Presses belt press

Other designs squee2e the cake between two permeable belts or between a screw conveyor of diminishing diameter, or pitch, and its permeable enclosure. The available filters which use mechanical compression can be classified into four principal categories, ie, membrane plate presses, tube presses, belt presses, and screw presses. 

Belt Presses Belt presses were fiiUy described in the section on filtration. The description here is intended to cover only the parts and designs that apply expression pressure by a mechanism in adchtion to the normal compression obtained from tensioning the belts and pulling them over rollers of smaller and smaller diameters. The tension on the belt produces a squeezing pressure on the filter cake proportional to the diameter of the rollers. Normally, that static pressure is calculated as P = 2T/D, where P is the pressure (psi), T is the tension on the belts (Ib/hnear in), and D is the roller diameter. This calculation results in values about one-half as great as the measured values because it ignores pressure created by drive torque and some other forces [Laros, Advances in Filtration and Separation Technology, 7 (System Approach to Separation and Filtration Process Equipment), pp. 505-510 (1993)]. 

Juice yield % Horizontal presse Belt presse... 

Belt Filter Presses Belt presses (Fig. 18-193) have two filter belts that move around rollers of different sizes to dewater the slurry. A typical belt press may have one or more of the following stages a preconditioning zone, a gravity drainage zone, a linear compression zone (low pressure), and a roller compression zone (high pressure). 

As shown in Table 2, the main intermediate treatment methods are machine treatment and chemical treatment. The machine treatment often utilizes compressive force, vacuum, and centrifugal force. For the treatment, machines such as a filter press, belt press, or screw decanter are used. In all machine treatments, the flow of the waste mud requires pretreatment in order to aggregate the waste mud. The water generated by the dehydration process is neutralized and disposed as sewage. The characteristics of the waste mud upon machine treatment depend on the dehydration machine and dehydration conditions. However, the water content is in the range as shown in Table 2 and moving it by truck is possible. 

Continuous Compression Filters. The variable chamber principle appHed to batch filtration, as described before, can also be used continuously in belt presses and screw presses. 

Originally designed for the continuous filtration of conditioned sewage sludges, as were most of the filter belt presses available, the Manor Tower press is increa singly used for the treatment of paper mill sludge, coal, or flocculated clay slurries. 

A belt press commonly uses two belts of woven material. Fmit mash is deposited on, and spread out evenly between, the two belts which converge and press the mash between them. The belts wrap around a series of successively smaller cylinders or pass between rollers (less efficient) for the pressing action. Juice yield for the wraparound belt press is 72%, and increases to 92% with secondary water addition (15). 

Expression Dewaterings of Fibrous Materials. Fibrous materials are frequently dewatered in belt-filter, screw, disk, and roU presses and in batch pot and cage presses. Table 1 Hsts appHcations of screw, roU, and pot presses. Screw and high pressure belt presses are continuous and have replaced batch pot and cage presses in most appHcations. Traditionally, however, batch presses have been used for squee2ing cocoa butter from cocoa beans, which require pressures up to 41 MPa (6000 psi) (39). A description of many types of batch presses is included in Reference 40. 

Fig. 7. Sohds content of sludges dewatered by C, soHd bowl centrifuge VF, vacuum filter BP, belt press FP, filter press, and DFP, diaphragm filter press...

Patzelt, R.R. and Hassick, D.E., Dewatering of steel-mill sludges by belt-press filtration, Section 13—Steel and Foundry Wastes, in Proceedings of the 39th Industrial Waste Conference, Purdue University, 469-485, 1984. 

Figure 7.22. Dorr-OIiver press-belt drum filter...

For filter belt presses and centrifuges, resistance to shear and mechanical pressure is the most important parameter. In general, floes produced by charge patch neutralization are stronger than those produced by inorganic salts alone. 

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