Andrew E Karr

Bio: Andrew E Karr is an academic researcher from Hoffmann-La Roche. The author has contributed to research in topics: Fermentation & Column (database). The author has an hindex of 4, co-authored 5 publications receiving 134 citations.

Performance of a reciprocating‐plate extraction column

Abstract: An open type of reciprocating-plate extraction column was developed, and it is proposed that the scaling up of such a column should be straightforward; that is, the height of an equivalent theoretical stage (H.E.T.S.) and the throughput per unit area should be independent of the diameter of the column. Plates having 5/8-in.–diameter holes and 62.8% free space were selected to minimize the resistance to countercurrent flow in the column. With this design low H.E.T.S. values were achieved at throughputs much higher than those reported for other columns. Thus for two systems the present column was shown to require the lowest volume of column to accomplish a given extraction job. Data were obtained in a 3-in.–diameter column on two systems, methyl isobutyl ketone-acetic acid-water and o-xylene-acetic acid-water. Throughputs studied on the first system ranged from 547 to 1,837 gal./hr./sq. ft., and the corresponding minimum H.E.T.S. values achieved were 4.3 and 7.5 in. respectively. For the second system minimum H.E.T.S. values of 7.7 and 9.1 in. were attained at throughputs of 424 and 804 gal./hr./sq. ft. respectively. Extraction column design procedures are discussed. The fabrication of the reciprocating-plate column is relatively simple, and this should encourage its use first in pilot-scale sizes and ultimately in large-scale columns.

Effect of unfavorable continuous phase density gradient on axial mixing

Abstract: Field experience with several industrial reciprocating plate liquid-liquid extraction columns indicated that large density gradients in the continuous phase resulted in excessive backmixing. Since there are no published data on the effect of higher density in the upper section compared to lower density in the bottom section of the column, experiments were performed with the calcium chloride brine-water system in a 76.2 mm diameter reciprocating plate column. Axial dispersion coefficients, E, were found to be 10–20 times higher than the values in systems with uniform densities. E decreased with increasing agitation to 30% of the value with no agitation. The effect of increasing flow rate of water up the column was to increase both E and the Peclet number. E was correlated with the density difference between any point in the column and tap water. Another correlation was obtained showing the effects of buoyant and mechanical energy input on axial dispersion.

Antibiotic production utilizing streptomyces refuineus var. thermotolerans

Abstract: Antibiotics having antitumor and antibacterial activity are produced by fermentation of thermophilic actimomycetes Streptomyces refuineus var. thermotolerans, having NRRL numbers 3,143 and 3,144, in a nutrient medium containing a protein source and a carbohydrate source, at 35* C. to 55* C., extracting the fermentation broth with a solvent and isolating the active fraction.

Mixing Through Oscillations and Pulsations—A Guide to Achieving Process Enhancements in the Chemical and Process Industries

Abstract: In this article we review the concepts and key developments of mixing enhancement through pulsation and oscillation. We focus on more recent research using oscillations in baffled tubes or columns, which generate discrete vortices as distinct from the more random type of flow produced by the well-established pulsed plate and reciprocating plate column devices. The scope of this review ranges from the basic chemical engineering concepts and key findings from recent research projects, including heat/mass transfer and residence time distribution (RTD); to applications and case studies involving specific reactions, e.g. polymerization and process intensification. We hope that this review will enable the reader to identify additional potential and perhaps an unexpectedly wide range of applications for the oscillatory baffled flow technology.

In situ extractive fermentation of acetone and butanol

Abstract: The productivity of the acetone-butanol fermentation was increased by continuously removing acetone and butanol from the fermentation broth during fed-batch culture. Whole broth containing viable cells of Clostridium acetobutylicum was cycled to a Karr reciprocating plate extraction column in which acetone and butanol were extracted into oleyl alcohol flowing counter-currently through the column. By continuously removing these toxic metabolites from the broth, end product inhibition was reduced, and a concentrated feed solution containing 300 g/L glucose was fermented at an overall butanol productivity of 1.0 g/L h, 70% higher than the productivity of normal batch fermentation. The continuous extraction process provides flexible operation and lends itself to process scale-up.

Extractive Fermentation of Acetone and Butanol: Process Design and Economic Evaluation

Abstract: Production de butanol (plus acetone et ethanol) par fermentation de melasse par Clostridium acetobutylicum. Etude economique comparative de 2 procedes: fermentation classique discontinue et fermentation avec extraction en continu du produit (extraction par l'alcool olleylique). Le second procede est environ 20% moins cher que le premier

Mass transfer between phases in microchannels : A review

Abstract: The multiphase micro-structured devices such as microchannels have been recently taken into consideration to replace the conventional equipment in different applications. The mass transfer coefficients and the interfacial area in the multiphase microchannels are much larger than those in the conventional equipment. This paper reviews the experimental studies on mass transfer in gas-liquid and liquid-liquid microchannels. Proposed flow pattern maps are compared. The featured researches corresponding to the effects of the operating conditions and the geometry of the microchannels on mass transfer are discussed. Literature review shows that influences of geometrical parameters are not investigated as extensively as those of operating conditions and thus, vague aspects of geometrical parameters effects exist. There are inconsistencies between results of some researchers and most of these are due to using dissimilar microchannel materials, unalike dominant mechanisms at different investigated operating conditions, different approaches to change the independent variable, etc.

A Systematic Study of the Effect of Geometrical Parameters on Mixing Time in Oscillatory Baffled Columns

Abstract: The systematic experimental investigation on the effect of baffle free area, baffle spacing and baffle thickness on mixing time in batch oscillatory baffled columns is reported where the form of oscillation can be achieved by either pulsing the fluid from the base of the column or oscillating the baffles at the top. Local concentration profiles are measured using conductivity probes at two locations along each column. The mixing time was determined based on the equilibrium concentration format. The experimental results have identified the optimal geometrical parameters for obtaining the lowest mixing times in such columns.