Gaseous fuels are limited to natural gas, blast furnace gas and coke oven gas, the first being a natural product and the two latter by-products from industrial processes. Though waste gases from certain processes may be considered as gaseous fuels, inasmuch as the question of combustion does not enter, the methods of utilizing them differ from that for combustible gaseous fuel, and the question will be dealt with separately.

Since coal is by far the most generally used of all fuels, this chapter will be devoted entirely to the formation, composition and distribution of the various grades, from anthracite to peat. The other fuels will be discussed in succeeding chapters and their combustion dealt with in connection with their composition.

Formation of Coal—All coals are of vegetable origin and are the remains of prehistoric forests. Destructive distillation due to great pressures and temperatures, has resolved the organic matter into its invariable ultimate constituents, carbon, hydrogen, oxygen and other substances, in varying proportions. The factors of time, depth of beds, disturbance of beds and the intrusion of mineral matter resulting from such disturbances have produced the variation in the degree of evolution from vegetable fiber to hard coal. This variation is shown chiefly in the content of carbon, and Table 35 shows the steps of such variation.

TABLE 35

APPROXIMATE CHEMICAL CHANGES FROM WOOD FIBER TO ANTHRACITE COAL

+ + -+ + -+ Substance Carbon Hydrogen Oxygen + + -+ + -+ Wood Fiber 52.65 5.25 42.10 Peat 59.57 5.96 34.47 Lignite 66.04 5.27 28.69 Earthy Brown Coal 73.18 5.68 21.14 Bituminous Coal 75.06 5.84 19.10 Semi-bituminous Coal 89.29 5.05 5.66 Anthracite Coal 91.58 3.96 4.46 + + -+ + -+

Composition of Coal—The uncombined carbon in coal is known as fixed carbon. Some of the carbon constituent is combined with hydrogen and this, together with other gaseous substances driven off by the application of heat, form that portion of the coal known as volatile matter. The fixed carbon and the volatile matter constitute the combustible. The oxygen and nitrogen contained in the volatile matter are not combustible, but custom has applied this term to that portion of the coal which is dry and free from ash, thus including the oxygen and nitrogen.

The other important substances entering into the composition of coal are moisture and the refractory earths which form the ash. The ash varies in different coals from 3 to 30 per cent and the moisture from 0.75 to 45 per cent of the total weight of the coal, depending upon the grade and the locality in which it is mined. A large percentage of ash is undesirable as it not only reduces the calorific value of the fuel, but chokes up the air passages in the furnace and through the fuel bed, thus preventing the rapid combustion necessary to high efficiency. If the coal contains an excessive quantity of sulphur, trouble will result from its harmful action on the metal of the boiler where moisture is present, and because it unites with the ash to form a fusible slag or clinker which will choke up the grate bars and form a solid mass in which large quantities of unconsumed carbon may be imbedded.

Moisture in coal may be more detrimental than ash in reducing the temperature of a furnace, as it is non-combustible, absorbs heat both in being evaporated and superheated to the temperature of the furnace gases. In some instances, however, a certain amount of moisture in a bituminous coal produces a mechanical action that assists in the combustion and makes it possible to develop higher capacities than with dry coal.

Classification of Coal—Custom has classified coals in accordance with the varying content of carbon and volatile matter in the combustible. Table 36 gives the approximate percentages of these constituents for the general classes of coals with the corresponding heat values per pound of combustible.

TABLE 36

APPROXIMATE COMPOSITION AND CALORIFIC VALUE OF GENERAL GRADES OF COAL ON BASIS OF COMBUSTIBLE

+ -+ + + Kind of Coal Per Cent of Combustible B. t. u. + + -+ Per Pound of Fixed Carbon Volatile Matter Combustible + -+ + -+ + Anthracite 97.0 to 92.5 3.0 to 7.5 14600 to 14800 Semi-anthracite 92.5 to 87.5 7.5 to 12.5 14700 to 15500 Semi-bituminous 87.5 to 75.0 12.5 to 25.0 15500 to 16000 Bituminous Eastern 75.0 to 60.0 25.0 to 40.0 14800 to 15300 Bituminous Western 65.0 to 50.0 35.0 to 50.0 13500 to 14800 Lignite Under 50 Over 50 11000 to 13500 + -+ + -+ +

Anthracite—The name anthracite, or hard coal, is applied to those dry coals containing from 3 to 7 per cent volatile matter and which do not swell when burned. True anthracite is hard, compact, lustrous and sometimes iridescent, and is characterized by few joints and clefts. Its specific gravity varies from 1.4 to 1.8. In burning, it kindles slowly and with difficulty, is hard to keep alight, and burns with a short, almost colorless flame, without smoke.

Semi-anthracite coal has less density, hardness and luster than true anthracite, and can be distinguished from it by the fact that when newly fractured it will soot the hands. Its specific gravity is ordinarily about 1.4. It kindles quite readily and burns more freely than the true anthracites.

Semi-bituminous coal is softer than anthracite, contains more volatile hydrocarbons, kindles more easily and burns more rapidly. It is ordinarily free burning, has a high calorific value and is of the highest order for steam generating purposes.

Bituminous coals are still softer than those described and contain still more volatile hydrocarbons. The difference between the semi-bituminous and the bituminous coals is an important one, economically. The former have an average heating value per pound of combustible about 6 per cent higher than the latter, and they burn with much less smoke in ordinary furnaces. The distinctive characteristic of the bituminous coals is the emission of yellow flame and smoke when burning. In color they range from pitch black to dark brown, having a resinous luster in the most compact specimens, and a silky luster in such specimens as show traces of vegetable fiber. The specific gravity is ordinarily about 1.3.

Bituminous coals are either of the caking or non-caking class. The former, when heated, fuse and swell in size; the latter burn freely, do not fuse, and are commonly known as free burning coals. Caking coals are rich in volatile hydrocarbons and are valuable in gas manufacture.

Bituminous coals absorb moisture from the atmosphere. The surface moisture can be removed by ordinary drying, but a portion of the water can be removed only by heating the coal to a temperature of about 250 degrees Fahrenheit.

Cannel coal is a variety of bituminous coal, rich in hydrogen and hydrocarbons, and is exceedingly valuable as a gas coal. It has a dull resinous luster and burns with a bright flame without fusing. Cannel coal is seldom used for steam coal, though it is sometimes mixed with semi-bituminous coal where an increased economy at high rates of combustion is desired. The composition of cannel coal is approximately as follows: fixed carbon, 26 to 55 per cent; volatile matter, 42 to 64 per cent; earthy matter, 2 to 14 per cent. Its specific gravity is approximately 1.24.

Lignite is organic matter in the earlier stages of its conversion into coal, and includes all varieties which are intermediate between peat and coal of the older formation. Its specific gravity is low, being 1.2 to 1.23, and when freshly mined it may contain as high as 50 per cent of moisture. Its appearance varies from a light brown, showing a distinctly woody structure, in the poorer varieties, to a black, with a pitchy luster resembling hard coal, in the best varieties. It is non-caking and burns with a bright but slightly smoky flame with moderate heat. It is easily broken, will not stand much handling in transportation, and if exposed to the weather will rapidly disintegrate, which will increase the difficulty of burning it.

Its composition varies over wide limits. The ash may run as low as one per cent and as high as 50 per cent. Its high content of moisture and the large quantity of air necessary for its combustion cause large stack losses. It is distinctly a low-grade fuel and is used almost entirely in the districts where mined, due to its cheapness.

Peat is organic matter in the first stages of its conversion into coal and is found in bogs and similar places. Its moisture content when cut is extremely high, averaging 75 or 80 per cent. It is unsuitable for fuel until dried and even then will contain as much as 30 per cent moisture. Its ash content when dry varies from 3 to 12 per cent. In this country, though large deposits of peat have been found, it has not as yet been found practicable to utilize it for steam generating purposes in competition with coal. In some European countries, however, the peat industry is common.

Distribution—The anthracite coals are, with some unimportant exceptions, confined to five small fields in Eastern Pennsylvania, as shown in the following list. These fields are given in the order of their hardness.

Lehigh or Eastern Middle Field Green Mountain District Black Creek District Hazelton District Beaver Meadow District Panther Creek District[33]

Mahanoy or Western Field[34] East Mahanoy District West Mahanoy District

Wyoming or Northern Field Carbondale District Scranton District Pittston District Wilkesbarre District Plymouth District

Schuylkill or Southern Field East Schuylkill District West Schuylkill District Louberry District

Lykens Valley or Southwestern Field Lykens Valley District Shamokin District[35]

Anthracite is also found in Pulaski and Wythe Counties, Virginia; along the border of Little Walker Mountain, and in Gunnison County, Colorado. The areas in Virginia are limited, however, while in Colorado the quality varies greatly in neighboring beds and even in the same bed. An anthracite bed in New Mexico was described in 1870 by Dr. R. W. Raymond, formerly United States Mining Commissioner.

