DARCC D A R C O D E P A R T M E N T · A T L A S POWDER C O M P A N Y Dorco General Sales Offices—60 EAST 42nd STREET, NEW YORK 17, N . Y . ATLAS POWDER C O M P A N Y , C A N A D A , LTD., B R A N T F O R D , C A N A D A
WET FEEDING . . . α convenient way to apply Darco to batch processes Feeding Darco in slurry form is widely used in b a t c h process treatment. It has t h e advantage of permitting easier measurement of D a r c o dosage, and reduces dust. T h e diagram illustrates a typical gravity-flow system. Darco is fed through a hopper into the slurry tank, where it is mixed with a predetermined vol ume of water, t o give a slurry of known concentration. A s D a r c o is needed, the required v o l u m e of WAtEB SUPPLY slurry is drawn off to the measuring 1 \ tank, and then transferred into the treatment tank. ^ Ο CARBON SLURRY PREPARATION AND STORAGE TANK
0 SLURRY OUTLET
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is
Mm
α ft
WET FEEDING OF O A R C O . DIAGRAMMATIC LAYOUT OF GRAVITY-OPERATED SYSTEM FOR ADDING DARCO IN SLURRY FORM
AUXILIARY MEASURING TANK
MECHANICALLY DRIVEN AGITATOR IMPURE UQUID
SLURRY
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-TREATMENT TANK
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V O L U M E
32.
NO.
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A commonly used slurry contains one pound of Darco per gallon. This concentration is prepared b y mixing 2,000 pounds of Darco w i t h about 1,800 gallons of water . . . making a total v o l u m e of 2,000 gallons of slurry. Concentrations higher than two pounds of D a r c o per gallon are not ordinarily used, because of diffi culty in agitation a n d transfer. T h e water in t h e slurry, of course, dilutes t h e solution being treated. Suppose, for example, t h a t a final solution should contain 2,000 pounds of solids per 1,000 gallons, and that 50 gallons of slurry are a d d e d during treatment. T o reach t h e required solids concentration, it w o u l d be ad visable t o start with a concentration of 2,000 pounds of solids per 955 gallons. T h e contents of t h e slurry tank should b e continuously agitated t o keep t h e slurry uniform in concen tration. Carbon settles o u t during periods of extended shutdown, and care should b e taken in starting the agitator motor until carbon is again in suspension. Darco's ready wettability, inciden tally, makes slurries easy t o prepare . . . keeps dust t o a minimum.
DECEMBER
6,
1954
Solving α colloid purification problem A problem of how t o purify colloidal sus pensions arose in connection with the filtration of blood plasma extender for military use. The same problem occurs in filtering such materials as pectin, egg albumen and other colloidal solutions, as well as strongly alkaline solutions. In such solutions, finely divided carbon refuses to hang together in clumps, as it normally does—that is the carbon is "pep tized" and it becomes hard t o filter out. Finely divided Darco can still be used in these instances, without resorting to more expensive and less highly adsorptive granular grades. The secret lies in the method of filtration. Instead of add ing Darco to the solution, where it will be peptized, just coat the filter with carbon and pump the solution through it. This way, the solution only contacts the Darco at the filter cake. Further recommendations: Pre-coat the filter with a "tight" diatomaceous earth filter aid, and add a faster filter aid to the solution along with the carbon.
Entrapped air may hinder decolorizing ability It sometimes happens that certain solu tions that are treated with carbon con tain materials sensitive to oxidation. In this case, air entrapped in the carbon may introduce enough oxygen t o cause intensification of color. Although such cases are relatively rare, they can be solved b y removing air from the pores of the carbon particles. The simplest way to do this is to boil Darco in the water or whatever solvent is to be used for 20 to 30 minutes. This displaces nearly all the entrapped oxygen, and greater effectiveness is realized from the carbon.
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