[Gasification] Fluidised Bed Reactor

[Kevin]

Dear GF
  ----- Original Message ----- 
  From: GFWHELL at aol.com 
  To: gasification at lists.bioenergylists.org 
  Sent: Thursday, November 28, 2013 11:51 AM
  Subject: Re: [Gasification] Fluidised Bed Reactor


  Kevin .

  What sort of reaction could be expected if we applied the high temperature exhaust from an IC engine into a "reactor" containing biomass and at the same time reheated the "reactor" using some of the volatile vapors so produced? 

  # My understanding of exhaust twemperatures is that they run something as follows: (Anyone who knows better, please correct me:):
                      Unloaded                        Loaded
  Diesel            ~300F=150C                ~ 752 F =400C Max
  Spark. Ig:        ~500F=260C            ~752 F =400C Max

  I conclude that even "hot engine exhaust would not be sufficient to operate the C + CO2 --> 2Co reaction that requires temperatures in excess of 700C to run.

  perhaps we could  also ionize the vapors produced within the reactor to above 5000  deg. which should yield a relatively low tar stream of gas .some of which could fuel the IC engine.

  # 5000 F would certainly run the above reaction. However, "Tars" areof the general formula CxHyOn. Such temperatures would certainly "partially crack" the tars, but probably would not "crack" them fully, to give a tar free gas. I am guessing you would end up with some CO, and some other tars of a different composition. However, they would likely be "heavier tars" that might be removed more easily.

  # The other issue is the energy required to "ionize" stuff at 5,000 degrees. 

  This does not compromise the laws of Thermodynamics.

  # Exactly! Although many have tried, I don't know of any who have succeeded.

  Best wishes,

  Kevin

  GF

  In a message dated 11/28/2013 9:55:19 A.M. Eastern Standard Time, kchisholm at ca.inter.net writes:
    Dear Dan

    Quoting Carefreeland at aol.com:

    > Doug and all,
    >     Would some sort of a high temp molecular cracker be  a good companion
    > to create a quality gas from a fluidised bed? Possibly some  steam and / or
    > preheated air .involved? Seems if you wrapped the exhaust back  through the
    > hottest part of the flame in a reactor tube this can be  accomplished.
    >     Sorry but I have been kinda outta the loop for a  while.

    # Start by appreciating the two Fundamental Rules of Thermodynamics  
    and Thermo Chemistry:
    Fundamental Rule #1: You can't get something for nothing
    Fundamental Rule #2: As a matter of fact, you can't even break even.

    For example, the reaction
    C + O2 --> CO2             (`1)
    is strongly exothermic, and gives off about 14,000 BTU per pound of  
    carbon that is oxidized.

    If there was insufficient O2, and the C was only burned to CO, as follows:
    C + 1/2O2 --> CO           (2)
    then only abut 4,000 BTU would be released  per pound of carbon.

    If we wanted to reverse reaction #1, we would have to put back 14,000 BTU/Lb C
    OR, in the case of a gasifier, where the reaction
    CO2 + C --> 2  CO         (3)
    is desired, we would have to "put back"  energy as follows:
    14,000 + 0 --> 2x4,000 + "X"
    14,000 --> 8,000 + "X"
    and it is obvious that "X" is 6,000 BTU, in order to respect  
    Fundamental Rule #1

    "Molecular Crackers" and "Catalysts" do indeed work, but only when the  
    fundamental need to add or remove energy from a reaction is respected.  
    As long as the "fundamental need for an energy balance" is respected,  
    then many things are possible.

    Best wishes,

    Kevin

    >
    >     Dan Dimiduk




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