EP0244429A1

EP0244429A1 - Process for selective or simultaneous elimination of noxious substances from smoke gas through irradiation of the smoke gas with electron-beams

Info

Publication number: EP0244429A1
Application number: EP86905294A
Authority: EP
Inventors: Ernst-Günter HOFMANN; Bernd-Peter Offermann
Original assignee: Licentia Patent Verwaltungs GmbH; Telefunken Systemtechnik AG
Current assignee: Telefunken Systemtechnik AG
Priority date: 1985-10-23
Filing date: 1986-09-20
Publication date: 1987-11-11
Also published as: FI872757A; WO1987002597A1; FI872757A0; DK294687D0; DK294687A; DE3620673A1; ES2003146A6

Abstract

Un procédé est utilisé pour éliminer sélectivement ou simultanément des matières toxiques, en particulier des oxydes de soufre et/ou des oxydes nitreux, contenues dans des gaz de fumée par l'irradiation de ceux-ci avec des faisceaux électroniques. Le procédé est appliqué en étapes successives, dans une chaîne formée d'au moins deux étages pourvus chacun d'au moins un accélérateur d'électrons ou d'une tête d'accélération d'électrons qui servent de source de faisceaux d'électrons. Le gaz de fumée est irradié par des doses partielles d'irradiation qui ensemble donnent la dose totale souhaitée d'irradiation. Le gaz de fumée est obligatoirement mélangé entre les étapes d'irradiation. La chambre d'irradiation de chaque étape est adaptée à la forme du champ d'irradiation, ses dimensions étant approximativement égales au rayon d'action effectif des rayons d'électrons utilisés dans la chambre d'irradiation.A method is used to selectively or simultaneously remove toxic materials, in particular sulfur oxides and / or nitrous oxides, contained in flue gases by irradiating them with electron beams. The method is applied in successive stages, in a chain formed of at least two stages each provided with at least one electron accelerator or an electron acceleration head which serve as a source of electron beams. The smoke gas is irradiated by partial doses of irradiation which together give the desired total dose of irradiation. The smoke gas must be mixed between the irradiation stages. The irradiation chamber of each stage is adapted to the shape of the irradiation field, its dimensions being approximately equal to the effective radius of action of the electron rays used in the irradiation chamber.

Description

"Process for the selective or simultaneous separation of pollutants from flue gases by irradiation of the flue gases with electron beams"

The invention relates to a method according to the preamble of claim 1.

The increasingly intensive use of IMatur and the consequent pollution of industrial waste and

Pollutants are increasingly facing efforts to preserve our natural environment. One of the outstanding problems here is the pollution of air, water and soil by air pollutant emissions from power plant and industrial firing systems, traffic and households. They contribute to the much-discussed "acid rain", "forest death" and the increasing "smog" situations. Sulfur oxide (SO) and nitrogen oxides (NO _x ) are considered essential pollutants for this today. The main culprits here are power plant and industrial firing. While the dedusting of flue gases has already largely been solved in large combustion plants, the emissions of sulfur oxide (SO _x ), especially sulfur dioxide (SO ₂ ), and nitrogen oxide (NO _x ) still pose considerable problems.

These pollutants are caused by o SO ₂ : by the sulfur content of the fuels o NO _x : by combustion processes in the combustion plants.

Measures to reduce pollutant emissions must therefore be applied to large combustion plants using fuel, the combustion plant or flue gas. The primary measures are the use of low-sulfur fuels, the pre-desulfurization of the fuels and the improvement of the combustion plants. However, these primary measures are not sufficient to achieve the prescribed limit values. This can only be achieved through secondary measures for exhaust gas purification, sometimes in combination with primary measures. With secondary measures, the flue gases generated are themselves subjected to the cleaning process.

Secondary processes for flue gas cleaning are known in many variants and z. T. introduced.

The reactions leading to the separation of SO _x and / or NO _x can be divided into the following reaction stages:

a) Formation of free radicals by electron radiation (and as a result of accompanying reactions) b) Oxidation of SO ₂ and NO _x c) Formation of H ₂ SO ₄ and HNO ₃ d) Reaction with NH ₃ to form solid ammonium compounds.

