36
I N D U S T R I A L A N D E N G I N E E R I N G CHEMIS’TRY
(123) Storrow, J . A., T r n a . Inst. Chem. Engrs. (London), 23, 32 (1945). (124) Storrow, J . A. and Willson, B. D., J . Soc. Chem. I n d . (London), 66,79 (1947). (125) Stutsman, b. F., and Brown, 0 G., CiLern. Enp. Progress, 45, 142, 139 (1’349). (126) Taeoker, R. G., and Hougen, 0. A., Ihid., 45, 188 (1949). (127) Tivy, V. V., St. L.,Petroleum Refiner, 27. No. 11, 603 (1948). (128) Tyner, Mack, Chem. Eng. Progrescl, 45 49 (1949). (129) Van Winldc, M., Petroleum Refiner, 28, No. 1, 88 (1949). ‘130) Volkov, V. I,., and Zhavoronkov, N. M., Khim. Prom., 1947, No. 9, 12. (131) Volokh, S &I , Azerbaldahaiwkoe Ntlftyannc Koha., 26, No. 6, 16 (19.47~
VOl. 42, No.,1
(132) Wilhelm, R. H., and Coiliev, D. W., INU.F ~ G CHEM., . 40 2350 (1949). (133) Williams, Brymer, Univ. Microfilms, Ann Arbor, M i r h . . Pub. 1123. (134) Williamson, A. T., Proc. R o y . SOC.(London),AP95, 97 (1,948) (135) Wojciechomski, M., J’. Chem. Xducation, 26, 132 (1949). (136) YnBesta, J. I,., and Achon, M. A., Analcs real SOC. e s ~ f i fh.putm., Ser. B.,44, 689 (1948). (137) Yu, IS., and Hickman, J. 13.. J . Chem. Education, 26, 207 (1949)(138) Yu, K. T., and Goull, J., C‘hiim. Eaig. Progrms, 44, 796 (194% H I?CEIV&D
Oi:tl)kif?r
18, 15144
ARTHUR D. Lirri-E, INC., CAMBRIDGE, MASS.
iX THE fall of 1947 the first High Vacuum Symposiurii (Y4) was held in Cambridge, Mass., to celebrate the accoml.dishments of high vacuum in World War I1 and to usher in a I I C K era of high vaci~umtechnology. That same year-end niarlced the last appearance of this review ( 9 9 ) ; in 1948 there was imufficient niaterial to command space. The paradox is sinipie: the symposium had celebrated the conclusion of pEn era and only in a remote and confused sense did it presage the birth of another. The era had reached its olimax il-ith the production of giant vacuum equipment (44,58) for the inagaetic and other separation processed for uranium (46),the produotion of magnesium, and the dehydration of biologicals and wartime foods; but the foundat,ions had been laid in the previous 15 years in electroiiics 2nd conimercial molecular distillation. After the Cambridge conference there hm been a pause for review and planning of new work. The iiitervening lull in inveiit>ionand publication should not be mistaken for inact,ivity. Greater volumes of materials are being procemod on molecular stills thnn ever before, and many new researetics w e knuwn t,o be in the embryonic stage. The low temperature distillation of water from fruit juices (48, 4 9 ) has reached gigantic proportions. The definition of whast is distillation and what is high vacuum has become broadened (S8), and it s e e n s necessary to introduce a new term. The author offers with appropriate misgivings, I h c wurd “niegavacuuni” to describe t,he transport uE large niaesw of gases a t pressures far below those previously avnilabie in heavy industry, hut, yet not approcching the submicron range of accepted high vacuum. To use current clichds, the latter handle vast volumes of “nothing,” the former, very considerable masses of “something.” One requiros a vacuum pump, the other a vamum engine or prime mover. Steam eject0rs’an.d high pressure oil vapor ejectors, both in multiple stage ( 3 Q ) ,have become available as prime movers. Besides the application to orange juice (@), megavacuums are being introduced with increasing success for the drying of coffee sirup (td), the melting of metals in the absence of sir (65),and reductive me”:allurgy (68) in general. If the va,cuum requirements of this new era are to be envisaged, it is only necessary t o note t8he giant nuclear fissicn mschines tJhat are being projected and the laments of the high v-acuim distillers (28). A11 require larger, quic’ker, higher, and cheaper vacuums. The most significant recent contribut,ions have been in the form of symposia, review, and boolts. Two important conferences on high vacuum have been held, one a t Glenea,gles, Scotland (10,1.9, 18, %9,43, 46, ,5J, 5 6 ) , under the auspices of t,hr
