Drying Bagnoli 1956

7/27/2019 Drying Bagnoli 1956

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DRYINGE. BAGNOLI

Engineering Research laboratory, Engineering Department,E. 1. du Pont de Nemours & Co., Inc. , Wilrnington, Del.

HIS review covers items that are bclieved t o he of interestto workers dealing with drying problems of a practical and atheoretical nature. It is arranged in thrcc sections: Drying

Fundamentals, Drying Methods, and Drying of Specific Ma-terials.

Much of the litera ture reviewed was descriptive , stressingmodifications or adaptations to existing drying techniques.A few articles presented information of a fundamental nature.However, as in the past, there is still a need for good funda-mental work in drying and for good operating data on plantscale dryers for comparison with t he results of small scale ex-periments to improve scale-up methods.

T

DRYING FUNDAMENTALSThe mechanism of freeze drying an d vacuum drying of wet

clay by evaporation in the absence of air was investigated byStrickland-Constable and Bruce ( @A ) , who found that thedrying rate of frozen clay depends primarily on the ra te of cscapeof vapor and t hat at constant heat input the drying rate of wetclay is constant above 21% nioisturr and then falls steeply to 6%moisture, which moisture is probably in the adsorbed conditionThese same authors (44A) also studied th e sublimation of pureice at t empr ratu res around -5O"C, a t prcsaures whcre the meanfree path is small compared nith the apparatus dimension.Spalding (41A) presented a method for calculating niass-trans-fer rates and considered, in particul ar, the case of simultaneousheat and mass transfcr as illustrat,ed by the net- and dry-bulbhygrometer. T w o pap rrs on the mechanism of drying prc-srnt ed at a meeting of the Inst itut ion of Chemical Engincersx-ere abstracted in Cheiiizcal Age. In the first of these, King andNenitt (22A)reported, on the basis of experiments in the dryingof beds of moist nonporous materials, the following drying rat epcriods: constant heating up rate, pseudo-constant rate, firstfalling rate, an d second falling rate. In the second paper,Corben and Sewitt (10A) extended their investigation of th emechanism of drying of solids to the drying of porous granularmaterials. Butler and Plewes (6.4) derived a theoretical relationfor the evaporation of a plane of solid material in to air in stream-line flow. Subsequently, Plewes, Butler, and Marshall (30A)found that experimental va,iorization rates for seven solids weregreater tha n predicted by this thcory. Polonskaya (81A, %A)investigated temperature and nioisture distributioiis during theconst ant-ra te drying of gypsum board.

The mechanism of liquid jet breakupvia? studied photographically by Richardson (MA ) , wh o dis-tinguished thrcc regimes of floiv, each resulting in a special typeof breakup-Le., capillary ripples which brenlc up into droplets,sinuous oscillation of the cylinder axis, and breakup due to airfriction. Harmon ( 1 f iA )extended previons theoretical work forpredicting the drop size t o be expected from a slow-bpced jetto the case where the fluid flows in fully developed laminar f l owas it issues from the nozzle. Bitron (2a) dcmonstrated thatthe A-ukiyama-Tanasaux equation for mean drop size in air

Sprays and Droplets.

atomization was applicable to atomization by supersonic airjets. Tho possibility of introducing errors in the mean dropsize by exclusion of many of th e smaller particles, t oo oftenignored in the past, was pointed out. Equations for the largestdrop size during atomization and a distribution function fromstatistical considerations were derived by Troesch (4fiA).

Marshall (27A) reviewed developments in the fields of a tom ita -tion and spray drying. Considered were the principles of je tbre aku p, the performance characteristics of apinning-disk,pneumatic, an d centrifugal or swirl-type atomizers; methods forpresenting drop-size distribution dat a; evaporation from dropsand sprays; and the factors involved in the design and per-formance of spray dryers. Combined with the previous work ofScltzer and Settclmeyer (4OA) , w ho placed their emphasis onspray drying equipment, an excellent compilation of t he in-formation in these fields is now available

