Document OEoMZXG8beE5RxYn8dXeMk5vj

2 SO, * V a lu e s in ta b le ta k e n c h ie fly fro m page 51 o f F u e l F lu e Oases p u b lish e d b y A m e rica n Oas Association. b Gas m easured a t 60 V a n d 30 in .'H g . * V a lu e (ro m "N ational Bureau of Standards. 368 K5 li oa S*3*2 HB Ions h 5 o9 Q 2tOo>* g5o3 OoS ' m3 az 8. < 2S sB 1 sH SS* ~iSf*gg. 03 Pao O Oao ps 30 o1n BB CHAPTER 14 1957 Guide Till o O 0 40 40 n w n 'O'-r-* io co T-4 tO >--HH -4< CeOo (O >0 *0 -h >u03 i-* *e> s U3 O ^ CO CO co IIII d co a> 3 Sgs co co co aa aa U5 IO o^4 OcOo <COg Ug3 I i i 18 lllii fH CO CO 40 H M 3 co UO ^H SScSnS ^ C<l C3 C C3 S22 i I I 123X22 o oo o> AAAA 40 05 C* 05 00 05 05 q o o d<M d+ q d co + d o St 5 ++ + <5 6 0 0 <M d n cq 3 0 3B d 0 <M D d 0 0 0 D 'O 0 0 q <N t H n cq d d w s*s O <N CO nD d O fl d S 0d 4<M d + + 4O 6C* . Q d CO + GQ <N d 0 . <N ++ + d CO, + + d d + CO * a .+ + tq 0 0 <N dd d tq tq d O c* 0 <N 0* (N I I ||1 S ooooiq&soo 0O M oc3 0 00 T3 *3 o a0o 0O X) 00a 030 3 S^x-5!ta0ai wWTaaf>3c>fl W*0b>3O> ^00a`8 P10pQ3 0 o o Fuels and Combustion 369 ing value so determined is termed the gross or higher heating value, and this is what is ordinarily meant when the heating value of a fuel is specified. In burning the fuel, however, the products of combustion are not cooled to the dew-point and the higher heating value cannot be utilized. When combustion is complete, the carbon in the fuel unites with oxygen to form carbon dioxide, CO2, the hydrogen unites with oxygen to form water vapor, H2O, and the nitrogen, being inert, passes through the re action without change. When combustion is incomplete, some of the carbon may unite with oxygen to form carbon monoxide, CO, and some of the hydrogen and hydrocarbon gases may not be burned at all. When carbon monoxide or other combustible gases are present in the flue gases, there is a loss of heat produced per unit of fuel consumed, and a lower combustion efficiency is obtained. Incomplete combustion may result from any or all of the following three conditions: (1) inadequate air supply, (2) insufficient mixing of air and gases, and (3) a temperature too low to produce ignition or maintain combustion. AIR REQUIRED FOR PERFECT COMBUSTION Air requirements for combustion of solid and liquid fuels are ordinarily expressed in pounds. On the other hand similar requirements for gaseous fuels are usually stated on a cubic foot basis. For solid and gaseous fuels this method of treatment corresponds to the standards of measurement commonly employed by these two industries. The weight of air required for perfect combustion per pound of solid or liquid fuel may be calculated after substitution of the proper percentages by weight of the various elements obtained from an ultimate analysis of the fuel in Equation 2. For gaseous fuels see Equation 3 for volume of air required. Solid or Liquid Fuels: ,, .. .. , . . 34.56 f"C , / 0\ Si rounds air required per pound fuel = ------ --i-1 H----- I -|-- 100 3 y 8/ 8 For Gaseous Fuels: (2) Cubic feet air required per cubic foot gas = 2.39 {CO + Hi) + 9.53 CH, + 16.68 CiH, + 23.82 CJJ, + 30.97 Ctfu, + 11.91 C,ffi 4- 14.29 CJI, + (3) 7.15 HtS -- 4.78 Os + 30.47 Illuminants Gaseous fuels may contain a wide variety of components classified as twummanfs, which are not separated by the usual methods of gas analysis. The principal ones in addition to ethylene and acetylene which are included *n Equation 3, with the air required per cubic foot of gas are: propylene, ^1.44; butylene, 28.58; pentene, 35.73; benzene, 35.73; toluene, 42.88; and xylene, 50.02. Since toluene and xylene are normally scrubbed from the ps before distribution, they may be disregarded in computing air required for a fuel gas. An approximate value of 30.47 (as shown in Equation 3) "ay- therefore, be employed. If ethylene and acetylene are included as wuminants, it is suggested that the value 19.65 be used. . If it is desired to make the gas calculations on a weight basis the equation expressed as follows: Pounds air required per pound fuel = 2.47 CO + 34.34 H, -f 17.27 CH, + 16.12 CtH, + 15.70 C,Ht + 15.49 CJhs + 13.30 C,H, + (4) 14.81 CtH, + 6.10 H - 4.32 0,