DE19740401C1 - Process breaks down industrial particulate or gaseous wastes in foam - Google Patents

Abstract

A process and assembly oxidize pollutants and other organic substances in gases, fluid and matrices of suspended solids especially during the oxidative use of electron beam processes. The substance that is to be treated is surrendered as a solution, a suspension, or gas, into a body of foam having fine bubbles and liquid, into which a liquid bearing an oxidizing agent has been sprayed. The ratio of liquid to gas is in the range from 3 to 1,000 m<3> and the foam is from 1 to 50 cm thick. The pollutants held in the foam are continually subjected to electron beam radiation at an energy level of between 0.05 and 15 MeV. An oxidizing agent is introduced to the foam while the foam is subjected to the radiation beam. Each electron beam passes through a succession of many bubbles and the enclosed gas, especially oxygen, generates ozone which is immediately and finely distributed throughout the foam. The substance in question is consumed by ozone, and not by other oxidizing substances or other organic or inorganic substances whose removal is required. A suitable assembly consists of: (I) a reaction chamber (1) (II) with a jet (2) (III) and with a fluid inlet pipe (3), (IV) a gas inlet (5), (V) a drain (4) to a droplet separator (6), (VI) an electron beam emitter (7) directed at the reaction zone (15), (VII) pumps (8), (VIII) blowers (9), (IX) dosing assembly (10) (X) and regulator (11).

Description

The invention relates to a method and the associated Device for the oxidative treatment of pollutants and other organic substances in gaseous, liquid and suspended solid matrices, the method in particular re improves the oxidative effect of electron radiation.

DE 36 25 232 A1 describes the degradation of polyhalogens hydrocarbons in thin aqueous layers electron beams accelerated with 150-350 kV.

When treating aqueous solutions, the electro Nen rays are usually produced by falling films or otherwise thin layers. The usable layer thickness is thereby determined by the penetration depth of the electron beams, the depends on the applied acceleration voltage and at the used electron accelerators between 0.1-2 cm is.

WO 97/13554 describes a process for breaking down organic pollutants, in which suspensions of luminophoric solids are irradiated with electron beams of 0.05 to 20 MeV in the acidic pH range and in the presence of H ₂ O ₂ or carboxylic acid.

DE 42 16 776 A1 relates to a detoxification process for halogenated aromatic hydrocarbons, in which a solution is kept in a fluidized bed by pumping around and, with simultaneous separate supply of an oxidizing agent such as ozone or H ₂ O _2, irradiation with ultraviolet light takes place.

While treating flue gases with electrons already radiate several plants in Japan, the USA and Poland Are used, the electron irradiation includes aqueous solutions Despite the many years of developments, the status of the Technology. In addition to high investment costs, this is also a good thing more specific sales and sometimes undesirable side breaks the causes. For example, in the case of electrons irradiation of polychlorinated dibenzodioxins and furans par allel to the desired oxidative breakdown also low chlo congeners that are more toxic than the octa chlorinated starting compounds. Cause of this dechlorination are reactions with hydrogen or other reducing agents Radiation products that coexist with hydroxyl radicals and other oxidizing radiation products the.

When the accelerated electrons are decelerated in aqueous layers, water molecules in H ₂ O ⁺ and e ^{- are} ionized along the electron path. H ₂ O ⁺ reacts in the course of 10 ^-12 s with neighboring water molecules with the formation of hydroxyl radicals (OH ^. ) And hydrogen ions (H ₃ O ⁺ ). The hydroxyl radicals have a high oxidation potential (2.8 V) and are significantly involved in the oxidative degradation of organic compounds. The released electrons e ^- can be hydrated by water molecules (e ^- _aq ) or form water molecules (H ₂ O *) excited with water ions, which in turn form hydroxyl radicals, hydrogen and hydrogen radicals.

In the electron irradiation of aqueous solutions, oxidizing and reducing reactive species are inevitably formed after about 10 ^-6 s, which react with the water constituents or with one another.

The reaction of the reducing species with hydroxylradi kalen leads to loss of yield and reduce the reaction the species with organic chlorine compounds mostly leads to undesirable dechlorination processes.  

