[Stoves] Metals in biofuels

[Tom Miles]

FS>I noticed boron was not included but boron is a big factor in glass 
making. Just wondering if it was looked into?

Boron does cause clinkering. It is not usually in fuels unless treated wood
is burned. In the US treated wood is permitted for burning so we ignore it
unless swe uspect that it is contributing to slagging.   


>Also; titanium is included but that seems to be a rare constituent in 
>biomass. Where would that come from? Is that really important?


Titanium is present to a small degree in fuels. It is included I think
becasue it can be used sin acid/base formulas. We have found that these
formulas for melts that seem to work for coal do not work well for biomass.


>Wondering if carbonates are only in the ash where a carbonate is added 
>(lime) or if it can form at the right temperature? I find a lot of 
>carbonates in ash samples.
Wood generally has high calcium. Calcim can react with CO2 in the gas to
form carbonates. Carbonates are formed in the same way in the preparation of
the sample. We use CO2 in the analysis to account for carbonates formed
during ashing.  


>If dirt is included in the biomass is the oxides that are already formed at
the start a problem with slagging? or is it neutral and the problems come
during elements in the biomass structure converting to oxides at the high
heat?
Is Si in soil (quartz) a problem or only the Si that has been taken up. by
plants (phytoliths)?

Oxides from dirt just add bulk to a deposit. when you have high dirt it you
usally find that clinkers are nothing more than pieces of dirt or sand bound
together by an adhesive or bonding material that is usually an alkali
compound like potassium chloride, potassium or sodium sulfate or similar.   

 >How is oxygen directly measured?

Oxygen is not measured directly but calculated by difference. 

>I think we should also add lead, arsenic and cadmium, perhaps zinc and 
selenium as toxins that come from treated wood, plant accumulation and 
additives that make toxic emissions.

Toxins are important to account for a soils analysis. The heavy metals
usually get sequestered by the sulfates (e.g. lead sulfate) formed on cool
surfaces.  

>I am thinking (hoping) that only the elements that dissolve in a hot acid
digest along with sulfate, chloride and phosphate is important for us and
not the 'rock' material left behind in the acid treatment when predicting
problems.

The hot acid digest is similar to the chemical fractionation (leaching in
water, dilute acid and strong acid) that we did in order to identify
components that volatilize during combustion (water an dilute acid soluble),
reactor during combustion (Strong acid soluble) and pass through interest
(residue from strong acid). We found that it is most useful to analyze for
the total quantity of components, such as total chlorine, rather than just
the soluble components because we found that in different fuels the
components had different degrees of solubility. this reflects the many forms
(usually hydroxides) they take in the plant itself.  

>Thanks - great report!  My head a centimeter bigger.

That's an asset, not generally a problem. 

I hope this helps.

Tom


 
 






Tom Miles wrote:

>Frank,
>
>For evaluating potential problems for slagging and fouling in gasifiers and
>combustors (e.g. stoves) we use ten elements in the ash reported as oxides:
>
>Silica (SiO2)
>Aluminum    (Al)
>Iron    (Fe)
>Titanium (TiO2)
>Phosphorous (P2O5)
>Calcium (CaO)
>Magnesium (MgO)
>Sulfur (SO3)
>Sodium (Na2O)
>Potassium (K2O)
>
>Plus
>Chloride (Cl)
>Carbon Dioxide (CO2) is measured to estimate losses on fusion. 
>
>We measure total chloride in the fuel and of source sulfur. These elements
>volatilize during combustion and can cause fusion and deposits. 
>
>You can see how we use these analyses in the report, "Alkali Deposits in
>Biomass Boiler", TRM Miles 1995 lined from my website www.trmiles.com or
>directly at http://www.trmiles.com/alkali/alkali.htm
>
>Many thanks for your help with the Gasifier Experimenters Kit (GEK) at
ETHOS
>this weekend. It was a big distraction for Charlie to set it up but I think
>it was worthwhile. 
>
>Kind regards,
>
>Tom
>  
>  
> 
>
>-----Original Message-----
>From: stoves-bounces at listserv.repp.org
>[mailto:stoves-bounces at listserv.repp.org] On Behalf Of frank
>Sent: Tuesday, January 27, 2009 4:35 PM
>To: Discussion of biomass cooking stoves
>Subject: [Stoves] Metals in biofuels
>
>
>Dear Stovers, charcoal makers and brick makers,
>
>Of the list of elements below I am wanting to know the ones that would 
>be of interest in regards to causing problems, volatile toxins and of 
>nutrient interest.
>I have already added As, Cd, Pb, Zn, to my list for possible toxins.
>I have added Ca, Mg, K, P for possible nutrients in left over char and ash
>I have added Na, and K that may be problems in making an ash that  forms 
>blocks (?).
>
>Any comments of problems or concern or interest of the following will 
>help me to put together a test program for testing biofuels.
>
>Thanks (again)
>
>Frank
>
>Aluminum    (Al)
>Boron    (B)
>Cobalt    (Co)
>Chromium    (Cr)
>Copper    (Cu)
>Iron    (Fe)
>Manganese    (Mn)
>Molybdenum    (Mo)
>Nickel    (Ni)
>Selenium    (Se)
>Chloride (Cl)
>Nitrate (NO3)
>Phosphate (PO4)
>Sulfate (SO4)
>
>
>Frank Shields
>Soil Control Lab
>42 Hangar way
>Watsonville, CA  95076
>(831) 724-5422 tel
>(831) 724-3188 fax
>frank at compostlab.com
>www.compostlab.com
>
>
>
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>
>
>  
>

-- 
Frank Shields
Soil Control Lab
42 Hangar way
Watsonville, CA  95076
(831) 724-5422 tel
(831) 724-3188 fax
frank at compostlab.com
www.compostlab.com