OCR Text |
Show Internal Furnace Boiler By O. W. OTT. THE Illustration shows a typo of rbollor commonly used In small heailns and power plants. 11 will bo noted that the entire apparatus Is self-contained self-contained and that no brickwork, except that for lining tho rear end of tho combustion chamber, Is required. re-quired. Tho steel boiler shell Is supported sup-ported on cast-iron saddles resting on sultablo foundation piers. Insldo of the stocl shell, and extending from end to end, 1s a corrugated lluo; tho remaining spuco between the "oiler shell and tho flue Is filled with fire-tubes fire-tubes exlondlng from head to head. Tho travel of tho gasos of combustion, combus-tion, after they leave the flrobed, is back through tho rear half of the corrugated cor-rugated flue, thonco forward through the tubes to tho uptake and stack, Tho air supply Is generally provided by natural draft from a steel stank extending directly upward from the uptake chamber, or by tho customary custom-ary brick or concrete staok to whloh the uptako is connected by moans of. breeching. In marlno practice, and in some stationary plants, the natural nat-ural draft from the stack Is augmented aug-mented by means of forced draft supplied sup-plied by a fan. An examination of the cut will show that tho customary location of the gTates in the front 'ond of the ' corrugated flue presents tho same obstacles ob-stacles to perfect combustion of the volatile matter in coal as tho common sotting of the hand-fired return tubular tu-bular boiler namely, that the closo proximity of the water-cooled corrugated cor-rugated shell has a vory decided dampening effect on proper mixing and Ignition. The space In which tho volatile gases from the fuel must be mixed with tho air drawn through the grates and then ignited boforo contact is mado with the comparatively compara-tively cold boiler surface. Is very limited; lim-ited; hence, to get complete combustion, combus-tion, tho gnses must be completely burned within a very few lnohes of the flrebed. Increases Difficulty. Tho addition of fuel to tho top of the fire increases the difficulty of obtaining ob-taining complete combustion by reducing re-ducing the air supply at the point where tho fuel Is added and by its blanket effect in preventing Ignition. With a uniform and even feed of coal, well distributed ovor the entire grate surface and a strong natural or foraed draft, It Is possible to burn coal containing a largo percentage of volatile matter with very little smoke; unfortunately, these conditions are seldom obtained. The opening of tho fire door when putting In fresh coal hap tho two-fold effect (as noted boforo) bo-foro) of admitting so much air as to chill the gases and of reducing the amount of air drawn through the grates and flrobed by tho stack. By eliminating tho opening of the door for tho feeding of coal nnd by depending de-pending entirely on forced draft for the air supply, the undorfeed stoker flveB very fair success in burning bl-umlnous bl-umlnous coal In this type of boiler wlthout smoke, where tho load Is fairly uniform, simply because It Is able to obtain fairly good mixing and .Ignition closo to tho surface of the fllThe surest way to obtain smokeless combustion and Increased economy in tho burning of bituminous coal with this typo of boiler is to remove tho grates from tho corrugated flue and placo them In a Dutch oven, in front of the boiler, wliero there Is space available In the boiler room, this should be done. Tho cost of making tho cbango will soon bo saved In fuel recovered re-covered by Improved evaporation, it must not bo lost sight of, however, In making audi a change, that the draft should be augmented by Increasing In-creasing the height of tho stack a small amount In ordor to take caro of the extra travel given to the gases of combustion. To Insure Air Supply. At the samo tlmo that a Dutch oven setting Is applied it Is alHO a good plan to Install tho rocking typo of grates Instead of the stationary grato bars shown In tho cut this to make It easy for tho fireman to maintain main-tain the flro In a clean condition and thus Insure a proper air supply. Where It Is Impossible to apply tho Dutch oven setting, tho only possibilities possibil-ities of reducing smoke rcBt with tho fireman, and a few rules might bo given. First Be sure that the flro does not become clogged up with ash and clinker, thus crippling tho air supply. sup-ply. Second Maintain as nearly as pos-slblo pos-slblo a uniform thickness of fire over tho entlro grate to insure an even distribution of air to all of tho flrebed. Third Uso tho ono shovelful method meth-od of firing and apply fresh coal In a thin layer on tho whitest part of the fire where tho possibilities of obtaining ob-taining ignition will bo tho best. Fourth Always be sure that the ohlmney dampor Is wide opon when fuel Is added. Fifth Do not leave the flro-door open any longer than absolutely necessary nec-essary for putting on coal. Take Care of Ashes. Sixth Do not allow aohea to accumulate accu-mulate under the grata to ouoh an extent ex-tent as to cut off tho air supply from any part of tho flro or to add to bao work of tho staok In pulling tho air Into tho ash-pit. Seventh Coal must never bo thrown In heaps on any part of tho flro. Eighth Any largo lumps of coal Bhould bo broken to egg size, so as to maintain the makeup of the fire as nearly uniform a3 possible. Finally, remember that tho more nearly complete combustion Is, tho loss will be the amount of coal to be shoveled on the grates, and that whllo the little and often method of firing fir-ing may seem to require moro physical phys-ical effort, It really economizes in tho total physical work required in shoveling shov-eling coal. |