Effect of flue gas flow on NOx formed by nitrate evaporation from fining agents
This internal study was carried out to analyse how the different flow patterns of regenerative end-port furnaces influences the NOx emissions resulting from nitrate fining.
Based on furnace and operation data of a former project a base case was set up.The furnace was designed as a regenerativ end-port furnace with two fuel injection lances and a dog house at the left furnace side seen in direction of the glass flow.
Based on this base case different flow pattern were realised by the implementation of additional burners, lances and adjustments of the current firing. Specific attention was paid to simulate the flow field and the pathways of the evaporations from the nitrate fining.
The simulation consideres locally different evaporation mass flows. Figure 1: Pathways of NOx formed in the fining zone from nitrate fining
Furnaces with one dog house show in general differences depending on the side of firing concerning refractory surface temperature, preheat and flue gas temperature and flue gas composition. Reasons are the asysmmetric batch pattern and different amount and position of false air intrusion through the dog house.
Firing at the doghouse side results in lower Nox-Emissions than firing at the opposite side. In studies conducted for non nitrate finning furnaces in general the contrary can be observed.
In cases with nitrate fining, significant amount of NOx cam from the batch. When firing above the batch the resulting NOx is transported through the furnace and the NOx is destroyed partly by a reburning mechanism. Firing opposite to the batch the from the batch resulting NOx is transported direct to the exhaust without significant reburning.