An experimental investigation was conducted into elucidating the mechanism of foam devolatilization. For the investigation, we have constructed two separate apparatuses of Plexiglas—one simulating the partially filled flow channel in a single‐screw devolatilizer, and the other simulating the partially filled, closed‐chamber (often referred to as the “C‐chamber),” in a twin‐screw devolatilizer. The test fluids employed were aqueous solutions of polyacrylamide having various concentrations. During the preparation of the test fluids, we controlled the amount of air entrapped in the liquid phase by varying the level of vacuum applied. The entrapped air stayed as fine gas bubbles dispersed in the polymer solution, and mixtures of the polymer solution and air bubbles were subjected to devolatilization experiments. In the use of a single‐screw devolatilizer, we have observed that: 1. The streamlines show circulatory flow patterns forming a singular point at a position slightly below the free surface, where small gas bubbles are trapped initially and become stationary, and 2. The small gas bubbles trapped at the stationary position coalesce later to form large gas bubbles, which then move slowly toward the free surface and are removed under vacuum from the system. In the use of twin‐screw devolatilizers, we have found that the degree of fill, the rotational direction of the screws, and the degree of intermeshing, (i. e., partially or fully intermeshing) greatly influence the amount of free surface available for the removal of volatiles, as well as the flow patterns in the liquid pool, and thus the devolatilization efficiency.
Correlations relate fly-ash resistivity to coal composition and cold-side collection efficiency to operating variables for low-sulfur coal applications. Hso-Pan Han and Edward N. Ziegler, Polytechnic Institute of New York, Brooklyn, N.Y. 11201 0.00027 would indicate good corre r" ation between these efficiencies between 99.5% and 99.8%. A P so, the data base CONCLUSIONS High resistivity of a fly ash diminishes the effectiveness of electrostatic precipitators by limiting the energization level at which the unit can operate. Resistivity is determined by specific minerals present in coal and the reac-Environmental Progress (Vol. 3, No. 3)
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