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‚§√ß°“√»÷°…“ “√¡≈æ‘…®“°°“√‡º“‰À¡â‡™◊ÈÕ‡æ≈‘ß™’«¡«≈ : °√≥’»÷°…“°“√„™â°“°ÕâÕ¬‡ªìπ‡™◊ÈÕ‡æ≈‘ß Pollutants Emissions from Biomass Combustion Industry in Thailand : A Case Study of Sugar Refinery Industry Wanna Laowagul*, Nittaya Milne* Sunthorn Ngodngam*, Phaka Sukasem*

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*»Ÿπ¬å«‘®—¬·≈–Ωñ°Õ∫√¡¥â“π ‘Ëß·«¥≈âÕ¡ °√¡ à߇ √‘¡§ÿ≥¿“æ ‘Ëß·«¥≈âÕ¡ ‡∑§‚π∏“π’ µ.§≈ÕßÀâ“ Õ.§≈ÕßÀ≈«ß ®.ª∑ÿ¡∏“π’ 12120 ‚∑√. 0-2577-1136 ‚∑√ “√. 0-2577-1138 Environmental Research and Training Center, Department of Environmental Quality Promotion. Technopolis. Klong 5 Klong Luang, Pathumthani 12120 e-mail: Wanna@deqp.go.th


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ABSTRACT Emissions of particulates, polycyclic aromatic hydrocarbons (PAHs), carbonmonoxide (CO) and carbondioxide (CO2) from bagasse combustion in the studied sugar refinery factory was carried out. The samples were taken at steady state of the process and at isokinetic condition. The results showed the quantities of particulates and PAHs in the samples that collected after the furnace was cleaned by blown out unburned hydrocarbon and ashes were lower than the samples that collected without cleansing furnace. Moreover, total PAHs concentration and their emission rate are found to be correspondent with total particulates and CO emissions. Concerning the characteristic profiles of PAHs, in particulate matters the most predominant was fluoranthene, the second most predominant was pyrene. In vapour phase, the most abundant PAHs was napthalene, the second abundant was phenanthrene.

1. Introduction At the most basic level, energy is essential for all human activities. Present energy use is mainly non-renewable fossil fuels, which are accounting for 82% of all energy consumption worldwide.1 However, disadvantages of combustion of fossil fuels are sulfur dioxide (SO2) and nitrogen oxide (NOx) emissions into the atmosphere, causing acid rain at the local and global scales, which seriously damage ecosystem and human »Ÿπ¬å«‘®—¬·≈–Ωñ°Õ∫√¡¥â“π ‘Ëß·«¥≈âÕ¡ °√¡ à߇ √‘¡§ÿ≥¿“æ ‘Ëß·«¥≈âÕ¡

health. Furthermore, there are intrinsic connection with worldûs problems of sustainable development, climate change, global warming and biodiversity. 2 As a result of growing worldwide concern about the environmental impact of fossil fuel consumption, the world is now apparently headed toward a commitment to develop energy systems that are less dependent on fossil fuels.3 To obtain sustainable and clean environment and to substitute the fossil fuel consumption, Thailand has elaborated on a program to stimulate the development and efficient use of renewable energy in the country since 1997. 4 Among renewable energy, biomass is an important renewable source of energy. It has been reported that, in Thailand, biomass energy started playing an important role, over 95% of all renewable energy sources used are biomass.1 It has been reported that the exploited biomass energy resources account for 26% of gross energy consumption in 1996. 5 Supply of biomass is available from many sources: forests, wood plantations, agricultural and industrial residues, and even municipal solid wastes. Based on Thailand energy situation 1997,6 it was found that bagasses are mostly used as source of energy in industries that is accounting for 80% of total biomass used as source of energy. The potential for utilising biomass residues as fuel is in various purposes such as fuels for steam or power generation in conventional combustion system and/or for combined power and steam production in industrial sector. In Thailand, direct combustion is one of the main processes of thermochemical biomass conversion for energy in industrial sector. However, in general, the major emissions from almost any means of combustion of biomass materials are air pollutants-notably particulates, methane (CH4), carbondioxide (CO2), carbonmonoxide §-35


