Some Aspects of the Mechanism of Formation of Smoke from the Combustion of Wood

F A Atiku,G Humphries,J M Jones,A R Lea-Langton,K D Bartle,A Williams,I Burns

doi:10.1021/acs.energyfuels.6b02639

Abstract

This paper is concerned with an investigation of the formation of soot from the combustion of some of the primary pyrolysis products formed during pine wood combustion. Comparisons are made between the combustion products of model compounds, furfural for cellulose and eugenol and anisole to represent lignin (and n-decane for comparison) with the smoke emissions from the previously studied combustion of pine wood. These compounds were burned in a diffusion flame burner, and the appearance and composition of the resulting particulate and the adsorbed polynuclear aromatic hydrocarbon (PAH) precursors were studied by transmission electron microscopy (TEM), mass spectrometry and pyrolysis gas chromatography mass spectrometry (Py-GC-MS). The reactions leading to soot formation were modeled. It was concluded that wood soot formation proceeded via pyrolytic breakdown followed by a mechanism based on HACA (H-abstraction–C2H2-addition) reactions with the participation of cyclopentadienyl intermediates, while eugeno...

Highlights

The combustion of wood is widely used as a major source of heat and power covering a range of thermal capacities from domestic appliances to large scale generation plants, the attraction being in that they use a renewable energy source which is approximately carbon dioxide neutral.[1]
Two major light-absorbing components of these particles are recognized:[5] black carbon (BC) which absorbs across the solar spectrum and lightabsorbing organic carbon (OC, or BrC, brown carbon, coated on the BC particles) which absorbs at short wavelengths
The deposition rates are a function of the soot volume fraction, the particle density and the thermophoretic drift, which in turn is a function of the temperature gradient at the boundary layer.[28]

Summary

INTRODUCTION

The combustion of wood is widely used as a major source of heat and power covering a range of thermal capacities from domestic appliances to large scale generation plants, the attraction being in that they use a renewable energy source which is approximately carbon dioxide neutral.[1]. We have proposed that the cellulose products can form smoke largely via the Habstraction−C2H2-addition, termed the HACA9 route, and the lignin decomposition products form smoke via an aromatic species mechanism.[10,11] Both hard and soft woods give similar devolatilization products the distribution of the products is different, this resulting from the differences in the lignin content. GC-MS analysis shows that the principal initial volatile decomposition products of pine a soft wood include carbohydrate-derived material such as levoglucosan and furans,[11,12] and at higher temperatures the guaiacols and syringols from the lignin In flames these decompose and form smaller but more thermally stable cyclic oxygenates and polycyclic aromatic compounds become significant species.[6,11,13] Some of the dominant primary products are furfuryl alcohol, furfural, and levoglucosan from the cellulose, and eugenol, isoeugenol, vanillin, and guaiacols from the lignin. In the present study we have extended our earlier work[13,20,21] on the processes leading to the formation of particulate soot

EXPERIMENTAL SECTION

RESULTS AND DISCUSSION

CONCLUSIONS

■ ACKNOWLEDGMENTS

■ REFERENCES