Part 26 (1/2)
[Illustration: 3520 Horse-power Installation of Babcock & Wilcox Boilers at the Portland Railway, Light and Power Co, Portland, Ore These Boilers are Equipped with Wood Refuse Extension Furnaces at the Front and Oil Burning Furnaces at the Mud Drum End]
SOLID FUELS OTHER THAN COAL AND THEIR COMBUSTION
Wood--Wood is vegetable tissue which has undergone no geological change
Usually the ternate those compact substances familiarly known as tree trunks and li from 30 per cent to 50 per cent When dried for a period of about a year in the atmosphere, the moisture content will be reduced to 18 or 20 per cent
TABLE 41
ULTIMATE analYSES AND CALORIFIC VALUES OF DRY WOOD (GOTTLIEB)
_______________________________________________________ | | | | | | | | | Kind | | | | | | B t u| | of | C | H | N | O | Ash | per | | Wood | | | | | | Pound | |________|_______|______|______|_______|______|_________| | | | | | | | | | Oak | 5016 | 602 | 009 | 4336 | 037 | 8316 | | Ash | 4918 | 627 | 007 | 4391 | 057 | 8480 | | Elm | 4899 | 620 | 006 | 4425 | 050 | 8510 | | Beech | 4906 | 611 | 009 | 4417 | 057 | 8391 | | Birch | 4888 | 606 | 010 | 4467 | 029 | 8586 | | Fir | 5036 | 592 | 005 | 4339 | 028 | 9063 | | Pine | 5031 | 620 | 004 | 4308 | 037 | 9153 | | Poplar | 4937 | 621 | 096 | 4160 | 186 | 7834[40]| | Willow | 4996 | 596 | 096 | 3956 | 337 | 7926[40]| |________|_______|______|______|_______|______|_________|
Wood is usually classified as hard wood, including oak, maple, hickory, birch, walnut and beech; and soft wood, including pine, fir, spruce, eleneral opinion, the heat value per pound of soft wood is slightly greater than the saives the chemical composition and the heat values of the co value of wood is considered equivalent to 04 that of bituiven in this table, it is to be remembered that while this value is based on air-dried wood, the moisture content is still about 20 per cent of the whole, and the heat produced in burning it will be diminished by this amount and by the heat required to evaporate the ases
The heat so absorbedthe loss due to moisture in the fuel, and the net calorific value deter wood, the question resolves itself into: 1st, the essential eleive maximum capacity and efficiency with this class of fuel; and 2nd, the construction which will entail the least labor in handling and feeding the fuel and re the refuse after coenerating purposes, is usually a waste product from some industrial process At the present tireater part of this class of fuel In such refuse the h as 60 per cent and the co different portions of the ed”
wood and slabs, and the percentage of each of these constituents s that have been passed through a ”hogging h the action of revolving knives, cuts or shreds the wood into a state in which it ives the moisture content and heat value of typical sawmill refuse from various woods
TABLE 42
MOISTURE AND CALORIFIC VALUE OF SAWMILL REFUSE _____________________________________________________________________ | | | | | | | | Per Cent | B t u | | Kind of Wood | Nature of Refuse | Moisture | per Pound | | | | | Dry Fuel | |_____________________|_______________________|__________|____________| | | | | | | Mexican White Pine | Sawdust and Hog Chips | 5190 | 9020 | | Yose Chips | 6285 | 9010 | | Redwood 75, | Sawdust, Box Mill | | | | Douglas Fir 25 | Refuse and Hog | 4220 | 8977[41] | | Redwood | Sawdust and Hog Chips | 5298 | 9040[41] | | Redwood | Sawdust and Hog Chips | 4911 | 9204[41] | | Fir, Hemlock, | | | | | Spruce and Cedar | Sawdust | 4206 | 8949[41] | |_____________________|_______________________|__________|____________|
It is essential in the burning of this class of fuel that a large combustion space be supplied, and on account of the usually high moisture content there should be much heated brickwork to radiate heat to the fuel bed and thus evaporate the moisture Extension furnaces of the proper size are usually essential for good results and when this fuel is used alone, grates dropped to the floor line with an ashpit below give additional volu a thick fuel bed A thick fuel bed is necessary in order to avoid excessive quantities of air passing through the boiler Where the fuel consists of hogged wood and sawdust alone, it is best to feed it autoh chutes on the top of the extension The best results are secured when the fuel is allowed to pile up in the furnace to a height of 3 or 4 feet in the form of a cone under each chute The fuel burns best when not disturbed in the furnace Each fuel chute, when a proper distance frorates and with the piles ht, will supply about 30 or 35 square feet of grate surface While large quantities of air are required for burning this fuel, excess air is as harmful as with coal, and care h fire doors or fuel chutes A strong natural draft usually is preferable to a blast with this fuel The action of blast is to ulation of the furnace conditionssurfaces and into the stack This unconsu out of the direct path of the gases will have a tendency to ignite provided any air reaches it, with results har connection This action is particularly objectionable if these particles are carried over into the base of a stack, where they will settle below the point at which the flue enters and if ignited may cause the stack to become overheated and buckle
