نمونه برداری و آنالیز آلاینده های خروجی دودکش

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کارگاه آموزشی نمونه برداری و آنالیز آلاینده های خروجی دودکش 

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آلاینده های خروجی دودکش " نمونه برداری ذرات خروجی دودکش " نمونه برداری کازهای خروجی دودکش 

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نمونه برداری از ذرات دودکش 

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نمونه برداری از ذرات دودکش تعبین محل نمونه برداری از دودکش تعبین نقاط نمونه برداری 

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تعبین محل نمونه برداری ۱- اگر طول دودکش ده برابر قطر دودکش باشد محل نمونه برداری در دو برابر قطر دودکش از بالا و هشت برابر طول دودکش از پایین انتخاب می شودلدر دودکش های چهارگوش قطرمعادل برابر است با 0)+را / 6۵ < 02)). ۳- اگر طول دودکش از ده برابر قطر دودکش بزرگتر بود محل نمونه برداری باید حدفاصل دو برابر قطر دودکش از بالا و هشت برابر قطر دودکش از پایین باشد. ۳- یک سوم طول دودکش از بالا ۴- دو برابر قطر دودکش از بالا و پنج برابر قطر دودکش از پایین 

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۵- در دودکش های که دارای اسکرابراند محل نمونه برداری بلیدبه اندازه حداقل 1.5 بالاتر از انتهای اسکرابر باشد. ع- در صورتيكه ارتفاع بالاى اسكرابر بيش از 000 باشد محل نمونه برداری در حد فاصل 2 از پایین و 9 از بالا ۷-در دودکش های افقی. محل نمهنه برداری در فاصله همان 6 از ورودی و 62 از خروجی بوده و در قسمت بالای دودکش انتخاب شود. 

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الزامات نقطه نمونه برداری " زاویه جریان گاز با محور دودکش کمتراز ۱۵ درجه باشد. جربان منفی محلی وجود نداشته باشد. حداقل فشار ۵ پاسکال باشد. طنسبت حداکثر سرعت نبه حداقل سرعت کمتر از ۳ به ۲ باشد. ‎Sampling location‏ ‎Flow angle <15°‏ ‎Negative flow none‏ ‎Pressure difference (Pitot tube) >5Pa‏ ‎Ratio of max. to min. velocity oA‏ ‎Straight length before the sampling plane 5 duct diameters‏ ‎Straight length after the sampling plane 5 duct diameter‏ Number of sampling points See Table 1 and Table 2 

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تعیین فقاط نمونه برداری قطر دودکش نوع دودکش از لحاظ شکل 

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1. sampling line 2. sampling plane 3. orifice 00 Bo 

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Table 1 — Minimum number of sampling points for circular ducts tange of duct min. no. of min. no. of sampling | min. no. of sampling diameters sampling lines points per diameter. points per plane. (M) (diameters) incl excl centre} 6۱ excl centre centre | centre 0,35-0,70 0,70-1,00 1,00-2,00 Using only one sample point may give rise to errors greater than those sp standard, 

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Table 2—Minimum number of sampling points for rectangular ducts minimum numsers of sampling points per plane 1 4 9 18 minimum numberof side dvsions* 3 range of sampling ۵ < 009 0,09 t9 0,39 0,038 0 1,50 > 1,60 * Other side divisions may be necessary, for example ifthe longest duct side length s more than twice the length of the shortest sde. ® Using only one sampling poini may give rie to errors greater than those specified inthis standard 

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MWY ۹۶ ۷۸۹ ۹۶ > | ام ای ام اک | < اص 

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Duct Diameters that Measurement Site is Upstream from Flow Disturbance 1(Distance A) 0, 1 0 25 50 Minimum Number of Traverse Points 8 8 2 3 4 5 6 7 8 9 10 Duct Diameters that Measurement Site is from Downstream to Flow Disturbance ' ‏معمماده)‎ 8( Figure 1-1. Minimum number of traverse points for particulate traverses 

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Duct Diameters that Measurement Site is Upstream from Flow Disturbance '(Distance A) 05 15 25 50 2 3 4 5 6 7 8 9 10 Duct Diameters that Measurement Site is from Downstream to Flow Disturbance ‘(Distance B) Figure 1-2. Minimum number of traverse points for velocity (nonparticulate) traverses Minsmum Number of Traverse Points. 8 8 

