Flue gas cleaning in power stations by using electron beam technology. Influence on PAH emissions

Fuel Processing Technology 88 (2007) 251 – 258 www.elsevier.com/locate/fuproc

Flue gas cleaning in power stations by using electron beam technology. Influence on PAH emissions M.S. Callén a , M.T. de la Cruz a , S. Marinov b , R. Murillo a , M. Stefanova b , A.M. Mastral a,⁎ a

b

Instituto de Carboquímica (CSIC), 50080 Zaragoza, Spain Institute of Organic Chemistry, Bulgarian Academy of Sciences (BAS), 1113 Sofia, Bulgaria Received 7 July 2006; received in revised form 5 October 2006; accepted 10 October 2006

Abstract The electron beam technology (EBT), proven treatment for SO2 and NOx removal, is applied to different power stations as hot gas cleaning system. In this paper, an assessment of this technique installed in a Bulgarian power station on organic emissions is analyzed. The Polycyclic Aromatic Hydrocarbons (PAH) content, not only emitted in the gas phase but also trapped in the solid phase, has been carried out before and after the irradiation. The main aim has been to know whether the EBT affects organic emissions, like PAH, as it happens with inorganic pollutants, like SO2 and NOx, studying EBT effects from an organic environmental point of view. The PAH quantification was performed by using a very sensitive analytical technique, gas chromatography with mass spectrometry mass spectrometry detection (GC–MS–MS). Results showed that PAH are influenced by the EBT showing a reduction of the most volatile PAH in the gas phase. PAH concentrations in the fertilizers obtained after irradiation were found to be similar to those in the fly ashes produced when no irradiation is applied. These fertilizers were considered like unpolluted soils being adequate for agriculture applications with PAH concentrations below the target value set up by the Dutch government. © 2006 Elsevier B.V. All rights reserved. Keywords: Electron beam technology; PAH; Combustion flue gas; Desulphurization

1. Introduction Pollution constitutes one of the main environmental problems in our society. The development of pollutant control technologies play a vital role to solve the environmental issues of the present time increasing the quality of life in the next century and promoting a healthy and green environment. One of these pollution sources is originated by the power generation being different the methods used for the flue gas treatment. The power generation industry as driven by air pollution requirements is keenly pursuing strategies to mitigate the emissions of sulphur dioxide (SO2), oxides of nitrogen (NOx), particulate matter (PM) and other pollutants from power plants. In fact, most countries around the world are now committed to limiting gas emissions from power plants and recent global

⁎ Corresponding author. Tel.: +34 976 733977; fax: +34 976 733318. E-mail address: [email protected] (A.M. Mastral). 0378-3820/$ - see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.fuproc.2006.10.006

treaties require all countries to pass and implement laws limiting national SO2 and NOx emissions. The methods to abate these main pollutants originated in power stations are wide and very varied. The most traditional ones consist of solid adsorbent addition (limestone, gypsum) [18], wet flue gas desulphurization scrubber systems [6], flue gas recirculation [30], low NOx burners, reburning, selective catalytic reduction (SCR) [28], selective non-catalytic reduction (SNCR) [3], use of activated adsorbents, electrostatic precipitators (ESPs) [25] and fabric filters, etc implying in some cases combustion modifications and others post-combustion treatments. A technology constituting one of the untraditional methods for flue gas cleaning is the EBT. This technology is recognized as an effective method for removing toxic components from flue gases [17] like NOx, SOx and VOC [7,8,15,19,20,33], in particular SO2 and NOx. The electron beam is generated by an electron accelerator and flows through a titanium foil window into the flue gas interacting with the flue gas and allowing abatement of pollutants. It works

252

M.S. Callén et al. / Fuel Processing Technology 88 (2007) 251–258

Fig. 1. The scheme of the EB installation.

