T H E J O U R N A L OF I N D C S T R I A L ALVD E N G I N E E R I N G C H E M I S T R Y less t h a n t h a t needed for a n y mechanical furnace of similar capacity. The power required for t h e above size kiln amounts t o a b o u t 2 0 H. P. 4-Its continuous action promotes fuel economy and large o u t p u t s per unit. N o time or fuel is lost in heating up i n d cooling down t h e kiln as with intermittent furnaces a n d t h e steady flame of t h e jet of burning powdered coal gives a much more uniform temperature t h a n is possible with furnaces which are fired by hand a n d hence into which cold air is continuously entering when t h e fire is stoked. The fuel saving of t h e rotary kiln over a reverberatory furnace amounts t o from go-jo per cent. j-Wet materials may be furnaced as well a s d r y , t h e upper p a r t of t h e kiln acting as a drier, a n d both fine material a n d lumps may be burned a t t h e same time. 6-The charge is a t all times under control a n d is advanced regularly through t h e kiln a t t h e desired rate. This r a t e may be changed a t will by quickening or retarding t h e speed a t which t h e kiln revolves. 7-High temperatures may be obtained a n d a n y fuel desired employed. Both oxidizing and reducing flames m a y be secured.
As t o processes t o which t h e rotary kiln is most applicable, these would seem t o us t o b e : I-Processes in which carbon dioxide, combined water or other volatile constituents are t o be driven off b y heat a n d a t temperatures below 2 7 0 0 ' F. 2-The oxidation of ores, chemicals, etc., whether this is accompanied b y burning of sulfur or other combustible elements or not. 3-The reduction of compounds where this can be accomplished by heat in a reducing atmosphere either with or without t h e use of a reducing agent. The kiln is particularly suited t o reducing processes where these consist in mixing a reducing agent with t h e compound t o be reduced a n d t h e mixture finely ground a n d furnaced. 4-Processes which consist in t h e formation of new compounds b y partially fusing or sintering a mixture of two or more materials. j-Processes which are designed t o merely change t h e physical s t a t e of a substance by just heating t h e material (either alone when fusible or with some fusible binder when not itself fusible) t o t h e point when t h e particles cohere t o form nodules or clinker of t h e desired size. Two or more of t h e above processes are often carried o u t in t h e same furnace, as for example in t h e manufacture of Portland cement, where t h e carbon dioxide is first driven off a n d then t h e silicates and aluminates of lime are formed. T h e rotary kiln is not suited t o reactions which are a t t e n d e d with marked fusion of t h e material, t h a t is, when t h e mass must become fluid before or in order for t h e reaction t o t a k e place. When t h e fusion takes place above t h e temperature a t which t h e reaction is completed, t h e rotary kiln may be employed with
Vol. 6, NO. 9
proper care t o control t h e temperature. Where only sintering takes place t h e kiln, of course, gives entire satisfaction a n d many reactions which ordinarily require fusion of t h e mass t o take place may be carried out completely without having t h e mass either molten or even pasty, by simply grinding t h e components finely a n d heating only t o t h e point of incipient fusion or sintering. Here t h e greater surface exposed allows t h e reaction t o t a k e place by diffusion. Examples of this are found in t h e process of making available phosphoric acid referred t o above a n d also in t h e burning of cement clinker. 202
hTORTH C A L V E R T
ST.
