Hot Gas Filtration and Heat Exchange in a Packed Bed Using Lapilli as a Granular Medium

Abstract

A study was conducted on gas filtration and heat exchange in a fixed-bed heat exchanger-filter (FHEF) where we have removed fine dust particles from gases and exchanged heat with the granular medium (Lapilli). The influence of a number of variables was examined including gas velocities, gas temperatures, concentration of dust, height of the FHEF, dust and granular mean size, and pressure drop. The collection efficiency was found to decrease with increasing temperature, and the pressure drop increases when the size of the granular medium decreases. A numerical model for gas filtration and heat exchange using the finite element method was developed. It predicts the two-dimensional transient response of both solid and fluid phases as well as the variation of the specific deposit and void fraction of the FHEF with time. The numerical model incorporates variation in void fraction, specific surface area of the medium, and transport coefficient because of the combined processes of filtration and heat exchange.

Moving bed syngas conditioning: Modelling

“…The cross-flow MBHEF concept for tar and particulate removal would provide a high contact area between gas and solids without either entrainment or elutriation of solids. Furthermore, to date, MBHEF systems have only been designed for heat transfer and hot gas particulate removal: to be optimised from an energy and exergy point of view [15]; to propose a modelling approach to predict dust filtration with the gas temperature and the dust particle diameter [31] or with the solid velocity [32]; to be improved by the analysis of their design, strong features and drawbacks and to point out their performance according to a patent review [33]; to study the feasibility of using Lapilli as granular medium [34]. Dealing with BFBG reactors, MBHEF systems could also act as a preheater of the gasifying agent as the exhaust gas is cooled down and conditioned to be used for power production in ICE's, GT's, etc (Fig.…”

Solid conduction effects and design criteria in moving bed heat exchangers

“…Also, they can be used to recover heat from a flow of solids to another flow of solids [10] or to dry a flow of solids [11]. On the other hand, different equipments have been proposed for hot gas particulate removal, such as electrostatic precipitators, ceramic filters, scrub bers, bag filters and granular filters [1,4,12,13]. Smid et al [14] made a complete review of the patent literature about moving bed filters and their equipment in different countries around the world.…”

Thermal Analysis and Optimization of a Heat Regenerator Composed of Two Coupled Moving Bed Heat Exchangers

“…However, the collected particles can clog the fileter and the pressure drop increases [Smid et al, 2005a]. The same difficulty is found in fixed granular beds [Socorro et al, 2006]. Different means have been developed to clean the surface of these filters.…”

“…Moving beds do not become clogged and can filter the gas at high temperatures, whereas ceramic filters have several problems to work at temperatures over [Longanbach, 1998]. Several studies can be found in the literature about flow patterns and particles velocity in moving beds, as for example the works by Hsiau et al [1999Hsiau et al [ , 2001Hsiau et al [ , 2005 as well as on the heat transfer between gas and particles in fixed or moving beds Macías-Machín et al, 1991;Achenbach, 1995;Henriquez and MaciasMachín, 1997;Socorro et al, 2006]. In contrast, there is not so much information about the optimization of the moving bed dimensions from an energy or exergy point of view [Soria-Verdugo et al, 2007].…”