Lignite dewatering under mechanical pressure, aided by superheated steam

摘要

Method for reducing water content of carbonaceous, finely-divided solids and/or sludges, especially of brown coal, in which water is held in fibrous cells by capillary action, superheated steam heats the material directly in a chamber, where surface pressure is exerted mechanically, the material is initially charged into a sealed pressure chamber preheated above 100 deg C, superheated steam at 150 deg C or above is admitted, the compaction pressure on the material corresponds to 5-8 bar of steam pressure introduced, and when the material reaches 125 deg C or more, steam injection is terminated, depending on the charged material grading, mechanical pressure is increased to 75 bar at most, reducing the residual moisture to some 20%, is described in DE 195 35 315. In this patent of addition, after opening the filter press, vapours arising are expanded into a connected chamber, from which they are let down uniformly under control, into a condenser. Also claimed is a filter press (5) to carry out the process. This has a slide valve (28) between pressure chamber and expansion chamber, over the distribution and charging belt. A further slide valve (90) seals the expansion chamber. These surround the dewatered brown coal slab from the previous cycle. A control valve connects the outlet of the expansion chamber to the vapour condenser (82). Also claimed is a control unit to carry out the process as described.