We herein offer yet more evidence that carbon dioxide emitted by coal-to-liquid, direct-liquefaction processes can be offset by the inclusion of cellulose in the CTL/BTL feed. Other references specify that cellulose (i.e., sawdust, cotton, old Intel's, etc.) can be added to the coal for co-processing into liquid fuels. In such combinations, inclusion of the cellulose actually helps to reduce the generation of some by-products that might be produced if coal were processed alone.
The excerpt:
"The Direct Liquefaction of Sawdust in Tetralin
Authors: G. Wang ; W. Li; H. Chen; B. Li
| Affiliation: | State Key Lab of Coal Conversion, Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan, P.R. China |
AbstractHydrogen liquefaction of sawdust in tetralin was performed in an autoclave at below conditions: temperature range from 200°C to 350°C; initial cool hydrogen pressure range from 4 to 10 MPa; reaction time range from 10 to 100 min. The effect of variables on the process of sawdust liquefaction was examined. The results indicate that the oil yield may range from 6.8 to 67.1% at different liquefaction conditions. Temperature has a remarkable effect than initial cool hydrogen pressure and reaction time on the process of sawdust liquefaction. With increasing temperature (200°C-350°C) the conversion, gas yield, H2 consumption and oil yield are all increased, but the yield of preasphaltene and asphaltene (PA + A) increases first (200°C-300°C) and then decreases (300°C-350°C). The high heating value of the products is higher than that of the feedstock. With the increase in initial cool H2 pressure (4-10 MPa), the conversion and gas yield are almost unchanged, the oil yield increases (36.86-57.06%), while the yield of PA + A decreases (28.07-16.27%). With increasing reaction time (10-100 min), both the conversion and the product distribution change little. The existence of H2 or tetralin improves both the conversion of sawdust and the oil yield." We'll note that "oil" yields of sawdust alone in this process are lower than other studies have reported for sawdust combined with coal. The synergy was noted by the other researchers, who posited that the cellulose acted, in addition to the tetralin, as a Hydrogen donor for the coal. And, it might well be that, not only does sawdust - cellulose - enhance the conversion coal into useable liquids, but coal does the same for cellulose. They both "work" better together than either alone, as far as efficiency of production goes, while cellulose also helps to reduce co-production of asphaltene and offsets some of the CO2 generated. And, again, "tetralin", as noted above, has been specified by West Virginia University as the best solvent so far identified for direct coal liquefaction. |