ISSN 0010-5082, Combustion, Explosion, and Shock Waves, 2018, Vol. 54, No. 3, pp. 325–336.
Pleiades Publishing, Ltd., 2018.
Original Russian Text
G.V. Kuznetsov, V.V. Salomatov, S.V. Syrodoy.
Ignition of Particles of Wet Woody Biomass under Convective
Diﬀusion of Water Vapor in the Near-Wall Region
G. V. Kuznetsov
, and S. V. Syrodoy
Published in Fizika Goreniya Vzryva, Vol. 54, No. 3, pp. 82–95, May–June, 2018.
Original article submitted September 1, 2017.
Abstract: This paper presents the results of an experimental and theoretical study of heat and
mass transfer during ignition of wet wood particles in a high-temperature gas medium. Experi-
ments were carried out in a setup which provides conditions similar to the combustion spaces of
boiler units. The main heat transfer parameters (ambient temperature) and integrated ignition
characteristics (ignition delay) were measured. The measurement error of these parameters did not
exceed 18%. The convective transfer of water vapor formed during evaporation of pore moisture
and pyrolysis products were found to have an insigniﬁcant eﬀect on the ignition characteristics and
conditions. From the results of the experiments, a mathematical model of the ignition process was
developed which describes the simultaneous occurrence of the main processes of thermal prepara-
tion under conditions of intense phase (evaporation of water) and thermochemical transformations
(thermal decomposition of the organic part of the fuel, thermochemical interaction between water
vapor and carbon coke, ignition of volatiles) taking into account the convective diﬀusion of water
vapor and pyrolysis products in the near-wall gas area during the induction period. The theoretical
ignition delay is in satisfactory (within the conﬁdence interval) agreement with the experimental
value. The numerical model of the diﬀusion ﬂame adequately (good agreement between experi-
mental and theoretical ignition delays) describes the ignition of a wet wood particle.
Keywords: wet wood particle, water evaporation, injection into the near-wall region, ignition of
volatiles, ignition of coke.
In recent years, there has been a continuous in-
crease in the role of woody biomass in the world energy
production as the main fuel for thermal power plants [1–
3]. Research in bioenergetics is developing the fastest
in Western Europe (Germany and Denmark) [4, 5] and
North America (USA and Canada) [6, 7].
Wood has a number of undoubted advantages over
traditional solid (coal), liquid (fuel oil), and gaseous
(natural gas) types of energy sources. The main of
these is that wood is practically the only renewable
Tomsk Polytechnic University, Tomsk, 634050 Russia;
Kutateladze Institute of Thermophysics, Siberian
Branch, Russian Academy of Sciences, Novosibirsk,
(in a relatively short period) type of fuel. Thus, the
forests of Western and Eastern Siberia, South Amer-
ica, and Canada are able to reproduce up to 1500 tons
of biomass from one hectare . In addition, wood
processing waste, whose storage is unreasonable due to
their high ﬁre hazard , can be used for the produc-
tion of wood pellets .
Woody biomass combustion, as a rule, proceeds
at relatively low temperatures (900–1400 K) ; ac-
cordingly, much less nitrogen oxides are formed than in
pulverized coal or oil-fueled power plants . In view
of the increased control of the compliance of environ-
mental regulations for the emissions of thermal power
plants , the latter circumstance can signiﬁcantly re-
duce the cost of the product (thermal and electric en-
ergy) for the consumer. It should also be noted that
wood fuel combustion produces a small amount of ash
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