Screen-bowl decanter

The screen-bowl decanter is a basic decanter with an extra cylindrical section attached to the end of the beach. This extra cylindrical section is perforated with a bar screen fitted on the inside wall. The cake is scrolled from the beach and over the screen to undergo further dewatering by filtration. Some rinsing may be added to the screen. The conveyor itself will be extended with a cylindrical section to perform the scrolling over the screen. This decanter can be built in co-current and countercurrent format, but has a narrow range of applications. It has been used in the low-temperature separation of para-xylene, and in coal washeries. On abrasive applications the bar screen must be resistant to erosion. Hard surfaced and carbide variants of bar screen have been used for such applications. 

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Scratch resistance, 19 582 SCR catalysts. See also Selective catalytic reduction (SCR) selection of, 20 100-101 types of, 20 99-100 SCR DENO plants, 20 101 Screen bowl decanter centrifuge,... 

A variant of the decanting centrifuge is the screen bowl decanter, shown in Figures 9.13 and 9.14. In this unit a further perforated section is attached to the smaller diameter end of the conical section. This is known as the screen and allows further drying and/or washing of the solids to take place. 

Figure 9.13. Screen bowl decanter centrifuge (cover removed)...

Figure 9.14. Screen bowl decanter centrifuge-principles of operation...

It must be remembered that there are many other types ol industrial fenlril ijge, bin these achieve separation by means of filtration rather than sedimentation — altiioiigh the screen-bowl decanter combines the two separation mechanisms.)... 

Figure 7.12 Screen-bowl decanter. (1) Feed pipe, (2) feed compartment, (3) feed compartment outlets, (4) bowl, (5) internal screw, (6) screen section, (7) gearbox, (8) discharge ports, (9) centrifuge case, (10) base frame.

In the alternative screen bowl design the conical section of the bowl is shortened and a supplementary cylindrical section is attached in an effort to promote more efficient separation. Other design variants rely on the addition of baffles, helical discs, vanes, conical disc stacks or fins, all of which alter the flow and/or residence time distributions within the centrifuge. Figure 1.15 shows an example of a decanter centrifuge fitted with a vane stack. 

Of the major design variants (all described in Chapter 2), the screen-bowl design was developed by Bird in the mid-1940s. Sharpies produced the first vertical, pressurisable decanter in 1958. and three-phase operation came along in the early 1960s. 

Another important organic chemical is p-xylene, whose production uses decanters suitable for low temperature operation, and fitted with a screen bowl. 

The range of supply is that of the KHD/Humboldt Wedag company, acquired by Bird Machine Co. There are a dozen basic models, available in several different bowl lengths, with co-current as well as counter-current How, three-phase and screen-bowl versions. Also includes Censor" Twin beach machine, for separation of solids by density Decanter sales... 

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