TECHNOLOGY FOCUS - INSTRUMENTATION AND TESTING - Preferred System: The system further comprises a polishing filter connected to the second retentate stream; or polishing filter receiving the second stage retentate stream and producing the auxiliary fuel stream from it. The system (S3) further comprises a polishing filter connected to the second liquid stage stream, where effluent liquid from the polishing filter becomes clean fuel. In the system (S3), the temperature of the first partial condenser is controlled to manage the condensing of the portion of the first vapor permeate stream. The system (S3) further comprises a second separation stage for separating the second liquid stage stream into a second vapor permeate stream and a second retentate stream; and a mixer to mix the first retentate stream and the second vapor permeate stream and returning the mixture to the primary fuel stream. Preferred Components: The second separation stage comprises a sulfur selective membrane maintained within a predetermined pervaporation temperature range and predetermined pervaporation vacuum range, operable to pass the second liquid stage stream into second vapor permeate stream and a second retentate stream. The first separation stage in system (S3) comprises a high flux selective membrane maintained within a predetermined pervaporation temperature range and a predetermined pervaporation vacuum range operable to separate the primary fuel stream into the first vapor permeate stream and the first retentate stream.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Process: The second retentate stream is sent to a polishing filter and the effluent liquid from the polishing filter becomes clean fuel for an auxiliary power unit. The step of isolating the second vapor permeate stream and second stage retentate includes passing the second liquid stage stream through a selective membrane maintained within a predetermined pervaporation temperature range and a predetermined pervaporation vacuum range. The process further involves sending the second stage retentate stream through a polishing filter. EXAMPLE - No suitable example given.