[Gasification] Fluidised Bed Reactor

Kevin kchisholm at ca.inter.net
Thu Nov 28 18:57:53 CST 2013


Dear GF
  ----- Original Message ----- 
  From: GFWHELL at aol.com 
  To: gasification at lists.bioenergylists.org 
  Sent: Thursday, November 28, 2013 8:32 PM
  Subject: Re: [Gasification] Fluidised Bed Reactor


  Phil,
   Why not make the exhaust manifold,  the structural part of the pyrolysis  section of our gasifier.
   A heavily loaded gasoline engine driving an alternator will produce enough waste heat to carbonize the biomass.

  # That would certainly work, as a pyrolyzer. The effect would be like a "heated retort." It would indeed produce char, and pyrolysis gas.

  # However, teh pyrolysis gas would be very tarry, and would not be suitable for "Engine Grade Gas" without adequate cleaning. However, it would be very good as a "Heating Grade Gas."

  Note that even with the higher exhaust temperatures for heavily loaded diesels indicated by Phil, the temperature is marginally low for the CO2 + C --> 2CO reaction to happen completely. 

  Best wishes,

  Kevin



  GF 

  In a message dated 11/28/2013 6:32:44 P.M. Eastern Standard Time, phil at marshbros.ca writes:
    Hi Kevin:

     

    A loaded diesel can easily run egt of 550-650C. Pyrometers are common on big diesels but it does depend on where the measurement is taken. 

     

    Phil Marsh

    Marshbros.

    250 569-7858

     

    From: Gasification [mailto:gasification-bounces at lists.bioenergylists.org] On Behalf Of Kevin
    Sent: November-28-13 12:27 PM
    To: Discussion of biomass pyrolysis and gasification
    Subject: Re: [Gasification] Fluidised Bed Reactor

     

    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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