor 1 in which the flares and illumination elements are burned in a controlled manner.
The tube reactor 1 is a reactor of heat-resistant steel without an internal lining. The flares and illumination elements are supplied to the tube reactor via a batchwise feed apparatus 4. Furthermore, the tube reactor i 8 supplied with fresh air via a pipe 3 via tangential nozzles 5. The crude gas formed in the combustion ls kept at above 1200'C for at least two seconds and then fed via the pipe 7 into the heat exchanger unit 9. The hot gas heats water which is fed into an heat exchanger and can then be fed into the hot water or heating clrculation of a heating station. The gas leaves the heat exchanger unit 9 via the pipe 11 and is fed into a multicyclone 13, where coarse particles are separated off. The coarse particles can be collected batchwise via a cellular wheel sluice 12 in storage containers 14. From the multi-cyclone, the gas is passed into fine dust f~lters 15 (A, -' 2~99222 B, C, D), where fine dust partl~les are ~eparated off.
The fine dust filters are cleaned from time to time, deposited solids being removed via discharge screw 16 and collected in storage containers 18. From the fine dust filters 15, the pure gas is then released into the environment via the pipe 17. Pipe 17 is provided with a connection 20, to feed the gas into a wet separation step~ if necessary.
Figure 2 shows a further preferred embodiment in which alternatively a tube reactor lOl or a trough reactor 102 can be used for the controlled combustion of the pyrotechnical material. The pyrotechnical material which is to be burned can be supplied to the tube reactor lO1 via a batchwise feed apparatus. When the trough reactor 102 is used, the material is supplied continu-ously via the hopper 106. Both reactors lOl, 102 are connected to the heat exchange system 109 via pipes 107 and 108, respectively. The gas is passed into the heat exchange system as in the embodiment described in Figure 1 and then via pipe 111 into the multicyclone 113 and from there into the fine dust filters 115 (A, ~, C, D).
Parts having the same function as in Figure l are desig-nated in Figure 2 by the same reference digits, increased by the number 100. In this embodiment, the gas emerging from the fine dust filters 115 can also be sub~ected to wet purification. For this purpose, it i~ fed via con-nection 120 and a pipe 119 into a rotary scrubbing unit 121 and supplied from there to one or more absorption unit~s) 123 which are provided with suitable wash vessels 124. The wa8h vessels 124 can be worked up batchwise. For this purpose, a neutralising solution is pumped from the neutralisation ves~el 126 via a pump 125 into the liquid present in the wash vessels. The neutralised solution is then released lnto the buffer tank 127. After the wet purification, the gas has ~uch a small proportion of impuritie~ that it can be released into the environment via pipe 128.
In Figure 3 a further embodiment of the apparatus of the present invention is ~hown. Parts having the ~ame '' 2~9~2%~

function as in Figure 2 are deslgnated in Figure 3 by the same reference digits, increased by the number 100. In the apparatus of the present invention as shown in Figure 3, the controlled combustion of pyrotechnical material A
and pyrotechnical material B is carried out in two separate reactors. Pyrotechnical material where pre-dominantly alkaline reaction products are formed is fed by means of feed apparatus 204 to the tube reactor 201 and is subjected to controlled combustion. The tube reactor 201 is a reactor comprising heat-resistant steel without an internal lining. Fresh air is fed to the tube reactor 201 via a pipe 203 via tangential nozzles 205.
The pyrotechnical material where predominantly acidic reaction products are formed is fed to the trough reactor 202 via the loading hopper 206 and is subjected to controlled combustion. The crude gas formed during the combustion in the tube reactor 201 is passed via pipe 207 to the trough reactor 202. The crude gases mix with one another in a high-temperature zone formed in the trough reactor 202 and are kept at above 1200-C for at least two seconds and fed via pipe 208 together into the heat exchanger unit 209. The hot gas heats water which is fed into the heat exchanger and which can be passed into the hot water or heating circulation of a heating station or for internal heat utilisation. The gas leaves the heat exchanger un~t 209 via the pipe 211, pipe 211 having dimensions such that the gas covers a sufficient distance to permit a reaction of the alkaline and acidic com-pounds. The gas is fed via pipe 211 lnto a multicyclone 213, where coarse particles are separated off. The coarse particles are removed batchwi~e via the cellular wheel sluice 212 and collected in storage container~ 214. From the multicyclone, the gas is passed into fine dust filters 215 (A, B, C, D), where fine dust particles are separated off. The fine dust filters are cleaned from time to time by blowing compressed air onto them, the fine dust being fed via the discharge screw 216 into storage container 218 and being collected there. After leaving the fine dust filters 215, the gas can either be 2~9g22'~

