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:[email protected]] 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 [email protected] www.controllabs.com From: Stoves [mailto:[email protected]] 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:[email protected]] On Behalf Of Frank Shields Sent: Wednesday, October 09, 2013 11:27 AM To: [email protected] 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 [email protected] www.controllabs.com
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