[Digestion] Mixing in digesters?

[Katahdin Energy Works]

Depends on the design.

We do tanks, and depending on the % of solids may include a bubbler in the
bottom of the tank. 

Other tanks include a heating core and agitator to have a uniform
temperature.

Temps are a concern; as is exposure to the two key microbe
groups--Acetogenic and methanogenic. We use imbedded colonies to maximize
exposure. 

There is a natural bubbling that occurs as solids sink to the bottom and get
acting upon.

CHD lagoons have a patented circulation system w/pumps and baffles.

I haven't check evaluations of agitator systems; remember injection is from
the bottom and that provides mixing; and digestion is from the bottom to the
top.  

In two tank designs; the acidification process is often a 'fast' one with a
lot of agitation; while the methane one sees solids somewhat settling and
methane given off bubbling to the top. 

Hope this helps.

Frank J. Heller, MPA
KATAHDIN ENERGY WORKS
12 Belmont St.
Brunswick, ME 04011-3004
207.729.6090
http://mysite.verizon.net/fjheller/


-----Original Message-----
From: digestion-bounces at listserv.repp.org
[mailto:digestion-bounces at listserv.repp.org] On Behalf Of Harmon Seaver
Sent: Wednesday, September 12, 2007 2:16 PM
To: Digestion at listserv.repp.org
Subject: [Digestion] Mixing in digesters?

   Someone just posted that  "well-stirred digesters with mixed contents
will always out-perform single feedstock digesters by volume". Sometime
back, when I asked about having a mobile digester (to provide fuel for a
 motorhome and process waste), I was told that it would not work because
disturbing the digester would cause it to stop working.
    So is mixing bad or good?

-- 
Harmon Seaver

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