Waste heat boiler (M/s Borsig Design) with secondary reformer outlet gas at 895 C tube side and BFW in shell side. Currently first exchanger inlet / outlet gas temperatures are running 895 and 629 C (operating design are 945/630 C) which is almost close to the design limits. Our plant is running smoothly after last turn around from last 13 months. Plant steam / gas ratio is 1.8 and front end load is 117.5%. HS steam is opened ~ 4.5 MeT/hr in air coil for controlling coil temperature.
We have previous history of WHB outlet temp operation of 655 C due to continuous plant operation. But right now we are more vigilant because our WHB condition is not appropriate due to tube leakages issues.
As WHB first exchanger outlet temperatures are reached to its operating design limit so we are planning to increase steam inside the air coil or directly inside primary reformer but we don’t have any previous experience.
I need opinion of ammonia plant experts about this problem and what do u think by increasing steam this fouling will decrease/ mitigate. Moreover, if someone has such kind of experience then please share.
The fouling in many cases may be from the refractory lining of secondary reformer and dust of the catalyst and if you increased the steaming time little during startup you observe some improvement but the best choice is mechanical cleaning for the tube side of WHB and deep inspection for the refractory of secondary reformer will be very crucial for mitigation of such problems
Note: some times the degradation of the catalyst is due to some poisons like chlorine leaks to process air suction of the P.Air COMP.
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