Document 8jyOY2kD9M9QVa87gzqVqO8o

I: Chemical Composition 01 Flyasti (ItfMDl Percent Carbon OS C Icon at fttO, t> F,0. Magnesium et MgO Calcium et CoQ Aluminum at AIiO, Sullur at SO, Titanium et TiO, Carbonate at CO, Silicon oi SiOe Pbotphoroet os fiOt UrvCvtennlnvd pH talus 0.37 36 2 20-26.8 0.06-4.77 0.t2-H.7t 9.81 -58.4 0.12-2431 030-2.8 0.05-2.6 17.1-63.6 0.07-47J 0.09-18.9 4.7-11.7 II: PartldB Size Olshlbutfon for Representative Flyash Samples, In Micron; Sample Mo. 1 2 3 4* S 6" 7*** 8 03 25.0 123 39.1 13.6 54.8 64.0 _ -- 5-10 16.6 163 16.8 51 263 16.1 -- -- 10-20 183 (23 24.0 3.2 9.1 2.1 -- -- 20-44 26.0 23 16.8 2.3 0.7 0.1 -- -- imoJJ. Tatet J*, f' than 44 * mm *Soano oi sample 1, but taken at outlet ol Uitallod mtckonical collector *'Cyclone-type furnace '"Stoker-fired ' t: w _____________________________________________________________________ e. 's Designs Cut Pump Costs AIR POLLUTION COflliiwW } MIIFICKER, Det/pn fishnet, Uenomf Rumps, f credited with the ability to raise dew point temperatures considerably.. So precipitator design must give proper weight to flue-gas properties and be capable of best operation at a tempera ture well above dewpoint to avoid cor rosion problems. Particle site and ahape. Table II, also play t part in precipitator effectiveness. The translucent, hollow spheres present in most flyashes range from below 10 microns up to 44. The irregular-shaped carbon particles commonly called grit, resulting from incomplete pulverizedcoal combustion, can be anywhere from 10 to' over 300 microns In size. Their shape varies from slivers to highly irreg ular sponge- and lace-like material. And their density proves low, about 0.7 against the average flyash specific grav ity ol 2.0 to 2.7. Fig. 2 shows the settling velocity for a spherical particle of 2.2 density in a gas temperature of 300 F, and Illustrates the striking decrease in settling rate with smaller particle diameters. Resistivity. As these particle# are pulled out of suspension theyballd up on the electrode surfaces to form layers averaging Vfc to % in. thick. The corona current from the high-tension wires has to pass through these layers to reach the grounded collecting plates. When the resistivity approaches the critical value of 2x)0,(> ohm/cm. sparking grows more Intensive and performance falls off. Normal resistivity level, though, ranges between 10* and I019-ohm cm. But certain chemical compounds, in 74 small quantities, act as conditioning agent*. They are, however, specific for each dust, and the proper one for any new dust type is found only by trial, ftmarch Corp over the years has dis closed and confirmed that sulfur trioxide in the quantities normally present in boiler gas serves os s conditioning agent, (i holds bulk resistivity below the critical 2xl0lo-ohra cm level. Specifying Precipitator*. With all tho considerations including the above that go into good precipitator design, this information is basic in specifying this equipment: (1) desired collection effi ciency (2) normal gas flow or efm rating (3) maximum gas flow or cfm voting (4) steam flow or boiler-load rating (5) gas temperature at the pre cipitator (6) permissible precipitator draft toss (7) type of coal and percent ash (8) particle size and maximum per cent combustible expected in ash (9) furnace and burner types (10) air pre heater design (11) precipitator location in power station (12) layout of con necting gas flues. Let's see, now, how well modem elec trostatic collectors meet design needs. Operating Problems. Even with the above basic requirements known, elec trostatic precipitators In years past suf fered from some relatively small but annoying operating problems. Chief, among them were cleaning of collected dust from electrodes, determining the ideol operating voltages snd currents, achieving effective and adequate ener gization. Iciest designs, like the one at Goudey SlaUoo, go a long way towsolving these problems. Continuous Rapping, lotermedM' system of rapping electrodes, eraployis| mechanical or pneumatic vibraton-ts clean off collected dust, reduces overall efficiency at cleaning time by only j!lS 3% or less. Yet the puffs this rnttbr1 gives off cause some public concern.,$ the equipment makers have hsd to'dj vise a method of continuous cleaning'] collecting electrodes. They've done this with a m*|nettt impulse rapper system bated on elect" and magnetic principles, iree o( -i objections of the earlier pneumatic,#/ mechanical approaches. A steel p* serving as the armature of ao magnet delivers the rapping action. ^ ( (hyrstron tube and dlatributor times and controls tho impulsive diajv charge of a condenser to excite the ptrj); net's solenoid eoil. Both intensity sodj^ frequency of rapping can be adjusted b^' varying the condenser voltage- - 7* From still another practical, op<r*J$ Ing point -- maintenance --this unit haa a decided advantage. There only one moving part, hermetically P**#p.' tested against atmospheric dirt *nd rosion, and permanently lubricited the time ol manufacture. D**>Pe?,\ claim ft fs now possible to rosJnMJa f/f clean stack at 98 to 99% efficiency w no trace of puffing or clouding and a high reliability. Operating Volfugo*. Industrial , _ clpltator performance proves supe^l (Continued on page 1961 ENOtNttttNO AND MANAGEMENT SECTION CcNTfltn/CAL PUMPS in process in.duetriea must do to many different jobs (hst manufacturers are carefully con sidering parts standardization wherever possible. Interchangeability reduces re pair-parts stock, gives the pump far greater versatility. Modern' Designs, Photos' show some advantages gained by pump standardisa tion. By simply changing volute covers, pump can be fittdd with a cooled Instead i of a noneooled stuffing box. You oan m alto change from a closed to a semiopen impeller without extensive work. Spacer-type couplings allow removal of entire rotor after spacer Is discon nected. Screws permit operator to adjust Impeller position axially. Rotor servic $if. ing fs simple. Other Innovations include a single, confined casing gasket, compact earitldgMype bearing housing, oversize bearings to extend the pump's useful ness, and a gland collecting chamber that eliminates need for a drip pan. Pomp manufacturers are devoting much time to study of process problems and you can expect many developments in the future. !*?v % ' '# 77