Coal and biomass slow pyrolysis reactions were investigated using thermogravimetric analysis close coupled to gas chromatography (TG-GC). The pyrolysis mass balance via this system was closed to >99 wt. %. Parallel in-situ Diffuse Reflectance Infrared Fourier-Transform Spectroscopy pyrolysis experiments were used to explain the mechanistic relationship between functional groups and volatile products. Gas and tar evolution profiles correspond to the loss of surface oxygenated functional groups and increases in char aromaticity during pyrolysis. Various pyrolysis conditions including heating rates, particle size, and reaction confinements were investigated secondary pyrolysis reactions via TG-GC. The investigation demonstrated that increasing the residence time of tar in the solid-gas interface by 0.23-0.31 seconds results in a 2.1-2.5 wt. % decrease in tar production with a commensurate 0.6-5.7 wt. % increase in solid product, a 40 wt. % increase in CH4, and a 10-30 wt. % increase in H 2 between 510 and 575 °C. Matrix-assisted laser desorption/ionization-time-of-flight mass spectroscopy (MALDI-TOF) measured the molecular weight distribution (MWD) of the pyrolysis tar product to be between 200 and 550 amu. Gas chromatographic-mass spectroscopy (GC-MS) was used to identify 120 distinct species in pyrolysis tar. Tar products of the different reaction conditions show that extended residence time of pyrolysis tars in the solid-gas interface decreased the average MWD, decreased the H/C ratio, and resulted in a more expansive speciation of nitrogen and sulfur species in the tar. Further investigations of tar show that coal tar vaporizes by 1000 ºC without producing secondary gas products or coke. Biomass was found to produce a 40 wt. % char product plus CO 2, CO, CH4, C2H4, C2H 6, and H2. The experimentally measured mass closure insists that the product distributions and profiles from slow pyrolysis are absolute and the error may be directly calculated. These are used to estimate the rates, kinetic parameters and number of reactions during pyrolysis.
|Commitee:||Castaldi, Marco J., Kretzschmar, Ilona, Quanci, John F., Rumschitzki, David, Tardos, Gabriel|
|School:||The City College of New York|
|School Location:||United States -- New York|
|Source:||DAI-B 78/08(E), Dissertation Abstracts International|
|Subjects:||Chemical engineering, Industrial engineering, Sustainability|
|Keywords:||Biochar, Biomass, Coal, Coke, Pyrolysis, Tar|
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