(CO) and hydrocarbons. Besides, polycyclic aromatic hydrocarbons (PAHs) can be formed in any combustion process.7 These pollutants may contribute to severe air pollution problems, especially, build-up of hazardous substances such as PAHs in the atmosphere. PAHs are toxic compounds and some of them are carcinogenic or mutagenic which make them have long been of concern as a potential human health hazard.8 In the atmosphere, PAHs can distribute between the gas and particle phases according to their volatility. PAHs are adsorbed predominantly on suspended particulate matter in the respiratory size range less than 5 µm.9 The study on air pollution by airborne PAHs in industry area indicated that PAHs were found mostly in particulate matter less than 2.1 µm.10 Thus, they can reach to human lung by inhalation and might contribute to lung cancer, localized skin effects, pulmonary and respiratory problems, genetic reproductive and developmental effect, behavioral, neurotoxic and other organ system effect.11 The other pollutants such as CO and particulate matter can have an influence for the risk of cardiovascular disease.12 CH4 and CO2 can create greenhouse effect which cause significant climate and geohydrological changes. Therefore, it is important to study their emissions from biomass combustion in industry in order to obtain a useful information for mitigation of those air pollutants emitted from this process in Thailand in which such studies are still scarce.

2. Methods and Materials The toxic pollutants such as PAHs, particulate, CO and CO2 will be investigated from sugar refinery. PAHs will be measured in both forms: gas and particulate. Eighteen PAHs were determined: napthalene (NAP), acenapthylene (ACY), acenapthene (ACE), fluorene (FLU) phenanthrene (PHE), anthracene §-36

(ANT), fluoranthene (FLA), pyrene (PYR), benzo(a)anthracene (BaA), chrysene (CHR), benzo(e)pyrene (BeP), benzo (b) fluoranthene (BbF), benzo(k)fluoranthene (BkF), benzo (a) pyrene (BaP), dibenzo(a,h) anthracene (DBahA), benzo(g,h,i)perylene (BghiP), indeno (1,2,3cd)pyrene (IP), and coronene (COR). 8 Samples were collected from the flue gas by isokinetic condition in accordance with the U.S.EPA. Modified Method 5. The flue gas samples were passed through a glass fiber filter of pore size 0.45 µm and then onto an XAD-2 adsorbent (Styrene divinyl benzene polymer beads). PAHs in the samples were analysed using High Performance Liquid Chromatograph (HPLC). CO and CO2 in flue gas samples were determined by Orsat Analyzer in accordance with U.S.EPA. Method 3.

2.1 PAHs and Particulates (a) Apparatus and Materials (i) Isokinetic source sampler manual method 5. Apex instruments Model MC-500 Series, it is designed to sample particulate pollutants. (ii) Modified method 5 glassware. Apex source testing equipment instruments, it contains a coolant recirculating pump, a sorbent trap, a horizontal (iii) Soxhelt extraction unit. Sibata, it is used for cleaning XAD-2 and glass wool. (iv) Glass fiber filter, size 8 cm diameter. Pallflex Products Corp. (v) Desiccator. Sibata (vi) Balance. Mettler, AE 240 (vii) Glass wool (viii) Forceps (ix) Funnel (x) Bottle, 100 ml (xi) Aluminum foil (xii) Ultrasonication bath. Elma, transsonic digitals (xiii) Centrifugal vaporizer. Eyela, »Ÿπ¬å«‘®—¬·≈–Ωñ°Õ∫√¡¥â“π ‘Ëß·«¥≈âÕ¡ °√¡ à߇ √‘¡§ÿ≥¿“æ ‘Ëß·«¥≈âÕ¡


