| 摘要 |
A continuous solvent pulping process is practiced with oxygen free gas (e.g. nitrogen) purges of all major treatment vessels (23, 24, 85, 103, 105) during the time when the process is arrested or terminated. The wood chips or other cellulosic fibrous material to be pulped is steamed in a first horizontal steaming zone (23) at a pressure of about 10-20 psi, and then in a second horizontal steaming zone (24) at a pressure of about 20-75 psi. Gases, including vaporized solvent (e.g. ethanol or other alcohol) are vented (via 30, 36) from the steaming zones, and solvent is added (at 39) to the steamed material prior to feeding to a high pressure feeder (11) . The high pressure feeder introduces the material into the top of a single digesting vessel (12), liquid and chips being separated at the top of the digester vessel without mechanical means that could cause a spark. Lignin containing liquid is withdrawn from a central portion (14) of the digester and passed through flash tanks (51-53) and ultimately for lignin and alcohol recovery. Washing -- which also may be practiced using solvent pulp from a batch system -- is accomplished by first continuously passing the pulp to a pressure diffuser (85), then to a first multi stage drum displacer washer (103), and then to a second multi stage drum displacer washer (105). <IMAGE> <IMAGE> <IMAGE> |