by diverting the flue gases through a process, before they escape from the chimney. Gases are cooled with a spray of water to 70–90 °C. Ammonia is added to the wet flue gas which is then exposed to low-energy electron radiation from an accelerator. The formation of aerosol droplets upon binary volume condensation of sulphuric and water vapours occurs giving rise to dissolution of other gaseous species in droplets and to liquid phase chain oxidation of SO2 [14]. As result, the toxic SO2 and NOx are transformed into other chemical forms and the formed aerosols are collected in a filter. Although it is a radiation process, no radioactivity is produced in the operation. This technology was originally developed in Japan, Germany and USA, some 20 years ago and in the time it became available for industrial scale applications in China and Poland whereas there is a pilot plant in Bulgaria. Some of the advantages of this technology are related to less costly installation and operation than conventional systems and meets the most stringent regulations. Furthermore, because ammonia is added to the wet flue gas, the end product of the scrubbing process is a fertilizer which seems to have agricultural value [11]. Because what would have been atmospheric pollutants are turned into useful fertilizer, there is less waste to be disposed of than in conventional processes. One of these EBT was installed in Bulgaria in the Maritza East 2 Thermal Power Plant as technology to remove NOx and SO2 emissions. Although the EB activation technology for desulphurization has been tested at this power station [11], the main aim of

this work is related to knowing the advantages that EB technology would imply from an environmental point of view regarding a particular group of organic compounds, the PAH abatement without producing other pollutants of high harmful character, not only in the gas phase but also in the solid phase. Taking into account the PAH formation mechanism [23,24,22] in combustion processes, it is expected that the introduction of the EB technology to the Maritza East power station would modify the organic radical concentration under these radiation conditions in such a way that the interaction between radicals would be also favored. This could modify not only the PAH concentration but also the PAH nature, which would be not only emitted in the gas phase but also adsorbed in the originated solids. In fact, there are publications that during EB treatment of the flue gases, volatile organic compounds (VOC), i.e. polycyclic aromatic compounds (PAC) were influenced as well [9,10]. It was found that the concentrations of aromatic compounds of small aromatic rings were reduced while the concentrations of large aromatic rings were increased. However, no bibliography has been found regarding the PAH contained in the solid products in power generation using EBT. In this paper, a total of 23 PAH including the 16 PAH established by US-EPA have been quantified in flue gas from coal combustion with and without the EBT at the inlet and the outlet of an irradiation chamber. In addition, the PAH trapped on solid phase, fly ashes proceeding from the coal combustion without

Table 1 Conditions of the pilot installation and the electron beam technique installed in the Maritza East power plant “Inlet” of irradiation camera “Outlet” of irradiation camera

Flue gases (m3/h)

Pressure (mbar)

NOx (mg/Nm3)

SO2 (mg/Nm3)

O2 (vol.%)

Particulate matter (mg/m3)

5994 8317

5.03 20.98

254 15

13156 510

15.21 16.94

24.0 176

Coefficients Energy (kW) (kW/h)

Voltage (kV)

Humidity (%)

Electricity (mA)

α (ammonium)

β (water

γ (air)

127.5 61,196

800

21

20.23

1.00

0.45

2.00

Dose (kGy)

Efficiency SO2 (%)

Preview

Actual

Preview

Actual

4.0

3.92

90.0

97.3 and 96.2

M.S. Callén et al. / Fuel Processing Technology 88 (2007) 251–258

EBT and the by-products obtained in the EBT, ammonium sulphate and ammonium nitrate, have also been quantified in order to compare the influence of EBT on these emissions. In this way, it is assessed on the one hand, the influence of the EBT on PAH emissions in gas phase and on the other hand, the possibility of using these by-products as fertilizers in the agriculture sector. Finally, the influence of this technique on the carcinogenity of the gas and solid samples has also been considered by calculating the BaP equivalent factor (BaPE). 2. Experimental 2.1. Pilot plant installation and sampling Experiments were performed in the Maritza East 2 Thermal Power plant (Fig. 1) by burning Maritza East lignite (ultimate analysis: C (daf) = 67.41%, H (daf) = 6.23%, Stotal (daf) = 5.61%, N (daf) = 0.66%; proximate analysis: moisture (ar) = 15.6%, ash (ar) = 18.5%. The conditions of the industrial plant and the electron beam technique are shown in Table 1. Two different samplings were carried out: the gas phase (flue gas) and the solid phase (fertilizer and fly ash). Regarding the gas phase samples, a proper trapping system for VOC in combustion flue gases at the inlet and outlet of the EB irradiation chamber was developed. The sampling was prepared by a condenser submerged in an ice bath for humidity decrease and a train of 3× XAD-2 resin cartridges (SKC 226-30-03). The volumes of passed gases were measured by the rotameters for SOx/NOx line. The gases velocities were in the range 40–50 l/h. Volumes of flue gases passed in traps were about 300 l. Concerning the solid phase samples, two samples from fly ashes were taken in the thermal power station without using the EBT. These samples were considered as reference samples as the PAH presence was assured. In addition, a total of four samples of the same experiment were collected corresponding to the by-products (ammonium sulphate and ammonium nitrate) generated by the EBT in order to analyze the PAH content after the electron beam irradiation. 2.2. PAH extraction With regard to the gas samples, condensers and cartridges for “inlet” and “outlet” were extracted by sonication using chloroform as solvent. XAD-2 adsorbents were placed in glass beakers and 10 ml chloroform poured. Samples were 3 × 15 min sonicated in ultrasound bath at 30 °C. All extracts were combined and concentrated at reduced pressure. The weights of extracts were in the range of 7–8 mg. Concerning the solid samples, the extraction was performed by Soxhlet during 16 h with DCM as solvent. The weights of solid samples extracted were in the range of 36 to 44 g. After concentration by rotary evaporator and N2 stream, samples were dried with extract weights in the range of 6.30 to 8.50 mg. After the addition of a solution containing surrogate standards (acenaphthene-d10, anthracene-d10, benzo(a)anthracene-d12, benzo(a)pyrene-d12, perylene-d12 and benzo(g,h,i)perylene-

253

d12), samples were cleaned up on a silica-gel column (previously cleaned and heated at 150 °C for at least 2 h) with DCM. The eluted was concentrated by N2 stream and the solvent exchanged to hexane. Before injection to the GC-MS-MS, 5 μl of pterphenyl native was added as internal standard to the samples with a final volume of 100 μl in hexane. 2.3. PAH quantification by GC/MS/MS The 23 PAH quantification (naphthalene (Np), acenaphthylene (Acy), acenaphthene (Ace), fluorene (Fl), phenanthrene (Phe), 2,5-/2,7-/4,5-dimethylphenanthrene (Dimephe), 1-methylphenanthrene (1-MePhe), 2-methylphenanthrene (2-MePhe), 2-/4-methylphenanthrene (2/4-MePhe), 9-methylphenanthrene (9-MePhe), anthracene (An), fluoranthene (Fth), pyrene (Py), benz[a]anthracene (BaA), chrysene (Chry), benzo[b]fluoranthene (BbF), benzo[k]fluoranthene (BkF), benzo[e]pyrene (BeP), benzo [a]pyrene (BaP), indeno[1,2,3-cd]pyrene (IcdP), dibenzo[a,h] anthracene (DahA), benzo[g,h,i]perylene (BghiP) and coronene (Co), including the 16 PAH established by US-EPA as priority pollutants, was carried out by the internal standard method using deuterated PAH surrogate standards. Blanks were also prepared and substracted to sample results. Samples were analyzed by GC (Varian GC 3800) equipped with a low bleeding Factor Four capillary column VF-5 ms (length: 30 m, ID: 0.25 mm; thickness: 0.25 μm) coupled to MS/MS detector (Saturn 2200) operating in electron impact mode (70 eV). The temperature time program at the working conditions of the GC/MS/MS was the following: 60 °C isotherm for 1 min, 10°/min till 300 °C and isotherm for 20 min. The injector was kept at constant temperature of 280 °C. Helium was used as Table 2 PAH concentration in the inlet (before EBT) and outlet (after EBT) samples taken in the gas phase PAH (μg/g extract)

Inlet

Naphthalene Acenaphthylene Acenaphthene Fluorene Phenanthrene Anthracene 2-MePhe + 2/4-MePhe 9-MePhe 1-MePhe DiMePhe Fluoranthene Pyrene Benzo(a)anthracene Chrysene Benzo(b + j)fluoranthene Benzo(k)fluoranthene Benzo(e)pyrene Benzo(a)pyrene Indeno(1,2,3-cd)pyrene Dibenzo(a,h)anthracene Benzo(g,h,i)perylene Coronene Total PAH

110.06 2.70 3.29 25.15 237.10 0.78 27.86 7.00 11.93 8.97 15.66 1.22 0.00 2.49 1.26 0.36 0.42 1.31 0.30 0.15 0.00 0.55 458.54

