摘要:

Although the cleaning of processing vessels has always been a significant source of waste, only recently have fundamental studies been undertaken to understand the cleaning process. The study described here began with a review of the literature on industrial cleaning practices. The literature was found to be mainly empirical. In order to provide a practical direction for research into the cleaning process, observations were made of a commercial batch processing facility. Based on these observations, short-term process improvements are suggested, and a new area for fundamental research is identified. @KEYWORDS Waste minimization Reflux cleaning Reactor Batch vessel.

ISSN:0098-6445    

DOI:10.1080/00986449308936114

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The effects of liquid surface tension (42.6 ∼ 72,4 mN/m) and viscosity (1 ∼214mPa • sn), liquid (0.01 ∼0.12m/s) and gas (0.01 ∼0.20m/s) velocities and particle sizes (1 — 8 mm) on phase holdup and mass transfer coefficient ( kLa) have been determined in a 0.142 m-I.D. × 2.0 m-high Plexiglas column. The gas phase holdup increases with liquid velocity, and the rate of increase in gas phase holdup sharply increases with gas velocity in the bed of surfactant solutions. In the beds of 1.0 and 1.7 mm glass beads, the bed contraction occurs whereas in the beds of 2.3 mm glass beads the bed contraction does not occur with an aqueous soltuion of ethanol (σ = 50.4 mN/m). The value of kLa increases with decreasing surface tension (σ ) but it decreases exponentially with increasing liquid viscosity in continuous bubble columns and three-phase fluidized beds. In three-phase fluidized beds with surfactant solutions, kLa increases with gas and liquid velocities and particle size. In three-phase fluidized beds of viscous or surfactant soltuions, kL,a can be estimated in terms of the energy dissipation rate based on the isotropic turbulence theory and a flow regime map is proposed based on the drift flux theory.

ISSN:0098-6445    

DOI:10.1080/00986449308936115

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

A reactor scale model (RSM) for a stagnation point, single wafer reactor for blanket tungsten LPCVD is used to calculate concentrations at the wafer surface. These concentrations and the wafer temperature, which is assumed to be measurable, are needed to determine the local tungsten deposition rate on the wafer and local film conformality (step coverage) in features on patterned wafers. Two feature scale models (FSMs) are used to determine step coverages in infinite trenches which have rectangular initial cross sections and an aspect ratio of five, as a function of reactor operating conditions; 1. a continuum-like diffusion-reaction model (DRM) for simultaneous Knudsen diffusion and heterogeneous surface reactions, and 2. a flux based model which includes ballistic transport of molecules and heterogeneous surface reactions (BTRM).|The RSM establishes “boundary conditions” for the feature scale models, by providing the flux of each species to the local wafer surface. Step coverages predicted using the FSMs with the reactant partial pressures at the wafer surface can be significantly lower than those predicted using reactant partial pressures at the reactor inlet, due to depletion of reactants. The flux based BTRM predicts higher step coverages than the DRM for the same wafer surface conditions.

ISSN:0098-6445    

DOI:10.1080/00986449308936116

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

A method is developed for predicting the zone-sharpening effect in linear gradient- and stepwise-elution chromatography of proteins. Numerical calculations have shown that the elution curve by different models are almost the same when the values of zone spreading parameters in the model are chosen so that the values of the number of the theoretical plates are equal. A good correlationship curve is established on the basis of the numerical calculations, from which the degree of the zone-sharpening can be easily predicted with a single dimensionless parameter.

ISSN:0098-6445    

DOI:10.1080/00986449308936117

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

A generalized dynamic mode! of a distributed staged (packed) fractionator is developed in this work. In particular we consider the dynamics of fractionators which employ structured packings as a means of achieving mass and heat transfer in multi-component systems.

ISSN:0098-6445    

DOI:10.1080/00986449308936118

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Videomicroscopy was used with a novel bead-pack micromodel to observe directly movement and distribution of toluene in the unsaturated zone during its initial entry, subsequent water infiltration and gravity drainage, and externally imposed fluctuations in the water table. In a partially water-saturated medium gravity drainage of toluene to the water table occurred as thin layers which flowed along continuous air-water interfaces, leaving a very low residual saturation. Experiments with presaturated toluene and water and with n-butanol and water showed that such drainage was faster and more complete for liquids that spread spontaneously on water, i.e., that had zero contact angle. However, whatever the spreading properties, drainage in such layers did not occur at all unless the gravitational driving force for downward flow exceeded the vertical capillary pressure gradient opposing flow. Toluene trapped in zones of low permeability or hydraulic conductivity during the first infiltration of water following toluene injection was not displaced during subsequent water infiltration and gravity drainage cycles. Fluctuations in the water table redistributed the toluene, in some cases trapping mobile toluene while in others mobilizing trapped toluene. The implications of these results for contamination and cleanup of ground water aquifers are discussed.

ISSN:0098-6445    

DOI:10.1080/00986449308936119

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor