Vapor equalizing tunnels

Equal liquid flow to each pass L, L2 = L3 = L4 Vapor equalizing tunnels Evenly distributed feed 12 34 i 12 " 34... 

Van Zele and Diener (1990) state that vapor fences can reduce the near-field concentrations of hazardous materials, but that concentrations increase with increasing downwind distance. Wind tunnel data show that vapor fences will reduce near-field concentrations by factors of 2 to 9, but the concentrations downwind at approximately 1000 m from the release point will eventually equal concentrations when no fence is in place. For a heavier-than-air cloud, there is no appreciable delay in the cloud s arrival time. 

Many modifications of the three types of contactors just discussed have been developed in an effort to reduce costs, reduce pressure drop, equalize vapor flow through each contactor, increase plate efficiencies, or, in general, improve the operating performance of the tower. An example of this for modification of bubble-cap towers is the old Uniflux tray originally developed by Socony-Vacuum, which consisted of a series of interlocking S-shaped sections which were assembled in the form of tunnel caps with slot outlets on one side only. Segmental downcomers, similar to the downcomers in conventional bubble-cap columns, were provided. The vapors issued from the Uniflux caps in... 

Orifice tunnel distributors consist of parallel troughs with perforations for liquid flow in the trough floors. Vapor rises in the space between the troughs. The troughs are often interconnected by cross channels that equalize liquid levels in different troughs (Fig. 3.6d). Level-equalizing channels are most important in coliunns greater than 10 ft in diameter (111, 349). 

Description of Experiments The Falcon Series of liquefied natural gas (LNG) spill experiments was performed by LLNL during the summer of 1987. These were the first tests performed at DOE s permanent Spill Test Facility. A series of five spills was performed on water within a vapor barrier structure as part of a joint government/industry study. These experiments were performed to evaluate the effectiveness of vapor fences as a mitigation technique for accidental releases of LNG. They also provided a database for the validation of wind tunnel and computer modeling simulations of vapor fence effects on LNG dispersion. Spills were made onto a water pond equipped with a circulation system to maximize evaporation to make the source evaporation rate as nearly equal to the spill rate as possible. 

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