Method for operating a heat exchanger (4, 12) comprising a gas conduit and a heat conduit, - according to which a predetermined gas is flowing through the gas conduit and a predetermined fluid compound working fluid is flowing through the heat conduit, - wherein the heat conduit is in in thermal communication with the gas conduit, - wherein the heat exchanger (4, 12) comprises a first section of a first section length, a second section of a second section length, and a third section of a third section length, - wherein the gas conduit spans, in direction of flow of the gas, the first section, the second section, and the third section, - wherein the heat conduit spans, in direction of flow of the working fluid, the third section, the first section, and the second section, - wherein the first section comprises a gas inlet for inletting the gas and the third section comprises a working fluid inlet for inletting the working fluid, - wherein the third section comprises a gas outlet for discharging the gas and the second section comprises a working fluid outlet for discharging the working fluid, - wherein the gas conduit is passed by the gas from the gas inlet to the gas outlet, - wherein the heat conduit is passed by the working fluid from the working fluid inlet to the working fluid outlet, and - characterized in that the first section length is selected such that the gas, when entering the operational heat exchanger (4, 12) through the gas inlet at a gas entry temperature of up to 700 °C, exceeds a decomposition temperature of the working fluid by up to 50 K upon exiting the first section, provided that the working fluid enters the first section in a liquid state of aggregation. - according to which a predetermined gas is flowing through the gas conduit and a predetermined fluid compound working fluid is flowing through the heat conduit, - wherein the heat conduit is in in thermal communication with the gas conduit, - wherein the heat exchanger (4, 12) comprises a first section of a first section length, a second section of a second section length, and a third section of a third section length, - wherein the gas conduit spans, in direction of flow of the gas, the first section, the second section, and the third section, - wherein the heat conduit spans, in direction of flow of the working fluid, the third section, the first section, and the second section, - wherein the first section comprises a gas inlet for inletting the gas and the third section comprises a working fluid inlet for inletting the working fluid, - wherein the third section comprises a gas outlet for discharging the gas and the second section comprises a working fluid outlet for discharging the working fluid, - wherein the gas conduit is passed by the gas from the gas inlet to the gas outlet, - wherein the heat conduit is passed by the working fluid from the working fluid inlet to the working fluid outlet, and - characterized in that the first section length is selected such that the gas, when entering the operational heat exchanger (4, 12) through the gas inlet at a gas entry temperature of up to 700 °C, exceeds a decomposition temperature of the working fluid by up to 50 K upon exiting the first section, provided that the working fluid enters the first section in a liquid state of aggregation.