Re: DIG-L: Thermophillic

["Saq" <info@ebl.co.uk>]

The Italians have worked well with = flexible liner  digesters maitained under vacuum but this can be an unnecessarily = complex  approach. I have never heard of any cold flexible liner systems in = Germany  dating back 20 years, does anyone have any published info? I visited = many  systems in Germany at that time. As far as I was aware the first = flexible liners  were systematically developed at Cornell in the late 70's. There were = two groups  subsequently active both using a flexible cover, but Bill Jewell = developed a  flexible covered base and Larry Walker was working on a concrete  pit.

Stephen Etheridge
----- Original Message -----
Simm To: <3d.htm>Jim <3d.htm>Groman
Cc:
Sent: Friday, February 18, 2000 = 8:06  AM
Subject: Re: DIG-L: = Thermophillic

To keep such a cover under vacuum wouldn't do the job.  Practically all lagoons in Germany have such a cover today. They are = kept  under a pressure 20 mm water column just like the rest of the system. = Their  egdes are usually submerged.

Few were ever torn off by storms. 
What might cause problems is air intruding the system thru the = U-shape  water-filled safety valve, as a result of lack of gas when pumping out = sludge.  According to a telephone conversation I once had with an insurance = company,  explosive atmospheres cause about 5 incidents yearly at Germany but I = have not  heard of one that was clearly related to a biogas plant. (Foul gas = occurs in  every sludge tank.)

Anthony Simm

At 03:19 PM 02/17/2000 = -0800,  you wrote:
 >>>>
Just an anecdote, since I am more interested in the = consequences  (biogas) of digestion than the process tself.\ I believe there are = many  "un-intentionally" hermophillic digesters in the form of covered = anaerobic  lagoons. Lagoon systems re used quite extensively in the meat = processing  industry and many times he project involves converting aerobic = lagoons to  anaerobic. This sually involves using a "rubber" cover which is = invariably  black. herefore it absorbs a lot of heat from the sun and the lagoon = quickly  heats to the thermophillic phase. Since many of these lagoons were  previously in service, they tended to hav a substantial fat and = grease layer  on top. Imagine the surprise of the first designers of these systems = when  the tarted pumping out 10 times as much gas as they expected! One = side note  as long as I brought up the ubject...if you have a covered lagoon = system,  make sure you draw out the biogas with a lower to keep the cover = under a  slight vacuum. This will prevent the cover from ballooning and = getting  ripped in the wind. For what its worth, I think lagoons can be an = effective  low cost system. Jim Groman Inside Sales Manager Vapor Product = Manager Varec  Vapor Control Inc. 714-229-3230 hone 714-952-2701 Fax 







DIGESTION List Sponsors, Archive and = Information  http://www.crest.org/renewables/digestion-list-archive  http://www.crest.org/renewables/biomass-info/ Beginners Tour of Biogas = = http://WWW.roseworthy.adelaide.edu.au/~pharris/biogas/beginners