Podbielniak centrifugal contactor

POD system The POD system consists of a Baker-Perkins Model A-l Contactor (that is, a Podbielniak centrifugal contactor) fabricated in stainless 316. A variable speed drive is capable of rotating the unit at speeds up to 10,000 rpm. The normal operating speed is 8100 rpm. 

One attempt to improve the situation has been successful for small to moderate scale operations where high purity is required—namely, the Podbielniak centrifugal counter-current contactor and separator, which dominates the solvent extraction phase of penicillin manufacture. 

Podbielniak WJ, Ziegenhorn GJ, Kaiser HR. Continuous soap washing and finishing, using multistage, countercurrent, centrifugal contactors. J Am Oil Chem Soc 1957 34 103-106. 

Fig. 26. Mechanically agitated industrial contactors, (a) mixer-settler (b) rotating-disk column (c) mixco column (d) asymmetric rotating-disk column (e) pulsed packed column (f) Podbielniak centrifugal extractor. (Reprinted from Doraiswamy, L. K and Sharma, M. M., Heterogeneous Reactions Analysis, Examples and Reactor Design, Vols. I and 2, 1984, John Wiley and Sons.)...

Extraction is a process that utilizes the difference in solubility of the product of interest between two immiscible phases. Liquid-liquid extraction is commonly used in classical biotechnological downstream processing for production of antibiotics and other small molecules. The second liquid phase is usually a water immiscible organic solvent. Reciprocating plate, Podbielniak centrifugal extractors, Delaval contactors, and Westfalia extraction-decanters are examples of some of the equipment available for carrying out extraction. 

Proprietary Extractors. Manufacturers or proprietary design extraction equipment (such as the Podbielniak Centrifugal Extractor or the RTL (raining bucket) Contactor) provide catalogs listing the relative capacities of the various sizes of equipment which are offered. Pilot equipment is usually available for determining extraction performance, and the manufacturer utilizes both the pilot data and experience with similar systems to provide assured commercial designs. 

The centrifuge contactor" developed by Podbielniak promises radical improvements in our methods of conducting fractionation and other countercurrent processes. In a bubble tower the separation of liquid and vapor between each plate is effected by means of gravity, whereas in the centrifuge contactor separation is facilitated by means of centrifugal force. 

The most common centrifugal extractor is the Podbielniak Contactor, as shown in cutaway view in Fig. 24. Essentially it is a sieve plate column that has been wrapped around a shaft and spun to create a multigravitational force to do both the redispersion and the separation. All fluids enter and leave through shaft passageways and mechanical seals. 

The Podbielniak and Alfa Laval centrifugal extractors are essentially continuous differential contactors. The Westfalia and Robatel centrifugal extractors contain discrete mechanical stages, and flow from one to another is effected by spill over discs and skimmers according to usual centrifugal clarifier practice. As the number of discrete stages is increased, the allowable flow rates are proportionately decreased. 

Multistage Podbielniak contactor centrifuges produce three to five stages of theoretical extraction in a single countercurrent pass, and are used in fermentation-hased pharmaceutical and food additive production facilities. 

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