Post combustion in the cupola shaft

The gases are combusted by an injection of air into the upper part of the charge or at a position above the charge top level. The airflow is adjusted so that the off-gases ignite spontaneously, due to their CO content and temperature. The injection nozzles can be placed on one or two levels. The partitioning of the airflow over the various levels, the choice of diameter and the 

A supporting burner may be provided to maintain the flame. When using very low coke charges (i.e. 6 - 8 %) the precautionary measure is reasonable. 

Installing post combustion on cold blast cupolas can be combined with a full retrofit to hot blast operation. In general, this choice is based on operational considerations. The characteristics of hot blast and long campaign furnaces are discussed in Section 2.4.1. 

Post combustion limits the emissions of CO and eliminates the majority of organic compounds. If not combusted, these would be captured in the dust or emitted through the chimney. Furthermore, post combustion reduces the risk of fire in the filter. 

This technique is known to avoid explosion risks under certain circumstances. The positive environmental effect is limited to those cases when the off-gas is burning autothermally most of the time. Otherwise, the energy consumption will counterbalance the CO reduction. 

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