High temperature ducting design for low pressure waste gas 1

[Stefan2211]

Dear Members,

I am looking for a some recommendation about the design of a low pressure ducting system from a high temperature kiln line. The operation data are as follows:
Max. operation pressure: 50 mbar
Operation temperatures: 300-850 Deg C depending on kiln zones.
Pipe sizes: 2"- 16"
Pipe materials < 500 Deg.C: S316 for various non flammable waste gases, mainly N2, traces of acetylene, ammonia
Pipe materials > 500 Deg.C: alloy 625 for pyrolysis waste gas, mainly N2 (625 required due to gas composition and temperature)
All waste gases will be injected in thermal oxidizers.

What would be the appropriate design ASME code since the gases. It is a large pilot plant and gas composition is not really determined. Gases are toxic and lead to fouling (condensation < 500 Deg.C). Therefore the piping will be executed with sufficient flange pipe spools for cleaning.
The current plant did not follow any specific design code as it does not fall under any pressure directive but due to waste gas composition and high temperatures there is a safety concern. ASME B31.8 is probably not required.

Thanks for any input

 

[1503-44]

Are you piping that to the injectors at with no pressure? What pressure is "low", That needs a number.

It is definately not a pipeline.

--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."

 

[Snickster]

For process plant piping I would think you would be designing to B31.3.

 

[georgeverghese]

For toxic gas, suggest using Class 150lb B31.3 piping, and avoid threaded fittings. For highly fouling gas, suggest using pipe roughness of say 1.0mm for pressure drop estimates. Acetylene LEL = 2.5% v/v.

 

[Stefan2211]

Dear 1503-44,

the pressure is max 50mbar as stated. It is the exhaust gas from a kiln for new battery anode materials.

 

[Stefan2211]

Dear georgeverghese and snickster,

Thanks you for your input. We will check B31.3. I agree threaded pipe is or better was a nightmare. The Korean piping company were not able to install threaded pipe with PTFE tape and the N2 supply system was leaking at least at 40% of connection. They had to do seal welds at the end. One of the issues also was the design of the system. The company I am working with designed acc to DIN/ISO but this piping materials are hard to get in Korea so threaded valves etc. did not fit properly. The second line will be ASME standard and design will be all done by a Korean engineering company.