Document M4vmyXLndE1NpQdmM2r079rEV

496 CHAPTER 33 1960 Guide AIR SUPPLY TO FUEL-BURNING EQUIPMBJT All rooms or spaces containing boilers, furnaces, water heaters, or any other fuel-burning equipment must be provided with a constant supply nf combustion air at adequate static pressure to insure proper combustion in the fuel burners. Additional air is required to replace air entering chimneys through draft hoods and barometric draft dampers, and also to provide ventilation in closely confined boiler and furnace rooms. Experience has shown that the ventilating air openings required in heater rooms depend not only on the size of the heating plant but also on the type of fuel being burned, the relative sue of the equipment room, the tightness of building construction, and the operation of exhaust fans or other devices which affect the static pressure in a building. Because of the number of variables involved in establish ing air requirements, and the variations in building' con struction and arrangement, there is no universally accepted rule for providing ventilating openings. However, the im portance of providing proper ventilation should not be underestimated, and a failure to do so may result in erratic or even dangerous operating conditions for equipment. Rules for providing air supply openings are found in technical standards,*1" in state and municipal building codes and in service and installation bulletins published by various manufacturers of fuel-burning appliances. Table 11 is a compilation of reasonably consistent data taken from a number of these sources, and should be used only as an aid to independent judgment for any particular installation. Ventilating air requirements are particularly critical for residential type appliances in closely confined rooms. Fig. 6 illustrates minimum requirements for this type of in stallation. REFERENCES ' Five Hundred Teste of Various Coals in Househeating Boilers (V. 5- Bureau of Mines Bulletin No. 276). * A. P. Kxatz, S. Konso, and D. W. Thompson: Combustion Efficiencies as Related to Performance of Domestic Heating Plants (University of Illinois, Engineering Experiment Station Circular No. 44). Quality of Anthracite as Prepared at Breakers (U. S. Bureau, of Mines Report of Investigation, 1935 R. I. 3283). `Hand Firing Soft Coal UiMer Power Plant Boilers (U. S. Bureau of Mines Technical Paper No. 80). *ASTM Test Designation D287-39. *ASTM Test Designation JD611-43T. 1W. A. Sullivan and E. B. Glendenning: Tomorrow's fuel oil (Fueloil and Oil Heat, Vol. 4, May 1945, p. 36). `The correlation of cetane number with other physical properties of diesel fuels (Journal of the Institute of Petroleum, VoL 30, 1944, p. 193). *K. M. Watson, E. F. Nelson, and G. B. Murphy: Char acterization of petroleum fractions (Industrial and Engineering Chemistry, VoL 27, December 1935, p. 1464). *J. C. Reid and A. B. Hersberger: Burning index for distillates {Fueloil and Oil Heal, Vol. 5, January 1947, p. 90). 8. P. Cauley and E. B. Delgass: Carbon hydrogen ratio of catalyticaily cracked distillate fuel oils {Oil and Gas Journal, Vol. 45, July 27, 1946, p. 166). **D. W. Locldin and G. V. Parmelee: Rating of fuel oils by a test unit (ASHVE Transactions, Vol. 57, 1951, p. 139). *Domestic Gas Range Research {American Gas Associa tion Laboratories Bulletin 7, p. 64). -W. R- Morgan: Condensation of Moisture in Flues (University of Illinois, Engineering Experiment Station Cir cular No. 22). * Effect of Soot on Heat Transmission in Boilers {U S. Bureau of Mines Report of Investigation No. 3272). "Effect of Soot on the Rating of on Oil-fired Healing Botler {National Bureau of Standards Report BMS 54). "P. Nicholls and C. W. Staples: Removal of Soot from Furnaces and Flues by the Use of Salts and Compounds (U. S. Bureau of Mines Bulletin No. 360). "American Standard for Installation of Gas Appliances and Gas Piping (American Gas Association, 1959, ASA 2 2130). "NBFU Standard far the Installation of Oil Burning Equipments (National Board of Fire Underwriters, NBFU Pamphlet No. 31). BIBLIOGRAPHY Haelam and Russell: Fuels and Their Combustion (McGraw-Hill Book Co., New York, 1926). A. D. Pratt: Principles of Combustion tn the Steam Boiler Furnace (Babcock ana Wilcox Co.). H. J. Rose and F. P. Lasseter: Smoke-producing tendencies in coals of various ranks (ASHVE Transactions, Vol. 45, 1939, p. 329). C. A. Barnes: Fundamentals of Combustion in Small Stokers (Bituminous Coal Research, Inc. Technical Report No. IV). A. P. Kratz, J. R. Fellows, and J. C. Miles: Hand-firing of Bituminous Coal tin the Home (Illinois Engineering Ex periment Station Circular No. 46). G. EL Cady: Classification and Selection of Illinois Coals {Illinois State Geological Survey Bulletin No. 62). Situimnotn Coal Reicardi, tnc^ J. M. Pilcher and R. A. Sherman: The Treatment of Coal unth Oil and Other Petroleum Products (Technical Report VI). ^ R. A. Sherman and G. W. Land: Dustiest Treatment of Coals with Materials Other Than Oil (Information Bulletin No. 4). Questions and Answers on the Use of Fuel Oil for Dustless Treatment (Information Bulletin No. 6). R. B. Engdahl: Application of Overfire Air Jets (Technical Report VII). Bureau of Mines PubGcafJonj: Henry Kreisaeer and F. K. Ovitz: Sampling and Analysing Flue Gases (Bulletin No. 97). P. Nicholls and B. A. Landry: Coke as a Domestic Heating Fuel (Report of Investigations, R. I. 2980). John Blieard, James Neil, and F. C. Houghten: Value of Coke, Anthracite, and Bituminous Coal for Generating Steam in a Low-pressure Cast-iron Boiler (Technical Paper No. 303). P. Nicholls: Effect of Preheat, and Distribution of Ash tn Fuel Beds (Bulletin 378). J. F. Barkley: Handbook, Questions and Answers for the Home Fireman (Revised). Anthracite Industries