Dense phase voidage, E D , dense phase superficial gas velocity, urn, and absolute bubble rise velocity, uB, were measured at pressures up to 8300 kPa in a pilot-scale, fluidized bed of Group A and boundary Group A/B powders. The mean equivalent bubble diameter, db, near the top of the bed was inferred from UB and known bed operating conditions. Increased pressure at fixed superficial gas velocity, u, , increased CD and uo, and decreased db for Group A powders. The marked decrease in inferred maximum bubble size, db,,, with increased pressure could not be explained by a decrease in gas contributing to bubble flow, u h , but rather appeared to be the result of a bubble instability phenomenon limiting bubble growth. SCOPEA complete understanding of pressurized fluidized beds requires knowledge of the effect of pressure on fundamental fluidization hydrodynamic properties. It is well known that increased pressure increases E D and UO, and decreases db in fluidized beds of Group A powders. Of fundamental importance is the extent to which these pressure effects occur and the reasons for them.Considerable interest has been given to the existence of a maximum stable bubble diameter, db,. in pressurized systems resulting from bubble splitting due either to particle "pickup" (Harrison et al., 1961) from the lower surface of rising bubbles or to Taylor instability (Clift et al., 1974) of the roof of the bubble. Bubbles have been seen to split both from above and from below in fluidized beds with the dominant mechanism of splitting being disputed. An alternate explanation for smaller bubbles is that bubble growth is limited by a reduced amount of gas contributing to bubble flow. Whether the reduced bubble size accompanying increased pressure results from reduced UB, and/or instabilities limiting bubble growth cannot be determined without simultaneous measurement of dense and bubble phase properties. To date, such measurements have not been made at pressures above 1200 kPa.In this work, E D , urn, and db,.. were measured in a pilotscale fluidized bed of 66 pm, 108 pm, and 171 pm powders at pressures up to 8300 kPa. Dense phase voidage, CD, and uo, were determined at all pressures by the bed collapse technique (Rietema, 1967), with the collapsing bed monitored by a high frequency response nuclear radiation density gauge. The absolute rise velocity of bubbles, UB, near the top of the bed was determined from cross-correlation analysis of multiple differential pressure, AP, transducer outputs. The bubble diameter db,, was then inferred from U B and known bed operating conditions. The experimental E D and UO, were compared to estimated values from available correlations, which account for density effects. In addition, a detailed analysis of the experimental results was done to determine if particle "pickup," Taylor instabilities, or reduced UB, could explain the observed decrease in db mu accompanying increased pressure. CONCLUSIONS AND SIGNIFICANCEThe magnitude of the pressure effect on E D , u h , and db,., was strongly depende...
The photochemical chlorination of sulfur dioxide was investigated experimentally. The photochemical reactor was the vortex‐stabilized arc radiation source described in Part I. Aqueous inorganic solutions, providing selective wavelength filtration, were circulated through the inner annular region. The outer annulus served as the reaction volume. The dependence of the reaction on wavelength, reaction gas inlet temperature, pressure, and reactant flow rate was investigated. The amount of sulfur dioxide in the mixture was varied from 1/6 to 2/3 atmosphere. The photochemical rate of formation of sulfuryl chloride is best described by the rate expression: where J is the volumetric rate of light absorption and where k0 and E have values of 0.0542 s1/2 and −2.6 kcal/gmol, respectively.
The Dow process for producing perfluorinated ionomeric membranes includes several emulsion copolymerizations involving gaseous tetrafluoroethylene and a second liquid phase monomer. The choice of the organic phase monomer depends on the desired product. The emulsion copolymerization reactor model was developed by extending the Smith‐Ewart‐Gardon theory for emulsion polymerization processes. Population balance techniques and Flory‐Huggins solution theory were applied. The resulting coupled partial differential equations were solved using the method of characteristics. The reactor model, with minimal adjustable parameters, predicts most polymerization results, including molecular weight, reaction rates in the three process stages, latex particle size, polymer composition, and the composition drift as a function of reaction time. The analysis and reactor model is used in the manufacturing process to set process conditions to obtain the desired properties in the polymer product.
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