The gasification of biomass in moving-bed gasifier coupled
with an internal combustion engine is very attractive in the
range of small powers. The physical and chemical characteristics
of the biomass and the conditions of the gasification
process determine the composition of the obtained gas and in
consequence also their properties. The whole gasification–
cleaning–combustion process in engine should be optimised to
achieve the objectives of maximum power and operation
reliability.
The characteristics of the gasification gas that affect most
quantitatively the engine power are the heating value, the
stoichiometric air–fuel ratio and the volume correction factor
of the mixture. These parameters combine in the so-called
factor EFQ. Typical values of this factor imply that the power
of an engine fuelled with producer gas is of the order of twothirds
of the corresponding conventional fuel. This can be
considered as a first order approximation of the power of an
engine working with such a gaseous fuel.
A more detailed prediction of engine performance requires
the use of computer simulation of several types. The authors
have used successfully a two-zone thermodynamic model to
predict engine performance. The thermodynamic model uses
the conservation equation for the unburned and burned zones,
the engine initial and operating conditions, and estimations of
laminar combustion speed. All these determine the development
of the combustion and the formation of pollutants. Model
results include the mass burned fraction, the pressure and
temperature evolution, and the associated values of engine
efficiency and indicated mean pressure. The detailed results for
power confirm the first order prediction based on the EFQ
parameter.