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TABLE 1-1 CROSS-SECTION LAYOUT FOR RECTANGULAR STACKS Number of tranverse points layout [Matrix 

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ha ‏ددا‎ ‎bo ‎hos 5 7د ls7.7 9 ‏هدجا‎ ‏وديا‎ ‏كدعا‎ 3 دم ‎ha‏ ۲ in hs. be. 9 bs. es. 3 13 1 همد »هد ‎bes‏ ‏عنما ‏مه ‏۹ ‏كدعا ‎cm‏ ‏هدم هوا 1 TABLE 1-2 LOCATION OF TRAVERSE POINTS IN CIRCULAR STACKS [Percent of stack diameter from inside wall to tranverse pofnt] [Number of traverse points on = diameter 5 ba 2 [aa his bs 1 hos bs.0 ۳۹ ۹ ۹ ‏مهدا یم‎ bs.0 [20.6 ‏عدن دجم‎ ‏دععا‎ Le ‏دجوا‎ دكا ‎bo.‏ ‏هده ۳ lrraverse lpoime 

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ود < فاصله نقطه نمونه برداری تا دیواره دودکش | عنقطه نمونه برداری روی قطر دودکش قطر دودکش 2 1 1 مقادیر ببصورتدرصد 101 تعداد نقاط نمونه برداری در یک مسیر قطر . ز شماره نقطه نمونه برداری خاص در طول آن قطر 

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For circular ducts where itis necessary to increase the number 21 sampling lines (diameters| or the number of sampling points{ecause of adverse fiow conditions for instance), the general formula 1 for calculating the distance, ftom the duct wal along the diameter, are 60 (82) (83) where incex of sampling point along the diameter number of sampling points along each sampling line (including the centre); number of sampling lines (diameters): distance of point i from the duct wall diameter of -he duct, in meters. 0 ng x 

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97 ۱24 221 a) 3 n=2 54 

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نمونه برداری ایزو کینتیک 

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:مواردی که باعث نمونه برداری صحیح می شود جريان كاز در دودکش از نظر سرعت. دما و فشار پایدار و یکنواخت باشد. جریان گاز در دودکش موازی با نازل باشد ” شرایط ایزوکینتیک در کل مدت نمونه برداری برقرار باشد. — نمونه ها از نقاط تعیین شده در هر خط نمونه برداری با دقت برداشته شود. انتخاب و طراحی مسیر نمونه برداریبه گهنه ای که متراکم و کنداسه شدن گازها و نشتی جلوگیری شود. ” کالیبره بودن تجهیزات 

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:مواردی که باعث نمونه برداری صحیح می شوند “در نمونه برداری های که فیلتر در خارج از دودکش قرار دارد ذرات رسوب كرده قبل از فيلتر شستشو. خشك و نوزين شود. توزین و نمونه برداری طبق روش استاندارد انجام شود. 

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فیلتر "7 راندمان بالای ۹۹/۵ برای ذرات ۰/۳ میکرومتر عدم واکنش با گازهای موجود در جریان هوا مقاوم به حرارت حداکثر وزن ذرات معلق روی فیلتر معادل با وزن فیلتر است. " فیلتر بایستی حداقل در دمای ۲۰ درجه بالاتر از دمای دود کش خشک شود. 

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134 Sampling — assemble the sampling train in the cleanest possible area, and check for possible leaks according to 7.4.2 requirements; — preheat the relevant parts of the sampling train up to the selected filtration temperature, e.9., stack temperature or recommended temperature of 160 °C +5 °C. Ensure that the port has been fully cleaned and insert the probe in the duct at a selected point, avoiding contact of the entry nozzle with any deposits within the duct. Seal the opening of the access port to minimise air in-leakage or exposure of operators to toxic gases; — estimate the isokinetic sampling rate from preliminary stack velocity, temperature, and dry gas molecular weight, and moisture content determinations; — tum the sampling probe until the entry nozzle is facing upstream within + 10°. Recalculate, if necessary, the isokinetic sampling rate based upon the flue gas velocity, temperature, and composition (if monitored) at the sampling point. Open the shut off device, start the suction device and adjust the flow rate in order to sample isokinetically within + 10 %; — the sampling duration at each selected point shall be identical. The total sampling duration shall be at least 30 min and a maximum dependant upon the constant nature of the process. Each point should be sampled for a minimum of 3 min; 

