January 1948
INDUSTRIAL AND ENGINEERING CHEMISTRY
(6) Bergstrom, It. E., and Lientz, J. It., Paper Trade J . , 125,No.1, 42 (1947). (7) Boelter, L. M. K., Gordon, H. S., and Griffen, J. R., IND. ENG. CHBM.,38,596 (1946). (8) Burke, J. P., and Mantius, E., Chem. Eng. Progress, 43, 237 (1947). (9) Chambers, F.S., and Peterson, R. F., Ibid., 43,219 (1947). (10) Delgado, 5. V.,Intern. Sugar J., 48,236 (1946). (11) Edling, G.,Pulp & Paper Ind., 19,No. 12,58 (1946). (12) Ernst, R.C.,U.S. Patent 2,403,174(July 2, 1946). (13) Flamant, A. C., Chalezir et ind., 28,8 (1947). (14) Foley, R.B., Trans. Am. Soc. Mech. Engrs., 69, 101 (1947). (15) Ford, C.E., Chem. Eng., 54,No.2, 132 (1947). (16) Fricke, G. A., Combustion, 17,No. 10,39 (1946). (17) GonsAlez Maiz, J. C., Intern. Sugar J . , 48,150 (1946). (18) Hedin, C. B.,Swedish Patent 113,423(Mar. 13,1945). (19) Hughes, J. S., U. S. Patent 2,384,747(Sept. 11, 1945). (20) Impapliazzo, A. M., Mech. Eng., 69,387 (1947). (21) Ireland, M. L., Trans. SOC.Naval Architects and Marine Engrs., 53.38 (1945). (22) Karlberg,‘ R.,Svensk Papperstidn., 49,412 (1946). (23) Kats, W., Chem. A p p . , 28,87(1941). (24) Larsen, R. H.,U. S. Patent 2,412,276(Dec. 10,1946). (25) Lee, C. A.,Chem. Eng., 53,No. 8 , 128 (1946).
25
(26) Lindquist, B. O.,Swedish Patent 113,680(Apr. 3 , 1945). (27) Loumiet, J., Intern. Sugar J., 48, 150 (1940). (28) Lur6, M.Yu., Izvestiya V T I , 15,No.3, 4 (1946). (29) McIntosh, W., Puper Trade J . , 123,No. 15,180 (1946). (30) Mujica, A. C., Cuba, 19,241 (1945). (31) Nyman, C., Svensk Papperstidn., 49,73(1946). (32) Nyquist, B. S., Swedish Patent 105,515(Sept. 15, 1942). (33) O’Connell, H. E., and Pettyjohn, E. S., Trans. Am. Inst. Chem. Engrs., 42, 795 (1946). (34) Powell, J. A., U. S. Patent 2,398,396(Apr. 16,1946). (35) Powell, 5. T.,Trans. Am. SOC.Mech. Engrs., 68,905 (1946). (36) Rachko, V. A.,J . Tech. Phys. (U.S.S.R.), 16,993 (1946). (37) Ibid., 16,713 (1946). (38) RamBn, T.,Svensk Papperstidn., 49,418 (1946). (39) Schumacher, J. C., Chem. Eng. Progress, 43, 177 (1947). (40) Seavoy, G. E.,Paper Ind. umd Paper World, 27, 1795 (1946). (41) Sillen, L. G., Svensk Papperstidn., 49,387 (1946). (42) Ulfsparre, S., Ibid., 49,383 (1946). (43) Ulmer, R.C., Power Plant Engr., 51, No. 1, 108 (1947). (44) Wiklund, O.,Socker Handl., 2 , 245 (1946). (45) Williamson, W. R.,U. S. Patent 2,392,893(Jan. 15, 1946). (46) Worthen, E.P., and Fox, B., Ibid., 2,384,226(Sept. 4,1945). RECEIVED November 28, 1947.
F ILTRATION OF KANSAS, LAWRENCE, KANS.