Semi-anthracite coals are found in a few small areas in the western part of the anthracite field. The largest of these beds is the Bernice in Sullivan County, Pennsylvania. Mr. William Kent, in his "Steam Boiler Economy", describes this as follows: "The Bernice semi-anthracite coal basin lies between Beech Creek on the north and Loyalsock Creek on the south. It is six miles long, east and west, and hardly a third of a mile across. An 8-foot vein of coal lies in a bed of 12 feet of coal and slate. The coal of this bed is the dividing line between anthracite and semi-anthracite, and is similar to the coal of the Lykens Valley District. Mine analyses give a range as follows: moisture, 0.65 to 1.97; volatile matter, 3.56 to 9.40; fixed carbon, 82.52 to 89.39; ash, 3.27 to 9.34; sulphur, 0.24 to 1.04."

Semi-bituminous coals are found on the eastern edge of the great Appalachian Field. Starting with Tioga and Bradford Counties of northern Pennsylvania, the bed runs southwest through Lycoming, Clearfield, Centre, Huntingdon, Cambria, Somerset and Fulton Counties, Pennsylvania; Allegheny County, Maryland; Buchannan, Dickinson, Lee, Russell, Scott, Tazewell and Wise Counties, Virginia; Mercer, McDowell, Fayette, Raleigh and Mineral Counties, West Virginia; and ending in northeastern Tennessee, where a small amount of semi-bituminous is mined.

The largest of the bituminous fields is the Appalachian. Beginning near the northern boundary of Pennsylvania, in the western portion of the State, it extends southwestward through West Virginia, touching Maryland and Virginia on their western borders, passing through southeastern Ohio, eastern Kentucky and central Tennessee, and ending in western Alabama, 900 miles from its northern extremity.

The next bituminous coal producing region to the west is the Northern Field, in north central Michigan. Still further to the west, and second in importance to the Appalachian Field, is the Eastern Interior Field. This covers, with the exception of the upper northern portion, nearly the entire State of Illinois, southwest Indiana and the western portion of Kentucky.

The Western Field extends through central and southern Iowa, western Missouri, southwestern Kansas, eastern Oklahoma and the west central portion of Arkansas. The Southwestern Field is confined entirely to the north central portion of Texas, in which State there are also two small isolated fields along the Rio Grande River.

The remaining bituminous fields are scattered through what may be termed the Rocky Mountain Region, extending from Montana to New Orleans. A partial list of these fields and their location follows:

Judith Basin Central Montana Bull Mountain Field Central Montana Yellowstone Region Southwestern Montana Big Horn Basin Region Southern Montana Big Horn Basin Region Northern Wyoming Black Hills Region Northeastern Wyoming Hanna Field Southern Wyoming Green River Region Southwestern Wyoming Yampa Field Northwestern Colorado North Park Field Northern Colorado Denver Region North Central Colorado Uinta Region Western Colorado Uinta Region Eastern Utah Southwestern Region Southwestern Utah Raton Mountain Region Southern Colorado Raton Mountain Region Northern New Mexico San Juan River Region Northwestern New Mexico Capitan Field Southern New Mexico

Along the Pacific Coast a few small fields are scattered in western California, southwestern Oregon, western and northwestern Washington.

Most of the coals in the above fields are on the border line between bituminous and lignite. They are really a low grade of bituminous coal and are known as sub-bituminous or black lignites.

Lignites—These resemble the brown coals of Europe and are found in the western states, Wyoming, New Mexico, Arizona, Utah, Montana, North Dakota, Nevada, California, Oregon and Washington. Many of the fields given as those containing bituminous coals in the western states also contain true lignite. Lignite is also found in the eastern part of Texas and in Oklahoma.

Alaska Coals—Coal has been found in Alaska and undoubtedly is of great value, though the extent and character of the fields have probably been exaggerated. Great quantities of lignite are known to exist, and in quality the coal ranges in character from lignite to anthracite. There are at present, however, only two fields of high-grade coals known, these being the Bering River Field, near Controllers Bay, and the Matanuska Field, at the head of Cooks Inlet. Both of these fields are known to contain both anthracite and high-grade bituminous coals, though as yet they cannot be said to have been opened up.

Weathering of Coal—The storage of coal has become within the last few years to a certain extent a necessity due to market conditions, danger of labor difficulties at the mines and in the railroads, and the crowding of transportation facilities. The first cause is probably the most important, and this is particularly true of anthracite coals where a sliding scale of prices is used according to the season of the year. While market conditions serve as one of the principal reasons for coal storage, most power plants and manufacturing plants feel compelled to protect their coal supply from the danger of strikes, car shortages and the like, and it is customary for large power plants, railroads and coal companies themselves, to store bituminous coal. Naval coaling stations are also an example of what is done along these lines.

Anthracite is the nearest approach to the ideal coal for storing. It is not subject to spontaneous ignition, and for this reason is unlimited in the amount that may be stored in one pile. With bituminous coals, however, the case is different. Most bituminous coals will ignite if placed in large enough piles and all suffer more or less from disintegration. Coal producers only store such coals as are least liable to ignite, and which will stand rehandling for shipment.

The changes which take place in stored coal are of two kinds: 1st, the oxidization of the inorganic matter such as pyrites; and 2nd, the direct oxidization of the organic matter of the actual coal.

The first change will result in an increased volume of the coal, and sometimes in an increased weight, and a marked disintegration. The changes due to direct oxidization of the coal substances usually cannot be detected by the eye, but as they involve the oxidization of the carbon and available hydrogen and the absorption of the oxygen by unsaturated hydrocarbons, they are the chief cause of the weathering losses in heat value. Numerous experiments have led to the conclusion that this is also the cause for spontaneous combustion.

Experiments to show loss in calorific heat values due to weathering indicate that such loss may be as high as 10 per cent when the coal is stored in the air, and 8.75 per cent when stored under water. It would appear that the higher the volatile content of the coal, the greater will be the loss in calorific value and the more subject to spontaneous ignition.

Some experiments made by Messrs. S. W. Parr and W. F. Wheeler, published in 1909 by the Experiment Station of the University of Illinois, indicate that coals of the nature found in Illinois and neighboring states are not affected seriously during storage from the standpoint of weight and heating value, the latter loss averaging about 3-1/2 per cent for the first year of storage. They found that the losses due to disintegration and to spontaneous ignition were of greater importance. Their conclusions agree with those deduced from the other experiments, viz., that the storing of a larger size coal than that which is to be used, will overcome to a certain extent the objection to disintegration, and that the larger sizes, besides being advantageous in respect to disintegration, are less liable to spontaneous ignition. Storage under water will, of course, entirely prevent any fire loss and, to a great extent, will stop disintegration and reduce the calorific losses to a minimum.

To minimize the danger of spontaneous ignition in storing coal, the piles should be thoroughly ventilated.

Pulverized Fuels—Considerable experimental work has been done with pulverized coal, utilizing either coal dust or pulverizing such coal as is too small to be burned in other ways. If satisfactorily fed to the furnace, it would appear to have several advantages. The dust burned in suspension would be more completely consumed than is the case with the solid coals, the production of smoke would be minimized, and the process would admit of an adjustment of the air supply to a point very close to the amount theoretically required. This is due to the fact that in burning there is an intimate mixture of the air and fuel. The principal objections have been in the inability to introduce the pulverized fuel into the furnace uniformly, the difficulty of reducing the fuel to the same degree of fineness, liability of explosion in the furnace due to improper mixture with the air, and the decreased capacity and efficiency resulting from the difficulty of keeping tube surfaces clean.

Pressed Fuels—In this class are those composed of the dust of some suitable combustible, pressed and cemented together by a substance possessing binding and in most cases inflammable properties. Such fuels, known as briquettes, are extensively used in foreign countries and consist of carbon or soft coal, too small to be burned in the ordinary way, mixed usually with pitch or coal tar. Much experimenting has been done in this country in briquetting fuels, the government having taken an active interest in the question, but as yet this class of fuel has not come into common use as the cost and difficulty of manufacture and handling have made it impossible to place it in the market at a price to successfully compete with coal.

Coke is a porous product consisting almost entirely of carbon remaining after certain manufacturing processes have distilled off the hydrocarbon gases of the fuel used. It is produced, first, from gas coal distilled in gas retorts; second, from gas or ordinary bituminous coals burned in special furnaces called coke ovens; and third, from petroleum by carrying the distillation of the residuum to a red heat.

Coke is a smokeless fuel. It readily absorbs moisture from the atmosphere and if not kept under cover its moisture content may be as much as 20 per cent of its own weight.

Gas-house coke is generally softer and more porous than oven coke, ignites more readily, and requires less draft for its combustion.



THE DETERMINATION OF HEATING VALUES OF FUELS

The heating value of a fuel may be determined either by a calculation from a chemical analysis or by burning a sample in a calorimeter.

In the former method the calculation should be based on an ultimate analysis, which reduces the fuel to its elementary constituents of carbon, hydrogen, oxygen, nitrogen, sulphur, ash and moisture, to secure a reasonable degree of accuracy. A proximate analysis, which determines only the percentage of moisture, fixed carbon, volatile matter and ash, without determining the ultimate composition of the volatile matter, cannot be used for computing the heat of combustion with the same degree of accuracy as an ultimate analysis, but estimates may be based on the ultimate analysis that are fairly correct.

