Application of Electron Beams for the Treatment of VOC Streams

Department of Material Development, Japan Atomic Energy Research Institute, 1233 Watanuki,. Takasaki, Gunma ... The unification of a self-shielding el...
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Ind. Eng. Chem. Res. 2004, 43, 1185-1191

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Application of Electron Beams for the Treatment of VOC Streams Koichi Hirota,*,† Hiroki Sakai,‡ Masakazu Washio,‡ and Takuji Kojima† Department of Material Development, Japan Atomic Energy Research Institute, 1233 Watanuki, Takasaki, Gunma 370-1292, Japan, and Advanced Research Institute for Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku-ku, Tokyo 169-8555, Japan

Electron-beam technology is based on using radical reactions to destroy air pollutants. Twenty volatile organic compounds (VOCs) were irradiated with electron beams in a laboratory-scale apparatus to examine the influence of the chemical structures of the VOCs from an energetic point of view. The experiments showed that the electron-beam energy required for 90% treatment could be roughly estimated from their chemical structures. The unification of a self-shielding electron accelerator with a reactor could reduce capital costs for electron-beam systems. Electronbeam technology is a promising method for the treatment of VOCs. Introduction Volatile organic compounds (VOCs) have been used and released not only from stationary sources such as petroleum marketing, chemical manufacturing, and the solvent use, but also from mobile sources such as vehicles, ships, and planes. There is much concern about the emission of VOCs to the environment because they are very harmful to the human body. The intake of VOCs into the body causes acute toxic symptoms including headaches, nausea, and the stimulation of the eyes and nose. Long-term exposure to VOCs increases the risk of mutagenicity and carcinogenicity. In addition, the emission of VOCs causes photochemical oxidant formation, stratospheric ozone depletion, and tropospheric ozone formation. These phenomena result in negative effects on our health. The Government of Japan promulgated a law on pollutant release and transfer register (PRTR) in 1999.1 The PRTR requires industrial corporations to report periodically which pollutants are released, their quantities, and to which environmental media. Three hundred fifty-four substances are listed as pollutants in the PRTR registry, including many VOCs. Many efforts have been made to reduce VOC emission by installing treatment technologies, reducing the quantities used, and recycling. However, VOC emissions to the atmosphere accounted for more than 80% of the total emission of 898 308 t/year to the environment in 2001, according to reports from the industrial corporations handling pollutants listed in the PRTR registry and the estimation of pollutant emissions from nonregistered corporations, mobile sources, and households.2 Figure 1 shows the emission amounts of the 10 highest-ranked substances reported by the PRTR in 2001. These 10 substances, of which 8 are VOCs, account for approximately 70% of the total emissions. Toluene, ranked as the first, is released during chemical processes in the printing, plastics, and pulp industries. The control of VOC emissions is not enough to save our lives and the environment. * To whom correspondence should be addressed. Tel.: +81-27-346-9421. Fax: +81-27-346-9687. E-mail: hirota@ taka.jaeri.go.jp. † Japan Atomic Energy Research Institute. ‡ Waseda University.

Figure 1. Emission amounts of the 10 highest-ranked chemical substances in Japan.2

There are two categories for VOC-treatment technologies.3-5 One comprises technologies for recovering VOCs, in which adsorption (Ads), absorption (Abs), and condensation (Cnd) are involved. Figure 2 shows the characteristics of VOC-treatment technologies as a function of VOC concentration and flow rate. Adsorption can treat a wide range of VOC streams from 1 to 100 000 m3N/h at a concentration of 10-10 000 ppm, where VOCs are trapped by adsorbing materials such as activated carbons and hydrophobic zeolites. The trapped VOCs are then stripped by steam for reuse. The exchange of the adsorbing materials is required every 4-5 years to maintain the high performance of the adsorption activity. Absorption is the process in which a solvent for absorbing VOCs is water or organic liquid, depending on whether the VOCs of interest are soluble or insoluble in water. The solvent is reused after the VOCs are separated by decantation or distillation. A more highly concentrated VOC stream can be treated by condensation technology. Other technologies that can destroy VOCs involve thermal incineration (TI), catalytic incineration (CI), and nonthermal plasma (NTP)

10.1021/ie0340746 CCC: $27.50 © 2004 American Chemical Society Published on Web 01/22/2004

