Review: Activated Carbon Filters in Respiratory Protective Equipment

Abstract

The review considers first the nature of airflow through granular carbon filters and the relationship between pressure drop and airflow rate. Equilibrium adsorption is then summarized, with particular emphasis on the volume filling of micropores, on which most of the theory of activated carbon performance is based. The dynamics of adsorption is studied, and the analytical solution of the fundamental dynamic adsorption equation is given, leading to the development of various equations used in practice for the description of breakthrough. The most fundamental dynamic parameter, the rate constant for adsorption, is discussed, and the effects of concentration, granule diameter, and air stream velocity are summarized. Extracts of a number of experimental observations with reference to specific adsorbates are given, followed by an account of the adsorption of mixtures of compounds. The effect of relative humidity is discussed. This is followed by an account of non-destructive tests, and the review ends with a summary and an indication of possible fruitful areas for research.

Design of Unsteady‐State Fixed‐Bed Processes for Heat Regeneration, Ad‐/Desorption, and Gas‐Solid Reactions

“…Three important unsteady-state fixed-bed processes are industrially applied and still the subject of intensive research in chemical engineering, particularly 2) and 3): 1) heat transfer from a hot gas to a cold fixed bed (or vice versa) in a heat regenerator, 2) adsorption and desorption of a gas to and from a solid adsorbent, and 3) regeneration of a coked catalyst by coke burn-off, as inspected in this article, but there are similar transient gassolid processes such as oxidation/reduction of metals/metal oxides or of catalysts with a metal as active component. The reader may ask, why a review is needed, as these processes are already in industrial operation for many decades and have been also discussed in textbooks and journals, for example, just to name a few, in [1][2][3][4][5][6][7][8][9][10][11] for heat regenerators, in [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27] for ad-/desorption, and in [12,[28][29][30] for coke burnoff. The answers to this question and the motivation for this review are: -The three processes have never been presented and analyzed connectedly in one article in spite of distinct analogies with regard to the transient nature, physicochemical background, and underlying differential equations (DEs).…”