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INTRODUCTIONT HE function of a boiler furnace is the generation of thema."imum amount of beat from a given quantity of aspecific fuel, and if such function is to be properly fulfilled,it is essential that the furnace operator understand the broaderprinciples involved in combustion. Unfortunately, from thestandpoint of efficient steam generation, the statement is toofrequently accepted as true that theoretical generalizations andmathematical Cannulae are of but little value to the operatingengineer. To an extent, such statements may be true, but onthe other hand it is to be remembered that combustion is purelya chemical phenomenon and as such can be properly investigatedand controlled only by chemical means. Experience resultingfrom the "cut and try" methods of ordinary actual practise inthe burning of inpidual fuels is unquestionably an importantfactor in the bringing about of efficient furnace results, but it isobvious that such results will be most readily secured when thisexperience is combined with a full knowledge of the theory ofcombustion and the proper application of the available methodsused in obtaining combustion data. Further, the importance ofsuch knowledge is today greater than it has ever been. Mostapparatus for the generation of power has reached a state ofdevelopment where there is but little likelihood of any great in-cre."lse in economy. The generally accepted types of steam boilerused in present day power plant practise have the inherent abilityto absorb heat efficiently and from this standpoint may be includedwith the apparatus from which much more cannot be expected.If we accept tbis statement as true, 34022
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the efficient generationof steam in the boiler proper becomes in reality a question ofefficient combustion, and it is this phase of boiler practise-the efficient generation of beat in the boiler furnace-in whichthere is the greatest and in fact the only field for appreciableimprovement.Power plant owners are coming more and more to appreciatethe necessity for intelligence in the boiler room-the reinforcingof experience in firing by a full knowledge of the theory of com-bustion-and in the growing number of plants where this needis realized suitable apparatus is installed for the determinationand checking of combustion results. In plants not so equipped,the possible savings due to the intelligent use of such apparatusand the proper application of the data so obtained in reducingpreventable losses, are in the aggregate enormous.THE CHEMISTRY OF COMBUSTIONT HE chemistry of combustion as applied to boiler furnacepractise is elementary, but (or a proper comprehension ofthe subject it seems advisable to include a brief con•sideration of the general principles involved, together with datacovering the combining qualities of the constituents of the fuelsordinarily encountered in steam generation.The smallest quantity of an element or a compound thatis capable of separate existence is taken as the physical unitof matter and is called a molecule. Molecules are composed ofatoms of elements which may be defined as the smallest unitof an element which can enter into or be expelled from a com-pound. Atoms never exist singly but in combination with oneor more atoms to form a molecule. Molecules of the elementarygases, such as oxygen, nitrogen and hydrogen, are supposed toconsist of two atoms.A chemical reaction between elements or compounds is arearrangement of the atoms of the constituent elements intoa new combination of molecules_ Such reactions always occurin accordance with fixed and invariable weight relations which arecharacteristic of the elements involved.
and definite volumetricchanges based on the number of gaseous molecules reacting andproduced.Elements are designated by symbols, and compounds bycombinations of the symbols of their constituent elements.Subscripts are affixed to the symbols to designate the numberof times the combining or atomic weight of the element occllrs.It follows that from the symbol of a compound so expressed andthe atomic weight of the elements involved, the proportionateparts by weight of the various constituents entering into the com-pound may be readily determined.The elementary substances encountered in combustion workare o:'l:ygen, nitrogen, hydrogen, carbon and sulphur. Thesymbols of these elements together with their atomic weightsarc given in Table I, page 10.COMBUSTIONCombustion is the phenomenon resulting from any chemicalcombination evolving heat. Oxygen is tbe sale supporter of combustion, and a combustible therefore may be defined as asubstance capable of combining with oxygen to produce heat.The speed of combustion depends upon the affinity of the com-bustible element for oxygen, and to a lesser extent upon theconditions under which combustion takes place. This speedmay vary from the very slow, as in the case of rust formation, tothe instantaneous, as in the explosion of confined powder.From the standpoint of heat production for steam generatingpurposes, combustion may be defined as the rapid combinationof the combustible elements of fuel with oxygen, while in thissense the term combustible implies the capacity of an elementfor combining rapidly with oxygen to produce beat.Combustion is said to be complete when the combustibleelements and compounds have united with aU of the oxygen withwhich they are capable of entering into combination. .TABLE 1ELEMENTS AND COMPOUNDS ENCOUNTERED IN COMBUSTiONAIO...ic W~i&tll Molecular Weilht"ol..... SoalHtule~ Sy...boly-.....n~ Approld_~ Appow;l_-~ -,.Cubo.• • • • • C• 12.005"t . . . SolidHydrogen • • • • M, '.008 • 201 5, GuOZYlen • • • • • 0, 16.00 ,. 32.00 3'GuSUlphUt • • • • • 5, 32.07 3'.... .. SolidNiuogent• • • • N, . ..."'. 28.0:11 ,8 GuCarbon Monoxide• CO • • • • • • 28.01 ,8 GuCarbon Dio.ride• • CO, • • • • • • ..~, .. GuMethane.• • • • CM,• • • • • • 16.03 •• GuAcetylene• • • • e,H,• •• • • • :;16.03 ,. GuEthylene• • • • C,Ht• • • • • • 28.03 ,8 GuEthane.• • • • • C,H.• • • • • • 3°•°5 3'GuSulphur Diozide• • SO,• • • • • • 64•07 .. G..Hydrogen Sulphide• M,S • • - • • •"""3'G..'Water Vapor• • • H~O • • • • • 18.02 ,8 VaporAu .• • • • • • . .• • • • • • 28•94'.G..-Atomlc .ymOOL1The. moleculu _I,ht of C has nol. been definlU!l,.