Filamentous coke growth

In what is considered a key finding of this investigation/ significant filamentous coke also formed on the surface of the Vycor tubes holding the sulfided coupons. This coke was found to contain both iron and nickel which had obviously been transferred from the Incoloy 800 coupons. Possibly the iron and nickel sulfides originally present on the coupons were liquefied or even volatilized and then transported to the Vycor surfaces where they catalyzed the growth of coke filaments. 

Observations near the edges of several recoked Incoloy 800 coupons indicated that the structure of the coke deposit varied considerably with depth as the coke metal interface was approached. The innermost layer i. e. the layer in contact with the coupon surface was observed to be a matrix of smooth and rather solid carbon. The outermost layer however consisted of the profuse filament growth which was described earlier from two-dimensional observations. This filamentous growth occurred in the region between the carbon matrix and the reacting gas phase. 

Finally, is observed that the rcw increases with the pcH4 [16-18] and with the reduction temperature, while it diminishes with the reaction temperature. The influence of the ph2 has no clear effect. The effect of the reaction temperature is due to the fact that high reaction temperatures favor gasification over the growth of coke filaments [15,19,26,27] which would explain the negative value of the activation energy apparent for the filament growth. 

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