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Figure 2. Characteristics of VOC-treatment technologies as a function of VOC concentration and flow rate.3-5

treatment. Incineration is usually costly and produces significant amounst of CO2 when treating VOCs in concentrations below 100 ppm because the supplemental fuel is required for combustion. Catalytic incineration cannot treat a VOC stream containing sulfur, phosphorus, and halogens because of the deactivation of the catalysts. Electron beams and electrical discharges are nonthermal plasmas that can treat lowerconcentration VOC streams at flow rates of 10-1-105 m3N/h. Electron-beam technology was found to destroy organic substances on the order of parts per trillion in a study on the treatment of dioxins and furans (PCDD/ Fs) in a flue gas from a municipal solid waste incinerator.6 The treatment of VOCs by nonthermal plasma is based on reactions with active species such as OH, HO2, O3, and thermal electrons. These species are produced by ion-molecule, charge-transfer, and neutralization reactions of the basic components of air with N2+, O2-, N, O, etc. (namely, primary products) produced by the ionization and excitation of the basic components of air with electron beams or discharge plasmas. The electronbeam energy absorbed in a target stream can be expressed in terms of an absorbed dose in units of Grays (Gy, 1 Gy ) 1 J/kg). A dose of 1 kGy can provide an energy of 1.19 J/L to gases at ambient temperature. When air absorbs an electron-beam energy of 100 eV, the following active species are stoichiometrically produced7 100 eV

4.43N2 ' 0.29N2* + 0.885N(2D) + 0.295N(2P) + 1.87N(4S) + 2.27N2+ + 0.69N+ + 2.96e- (1) 5.377O2

100 eV

'

0.077O2* + 2.25O(1D) + 2.8O(3P) + 0.18 O* + 2.07O2+ + 1.23O+ + 3.3e- (2)

100 eV

7.33H2O ' 0.51H2 + 0.46O(3P) + 4.25OH + 4.15H + 1.99H2O+ + 0.01H2+ + 0.57OH+ + 0.67H+ + 0.06O+ + 3.3e- (3) 7.54CO2

100 eV

'

4.72CO + 5.16O(3P) + 2.24CO2+ + 0.51CO+ + 0.07C+ + 0.21O+ + 3.03e- (4)

The symbols such as 2D and 2P express the electric configurations of the atoms. For instance, O(3P) and

O(1D) are the triplet ground state and singlet excited state, respectively, of the oxygen atom. Penetrante et al. conducted VOC treatments using electron beams and pulse corona discharges, in which the discharge plasma required more energy to obtain same decomposition efficiency as the electron beam.8 Electron-beam technology is a promising method for treating VOCs at low concentrations. Many studies on the electron-beam treatment of VOCs have been performed at both the laboratory9-17 and pilot18-21 scales. However, few data are available for a feasibility study of this technology. It is very important to clarify how much electron-beam energy is required to destroy VOCs, as the energy accounts for a large part of operating costs of an electron-beam system. The aim of this study is to examine the influence of the chemical structure of the target VOC on electronbeam treatment from the energetic point of view. Twenty volatile organic compounds in the four groups of aromatics, aliphatics, and alicyclic hydrocarbons, and other toxic substances were irradiated to obtain the input energy required for 90% decomposition. Capital costs for electron-beam facilities for VOC treatment are estimated using the results presented in this work. The design of an electron accelerator with reactor is proposed for the economical treatment of VOCs. Experimental Section Reactor Experiments. Laboratory-scale experiments on electron-beam treatment were carried out for the 20 VOCs. Figure 3 shows a schematic flow of the electron-beam treatment system used. Sample gases containing the VOCs were prepared using a gas generator (GASTEC, permeater PD-1B-2) with a carrier gas of pure air (CO, CO2, CH4 < 1 ppm) and were diluted with air bubbling into water. Initial concentrations of 10 ppm in the sample gases were confirmed using a total organic carbon detector (Shimadzu, TOC-VCPH) before irradiation. A gas chromatograph (Shimadzu, GC-14B) placed downstream of the reactor [200 (length) × 70 (width) × 30 (height) mm3] was used to measure the concentrations of the VOCs during irradiation. Electron beams were generated by an electron accelerator (Iwasaki, Electrocurtain CB175/15/180LS) that supplied 170 kV with a current of up to 10 mA and were directly used to irradiate the sample gases through a thickness of 13 µm of titanium attached to a window [10 (length) × 70 (width) mm2] of the reactor. Gaseous substances, produced by the decomposition of the VOCs with electron beams, were analyzed using a Fourier transform infrared spectrometer (Perkin-Elmer, Spectrum 2000) having a gas cell with a 20-m path length at a resolution of 0.1 cm-1. The electron-beam energy absorbed by the sample gases was changed with the current of the accelerator. The temperature of the sample gases was controlled at 25 °C using a chiller (Taitec, CH-602BF) circulating water to cooling jackets attached to the top and bottom of the reactor. The water concentration in the sample gases was monitored using a moisture detector (Shimadzu, MAH-D). The total flow rate of the sample gases was 5 L/min, and the irradiation time was approximately 0.21 s. Air dosimetry was conducted using pure N2O gas to calculate a dose rate (kGy mA-1 s-1) in this system. This calculation is based on a nitrogen production of 10 molecules when an electron-beam energy of 100 eV is absorbed by pure N2O.22 When the current of the

