Anisotropic coke formation during coal slurry heating in the coal liquefaction process

✍ Scribed by F.F. Tao; L.D. Brown

• Publisher: Elsevier Science
• Year: 1988
• Tongue: English
• Weight: 909 KB
• Volume: 67
• Category: Article
• ISSN: 0016-2361
• DOI: 10.1016/0016-2361(88)90003-8

✦ Synopsis

Coke formed during early operations of the coal slurry preheater in the 250 t d -' EDS coal liquefaction pilot plant (ECLP) was examined by polarized light microscopy. The coke was optically anisotropic, having mosaic textures resulting from mesophase carbonization. The presence of mesophase in heated coal slurry was evidenced by the formation of micrometre-sized hydrocarbon spherules in the coal residue from laboratory tests under simulated ECLP preheater conditions. These spherules are thought to act as adhesives, causing deposit formation on the preheater wall. Pyrolysis of these wall deposits results in anisotropic coke formation. Preheater wall temperature and solvent quality control coking severity. Model solvent studies revealed that donor hydrogen plays the most important role in mitigating coke formation during coal slurry heating. Improvement in solvency (increase in Hildebrand solubility parameter) of the solvent is also effective in increasing the coal dissolution and reducing the coking tendency.