BLACK LIQUOR GASIFIER GAS-TURBINE COGENERATION

The kraft process dominates pulp and paper production worldwide. Black liquor, a mixture of lignin and inorganic chemicals, is generated in this process as fiber is extracted from wood. At most kraft mills toda y, black liquor is burned in Tomlinson boilers to produce steam for on -site heat and power and to recover the inorganic chemicals for reuse in the process. Globally, the black liquor generation rate is about 85 ,000 MWfuel (or 0.5 million tonnes of dry solids per day), with nearly 50 percent of this in North America. The majority of presently instal led Tomlinson boilers will reach the end of their useful lives during the next 5 to 20 years. As a replacement for Tomlinson-based cogenerat ion, black liquor-gasifier/gas turbine cogeneration promises higher el ectrical efficiency, with prospective environmental, safety, and capit al cost benefits for kraft mills. Several companies are pursuing comme rcialization of black liquor gasification for gas turbine applications . This paper presents results of detailed performance modeling of gasi fier/gas turbine cogeneration systems using different black liquor gas ifiers modeled on proposed commercial designs.