(13rit’ish)Society of Chemical Industry, and theother in Caslbriclgc(34.). A full report (1,14,19,SS,S6,56,38,42,44,48,60,61, &+; 5 7 ) of ihe latter meeting has been available to readers of this journal since May, 1948. Some of the contributors presented, substantially similar papers ( 1 , 19) at both meetings, but, the stress v a s on technique (S6), measurement (14, 48), and megavacuums a t the American event and on high vacuum processes a t the British gathering. Notable communications ai; Ihm. bridge were the description of wax-born methods of loak detec lion and of measuring pressures from 10 mm. downward. The Gleneagles meeting opened with a broad survey by C ) i i 4 man (18) of the theory underlying vacuum technique. S w a l l o ~ and Gourlay (56) surveyed vacuum evaporation for the metalization of surfmes arid the purification of high polymers and na,turnl oils from low molecular weight contaminants. Morse (@) described American equipment in the megavacuum range for orange juice and biologicals, and Stauffer (JS), also from National Research Corporation, described the reduction and distilla tion of magnesium and calcium. ‘4paper of some interest for thie review was Fawcett’s appraisal of molecular distillation ( 2 3 ) As a leader of .the British school in the early days, %an-cet,t’s opinion, as follov;~ (condensed), after some years of scpa,la t inii has both debcbment and matnrity: Iloleculsr distillaticxi i h R process for the rather special case :tiid is not likely, in the present, form, tlo become a generally applied proc,ess on the commercial scale. One such special case is vitamin .4., where favorable factors have led to success. The iiwelopment. of cheap and effective molecular fractiona,ting columns of 10 to 20 molecula~plates would make the process of much more general applicability and value t o the Fheniicai engineer. To achieve this, a radical redesign of existing titi118 appears necessary.
It will be interesting to observe whether the challenge facing the moIecnl.ar still will. be met during the next few years. That it,s proponents have not lost faith is evidenced by other excellent reviews (11, 46), profusely illustrated. The very recent appraisal by Jaeckel and Oetjen (37) from. the Leybold laboratory, commands attention. Even more commanding, and indced, perhaps the most important event. in the period under review is the publication of Dushman’s long-awaited book ( 2 0 ) . Uniqut?; t~ll-inclusive, and accurat,e, i t will nevertheless irk the practical reader by its intellectual nutidiness and lack of selectivity. It? influence will be profound. Minor moclib’cations have appeared in the laboratory art, The falling-film still, which viould have seemed to defy further variation, has been altered (5)) to accommodate samples of I to 5 grams. Evaporation is done from the inside of a hot glaszi tnbr
!January 1950
INDUSTRIAL AND ENGINEERING CHEMISTRY
ure 1.
37
Vacuum Chamber Used for Coating Condenser Paper with Zinc
and condensate is collected on a concentric water-cooled pipe. The still is turned upside down to produce the right side up for the third, and so on. Another (2%) with internal condenser is of the Quackenbush pattern, with moving parts eljminated. The 5-inch laboratory c still, which made its debut a t the Cambridge sympo appeared on the market and in print (6). The thermal hazard connected with its use is said to be lower, by a factor of 10, than achieved previously. Madorsky (41) has continued his re, searches in distillation, using a pot still for the pyrolytic fractionation of polystyrene in high vacuum, A variation (3)of the high vacuum, short-necked boiling-point still has been described; i t allows distillation or deodorization of glyceride oils with ordinary glass equipment in the laboratory. An extremely small microstill (1)in the form of a modified test tube, has new and useful condensing features. A British patent (16) descr path fractionating columns containing a rotary cool within a heated tube. “Voltalized” glyceride oils have been analyzed by the molecular still (7) in Italy. The theory of cyclicbatch molecular distillation has been questioned and extended ($9). The elimination curve technique has been applied by Fletcher, Hodge, and others to charting the relative volatilities of a large number of sterol esters (3.4). The unavoidably rather unsatisfactory data have been rationalized by the use of probits. Comprehensive data have been obtained or compiled for the high vacuum fluid dibutyl phthalate (6). The alkyl silicanes have been introduced as thermally stable vacuum pump oils; a preferred compound is tetra-n-octyl silicane ( 4 ) . I n commercial distillations a guided-film falling column still ‘has been described where the preheated distilland is allowed to flow downward in a high vacuum between guide posts, to which it remains attached by surface tension (23). A perforated leaf condenser been patented for use in large centrifugal stills; and thew from these stills is to be re-used in the boiler of the vacuum pump whirh evhausts the still (39).
