Wetting internal

With particles that are formed by an agglomeration process, there is internal surface area which can be wet by the solvent. A simplified case of internal porosity is that of a horizontal capillary where gravity can be neglected. The rate of penetration of a liquid into the tube, dl dt, is given by the Washburn equation [14]  

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Eliminate turned-down vents from safety relief valves, i.e., upside down U. Possible accidental ignition of releases from such vents wiU likely result in flame impingement on the top external surface of the tank, above the internal wetted surface. BLEXT Some means to handle rainwater from a desirable upward vertical vent have been listed by Bodurtha (ibid., April 1988). Moreover, a safety relief valve must function properly when required and must be sized properly to help prevent an explosion. 

Two kinds of wetting must be defined for porous catalysts— internal wetting, which is the amount of internal area wetted by the liquid, and external wetting, which is the amount of the... 

A problem arising when using hydraulic density is the possibility of partial internal wetting of the porous particle. Using eq. (3.358), it is assumed that the pores are totally filled with liquid, which is generally, but not always, true. This is why several authors correlate data to particle density, which normally, is a given and well-defined parameter. Furthermore, for the same reason, some authors use models to indirectly determine hydraulic density. 

According to the data for volumetric mass transfer coefficient measured in the device on a small pilot plant scale, for a certain load of flue gas to be processed, the required total volume of the reactor under consideration would be very small, only about 1/3 that of existing wet FGD equipment. In addition, the arrangement of the internal wet cyclone shown in Fig. 7.23 enables the reactor to have simultaneously high ash-removal efficiency. The reactor is especially suitable for the wet desulfurization of flue gas with hydrated lime or dilute ammonia solution as the absorbent. The design of the large-scale reactor suitable for a power station has now been accomplished and is expected to be applied industrially in the very near future. 

A few reactor models have recently been proposed (30-31) for prediction of integral trickle-bed reactor performance when the gaseous reactant is limiting. Common features or assumptions include i) gas-to-liquid and liquid-to-solid external mass transfer resistances are present, ii) internal particle diffusion resistance is present, iii) catalyst particles are completely externally and internally wetted, iv) gas solubility can be described by Henry s law, v) isothermal operation, vi) the axial-dispersion model can be used to describe deviations from plug-flow, and vii) the intrinsic reaction kinetics exhibit first-order behavior. A few others have used similar assumptions except were developed for nonlinear kinetics (27—28). Only in a couple of instances (7,13, 29) was incomplete external catalyst wetting accounted for. 

To ensure the cleanliness of the ceramic membrane gas filters, the housing typically made of stainless steel should have electropolished internal wetted surfaces and welded parts free of flux materials. In addition, considerations need to be given to the materials of construction for housing (e.g., stainless steel) and seals. 

FA Hessari, SK Bhatia. Reaction rate hysterisis in a single partially internally wetted catalyst pellet Experiment and modelling. Chem Eng Sci 51 1241-1256,1996. 

Internal wetted pore fraction (nomalized) Volumetric Faradaic current density Effective Volumetric Faradaic current density including effectiveness factor of agglomerates... 

This special design and technique ensures that the solid component is thoroughly internally wetted, hence its name, InterWet. 

Jaguste, DJ4. and Bhatia, S.K., Partial internal wetting of catalyst particles hysteresis effects, AIChEJ., 37, 650 660, 1991. 

Bhatia, S.K., Steady-state multiplicity and partial internal wetting of catalyst particles, AIChE J., 34, 969 979, 1988. 

The concentration gradients inside the catalyst particles and fine solid deposit (Figure 5.7c and d) are given by the equations describing the simultaneous mass transport and reaction within the catalyst particles and the diffusion within the solid deposit considering that the reactants diffusion occurs in the liquid phase by virtue of completely internally wetted catalysts ... 

Cheung, R, Fairweather, J. D., and Schwartz, D. T. 2009. Characterization of internal wetting in polymer electrolyte membrane gas diffusion layers. Journal of Power Sources 187 487-492. 

A. H. Barber, S. R. Cohen, and H. D. Wagner, External and internal wetting of carbon nanotubes with organic liquids, Phys. Rev. B, 71, 115443 (2005]. 

The wetting (liophobic/liophillic) properties of porous materials can be characterized by the (internal) wetting angles of the correponding liquids in the pores. 

In 1921, E. W. Washburn proposed a method for determining the internal wetting angle of water in porous media. This method is based on measuring the rate of water rise in a suspended sample of the porous material. It is not apphcable for partially hydrophobic materials. 

The second case implies that the pores in the catalyst pellets are not interconnected and that the fraction of internal wetting corresponds directly to external wetting. This in general is not the case when dealing with real catalysis and hydrocarbon feeds which readily wet internal pore structures (22). 

It is instructive to consider first a siiqtler problem, namely that of a reaction on a partly externally but coiqtletely internally wetted catalyst pellet. This case is of Interest in particular for hydrocarbon feeds which presumably readily wet the internal pore structure. Clearly if the kinetic rate is very slow the reduction in the "supply area" i.e. external area wetted through which reactants arrive to the pellet will hardly affect pellet utilization but for higher kinetic rates a reduction in utilization due to Incomplete external wetting should become apparent. 

In the first attempt, the full water quench directly downstream of the reaction chamber was designed as an internally wetted dip tube leading the raw gas through a water bath. Because the stability of the water film on the inner surface of the tube was disturbed due to temperature, pressure, or throughput fluctuations, slag deposition and corrosion occurred frequently (Franke, P. (2011) Shift... 

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