A poor mixing or laneing action in the furnace may result in a pulsating effect of the gases in the setting. This action may at times be remedied by admitting more air to the furnace. On account of the possibility of a pulsating action of the gases under certain conditions and the puffs or explosions, settings for this class of work should be carefully constructed and thoroughly buckstayed and tied.
Natural Gas—Natural gas from different localities varies considerably in composition and heating value. In [Table 50] there is given a number of analyses and heat values for natural gas from various localities.
This fuel is used for steam generating purposes to a considerable extent in some localities, though such use is apparently decreasing. It is best burned by employing a large number of small burners, each being capable of handling 30 nominal rated horse power. The use of a large number of burners obviates the danger of any laneing or blowpipe action, which might be present where large burners are used. Ordinarily, such a gas, as it enters the burners, is under a pressure of about 8 ounces. For the purpose of comparison, all observations should be based on gas reduced to the standard conditions of temperature and pressure, namely 32 degrees Fahrenheit and 14.7 pounds per square inch. When the temperature and pressure corresponding to meter readings are known, the volume of gas under standard conditions may be obtained by multiplying the meter readings in cubic feet by 33.54 P/T, in which P equals the absolute pressure in pounds per square inch and T equals the absolute temperature of the gas at the meter. In boiler testing work, the evaporation should always be reduced to that per cubic foot of gas under standard conditions.
|
When natural gas is the only fuel, the burners should be evenly distributed over the lower portion of the boiler front. If the fuel is used as an auxiliary to coal, the burners may be placed through the fire front. A large combustion space is essential and a volume of .75 cubic feet per rated horse power will be found to give good [Pg 230]
[Pg 231] results. The burners should be of a design which give the gas and air a rotary motion to insure a proper mixture. A checkerwork wall is sometimes placed in the furnace about 3 feet from the burners to break up the flame, but with a good design of burner this is unnecessary. Where the gas is burned alone and no grates are furnished, good results are secured by inclining the burner downward to the rear at a slight angle.
1600 Horse-power Installation of Babcock & Wilcox Boilers and Superheaters at the Carnegie Natural Gas Co., Underwood, W. Va. Natural Gas is the Fuel Burned under these Boilers
By-product Coke Oven Gas—By-product coke oven gas is a product of the destructive distillation of coal in a distilling or by-product coke oven. In this class of apparatus the gases, instead of being burned at the point of their origin, as in a beehive or retort coke oven, are taken from the oven through an uptake pipe, cooled and yield as by-products tar, ammonia, illuminating and fuel gas. A certain portion of the gas product is burned in the ovens and the remainder used or sold for illuminating or fuel purposes, the methods of utilizing the gas varying with plant operation and locality.
[Table 51] gives the analyses and heat value of certain samples of by-product coke oven gas utilized for fuel purposes.