BALTIMORE
A COMBINATION WATER SOFTENER AND STORAGE TANK' B y I,. M BOOTH
Any water purification process implies t h a t t h e purified water is t o be used. How best t o store this water between t h e time it is purified a n d used is a matter for consideration. I n some industrial plants, t h e rate of use of water is fairly constant throughout t h e d a y , t h e water is used a s fast as it is softened a n d no storage is necessary. hIost water users, however, have one or more considerable peaks in their load requiring t h e delivery of large volumes of purified water during a short space of time. The usual plan h a s been t o provide a separate t a n k or reservoir. During t h e past t e n years a great many softeners equipped with excelsior filters, affording storage capacity for one hour's flow (more or less)-sufficient for ordinary requirements of a n industrial or power plant-have been built. Usually, this storage capacity is provided by increasing t h e height of t h e t a n k s a few feet above the filter t o gain t h e desired volume. A softener arranged t o include storage capacity above t h e filter is shown in Fig. I . This provision for storage capacity, while adequate t o serve t h e needs of most power plants, necessitates t h e use of raw water for. perhaps, half a day, twice each year, in order t o provide opportunity t o change t h e filtering material. T o use raw water, pumped directly t o the feed water heater for boiler feed, for such a brief interval, is not especially objectionable. For railway water stations, however, such a plan has very little t o commend i t , because during t h e periods of filter cleaning, there would be no water available, stored a t sufficient height, t o fill a locomotive tender in t h e usual short period. The best water softening practice in vogue a t t h e time t h e first modern water softeners were imported from Europe, late in t h e nineteenth century, called for t h e use of filters t o clarify the imperfectly settled water. Usually, these filters were constructed of excelsior '' (wood shavings), Careful observations of softeners operated a t a small fraction of t h e rated capacity-corresponding t o more liberal designreadily demonstrated t h a t if t h e rate of upflow in t h e settling space were restricted t o a very slow flow, 1 Presented at the 6 t h Semi-annual Meeting of the American Institute of Chemical Engineers, Troy, N Y , June li-20. 1914
T H E J O L 7 R N d L O F I X D C S T R I A L ,4 N D E N G I I V E E R I S G C H E M I S T R Y
Sept.. 1914
practically n o suspended matter reached t h e filter. By gradually adopting more liberal standards of settling
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feature of water softener construction, i t becomes a simple problem t o add any reasonable amount of pure water storage. As a result of several years practical experience a n d study, having in mind the possible elimination of
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I Ai m
8. -.. -. .' F I G . III-\%'IATER
SOFTENER-cAP.4CITY 5,000 GALLOSSP E R HR National Malleable Castings C o . , Toledo, Ohio
the filter. the softener a t the foundry of the National ~ I a l l e a b l eCastings Company. Toledo, Ohio, as shown in Figs. I1 and 111. was designed and installed t o soften SOFTESER-CAPACITY .zn,noo GALLOXS P E R HR D a y t o n Power a n d Light Co.. D a y t o n , Ohio
FIG.I-\VATER
tank design. the point is soon reached when the expense of installing and maintaining a filter for purifying boiler feed water is not justified.
FIG.IV--TVATER SOFTESER-CIPACITYSo.nn0 GALLOSSP E R HR Chicago. Rock Island and Pacific Raiiway. Burr Oak, Ill.
FIG. ~ I - ~ ' A T E SRO F T E S Z R - C A P A C I T Y 5,000 GALLONS P E R HR. National 3 I d l e a b l e Castings Co., Toledo, Ohio
After demonstrating t h a t the filter is not a n essential
and clarify hard and sewage laden muddy hIauniee River water for boiler feed. Nore rapid progress toward the development of the '' So-Filter " softener for purifying boiler feed water would have been possible except for the popular preju-
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dice favoring t h e use of a filter of some kind. The average individual cannot conceire how it would be possible t o simplify a n d improve a softener b y omitting t h e filter. Several of these " No-Filter" installations having been made, a n d having demonstrated their fitness t o meet t h e requirements, the construction of a '' No-Filter" softener equipped t o store purified water, has become a commercial proposition. -4 typical installation of this kind is shown in Fig. IV. Somewhat more t h a n t h e upper half of this t a n k , which is 4 0 feet high, is devoted t o the storage of softened water. Fig. V shows t h e general arrangement of this softener.
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t h a n t h e rated capacity of j0,oOo gallons per hour, the time of flow is proportionately longer. T h e action of t h e softening t a n k mechanical agitators in preparing t h e precipitate for sedimentation is described below and is shown in Figs. V I 1 a n d V I I I . F r o m t h e softening t a n k t h e water flows upward through t h e settling space a t a r a t e of 3.61 feet per hour, which is sufficiently slow t o effect clarification of t h i s particular water. The time of flow from t h e b o t t o m of t h e softening t a n k t o t h e outlet corresbonds t o 4.4 hours when t h e softener is operated a t rated capacity. There is available for immediate use 308,000 gallons of softened water above t h e outlet. This volume is
FIG. V-WATER CAPACITY
SOFTENER
50,000 GALLONSP E R HR
Chicago. Rock Island and Pacific Railway, Burr Oak, Ill.