model CVE-200D (xiv) Vortex genie 2, model G-560 E (USA) (xv) Dry thermo unit. Taitec, model DTU-1B (xvi) High performance liquid chromatograph (HPLC). (b) Chemicals (i) XAD-2 adsorbent (Styrene divinylbenzene polymer beads). Organo CO. (ii) Blue silica gel, size 6 mesh, Nacalai tesque. (iii) Deionized distilled water (iv) Solvents: acetone, dichloromethane, methanol, acetonitrile. Chromatographic grade, Merck, Germany. (c) Preparation of sampling equipment (i) Desiccate the filter at least 24 hours and weight until constant weight. This procedure was done before and after collecting samples. (ii) Clean up the sampling train before sample collection using acetone and dichloromethane. (iii) Clean up XAD-2 adsorbent and glass wool before sample collection by soxhlet extractor for 16 hours.

A schematic of the sampling train is shown in Figure 1. Due to a lot of intercomponent connections in particular probe assembly and modular sample case, the sampling may be leak, therefore, the leak-check is necessary. (d) Leak checking procedure (i) Pre-test leak check: Assemble the sampling train, turn on and set the filter and probe heating systems at the desired operating temperature 120 ÌC. Then check if there is any leak on the sampling train at the sampling site by plugging the nozzle and pulling 15 inch Hg vacuum. Start the pump and stop when the desired vacuum is reached. If the leakage rate is found to be no greater than 0.00057 m3/min. or 4% of the average sampling rate, the results are acceptable. (ii) Post-test leak check: The leakcheck is done with the same procedures as the pre-test leak check, except that it is conducted at a vacuum greater than or equal to the maximum value reached during the sampling run. If the leakage rate is found to be no greater than 0.00057 m3/min. or 4% of the average sampling rate, the results are acceptable.

Figure 1 Modified method 5 sampling train

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In this study, five samples were taken from 12 points grid across the stack of sugar refinery industry at isokinetic condition during bagasse combustion period. The shape of stack is circular. Stack height is 33 m. Inside stack diameter is 3.5 m. Its area is 9.62 m2. (e) Analysis (i) PAHs in particulate The filter sample was cut into 2 pieces of 2.5 cm diameter by a puncher. The sample was extracted with 15 ml of dichloromethane using ultrasonic bath for 20 minutes. The extract was then be analyzed using HPLC. (ii) PAHs in gas phase Twenty grams of XAD-2 adsorbent was extracted with 150 ml of dichloromethane / hexane mixture (2:1) using ultrasonic bath for 30 minutes. The extract was then be analyzed using HPLC. The probe and filter holder were also extracted and analyzed using HPLC. The remaining concentrations found on these glasswares were added to each sample. Fifty microliters of sample was injected into an injector of HPLC. Acetronitrile and water were used as the mobile phases, which were deoxygenated by bubbling helium through the solvent during the measurement. The sample was carried over through the

column by 50% acetronitrile from pump A, mixed with water from pump B by a dynamic mixer for 5 minutes and changed by linear gradient program. The analytical condition is shown in Table 1. The flow rate for the mobile phase was 1.0 ml/min. The samples were separated by octadecylsilane-bonded C18 (reversed-phase column). The selected PAHs were detected by scanning fluorescence detector of which their excitation and emission wavelength automatically set by a time program to detect each PAHs selectively and sensitivity. Detection wavelength for each PAHs was shown in Table 2.

2.2 CO and CO2 (a) Apparatus (i) Measuring burette with a water jacket, 100 ml (ii) Aspirator bottle, 125 ml (iii) Absorption pipettes filled with glass tubes, 3 sets (iv) Manifold complete with four glass stopcocks (v) Manifold with a rubber bag (vi) Inlet U-tube There are rubber tube connections between the manifold and the three pipettes, and between the manifold and the burette.

