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FILE NAME: Trade Publications (TR) DATE: 1947 Aug DOC#: TR048 DOCUMENT DESCRIPTION: Trade Journal Article - Recovering Asbestos Floats with Dust Collectors AUGUST, 1947 Bror Nordberg Editor R ock P roducts THE INDUSTRY'S RECOGNIZED AUTHORITY Stanley A. Phillips Pubication M anager This Month We Hear A New Age of Long Rotary Kilns . . Br or N ordberg Rodens Notes-Woes From Unstable Dollars Labor Relation Trends r Nathan C. Roekwood The Personal Sideof the News Industry News * Hints, and Helps New Machinery \ Recovering Asbestos Floats with bust Collectors l . J. W iesihhous Processing Aggregates for Big Dam Cumberland Q uarries. Inc., operates tw o plants to prepare aggregates for W o lf re e k daiti id K entucky - D avid Module Supplying Ready Mix and Concrete Block Market W . B. len h a rt Potash Concentration Cement Section -- Trends In Cement Manufacture Jam es A. Barr> Jr. Bror Nordberg Long Kiln vs. Short Kith Performance Barge Haulage and New Terminals Extend Cement Markets Mathematical Problems of Proportioning .Raw Materials Ralph W. Hubbs High Efficiency in Stack Dust Recovery Bror Nordberg From Aluminum to Cement Manufacture Double Capacity of Sweden's Most Modern Cement Plant Insulation in Rotary Kilns w . r. ante 87 89 91 93 97 100 102 104 109 111 112 116 122 126 132 134 138 142 145 Specific Heat Data for Evaluation Of Lime Kiln Performance J. A. M urray New Developments in Cement, Lime and Concrete Block Business Booming in the Pacific Northwest ' W . B. len ha rt Methods and Machines Which Have Cut Larg Pipe Costs Steam Plus Hot Air for Preshrinking Labor Requirements Data for Concrete Pipe A llred W . Collier and Clyde Stone brand Opera Sells Ready Mixed Concrete W . B. Lenhart Building Houses Using Large Precast Sections 143 154 193 198 200 202 206 Contributing Sditors Victor J. Azbe Dr. F. O. Anderegg M. W . Loving Jomes A. Barr, Jr. H. M. G o od enow , Dir. of Circulation C. P. Teols, Field Representative M. A . Cotter, Circulation Service Tho rnell B arn es, D irector of Research M ilton M. M y e rs, A rt Director C. M. H ancock, Production Manager District Offices Eastern A re a -- E. H . St. Jules, Man a g e r; Jo h n F. L ockitt, A ssistant, 522 F ifth Ave , N ew Y ork 18, Tel. Mur ray H ill 2-7888. C e n tra l A re a -- F. S. Ruggies, Man ager, H an n a B ldg., Cleveland 15, Tel. Main 4362. M idw est A re a -- M. B. N ylund, Man ager, 309 W . Jack so n BIvcf., Chicago 6, Tel. H a rriso n 7890. W estern A re a -- L. C. Thaon, Man ager, 309 W est Jackson Blvd., Chi cago 6, Tel. H arriso n 7890. Pacific A re a -- D uncan Scott & Co., Mills Bldg.. San Francisco 4. let. Garfield 1-7950 In Los Angeles 13, 408 Pershing Square Bldg., Tel. .Michigan t>203. London, En g lan d -- Ernest R. Gauley, M anaging Director, Maclean-Hunter, L td., Sun Life of Canada Bldg-, T ra fa lg a r Square, L ondon, S. W. I- BOCK PRO DU CTS is published monthly by M A C LEA N -H U N TER Publishing Corporation, XW West Jackson Blvd., Chicago 6 , tHinws worate Hunter, President; John R Thompson. Vice Pres * dent; J . L F razie r, Secretary. Copyright, Entered as second-class matter, Jan. 3 ,* r v l - , the Chicago, HI. post office under the act 0 3 , 1679. Additional entry at Milwaukee, w is. SU BSCRIPTIO N INFORMATION Subscription P rice : United States Canada, one year, $2 0 0 ; two years, years, $4 .0 0 . Pan American, one year, $ 4 .U v, years, $ 7 .0 0 ; three years, $ 1 0.00. A ll rtM r OT eign, one year, $6 0 0 ; two years, 512.UU years, $1 5 .0 0 . Twenty-five cents for single COpio. Indexed in the Industrial A rts Index. * Canadian subscriptions and remittances may B g in Canadian funds to ROCK PRODUCTS, Box 100, Terminal "A " Toronto, Canada. To Subscribers-- Date on wrapper indlWtfcS with which your subscription expires...M to have address changed, give old as well address. : ;; ; ? v -* ; ; 1 j i ; - > t 5 D u s t C o liectio n - Recovering A S B E S T O S Floats with Dust Collectors DUST clouds asbestos created in have long the m defied illing of efficient and economical collection and it is only recently th a t this problem has been successfully solved. Because of the v ast q u an tities of asbestos lost in the form of dust and because of the high m arket value of these "floats" at the present tim e, it m ay be well to consider some of the facto rs involved in the collection of asbestos. The physical properties of asbestos, while not unique individually, present a combination of problems which are a tax un the ingenuity of the d u st col lector engineei. A few of these prop erties a re : 1. F ib ro u s n a tu re . T h e c h a ra c te ris tic of a libre is th a t it has a tendency to interlace and form a m at which m akes pneum atic handling difficult. 