[Stoves] Characteristics of biochar was Re: [biochar] grassifier & cedar chip char

[Paul Anderson]

Crispin,

The influence of the coal industry on the testing is not a perfect match 
for what biomass gasification is all about and the testing of biomass 
and biochar.

Biomass can be 50% carbon, but with decay it will all go to CO2.      
Fixed carbon must be created in the carbonization process.

In Atlanta airport about to fly to Uganda for 3 weeks.   I hope that 
others will comment, and not rely on me to reply.

Paul

Paul S. Anderson, PhD  aka "Dr TLUD"
Email:  psanders at ilstu.edu   Skype: paultlud  Phone: +1-309-452-7072
Website:  www.drtlud.com

On 2/5/2013 10:09 AM, Crispin Pemberton-Pigott wrote:
>
> Dear Paul
>
> 1.As far as I know, there is no "fixed carbon" in the biomass. It is 
> fixed during the process of carbonization/pyrolysis.
>
> That is the problem -- it you give a sample of wood to a lab and they 
> perform a 'coal analysis test' on it you will get a report on the 
> amount of 'fixed carbon'. The point I was making is that it is a 
> metric of convenience arising from the test procedure, not a reference 
> to a material property.
>
>
> 2.  Some biomass such as seeds have "oils" that vaporize or are 
> volatile.   They are generally not pyrolyzed.   However, the lignin 
> and other "stuff" in biomass is what is pyrolyzed and gives off 
> pyrolytic gases that are volatile.   At low temperatures, the future 
> volatiles are not yet in a form that can be called volatile.   But 
> they will volatize when subjected to higher temperatures.
>
> I will accept what the chemist eventually clarify for us.
>
> The % Volatiles are defined as that fraction that will boil 
> (literally) at a given temperature. Choose you temperature. So when 
> using a defined method, the result changes with the temperature your use.
>
> See for example http://www.sigmatest.org/Coal-Testing-India.html
>
> "*Proximate analysis - Moisture, Volatile matter, Ash and Fixed Carbon: *
>
> "Proximate analysis indicates the percentage by weight of the Fixed 
> Carbon, Volatiles, Ash, and Moisture Content in coal. The amounts of 
> fixed carbon and volatile combustible matter directly contribute to 
> the heating value of coal. Fixed carbon acts as a main heat generator 
> during burning. High volatile matter content indicates easy ignition 
> of fuel. The ash content is important in the design of the furnace 
> grate, combustion volume, pollution control equipment and ash handling 
> systems of a furnace."
>
> This week we tried to get some tests of fuel content and were offered 
> 'coal analysis' tests. It all sounds good but if you look into the 
> procedure, you are not getting what you think -- i.e. it is not an 
> analysis of the elements that we are used to talking about in the 
> biomass fuel biz.
>
> Getting a lab test result of this type using an instrument designed to 
> do ANSI/ASTM D3172 tests 
> http://www.marsap.com/anamedinstru.com/coal.shtml  and turning it into 
> a 'standard' analysis is quite messy and I have a spreadsheet for 
> doing that if you need it. It was necessary for the Asian Dev Bank 
> (which built the SEET Lab) to do this because all that is available is 
> standard coal analyses, but the HTP test method is more scientific in 
> the sense that it uses the chemical composition of the fuel, not an 
> approximation of it.  It is also necessary to get the 'as received, 
> ash-free' heat content. Coal analysis methods gives AR (as received 
> moisture), AD (after drying but not 'actually dry') and FC (fixed 
> carbon, but not 'actual carbon' content). It also view some of the 
> moisture as 'inherent'.
>
> There are two things which come back 'wrong': the moisture content and 
> the carbon content. Finding out what the carbon content of the 
> volatiles was is nearly impossible. The right approach is XRD and XRF.
>
> To give you an idea of how far wrong the method is for determining 
> Carbon, here is a standard test result of some coals and sawdust 
> briquette. It is well known that the sawdust contains about 50% 
> Carbon. It was rated as having 16% 'fixed carbon'. In other words it 
> is basically a useless measurement when it comes to biochar (or 
> anything else).
>
> Regards
>
> Crispin
>

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