Table 1 Analytical conditions Main Column: Wakosil II-5 C18 AR 4.6 mm I.D x 30 mm Guard Column: Wakosil II-5 C18 AR 4.6 mm I.D x 250 mm Solvent Composition Mobile Phase: 50% Acetonitrile/50% Water 85% Acetonitrile/15% Water 85% Acetonitrile/15% Water 100% Acetonitrile 100% Acetronitrile Column Oven: 40 ÌC Flow Rate: 1.0 ml/min Injection Volume: 50 µl Detector: Scanning fluorescence detector

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Time(min) 5 20 35 40 60

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Table 2 Determination of selected PAHs by HPLC/scanning fluorescence detector PAHs Compound

Concentration mg/ml

Excitation Wavelength

Emission Wavelength

Retention Time (min)

%RSD

Napthalene Acenapthylene Acenapthene Fluorene Phenanthene Anthracene Fluoranthene Pyrene BaA Chrysene BeP BbF BkF BaP DbahA BghiP Indeno(1,2,3-cd)pyrene Coronene

0.018 0.010 0.013 0.016 0.006 0.003 0.008 0.009 0.002 0.004 0.008 0.004 0.002 0.008 0.006 0.006 0.012 0.006

280 280 288 259 250 250 250 270 250 250 290 290 290 290 290 290 300 302

335 330 322 306 370 450 450 390 405 405 410 410 410 410 410 410 500 445

16.03 19.39 19.42 19.46 20.31 21.39 22.33 23.22 25.61 26.16 28.03 28.48 29.90 31.62 33.82 36.16 37.48 47.34

0.20 0.10 0.24 0.17 0.12 0.11 0.07 0.09 0.17 0.27 0.17 0.15 0.10 0.06 0.08 0.10 0.11 0.07

There is also tubing for the aspirator bottle connection. (b) Chemicals (i) Distilled water (ii) Cuprous chloride (CuCl) (iii) Ammonia (iv) Ammonium chloride (NH4Cl) (v) Pyrogallol (C6H3 (OH)3) (vi) Potassium hydroxide (KOH) (vii) Sodium chloride (NaCl) (viii) Sulfuric acid (H2SO4) (ix) Methyl orange (c) Preparation of Absorption Reagents (i) Absorbing solution for CO (Cuprous Chloride Solution) Dissolve 12 g of NH4Cl with 360 ml of distilled water. Add 120 g of cuprous chloride and 570 ml of 25% ammonium hydroxide to the NH4Cl solution. This solution should be kept in the container, which has small pieces of copper. (ii) Absorbing solution for O2 (Pyrogallol solution) »Ÿπ¬å«‘®—¬·≈–Ωñ°Õ∫√¡¥â“π ‘Ëß·«¥≈âÕ¡ °√¡ à߇ √‘¡§ÿ≥¿“æ ‘Ëß·«¥≈âÕ¡

Dissolve 60 g of pyrogallol with 100 ml of distilled water and 30 g of KOH with 100 ml of distilled water. Mix the solution of pyrogallol and KOH before use. (iii) Absorbing solution for CO2 (Potassium Hydroxide Solution) Dissolve 200 g of KOH with 400 ml of distilled water. (vi) Blocking water Dissolve 22 g of NaCl with 78 g of distilled water and add small amount of sulfuric acid and methyl orange. CO, CO2, O2 and N2 gas were collected in 20 Tedlar bag and analyzed by Orsat analyzer.

3. Results and Discussion Emissions of particulate, CO, CO2 and PAHs from bagasse combustion in the studied sugar refinery factory in Ratchaburi Province, Thailand were investigated. Five samples were taken at isokinetic condition from stack of sugar refinery industry at Ratchaburi Province in the central region of §-39


Thailand during 24-26 February 2000. Sampling condition is shown in Table 3. Stack temperature is ranging from 224 ÌC to 229 ÌC. Percentage of isokinetic ranged from 95% to 101%. For sample collection, it has to be mentioned that the sample no.1 and no.4 were collected after the furnace was cleaned and unburned hydrocarbons and ashes were blown out, while other samples were collected without cleansing state. This would lead to the different in concentration of each parameter. The results of particulate, CO and CO2 in five samples are shown in Table 4.