F
ILTRATION work of which published accounts have appeared during the past year reflects a return to a rate of development and application characteristic of peacetime industry, notwithstanding the occmional reports of war-born activities which continue to be divulged. The effects of the war are still noticeable, however; the fact that the majority of the researches, inventions, and industrial applications described originated on this continent may be attributed in large part to an economy, productivity, and academic continuity relatively less disturbed by the war here than in other parts of the world. It is encouraging that this year has brought an increase in scientific and technical publications from Europe and Eurasia, an increase which we trust will continue. The scope of this review, like that of last year’s, is the field of conventional filtration, excluding sedimentary liquid-solid separations (sedimentation, elutriation, centrifugation) and gas clarification. A few articles unintentionalIy omitted from the last review are included. Completeness of coverage is not claimed; in general, the items reported are those believed to be of broadest interest or those contributing quantitative information. Theory. The importrtncc of porosity in determining the permeability of a filter cake has again been declared. Following the suggestion of Ruth’s earliest papers, Belkin (10) presented a form of the filtration equation involving cake porosity. His equation includes a term which characterizes compressibility and another term which is a function of the specific cake resistance, but it does not attempt tto define the effect of solid particle size. Reevcs (61) pointed out that, since filtration rate is inversely proportional to filtrate viscosity, a viscous liquid may be diluted advantageously with a low viscosity solvent before filtration. When the high viscosity inatcrial is the desired product, however, continued dilution ultimatcly bccomes uneconomical. Reeves dcrived the theoretical optimum degree of dilution by using an empirical relation between the viscosities of the two liquids involved and the composition of the mixture. He showed that his theoretical optimum rtgrccd well with values determined experi-
mentally. This method is applicable only when dilution of the filtrate is permissible. Viscose filtration and the accompanying problem of filter medium plugging have been approached theoretically by Bergek and Ouchterlony (IS). These investigators ascribed the plugging of the filter medium in part to the deterioration of xanthate aggregates because of the shearing stress encountered, and they related plugging quantitatively to the structure and concentration of the dispersed cellulosic particles. The most recent attack of filtration theory is that of Brownell and Kate (18). Only the first of three installments of their paper had been published a t the time this review was prepared, however; a report of their work will be deferred, therefore, until the entire series of articles has appeared. Equipment. The attention of the chemical process and related industries continues to focus on rotary vacuum filters. Semiworks machines of this type have been described in both British (9) and American (36) use, the lat,ter by Hignett in connection with a pilot plant for the extraction of aluminum from clay. Hignett presented operating data for two %foot drum filters but failed to state cake thickness and final moisture content. RRck (60) summarized the performance of a B-foot-diameter by 4-foot-face drum filter which dewaters finely ground fluorspar from an initial concentration of 60-65y0 solids to a final moisture content of S-lO%. Klein, McCall, and Liente (49) related a method of washing paper pulp countercurrently in five stages by means of three rotary vacuum filters, two of which had two sets of washing sprays and dual filtrate receiving lines. These investigators studied the effects of washing rate, quantity of wash, and pulp type. They reported handlingcapacity figures. Talmud and Khazin (67) discussed various types of equipment, including vacuum filters, suitable for filtering alumina suspensions. Peterson and Peterson (67) modified the double-drum filter to invent a truly continuous precoat filter. The precoat is picked up from tanks at the bottom of the drums (as in ordinary vacuum filtration), while the slurry is applied at the top of the drums from a slurry pool contained in the pinch between the cylinders.
