drying

I I I CHEMICAL ENGINEERING REVIEWS I

I I Drying OPERATIONS REVIEW

As IN past years! the drying literature consisted predominantly of descriptive articles that emphasized the dryer type and/or drying conditions required to satisfy product quality considerations for specific materials. .4 feiv articles reported the results of fundamental studies, -4 minimum of information \vas pub- lished on the performance characteristics of small-scale or plant-size dryers from which scale-up relationships could be developed, Drying is still an art and little work was done during the past year to bring it to the level of develop- ment of many of the other unit operations.

Drying Fundamentals

General and Review Articles. Chapters on drying were included in textbooks on the unit operations of chemical engineering by Coulson and Richardson ( 7 7A) and Badger and Ban- chero ( 3 A ) . Each comprises a discus- sion of drying fundamentals and a de- scription of the more common types of

dryers. .I similar chapter was contained in .4gricultui a1 Process Enxinetring (22'4). Each of these would serve as an adequate introduction to the field of drying. Two brief chapters on drj,ing and dryers were included in a text edited by hIolloy i l1.i). The second edition of von Loesecke's "Drying and Dehydration of Foods" (6'.l.4), which appeared during 1953, presents a Lvealth of information on the numerous techniques used in the food industry. The various types of dryers are discussed briefly. The sub- ject of dryer design is limited to the design of tunnel dryers. A complete cover- age of tunnel dryers was included in .4dvuncrs in Food Research (28-i). The major topics covered Fvere : classification, mechanical construction, auxiliaries, typical commercial units, and theory of tunnel dehydration.

Lapple (.329. <?3'4) reviewed the theory. types, and comparati\,e advantages of various dryers and presented data for estimation of dryer costs. A similar revieiv, limited to rotary dryers, \vas prepared by Russell (?3.4). Cost

EN0 BAGNOLI has been a member of the Engineering Re- search Laboratory, Engineering Department, E. I. du Pont de Nemours & Co., Inc., since 1952, working primarily in the field of drying. He attended the University of Delaware, where he obtained the B.Ch.E. in 1949 and M.Ch.E. in 1950. Bagnoli i s a member of the AMERICAN CHEMICAL SOCIETY and the American Institute of Chemical Engineers.

estimates from the data of t1i i .x papers differ appreciably. Data for cstini,Lting the cost of vacuum-shelf3 v~~cuuln-rcjtal'~, and frccze dryers were ~x~blished by Crites (/?A) and, for drum dryers, by Maguire (37.4). Hardy (20-41) anal!-zrd spray drying costs for a detergrnt dryer and noted that labor rcprrsents the largest single cust item.

The theory and Inmice of sonic of the nrwer trchniqurs in dr!inq tverc coil- sidered by Marshall (.38:1. L30A), \ \ M e \$'alter (rS5d) discussed the efficiency of operation of various dryrr t y i n used in the U, S. chemical industry. Lane and Stern (,3/.4) described the application of superheated steam for drying and claimed that smaller equipment is required Ivhen steam rather than air is used, because of the higher heat-transfer coefficients obtainrd when \ral)orizing lvater with superheated stcarn. Jorder (27<4) noted that increased production in the textile industry has resulted from the use of steam nozzle drying.

The principles of dryinq \vert rc- viewed briefly by Hiunphrc connection nith leather d poorer color o f rapidly drird Icather \cas atwibuted 10 the higli c~ni~cntration of soluble material at tht: surfact.; this high concentration results from liquor migration to the surface and subsrqucnt evaporation of watcar. Kncule and Schlachter (2S.4) disclosed a nirthod for predicting the drying timc. during the falling rate period for porous hygroscopic materials which exhibit a nioisturc distribution that is approximatel>, I)cirat)olic. Rate data for both the constant- and falling-rate drying of a silica-alumina hydro- gel were presented by Ixbis and Kiirtis (34A). Jopling (26,1) reported that gelatin films swell least when the layer during drying is a t about 35' C. The drying of hydrophilic plastics and the advantages of vacuum drying were discussed by Haas (764 77A) .

