Simultaneous condensation and reaction of metal compound vapors in porous solids

Abstract

High-temperature interactions of metal compound vapors with solids are important in processes like coal conversion, waste incineration, catalyst poisoning, chemical vapor deposition, and chemical vapor infiltration. In this study, the interactions of alkali-metal vapors with porous aluminosilicate solids are investigated. This system exhibits many general features of interactions of metal compound vapors with porous solids. In general, depending on the metal compound vapor concentration, two sorption mechanisms are possible: (a) direct reaction of metal vapor with the solid; (b) condensation in the pores of the solid and subsequent reaction of condensate with the solid. The important kinetic parameters for both mechanisms are determined. The fraction of alkali metal captured due to pore condensation increases with an increase in temperature. A theoretical model has been developed to simulate the processes of surface condensation, pore condensation, and chemical reaction occurring during interactions of saturated metal compound vapors with porous solids.

A Mechanistic Study of Vanadium-Sorbent Surface Interaction at High Temperature

“…In recent years, various studies (Linak et al 2003;Mahuli et al 1997;Scotto et al 1994;Uberoi and Shadman 1991) have been conducted using mineral sorbents to capture toxic metals. Figure 1 illustrates the formation mechanism of submicron-sized vanadium particles, as well as the sorbent injection technique.…”

“…Thus the metal-sorbent particles can be easily collected using traditional particulate control devices. Prior studies (Scotto et al 1994;Uberoi and Shadman 1991;Linak et al 1995) used silica, alumina and various naturally available materials (i.e., bauxite, kaolinite, and lime) to capture lead, nickel, and cadmium. Venkatesh et al (1996) evaluated various mineral sorbents constituting a spectrum of alumino-silicate compounds and a pulgite clay for immobilization of several trace metallic species.…”

“…On the other hand, if the metal vapor has nucleated, the mass transfer process involves coagulation of the metal aerosol with other particles. In many previous studies of metal-sorbent interaction (Carey et al 2000;Linak and Wendt 1998;Linak et al 1995;Uberoi and Shadman 1991), the dominant mechanism was condensation because the sorbent was injected where the temperature was very high and the metals were initially in the vapor phase. To determine whether coagulation of fine aerosols with coarse aerosols could scavenge fine aerosols, Friedlander et al (1991) derived a simple analytical criterion.…”

“…Previous sorbent studies of arsenic and alkali metals (Mahuli et al 1997;Punjak et al 1989;Uberoi and Shadman 1991) demonstrated that the dominant mechanism of surface interaction was chemical adsorption according to their X-Ray Diffraction (XRD) measurements. Although the magnitude of interaction was much less than with chemical adsorption, physical adsorption was identified in some sorbent-metal systems (Iida et al 2004;Chen et al 2001;Punjak et al 1989).…”

Comparison of Hg0 capture efficiencies of three in situ generated sorbents

“…1998 . Sorbent particles have been demonstrated to be effective for the capture of certain toxic metals in combustion environ-Ž ments Uberoi andShadman, 1990, 1992;Ho et al, 1992;. Gullet and Ragnunathan, 1994;Biswas and Wu, 1998 .…”