Abstract: A process is described in which an elastic fluid is contacted with a particulate solid. This comprises providing a substantially vertical elongate tubular containment zone (1) containing a charge of the particulate solid (5), the volume of the containment zone (1) being greater than the settled volume of the particulate solid (5). An upper retainer means (3) is mounted at the upper end of the containment zone (1), the upper retainer means (3) being permeable to the fluid but adapted to retain particulate solid (5) in the containment zone (1). A follower means (4) is movably mounted in the containment zone (1) beneath the charge of particulate solid (5) for movement upwardly from the lower end of the containment zone (1) upon upward flow of elastic fluid through the containment zone (1) at a rate beyond a threshold rate.

Abstract: A steam reforming furnace (F) has a plurality of substantially vertical reformer tubes (T). Each reformer tube (T) has a feed inlet (P) at its lower end, an outlet at its upper end, and a catalyst containment zone disposed intermediate its upper and lower ends and contains a charge of a particulate steam reforming catalyst (C) which is insufficient to fill completely the catalyst containment zone. An upper retainer means (3) is mounted at the upper end of the catalyst containment zone and is permeable to gas or vapour but retains particles of the catalyst (C) in the catalyst containment zone. A follower means (4; 24) is movably mounted in the catalyst containment zone beneath the charge catalyst (C) for movement upwardly from a lower end of the containment zone upon upward flow of gas through the catalyst containment zone at a rate beyond a threshold rate.