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INDUSTRIAL AND ENGINEERING CHEMISTRY
change. On the other hand, the high cost of filtration, the loss of some of the valuable filtrate during a spool change, and the possibility of char by-passing the filter during a surging flow present difficult problems. PULPFILTER.The No. 1 Kiefer pulp filter consists of a series of cotton pulp pads made similarly to the large pulp filter pads but with a smaller diameter. A large volume can be filtered before it is necessary to repack the filter, its operation is intermittent, it is cheaper to operate than a commercial filter. But this type has several disadvantages: The filter has to be proofed up before bottling operations begin in order to avoid a low-proof product in the bottle; it is difficult to prepare the pulp filter pads; the filter has a tendency to blow out if not packed properly; the liquid remaining in the pads has to be recovered, and there is some loss; and a very high pressure drop occurs as the pads become dirty. STOKEFILTER.This Le Val filter is similar to the larger stone filter previously discussed, except that it is smaller in size. However, it is not possible to backwash the filter on the bottling line because of the dilution factor. No precoat is used on the stones a t this stage of the operation as the stone itself acts as the filtering medium. The stones may be obtained with various permeabilities, depending upon the flow rate and clarity of product desired. Advantages to be cited for this filter are many: The filtration is practically fool-proof; higher flow rates and lower pressure drops are obtained; when the filters become dirty, the flow rate decreases without danger of blowing out the filter; filtration cost is very low; the filter is easily cleaned by backwashing and scrubbing the stone surface; stones have a long life and are available with various permeabilities; no precoat is necessary. But the stones may plug up after long service, and have to be replaced or cleaned by drastic means.
Vol. 34, No. 10
Summary of Bottling Filters
A comparison of the operating data and the relative cost of operation for the bottling filters is shown in Table V. The cost figures were based on materials and labor.
TABLE JT. OPERATING COSTSOR BOTTLING FILTERS Av.
Filter Spool
Pulp
Stone
T o t a l Gal. Filtered 86,000 183,000 185,000
Area Sq. Fd. 5.24
22.3 4.5
gzr Gal.) Min. 30 30
30
Pressure Drop. cost/ LbdSq. In. 1000 Gal., Start 5 18
2
End
.*
34 35
Cents 6.8 4.9 0.6
The cotton spool filter has the lon-est throughput and the highest operating cost. The pulp filter has the largest surface area and a greater pressure drop. The stone filter has the smallest surface area, greatest throughput, highest flow rate, and lowest pressure drop for a clean filter; the stone does not require that the filtering medium be replaced and has the lowest operating cost.
Acknowledgment The writers wish to thank George J. Burcal for the data and arrangement of the pulp filters. They are also indebted to Ramon I. Lindberg and Nelson W, Morley for able assistance in collecting the data, and to the manufacturers of the various types of equipment. PRBBENTED before t h e Division of Industrial Chemistry a t the 103rd Meeting of t h e AMIERICAN CHExIcAL SOCIETY, Memphis, Tenn.
UTILIZATION OF PICKLE LIQUOR F. J. VAN ANTWERPEN 60 East 42nd Street, New York,
Pi. Y.
HE booming production of steel in a wartime United States accentuates an ever present problem to the steel companies-that of successfully disposing of millions of gallons of pickling solution after acid and iron content become unsatisfactory for best efficiency. The acid used most frequently for pickling is sulfuric, the salt thereby produced in solution being ferrous sulfate. These two materials would be the recoverable values; this fact has been the cause of the long delay in the construction of costly treatment plants necessary for the whole recovery program in the steel industry, for iron and sulfuric acid are two of t h e cheapest industrial materials available in the United States. If other recoverable substances of value were present, there would probably be no waste problem. There are niany schemes for the recovery of both of these materials from the waste; but, usually, not until legislation prohibits the dumping of acid in streams do the companies act to eliminate the nuisance. Some steel companies recover copperas for use in pigment manufacture and water and sewage
T
treatment, and others have installed waste treatment plants of their own accord; but by and large the problem is still unsolved. A greatly increased steel production will have the instant effect of making this problem more serious than ever. If no positive program for dealing vdth this waste is forthcoming, v,-ell nigh irreparable damage may be caused by increasing the acid load of the rivers and streams, for although most of the acid load in rivers comes from the drainings of coal mines, the steel mill effluent also carries a considerable portion of the blame. illany programs and plans have been designed to eliminate this headache of the steel industry. One of them, conceived during the depression years, has been operating on a minor scale nhile experiments with building materials made from a recovery product were being made. These experiments are now being concluded and may signal a n expansion of the recovery progress in the steel industry and a n intensive drive to introduce the building materials to the general public.
INDUSTRIAL AND ENGINEERING CHEMISTRY
October, 1942
W A L L O F THE
Monwr
ST.
