The flame temperature in reheat furnace can be raised by enriching the combustion air with oxygen. Thermal processing equipment which previously had to rely on high-quality fossil fuels can now be operated with previously unusable process gases and biogases. This benefit arises by oxygen enrichment. To produce O2 at low cost, a new method involving ceramic membranes was developed in a collaborative project. Following this, investigations were conducted on the lab-scale furnace to determine whether the combination of high-calorific gas and air could be replaced by a combination of low calorific gas and oxygen for use in reheating furnaces. It was demonstrated that the necessary furnace chamber temperature can also be achieved with low-calorific gases.