Fuel Staging for No
            <sub>x</sub>
            , Reduction in Automatic Wood Furnaces

Salzmann, R.; Nussbaumer, T.

doi:10.1002/9780470694954.ch77

Cited by 1 publication

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“…The aim of the work presented is to investigate whether a new concept for fuel staging based on fixed bed systems is suitable for the NO x reduction of nonpulverized wood fuels . Focus of the research is the elaboration of the optimum combustion conditions for an efficient NO x reduction.…”

Section: Introductionmentioning

confidence: 99%

Fuel Staging for NO_x Reduction in Biomass Combustion: Experiments and Modeling

Salzmann¹,

Nußbaumer²

2001

Energy Fuels

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With increasing use of biomass in combustion processes, the reduction of the related NO x emissions which originate mainly from the fuel nitrogen becomes more and more important. Efficient primary measures for NO x reduction are staged combustion techniques. Air staging has been investigated earlier and has found its way into practice. Since fuel staging has not been applied with nonpulverized biomass yet, the aim of the present work was to investigate the potential of fuel staging for NO x reduction in fixed bed systems. For this purpose, a prototype understoker furnace of 75 kW thermal input with two fuel beds in series was developed. Experiments were performed with wood chips (low nitrogen content) and UF-chipboards (high nitrogen content) to investigate the influences of the main process parameters, i.e., stoichiometric ratio, temperatures, residence time, and fuel properties on the conversion of fuel nitrogen to N-species. The most important parameters were found to be the temperature and the stoichiometric ratio in the reburn zone. The potential of fuel staging was measured and compared with air staging and unstaged combustion. The experiments show that low NO x emissions are already achievable with fuel staging at lower temperatures than with air staging, i.e., 900−1000 °C, and at a stoichiometric ratio of 0.85 in the reduction zone. The NO x reduction achieved under optimum conditions for UF-chipboard as main fuel was 78% which is higher than with air staging, where 72% NO x reduction was measured. For wood chips both measures attained about 66%. The nitrogen conversion during air and fuel staging has also been simulated using a furnace model based on ideal flow patterns as perfectly stirred reactors and plug flow reactors. A detailed reaction mechanism including the nitrogen chemistry (GRI-Mech 2.11) was implemented. The trends found with this model are in good agreement with the experiments and they indicate that even higher NO x reduction may be reached with improved process design. The investigations show that fuel staging is a promising technology for NO x reduction also for fixed bed biomass furnaces.

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Section: Introductionmentioning

confidence: 99%