Moisture Movement. The various physical concepts relating to moisture movement in solids were analyzed by Babbitt (2.4) in terms of a driving force

476 INDUSTRIAL AND ENGINEERING CHEMISTRY

I

B-1 Fleissner & Sohn staple dryer. ( 1 ) recirculation blower; (2), (3) air heaters; (4) perforated drum; (5) staple layer; (6) sheet metal seal; (7), (9 ) feeders; (8) opener

and a resistance for vapor, liquid, solid, chemical compound, adsorbed, and dis- solved water. Hadley and Eisenstadt (78A) studied the movement of moisture in granular media by means of radioactive tracers and reported that above a critical moisture content of 470 there exists a circulation of vapor away from the hot region and of liquid toward it. Whelan and others (69A) presented results on the rate of diffusion through laminae of plastic films, textile fabrics, and perforated metal plates. Exptri- ments by Mitton (43A) with both steady- state and unsteady-state diffusion of water vapor in leather showed that most of the vapor transport occurred through capillary spaces. Stamm (584 reported that diffusion constants for diffusion of water into uncoated cellophane increase exponentially with fractional water vol- ume. The water permeability of paint films was studied by Weinman (67A).

The unsteady-state equation for diffusion in a sphere was found applicable to the drying of wheat kernels by Becker and Sallans (44. In the moisture range of practical importance, 12 to 30%, the diffusion constant was independent of moisture. Nissan and Kaye (474 and Nissan (464 applied the equation for unsteady-state heat conduction in an infinite slab to the drying of sheet materials on heated cylinders. Calculated values agreed surprisingly well with results obtained on a Fourdrinier newsprint machine. McEwen and O'Callaghan (354 extended the work on through- flow drying of wheat with an investigation of the effect of air humidity. These latest results agreed with those previ- ously correlated by the limiting form of the diffusion law (55A).

Sprays and Droplets. Hinze (24A) attempted to systematize the ways in which a globule can break up. He concludes that it may be possible to obtain an expression for the largest drop for the case of break-up of a globule in viscous flow, break-up of drops in an air stream, and emulsification in tur- bulent flow. The effect of an acoustic field on the disintegration of a liquid jet was studied by Miesse (42A). Imposing

the field perpendicular to the jet caused dispersion while causing the field to act in an axial resonant chamber served to coalesce the drops. Miesse (47A) also summarized and evaluated various theories of liquid jet disintegration according to their ability to correlate wave length, maximum drop size, and break- up length. Magarvey and Taylor (36A) noted that drops in free fall are deformed to such a degree before terminal velocity is reached that the center of the flattened drop bulges upward and the drop opens like a parachute; smaller drops assume a reasonably stable shape at terminal velocity.

Troesch (67A, 6.24) derived from sta- tistical considerations an equation for drop-size distribution, reviewed the various methods of liquid jet break-up, and presented an equation for predicting the largest drop produced by a swirl- type atomizer or a two-fluid atomizer in which the liquid is injected perpendicular to the air flow. The performance of vaned-disk atomizers was investigated by Herring and Marshall (23A) . The spray-weight and drop- size distribution were correlated empiri- cally in terms of disk diameter, disk speed, vane dimensions, number, and feed rate. Radcliffe (49A) studied the effect of geometry variations on the performance of a particular type of swirl atomizer. A device for producing a stream of uniform drops of liquid was described by Rayner and Haliburton (50A).

During the past several years numerous investigators have shown that an equation of the form

D' D,P - At

Do = initial drop diameter D = drop diameter at any time A = evaporation constant t = time

applies to the burning of a drop or to the evaporation of a drop in a high-temperature gas. Four papers covered the effect of several variables on the evaporation constant. Kobayasi ( 3 0 4 investigated the behavior of some fifteen fuels in a high-temperature environment, where the droplet begins to burn by self-

ignition. Goldsmith (75A) found that the evaporation constant for benzene varied as the 0.4 power of pressure, that the effect of environment gas composition on the evaporation constant for benzene and n-heptane is predicted by diffusion theory, and that the evaporation constant is only slightly dependent on temperature. The evaporation constants for two and five droplets burning in close proximity were measured by Rex and others (574 . Preliminary results indicated that for the two-droplet arrangement and for the center droplet of the five-drop square array the evaporation constant is invariant with time. Using an interesting photographic technique, Bolt and Boyle (.5A) studied the burning rate of a cloud of fuel droplets of uniform size-70 to 130 microns in diameter. Evaporation constants were found to be about half those reported by Godsave (744 and Kobayasi (30A) for appreciably larger satisfactory droplets. This discrepancy is probably due to interaction with adjacent droplets.

