Document DDGxzDyyEaO8r5QGb4EqL15dN

n DRIVES AMD CONTROLS ploced in convenient location for cleaning end molnlenonce. SCHCMATIC DIAGRAM shows electrleol ^ Fuel-feed controllers ttand olangtldo m-g sets, with the vorioblo-spced motors above connections for tha vorlobla-speed drives ; An overhead flight conveyor brings wood refuse to the boiler room. A la. pored hopper connects the conveyors overhead to a horizontal, tapered feed aeraw driven, by a variable-speed do motor. From the feeder trough the fuel flows by gravity to the furnace top, to drop on the pile in the dutch-oven cell. Combustion is completed in the main furnace of the 3-drwn bent-tube 7000eq-ft Erie City 3-pass boilers. As shown in the diagram, air is drawn from above the furnace top, under the firing deck and up the boiler front to a warm-air duct Fresh air, from within the boiler house and from the roof, flows alongside the stack up take to the eame warm-air duet, which supplies the forced-draft fan with lightly preheated air. Much of the control hookup follows essentially conventional practice. The boiler-outlet damper is regulated di rectly from furnace pressure. A steampressure controller operates the forceddraft-fan outlet damper, the foe being driven by a constant-speed motor. A fuel-feed controller actuates the genera tor rheostat of the typical Westlnghouse Ward-Leonerd variable-speed-drive sys tem diagrammed above. This arrange ment regulates the speed of the dc feed-screw motor, controlling rate of adding fuel to the pile. The fuel-feed controller is primarily responsive to a steom-flow controller. To compensate for differences in fuel conditions (relative amounts of saw dust, shavings and hogged fuel, per centage of moisture, eto) an additional secondary control to maintain desired air-fuel ratio seemed necessary. Brillioncy Central. For this purpose, a photoelectric cell in the boiler fur nace rear wail measures brilliancy of the flame and gas stream leaving tha dutch-oven furnace and, through an averaging relay, works with tha steamflow controller to adjust fuel feed. With this arrongement, an Increase in brilli ancy shows an ezecss of air and a need for more fuel, while a decrease in bril liancy Indicatea need for cutting down fuel feed. In normal operation, increased steam demand Is reflected quickly in an in crease in forced-draft air. Aa steam flow changes, fuel feed is increased proportionately, with the brilliancy controller acting to correct any change in air-fuel ratio and to maintain com bustion at maximum efficiency. Rate of fuel feed U indicated on a dial at each feed controller; draft gages, steamffow-airflow meters and other boiler instruments are grouped*on a panel on the firing deck (see photos and diagrams). Selector valves on (he panel permit switching from auto matic to manual control as desired. Hand orssl tests reveal that this con trol method automatically holds ex cess air within 2% plus or minus, si jj any rating from 20,000 to 60,000 lb of steam per hr. To do this, the brilliancy control regulates the height of the fuel pile on the grate, depending on the type of fuel being burned at any time, and j maintains a clean fire, free from smoke. ,y Cos analyses indicato approximately 22% excess air al bigb ratings and J about 40% at low, with CO, at about 16-17% and no CO. The steemflow-afrflow meter was found to be an excellent operating In dex, correlating closely with* the brll- ^ liancy values. For example, a deviation ; in excess air shown by the boiler meter etso oppeors on tbo brilUency-meter chart and Is promptly corrected. When 1-, burning wet hogged fuel (epproxt- \ mately SS to 65% moisture) the boiler meter shows about 10% lower steam j.` flow than air flow because of the high loss represented by evaporation. 11 Successful Eipartance. Our experi- ? ence indicates the brilliancy control to r bo of great help in compensating for .< varying fuel conditions and correcting .V the primary fuel-feed adjustment to '> maintain desired air-fuel ratio. The j* installation of automatic feeding, as a ; whole, has, in addition to conserving i now-valuabfa wood-refuse fuel, made it j easy to hold boiler output to desired ) levels. With hand firing the output -j could not be controlled closely and varied over a wide range. Removal of Silica in a Sludge-Blanket Hot-Process Softener By J O YODER, v/co-protidanf, Tfte Ptnwitft Co; H Y CARBONNIIR, oiilflonl technical director end A H MORRIS, senior chemical engineer. Union Bag A Paper Corporation Two yean' experience using sludge, which accumulates in hot-process lime-soda softener, to give longer contact between mD9neslum hydroxide and water, betters silica removal *Thb OUTSTARDtKC PROBLEM In the treatment of boiler water ot the Sevan"lh pl*ni ol ilio Union Bag ft P.por Corporation has always been the re- of silica. The raw water, which 11 Pumped from deep wells, has a silica content of approximately 55 ppm. In view of this problem, it was decided to install a new type of hot-process softener recently developed by The Permutit Company. A 72,000-gph softener of this type was installed and put into operation in November, 1945, Fig. 1. MORE CAPACITY REQUIRED Prior to the installation ol the new unit, makeup waa treated by conven tional hot lime-aoda softeners. Nine years of operation with the old plant followed by two years of operation with the new plant have shown that the latter provides more efficient silica removal, as well as better hardness and turbidity reduction In the effluent. Feedwater to the 450-psi boilers con sists of 35 percent makeup, the re mainder being condensate. The makeup was provided by one hot-proccss limoaoda softener of conventional design, Fig. 2, when the paper mill began op erations. As tho plant grew, similar units were installed until five with a total capacity of 52,000 gpli were op erating in parallel. Each softener had separate chemical-feeding equipment. When Increased feedwater demand called for still greater capacity, it was decided to install a 72,000-gph softener of the new sludge-blanket design. Al though development of this type sof tener for silica removal was still in 74 (196) POWER July 194# J L July 1948 (}<N) 74