Document KJ93p97bJZ2MgdMJb10bZJx7K

More TECHNICAL BRIEFS. most talked-about Air pollution condi tions, and also one of ihe most thor oughly investigated. The answer to these seemingly con tradictory facts lies in o new type of pollution: the emission of apparently harmless gases which, under the influ ence of the abundant sunlight, gradual ly change into physiologically active constituents that cause discomfort and eye irritation to man, and serious dam age to sensitive leafy crops. The salient determinants are meteorogical and topo graphical---the combination of sunshine, the Pacific inversion, and the mountain chains hemming the Los Angeles Basin on three sides. Yet, there is no reason to believe that this type of air pollution cannot or does not exist in other parts of the country. It may be that the un favorable conditions merely occur much more frequently in Los Angoles. APCA roper. No number. Th* RoU of the Area Survay in Dust Control. By R B Engdahl, Dattelle Me morial Institute. An attempt has been made to point out that on the dust phase of air pollu tion the many extraneous variables in teracting at any point limit greatly the value of dato taken at one point only. Simultaneous measurements at many points over an area are required to give a picture that will show the'influence of the main variables of Interest. The principal practical tool available for such an area survey is the simple dirtfall station. Some modifications show promise. equivalent means for getting the pic ture on suspended dust are not avail able. And (lie rapid weight-wise dilu tion of ultrafine, highly visible clouds of fine dust by the larger dust particles normally raised In an Inhabited area make chemical identification of the vis ible components of tbe cloud extremely difficult. An unusual example of the difficulty of Identifying Ute origin of finely deposited dust is tho problem of distinguishing between fiyosh and me teoric dust. The need la great for research to improve existing means for all kinds of dust measurement and to develop en tirely new and more rapid means for such measurements. APCA Paper. No number. Internal Flew Problems In MechanicalCentrifugal Dust Collectors. By E It R Pegg and D W Gibbs, Aerolec Corp. U has long been recognized by those familiar with multipie-tube centrifugal collectors that factors other than the design of the individual tubes are of paramount importance to proper opera tion, nmi, in the past, some installations have obtained efficiencies very much lower than would be obtained from in dependent tubes. This bos been true of most designs of this general type and probabty would be Uue of all U com plete Information could be assembled. Barring any more obvious sources of trouble, the factor usually responsible for poor performance is so-oalled "re circulation." This refers to a secondary gas flow between tubes through the dust discharge section, and is caused by un balance in the main flow through the tubes. The term recirculation, white not exactly descriptive of the condi tions exisling, has become established through usage end lack of a better term. This flow through the dust discharge section leaves some tubes in Uie same direction as the dust discharge and enters others in the opposite direction. Flow in the same direction as the dust discharge is of little concern. However, flow opposite to the dust discharge up sets the normal action In the lube ond inhibits or prevents the discharge of dust as well as re-enirsining dust already collected by other tubes. Consequently, serious dust losses occur if the second ary flow is sufficiently large. A more commonly recognized similar condition exists if the hopper is under negative pressure and leakage into the hopper occurs. Lengthy experiments developed a highly effective outlet shield for Indi vidual tubes. Just how these shields pro duce relatively high degree of balance Is based partly on conjecture. However, TO 08TAIN COMPLETE TEXT Material /or these abstracts comas from the following sources unless otherwise jtated. Order complete paper from sources, not Power. Air Pollution Control Assn, an nual meeting. Lord Baltimore Hotel, Baltimore, Md. May 24-29. 1953. Identified by initials APCA and obtainable in proceedings printed and distributed by R C Griebiing, exec secy, 4400 Fifth Ave, Pittsburgh 13, Po. American Petroleum Institute, mid-year meeting. Hotel Commo dore, New York, N. Y. May U-IS, 1953, Identified by initials API and obtainable through API, 50 XT 50th St, New York, N. Y. directional vanes which discL?J gas in the desired direction. This to streamline the flow Bnd mini: turbulence. Also, they have aa tional effect on lha flow , rear. The data shows that ifo reduced the differentia) front In rear In the gas outlet compan practically to zero, at th Une they have promoted balance in the discharge compartment. ,, Probably because of the leductloa; outlet losses they hove caused only minor change in the overall drop. Another effect of the thiel which is not thoroughly covered in tn data yet available, is that tbey teed u improve top tn bottom gos dittrlbuifei by more properly directing the flow. APCA Paper. No number, Got Distribution In Cloetrostotic clpllolors. By S IF Randolph, Koppen Co, Inc. Uniform distribution of tbe gas through the treatment tone of tbe pu cipitator is essential for good operatho ond removal of entrained dust. This it true not merely because of the obvious possible observation that when the foul gat passes through only part of the treatment zone, that part is overloaded and the rest is relatively idle, (t is also true because of the exponential char acter of the performance efficiency formula that describes the phenomenon of elecuostalio dust collection. Under a given set of circumstances there is a specific velocity or rate of gas flow required to produce a desired. cleaning efficiency. A host of other de sign factors are, of course, involved but the velocity at which the gas is passed through the precipitator is a centra! ond important one. Thus, if design curves show that o desired cleaning result on a given got is obtainable el a treatment tone velocity of 5 ft par sec, the area of tbo cross section of tbe precipitator Is defined. If, for instance, the volume of gos to be treated is 1,500 cubic (cct per second, the cross-sections) area of the precipitator treatment sans must ba 300 squara feet, thus creating a 5 foot per second velocity. Poor cleaning performance lo a bat tery of four electrostatic precipitators cleaning blast furnace gas was attrib uted to poor distribution of tbe gas Into tbe precipitator treatment zones. The precipitators were arranged In parallel along a manifold. The manifold was fed by a single main. Field operating con ditions prevented adequate direct meas urement of flow characteristics. (Continued on page 244) 174 READER SERVICE SECTION POWH I cO*<* A/ways ready to serve you... !S%\ nrw .1, IMl with a coal thats exactly rit Name your choice^-iftMBituroinousland" along . the Baltimore & Ohio, we have iff Here Nature has stored e supply of economical heat ond energy sufficient to last for centuries. BdtO Bituminous coals exist in wide variety. The mines that produce them are thoroughly mechanized so that costs are kept low, size and quality uniform. Nearness to industrial centers results in low transportaiiqn costs, ond the ease of storing removes the need for expensive facili ties. Furthermore, new methods and equipment' have increased the burning value ofBituminous. ASK OUR M'AJ N" f* 1Le*t h>i!m" ddiirreecctt yy<ou to the best coal for your needs, and explain proper firing methods. You'll be more than pleased at the improved efficiency, economy, ond cleanli ness of B&O Bituminous. BITUMINOUS COALS FOR EVERY PURPOSE -- ----- aiTIMORE & OHIO RAILROAD OCTOBER TSS3