Outlet 3.43 0.74 2.77 4.91 23.99 0.39 5.38 2.79 3.02 2.68 1.46 0.71 9.13 0.74 0.70 0.31 0.30 1.83 0.48 0.47 0.00 2.11 68.34

254

M.S. Callén et al. / Fuel Processing Technology 88 (2007) 251–258

Fig. 2. Removal efficiency of PAH in flue gases under EBT.

carrier gas at a constant flow of 1 ml/min and transfer line was heated at 280 °C. In all cases, 1 μl of sample was injected in splitless mode (1/50, split valve closed for 3.5 min). In order to check the analytical accuracy and precision, analyses of an appropriate standard reference material (SRM 1649) of the National Institute of Standards and Technology (NIST) were used. Measured values were comparable to certified values with a precision between 1% (for 1-MePhe) and 28% for all compounds. 3. Results and discussion 3.1. PAH gas emissions The influence of the electron irradiation in the pilot plant was investigated by analyzing the PAH concentrations in the gas phase samples: “inlet” and “outlet”, without and with the EB technology. Samples without the irradiation were taken as blanks. After the irradiation, the total of PAH decreased considerably from 458 to 68 μg/g (see Table 2) implying a reduction of the 85% in the total PAH emissions. Np (24%) and

Fig. 3. Percentage of PAH aromatic rings before “inlet” and after “outlet” using the EBT in flue gases.

Phe (51.7%) were the majority PAH emitted in “inlet” corresponding to PAH with two and three aromatic rings and characterized by a low carcinogenic character. Other PAH with a contribution to the total of PAH were Fl, 2/4-MePhe, 1-MePhe and Fth, light PAH with 3 and 4 aromatic rings. The gas sample corresponding to the “outlet”, after the electron beam treatment, underwent a different PAH distribution. Phe (35%) was the majority PAH emitted followed by BaA, 2 + 2/4-MePhe, Fl and Np. Nevertheless, an increase in the concentration of some heavy PAH was observed. These PAH were BaA, BaP, IcdP, DahA and Co. With the exception of Co, this PAH increase was related to PAH with high carcinogenicity. Fig. 2 shows the efficiency of PAH removal in flue gases under the EB irradiation. It is observed that the EB shows high Table 3 PAH concentration in the fly ashes (Ref 1 and Ref 2) collected in the power station without EBT PAH (μg/g extract)

Ref 1

Ref 2

Naphthalene Acenaphthylene Acenaphthene Fluorene Phenanthrene Anthracene 2-MePhe + 2/4-MePhe 9-MePhe 1-MePhe DiMePhe Fluoranthene Pyrene Benzo(a)anthracene Chrysene Benzo(b + j)fluoranthene Benzo(k)fluoranthene Benzo(e)pyrene Benzo(a)pyrene Indeno(1,2,3-cd)pyrene + DahA Benzo(g,h,i)perylene Coronene Total PAH

1.05 1.36 1.25 12.98 200.50 3.83 30.00 24.09 19.89 32.33 36.28 19.81 2.49 5.34 4.82 0.00 2.45 1.02 9.76 5.23 – 414.48

1.53 1.90 2.03 16.37 144.64 2.47 27.15 18.38 16.46 26.99 25.37 9.76 2.67 5.45 8.04 0.00 2.85 0.00 3.85 1.82 – 317.72

M.S. Callén et al. / Fuel Processing Technology 88 (2007) 251–258

255

Fig. 4. PAH average concentration (μg/g extract) and standard deviation in the by-products collected in the power station after using the EBT.

efficiency to destroy PAH of low molecular weight like Np, Acy, Fl, Phe, 2 + 2/4-MePhe, Fth and Chry. On the contrary, an increase in the concentration of PAH of high molecular weight is observed (BaA, DahA, BghiP, Co). Fig. 3 shows the distribution of PAH according to the number of aromatic rings for the inlet and outlet gases. The application of the irradiation shows a decrease in the 2 aromatic rings with an increase in the 4, 5, 6–7 aromatic rings. This increase in the number of aromatic rings could affect the toxicity of the samples. In this way, the toxicity of flue gas before and

after the irradiation was calculated by using the benzo[a]pyrene equivalent concentrations (BaPE). The BaPE was calculated by taking into account the formula: BaPE ¼ BaA  0:06 þ BFa  0:07 þ BaP þ Dða; hÞA  0:6 þ IPY  0:08

ð1Þ

where BFa includes all benzofluoranthene isomers and by summing the concentrations of the individual PAH on the basis of their comparative potency as carcinogens [4,5].