allurgy (SS),which may be considered to vaporation, and smelting of metals under number of reviews (13, 16, 53). Condenser paper has been coated with zinc in a vacuum chamber by evaporation (17), Figure 1. Metallic lithium has been prepared
Among miscellaneous publications of interest t o the vacuum chemist, are the paper by Whitehurst on process application (69),a comprehensive account of laboratory pumping systems by Sullivan (66),and papers (16, 17) on vacuum calculation and technology. Two excellent critiques (8) of methods of measuring pumping speeds (14) in high vacuum should on no account be missed, A French review ( 4 7 ) has appeared on this subject and comparative measurements have been made on five common gaRes (96). LITERATURE CITED
(1) Apker, L. R., IND. ENQ.CHEM.,40,778-9 (1948). 1. Chem., 21,632-3 (1949).
. Oil Chem. Soc., 26,1045 (1949). (3) Barnitz, E.S., (4) Baxter, J. C;. (to Distillation Products, Ino.), U. 5. Patent 2.464.369 [March 15.1949). (5) Berman, S., Mplniohuk, A. A., and Othmer, D. F., IND. ENQ CElEM., 40,1312-19(1948). (6) Biehler, R. M., Hiokman, K., and Perry, E. S., A n a l . Chem., 21, 638 (1949). (7) Blasco, E., end Vian, A., Combustibles (Zarauoza). 6. No. 33/34. . 55-8 (1946). (8) Blears, J., and Hill, R. W., Rev. Sci. Instruments, 19, 847-51 (1947). (9) Breger, I. A.,A n d Chem., 20,980-2 (1948). (10) Buroh, C . R., Chemistry &Industry, 1949,No.5,p. 87. (11) Carman, P. C., Trans. Faraday SOC.,44,529-36 (1948). (12) Chemistry & Industry, High Vacua Convention supplcmrt~i. 1948,NO,32,pp. 87-8; NO.41,pp. S3-32. (13) Oolumbier, L.,Rev. met., 44,374-9 (1947).
INDUSTRIAL AND ENGINEERING CHEMISTRY
38
(14) Dayton, B. B., INU. ENC.CHEM., 40, 795-803, 1948. (15) Distillation Products, Inc., Brit. Patent 595,096 (Nov. 26, 1947). (16) Dryer, W. B., Chem. Eng., 54, 122-4 (1947). (17) Ibid., 127-31. (18) Dushman, S., Chemistry & Industry, 1948, No. 41, p. 53. (19) Dushman, S., IND.ENC.CHEM., 40, 778 (1948). (20) Dushman, S., “Scientific Foundations of High Vacuum Technique,” p. 882, New York, John Wiley & Sons, 1949. (21) Epstein, S., Proc. Conf. Chem., Chern. Inst. Canada, p. 108-16 (1947). (22) Fawcett, E. W. M.,Chemistry & Industry, 1948, No. 41, pp. 527-33. !23) Ferris, S. W., Lampson, E. R., and Smith, D. M. (to Atlantic Refining Co.), U. S. Patent 2,447,746 (Aug. 24, 1948). (24) Fletcher, G. L., Lasalaco, M., Cobler, J. C., and Hodge, H. C., Anal. Chem., 20, 943-8 (1948). (25) Fluke, D., Reu. SCi. Instruments, 19, 665-6 (1948). (26) Fox, K., Stauffer, R. A., and DiPietro, W. O., Iron Age (Feb. 19, 1948). (27) Godley, P.,Ibid. (April 1, 1948). (28) Gold, iM.H., Anal. Chem., 21, 636-7 (1949). (29) Hickman, K.,, IND.ENG.CHSM.,40, 16-18 (1948). (30) Hickman, K. (to Distillation Products, h e . ) , Ti. 8. Patent 2,455,059 (March 29, 1949). (31) Ibid., 2,465,590 (Nov. 30, 1948). (32) Hobby, A. C., Ibid., 2,443,070 (June 1948). (33) Huebler, J., IND. ENG.CHEY.,40, 825-32 (1948). ENG.CHEM., 40, 778-847 (1948). (34) IND. (35) Jacobs, R. B., Ibid., 791-4. (36) Jacobs, R. B., and Kappf, S. E., Ibid., 842-5. (37) Jaeckel, R., and Oetien, G. W., Chsmie-Ingenieur Technick, 21, 169-76 (1949).