In case of CO and CO2 It can be seen that CO:CO2 proportion in sample no.1, 3, 4 and 5 are about 1:37, 1:30, 1:34 and 1:22, respectively. But CO:CO2 proportion in sample no.2 is about 1:11. It can be explained that during sampling of sample no.2, incomplete combustion of hydrocarbon might have been occurred. Therefore, the rate of CO formation was found to be higher than the rate of CO2 formation. Possible reactions mechanism of CO formation are as follows: 13

Table 3 Sampling condition of bagasse combustion at sugar refinery industry in Ratchaburi Province

No.1 0.85 1.10 0.000095 0.198

No.2 0.85 1.10 0.000095 0.140

Sample No.3 0.85 1.10 0.000095 0.331

146 0.184 30.0

104 0.169 29.5

244 0.198 29.8

126 0.162 29.9

121 0.123 29.8

27.7

27.6

27.5

28.0

28.4

10.5

10.5

14.0

9.0

13.3

762 226 14.8 250091

763 228 14.9 255548

762 224 17.1 285719

763 225 13.6 237236

762 229 16.5 299121

32 1.076

26 0.841

32 1.494

36 1.050

25 1.267

1.046

0.823

1.472

1.029

1.252

98.5

95.2

96.0

98.9

101

Condition Pitot coefficient Probe tip diameter (cm.) Pitot tip area (m2.) Volume H2O vapor, standard conditions* (m3.) Total H2O collected (ml.) Water vapor in gas stream Dry molecular weight, stack gas (g/g-mole) Molecular weight, wet basis (g/g-mole) Average stack gas velocity head (mmH2O) Stack pressure, absolute (mmHg) Average stack temperature ( ÌC ) Average stack gas velocity (m/sec.) Stack flowrate, dry standard condition (m3/h) Net time of run (min) Volume dry gas, meter conditions (m3) Volume dry gas, standard condition (m3) Percent isokinetic %

No.4 0.85 1.10 0.000095 0.171

No.5 0.85 1.10 0.000095 0.164

Note : * Standard Condition at 25 ÌC, 760 mmHg

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O + CO2

O2 + CO

CO + OH

CO2+ H

or CO may be formed from decomposition of unstable intermediate present during thermal cracking of biomass species. This can be explained by the reaction below: RCO

R + CO

It is also suspected that during sampling of sample no.2, the remaining unburned hydrocarbon in the furnace from previous combustion process might have undergone further combustion that result in CO formation.

In case of particulate matters emission It is found that concentration of particulate matter of sample no.1, 3, 4 and 5 are still below the maximum permitted quantity in the Thailand Industrial Emission Standards, which was issued under Factory Act, B.E. 2535 (1992) (particulate matter equal to 400 mg/Nm3).14 For sample no.2, the concentration of particulate matter is over the above

standard. This may be caused by 1. Particulate matter emitted from combustion of biomass has three possible sources: (i) Matter which was not combustible; (ii) Matter which was capable of being burned but was not burned; and (iii) Matter formed during the process of combustion. 2. The mechanisms for the formation of soot involve the dehydrogenation of organics and polymerization leading to formation of large carbonaceous particles.15 In this study, eighteen compounds of PAHs; NAP, ACY, ACE, FLU, PHE, ANT, FLA, PYR, BaA, CHR, BeP, BbF, BkF, BaP, DBahA, BghiP, IP, COR were determined in considerations of carcinogenicity and prevalence in the atmosphere. These PAHs were analyzed by HPLC with equipped with scanning fluorescence detector. It was found that the peak of acenapthylene, acenapthene and fluorene could not be separated, in which they may be co-eluted together at the excitation wavelength of 280 nm and the emission wavelength of 330 nm. Therefore, acenapthylene, acenapthene and fluorene were be detected and quantified at fixed