Alternatively, it has also been proposed to thermally split the ammonium compounds again, to recover NH ₃ and from the end products (O ₂ , N ₂ , SO ₂ ) to process the rich gas (SO ₂ ) obtained. Other absorption media, e.g. B. CaO / Ca (OH) ₂ , have been proposed or used.

The method can be used both for the selective deposition of a

Pollutant component as well as for the simultaneous separation of several pollutant components, in particular SO _x and NO _x , are used.

In some known test or pilot plants after the

EBDS processes the flue gas with one pass through the radiation field in a radiation chamber on one or two sides. Here, the requirement for the best possible use of the electron radiation used is generally offset by the need for the most effective possible conversion of the harmful gases. The latter requires the flue gas to be irradiated as evenly as possible. As a rule, both requirements contradict each other. In the case of one-sided irradiation, because of the decreasing intensity of the radiation along its direction of propagation, a locally highly divergent, overall poor efficiency in the conversion of the pollutants can be achieved (in some cases less than 50%).

Conceptually, attempts have been made to achieve the most homogeneous radiation possible for the flue gases by building up a quasi-homogeneous radiation field which is formed by superimposing the radiation fields of two or more accelerators. In this sense, attempts have also been made in the previously known EBDS systems to achieve the most homogeneous possible irradiation with the required dose by using "electron guns" in pairs. However, this is only possible with overexposure or underexposure of individual batches of the radiation material (flue gas) and also a loss in efficiency. Based on the finding that the degree of separation of the pollutants in the flue gas - but especially that of the nitrogen oxides when the flue gases are irradiated once - tends to be in the range of low dose values (≤ 1 Mrad or ≤ 10 Kgray). increasing gradually with the (absorbed) dose, but then reaching a maximum after a less strong increase and then even decreasing again, step-wise irradiation was also proposed to improve the degree of separation, but without simultaneously ensuring optimum use of energy and radiation and homogeneous radiation of the flue gas .

The latter is not least a question of the mutual adjustment of radiation field, flue gas throughput and farm and dimensions of the radiation chamber, as well as the operational safety and transparency of the electron beam exit window used. In the commonly used low energy accelerators with radiation energies below about 300 KeV, however, it is known that only relatively thin, mechanically and thermally unstable window films can be used because of the otherwise severe energy loss, which must then be cooled and supported, e.g. B. by built-in webs, grids or perforated plates. This in turn lowers the transparency and thus the efficiency of the arrangement. In addition, these windows (foils made of light metal, for example titanium or titanium alloys) are generally directly exposed to the irradiated flue gas and thus to its influences which impair operational safety.

In summary, the following disadvantages should be noted in the EBDS systems and proposals that have become known so far: a) the insufficient mutual coordination of the amount of flue gas generated per unit of time, radiation (reaction) chamber dimensions and shape and the electron beam energy, and b) the often high absorption losses in the Electron accelerator and / or radiation chamber windows, c) the inhomogeneous radiation of the flue gases as they pass through the radiation chamber. All of this affects the energy / radiation efficiency of the process and thus its economy.

The invention has for its object to provide a method of the type mentioned, in which the above-mentioned disadvantages by suitable process control (steps), by a suitable choice of radiation energy and by mutual adaptation of the radiation field to the shape and dimensions of the flue gas channels and reaction chambers (radiation chambers) can be avoided and an optimal radiation efficiency is ensured, which leads to a reduction in the expenditure on equipment and the primary energy to be used and thus to an optimization of the method.

The object is achieved by the characterizing method steps of claim 1.

Embodiments of the invention are described in subclaims 2 to 14.

Devices for carrying out the method can be seen from subclaims 15 to 27.

Since it is known that in the EBDS method the required radiation dose is almost independent of the dose rate and the separation rate of the pollutant can be improved by fractional irradiation, a step-by-step irradiation is proposed in order to avoid the above-mentioned night silences, in which, according to the inventive concept, the irradiation in succession with partial radiation doses takes place, the desired total radiation dose results as the sum of the partial doses, the flue gas is forcibly mixed between the radiation stages and the radiation chamber assigned to each stage is adapted to the shape of the radiation field and its dimensions are approximately equal to the effective range of the blinded electron radiation in the radiation chamber. In this case, the gradual irradiation with partial doses, which correspond to the total dose required, in conjunction with the forced mixing between the individual stages and the adaptation of the irradiation chamber to the shape and dimensions of the respective irradiation field on the one hand ensures maximum use of the electron radiation in each individual stage without one To have to generate a homogeneous radiation field, and on the other hand, due to the statistical intermixing between the individual irradiation stages with increasing number of stages, supplies an increasingly homogeneously irradiated flue gas. This enables quasi-homogeneous radiation with better beam utilization (efficiency also taking into account window losses greater than 75%) and thus a reduction in energy consumption and the box.