Ingebo (18A) measured the vaporization ratcs and dragcocfficients for iso-octane sprays in a turbulent gas streamDra g coefficients were correlated empirically, and the vaporiza-tion rates based on a mean diameter agreed with single-dropletdat a. The ballistics of an evaporating droplet injccted counter-curient t o the air flow direction were developed by Miesse(289, 2.9.4), who later showed that his analysis was consistentwith the evperimental rrsults obtained by Ingebo (18A). Usingsuspensions of controlled, uniform size, Burgoyne and Cohen( 4 4 ) studicd the effcct of drop size on flame propagation andfound that below 10 microns the suspension behaved as a vapor,

hilc above 40 microns the droplets burn individually in theirown air envelope, one burning drop igniting adjacent oncs.

Garner and Grafton (13A) correlated their results for the dis-solution of benzoic acid spheres in water by an equation differingfrom Frossling's equation, principally in the constant term.Expressions for the burning rate of a fuel droplct, the tem-perature of th e flame front, and the radius of thc combustionsurface weie obtained by Goldsmith and Penner (14-4). Evap-oration rates of single droplets rreie measured by Kobayasi(23AEquilibrium Moisture and Moisture Movemen t. Equilibriunimoisture and rat e of approach to equilibrium data for dr y beanswcre determined by TTcston and Morris (49A) and equilibriummoistures for whole grain edible forms of rice were nieasurcd byHouston and Kester ( 1 7 A ) . Davis ( 1 f A ) presented a chartfor conveniently obtaining the water vapor pressure over aqiicoussolutions of hydrogen bromide Levine and Fagerson (25.4)described a simple apparatus for determining the equilibriummoisture of foods.

Moisture movement in soils because of a ther inal gradientm a s investigated throretically and experimcntally hy Rollins,Spangler, and Kirliham (37A). These investigators and Taylorand Cavazza (.&A) repor t a movement of moisture largely asvapor from warm to cool regions with a returning flow of liquid.A hIoisturescope, a portable unit using atoluene distillation mrthod, for determining the moisture contentof mnterisls, iq avaiizblr from Hafco Srientific Instruments and

Moisture Analysis.

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DRYINGDevclopment Co . (8,4). Schwartzman (S 3a ) compared themoisture determination in coffee by toluene distillation withoven drying. A device based on the pressure developed by re-act,ion of water and calcium carbide for the rapid indication ofsurface moisture in powdered, granulated, or fibrous materials isavailable from Hey1 and Patterson ( 7 A ) . Gray and Whelan( 1 68 ) showed that the moisture content of coal could be con-veiiiently determined with an accuracy of about 5% over therange from 15 to 40% by measuring the heat effect due to mix-ing with sulfuric acid. Fetzer and Ili rst (12a) urveyed moisturedetermination methods for gluten and sweetened feeds. 3vacuum drying device for determining water in emulsions, oint-ments, pastes, or in very viscous materials \vas dcscribcd by Pur r(3SA). Jensen, Kelley, and Burtoii (13$) adapted high-fre-quency techniques to the determination of moisture in salts. Theuse of formamide as an extraction solvent with Karl Fischerreagent in determining the moisture content of foods was in-vestigated by McComb and Wright (%A) , \Tho found that theirresults did not always agree with vacuuni-oven values.

Hygrometry. il measuring appa ratu s for the continuous deter-mination of gas moisture based on the fogging of a polished sur-face was described by Ripka (MA) . Moisture-sensitive ele-ments of white pine shavings are comparable with hair-typeelements in accuracy, stability, and response rate according toCase (64). The dependence of electrical resistance of strips ofgelatin, agar, poly (vinyl alcohol), and other similar materials ont,he relative humidity of th e surrounding atmosphere was showngraphically by Kersten ( 2 lA ) ,mho also described the successfulcontrol of the humidity of a chamber by units made from severalof these materials in connection with a suitable electronic circuit.Webb and Neugebauer ( 4 7A ) described a method for the rapid,continuous determination of water vapor in air by measuring itsdielectric constant. .4 rapid-response hygrometer whose act,iondepends on the change produced in electrical resistance of a thinfilm of potassium dihydrogen phosphate or similar salt by achange in humidity was reported by the Kational Bu reau ofStandards (3-4). The development and testing of an electronicinstrument, the Teka Dieleetrometer, for det>erminirigmoisturein oil or natu ral gas \\-ere reported by Weisbcclwr ( 4 8 4 ) . I t isclaimed that the instrument not only measures samples, but willalso measure directly in the pipe or vessel under process condi-t i o ~ ~ ~ .recording hygrometer based on the humidity-dependentstreamer corona discharge from a pointed wire to a plane sur-face in air was constructed by Anderson, Hertz, and Rufelt( 1 A ) . White (5OA) described a hygrometer employing an alu-mina core saturated wit,h a cheniical solution which absorbsatniosphcric moisture and so becomes electrically conductive.il continuous compression hygrometer in which fogging of apolished metal surface is used to indicate humidity was re-ported by Rrady and Rrailsford (3-4).

