Tank-Vertical Leaf Filters

For more efficient leaf cleaning, horizontal tank-vertical leaf filters are made with various types of movable sluices. 

FIGURE 22.32 Vertical tank vertical leaf filter. 

FIGURE 58.4 Vertical tank, vertical leaf filter. (From Shirato, M. et al.. Filtration—Principles and Practice, eds. M.J. Matteson and C. Orr, Marcel Dekker, New York, pp. 299-423, 1987. With permission.)... 

Monel and lined carbon steel are standard materials of construction for filter vessels. Linings are similar to those used in primary filters. Figure 7.60 shows a typical vertical-tank vertical-leaf filter. The stream to be filtered enters the body of the tank. A bottom connection is shown, but there are other options. The leaves are arranged vertically, and flow is from the outside to the inside of the leaves. Filtrate collects in a pipe at the bottom this also serves as support for the filter elements. The tank also has drain, vent, and compressed air connections. The detail shows one type of assembly that can simply be lifted from the effluent pipe. O-rings supply the seals. 

Pressure-vessel leaf filters (a) vertical-tank, vertical-leaf filter, and (b) horizontal-leaf filter. 

Vertical-tank, vertical-leaf filters (Figure 12.6)... 

Pressure leaf filters are supplied in a wide range of size and materials of construction. One typical design is the Verti-jet unit with a vertical tank and vertical leaf filter, as shown in Figure 7.12, with rectangular leaves mounted individually but connected to a common outlet manifold. For sluice cleaning either a stationary or oscillating jet system... 

Various filter designs are available to the industry, including plate and frame filter presses, horizontal tank/ vertical leaf pressure filters with retractable bundles or shells, and vertical tank/vertical leaf pressure filters. The latter (Figure 29) has been accepted by the industry as perhaps the best overall choice in terms of price, performance, space requirements, and ease of automation. Filter sizes up to 85-m filter area/filter are available with this model. However, the horizontal tank/vertical leaf model with either retractable bundle or retractable shell also has its proponents. Commonly, a major factor in deciding on this type filter is the fact that these units are available in sizes up to 200-m filter area/filter. 

Horizontal Tank-Vertical Leaf ("H" Style) Filters... 

In comparison with nutsche filters, leaf filters provide more filtration area in the same volume of a pressure vessel. They are more suitable for handling larger quantities of slurry. Leaf filters can be subdivided into four classes in accord with the vertical or horizontal position of the tanks and leaves. In Figures 22.32 and 22.33, vertical leaves are shown in vertical and horizontal tanks. For vertical leaf filters, to prevent cake dropping, the cake thickness is normally restricted to 3.5 to 4.0... 

Vertical tank with vertical leaf filters i.e., Niagara, Angola, and Pronto. 

Pressure Leaf Filters Sometimes called tank filters, they consist of flat filtering elements (leaves) supported in a pressure shell. The leaves are circ ilar, arc-sided, or rectangular, and they have filtering surfaces on both faces. The shell is a cylindrical or conical tank. Its axis may be horizontal or vertical, and the filter type is described by its shell axis orientation. 

Vertical pre.s.sure leaf filters. These filters have vertical, paraUel, rec tangular leaves mounted in an upright cylindrical pressure tank. The leaves usually are of such different widths as to aUowthem to conform to the curvature of the tank and to fill it without waste space. The leaves often rest on a filtrate manifold, the connec tion being sealed by an O ring, so that they can be lifted individuaUy from the top of the fil-... 

This filter has leaves, or tubes, arranged vertically in an open tank, and connected to a discharge manifold. Liquid is drawn through the filter elements by a pump coimected to the discharge manifold. Vacuum leaf filters have advantages of low cost (no pressure vessel) and ease of inspection. 

Sheli-and-leaf filters. For filtering under higher pressures than are possible in a plate-and-frame press, to economize on labor, or where more effectivv washing of tlie cake is necessary, a shell-and-leaf filter may be used. In the horizontal-tank design shown in Fig. 30.6 a set of vertical leaves is held on a retractable rack. The... 

A tank-tube filter (Figure 58.7) is essentially the same as vertical-leaf type, except that hollow tubular elements are mounted... 

Many types of filter are supplied for this sort of operation. In chlor-alkali brine treatment, the two most frequently encountered are the pressure leaf filter and the candle filter. Both types are capable of removing submicron particles and producing a filtrate with less than 1 ppm of suspended solids. A leaf filter, as the name implies, contains a number of thin, flat elements that are active on both sides. In chlor-alkali brine plants, the leaves normally are suspended vertically in a tank. The tank may be horizontal, in which case the leaves are circles or rounded squares, or vertical, in which case the leaves are approximately rectangular and of different widths. 

A candle filter contains a number of cylindrical elements in a vertical tank, using materials of construction similar to those used in leaf filters. The elements can be built up, in modules similar to those used in mist eliminators (Section 9.1.5), or they can be solid cylinders made of carbon or a ceramic. The latter are porous, with walls about... 

Figure 3. Details of a typical vertical leaf pressure filter with vertical tank orientation.

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