{8 gas passage normal to the ere iY Made of bricks and concrete used to pet name given to a steel chimney, P = barometric pressure Ra = gas constant of air T. = absolute temperature of air of Flue Gas, py where Ry = gas constant of flue gaswhere: H = height of the chimney Volume Flow Rate of Flue Gas, Q, where: mg = mass of flue'gas © Theoretical Velocity of flue gas, V_ st diameter at the top. *|: use the smalle For tapering chimney, Past Me: A steam boiler dry flue gases temperature of temperature o is 994.78 kg chimney base Determine the a 30 b. 40 Slit Solving for th hy = 0 =0 Solving for de Po =|E)Pnoe.ems in power PLANT ENGINEERING @pPart 16:Chimney + Seta neae rion dry flue Coler Plant consumes 9000 kg of coal per hour and produces 20 kg of temperate S8,PeF kg of coal fired. Outside air temperature is 32°C, average temperature of the flue gas entering the chimney is 343°C and the average 7 mperature of the dry flue gas in the chimney is 260°C. The gage fluid density Chinn28 ko per m and the theoretical draft of 2.286 om of H,O at the Ianey base is needed when the barometric pressure is 760 mm Hg. Psternina the height of the chintney in meters. . 50 b. 40 d, 60 Solving for the draft head, hy : “= 0.02286 [ 994.78 (0.00981) ] = 0.2231 kPa Solving for densities of air and gas: Pp Rala = 101.325 (0.287)(32 +273) = 1.1575 kg/m? 101.325 © [8319260 4.273) 30 = 0,686 kg/m? 0231 (1.1575 -0.686)(0.00981) thus; © H = 48.23m"ot ME Board Problem ’ | draft required fc * Prime 1p te ae stack are 15% of thea I 6.239 cm : Se \ sont in meters. Assume that the fue at, calcu ae the % Panta moc and molecular weight of 30. Assume alr fh a le sited sa Atm a 215 220 erature of 219¢. perature ¢ th oy b, 230 ahaa : solving for total draft, hy, : hy = 6.239 + 0.15h, hy = 7.34 cm of water 0.073(9.81) 0.72 kPa Solving for the densities of air and gas ; pat Rala " Pe 101.325 (0.287)(21+273) = 1.20 kg/m? ehh, Rly 101.325 (22 1494279 30 = 0,866 kg/m? —___0722 = (7.20-0,666)(0-00981) "H = 219.74mA steam 21.78 on a rate With economizer and air heater has an over-all draft loss of 101.3 KPa grater If the stack gases are at 177°C and if the atmosphere is at needed eh, 26°C. What Is the theoretical height of the stack in meter is pen no draft fans are used? feoasiste {ons are used? Assume tat the gas constant for the 545 4. 550 Pa Py Solving for total draft, hy : hy = height x density = 0.2178 ( 1000) | = 217.80 kg/om? Solving for densities of air and gas * (0.287)(26+273) 1.18 ko/m? = Po % * Rely 101.325 ___ = 9287(177+273) = 0.784 kg/m? _ 28 = (118-0.764) 550ma ¢ REINS Chimnay 4 | post ME Board Problem + fired steam boiler uses 3000 kg of ct : dl Ag coat jon is 15.5 Kg per kg coal at barometic essa Fequired fof s has a temperature of 2g50c and an Verage molecyiay, flue 9a uming an ash loss of 11% ang allowable gas Velocity aameter of the chimney, a 191m © 2.62 m b, 182m 4. 2.93 m f . The ular Weight of 30, of 7.5 ™/s, find the Shion Q = A Vacuat Solving for Q : The gas constant R: 8.314 c 30 = 0.277 Amount of air required: 15.5 ( 3000 ) = 46,500 kg/hr 8Y mass balance: Mat Me = Magy + Mg 500 +3009 = 9.11(3000) + m, t ™ = 49,170 kg/hr from: PV = mrT 98.2y, = (2270 73) 5 3600 |-277)205 +2 ) Yo = Q= 21.498 m/s ‘en; Substituting : 2L.49g _ xD? 498 = 05) "Ds 191m* Prime's Power Plant Engineering Reviewer by Capote & Mandawe ce ey CaP Oe & Me S. Past ME Board Problem The over-all draft loss of steam generating unit is 400 mm water. Air enters at 101.325 kPa , 26°C and the average flue gas temperature Is found to be 250°C. if no draft fans are to be installed, what is the height of the chimney ? Assume Ry = 0.277 kI/ka-K. a. 831.60m ©. 