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Figure 3. Schematic flow of an electron-beam treatment system. Table 1. Calculated Input Energy Densities (β), Scavenging Reaction Factors (γ), G Values, and Energies Required for 90% Decomposition (E90) VOC

Figure 4. Electron-beam treatment profiles of benzene (b), hexane (2), methanol ([), and cyclohexane (9).

accelerator was plotted against the concentration of nitrogen produced, an excellent linear relation was obtained with a regression coefficient of more than 0.99. The dose rate was determined to be 7.68 kGy mA-1 s-1. Experiments were started by electron-beam irradiation at a dose of 1-2 kGy when the initial concentrations of VOCs were steady at 10 ppm. Parts of the irradiated gases were sampled approximately 3 and 6 min after irradiation using the gas chromatograph and FTIR spectrometer. The current of the accelerator was increased after the sampling, and the same procedure was conducted up to 12 kGy. Reagents of purity higher than 97% were used in all experiments. All reagents were used without further purification. Results and Discussion Treatment of VOCs. The decomposition profiles of the 20 VOCs were examined at adsorbed doses ranging from 1 to 12 kGy. Figure 4 shows the remaining concentrations of the representative VOCs in the four groups. Fits to the experimental data points (solid lines in Figure 4) were obtained using the expression [X] ) [X]0 exp(-E/β)γ, where [X]0 is the initial concentration of VOCs, E is the input energy density (J/L), β is the experimental holding factor, and γ (0 < γ < 1) is the scavenging reaction factor.23 Volatile organic compounds having lower values of β can be decomposed with less

β (J/L)

γ

G value

E90 (J/L)

cyclohexane cyclohexene 1,3-cyclohexadiene 1,4-cyclohexadeine benzene

Group I 1.7 0.5 0.4 0.5 5.1

0.6 1.0 1.0 0.9 0.6

1.5 3.0 3.2 3.0 0.6

6.8 1.1 0.8 1.2 19.5

1-hexene trans-2-hexene trans-3-hexene

Group II 1.5 0.9 1.3 0.8 1.3 0.8

1.6 1.8 1.8

3.8 3.6 4.0

toluene o-xylene m-xylene p-xylene ethylbenzene

Group III 1.5 0.6 1.0 0.6 0.7 0.4 0.7 0.4 1.4 0.6

1.6 2.1 2.5 2.6 1.7

7.0 4.4 4.9 5.8 6.3

pentane hexane heptane

Group IV 3.7 0.5 3.3 0.6 3.2 0.7

0.8 0.9 0.9

17.2 13.0 10.2

Group V 2.8 0.7 1.3 0.5 33.0 0.6 75.5 0.5

1.0 1.8 0.1 0.04

9.7 6.7 150.3 387.4

methanol trichloroethylene acetone dichloromethane

energy input of electron beams. Given that the active species in eqs 1-4 can oxidize not only VOCs but also fragmentation substances produced by the reactions of the VOCs with the active species, scavenging reactions of the active species with the fragmentation substances impede the efficient oxidation of the VOCs. The influence of these scavenging reactions was corrected using the value of γ. Good fittings were obtained for benzene, hexane, cyclohexane, and methanol with β values of 5.1, 3.3, 1.7, and 2.8 and γ values of 0.6, 0.6, 0.6, and 0.7, respectively. This indicates that benzene required a higher energy to obtain 64% decomposition efficiency than the three other compounds. The scavenging reactions comparably did not occur in the irradiation of methanol. A variety of β and γ values were obtained from experiments on the treatment of the 20 VOCs, as shown in Table 1. Organic substances having CdC bonds in group I (carbocyclics with six carbons), group II (nolefins with six carbons), and group III (aromatics with substitutions) gave lower values of β (β < 2.0) as the bonds played the role of electron donors and readily reacted with the active species. The value of β decreased with increasing number of CdC bonds in group I. This

