Cake control mechanisms

Figure 10.11 Fouling and cake control mechanisms by bubbles outside fibers. (Adapted from Cui et al., 2003).

Selective deposition is indicated by poor separation of the solids fi om the filter cloth The presence of a heavy reridnal cake on the sur ce, after cake discharge, may be fire resuh of preferential deposition of fines. One control mechanism here is to increase the effective solids conemtration before filtration, e.g. by settling or hydrocyclones. As discussed in later sections dealing with particulate bridging increases in concentration generally lead to the creation of stable bridges. 

The lower half of the settler is a low turbulence zone that allows the sulfur to settle on the bottom cone and gradually drain to the clarifier/filter system through a diaphragm control valve. The clarifier/filter system separates the sulfur product from the residual catalyst solution in the slurry. Most of the catalyst solution is decanted via the clarification mode. The primary use of the filters is to attain final dewatering after the clarifier tank is full of sulfur. The filtered solution is pumped back to the oxidizer through a surge tank, while the damp sulfur-cake is mechanically removed from the filter and stored. 

Feed slurry is introduced into the basket through either single or multiple feed pipes, or by other means such as rotating feed cone to help distribute the solids on the basket wall. In most cases, feed slurry is introduced at an intermediate speed, although in some applications (FGD gypsum, for one), feeding is done at full speed. There are several methods available to control the feed and cake level such as mechanical, paddle-type feelers, capacitance probes, ultrasonic sensors, feed totalizer, or load cells. 

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