Boosting Incoming Gas Supply

[richard5]

I need to boost an incoming natural gas supply of 22mb to 120mb. The process that it supplies, aluminium melting furnaces, are always cycling so the flow rate is very dynamic, from very low flow (10000 cfh) to max (90000 cfh). I have installed a booster fan (as per IGE/UP/2) but I am experiencing high temp at the booster at low flow. I need an alternative solution or any help is appreciated. A by-pass over the boosters to allow flow at min demand does not work, i've tried.

 

[JeffHofacre]

Are you throttling flow on the discharge of your booster fan? A better method would be variable inlet vane control which is more efficient and will heat the gas less. However, the lowest practical throttling is based on leakage through the vanes.

Here are different solutions:
1. Change to inlet vane control. Doubtful that this will enable low enough turndown.
2. Install two fans in parallel. Run one or two fans depending on capacity with inlet vane control.
3. A two speed motor combined with inlet vanes.
4. A variable speed drive would be the cadillac solution.

Reference Fan Engineering published by Howden Buffalo chapter 15 "Fan Control". This discusses the plusses and minuses of each control.

 

[IRstuff]

One thing that might help is a buffer tank to provide the reserve. This would allow you to handle the flow dynamic range without tapping out the main feed.

TTFN

 

[Yeldud]

We have a gas booster project that will experience high turndown of the gas flow. The booster manufacturer is supplying a small water to gas heat exchanger to cool a portion of gas which then recirculates through the gas compressor through a small bypass. This provides cooler gas flow over the motor, and keeps booster from operating in it's surge region. Spencer Turbine is the supplier. They use a current sensor to determine when the booster is approaching an unacceptable operating point (surge).