26
INDUSTRIAL AND ENGINEERING CHEMISTRY Modern aand-and-gravel gravity water filters were the subject
of a paper by Holloway (37). Data for the first year of operation of these 196-square-foot filters were given, but unfortunately the fluid head under which they operated was not stated. I n the way of new equipment, McGovern and Dickerman (47) described the Finkh screen, used for deknotting and cleaning wood pulp in Germany. Kew inventions of more general process use include a filter press (9) comprising wedge-shaped plates and frames, and a horizontal-plate sand filter ( 5 6 ) designed for handling yeast. A white-water clarifying device known as the Marx filter has been described ( 1 1 ) . The term is a misnomer, as the “filter” is actually a continuous sedimentation tank. Clarifying filters adaptable for oil purification have been classified by Corrigan (26) as mechanical (strainers for removing gross particles), absorbent (micronic filters for removing very fine solids), and adsorbent (activated-clay filters which adsorb certain soluble constituents); as full-flow (all the oil circulating through the filter in series with the engine) and by-pass (a portion of the oil passing through the filter, which is in parallel with the engine). Nutt (53) described methods and precautions to be followed in using such filters for Diesel lubricant conditioning; his paper, an excellent and thorough one, was later reviewed briefly by Nelson (50), who emphasized the danger of removing addition agents from additive-type oils if they are circulated through an adsorbent filter. New modifications of clarifying filters include absorbent-type cartridges (46, 5 2 ) , line strainers (40, 75), a fabric-covered cylindrical element ( 1 7 ) , and a filter equipped with a manual cleaning comb (70)for scraping away accumulated solids. Bliss (16) presented valuable up-to-date estimates of the first cost of plate-and-frame and recessed-plate filter presses made of various materials, of Sweetland pressure filters, and of Oliver vacuum filters. He gave also high-spot figures for filter accessories. Miller (48)reviewed briefly filtration equipment advances in America for 1946-47. Methods. A number of investigators have directed their efforts toward developing or improving methods of using fdters. Schnacky (64) devised a means of controlling a constant-rate pressure filtration a t precisely constant filtrate discharge rates, allowing for gradual displacement of the prefilt retention volume by the accumulating cake. Morse (49)adapted a vacuum leaf to the removal and dewatering of froth directly from the top of a flotation cell. Booth (16) patented a backwashing technique in which filtrate rises into an accumulation chamber, trapping and compressing air which subsequently provides the backwashing driving force. A Dutch patent (64) described a method of introducing the prefilt directly into the center of a mass of sand serving as the filter medium. Cavanaugh (20) worked out a filtering cycle in an agitated nutsche which permits coarse particles to settle onto the filtering surface fist to provide a more permeable cake. The cake may be reslurried on the filter for thorough washing. Ballou ( 7 ) described a method of washing the cake in a Sweetland press for maximum sugar sirup recovery. Two authors have contributed information on the preconditioning of slurries to improve filtration. Hay (55)evaluated the effect of colloidal silica in water flocculation, reporting that high filtration rates (3-6 gallotis per square foot per minute) resulted during both hot and cold weather, with good clarity of filtrate. Of greater interest to process engineers, perhaps, is Losee’s report (45) that a O.OOl-O.002% agar-agar solution will convert slimy calcium sulfate into a readily filterable precipitate. Pugh (59) announced the formation of a research group in Britain to study methods and mechanics of water filtration. Clark @ I ) wrote of a successful training program for new water filtration-plant operators; such a program might be adopted to advantage by chemical process plants, particularly those em-