For an energetic optimization of the process, it is also important that in all flue gas cleaning processes per unit of time relatively large amounts of flue gas are generated and "processed" at normal pressure. In coal-fired power plants, for example, around 360,000 cbm of flue gas are generated every hour. The linear dimensions of the flue gas ducts are up to about 5 m. In the technical implementation of the electron irradiation process, the penetrability of the electron radiation generated and the radiation energy that is decisive for it must be coordinated with the density of the flue gas and the dimensions of the radiation chamber (reactor). This advantageously requires systems with radiation energies in the range 500 to 1000 KeV.

In the energy range from 500 to 1000 KeV, which is mentioned as advantageous, the percentage energy losses in the electron beam window (with the same thickness) are far lower than bsi low-energy accelerators. With regard to mechanical stability and thermal resilience, the window can be made thicker (about 30 · 10 ^-3 mm titanium or titanium alloy) without it being mechanical, the transparency impairing support. In addition, it can also advantageously be designed as a double window, with the cooling medium (inert gas or flue gas-free air) flowing through the intermediate space, so that the jet exit window of the accelerator is not directly exposed to the influences of the flue gas loaded with pollutants and additives (e.g. ammonia) is, which in turn has a positive effect on the operational safety of the system. Such a double system, consisting of two titanium foils, each 30 · 10 ^-3 mm thick, would have been B. at 1000 KeV a transparency of approx. 92%, at 500 KeV of approx. 80%, at 300 KeV however only approx. 55% and at 200 KeV still approx. 35%.

In order to make the method effective according to the inventive concept, at least two, but preferably three or more stages should be used in series and form a line, means for turbulent mixing of the radiation material being provided between the stages (e.g. blowers, impellers, Baffles).

A variant of the mixing consists in the fact that the media are guided during the irradiation in such a way that gas volumes which are exposed to a relatively high radiation dose during the first irradiation are passed through in areas under the radiation source where they have a low radiation exposure are exposed, while at the same time gas volumes which are exposed to a relatively low radiation dose during the first irradiation are carried out with further irradiation in areas under the radiation source in which they are exposed to a high radiation exposure. Mixing of the partial volumes can take place simultaneously between the individual irradiation processes.

One embodiment of the invention is that the first radiation with a partial dose of 60% to 100% and the second irradiation with a partial dose of 10% to 30% and vice versa.

With n sub-stages (n> 2), the method can be carried out analogously if the radiation channel of each of the n stages into the

Segments a ₁ , a ₂ ... a _{n is} divided and each partial volume as it passes through the n stages from a. To a ₂ . , , transferred to a.

The method according to the inventive concept is also not limited to the use of ammonia as absorbent, which is known per se. Other substances of a similar type would also be conceivable, in particular if the required radiation dose can be reduced thereby and / or other reaction products are to be obtained. The dose can also be reduced by adding reaction-accelerating additives and / or water additives and / or additional electric fields within the radiation chambers. In conjunction with the measures mentioned above, this further increases the efficiency and economy of the process.

FIGS. 1 to 8 show exemplary embodiments of systems for carrying out the method according to the invention. The same reference numerals are used in the individual figures for the corresponding components.

The system shown in FIG. 1 has three electron radiation devices 1 connected in series, each of which emits a partial radiation dose. The partial doses result in the sum total effect of the desired total radiation dose, which, for. B. could also be supplied by five individual electron irradiation devices. A mixing device 2, which mixes the irradiated flue gas mixture, is arranged after each electron irradiation device. Before the flue gas enters the first radiation stage, it is in a collecting device 3 from Fly ash cleaned and enriched in an additional device 4 with, for example, ammonia in a preferably stochiometric ratio to sulfur dioxide (SO ₂ ) and nitrogen oxide (NO _x ).

