Catalyst flux

Radial density gradients in FCC and other large-diameter pneumatic transfer risers reflect gas—soHd maldistributions and reduce product yields. Cold-flow units are used to measure the transverse catalyst profiles as functions of gas velocity, catalyst flux, and inlet design. Impacts of measured flow distributions have been evaluated using a simple four lump kinetic model and assuming dispersed catalyst clusters where all the reactions are assumed to occur coupled with a continuous gas phase. A 3 wt % conversion advantage is determined for injection feed around the riser circumference as compared with an axial injection design (28). 

External Dilute-Phase Upflow Cooler. The external ddute-phase upflow design (68) offers some control in the range of heat removal duties but generates relatively low heat-transfer coefficients [60—170 W/(m K)]- This design substantially increases the surface area requirement and thereby reduces the ultimate duty that can be achieved from a single bundle. In addition, poor mechanical rehabdity has been continuously experienced because of excessive erosion at the lower tube sheets as a result of the high catalyst fluxes and gas velocities imposed. 

Structural, Al alloy Oxidation catalyst Fluxes, enamel frit Glass, ceramics Detergents Fire retardants Rubber catalyst Photographic Antiknock agents Medicinals Fertilizers... 

HBF4 (aq) and metal fluoroborates electroplating of metals, catalysts, fluxing in metal processing and surface treatment. HzSiF6 and its salts fluoridation of water, glass and ceramics manufacture, metal-ore treatment. 

Catalyst flux Stripping steam rate Stripping steam superficial velocity Catalyst residence time Steam quality 500-700 Ib/min/ft" (40 to 55 kg/sec/m ) 2-5 lb/1,000 lb of circulating catalyst 0.5-0.75 ft/sec (.15-.25 m/sec) 1-2 minutes Superheated 100°F (55°C)... 

Catalyst flux is defined as catalyst circulation rate divided by the full cross-sectional area of the stripper. For efficient stripping, it is desirable to minimize the catalyst flux to reduce the carryover of hydrogen-rich hydrocarbons into the regenerator. 

Miscellaneous bromine uses are in catalysts, fluxes, precious metal recovery, hair care products, food additives, flotation agents in ore treatment, solvents, refrigerants, quartz-halide light bulbs, some lasers, some photovoltaic batteries, and some electrically conductive polymers. 

FIGURE 12.25 Evaluation of operating strategy to enhance gasoline yield (from Gao et al., 1999). Unit II Standard operation of riser reactor Cases 1-3 represent water injected at a riser height of I 1.4m. Case I Tregen = 602.3°C, catalyst flux = 9.93 kgs . Case 2 Increased (3.5%) temperature of regenerated catalyst. Case 3 Increased (20%) catalyst flux. 

Use Source of cesium, catalyst, fluxes, welding materials, ion propulsion, thermocouple units. 

To model the transport of a multicomponent mixture through porous catalysts, flux relations should be developed. There are two geometrical models of gas transport in porous media with different trends of flux relations (Jackson, 1977). These models are the capillary network model and the dusty gas model. 

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