2. F ria b ility . A sb esto s h a s th e a b il ity of bieaking down successively into sm aller and sm aller fibres, thus u lti m ately creating a dust of such m inute particle size th a t it becomes suspect of being hazardous. This moans th at a successful collector m ust have an extrem ely high degree of efficiency fo r p a rtic le s of a size sm a lle r th a n 10 m icrons. 3. E ffect of M oistu re. A s th e p a r ticle size decreases it becomes in creas ingly affected by m oisture which, when p resen t in excessive am ounts, causes 'M arket Research Engineer, Am erican Whet)abrator & E q uipm ent Corp. By L. J. WIESCHHAUS the dust to " cake" in a solid, im perm e able la y e r on any filter medium. 4. Low a p p a r e n t specific g ra v ity . A lthough its real specific g ra v ity is 2.54 to 2.59, finely divided asb esto s h as an a p p a re n t specific g rav ity of only about 1/4 or 1/5 of th a t figure. The fibrous, fluffy n a tu re of the m aterial is a serious han d icap in any settlin g operations. These are the principal physical characteristics which are im p o rtan t for considering the problem of dust recovery in this in d u stry . Types of Collectors In the m illing of asbestos the p rin cipal sources of dust are in the crush ing, sizing and grading operations. All of these are controlled by p relim inary cyclone type collectors and the success w ith w hich the dust is re moved from the source depends p ri m arily upon the design of the hood arran g em en t. U n fo rtu n a te ly , th e low velocity cyclone type collectors gener ally used are often inefficient w ith respect to settlin g out th e finer sized particles, and it is in the collection of dust from the discharge of these cy clones th a t the real problem of dust control arises in the asbestos industry. One secondary form of collector which h as been used in practically all F9 - 1: P o rtlo l view of the c o lle c to r in s ta lle d a t the John so n's C o m ill in T h e tto rd M in e s, QuebecFour of th e six collectors are visible- Inspection window m ay be seen to the right 104 ROCK P R O D U C T S . A u a u s i 10d.7 a sb e sto s m ills is th e d u st shed TV , dust shed serves two main purposed (1) it serves as a settling cham ber^ th a t la r g e p o rtio n of the eJBlle^ from the cyclones can settle out b g rav ity before it is discharged into th open a ir and (2) by removing the discharge poin t to a remote point from th e mill proper, it seeks to as su re th a t m ost of th e d u st will be car ried aw ay by the wind rath er than being retu rn ed to the working area One obvious d is a d v a n ta g e of this m ethod is t h a t it p e rm its v a st quanti tie s of d u s t of low p a rtic le size to float over the surrounding area. A n o th er m ethod of dust prevention w hich h a s been trie d is "wet" proc essing. T his m ethod does serve to elim inate a g reat deal of the dust nor m ally a tte n d a n t on asbestos prepara tion, how ever, it resulted in almost in s u rm o u n ta b le p io d u ctio n difficulties. The tim e required and the handling problem s encountered in drying the m aterial a t the proper tem perature m ade th e process im p ractical. Also, a certain am ount of handling was re q u ired a f t e r th e m a te ria l had been dried and it w as still necessary to provide some so rt of d u st collection m ethods fo r the dust created in this operation. A n o th er type of collector which has been used in th is in d u s try and which h a s m e t w ith considerable success is th e e l e c t r o s t a t i c type of collector. E lectro static collectors, however, have tw o serious d raw b ack s: F irst, the cost of th e orig in al in stallatio n Varies with th e degree of efficiency desired, and the relationship between cost and ef ficiency is th a t of an acutely rising curve, ra th e r th a