A device 5 serves to regulate the temperature of the mixture from which the reaction products (ammonium sulfate / nitrate) are withdrawn in a collecting device 7 after passage through the electron irradiation and mixing devices 1 and 2, respectively, before being drawn off into the chimney denoted by 6. This is powdery failure.

In the plant shown in FIG. 2, the fly ash is caught in the collecting device 3, the addition of the additives by means of the additional device 4, the mixing in the mixing device 2 and the temperature control using the device 5 again at the entrance of the process line. On the other hand, the separation of the reaction products (powdery precipitates) is carried out decentrally after each irradiation and mixing stage 1 or 2 by decentralized devices 7.

According to the embodiment variant according to FIG. 3, the fly ash is caught at the beginning of the process line. The powdery failures are precipitated at the end of the process line. The addition of additives, e.g. B. of ammonia or possibly other substances, the temperature control and the radiation are decentralized gradually.

Another variant is shown in FIG. 4. Here, only the fly ash is caught (centrally) at the entrance of the process line, while the other process steps are modular and each include additional addition, temperature control, radiation part and separation of the powdery failures. Mixing (2) takes place between the module components. It is practically a combination of the systems from FIGS. 2 and 3. In all process variants, the necessary auxiliary and measuring means, of course. B. pumps, separators, filters, temperature control units, measuring and control devices for the composition of the incoming and outgoing flue gas, dis reaction temperature and the regulated addition of additives integrated.

The exemplary embodiments shown in FIGS. 1 to 4 show systems for carrying out the method according to the invention, as are primarily used for the simultaneous deposition of SO _x and NO _x . It goes without saying that when using the dsr in the exemplary embodiments shown in FIGS. 1 to 4 for the selective separation of NO _x before or after a flue gas desulfurization system, the chimneys labeled 6 or the collecting devices labeled 3 for fly ash can be dispensed with, since these generally are connected upstream or downstream of the desulfurization plants.

FIG. 5 shows a special design proposal for a simultaneous system based on the inventive concept for a power plant block 100 MW _el , the electrical supply devices being designated by (5).

The following assumptions are made:

- Firing plant for hard coal with 1% S content

- Flue gas margin generated M = 360,000 m ³ / h

- efficiency = 75%

- Flue gas density g = 1.3 kg / m ³

- radiation dose D = 1.5 Mrad This results in the required beam power L _{100 of} the accelerator system for a 100 MW _el block

0 _u

2.6% of the block power is therefore required for the irradiation! This would be less than with other chem.-therm. Flue gas cleaning process. The required beam power of 2.6 MW could e.g. are realized with three 800 KV / 1000 KW radiation systems, each of which has five radiation heads with an output of 800 KV / 250 mA.

According to the systems shown in FIG. 5, the five radiation heads of each partial system can be connected in series in the sense of the inventive concept, mixing between the stages so that they form a partial line for 1/3 of the amount of flue gas, ie 120,000 m ³ / h. The three sub-lines can then either be operated in series or in parallel (as shown in FIG. 5), each sub-line optionally being operated independently of the others or being shut down. This enables individual adaptation to the load being driven. First of all, only one line is used; Only when the capacity of one line is insufficient with thorough mixing is it intended to gradually use the other.

When using the system for selective denitrification shown in FIG. 5, because of the required lower radiation dose (about 0.6 Mrad), a correspondingly larger power plant block (about 250 MW _el ) can be denitrified, or in this case the above-mentioned one is used

Power plant block of 100 MW _el only one of the three subsystems shown in Figure 5 required. According to the system shown in FIG. 5, the five radiation heads of each partial system can be connected in series in the sense of the inventive concept, mixing between the stages and forming a partial line for 1/3 of the amount of belly gas, ie 120,000 m ³ / h. The three sub-lines can then either be operated in series or in parallel (as shown in FIG. 5), each sub-line optionally being operated independently of the others or being shut down. This enables individual adaptation to the load being driven. The series is primarily used; Only when the throughput of the purified abdominal gas is not sufficient with sufficient mixing is it intended to carry out the parallel operation.

The structural design of one of the three sub-lines described in FIG. 8 is shown by way of example in FIG. 6.

