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Journal of Science & Technology 99 (2014) 022-026 Emission Factors of Selected Air Pollutants of Pulverized Coal-Fired Power Plants Nghiem Trung Dung*, Tong Duy Cuong, Pham Ngoc Hai Hanoi Umversity ofScience and Technology, No 1, Dai Co Viet Str., Hai Ba Trung, Ha Noi, Viel Nam Received February 28, 2014; accepted- April 22 2014 The emissions of selected air pollutants of pulverized coal-fired power plants, namely Uong Bi and Quang Nmh were studied Existing sampling ports of the plants were used for the monitoring PM was collected isokinetically using a stack sampler, Metlab (Sweden) The concentrations of gaseous pollutants were measured by a combustion gas analyzer, Quintox KM - 9106 (UK) The emission factors of PM, CO, SO2 and NOx for UB, on the basis of coal consumed (g/kg) and electricity produced (g/kWh) are 4.91 and 3.45; 3.84 and 2.69; 18.91 and 13.25; 5.86 and 4.11 respectively For QN1, the emission factors of PM, CO SO2 and NOx are 0.16 and 0.07; 0.65 and 0.30; 0.18 and 0.08; 3.17 and 1.46 respectively Emission factors obtained in this study can be used for the air quality management of these plants in particular and of the thermal power sector in general Keywords: Emission factor, coal-fired power plant, air pollution, Uong Bi, Quang Nmh Introduction An emission factor (EF), which relates the quantity of air pollutants released from a source to some activity associated with those emissions, is a cost-effective tool to estimate the afr emission There are some accessible databases of emission factors from organizations such as the United States Environmental Protection Agency (US EPA) [1], the Worid Health Organization (WHO) [2] and the Intergovernmental Panel on Climate Change (IPCC) [3] However, an emission factor is a fijnction of many parameters including source type, design and age; input material type and quality; and air pollution control devices [4] So, each country needs to have its database of emission factors associated with its own level of technology However, such data are still scarce in Viemam To the best of our knowledge, no data on the emission factors of coal-fired power plants of Vietnam are found in the open literature This study is, therefore, aimed at the development of the emission factors for pulverized coal-fired power plants in Vietnam Materials and methods Selection of plants to be studied- Currently, in Vietnam, there are 14 coal-ffred power plants in operation (excluding small plants which not belong to EVN and VINACOMIN) hi which, 50% plants use the pulverized technology and the remammg ones use the circulating fluidized bed technology This study was designed to focus on ' Corresponding Author Tel: (+84) 912.238 486 E-mail: dung.nghiemtrung@hust.edu.vn plants using the pulverized technology Two plants, old and new, were selected to be studied The old one is Uong Bi coal-fired power plant (UB) in Uong Bi town, Quang Minh province UB started to operate in 1977 UB was designed with boilers (numbered from to 8) having the same technical specifications with the total capacity of 110 MW However, until monitonng time, only boilers (namely 5, 6, and 8) can be used The new one is Quang Ninh coal-fired power plant (QNl) in Ha Long city, Quang Ninh province QNl started to operate in 2009 QNl was designed with boilers (namely and 2) having the same technical specifications with the total capacity of 600 MW, Summary information collected at these plants IS presented m Table Selection ofthe monitoring time: Monitoring time was selected based on the monthly coal consumption of the plants in 2-3 previous years as shovm in Figure From Figure 1, April was considered to be representative for flie activities of the plants as their coal consumptions were in the average level April, therefore, was selected for monitoring For UB, monitoring activities were conducted on 6'" April, 2011 At that time, only boilers No and were in operation For QNl, monitoring activities were conducted on 7* April, 2011 and on that day, only boiler No was in operation Monitoring: Monitoring sites in UB and QNl are shown in Figure Existing sampling ports ofthe plants were used for the monitoring These sampling ports meet the requirement of 8D downstream and 2D upstream for the monitoring of PM by US EPA Method Where, D is interna! diameter for the case journal oi sicience & Technology 99 (2014) 022-026 of QNl and intemal equivalent diameter for the case of UB Internal equivalent diameter = 4(cross section/penmeter) Of course, these sampling ports are fully suitable for the monitoring of gaseous pollutants Three traverse points with the distances from the inside wall of the stack being 0.6, 0.8 and 1.0 m were used per sampling port (cross section) Table Summary