Laboratories Publications: Comparison of Sizes, Egg, Stove and Chestnut Anthracite (Report 2015). Domestic Survey (Report 2018). Utilisation of Anthracite for Domestic Healing (Report 2062). The Crater Method of Firing (Report 2204). Anthracite Industrie* Manual (Report 2403). Oil and Cos Publications: J. A. Moyer: Gil Fuels and Burners (McGraw-Hill Book Co., New York, 1937). Combustion ("Industrial Gas Series," American Gas-As sociation). Comfort Healing (American Gas Association). Gaseous Fuels (American Gas Association, 1954). F. H. Faust and G. T. Kaufman: Handbook of Oil Burning (Oil-Heat Institute of America, 1951). E. R. Weaver: Formulas and graphs for representing the interchangeability of fuel gases (National Bureau of Standards Journal of Research, 1951, Research Paper R. P. 2193). Lewis and von Elbe: Combustion Flames and Explosions of Gases (Academic Press, New York, 1951). CHAPTER 34 AUTOMATIC FUEL-BURNING EQUIPMENT Classification of Stokers, Combustion Process and Adjustments, Furnoce Design, Rating,- Classification of OH Burners, Combustion Process, Combustion Chamber Design; Commercial and Industrial Oil Burners, Types of Burners; Storing and Handling Heavy Fuel Oil; Oil Storage Tanks and Piping; Classification of Gas-Fired Heating Equipment, Combustion Process, Ratings; Sizing of Gas Piping, Commercial and Industrial Gas Equipment; Fuel-Burning Rates; Controls for Automatic Equipment A UTOMATIC mechanical equipment for the combustion Jy of solid, liquid, and gaseous fuels is considered in this chapter. The type of fuel to be burned affects the design of the heat exchanger (furnace, boiler, etc.); therefore, one should refer to Chapter 35, Heating Boilers, Furnaces, Space Heaters when considering fuels and fuel-burning equipment. Some heat exchangers are designed specifically for one type of fuel. As a result, maximum efficiency and best perform ance require the simultaneous consideration of fuel and fuelburning equipment during the initial stages of equipment selection. MECHANICAL STOKERS A mechanical stoker is a device that feeds a solid fuel into a combustion chamber, provides a supply of air for burning the fuel under automatic control and, in'some cases, incor porates a means of removing the ash and refuse of combus tion automatically. Coal can be burned more efficiently by a mechanical stoker than by hand firing because the stoker provides a uniform rate of fuel feed, better distribution in'the fuel bed, and positive control of the air supplied for com bustion. In many cities, measures for control of excess smoke re quire installation of stokers even in residences, unless fuel used contains less volatile matter than bituminous coal. Classification of Stokers According to Capacity Stokers may be classified roughly according to their coal burning capacities, as follows: coke. The U. S. Department of Commerce has issued com mercial standards for household anthracite stokers.1 Units are available in either the hopper type, as shown in Fig. 1, or in the bin-feed type as shown in Fig. 2. Some stokers, particularly those designed for use with anthracite, automatically remove ash from the ashpit and deposit it in an ash receptacle. Most of the bituminous models, however, require hand removal of the ash from the fuel bed after it is fused into a clinker. Stokers in this class feed coal to the furnace intermittently in accordance with temperature or pressure demands. A special control is used to insure sufficient stoker operation to maintain a fire during periods when do heat is required. Gass 2 Stokers Stokers of this class are usually of the underfeed motordriven screw type, Fig. 3, and are used extensively for heat ing apartments, schools, hotels, and industrial plants. They are also built in plunger-feed type, Fig. 4, with electric motor or steam or hydraulic cylinder coal feed drive. The tuyeres and retort design vary according to the fuel and load condi tions. They are available for burning all types of anthracite, bituminous and lignite coals. Stationary type grates or dead plates surround the retort of bituminous models to collect the ash and clinkers which are removed periodically by hand. Anthracite stokers in this class may be equipped with moving grates that discharge the ash into a pit, below the grates, having capacity for several weeks of ash accumulation. Class 1 10 to 100 lb per hr Class 2 100 to 300 lb per hr Class 3 300 to 1200 lb per hr Class 4 over 1200 lb per hr Cass 1 Stokers These stokers are used primarily for home heating and are designed for quiet, automatic operation. Simple, trouble-free construction and attractive appearance are desirable charac teristics of these small units. ^ A common stoker in this class (Fig. 1) consists essentially of a coal hopper, a screw for conveying the coal from the hopper to the retort, a fan that supplies the air for com bustion, a transmission for driving the coal feed worm, and an electric motor for supplying power for coal feed and air supply. Air for combustion is admitted to the fuel through tuyeres at the top of the retort which may be either round or rec tangular. Stokers in this class are made for burning anthra cite, bituminous, semi-bituminous, and lignite coals, and Gass 3 and 4 Stokers These stokers are: underfeed side cleaning, underfeed rear cleaning, overfeed flat grate, or overfeed inclined grate type. Underfeed side cleaning stokers are made in sizes up to about 500 boiler horsepower (or approximately 17 million Btuh). They are not so varied in design as those in the smaller classes, although the principle of operation is simi lar. A stoker of this type is illustrated in Fig. 4. / The rear cleaning underfeed stoker is usually of the mul- Fig. 1 .... Underfeed Stoker, Hopper Type, -Cass I 497