Fig. 5. PAH percentage in the by-products collected in the power station after using the EBT (fertilizer) and before using the EBT (fly ash).

256

M.S. Callén et al. / Fuel Processing Technology 88 (2007) 251–258

Fig. 6. Removal efficiency of PAH under EBT in the by-products obtained.

By applying this formula, the BaPE increased from 1.5 μg/g in the “inlet” to 2.8 μg/g in the “outlet”. This was mainly due to the increase in the BaA concentration after the EB irradiation. Other authors [9] have also reported results concerning PAH in flue gases after EBT was installed in a power plant in Poland. They obtained a decrease in PAH emissions, especially in the concentrations of hydrocarbons of small aromatic rings, while the concentration of PAH of large aromatic rings increased, increasing the toxicity of these compounds. It seems to be that the application of the EB promotes the formation of radicals that tend to stabilize forming larger aromatic rings, with an important reduction in the PAH of lowest molecular weight, 2 aromatic rings and a remarkable increase in 4, 5, 6–7 aromatic rings (see Fig. 3). The mechanism implied in the behaviour of PAH molecules under irradiation has been explained by considering that the OH radicals play an important role in PAH destruction forming unstable OH-adduct [2]. Two temperature ranges have been considered. In the case of low temperatures (T b 80 °C), the conversion of aromatic molecules seems to occur in direction of decrease in the number of aromatic rings [2]. At high temperatures (T N 120 °C) [13,29] the reaction of OH radical with aromatic molecule leads to the competition of two processes: decomposition and growth of the aromatic structure under interaction with acetylene.

Firstly, it was proved that PAH are present in coal combustion fly ash without using the EBT (see Table 3) and these results were compared to the ones obtained for 4 representative samples corresponding to fertilizers. Fig. 4 shows the average PAH concentration and the standard deviation for the four samples of fertilizers, showing coherent results with standard deviations lower than 18 μg/g. Regarding the total of PAH for the two kinds of solid waste, the obtained values were quite similar with a slight decrease in the fertilizer sample versus the fly ashes (325.6 μg/ g, 366.1 μg/g). The majority PAH trapped in the fly ashes were Phe (47%), Fth (8.4%) and MePhe (26%) (Fig. 5) all of them compounds with 3 aromatic rings. In the case of the fertilizer samples (Fig. 5), the majority PAH trapped were Flt (30%), Phe (26%) and Py (13%), PAH of 3 and 4 aromatic rings with an increase in the 4 aromatic rings' PAH. Fig. 6 shows the removal efficiency in the solid products obtained after the EBT application. A high efficiency was observed to destroy PAH like Np, Ace, IcdP + DahA and 1MePhe. In addition, an increase in the concentration of other PAH like An, Fth, Py, BaP and Co was produced. Fig. 7 presents the distribution of PAH by number of aromatic rings in the two different solid wastes. After the

3.2. PAH trapped in the solid phase The EBT is based on the transformation of the main pollutants, SO2 and NOx into acids which are converted into salts by the addition of neutralizing species (e.g. ammonia) and removed from the flue gases by dry electrostatic precipitators. It was interesting from an environmental point of view, to know the PAH concentrations in these by-products as they are used as fertilizers in the agriculture sector. In this way, it would be possible to assess whether the agronomic benefits ensuing from their use in agriculture are not written off by the chemical contamination that could follow in underground water and by some vegetable root adsorption.

Fig. 7. Percentage of PAH aromatic rings obtained in the waste solids, fly ashes (without EBT) and fertilizers (with EBT).

