Document N2VNNKJZw8JBL12Y7937kVMmp

ijy^e ifl atorage; thU may be aggra time of sampling and analyals depends of moisture, ash and volatile matter vated by mixing oil* of different char- on the kind of coal, slxe, weather con from 100% yields a percentage called H when deliveries from two ditions, and method of handling sample. fixed carbon. Sources go into the same tank. These Following paragraphs discuss the iwtpfcor. Although it bums, sulphur 'sJmpl* tale* nvid trouble when oils various characteristics of coal (those., In coal is an undesirable element for '^e mixed: (1) Straight-mn residuals reported in proximate analyses and power-plant use. It plays a part In r^n be mixed with any straight-run. others) end how they affect the value clinkering and slagging, in corrosion ipraduct, and cracked residuals with of coal in power-plant operation. For of air heaters, economixers, breeching, (jgtlght-run residual (2) cracked dis* details on equipment end procedures and stacks, and in spontaneous com ;bQste can be added as a third eonstitu. for testing cool, consult ASTM Stand- bustion of stored coal. It occurs mainly Wt. but (3) cracked residual cannot atdt on Cool and Coke (1948), as iron sulphide (commonly known be added to straight-run distillate. Moisivra. All coal contains some as pyrites), as organic sulphur, end natural moisture (1 to 3% in Eastern in small amounts as sulphates. Only * JK I Thrce-hundred-mil- coals and up to 40% in 'some lignites). total sulphur la measured,' although { I B^RI lion years ago, in This inherent moisture lies in the pores It is known that iron Combined with swamp forests of the and forms a true part of the coal, being the sulphur shares the blame for 'Carboniferous Age, the foundation of retained when it Is air .dried. Surface troubles laid to sulphur. tour present reserves was laid. For 50 moisture depends on conditions in the . Aih Nsien. Temperature at which ash 'sllllon years, giant trees and ferns mine, and during transit. fuaea is measured by beating cones 'grew and fell, to decay and form rich Moisture must be transported, han of osh in a furnace arranged to produce pest bogs. Floods buried the bogs dled and stored: its presence in large a reducing atmosphere. Temperature at under layers of sediment, only to sub- amounts Increases cost and difficulty which the cone fuses down to a round fu'de and permit the growth-and-decay of these operations. Looked ot another lump Is called eottening or ash-fusion cycle to begin again. As millions of way, moisture replaces an equal temperature. Other temperatures some years passed, pressure, heat and time amount of combustible material and times observed include that at which 'worked to drive off some volatile mat thus decreases the heat content per lb. (1) cone tip starts to bend (initial de ter, to harden the mats, and to turn It In addition, some heat liberated In the formation temperature) and (2) cone into the carbon-substance we call coal. furnace goes to evaporating moisture spreads out in a flat layer (Suid). Different kinds contain different in the fuel end superheating the vapor; Ash-fusion temperature (and some amounts of carbon substance depend this moieture loss con be figured from times the spread between initial and ing on the age of the deposit and the the chart on page 117.' softening, or softening and fluid tem 1conditions under which it formed. Next Lto the original peat, the "youngest" MINERAL IMPURITIES peratures) serves as the best single indicator of clinkering and slagging form is /ignite, high in moisture and AiH. This incombustible mineral tendencies under given fuel-bed and low In Axed carbon. Older coals, higher matter, left behind when coal bums furnace conditions. io "rank," contain more Axed corbon. completely, differs from "ashes," as Maoritig Vohi*. If a coat sample is . Analyses. Various tests end methods the power-plant man knows them, be- burned in a "bomb" calorimeter filled ,ef analysis express coal qualities In eouse ashes taken from a furnace with oxygen under pressure, the higher ,figures Instead of words. Principal char always contain some unbumed coal. heating value la measured. The con acteristics are expressed In what Is Like moisture, ash is an Impurity sumer buys energy units when he buys known as a proximate analysis, as dis that increases shipping and handling fuel, and so the heating value plays E tinguished from an ultimate anaiytit, which shows the exoct chemical com position of a fuel, without paying any costs, (t must be removed from the furnace arid the plant, usually requir ing additional equipment and expense. a basic pert in judging fuel values. Sometimes heating value of fuel may affect maximum capacity of a plant. sttention to the physical form in which Recent research shows that amount ; tb compounds appear. As we have and character of ash constitutes the PULVERIZING QUALITIES wen, this gives data needed for com biggest single factor in fuel-bed and OrlndafalQty. Wide use of pulverised- bustion calculations. furnace problems like clinkering and fuel firing brought a need for tests to ,, For a better picture of coal's behav- slagging. An Increase In ash content show the relative ease or difficulty of fj lor in furnace, the proximate analysis usually meona an increase in carbon grinding different kinds of coal. ASTM determines the percentage of (1) moia- carried to the ashpit. tentatively approves two methods. toe (]) ash (3) volatile matter and (4) Voiotn* Matter. In a way not yet ball-mill and Herdgmve. The first d*ed carbon. These percentages add up clearly known, coal holds combustible measures relative amounts of energy io 100. In addition, it Is customary to gases such as methape and other hy needed to pulverise different cools by determine: (1) total amount of sulphur, drocarbons, hydrogen and carbon finding the number of boll-mill rev ** separate percentage (2) aih-fuaion monoxide, end Incombustible gases like olutions needed to grind a sample so ,tttperature, and (3) beating value. carbon dioxide and nitrogen. Heat re 80% passes a 200-mesh sieve (74 mi deponing Analyses. There are five leases these gases. crons). The ball-mill grind&biiity in i **)* to report an analysis, although Percentage of volatile matter indi dex, in percent, is found by dividing l *dy the first three are likely to be met cates the amount of gaseous fuel pres number of revolutions Into 50,000. Power-plant work: (1) as received ent and thus, bears a direct relationship Ini the Herdgrove test, a prepared '*) >lr dried (3) moisture free (4) to firing mechanics. It affects furnace sample receives a definite amount of BIK* *ree' 8IU* ^ mois- volume and arrangement of heating grinding energy In a miniature pul end mineral free. As the name surfaces. veriser; results are measured by weigh . bfiplies, the as-rcceived analysis re- FUrti Carbon. When the volatile mat ing amount possing a 200-mesh sieve. ; J*ri the condition of coal as delivered ter distills off, a solid fuel Is left, con Multiplying weight passing the sieve 1 tbe laboratory. This comes closest sisting, in the main, of carbon, but by 6.93 and adding 13 to the product diving the conditions as shipped or containing some hydrogen, oxygen, gives Hardgrove grindabiUty. **dted. the values desired In practical sulphur and nitrogen not driven off Orindobility values do not give a toss oxgain of moisture between with the gases. Subtracting percentage direct comparison of pulveriser capac- * Decorator 17<S