Solvent Extraction - continued.

The figure provided here illustrates a schematic for a solvent extraction system for aromatics.

The purpose of solvent extraction is to prevent corrosion, protect catalyst in subsequent processes, and improve finished products. The extraction process removes unsaturated, aromatic hydrocarbons from lubricant and grease stocks.

The feed is routed to a rotating disc contactor, as shown in the figure. In the system shown, furfural is used as the solvent. The solvent, furfural, is introduced into the tower at the top. This establishes a counter-current flow between the two fluids. As furfural moves downward, it mixes (extracts) the desirable chemicals.

At the bottom, a mixture of furfural and the extracted chemical is drawn out and routed to a heater on the left hand side. The heater raises the temperature of the mixture and routes it to the distillation column on the left hand side. In this column (an evaporator), the two components separate. The furfural rises to the top and the extract (the chemical we wanted to extract) is collected at the bottom.

Similarly, the undesirable substances (and furfural) are routed to the evaporator on the right hand side. In this case, raffinate (undesirable impurities) are collected at the bottom of the column.