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is consistent with the results for hexane and hexenes. However, the treatment of benzene required much more electron-beam energy than did that of alicyclics in group I. The resonance structure of benzene resulted in a lower reactivity toward the active species. Substituted groups on the aromatic ring in group III also affected the reactivity, with the value of β decreasing with increasing number of substituents (-CH3) from toluene to xylenes. In group IV (n-paraffins), organic substances with long carbon chains readily succumbed to electron-beam treatment. It is very difficult to treat acetone and dichloromethane without the combination of any other treatment systems. In general, a higher reactivity (i.e., a lower value of β) of target VOC toward the active species depresses the scavenging reactions. However, the values of γ for the aromatics in group III are relatively lower than those for the alicyclics in group I. In an electron-beam process, a hydroxyl radical (OH), one of the active species, is considered to be an initiator for the oxidation of VOCs, similarly to reactions observed in the atmosphere.24-26 In atmospheric chemistry, the ring cleavage of aromatics having substituent groups at different positions was initiated through reactions with OH radicals and produced fragmentation substances having CdC bonds such as 3-hexene-2,5-dione, butenedial, and 4-oxo-2-pentenal.27,28 These fragmentation substances were probably produced by the irradiation of the aromatics in group III. They still had a high reactivity toward the active species, which induced the scavenging reactions. A chain reaction with trichloroethylene caused a higher reactivity with a lower value of γ.14 The number of molecules decomposed per 100 eV of electron-beam energy (G value) was calculated using the values of β and γ at the first stage of VOC oxidation (0-1 kGy), as shown in Table 1. Irradiation with electron beams at a lower dose reflects the initial stage of the oxidation through reactions with OH radicals produced by the irradiation. Consequently, straight lines in plots of log kOH vs G were obtained using the rate constants for reactions with OH radicals,29,30 as shown in Figure 5, with regression coefficients of 0.77, 0.72, 0.95, and 0.95 for the aromatics, alicyclics, aliphatics, and other toxic substances, respectively. The good relation for the each group indicates that the OH radicals play an important role in the initial oxidation of the 20 VOCs and that the degree of their contribution depends on the chemical structures of the VOCs. The last column in Table 1 lists the electron-beam energies required for a 90% treatment of the target VOCs (E90), which were calculated using the values of β and γ. The VOCs with lower values of E90 were readily oxidized with electron beams. In general, the electronbeam energy required for the treatment of a VOC stream is a very important factor, in addition to the flow rate and concentration, to determine the outline of an electron-beam system such as the specification of the electron accelerator and the design of the reactor. The value of E90 could not be obtained without electron-beam experiments because many radicals produced by the irradiation are associated with the oxidation of VOCs. However, if the value is estimated using proper figures without the experiments, it would be economically and technologically a great help in the design of an electronbeam treatment system. The values of E90 in Table 1 were plotted against the rate constants for the reactions

Figure 5. Correlation of rate constants for reactions with OH radicals and G values: (b) aromatics, (9) alicyclics, (2) aliphatics, ([) others.

Figure 6. Correlation of rate constants for reactions with OH radicals and input energies required for 90% treatment: (b) aromatics, (9) alicyclics, (2) aliphatics.

of OH radicals with the corresponding VOCs (kOH), as shown in Figure 6. Linear relations were obtained with regression coefficients of 0.48, 0.67, and 0.78 for the aromatics, alicyclics, and aliphatics, respectively. The lower coefficient for the aromatics was due to the high energy requirement of benzene oxidation, indicating that active species other than OH radicals contributed to the oxidation. The electron-beam energy required for 90% treatment of a target VOC can be estimated using the rate constants for reactions with OH radicals. Reaction Products. A few studies have been carried out for the identification of reaction products from the electron-beam irradiation of gaseous VOCs,11,31,32 in which CO2 and CO were the main gaseous products, with small amounts of organic acids such as formic, acetic, and R-ketoglutaric acids. Particles were also