I
The water enters at t h e inlet a n d passes t o a n overshot waterwheel which furnishes t h e power t o drive t h e agitator in t h e softening t a n k , as well as t h e agitator in t h e chemical t a n k a t ground level. This same power also operates t h e chemical feed pumps. One of these pumps delivers t h e chemical solution t o t h e chemical r e g d a t o r located on t h e chemical t a n k , a n d t h e other elevates t h e solution which has been measured b y t h e chemical regulator, t o t h e t o p of t h e softening t a n k , where i t meets t h e raw water which has passed over t h e waterwheel. T h e downflowing water a n d chemicals are thoroughly mixed in this softening t a n k , during a period of twentyeight t o forty-eight minutes, depending on t h e amount of water in t h e storage space. When operated a t less
sufficient t o meet t h e demands of a large locomotive terminal a n d freight yard. Fig. VI shows in detail t h e manner of handling t h e chemical solution. T h e reagents used are hydrated lime a n d soda ash. The low lift p u m p takes its suction through a strainer screen near t h e bottom of the chemical solution. t a n k . T h e solution is delivered t o t h e inlet compartment of t h e chemical regulator, mounted on t h e chemical tank. T h e level of t h e solution in this compartment is maintained a t constant height, for t h e reason t h a t sufficient solution is delivered into i t t o keep t h e solution continually overflowing t h e inner weir. The excess solution returns t o t h e chemical t a n k . A uniform flow of solution, sufficient t o treat j0,oOo
Sept.. 1 9 1 4
T H E J O C R , V A L O F I S D L - S T R I A L A N D ESGIA\-EERISG C H E M I S T R Y
gallons of water per hour, from t h e inlet compartment flows through t h e s t a n d a r d orifices, which are always under a constant head. T h e n t h e softener is r u n a t full capacity, all of this solution is required; b u t if, for instance. i t is '3perating a t one-half capacity, as shown in t h e detail view of t h e chemical regulator, only one-half of t h e maximum flow of solution passes down t h e feed chute t o t h e high lift p u m p , b y means of which i t is delivered t o t h e softening tiink. T h e other fifty per cent, vvhich passes t h e cut-off plate on t h e other side, returns directly t o t h e chemical t a n k . Similarly t h e feed is directly proportional t o t h e a m o u n t of water entering t h e softener for all other rates of flow. T h e chemical regulator cut-off plate is actuated
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t h e chemical regulator a n d t h u s control t h e proportional feeding of t h e chemical solution. Aside from a liberal design of settling t a n k s , there is one other important feature of this t y p e of softener which materially assists t h e settling t a n k t o deliver a clear water. This is t h e provision for mechanical agitation in t h e softening t a n k . T h e agitation is continued sufficiently long not only t o thoroughly distribute a n d mix t h e chemicals with t h e water b u t also t o insure coagulation of t h e precipitate, so t h a t it will settle promptly as soon as t h e quiet condition of t h e settling t a n k is met. Fig. VI1 is a n example of t h e influence of mechanical agitation as compared with another softening experi-
U
FIG.VI-XX'ATER
SOFTENER-CAPACITY 50 000 GALLONS PER H R . Chicago, Rock Island and Pacific Railmay, B u r r Oak, I11
.and controlled by a float riding in a t a n k supplied with water which has passed over t h e waterwheel. T h e varying heights of water i n t h e lower p a r t of t h e wheel box are transmitted t o t h e float t a n k through a n equalizing pipe. T h e outlet f o r t h e h a r d water f r o m t h e \Theel box, i n t o t h e softening t a n k is through a Sutro weir, t h e general shape of which is shown in t h e detailed view. T h e extreme width of this weir opening is z j inches. I n wew of t h e fact t h a t t h e heigAt of t h e water flowing through t h e Sutro men is at all times directly proportional t o t h e q u a n t i t y , i t mill be seen t h a t t h e vertical movements of t h e regulating float are always proportional t o t h e q u a n t i t y of water flowing. T h e vertical movement5 of this float are transmitted b y means of a lever, Iinks, a n d bell crank t o t h e cut-off plate of
ment similar in all respects, with t h e exception t h a t only a slight mixing wa9 given in 1-11-b,t h e " u n stirred," whereas, T'II-a h a d been subjected t o t h e kind of agitation which experience has shown t o be t h e most sufficient for precipitates of this kind. T h e photograph (Fig. V11) was t a k e n a t t h e end of three minutes folloming t h e addition of chemicals a t t h e r a t e of I 9 lbs of lime a n d 1.2 lbs. of soda ash per thousand gallons. T h e raw water in this case h a d a hardness of 2 8 j , a n d a n alkalinity of 2 3 j parts per million, corresponding in grains per C . S. gallon t o 16.6 a n d 13.7, respectlr-ely. I n t h e experiment w t h Sample b there was only
