Document 15nevzvbEJoNNrwbM9bqzJmNX

FILE NAME: Trade Publications (TR) DATE: 1940 June DOC#: TR044 DOCUMENT DESCRIPTION: Trade Journal Article - Making Progress in Control of Industrial Dusts Charter Member Associated Business Papers C o n c r e t e , with which has been com bined Cement Age, New York, and Concrete Engineering, Cleveland, is devoted to the Proper Use o f Concrete and the Manufacture of Cement. Published m onthly by Concrete Publishing Corporation 400 West Madison Street Chicago, Illinois Telephone CENtrai 8822 Louis Broukman, Jr.. Publisher L. Moeller. Circulation Manager Donald T. Papineau, Promotion Manager Representatives New York City E. Macdonald Bacon 17 West -15th--Room 909 Loagacre 3*5260 San Francisco'- Don Haiwav 155 Montgomery Street Exbrook 6029 Lo< Angeles: Don Harway Sc Co. 318 West Ninth Street Tucker 97Q6 T h e C em ent M ill E d itio n o f C oncrete The Cement Mill Edition of Concrete is edited exclusively for those interested in the manufacture of Portland cement and related products. Its pages are devoted to discussions of plant design, management, operation, production, effi ciency, chemical research and control, quarry op eration. progress and news of the industry. The Cement Mill Edition also contains all the material published in the corresponding Regular Edition and *a provides news of the uses and merchandising of the materials whose m anufacture is discussed in the Milt Edition. The Regular Section furnishes mill operating official? and mill executives valuable points of con tact with the users of the materials they produce. The subscription price L $3.00 a year in the United States and its possessions, and Mexico. One Dollar additional for postage in all other countries. Current copies, 40 cents each. Charier Member Volume 48 June. 1940 Number 6 Norman M. Stineman, Editor J. C. Witt, Consulting Editor CONTENTS How Slurry Filters Solved a Biq Problem in Wet-Process Manu facture ......... ........ ............... - ........................................................... 1S2 Monolith's Huge New Kiln Expands Its Manufacturing Capacity 183 Saranac Laboratory Pushing Studies of Silica Dust ...................... 184 Pozzolanic Minerals .................................................. .......................... 184 Wet Types of Equipment for Separation of Fly A s h ...................... 185 X-Ray Alone Can Not Determine Extent of Injury from Silicosis 186 Discuss Selection and Utilization, of Coal at Big Fuel Conference 187 Find Sickness Among Workers Big Loss to Industry................. .. 188 Time Studies of Quarry Drilling ................................................... 189 Civic Center Building to Honor Founder of Ceraeat Company . . 190 Editorial Discussion ................. ................................................... 191 A Brilliant Record in Safety- Fuel Efficiency Approaches Limit Five Types of Cement Making Progress in Control of Industrial Dusts ............................ 192 Design Problems Involved in Burning Pulverised Midwestern Coats--By Martin Frisch............................. 193 Calcium-Aluminate Cement ............................ 194 Great Industrial Leader Passes Away in M ilwaukee..................... 194 Mill Equipment ....................................................................... 195 Men and M ills...................................................................................... 196 Q) Advertisers' Index Paqe 40 CONCRETE is indexed in INDUSTRIAL ARTS INDEX, which may be consulted in any Technical or Public Library. Audit Bureau of Circulations ____ N C R E T E -- Cemsnt Mill Section -- June. 1940 Copyright, 1940, by Concrete Publishing Corp. Page 181 EMEISIT MILL Making Progress in Control of Industrial Dusts several liquids with widely different physical properties, trichlorethylene water, toluol, triethylene glycol, the min imum ventilation requirements at vari ous temperatures and evaporative rates have been determined. This phase of the work is now nearing completion. IN 1938 the Air Hygiene Foundation established two fellowships at the Harvard School of Public Health. At present, these are held by two engineers working toward the Doctorate of Science Degree in Industrial Sanitation. The thesis work of these men is directed to ward problems of direct interest to Foundation members. What Sizes? An important problem in silicosis prevention and in the appraisal of sili cosis risks is, "What is the most potent size of silica particles?" It is recog nized that the most dangerous sizes are certainly below 3 microns (a micron is 1/25.000 of an inchl, but whether there are critical differences here between par ticles of 0.5. 1. and 2 microns has not been studied. Accordingly, ground flint (99.7 per cent free silica t was separated into four fractions. 3.30. 1.05. 