An ultimate analysis requires the services of a competent chemist, and the methods to be employed in such a determination will be found in any standard book on engineering chemistry. An ultimate analysis, while resolving the fuel into its elementary constituents, does not reveal how these may have been combined in the fuel. The manner of their combination undoubtedly has a direct effect upon their calorific value, as fuels having almost identical ultimate analyses show a difference in heating value when tested in a calorimeter. Such a difference, however, is slight, and very close approximations may be computed from the ultimate analysis.

Ultimate analyses are given on both a moist and a dry fuel basis. Inasmuch as the latter is the basis generally accepted for the comparison of data, it would appear that it is the best basis on which to report such an analysis. When an analysis is given on a moist fuel basis it may be readily converted to a dry basis by dividing the percentages of the various constituents by one minus the percentage of moisture, reporting the moisture content separately.

Moist Fuel Dry Fuel

C 83.95 84.45 H 4.23 4.25 O 3.02 3.04 N 1.27 1.28 S .91 .91 Ash 6.03 6.07 ——— 100.00

Moisture .59 .59 ——— 100.00

Calculations from an Ultimate Analysis—The first formula for the calculation of heating values from the composition of a fuel as determined from an ultimate analysis is due to Dulong, and this formula, slightly modified, is the most commonly used to-day. Other formulae have been proposed, some of which are more accurate for certain specific classes of fuel, but all have their basis in Dulong's formula, the accepted modified form of which is:

Heat units in B. t. u. per pound of dry fuel =

O 14,600 C + 62,000(H - -) + 4000 S (18) 8

where C, H, O and S are the proportionate parts by weight of carbon, hydrogen, oxygen and sulphur.

Assume a coal of the composition given. Substituting in this formula (18),

Heating value per pound of dry coal

( .0304) = 14,600 x .8445 + 62,000 (.0425 - ——-) + 4000 x .0091 = 14,765 B. t. u. ( 8 )

This coal, by a calorimetric test, showed 14,843 B. t. u., and from a comparison the degree of accuracy of the formula will be noted.

The investigation of Lord and Haas in this country, Mabler in France, and Bunte in Germany, all show that Dulong's formula gives results nearly identical with those obtained from calorimetric tests and may be safely applied to all solid fuels except cannel coal, lignite, turf and wood, provided the ultimate analysis is correct. This practically limits its use to coal. The limiting features are the presence of hydrogen and carbon united in the form of hydrocarbons. Such hydrocarbons are present in coals in small quantities, but they have positive and negative heats of combination, and in coals these appear to offset each other, certainly sufficiently to apply the formula to such fuels.

High and Low Heat Value of Fuels—In any fuel containing hydrogen the calorific value as found by the calorimeter is higher than that obtainable under most working conditions in boiler practice by an amount equal to the latent heat of the volatilization of water. This heat would reappear when the vapor was condensed, though in ordinary practice the vapor passes away uncondensed. This fact gives rise to a distinction in heat values into the so-called "higher" and "lower" calorific values. The higher value, i. e., the one determined by the calorimeter, is the only scientific unit, is the value which should be used in boiler testing work, and is the one recommended by the American Society of Mechanical Engineers.

There is no absolute measure of the lower heat of combustion, and in view of the wide difference in opinion among physicists as to the deductions to be made from the higher or absolute unit in this determination, the lower value must be considered an artificial unit. The lower value entails the use of an ultimate analysis and involves assumptions that would make the employment of such a unit impracticable for commercial work. The use of the low value may also lead to error and is in no way to be recommended for boiler practice.

An example of its illogical use may be shown by the consideration of a boiler operated in connection with a special economizer where the vapor produced by hydrogen is partially condensed by the economizer. If the low value were used in computing the boiler efficiency, it is obvious that the total efficiency of the combined boiler and economizer must be in error through crediting the combination with the heat imparted in condensing the vapor and not charging such heat to the heat value of the coal.

Heating Value of Gaseous Fuels—The method of computing calorific values from an ultimate analysis is particularly adapted to solid fuels, with the exceptions already noted. The heating value of gaseous fuels may be calculated by Dulong's formula provided another term is added to provide for any carbon monoxide present. Such a method, however, involves the separating of the constituent gases into their elementary gases, which is oftentimes difficult and liable to simple arithmetical error. As the combustible portion of gaseous fuels is ordinarily composed of hydrogen, carbon monoxide and certain hydrocarbons, a determination of the calorific value is much more readily obtained by a separation into their constituent gases and a computation of the calorific value from a table of such values of the constituents. Table 37 gives the calorific value of the more common combustible gases, together with the theoretical amount of air required for their combustion.

TABLE 37

WEIGHT AND CALORIFIC VALUE OF VARIOUS GASES AT 32 DEGREES FAHRENHEIT AND ATMOSPHERIC PRESSURE WITH THEORETICAL AMOUNT OF AIR REQUIRED FOR COMBUSTION

- - - Gas Symbol Cubic B.t.u B.t.u. Cubic Feet Cubic Feet Feet per per of Air of Air of Gas Pound Cubic Required Required per Foot per Pound Per Cubic Pound of Gas Foot of Gas - - - Hydrogen H 177.90 62000 349 428.25 2.41 Carbon Monoxide CO 12.81 4450 347 30.60 2.39 Methane CH_{4} 22.37 23550 1053 214.00 9.57 Acetylene C_{2}H_{2} 13.79 21465 1556 164.87 11.93 Olefiant Gas C_{2}H_{4} 12.80 21440 1675 183.60 14.33 Ethane C_{2}H_{6} 11.94 22230 1862 199.88 16.74 - - -

In applying this table, as gas analyses may be reported either by weight or volume, there is given in Table 33[36] a method of changing from volumetric analysis to analysis by weight.

Examples:

1st. Assume a blast furnace gas, the analysis of which in percentages by weight is, oxygen = 2.7, carbon monoxide = 19.5, carbon dioxide = 18.7, nitrogen = 59.1. Here the only combustible gas is the carbon monoxide, and the heat value will be,

0.195 x 4450 = 867.75 B. t. u. per pound.

The net volume of air required to burn one pound of this gas will be,

0.195 x 30.6 = 5.967 cubic feet.

2nd. Assume a natural gas, the analysis of which in percentages by volume is oxygen = 0.40, carbon monoxide = 0.95, carbon dioxide = 0.34, olefiant gas (C_{2}H_{4}) = 0.66, ethane (C_{2}H_{6}) = 3.55, marsh gas (CH_{4}) = 72.15 and hydrogen = 21.95. All but the oxygen and the carbon dioxide are combustibles, and the heat per cubic foot will be,

From CO = 0.0095 x 347 = 3.30 C_{2}H_{4} = 0.0066 x 1675 = 11.05 C_{2}H_{6} = 0.0355 x 1862 = 66.10 CH_{4} = 0.7215 x 1050 = 757.58 H = 0.2195 x 349 = 76.61 ——— B. t. u. per cubic foot 914.64

The net air required for combustion of one cubic foot of the gas will be,

CO = 0.0095 x 2.39 = 0.02 C_{2}H_{4} = 0.0066 x 14.33 = 0.09 C_{2}H_{6} = 0.0355 x 16.74 = 0.59 CH_{4} = 0.7215 x 9.57 = 6.90 H = 0.2195 x 2.41 = 0.53 —— Total net air per cubic foot 8.13

Proximate Analysis—The proximate analysis of a fuel gives its proportions by weight of fixed carbon, volatile combustible matter, moisture and ash. A method of making such an analysis which has been found to give eminently satisfactory results is described below.

From the coal sample obtained on the boiler trial, an average sample of approximately 40 grams is broken up and weighed. A good means of reducing such a sample is passing it through an ordinary coffee mill. This sample should be placed in a double-walled air bath, which should be kept at an approximately constant temperature of 105 degrees centigrade, the sample being weighed at intervals until a minimum is reached. The percentage of moisture can be calculated from the loss in such a drying.

For the determination of the remainder of the analysis, and the heating value of the fuel, a portion of this dried sample should be thoroughly pulverized, and if it is to be kept, should be placed in an air-tight receptacle. One gram of the pulverized sample should be weighed into a porcelain crucible equipped with a well fitting lid. This crucible should be supported on a platinum triangle and heated for seven minutes over the full flame of a Bunsen burner. At the end of such time the sample should be placed in a desiccator containing calcium chloride, and when cooled should be weighed. From the loss the percentage of volatile combustible matter may be readily calculated.

The same sample from which the volatile matter has been driven should be used in the determination of the percentage of ash. This percentage is obtained by burning the fixed carbon over a Bunsen burner or in a muffle furnace. The burning should be kept up until a constant weight is secured, and it may be assisted by stirring with a platinum rod. The weight of the residue determines the percentage of ash, and the percentage of fixed carbon is easily calculated from the loss during the determination of ash after the volatile matter has been driven off.

Proximate analyses may be made and reported on a moist or dry basis. The dry basis is that ordinarily accepted, and this is the basis adopted throughout this book. The method of converting from a moist to a dry basis is the same as described in the case of an ultimate analysis. A proximate analysis is easily made, gives information as to the general characteristics of a fuel and of its relative heating value.

Table 38 gives the proximate analysis and calorific value of a number of representative coals found in the United States.

