Pyrolysis Using Solid Heat Carrier Of Lignite And Characteristics Of Products

Coal pyrolysis, especially fast pyrolysis with the solid heat carrier, can obtain oil and gas products under mild reaction conditions which is a clean and high efficient way of coal utilization. However, owning to the weak regulation function of solid heat carrier on pyrolysis products, there are some drawbacks with this technology, such as heavy tar content, pipe blockage, and difficulty in separating the oil from the dust, which will surely affect the long-term stable operation of the system. This research combined the catalytic process of coal pyrolysis with solid heat carrier, and investigated the impact of various solid heat carriers on the distribution and composition of the pyrolysis products. The selected heat carrier was improved its capability to achieve a high yield of the coal conversion and the light tar.Firstly, using the silica sand as a heat carrier, the effect of reaction conditions on the distribution and composition of the products of coal pyrolysis was investigated. The results showed that the impact of reaction time on the distribution and composition of the products is not obvious. After 30 min, the yield of the volatile was unchanged. Temperature was the main affecting factors, which can influence the distribution of liquid and gas products. Showing a tendency of increasing before reducing,, the yield of tar reached its maximum at 550℃. The yields of volatile increased with increasing coal particle size. The most appropriate reaction conditions were 550℃,30 min and 1.10～2.20 mm.In addition, the impact of different solid heat carriers on the coal pyrolysis was studied under the optimum conditions, and the effects follows the order: FCC spent catalyst> red mud> ceramsite≈olivine> silica sand. Abundant in Fe and Ca, olivine, red mud and ceramsite can reduce asphaltene yield in that Fe and Ca can promote the asphaltene fragmentation reactions. And the acting part of the FCC spent catalyst was acidic active center. The asphaltene yield was less than 20%. Meanwhile, the yield of the light tar also decreased, and the extent to which it decreased was in accordance with the effects. Among them, olivine had little effect on the yield of light tar while reducing the heavy tar.Finally, the olivine-based catalyst was prepared. The optimum content of Co in olivine was examined. Optimum effect would be yield when content of Co in olivine was 5%. Co-impregnated olivine can change the distribution of the H of volatiles within the coal and maintained the H in the liquid production, and transferred the heavy components into the light tar and gas. As a result, compared with the olivine sand, Co/olivine had an increasing tar yield by 19.2% while the yield of the light oil can reach up to 5.1%, and the content of the light oil, phenol oil and naphthalene oil increased by 19.6%,17% and 15.2% respectively; meanwhile, the ingredient of H2 and CH4 had an evident decline in gaseous products.