1.04. and 0.62 microns, and the fractions cleared, as far as possible from particles other than the sizes stated. Sterile suspensions of these fractions were then injected into the ear veins of rabbits twice at threemonth intervals, and the animals were killed and autopsied periodically. Preliminary examination of liver sec tions indicate that the fine particles are more rapidly taken up bv cells than are the larger ones. Later examinations showed no striking effects with the two larger sizes (3.30 and 1.65 microns!, while it looks as if the third and fourth (1.04 and 0.62 microns! produced the greatest changes. The final report on this study will be ready in about eight months. W hy Engineers Want to Know The reason engineers want the in formation which we hope this study will bring is that we are responsible for meas uring degrees of dustiness in workplaces and for controlling conditions. Also, we must design dust respirators. We would like to know what, physiologically, are the most important sized particles; and Report of Preventive Encineerine Committee of the A r Hypiene Foundation. Pittsburgh. Penna.. prepa-ed h> Prof. Philip Drinker, of H ar\a-d. eh -irman of the committee. then we can focus our efforts particularly against them. An engineering corollary to this prob lem is " What is the most difficult size dust particle to wet when floating in air?" and "^Ttat can be done to make the mod ern air washer into a more efficient dust catcher?'' These questions are impor tant to the air-conditioning industry and to all plants where air is cleaned by wet methods. The graduate student who is working on the dust injections is studving commercial air washers with a par ticular view to the possible application of wetting agents (surface-active agents I. An incentive to the study of this problem has been the remarkable progress re cently in the separation of non-metallic dusts by flotation, a method considered inapplicable to industry only a few years ago. Interest Increasing As evidenced by the number of papets published in the last year, interest in the vapors from organic compounds has be come widespread. Firms selling equip ment or materials in which such solvents are in any way concerned are generally alert to the problem. Methods for detect ing and for recording such substances are being reported from numerous lab oratories. At least three large firms have arrangements for investigating the po tential risks of one new compound after another and thus to determine under what conditions they can be marketed and used safely. As compared with the silicosis field, it is likely that the inter est and activity in these directions will increase rather than diminish as new compounds continually are being devel oped. The design of electro-plating tanks, baths, and vats using toxic solvents and liquids has not yet been placed on a rational basis. The purpose of the sec ond Foundation research now in prog ress at Harvard is to investigate the char acteristics of these solvent tanks and to provide a rational basis of design hy studying their performance under vari ous conditions. Small tanks, with lateral exhaust on one or two sides, have been used. Taking With reasonable surety it may he stated that the required ventilation in CFM (cubic ft. per minute 1 varies as the evaporative rate to an exponent. The use of a minimum quantity, rather than a minimum velocity, has been found neces sary in the case of fumes, vapors, and mists, and it is believed that this work gives adequate basis to that fact. The second phase of the work has been to ascertain the velocity characteristics of these tanks. The velocities at all four tank corners and at the sampling point are being determined to find which loca tion will give the best and most satis factory correlation with vapor concen tration. Dust-Counting Instruments In addition to the above work, a new vapor-pressure instrument for determin ing organic solvents in air has been de veloped. Also, a new dust-counting in strument revision was made. The development of instruments for recording continuously low concentra tions of toxic vapors should interest the members of this Foundation. Many firms using toxic solvents must either continue to use them or else take up an entirely ncv. line of manufacture--often they can not use harmless substitutes. Under such conditions, the plant management requires periodic sampling of the air to find out if ventilation is as it should be. Recorders are available today for car bon monoxide, sulfur dioxide, hydrogen sulfide, carbon disulfide, mercury vapor, and carbon dioxide, while continuous alarms or detectors for inflammable gas mixtures are in fairly general use. It is well within the realm of practical mat ters to develop instruments which will furnish reliable records, 24 hours a day, of air pollution from low concentrations of substances, such as benzol or carbon tetrachloride. We have every intention of pursuing the problem further in our work for the Foundation at Harvard. N ew Idea in Silicosis Control A? the result of Dr. L. U. Gardner's medical research, hacked by manv field studies bv others, notably the United Slates Public Health Service, it is now possible to outline and carry out. with reasonable assurance, a reasonable dust- Page 192 June, 1940 -- C O N C R E T E -- Cement Mill Section control inands inedicit such as of silic what th U: know t 1 gPs ca OUL r be tant cl adequa 1. 2. 3. 