TABLE 38

APPROXIMATE COMPOSITION AND CALORIFIC VALUE OF CERTAIN TYPICAL AMERICAN COALS

No. State County Field, Bed Mine Size or Vein ANTHRACITES 1 Pa. Carbon Lehigh Beaver Meadow 2 Pa. Dauphin Schuylkill Buckwheat 3 Pa. Lackawanna Wyoming Belleview No. 2 Buck. 4 Pa. Lackawanna Wyoming Johnson Culm. 5 Pa. Luzerne Wyoming Pittston No. 2 Buck. 6 Pa. Luzerne Wyoming Mammoth Large 7 Pa. Luzerne Wyoming Exeter Rice 8 Pa. Northumberland Schuylkill Treverton 9 Pa. Schuylkill Schuylkill Buck Mountain 10 Pa. Schuylkill York Farm Buckwheat 11 Pa. Victoria Buckwheat 12 Pa. Carbon Lehigh Lehigh & Buck. & Pea Wilkes C. Co. 13 Pa. Carbon Lehigh Buckwheat 14 Pa. Lackawanna Del. & Hud. Co. No. 1 Buck. SEMI-ANTHRACITES 15 Pa. Lycoming Loyalsock 16 Pa. Sullivan Lopez 17 Pa. Sullivan Bernice SEMI-BITUMINOUS 18 Md. Alleghany Big Vein, George's Crk. 19 Md. Alleghany George's Creek 20 Md. Alleghany George's Creek 21 Md. Alleghany George's Creek Ocean No. 7 Mine run 22 Md. Alleghany Cumberland 23 Md. Garrett Washington Mine run No. 3 24 Pa. Bradford Long Valley 25 Pa. Tioga Antrim 26 Pa. Cambria "B" or Miller Soriman Shaft C. Co. 27 Pa. Cambria "B" or Miller Henrietta 28 Pa. Cambria "B" or Miller Penker 29 Pa. Cambria "B" or Miller Lancashire 30 Pa. Cambria Lower Penn. C. & C. Mine run Kittanning Co. No. 3 31 Pa. Cambria Upper Valley Mine run Kittanning 32 Pa. Clearfield Lower Eureka Mine run Kittanning 33 Pa. Clearfield Ghem Mine run 34 Pa. Clearfield Osceola 35 Pa. Clearfield Reynoldsville 36 Pa. Clearfield Atlantic- Mine run Clearfield 37 Pa. Huntington Barnet & Fulton Carbon Mine run 38 Pa. Huntington Rock Hill Mine run 39 Pa. Somerset Lower Kimmelton Mine run Kittanning 40 Pa. Somerset "C" Prime Vein Jenner Mine run

____________ Proximate Analysis (Dry Coal) B. t. u. No. _______ Per Pound Authority Moisture Volatile Fixed Ash Dry Matter Carbon Coal _ __ __ __ __ __ ___ _ __ __ __ __ __ ___ 1 1.50 2.41 90.30 7.29 Gale 2 2.15 12.88 78.23 8.89 13137 Whitham 3 8.29 7.81 77.19 15.00 12341 Sadtler 4 13.90 11.16 65.96 22.88 10591 B. & W. Co. 5 3.66 4.40 78.96 16.64 12865 B. & W. Co. 6 4.00 3.44 90.59 5.97 13720 Carpenter 7 0.25 8.18 79.61 12.21 12400 B. & W. Co. 8 0.84 6.73 86.39 6.88 Isherwood 9 3.17 92.41 4.42 14220 Carpenter 10 0.81 5.51 75.90 18.59 11430 11 4.30 0.55 86.73 12.72 12642 B. & W. Co. 12 1.57 6.27 66.53 27.20 12848 B. & W. Co. 13 5.00 81.00 14.00 11800 Carpenter 14 6.20 11.60 12100 Denton _ __ __ __ __ __ ___ _ __ __ __ __ __ ___ 15 1.30 8.72 84.44 6.84 16 5.48 7.53 81.00 11.47 13547 B. & W. Co. 17 1.29 8.21 84.43 7.36 _ __ __ __ __ __ ___ _ __ __ __ __ __ ___ 18 3.50 21.33 72.47 6.20 14682 B. & W. Co. 19 3.63 16.27 76.93 6.80 14695 B. & W. Co. 20 2.28 19.43 77.44 6.13 14793 B. & W. Co. 21 1.13 14451 B. & W. Co. 22 1.50 17.26 76.65 6.09 14700 23 2.33 14.38 74.93 10.49 14033 U. S. Geo. S. [37] 24 1.55 20.33 68.38 11.29 12965 25 2.19 18.43 71.87 9.70 13500 26 3.40 20.70 71.84 7.46 14484 N. Y. Ed. Co. 27 1.23 18.37 75.28 6.45 14770 So. Eng. Co. 28 3.64 21.34 70.48 8.18 14401 B. & W. Co. 29 4.38 21.20 70.27 8.53 14453 B. & W. Co. 30 3.51 17.43 75.69 6.88 14279 U. S. Geo. S. 31 3.40 14.89 75.03 10.08 14152 B. & W. Co. 32 5.90 16.71 77.22 6.07 14843 U. S. Geo. S. 33 3.43 17.53 69.67 12.80 13744 B. & W. Co. 34 1.24 25.43 68.56 6.01 13589 B. & W. Co. 35 2.91 21.55 69.03 9.42 14685 B. & W. Co. 36 1.55 23.36 71.15 5.94 13963 Whitham 37 4.50 18.34 73.06 8.60 13770 B. & W. Co. 38 5.91 17.58 73.44 8.99 14105 B. & W. Co. 39 3.09 17.84 70.47 11.69 13424 U. S. Geo. S. 40 9.37 16.47 75.76 7.77 14507 P. R. R. _ __ __ __ __ __ ___

APPROXIMATE COMPOSITION AND CALORIFIC VALUE OF CERTAIN TYPICAL AMERICAN COALS—Continued

_____________ No. State County Field, Bed Mine Size or Vein _ __ ___ ___ ___ ___ 41 W. Va. Fayette New River Rush Run Mine run 42 W. Va. Fayette New River Loup Creek 43 W. Va. Fayette New River Slack 44 W. Va. Fayette New River Mine run 45 W. Va. Fayette New River Rush Run Mine run 46 W. Va. McDowell Pocahontas Zenith Mine run No. 3 47 W. Va. McDowell Tug River Big Sandy Mine run 48 W. Va. Mercer Pocahontas Mora Lump 49 W. Va. Mineral Elk Garden 50 W. Va. McDowell Pocahontas Flat Top Mine run 51 W. Va. McDowell Pocahontas Flat Top Slack 52 W. Va. McDowell Pocahontas Flat Top Lump _ __ ___ ___ ___ ___ BITUMINOUS _ __ _________ ___ 53 Ala. Bibb Cahaba Hill Creek Mine run 54 Ala. Jefferson Pratt Pratt No. 13 55 Ala. Jefferson Pratt Warner Mine run 56 Ala. Jefferson Coalburg Mine run 57 Ala. Walker Horse Creek Ivy C. & I. Nut Co. No. 8 58 Ala. Walker Jagger Galloway C. Mine run Co. No. 5 59 Ark. Franklin Denning Western No. 4 Nut 60 Ark. Sebastian Jenny Lind Mine No. 12 Lump 61 Ark. Sebastian Huntington Cherokee Mine run 62 Col. Boulder South Platte Lafayette Mine run 63 Col. Boulder Laramie Simson Mine run 64 Col. Fremont Canon City Chandler Nut and Slack 65 Col. Las Animas Trinidad Hastings Nut 66 Col. Las Animas Trinidad Moreley Slack 67 Col. Routt Yampa Oak Creek 68 Ill. Christian Pana Penwell Col. Lump 69 Ill. Franklin No. 6 Benton Egg 70 Ill. Franklin Big Muddy Zeigler 3/4 inch 71 Ill. Jackson Big Muddy 72 Ill. La Salle Streator 73 Ill. La Salle Streator Marseilles Mine run 74 Ill. Macoupin Nilwood Mine No. 2 Screenings 75 Ill. Macoupin Mt. Olive Mine No. 2 Mine run 76 Ill. Madison Belleville Donk Bros. Lump 77 Ill. Madison Glen Carbon Mine run 78 Ill. Marion Odin Lump 79 Ill. Mercer Gilchrist Screenings 80 Ill. Montgomery Pana or No. 5 Coffeen Mine run 81 Ill. Peoria No. 5 Empire 82 Ill. Perry Du Quoin Number 1 Screenings _ __ ___ ___ ___ ___