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— check the flue gas velocity and sampled gas volumetric flow rate at each sampling point at least every 3 min in order to recalculate the isokinetic sampling rate, Adjust the sample train rate so that it differs from isokinetic sampling by not more than + 10 %, it means that the isokinetic sampling index is 0,9 + 1,1; — do not stop sampling when moving the sampling train to the next sampling point in the same sampling line. If the flue gas velocity or temperature changes at the new sampling point, recalculate the necessary isokinetic sampling rate and adjust the flow rate of the sampling system immediately; or, if a flow rate adjustment is insufficient to achieve isokinetic sampling, stop the test and replace the nozzle with one appropriate to the sampling conditions; — af least every 3 min record the sampling time and all parameters necessary for checking both isokinetic sampling index and stability of ducted gas flow; — after completing sampling at all the selected points of the sampling line, close the shut off device and the suction device, remove the sampling tran from the duct and reposition it on the next sampling line; NOTE 1 Fora low dust concentration measurement, its generally better to use only one fiter for a complete measurement (cumulative sampling). 

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8 Additional aspects 81. Thermal behaviour of particulate matter Emitted dusts are generally thermally stable. However, on some processes the gases to be sampled contain unstable or semi-volatile compounds (i.e. in particulate form at low temperature, in gaseous form at higher temperature). In such a case the measured concentration depends on the fitration temperature andlor on the tying temperature before final weighing, Such phenomena have been reported in various industries: — power plant equipped with desulphurisation processes, because the occurrence of hydrates; — heavy fuel ol power plants or diesel engines, because $0, andlor organic compounds; — lass furmaces, because the occurrence of semi volatile boron compounds has been experienced; 

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Differences in the measured dust concentrations (up to factor 10) have been experienced and therefore in such cases the measured results shall be associated with a stated temperature (ie. the highest temperature sustained by the sampled dust before weighing). Because of the extreme variety of the situations, which may be encountered, itis not possible to find a conventional temperature which could be relevant in all the cases. However, since the complete trapping of volatile compounds would necessitate a very low fitration temperature and special care during sampling, more reproducible results may be achieved if these compounds are not trapped or are further evaporated when drying. Itis the reason why a conventional temperature of 160 °C, which leads to void trapping of most volatile compounds and to decompose most of hydrates is generally convenient. According to this convention, parts of the sampling train to be weighed should therefore be : a) conditioned at 180 °C before sampling: b) set at any temperature equal or less than 160 °C during sampling; ¢) conditioned at 160 °C after sampling. 

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مراحل نمونه برداری ذرات دودکش تعیین سرعت گاز در دودکش "انتخاب دبی و نازل مناسب جهت نمونه برداری ایزوکینتیک قرار دادن فیلتر وزن شده در فیلتر هلدر "" شروع نمونه برداری و یادداشت حجم هوا از کنتور دستگاه در ابتدا 9 انتهاى نمونه برداری " خشک کردن و توزین فیلتر و تعیین جرم ذرات در واحد حجم 

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نمونه برداری در شرایطی که فیلتر داخل دودکش قرار دارد 

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نمونه برداری در شرایطی که فیلتر خارج از دودکش قرار دارد 

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منال ۱- وزن اولبه فبلتر ۰ گرم ۲- وزن فبلتر بعد از نمونه برداری ۰ گرم ۳- اختلاف وزن ۵ گرم با ۵مبلی گرم ۴- حجم هوای برداشتی ‎my‏ ‏۵-غلظت ذرات در شرابط بهره برداری م ا ‎tur‏ m 