The equations for the psychrometer were considered bySpnncer-Gregory (43-4) from aspects of the kinetic theory ofgases in order to develop an adequat'e theoretical background.Sato and Yamazaki (38.4) derived an equation for the adiabatic

E. BAGNOLI bas been a member ofthe Engineering Research Laboratory,Engineering Department, E. I. du Pontde Nemours & Co., since 1952, work-ing primarily in the field of drying.He attended the University of Dela-ware, where he obtained the B.Ch.E.in 1949 and M.Ch.E. in 1950. Bagnoliis a member of the American ChemicalSociety and the American Institute ofChemical Engineers.

cooling line which is applicable to any gas-liquid system with-out assuming constant liquid temperature. Kayse (IOA) pre-pared and illustrated the use of a humidity chart showing dry-bulb temperatures t o 1500' F. and dew points to 175" F., nhileLandsbaum, Dodds, and Stutzman (948) calculated humiditiesof compressed air at pressures to 1000 atm. and temperaturesfrom 50" to 200" F. il nomograph showing the variation ill the100% absolute humidity with absolute pressure or altitude w a ~prepared by Rhoden ( S 4 A ) .DRYING METHODS

Rotary Dryers. Rockwell and others (SOB) evaluated a dryerfor apple Flices consisting of a perforated, rotating sheet-metaldrum with the drying air delivered through the bed of ninterialby air ducts located along the dryer. Uniform trea tmen t andrednced mechanical damage to the material are claimed to re-sult from this drying scheme. Pierce (28R) described a typicalDchydrO-mat dryer installation and gave performanee data fora unit used to dry fish meal. Spraul (SIB)evaluated conven-tional equations for estimating the relationship between per-centage holdup and retention in rotar y air dryers for 25 materialsand concluded th at all the equations tested were limited in therange ovcr which they are valid and t ha t i t was not posssible t opredict their useful range. Theoretical equations for the holdupand holding time in a rotary kiln with a ring wcir were derivedby Koutsuma (19B). An item in Chemical E n g i n e e r i n g ( 6 B idescribcd rotary-kiln installations exhibiting high thermalefficiencies. The temperature patt ern and heat exchange for ahypothetical frit ealciner mere analyzed by Helmbold ( I @ ) .Rauer ( S R ) and Borofsky (@) discussed the control of rotarykilns The largest steam tube rotary dryer in the world, 10 feetin diameter and 100 feet long and built by General AmericanTransportation Co., was noted by Alcoa ( I B ) . Since then,another dryer having the same diameter but 10 feet longer w asbuilt by GATX.

Pneuma tic Conveying Dryers. Drying data for a variety ofmaterials in a pneumatic conveying dryer were obtained byKamei and Toei ( I 7 B , 18B),who concluded tha t the initial dryingra te was high, falling off rapidly to a nearly constant valueKeel and others (8@) investigated the performance of an a ir-lift dryer for piedrying of potato granulcs, with final dryingtaking place in a continuous fluidized bed dryer. Th e resiiltsof experiments on pota to granule drying in a pneumatic convey-ing dryer were described by Cooley and others ( IOB) .

