200 kg/h of ground roasted coffee, which contains 8% soluble solids, 2% water, and 90% inert insoluble solids. In order to obtain an extract with high soluble solids content without having to...

200 kg/h of ground roasted coffee, which contains 8% soluble solids, 2% water, and 90% inert insoluble solids. In order to obtain an extract with high soluble solids content without having to concentrate it for spray drying, a countercurrent extraction process is to be used to prepare the extract. It is desired that the final extract contain 0.15 kg soluble/ kg water and that the soluble of the spent coffee grounds does not exceed 0.008 kg/kg dry inert solids. The coffee grounds carry 1.3 kg water/kg of soluble-free inert solids and this quantity is constant with the solute concentration in the extract. Determine the mass flow rate of solvent needed in kg per hour.