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Figure 7. Carbon concentration ratios of CO2 + CO to VOCs oxidized by 90% with electron beams.

important products in the cases of aromatics, alicyclics, and aliphatics. Figure 7 shows the carbon concentration ratios of CO2 and CO for the VOCs oxidized by 90%. As predicted, significant amounts of CO2 and CO were produced from the VOCs whose fragmentation substances favored scavenging reactions (i.e., had lower values of γ), and higher ratios were obtained from the VOCs having lower values of γ such as benzene, toluene, cyclohexane, pentane, and hexane. However, lower possibilities for the scavenging reactions resulted in higher ratios in the case of the aromatics. For instance, the ratio for benzene oxidation (γ ) 0.6) was approximately twice that for p-xylene oxidation (γ ) 0.4). The ratios for the aromatics were related to the number of carbons in a given molecule rather than the degree of the scavenging reactions. When irradiated with electron beams, the aromatics having substituent groups gave rise to various kinds of fragmentation substances having higher reactivities for oxidation. Although the fragmentation substances scavenged the active species, they were not completely oxidized during irradiation. Cost for Destroying VOCs. An accelerator having a power of 1 kW can theoretically treat air pollution of approximately 2800 m3N/h at a dose of 1 kGy. However, electron beams generated by the accelerator lose some energy before being absorbed into the air pollution. There are two obstacles to absorption of the electronbeam energy. One is a sheet of metal foil attached to the reactor window. The material of the window is generally made of titanium. The other is air in the narrow gap between the outlet of the accelerator and the reactor window. This air gap can avoid the vacuum destruction of the accelerator by an impact when the metal window is accidentally broken. The extent of the energy loss caused by these obstacles depends on their thickness and density. For instance, electron beams accelerated at 300 kV lose approximately 18% of their energy at ambient temperature when penetrating an air gap of 2.5 cm and a titanium window with a thickness of 13 µm. Also, it is necessary to take the energy conversion from electricity to electron beams into account to determine the process efficiency [in units of (m3N/h)/kW] of an electron-beam system. Approximately 440 m3/h of air pollution containing VOCs with an E90 of 5.0 J/L would be treated by an electron-beam energy of 1 kW at ambient temperature when the total energy loss is 26%. Many accelerators (300-900 kV) have been installed at facilities to treat air pollution (1000-48 000 m3N/h)

Figure 8. Price of accelerator as a function of accelerator power in Japan. Table 2. Components of Annualized Costs (×103U.S.$) for 90% Treatment of VOCs capital cost utilities maintenance recovered solvent credit net annualized costs

electron beam

carbon adsorption

5200 750 90 0 1187

5800 5000 250 25 5612

containing VOCs, dioxin, and NOx in our feasibility studies of an electron-beam system. The prices of the accelerators had a linear relation against their power, as shown in Figure 8. This linear relation indicates that 1 W of accelerator power costs approximately 10 U.S.$ in Japan. This is higher than international costs reported by Frank33 and Paur.34 However, electron-beam technology presents an economic advantage in the treatment of VOCs. As shown in Figure 2, an adsorption technology is a competitor when treating a lower concentration of VOCs. Thus, annualized costs are estimated for electron-beam and carbon adsorption systems. Table 2 provides annualized costs for the systems to treat a VOC stream of 40 000 m3N/h at a concentration of less than 100 ppm. An electron-beam system consists of two accelerators (300 kV, 500 mA), reactors, chillers, an induced fan, and a house installing these pieces of equipment to obtain more than 90% decomposition of VOCs at a dose of 15 kGy. If many particles are produced during irradiation, they should be dissolved in water and irradiated with electron beams again. A treatment unit for the wastewater is included in the capital cost. Utilities for the electron-beam system include electricity to all equipment. The electricity cost is based on an estimate of $0.125/kWh. A carbon adsorption system usually has two fixed beds of activated carbon. One fixed bed of activated carbon undergoes steam regeneration while the other is treating a VOC stream. The steam contaminated with the VOC vapor is condensed, after which the VOC and water can be separated for reuse of the organic solvent. The carbon adsorption system includes the units, steam generators, and condensers. The electricity cost for the steam accounts for approximately 65% of the utilities.

