Urgent: Factors affecting denitration in catalytic cracking
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When the standby main fan is started up in a catalytic cracking unit, the most significant change is a decrease in pressure. Why then does the NOX content in the regenerated flue gas increase significantly? And why does the NOX level after treatment by the subsequent denitration SCR unit also exceed the specified limits? Does anyone know why the NOX generation is high when a backup unit is in use, and how can the denitration efficiency of the SCR be ensured?
It is because the increase in flue gas temperature generates a large amount of hot nitrogen; when the flue gas engine is in operation, its temperature drops after doing work, resulting in less hot nitrogen being produced. However, when the standby engine is activated, the flue gas does not do work and its temperature remains high, which leads to the generation of a large amount of hot nitrogen within the boiler system. If no other denitration measures are taken, this will result in excessive NOX levels. This may not be entirely accurate; I would appreciate it if experts could correct me.
Why does the pressure decrease when starting a standby machine? Is it that the pressing head of the backup machine isn’t sufficient? Has the processing volume decreased when a backup unit is used, resulting in an increase in oxygen content? For example, the oxygen content is 2% under normal conditions, but it exceeds 4% when a backup unit is in use?
We have newly installed flue gas desulfurization equipment, but the post-desulfurization section has not been put into use yet. The level of NOX in the flue gas (on an equivalent basis) changes significantly with the main air flow rate; currently, it is required to keep the oxygen content in the flue gas at around 2. The power of the standby unit might be different from that of the main unit