Green cokes

Pushing Smoke, particulates (dust), SO2 Minimizing green-coke pushing, scrubbers and baghouses... 

Removal of volatile matter to about 0.5 wt% can be accomplished by calcming in a rotary kiln, rotary hearth, or vertical shaft calcmer All of these processes heat green coke to temperatures in excess of 1000°C where shrinkage and subsequent densification take place. The volatile components are comprised primarily of methane, ethane, hydrogen, and hydi ogen sulfide gases which can be employed as fuel for process heat. 

Raw coal NMP-extract Residue Green coke Calcined coke... 

All subsequent green coke operations were made in a second coker, which was fashioned from steel pipe approximately 18 cm in diameter and 25 cm in length. A metal plate was welded to one end and a metal collar was welded to the other end such that a steel lid could be bolted to the system. Typically, about 250 to 500 g of pitch were sealed imder nitrogen in the coker reactor and the system placed in a large temperature-programmable furnace. The heat treatment process was as follows. The temperature was raised 5°C/min to 350 °C and then l°C/min to 425°C and the temperature held at 425°C for 90 minutes. Finally the temperature was raised further at 3°C/min to between 500 and 600°C, and held there for 3 hours. The coker was cooled to room temperature and the material recovered to determine green coke yield. 

The green cokes were calcined by placing a weighed amount of green coke into an alumina tube. The tube was fitted with end caps to allow for a constant purge of nitrogen. The alumina tube was then inserted into a high-temperature furnace and the temperature raised to about 1000°C for a period between 30 and 60 minutes. The furnace was turned off, cooled to room temperature, and the product recovered to determine the calcined coke yield. 

Table 17. Effect of hydrogenation on green coke yields...

Table 18. Effect of blending hydrogenated coal-dcrived pitch and coal extract on green coke yields, WVGS 13421...

Blending ratio Green coke yield, wt% TGA yield, u[Pg.225]

Figure 1. Optical photomicrographs of green cokes derived from WVGS 13421 pitches top, EXT middle, 75 25 EXT HEXT450 bottom, HEXT450... 

The coke for synthetic graphite is also calcined before further processing. It is calcined until a sample of —35 + 100 mesh material shows an electrical resistivity of less than 0.05 ohm-inch. The same type of calciners are used that are used to calcine coke for the aluminum industry (29). The calcined coke retains a major portion of the sulfur present in the green petroleum coke (1). Low-sulfur, green coke is preferred. 

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