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Conditions of dead zone forming in porous catalyst pellets

Król G., Szukiewicz M.

Chemical and Process Engineering

2018

Vol. 39, nr 1

129-–138

In the present work the results of the investigations on dead zone formation conditions in catalyst pellet are discussed. A new, simple method of determining the types of kinetic equations for which such a zone can appear was developed on the basis of simple mathematical transformations. It was shown that: (i) pellet geometry has no influence on necessary conditions of the origination of dead zone (ii) only driving-force term (in the sense of Langmuir-Hinshelwood-Hougen-Watson kinetic approach) decides if a dead zone is formed. A new algorithm which allows fast and precise evaluation of critical Thiele modulus Fcrit (in a catalyst pellet for F>Fcrit the dead zone appears) was proposed and tested.

Structured catalytic reactor for VOC combustion

Kołodziej A., Łojewska J., Kleszcz T.

Polish Journal of Chemical Technology

2007

Vol. 9, nr 1

10-14

VOC emission has recently become a challenge for environmental protection. Catalytic combustion seems a promising method of VOC removal, however, there are still more specific demands concerning the process. The reactor design has to assure enhanced transfer properties accompanied by low flow resistance to reduce the pumping costs. Neither the packed beds nor the classic ceramic monoliths are able to fulfil the requirements. To solve the problem we propose a wire gauze structure composed of several gauze sheets staked. A number of mass transfer and flow resistance experiments were performed for two gauze types and correlations were derived for the Sherwood number and the friction factor. The results were found to be in a reasonable agreement with the literature available. The studied gauze structures were compared with a classic monolith for the assumed case study. The calculated length of the gauze structured reactor was significantly shorter, up to ten times, when compared with a classic ceramic monolith, but the pressure drop was higher.