Vol. 40, No. 1
ploying Sweetland presses and other filters requiring close, skilled attention from the operator. FILTERMEDIA. No new synthetic polymeric fabrics have been introduced as filter media during the past year. A patent (62) has issued, however, which claims a synthetic textile material comprising a copolymer of a vinvl halide and acrylonitrile, said to be dimensionally stable a t 100” C. Such a material would have chemical inertness equal to or greater than that of Vinyon and would extend the operating temperature range of the latter material. It is believed that efforts are being made to develop this new fabric. Of the synthetic textiles now in industrial use, Saran has been discussed by Fetter (29), who lists as its advantages its inertness, its high tensile strength, and its abrasion resistance; its disadvantages are its shrinkage above 150” F., its loss of tensile strength at 200’ F., its ease of plugging and bleeding (it is woven from monofils), and its cost. Karslo (41)recommended a cement consisting of Vinyon dissolved in ethylene dichloride for use in patching Vinyon filter cloths. Holes to match the filter-press ports may be cut in filter fabrics accurately, quickly, and cleanly by use of a die which is placed in the press port. Such a die has been described and pictured (4). A fabriclike medium made from a wire screen coated with a pile of flocking fibers has been disclosed by Ferrante (38). A new design of screen plate for cleaning wood-pulp suspensions was the subject of a patent issued to Orton (55). Some asbestos filter pads have the ability to remove bacteria as well a s macro particles; Epstein (26) has proposed a test procedure for determining the bacteria-removing effectiveness of such media. An untried medium should be so tested before it is accepted as a bacterial filter. Granular filter media, as might be expected, seem to have found no new uses in chemical industry. For water clarification, however, Anthrafilt (sized anthracite) continues to displace sand (5). Billings (14) and Gurney (SI) have confirmed the earlier reports of advantages sufficiently great to justify the price of Anthrafilt (140% of that of sand). The material appears to be under study in Russia as a fdter medium (39). Sand, nevertheless, is still widely used in water filters. Strickland (66) has pointed out the undesirability of allowing sand particles to become heavily coated with scale and has recommended a cleaning procedure which employs sodium hydroxide. An instance of the use of a granular medium for sugar clarification has been related by Wickenden ( 7 l ) , who described a charcoal bed which simultaneously clarifies and decolorizes sirup. The process reported is said to be particularly effective in utilizing the full adsorptive capacity of the charcoal. An interesting new line filter for water (65)consists of a rotating cylindrical shell filled with balls, the axis of the shell being parallel to the line in which it is placed. The shell is removable for servicing. The advantages of this device are not apparent. Filter Aids. Papers of the past year which have discussed filter aids have all been limited to a consideration of diatomaceous silica. Bentley ( l a ) reported that kieselguhr has made feasible the filtration of unfermented peach pulp, a material which filters slowly and to a very wet cake without filter aid. Halvorsen (3‘4) described the application of diatomaceous earth t o the clarification of paper-mill waters by means of a continuous vacuum precoat filter. Although the conclusion that a completely closed water system can result is difficult to accept, Halvorsen’s report nevertheless is an interesting account of considerable value in that it records data from actual plant filtrations. The use of kieselguhr in filtering low grade sugar sirups (51) and potable water (6), already the subject of several papers, has been discussed further. Jones and Brady (S9) found that diatomaceous silica will remove cercariae from water; the removal was quantitative for the coarsest as well as the finest grade of filter aid. To deposit a uniform, satisfactory precoat of filter aid requires
