Extraction processes principal scheme

The principal scheme of an extraction process is depicted in Fig. 6.0-1. The feed is brought into intimate contact with the solvent to enhance mass transfer between the two phases. Then the phases are separated. The raffinate is withdrawn from the unit. The loaded solvent (extract) is fed in to a regenerator for further processing. The regenerated solvent is reeycled to the extractor. 

Layered-type structure, 92-100 Lewis acidity, 15 Liquid - liquid extraction collective, 276-277 counter-current scheme, 272 equipment, 273 extractants, 279-281 mechanism, 274-276 multistage counter-current, 271 multistage cross-current, 270 one-stage process, 270 principals, 267-269 process performance, 282-283 process schemes, 277,278, selective, 277-278 with 2-octanol, 284-291... 

There is little question that the petrochemical refinery can perform its function technically. Whether it can also do so economically and commercially is a complex question which is discussed later. It is possible to consider direct cracking of whole crude into olefins, but such processes —pioneered principally in Germany, France, and Japan—are as yet comparatively new and untried commercially. A more likely route to the petrochemical refinery involves integrating both conventional coil cracking for olefin manufacture and extraction of aromatics from reformed and cracked naphthas with conventional refinery units. Such a refinery would produce primarily ethylene, propylene, butadiene, and aromatics. Other variations and other chemicals are possible, but the steam cracker and the aromatics extraction unit are the backbone of most schemes. 

Alkyl pyrocatechol extractants provide greater group separation factors. Eu/Am separation factors of 70 have been reported for a non-equilibrium extraction in the system 4-(a,(z-dioctylethyl)-pyrocatechol/NaOH/DTPA (diethylenetriamine-N, N, N, N, N-pentaacetic acid) (or DTPP - diethylenetriamine-N, N, N, N", N"-pentameth-ylenephosphonic acid) (Karalova et al. 1982). The separation factors are based mainly on the difference in the rates of the metal-DTPA (or DTPP) complexation equilibria for Eu and Am. They are therefore highly dependent on the contact time. A principal limitation of the practical application of such a separation scheme is the relatively long contact times (> 10 min) required for extraction. However, the slow equilibration compares favorably with that for other lanthanide-actinide separation processes (e.g. TALSPEAK, section 7). 

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