Moisture Analysis. The moisture content of guncotton and nitrocellulose was determined by Miaud (40A), using a dielectric drying technique.

Equilibrium Moisture. Relative hu- midities above saturated salt solutions were measured by Richardson and Mal- thus (52A) ; a series of salts for controlling the relative humidity between 7 and 6OY0 was listed. Vapor pressure of 14 concen- . trations of aqueous sulfuric acid was measured over the temperature range 0' to 100' C. by Tarasenkov (59A). Equi- librium moistures of palm kernels were determined by Somade ( 5 7 4 and for rough rice by Breese ( 6 4 .

Hygrometry. Penman (48.4) pub- lished a monograph on humidity. Han- kison ( 7 9 4 explained dew point from a nontechnical standpoint. Thomas (60A) discussed methods for measuring humidity, commercial equipment for each method.

A new method developed by Mine Safety Appliances Co. for recording low concentrations of water vapor in air or gas streams was described in Chemical Engineering (8A) . A technique for meas-

VOL. 49, NO. 3, PART II MARCH 1957 4 7 7

Freeze drying has apparently been relegated to its proper position as a technique for drying expensive, heat-sensitive materials which cannot be dried by any other method.

Hygrometers Fast responding glass bank sensing

(68-4) element coated with potassium metaphosphate

Corona discharge

Thermocouple linear calibration 10

Plastic wafer (45-4) resistance changes with moisture content

Portable dew point GE, based on dew indicator (10-4) formation on

Capacitance resist- changes in electrical ance ( 1 3 9 ) properties of

anodized aluminum indicate relative humidity

(1 A)

(6Gd) to 30 mm. H g

cooled mirror

uring dew points as low as -80” C. !vas announced by Du Pont (70A).

The calibration is independent of temperature over the range 0’ to 80” C. Underwood and Houslip (63.4) investigated a capacitance hygrometer whose sensing element consists of an aluminum rod, one end of \chich is anodized and then coated with a layer of colloidal graphite. A simple apparatus for producing humidity step functions at room temperature using saturated salt solutions was described by Hasegaiva and others (27‘4). The dielectric constant of air con- taining various amounts of water vapor was measured by Saito (.i-l.-i). .4 three- dimensional psychrometric cam for con- tinuously “computing” relative humidity from wet- and dry-bulb temperatures measured by resistance thermometers was described by Burlage (7.4). Various techniques for controlling the dew point of furnace atmospheres ivere described by Slater (56&4).

Drying Methods

Spray Dryers. The portion on the combustion of liquid fuels in “Some Fundamentals of Combustion” (-13B) should be of interest to those concerned Lvith spray drying. Marshall (ZSB) considered a number of aspects of heat and mass transfer in spray drying. By taking into account the heat required to raise the temperature of the vapor dif- fusing from an evaporated drop to the main stream temperature, Marshall derived a correction term to be applied to the normally used heat-transfer coef- ficient. Results of experiments on burn-

478 INDUSTRIAL AND ENGINEERING CHEM

ing single drops Ivere cited indicating that heat-transfer coefficients may he only 0.1 of those predicted from conventional equations [see also Colburn? .A. P., and Drew, T. B., Trans. Am. Inst. C h m . Engrs. 33, 167 (1937)l. Ranz (.J7B) included this same effect of mass transfer on heat transfer in his solution of the steady-state heat-conduction equation to a vaporizing drop. hfeyer (32B) attempted, Ivith little successt to correlate effects of feed rate and disk speed on particle size obrained by spray drying ivirh results from previous rotating-disk atomization studies.