ANDREWSSCHOOL FOR GIRLSBEINGCONSTRUCTED
OF
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4 X 4 X 8 I N C H FERRON BLOCKS
The building material is known as Ferron (2) and is a development of H. S. Colton and M. J. Rentschler of the Allied Development Corporation (1). At present the only commercial installation using the Colton-Rentschler Ferron process is that of the Sharon Steel Corporation plant. It has been in operation a little over two years and daily treats about 25 tons of pickle liquor. However the building materials which can be made from the recovered product, such as shingles, insulating and plastic board or acoustical facings, are not in quantity production because a market for these substances has not been extensively developed. Consequently, the final shaping steps are not done in the Sharon operations.
Ferron Process Like several other solutions to the pickle liquor problem, neutralization of the acid is the primary reaction. As discharged from the pickling vats, the rejected pickle solution usually has about 17 to 25 per cent ferrous sulfate and from 2 to 7 sulfuric acid. In the Ferron process the dumped pickle liquor is collected in a storage tank large enough to contain several days’ waste. From this storage tank it is pumped to a
CLOSE-UPOF FERROS SHIKGLES USEDON AX ExPERIMENTAL HOUSE( ~ H O W XIN CIRCLE) WHICH IS CONsTRUCTED ENTIRELY FROM FERRON MATERIALS
CARSOF FERRON COMINGFROM
THE
DRYER
rubber-lined agitation kettle of about 2000gallon capacity. Dilution to an acid content of about 2 per cent is made, and a t the same time a filler is added, such as ground newsprint, mbestos, cinders, clay, or wood fiber, amounting to 2-25 per cent by weight of the batch. An alkaline material t o neutralize the acidic constituents is then run into the mix. I n practice this is
INDUSTRIAL AND ENGINEERING CHEMISTRY
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Vol. 34, No. 10
slaked lime made from tated slurry, instead of a low-magnesium limebeing filtered in a platestone. For the Sharon and-frame press, is operations the limestone pumped to the board is usually obtained from press where it is retained t h e S a n d u s k y , Ohio, by a fine wire screen. area. T h e alkaline When the press closes, material, according to the pressure rises to 1500 the covering p a t e n t s , pounds per square inch must be a calcium comand the mater is forced pound, and mention is through the screen. made of the oxide, the After a short retention hydroxide, and the cartime the press opens up, bonate. For best t h e p r e s s e d board is operating conditions preejected, a n d a n o t h e r cipitation ought t o take c y c l e is b e g u n . -411 place a t a temperature o p e r a t i o n s are autoabove 140" F. because matic. Moisture content of the board is about 25 the resulting gel in subsequent operations will per cent, a n d d r y i n g operations are practifilter better. The precipitate obtained is a cally the same as those for the pugged material, mixture of calcium sulwith the exception that fate and iron hydroxide, air drying is often used the latter principally in instead of gas-oven drythe ferrous state. Complete neutralization and ing. The objective of the precipitation in the plant Ferron process is twoequipment takes about fold: to eliminate a serione hour, and the pH of the supernatant and ous waste problem in mother liquor is about 11. steel producing areas and The slurry, about 20 t o produce useful materials from the waste. per cent solids, may now The first objective is well be filtered, as was done in early installations. or realized. T h e l i q u o r sent t o board presses for discharged from the rePRESSFOR MAKINGFERRON PLASTER BOARDFROV THINSLURRY e l i m i n a t i o n of water. covery plant will, it is claimed, in no way conThe filter presses used taminate the streams or are standard plate-andsewers into which it is discharged. The pH is high (about 11), frame fed by plunger pump working at a pressure of about 100 pounds per square inch. The gel filters rapidly but and all iron and heavy metals have been precipitated; considering the origin and processing, it is not strange that bacteria needs considerable pressure t o reduce the cake t o the 50 per are absent. The second objective may well now begin to cent water content considered ideal for the next operation of pugging. After the presses-are opened, the cake drops into be realized as the various weathering tests are completed. a pug mill where it is h o m o g e n i z e d and exPhysical Properties truded in a continuous and Uses block form. This form may be cut into any T h e w e i g h t of t h e finished Ferron will deshape desired or conpend upon the filler and venient for the drying operation which follows. pressure used. The unOvens used in drying filled material will vary according to the ratio of the extruded material are gas-fired a t 300" F. Thin c a l c i u m s u l f a t e and boards are sometimes ferrous hydroxide presair-dried. ent; the patents state that usually such proporThe newer technique tions are 60 per cent calin handling the precipitated slurry calls for cium sulfate and 40 per high-pressure extraction cent ferrous hydroxide. The range of the board of the water on a board press, and this method is produced is controlled also by the pressing and used for production of w a l l b o a r d . The filler extruding, a light pressadded before the lime ing leaving more water in HOUSEBEIXGCONSTRUCTED WITH FERROS (DARK SECTIONS) the undried board and neutralization is wood AND AKOTHERSTANDARD PLASTER BOARDFOR COMPARISOK consequently more air fiber, and the precipi-
