THEORETICAL STUDY OF THE PYROLYSIS PROCESS IN A THIN FIXED BED IN A TWO-STAGE THERMOCHEMICAL PROCESSING PLANT FOR POPLAR WOOD CHIPS

• Дата: 2026
• Автори: Rokhman, B. B., Kobzar , S. G., Chetveryk , H. О.
• Формат: Стаття
• Мова: Українська
• Опубліковано: Institute of Renewable Energy National Academy of Sciences of Ukraine 2026
• Теми: fixed bed; biomass; thermal conductivity; pyrolysis; steam-air gasification; heat transfer; gas; temperature.
• Онлайн доступ: https://ve.org.ua/index.php/journal/article/view/644
• Назва журналу: Vidnovluvana energetika

An original method is proposed for producing two synthetic gases – one of medium calorific value and one of low calorific value – from poplar wood chips in a single unit. The medium-calorific gas is obtained through the pyrolysis of biomass in a thin fixed bed 20 mm thick, under the influence of two external heat sources. The 225-mm-high pyrolyzer is located between a 230×5-mm-diameter outer tube and a 180×5-mm-diameter inner tube, the surfaces of which are covered with 2-mm-thick ceramic insulation. After heating the pyrolyzer surfaces to a temperature of 950–960 °C, dried poplar chips are fed into the outer tube, and specific heat fluxes of 0–150 kJ/(s·m²) are applied to the ceramic insulation surfaces of the outer and inner tubes. Part of the poplar chip fractions penetrates the thin annular intertube space, while the remainder forms a particle bed (clusters) at the pyrolyzer inlet. A rotating agitator made of flexible metal rods is used to break up the clusters, allowing a thin, fixed layer to form. Various modes of poplar chip pyrolysis were considered: 1) external heat fluxes are zero, and the pyrolysis process occurs due to heat accumulated in the metal and ceramics, preheated to a temperature of 950 °C. The time required to heat the bed to a minimum particle temperature of 760 °C is 21 s; 2) the heat flux to the insulation of the outer tube is 80 kJ/(s·m²), and to the insulation of the inner tube is 70 kJ/(s·m²). The minimum heating temperature of biomass particles during the 18-second cycle is 670 °C, and the heating rate of the bed reaches 1,900 °C/min, which is an indicator of rapid pyrolysis. After the cycle, the release of volatile substances ceases, and a 8% tar fraction remains, which is converted into a light gas within 3 seconds through a cracking process; that is, the pyrolysis gas consists solely of secondary gas.