Coulter (77B) considers a number of factors involved in the production of spray-dried milk. The characteristics of Ivheat gluten obtained by spray drying in a two-fluid atomizer spray dryer were studied by hIcConnel1 (26B). Asdell (2B) dried paper-coating clays in a spray dryer and concluded that spray drying, for the first time, offers a means of processing clay to less than lyO moisture without the danger of developing hard particles. Average drying time of 30 seconds quoted in this article appears exceptionally long. Food Engineering (7-1B) described a spray-drying installation for improved quality food flavors. According to Mazur and FYes- ton (37B). the rapid drying achieved in a spray dryer is considerably less harmful to spores of Aspergillus.flaois and Pestdotia polmarum than is the slow drying obtained in freeze drying. The equipment used in this study is intriguing-a two- fluid nozzle located in the mouth of a 5-gallon carboy. Gauvin (76B) described Xvhat he terms the “atomized suspension technique.” This involves atom- izing a slurry or solution into the top of a chamber whose walls are maintained at an elevated temperature, creating a finely divided suspension of droplets dis- persed in the vapor produced by their own evaporation. Suggested applica- tions are in drying, evaporation, or chemical reaction.

Rotary Dryers. The retention time in a rotary dryer \vas measured by Miskell and Marshall (33B), urilizing a radioactive salt to coat the sand particles and then monitoring the radioactivity of the product. The relative standard deviation, defined as the difference in time required for 50 and 84.13y0 of the tracer to be discharged divided by the time required for 50c/;! of the tracer to be discharged. \vas found to he a

ilSTRY

minimuni at a dr)-er holdup of 7.5 to Data such ;is these are very im-

portant Lvhen 1)roduct qualiry rcquircs that drying be carried out uniformly for all of the particles. An investigation of matrrial rnoveinrnt in a rotary kiln also using a radioactivr tracrr, \vas carried out hy Kutlc ( 1 3 ) . He noted that the rate of movement \vas different, not only fur diff’ercnt kilns, but also in different sections of the samc kiln. ;i new combination ball mill and ro-

tary kiln, developed at the Brookhaven Sational Laboratory, was described in Chcmiral Enfinwing (8%’). The tialls are reported to do little grinding but serve to keep the solids from agglomerat- ing and to improve the hrat-transfer rate. Azbe (3B) discussed the pcr- formance characteristics of rotary kilns and suggested the use of the i b b e scq- mented rotary kiln to eliminate many of the difficulties normally encountered. According to Brisbane (GB), the life of refractory linings can be increased through the use of stiffening rings.

Freeze Dryers. Freeze drying has apparently been relegated to its proper position as a technique for drying expensive, heat-sensitive materials which cannot be dried by any other method.

.

Freeze Drying

High vacuum fundamentals Fundamentals Lab scale freeze drying Microorganism preservation Tissue preservation Large scale freeze drying Lab scale apparatus Tissue drying equipment

The use of freeze drying for s tudyiq the diffusion of an acid dye into gelatin was reported by Pontius and others

Infrared and Dielectric Dryers. Experimental results on the infrared drying of clay \vue correlated empiri- cally for both the constant- and falling- rate periods by \\,*\:OO and others (‘7SB). These authors nored that infrared drying is uneconomical in the falling-rate period because of the small amount of moisture removed per unit of energy.

combination radiant heat and hot

(dun) .

DRYING

air dryer developed by Herbert Products Co. was described in Tappi (7B) and Paper Trade Journal (35B). Designed for drying printing and coatings on films and paper, the dryer is claimed to have flexibility, efficiency, and econ- omy. Hultgreen (27B) reported that an electric infrared oven of new design has many advantages for paper machines and converting equipment. He also suggested as advantageous the application of radiant energy at the beginning and in some cases at the end of conventional drying sections while retaining more conventional methods in the middle of the drying process. The use of radiant burners and flame-im- pingement techniques in paper and film processing was described by Mann (27B). Baking of finishes by infrared heat, an area in which infrared heating finds wide application, was discussed by several authors (9B, 75B, 77B, 228, 34B, 44B). The use of infrared ovens in the chemical industry was considered by Deribere (72B). Knight (25B) described a laboratory drying apparatus in which heat is developed in electrically conductive glass.

