Part 24 (2/2)
In the case of Mr Peabody's deductions M was found to be approximately 2 and formula (21) becomes directly, C = R + (N - 1)R' or formula (20)
The corrections to be made, as secured by the use of this formula, are very close to those secured by Pfaundler's method, where the point of maximum temperature is notWhere a longer period than this is indicated in the chart of plotted temperatures, the approxi and the maximum temperature is increased, the plotted results are further and further away froht line curve Where this period is not over five intervals, or two and a half ht line curve may be plotted by eye, and ordinarily the radiation correction to be applied may be determined very closely from such an approximated curve
Peabody's approxiive results within 003 degrees Fahrenheit for the liood as described The value of M, which is not necessarily a whole nuh in all probability such a value is a constant for any individual calorimeter which is properly operated
The correction for radiation as found on page 188 is in all instances to be added to the range of te point and the point chosen froe ives the heat of coether with that evolved by the burning of the fuse wire
The heat evolved by the burning of the fuse wire is found froht of wire burned and the heat of coraht of wire used by 17, the result being in grararade
Other small corrections to be made are those for the formation of nitric acid and for the combustion of sulphur to sulphuric acid instead of sulphur dioxide, due to the en than would be possible in the atmosphere
To make these corrections the bomb of the calorimeter is carefully washed out ater after each test and the a this water with a standard solution of a assumed to be nitric acid Each cubic centi solution used is equivalent to a correction of 265 calories
As part of acidity is due to the formation of sulphuric acid, a further correction is necessary In burning sulphuric acid the heat evolved per gram of sulphur is 2230 calories in excess of the heat which would be evolved if the sulphur burned to sulphur dioxide, or 223 calories for each per cent of sulphur in the coal One cubic centirams of sulphur as sulphuric acid, or to 0286 223 = 638 calories It is evident therefore that afterthe nu by the heat factor for nitric acid (265) a further correction of 638 - 265 = 373 is necessary for each cubic centi sulphuric instead of nitric acid This correction will be 373/0297 = 13 units for each 001 gram of sulphur in the coal
The total correction therefore for the aqueous nitric and sulphuric acid is found by13 calories for each 001 gram of sulphur in the coal This total correction is to be deducted froe and the amount equivalent to the calorimeter
After each test the pan in which the coal has been burned must be carefully exaone complete combustion The presence of black specks ordinarily indicates unburned coal, and often will be found where the coal contains bone or slate Where such specks are found the tests should be repeated In testing any fuel where it is found difficult to cohed aht of fuel and naphthaline being approxiram The naphthaline has a known heat of co obtainable from the United States Bureau of Standards, and from the combined heat of combustion of the fuel and naphthaline that of the for of a definite weight of standard naphthalinethe calorimeter as a whole
COMBUSTION OF COAL
The coe, and the reatly to suit the various coals and the innumerable types of furnaces in which they are burned, that any instructions given for the handling of different fuels eneral character For each kind of coal there is soive the best results for each individual set of conditions General rules can be suggested, but the best results can be obtained only by following such methods as experience and practice show to be the best suited to the specific conditions
The question of draft is an all important factor If this be insufficient, proper combustion is ireat enough to draw the necessary aases may pass off only partially consumed On the other hand, an excessive draft may cause losses due to the excess quantities of air drawn through holes in the fire Where coal is burned however, there are rarely complaints froulated by the boiler daive only the draft necessary for the particular rate of combustion desired The draft required for various kinds of fuel is treated in detail in the chapter on ”Chimneys and Draft” In this chapter it will be assuulated to give the best results for each kind of coal
TABLE 40
ANTHRACITE COAL SIZES
_________________________________________________________________ | | | | | | | Testing Segments | | | Round Mesh | Standard Square | | | | Mesh | | Trade Name |__________________|__________________| | | | | | | | | Through | Over | Through | Over | | | Inches | Inches | Inches | Inches | |___________________________|_________|________|_________|________| | | | | | | | Broken | 4-1/2 | 3-1/4 | 4 | 2-3/4 | | Egg | 3-1/4 | 2-3/8 | 2-3/4 | 2 | | Stove | 2-3/8 | 1-5/8 | 2 | 1-3/8 | | Chestnut | 1-5/8 | 7/8 | 1-3/8 | 3/4 | | Pea | 7/8 | 5/8 | 3/4 | 1/2 | | No 1 Buckwheat | 5/8 | 3/8 | 1/2 | 1/4 | | No 2 Buckwheat or Rice | 3/8 | 3/16 | 1/4 | 1/8 | | No 3 Buckwheat or Barley | 3/16 | 3/32 | 1/8 | 1/16 | |___________________________|_________|________|_________|________|
Anthracite--Anthracite coal is ordinarily iven in Table 40
The larger sizes of anthracite are rarely used for co purposes as the demand for domestic use now lienerally found are Nos 1, 2 and 3 buckwheat In soe of bituminous coal, say, 10 per cent, is sometimes mixed with the anthracite and beneficial results secured both in economy and capacity
Anthracite coal should be fired evenly, in small quantities and at frequent intervals If this method is not followed, dead spots will appear in the fire, and if the fire gets too irregular through burning in patches, nothing can be done to rerade of fuel has been fired it should be left alone, and the fire tools used as little as possible Owing to the difficulty of igniting this fuel, carefires
The intervals of cleaning will, of course, depend upon the nature of the coal and the rate of coh combustion rates, fires will have to be cleaned twice on each eight-hour shi+ft As the fires become dirty the thickness of the fuel bed will increase, until this depthperiod In cleaning, the following practice is usually followed: The good coal on the forward half of the grate is pushed to the rear half, and the refuse on the front portion either pulled out or duood coal is then pulled forward onto the front part of the grate and the refuse on the rear section duood coal is then spread evenly over the whole grate surface and the fire built up with fresh coal
A ratio of grate surface to heating surface of 1 to from 35 to 40 will under ordinary conditions develop the rated capacity of a boiler when burning anthracite buckwheat Where the finer sizes are used, or where overloads are desirable, however, this ratio should preferably be 1 to 25 and a forced blast should be used Grates 10 feet deep with a slope of 1 inches to the foot can be handled corates 12 feet deep with the sarates over 8 feet in depth are necessary, shaking grates or overlapping durates rate surface or to the rear section Air openings in the grate bars should be made from 3/16 inch in width for No 3 buckwheat to 5/16 inch for No 1 buckwheat It is is be unifor holes in the fire, and it is for this reason that overlapping grates are recommended
No air should be admitted over the fire Steam is sometimes introduced into the ashpit to soften any clinker that may form, but the quantity of steam should be limited to that required for this purpose The stea blast will in certain instances assist in softening the clinker, but a reater quantity may be used by such an apparatus than is required for this purpose Corates have proved of advantage inin the ignition of fresh coal
Stacks used with forced blast should be of such size as to insure a slight suction in the furnace under any conditions of operation A blast up to 3 inches of water should be available for the finer sizes supplied by engine driven fans, automatically controlled by the boiler pressure