Researches On Soot-releasing Characteristics And Mechanism During Biomass Burning

Soot is the main component of atmospheric fine particles, primarilyfrom biomass and fossil fuel burning. Soot is caused by incompletecombustion of fuel, and it has a very great harm on humans and theenvironment. This paper uses cotton straw and saw dust as the main researchobjects, setting different combustion conditions, combusting in a tubefurnace and sampling. Observation of collected samples of appearance foundthat as the temperature and oxygen content increases, soot carbonizationlevel increases, generated graphite-like carbon gradually increased, leadingto the color of sample gradually deepened. For cotton straw and saw dust,longer the burning time, soot concentration collected is higher. When thetemperature exceeded400°C, biomass went into high temperaturecombustion and then the soot occurred secondary cracking, which constantlyimpelled gas yield to increase and soot and carbon production to decrease.Using TEM-EDX and GC-MS, we studied soot physico-chemicalcharacteristics and analyzed biomass combustion of soot formationmechanism under different conditions of combustion. By the observation ofTEM-EDX we analyzed microstructure of soot and configuration changes,and most soot particles are like capsule and sphere. So higher temperatureand oxygen level are beneficial to the volatilization of organic carbon anddehydrogenation reaction, which would make soot diameter smaller; thecollision and coagulation of finer soot would turn the single particle intochains and nets, so the arrangement would be in order. Using gaschromatography-mass spectrometry detected the main compositions ofbiomass combustion are phenols, aldehydes, furfural furans, alkanes, andolefins. Furfural compounds may come from ether bond of main chain onbiomass polymer breaking. As the temperature increases, Carbonyl, C-O andC-H bonds of char groups occur fracture and restructure reactions,generating CO, CO₂, H₂O and olefins and so on. Residual carbon of celluloseoccurs aromatic transformation, carbonization, rearrangement reaction,generating large amounts of aromatic compounds of phenols withoxygen-containing functional groups, aldehydes, ketones and so on. In thispaper, it provided a scientific basis for soot emissions reduction duringbiomass burning through the researches on soot-releasing characteristics andmechanism.