THERMAL DEVICE, ITS USE, AND METHOD FOR HEATING A HEAT TRANSFER MEDIUM

A thermal device comprising some heat exchanger pipe of a flow duct for gases in the flow duct. The pipe comprises a first section which further comprises a second section. The second section of the heat exchanger pipe comprises an inner pipe for transferring heat transfer medium and for recovering heat into the heat transfer medium; an outer pipe that radially encloses said part of the inner pipe; and a medium layer placed between the outer pipe and the part of the inner pipe. The second section of the heat exchanger pipe extends in a straight line or bends less than 90 degrees. Furthermore, the first section is insulated in its entirety, or non-insulated in the vicinity of other heat recovery surfaces only. A wall of the device comprises a protrusion that makes the flow duct for gases narrower. Said first section of the heat exchanger pipe extends from said protrusion. The use of the device in such a way that the temperature of the heat transfer medium flowing in the inner pipe is at least 500°C, and/or in such a way that the temperature of the outer surface of the outer pipe is higher than 600°C, and/or in such a way that means for feeding an auxiliary agent are used for feeding an auxiliary agent to the thermal device. Furthermore, a method for heating a heat transfer medium, in which method said thermal device is used.