Porous sphere

A tubular reactor is to be designed for the synthesis of methanol from a stoichiometric mixture of CO and Hj. The reaction occurs in the vapor phase using a solid catalyst in the form of porous spheres CO + 2H2 = CH3OH. The average mixture physical and thermodynamic data at 500 K and 10 Mpa are... 

Porous spheres 3 mm in diameter, packed in tubes 40 mm internal diameter... 

Hermans, JJ, Sedimentation and Electrophoresis of Porous Spheres, Journal of Polymer Science 18, 527, 1955. 

Locke, BR Arce, P, Modeling Electrophoretic Transport of Polyelectrolytes in Beds of Non-porous Spheres, Separation Technology 3, 111, 1993. 

Lumpkin, O, Electrophoretic Mobility of a Porous Sphere Through Gel-Like Obstacles Hy-drodnamic Interactions, Journal of Chemical Physics 81, 5201, 1984. 

Figure 5.34. Normalized concentration profiles in a porous sphere for different values of the Thiele modulus. Note that if the latter is large, only a small part of the catalyst near the surface contributes to conversion.

The result of integration of second order reaction in a porous sphere is correlated by the curve fit,... 

A catalyst bed is made up of porous spheres of 0.2 cm radius and with... 

A reactor is packed with four equal layers of porous spheres of diameters 1.0, 0.3m 0.09 and 0.027 cm. The reaction is second order. Additional... 

A catalyst mass is made up of a mixture of porous spheres with a range of diameters. The average diameters of 10% cuts are shown. A second order reaction with k = 2.5 and C0 = 1.2 is performed in a PFR. The Thiele modulus... 

A catalyst bed contains a uniform mixture of equivolume porous spheres and cubes with two pairs of opposite faces sealed to diffusion. Accordingly the cubes may be regarded as slabs with diffusion through two faces. The spheres have a diameter of 0.02 ft, so cubes of the same volume have edges of 0.01614 ft. 

Piret et al.(3> attempted to reproduce the conditions in a porous solid using banks of capillary tubes, beds of glass beads and porous spheres, and measured the rate of transfer of a salt as solute through water to the outside of the system. It was shown that the rate of mass transfer is that predicted for an unsteady transfer process and that the shape of the pores could be satisfactorily taken into account. 

The form of Boq and Blq presented in Eq. (6.120) is based on the assumption that the fuel droplet has infinite thermal conductivity, that is, the temperature of the droplet is Ts throughout. But in an actual porous sphere experiment, the fuel enters the center of the sphere at some temperature 7) and reaches Ts at the sphere surface. For a large sphere, the enthalpy required to raise the cool entering liquid to the surface temperature is cpi(Ts — 7)) where cpi is the specific heat of the liquid fuel. To obtain an estimate of B that gives a conservative (lower) result of the burning rate for this type of condition, one could replace Lv by... 

Experimental evidence from a porous sphere burning rate measurement in a low Reynolds number laminar flow condition confirms that the mass burning rate per unit area can be represented by... 

Although pyrophoric metals can come in various shapes (spherical, porous spheres or flakes), the calculation to be shown will be based on spherical particles. Since it is the surface area to volume ratio that determines the critical condition, then it would be obvious for a metal flake (which would be pyrophoric) to have a smaller mass than a sphere of the same metal. Due to surface temperature, however, pyrophoric flakes will become spheres as the metal melts. 

The technique of Gel Permeation Chromatography (GPC) was Introduced by Moore and Hendrickson (1,2 ) in 1964 for determining molecular weight distributions of polymer samples. The chromatographic column packings used for this new technique consisted of porous spheres of crossllnked styrene-divlnyl benzene resins (37-75ym) that were subsequently available as a family of columns under the name Styragel. Analytical column dimensions were 7.8 mm I.D. X 4 ft (122 cm). 

The polydivinybenzene colloids prepared by the aerosol technique were carbonized to yield uniform porous spheres of carbon of relative high specific surface areas (69). 

The rate of diffusion for non-flow conditions of the fluid along the radial direction of a porous sphere is analogous to Fick s law, and is as follows ... 

The effect of an inert material on M was observed in a series of tests on the burning rates of aqueous ethyl alcohol solutions from a wetted porous sphere (62). As is to be... 

FLAME EXTINCTION FROM THE UPSTREAM PORTION OF A DROP IN MOTION. In his studies of the influence of relative air velocity on the combustion of liquid fuel spheres, Spalding (51, 56) noted a critical velocity above which flame could not be supported at the upstream portion of the sphere. He observed that the flame blew off and resided solely in the sphere s wake. In tests with kerosine, the air (20° C.) velocity at extinction varied linearly with sphere diameter (range 0.7 to 2.6 cm.), and the ratio Ubi2n was about 100 seconds-1. A similar result is obtained from the data on flame extinction of burning camphor spheres (15, 59). The near proportionality between extinction velocity and diameter was taken as supporting evidence for a theory on flame extinction advanced by Spalding (59). More recent experimental work with porous spheres and n-butyl alcohol as fuel does not support this relationship (1), because it was found that the extinction velocity is proportional to the square root of the drop diameter. 

When the flow of air past a burning liquid sphere is increased, the distance of the luminous portion of the flame from the forward stagnation point of the sphere decreases. Spalding (51) reports that at flame extinction the flame distance is a constant (0.9 mm.) for kerosine-wetted spheres (0.7 to 2.6 cm. in diameter). Recently the same constant value has been obtained with ethyl- and n-butyl alcohol-wetted porous spheres (1). 

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