APPROXIMATE COMPOSITION AND CALORIFIC VALUE OF CERTAIN TYPICAL AMERICAN COALS—Continued

____________ Proximate Analysis (Dry Coal) B. t. u. No. _______ Per Pound Authority Moisture Volatile Fixed Ash Dry Matter Carbon Coal _ __ __ __ __ __ ___ 41 2.14 22.87 71.56 5.57 14959 U. S. Geo. S. 42 0.55 19.36 78.48 2.16 14975 Hill 43 6.66 20.94 73.16 5.90 14412 B. & W. Co. 44 2.16 17.82 75.66 6.52 14786 B. & W. Co. 45 0.94 22.16 75.85 1.99 15007 B. & W. Co. 46 4.85 17.14 76.54 6.32 14480 U. S. Geo. S. 47 1.58 18.55 76.44 4.91 15170 U. S. Geo. S. 48 1.74 18.55 75.15 6.30 15015 U. S. Geo. S. 49 2.10 15.70 75.40 8.90 14195 B. & W. Co. 50 0.52 24.02 74.59 1.39 14490 B. & W. Co. 51 3.24 15.33 77.60 7.07 14653 B. & W. Co. 52 3.63 16.03 78.04 5.93 14956 B. & W. Co. _ __ __ __ __ __ ___ _ __ __ __ __ __ ___ 53 6.19 28.58 55.60 15.82 12576 B. & W. Co. 54 4.29 25.78 67.68 6.54 14482 B. & W. Co. 55 2.51 27.80 61.50 10.70 13628 U. S. Geo. S. 56 0.94 31.34 65.65 3.01 14513 B. & W. Co. 57 2.56 31.82 53.89 14.29 12937 U. S. Geo. S. 58 4.83 34.65 51.12 14.03 12976 U. S. Geo. S. 59 2.22 12.83 75.35 11.82 U. S. Geo. S. 60 1.07 17.04 74.45 8.51 14252 U. S. Geo. S. 61 0.97 19.87 70.30 9.83 14159 U. S. Geo. S. 62 19.48 38.80 49.00 12.20 11939 B. & W. Co. 63 19.78 44.69 48.62 6.69 12577 U. S. Geo. S. 64 9.37 38.10 51.75 10.15 11850 B. & W. Co. 65 2.15 31.07 53.40 15.53 12547 B. & W. Co. 66 1.88 28.47 55.58 15.95 12703 B. & W. Co. 67 6.67 42.91 55.64 1.45 Hill 68 8.05 43.67 49.97 6.36 10900 Jones 69 8.31 34.52 54.05 11.43 11727 U. S. Geo. S. 70 13.28 31.97 57.37 10.66 12857 U. S. Geo. S. 71 4.85 31.55 62.19 6.26 11466 Breckenridge 72 8.40 41.76 51.42 6.82 11727 Breckenridge 73 12.98 43.73 49.13 7.14 10899 B. & W. Co. 74 13.34 34.75 44.55 20.70 10781 B. & W. Co. 75 13.54 41.28 46.30 12.42 10807 U. S. Geo. S. 76 13.47 38.69 48.07 13.24 12427 U. S. Geo. S. 77 9.78 38.18 51.52 10.30 11672 Bryan 78 6.20 42.91 49.06 8.03 11880 Breckenridge 79 8.50 36.17 41.64 22.19 10497 Breckenridge 80 11.93 34.05 49.85 16.10 10303 U. S. Geo. S. 81 17.64 31.91 46.17 21.92 10705 B. & W. Co. 82 9.81 33.67 48.36 17.97 11229 B. & W. Co. _ __ __ __ __ __ ___

APPROXIMATE COMPOSITION AND CALORIFIC VALUE OF CERTAIN TYPICAL AMERICAN COALS—Continued

No. State County Field, Bed Mine Size or Vein 83 Ill. Perry Du Quoin Willis Mine run 84 Ill. Sangamon Pawnee Slack 85 Ill. St. Clair Standard Nigger Hollow Mine run 86 Ill. St. Clair Standard Maryville Mine run 87 Ill. Williamson Big Muddy Daws Mine run 88 Ill. Williamson Carterville Carterville or No. 7 89 Ill. Williamson Carterville Burr Nut, Pea or No. 7 and Slack 90 Ind. Brazil Brazil Gartside Block 91 Ind. Clay Louise Block 92 Ind. Green Island City Mine run 93 Ind. Knox Vein No. 5 Tecumseh Mine run 94 Ind. Parke Vein No. 6 Parke Coal Co. Lump 95 Ind. Sullivan Sullivan No. 6 Mildred Washed 96 Ind. Vigo Number 6 Fontanet Mine run 97 Ind. Vigo Number 7 Red Bird Mine run 98 Iowa Appanoose Mystic Mine No. 3 Lump 99 Iowa Lucas Lucas Inland No. 1 Mine run 100 Iowa Marion Big Vein Liberty No. 5 Mine run 101 Iowa Polk Third Seam Altoona No. 4 Lump 102 Iowa Wapello Wapello Lump 103 Kan. Cherokee Weir Pittsburgh Southwestern Lump Dev. Co. 104 Kan. Cherokee Cherokee Screenings 105 Kan. Cherokee Cherokee Lump 106 Kan. Linn Boicourt Lump 107 Ky. Bell Straight Creek Str. Ck. C. & Mine run C. Co. 108 Ky. Hopkins Bed No. 9 Earlington Lump 109 Ky. Hopkins Bed No. 9 Barnsley Mine run 110 Ky. Hopkins Vein No. 14 Nebo Pea and Slack 111 Ky. Johnson Vein No. 1 Miller's Creek Mine run 112 Ky. Mulenburg Bed No. 9 Pierce Pea and Slack 113 Ky. Pulaski Greensburg 114 Ky. Webster Bed No. 9 Pea and Slack 115 Ky. Whitley Jellico Nut and Slack 116 Mo. Adair Danforth Mine run 117 Mo. Bates Rich Hill New Home Mine run 118 Mo. Clay Lexington Mo. City Coal Co. 119 Mo. Lafayette Waverly Buckthorn 120 Mo. Lafayette Waverly Higbee 121 Mo. Linn Bevier Marceline 122 Mo. Macon Bevier Northwest Coal Co. 123 Mo. Morgan Morgan Co. Morgan Co. Mine run Coal Co. 124 Mo. Putnam Mendotta Mendotta No. 8 125 N.Mex. McKinley Gallup Gibson Pea and Slack

____________ Proximate Analysis (Dry Coal) B. t. u. No. _______ Per Pound Authority Moisture Volatile Fixed Ash Dry Matter Carbon Coal _ __ __ __ __ __ ___ 83 7.22 33.06 53.97 12.97 11352 U. S. Geo. S. 84 4.81 41.53 39.62 18.85 10220 Jones 85 14.39 32.90 44.84 22.26 11059 B. & W. Co. 86 15.71 38.10 41.10 20.80 10999 B. & W. Co. 87 8.17 34.33 52.50 13.17 12643 U. S. Geo. S. 88 4.66 35.65 56.86 7.49 12286 Univ. of Ill. 89 11.91 33.70 55.90 10.40 12932 B. & W. Co. 90 2.83 40.03 51.97 8.00 13375 Stillman 91 0.83 39.70 52.28 8.02 13248 Jones 92 6.17 35.42 53.55 11.03 11916 Dearborn 93 10.73 35.75 54.46 9.79 12911 B. & W. Co. 94 10.72 44.02 46.33 9.65 11767 U. S. Geo. S. 95 16.59 42.17 48.44 9.59 13377 U. S. Geo. S. 96 2.28 34.95 50.50 14.55 11920 Dearborn 97 11.62 41.17 46.76 12.07 12740 U. S. Geo. S. 98 13.48 39.40 43.09 17.51 11678 U. S. Geo. S. 99 16.01 37.82 46.24 15.94 11963 U. S. Geo. S. 100 14.88 41.53 39.63 18.84 11443 U. S. Geo. S. 101 12.44 41.27 40.86 17.87 11671 U. S. Geo. S. 102 8.69 36.23 43.68 20.09 11443 U. S. Geo. S. 103 4.31 33.88 53.67 12.45 13144 U. S. Geo. S. 104 6.16 35.56 46.90 17.54 10175 Jones 105 1.81 34.77 52.77 12.46 12557 Jones 106 4.74 36.59 47.07 16.34 10392 Jones 107 2.89 36.67 57.24 6.09 14362 U. S. Geo. S. 108 6.89 40.30 55.16 4.54 13381 St. Col. Ky. 109 7.92 40.53 48.70 10.77 13036 U. S. Geo. S. 110 8.02 31.91 54.02 14.07 12448 B. & W. Co. 111 5.12 38.46 58.63 2.91 13743 U. S. Geo. S. 112 9.22 33.94 52.18 13.88 12229 B. & W. Co. 113 2.80 26.54 63.58 9.88 14095 N. Y. Ed. Co. 114 7.30 31.08 60.72 8.20 13600 B. & W. Co. 115 3.82 31.82 58.78 9.40 13175 B. & W. Co. 116 9.00 30.55 46.26 23.19 9889 B. & W. Co. 117 7.28 37.62 43.83 18.55 12109 U. S. Geo. S. 118 12.45 39.39 48.47 12.14 12875 Univ. of Mo. 119 8.58 41.78 45.99 12.23 12735 Univ. of Mo. 120 10.84 31.72 55.29 12.99 12500 Univ. of Mo. 121 9.45 36.72 52.20 11.08 13180 Univ. of Mo. 122 13.09 37.83 42.95 19.22 11500 U. S. Geo. S. 123 12.24 45.69 47.98 6.33 14197 U. S. Geo. S. 124 20.78 39.36 50.00 10.64 12602 U. S. Geo. S. 125 12.17 36.31 51.17 12.52 12126 B. & W. Co. _ __ __ __ __ __ ___

