Liquid Extractors

An aqueous feed of 30,260 Ib/hr of 22 wt% acetic acid is contacted with 71,100 Ib/hr of a solvent of 96.5 wt% ethyl acetate at 100°F and 25 psia to extract 99.8% of the acetic acid. A process simulation program computes 6 equilibrium stages for the separation. The densities of the two entering liquid phases are 62.4 Ib/fP for the feed and 55.0 Ib/ft for the solvent. Estimate the size and f.o.b. purchase cost of an RDC liquid-liquid extraction column for a CE cost index of 410. 

The total volumetric flow rate through the column = 485 + 1,293 = 1,778 fP/hr 

For a maximum throughput of 120 ft /hr-ft cited above, the minimum cross-sectional area for 

Because the feed contains water and acetic acid, assume stainless-steel construction with a material factor of 2.0 and correct for the cost index. This gives an estimated f.o.b. purchase cost of 

Commercial membrane separation processes include reverse osmosis, gas permeation, dialysis, electrodialysis, pervaporation, ultrafiltration, and microfiltration. Membranes are mainly synthetic or natural polymers in the form of sheets that are spiral wound or hollow fibers that are bundled together. Reverse osmosis, operating at a feed pressure of 1,000 psia, produces water of 99.95% purity from seawater (3.5 wt% dissolved salts) at a 45% recovery, or with a feed pressure of 250 psia from brackish water (less than 0.5 wt% dissolved salts). Bare-module costs of reverse osmosis plants based on purified water rate in gallons per day are included in Table 16.32. Other membrane separation costs in Table 16.32 are f.o.b. purchase costs. 

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Plot of extraction efficiency versus pH of the aqueous phase for the liquid-liquid extractor of the molecular weak acid in Example 7.16. 

The three-necked flask is charged with 750 ml. of formamide, 25 ml. of water, and 50 g. of ammonium chloride (Note 2). The mixture is heated to 180-190° in an oil bath, and 400 g. (3.02 moles) of 4,4-dimethoxy-2-butanone (Note 3) is added dropwise with stirring over the course of 6 hours (Note 4). The flow of cooling water in the reflux condenser should be adjusted to a rate such that the methanol and methyl formate formed during the reaction distil out (Note 5). After all the acetal has been added, heating is continued for 1 hour (Note 6). The mixture is allowed to cool and is poured into 1 1. of IN sodium hydroxide. The resultant solution is extracted with chloroform in a liquid-liquid extractor for 24 hours. The chloroform is separated, dried over sodium sulfate, and removed by distillation through a short column on a steam bath. 

The conventional process consists of a reactor followed by eight distillation columns, one liquid-liquid extractor and a decantor. The reactive distillation process consists of one column that produces high-purity methyl acetate that does not require additional purification and there is no need to recover unconverted reactant. The reactive distillation process costs one fifth of the conventional process and consumes only one fifth of the energy. 

The concept of extractive reaction, which was conceived over 40 years ago, has connections with acid hydrolysis of pentosans in an aqueous medium to give furfural, which readily polymerizes in the presence of an acid. The use of a water-immiscible solvent, such as tetralin allows the labile furfural to be extracted and thus prevents polymerization, increases the yield, and improves the recovery procedures. In the recent past an interesting and useful method has been suggested by Rivalier et al. (1995) for acid-catalysed dehydration of hexoses to 5-hydroxy methyl furfural. Here, a new solid-liquid-liquid extractor reactor has been suggested with zeolites in protonic form like H-Y-faujasite, H-mordenite, H-beta, and H-ZSM-5, in suspension in the aqueous phase and with simultaneous extraction of the intermediate product with a solvent, like methyl Aobutyl ketone, circulating countercurrently. 

Figure 4.23. Differential element of height, AZ, for a liquid-liquid extractor with axial mixing in both phases.

Figure 8.5 Apparatus for liquid extraction. A, bubblers and iepingers B, lighter-than and heavy-than water continuous liquid-liquid extractors c, droplet countercurrent chronatograph.

Figure 8.6 Apparatus used for saeple preparation involving solvent extraction. A, heavier-than-water continuous liquid-liquid extractor B, pressurized Soxhlet extractor for use with supercritical fluids C, Kudema-Danlsh evaporative concentrator 0, autonated evaporative concentrator.

Oberg, A.G., Jones, S.C. Liquid-Liquid Extraction, Chemical Engineering, July 22, 1963, p. 119. Nemunaitis, R.R., Eckert, J.S., Foote, E.H., Rollison, L.R. Packed Liquid-Liquid Extractors, ... 