released into the environment via plpe 217 ~f it is sufficiently pure or fed to a wet purification ~tage, in which case it ls fed via pipe 219 ~nto a rotary scrubbing unit 221. After the rotary scrubbing, it i8 passed through one or more absorption unit(s) 223 which are provided with suitable wash vessels 224, after which the gas has such a low content of impurities that it can be released into the environment via pipe 228. For disposal, a neutralising solution is pumped from the neutralisation vessel 226 via the pump 225 into the liquid present in the wash vessels 224, and the neutralised solution is then discharged into the buffer tank 227.
Apart from these three plants described, the individual elements of the apparatuses according to the invention can be connected in series in any manner, depending on the pyrotechnical material used and on the resulting composition of the flue gas.
According to the invention, processes and an apparatus are provided in order to work up various types of pyrotechnical material safely and without pollution of the environment, valuable material and energy being recovered at the same time.
The invention is illustrated by the following examples:

Example 1 In a reactlon chamber, propellant charges were first reacted at a flow rate of 100 kg/h. The propellant charges were burned with excess air at a temperature of about 800 C without additional heating. Of the 13.7 kg/h of nitrogen introduced as part of the propellant charges, 5~ was converted to NO2. The waste gas contained 6294 mg/m3 (S.T.P.) of NO2, based on a waste gas contain-ing 11% of oxygen. In a second reaction, S0 kg/h of propellant charge were disposed of together with 100 kg of active material of the signal salt of the green hand flare. Although the lntroduct~on of nitrogen in the mixture to be disposed off wa reduced only from 13.7 kg/h to 11.16 kg/h, on the other hand the output of 2~9~222 - 18 - BU 46/4~
oxides of nitrogen decreased from 6294 m~/m3 (S.T.P.) to 200 mg/m3 (S.T.P.) (98 ppm by volume).
As a result of the reducing effect of the actlve materials reacted, the NO content of the waste gas initially decreased as a result of the increasing reaction temperature. On further cooling of the gas, formation of nitrates and especially of nitrites took place on the way from the heat exchanger to the coarse filter, the said nitrates and nitrites in turn reacting with alkaline earth metal compounds present in the gas to form alkaline earth metal nitrates and nitrites.

Example 2 The propellant charge flow rate used in Example 1 (about 50 kg~h) was reacted in a reaction chamber together with a combustion salt which consisted of 52% of magnesium powder and 48% of NaNO3.
The thermite-like mixture reached temperatures of more than 2000 C during its reaction and simultaneously led to lncreased reduction of the NOX groups formed during the combustion of the propellant charges. As a result of the reaction temperature being higher than in Example 1, it was possible further to reduce the NOX
content in the ~as.

Example 3 Irritant elements whlch contained 64% of hexachlorocyclohexane, 34~ of aluminium, 1.25~ of liquid paraffin and 0.75~ of chloroazetophenone were reacted together with combustion salt for flares, whlch salt contained 75% of KNO3, 15% of magnesium and 10% of iditol. 50 kg cf the irritant active material contained 23.5 kg of chlorine. The chlorine of the irritant reacted during the oxidative process in primary and secondary reaction steps with formation of potassium chloride and magnesium chloride in addition to aluminium chloride.
Without the addition of further chemical poten-tials, it was possible, by pairing the two sub~tances to be disposed of, to reduce the HCl content of the waste ~ ~992~s~

gas to s 5 mg/m3 ~S.T.P.), based on the pure gas.

Example 4 75 kg~h of propellant charge were burned with 50 kg of fuel oil in a separate reaction chamber 1. The resultin~ crude gases reached a temperature of more than 1200~C. 10~ of the nitrogen present in the propellant charge were converted to NOX. The resulting crude gas flow, which contained 2009 m3 (S.T.P.)/h, corresponding to 2050 mg/m3 (S.T.P.) of NOX, was fed completely or partly to a reaction chamber 2 in which propellant char~es according to Claim 1 were reacted. The NOX fed in with the crude gas was further reduced analogously to the reaction of Example 1 by the reducing and catalytic effect of the pyrotechnical propellant charges and combined in the remaining part with the oxidic dusts to give a content of nitrites which was effective for the process gas purification. By splitting the process gas stream fed into the reaction chamber 2, it was possible to control the process gas stream from reaction chamber 2 in such a way that the NOX values of the resulting pure gas corresponded to the standards < 200 mg/m3 (S.T.P.) with 11% of ~2 in the waste gas.

