To examine agglomeration of bed materials and ash deposition in fluidized bed combustion systems, MTI uses a small-scale combustor to expose bed materials to coal ash as a function of combustion conditions, bed temperature, and fluidization velocity.
Test conditions vary based on fuel type and bed-material composition. The fluidized-bed combustor design includes an advanced heat-exchange deposition probe, which is located above the bed in the gas stream. MTI designed this heat exchange system for advanced power systems, and we are currently in the development and testing phase as part of a Phase II National Science Foundation SBIR grant.
After testing, MTI examines samples of bed material, agglomerates (if present), ash deposits, cyclone ash, and filter ash using scanning electron microscope (SEM) morphological analysis. This data is used to determine the compositions, coating thickness on bed particles, and bonding materials in ash deposits.
Examples of testing various bed material combinations for a petroleum coke fired system
MTI’s small-scale fluidized bed combustion testing equipment is used to test and screen bed materials and additives for their bed-agglomeration and ash-deposition potential in fluidized-bed combustion systems. The feeder for the fluidized-bed system works best with material sized between -40 mesh and +200 mesh. The fuel and additives used in fuels and fuel blends are sized to meet this requirement. The bed material used in the testing is usually sized to -4 mesh. The test bed temperature can range up to 1750°F. Tests are typically run with feeding the fuel blends for a total of eight hours (480 minutes).
The figure above illustrates some of the results of agglomeration testing with and without additives using the small-scale fluidized bed system.