926.65 m b. 722.58 m d. 599.11 m Pa-Py Solving for total draft, hy, : hw = 0.4 (1000) = 400 kg/cm? Solving for densities of air and gas Pa 101.325, © (0.287)(26+273) 1.18 kg/m? 10.277(250+273) = 0.699 kg/m? 00 (1.18-0.699) 831,60 mryvis, : ae Chapter 1g fc 4 * supplementary Problem himuiey * what is the height of the chimny ir dens ey if the a —= air densities are 1 kg/m? ay Irving and ae. 50.82 m M15 kal respecte © 3 Pa and tne & 80 b, 71.16 m © 61.16 m 9s AL 4. 80.22 m aes Slit h H A Py Las _ 0.30 . ~ (1.5-1)(0.00981) sm thus ; © H =61.16m % 7. Supplementary Problem ‘ then; § If the air required for combustion is 20 kg per kg of coal and the boiler uses 3000 kg of coal per hr, determine the mass of gas entering the chimney. Assume an ash loss of 15%. a. 40,644 kg/hr c. 62,550 kg/hr b. 70,200 kg/hr d. 50,500 kg/hr Shatin M+ Man = mM, + Mm where: Ma = 20 my m, = 20m ™, + 0.15m, = 20m, + Mr m, = 20.85 mr m, = 20.85 (3000) thus; = m, = 62,550 kg/hr% Prime's Power Plant Engineering Reviewer by Capote & Mandawe a ipplementary Problem A 15 kg gas enters a chimney at 10 m/s. If the temperature and pressure of a Gas are 26°C and 100 kPa respectively, what is the diameter of the chimney. Use R = 0,287 W/kg-K. a 157m c. 222m b. 265m d.. 1.28m Slot Q= A Vectuat Solving for Q: Q= vy = Talo Po = 15(0.287)(26 +273) 100 = 12.87 ms then; Substituting: 2 12.87 = = (10) thus; 2 D= 128m 4 9. Supplementary Problem 4 39.5 m high chimney of radial brick masonry is described by the folowing top and bottom dimensions, D, = 1.9 m, d2 = 1.5 m, Dy = 3.2 m, dy = 2.3 m. Determine the moment due to wind load. a, 172,051 kg-m ©. 150,160 kg-m b. 160,388 kg-m d. 182,030 kg-m Slane 2 M=Pyh= a (2R2 +R) i = 300139.5)* (0.95)+1.6] thus; = M = 182,030 kg-mi Chapter 1 4 Oe Boy mamey + sooneee er plant, 5 kg of coal | o Is consumed In hat 25 kg of dry flue gas is produ poco wand re average temperature of the fe oon ae ca 3 ne average temperature of the flue gas inside chimney ical draft. of 5-cm of water at the base of ee i the chimney fuid specific volume is 0:0025 m’/kg, If the molecular : z PH leat the height of the chimney, nam aasm 52.86 m & 36.27 d, 55.42 m solving for Rw? 1 y= 0.05 (acta) = 20 kg/m? Solving for da and dy : py = — 101.0325 _ 0,287(25+273) = 1,185 kg/m? by = b_ 101.325 8.3143 a 50 +273) 0.699 kg/m?* Pri Power Plant Engineering Reviewer by Capote & Mandawe XVI-11 11, Past ME Board Problem A power plant is situated at an altitude having an ambient air at 96.53 kPa and 23.88°C. Flue gases at a rate of 5 kg/s enter the stack at 200°C and leaves at 160°C. The flow gases gravimetric analysis are 18% CO2, 7% Oz, and 75% Nz. Calculate the diameter of the stack in meters for a driving pressure of 0.20 kPa. Note: The actual velocity is 40% of the theoretical velocity. a 0.75m . ©. 0.95 b. 085m 4, 1.15 Sloane The molecular weight and gas constant of flue gas : co, 18% 9218 - g.00409 0.07 0; 7 =- = 0.00219 2 % oo 0. 0.75 = = 0.0267 75% Sz 8 Total 0.03306 nose 2 28 200+160 _ sgqo¢ 2 it 9653 | - (0.287)(180+273) ~ 0775 kal Vineoretial = y2gh i 0.775(0.00981) = 9.09 m/s Solving for the volume flow rate: (Q) Q=AV 5 (x3 aims = (5")o9)