Evolution and mechanism of a new index liquid-gas ratio (LGR) in coking of coal blending

Direct coal liquefaction residue (DCLR) was blended with five bituminous coals to prepare crucible coke in the laboratory. A new index liquid-gas ratio (LGR) was defined to quantify relative amounts of liquid phase and gas phase during coking. Great attention was paid to the early stage of coking (400−600 ℃) and then LGR was modified to LGR(t). Relationships and mechanism between LGR, LGR(t) and coke strength were investigated and summarized. Results showed that when high caking property coal ratios was inadequate (< 60 %), the higher LGR was, the larger coke strength was. When high caking property coal ratios was over 60 %, LGR was over 37 mm and coke strength could be guaranteed. Besides, polynomial fitting results of LGR and CSR* showed that coke strength increased sharply and then decreased slightly when LGR increased from 20 to 40 mm. The optimal LGR of coal blends was 37 mm and rational LGR range was from 33 to 40 mm. It was also found that LGR(t) needed to be at least 90 mm at the peak temperature during the early stage of coking. In addition, DCLR ratio in blending system needed to be controlled within 5%. Otherwise, the content of gas was inadequate enough to squeeze large amounts of metaplast into holes at the temperature range 400–430 ℃. Finally, it was concluded that high quality coke could be obtained with two requirements: high caking property coal ratios was abundant (> 60 %) and the content of gas druing coking matched the content of metaplast (rational LGR and LGR(t)).