Showing papers by "Sankaran Sundaresan published in 1986"

Cocurrent downflow of air and water in a two‐dimensional packed column

Abstract: Multiple hydrodynamic states were observed during cocurrent down-flow of air and water under trickling flow conditions in a packed bed of rectangular cross section. Although the multiplicity was exhibited by both pressure gradient and liquid holdup, the pressure gradient showed the largest variations at identical conditions. The multiplicity is interpreted as being due to the liquid flowing in two different modes, namely, film flow and rivulet flow. The characteristics of pulsing flow in a packed bed of rectangular cross section were found to be appreciably different from those reported in the literature for flow in small-diameter cylindrical columns. The most significant observation in the packed bed of rectangular cross section was that the pulses did not always span the column cross section, unlike the case in small-diameter columns. The lower pressure drop and pulse velocity in the packed bed of rectangular cross section are believed to result from the bypassing of gas around the edge of the pulses. The location of the pulses was found to depend on the quality of gas and liquid distribution at the top of the column, and the shape of the top surface of the packing. A distributor configuration in which the gas was injected directly into the bed was found to be the most desirable, and is recommended in industrial practice.

Optimal distribution of multifunctional catalysts in a packed bed reactor

Abstract: The problem of the optimal distribution of two multifunctional catalysts is analyzed. Two methods for obtaining optimal catalyst profiles, an analytic-numeric method and the method of steepest ascent, are compared. Though the analytic-numeric method yields a more accurate solution, the method of steepest ascent is usually easier to apply. Optimal catalyst loading profiles are determined for two cases of commercial interest: selective oxidation of butene and naphtha reforming with bimetallic catalysts- A sequential loading of the bismuth molybdate and the vanadium phosphate catalysis is recommended for low butene concentration levels, while at higher butene levels a mixed loading of the two catalysts may be desirable. For commonly encountered naphtha feedstocks a sequential loading of the Pt-Re and the Pt-Ir catalysts tends to be optimal. These compare well with experimental evidence in the literature.

Cleanup of PCB Contaminated Soils and Sludges by a Solvent Extraction Process: A Case Study

Abstract: The feasibility of cleaning PCB contaminated solids via a solvent extraction route was studied using the cleanup of the dried sludge from the Winston-Thomas tertiary lagoon as a test problem When compared with direct incineration of the sludge, the solvent extraction route has at least 3 shortcomings First, the solvent extraction route is unable to achieve the same cleanup quality as the direct incineration Second, the hazardous nature of the material handled requires that the extraction process be carefully designed to be virtually leak-proof and this will be difficult and expensive Third, it is inevitable that trace levels of solvent will be left behind in the processed sludge and this may be undesirable On the positive side, when very large amounts of solids contaminated at low (yet unacceptable) levels are to be cleaned, the solvent extraction route may be economically more attractive than direct incineration On the basis of desorption characteristics determined from bench-scale experiments, the economics of cleanup of Winston-Thomas tertiary lagoon sludge via solvent extraction route and direct incineration are compared The fractionation unit is the single most important unit in the solvent extraction process A clever design of this unit will have a significant impact on the economics of the cleanup via solvent extraction route