100% saturated biogas pipeline velocity

[JohnWeal]

Hello,

We have a centrifugal blower which is to raise the incline gas pressure from 17 mbar to 120 mbar for putting into a boiler. There is no process unit for removing moisture. (The client is taking all risks should this affect the burner/boiler or any other components)
We do have condensate knock out pots for collecting cooled gas condensate and all pipeline are on a gradient.

The temperature is assumed 20 deg C.

What wou.d be the preferred gas velocity in the pipeline? The pipelines are 100 to 200 diameter made from SS316L.

Regards
John

 

[LittleInch]

See

https://www.eng-tips.com/viewthread.cfm?qid=441652

It's really about pressure drop at these sorts of pressures.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[georgeverghese]

It sounds like you havent run the pressure drop calcs in the 2+weeks since your last post on this same topic. If you dont have any one around you who can, post us a PID and full piping isometric of this line (with a bill of materials) from the blower to the burner and some one may volunteer to help you out. Also state the design case flowrate, highest gas mol wt, gas composition, P1/T1 and required P2 at the burner gas supply flange. Also state pressure drops incurred for any inline flow elements, filters, flame arrestors, any other relevant info. Line hydraulics would be based on single phase gas since the line has no liquid holdup , given there are drain pots at all low points.

I can see the sense in the max recommended 3m/sec upper limit for gas velocity stated in the vendor manual @bimr posted in the previous thread (probably to avoid liquid surging in flooded supply lines which in turn may be due to failure of condensate pot draining mechanisms), but the required gas velocity for this case may be even lower to get to the required P2. If you have reliable condensate draining, then maybe you could exceed 3m/sec - tell us whether you wish to stay within the 3m/sec limit or allow for higher velocity in your reply.

Also tell us whether the burner is a natural draft or a forced draught burner. And the lowest gas flowrate the burners are required to operate at - we dont want a flashback into the gas line at very low forward velocity.

 

[LittleInch]

Sorry, didn't look at the poster of both of those. For future, if this is a follow up post, please refer and link to the previous one so we all understand the background and what else has been posted.

I agree with George and the issue is almost certainly one of entrained liquid droplets in the gas impacting on burner performance.

You might want to think about a larger pipe size just before the burners with a knock out pot to slow the velocity down to 1-2m/sec, but use 3-5 in the main supply piping, but we have no idea of lengths, velocities you have at the moment etc

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.