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View Diary: Sunday Train: Unleashing the Political Power of Bio-Coal (128 comments)

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  •  How is ash handling a more serious problem (0+ / 0-)

    ... with charcoal with a lower ash content than the coal already being used? I'd like a reference to what the specific problem is with charcoal, either replacing or co-firing coal-fired power plants.

    Indeed, lower ash content would be one of the substantial benefits of biocoal over torrefied biomass, since production in excess of 300°C produces charcoal, not the torrefied biomass created at 230-280°C.

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    by BruceMcF on Wed Oct 02, 2013 at 04:52:18 AM PDT

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    •  Two papers come to mind (0+ / 0-)

      There really has been a lot of work in this area. Two very good technical papers that I'd suggest are:

      Title: Biomass-coal co-combustion: opportunity for affordable renewable energy
      by Larry Baxter,
      FUEL  Volume: 84   Issue: 10   Pages: 1295-1302   DOI: 10.1016/j.fuel.2004.09.023   Published: JUL 2005

      and

      Title: The behavior of inorganic material in biomass-fired power boilers: field and laboratory experiences
      Authors: Baxter, LL; Miles, TR; Miles, TR; et al.
      Source: FUEL PROCESSING TECHNOLOGY  Volume: 54   Issue: 1-3   Pages: 47-78   DOI: 10.1016/S0378-3820(97)00060-X   Published: MAR 1998

      Search for "biomass alkali ash deposition", and you'll find enough for full-time study for a year or two.

      The problems are solvable, but, for the time being, expensive. And retrofitting a coal plant takes careful planning.

      -5.38, -2.97
      The NRA doesn't represent the interests of gun owners. So why are you still a member?

      by ChuckInReno on Wed Oct 02, 2013 at 12:45:55 PM PDT

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      •  But is that torrefied wood ... (0+ / 0-)

        ... or is it flash carbonization charcoal? For example, when I read regarding fine fly ash:

        The basic mechanisms concerning aerosol formation in combustion processes are, in general, well known from former research work [5]. Volatile ash forming compounds, which are in the specific case of biomass combustion K, Na, S, Cl as well as easily volatile heavy metals (Zn and Cd), are released from the fuel into the gas phase and subsequently undergo gas phase reactions. ...
        ... clearly that ash formation is much less problematic with flash carbonized charcoal than with torrefied wood, since the bulk of those volatiles are emitted in the exhaust of the flash carbonization reactor.

        We simply cannot look at biomass that has been converted to charcoal at around 500°C in an aerobic process under pressure and biomass that has been converted to a charred and dried torrefied product in an anaerobic process at 230-280°C and treat them as if they are chemically similar.

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        by BruceMcF on Wed Oct 02, 2013 at 02:31:55 PM PDT

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        •  Carbonized biomass (0+ / 0-)

          There are many ways to produce carbonized biomass, including traditional charcoal process, torrefaction, hydrothermal carbonization, gasification, and even pyrolysis. The char you produce has some commonalities, and some differences. To generalize way too much, the inorganic fraction (i.e., the ash) are pretty similar. These fraction do not oxidize in a boiler, but must be removed. They can volatilize, which really creates havoc on boiler surfaces. No matter how you treat the biomass, it's unlikely that you will leach out the minerals. They stay behind. The organic fractions, on the other hand, are really different in the different chars. They have a different ultimate and proximate analysis. They certainly burn differently. But under most circumstances, the ash they leave behind is similar.

          -5.38, -2.97
          The NRA doesn't represent the interests of gun owners. So why are you still a member?

          by ChuckInReno on Thu Oct 03, 2013 at 02:53:48 AM PDT

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          •  From the reference you gave indirectly ... (0+ / 0-)

            ... that is, from googling on the search term that you gave, refer to torrefied wood or similar product. And the descriptions I have of charcoal versus torrefied wood is that the ash content is substantially higher in torrefied wood.

            You say:

            They can volatilize, which really creates havoc on boiler surfaces.
            But don't say why they won't volatilize during pyrolysis under pressure. That would seem to be the most likely reason for the reported differences in ash content.

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            by BruceMcF on Fri Oct 04, 2013 at 01:24:39 AM PDT

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            •  Biochar (0+ / 0-)

              Obviously, you're very interested in these topics. By me answering your questions, one at a time, you'll never get the level of mastery you're seeking, and I'll run out of patience.

              These are pretty sophisticated topics. There is a LOT written in the open literature. If you've gotten through two semesters of freshman chemistry, I think you'll be able to comprehend most of it. (If you haven't then that's where I'd suggest you start.) Just keep reading, and you'll learn. There's no shortcut, though- it takes a lot of time, measured in years, not days, to become proficient in these topics.

              Good luck!

              -5.38, -2.97
              The NRA doesn't represent the interests of gun owners. So why are you still a member?

              by ChuckInReno on Fri Oct 04, 2013 at 03:44:28 AM PDT

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              •  From what I've seen ... (0+ / 0-)

                ... since, this is an issue of the relative pricing, since on a patent search aimed at torreffied wood, the majority of the ash content can be removed from powdered torrefied wood by mechanical means.

                The specific problem at hand seems to be less severe than the problems of disposal of coal ash, except that part of the costs of the disposal of coal ash are allowed to be externalized, so this point appears to be pointing out that while existing coal-fired power plants can be powered entirely by cleaner burning biocoal, it will be less labor intensive if it is done with a pre-processing step that removes much of the non carbon ash content.

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                by BruceMcF on Fri Oct 04, 2013 at 03:49:41 PM PDT

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