M.S. Callén et al. / Fuel Processing Technology 88 (2007) 251–258 Table 4 PAH concentration in four fertilizers (F 1, F 2, F 3 and F 4) obtained after the EBT and Dutch target value for unpolluted soil [32] PAH (μg/kg fertilizer)

F1

F2

F3

F4

Dutch target value (μg/kg)

Naphthalene 0.00 0.00 0.00 0.00 Acenaphthylene 0.22 0.11 0.36 0.33 Acenaphthene 0.04 0.03 0.11 0.12 Fluorene 1.13 1.51 2.59 2.53 Phenanthrene 13.25 15.66 17.62 13.57 45 Anthracene 1.19 1.80 2.11 2.38 50 2-MePhe + 2/4-MePhe 4.28 4.97 4.09 4.02 9-MePhe 2.28 1.90 1.58 1.70 1-MePhe 1.42 1.30 0.79 0.83 DiMePhe 3.24 3.05 1.54 1.21 Fluoranthene 13.99 16.98 19.13 18.30 20 Pyrene 7.27 6.32 6.74 9.83 Benzo(a)anthracene 0.57 0.53 0.51 0.61 20 Chrysene 0.77 0.72 0.73 0.99 20 Benzo(b + j)fluoranthene 1.00 0.77 0.58 0.75 Benzo(k)fluoranthene 25 Benzo(e)pyrene 0.35 0.23 0.15 0.25 Benzo(a)pyrene 0.23 0.27 0.40 0.41 Indeno(1,2,3-cd)pyrene + DahA 0.60 0.35 0.30 0.58 25 a Benzo(g,h,i)perylene 0.65 0.39 0.48 0.73 20 Coronene 0.91 0.56 0.45 0.83 Total PAH 53.39 57.46 60.27 59.96 a

Indeno(1,2,3-cd)pyrene.

application of the irradiation, three aromatic rings PAH decrease is observed with an increase in the concentration of four aromatic rings. The shift to PAH of larger aromatic rings obtained in the fertilizers could affect the global toxicity of the waste solids. In this way, the BaPE was also calculated for the solid samples before and after using the EBT in order to know the toxicity of the samples. A slight increase in the BaPE value from 1.6 μg/g to 2.6 μg/g was observed in the solids obtained before and after the irradiation. When the total PAH trapped in the fertilizers was calculated per kg fertilizer, the total PAH average concentration was 57.8 μg/kg fertilizers (Table 4). The determined concentration was much lower than the intervention value for soil sanitation, as used by the Dutch government that is 40,000 μg PAH/kg [31,32]. Intervention values indicate that the functional properties of the soil are seriously impaired or threatened for human, plant and animal life. They are representative of the level above which there is a serious case of soil contamination. At the same time, the total PAH average concentration of 57.8 μg/kg fertilizers was lower than the target value set by Dutch government for unpolluted soils, 1000 μg/kg [31,32] taking into account a total of 10 PAH (Np, An, Ph, Fth, BaA, Chry, BaP, BghiP, BkF and IcdP). Target values indicate a sustainable soil quality. The functional properties of the soil are undamaged or fully recovered. BaP, a known carcinogenic PAH according to the estimation of the International Agency for Research on Cancer [21], was below the target level of BaP = 25 μg/kg set by the Dutch government for soil samples. The same happened with the target level for the following PAH: Phe: 45, An: 50, Fth: 20,

257

Chry: 20, BaA: 20, BkF: 25, BghiP: 20 and IcdP: 25 μg/kg (Table 4). Data found on the literature regarding background PAH concentrations in Bulgaria of 2–22 μg/kg [1] and the suggested level of endogenous total PAH concentrations in soils of 1– 10 μg/kg [12] were compared to the ones obtained in the solid by-products obtained in this work. It could be concluded that the fertilizers were contaminated above the natural and background level. Nevertheless and in accordance with the range of background PAH levels of soil in Italy, 100–1000 μg/ kg [26] and of up to 1000 μg/kg in Czech Republic [27] the fertilizer samples were not contaminated. The same conclusion could be observed by comparing the mean value of PAH, 57.8 μg/kg found in this work with mean values as 300–400 μg/ kg found for rural European soils PAH levels [16]. Therefore and considering the PAH levels in the by-products obtained after the EB irradiation, it was deduced that fertilizers could be considered as unpolluted soils and they could be used in the agricultural sector without possible harm for human health. 4. Conclusions Although the EBT is a proved technology to abate NOx and SO2 emissions in flue gas from combustion, in this paper it is shown that this technology produces modifications in the concentrations of organic compounds, in particular PAH. On the one hand, it is advantageous from PAH atmospheric environmental point of view as the total PAH concentration in flue gas decreases one order of magnitude after the application of this irradiation. On the other hand, an increase in the aromatic ring PAH concentration is produced with a slight increase in the sample toxicity. With regard to the solid products generated during the EBT and taking into account the total of PAH, quite similar results are obtained with and without the EB irradiation. Again, a slight increase is observed in the toxicity of the by-products obtained after the irradiation. However, the PAH concentrations are below the target value set up by Dutch government for unpolluted soils and the by-products obtained after the EBT could be used as fertilizers without posterior pollution problems. Acknowledgments The authors would like to thank the authorities of Maritza East TPP-2 for the possibility to run the experiments on EB pilot installation as well as the EB engineering staff for the help and advice. The study was performed in the frame of CSIC—Spain/ BAS—Bulgaria collaboration and in the frame of the IAEA, Contract No. 13133/R1. References [1] I. Atanassov, K. Terytze, A. Atanassov, Background values for heavy metals, PAHs and PCBs in the soil of Bulgaria, assessment of the quality of contaminated soils and sites in Central and Eastern European Countries (CEEC) and New Independent States (NIS), in: K. Terytze, I. Atanassov (Eds.), Proceeding of International Workshop, Sofia, Bulgaria, 2001, pp. 83–103.

