The invention provides a dryer for drying particulate material, comprising at least one substantially vertical elongate container having an upper inlet (56a, 56b) for receiving a charge of moisture containing particulate material; a lower outlet (22) for discharging dried particulate material, whereby said particulate material travels under the influence of gravity from said inlet to said outlet; at least one substantially vertical gas permeable wall (20a, 20b) through which a drying gas can pass to contact said particulate material; said dryer also comprising at least one plenum (48, 50) on an exterior surface of said at least one gas permeable wall, covering ingress (38a) and egress openings within said at least one gas permeable wall.