JOURNAL OP SCIENCE A TECHNOLOGY * No 87 2012 DETERMINATION OF EMISSION FACTORS FOR COKE QUENCHING xAC DINH H$ S6 PHAT THAI CHO C6NG E)0AN DAP C6C Nguyen Thi Thu Thuy Nghiem Trung Dung Thai Nguyen Univ[.]
JOURNAL OP SCIENCE A TECHNOLOGY * No 87 - 2012 DETERMINATION OF EMISSION FACTORS FOR COKE QUENCHING xAC DINH H$ S6 PHAT THAI CHO C6NG E)0AN DAP C6C Nguyen Thi Thu Thuy Nghiem Trung Dung Thai Nguyen University of Technology Hanoi University of Science and Technology Received March 2,2012; accepted April 26,2012 ABSTRACT Emission factors of selected air pollutants being CO COa SO2 and NO for coke quenching of the Coking Factory of Thai Nguyen Iron and Steel Joint Stock Company ware studied Concentratkins of these pollutants were measured by a combuslkin gas analyzer Qulntox KM - 9106 Based on data monitored, funi^kyns on the correlations between the emission and the time during coke quenching were determined Total emissions and emission factors of Ihe pollutants for the process were detennined Emisston factors obtained in this study are In the same range with those of other studies T6M TAT OS tiin hdnh nghidn cOv xdc dinh h$ s6 phdt thdi cOa m^t s6 chit d nhiim khdng gdm CO, COi, SO2 vd NO cho cdng ao$n d$p c6c cOa Nhd mdy C6c hda thudc COng ty C6 phin Gang thdp Thdi Nguydn Ndng dd cdc chit nhiim dugc b&ng thiit bi Quintox KM - 9106 Tr6n cos&s6 li$u quan trie, dd xdc dinh dugc hdm tucmg quan glOa m&c dd phdt thdi vd ttt&i gian qud trinh d$p cdc Tir dd, tdng mirc phdt thdi cOng nhu h$ s6 phdt thdi cdc chit nhiim cho cdng do^n ndy dd dugc xdc djnh- Hd sd phdt thdi thu dugc & nghidn cim ndy nim tmng cung mdt cip dd so v&i mdt sd nghidn ciiu tuang tu khdc INTRODUCTION An emission factor is a tool that is used to estimate air pollutant emissions lb the atmosphere It relates tiie quantity of pollutants released from a source to some activity associated with those emissions Emission factors have long been used as a cost-effective means to develop area-wide emission inventories Emission inventories are fundamental tools for air quality management They are used for identifying major contributors of air pollutants, developing emission control strategies, determining applicability of permining programmes, and other related applications by an array of users including stale and local agencies, consultants, and industry in many countries in the worid [I] However, data on emission factors for industries are still scarce in developing countries including Vietnam To the best of our knowlegde, no data on the emission factors of iron and steel industry of Vietnam are available in the open literature This study is, therefore, aimed at Ihe development of the emission factors of iron and steel industry in Vietnamese conditions This paper presents preleminary results on Ihe emission factoid of coke quenching for Thai Nguyen Iron and Steel Joint Stock Company i MATERIALS AND METHODS Site description: The study was conducted at the Coking Factor)' of Thai Nguyen Iron and Steel Joint Slock Company Coal used for coking is from Phan Me and Lang Cam mines or imported from China These sources of coal are then mixed together to get suitable composition for coking (ash: 13 -17%, S content < l,5*'o, volatile maner: 17-30%, moisture < 8%) Mixed coal is baked in an airiess furnace (carbonization process) When lemperature is reached to 950 -1050 °C baked coal is pushed out of the furnace and brought to quenching lower Therefore, selected pollutants are mainly produced after the coke is pushed out of the carbonization furnace including the step of coke quenching Coking is conducted in batch-mode, about 20 minutes for each balch The flue gas of coke quenching, after being treated by a spray tower scrubber (made of stainless steel, 4m high) and a tray tower absorber (made of stainless steel, 6.2 m high), is emitted into the atmosphere at the height of JOURNAL OF SCIENCE & TECHNOLOGY * No 87 - 2012 Quenching pump Quenching tower Coke 4.''Wtittp^ray Sucking orifice Flue gas pipe Water 2i&? 