Upgrading of Yi’an gas coal by low temperature pyrolysis under different atmospheres

The quality of Yi’an gas coal before and after low temperature upgrading under either a N2 or H2 atmosphere was examined by thermogravimetric and infrared analyses. The effect of upgrading on the prepared coke quality was analyzed. The results show that the carboxyl and phenolic hydroxyls in the coal molecular structure are removed after upgrading by low temperature pyrolysis under either N2 or H2 atmospheres. This improves coal caking properties to a certain extent. The upgrading effect under a H2 atmosphere is remarkably better than the effect observed after upgrading under N2. Compared to coke obtained from raw coal, the compressive- and micro-strength of the cokes obtained from upgraded coal are greatly improved. The effect on coke reactivity with CO2 is not significant. The best upgrading temperature for Yi’an gas coal under either a N2 or H2 atmosphere is 250 or 275 °C respectively.