The Conditions and Characteristics of Wood Particles Ignition in the Stream of the High Temperature Gases

ABSTRACT

The results of the experimental and theoretical studies of the ignition processes of the single woody biomass particles have been given. The experiments have been carried out on the setup, providing the closest conditions to the combustion space of the boiler units. The main parameters of heat transfer (the ambient temperature T_g) and the main characteristic of the process—the ignition delay time (t_ign) have been registered. The equipment has been used in the experiments providing with high precision the determination of the main conditions and characteristics of ignition. According to the results of the experiments, the mathematical model has been formulated describing the heating and thermal decomposition of the wood taking into account the formation of the gaseous and solid products. The model also describes the moisture evaporation, the thermochemical interaction of water vapor and carbon coke, and oxidation of the pyrolysis products with oxygen in the gas area. The nature of the relations of the heat exchange conditions, the temperature field of the particle, and ignition dynamics has been determined. It has been shown that the determining factor is not only the content of the volatiles and moisture of wood, but also the distribution of moisture in the particle. The record of the distribution of moisture content across the thickness of the layer results in the change of moisture from 0% to 60% to increase the time delay of the ignition 2–3 times. The relation has been determined between the particle size, the moisture content, and the ignition delay time.

KEYWORDS:

• Biomass
• Heat and mass transfer
• Ignition
• Wet wood

Additional information

Funding

This work was supported by Ministry of Education and Science of the Russian Federation (NSH-7538-2016.8.).