4Bp«M*Bt iA': S e t t i l n g a5«.i-Water I g ' j i - S u p p l y pump 17 Monitoring port Fig I Diagram of the flue gas ireatmenl system and monitoring 33m via an exhaust pipe on the lop of the absorber This exhaust pipe is 2m high and I m in diameter There is a monitoring port located at 1.5 m fitim the open end of this exhaust pine This monitoring port was used for the study Monitoring: Monitoring was conducted on October, 2011, based on US EPA Methods 1-3 Concentrations of selected air pollutants in the flue gas were directiy measured by a combustion gas analyzer, Quintox KM - 9106 (Kane May, UK) Results are automatically converted and reported to the conditions of "C and I atm by the analyzer In order to obtain the net concentrations of these pollutants in Ihe fiue gas, their levels in the ambient air surrounding were also monitored Detection limits of Ihe equipment for the monitoring are CO - 0.01%, CO2 - 0.01%, SO2 - I ppm and NO - ppm Measurement was conducted for three batches of coke quenching For each batch, monitoring was done in five times at the following moments- (LI), (L2), 10 (L3), 15 (L4) and 20 (L5) minutes Temperature and velocity of the flue gas were also measured port coke quenching was determined Type of a function was chosen based on the least standard error using SPSS 16.0 Standard error is calculated by the following formula: SE = ^— n-2 Where, e, is error and n is sample size Once the type of a function is determined, parameters of this function are calculated by least-squares method The total emission of a pollutant is then obtained by integrating the function of this pollutant for the whole time (t) of a batch Total emission ^\f{i)dt Finally, the emission factor of each pollutant is calculated by dividing the total emission by the amount of coal used or the amount of coke produced per batch R E S U L T S ANS DISCUSSIONS Calculation- Emissions of the pollutants are decreased with time in a batch Therefore, in order to get the total emission of each pollutant, function on the correlation between the emission and the time for each pollutant during Average concentrations of the pollutants monitored in the flue gas of coke quenching are shown in Table I JOURNAL OF SCIENCE & TECHNOLOGV • No 87.20U Pollutant CO CO, SO, m r m Table I Summary information of the flue eas ofcoke quenching Average concentration (mn/Nm ) Flow rale U (n-1) U (n-3) L! (n-3) LI (n-1) (Nm'/s) 272.W20J 808,9*80.6 2S74.7±16r>.5 I298,6±I09.0 U(n-l) 118.6*7.1 25142.9±1795.9 11)775.511795.92 5986.4* J036.9 2394Atl036.8 628.6 153I.5±M.4 1075 9H0.9 570.5*22.2 50.9*10.4 178.7*11.8 180.819.4 104.4*2.7 89 2*3.4 35.7*4.6 25.5*2.0 n immber of memuratuetils al each moment (point); normal coiutlllon: 25 "C and I atm 75.4 13.2 Immediately after being pushed out of the carbonization furnace, the temperature of coke is still high, about 950^ At this lemperature, CO and COj can be generated by the reactions of C (coke) with not only Oj but also H:0: C ^ HjO -> CO + HI Table Total emissions of selected pollutants In coke quenching Formulafor Emission Pollutant calculation |50.28e-°''V/ CO and C + 2HiO -> CO2 + 2Hi Therefore, as seen from Table 1, in Ihc first ten minutes, the concentrations of CO, CO] and SO2 were very high Especially, the concentrations of two hazardous pollutants CO and SO; exceeded Ihe respective limit values of QCVN 19: 2009/BTNMT (column B) [2] However, NO in the flue gas was not so high and did not exceed the respective standard of QCVN !9:2009/BTNMT [2] This can be understood because the maximum temperature of the coke in this process was around 950 °C At or below this temperature, the formation of Ihermal NO from the combustion is negligible Furthermore, at higher temperature in the earlier carbonization process, most of nitrogen and other volatile organic matter in the coal can be considered to be gone, meaning that the fuel NO and prompt NO are low [3J This results in the tow concentration of NO in the flue gas Based on the monitoring data, different curves were screened using the software of SPSS 16.0 as shown in Figure And exponential function was chosen as it has the least SE It means that the emission rate of a pollutant in coke quenching follows "firstorder" kinetics Parameters of the exponential function for each pollutant were then determined by least-squares method and are shown in Table CO, j498.82c-°"'olf SO} |38.57«?