The process known to date is also known Use of oxidizing chemicals, preferably hydrogen peroxide, which, however, increase operating costs. At height Ren hydrogen peroxide concentrations was with UV irradiation also a radical scavenger effect against hydroxyl radicals len observed (Schulte, P. et al., WLB Wasser, Luft und Boden 9/1991, pp. 55-58), which led to a reduction in yield. The proportion can also be reduced with pretreatment with ozone render species not critical during irradiation be reduced since ozone is only soluble in water to a limited extent is and the dissolved ozone due to its high reactivity (Oxidation potential 2.07 V) through other ingredients up to for radiation has already been largely eliminated.

The invention is therefore based on the object partially reducing species in electron radiation to reduce siger, especially aqueous systems and thus to improve the oxidative degradation of organic substances.

Another object of the invention is to provide provision of a method and a device with which Liquids or gases pollutants continuously and almost can be completely removed.

According to the invention, the process for the oxidative degradation of pollutants by electron radiation consists in that a substance to be treated in the form of a solution, a suspension or a gas is fed to a foam-like structured gas-liquid zone with finely divided gas bubbles in the liquid, the liquid-gas Ratio is in the range of 3 to 800 l / m ³ , and the foam zone formed in a reaction space of 1 to 50 cm in height with the pollutants contained therein is continuously exposed to electron beam radiation with an energy of 0.05 to 150 MeV.

When irradiating this dynamic foam zone through each electron beam penetrates several aqueous and gaseous ones Areas. When penetrating the gas, e.g. B. forms of air the electron beam from oxygen the effective oxidation medium ozone, due to the fine gas-liquid distribution immediately after  its formation is evenly distributed in the foam zone. This ensures that reducing species by ozone ver need and not with oxidizing species or decompose organic or inorganic substances can.

An additional advantage of the solution according to the invention is that pollutant molecules in a first Reaction step directly through the electron beams or were attacked by the generated hydroxyl radicals the ozone formed is further oxidatively degraded before it stabilize again with the formation of new pollutants can. An example of this is the formation of polychlorinated Dibenzofurans from polychlorinated dibenzodioxins in the conventional radiation in thin layers.

Parallel to the formation of ozone, electron beams are used Air also forms nitrogen oxides, which also reduce emissions binding species.

The foam zone according to the invention is advantageously by Spray the liquid through nozzles and introduce the gas generated in countercurrent to the sprayed liquid. It can by adjusting the liquid / gas ratio for e.g. B. the carrier medium water and the carrier gas air a desired Height of the foam zone depending on the type of nozzle and - Arrangement obtained from a specialist without any particular problems the. If necessary, one with pollutants or medium enriched with other organic compounds, in which due to a certain self-foaming power added hesitantly or provided foam-destroying measures can be.

Standard nozzles with perforated plates are suitable as nozzles or swirl inserts with which the rivers to be irradiated liquid together with the countercurrent gas, which, for. B. is sucked in, producing fine and very fine bubbles of foam can.

Oxygen or an oxygen / stick is suitable as the gas substance-gas mixture, e.g. B. air. The gas can pass after passing through the  Foam zone and if necessary passing another wash step back into the circuit with the liquid to be treated be used in the process, whereby any cleaning of small amounts of residual ozone can be eliminated.

The foam zone formed according to the invention can be advantageous have a height of 3 to 20 cm, but the height or Thickness of the foam zone strongly depends on the liquid-gas ratio and is dependent on the radiation dose.

This foam zone is also advantageous in one tubular reaction chamber formed.

The parameters of the electron radiation with a single Flow of sprayed liquid through the foam zone can be set as follows: radiation dose 0.3 to 500 kGy, beam current 1 to 50 mA, acceleration energy 0.05 up to 15 MeV. In another run, e.g. B. in rows circuit, for example, the radiation dose can also ge be changed.

The pollutants to be removed or other organi substances can be dissolved or suspended in the carrier media available.

The method according to the invention differs by the one that occurs immediately in the irradiated liquid Ozone formation fundamentally thinner from electron radiation Layers and other known treatment solutions Irradiation with the addition of oxidizing agents.

In contrast to known methods of irradiation thin layers is made possible by the new process without the addition of Oxidizing agent the proportion of reducing species clearly reduced and thus the radiation energy related sales increased and undesirable reduction reactions excluded or greatly reduced.