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Figure 10. Proposed unit of an electron accelerator with a reactor.

Figure 9. Capital costs for electron-beam systems with house(b) and self- (9) shielding as a function of accelerator price.

Carbon replacement assuming a 5-year life costs $170,000/year. Recovered solvent credit should be included as a part of the annualized cost. Depending on the value of recovered solvents, this credit was estimated to be $25,000. The estimation of the net annualized costs was based on a 15-year operation of the systems, indicating that the electron-beam system is economically viable for the treatment of VOC streams. The reuse of recovered solvents in the adsorption system provides a good example of environmentally friendly technology. The type of accelerator used affects the price of a house for installing an electron-beam system. In general, X-rays (bremsstrahlung) generated using more than middle voltage of accelerators (>300 kV) have to be shielded by surrounding the house with a wall of thick concrete (namely, house-shielding), which raises capital costs for the system. In contrast, a low-energy accelerator itself can be covered with lead to shield X-rays (namely, self-shielding), so that no other shielding is required. Figure 9 shows capital costs for electronbeam systems with house- and self-shielding as a function of accelerator price. The electron-beam systems with the house-shielding raise the capital costs by a factor of 3 compared those with self-shielding. This estimation is based on the installation of one accelerator in an electron-beam system. The following relations were obtained from this figure concerning VOC treatment with electron beams

capital costs (million U.S.$) ) 1.68 × 10-6

QE90 + 5.90 (6) f1f2

Conclusions

capital costs (million U.S.$) ) 1.51 × 10-6

Capital costs for electron-beam systems with self- and house-shielding can be obtained from eqs 6 and 7, respectively. A self-shielding system having one accelerator (300 kV, 500 mA) could treat a VOC stream of ∼30 000 m3N/h as many VOCs have E90 values of less than 10 J/L, as shown in Table 1. Thus, it is worth choosing one middle-energy (house-shielding) or a few low-energy (self-shielding) accelerators for the treatment of a VOC stream at a flow rate of more than approximately 30 000 m3N/h. When a few accelerators are installed, the total cost can be calculated by the sum of the capital costs and the accelerator price. Design of an Electron Accelerator with a Reactor. A basic study on the treatment of air pollutants was required at the laboratory scale for the construction of electron-beam facilities.35 Each facility had its own design to meet the demand of target treatment performance, which took much investment and time. Part of the design should be combined to save effort. One effective way of combining can be achieved by the unification of an electron accelerator with a reactor as an irradiation zone is the most important part and costly in an electron-beam system. Figure 10 shows a proposed unit of an electron accelerator with a reactor. The unit consist of a self-shielding accelerator supplied at 300 kV and a reactor with dimensions 200 (length) × 150 (width) × 50 (height) cm3. The window of the reactor is coated by a 13-µm titanium foil, and the air gap between the outlet of the accelerator and the window is 2.5 cm. The total energy loss in this unit, i.e., the value of f1f2 in eq 6, is 0.74. This loss reduces the range of electron beams in the VOC stream inside the reactor from 60 to 50 cm at ambient temperature, which reflects the design of the reactor. This unit can treat a VOC stream with a process efficiency of 2000/E90 [(m3N/ h)/kW].

QE90 + 1.58 (7) f1f2

where Q is the flow rate of the VOC stream (m3N/h); f1 (0 < f1 < 1) is the energy loss factor for the two obstacles, as previously described; and f2 (0 < f2 < 1) is the energy conversion factor from electricity to electron beams.

The irradiation of the 20 VOCs showed that electronbeam technology is a promising method for the treatment of aromatics, alicyclics, aliphatics, methanol, and trichloroethylene. The chemical structures of these compounds affected the energetic figures of an electronbeam technology such as the G value and electron-beam energy required for 90% treatment (E90). These values were roughly estimated from the rate constants for

