Development of the Monolith Froth Reactor for Catalytic Wet Oxidation of CELSS Model Wastes
The aqueous phase oxidation of acetic acid, used as a model compound for the treatment of CELSS (Controlled Ecological Life Support System) waste, was carried out in the monolith froth reactor which utilizes two-phase flow in the monolith channels. The catalytic oxidation of acetic acid was carried out over a Pt/Al2O3 catalyst, prepared at The University of Tulsa, at temperatures and pressures below the critical point of water. The effect of externally controllable parameters (temperature, liquid flow rate, distributor plate orifice size, pitch, and catalyst distance from the distributor plate) on the rate of acetic acid oxidation was investigated. Results indicate reaction rate increased with increasing temperature and exhibited a maximum with respect to liquid flow rate. The apparent activation energy calculated from reaction rate data was 99.7 kJ/mol. This value is similar to values reported for the oxidation of acetic acid in other systems and is comparable to intrinsic values calculated for oxidation reactions. The kinetic data were modeled using simple power law kinetics. The effect of "froth" feed system characteristics was also investigated. Results indicate that the reaction rate exhibits a maximum with respect to distributor plate orifice size, pitch, and catalyst distance from the distributor plate. Fundamental results obtained were used to extrapolate where the complete removal of acetic acid would be obtained and for the design and operation of a full scale CELSS treatment system.
Trickle-Bed Oxidation Reactors
Abstract For reactions necesitating a solid catalyst and which invoive both reisuvely volatile and nonvclarile reactants, three-phase reactirs are required. Equipment used to achieve intimate contacting of the three phases has been procominantly in the form of slurry reactors, analogous to the stirred-tank homogenous system, or fixed-bed reactors in which the two fluid phases flow through a stationary bed of catalyst particles. Trickle-bed reactors are a type ofthe second classification in which both gas and liquid flow downward through the catalyst bed. Such systems avoid the disadvantage of separating small catalyst particles from the fluid product streams associated with slurry reactors, and also avoid the limitation of flow rates uncountered with upflow or countercurrent flow through fixed beds.
Coating the inside of a capillary of square cross section
Abstract Coating the walls of a capillary is usually done in two steps: (1) wetting or filling the capillary with a viscous fluid, and (2) clearing the capillary by forcing air through it. Clearing amounts to driving the wetting viscous fluid out of the capillary by another immiscible fluid. When air is blown into one end of a tube containing the viscous fluid, a “bubble” forms with the back end open. The bubble travels down the tube forcing some of the liquid out and leaving behind a fraction, in the form of a uniform film covering the walls. This paper reports flow visualization in capillaries of square cross secton. Visualization of the bubble was done by viewing both side and diagonal planes of the capillary in order to analyze the effect of the square cross section. Measurements from the captured images were used to characterize the shape of the fluid—fluid interface. The coating thickness of liquid deposited on the capillary walls was measured as the fraction of the capillary volume occupied by the liquid. The results for a wide range of capillary numbers show that this fraction increased monotonically with increasing capillary number, approaching an asymptotic limit of 0.64. Sequential particle tracking techniques were used to determine the flow field in different regions surrounding the bubble. A semi-quantitative comparison of the flow behavior, in capillaries of square and circular cross section, has been carried out.