Principle of post combustion and off-gas cooling in cold blast cupolas

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. 

If the cupola off-gas does not ignite spontaneously, the installation of ignition or support burners is necessary. These ineur a significant power use and increase the overall flue-gas volume. 

Two configurations of (in-shaft post combustion and) cooling on cold blast cupolas were studied on an industrial scale and compared by CTIF cupola I was equipped with a water injection in the cupola shaft, a cyclone and a bag filter, cupola J was equipped with a gas-air heat-exchanger, a cyclone and a bag filter. Operational data are given in Table 4.39. Results of the measurement campaigns and reference to the applicable legislation are given in Table 4.40. 

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Figure 4.15 Principle of post combustion and off-gas cooling in cold blast cupolas [157, Godinot, et al., 1999]...

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