Example 5 Propellant charges were burned continuously in a reaction chamber with the addition of combustion air, supported by an oil or gas burner. At the same tlme, powdered reaction products of the disposed pyrotechnical active materials which contained potassium oxide, magnesium oxide, barium oxide, etc., were introduced into the reaction zone. These reactive dusts were thoroughly mixed with the crude gas and discharged via an after-com-bustion chamber. The dusts further increased formation of N2 from the nitro groups of the propellant charges and, during the subsequent removal of dust from the gas at temperatures below 200 ~, aqain led to the formation of nitrites/nitrate~ and thus to the reduction of the NOX
content of the process gas.

Claims

1. Process for working up pyrotechnical material, characterised in that I. the pyrotechnical material is burned in a controlled manner, and a crude gas formed is passed through a high-temperature region in which the gas is exposed to a temperature of at least 1200°C over a predetermined period in order to decompose organic substances still present;
II. the crude gas formed during the combustion is cooled to a temperature below 400°C;
III. the crude gas is purified under dry conditions by first feeding it into a preliminary separator, coarse particles being separated off, and then feeding the crude gas via fine dust filters in order to separate off finely divided solids, or IV. the crude gas is purified under wet conditions by first passing it through a rotary scrubber and then passing it via one or more absorption units, and V. the purified gas is released as waste air.

2. Process according to Claim 1, characterised in that the pyrotechnical material worked up comprises flares, illumination pyrotechnics, propellant charges, rocket propellant charges or smoke elements.

3. Process according to Claim 1, characterised in that the pyrotechnical material is burned in a trough reactor which has a mobile trough below the combustion chamber for receiving melting material and falling slag.

4. Process according to Claim 1 or 2, characterised in that the pyrotechnical material is burned in a tube reactor to which air is supplied via tangential nozzles and is passed over tangential plates in such a way that it flows along the wall of the tube reactor and cools the steel jacket.

5. Process for working up pyrotechnical material, characterised in that I. pyrotechnical material A, where predominantly alkaline reaction products are formed, and pyrotechnical material B, where predominantly acidic reaction products are formed, are subjected to controlled combustion, and produce combined crude gases, II. the combined crude gases are cooled to a temperature below 400°C, III. the combined crude gases are purified under dry conditions by first feeding them into a preliminary separator, coarse particles being separated off, and then feeding the crude gas via fine dust filters in order to separate off finely divided solids, or IV. the crude gas is purified under wet conditions by first passing it through a rotary scrubber and then passing it via one or more absorption unit(s), and V. the purified gas is released as waste air.

6. Process according to Claim 5, characterised in that flares, illumination pyrotechnics or thermite-like charges are worked up as pyrotechnical material A.

7. Process according to Claim 5, characterised in that propellant charges, rocket propellant charges, smoke and irritant elements or coloured smokes are worked up as pyrotechnical material B.

8. Process according to Claim 6, characterised in that propellant charges, rocket propellant charges, smoke and irritant elements or coloured smokes are worked up as pyrotechnical material B.

9. Process according to any one of claims 5 to 8, characterised in that the pyrotechnical material A and the pyrotechnical material B are burned separately and the crude gases are then combined before cooling according to stage II.

10. Process according to Claim 9, characterised in that the pyrotechnical material A is burned in a tube reactor to which air is fed via tangential nozzles and is passed over tangential plates so that it flows along the wall of the steel reactor and cools the steel jacket, and the pyrotechnical material B is burned in a trough reactor or rotary kiln which is lined with refractory material.

11. Process according to any one of Claims 5 to 8, characterised in that pyrotechnical material A and pyrotechnical material B are burned simultaneously in one reactor.

12. Process according to any one of claims 5 to 8 or 10 characterised in that, instead of pyrotechnical material A, magnesium, aluminium or iron powder are burned together with the pyrotechnical material B.

13. Process according to claim 9 characterised in that, instead of pyrotechnical material A, magnesium, aluminium or iron powder are burned together with the pyrotechnical material B.

14. Process according to claim 11 characterised in that, instead of pyrotechnical material A, magnesium, aluminium or iron powder are burned together with the pyrotechnical material B.

15. Process according to any one of claims 5 to 8, 10, 13 or 14, characterised in that the crude gas is purified under reduced pressure.

16. Process according to claim 12, characterised in that the crude gas is purified under reduced pressure.

17. Process according to any one of claims 5 to 8, 10, 13, 14 or 16 characterised in that, in stage (I), the crude gas is heated to a temperature of up to 2000°C.

18. Process according to claim 15 characterised in that, in stage (I), the crude gas is heated to a temperature of up to 2000°C.

19. Process according to any one of claims 5 to 8, 10, 13, 14, 16 or 18 characterised in that, in stage (II), the crude gas for the dry purification is cooled to a temperature below 200°C.

