Solvent extractors

Dionex Accelerated Solvent Extractor (ASE200) with 11- and 22-mL extractor cells... 

During the investigation of pollution in coastal seawaters, Werner and Waldichuk [24] pointed out the need for concentrating and isolating trace amounts of certain substances with a continuous solvent extractor. They constructed a modified Scheibel apparatus by changing the organic solvent cycle system. 

The handling and disposal problems associated with the use of liquid solvent extractors have resulted in increased attention to the separation and preconcentration of organic compounds in water by collection in synthetic polymers followed by elution with an organic solvent (2). For example, selective collection and concentration of organic bases on methylacrylic ester resin from dilute water samples have been reported (3). Such collection techniques are especially well-suited to flow-injection measurement techniques. In this study, ionizable organic analytes such as salicylic acid and 8-hydroxyquinoline (oxine) were extracted into a polymer and then back extracted by an aqueous solution. Amperometric measurement using a flow-injection technique was employed to monitor the process. 

Wennrich et al. [167] investigated the capabilities of coupling accelerated solvent extraction with water as the extraction solvent and solid-phase microextraction to determine chlorophenols in polluted soils. Subcritical water extraction was performed using a commercially available accelerated solvent extractor. This system solves the problem of the analytes partitioning back to the soil matrix, which can occur in straightforward subcritical water extraction because in the Wennrich et al. method [167] the aqueous phase and the soil are separated under the extraction conditions. 

Research and development on other nondispersive forms of contactors, e.g., Hi-Gee solvent extractors that give a high efficiency per unit volume, and contactors effective with very short residence times, e.g., improvement on the centrifugal extractor, has been reported. 

The ground plant samples are weighed (typically 7 to 20 g, depending on plant part) and extracted in a semi-automated process utilizing a Dionex ASE300 accelerated solvent extractor system. The samples are placed in stainless steel cells and sealed. Approximately 33 to 66 mL of 95% EtOH are added and the cells are placed under 1500 PSI, preheated for 5 min to 40°C and held at this temperature... 

Separation of oil from crushed seed by draining squeezing cooked mash in cloths by lever, wedge or hydraulic presses continuous screw presses, or by solvent extractors. 

Fig. 34.13. Rectangular loop-type continuous countercurrent solvent extractor. (Courtesy of Crown Iron Works Company, Minneapolis, MN.)...

Hardly any batch-type oilseed solvent extractors remain. Three of the more popular types currently manufactured include (1) shallow bed-type extractors, where a 0.5-1.5 m thick layer of collets or flakes is pulled across a linear screen and extracted by drenching with a countercurrent flowing miscella consisting of solvent and solubilized oil (Fig. 34.13) (2) diffusion belt type, where deeper beds of collets or flakes are conveyed on a woven mesh or folding-pan belt while drenched in countercur-... 

Horizontal basket or moving bed solvent extractors are preferred over vertical tower extractors in processing safflower cake. The fibrous nature of safflower provides a natural channel through which the solvent can move, and the bed acts as a natural filter medium. Tower extractors generally have problems extracting... 

The processing of soybeans has been described in more detail elsewhere than can be done here (132-134). Oil is recovered today by either mechanical means or through the use of organic solvents. In the preindustrial revolution period, soybeans were merely pressed with lever or animal-driven screw-operated batch presses. Around the turn of the Twentieth Century, when soybeans became a viable commercial crop in the United States, steam-powered hydraulic batch presses were used. Today, electric-powered continuous screw-presses, often referred to as expellers (but this is a trademarked name for screw presses manufactured by one supplier), or continuous countercurrent solvent extractors are used. 

The Blaw Knox Company of Buffalo, New York, invented a rotary-type continuous solvent extractor in 1958 (12). The rotary-type extractor held the material in... 

The prepared oleaginous material is conveyed from the seed preparation process to the solvent extraction process and enters the solvent extractor. The solvent... 

There are six parameters that affect the performance of the solvent extractor apparatus. These six parameters are outlined below. 

After the prepared material has had its oil extracted in the solvent extractor, it is conveyed to the meal desolventizer toaster, commonly referred to as the DT. The material entering the DT is typically at the extractor temperature of 60°C, and it contains 25-35 %(w/w) of solvent. The primary purpose of the DT is to remove the solvent from the meal fraction so that the solvent can be recovered. 

Extrusion converts ground, rolled, flaked, or prepressed oilseeds into porous collets that handle very well in solvent extractors. Extrusion can also pretreat, in... 

Some oilseeds are normally prepressed in screw-presses to mpture the oil cells and partially reduce the oil level. The cake from the screw-press is then cooled and either cmmbled and flaked or sent directly to a solvent extractor. The hot, tacky press-cake can also be formed into porous collets by extmsion. Enough steam is injected into the expander to raise the moisture 2-A percentage points. This allows the expander to transform the cake into porous collets. This must be done on stream, before the cake has had a chance to cool and harden. Once cool and hard, protein denatures, and the cake can no longer be transformed into a tacky, inflatable condition. 

Hydraulic cone chokes can be mounted on closed-wall or slotted-wall extruders. Cake flowing across the cone to atmosphere expands with internal pores similar to collets from dies. The sheets of cake dropping from the cone break up in transit to the solvent extractor similar to the way collets break up. 

In this application, the expander replaces the cooking tray in a stack cooker and cooks the oilseed at 190-221°F. If the oilseed is going to a solvent extractor, it would continue to a prepress or collet expander (same as flakes from a cooker). If the oilseed is going to a fullpress, then drying to optimum crushing moisture (2-3%) is stiU required. 

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