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T H E J O l ~ K . V . 4I, O F I N I l U S T R I . 4 L A N D E N G I N E E R I N G C H E M I S T R Y
a slight mixing of t h e water caused h y eight revolutions of the agitator whereas Sample a was stirred €or three minutes, at the end of which time the precipitate
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is stored at a considernhle elevation suitable for delivery, without pumping, l o feed water heater or iocomotive tender. 136 LiQriaTY STREBI: NEW YORK
A NEW SEAL FOR THE PREVENTION OF AERATION IN DEAERATED LIQUIDS By F a i a r N A C X ~ M A N I I I Krfeived August 3 . 1Y14
O-SfiiirCd. h---Trnstiirrd Fco. V11- -WATT.R SUFICUING C x ~ ~ i i i a s ~ ~ s -1 -3. ~n or nr 3 MINSITZS
had become fairly well coagulated. The slight blur in Sample shows t h a t while the st,irring had ceased. the precipitate had not yct come t o rest. Fig. VI11 shows t h e same samplcs. neither of which has been touched since t h e first photograph was taken. The second pholograph shows t h e difference a t t h e end oi six minutes, by which time the prccipit a t e in Sampic a had almost completely settled, wliereas Sample b , as may be noted, shows its precipitate t o he very much behind in derelopment. These simple experiments demonstrate clearly t h e advantage gained b y the proper kind of mechanical agitation while the precipilate is in process of formation.
There have heen several devices recommended for preventing t h e absorption of atmospheric oxygen in t h e methylene blue test for putrescibility. Among t h e devices recommended arc: Jackson’s bulb pipetteZ and Buswell’s capillary C - t u h ~ . ~ T h e Bunsen valve shown in t h e figure has given very satisfactory results at t h e Sewage Testing Station of the Sanitary District of Chicago. T h e valve consists of: a rubber stopper “ a , ” through which it glass I I tube, “ h , ” passes; rubber I t t u h e “ c ” is attached t o t h e upper end of t h e glass tuhe and closed with a glass rod, “d.” Ordinarily, a slit is iised in t h e rubher tubing, b u t in t h i s case a few pinholes were punched in t h e tubing a s shown at “ c . ” T h e pinholes open and allow the gases t o escape b u t close b y pressure from without and thereby prevent the incress oi air. T h e b o t t l e is tilled with t h e liquid undcr examination and the rubber stopper with valve iorced in place. The liquid rises i n t h e glass and riihlicr tubing, thereby displacing practically nil of t h e air in t h e tube. T o show t h a t thc Hiinsen valre prcvents reacration, water-sewage mixtures wcre prepitred and placed in bottles with incthylcne blue, iising cork, glass a n d Bunsen valve seal as stoppers and then incubated a t s i o C. T h e temperatures of thc mistures beiore placing them in t h e incubator werc about xgO C. I n the case of t h e cork and glass, the stoppers loosened t o allow some Iiquid t o escape, due t o the expansion of t h e liquid. T h e Bunsen valve cared for this expansion very satisfactorily. After t h e liquids decolorized, t h e bottles were taken out, of the incubator a n d gradually cooled. Reabsorption took place rapidly in t h e bottles stoppered with glass a n d cork, as shown b y t h e reappearance of t h e methylene blue, whereas practically n o blue appeared in t h e Bunsen valved bottle. The rubher tube on the Bunsen valve collapsed, t h u s preventing t h e absorption of air b y t h e liquid. I n a series of tests with methylenc blue and a putres-
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As already stated, t h e use of niechanicnl agitation plays nn important r6le in t h e “ No-Filter” soitener, which makes feasible t h e storage of a largc volume of softencd water in t h e samc unit with t h e softener. Some of the advantages a i this softcncr are: I-All handling a n d regulation of chemicals is accompiished a t ground lcvcl. z-Mechanical agitation for the softening tank is provided. 3--Thcre is sufficiently slow upward Aow in t h e settling space to deliver a clear effluent. 4-- Convenient arrangement of storage capacity. T h e combination of the softcning a n d storage features results in a saving of ground space as well as in cost of t h e plant. No separate foundation is nccessary. I t is a n important advantage t h a t t h e water
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Assistant Chemist, Thc Sanitary District ot Chicago. Jackson and fiorfon. THISl o u a a n i . 1 (1YOY). 3 2 8 . Nuiwcll, I b i d . . 6 (1914). 325.
