Simulation of the dynamic behavior of deep bed filters

Abstract

A simulation procedure for predicting the dynamic behavior of a deep bed filter over the entire practicable range of filter operation is developed. The method is based on synthesizing available quantitative results relating to filtration, and to porous media flows, within an overall framework which views the process to consist of two principal stages dominated by appropriate limiting deposition modes. Evaluation of the results through comparison with available data indicates, to the extent the nature of these types of data permits, that the method is surprisingly effective and even capable of predicting on satisfactorily quantitative basis some intricate details of observed filter behavior. CHI SCOPEThis work is concerned with the development of a simulation procedure capable of predicting the dynamic behavior of a deep bed filter over the broadest practicable range of the pertinent variables involved, including, in particular, the value of the specific deposit. The method presented here was developed by assimilating available quantitative results relating to porous media flows, and to filtration, in the context of a conceptual framework which views the process, and its progressive evolution, to consist of two consecutive stages, each dominated by an appropriate limiting deposition mode. This picture of the process is supportable on the basis of observed filter behavior and does, moreover, provide the means for integrating results based on the two main collector types (the spherical and the constricted tube models) into the overall simulation scheme. The method we present incorporates the transformation, first suggested by Herzig et al. (1970), which reduces the governing conservation equations into a set of ordinary differential equations, thereby leading to considerable savings in computational effort. CONCLUSIONS AND SIGNIFICANCEDeep bed filtration is a subject which has, in recent years, developed a rich and varied literature. Despite the dramatic progress in our understanding which this has produced, a comprehensive method capable of predicting the dynamic behavior of a filter over its entire operational span has remained out of reach. No doubt the uncertainties surrounding some aspects of the nature of the deposition process, particularly the critical ones relating to the nature of the distribution of the deposited matter within the media and its evolution with progressive deposition, have stood as the main impediments obstructing progress towards such a general predictive scheme. In this work this problem is resolved by postulating an overall picture of the filtration process which views it to consist of two consecutive stages: a first stage dominated by deposition according to a smooth coating mode and assumed to endure until the specific deposit attains a prescribed transition value, followed by a second stage corresponding to transition to deposition by the constriction clogging mode. This picture of the process, though somewhat idealized, is in the main consistent with observed filter behavior.However...

Modeling of the deep granular bed clogging by nanoparticles

“…This assumption has been widely used in the clogging models presented in the introduction [9,13]. To validate it, carbon nanoparticles deposited under predominant Brownian diffusion on a line of magnetic beads were observed under a microscope.…”

“…To overcome these issues, Tien et al [9] developed a hybrid model for the liquid filtration of 6-µm-diameter particles, by splitting the deposition process into two steps. Thus, the deposit was initially considered to form a smooth layer over the grains, and then to gradually obstruct the pore space causing a decrease in the number of pores available to induce flow.…”

Intéraction entre les particules d'alumines, les alliages d'aluminium et ses inclusions durant la filtration d'aluminium avant la coulée /

“…The physical simulation techniques and computer-based mathematical models [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27] were used in aluminum industry to have a fairly good understanding of the thermal and hydrodynamic aspects of the filtration process during the last two decades. However, the experimental studies were carried out mostly with water since it is very difficult and costly to carry out aluminum filtration studies in the laboratory.…”

“…It is stated that particulate type and size, fluid approach velocity, temperature and media characteristics are important parameters which determine the relative dominance of each force mentioned above. However, studies [18,21,[91][92][93] conducted on the description of potential capture mechanisms in aqueous systems indicated that pressure/Van der Waals forces/double layer forces are responsible for particle attachment.…”

Filtration of Fine Particles by Multiple Liquid Droplet and Gas Bubble Systems

“…The problem of removing small particles from gases or liquids has become increasingly important, and many theoretical and experimental studies have been conducted (Yeh and Liu, 1974;Gebhart et al, 1973;Paretsky et al, 1971;Liu and Wang, 1997;Tien et al, 1979;Lee and Gieseke, 1979). The motion and capture of particles by an ensemble of fluid spheres can be applied directly to the problem of wet scrubbers or to the capture of particles by bubbles in a water pool.…”