Q & A > Question Details
In our hydrogen generation unit, a waste heat boiler functions to recover reformer O/L heat to produce HP steam. Boiler is single pass shell and tube exchanger with fixed tube. Since last year the boiler is not able to recover heat upto expectation as indicated by the raised process gas O/L temperature. The process gas O/L temperature is now around 288oC instead of 265 oC earlier. In the last 2 shutdowns the tubes have been cleaned thoroughly from inside but no benefit observed. Now it is suspected that there is fouling (maybe of silica) on the shell side. There is no provision to open and clean the shell side assembly. Is there is any technology available for online removal of such fouling (maybe some kind of chemical cleaning)?
25/08/2020 A: S Sivasankaran SABANAYAGAM, CPCL, cpclsiva@yahoo.com
1. Chemical cleaning of the BFW/ steam circuit of the process gas boiler may be attempted during shutdown of the plant. However the entire BFW / Steam system including steam drum and convection coils needs to be included in this process in forced circulation of chemicals.
2. Inspection of tubes' external surface through the drain nozzle of the shell by videoscope may provide information on external condition (whether a tube's external surface / shell internal surface is fouled or not) based on which further action can be initiated .
3. High process gas O/L temperature is also possible if the bypass control valve malfunctions. Please inspect closely including its functionality during the next opportunity if not done so far.