January 1948
v
INDUSTRIAL AND ENGINEERING CHEMISTRY
a uniform slurry, not always easily obtainable when a nonaqueous solvent must be used. Kollenberg and Peet (43) devised a successful method of precoating from a hydrocarbon slurry of kieselguhr: a small amount of alkali metal hydroxide added to the slurry produces the desired degree of dispersion, A readable general description of diatomaceous silica filter aids (24) and of their possible uses, and a manual (26)outlining in detail a laboratory procedure for selecting the type and quantity of filter aid to be used have been prepared by one of the vendors. New deposits of diatomaceous earth have been discovered in Texas (l and ? in Turkey ‘) (1). Miscellaneous Dewatering Methods Related to Filtration. A few papers have reported the separation of solids from liquids by methods outside the field of strict filtration, but related to it. For example, clay which cannot be filtered economically sometimes can be dewatered electrophoretically. Fisher and Peck (30)have developed for this application a continuous catephoretic drum resembling a rotating drum filter. Gurnham and Masson (8.2) studied the expression of liquids from fibrous materials under various conditions of compressive stress and sample size. As a result of their study they formulated a correlation in terms of the applied pressure and the resulting compressed volume of the sample. Scale-up data are needed to extend the usefulness of their correlation. Equipment for the exhaustion of beet slices (23)and for the continuous washing and dewatering of kraft pulp (19) by expression has been described by other investigators. A new continuous slurry thickener has been patented by Teale (68). This device has horizontal plates and frames, with filtrate removal occurring only from one face of the frame. The drainage plate is undulated for the stated purpose of increasing turbulence in the slurry chamber. Laboratory Apparatus and Methods. A few modifications of filtration equipment for the analytical and chemical research laboratory have been described. These include a small vacuum decanter involving a hypodermic needle (8),-an all-glass design lor micro- and semimicrofiltration ($8), end an ingenious vacuum filter (63) deriving its source of vacuum from its own receiver, from which all the air has been expelled by boiling it in water or the filtrate from a preceding determination. There has been announced ( 9 ) a reagent said to prevent the creep of analytical precipitates along a filter paper. Wise (7%) has reported a new technique for filtering lignin during its determination. Plumier (68) gave directions for the ultrafiltration of iron from blood, and Trautmann (69) observed the partial retention of dissolved crystalloids on an ultrafiltration membrane. Slight reduction in the concentration of potassium permanganate in aqueous solution results from filtering the solution through paper or cotton batting (caused by adsorption), but the losses are not great enough to invalidate the method (44). Conclusion. The past year has brought few advances in filtration theory or the evolution of new equipment designs. It has seen the publication of some semiworks and plant data, most of which would be more valuable if they were more detailed. It is hoped that universities, vendors of filtration equipment, and process engineers will continue to publish the quantitative results of investigations intended to correlate filtration theory with field practice. LITERATURE CITED
(1) Altini, E., and Iruak, L It., Rev facullb sci. univ. Istaribul, B I I , NO. 2, 131-4 (1916:. (2) Anonymous, Chem. A g e (London), 56,524-5 (19471. (3) Anonymous, Chem. Inds., 59,546 (1946). (4) Ibid., 60,538 (1947). (5) Anonymous, Paper Trade J., 125,No.17,14 (1947). (6) Applebauin, S.B . Water R. Sewage Works, 93,308-10 (1946). (7) Ballou, F.W., Sugar, 41,No. 11,30(1946). (8) Barker, N.A., Pharm. J . , 158,11 (1947). (9) Barnett, I,. S.,U. S.Patent 2,418,153(Apr. 1,1947). (10) Belkm, -4. G., Khim.Prom.. 1946,No. 7/8,10-14.
27