Th e operation of a pilot plan t for flash drying of coal wasdescribed by Tanno and Sasaki ( S CB) . Equipment and operat-ing results of a pneumatic conveying dryer for ammonium sulfa tewere described by Ka,gano and Akizawa (ISB). Chenicul Bn-gineering (8B) notes that the Parry dryer used principally forcoal drying in the pa st is now being marketed for other granularmaterials.

Buckham and Moulton ( 5 B ) investigated thegas recirculation and particle expansion in spray drying. Th ryfound th at t he extent of vertical gas mixing bccause of the jeteffect of thc high-velocity inle t air stream and localized volumecontraction due to cooling from the spray indicated relativelyconstant gas temp tmti ire in the drying zone. The spread ofresidence times of the smaller particles was greater th an expected.Ismberg (16R) described a spray drying installation in whichflue gnscs from boilers are used t o supply the heat. Parke r(26B)patented a drying scheme in which t,hc material to be driedis sprayed into a Venturi section to get high velocities prior toeiitrririg an expansion chamber. The Minerals and ChemicalsCorp.'s spray drying method for processing kaolin was describedin Chemacul Enganeering (76')

Vacuum and Laboratory Dryers. Saunders ( S I B ) found thatthe drying ra te of milk crum b in a varuum shelf oven falls from

Spray Dryers.

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UNIT OPERATIONS REVIEW

Superheated steam drying of textiles offers efficiency andimproved product characteristics . . .

th e start and is influenccd mare by the degree of vacuum andmoisture content of the cake than by the shelf temperature.The design and operating technique of a vacuum oven for ana-lytical work in determining solids in cane molasses were describedby Gardiner and Farmiloe (f2R).An American Society fo rTesting Materials bulletin (BR) reports that the PrecisionScientific Co. has redesigned its Thelco vacuum oven for greateraccuracy and durability.

Pawson (27B) described the construction and performanceof an electrically heated drying oven for plant materials . C h e m i -c al T r a d e J o u r n a l (9R) reported that the General Electric Co ,Ltd , has designed an oven for drying powders and chemicalswhich has provision for a great number of charge-carrying traysand a forced circulation system fo r ensuring air flow parallel t othe tray surfaces.

Freeze Drying. Xeumann and hIatx ( 2 5 B ) describe theprinciples of freeze drying and some typical assemblies 1%hich areeJpecially suitable for preserving highly sensitive materials.Physical consideration b y M atz (2ZB)on the freezing of water in-dicated that a sensitive substance should be frozen rapidly if itsstructure is to remain unaltered. Two stagrs of freeze dryingwere also described-i.e., the primary stage in which conipactice is removed and a second stage requiring higher vacuum i nwhich the adsorbed water film is removed. hIatz (22B)describedequipment for carrying out freeze drying and pointed out that B

Internal and external view of worlds largest steam-tube rot ary dryer-10 ft. in diameter, 110 ft . long

COURTESY QENERAL AMERICAN TRANSPORTArlON 00 .

solid material should bc finely divided and thinly distributedduring drying. Tappel ( % E ) described a simple, inexpensivelaboratory apparatus fo r earrying o u t freeze drying. Pre-cautions to observe in using liquid propane for rapid freezing

Vol. 48 , No. 302 I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y


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DRYINGwcre discussed by Stephenson (33B . Mary, Christensen, andB ed (20H) reported that freeze drying facilitated the extractionof chlorophyll from thc leaves of drug plants and t hat more totalchlorophyll was obtained by freeze drying than by oven drying.

Miscellaneous Dryers. Various types of ovens or drying roomafor drying of furni ture finishes, well as the associated controlequipment and conveyers, were discussed by Herdlein ( 1 5B ) .Different types of dryers such as multiple-hand, falling-tray,convector type, continuous-tray, and others were described byWalter ( 3 7B ) . Grose and Duffield ( 1 3B ) considered the opera-tions of drying and evaporating in the food industry and th emethods and equipment involved. O n the basis of running costs,they emphasized again that substantial savings can be effectedby removing, where feasible, a9 much water as possible byevaporators or other suitable means before final drying. Typicaloperations involving the contacting of solids and gases, includ-ing drying, the factors involved, and the commercial equipmentfor carrying out the operations, were reviewed by Vener andRobinson (36B). Frame ( 2 f B )discussed the construction of adryer attached directly to a tunnel kiln. A continuous fluidized-aolids dryerI operating much the same as a distillation column,was patented by Richardson, Jloise, and Turpin (29B).