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reactions with OH radicals, which are technologically and economically helpful for the application of an electron-bam system at the industrial scale. The cost analysis showed that a system having a self-shielding accelerator provided an advantage for the treatment of VOCs at a flow rate of ∼30 000 m3N/h. The unification of a self-shielding accelerator with a reactor is important in reducing the capital costs of the system, which supports the introduction of this technology to the market. Literature Cited (1) Japan Ministry of the Environment. Law Concerning Reporting, etc. of Releases to the Environment of Specific Chemical Substances and Promoting Improvements in Their Management. Provisional English translation available at http://www.env.go.jp/ en/lar/law-prtr/index.html (accessed Nov 2003). (2) Japan Ministry of the Environment. Emission Inventory of Chemical Substances. Available at http://www.prtr-info.jp/index.html (accessed Nov 2003) (in Japanese). (3) Control Techniques for Volatile Organic Compound Emissions from Stationary Sources; U.S. Environmental Protection Agency, U.S. Government printing Office: Washington, DC, 1994. (4) Dueso, N. In Characterization and Control of Odours and VOC in the Process Industries; Vigneron, S., Hermia, J., Chaouki, J., Eds.; Studies in Environmental Science 61; Elsevier: New York, 1994; pp 263-276. (5) Odic, E.; Paradisi, M.; Rea, M.; Parissi, L.; Goldman, A.; Goldman, M. In The Modern Problems of Electrostatics with Applications in Environment Protection; Inculet, I. I., Tanasescu, F. T., Cramariuc, R., Eds.; NATO Science Series; 2. Environmental Security 63; Kluwer Academic Publishers: Dordrecht, The Netherlands, 1999; pp 143-160. (6) Hirota, K.; Hakoda, T.; Taguchi, M.; Takigami, M.; Kim, H.; Kojima, T. Application of Electron Beam for the Reduction of PCDD/F Emission from Municipal Solid Waste Incinerators. Environ. Sci. Technol. 2003, 37, 3164. (7) Ma¨tzing, H. In Proceedings of an International Symposium on Applications of Isotopes and Radiation in Conservation of the Environment; IAEA-SM-325/186; Unipub AS: Oslo, Norway, 1992; pp 115-124. (8) Penetrante, B. M.; Hsiao, M. C.; Bardsley, J. N.; Merritt, B. T.; Vogtlin, G. E.; Kuthi, A.; Burkhart, C. P.; Bayless, J. R. In Environmental Applications of Ionizing Radiation; Cooper, W. J., Curry, R. D., O’Shea, K. E., Eds.; John Willey & Sons: New York, 1998; pp 305-323. (9) Han, D. H.; Stuchinskaya, T.; Won, Y. S.; Lim. J. K. Oxidative Decomposition of Aromatic Hydrocarbons by Electron Beam Irradiation. Radiat. Phys. Chem. 2003, 67, 51. (10) Hirota, K.; Arai, H.; Hashimoto, S. Electron-beam Decomposition of Carbon Tetrachloride in Air/Nitrogen. Bull. Chem. Soc. Jpn. 2000, 73, 2719. (11) Hirota, K.; Hakoda, T.; Arai, H.; Hashimoto, S. Electronbeam Decomposition of Vaporized VOCs in Air. Radiat. Phys. Chem. 2002, 65, 415. (12) Kim. H.-H.; Hakoda, T.; Kojima, T. Decomposition of Gasphase Diphenylether at 473 K by Electron Beam Generated Plasma. J. Phys. D: Appl. Phys. 2003, 36 473. (13) Kim, J.-C. Factor Affecting Aromatic VOC Removal by Electron Beam Treatment. Radiat. Phys. Chem. 2002, 65, 429. (14) Nichipor H.; Dashouk, E.; Chmielewski, A. G.; Zimek Z.; Bulka, S. A Theoretical Study on Decomposition of Carbon Tetrachloride, Trichloroethylene and Ethyl Chloride in Dry Air under the Influence of an Electron Beam. Radiat. Phys. Chem. 2000, 57, 519. (15) Nichipor, H.; Dashouk, E.; Yacko, S.; Chmielewski, A. G.; Zimek, Z.; Sun, Y. Chlorinated Hydrocarbons and PAH Decomposition in Dry and Humid Air by Electron Beam Irradiation. Radiat. Phys. Chem. 2002, 65, 423. (16) Vitale, S. A.; Hadidi, K.; Cohn D. R.; Bromberg, L. Decomposition of 1,1-Dichloroethane and 1,1-Dichloroethene in an Electron Beam Generated Plasma Reactor. J. Appl. Phys. 1997, 81, 2863.

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Received for review August 18, 2003 Revised manuscript received November 11, 2003 Accepted December 17, 2003 IE0340746