Regarding the SCR interlock scheme
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SCR processes generally incorporate low-temperature interlocks and high-temperature interlocks, but these two types of interlocks can be fatal for catalytic cracking units. In fact, the temperature control required in SCR systems is not as stringent as that needed for reaction temperatures; is it really necessary to have interlock shutdown systems?
Our SCR is equipped only with an interlock for low dilution air flow, and it’s just an interlock related to ammonia injection; it should have no impact on the catalytic unit itself
The low-temperature interlock is designed primarily to prevent side reactions from occurring at low temperatures, namely the formation of ammonium sulfate (ABS), while the high-temperature interlock is intended to avoid sintering of the catalyst due to excessively high temperatures; however, we have not installed a high-temperature interlock. Interlock shutdown is not necessary; low temperature triggers an interlock to stop ammonia injection, while such a mechanism is not in place for high temperatures. We have a water protection section at the front of our boiler, as well as an interlock that sprays steam and water when the flue gases reach high temperatures.