DRYING SPECIFIC MATERIALSFood and Agricultural Products. Hos kns and Hoskins ( f 3 C )

described the opera ting principles of macaroni and spaghettidryers. Orange juice powder, prepared in a vacu um shelf oven,was found by Strashun and Tal burt (d7C) to he easily reconsti-tuted, a nd they noted tha t operation a t vacuums higher thannormally employed substantially increased the product bulkvolume. Tal bur t, Hendel, and Lcgault (MC) iscussed someof the factors involved in in-package desiccation of foods. Hen-del and Legault ( I l C ) showed that the rate of in-package desic-cation of various foods increased at higher temperatures and thatthe rate was markedly affected by container size and locationof the desiccant.

The results of tests to determine the effect of building, duct,and fan arrangement on the drying of oats and corn with un-heated air was reported by Hukill ( 2 6 C ) . Downs and Compton( 4 C )showed th at drying of crops on the farm with heated ai r waseconomical,

Hall ( 9C) discussed a method for analysis of air flow in graindrying struc tures of nonrectangular cross section. Johnson andDale (19C) presented a method for nieasiiring the energy re -quired to vaporize grain moisture during drying and includeddsta obtained in drying tests on wheat and shelled corn.

Th e mechanism of web contraction during drying wasdiscussed by Itance ( 2 3 2 ) . IvarsJon (28C ) presented quantita-tive da ta on the introduction of stress into laboratory-made papersheets during drying and a method for calculating drying stressesbased on thermodynamic data for the sample under test.

The application of far-infrared heating in the paper industryw as considered by Thomson, Dalheim, and Stannett (dnC),and in a communication in Paper Trade Journal ( 2 2C ) .

The use of infra-air jets-ceramic infrared elements combinedwith high velocity cold air and eshmst -in paper converting wasdescribed by IIult'green ( f 6C ) .

Textiles. London ( 2 l C ) eported on the performance of a high-temperature steam drying installation in finishing different fah-rics. The production of a 50-foot dryer was reported to equalth at of a 150-foot dryer using other heat sources. The prin-ciples of operation and the advantages of th e Vapo-Jet dryerwere discussed by Hunter ( f 7C ) . .Itudy of th e principles andpractical considerations involved in the development of high-efficiency fabric-drying systems covering both hot air andsuperheated steam drying was reported by Egerton (5C, SC).Sta rting with th e general drying curve for textiles, Walter(3fC) discusses hot-air dryers and cylinder drying machirics and

Paper.

offers a simplified theory of drying. General directions enabl ingthe operator of a textile mill to evaluate his drying operationwere presented by Roesler (2&'). A patent for the tension-freedrying of endless filaments was obtained by Torke, Koch, andDiem (JOC).

Gases. The effects of several operating variables in the adia-batic drying of air using a synthet ic bead-type desiccant werestudied by Grayson ( 7C ) . An empirical method for predictingthe effect of variables on the performance of packed-bed de-huniidificrs was presented by Ross and McLaughlin (%CjThe effort involved in obtaining data in order to apply themethod makes it of doubtful usefulness. Sorption drying ofair or other gases was discussed by Waterhouse (8%') as an aidin choosing whether sorption or cooling should be used in aspecific case. Her rman n ( f 8 C ) evaluated granular silica geifor natural gas dehydration. Equipment and techniques forobtaining reliable data on moisture equilibria between soliddesiccants and refrigerants were described by Gully, Tooke, antiBartlett (8C). The various factors involved and techniques forobtaining dry instrument air were considered by Hankison(lac) nd Simpson (26C).

Copeland (K),n a discussion ofhigh-frequency drying of clay plates, concluded tha t the methodhas considerable advantage over more orthodox methods, but atpresent the costs are high. The solution of several probl em byusing space heaters in ceramics drying was described by Coupe(3C). The advantages of drying soap by spraying into a vacuumflash chamber were discussed by Lanteri (IOC). Hughes (14C)describes in detail a rotary-dryer installation for phosphate rockProper operating conditions for preventing nitrogen loss in fer-tilizer drying were determined by Bridger and Burzlaff ( I C )

Miscellaneous Materials.

