Flame Propagation Characteristics in the Boundary Layer of the Bio-Water-Coal Fuel Particle During its Ignition

ABSTRACT

The article presents the experimental research results of the flame propagation processes in the small vicinity of Bio-WCF particles during their ignition. According to the experimental researches, there have been obtained characteristic ignition delay times (t_ign) and times of full engulfment of the fuel particle in fire (t_sf). We have analyzed the influence of metamorphism degree of fuel basic component (coal) and sort of biomass on characteristics of these processes. It has been shown that increase in concentration of biomass in fuel leads to decrease in ignition delay times and fire propagation in boundary layer of the Bio-WCF particle. We have recognized that the oxidizer temperature (T_g) strongly influences the fire propagation dynamic in small volume vicinity of fuel particles. Also, we have observed that the effect of influence of oxidizer temperature (T_g) on the time of full engulfment of the fuel particle in fire (t_sf) differs from the predicted once. Increase in T_g in a certain period of changes in its values (T_g = 1073–1273 K) leads to increase in time of full engulfment of the Bio-WCF particle in fire. The hypothesis describes the influence of ambient temperature on t_sf was formulated.

We have substantiated the hypothesis using the results of mathematical modeling. This hypothesis describes the physical mechanism of the influence of water vapors, which are formed during intrapore moisture evaporation on characteristics and conditions of volatile combustion in the boundary layer of the fuel particle.

KEYWORDS:

• Water-coal fuel
• bio-water-coal fuel
• biomass
• ignition
• flame propagation

Nomenclature

Abbreviations

Bio-WCF - Bio-coal-water fuel (or fuel coal/biomass/water) - Bio-water-coal fuel is a mixture of a finely divided biomass (various types), coal, and water. Under these conditions, the technology of bio-water-coal fuel is a promising method of co-firing coal and biomass. These technologies belong to the new environmentally friendly (relatively) fuel-combustion technologies of the future.

WCF – coal-water fuel - The mixture of a finely divided coal (different coal) and water.

FCM - Forest combustible material — forest combustible material (or forest biomass) is a complex of the forest plants, their morphological parts, plant remains of varying degrees of biological decomposition, leaf, or coniferous litter, which can ignite and sustain combustion

RES - Renewable energy sources - Energy resources of constantly existing natural processes on the planet, as well as energy resources of waste products of biocoenoses of plant and animal origin.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the grant of the President of the Russian Federation MK-89.2021.4.