Table 4 Flue gas condition of bagasse combustion and emissions of particulate, CO and CO2 Sample

Date

No. 1

24/2/00

Stack Temperature ( ÌC) 226

No. 2

24/2/00

228

21.3

No. 3

25/2/00

224

30.2

No. 4

25/2/00

225

31.0

No. 5

26/2/00

229

25.7

%Excess %CO Air (ppm) 35.7

0.3 (3000) 0.8 (8000) 0.4 (4000) 0.3 (3000) 0.5 (5000)

%CO2 11.0

Concentration of Emission Rate of Particulate Particulate (mg/m3)* (kg/hr) 319.3 47.8

8.5

669.6

102.2

10.6

368.1

59.1

10.2

344.4

52.4

10.1

375.5

67.3

Note : * = condition at 250 ( ÌC), 760 mmHg »Ÿπ¬å«‘®—¬·≈–Ωñ°Õ∫√¡¥â“π ‘Ëß·«¥≈âÕ¡ °√¡ à߇ √‘¡§ÿ≥¿“æ ‘Ëß·«¥≈âÕ¡

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excitation wavelength at 280, 288 and 259, respectively, and fixed emission wavelength at 330, 322 and 306, respectively. These conditions were studied and approved by previous researcher.16 The typical chromatogram for PAH standard solution is shown in Figure 2. In this study, repeatability test and calibration curve for each PAH were performed. It was found that the percentage of relative standard deviation for repeatability of retention time, peak area and peak height was less than 10%. For the standard calibration curves for each PAH, the peak area of each curve is directly proportional to the concentration of PAH; and the correlation coefficient (r) of each curve is above 0.9866. The peak height of each PAH also is directly proportional to the concentration of PAH; and the correlation coefficient (r) of each curve is above 0.9959.

In case of PAHs emission It is noticed that in all samples, DBahA was not found in both particulate and gas phase. Total PAHs concentration in particulate was found to be correspondent §-42

with total particulate concentration. In addition, total PAHs emission rate in particulate was also found to be correspondent with total particulate emission rate (see Figure 3). Concerning the characteristic profiles of PAHs in this study, it is evidenced that the most predominant PAHs in particulate was fluoranthene. The second most predominant was pyrene. The rest were BaP, naphthalene, BeP, acenapthene, phenanthrene, BbF, chrysene, anthracene, BaA, BghiP, indeno (1,2,3cd)pyrene, BkF, coronene, fluorene and acenapthylene. The most abundant PAHs in gas phase was naphthalene. The second most abundant was phenanthrene. The rest were fluorene, fluoranthene, pyrene, acenapthene, anthracene and acenapthylene. The minor concentration of PAHs in gas phase were coronene, BkF, indeno(1,2,3-cd)pyrene, BghiP, BbF, chrysene, BaA, BeP and BaP, which were generally high molecular weight PAHs. About 3.7% of total PAHs in particulate were trapped on glass fiber filter, which has a pore size of 0.45 µm. The major percentage of PAHs was passing through the filter, then trapped by the XAD-2 resin, and then be analysed. In Figure 4, it was found that the »Ÿπ¬å«‘®—¬·≈–Ωñ°Õ∫√¡¥â“π ‘Ëß·«¥≈âÕ¡ °√¡ à߇ √‘¡§ÿ≥¿“æ ‘Ëß·«¥≈âÕ¡


percentage contribution of napthalene, acenapthylene, acenapthene, fluorene, phenanthrene, anthracene, fluoranthene and pyrene appear predominantly in the vapours which have particle size of less than 0.45 µm. When compare PAHs concentration among samples, it is remarkably indicated that the total PAHs concentration and emission rate in samples No.2 are highest. This can be explained that incomplete combustion may have been occurred or the hydrocarbon species in the vapours may be undergone further reaction to form PAHs especially low molecular weight PAHs such as napthalene.