258

M.S. Callén et al. / Fuel Processing Technology 88 (2007) 251–258

[2] R. Atkinson, Atmospheric chemistry of VOCs and NOx, Atmospheric Environment 34 (12–14) (2000) 2063–2101. [3] S.W. Bae, S.A. Roh, S.D. Kim, NO removal by reducing agents and additives in the selective non-catalytic reduction (SNCR) process, Chemosphere 65 (2006) 170–175. [4] A. Cecinato, Polynuclear aromatic hydrocarbons (PAH), Benz(a)pyrene (BaPy) and nitrated-PAH (NPAH) in suspended particulate matter, Annali di Chimica 87 (1997) 483–496. [5] A. Cecinato, M. Repetto, E. Guerriero, I. Allegrini, Levels and sources of polynuclear aromatic hydrocarbons in the Genoa–Cornigliano area, in: C.A. Brebbia, C.F. Ratto, H. Power (Eds.), Proceedings of Air Pollution VI, WIT Press, Southampton, 1998, pp. 587–596. [6] T.-W. Chien, H. Chu, Removal of SO2 and NO from flue gas by wet scrubbing using an aqueous NaClO2 solution, Journal of Hazardous Materials 80 (1–3) (2000) 43–57. [7] A.G. Chmielewski, Z. Zimek, P. Panta, W. Drabik, The double window for electron-beam injection into the flue-gas process vessel, Radiation Physics and Chemistry 45 (1995) 1029. [8] A.G. Chmielewski, E. Iller, Z. Zimek, M. Romanowski, K. Koperski, Industrial demonstration plant for electron-beam flue-gas treatment, Radiation Physics and Chemistry 46 (1995) 1063. [9] A.G. Chmielewski, Y.-X. Sun, J. Licki, S. Bulka, K. Kubica, Z. Zimek, NOx and PAHs removal from industrial flue gas by using electron beam technology with alcohol addition, Radiation Physics and Chemistry 67 (2003) 555–560. [10] A.G. Chmielewski, A. Ostapczuk, J. Licki, PAH removal from flue gas by electron beam treatment — pilot plant installation, Proc. of the IEAE Consulting Meeting on Radiation Processing of Gaseous and Liquid Effluents, Sofia, Bulgaria, 2004, pp. 55–65. [11] N. Doutskinov, Results of the start-up operation of a pilot installation for electron beam flue gases treatment in the Maritza-East-2 Thermal Power Plant, Proc. of the IEAE Consulting Meeting on Radiation Processing of Gaseous and Liquid Effluents, Sofia, Bulgaria, 2004, pp. 34–42. [12] N.T.J. Edwards, Polycyclic aromatic hydrocarbons (PAHs) in the terrestrial environment – a review, Journal of Environmental Quality 12 (1983) 427–441. [13] M. Frenklach, Reaction mechanism of soot formation in flames, Physical Chemistry Chemical Physics 4 (11) (2002) 2028–2037. [14] G. Gerasimov, Modelling study of electron beam polycyclic and nitropolycyclic aromatic hydrocarbons treatment, Radiation Physics and Chemistry 76 (1) (2007) 27–36. [15] N. Getoff, World Resource Review 9 (1997) 86. [16] I. Holoubek, A. Kocan, I. Holoubkova, K. Hilscherova, J. Kohoutek, J. Falandysz, O. Roots, Persistent, bioaccumulative and toxic chemicals in central and eastern European countries—state-of-the-art report, TOCOEN Report No. 150a (CD), Brno, Czech Republic, 2000. [17] Y. Hoshi, et al., Electron processing systems for environment applications, Proc. of International Symposium on Radiation Technology for Conservation of the Environment (Zakopane, Poland), IAEA-SM-350/35), 1997. [18] W.Z. Khan, B.M. Gibbs, SOX emissions from a fluidized-bed combustor with and without limestone addition, Energy 21 (2) (1996) 105–113.