4. The influent and pt two de equipm heat-ab gas pas ing sup Easy tc Most easy to when q their te they' at ever, tl easily, coals a other n Whe the fur desired minimi partich tides less un pass oi space 1 exit. 5 heat h Preset Conferei 1940. CON S-. k.1 a 1IkJ, control program, industry neither de mands nor expects from experimental medicine great precision in these matters, such as toxic limits in air. In the field of silicosis they have very nearly got what they need, and certainly they non know very clearly how main missing gaps can be filled out. It is of some interest that the use of aluminum dust in the treatment of men who have had exposures to silicotic dust has definitely been suggested at least twice; once, to an important mining group, and again to the granite cutters' union. Furthermore, patents on the use of aluminum dust, both for the preven tion and for the treatment of silicosis, have been granted. What place, if any, the use of alum inum or other protector dusts may even tually have in silicosis control remains to be seen, fu the meantime, we see no reason to reduce either engineering or medical control in any way whatever. D esign Problem s Involved in Burning Pulverized Midwest Coals By MARTIN FRISCH Chief Engineer. Pulverizer Division Foster-Wheeler Corporation. New York City PULVERIZED Midwestern coals may be successfully used if four impor tant characteristics of these fuels are adequately provided for. These are; I. Low ash softening and fusion temperatures. 2. Small coking tendency. 3. Generally high total moisture content. L Loiv to moderate grindabilitv. The two last characteristics primarily influence the choice of coal preparation and pulverizing equipment. The other two determine the design of the firing equipment, extent and disposition of heat-absorbing surfaces, arrangement of gas passages and provisions for controll ing superheat. Easy to Bum Most Midwestern coals are extremelv easy to burn in pulverized form, even when quite coarsely pulverized, because their tendency to coke is small. Hence they are naturally free-burning. How ever, the ash in most of the coals slag; easily, and for this reason alone these coals are more troublesome than most other native coals. Whether or not it is possible to reduce the furnace-exit temperature as much as desired, the slagging tendency may be minimized by fine pulverization. Fine particles burn faster than coarse par ticles and may be expected to contain less unburned fuel residues when they pass out of the flame into the clear gas space between the flame and the furnace exit. Such particles can then give up heat by radiation to cold surrounding Presented at Third Annual Midwest Power Conference, Chicago. Illinois. April 9 and 10. 1940. wall surfaces. If the paiticle path with respect to the furnace cooling surfaces and the flame is correct, the rate of heat dissipated by radiation from the particle will exceed the rate of heat reception by the particle bv radiation from the flame and bv convection from the surrounding Additional Cost Ofiset The additional cost of grinding tine will be partially offset by fuel savings due to reduced carbon loss, and more than offset bv the reduced cost of clean ing. For example, experience indicates that in the average installation burning Illi nois coal one may expect the relationship between fineness, fuel loss due to incom plete combustion in terms of the fuel fired, power consumption and mainte nance, to be approximate!) as follows for a ball-mill job. Ftnrne-s -- per cent through 200-mesh Fuel loss Hue to in complete combustion--per cent ot fuel fired Fuel loss, lb, per ton burned . . . Power consumption --KWH ton .. Coal equivalent of power. L.5 lb ./ KWH ............. Maintenance costs --cents per ton Coal equivalent of maintenance cnst for coal at $5.00 a ton Net coal equivalent of carbon loss-- power consumption --maintenance Per cent of coal fired 65 70 80 90 1.5 1.3 1.0 0.7 30 26 20 14 13 15 21 30 19.3 22 5 31.5 45 0.9 1.0 1.4 2.0 3.6 t.O 5 6 8.0 53.1 52.5 57.1 67.0 3.66 1.63 2.86 3 35 Economical Fineness Under these conditions the minimum coal consumption occurs at a fineness of about 70 per cent through 200-mesh. If the power consumption or its coal equiv alent is lower, or the carbon loss higher, the economical fineness is higher. Ac tually, one may safely conclude that con siderable increases in fineness may be made without materially increasing the overall fuel cost. Conclusion The chief problem in the utilization of Midwestern coals with low ash fusion temperature is slag control. High fine ness minimizes slag troubles and is justi fiable for Midwestern coals even though not entirely justifiable on the basis of effect on efficiencv. QUARRY DRILLING ( Continued from, page IS91 churn drills of intermediate size, hut less than large drills. 4. Cut less volume of hole per hour of shift time than churn drills. 3. Break more rock per hour of drilling time and shift time than churn drills of intermediate size, but less than large churn drills. Individual tests scatter vvidelv and mav C hurn in diam et 1. Operate at slightly lower time efficiency than larger churn drills. (This difference may be due entirely to small sample. I 2. Operate at higher time efficiency than hammer drills as a group. 3. Occupy a position intermediate between hammer drills and larger churn drills, in rock broken per volume of hole drilled. 4. Drill greater volume of hole than hammer drills during shift time, and less than larger churn drills. 5. Produce less rock per hour than hammer drills or larger churn drills. C O N C R E T E -- C em ent Mill Section -- June, 1940 Page 193 40 CONCRETE June, 1940 THE NEW NINTH (1940) EDITION O F I Advertisers' Index I THE BUILDING ESTIMATOR S REFERENCE BOOK 1.678 Pages A lla n M fg. & W e ld in g C om pany ................... ...................39 A m erican C olloid C o ............................................................................ 31 A n c h o r C o n c rete M chy. 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