A particular problem when irradiating thin layers ten are the shallow penetration depth of the electron beams and the concentration gradients caused by laminar flow in the border areas of the penetration depth. Because the depth of penetration depends on the mass per unit area of the irradiated medium  in the method according to the invention depending on the liquid gas Ratio a mixture with 2-10 times thicker layers be irradiated as water.

Concentration gradients are within the dynamic Foam zone balanced. The random uneven distribution The solution particles in the radiation zone are treated with several pumping cycles eliminated during the irradiation.

In the known arrangements for radiation possible throughput and duration of irradiation by the flow of the irradiated layer and the dimensions of the emitter given.

Another problem with known technical radiation is the necessary uniformity of the layer thickness with usual beam window widths of about 1 m. Even Liquid layer thicknesses from about 5 mm are in pure solutions possible. In solids-laden solutions and in smaller ones Layer thicknesses, on the other hand, must have a yield-reducing difference moderations are calculated, so that in these plants to Compensation for thicker layers and thus stronger electrons accelerators with higher energies are required.

The variability of the new process allows for the greater layer thickness and the continuous multiple radiation also the use of smaller electron accelerators with lower acceleration energies and less shielding tion, so that mobile systems can be erected more easily.

The liquid-gas ratio can be used by the th nozzle type can be varied over a wide range. So that is a simultaneous treatment of waste water and waste air in one Irradiation device possible, which makes the application possible significantly expand the possibilities of the new process.

The variability of throughput and irradiation time new plant also enables treatment of large water quantities with low radiation doses, by which a kill bacteria, viruses and other harmful germs.

Because the air from the radiation room through the foam zone  is sucked, the ozone formed in the radiation room be used in addition and does not have to be required Exhaust air purification systems are decomposed.

The method according to the invention can be carried out that either the foam zone from a carrier gas and a generates the liquid medium containing pollutants, or the foam zone from a gas containing the pollutants and generated in a liquid medium, or the foam zone from a gas containing pollutants and a liquid medium containing pollutants.

As pollutants by the inventive method can be converted into environmentally neutral materials probably organic pollutants, such as B. dioxins as well as anorga niche pollutants in question.

The invention also relates to a device for treatment treatment of pollutants by electron radiation, marked net through a reaction space with at least one therein perpendicular to the upper end of the reaction chamber arranged nozzle, feed Lines for a liquid medium to the nozzle, one above the nozzle and in the upper part of the reaction chamber Gas supply, a discharge line arranged below the nozzle to a droplet separator, one outside the reaction area mes above the nozzle vertically or horizontally to the zone above the electron beam device, pumps, Blowers and regulators for regulated funding the material flows and means for deriving the cleaned rivers liquids or gases.

There can be several nozzles in different positions can be arranged to each other to a desired shape and / or To generate the size of the foam zone.

The method according to the invention is advantageously carried out in this way performed that in a tub under the entire radiation zone 1-30 open reactor tube modules arranged on both sides are par according to the respective task allelic or in series.  

The liquid to be irradiated is fed to the modules via side connecting pieces with a pressure of 2-10 bar and atomized upwards in the tube through a nozzle. The liquid throughput depends on the pipe diameter and the type of nozzle and is, for example, for a pipe with a nominal diameter of 100 (100 mm diameter) between 0.3 and 3 m ³ / h.

In countercurrent, a gas, e.g. B. Air sucks ge through the foam zone formed with this gas and led below the nozzle to a drop separator. With the quantities of liquid specified above, the quantities of air drawn through are between 0.3 and 1000 Nm ³ / h.

The pressure loss across the foam zone is depending on Flow 5-30 mbar.

Another advantage of the solution found is that the radiation takes place in several reactor tube modules, which can be connected in parallel or in series, so that a high adaptability in terms of throughput and irradiation time is possible.

The droplet separator and reaction tube stand with the bottom open ends in the tub in which the draining Collect solutions and the next reaction via circulation pumps modules are fed or pumped out. Through intermediate weirs the material flows are assigned to the corresponding cycles net.

Because the system used works with a low vacuum and advantageous z. B. ambient air is sucked in Reaction tubes from individual segments through plug connections be assembled so that easy disassembly and Cleaning is possible.