20. Process according to claim 17 characterised in that, in stage (II), the crude gas for the dry purification is cooled to a temperature below 200°C.

21. Process according to any one of claims 5 to 8, 10, 13, 14, 16, 18 or 20, characterised in that, in stage III, the crude gas which is supplied directly to the wet purification is cooled to a temperature below 140°C.

22. Process according to claim 19, characterised in that, in stage III, the crude gas which is supplied directly to the wet purification is cooled to a temperature below 140°C.

23. Process according to any one of claims 5 to 8, 10, 13, 14, 16, 18, 20 or 22, characterised in that, in stage (III), a multicyclone is used as the preliminary separator.

24. Process according to claim 21, characterised in that, in stage (III), a multicyclone is used as the preliminary separator.

25. Process according to any one of claims 5 to 8, 10, 13, 14, 16, 18, 20, 22 or 24, characterised in that, in stage (IV), a Venturi scrubber is located upstream of the rotary scrubber.

26. Process according to claim 23, characterised in that, in stage (IV), a Venturi scrubber is located upstream of the rotary scrubber.

27. Process according to any one of claims 5 to 8, 10, 13, 14, 16, 18, 20, 22, 24, or 26, characterised in that, in stage (IV), packed columns or tray columns are used as the absorption unit.

28. Process according to claim 25, characterised in that, in stage (IV), packed columns or tray columns are used as the absorption unit.

29. Apparatus for working up pyrotechnical material, characterised by A) one or more reactors for the controlled combustion of pyrotechnical material;
B) a heat exchanger unit for cooling the crude gas to a temperature of below 400°C;
C) a preliminary separator for separating off coarse particles; and D) one or more fine dust filters.

30. Apparatus according to claim 29, characterised in that it additionally comprises E) a scrubbing apparatus for scrubbing the crude gas and F) one or more absorption unit(s), where the individual components (A) to (F) being connected to one another in any manner, depending on requirements.

31. Apparatus according to Claim 30, characterised in that the components (A), (B), (E) and (F) are connected in series.

32. A process for the environmentally safe destruction of pyrotechnic material comprising:
(a) burning pyrotechnic material in a controlled manner in a combustion chamber to form slag and a crude gas;
(b) passing the crude gas through a high-temperature region at a temperature of at least 1200°C for at least two seconds;
(c) cooling said crude gas to a temperature less than 400°C;
(d) purifying the crude gas by at least one of the following means:
(i) under dry conditions by feeding said crude gas into a preliminary separator to remove coarse particles and to at least one fine dust filter to remove fine dust; and (ii) under wet conditions feeding the gas through a rotary scrubber and at least one adsorption zone; and (e) releasing the resultant purified crude gas as waste air.

33. A process for destroying pyrotechnical material comprising pyrotechnical material A which forms predominantly alkaline reaction products and pyrotechnic material B which forms predominantly acidic reaction products comprising the steps of:
I. subjecting pyrotechnic material A and pyrotechnical material B to combustion to produce crude gases;
II. cooling the combined crude gases to below 400°C;
III. purifying the combined crude gases by at least one of the following means:
A. under dry conditions by feeding such gases first into a preliminary separator to separate coarse particles, and then through fine dust filters to separate finely divided solids; and B. under wet conditions by passing the crude gases first through a rotary scrubber and then through one or more absorption units;
and IV. releasing the purified gas.

34. A process for destroying pyrotechnic material comprising pyrotechnic material B which forms predominantly acidic reaction products and a second material which is magnesium, aluminum or iron powder comprising the steps of:
I. subjecting pyrotechnic material B and the second material to combustion to produce crude gases;
II. cooling the combined crude gases to below 400°C;
III. purifying the combined crude gases by at least one of the following means:
A. under dry conditions by feeding such gases first into a preliminary separator to separate coarse particles, and then through fine dust filters to separate finely divided solids; and B. under wet conditions by passing the crude gases first through a rotary scrubber and then through one or more absorption units;
and IV. releasing the purified gas.

35. A process for destroying pyrotechnic material comprising pyrotechnic material A which forms predominantly alkaline reaction products and a second material which is ammonia or an amine comprising the steps of:
I. subjecting pyrotechnic material A and the second material to combustion to produce crude gases;
II. cooling the combined crude gases to below 400°C;
III. purifying the combined crude gases by at least one of the following means;
A. under dry conditions by feeding such gases first into a preliminary separator to separate coarse particles, and then through fine dust filters to separate finely divided solids; and B. under wet conditions by passing the crude gases first through a rotary scrubber and then through one or more absorption units;
and IV. releasing the purified gas.