Columns countercurrent

The Phillips process is a two-stage crystallisation process that uses a pulsed column in the second stage to purify the crystals (79,80). In the pulsed column, countercurrent contact of the high purity PX Hquid with cold crystals results in displacement of impurities. In the first stage, a rotary filter is used. In both stages, scraped surface chillers are used. This process was commercialized in 1957, but no plants in operation as of 1996 use this technology. 

Packed column Countercurrent, cocurrent Differential Liquid and/or gas Absorption, rectification, stripping, humidification, dehi i midi ficati o n... 

Mass transfer processes involving two fluid streams are frequently carried out in a column countercurrent flow is usually employed although co-current flow may be advantageous in some circumstances. There are two principal ways in which the two streams may be brought into contact in a continuous process so as to permit mass transfer to take place between them, and these are termed stagewise processes and continuous differential contact processes. 

This uncatalyzed reaction occurs at an acceptable rate at room temperature (298 K), a = (15/14)aq/(15/14)gas = 1.055. The value calculated from spectroscopic data is 1.096 (Chapter 4), so parasitic bleed to species other than NO(g) and HN03(aq) is indicated (the chemistry shown in Equation8.13 is oversimplified). In the exchange aqueous acid trickles down through a packed column countercurrent to a rising NO stream. A two column cascade was employed in which 4% of the acid flow is... 

Figure 3. Selectivity factor S as a function of kgHts in the negligible interaction regime. Key O, stirred cell reactor +, wetted wall column, cocurrent and X. wetted wall column (countercurrent).

Packed column Countercurrent flow Co-flow 10-350 10-1700 Micro bubble column (1100 x170 pm) Isopropanol (observation) 5100... 

The process used by Taylor and Spindel is illustrated in Fig. 13.41. liquid aqueous HNO3 flows downward through a packed column countercurrent to an upflowing gas stream consisting largely of NO with lesser amounts of other nitrogen compounds. Nitric acid containing the... 

Aumann, L. and Morbidelli, M. (2008) A semicontinuous 3-column countercurrent solvent gradient purification (MCSGP) process. Biotech. Bioeng., 99, 728-733. 

A schematic diagram of a distillation column is shown in Figure 7.33. The column contains a series of trays (also called plates or stages) which are usually perforated metal plates. Vapour passes up the column countercurrent to the liquid which flows across each tray and down the downcomers. As vapour bubbles through the liquid on a tray there is mass transfer between phases and... 

The second method of experimentally simulating an absorber is to make what might be called an "integral" or "complete" model. Here not only the microscopic scale, but also the macroscopic scale issues are considered. Such a model would have the same mode of operation (for packed columns, countercurrent for instance) into which feeds of gas and liquid at the right composition, pressure and temperature are fed in the right ratio of feed-rates and the compositions of the emerging streams have the same values as would be obtained from the industrial equipment which is being modeled. 

The separation of a mixture containing sublimable components is carried out by fractional sublimation in countercurrent columns. The finely distributed solid phase trickles down the column countercurrently to the upflowing sublimate vapor (Fig. 7-43). For the treatment of binary mixtures, the lighter sublimable component is withdrawn from the top and the heavier sublimable component is withdrawn from the bottom of the column. Some of the lighter sublimable component is used as solid reflux at the top of the column [7.55]. 

Packed towers and plate columns (countercurrent flow)... 

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