Stills centrifugal still

In the rotating-disk (centrifugal) stills, the distilland is allowed to flow over a heated rotating disk (Fig. 1-41) and forms a thin film. 

About how fast does a centrifugal still turn and what is a typical capacity ... 

The syrup (mother liquor) separated in the centrifuge still contains sucrose which has to be recovered in further crystallization steps. In this way, there is a multi-stage process of crystallization yielding a final mother liquor (known as molasses) from which the sucrose cannot be economically further crystallized. 

The salt removed in the solid bowl centrifuges is of less value than that removed in the primary (pusher) centrifuges. It usually is allowed to drop into a tank in which it is redissolved in the cell liquor and then recycled to the evaporators. The solid-bowl centrifugate still contains traces (<0.1%) of very line solid salt. The next step therefore is filtration, described below in Section 9.3.2.6. Some of the salt fixtm the centrifuges may be used in that step. 

More accurately, we can use the method of combination differences, while still neglecting centrifugal distortion, to obtain B" and B. Transitions having wavenumbers v[5(J — 2)] and v[0 J + 2)] have a common upper state so that the corresponding combination difference A4F(J) is a function of B" only ... 

In the older method, still used in some CIS and East European tar refineries, the naphthalene oil is cooled to ambient temperatures in pans, the residual oil is separated from the crystals, and the cmde drained naphthalene is macerated and centrifuged. The so-called whizzed naphthalene crystallizes at ca 72—76°C. This product is subjected to 35 MPa (350 atm) at 60—70°C for several minutes in a mechanical press. The lower melting layers of the crystals ate expressed as Hquid, giving a product crystallizing at 78—78.5°C (95.5—96.5% pure). This grade, satisfactory for oxidation to phthaHc anhydride, is referred to as hot-pressed or phthaHc-grade naphthalene. 

On the completion of nitration the batch is dropped from the reaction vessel into a centrifuge and the acid mixture spun off and recovered. The nitrated linters, which still contain appreciable quantities of acid, are then plunged into a drowning tank, where the nitric acid is diluted with a large volume of water. The resultant ester is then pumped, as a slurry, into storage vats which may hold the products of several nitrations. 

If still greater force is required, a positive pressure in excess of atmospheric can be applied to the suspension by a pump. This motive force may be in the form of compressed air introduced in a montejus, or the suspension may be directly forced through a pump acting against the filter medium (as in the case of a filter press), or centrifugal force may be used to drive the suspension through a filter medium as is done in screen centrifuges. 

Wiped film stills in place of continuous still pots —Centrifugal extractors in place of extraction columns —Flash dryers in place of tray dryers —Continuous reactors in place of batch —Plug flow reactors in place of CFSTRs —Continuous in-line mixers in place of mixing vessels... 

The stuffing box of the equipment, especially centrifugal pumps, should always be vented before startup. Even though the pump has a flooded suction, it is still possible that air may be trapped in the top of the stuffing box after the initial liquid purge of the pump. 

No matter the duty (utilities excepted), most boiler plant systems employ electric motor-driven, single-stage or multistage centrifugal pumps to supply FW. These may be of conventional design or derivations such as a turbine pump. However, steam-driven reciprocating FW pumps (steam pumps) are still employed in some countries and for certain smaller applications. 

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