(11) Benson, C. A.,and Brakewood, H. E., Paper Trade J., 124,No. 17,72-4 (1947). (12) Bentley, D. S.,Food Inds., 19,1359-62,1470 (1947). (13) Bergek, T., and Ouchterlony, T., Svensk Popperstidn., 49,470-83 (1946). (14) Billings, L. C., Southwest Water Works J., 28, No. 3, 18-20 (1946). (15) Bliss, H., Chem. Eng., 54,No. 5,131-2 (1947). (16) Booth, G.M., U. 5. Patent 2,423,172(July 1, 1947). (17) Briggs, S.W., Zbid., 2,420,414 (May 13,1947). (18) Brownell, L. E., and Katz, D. L., Chem. Eng. Progress, 43,53748 (1947). (19) Brumley, G. W., Paper Trade J.,124,No. 18,334 (1947). (20) Cavanaugh, R. M., U. 8. Patent 2,404,215(July 16,1946). (21) Clark, A. E., Water & Sewage Works, 93,311-12(1946). (22) Corrigan, B., Iron Age, 159,No. 14,56-62(1947). (23) Devos, P., Bull. assoc. chim., 63,196-201 (1946). (24) Dicalite Co., “Dicalite Filteraids,” Bull. B-11,1946. (25) Dicalite Co. “Instruction Manual Bomb Filter Filtration Tests,” 1945. (26) Epstein, S.S.,FoodZnds., 19,1070-1,1168 (1947). (27) Evans, G. L., Univ. Texas Pub. 4301,239-43(1946). (Aug. 5,1947). (28) Ferrante, J., U.S. Patent 2,425,235 (29) Fetter, E. C., C h m . Eng., 54,No. 2,129 (1947). (30) Fisher, H. F., and Peck, E. C., U. S. Patent 2,406,820 (Sept. 3, (1946). (31) Gurney, W. B., Proc. 9th Ann. Short Course for Water & Sewage Plant Superintendents and Operators (1946),Eng. Ezpt. Sta. Bull. Series 10,La. State Univ.-Agr. & Mech. College, pp. 718 (1947). (32) Gurnham, C. F.,and Masson, H. J., IND. ENG.CHEM.,38,130915 (1946). (33) Gurvich, 8.M., Elek. Stantsii, 17,No. 8 , 27-30 (1946). (34) Halvorsen, 0.G., Paper Trade J., 125,No. 18,37-41 (1947). (35) Hay, H.R., Water & S w a g e Works, 93,353-8,479-82(1946). (36) Hignett, T.P., IND.ENG.CHEM.,39,1057-8 (1947). (37) Holloway, H.F., J. Am. Water Works Assoc.. 38,361-8 (1947). (38) Hudswell, F.,Metallurgia, 35,50 (1946). (39) Jones, M. F.,and Brady, F. J., U.S. Pub. Health Repts., 61, 1538-43 (1946). (40) Juhasz, S.,U.S. Patent 2,424,932 (July 29,1947). (41) Karslo, J., Chem. Eng., 54,No. 5,156-7 (1947). (42) Klein, M., McCall, F. S., and Lientz, J. R., Paper Trade J., 124, NO.5,44-9 (1947). (43) Kollenberg, C. H., and Peet, N. P., U. 8. Patent 2,423,780(July 8,1947). (44) Korabel’skii, P. N., Farmatsiya, 9,No. 1,23-6 (1946). (46) Losee, E. M., Can. Chem. Process Inds., 30, No. 11,90 (1946). (46) McCann, C. S.,U. S. Patent 2,427,733(Sept. 23,1947). (47) McGovern, J. N.,and Dickerman, G. K., Paper Trade J . , 124, No. 2,18T (1947). (48) Miller, S.A., Chem. Inds., 61, 412-13 (1947). (49) Morse, A. R., U. S. Patent 2,411,288 (Nov. 19,1946). (50) Nelson, J. A,, Power Plant Eng., 51, No.4,122-6 (1947). (51) Nelson, W.J., Food Inds., 18,1852-3 (1946). (52) Newman, W. J., U. S. Patent 2,413,991 (Jan. 7,1947). (53) Nutt, H. V., S A E Journal, 52,573-85,608 (1944). (54) N.V. de Bataafsche Petroleum Maatschappij, Dutch Paten 58,555(Dec. 16,1946). (55) Orton, S.T., Jr., U. S. Patent 2,419,155(April 15,1947). (56) Perov, S.P., Russian Patent 65,999(Mar. 31, 1946). (57) Peterson, C. L., and Peterson, C. J., U. S. Patent 2,403,03 (July 2,1946). (58) Plumier, M., Compt. rend. soc. b i d , 140,803-5 (1940). (59) Pugh, N. J., J . Inst. Water Engrs., 1, 69-77 (1947). (60) Reck, W.H., Deco Trefoil, 11,No. 5,8-9 (1947). (61) Reeves, E.J.,IND. ENG.CHEM.,39,203-6(1947). (62) Rugeley, E. W., Feild, T. A., Jr., and Petrokubi, J. L., U. S Patent 2,420,565(May 13,1947). (63) Schlumbohm, P., ZbiQ., 2,409,226 (Oct. 15,1946). (64) Schnacky, J.F., Chem. Eng., 54,No. 9,138(1947). (65) Shandor, M. E., and Donath, R., U. S. Patent 2,418,989(Apr. 15,1947). (66) Strickland G. H., Eng. mtd Contract Record, 60,No. 3,78,80, 82 (1947). (67) Talmud, I. L.,and Khazin, L. G., Tsvetnye Metal., 19,No. 4,2532 (1946). (68) Teale, H. A., U. S. Patent 2,407,303(Sept. 10,1946). (69) Trautmann, S., Compt. rend. soc. biol., 140,889-90 (1946). and Stokes, E. A., U. S. Patent 2,408,130(Sept. (70) Vokes, C. G., 24,1946). (71) Wickenden, L., Sugar, 42,No. 1,32-5 (1947). (72) Wise, L. E., Chemist-Analyst, 36,8-9 (1947). (73) Zech, A., U.S. Patent 2,427,320(Sept. 9,1947). RECEIVED November 10, 1947.