PACED
by symposia on drying in the Ketherlands, Great BritainL,and the United States in the past year, the quantity and, in general, the quality of literature on the unit operation oFdrying increased markedly. A number of fundamental investigations were reported as well as the usual number of descriptive and review articles. Because of this increase i t was impossible to cover the literature in this short review article as thoroughly as it has been covered in past years. Only about 35% of the available literature is discussed although every effort was made to cover all of the important developments. For those people who are interested. a, list of the articles on drvine. not covered by this review, has been prepared and filed with the American Documentation Institute. I
Y l
INFRARED DRYING
Once again this method of drying, which employs radiant energy of the infrared wave length for supplying heat to the material being dried, received, in number of words printed, greater attention than any other drying method. Most of the literature was, however, descriptive and still posed the same arguments of: (A) convection against radiant heat drying; (B) gas-fired against electrical installations; and (C) short against long wave-length radiation. It is becoming more generally conceded, however, that except for paints, other surface coatings, and some specialty items, the principal role of infrared energy will be in assisting or boosting the capacity of other drying methods. It is particularly advantageous to combine convection and radiation drying in a single unit. Poeschmann (161) and Malins (140) presented general reviews of the mechanism of radiant heat transfer and some of the
Vol. 42, No. 1
(38) Kraft, W . W., IND. ENG.CHEM.? 40,807-20 (1948). (39) Laurent, P., and Duhavel, M. J., Conapt. rend., 225, 674-6 (1947). (40) Louis, M., Rev. inst. franq pQtrole et A n n . combustibles liquiderr, 3, 192-8 (1948). (41) Madorsky, S . L., and Straus, S.,IND.ENG.CHEY.,40, 848-53 (1948). (42) Mellen, G. L., Ibid., 40, 787-90 (1948). (43) Morse, Richard, Chemistry & Industry, 1948, No. 41, 13-18. 40, 783-6 (1948). (44) Normand, C. E., IND.ENG.CHEM., (45) Olifant, M. L. E., Chemistry & Industry, 1949, No. 6, p. 8h (46) Rose, A., Anal. Chem., 21, 81-4 (1949). (47) Roy-Pochon, C., L e Vide, 2, 333-48 (1947). (48) Sohroeder, A. L., and Colton, E . H., IND.ENG.CHEY.,40, 803-7 (1948). (49) Schroedes, A. L., and Schwartz, H. W., Chem. Eng. Progress 45, 370-6 (1949). (50) Schwartr, €1.w., IND. ENG.CHEM., 40, 2028-33 (1948). (51) Shaler, A. J., and Wolf, W., Ibid., 838-42. (52) Stauffer, R. A., Am. Inst. Mining M e t . Engrs., Tech. Pub 2268, 1-10 (1949). (53) Stauffer, R. A., Chemistry & Industry, 1948, No. 41, pp. S19-26. (54) Stauffer, R. A., Fox, K., and DiPietro, W. O., IND.ENG.CHEM., 40, 820-5 (1948). (55) Sullivan, H. M., Rev. Sci. Instruments, 19$1-15 (1948). (56) Swallow, F. C., and Gourlay, F. J., Chemistry & Industry, 1948, NO.41, pp. 59-12. (57) Tucker, W . H., and Sherwood, T. R.,IND.ENG.CHEM.,40, 832-8 (1948). (58) Weingartner, H. C., Ibid., 40,780-2 (1948). (59) Whitehurst, B. W., Chem. E-ng.. 54, 98 -102 (1947).
RECEIVED October 10, 1949.
general applications. Other general articles on electric infrared heating and drying applications were published by Goodell (92), Dume (Yd), and SIanders (141). Factors influencing electric infrared tunnel design ($5)and safety precautions ( 1 6 ) have been discussed. Perhaps two of the best papers discussed factors inkluericing the infrared drying of textiles. One of these by Paul and Wilhelm (159) reports the results of a study of the effects of air humidity, velocity, and temperature, intensity of radiant eneigyt sample thickness, and optical properties of the material dricd on the drying of woven and matted wool felts, woven wool crepe. and absorbent cotton batting. The results of this study confirmed the results of other workers in the field-namely, that the mechanism of drying by infrared radiation is similar to that of convection drying. Some penetration of infrared rays into the textile samples was noted. Complementing this investigation was another by Wilhelm and Smith ($88) in which the transmittance, reflectance, and absorptance of near infrared radiation by textile materials was studied. Factors influencing these properties were quantitatively evaluated and theoretical relations were developed. Dyes had a pronounced effect on the transmittance. Casey and Feil(57) presented codt information for the infritred drying of textiles based on actual installations and compared these costs with the cost by other drying methods. The advantages of predrying textiles and paper with gas infrared heaters were outlined by Van Kampen ($18). Garland (85) claimed that gas-fired infrared units are an inexpensive means for increasing the capacity of existing paper dryers if they are installed a t the wet end. The vast is said to be much less than electric infrared