The radiation system is housed in separate trees 9a and 9b, the abdominal gas channel 10 with the radiation chambers (11) and the intermixing stages (2) lying in the actual radiation chamber (9b) below the earth's surface, so that a minimum of structural radiation protection is required here . The belly gases to be treated are supplied and discharged - also for reasons of radiation protection - from the above-standard flue gas ducts arranged above labyrinth-shaped ducts (12) with the thickness required for the radiation shielding.

Outside the radiation chamber (9b), a collection device for fly ash and dust (3) and a device for adding additives, for example H ₂ O, NH ₃ , (4) and a temperature control device (5) are connected upstream of the radiation stage in the flue gas supply duct. In the exit channel, the resulting reaction products, for example ammonium sulfate / nitrate, are withdrawn from the belly gas in the collecting device (7). It goes without saying that the collecting device (3) can be omitted if the belly gas supplied has previously been cleaned of fly ash and dust.

For the part line described in FIG. 6, the radiation system consists, for example, of five stages, each with a radiation head (1) more common Type (with scanner) and a central electrical supply unit (8) (e.g. a high-voltage cascade generator). The individual radiation heads (1) are flanged equidistantly in a star shape to the supply unit (8) via T-shaped flanges (13). Their outer jackets form a common pressure vessel, which is at earth potential, which is filled with compressed gas (eg 6 atü sulfur hexafluoride) for better insulation, cooling and safe contact of the high-voltage components.

The concentric arrangement of the (high-voltage) supply unit and the radiation heads enables a space-saving, functional and maintenance-friendly construction of the system.

The setting, control and regulation of the electrical parameters (high voltage, beam current, etc.) is carried out centrally and uniformly for the system.

The basic structure of one of the five radiation stages of the partial line described in FIG. 6 is shown in FIG. 7a and the associated side view 7b.

The radiation head (1) here consists of an evacuated, multi-stage accelerator tube (14) with an electron gun (15) arranged at a negative high-voltage potential (against earth). The electrons are generated in it and accelerated under the influence of the applied DC voltage of preferably 600 to 1000 kV to the corresponding energy (600 to 1000 keV). In this arrangement, the high-voltage poles (16) of the individual accelerator tubes are connected to the high-voltage pole of the supply unit (8), not shown, by concentric feeders (17) lying inside the flange-like connections (13) insulated with compressed gas. With this arrangement, the cable connections, which are often susceptible to interference in other versions, are avoided and maximum operational reliability is achieved in the voltage range mentioned.

The electron beams (18) generated in the electron gun (15) and accelerated in the accelerator tube (14) are by means of a deflection magnet (19) fanned out in the scanner (20). The fanned out electron beams (18a) then pass through a thin window (21), which is largely transparent to electron beams, preferably from a 15-30 mμ thick film of titanium or a titanium alloy, into the intermediate space (22) and after penetrating an adjacent second window (23 ) approximately the same transparency into the radiation chamber (11) integrated in the abdominal gas channel.

The double window is cooled in the intermediate space (22) between the two windows (21) and (23) by a gas stream (24), preferably an inert gas or a flue gas-free air stream, in which the heat generated by partial absorption of the electrons in the window material is dissipated. Devices (25) can be provided on the window (23) which closes the radiation chamber (11) and has no (significant) pressure difference in order to clean and / or renew it continuously or discontinuously during operation and / or during breaks . Such devices (25) can e.g. consist of running or reversing winders and unwinders with a scraper.

If a flue gas-free air flow is used for cooling, it can be returned to the entrance of the radiation chamber (11) after passing through the intermediate space (22), so that the reaction products, in particular ozone, generated by interaction with the electron radiation intensify the direct electron beam effect in the belly gas.

The advantage of this arrangement over known window arrangements is that

- The window (21) closing the evacuated scanner (20), which is under a pressure difference of about 1 atm, is not exposed to the direct influence of the belly gas (26) and thus influences of corrosion and deposits are avoided,

- The window (23) closing the radiation chamber (11) can be cleaned and / or renewed,

- Due to the air cooling, the energy losses in the double window system can be kept small (for example under 15%) with the electron energies under consideration (600 to 1000 keV) and - Mechanically more sensitive windows with high loss rates, such as those used as single windows with web support, some with water cooling for electron beams with energies less than 500 keV, can be avoided. This also results in the service life, operational safety and efficiency of the device.