A further improvement in the effectiveness of the device can be installed by installing a grid or net at the level of Connection with the electron beam effective area the foam zone in which the grid or mesh is made with a connected or unconnected layer, which consists of one or more substances which are responsible for the  catalytic ozone fission are effective. Such substances are z. B. Mixed oxides, which are approximately 20% by weight of CuO and 50% by weight from MnO or, for example, from iron oxide and manganese oxide stand.

The invention is illustrated below by examples are explained. Show in the accompanying drawing

Fig. 1 Schematic representation of the method according to the invention and the device components.

The device consists of a reaction chamber 1 with a nozzle 2 arranged therein perpendicular to the upper end of the reaction chamber 1 ; a feed line 3 for a liquid medium to the nozzle 2 , the medium forming a foam zone above the nozzle during atomization and mixing with gases; an air supply 5 arranged above the formed foam zone in the upper part of the reaction space 1 , a discharge line 4 arranged below half the nozzle 2 to a droplet separator 6 located outside the reaction space, one above the nozzle 2 and outside the reaction space arranged vertically to the foam zone 15 above the nozzle commercially available electron beam device 7. Furthermore, pumps 8 , blowers 9 , metering devices 10 and regulating devices 11 for regulated conveyance of the material flows and devices for discharging the cleaned liquids or gases are provided, for. B. A filter 13. To protect the beam exit, a protective film 14 is provided with a beam window located therein. In the foam zone 15 , a grid 16 can be arranged with catalysts.

All of the following sample examinations were performed using air as Gas and solutions from the specified ingredients in ent salted water (deionized).

example 1

7 l of a solution with 493 mg / l of the dye rhodamine B and 280 mg / l of a defoamer were acidified to pH 3 with sulfuric acid and irradiated with the following parameters:

• - Reaction tube diameter: 100 mm
• - Solution throughput: 1200 l / h
• - Solution form: 0.3 MPa
• - Air flow: 120 m ³ iN / h *
• - Pressure drop in the foam zone: 1 kPa
• - Thickness of the foam zone approx .: 3 cm
• - Acceleration voltage: 1.5 MeV
• - Beam current: 7.2 mA
• - absorbed radiation dose: 40 kGy
  * m ³ air in standard condition per hour

The rhodamine B content decreased by 399 mg / l to 93.8 mg / l. This corresponds to a breakdown of 10 mg / kGy absorbed radiation.

Example 2

900 g puncture-proof, dioxin-contaminated sewage sludge (dry substance TS) - Content 128 g / kg) was suspended in 7 l of deionized water. This suspension was in an apparatus according to the above described parameters irradiated with a dose of 120 kGy. In Table 1 below are the values for 5 dioxin cones genere in the feed and in the treated suspension specified. Congeners are chemical compounds with the same Molecular structure, which is distinguished only by the number and arrangement differentiate individual atoms.  

Table 1

Due to the radiation, all congeners became a extensive reduction of dioxins achieved. In the irradiated In suspension, the sum of the PCDD was only 2.4% of the end current value.

Example 3

With otherwise the same parameters as in example 2, except that the foam zone was 10 cm irradiated with a dose of 200 kGy.

In Table 2 below, the values for 5 are Dioxin congeners in international toxicity equivalents (I - TE) ng / kg dry matter (TS) in the feed and in of the treated suspension.  

Table 2

Due to the radiation, all congeners became a extensive reduction of toxicity equivalents achieved. In the irradiated suspension was the sum of the toxicity equivalents only 7.2% of the initial value.

Example 4

The following Table 3 shows that according to the Invention according method and in contrast to previously known Ver driving results despite high dioxin breakdown rates additional furans are formed, but also the conces tration of polychlorinated dibenzofurans is reduced. With the same parameters as in Example 1, a Irradiated dose of 120 kGy.  

Table 3

The radiation was used despite extensive degradation the dioxins still a simultaneous breakdown of the furans by one Third reached. This confirms that through the existing Ozone accelerates the oxidative degradation of dioxins and one Stabilization of the opened dioxin ring molecules by Fu ring formation is reduced.

