Filtration of Lignin from a Lignocellulose-Based Ethanol Pilot Plant

An increasing demand for bio-based vehicle fuels and impending harsher regulations of CO2 emissions are driving the development of a second generation of ethanol fuel processes. These processes will increase yields and make new feedstocks available, as they are designed to handle lignocellulosic materials such as wood. In order to achieve a sound financial economy of such a process, as well as an acceptable degree of energy efficiency, it is of the utmost importance that the lignin produced has a high dry content. An experimental study was conducted on lignin slurry from a pilot plant in the north of Sweden, in which the lignin slurry was filtered, pressed, and characterized. The dewatering was evaluated with the classical filtration equation by determining the average specific filtration resistance of the filter cakes. Compared with previous work, relatively low values of the specific filtration resistance were obtained. It is probable that the low values were an effect of the high amount of cellulose fibers present in the lignin residue. Cellulose content of the material produced in a commercially viable process will be much lower and likely result in increased filtration resistance as shown in previous work. Determination of local filtration properties is necessary for efficient design and scale-up of dewatering equipment for compressible materials. To the authors' knowledge, the local results presented are the first such measurements on material that has been produced in a pilot plant