information collected at the two plants Plant UB QNl Burning rate of coal (tone/boiler h) Air poliution control device (designed efficiency) PM ESP (> 98%) None SO2 NO, None PM ESP (> 99%) Absorber (95%) SO2 NO, None Excess air(%) 132.5 30 854,4 3-5 Staclc height (m) 100 150 Chemical composition of coal (%) Element C H N S UB 64-67 1.3 1.2 0.35 0.95 ONI 61-67 2.4 2.0 0.55 0.44 Monthy coal consumption o f t h e plants -UB2009 -B-UBZOIO -A—UB2011 -»«—QN12010 —«—QNlZOll Jan Feb Mar Apr Ma Aug Sep Oc Fig Monthly coal consumption ofthe plants in 2009, 2010 and 2011 QNl J ESP I Fig Description ofthe monitoring sites boiler No.Ol |aiid02 Journal OfScience & Technology 99 (2014) 022-026 Monitoring was conducted based on US EPA Methods 1, and Composite samples of PM were collected isokmetically on the glass fibre filters using a stack sampler of Metlab (Sweden) Sampling time per traverse point is 15-20 min, i.e., about Ih per composite sample Concentrations of gaseous pollutants m the flue gas were measured by a combustion gas analyzer of Quintox KM-9106 (UK) Results are automatically converted to the normal conditions of 25°C and atm by the analyzer For each site, monitoring was done in three times, in every ten minutes Temperature and velocity of the flue gas were also measured Calculation: Emission factors are calculated on the basis of amount of coal consumed and electricity produced in a shift Results and discussions 3.1 Concentrations of air pollutants The concentrations of selected air pollutants m the flue gas of the two plants are presented in Table At UB on the monitoring day, the ESP of boiler No was in malfunction then data of PM measured at this site are not used Comparison with QCVN 22:2009/BTNMT and QCVN 19:2009/BTNMT (for CO only) indicates that, for UB (column A, Kp=l and Kv=0.8), the concentration of SO2 in the flue gas exceeded the limit value; while for QNl (column B, Kp=0 85, Kv=0.6 and volatile matter < 10%), the concentration of NO^ was higher than limit value The concentrations of selected air pollutants except NOx in the flue gas of UB are higher than those of Q N l The concentration of each air pollutant in the flue gas is influenced by a number of factors including the burning rate of coal (BR), the flow rate (FR) and the emission factor (EF) For NO,, the ratio of (BRQNI/BRUB)/[(FRQNI/FRUB).(EFONI/EFUB)] * 1,5 >1, therefore, the concentration of NOs in the flue gas of QNl is higher than that of UB On the contrary, for the remaining air pollutants, these ratios 1) also reflects tiiis fact This leads to lower temperature and lower concenO-ation of oxygen in the combustion zone [5, 6] resulting in a significam reduction ofthe emissions of all types of nitric oxides (thermal, prompt and fuel) [6] in Q N l compared with those in UB The second and minor reason is that, NO2, an acidic gas, in the mixture of NOx can be absorbed by the lime slurry in the lime absorber of Q N l Of course, it is needed to take the nitrogen content of coal into account As the nitrogen content of coal in Q N l (0.55%) is higher than fliat in UB (0.35%) then the emission of fUel NO in the former might be higher than that in the latter However, according to Noel de Nevers [6], the fi-action of fiiel nitrogen that can be converted to NOx in the flue gas is typically 20-50%i and much depends on the concentration of oxygen in the high-temperature part of the flame, meaning that, it can be minimized if excess air is minimized and vice versa Therefore, as mentioned earlier, this fraction could be lowered to about 20 % for QN and raised to about 50% for UB It means that the difference in the emissions of fuel NO between QNl (about 0.55 * 20%) and UB (about 0.35 * 50%) can be negligible The sulfur in coal can be existed in a number of forms includmg the form of chemically bond sulfiir and iron pyrite (FeSz) When the coal is bumed, almost all of the sulfur in the fiiel, whatever chemically bond or pyritic, is converted to SO: and earned along with stack gas [6] This means that the theoretical (calculated) emission factor of SO2 for UB (without control device for sulfur dioxide), which is based on the sulfur content of the coal (0.95%), would be about 19 g/kg coal This calculated value is equivalent to the measured one of this parameter (18.91g/kg coal) supposing that data obtained in this study are reliable The comparison of emission factors is shown in Table Generally, the emission factors in this study can be considered to be in the same range wi^ those of other studies This may, again, reflect the reliability ofthe emission factors obtained although il is understood that, the comparison, in many cases, is relative as the emission factor is a function of severai parameters mcluding the type and quality of ftiel, the