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Tham khảo tài liệu 'carbon materials for advanced technologies part 8', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 225 Table 17. Effect of hydrogenation on green coke yields Coal Green coke yield wt TGA yield wt WVGS 13407 71.4 71.0 EXT HEXT350 60.3 WVGS 13421 EXT 71.2 80.0 HEXT400 62.8 HEXT450 57.1 51.0 WVGS 13423 EXT 70.3 61.5 HEXT450 52.3 34.0 Table 18. Effect of blending hydrogenated coal-derived pitch and coal extract on green coke yields WVGS 13421 Blending ratio Green coke yield wt TGA yield wt 100-0 EXT HEXT450 71.2 80 0 75.25 EXTHEXT450 69.6 63.5 25 75 EXTHEXT450 62.9 52.9 0T00 EXT HEXT450 57.1 51.0 Table 19. Effect of blending hydrogenated coal-derived pitch and coal extract on green coke yields WVGS 13423 Blending ratio Green coke yield wt TGA yield wt 100 0 EXT HEXT450 70.3 61.5 75 25 EXTHEXT450 61.7 57.7 25 75 EXT HEXT450 47.2 40.4 0 100 EXT HEXT450 52 3 34.0 Table 20 reports the yield of calcined cokes for several of the graphite precursors. The high-coke yields indicate that most of the volatiles were lost during the green coking operation. Since no visible tar or smoke occurred during calcination most of the weight loss is attributed to evolution of hydrogen non-condensable hydrocarbons and other light gases. 3.2 Analysis of cokes by optical microscopy Polarized light photomicrographs were taken of the green and calcined cokes as well as their corresponding test graphites. The untreated exfract cokes are characterized by very small anisotropic domains on the order of 3 microns or less. This type of optical structure is believed to be highly desirable for nuclear graphite applications. 226 Table 20. Yield of calcined coke for wvu test graphites__ Calcined coke yield. wt WVGS 13421 HEXT400 93.8 75 25 EXT HEXT400 96.1 60 40 EXT HEXT350 95.5 EXT 92.8 75 25 EXT HEXT450 91.6 25 75 EXT HEXT450 92.7 HEXT450 94.2 WVGS 13423 EXT 87.0 75 27 EXT HEXT450 91.1 25 75 EXT HEXT450 93.1 HEXT450 92.0 In contrast the hydrogenated extracts show much larger anisotropic domain structures increasing in size with increasing hydrogenation severity which is consistent with