APPROXIMATE COMPOSITION AND CALORIFIC VALUE OF CERTAIN TYPICAL AMERICAN COALS—Continued

No. State County Field, Bed Mine Size or Vein 126 Ohio Athens Hocking Valley Sunday Creek Slack 127 Ohio Belmont Pittsburgh Neff Coal Co. Mine run No. 8 128 Ohio Columbiana Middle Palestine Kittanning 129 Ohio Coshocton Middle Morgan Run Mine run Kittanning 130 Ohio Guernsey Vein No. 7 Little Kate 131 Ohio Hocking Hocking Valley Lump 132 Ohio Hocking Hocking Valley 133 Ohio Jackson Brookville Superior Mine run Coal Co. 134 Ohio Jackson Lower Superior Mine run Kittanning Coal Co. 135 Ohio Jackson Quakertown Wellston 136 Ohio Jefferson Pittsburgh Crow Hollow 3/4 inch or No. 8 137 Ohio Jefferson Pittsburgh Rush Run No. 1 3/4 inch or No. 8 138 Ohio Perry Hocking Congo 139 Ohio Stark Massillon Slack 140 Ohio Vinton Brookville Clarion Nut and or No. 4 Slack 141 Okla. Choctaw McAlester Edwards No. 1 Mine run 142 Okla. Choctaw McAlester Adamson Slack 143 Okla. Creek Henrietta Lump and Slack 144 Pa. Allegheny Pittsburgh Slack 3rd Pool 145 Pa. Allegheny Monongahela Turtle Creek 146 Pa. Allegheny Pittsburgh Bertha 3/4 inch 147 Pa. Cambria Beach Creek Slack 148 Pa. Cambria Miller Lincoln Mine run 149 Pa. Clarion Lower Freeport 150 Pa. Fayette Connellsville Slack 151 Pa. Greene Youghiogheny Lump 152 Pa. Greene Westmoreland Screenings 153 Pa. Indiana Iselin Mine run 154 Pa. Jefferson Punxsutawney Mine run 155 Pa. Lawrence Middle Kittanning 156 Pa. Mercer Taylor 157 Pa. Washington Pittsburgh Ellsworth 158 Pa. Washington Youghiogheny Anderson 3/4 inch 159 Pa. Westmoreland Pittsburgh Scott Haven Lump 160 Tenn. Campbell Jellico 161 Tenn. Claiborne Mingo 162 Tenn. Marion Etna 163 Tenn. Morgan Brushy Mt. 164 Tenn. Scott Glen Mary No. 4 Glen Mary 165 Tex. Maverick Eagle Pass 166 Tex. Paolo Pinto Thurber Mine run 167 Tex. Paolo Pinto Strawn Mine run 168 Va. Henrico Gayton

____________ Proximate Analysis (Dry Coal) B. t. u. No. _______ Per Pound Authority Moisture Volatile Fixed Ash Dry Matter Carbon Coal _ __ __ __ __ __ ___ 126 12.16 34.64 53.10 12.26 12214 127 5.31 38.78 52.22 9.00 12843 U. S. Geo. S. 128 2.15 37.57 51.80 10.63 13370 Lord & Haas 129 41.76 45.24 13.00 13239 B. & W. Co. 130 6.19 33.02 59.96 7.02 13634 B. & W. Co. 131 6.45 39.12 50.08 10.80 12700 Lord & Haas 132 2.60 40.80 47.60 11.60 12175 Jones 133 7.59 38.45 43.99 17.56 11704 U. S. Geo. S. 134 8.99 41.43 50.06 8.51 13113 U. S. Geo. S. 135 3.38 35.26 54.18 7.56 12506 Hill 136 4.04 40.08 52.27 9.65 13374 U. S. Geo. S. 137 4.74 36.08 54.81 9.11 13532 U. S. Geo. S. 138 6 41 38.33 46.71 14.96 12284 B. & W. Co. 139 6.67 40.02 46.46 13.52 11860 B. & W. Co. 140 2.47 42.38 50.39 6.23 13421 U. S. Geo. S. 141 4.79 39.18 49.97 10.85 13005 U. S. Geo. S. 142 4.72 28.54 58.17 13.29 12105 B. & W. Co. 143 7.65 36.77 50.14 13.09 12834 U. S. Geo. S. 144 1.77 32.06 57.11 10.83 13205 Carpenter 145 1.75 36.85 53.94 9.21 13480 Lord & Haas 146 2.61 35.86 57.81 6.33 13997 U. S. Geo. S. 147 3.01 32.87 55.86 11.27 13755 B. & W. Co. 148 5.39 30.83 61.05 8.12 13600 B. & W. Co. 149 0.54 35.93 57.66 6.41 13547 150 1.85 28.73 63.22 7.95 13775 Whitham 151 1.25 32.60 54.70 12.70 13100 B. & W. Co. 152 11.12 31.67 55.61 12.72 13100 P. R. R. 153 2.70 29.33 63.56 7.11 14220 B. & W. Co. 154 3.38 29.33 64.93 5.73 14781 B. & W. Co. 155 0.70 37.06 56.24 6.70 13840 Lord & Haas 156 4.18 32.19 55.55 12.26 12820 B. & W. Co. 157 2.46 35.35 58.46 6.19 14013 U. S. Geo. S. 158 1.00 39.29 54.80 5.91 13729 Jones 159 4.06 32.91 59.78 7.31 13934 B. & W. Co. 160 1.80 37.76 62.12 1.12 13846 U. S. Navy 161 4.40 34.31 59.22 6.47 U. S. Geo. S. 162 3.16 32.98 56.59 10.43 163 1.77 33.46 54.73 11.87 13824 B. & W. Co. 164 1.53 40.80 56.78 2.42 14625 Ky. State Col. 165 5.42 33.73 44.89 21.38 10945 B. & W. Co. 166 1.90 36.01 49.09 14.90 12760 B. & W. Co. 167 4.19 35.40 52.98 11.62 13202 B. & W. Co. 168 0.82 17.14 74.92 7.94 14363 B. & W. Co. _ __ __ __ __ __ ___

APPROXIMATE COMPOSITION AND CALORIFIC VALUE OF CERTAIN TYPICAL AMERICAN COALS—Continued

No. State County Field, Bed Mine Size or Vein 169 Va. Lee Darby Darby 1-1/2 inch 170 Va. Lee McConnel Wilson Mine run 171 Va. Wise Upper Banner Coburn 3-1/2 inch 172 Va. Rockingham Clover Hill 173 Va. Russel Clinchfield 174 Va. Monongahela Bernmont 175 W. Va. Harrison Pittsburgh Ocean Mine run 176 W. Va. Harrison Girard Nut, Pea and Slack 177 W. Va. Kanawha Winifrede Winifrede 178 W. Va. Kanawha Keystone Keystone Mine run 179 W. Va. Logan Island Creek Nut and Slack 180 W. Va. Marion Fairmont Kingmont 181 W. Va. Mingo Thacker Maritime 182 W. Va. Mingo Glen Alum Glen Alum Mine run 183 W. Va. Preston Bakerstown 184 W. Va. Putnam Pittsburgh Black Betsy Bug dust 185 W. Va. Randolph Upper Freeport Coalton Lump and Nut LIGNITES AND LIGNITIC COALS 186 Col. Boulder Rex 187 Col. El Paso Curtis 188 Col. El Paso Pike View 189 Col. Gunnison South Platte Mt. Carbon 190 Col. Las Animas Acme 191 Col. Lehigh 192 N. Dak. McLean Eckland Mine run 193 N. Dak. McLean Wilton Lump 194 N. Dak. McLean Casino 195 N. Dak. Stark Lehigh Lehigh Mine run 196 N. Dak. William Williston Mine run 197 N. Dak. William Williston Mine run 198 Tex. Bastrop Bastrop Glenham 199 Tex. Houston Crockett 200 Tex. Houston Houston C. & C. Co. 201 Tex. Milam Rockdale Worley 202 Tex. Robertson Calvert Coaling No. 1 203 Tex. Wood Hoyt Consumer's Lig. Co. 204 Tex. Wood Hoyt 205 Wash. King Black Diamond 206 Wyo. Carbon Hanna Mine run 207 Wyo. Crook Black Hills Stilwell Coal Co. 208 Wyo. Sheridan Sheridan Monarch 209 Wyo. Sweetwater Rock Spring Screenings 210 Wyo. Uinta Adaville Lazeart