Ahnoff and Josefsson [18] built a solvent extraction apparatus for river work which was later modified into their in situ extractor [ 17]. The unit as described in the earlier work could easily be adapted for seawater analysis. A unit based on a Teflon helix liquid-liquid extractor, some 332 feet (101.5 metres) in length, was constructed by Wu and Suffet [19]. The extractor was optimized for the removal of organophosphorus compounds, specifically pesticides, with an efficiency of around 80%. For some compounds, these continuous extraction methods should be the methods of choice and should be explored. 

Dynamic Modelling of a Liquid-Liquid Extractor with Axial Mixing in Both Phases... 

Freon 11) using a liquid-liquid extractor at 28-30 °C. Next, the extract was concen-... 

The extraction was performed with a liquid-liquid extractor 50 mb of dichloromethane (Merck) and 50 mb of sample were used. It was maintained for 24 h. (Adapted from Fraile et ab, 2000)... 

For the determination of cresol in water, CLP guidelines state that the aqueous sample be brought to pH 11 by the addition of sodium hydroxide (NaOH). The basic mixture is then extracted with methylene chloride either in a separatory funnel or a continuous liquid-liquid extractor. The aqueous phase is then acidified to pH 2 and reextracted with methylene chloride. This second extract is concentrated by evaporation and subjected to GC/mass spectrometry (MS) analysis for identification and quantification. 

The objectives of liquid mixing in stirred tanks are to (i) make the liquid concentration as uniform as possible (ii) suspend the particles or cells in the liquid (iii) disperse the liquid droplets in another immiscible liquid, as in the case of a liquid-liquid extractor (iv) disperse gas as bubbles in a liquid in the case of aerated (gassed) stirred tanks and (v) transfer heat from or to a liquid in the tank, through the tank wall, or to the wall of coiled tube installed in the tank. 

Continuous Liquid-Liquid Extractor for the Isolation and Concentration of Nonpolar Organic Compounds... 

BAKER AND SUFFET Continuous Liquid-Liquid Extractor... 

Continuous liquid-liquid extractors (CLLEs) using a small amount of solvent that is continuously recycled would be more effective for this type of sampling. A CLLE system would be less affected by solvent contaminants, and less solvent would be needed. 

Figure 2. Schematic diagram of the continuous liquid-liquid extractor. (Reproduced with permission from reference 14.)...

BAKER and suffet Continuous Liquid-Liquid Extractor 585... 

The racemic mixture of the knot was converted into diastereomers using a liquid-liquid extractor taking advantage of the solubility of potassium triflate in water compared to the insolubility of binaphthylphosphate salts. 

TABLE 14.2. Features and Industrial Applications of Liquid-Liquid Extractors... 

K.H. Reissinger and J. Schroter, Selection criteria for liquid-liquid extractors, Chem. Eng., 109-118 (6 Nov. 1978) also Encycl. Chem. Process. Des. 21,125-149 (1984). 

Polycyclic aromatic hydrocarbons Miniaturised liquid-liquid extractor (100 xl solvents) [84]... 

Aqueous samples are extracted with methylene chloride by liquid-liquid extraction in a separatory funnel or a liquid-liquid extractor. The extract is concentrated to 1 mL for GC analysis. If HPLC analysis were to be performed, methylene chloride should be exchanged to acetonitrile by evaporating the solvent extract with a few mL of acetonitrile and adjusting the final volume to 1 mL. 

Aqueous samples are extracted with methylene chloride using a separatory funnel or a continuous liquid-liquid extractor. Solid samples are extracted with methylene chloride-acetone mixture (1 1) by either sonication or Soxhlett extraction. The methylene chloride extract should be finally exchanged to hexane or iso-octane or methyl tert-butyl ether. The latter solvents should be mixed with acetone during solvent exchange. The extracts should then be cleaned up by Florisil. Often Florisil cleanup reduces the percent recovery of analyte to less than 85%. A preliminary screening of the extract should, therefore, be done to determine the presence of interference and the necessity of florisil cleanup. Gel permeation cleanup also lowers the analyte recovery and thus is not recommended. If a FPD is used in the GC analysis, the presence of elemental sulfur can mask the analyte peaks. In such a case, sulfur cleanup should be performed. Sample extraction and cleanup procedures are described in Chapter 1.5. 

Contactors have a number of advantages compared to simple liquid/gas absorb-er/strippers or liquid/liquid extractors. Perhaps the most important advantage is high surface area per volume. The contact area of membrane contactors compared to traditional contactor columns is shown in Table 13.2. Membrane contactors provide 10-fold higher contactor areas than equivalent-sized towers. This makes membrane... 

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