a
October, 1942
4
I N D U S T R I A L AWB E ; N G I N E E B I N G C H E M I S T R Y
spaces when dry. Partial drying before pressing is still another technique, used t o obtain hard, dense masses of Ferron; the range of board produced has been from 20 t o 125 pounds per cubic foot. The lighter material is not so strong as the denser but is satisfactory for wallboard and possesses good insulating properties. The remarkable strength of the dense material is utilized for molded objects. The drying operation is necessary for high-strength products since it causes the material to set; without this setting the material would be crumbly. As first formed, the moist cake is green, but drying and oxidation cause a color change to brown, possibly due to the oxidation of the iron products. The modulus of rupture of Ferron sheets used in thin panels for wallboards is low because they need to be pressed lightly to give the porosity necessary for good insulating properties. Yet this same action of light pressing prevents the material from having high strength. This problem has been solved by the chance discovery that the addition of a small amount of a true colloid to the wet mass along with the filler before pressing will greatly increase strength characteristics. For example, 2 per cent of starch will increase rupture strength 300 per cent, and 8 per cent of asphalt emulsion increases strength by 500 per cent. The preferred commercial trer*tment requires the addition of 5 per cent asphalt. Rosin, milk, and waste sulfite liquor all confer the same beneficial properties even though this would seem to be contrary to the result generally expected. The physical reason for this strengthening of the wallboard is not known. The theory is that the colloidal gel structure, being different in size from that of the Ferron, causes an interlacing which produces a much stronger substance. Ferron containing 25 per cent of a filler such as wood fiber and waste straw would have about 50 per cent dead air space by volume due to the porous microscopic structure. The insulating properties of this material are very good. It has an over-all heat transfer coefficient of 0.55 B. t. u. per square foot/ hour/inch/" F. The value for cork is 0.30 and for 85 per cent magnesia is 0.47, so Ferron has rather a good record in this field. The 0.55 heat transfer coefficient is for porous light building board. Heavier building blocks for furnace insulation or heavy construction do not have the same value. A block with a density of 100 pounds per cubic foot has a transfer coefficient of 0.85 B. t. u. per square foot/hour/inch/ " F. Ferron is fireproof and may safely be used up to 900" F.; this limit is raised to 2000" F. when 20 per cent of clay is included. The product may be worked with the usual tools, for it is easily sawed, planed, or drilled. Nails and the like are held firmly; it is noncorrosive, accepts paint and varnish, may be
1141
plastered, and does not burn or decay. It is waterproofed by a coating of a 1-2 per cent solution of sodium silicate, a necessary treatment because Ferron becomes weak from continual soaking or wetting with water. Aside from building materials, one other important market has been opened up in the ceramic industry. If clay and the wet Ferron are mixed in proportions of about 1 t o 1, the resulting mixture may be fired immediately without prior drying. Spalling is eliminated, which is a novel feature in objects formed and subjected to firing without intermediate drying. The resulting "ceramic" is porous to the extent of the Ferron included. I n the proportion cited above, weight reduction would be about 60 per cent. This makes for a much lighter ware with greatly improved heat insulating properties.
costs Preliminary estimates placed costs a t $3 to $4 per ton of Ferron produced. A ton of Ferron represents 500 gallons of pickle liquor in the normal concentration as used in the recovery process, and this makes the estimated cost about $2 per ton of pickle liquor. However, actual figures run higher. A plant treating 25 tons of pickle liquor per day costs $40,000 per year. This is about $4.50 per ton of pickle liquor, or a cost of $9 per ton of Ferron produced. The plastic board which will probably be the chief product as markets develop can be produced a t $6 to $7 per 1000 square feet. This is for a board */g inch thick, 10 inches wide, and 48 inches long. inch thick will be double, or $12 per 1000 Cost for a board square feet. Several houses using the Ferron plastic board have been built, and no serious drawback has been found. The Mount St. Andrews School for Girls a t Willoughby, Ohio, has used Ferron in its auditorium. Shingles have been made from Ferron. As a practical weathering test a small house was constructed on Whisky Island outside Cleveland. Ferron shingles were placed over Ferron sheathing, and Ferron plasterboard was used on the inside. Some interior portions were given finished plaster coatings, others only rough plaster, and some spots were not finished a t all. The weathering tests have been in progress for two winters and no trouble has yet been experienced. Whether or not such building materials find wide acceptance, however, depends upon the steel industry and the marketing policies of the development company.
Literature Cited (1) Colton, H. S., and Rentsohler, M. J., U. S. Patents 2,163,344, 2,154,271, 2,211,593, 2,231,959 (1935) ; 2,240,254 (1939). (2) Hodge, W. W., IND. ENG.CHEM., 31, 1373 (1939).
FILTPJR PRESSING
FERRON
