High-Speed Tube Gas-Liquid Apparatuses

Abstract

Tube process apparatuses are well known and used extensively in chemical and other branches of the industry. Film-type heat- and mass-exchange tube apparatuses [1], employed primarily for countercurrent processes, in which the gas flows from the bottom up in the opposite direction (countercurrent) to the liquid film flowing down the inner surface of the vertical working tubes, constitute a special group. Countercurrent apparatuses are usable only at low gas velocities (up to 3 m/sec). Over the past few decades, development of high-speed tube cocurrent (unidirectional flow) apparatuses, where the gas moves at high speeds (10‐40 m/sec) and entrains the liquid film in the direction of its motion, has been pursued vigorously. These apparatuses have not been studied well enough and are used seldom [2‐4]. However, thanks to the great intensity of the processes that take place in them, they are the most promising [5]. In well-known classifications, the place of tube apparatuses is not clearly marked, so they may be regarded as a separate, independent type of gas-liquid apparatuses. The common design feature of this type is a tube, down the surface of which flows a liquid film. Depending on the direction and speed of the gas flow in the tubes, all tubular contact elements may be divided into four groups: 1. Elements for descending cocurrent flow: in vertical tubes conditions are created for descending coflow of the gas and the liquid film. The gas speed range is virtually unlimited (as much as several scores of meters per second). 2. Elements for countercurrent flow: in a vertical tube the liquid flows from the top down in the form of a film and the gas, from the bottom up. The gas speed must not be greater than the flooding speed. 3. Elements for ascending cocurrent flow: the gas moves through a vertical tube from the bottom up at a speed greater than the flooding speed and entrains the liquid film on the wall in the direction of its motion. The common feature of the above three groups is vertical arrangement of the tubes. 4. Elements for horizontal cocurrent flow: the gas and the liquid film move in the same direction through a horizontal tube. The gas speed range is unlimited, but speeds at which a closed liquid film is formed are more preferable. Four different methods of delivery of the flooding liquid are distinguishable in each of the above groups: ‐ film delivery: the liquid enters the tube inlet in the form of a closed annular film along the tube wall; ‐ spray delivery: the liquid is fed in the form of sprays dispersed in the gas stream; while moving through the tube, the sprays partly or almost fully settle on the tube wall and form a film;