A process for thermal treatment of a sulfur-containing ore in which the ore is calcined at temperatures of between 600 and 1200° C. in the presence of oxygen in a reactor so that between 1 and 90% by weight of sulfur contained in the ore is burned to sulfur dioxide and impurities contained are driven off in gaseous form. The exhaust gas being produced and containing the sulfur dioxide is fed into a gas purification comprising at least one component and/or the calcined ore is fed into at least one further process stage. An exhaust gas from the gas purification and/or the process stage and/or a gas used for cooling within the gas purification or for cooling within a further process stage is at least partially returned back into the reactor as recycling gas having a temperature of >100° C.