Among
the liquid fuels supporting the decarbonization of the energy
conversion chain, alcohols play a key role. Mainly considered for
engine application, their use in stationary systems designed for power
generation is receiving considerable attention but requires further
investigation. This work aims at demonstrating the feasibility of
thermochemical conversion of low-molecular-weight alcohols, methanol,
ethanol, and 1-butanol, in a small-scale unit exercised under moderate
or intense low-oxygen dilution combustion conditions. The highly recirculated
flow field configuration allows for the stabilization of the process
over a wide range of reactor temperatures. The experimental campaign
is carried out by varying the mixture equivalence ratio and the thermal
power. The burner was exercised with different gas feeding configurations,
namely, premixed and non-premixed. Experimental results are reported
in terms of operational temperatures and pollutant emissions (CO and
NO
x
). For all of the fuels and thermal
power, it was possible to reach NO
x
levels
lower than 20 ppm and CO below 40 ppm for a wider range of the mixture
equivalence ratio than hydrocarbon fuels. Despite similarities in
the temperature profiles and CO emissions, NO
x
levels increase with the complexity of the alcohol molecules
and their distribution is also a function of the injection strategy.
Simulations in a perfectly stirred reactor and in a counterflow diffusion
flame were performed to provide insights into the key factors controlling
the NO
x
emission levels and distribution.
Numerical results with a perfectly stirred reactor model show the
role of NO
x
chemistry in determining the
different emission levels of the three alcohols. On the other hand,
simulations with a counterflow diffusion flame suggest that the separate
reactant supply to the combustion chamber represents the key parameter
in determining the experimental NO
x
distribution
in the non-premixed mode.