____________ Proximate Analysis (Dry Coal) B. t. u. No. _______ Per Pound Authority Moisture Volatile Fixed Ash Dry Matter Carbon Coal _ __ __ __ __ __ ___ 169 4.35 38.46 56.91 4.63 13939 U. S. Geo. S. 170 3.35 36.35 57.88 5.77 13931 U. S. Geo. S. 171 3.05 32.65 62.73 4.62 14470 U. S. Geo. S. 172 31.77 57.98 10.25 13103 173 2.00 35.72 56.12 8.16 14200 174 32.00 59.90 8.10 13424 Carpenter 175 2.47 39.35 52.78 7.87 14202 U. S. Geo. S. 176 36.66 57.49 5.85 14548 B. & W. Co. 177 1.05 32.74 64.38 2.88 14111 Hill 178 2.21 33.29 58.61 8.10 14202 U. S. Geo. S. 179 1.12 38.61 55.91 5.48 14273 Hill 180 1.90 35.31 57.34 7.35 14198 U. S. Geo. S. 181 0.68 31.89 63.48 4.63 14126 Hill 182 3.02 33.81 59.45 6.74 14414 U. S. Geo. S. 183 4.14 29.09 63.50 7.41 14546 U. S. Geo. S. 184 7.41 32.84 53.96 13.20 12568 B. & W. Co. 185 2.11 29.57 59.93 10.50 13854 U. S. Geo. S. _ __ __ __ __ __ ___ _ __ __ __ __ __ ___ 186 16.05 42.12 47.97 9.91 10678 B. & W. Co. 187 23.25 42.11 49.38 8.51 11090 B. & W. Co. 188 23.77 48.70 41.47 9.83 10629 B. & W. Co. 189 20.38 46.38 47.50 6.12 190 16.74 47.90 44.60 7.50 Col. Sc. of M. 191 18.30 45.29 44.67 10.04 192 29.65 45.56 47.05 7.39 10553 Lord 193 35.96 49.84 38.05 12.11 11036 U. S. Geo. S. 194 29.65 46.56 38.70 14.74 Lord 195 35.84 43.84 39.59 16.57 10121 U. S. Geo. S. 196 41.76 39.37 48.09 12.54 10121 B. & W. Co. 197 42.74 40.83 47.79 11.38 10271 B. & W. Co. 198 32.77 42.76 36.88 20.36 8958 B. & W. Co. 199 23.27 40.95 38.37 20.68 10886 U. S. Geo. S. 200 31.48 46.93 34.40 18.87 10176 B. & W. Co. 201 32.48 43.04 41.14 15.82 10021 B. & W. Co. 202 32.01 43.70 43.08 13.22 10753 B. & W. Co. 203 33.98 46.97 41.40 11.63 10600 U. S. Geo. S. 204 30.25 43.27 41.46 15.27 10597 205 3.71 48.72 46.56 4.72 Gale 206 6.44 51.32 43.00 5.68 11607 B. & W. Co. 207 19.08 45.21 46.42 8.37 12641 U. S. Geo. S. 208 21.18 51.87 40.43 7.70 12316 U. S. Geo. S. 209 7.70 38.57 56.99 4.44 12534 B. & W. Co. 210 19.15 45.50 48.11 6.39 9868 U. S. Geo. S. _ __ __ __ __ __ ___



TABLE 39

SHOWING RELATION BETWEEN PROXIMATE AND ULTIMATE ANALYSES OF COAL

========================================================================= Common in Proximate & Proximate Ultimate Analysis Ultimate Analysis Analysis - - V H N M o y i S o l M C C d O t u i S a a F a a r x r l s t t t i r r o y o p t a Field i t x b b g g g h A u t or l e e o o e e e e s r e Bed Mine e r d n n n n n r h e - - - - - - - - Icy Coal & Iron Horse Co. Ala Creek No. 8 31.81 53.90 72.02 4.78 6.45 1.66 .80 14.29 2.56 - - - - - - - Central C. & C. Hunt- Co. Ark ington No. 3 18.99 67.71 76.37 3.90 3.71 1.49 1.23 13.30 1.99 - - - - - - - - Pana Clover or Leaf, Ill No. 5 No. 1 37.22 45.64 63.04 4.49 10.04 1.28 4.01 17.14 13.19 - - - - - - - - No. 5, Warrick Ind Co. Electric 41.85 44.45 68.08 4.78 7.56 1.35 4.53 13.70 9.11 - - - - - - - - No. 11, St. Hopkins Bernard, Ky Co. No. 11 41.10 49.60 72.22 5.06 8.44 1.33 3.65 9.30 7.76 - - - - - - - - "B" or Lower Kittan- Eureka, Pa ning No. 31 16.71 77.22 84.45 4.25 3.04 1.28 .91 6.07 .56 - - - - - - - - Indiana Pa Co. 29.55 62.64 79.86 5.02 4.27 1.86 1.18 7.81 2.90 - - - - - - - - W. Fire Rush Va Creek Run 22.87 71.56 83.71 4.64 3.67 1.70 .71 5.57 2.14 =========================================================================

Table 39 gives for comparison the ultimate and proximate analyses of certain of the coals with which tests were made in the coal testing plant of the United States Geological Survey at the Louisiana Purchase Exposition at St. Louis.

The heating value of a fuel cannot be directly computed from a proximate analysis, due to the fact that the volatile content varies widely in different fuels in composition and in heating value.

Some methods have been advanced for estimating the calorific value of coals from the proximate analysis. William Kent[38] deducted from Mahler's tests of European coals the approximate heating value dependent upon the content of fixed carbon in the combustible. The relation as deduced by Kent between the heat and value per pound of combustible and the per cent of fixed carbon referred to combustible is represented graphically by Fig. 23.

Goutal gives another method of determining the heat value from a proximate analysis, in which the carbon is given a fixed value and the heating value of the volatile matter is considered as a function of its percentage referred to combustible. Goutal's method checks closely with Kent's determinations.

All the formulae, however, for computing the calorific value of coals from a proximate analysis are ordinarily limited to certain classes of fuels. Mr. Kent, for instance, states that his deductions are correct within a close limit for fuels containing more than 60 per cent of fixed carbon in the combustible, while for those containing a lower percentage, the error may be as great as 4 per cent, either high or low.

While the use of such computations will serve where approximate results only are required, that they are approximate should be thoroughly understood.

Calorimetry—An ultimate or a proximate analysis of a fuel is useful in determining its general characteristics, and as described on page 183, may be used in the calculation of the approximate heating value. Where the efficiency of a boiler is to be computed, however, this heating value should in all instances be determined accurately by means of a fuel calorimeter.

[Graph: B.T.U. per Pound of Combustible against Per Cent of Fixed Carbon in Combustible

Fig. 23. Graphic Representation of Relation between Heat Value Per Pound of Combustible and Fixed Carbon in Combustible as Deduced by Wm. Kent.]

In such an apparatus the fuel is completely burned and the heat generated by such combustion is absorbed by water, the amount of heat being calculated from the elevation in the temperature of the water. A calorimeter which has been accepted as the best for such work is one in which the fuel is burned in a steel bomb filled with compressed oxygen. The function of the oxygen, which is ordinarily under a pressure of about 25 atmospheres, is to cause the rapid and complete combustion of the fuel sample. The fuel is ignited by means of an electric current, allowance being made for the heat produced by such current, and by the burning of the fuse wire.

A calorimeter of this type which will be found to give satisfactory results is that of M. Pierre Mahler, illustrated in Fig. 24 and consisting of the following parts:

A water jacket A, which maintains constant conditions outside of the calorimeter proper, and thus makes possible a more accurate computation of radiation losses.

The porcelain lined steel bomb B, in which the combustion of the fuel takes place in compressed oxygen.



The platinum pan C, for holding the fuel.

The calorimeter proper D, surrounding the bomb and containing a definite weighed amount of water.

An electrode E, connecting with the fuse wire F, for igniting the fuel placed in the pan C.

A support G, for a water agitator.

A thermometer I, for temperature determination of the water in the calorimeter. The thermometer is best supported by a stand independent of the calorimeter, so that it may not be moved by tremors in the parts of the calorimeter, which would render the making of readings difficult. To obtain accuracy of readings, they should be made through a telescope or eyeglass.

A spring and screw device for revolving the agitator.

A lever L, by the movement of which the agitator is revolved.

A pressure gauge M, for noting the amount of oxygen admitted to the bomb. Between 20 and 25 atmospheres are ordinarily employed.

An oxygen tank O.

A battery or batteries P, the current from which heats the fuse wire used to ignite the fuel.

This or a similar calorimeter is used in the determination of the heat of combustion of solid or liquid fuels. Whatever the fuel to be tested, too much importance cannot be given to the securing of an average sample. Where coal is to be tested, tests should be made from a portion of the dried and pulverized laboratory sample, the methods of obtaining which have been described. In considering the methods of calorimeter determination, the remarks applied to coal are equally applicable to any solid fuel, and such changes in methods as are necessary for liquid fuels will be self-evident from the same description.

Approximately one gram of the pulverized dried coal sample should be placed directly in the pan of the calorimeter. There is some danger in the using of a pulverized sample from the fact that some of it may be blown out of the pan when oxygen is admitted. This may be at least partially overcome by forming about two grams into a briquette by the use of a cylinder equipped with a plunger and a screw press. Such a briquette should be broken and approximately one gram used. If a pulverized sample is used, care should be taken to admit oxygen slowly to prevent blowing the coal out of the pan. The weight of the sample is limited to approximately one gram since the calorimeter is proportioned for the combustion of about this weight when under an oxygen pressure of about 25 atmospheres.

A piece of fine iron wire is connected to the lower end of the plunger to form a fuse for igniting the sample. The weight of iron wire used is determined, and if after combustion a portion has not been burned, the weight of such portion is determined. In placing the sample in the pan, and in adjusting the fuse, the top of the calorimeter is removed. It is then replaced and carefully screwed into place on the bomb by means of a long handled wrench furnished for the purpose.

