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. In the process the elastic fluid is caused to flow upwardly through the containment zone (1) at a rate which is sufficient to cause particulate solid (5) to rise up towards the upper end of the containment zone and form a cushion of particulate solid (5) against the underside of the upper retainer means (3). This rate is in excess of the threshold rate so as to cause the follower means (4) to move upwardly until it abuts against the underside of the cushion of particulate solid (5). The invention also provides an apparatus suitable for carrying out such a process and a method of loading a particulate solid into a substantially vertical tube.