Vertical vessel leaf 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. 

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

Horizontal Vessel, Vertical Leaf Filters. In a cylindrical vessel with a horizontal axis (Fig. 18), the vertical leaves can be arranged either laterally or longitudinally. The latter, less common, arrangement may be designed as the vertical vessel, vertical leaf filters but mounted horizontally. Its design is suitable for smaller duties and the leaves can be withdrawn individually through the opening end of the vessel. 

Vertical Vessel, Horizontal Leaf Filters. These filters, like all horizontal leaf filters, are advantageous where the flow is intermittent or where thorough cake washing is required. Filtration areas are limited to about 45 m. ... 

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... 

FIGURE 22.33 Horizontal-vessel, vertical-leaf filter. 

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. 

Multi (vertical) element leaf pressure filter, horizontal vessel (Sections... 

One operational problem with these filters is concerned with the disposal of the heel of unfiltered slurry which is still in the vessel at the end of the filtration period. This is particularly troublesome with the vertical-leaf filters because compressed air cannot be used to complete the filtration of this heel... 

In general, the horizontal-vessel, vertical-leaf filters with the leaves arranged laterally can be designed up to filtration areas of 300 m. Cake washing is possible but it must be carried out with caution because there is a danger of the cake falling off. 

Vertical-vessel, horizontal-leaf filters (Figure 12.8)... 

Figure 12.8 A vertical-vessel, horizontal-leaf filter...

Vacuum leaf filters are less common, although cheaper than the pressurized version, because of the lack of a pressure vessel. They consist of an open tank full of the liquid to be filtered, into which the array of vertical leaves is submerged. Vacuum is applied through the filtrate manifold, and cake builds up on the leaves until cake removal becomes due. This kind of filter is mostly used with precoat as a clarifying filter, which is not only cheaper but also more easily inspected and maintained. 

During operation the slurry is pumped under pressure into a vessel that is fitted with a stack of vertical leaves that serve as filter elements. Each leaf has a centrally located neck at its bottom which is inserted into a manifold that collects the filtrate. The leaf is constructed with ribs on both sides to allow free flow of filtrate towards the neck and is covered with coarse mesh screens that support the finer woven metal screens or filter cloth that retain the cake. The space between the leaves may... 

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. 

These units are sometimes described as pressure vessel filters the vessels used to contain the filter dements are cylindrical designs, positioned vertically or horizontally. These vessels operate in batch mode, with filter cycles similar to plate and fimne filters. The variations available in the type of elements (leaf or candle) and its position in the pressure vessel, lead to a large number of available designs [Purchas, 1981], General operating features of pressure vessel filters have been described [Bosley, 1986] these units are considered to be cleaner and more reliable than other pressure filters, provided adequate attention is given to filter cake properties. 

The tank-leaf pressure filter (Figure 50.4) features a number of leaves (filtering elements) suspended within a closed vessel. Common variations involve the arrangement of the tank and leaves into various vertical and horizontal combinations. Vertical tanks normally contain vertical leaves whereas horizontal tanks may have either vertical or horizontal leaves. The leaves are hollow shells fitted with support grids and covered with a metal gauze or woven fabric. They... 

A tank-tube filter (Figure 50.7) is essentially the same as vertieal-leaf type, exeept that hollow tubular elements are mounted in a pressure vessel. This type may be eompetitive with the vertical-leaf type, when a dry-cake diseharge is not required. Filtrate flows through the filtering tubes into a discharge manifold whereas solids deposit outside. The tubes may be made of porous earbon, porous eeramic, plastic, sintered metal. 

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