Excessive nitrogen oxides in catalyzed flue gas
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Catalytic flue gas treatment removes sulfur but not nitrogen oxides. It turns out that the nitrogen content is very low and also quite stable. Currently, it is both unstable and exceeds the limits; the properties of the raw material have not changed much. How should this be handled?
Let’s first check whether it’s a problem with the instrument display; there’s not much that can be done, and flue gas desulfurization is merely a means of removing sulfur
The best solution is to install denitration facilities; another option is to try reducing the flue gas temperature, or to use ammonia or urea in injection at the end of the flue gas emission process, with relatively low costs
There must be a reason why it wasn’t a problem before but is now; until that reason is identified, no measures should be taken blindly. Both desulfurization and denitrification are monitored by online instruments, and it is possible that there could be issues with these instruments; therefore, it is feasible to take samples of the flue gas for analysis. If the values obtained from such analysis are similar to those measured by the online instruments, then instrument failures can be ruled out. Therefore, there are only two possible reasons for the excessive nitrogen compound content: one is a high level of nitrogen compounds in the raw materials, and this can be addressed by adjusting the ratio of these raw materials, thereby reducing the proportion of those with high nitrogen content and thus lowering the nitrogen compounds in the flue gases ； Secondly, if the flue gas temperature is too high, more nitrogen oxides are produced as a result of the reaction between oxygen and nitrogen; this issue can be addressed by lowering the flue gas temperature.
What denitration equipment does your company use?
We don’t have any flue gas treatment facilities; previously, for dry catalysis, SCR was used for emission removal
Does adding alkali solution work effectively against sulfur dioxide?
If the levels exceed the limits occasionally, check whether the line calibration instrument is functioning properly. If the instrument is fine, consider adding denitration agents on the side of the regenerator
By reducing the oxygen content and the temperature of the regenerator, CO can reduce NO when the coking effect is poor; denitration additives can also be used, with effects becoming apparent within about half a month.
Was a combustion accelerator added along with the catalyst?