Final Report: Demonstration of Use of Torrefied Biomass in Electric Power Generation

Abstract

During this task, a literature review was produced that highlighted some of the characteristics of torrefied fuels and the various efforts to develop commercial systems for its routine production (APPENDIX A). The report highlights work in Europe and subsequent work undertaken during this project and illustrates that energy contents approaching sub-bituminous coal can be produced, but also indicates that the new fuel is chemically reactive and must be handled appropriately. In addition, the results indicate that the biological reactivity relative to white pellets is dramatically reduced. The raw torrefied, undensified fuel is moisture resistant, but densified materials have less moisture resistance and can degrade depending on the binders used in producing the compacted fuel materials. Therefore, the ability to concentrate the energy levels while simultaneously meeting various physical property requirements was noted as an active development by European investigators and a key focus area for the work undertaken by the Natural Resources Research Institute (NRRI). Various tests were completed in using torrefied fuel produced under a variety of conditions. The first test was conducted by Southern Company’s Gulf Power Subsidiary at the Plant Scholz in Florida before active implementation of this project. The test demonstrated that material substitution up to 100% could be attained using torrefied fuels as a coal substitute. The test also indicated that the material is reactive and must be handled similarly to sub-bituminous coal. This test also indicated that further enhancement of torrefied fuel properties should be undertaken in order to improve the overall efficiency of the fuels in power plant operations. The work undertaken at Plant Scholz will be summarized in this report. The trials at the various power plants clearly have shown that torrefied fuels can be a significant substitute for sub-bituminous coal without massive capital expenses to accommodate the use of the advanced biomass-based fuel. But it is also very clear that substantial improvements in physical properties that allow reductions in dust generation, improved moisture resistance, and reduced operator intervention relative to coal are still desired. The tests at the power plants noted illustrate that significant growth in knowledge for use of this new fuel is attained as the trial size increases and as the characteristics of the fuel are more clearly understood.