Besser and Piret (5B) reported the results of dielectric drying of gelatin and paper pulp. Solids temperature during dryiog was maintained constant by a suitable controller and the authors sug- gest this as’a potentially useful technique in studying drying fundamentals. Com- parison of controlled-temperature dielectric drying data with data for air drying, under the same conditions of air temperature, velocity, humidity, and sample thickness shows that the rate for dielectric drying is nearly double in the initial stages but that the rates become equal in the later stages.

Pneumatic Conveying Dryers. Corder and others (70B) presented data on the effect of gas temperatuie, solids rate, and feed moisture on the performance of a pneumatic conveying dryer for sawdust. Kamei and others (23B) carried out studies on the drying of several plastics and inorganic materials and analyzed the motion of the particles in a pneumatic conveying dryer (24B).

Miscellaneous Dryers. Mathur and Gishler (30B) described the “spouted bed” technique for drying wheat. This modified fluidized-bed method, uses an ejector in the bottom of the drying bed to cause recirculation of the solids being dried when these solids are too coarse and uniform to fluidize satisfactorily. A previous paper (29B) analyzed the flow characteristics of a spouted bed. A unique drying scheme for staple fibers was described by Pfeiffer (36B). This dryer consists of a series of perforated drums which are connected to the suction side of a fan. Each drum is provided with a seal over half its circumference, so

that the air flows alternately through the top half and bottom half of succeeding drums. The staple being dried is held in contact with the drum by suction and in passing from one drum to the next the layer is turned top for bottom, equivalent to the reversal in air flow direction often used in conveying screen dryers.

A drying and heating machine using jets of high velocity air has been developed by the Spooner Dryer and En- gineering Co., Ltd. (37B). Units are being used extensively for fusing poly- vinyl chloride and fabric. A hopper dryer for plastic materials, using condi- tioned air of low relative humidity is being evaluated by C. H. Whitlock Associates (39B). A humidity-controlled drying oven for nylon, capable of evapo- rating 24 pounds of water per day, was announced by Injection Molders Supply Co. of Cleveland (38B).

Drying Specific Materials

Food and Agricultural Products. The advantages of continuous belt drying over batch tray drying were noted by Havighorst (4C). The vacuum contact plate method for drying foodstuffs was described by Hay (5C). This dryer is basically a tray dryer with movable heating plates to compensate for stock shrinkage during drying. It is claimed that satisfactory heat transfer by conduction from plates to stock is ensured throughout the drying process. Gooding and Rolfe (2C) evaluated the above drying scheme for various foodstuffs, and reported that it is possible to produce a much wider and superior range of dehydrated foodstuffs than could be prepared by ordinary hot-air drying methods. The main limitation cited is the high cost of equipment. The operational details of a belt-trough dryer were described by Lowe (6C). The stock is carried on an endless flexible belt sup- ported between rollers to form a trough. The stock moves in a spiral with the discharge at right angles to the direction of motion of the belt.

Textiles. Laboratory experiments to evaluate various dryers for retted flax, which led to the installation of a direct- fired conveyor dryer, were discussed by Powell ( 7OC). Performance figures for a furnace burning flax shives to serve as fuel for drying retted flax were presented by Sayles (77C). Pinault (9C) reported that a Smith, Drum & Co. dryer reduced the drying time of package yarn by 90% and substantially eliminated color migration. I n drying tightly wound yarn packages the limiting factor is the air flbw. A remedy suggested by Thies (73C) is to, operate the drying system under pressure, thus permitting a

larger amount of heat to be supplied at the same gas velocity. A German report on yarn drying in package form was summarized by Skinner’s Silk & Rayon Record (72C). The influence of air humidity on the quality of dried textiles was discussed by Meier-Windhorst

The various functions of the dryer felt in paper drying were discussed by Van Patten ( 7 4 2 ) . Harper (3C) reported that a 12 to 15% increase in drying capacity results from elevating the temperature of the paper sheet and thus permits more rapid drainage.

