Multi-element candle filter

If filtration takes place at constant pressure then the equations presented for the tube press in Section 6.2.1.3 are also valid for the multi-element candle filter noting that = n,ndh where n, is the total number of candles in the filter. When filtration takes place at variable pressure then it is necessary to impose the pump curve characteristics to relate Ap and q and a numerical solution to equation (6.17) is generally required. For the special case of variable pressure/constant rate filtration with a positive displacement pump 

If the maximum pumping pressure is reached before cake formation is complete then constant pressure filtration occurs when tj (t ),. Over this constant pressure period cake formation continues according to the general 

In the tube press and aU variants of the diaphragm press, elastomeric diaphragms can be inflated at a constant pressure to facilitate compression deiiquoring of the filter cake(s). This consolidation is most frequently performed immediately following cake formation to remove unwanted liquors and/or improve the distribution of cake solids to aid subsequent cake washing and/or gas deiiquoring. In a typical press the duration of cake compression equals the total filtration time such that = t g. 

Noting that the mass of solids in the cake remains constant, i.e. where the subscript pf indicates the value at the end of the previous phase in the cycle, the cake properties during compression deiiquoring are related to the compression pressure (ApJ by 

Noting the value of given above, in all variants of the diaphragm press the 

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For filter presses, the horizontal diaphragm press and the vertical, double sided press the active filter area during deliquoring = Af/2. For the tube press this area is approximated by A nh(d + and for the multi-element candle filter A = nh(d + Lp )n,. In all other batch filters and presses A = Af. With and M known, the other time dependent parameters are given by... 

Multi-element candle Multi-element leaf Plate frame press Precoat Nutsche and multielement leaf Precoat plate frame press Recessed plate filter press Sheet filter Single leaf Nutsche Bag Cartridge Dead-end membrane Fibre bed Low shear crossflow Sand bed Simplex strainer Belt press Duplex strainer High shear crossflow Rotary disc Rotary drum Sand bed Tower press Diaphragm filter press Expression (screw) press Horizontal element tube press Vertical diaphragm filter press Vertical element tube press... 

A multi-element pressure filter comprises a cyhndrical vessel inside which a number of horizontal or vertical porous elements covered by filter cloths are placed (see Figures 1.29 and 1.30). The process suspension, which may be toxic, volatile or flammable, is pumped into the vessel at pressures up to 500 kPa. The positive pressure induces cakes to form on the outer surfaces of the cloths and filtrate is transported away through the elements and a suitable manifold system. Either flat elements, in the form of square, circular or rectangular leaves, or tubular candles are used. They are spaced sufficiently to avoid the possibility of cakes touching on adjacent elements. The pressure... 

Single leaf (pressure Nutsche) filter Multi-element (tubular candle) 6 6 6 6 8 -... 

Multi-element filter - horizontal and vertical leaf, candle Y Y... 

Multi-element leaf and candle pressure filters... 

Number of tilting pans, plates, frames or chambers Number of candles or leaves in a multi-element filter Capillary number Dimensionless pressure Pressure in air phase. Pa... 

With that definition of a candle filter understood to be the basic one, it must be accepted that the term is used of any multi-tubular filter with hanging elements. These elements can be almost any kind of cartridge filter. A tube plate with an array of cartridge elements is shown in Figure 3.48. 

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