During the recovery of the liquor, thick liquor is oxidatively burned, resulting in magnesium oxide dust and SO2 gas. The MgO dust is taken up in water and brought into contact with the SO2-containing waste gas from the liquor combustion to form magnesium bisulphite liquor again.
Air consists of 78 % nitrogen, 21 % oxygen, just less than 1 % argon and other gases. In combustion processes that use air as an oxidant, the high nitrogen content is a limiting factor, since a portion of the energy generated is only used for heating of the inert gas and is therefore lost to the process.
The addition of oxygen to an air stream increases the oxygen concentration and thus at the same time improves the firing efficiency of the combustion. The technology of oxygen addition in combustion processes is flexible and can be applied to almost all types of furnaces, such as shaft furnaces, rotary drum ovens, grate firing ovens, fluidised bed ovens, deck ovens, etc.
Oxygen enrichment leads to
- Significantly increased capacities
- Reduction in energy use
- Optimisation of the entire process
In order to exploit the full potential when burning the thick liquor, it is necessary to generate a homogeneous gas mixture over the shortest possible route.