Overflow Arrangements

Sedimentation systems consist of a collection of components, each of which can be supplied in a number of variations. The basic components are the same, whether the system is for thickening or clarifying tank, drive-support structure, drive unit and lifting device, rake structure, feedwell, overflow arrangement, underflow arrangement, instrumentation, and flocculation facilities. 

An abrupt increase in heat to the reboiler may back up liquid to the first tray. The overflow arrangement in Figure 4.7a to d provides some protection against flooding in such circumstances. 

Liquid is withdrawn from the redistributor either via an overflow pipe or using a submerged drawoff nozzle. When an overflow arrangement is used, the drawoff may frequently run dry, and flow to downstream units may be intermittent or unstable. When a submerged drawoff nozzle is used, excessive drawoff rates may lower the liquid level in the redistributor and cause poor distribution to the bed below. 

Providing overflow arrangements to prevent excessively high liquid levels in storage tanks... 

The coarse calciae cooler operates at 300°C, while the waste-heat boiler cools the gas to 350°C. The tubes ia the boilers have a chain-shaking arrangement operated by paeumatic hammers. Steam productioa is 0.78 kg/kg of dry coaceatrate. The only trouble with dust reported is ia the connection betweea the reactor and waste-heat boiler. It is necessary to cool the gas stream quickly to avoid sulfation, but even so the carry-over calciae coataias oa the order of four times more sulfate than the coarse overflow. In this plant, the composite calciae is 0.1% sulfide and 2.2% sulfate sulfur. 

Cleaners. Cleaner formulations can be classified with respect to the abiUty to emulsify oils, keep them in solution or to reject oils, spHt them out of solution. The latter type loosens the oil, and the separated oil does not dissolve but is rejected, and usually floats to the top of the cleaner solution. For the cleaner that rejects oil, the tank needs to be skimmed constantly. This is most easily accompHshed usiag the overflow weir, sump, and recirculating pump arrangement. OH-rejecting cleaners last longer. 

The classifying operation is carried out in a pool of fluid pulp confined in a tank arranged to allow the coarse solids to settle out, whereupon they are removed by gravity, mechanical means, or induced pressure. Solids which do not settle report as overflow. Mesh of sepa-... 

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