Predicting black liquor gasification combined cycle powerhouse performance accounting for off-design gas turbine operation

Estimating potential electric power generation in the pulping industry by implementing black liquor gasification combined cycle (BLGCC) technology is an important issue, given the anticipated future demand for "green" electricity. Full-scale BLGCC technology has not yet been commercially demonstrated. Therefore, performance studies of this technology require the use of computer simulation tools, with the pertaining challenge of simulating gas turbine operation on gasified black liquor fuel. Exact future plant size is usually unknown; therefore many studies adopt a simplified model assuming an engine sized to match the available fuel stream, with generic characteristics representative of a given class of engine. The performance of a fixed size engine operating at off-design conditions on low calorific value fuel is in most cases lower. This work attempts to quantify the resulting difference between performance estimates based on these two assumptions. The calculations are performed for a BLGCC powerhouse integrated with the Swedish KAM reference pulp mill, for which the biofuel (bark and black liquor) available on-site is more than sufficient to satisfy the mill steam demand. The surplus can therefore be used for additional power generation, which however implies the use of low efficiency condensing steam turbine units. Alternatively, surplus biofuel can be exported for use elsewhere. This study investigates both of these options. (C) 2003 Elsevier Ltd. All rights reserved.