[Stoves] Lime residue in stack?

[Tom Miles]

Liming capacity has always been the selling point for wood ash. In the 1990s
about 95% of the wood ash from biomass plants was land applied for soil
improvement. Now much of the ash is land filled because biomass plants
sometimes burn urban wood waste. The biomass plants cannot guarantee that
the ash from the urban wood waste will pass environmental regulations for
metals. They mostly will but it is cheaper to send it to the land fill than
to test for compliance.

 

Our study stimulated literally thousands of studies and caused some changes
in the way some boilers are designed and ash is handled. Each year I review
several papers on the topic for academic journals. Today we see the same
patterns in the way ash transforms during combustion.  Better analytical
tools have confirmed many of our conclusions. The relationships between
elements in the ash are better understood. It is now possible to model what
will happen to wood ash in a boiler with acceptable levels of accuracy. 

 

Next week at the Biochar conference we will hear that if wood ash contains
60% or more charcoal then it will behave more like biochar. If it has less
carbon then it will behave like ash. Producers are finding markets for both
qualities of wood ash. This should also apply to wood ash from cooking
stoves. We need people to try it. 

 

Tom     

 

From: Stoves [mailto:stoves-bounces at lists.bioenergylists.org] On Behalf Of
Frank Shields
Sent: Wednesday, October 09, 2013 12:18 PM
To: 'Discussion of biomass cooking stoves'
Subject: Re: [Stoves] Lime residue in stack?

 

Tom,

 

Guess I will wait until I get a sample but at least it seems there is a good
possibility the 'waste' material will be a good candidate for what we want
to use it for, namely to raise the pH of a solution with some cheap (free or
pay to take) material. Great report!  I see I already have a copy on my
computer and used a different section to assemble a test package for
remaining ash. I think the presence of Si is the potential big problems. 

 

Frank

 

 

Frank Shields

Control Laboratories; Inc.

42 Hangar Way

Watsonville, CA  95076

(831) 724-5422 tel

(831) 724-3188 fax

frank at biocharlab.com

www.controllabs.com

 

 

 

 

 

From: Stoves [mailto:stoves-bounces at lists.bioenergylists.org] On Behalf Of
Tom Miles
Sent: Wednesday, October 09, 2013 11:47 AM
To: 'Discussion of biomass cooking stoves'
Subject: Re: [Stoves] Lime residue in stack?

 

Frank

 

See http://www.trmiles.com/alkali/Alkali_Report.pdf

"Alkali Deposits Found In Biomass Power Plants A Preliminary Investigation
of their Extent and Nature"

 

In that study we looked at the composition of the fuel ash and the way it is
transformed as it is burned in the furnace, cooled in the boiler, and
captured in the pollution control devices. You will find some of the
mineralogy (forms of ash) recorded in the appendices. 

 

We find that ash that is removed from the furnace section (grate ash) is
very similar to the ash in the fuel. Ash that is removed from the boiler and
pollution control devices largely consists of salts that are formed from low
melting elements that have volatilized from the fuel (K, NA) and reacted
with other low melting elements (S, P, CL) to form alkali salts. Particles
that leave the furnace are often enriched in these salts. Because of the
high calcium content of biomass fuels you also get carbonates. (Carbonates
are also an artifact of calcining the ash sample for analysis).  

 

Large particle collected in the primary cyclone of a biomass plant tend to
be very high in carbon. We have found these chars can be good "biochars."
The small particles that pass through the cyclone and are captured in
pollution control devices (electrostatic precipitator or baghouse) are often
the alkali salts. The condense on air and water tubes and cause corrosion.
In s stove they might corrode the pot or chamber over time, especially if
they are exposed to moisture. 

 

So you can see that the burner, whether it is a cooking stove or industrial
furnace, separates - or fractionates - the fuel into carbon (CO2, char).
salt enriched minerals, water and gases (N2).  

 

Tom      

 

 

From: Stoves [mailto:stoves-bounces at lists.bioenergylists.org] On Behalf Of
Frank Shields
Sent: Wednesday, October 09, 2013 11:27 AM
To: stoves at lists.bioenergylists.org
Subject: [Stoves] Lime residue in stack?

 

Greetings Stovers

 

I am being asked to test a sample of a "lime residue" from a stack of a
power plant(?) to see if can be used in agriculture or in chemical
manufacturing. Is there such a thing as carbonates or oxides formed in
stacks? In pure enough quantity. I was thinking most all the residue was
from organics (tars) depositing on the walls. Not sure what the fuel is but
I think is a big operation in Australia.

 

Thanks

 

Frank

  

 

Frank Shields

Control Laboratories; Inc.

42 Hangar Way

Watsonville, CA  95076

(831) 724-5422 tel

(831) 724-3188 fax

frank at biocharlab.com

www.controllabs.com

 

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