Mazer (7C) described his invention, involving the application of steam at various suction points of a paper machine. Increased drainage results, as the steam drawn through the sheet and into the suction box heats and reduces the viscosity of the waterin the wet sheet and increases the suction because of con- densation. White (75C) investigated the behavior of the condensate layer inside a dryer drum. An empirical equation for predicting rimming speed-that speed at which the condensate moves as a film around the periphery of the drum-was presented. The dynamics of the condensate and the performance of the siphon system are related, while the latter is also affected by drum speed, pressure difference, location and geometry of the siphon. Cirrito (7C) analyzed the heat transfer effects in a paper dryer and suggested methods for improving heat- transfer coefficients.

(8C) * Paper.

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Drying Fundamentals

(1A) Anderson, N. E., Hertz, C. H.? 2. angew. Phys. 1, 361-6 (1955).

(2A) Babbitt, J. D., ASTM Bull. No. 212, 58-61 (1956).

(3A) Badger, W. L., Banchero, J. T. , “Introduction to Chemical Engi- neering,” pp. 469-519, McGraw- Hill, New York, 1955.

(4A) Becker, H. A., Sallans, H. R., Cereal Chem. 32,212-26 (1955).

(5A) Bolt, J. A., Boyle, T. A., Trans. Am. Sac. Mech. Engrs. 78, 609-14 (1956).

(6A) Breese, M. H., Cereal Chem. 32,

(7A) Burlage, H., Jr., lnstrument Society of

(8A) Chem. Eng. 63, 236, 238, 240 (1956). (9A) Chem. Eng. News 34,56 (1956).

481-7 (1955).

America J . 2, 298-300 (1955).

(10A) Zbid., p. 1932. (11A) Coulson, J. M., Richardson, J. F.,

“Chemical Engineering,” vol. 11, “Unit Operations,” pp. 832-67, McGraw-Hill, New York, 1955.

(12A) Crites, G. J., Chem. Eng. Costs Quart. 6,4-11 (1956).

(1 3A) Cuttings, C. L., Jason, A. C., Wood, J. L., J. Sci. Instr. 32, 425-31 (1955).

VOL. 49, NO.. 3, PART I I MARCH 1957 479

UNIT OPERATIONS REVIEW

(14A)

(1 5A)

(16A)

(17.4)

(18A)

(19.4)

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Herring, W. Sf., Jr., Slarshall, W. R., Jr., Am. Inst. Cliem. Engrs. J . 1,200-9 (1955).

Hinze, J. O., Ibid., 1,289-95 (1955). Humphreys, F. E., J. Soc. Leather

Tradcs’ Chemists 39. 307-20 (1 955 3. Jopling, D. W.. J . ’App l . Chem. 6,

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Chcm. Eng. 62, 191-210 (1955) Lapple, W. C., Clark, W. E.,

Dybdal, E. C., Ibid., 62, 177-200 (1955).

Lebis, E. H., Burtis, T. A., Am. Inst. Chem. E n u s . J . 1. 329-34 11955).

McEwen, E., O‘Callaghan, ‘J. R., Trans. Inst. Chem. Engrs. (London)

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33, 135-54 (1955).

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Ibid., pp. 62-7 2. Miaud, P., Mtm. poudres 37, 465-9’

7, 37-40 (1955).

11955). X‘fieSSe, ‘c. c . , IND. ENG. CHEM. 47. 1690-701 11955).

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25, 525-31 (1955).

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neeiing ‘Processes and Equrp- ment.’: DD. 193-210. LYvman 8: Sons,‘ L;Adon, 1955.’ ’

.Moody’s Industrials, Jan. 28, 1956. Nissan. A. H., Chemistry @ Industry, 1956, 198-211.

Nissan, A. H., Kaye, W. G., Tabpi .. 38, 385-98 (1955).

Penman, H. L., “Humidity,” In- stitute of Physics Monographs for Students, London, 1955.

