Materials performance in high-temperature black liquor gasification

Combined cycle gasification of the black liquor waste stream generated in pulp and paper mills offers the potential for more efficient recovery of the energy content of the stream as well as a reduction in emissions and operation of a system without the potential for molten smelt - water explosions. Many companies and organizations have studied, proposed and/or developed black liquor gasification systems. Two of these have been taken to the stage of implementation in operating North American mills. The lower temperature process is being employed at two semi-chem mills; one in Big Island, Virginia, and one in Trenton, Ontario. The higher temperature process is being used at a kraft mill in New Bern, North Carolina. For both processes, the performance of containment materials has been a serious issue. With the higher temperature process, degradation of both refractory and metallic components are a cause for concern. This paper describes the refractories and alloys used in this gasifier, laboratory studies to identify improved refractories, and real-time measurements to monitor the expansion of the refractory. The work has led to the selection of materials that should give considerably longer lifetime than the previously used refractories.