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۶-محاسبه غلظت در شرابط مرطوب: دج چاه Cinw= Cis ‎Cinta‏ | غلظت ذرات در شرایط نرمال مرطوب 8 : غلظت ذرات در شرايط بهره برداری 1 :دما گاز در شرایط بهره برداری 1 ‎Ty‏ : دمای استاندارد 180 ۲۱۳,۱۵ ‎Py,‏ فشار استاندارد ( ۳۵ ۱۰۱۳۲۳ 2 : فشار در شرایط بهره برداری(08) ‎ ‏شرايط دما و فشار دودکش 7 : ۳۶۹ درجه سانتیگراد ‏۶ ۸۳۵۲۲۰ پاسکال ‎273.15+369 101323 = 460% ‎Cinw='°" Saas 3500 273115 83522 m 

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۷-محاسبه غلظت در شرابط خشک: 100 10-7 موسرل < م6 ‎ol SoBe: Cua‏ در شرابط نرمال خشک ‎if‏ رطوبت گاز بر حسب درصد( ۲ درصد) ‎= 460 0 100-2 ‎Cina 00- i ‏غلظت ذرات در شرابط خشک معادل ۰ مبلی گرم در مترمکعب مي باشد. 

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نمونه برداری گازهای دودکش تعیین محل نمونه برداري تعیین نقاط نمونه برداري 

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9.2.1 Oxygen correction factor 2 Ona 2 ‏مر‎ Ose; is the reference percentage volume content of 0,; Onneas is the measured percentage volume content of Q. 

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پارامترهای معمول در سنجش گازهای محیطی اکسیژن منوکسیدنیتروژن " دی اکسیدنیتروژن دی اکسیدگوگرد کل هیدروکربن ها بر پایه متان 7 سولفیدهیدروژن "دی اکسیدکرین 

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دستگاه های موجود در بازار ایران جهت آنالیز کازهای دودکش Lancom III — Testo — Varo Plus(MRU) ~ 

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‎Se‏ )0( ات۱ ‎ ‎ ‎| Unit | Resolution | Discription of formula ‏با‎ | 1 2114-0 / 2 ۷ App = apn] 1-4 ‎ ‎ 

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۱0000۵0000۵۵۵۵۵۵ o is} 0 ۱ So ددم ۲ ۷ 2۱111 - ۲ 2 ۹ ضر ‎Butane:‏ نید 1 2 ۱ 1 2 1 1 Tse it 

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تبدیل و اصلاح نتایج اندازه گیری ‎Converting air pollutant concentrations‏ 1 ‎Correcting concentrations for altitude‏ 2 ‎Correcting concentrations for reference conditions‏ 3 ‎Correcting to a dry basis‏ 3.1 ‎Correcting to a reference oxygen content‏ 3.2 ‎Correcting to a reference carbon dioxide content‏ 3.3 

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تبدیل 0010 به ۱۳۵/0 1211110146 Clug! nt) = ‏سر‎ 10 ppnxMw 273 Mat Cg a 89 ‏هم‎ atm 1 ‏م‎ 2731) 2522 

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ميزان 00 در كار خروجى از ددکنی که ‎Jai VN atm gla ۲۰۰ ٩6‏ رده رز ۱۵۰۰۰ است. مد > برحسب ‎git‏ حساب كنيد ‎wt‏ ‏اند حجم گاز را در شرایط دلهشده از نظر دما و فشار حساب می‌کنیم: 1 43 1 رود لمكم روهط 114 1 سبس ميزان كاز رحسب لقأل به دست موأوريم: 1000 ف وو لور ه تاو 119*10 < 

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تصحیح غلظت با توجه به ارتفاع . 288-0۳۳ ) 8 ات Given an air poltant concentration at sea-level atmospheric pressure, the concentration at higher attudes can be obtained fom ths equation: 288-۳ )| تست vere h= alte, in km P = atmospheric pressure at sea level ۱ resure at atu h c = Airpolfant concentration, n mass per unt volume at sea eel atmospheric pressure and specified temperate T C= Concentration, in mass per unit volume at attudsh and specified temperature T ‘As an example, given an air pollutant concentration of 260 mg/m at sea level, calculate the equivalent pollutant concentration at an altitude of 2800 meters: C= 260 x [{ 288 -(6.5)2.8) }/ 286] * = 260 x 0.71 = 185 mglm* 

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Correcting to a dy basis Fase eigen an atc add a cut ee aoa polit ‏هرا و‎ soln cocetton.Theflwng auction canbe sa to coecthe messed ‘vet bas concn oas concent ‎bass‏ 9 دی > نار 1-۲ ‎ee‏ ‎C= Concent tha prin te ents‏ ‎ww fazion oy slg, oft ented eas‏ ‎As avenge tas concerto lop nage hang (Dome pant er au wad aa ‎Canis =40=(1-1f0}= 44g. 