n a stra ig h t line. Second, fo r m axim um efficiency, an electro static collector m ust be designed fo r operation at a fa irly definite dust co n cen tratio n and its efficiency drops off w hen it is used at any other con cen tratio n . In a d ap tin g a collector of th is type to the asbestos industries it m ust be designed for median opera tion and hence cannot be expected to o p e ra te a t its m axim um efficiency at all tim es. The reason for this is the g re a t v a ria tio n in dust load which re s u lts fro m v a ria tio n s in rock, rock te m p e ra tu re , mill tem perature, mois tu re conditions, etc. Even u n d er the m ost ideal condi tions, and especially so under the op e ra tin g conditions which prevail in the asbestos industry, there is a cer tain am ount of effluent from electro s ta tic collectors. E v en though the col le c to r m ay be 98 or 99 p e r cent overall efficient, th e effluent is visible, which alien! tures eficou io f prop* K~ed f* 'floats Fri Seal c f t scribi \ consi' i in de : die tl Be- : parti of si f- offer : to th with tant do ai ! Be : with it is and so th "Site The medi the This reve cycls dot! Ci asbe eaki B; ful , low best in p will it ij elea thui that in < bag the Fill A of ; tos Co., wbi in moi 1 was a si a a sockdogical d isad v an ta g e . and it j5 of v ery ?ma!l p a ititle 'ize. T his trpe of collector doe? have tw o dis tinct a d v a n ta g e ' over most other col lectors in th a t it has very low power requirem ents and very low hack p res sure. A nother type of collector which h a ' peen trie d in th e asb esto s in d u stry . and which has met with considerable success, is th e filter type. F ilte r type collectors, when rising ordinary cloths, me at a d isadvantage in certain oper ations w here extrem ely high tem pera tures or high m oisture contents are encountered or in collecting m a te ria l of a viscous n a tu re , however, when properly applied, they are ideally su it ed fo r a m a te ria l such a s asbestos floats. From a consideration of the phys ical c h a ra c te ristic s o f asbestos, as de scribed above, it will be seen th a t considerable care m ust be exercised in designing an y type of filter to h a n dle this m a te ria l. Because of the fibrous nature of the particles, the filter m aterial m ust be of such a m a te ria l and weave as to offer the least possible encouragem ent to the fibre to in te rla c e and interlock with th e fa b ric . T his is very im p o r tant if th e sh a k in g m echanism is to do an efficient job of cleaning th e bags. Because of the friability of asbestos with its r e s u lta n t sm all p a rtic le size, it is im p o rta n t th a t th e clean in g cycle and cleaning m echanism be designed so th at th ey leave a c e rta in am ount of "filter cak e" in the bags at all times. The "filter c ak e" is the a ctu a l filterin g medium and is ab solutely n ecessary if the fine p a rtic le s a re to be stopped. This, in cid en tally , p ro h ib its th e use of reverse a ir flow d u rin g the cleaning cycle since th is p ractice g e t ' th e filter cloth too clean. Care m ust be exercised to keep the asbestos reasonably d ry to prevent caking in th e collector. Bag proportions m ust be given care ful consideration because of the v ery low apparent specific g ra v ity of a s bestos. I f the b ag le n g th is too g re a t ln proportion to th e d iam ete r, th e bag ^11 form a tr a p p in g s tru c tu r e w hen d Is shaken, g re a tly h a m p e rin g th e cleaning operation. A useful rule of thumb developed d u rin g th e y e a rs that m etallurgic bag houses have been in operation is t h a t th e len g th of a bag shall n o t be g re a te r th a n 30 tim es the diam eter. filter Type Operates Successfully An exam ple of th e successful use a filter type collector in the asbes9 industry is presented by Johnson's ; Ltd., T h e tfo rd M ines. Quebec. ^ ieh has had such an in sta lla tio n operation now fo r m ore than six months. iy" firs t step in th is in sta lla tio n a , S , P urchase by Jo h n s o n 's Co. of utal! 5000 c.f.m . collector to be used (C o n tin u e d on f-iipe Fig. 2 E le c tn c o l con tro l p a n el. Ind ivid u a l m anom eters are supplied for eoch collector unit to p ro vide check on com pleteness with w hich collectors ore shut o ff during sh aking operation. To the e xtrem e rig h t is e le c tric a l tim er controlling sh a kin g cycle Fig . 