Horizontal tank filter

FIG. 18-119 Cutaway of a horizontal tank filter with dry-cake-discharge features. (United States Filter.)... 

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. 

FIG. 18-118 Horizontal-tank pressure leaf filter designed for dry cake discharge. Sparkler Filter, Inc.)... 

The horizontal plate filter requires attention on a regular basis to safety devices and automation features that accompany modern filters. The space above the filter should have a hoisting device and sufficient headroom to lift the entire disc stack and move it horizontally to a location adjacent to the filter tank. It is recommended to have a special rig that will hold the plate stack for maintenance since the bigger ones may reach a length 3 meters or more. Space must also be allocated for the cover which may be either if it is hinged or removed. 

Backwashing can be by water alone or by an air scour and water. Usually where high volumes of water are encountered a horizontal type is used because the tank length can be increased proportional to the volume. However, horizontal tanks are restricted to lower levels of suspended solids because of limitations in media bed depth. They are also prone to the risk of the underbed shifting, with a consequential decrease in filtering efficiency. 

The feed rate is manually set as required for either pH or reactant stoichiometry control. Soda ash is added to the fourth reactor as sodium makeup. Reactor effluent slurry flows by gravity to the thickener centerwell. Clarified liquor overflows from the thickener to the forward feed hold tank from which it is pumped to the tray tower. A horizontal belt filter is used for further dewatering of the thickener underflow solids. 

Multimedia pressure filters can be vertically or horizontally oriented. Figure 8.7 shows a vertical filter while Figure 8.8 shows a horizontal multimedia pressure filter. Horizontal multimedia filters are separated internally into "tanks" or compartments. Each tank acts as an individual filter. When it is time to backwash one of the tanks, the effluent from the other tanks provides the backwash water. The key in selecting horizontal filters is that the filter should have enough internal tanks so that productivity (required effluent flow rate plus the... 

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... 

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

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... 

The tray filter (Figure 58.6) consists of a series of trays in a horizontal tank open at one end. Each tray is normally drained through an individual outlet to a manifold outside the tank. Piping is arranged so that the liquid may be transferred from the bottom of the tank to the top tray and to the other trays by... 

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

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... 

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