Unsteady flow in a diffuser

摘要: The flushing of sugar from crushed and shredded cane fibres by gravity-facilitated flow takes place in a device called a diffuser. Crushed and shredded cane at the front end of the diffuser moves steadily toward the back end and fresh water is sprayed onto the top of the cane at the back end. The water is collected after percolating through the bed (removing sugar in the process) and is collected in trays from which it is pumped back and sprayed on the pulp again-this time further upstream. This counter-current extraction process is continued until the now concentrated sugar-water solution reaches the front end of the diffuser from where it is removed for further processessing. Operational difficulties arise because the permeability of the consignment can vary and this can cause either local flooding or drying, resulting in nonuniform (and therefore inefficient) sugar extraction. The project aim was to