| 摘要 |
The main aspect of the present invention is based on introducing process fluid into a compressive pretreatment stage, in an environment of elevated temperature and pressure, thereby initiating lignin dissolution in the chips at a point farther upstream than was previously known. In a preferred implementation of the present invention, this process fluid includes recycled process reagents drawn from process lines farther downstream. In another aspect of the invention, some of this process fluid is extracted as pressate during compression of the chips, and the pressate is reintroduced downstream, into the plant's recovery system. In a particularly effective implementation of the invention, the feed material is delivered under pressure to a compression device which has a variable speed motor such that the duration of exposure of the chips experience an initial processing of consolidation and extraction of fluids through the walls of the compression device into a pressurized collar or flash tank. THereafter the material is further consolidated at a high compression in the ratio of at least 3 to 1 and up to 8 to 1 or more, before discharge. The relative duration of the exposure of the material as between the consolidation phase and the high compression phase, can be pre-established by, for example, the relative screw shaft lengths and wall characteristics defining these regions. |