BibliographyDRYING FUNDAMENTALS(la) Anderson,N.E., ertz, C. 13.. Rufelt, H.. Physiol. Planlarum(2.4) Bitron, M. D., IND. ENQ.CHEM. 7 , 23-8 (1966).(3-1) radu. J. M., Brailsford. H. D.. I S A J . 2. No. , 22-3 (1955).

7, NO. , 753-67 (1954).

(4-1)Burgoyne, J . H., Cohen, L., Proc. Roy. SOC.(London) A225,376-92 11954).(5-1) utler, R.'M., 'Plewea, A. C., Chem. Eng. Progr. Sumposium(6-1)Csse, J. W., Ins truments and Automat ion 27 , No . 7, 1076-7Ser. 50 , No.10, 121-7 (1954).(1954).(7.4) Chem. Processin0 17 . N o 7, 100 (1954).(82%)(9-1)(loa)(11.1)(12A)(13.4)(14-4)(1 .1)(16.4)(174(18-4)(19-4)(20.1)(2lA)( 22A )(23-4)( 2 4 4(254)(26-4)

- .Ibid., . 105.Ibid.. No. 11. 63 (1954)Corben, R. W.; 'ewitt. D. SX., Chent. Age 72, No . 185%'Davis, D. S., C h m . Eng . 62 , N o. 3, 08 (1955).Fetzer, W. .. irst. L. C , J . Assoc. O f i . Am. Chemists 38.475-80 (1955).

- -130-40 (1955).Garner, F. H., Grafton, R. W. , Proc. Roy. SOC.(London) 224,Goldsmith, M., Penner, S. S., Je t Propulsion 2 4 , 24.551Gray, V. ll., Whelan, P. F., Chemistry Le: Indus try 1955, N o ,Harmon, D. B., r. , J.Frank l in Inst. 259, 519-22 (1955).IIouston. D. F.. Kester E. B.. Food Technol. 8. 302-4 (19541.

64-82 (1954).(1954).6.126-8.

. IIngebo. R . D., Natl. Adtiismy Comm. Aeronaut., Tech. M e m .Jensen, F. W.. Kelley, R f . J. , Burton, 11.B , Jr., Anal . Chem3265 (1954).26,1716-19 (1954).(1955).Kayse, J. R., Air Condituning, Heating, Ventilating 52 , 86-91)Kersten. H., Science 121, 98-9 (1954).King, A. R.,Newitt, D. M. , Chem. Age 72, 478-80 (1955).Kobaymi, K.. Tech. Repts. Tbhoicu Im p. Uniu. 18, 209-22(1954); Engrs. DiQest 15,No. 11 , 463 (1954).Landsbaum, E. M., odds, W. S., Stutzman, L. F., IN DEND.CHEM. 7, 101-3 (1955).Levine, A. 5.. Fagerson, I. S., a p p i 37, No. , 299 (1954).WcComb, E. A.,Wright, H. Sl., Food Technol. 8, 73-3(1954).

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S ign i f icant advances continue t o be made in the understanding and pract ice o fthe operat ion o f dry ing . Especial ly important , l th ink, i s t he g rowth o f quan t i fa-f iv e in format ion abo ut e f fects o f dry ing condi t ions on propert ies o f the dryproduct . On e af ter another, complexi t ies o f actua l indust r ial dry ing pract ice arebeing a t tacked through extensions o f theory and deve lopment o f new com pufa-t iona l techn iques. Comm ercial adopt io n o f cont inuous vacuum dryers for h eat -sensit ive materials exemplif ies the strong trend toward complete mechanizat ionand au tomafic con t ro l o f the d ry in g operat ion .

