The gas produced in the BOF has a temperature of approximately 1200°C and a flow rate of approximately 50-100 Nm³/t-steel. The gas contains approximately 70-80% CO when leaving the BOF and has a heating value of approximately 8.8 MJ/Nm³ (NEDO, 2008) or 0.84GJ/t-steel (IEA, 2007). Therefore, recovery of the sensible and latent heat from BOF presents the single most important opportuniy for energy efficiency in BOF. This can also  make the process a net energy producer.  However, the gas production in the BOF is intermittent, show high temperature and composition variations, and is dirty.  Consequently, in most plants this gas is still flared (IEA, 2007). 

Heat recovery processes are classified as combustion and non-combustion methods. In the combustion method, the CO leaving the furnace is allowed to combust by letting large amounts of air to enter the exhaust hood.  The resulting hot gas from the combustion is then used in a heat recovery boiler to produce high pressure steam.  

In the non-combustion method, conversion of CO to CO₂ (i.e. combustion) is prevented.  The sensible heat of the CO-rich off-gas is first recovered in a waste heat boiler, generating high pressure steam. The gas is subsequently cleaned and stored and used as a fuel by mixing with other by-product gases (coke oven gas, blast furnace gas).  Non-combustion method recovers about 70% of the latent heat and sensible heat.