“Investigation of pelletized biomass thermal deformations during pyrolysis” Doctoral Thesis

Author, Institution: Rolandas Paulauskas, Lithuanian Energy Institute

Science Area, Field of Science: Technological Sciences, Energetics and Power Engineering – 06T

Scientific Supervisor:  Dr. Algis DŽIUGYS (Lithuanian Energy Institute, Technological Sciences, Energetics and Power Engineering – 06T)

Dissertation Defence Board of Energetics and Power Engineering Science Field:
Habil. Dr. Algirdas KALIATKA (Lithuanian Energy Institute, Technological Sciences, Energetics and Power Engineering – 06T) – Chairman,
Dr. Sigitas RIMKEVIČIUS (Lithuanian Energy Institute, Technological Sciences, Energetics and Power Engineering – 06T),
Dr. Egidijus URBONAVIČIUS (Lithuanian Energy Institute, Technological Sciences, Energetics and Power Engineering – 06T),
Prof. Dr. Saulius VASAREVIČIUS (Vilnius Gediminas Technical University, Technological Sciences, Environmental Engineering – 04T),
Dr. Francesco ZIMBARDI (Italian National Agency for New Technologies, Energy and Sustainable Economic Development, Technological Sciences, Energetics and Power Engineering – 06T).

The Doctoral Dissertation is available at the libraries of Kaunas University of Technology (K. Donelaičio St. 20, Kaunas) and Lithuanian Energy Institute (Breslaujos g. 3, Kaunas)

Annotation:

Increasing requirements for environmental protection, renewable fuel resources are increasingly being used for electricity and heat production. Due to increased demand for biofuels, searching for ways to use low-quality renewable fuel resources (forest floor, needles, chicken litter, etc.). One of technological ways to convert biomass into heat or electrical energy is gasification process in which the solid fraction is converted into fuel gas. However, gasification of wood pellets in downdraft gasifier is confronted with the problem of granulated fuel agglomeration. It occurs when the wood pellets are moving from the pyrolysis zone to the oxidation zone and pellets stick together in lumps, which disrupts the movement of fuel and stops further process. In order to determine the origin of the adhesion of wood pellets, it is necessary to investigate size changes and mass loss of biomass (wood particles, wood pellets and wheat straw pellets) at high temperatures. According to this, experimental investigations were performed in the electrically heated horizontal furnace from 300 °C to 900 °C temperature at an inert ambient. Results revealed that pelletized biomass expands at a low temperature (400 °C) due to obstructed evaporation of volatile species. The biomass pellets start to shrink as the emission of volatiles intensifies. As temperature increases till 650 °C, swelling of the pellets intensifies. 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 obtained results, mathematical equations, describing the evolution of biomass thermal deformations with increasing heating temperature, were developed.