you can also try hooking the gas up to the beer out post (use some lube here so it comes off after) and push the co2 through the beer. keep bleeding it off as you do it and see if that speeds it up at all.
That's been my experience with sulfur – tends to blow off after a week or two of purging and refilling the headspace of the keg.
Never turns out the best beer, but it is OK after sulfur dissipates.
My suspicion is that most sulfur comes from yeast stress due to over-pitching AND/OR insufficient FAN.
Recent Trial—German Hefe
- Pitching rate: 15e6 cells/mL (common is 5–7e6 cells/mL)
- Result: Complete loss of banana & huge sulfur production & green-beer diacetyl production.
- Reasoning: Older (less healthy) cell population resulted in stressed yeast – coupled with lack of necessary nutrients to support such a large population of yeast (particularly amino-acids which may be lacking in wheat)
Edit – also saw this article on overpitching/diacetyl – may not be directly useful: http://www.ifrj.upm.edu.my/16%20(4)%202009/11%20IFRJ-2009-112%20Nguyen%20Vietnam%202nd%20proof.pdf