The high-energy electron beams that enter the radiation chamber (11) after passing through the double-window system interact with the flue gas and its pollutants and additives at the same time and gradually lose their energy. The energy distribution in the resulting three-dimensional radiation field, characterized by its isodose distribution (27), is determined by the geometry (in FIG. 10, for example, by fanning out) of the primary electron radiation, its energy-dependent range of fiesta B _R when it emerges from the double-window system and the likewise energy-dependent scattering. While the remaining range B _{R increases} with increasing energy of the (primary) electron radiation, the scattering decreases with increasing energy. Accordingly, different field distributions (isodoses) of the type sketched in FIG. 10 result with different primary electron energies (acceleration voltages).

The shape and size of the radiation chamber (11) are dimensioned so that, on the one hand, as large a part of the radiation field as possible can be used for irradiating the flue gas, but on the other hand the abdominal gas channel and the radiation chamber (11) should not be made unnecessarily large, that it encloses the radiation field spatially as completely as possible, but preferably at least the 5% isodose characteristic curve, while at the same time an interaction with the temperature control device (5) temperature-regulates the wall of the radiation chamber (11) in accordance with the most favorable reaction temperature of the abdominal gas. In this way, a high utilization of the electron radiation radiated into the radiation chamber is achieved with an inhomogeneous dose distribution in the fusing gas flowing through. A homogenization of the dose distribution in the flue gas is achieved according to the inventive concept in that several such irradiation stages are operated in series to form a (partial) line, the flue gas flowing through being mixed between the stages, and the target radiation dose of the (partial) line is balanced the (multiple folds) effect of the individual stages.

The mixing itself can take place in different ways. Figure 8 gives examples a, b and c. The illustrations in principle represent a section along the line E - F of FIG. 6. For the sake of simplicity, however, only three (of the five irradiation heads (1) shown in FIG. 6) are shown. In Figure 8, the flue gas to be irradiated (26) flows from the left side of the picture through the additional and temperature control device (4, 5) through the labyrinthine channel (12) into the radiation zone located underground with the three radiation chambers (11) and passes through another labyrinthine channel section (12) in the collecting device (7) and from there (into the chimney, not shown). The flue gas is mixed in two mixing stages between the three radiation chambers.

In Example 8a, the mixing stages consist of (rotating) fans

(28). In example 8b, the mixing is carried out by a (turbulence-generating) design of the abdominal gas channel between the radiation chambers (1), e.g. achieved by multiply kinked channel sections (29). Finally, in example 8c there are also elements (30) determining the flow and / or flow direction, e.g. special grids or lamella inserts, intended for thorough mixing.

It goes without saying that such mixing aids can be used individually or in combination.

Claims

PATENT CLAIMS

1. A method for the selective or simultaneous separation of pollutants, in particular sulfur and / or nitrogen oxides from flue gas by irradiating the flue gases with electron beams, the method being carried out successively in stages, and at least two stages, each forming a process line are used, which are equipped with at least one electron accelerator or electron accelerator head as the electron beam source, characterized in that the irradiation of the flue gas is carried out successively with partial irradiation doses, which as a sum result in the desired total radiation dose, that the flue gas is forcibly mixed between the irradiation stages, and that the radiation chamber is adapted to each stage of the farm of the radiation field and its dimensions are approximately equal to the effective range of those used

Electron radiation can be selected in the radiation chamber.

2. The method according to claim 1, characterized in that additives are added centrally after deduction of the fly ash, dust and particles before the radiation stages.

3. The method according to claim 1, characterized in that additives are added decentrally after deduction of the fly ash, dust and particles before each of the individual radiation stages.

4. Process according to claim 2 or 3, characterized by the fact that the additives partly contain reaction-accelerating substances.

5. The method according to claim 1, characterized in that the separation of the reaction products at the end of the process line before blowing into the chimney (chimney) is carried out centrally.

6. The method according to claim 1, characterized in that the deposition of the reaction products is carried out decentrally after each irradiation stage.

7. The method according to claim 1, characterized in that the flue gas is mixed turbulently between the radiation stages by static means.

8. The method according to claim 1, characterized in that the flue gas is mixed between the irradiation stages by dynamic means.

