Modifications to Structured Packings to Increase Their Capacity
The hydraulic performance of structured packed columns is characterized by parameters such as loading point, flooding point, and dry and wet pressure-drop. These parameters can be positively influenced by optimizing the transition areas between two adjacent packing layers. Tests have been done in a two-phase test rig with a rectangular column made of perspex. The test medium is a liquid hydrocarbon in counterflow to saturated nitrogen gas. The performance of different packing structures at the layer-to-layer transition zone and the addition of vane-type elements between two packing layers was evaluated. Several packing modifications were tested and the results were compared with those of a non-modified packing. The intentions of this work are: to rank the modifications of structured packings with respect to the achieved capacity increase; to determine whether flooding is initiated in the core of the corrugated packing or in the transition area in spite of the modifications made on the lower or top side of the packing sheets; and to find out how the loading point is influenced by the modifications.
Applied aspects for enhanced CO2 capture from reformer gas: Comparison between the performance of valve tray absorber and packed column, Part I
Abstract The CO 2 capture from reformer gas is a technique to reduce greenhouse gas emissions. In this investigation, monoethanolamine (MEA) solution was employed as absorbent for the CO 2 capture in valve tray column. The electrolyte NRTL and Redlich–Kwong equations were used to simulate the CO 2 -H 2 O-MEA system. The calculated results were validated by the data obtained from an industrial scale absorber. The effects of operational factors such as pressure, gas flow rate, MEA concentration, lean-MEA and inlet gas temperatures were evaluated on the performance of tray and packed columns. The optimum structured packing was determined and the appropriate conditions for achieving the maximum capacity were discussed in details. It was concluded that Mellapak Plus 452Y can provide the maximal capacity with an acceptable level of efficiency if operational pressure considered being lower than 2.5 bar. When the structured column operates at pressure of 3.5 bar, the Mellapak 350X is the appropriate choice to increase the absorption capacity. The reported results can be useful in industrial applications.
Pharmacokinetics of amikacin and chloramphenicol in the aqueous humor of rabbits
Composite data describing ocular pharmacokinetics are unreliable because of intersubject variation. To address this problem, an animal model was developed in which multiple aqueous samples from single subjects were obtained. Following direct anterior chamber or intravenous administration of amikacin or chloramphenicol, pharmacokinetic analysis of drug concentrations in the serum and anterior chamber was performed by using a nonlinear least-squares regression program. The number of anterior chamber paracenteses performed did not alter the beta elimination rates or percent penetration into the anterior chamber. The aqueous humor and peripheral-compartment terminal slopes were identical. These data indicate that complete ocular concentration-time curves can be obtained without altering antibiotic pharmacokinetics. Following direct injection into the anterior chamber, the elimination rates for both antibiotics followed a one-compartment model, whereas those following intravenous administration best fit an open, first-order, two-compartment model. Following intravenous administration, the anterior chamber elimination rate constants for both drugs were equal to that of the serum and significantly longer than that following direct injection. The elimination rates of both drugs following direct injection were similar. Systemic administration resulted in drug levels in aqueous humor that persisted longer than those following direct injection. Chloramphenicol, a lipophilic compound, gave higher mean concentrations in aqueous humor than did amikacin. Our model provides a new approach which rigorously examines ocular pharmacokinetics and provides data which suggest that for selected compounds the parenteral route of administration is preferable.