Vertical leaf pressure filter

Vertical Pressure Leaf Filters are essentially the same as Horizontal Plate Filters except for the orientation of the filter elements which are vertical rather than horizontal. They are applied for the polishing slurries with very lov solids content of 1-5% or for cake filtration with a solids concentration of 20-25%. As with the horizontal plate filter the vertical leaf filters are also well suited for handling flammable, toxic and corrosive materials since they are autoclaved and designed for hazardous environments when high pressure and safe operation are required. Likewise, they may be readily jacketed for applications whenever hot or cold temperatures are to be preserved.The largest leaf filters in horizontal vessels have a filtration area of 300 m and vertical vessels 100 m both designed for an operating pressure of 6 bar. 

The operation of a vertical pressure leaf filter is labor intensive and requires a complex manipulation of valves so present day installations are in most cases fully automated. The operational steps are as follows ... 

Another type of filter in use today is a horizontal (or vertical) pressure leaf filter with a special cake squeezing device. Between each pair of hollow filter leaves is an impermeable flexible diaphragm that can, when inflated, apply pressure on one side of each adjacent leaf. As the cake forms, the pressure on the leaf side is less than on the chamber side. The diaphragms move toward the leaf, compressing the olein from the stearine cake. 

Figure 29. Vertical pressure leaf filter. (Courtesy LFC Lochem B. V.) (This figure is available in full color at http //www.mrw.interscience.wiley.com/biofp.)...

Vertical pressure leaf filters. These filters have vertical, parallel, rectangular leaves mounted in an upright cylindrical pressure tank. The leaves usually are of such different widths as to allow them to conform to the curvature of the tank and to fill it without waste space. The leaves often rest on a filtrate manifold, the connection being sealed by an O ring, so that they can be lifted individually from the top of the bind repair. A scavenger leaf frequently is installed in... 

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. 

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... 

Pressure leaf filters are available with filtering areas of 930 cm2 (1 ft2) (laboratory size) up to about 440 m2 (4734 fir) for vertical filters and 158 m2 (1700 ft2) for horizontal ones. Leaf spacings range from 5 to 15 cm (2 to 6 in) but are seldom less than 7.5 cm (3 in) since 1.3 to 2.5 cm (0.5 to 1 in) should be left open between surfaces. 

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. 

Fabric stretch arises in several types of filter, but the cause can depend on the design and operation of the filter. In filter presses and both vacuum and pressure leaf filters stretch may occur as a result of the vertical pull of heavy filter cakes on the cloth during cake discharge in filter presses the stretch can result in portholes in the cloth being pulled out of alignment with the holes... 

The OMD leaf filter (Stella Meta Filters) is a vertical leaf filter with a mbber diaphragm suspended between the leaves. The cake that forms on the leaves eventually reaches the diaphragm at which point pump pressure is used to inflate the diaphragm and compress the cake. The cake discharge is by vibration. 

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. 

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... 

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... 

Pressure leaf type These units had a much larger filtration area and capacity to hold sludge. The units had a number of stainless steel filter leaves arranged vertically. These had exit nozzles at the bottoms fixed on a manifold which carried the filtered sulfur outside the vessel. 

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