W. B. V A N ARSDEL, Asst. Chie fWestern Utilization Research BranchAgricultural Research ServiceU.S. Depa rtmen t of Agriculture(27A) Marshall, W. R., Jr., Chem. Eng. Progr. Monograph Ser. 50,(%A) Miesse, C. C., Je t Propu ls ion 24, 237-44 (1954).(29A) Ibid. , 25, 36 (1955).(30A) Plewes, A. C., Butler, R. M., Marshall, H. E., Chem. Eng.(31A) Polonskaya, F. M., Zhur . Tekh . F iz . 23, 796-801 (1953).(33A) Purr, A., Fette u. Seifen 56 , 1006-10 (1954).(34A) Rhoden, M., Chem. Eng. 62, No. 1, 212 (1955).(366) Richardson, E. G ., Appl. Sci. Research A4, 374-80 (1954).(36A) Ripka, L. ., Chem.-Ing.-Tech. 26, 440 (1954).(37A) Rollins, R. L., Spangler, M. G., Kirkham, D., HighwayResearch Board, Proc. 33, 492-508 (1954).(38A) Sato, T., Yamasaki, A., Chem. Eng. ( J a p a n ) 18, 212-15(3QA) Schwartaman, G.. J . Aasoc. Ofic . Agr. Chemists 36, 661-3(40A) Seltzer, E., Settelmeyer,J. T., Advances in Food Research,(41A) Spalding, D. B., Proc. Ins t . Mech . Engrs. ( L o n d o n ) 168, 545-(42A) Spencer-Gregory, H., Instrlament Practice 8, 508-13 (1954).(43A) Strickland-Constable, R. F., Bruce, E. W., Trans. ns t . Chem.(44A) Ibid., 32, 191-8 (1954).(46A) Taylor, S. A., Cavarea, L., Soil Sc i . SOC.Amer., Proc. 18,351-8 (1954).(46A) Troesch, H. A., Chem.-Ing.-Tech. 26, 311-20 (1954).(47A) Webb, P., Neugebauer, AI . K ., Reu. Sci. In&. 25, 1212-17(48A) Weisbecker, H . B., Oi l Ga s J . 53, No. 24, 118 (1954).(498) Weston, W. J.. Morris, H. J., Food Technol. 8, 353 (1954).(60A) White, W. C., Elec. Eng. 73, 1084-7 (1954).

No. 2 (1954).

P r o p . 50, 77-80 (1954).(32A) Ibid., 23, 802-5 (1953).

(1954).(1953).vol. 2, pp. 39S520, Academic Press, New York, 1949.70 (1954).

Engrs. 32, 199-203 (1954).

(1954).

DRYING METHODS(1B) Aluminum Co. of America, Heat Exchanger Bulletin, 1954.(2B) A S T M B ul l. , No. 201, 78, 1954.(3B) Bauer, W. G., Chent. E n g . 61, No. 5, 193-200 (1954).(4B) Borofsky, H., Brick & Clay Record 125, No. 5, 68-9 (1954).(5B) Buckham, J . A., Moulton, R. W., Chem. E r ~ g . rogr . 51, 126-(6B) Chem. Eng. 61, No. 10, 181-4 (1954).33 (1955).(7B) Ibid., 62, NO. 1, 118-20 (1955).(8B) Ibid., 62, NO.6 , 306-8 (1955).(9B) Chem. Trade J . 135, No. 3515, 998 (1954).(10B) Cooley, A. M., Severson, D. E., others, Food Technol. 8,

(11B) Frame, D. P., Am. Ceram. SOC. u l l . 33, No. 7, 216-17 (1954).(12R) Gardiner, S. D., Farmiloe, F. J., Analys t 79, 447-53 (1954).(13B) Grose, J. W., Duffield, G. H., Chemistry & Indus try 1954,(14B) Helmbold, P. A.. Chimie Ce: Indudtrie 70, 672-6 (1953).(15B) Herdlein, W , nd . F in ish ing 30, No. 12, 46-50 (1954).(16B) Isenberg, Y. H. , IND. NC. CHEM.46, No. 11, 105-106A(17B) Kamei, S., Toei, R ., Chem.-Ing.-Tech 26, No. 1, 1-9 (1954).(18B) Kamei, S., Toei, X.,Mem. Fac. Eng. K ~ o t oU n i v . 16, 14-48(19B) Koutsuma, &I.,Chem. Eng. ( J a p a n ) 19, 99-103 (1955)(20B) Mary, N. Y . ,Christensen, B.V., Beal, J. L., J . Am. P h a r m .(21B) Mate, G. , V a k u u m T ec h. 3, 109-14 (1955).(22B) Ib id . , 3, 115-23 (1955).