Whether natural draft or blast is used,surfaces and these should be cleaned regularly tocha should be provided for this unconsumed fuel, and these should be kept clean
With proper draft conditions, 150 pounds of this fuel containing about 30 to 40 per cent of rate surface per hour, and in a properly designed furnace one square foot of grate surface can develop from 5 to 6 boiler horse power Where the wood contains 50 per cent of ure on obtaining rate surface
Dry sawdust, chips and blocks are also used as fuel inindustries Here, as with the ood, ample combustion space should be supplied, but as this fuel is ordinarily kiln dried, large brickwork surfaces in the furnace are not necessary for the evaporation of moisture in the fuel This fuel h these are not required unless they are necessary to secure an added furnace volurate surface, or where such an arrangement must be used to allow for a fuel bed of sufficient thickness Depth of fuel bed with the dry fuel is as important as with the moist fuel If extension furnaces are used with this dry wood, care n that there is no excessive throttling of the gases in the furnace, or brickwork trouble will result In Babcock & Wilcox boilers this fuel may be burned without extension furnaces, provided that the boilers are set at a sufficient height to provide ample combustion space and to allow for proper depth of fuel bed
Sorates to the floor line and excavating for an ashpit Where the fuel is largely sawdust, it h inclined chutes The oldsawdust by means of air suction and blast were such that the ah such chutes was excessive, but with improved ligible quantity The blocks and refuse which cannot be handled through chutes h fire doors in the front of the boiler, which should be er sizes of fuel As et fuel, there will be a quantity of unconsu surfaces must be kept clean
In a few localities cord wood is burned With this as with other classes of wood fuel, a large coe of moisture in cord wood may make it necessary to use an extension furnace, but ordinarily this is not required A the grates to the floor line, large double-deck fire doors being supplied at the usual fire door level through which the wood is thrown by hand Air is adh an excavated ashpit The side, front and rear walls of the furnace should be corbelled out to cover about one-third of the total grate surface This prevents cold air frorate surface Cord wood and slabs forh which the frictional loss of the air is ed material The corate surface ths of 4 feet or 4 feet 6 inches, and the depth of the grates should be kept approxiasse is the refuse of sugar cane from which the juice has been extracted by pressure between the rolls of the asse has been considered the natural fuel for sugar plantations, and in view of the importance of the industry a word of history relative to the use of this fuel is not out of place
When the ar was in its infancy the cane was passed through but a single mill and the defecation and concentration of the saccharine juice took place in a series of vessels mounted one after another over a common fire at one end and connected to a stack at the opposite end This prilish colonies as the ”Open Wall” and in the Spanish-American countries as the ”Jamaica Train”
The evaporation and concentration of the juice in the open air and over a direct fire required such quantities of fuel, and the bagasse, in fact, played such an iar, that oftentiree of extraction, which was already loould be sacrificed to the necessity of obtaining a bagasse that ht be readily burned
The furnaces in use with these methods were as priasse could be burned in the it This naturally required an enor and collecting and frequently entailed a shutting down of the mill, because a shoould spoil the supply which had been dried
The difficulties arising fro this fuel caused a widespread atte out of a furnace which would successfully burn green bagasse Sons were reen bagasse furnaces were installed These did not come up to expectations, however, and almost invariably they were abandoned and recourse had to be taken to the oldin the sun
Froar industry may be dated Slavery was almost universally abolished and it became necessary to pay for labor