The development of opto-acoustic diagnostic systems for industrial thermal processing plants

The inner walls and construction elements of industrial furnaces and boilers are undergoing a steady degradation caused by thermal and mechanical stresses as well as erosion and aging processes. This may result in efficiency losses, decreasing product quality and increasing maintenance costs. The inspection and analysis of combustion processes, treated products and inner facilities is often only possible during running processes. Otherwise the reasons for problems or defects could not be identified. It is possible to derive necessary information from both thermal radiation and acoustic signals. Using just the information of the visible wave length it is possible to reach absolute accuracy levels of ~7 K at 1000 °C and above. Hence it is possible to determine heat bridges and not homogeneous heating processes on the inner surfaces of furnace walls and on the product. This allows the detection of cracks and damages in furnace structures and products.