263-9 (1954).

pp. 1464-74.

(1954).

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Assoc., Sci. Ed . 43, 554-7 (1954).

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Patent 2,702,434 (Feb. 22, 1955).(1954).

65-70 (1952).

(1955).

DRYING SPECIFIC MATERIALS(IC) Bridger, G. L. , Burslaff, J., 3. A p . Food Chem. 2, 1170-3(2C) Copeland, S., Ceram. I n d . 62, No. 3, 78-80 (1954).(3C) Coupe, G. II., Am. Ceram. S O C .Bul l . 33, No. 9, 277 (1954).(4C) Downs, E. S. , Compton, E. A., A g r . Eng. 36, No. 2, 90--2(5C) Egerton, G. S. , rit.R a y o n & Silk J . 31, No. 365, 56-9 (19%).(7C) Grayson, H. G., IND. r a . CHEX. 7, 41-5 (1955).(8C) Gully, A. J., Tooke, H. A., Bartlett, L. H., R ef r ig . E ~ Q .2,(gc) Hall, c. W., Agr. Eng . 36, No. 4, 247, 260 (1955).

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(1955).(6C) Ibid. , 31, NO. 366.49-52 (1954).

No . 4, 62 (1954).(l ac ) Hankison, P., Ins truments & Automat ion 28, 625-7 (1956).(llc)Hcndel, C. E., Legault, R. R. , Food Technol. 8, 189-91(12C) Herrmann, R. H., Oil Gas J. 3, 3-0.0, 144-7 (1955).(lac)Hoskins, W. G., Hoskins. C. M., Food Eng. 27, 107 (1955).(14C) Hughes, C. V. O., Rock Products 57, No. 6, 78-81 (1954).(15C) Hukill, W. V., Agr. Eng. 35, No. 6, 393-5 (1954).(16C) Hultgreen, O., Paper Trade J . 139, No. 16, 41 (1954).(17C) Hunter, J. W., Am . Dye8tu.f Re ptr . 43, No. 8, 236-8 (1954).(18C) Ivarsson, B. W., Tappi 37, No. 12, 634-9 (1954).(192) Johnson, H. K., Dale,A. C., A g r . Eng. 35, No. 10, 705 (1954).(20C) Lanteri, A., Soap Ce: Chem. Specialties 30, No. 11, 42-46(212) London, M. , Textile World 104,No. 9, 84-5 (1954).(22C) P a p e r T m d e J . 138, No. 46. 108-9 (1954).(23C) Ranco, I.F., T a p p i 37, N o. 12, 640-54 (1954).(242) Roesler, R. , helliand Textilber. 35, No. 9, 1020-1 (1954).(25C) Ross, \Y. L., McLaughlin, E. R., Heating, P i p i n g , Ai? Con&(26C) Simpson, G. L., Ins truments & Automation 28, No. 5, 800-2(27C) Strlzshun,S. I. ,Talburt, W. .. Food Technol. 8 , 40-4 (1954).(28C) Talburt, Wr. F. , Hendel, C. E. , Legault, R. R. , ood Ew. 26 ,(29C) Thomson, W. L., Dalhcim, S. , tannett, V. T., T a p p i 38,(30C) Torke, E., Koch, F., Diem, W., U. S. Patent 2,698,489 (Jan.4,(31C) Walter, L., MMelZiand Teztilber. 35, No. 12, 1366-9 (1954).(32C) Waterhouse, F. M ., Chem. Eng. 61, No. 6, 237-42 (1954).

(1954).

(1954).

tioning 27, No . 5, 169-74 (1955).(1955).

N o. 4, 9 (1954).No. 4, 32A (1955).1955).

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Drying Bagnoli 1956