[19] J.-C. Kim, Factors affecting VOC removal by electron beam treatment, Radiation Physics and Chemistry 65 (2002) 429–435. [20] J. Licki, A.G. Chmielewski, E. Iller, Z. Zimek, J. Mazurek, L. Sobolewski, Electron beam flue gas treatment for multicomponent air pollution control, Applied Energy 75 (2003) 145–154. [21] E. Manoli, C. Samara, I. Konstantinou, T. Albanis, Polycyclic aromatic hydrocarbons in the bulk precipitation and surface water of Northern Greece, Chemosphere 41 (2000) 1845–1855. [22] A.M. Mastral, M.S. Callén, A review on polycyclic aromatic hydrocarbon (PAH) emissions from energy generation, Environmental Science and Technology 34 (15) (2000) 3051–3057. [23] A.M. Mastral, M.S. Callén, R. Murillo, T. García, Combustion of high calorific value waste material. Organic atmospheric pollution, Environmental Science and Technology 33 (1999) 4155–4158. [24] A.M. Mastral, M.S. Callén, T. García, Polyaromatic environmental impact in coal-tire blend atmospheric fluidized bed (afb) combustion, Energy and Fuels 14 (2000) 164–168. [25] R. Meij, B. te Winkel, The emissions and environmental impact of PM10 and trace elements from a modern coal-fired power plant equipped with ESP and wet FGD, Fuel Processing Technology 85 (6–7) (2004) 641–656. [26] S. Minissi, D. Caccese, F. Passafiume, A. Grella, E. Ciccotti, M. Rizzoni, Mutagenicity (micronuclear test in Vicia fabaroot tips), polycyclic aromatic hydrocarbons and heavy metal content of sediment collected in Tiber river and its tributaries within the urban area of Rome, Mutation Research 420 (1998) 77–84. [27] M. Sanka, Program of soil monitoring and register of contaminated sites in the Czech Republic: their role as database sources in state administration and for setting the limit values in soil, Assessment of the quality of contaminated soils and sites in Central and Eastern European Countries (CEEC) and New Independent States (NIS), in: K. Terytze, I. Atanassov (Eds.), Proceeding of International Workshop, Sofia, Bulgaria, 2001, pp. 33–36. [28] G. Saracco, V. Specchia, Simultaneous removal of nitrogen oxides and flyash from coal-based power-plant flue gases, Applied Thermal Engineering 18 (11) (1998) 1025–1035. [29] W.R. Stockwell, A homogeneous gas phase mechanism for use in a regional acid deposition model, Atmospheric Environment 20 (8) (1986) 1615–1632. [30] H. Teng, T.-S. Huang, Control of NOx emissions through combustion modifications for reheating furnaces in steel plants, Fuel 75 (2) (1996) 149–156. [31] T.C. Van Brummelen, R.A. Verweij, S.A. Wedzinga, C.A.M. Van Gestel, Enrichment of polycyclic hydrocarbons in forest soils near a blast furnace plant, Chemosphere 32 (1996) 293–314. [32] VROM, Intervention Values and Target Values: Soil Quality Standards, Netherlands Ministry of Housing, Spatial Planning and Environment, Department of Soil Protection, The Hague, Netherlands, 1994. [33] W. Zhangfa, International Energy Agency (IEA) Coal Research/The Clean Coal Centre/Materials for FGD systems, , 2000.