technology of combustion/process, the type 'ant efficiency of air pollution control devices etc Journal ofScience & Technology 99 (2014) 022-026 Table Selected data of the flue gas monitored at the two plants Flow rate of flue Concentration, mg/Nm^(25''C va latm) c , Temp, of flue Velocity of Sample code *^ ,o„, flue gas (m/s) I gas (Nm^/h) | PM | CO | SO2 I NOx(as NO ^ I gas ("C) Uong Bi coal-fired power plant UB5-1 112 16.5 356400 189 807 328 UB5-2 112 17.1 369360 219.7 355 381 1075 UB5-3 112 17.2 395 371520 215 1330 UB8-1 111 6.1 131760 422 266 1570 UB8-2 111 6.5 140400 455 204 1720 UB8-3 112 6.7 144720 186 1693 451 Average 111,7 11,7 252360 219,7 240,2 1365,8 401,0 Quang Ninhl coal-firet power plan QN-1 82 19.4 493670 94 563 57 ON-2 84 24.6 625993 28.2 23 116 567 ON-3 25.4 84 646351 139 23 593 Average 83,3 23,1 588671 28.2 34,3 116,3 574,3 Colunm A 400 1500 1000(asNO2) , QCVN 22:2009/BTNMT Column B 200 500 1000(asNO2) (coal, volatile matter < 10%) QCVN19:2009/BTNMT Column A and B 1000 - - - - ! Table Emission factors of selected air poUulants of the plants Sample code Emission factor CO SO2 g/kg coal g/kWh g/kg coal g/kWh Uong Bi coal-fired power plant 4.12 17.59 12.34 89 8.61 6.04 24.29 17.04 4.89 3.43 30.22 21.21 2.09 1.46 12.33 8.62 1.71 1.19 14.40 10.06 160 1.12 14.61 10.21 3,84 2,69 18,91 13,25 Quang Ninhl coal-firec power plant 0.43 0.20 0.26 0.12 0.68 0.31 0.13 0.06 0.14 0.84 0.39 0.06 0,65 0,30 0,18 0,08 PM g/kg coal g/kWh UB5-1 UB5-2 UB5-3 UB8-1 , UB8-2 UB8-3 Average 4.79 4.96 4.99 36 3.48 3.50 4,91 3,45 QN-1 QN-2 QN-3 Average 0.13 0.17 0.17 0,16 0.06 0.08 0.08 0,07 * N O , (as NO) g/kg coal g/kWh 7.15 8.02 8.98 3.31 3.81 3.89 5,86 5.02 5.63 6.30 2.32 2.66 2.72 4,11 2.60 3.32 3.59 3,17 1.20 1.53 1.66 1,46 Table Comparison of emission factors in this study with others Emission factor, g/kWh Plant Source PM SO2 N O , (as NO) UB 3.45 13.25 4.11 QNl 0.07 0.08 1.46 This study ' India China 0.21 7.2 4.3 1.56 2.15 [7]; Average data of 10 coal-fired power plants in India having the designed capacity of each boiler from 50 to 500 MW, ESP (> 99%) for PM control, no control devices for NOx and SO2, excess air of 20.5% [8]: Average data of 15 coal-fired power plants in China having the designed capacity from 125 to 600 MW, ESP (> 95%) for PM control, lime absorbers (> 95%) for SO2 control, no control devices for NOx Journal of Science & Technology 99 (2014) 022-026 Conclusions The emission factors of air pollutants being PM, CO, SO2 and NO^, on the basis of coal consumed and electricity produced, for the pulverized coal-fired power plants being Uong Bi and Quang Ninh 1, were determined The calculated value ofthe emission factor of SO2 for UB well agrees with the measured one supposing that the emission factors obtained in this study are reliable data This study, therefore, contributes to Vietnam database of emission factors for pulverized coal-fired power plants in particular and for industries in general Emission factors obtained in this study can be used for the air quality management of these plants in particular and ofthe thermal power sector in general References [I] U.S Environmental Protection Agency, Compilation of Air Pollutant Emission Factors, AP-42 5th Ed , Vol,l, 2002 [2] World Health Organization Assessment of sources of air, water, and land pollution, A guide to rapid source inventory techniques and their use in formulating environmental control strategies Part one' Rapid inventory techniques in environmental pollution Geneva, 1993 [3] Amit Garg, Kainou Kazunan and Tinus Pulles IPCC Guidelines for National Greenhouse Gas Inventories Volume 2: Energy, 2006 [4] US Environmental Protection Agency Procedures for Preparing Emission Factor Documents USA, 1997 [5] Kenneth Wark, Cevil F Warner and Wayne T, Davis, Air pollution - Its ongin and control Addison Wesley Longman, Inc., 1998 [6] Noel de Nevers Air pollution control engineenng, 2"'' Edition McGraw-Hill Inc., New York, 2000 [7] Moli L Mittal, Chhemendra Sharma and Richa Singh Estimates of Emissions from Coal Fired Thermal Power Plants in India, 2012, Accessed on 15 February 2014 at [8] http://www.epa.gov/ttnchiel/conference/ei20/session5/ mmittal.pdf [9] Dongmei Li, Yang Guo, Yuan Li, Pengguo Ding, Qiang Wang and Zhenqian Cao Air Pollutant Emissions from Coal-Fired Power Plants Open Joumal of An- Pollution 1: 37-41, 2012 Accessed on 12 May 2014athttp.//dx.doi.OTg/10.4236/ojap.2012.12005 ... 10%), the concentration of NO^ was higher than limit value The concentrations of selected air pollutants except NOx in the flue gas of UB are higher than those of Q N l The concentration of... flue gas of QNl is higher than that of UB On the contrary, for the remaining air pollutants, these ratios
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