A Laboratory-Size Leaf-Type Pressure Filter J
J
T. F. CLARK, N. PORGES,
AND
T
The filter case consists of a 11.25-em. (4.5-inch) square tubular section and top and bottom closing plates [1.25 cm. (0.5 inch) thick and 15 cm. (6 inches) square]. The tubular section was made from four plates, each 0.625 X 11.25 X 12.5 em. (0.25 x 4.5 X 5 inches). The short sides of these plates were mitered and welded together with the same metal by means of atomic hydrogen. The top and bottom plates were held in place by eight steel tie rods threaded through the bottom plate and secured by lock nuts. Rubber gaskets a t top and bottom prevented leakage. Three filter-leaf assemblies (Figures 3 and 4) adaptable for either top or bottom drainage provided the actual filtering elements. The square leaf frames with 7.5-em. (3-inch) openings were 1.875 cm. (0.75 inch) thick. The inner edges of the frame were rounded to prevent cutting of the filter cloths. In the top of the frame a hole n-as drilled and tapped from both ends for I/s-inch aluminum tubing to provide means for carrying away the filtrate. (Dimensions x-ith reference to tubing sizes are I. P. S.) The section of tubing within t,he frame (Figure 3) was removable so that top drainage might also be accomplished. Each frame was covered with woven aluminum filter cloth held in place by aluminum retainers, or frame covers, 0.156 cm. (0.0625 inch) thick, the shape of which corresponded to that of the leaf frames. Stainless-steel machine screws and nuts securely held the frame covers and filter cloths to the frames. A header block and manifold assembly provided means for consolidation and discharge of the filtrate. This block was constructed from a piece of 2.5 X 5 em. (1 X 2 inch) aluminum bar stock 15 em. (6 inches) long, fitted with a thin rubber gasket, and bolted to the top plate as shown in Figure 4. Three holes were drilled vertically through the top plate and header block to accommodate the discharge tubes from the filter leaves. Three discharge ports were drilled on one side of t,he block to meet the vertical holes, and lvere tapped for l/s-inch pipe connections to the manifold. The small size of this filter unit necessitated displacement of the end discharge ports to allow sufficient clearance for 0.31-cm. (0.125-inch) aluminum unions. The discharge tubes from the top of the filter leaves extended through the vertical holes in the header block and were secured a t the upper ends by 0.31-cm. (0.125-inch) aluminum pipe caps. Leakage of the filtrate was revented by means of rubber gaskets between the top plate a n l a t e r leaves and by a combination of rubber gaskets and aluminum washers between the pipe caps and header block. A 0.625-cm. (0.25-inch) hole, drilled in the discharge tube a t the position of the discharge port in the header block, permitted the filtrate to pass from the tubes to the manifold. Short aluminum nipples and unions connected the header block to the manifold. Three holes were drilled and tapped for l/B-inch tubing in a section of 1/2-inch aluminum pipe in positions corresponding to
HE need of a small closed filter for laboratory operations !\-as indicated during the studies of pilot-plant scale ( 1 ) and semicontiiiuous ( 3 ) production of gluconic acid by fermentation of glucose solutions. For the purpose of repeated noncontaminateci recovery of mycelia for reuse in mold fermentations, several conditions must be met. The filter must be easily and positively sterilized, prevent the ingress of contaminating organisms, facilitate the return of mycelia to the fermenter, and be constructed of materials which d o not inhibit further activity of the fermenting organism.
FIGURE 1.
ASSEMBLED
1
S. I. IRONOVSKY, Agricultural By-products Laboratory, .imes, Iowa
FILTER READY FOR OPERATIOS
I n general, commercial pressure filters of the leaf type are satisfactory for pilot-plant studies, but the relatively large size of such units is objectionable for laboratory studies where comparatively small quantities of solids are handled. Therefore, for use in conjunction with fermentation studies in small, rotary, aluminum drums ( d ) , a small leaf-type pressure filter was designed and constructed of aluminum a t this laboratory. The selection of material for such a filter, however, depends entirely upon the nature of the substances to be filtered.
Design and Construction The assembled filter and its various component parts are shown in Figures 1 to 4. With the exception of the stainless-steel machine screws and the external tie rods, the filter assembly was fabricated from commercially pure aluminum alloys.
FIGURE2. 75 5
FILTER CASE
AND T O P ASSEMBLY,
SHOWING FILTER LEAVES