The bomb is then placed in the calorimeter, which has been filled with a definite amount of water. This weight is the "water equivalent" of the apparatus, i. e., the weight of water, the temperature of which would be increased one degree for an equivalent increase in the temperature of the combined apparatus. It may be determined by calculation from the weights and specific heats of the various parts of the apparatus. Such a determination is liable to error, however, as the weight of the bomb lining can only be approximated, and a considerable portion of the apparatus is not submerged. Another method of making such a determination is by the adding of definite weights of warm water to definite amounts of cooler water in the calorimeter and taking an average of a number of experiments. The best method for the making of such a determination is probably the burning of a definite amount of resublimed naphthaline whose heat of combustion is known.

The temperature of the water in the water jacket of the calorimeter should be approximately that of the surrounding atmosphere. The temperature of the weighed amount of water in the calorimeter is made by some experimenters slightly greater than that of the surrounding air in order that the initial correction for radiation will be in the same direction as the final correction. Other experimenters start from a temperature the same or slightly lower than the temperature of the room, on the basis that the temperature after combustion will be slightly higher than the room temperature and the radiation correction be either a minimum or entirely eliminated.

While no experiments have been made to show conclusively which of these methods is the better, the latter is generally used.

After the bomb has been placed in the calorimeter, it is filled with oxygen from a tank until the pressure reaches from 20 to 25 atmospheres. The lower pressure will be sufficient in all but exceptional cases. Connection is then made to a current from the dry batteries in series so arranged as to allow completion of the circuit with a switch. The current from a lighting system should not be used for ignition, as there is danger from sparking in burning the fuse, which may effect the results. The apparatus is then ready for the test.

Unquestionably the best method of taking data is by the use of co-ordinate paper and a plotting of the data with temperatures and time intervals as ordinates and abscissae. Such a graphic representation is shown in Fig. 25.

[Graph: Temperature—deg. C. against Time—Hours and Minutes

Fig. 25. Graphic Method of Recording Bomb Calorimeter Results]

After the bomb is placed in the calorimeter, and before the coal is ignited, readings of the temperature of the water should be taken at one minute intervals for a period long enough to insure a constant rate of change, and in this way determine the initial radiation. The coal is then ignited by completing the circuit, the temperature at the instant the circuit is closed being considered the temperature at the beginning of the combustion. After ignition the readings should be taken at one-half minute intervals, though because of the rapidity of the mercury's rise approximate readings only may be possible for at least a minute after the firing, such readings, however, being sufficiently accurate for this period. The one-half minute readings should be taken after ignition for five minutes, and for, say, five minutes longer at minute intervals to determine accurately the final rate of radiation.

Fig. 25 shows the results of such readings, plotted in accordance with the method suggested. It now remains to compute the results from this plotted data.

The radiation correction is first applied. Probably the most accurate manner of making such correction is by the use of Pfaundler's method, which is a modification of that of Regnault. This assumes that in starting with an initial rate of radiation, as represented by the inclination of the line AB, Fig. 25, and ending with a final radiation represented by the inclination of the line CD, Fig. 25, that the rate of radiation for the intermediate temperatures between the points B and C are proportional to the initial and final rates. That is, the rate of radiation at a point midway between B and C will be the mean between the initial and final rates; the rate of radiation at a point three-quarters of the distance between B and C would be the rate at B plus three-quarters of the difference in rates at B and C, etc. This method differs from Regnault's in that the radiation was assumed by Regnault to be in each case proportional to the difference in temperatures between the water of the calorimeter and the surrounding air plus a constant found for each experiment. Pfaundler's method is more simple than that of Regnault, and the results by the two methods are in practical agreement.

Expressed as a formula, Pfaundler's method is, though not in form given by him:

R' - R C = N R + (T" - T) (19) T' - T

Where C = correction in degree centigrade, N = number of intervals over which correction is made, R = initial radiation in degrees per interval, R' = final radiation in degrees per interval, T = average temperature for period through which initial radiation is computed, T" = average temperature over period of combustion[39], T' = average temperature over period through which final radiation is computed.[39]

The application of this formula to Fig. 25 is as follows:

As already stated, the temperature at the beginning of combustion is the reading just before the current is turned on, or B in Fig. 25. The point C or the temperature at which combustion is presumably completed, should be taken at a point which falls well within the established final rate of radiation, and not at the maximum temperature that the thermometer indicates in the test, unless it lies on the straight line determining the final radiation. This is due to the fact that in certain instances local conditions will cause the thermometer to read higher than it should during the time that the bomb is transmitting heat to the water rapidly, and at other times the maximum temperature might be lower than that which would be indicated were readings to be taken at intervals of less than one-half minute, i. e., the point of maximum temperature will fall below the line determined by the final rate of radiation. With this understanding AB, Fig. 25, represents the time of initial radiation, BC the time of combustion, and CD the time of final radiation. Therefore to apply Pfaundler's correction, formula (19), to the data as represented by Fig. 25.

N = 6, R = 0, R' = .01, T = 20.29, T' = 22.83,

20.29 + 22.54 + 22.84 + 22.88 + 22.87 + 22.86 T" = ——————————————————————- = 22.36 6

.01 - 0 C = 6 0 + -(22.36 - 20.29) 22.85 - 20.29

= 6 x .008 = .048

Pfaundler's formula while simple is rather long. Mr. E. H. Peabody has devised a simpler formula with which, under proper conditions, the variation from correction as found by Pfaundler's method is negligible.

It was noted throughout an extended series of calorimeter tests that the maximum temperature was reached by the thermometer slightly over one minute after the time of firing. If this period between the time of firing and the maximum temperature reported was exactly one minute, the radiation through this period would equal the radiation per one-half minute before firing plus the radiation per one-half minute after the maximum temperature is reached; or, the radiation through the one minute interval would be the average of the radiation per minute before firing and the radiation per minute after the maximum. A plotted chart of temperatures would take the form of a curve of three straight lines (B, C', D) in Fig. 25. Under such conditions, using the notation as in formula (19) the correction would become,

2R + 2R' C = ———- + (N - 2)R', or R + (N - 1)R' (20) 2

This formula may be generalized for conditions where the maximum temperature is reached after a period of more than one minute as follows:

Let M = the number of intervals between the time of firing and the maximum temperature. Then the radiation through this period will be an average of the radiation for M intervals before firing and for M intervals after the maximum is recorded, or

MR + MR' M M C = ———- + (N - M)R' = - R + (N - -)R' (21) 2 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 not more than five intervals later than the point of firing. Where a longer period than this is indicated in the chart of plotted temperatures, the approximate formula should not be used. As the period between firing and the maximum temperature is increased, the plotted results are further and further away from the theoretical straight line curve. Where this period is not over five intervals, or two and a half minutes, an approximation of the straight 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 approximate formula has been found from a number of tests to give results within .003 degrees Fahrenheit for the limits within which its application holds good as described. The value of M, which is not necessarily a whole number, should be determined for each test, though 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 temperature between the firing point and the point chosen from which the final radiation is calculated. This corrected range multiplied by the water equivalent of the calorimeter gives the heat of combustion in calories of the coal burned in the calorimeter together with that evolved by the burning of the fuse wire. The heat evolved by the burning of the fuse wire is found from the determination of the actual weight of wire burned and the heat of combustion of one milligram of the wire (1.7 calories), i. e., multiply the weight of wire used by 1.7, the result being in gram calories or the heat required to raise one gram of water one degree centigrade.

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 more complete combustion in the presence of oxygen than would be possible in the atmosphere.

To make these corrections the bomb of the calorimeter is carefully washed out with water after each test and the amount of acid determined from titrating this water with a standard solution of ammonia or of caustic soda, all of the acid being assumed to be nitric acid. Each cubic centimeter of the ammonia titrating solution used is equivalent to a correction of 2.65 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 22.3 calories for each per cent of sulphur in the coal. One cubic centimeter of the ammonia solution is equivalent to 0.00286 grams of sulphur as sulphuric acid, or to 0.286 x 22.3 = 6.38 calories. It is evident therefore that after multiplying the number of cubic centimeters used in titrating by the heat factor for nitric acid (2.65) a further correction of 6.38 - 2.65 = 3.73 is necessary for each cubic centimeter used in titrating sulphuric instead of nitric acid. This correction will be 3.73/0.297 = 13 units for each 0.01 gram of sulphur in the coal.

The total correction therefore for the aqueous nitric and sulphuric acid is found by multiplying the ammonia by 2.65 and adding 13 calories for each 0.01 gram of sulphur in the coal. This total correction is to be deducted from the heat value as found from the corrected range and the amount equivalent to the calorimeter.

After each test the pan in which the coal has been burned must be carefully examined to make sure that all of the sample has undergone 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 completely consume a sample, a weighed amount of naphthaline may be added, the total weight of fuel and naphthaline being approximately one gram. The naphthaline has a known heat of combustion, samples for this purpose being obtainable from the United States Bureau of Standards, and from the combined heat of combustion of the fuel and naphthaline that of the former may be readily computed.

The heat evolved in burning of a definite weight of standard naphthaline may also be used as a means of calibrating the calorimeter as a whole.



COMBUSTION OF COAL

The composition of coal varies over such a wide range, and the methods of firing have to be altered so greatly 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 must of necessity be of the most general character. For each kind of coal there is some method of firing which will give 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.