-*""V/ 1 NO » ' l3.\5e-""til 380.98 (g/batch) 4032.26 (g/balch) 357.72 (g/batch) 33.90 (g/batch) 3.2 F.mission factors Emission factors of each pollutant, coalbased and coke-based, are obtained by dividing the total emission by the quantity of coal used/batch and quantity of coke produced/batch respectively These results are presented in Table Data on the emission factors of gaseous pollutants available in the open literature are mainly for the whole coking process Data for specific steps of this process are very scarce Some of Ihem the step of coke furnace pushing and controlled door leak emission are presented in Table Generally, the emission factors in Ihis study can be considered to be in the same range with those of other studies This may reflect the reliability of the emission factors obtained although it is understood that, the comparison, in many cases, is relative as emission factor is a function of several factors including fuel quality conditions of combustion/process, air pollution control system etc JOURNAL OF SCIENCE & TECHNOLOGY * No 87 - 2012 y = 38.57e-"°" SE-0.314 CuMc * ExpoticniiBl Fig Differeni curves used in screening Table Emission factors of selected pollutants in coke quenching Averse amount of coal/batch (kg) 7900 Average amount of coke/batch (kg) 6500 CO Coalbased 0.048 Cokebased 0.059 Emission factor (g/kg) CO; SO: Coal- Coke- Coal- Cokebased based based based 0.055 0.510 0.620 0.045 Coalbased 0.004 NO Cokebased 0.005 Table Comparision of emission factors in this study with others Pollutants CO CO, so, step of coke furnace pushing [4] 0.032 8.000 0.049 Controlled door leak emission (4] 0011 0.02 Whole coking process (UNEP, cited by [5]) 0.8 04 32 This study 048 0.510 0.045 JOURNAL OF SCIENCE & TECHNOLOGY • No 87 • 2012 CONCLUSIONS Emission factors of selected air pollutants being CO, COi, SOi, and NO, coal-based and coke-based, for coke quenching ofThai Nguyen Iron and Steel Joint Stock Company were determined This is a significant contribution to Vielnam database of emission factors for coking process in particular and for iron and steel industry in general TTiese emission factors can be used for emissions inventory and air quality management al the company Methodology used in this study can be !^)plied to other iron and steel industrial enterprises in the country REFERENCES US Environmental Protection Agency Procedures for Preparing Emission Factor Documents USA, 1997 MONRE QCVN i9:2009/BTNMT - National Technical Regulation on Industrial Emisston of Inorganic Substances and Dusts Hanoi 2009 Noel de Nevers Air pollution control engineering 2'*' Edition McGraw-Hill Inc., New York, 2000 US Environmental Protection Agency "Emission Factor Documentation for AP-42, Section 12.2: Coke Produclion " USA, 2008 Ci^c thfim djnh vk dinh gid xAc d$ng moi irudng -T^ng cue m6t trudng."Hudng d i n t$p b t o c i o ddnh gid tdc d$ng m6i trudng dy dn luy^n gang, thip" Hd N^i 2009 Author's address: Nghiem Trung Dung-Tel (+84)912238486- Email: ngtdung-inesl@maii.huLedu.vn School of Environmental Science and Technology' Hanoi University of Science and Technology No Dai Co Viet Str., Ha Noi, Viet Nam ... velocity of the flue gas were also measured port coke quenching was determined Type of a function was chosen based on the least standard error using SPSS 16.0 Standard error is calculated by the following... curves were screened using the software of SPSS 16.0 as shown in Figure And exponential function was chosen as it has the least SE It means that the emission rate of a pollutant in coke quenching follows... 2009 Author''s address: Nghiem Trung Dung-Tel (+84)912238486- Email: ngtdung-inesl@maii.huLedu.vn School of Environmental Science and Technology'' Hanoi University of Science and Technology No Dai