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Correcting to a reference oxygen content Te‘lonngequion can be used coved a masue pliant concen ac aid ges wth a eased Op cone to an egal plat crcantaton nay ented gas tha specie erence amour of" اه سم °°" 00-0 تا تاه مه اجه ها و دهع ‎C= measured conan in a dry gas hang a measured volume Q‏ ‎‘Asan example a measured NOx concentration oF46 gpm indy gas hang & valu a Opis:‏ ‎por Oe‏ 209-5]=507(+ }209-3{ ‎‘hen coneced toa dy gos hang a speci rence cot of 3 volume‏ ‎Hi:‏ ‎«The measured gas concentration Cq st fst be comected toa dry basis before using te above equation,‏ 

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Correcting toa reference carbon xi content bal Tre lingequcin can ese uct meas par concern in tented gas ang amas CO crit an eq pla concen a site ‏وان‎ anu COs" 0اه و ‎vee‏ ‎COp‏ رل تین دراه ‎emia comet fa‏ = ‎meu concttton a dy as ang amegsuel os Cp‏ =( ‎Aenean aneaud aes cnn 20 nh? dy gs asa ese le hi‏ ۱ ‎ihn coca tac gas aga ged wee 0, come on‏ 

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EXAMPLE 1: volume correction A volume of 20m! was drawn from a sptometer at 20°C and 700mm Hi, What was the standard volume drawn? Solution; Using the ideal gas equation in state | and state 2 conditions, the equation V, = V,(P\T,/P,7;) can be applied to this case, where /, = volume at condition 2 (standard condition to be determined) V, = volume at condition | = 20m P, = pressure at condition | = 700mmHg P; = pressure at condition 2 = 760mmHg 7 = temperature at condition | = 20°C +273 = 293 K T, = temperature at condition 2 = 25°C +273 = 298 K Vy = (20% 100 x 298) (760 x 293) = 187m! 

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Conversion of ppm into ug/nt As ai applied example, consider using the ideal gas equation to help develop a conver- sion factor with which ppm can be converted into g/m’. Begin with the definition: | ppm = (moles of product)/(10° moles of air) Note: This is basically a volume measure; the definition is based on T=25°C and P=760mmHg. Recall here that a mole of any gas will occupy a volume of 22.4 liters when P = 760mmHg and T =0°C. The definition of ppm is based on T = 25°C; therefore, one must calculate the new volume using Eq. (1.1) Va[Vi = (Pi/PXD/T)) Normally, a constant pressure is assumed between conditions | and 2, such that ۲۱2۲۷۱۳/۲۸ < 2246273 +253 = 24 Sliter 

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Determination of Excess Air Another type of calculation often necessary involves combustion equipment stack gas samples obtained by Orsat analysis. Before outlining the fundamental basis of correctio: would be well to note several aspects of the problem. The stack sampling is leaving a combustion device contains certain levels of pollutants, which can be made to appear smaller if the total gas quantity is increased by adding nonpoilutant gas to the stream. For example, consider the ideal combustion of carbon monoxide with air (EPA-80/02, p. 5-4). CO + 0.5(0; + 3.76Nz) + CO; + L88N; as) Here, the percentage of CO, in the flue gas is %CO; = (mole of CO;)/(mole of CO; + mole of Nz) / + 1.88) 34.8% by volume ‘Suppose the same mole of CO were burned with 100% excess air? The combustion reaction now is given by CO + O2 + 3.76N2 — COz + 0.502 + 3.76N2 «6 Now the total moles of product is given by I mole CO; + 0.5 mole %CO, = 1/5.26 = 19.0% +3.76 mole Nz = 5.26 moles by volume Here the volume fraction of CO; was reduced by adding more air—in effect a dilution of the products by additional air. The original 2.88 moles of flue gas also could have been diluted through the addition of steam, a practice which is fundamentally possible since flue gas temperatures are normally higher than dew point temperatures. Suppose one added two moles of steam to the flue gas of Eq. (1.5): CO, + 1.88N, +2 moles steam 7 Now there are 4.88 moles of product and the CO; percentage would be %COz = 1/488 20.5% by volume 