3 : In le t d u ct w hich corries dust lad en oir into collector hoppers Fig. 4 : Underside of cell plate. Note that none of the tubes ore bridged over in spite of the "dinging" nature of the osbestos fibers r\ :.i Q -, m ?! I P 1I , * If? -lM! F o r d e ta ile d in f o r m a tio n on C le v e la n d S c re e n S e c tio n A s s e m b lie s v. r ite to d a y f o r B U L L E T I N N o . S. THE CLEVELAND WIRE CLOTH & MFC. CO. 3574 E. 7* STREET ; CLEVELAND 5,OHIO SAUERMAN MACHINES dig, haul and dump for few cents a yard! Where materials are to be moved distances ol several hundred ieet or more, a SAUERMAN Drag Scrapr or Cableway can cut the cost per cubic yard to a low figure because the complete movement of material to a plant or to and from a stockpile is handled by a single machine. A rapid, steady flow of material is assured with minimum use of labor and moderate expenditure of power. SAUERMAN p o w e r s c r a p e r Storing ond reclaim ing crushed silic a at d ryin g planT. G e t the Sau erm a n C a ta lo g a n d see fo r yo u rs e lf ho*- others h a v e cut costs on a ll kin d s o f d ig -and - haul v-'ork The first cost of a SAUERMAN Machine is reasonable, maintenance amounts to very little, and the sim plicity of operation makes it possible to place the control of even the larg est installation in the hands of one operator. Moreover, the machine is very flexible and is easily adapted to changes in ground conditions. fir m . A l IF d H A W n o n e iw r Asbestos Dust I C on tinu ed from p ig e j j a s an e x p e rim e n ta l u n it. This ,,,,n to r w as tapped into the dust svrt'*' and subjected to a series te s ts by th e com pany's engineer* tT purpose of the teste w as to d e t e n ^ f 1-- the optim um air-cloth rati- 2 " the cleanliness 0f the discharge a ir. 3-- the back p ressu res resulting f roJ various operating procedures; and 4TM the effectiveness of the shaking meek an ism . T he f o u r th p o in t w as the one about which the g reatest doubt exist- ' ed and it received the most rigid tests. On several occasions asbestos floats w ere a c tu a lly shoveled into the col lector u n til th e bags were stuffed and the collector then sh u t off and shaken The back pressure returned to normai alm ost im m ediately. T hese tests showed th a t the filter w ould h a n d le a n a ir flow of 4y%c.f.m. per square foot of cloth and, w ith an o p e ra tin g an d clea n in g cycle of 40 m in u tes, the back p ressu re varied be tw een y2 an d 1 ]-> in. of w ater. The discharged a ir w as well w ithin the s ta n d a rd h e a lth req u irem ents of less th a n 10 m illion particles sm aller than 10 m icrons in one cubic foot of air. On th e b a sis o f th ese teste a 460,000 c.f.m . u n it w as purchased and in stalled to handle the complete dust load from th is mill. The entire installation was made w ith p ractically no interruption in the r e g u la r o p e ra tio n of th e mill. I t is estim ated th a t a p p r o x i m a t e ly two hours of o p eratin g tim e were lost w hen th e dust collector was being sw itched into the system. F ig s. 1 th ro u g h 4 show the con stru ctio n and o p erating featu res of th e collector a s it is in stalled. T his Is a bag type collector w ith bags of sa te e n w eave co tto n fab ric, 8 in. in d iam eter and 17 ft. 6 in. long. Spring steel bands hold the bottom of the b ags in alum inum cell plates whfle the tops of the bags are suspended from the shaking mechanism. The sh a k in g m ech a n ism consists of a djoto r driven eccentric which transm its a horizontal shaking action to the b a g s. T h e re s u ltin g b ag motion is sim ilar to th a t obtained when a small ru g is shaken by hand. The spring steel clam ping arrangem ent a t the cell plate p erm its easy bag replace m ent. One m an can remove and re place a hag of th is type in less than one m inute. There are six collecting units ar ran g ed in such a w ay th a t five are alw ays in operation while the sixth is b ein g cleaned. The cleaning cycle is controlled autom atically by an elec tric tim ing- m echanism shown in Fig. 2, and it o p erates on a p r e d e t e r m i n e d tim e cycle. A t the proper time the electrical control m