Excess stagnant material

Another operational problem is that of limited live capacity. This is usually one of the results of rathole formation. To correct this it is necessary to change the flow pattern from funnel flow to mass flow or at least expanded flow. 

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A reartant A diffuses into a stagnant liquid film where the concentration of excess reactant B remains essentially constant at C q. At the inlet face the concentration is Making the material balance over a differential dz of the distance leads to the second-order diffusional equation,... 

The gap resistance was further rationalized in subsequent work. It was shown that the associated heat transfer mechanism relies primarily on heat conduction across the stagnant gas film, trapped in the gap between tbe monolith and the inner reactor tube wall. In fact, the gap resistance was inversely proportional to the gap size evaluated under the reaction conditions (so differential thermal expansion of the monolith and tube materials should be considered), and directly proportional to the gas-phase conductivity, as evidenced by heat transfer measurements with N2-He mixtures of different compositions. Estimates for h in excess of 700 W/(m K) were obtained when using pure He. 

Although sulfur dioxide is not a particularly toxic material, episodes have occurred in which increased deaths have been associated with high levels of sulfur dioxide in the atmosphere. The most notable such incident occurred in London in December 1952 when a stagnant layer of dense fog and black coal smoke accompanied by high levels of sulfur dioxide descended on the city for days, a period during which thousands of excess deaths were recorded. Because of particles and fog in the atmosphere, visibility descended to near zero, and the fine particulate pollution was so bad that even the underwear of exposed people was soiled by it. 

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