Torrefaction of biomass pellets using the thermogravimetric analyser

Greater heating values, greater energy density and improved physical properties such as shape stability, homogeneity and hydrophobic behaviour are advantages of torrefied biomass. All this leads to an overall reduction in transport costs, storage capacity and to lower requirements for factory equipment. The properties of the different types of biomass used before and after torrefaction and the effect of torrefaction at the different process conditions were studied. For the laboratory tests of torrefaction, wood and grass waste biomass were used. For these selected materials, a number of measurements were performed to verify the most suitable torrefaction conditions (heating temperature and retention time). Experiments were carried out on a small scale on TGA 701 (LECO). Waste biomass was heated to a final temperature of 200, 225, 250, 275 and 300 degrees C with a retention time at these temperatures of 10, 20 and 45 min. The heating rate was set up to 15 degrees C min(-1). The determination of the appropriate temperature depended on the optimum ratio between mass loss and higher heating values (in case of grassy material from 200 to 225 degrees C and for woody material at 250 degrees C). From the results we can state that it is possible to do fast and exact test in TGA before the torrefaction process on the pilot unit to shorten the whole process.Web of Scienc

Product distribution and sulfur behavior in coal pyrolysis

Pyrolysis experiments of six differently ranked Chinese coals and one German coal were carried out systematically at ambient pressure. The effect of different pyrolysis conditions, including coal properties, temperature, drying of coal, on the product distribution and the behavior of sulfur in coal were investigated. The results indicated that, besides coal properties, temperature is the most important factor which affect the product distribution of pyrolysis. CO and CO2 yields in gas product are related to the oxygen content in the coal sample. Except for the sample of Datong (DT) coal, the CO and CO2 yield increases linearly with the increase in O/C atomic ratio of coal; sulfur-containing gas (H2S and COS) yield depends directly on sulfur content in the coal. With the increase in total sulfur content, pyrite sulfur content or organic sulfur content of coal, the sulfur containing gas increases substantially. Sulfur removal during coal pyrolysis at different conditions varies from 15\% to 40\% depending on coal sample, pyrolysis temperature and time. For most coal samples, the sulfur content in char is less than that in its original sample, but some exception was also found. X-ray photoelectron spectroscopy (XPS) analyses suggest that difference in sulfur removal may be partly attributed to the difference in sulfur contents in the bulk and on the surface for different coals. (C) 2004 Elsevier B.V. All rights reserved