The at least one gas permeable wall preferably includes a plurality of openings therethrough
. The openings are preferably of a size such that the drying gas is able to pass into and out of the container but such that the particulate material cannot pass through the openings. The following discussion will focus on the use of air as the drying gas, however, it is to be understood that other suitable gases (for example, CO2, N2, etc. which may be derived from combustion waste gases) could instead be used. Preferably the drying gas is either directly derived from another industrial process that produces suitable gas or is recycled from earlier use in the mesh belt dryer or from use in another section of the drying plant. If using recycled drying gas it is preferred to incorporate a desiccator or refrigerator within the gas flow after exit from the air outlet to de-humidify the gas. This is also a convenient way of recovering water that may then be put to another use. In the case where the drying gas is heated above ambient temperature this will preferably be achieved using waste heat from another industrial process.