Example 5

7 l of a solution with 16.3 mg / l As ₂ O ₃ were irradiated at pH 8 and the same parameters as in Example 1. After irradiation, the As ₂ O ₃ content was less than 0.5 mg / l. Over 97% of the trivalent arsenic was oxidized to the pentavalent arsenic, which is easier to separate by precipitation with iron salts from drinking water.

The following comparative examples show results with the same electron accelerator when irradiated in thin layers (3-4 mm) were.  

Comparative Example 1

In previous attempts, a solution with the 12-fold was low rigorous concentration of 80 mg / l rhodamine B and a ver comparable detergent additive of 260 mg / l in trays a layer thickness of 3 mm with 1.5 MeV electron gun and a dose of 5 kGy. The ge found residual concentration after irradiation was 18.9 mg / l, corresponding to a reduction of 21.1 mg / l or 4.2 mg / kGy absorbed radiation.

The specific rhodamine breakdown was therefore less than half of the breakdown at radiation after invent method according to the invention.

Comparative Example 2

Suspensions were made from 1.25 l of demineralized water and 247 g of the sewage sludge used in Examples 2-4 and several samples were irradiated with different additives in flat dishes with layer thicknesses of 3-4 mm with the following parameters:

• - Acceleration energy 1.5 MeV
• - Beam current: 7.2 mA
• - absorbed radiation dose: 450 kGy

For better comparability, the results were based on Converted equal amounts of dry matter sewage sludge. In Table 4 below, the values are the best Sample for 5 dioxin congeners in the feed and in the treated suspension specified.  

Table 4

Despite the larger absorbed dose, the "static" radiation in thin layers with all con genere achieved a lower degradation of the dioxins than in the radiation in the foam zone elec electron beam reactor. In the "static" radiation was the sum of the PCDD is 5.3% of the initial value, while in the foam zone electron beam reactor according to the invention despite lower dose was reduced to 2.4%.

Comparative Example 3

In Table 5 below, the values for 5 are Dioxin congeners in international toxicity equivalents (I - TE) ng / kg dry matter (TS) in the feed and in the best sample of the "static" irradiated suspension give.  

Table 5

Despite the larger absorbed dose, the "static" radiation in thin layers with all con are less likely to decrease toxicity equivalents achieved than with the irradiation in the invention Foam zone reactor. In the "static" radiation was the sum of the toxicity equivalents 19.3% of the starting value tes while in the foam zone reactor despite lower Dose was reduced to 7.2%.

Comparative Example 4

The following Table 6 shows that after the conventional radiation processes at high dioxin degradation rates additional furans are formed.

In Table 6 below, the values of the be Most sample for 5 dioxin congeners in the feed and in of the treated suspension. Here too was again with the same parameters as in Comparative Example 1, with irradiated at a dose of 450 kGy.  

Table 6

By breaking down the dioxins in the "static" loading Radiation in layers were due to insufficient ozone concentration furans additionally formed in the suspension, so that their share increased by 19%.

The results show that the inventive Process against electron radiation from thin, homogeneous layers significant improvements in the Zer Settlement of poorly degradable polychlorinated dibenzofurans and polychlorinated dibenzodioxins.

Even for simpler pollutants, the advantages of the new process mentioned give better results, so that a broad, cost-effective application is possible in the following areas:

• - Dyeing effluent from the textile industry with the following Dye groups: direct dyes, reactive dyes, acid re or metal complex dyes, disperse dyes
• - Carbon disulfide (CS ₂ ) -containing exhaust air and waste water from viscose silk production or from extraction processes
• - Groundwater containing herbicides or pesticides from earlier agricultural applications
• - Exhaust air and waste water from the pharmaceutical industry Solvents and extractants (aromatics, chlorinated hydrocarbons substances) or special preservatives (e.g. thiomer sal)
• - Exhaust air and waste water from the chemical industry with oxi formable inorganic (sulfides, cyanides, nitrites, arsenic te) and organic (amines, sulfonic acids, mercaptans, Disulfides, thiophenols, phosphonic acids) ingredients
• - Waste water from the pulp industry with poorly degradable Lignin components
• - Cyanide and nitrite-containing hardening ice salts from steel Industry
• - Wastewater from metal processing and manufacture of Products of the electroplating industry with cyanides, complex Cyanides, nitrites, sulfides, selenides, thiocyanates, com plex compounds from NTA, EDTA, citric acid, tartaric acid with Copper, nickel, zinc, cadmium
• - Drinking water treatment with disinfection, elimination annoying odors and colorings, as well as improvement the separability of harmful ingredients such as humic acid bound iron or manganese, arsenite, organochlorine ver bonds

