A client is looking for a special waste heat boiler. He would like to use the heat of the combustion gases at a temperature of 1.200°C. The heat must be absorbed in two steps. The first step is at a high level where intense cooling of the tubes must be guaranteed. The inlet of the tubes must also be resistant to the high temperatures. In the second step, the hot gasses cool down further to a lower level where the temperatures on the tube side are less critical.