Countercurrent exchange

About: Countercurrent exchange is a research topic. Over the lifetime, 2255 publications have been published within this topic receiving 28687 citations. The topic is also known as: Countercurrent exchange.

Reduced gas holdup in catalytic reactor

Abstract: A reactor for refining resid includes an elongated vertical vessel containing a bed of catalyst which is expanded or ebullated by a liquid/gas mixture. The mixture rises in an updraft through the bed and then is recirculated with an increased velocity by an ebullating pump. To reduce gas holdup of the ebullated bed and to promote a more uniform flow, the gas is entrapped by two cascaded stages of baffles which have an internal conical shape to guide, direct, and entrap the gas. One of these two stages has a shape which creates a countercurrent in the flowing liquid to deflect any catalyst particles which might otherwise be elutriated by the increased velocity.

Relationship between residence time, fluid dynamics and efficiency in countercurrent flow equipment†

Abstract: The suitability of any item of equipment for a given thermal separation process cannot always be judged solely in the light of efficient and loading range data. In vacuum rectification, involving a large number of theoretical stages, the vapour pressure drop per transfer unit exerts a considerable effect on the energy consumption and thus largely governs the choice of column fittings. Furthermore, the pressure drop per transfer unit determines the temperature at the bottom of a rectification column and, hence, the suitability of the equipment for the separation of heat-sensitive products. It is also an important criterion for compressor requirements in absorption processes. Another factor of considerable importance in separating heat-sensitive mixtures by distillation is the time during which the product, particularly the liquid phase, is exposed to a given temperature in the column. Therefore, a standardized liquid residence time has been adopted to evaluate the systems in their entirely. This residence time depends on the hydrodynamic conditions in the column and is thus closely related to pressure drop and efficiency. Further important factors, which may decide the selection of column internals, are the specific volume and mass of the column. Based on theoretical considerations, a flow model is derived for describing the main loading range of countercurrent packed columns; the relationships between the above mentioned parameters are presented.

On the Isotope Separation by Counter-current Gas Centrifuge, (I)

Abstract: The influence of a gas flow pattern in a rotor of a countercurrent gas centrifuge upon the separation factor and the separative power is studied. The optimum gas concentration gradient, at which the centrifuge has maximum separative power, us obtained from the equation of the diffusion velocity. The equations with respect to the separation properties are derived in two regions of the rotor separately, one of which is an upper part above the feed point as a stripping section, the other a lower part as an enriching section. The effects of the radial concentration gradient on the performance of the centrifuge are considered by means of the flow pattern coefficient K, which depends only upon the flow pattern and approaches the maximum value, unity, as the neutral layer between the counter currents approaches the rotor wall.

Art of effecting countercurrent contact between fluids

Abstract: The present invention relates to improvements in the art of effecting countercurrent contact between fluids and more particularly between liquids and vapors or gases, or between liquids of different densities that are more or less completely immiscible. It is particularly adapted for the distillation...