Claims (19)

1. A process for the oxidative degradation of pollutants by electron radiation, characterized in that a substance to be treated in the form of a solution, a suspension or a gas of a foam-like structured gas-liquid liquid zone with finely divided gas bubbles in the liquid, the liquid being supplied Gas ratio is in the range of 3 to 800 l / m ³ , and the foam zone formed in a reaction space of 1 to 50 cm in height with the pollutants contained therein is continuously exposed to electron beams with an energy of 0.05 to 15 MeV . 2. The method according to claim 1, characterized in that the foam zone by spraying the liquid through nozzles and introducing the gas in counterflow to the sprayed rivers liquid is generated. 3. The method according to claim 2, characterized in that spraying through nozzles with built-in perforated plates and / - or swirl devices. 4. The method according to claim 1, characterized in that as gas oxygen or an oxygen-nitrogen gas mixture is introduced. 5. The method according to any one of claims 1 to 4, characterized ge indicates that the gas is circulated. 6. The method according to any one of claims 1 to 5, characterized ge indicates that this is in countercurrent to the sprayed rivers  liquid passed after passing through the foam zone liquid medium contaminated or unpolluted is directed through. 7. The method according to claim 1, characterized in that a foam zone with a height of 3 to 20 cm is created. 8. The method according to claim 1, characterized in that the foam zone is formed in a tube as a reaction space becomes. 9. The method according to claim 1, characterized in that the parameters of the electron radiation with one pass run the sprayed liquid through the foam zone like can be set as follows: radiation dose 0.3 to 500 kGy, Beam current 1 to 50 mA, acceleration energy 0.05 to 15 MeV. 10. The method according to claim 1, characterized in that one the foam zone from a carrier gas and one the harmful produced liquid medium containing substances. 11. The method according to claim 1, characterized in that one the foam zone from a containing the pollutants Gas and a liquid medium generated. 12. The method according to claim 1, characterized in that the foam zone from a gas containing pollutants and a liquid medium containing pollutants. 13. The method according to any one of claims 1 to 12, characterized ge indicates that air is the carrier gas and liquid medi to be used for water. 14. The method according to any one of claims 1 to 13, characterized characterized in that in the foam zone acting catalytically  Solids for ozone decomposition are introduced in the form of a or more grids coated with the catalyst or Networks or a catalyst lying on a network layer. 15. A device for performing the method according to claim 1, characterized by a reaction chamber ( 1 ) with at least one therein arranged perpendicular to the upper end of the reaction chamber ( 1 ) nozzle ( 2 ); Feed lines ( 3 ) to the nozzle ( 2 ) for a liquid medium; a gas supply ( 5 ) arranged above the nozzle ( 2 ) and in the upper part of the reaction space ( 1 ); a discharge line ( 4 ) to a droplet separator ( 6 ) arranged below the nozzle ( 2 ); one above the nozzle ( 2 ) and outside the reaction chamber ( 1 ) vertically or horizontally to the zone ( 15 ) above the nozzle arranged electron beam device ( 7 ); Pumps ( 8 ); Blower ( 9 ); Dosing devices ( 10 ) and regulating devices ( 11 ) for the regulated conveyance of the material flows and means for discharging the cleaned liquids or gases and for protection against uncontrolled electron beam leakage. 16. The apparatus according to claim 15, characterized in that the reaction chamber is tubular. 17. The apparatus according to claim 16, characterized in that the tubular reaction space vertically in a tub with the treated or to be treated liquid medium stands. 18. The apparatus according to claim 16 or 17, characterized records that several tubular reaction spaces, in particular one of the beam window area of the electron beam direction corresponding cross-sectional area on tubular Reaction rooms, parallel or in series to a reactor dul are united.   19. The apparatus according to claim 18, characterized in that the reaction spaces by shut-off devices, in particular Weirs are separated.