4. Conclusion From the finding of this study, it is concluded that the factory could improve their process and reduce pollutant emissions by better maintenance and regular cleaning or good house keeping. The alternative options are improve biomass feed rate or fuel blending.

Figure 3 Relationship between total particulate and total PAHs emission

5. Acknowledgements This study was sponsored by the Swedish International Development Cooperation Agency (Sida). We gratefully acknowledge

Figure 4 PAHs profiles of bagasse combustion from sugar refinery factory »Ÿπ¬å«‘®—¬·≈–Ωñ°Õ∫√¡¥â“π ‘Ëß·«¥≈âÕ¡ °√¡ à߇ √‘¡§ÿ≥¿“æ ‘Ëß·«¥≈âÕ¡

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the Asian Institute of Technology for project cooperation. We are extremely grateful to the Banpong Sugar Refinery Factory staffs for their assistants. We also deeply grateful to Mr. Pornchai Patiwanaruk, Environmental Research and Training Center, for his assistant to collect the samples from stack.

6. Reference 1. National Energy Policy Office, Renewable Energy and Energy Conservation Division, (1996), Policy Document on Renewable Energy and Rural Industry, Bangkok. 2. J.W. Twidell, (1993), Clean Energy Supply and Use, In Clean Technology and the Environment, Chapter 11, p. 316. 3. C. Flavin, and N. Lenssen, (1991), A Renewable Energy Future, Environmental Science and Technology, 25(5), p. 834. 4. National Energy Policy Office, (1998), Investigation of Pricing Incentives in a Renewable Energy Strategy. 5. Department of Energy Development and Promotion, Thailand Energy Situation 1996. 6. Department of Energy Development and Promotion, Thailand Energy Situation 1997. 7. D.L. Klass, and G.H. Emart, (1981), Fuel from Biomass and Waste, p.491. 8. International Agency for Research in Cancer (IARC), (1983), Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Humans: Polynuclear Aromatic Compounds, Part 1, Chemical, Environmental and Experimental Data, 32, pp 33-451. 9. K. Peltonen and T. Kuljukka, (1995), Review Air Sampling and Analysis of Polycyclic Aromatic Hydrocarbons, Journal of Chromatography A, 710, pp. 93-108.

10. G. Hathairatana, (1999), A Study on Air Pollution by Airborne Polycyclic Aromatic Hydrocarbons (PAHs) in Bangkok Urban Atmosphere, Ph.D Thesis of Environmental Engineering, Asian Institute of Technology, Bangkok, Thailand. 11. R.M. Harrison, D.J.T. Smith and L. Luhana, (1996). Source Apportionment of Atmospheric Polycyclic Aromatic Hydrocarbons Collected from an Urban Location in Birmingham, U.K., Environmental Science Technology, 30 (3), pp. 825-832. 12. Swedish Environmental Protection Agency, (1993), Environment and Public Health, An Epidemiological Research Programme Report, 4182, pp.79-85. 13. G.J. Minkoff and C.F.H. Tipper, (1962), Chemistry of Combustion Reactions, Butterworths, London, pp.133-147. 14. Industrial Environment Division, Ministry of Industry, (1993), Industrial Emission Standards, Vol. 109, Part 108, Published in the Royal Government Gazette, dated October 16. 15. N.A. Chigier, (1980), Pollution Formation and Destruction in Flames-Introduction, Prog. Energy Combust. Sci., Vol 6, pp. 4-15. 16. H. Mutsushita, Y. Takahashi, S. Azuma, H. Hiroi and T. Amagai, (1994), Development of Highly Sensitive Automatic Analysis for Polymuclear Aromatic Hydrocarbons in Airborne Particulates and Its Application to the Survey of Indoor Pollution, Proceeding of the International Conference on Indoor Air Quality, International Association for Indoor Air Quality, Rotlenflush, Switzerland, pp. 236-243.

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