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Clearly, the volume fraction of any gas present in the flue gas can be reduced by dilution, either by adding air or steam. It is for this reason that combustion equipment emission standards are written with a specified amount of excess air and based on dry flue gas, Flue gases which indicate combustion occurred with excess air different from 50% require correc- tion of observed concentration to that which would have been realized with 50% excess air. Stack gas measurements are usually made with the Orsat apparatus, an absorption device with separate chambers to remove CO;, CO, and O) from the flue gas in a manner permitting measurement of percentage of each present on a volume basis. The device is designed so that a dry basis measurement is realized. Excess air can be determined from the Orsat readings by computation as follows: Consider the complete combustion of carbon with air: C +0) +3.76N; > CO; +3.76N> (1.8) Here the product contains only CO: + Nz. With excess air, the reaction becomes CH (1 + 6903 + (1 + €)3.76Nz > CO + €Os + (1 + €)3.76N3 9 where ¢ is the number of moles of excess O, in the excess air. By definition, the percent of excess air is eA, = (Ay — AQ/A,M100) (1.10) = moles of actual air used in the combustion process moles of theoretical air (stoichiometric air) used ai combustion Ae = excess air ‘The theoretical air is ‏ی‎ + 3.76N2 from Eq. (1.8) with the actual air (1 + €)O, + (1 + €)3.76N> as given by Eq. (1.9). Combining Eqs. (1.8), (1.9) and (1.10): %Ae = (CO: + €3.76N2)/(Oz + 3.76N2)]100% aan where 4, 4 00% of stoichiometric 

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Equation (1.11) requires knowledge of the excess oxygen ¢ in order to compute the excess air. Actually, the Orsat analysis contains the information to accomplish the same result based on knowledge of the product composition alonc. Note that oxygen can only appeal the product if excess air combustion. Noting product with a subscript p: C+ +0902 + )۱ + €)3.76N2 > COxy + Ory + Noy 02 ‎the excess air required‏ موم ‎€)3.76Nz, the nitrogen which was part of the total air supplied‏ 14 ‎moles of excess air‏ ‎ ‎ ‎Now the nitrogen present in the product came from the combustion air (unless fuel contained significant nitrogen). Therefore, the actual O; supplied can be determined by computing the moles O2 which were associated with Nap. In air, | mole of O, is associated with 3.76 moles of Nz (by volume); therefore, for Nz» moles of nitrogen, the oxygen supplied is given by ‎ ‎©; supplied = Nzp/3.76 = 0.264Nap (13) ‏ها‎ ‎ ‎The theoretical Oy is 0.264Noy From Eq. (1.10) ‎Yode = WAs — A)/AJA00) = (10.2642, — (0.264N2, — O2p)1/(0.264N2y — O2p)} 100% [O25 /(0.264N oy — O2,)\(100) ‏واه‎ ‎ ‎If the combustion produced both CO and CO; (case of incomplete combustion), the measured must be reduced by the amount of oxygen which would have combined with ‎to form CO. ‘Then: ‎[O2p ~ 0.SCOp]/[0.264N 3, ~ (Ozp — 0.5CO,)]}100% 0 ‎ ‏لا ‎In each case, the quantity introduced is the percentage of each constituent as measured by the Orsat analyzer. 

صفحه 52:
(1) (1.2) (13) Volume equation: V/V, =(P,/P3)(T>/T\) Density equation: px/p, = (Ps/Py)(T\/T>) Concentration equation: Cy/C, = (P,/P\\(T,/T2) = volume at condition | volume at condition 2 pressure at condition 1 pressure at condition 2 absolute temperature at condition | absolute temperature at condition 2 density at condition | density at condition 2 = concentration at condition | = concentration at condition 2 ۱ ۱ ۱۱ ۱ ۱ ۱ 1 / Vy 2 5 1 11 0 8 0 GO where