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S. S., J . Am. Rocket SOC. 26, 179-87 11956).

Richardson, G. hf.: Malthus. R. S., J . .4ppl. Chem. 5, 557-66 (1955).

(53A) Russell, R. J., Chem. Eng. Costs Quart. 5, 96 (1955).

(54A) Saito, S., Proc. I.R.E. 43, 1009 (1955).

(55A) Simmonds, W. H. C., Ward, G. J., McEwen, E., Trans. Inst. C h m . Engrs. (London) 31, 265-88 (1953).

(56.4) Slater, F. E., Instruments and Automa- tion 28, 1720-4 (1955).

(57.A) Somade, B., J. Sci. FoodAgr. 6,425-7 (1955).

(58.4) Stamm, A. J., J . Phys. Chem. 60, 76-86 (1956).

(59A) Tarasenkov, D. N., J . Appl. Chem. (U.S.S.R.) 28, 1053-8 (1955) (English translation).

(60.4) Thomas, B. W., IND. ENG. CHEM.

(61A) Troesch, H. A,, Engrs’. Digest 16,

(62‘4) Ibid., pp. 436-8. (63.4) Underwood, C. R., Houslip, R. C.,

J . Sci. Instr. 32, 432-6 (1955). (644) von Loesecke, H. W., “Drying and

Dehydration of Foods,” 2nd ed., Reinhold, New York, 1955.

(65‘4) Walter, L., Chaleur tY ind. 36, 256-62 (1955).

(66A) Webb, C. G., Rajaratnam, A. , J. Sei. Instr. 33, 132-4 (1956).

(67.4) Weinman, K., Farbe u. Lack 61,

(68A) Wexler, .4., others, J . Research Sat2.

(69‘4) Whelan, M. E., others, Textile

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315-23 (1955).

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Drying Methods

(1B) Annear, D. I. , Lab. Practice 5 , 102-5

(2B) Asdell, B. K., Tappi 38, 476-81 (1956).

I 1 9.5.5 ). (3B) Azbe, V. J., Rock Products 58, No. 2 ,

101 ; No. 3, 82: No. 5, 77; No. 6, 108; No. 7, 58; No. 8, 154: No. 9, 70; No. 10, 118 (1955).

(4B) Bell, L. G. E., Lab. Practice 5, 139-42 (1956).

(5B) Besser, E. ‘D., -Piret, E. L., Chem.

(6B) Brisbane, S. M., Mtnine Ene. 8, 205, Eng. Progr. 51,405-10 (1955).

- - 210-12 (1956).

(7B) Carswell, C., Tappi 39, 191.4-2.1 (1956).

(8B) Chhz. E i g . 63,120-2 (1956). (9B) Coppa-Zuccari, M., Peintures, p ig-

ments, cernis 32, 140-2 (1956). (10B) Corder, S. E., Morris, C. O.,

htherton, G. H., Afech. Eng. 78,

(11B) Coulter, S. T., J . Dairy Sei. 38, 1180-4 (1955).

(12B) Deribere, M., Chimie 3 industrie

(13B) Emmart, E. W., Crisp, L. K., Reo. Sei. Instr. 27, 315-18 (1956).

(14B) Food Eng. 28, 76-8, 155 (1956). ( l 5 B ) Gauss, J. M., Ind. Finishing 31, 26

627-9 (1956).

73, 913-8 (1955).

(1955). (16B) Gauvin,‘ W. H., Chem. in Can. i ,

(17B) Gaynes, N. I., Ind. Fznishing 32, 30

(18B) Greaves, R. I. N., Lab. Practice 5 ,

48-56 (1955).

(1956).

53-5 11956). (19B) Harris, R. J. C., Ihid., 5, 53-5 (1956). 120B) Holland. F.. Brit. Communs. @

INDUSTRIAL AND ENGINEERING CHEMISTRY

Electrinics2, 62-3 (1955). Hultgreen, O., Paper Trade J . 140,

47-50 (1956). Hunt, F., Electroplating and Metal

Finishing 8, 343-6, 366 (1955). Kamei, S., Towei, R., Hiraoka, Xf.,

Chem. Eng. ( J u p a n ) 20, 55-60 ( 1 9 5 6 11.

