| Abstract [eng] |
Renewable fuel resources are widely used to produce electricity and heat. The growing demand for these stocks and their price results in searching for ways how to use low-quality biofuels. One of the ways is gasification. During this process, the solid fuel is gasified and turned into higher quality gas, which is used to generate heat or electricity. However, use of granulated biofuel for the gasification results in fuel agglomeration. Biomass pellets stick together moving from the pyrolysis zone to the oxidation zone due to the initial expansion of pellets and stop the further gasification. In order to determine the causes of biofuel agglomeration, experimental investigations of wood particle, wood pellet and straw pellet thermal deformation during pyrolysis from 300 °C to 900 temperature, where the changes of samples diameter are captured over time and measured the mass and center temperature of the samples, were performed. Results revealed that pelletized biomass expands at a low temperature (400 °C) due to complicated release of volatile species and intensifying the release of volatiles species shrinkage begins. As the temperature increases, swelling of the pellets intensifies and at the temperatures higher than 650°C, swelling of the pellets diminishes and starting from the temperatures of 850°C, the swelling phenomenon disappears. According to the set of terms of biomass deformation patterns, a mathematical equation triggering wood chips, wood pellets and straw pellets diameter changes dependent on temperature. According to the determined regularities of biomass thermal deformations, mathematical equations, describing the evolution of biomass thermal deformations with increasing heating temperature, were developed. |
