Conventional rectangular plate

Plate-and-Frame Filter Presses. In the conventional plate-and-frame press (Fig. 14), a sequence of perforated square, or rectangular, plates alternating with hoUow frames is mounted on suitable supports and pressed together with hydrauHc or screw-driven rams. The plates are covered with a filter cloth which also forms the sealing gasket. The slurry is pumped iato the frames and the filtrate is drained from the plates. 

Two sets of equipment were used for coagulation experiments - a conventional jar testing apparatus with six 500 mL cylindrical beakers with an overhead stirrer each, and a Heidoloph RZ R2021 overhead stirrer. The paddle was identical for both stirrer types (1 cm by 4 cm rectangular plate). The jar tests were used for screening tests and MF experiments. In that case the FeCl r was added from a 20 mM (5.4 gL FcCls 6H2O) stock solution, the soludon was then rapidly mixed at 100 rpm for 2 minutes and then at 25 rpm for 20 minutes. The method was adapted from Dennett et al. (1996). 

Complex samples that are not completely separated with the conventional vertical development can be subjected to two-dimensional TLC. In this case, only one sample is applied at one of the lower comers of the rectangular plate. In the first dimension, the plate is vertically developed and the mobile phase is removed by evaporation. Following this, the plate is rotated 90° such that the separated sample forms a new sample line at the bottom of the plate. The second dimension is carried out using vertical development with a second (different) mobile phase. Although more complex samples can be separated using this mode of TLC, it is not possible to mn more than one sample at a time (Figure 4.4). 

Fig. 39. Schematic showing the basics of cell projection. The desired beam shape is selected by steering the electron beam through the appropriate pattern in the aperture plate. By using a rectangular aperture the system can operate like a conventional direct-write e-beam tool, so any shape of pattern can be...

Selection of Type of Thickener or Clarifier Selection of the type of unit thickener or clarifier depends primarily on the optimization of performance requirements, installation cost and operating cost. For example, the inclined-plate type of clarifier provides for less solids-holding capacity than a circular or rectangular clarifier, but at a lower installation cost. The high-density thickener maximizes underflow solids concentration, requiring a higher torque rating than conventional thickeners. 

The conventional approach is to perform the development in closed standard rectangular tanks lined with filter paper to saturate the atmosphere with the mobile-phase vapors. Equal, and in many cases better, results are achieved by development in open cylindrical containers where a fixed volume of the mobile phase is added, passed through the plate, and permitted to evaporate from the upper edge of the plate. 

The total incoming flow of feed can be treated with air under pressure, but it is more usual to introduce the air into a recycle stream of cleaned liquid and to allow the bubbles to develop in the flotation chamber at the point where the recycle stream enters. The feed stream is pretreated with chemicals, if necessary, prior to its introduction to the flotation chamber where it meets the bubble blanket. The fine particles in the supension are captured by the bubbles and are floated up to the surface where they form a thick scum which is removed by a continuous mechanical scraper. Some solids will settle fi om most feed streams and it is usual to provide for the withdrawal of accumulated silt fiom the base of the chamber. Figure 7.13 shows a conventional diflused air flotation system housed in a rectangular tank and Figure 7.14 a DAF unit which incorporates an inclined plate settler to capture by sedimentation those particles that escape flotation. 

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