absolutely right what 21121956 has said.
Alternatively you could work with heat tracing instead of steam when steam is not always available, but in this case you need to double your system (steam and heat tracing)
and the continous circulation is necessary anyway.
I also would recommend to do some gas velocity calculations or better a 3D-CFD-Simulation.
I assume because of the low velocity the soot will stay on the surfaces at the bottom of the turnaround.
It is also dependent of the swirl situation of the flow and the temperature(s) in the combustion...
Who have experience with the cleaning of coke oven gas with more than 20 mg/Nm3 tar ?
The client want to safe money and we have the job already.
It´s too late for a fundamental solution with a washer and/or and electrostatic precepitator before and we only get 50 kPa. (max. 10 kPa are free)...