Wall-to-liquid mass transfer in fluidized beds and vertical transport of inert particles

Abstract

Mass transfer coefficients in single phase flow, liquid fluidized beds and vertical hydraulic transport of spherical inert particles were studied experimentally using 40 mm and 25.4 mm diameter columns. The mass transfer data were obtained by studying the transfer of benzoic acid from a tube segment to water using the dissolution method. In all runs, the mass transfer rates were determined in the presence of spherical glass particles 1.2, 1.94 and 2.98 mm in diameter. The influence of different parameters, such as liquid velocity, particles size and voids on mass transfer in fluidized beds and hydraulic transport are presented. The data for mass transfer in all the investigated systems are shown using the Sherwood number (Sh) and mass transfer factor - Colburn factor (jD) - as a function of Reynolds number (Re) for the particles and for the column. The data for mass transfer in particulate fluidized beds and for vertical hydraulic transport of spherical particles were correlated by treating the flowing fluid-particle mixture as a pseudo fluid by introducing a modified mixture Reynolds number (Rem). A new correlation for the mass transfer factor in fluidized beds and in vertical hydraulic transport is proposed.

U ovom radu je eksperimentalno ispitivan prelaz mase između zida i fluida pri strujanju fluida kroz kolonu i u prisustvu fluidizovanih sfernih inertnih čestica i čestica u transportu. Za određivanje koeficijenta prelaza mase korišćena je metoda praćenja rastvaranja slabo rastvorne supstance - benzoeve kiseline - sa dela zida kolone u vodi. Korišćene su kolone prečnika 40 mm i 25,4 mm, a kao inertne čestice korišćene su staklene sfere prečnika 1,2; 1,94 i 2,98 mm. Prikazani su uticaji različitih parametara kao što su brzina fluida, veličina čestica i poroznost sloja na koeficijent prelaza mase u fluidizovanim slojevima i pri vertikalnom transportu čestica. Eksperimentalni rezultati su prikazani u obliku zavisnosti Šervudovog broja i faktora prenosa mase od Rejnoldsovih brojeva za kolonu i čestice. Uvedena je i veličina pseudofluid koja tretira dvofazni sistem tečnost-čestice kao suspenziju odakle je proistekao modifikovani Rejnoldsov broj mešanja. Uvođenjem ovih veličina data je i završna eksperimentalna korelacija, jedinstvena za fluidizovane slojeve i vertikalni transport čestica. .