9. The method according to claim 1, 7 or 8, characterized in that the media are guided during the irradiation in such a way that the gas volumes which are exposed to a relatively high radiation dose during the first irradiation are passed through in areas under the radiation source during a further irradiation, in which they are exposed to a low level of radiation.

10. The method according to claim 1, 7 or 8, characterized in that the media are guided during the irradiation in such a way that gas volumes which are exposed to a relatively low radiation dose during the first irradiation are passed through in areas under the radiation source during a further irradiation in which they are exposed to high levels of radiation.

11. A method according to claim 9 or 10, characterized in that the first radiation with a partial dose of 60% to

100% and the second irradiation with a partial dose of 10% to 30% is carried out.

12. The method according to claim 1, characterized in that the radiation chambers enclose the radiation field spatially as completely as possible, but preferably at least its 5% isodose characteristic.

13. The method according to claim 1, characterized in that the energy of the electron radiation used is at least 500 keV.

14. The method according to claim 1, characterized in that the energy of the electron radiation used is preferably used in the range 600 to 1000 keV.

15. Device for performing the method according to one of claims 1 to 14, characterized in that in each case a mixing device (2) of a collecting device (3) for fly ash and an additional device (4), the at least two electron irradiation devices (1) are arranged in series , and that the series-connected electron irradiation devices (1) are followed by a collecting device (7) receiving the reaction products and a chimney (Fig. 1).

16. Device for carrying out the method according to one of claims 1 to 14, characterized in that at least two irradiation stages connect to a collecting device (3) for fly ash and to an additional device (4), each with an electron irradiation device (7), a mixing device (2) and a collecting device (7) for the reaction products, and that the last collecting device (7) is connected directly to the vent (6) (Fig. 2).

17. Device for carrying out the method according to one of claims 1 to 14, characterized in that a collecting device (3) for fly ash is followed by a at least two-stage irradiation arrangement, that each stage has an additional device (4), a temperature control device (5) and an electron irradiation device (1) that a mixing device (2) is provided between the stages and that the last stage is connected to a collecting device (7) for the reaction products with a downstream chimney (6) (Fig. 3).

18. Device for performing the method according to one of claims 1 to 14, characterized in that an at least two-stage radiation system is preceded by a collecting device (3) for fly ash and a chimney (6) is connected in series, and that each stage of the radiation system from an electron beam device ( 1), a mixing device (2), an additional device (4), a temperature control device (5) and a collecting device (7) for the reaction products (Fig. 4).

19. The apparatus for performing the method according to claim 15, 16, 17 or 18, characterized in that the window system consists of two windows largely transparent to electron beams, one of which is the accelerator tube against the outside and the other the radiation chamber complete, both windows are arranged in series in the direction of the primary electron beams and the space is cooled with a gas flow through it (Fig. 7a and 7b).

20. The apparatus according to claim 19, characterized in that the space between the two Fe.nstern is cooled with an inert gas (eg N ₂ ).

21. The apparatus according to claim 19, characterized in that the space between the two windows is cooled with a smoke-free air flow.

22.The device according to claim 21, characterized in that the air flow is passed after passing the space between the two windows in the entrance of the associated radiation chamber and its reaction products generated by interaction with the electron beam intensify the separation effect in the flue gas.

23. The device according to claim 19, characterized in that at least the window closing the accelerator tube consists of a 15 to 40 mμ thick film made of titanium or a titanium alloy.

24. The device according to claim 19 or 20, characterized in that the window closing the radiation chamber consists of a 15 to 40 mμ thick foil made of titanium or a titanium alloy, or of another metal foil (e.g. aluminum) with appropriate transparency for the electron beams.

25. The device according to claim 19 or 24, characterized in that the window closing the radiation chamber is provided with devices to clean and / or renew it continuously or discontinuously during operation and / or during breaks.

26. The apparatus according to claim 25, characterized in that the device consists of running or reversing winders and unwinders with stripping devices.

27. The apparatus for performing the method according to claim 15, 16, 17 or 18, characterized in that the radiation system consists of at least two radiation heads and a central electrical supply unit, the radiation heads being flanged equidistantly via T-shaped flanges to the supply unit, their outer shells form a common pressure vessel with that of the supply unit and the high-voltage poles of the accelerator heads are connected to the supply unit via feeds lying concentrically within the T-shaped flanges (FIG. 6).