echanism causes an elec tro-pneum atic valve to close the dust i"5 d ro p p ed dow n in to the h opper t,e]ow. F ' ora th ere it is c a rrie d by mean? of a screw conveyor to one end of the ho p p er w h e re 'it drops throug-h n chute to a conveyor box in the floor j,e]ow. A d ra g chain in th is conveyor duct c arries th e floats from all six collectors to a cen tral point of dis charge w here it is graded and bagged for shipment. Only once h as any difficulty been encountered in the m aintenance of proper back pressure. This occurred when an exceptionally w et batch of rock was being processed and the moisture content of the dust was su f ficient to cause an alm ost im perm eable cake to build u p in the b ag s. T his was corrected by the sim ple expedient of shutting off th e w et rock and circu lating dry dust through th e collector until the p ressu re re tu rn e d to norm al. This is an " all p re s s u re '' system with the necessary p ressu re being supplied th ro u g h th e cyclone se p a ra tors used in th e g ra d in g process. No supplementary fans w e re r e q u i r e d when the dust collector w as added to the system . T he ad d itio n al pow er r e quired to overcom e th e re s ista n c e of the system w as provided by u sin g an Improved type of fa n w heel w hich Increased the fa n p erfo rm an ce and jfflciency to such a d eg ree th a t n o t a iingle h o rsep o w er w as added to th e ntal fan load. No serious trouble has been eneounered since the installation w ent into tperation alth o u g h it is c u rre n tly beng operated a t a 10 p e r cent overoad. A p p ro x im a te ly 22 to n s p er day if m a rk etab le asb esto s is b ein g col ectad. T h is m a te ria l is all re g rad ed tnd bagged acc o rd in g to its m a rk e t lassifieation. dement Production Bureau of M in es re p o rts t h a t prouction of finished P o rtlan d cem ent uring A pril, 1947, to taled 14,566,000 >bl. or 15 p e r c e n t g r e a te r th a n th a t eported fo r A pril, 1946. Mill shiprents reached 15,414,000 bbl., a figure ssentially the sam e as th a t reported or A pril o f th e p rev io u s y e a r. Stocks f finished P o rtlan d cem ent on A pril 0, 1947, w ere 21,330,000 bbl., a n in case of 34 p er cent over th a t reorted fo r A p ril. 1946. Dem and for :ment w as h ig h er in 10 d istricts and w er in nine, th a n th a t in A pril of t year. T h e lo n g -te rm tr e n d in proaction of finished P o rtlan d cem ent retinues up w ard , in creasin g d uring re first fo u r m o n th s o f 1947 a t an ferage ra te o f 2,989,000 bbl. per with. The follow ing statem en t gives the iation of p ro d u ctio n to c a p a c ity , and compared w ith the estim ated ca v ity a t th e close of A pril, 1947 and Prll, 1946. ratio (p e r c e n t i o f pr o d u c t i o n TO CAPACITY Apr. Apr. Mar. Feb. Jan. e month month. 1947 1946 1947 1947 1947 74.0 64.0 69.0 68.0 66.0 73.0 50.0 72.0 71 0 70.0 "POWER KING" TRANSMISSION BELTING . . . m ade o f pre-w ar q u a lity n a tu ra l ru b b e r to give it th e extra strength, grip and long life that guarantees steady pow er to your prim ary or interm ediate crushers. Friction surface, raw edge construction, espe cially d esign ed fo r m in im u m stretch and firm contact w ith p u lley s at high speeds. P lies of specially built duck provide exceptional longi tudinal strength. H igh quality friction betw een p lies contains rich sk im s o f rubber to assu re m axim um flexib ility and to elim in a te all risk o f " bootlegging" . Edges treated to keep out m oisture. Available from stock in all widths to 48", in 33- and 35-ounce duck. Can be m ade endless if desired. C ontact O ur N earest B ranch fo r Prices GOODALL RUBBER CO., INC. THE GOODALL-WHITEHEAD COMPANIES Philadelphia Trenton New York Boston Pittsburgh Chicago St. Paul Los Angeles San Francisco Seattle * Salt Lake City Houston Factory: Trenton, N. i. Fst. 1870 LONGER PROD FARREL-BA< CRUSHERS Permanent strength and operating effi ciency is engineered into these crushers at every vital point. Farrel-Bacon will provide industrial units or completely designed and equipped plants, including screens, eleva tors and conveyors. Also other types of mine, quarry, sand and gravel plant ma chinery. Write for complete information. $a ; okJ E | ROCK PRODUCTS, August, 1947 17?