Pyrolysis is often a first step in the incineration process, especially of the hazardous waste. One of examples of such installation is presented in the paper cylindrical pyrolysis chamber, applied in the incineration plant for medical waste. In the chamber the carbonisation of the waste takes place and the products, such as volatiles and carbonisate are burned in the cylindrical combustion chamber surrounding the pyrolysis chamber. Such configuration provides the heat transport from the flue gases to the carbonising material. To model the processes taking place in the pyrolysis chamber the energy and mass balance equations have been defined. The system of equations was solved for the exemplary material, such as wood sawdust, of a known thermophysical properties. Results are presented as diagrams of various parameters inside the two-dimension domain of the chamber.