(24B) Ibid., pp. 60-5. (25B) Knight, C. A , , Chemist Analyst 44,

108 11955). (26B) McConnel1,’W. B., Can. J . 7’echnol.

(27B) Mann, C. P., Mcch. Eng. 77, 219-22 33, 256-64 (1955). (,nCC\ ( I 7 J J J .

(28B) Marshall, W. R., Jr., Trans. ‘4m. Sac. Mech. Engrs. 77, 1377-85 (1955).

(29B) Mathur, K. B., Gishler, P. E., Am. Inst. Chem. Engrs’. J . 1, 157--64 (1955).

(30B) Mathur, K. B., Gishler, P. E.. J . Appl. Chem. (London) 5 , 624-36 (1955).

131B) Mazur. P.. Weston. W. H.. J . Bactbriol. 71, 257--66 (1956). ’

(32B) hleyer, F. W., Chem. Eng. Progr. 51,

(33B) Miskell, F., Marshall, W. R., Jr., Ihid., 52, 355-485 (1956).

(34B) Orlicek. A. F.. Chem.-Ine.-Tech. 27.

528-30 (1955).

\ I

84-7 (1955).’ (35B) Paper Trade J . 139, 33 (1955). (36B) Pfeiffer, O., Rcyon, Zellwolle u.

(37B) Plastics (London) 20, 418-21 (1955 1 . (38B) Plastics ,Vew Letter 16, 1 (1956). (39B) Ibid., p. 3. (40B) Pontius, R. B., Kaplan, h?. L..

Husney, R. M., J . Phys. Cheni.

(41B) Ranz, LV. E., Trans. Am. Sac. .‘lfech. Engrr. 78, 909-13 (1956).

(42B) Rutle, J., Pit and Quarry 48, 120-1 (1955).

(43B) Spalding, D. B., “Some Funda- mentals of Combustion,” pp. 122-43, Academic Press, New York, 1955.

(44B) Stack, L., Ind. Finishing 31, 76 (1 955 i.

Chemiefasern 1955, 824-6, 828-9.

60, 9-12 (1956).

(45B) L’allet, M. .A,, Lab. Practice 5 , 169.-

(46B) LVatzkc, E., .Vaturwisscnschaften 43,

147B) L.Veil. F. C., Chcm. Products 18,

73 (1956).

83 (1956).

183-5 (1955). 148B) LVoo. D., Simon, H. P., Jones, P. R.,

.I. Am. Ceram. Soc. 38, 383-8 (1955).

Drying Specific Materials

(1C) Cirrito, A. J., Paper .Will .Vms 78

i2C1 Goodine. E. G. B.. Kolfe, E. J.. 48 (1955).

\ ,

,J . ScL’Food Agr. 6,’427-33 (1955): (3C) Harper, J. C., Tappi 38, 229-33

(1955). (4C) Havighorst, C. R., Food Rng. 27,

(5Cj Hay, J. M., J . Sei. Food A g r . 6 ,

( 6 C ) Lowe, E., others, Food Eng. 27, 43-4

( 7 C ) Mazer, J . , Paper Trade J . 140, 34

(8C3 Meier-LVindhorst, A, , ilfelliand

(9C) Pinault, R. W., Textile It’orld 106,

(1OC3 Powell, R. W., J. Inst. Fuel 28, 69-76

(1lC) Sayles, C. P., J . Inst. Fuel 28, 77-80

(12C) Skinner’s Silk 3 Rayon Record, 506-7

(13C) Thies, F., Am. DyestuJ Reptr. 45,

63-5, 212 (1955).

433-40 (1955).

(1955).

(1956).

Textilher. 36, 276-80 (1955).

100 (1956).

(1955).

(1955).

(1956).

95-8 (1956). (14C) Van Patten, M. D., Paper Mill ,Vews

(15C) White, R. E., Tappi 39, 228-33 78, 118 (1955).

(1956).

drying

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