Extractions raffinate

The cyclic steady state SMB performance is characterized by four parameters purity, recovery, solvent consumption, and adsorbent productivity. Extract (raffinate) purity is the ratio between the concentration of the more retained component (less retained) and the total concentration of the two species in the extract (raffinate). The recovery is the amount of the target species obtained in the desired product stream per total amount of the same species fed into the system. Solvent consumption is the total amount of solvent used (in eluent and feed) per unit of racemic amount treated. Productivity is the amount of racemic mixture treated per volume of adsorbent bed and per unit of time. 

Determining the effects of impurity build-up on recycle of the extraction raffinate to the heap leaching operation, and on recycle in the extraction and electrowinning circuits ... 

Here again, few data are available on the solubility of the various diluents, in either its use or being studied for use in solvent extraction circuits. Although this is expected to be low (<2ppm), what few data are available apply to water and not to solvent extraction raffinates (see, however Chapter 2). 

The process flow sheet was first tested for direct leaching of steel mill flue dust and production of zinc metal by electrowinning. The tests were performed in a continuously operating pilot plant, producing 10-20 kg/day zinc metal. The same pilot plant was then used for treating copper/zinc-rich brass mill flue dust in a closed loop operation, recycling all the zinc solvent extraction raffinate to the copper circuit leach section. In the zinc circuit leach section, only the amount of zinc rich dust necessary for neutralization of the copper solvent extraction raffinate was used. The results obtained from the pilot plant tests indicated contamination problems within the solvent extraction loops. The estimation of economic data showed a weak return on the assets compared with the alkali route, and sensitivity toward the raw material price. 

Excess ammonia is evaporated from the resulting extraction raffinate and zinc is precipitated as carbonate by the remaining ammonium carbonate in the solution or by addition of carbon dioxide. The evaporated ammonia is absorbed in the filtrate and recycled to the leaching step. 

Name Feed Extract Raffinate Process details... 

Finally, as SMB is now proposed for biochemical applications, great care must be taken for all the good manufacturing practice (GMP) issues (cleaning, reproducibility, software validation, etc.). Moreover, as SMB is probably always linked with a device enabling product recovery in the extract-raffinate streams and/or solvent recycling, these solvent-handling devices should be considered as part of the SMB. 

For a given feed concentration, the design of the TMB relies mainly on the adequate choice of the different flow rates recycle, feed, eluent, extract, raffinate, and solid (equivalent to a shift period in SMB). 

The primary products are fed at the top of the extraction column. The composition of feed, extract, raffinate, and extractant is analysed in dependence on superficial velocity of the gaseous (continuous) phase. In two series of experiments either the phase ratio or the spraying density are kept constant. The stage construction is made by means of a computer program. 

The extract-raffinate data fi om the first figure is used to develop the Ponchon-Savarit digram. The solvent content of the raffinate is low and Yr is considered zero. Xp, X , and Xb are located at values of 0.40, 0.98, and 0.01, respectively. The upper operating point Pd is located using the given reflux ratio of 7.7. Thus,... 

The pregnant organic phase is usually scrubbed twice with 0.03 N HCl (the first scrub is 0.03 N HNO3 if the feed solution had been in the nitrate form). The volume of each scrub is one-third of the organic-phase volume. Each scrub is mixed with the organic phase by air-sparging at least 30 minutes. The scrub raffinates are usually combined with the extraction raffinate to provide a composite feed for a second-stage extraction. 

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