A method of producing abrasion resistant coke from brown coal briquets in a shaft furnace comprises charging the coke briquets into the top of the furnace and removing coke from the bottom of the furnace while directing inert hot combustion gases into the furnace and through the briquets at a plurality of vertically spaced levels throughout the height of the shaft furnace. Gases are directed at temperatures to effect and successively lower stages of the furnace the preheating, predrying, carbonization, and cooling of the charge. Gases are collected in each of the preheating and predrying stages by the use of a tubular suction arm which extends substantially across the width of the furnace and includes a performated bottom and sidewalls which extend partly below the bottom and are provided with a saw-tooth configuration so as to withdraw the gases through the space below the bottom and through the perforations of the bottom and to effect entrainment of dust from the charge in so doing. The shaft furnace includes means for circulating the hot gases into each of the stages. Hot inert combustion gases are introduced into the circulating gases to avoid condensation of liquids.