[Bioconversion] Re: emissions

[Les Blevins]

Jonathan,

Thanks for your inquiry on emissions.

As I am sure you know air and ash emissions are complex issues.

My company's furnace design incorporates features to minimize emissions of particulates and toxic gasses. One such feature is it's lined with firebrick or other refractory to achieve higher temperatures by directing radiant heat back at the fuel in the chamber. When burning fuels (such as wood for example) are in a chamber and close to the chamber wall, and when that wall takes on a highly reflective surface it will tend to reflect heat back at the fuel and this "superheats" the fuel and this causes it give up its stored chemical energy into an environment that is hotter and more conducive to cleaner burning.

I notice you also mentioned dual stage burning. This is also included in my design. Duel stage burning is achieved in the AAEC furnace by taking the smoke from the high (rich) smoke zone out of the furnace and reintroducing it back into the furnace under the hot zone and burning the smoke by passing it through the hot zone where the unburned products of first stage combustion are consumed. This is considerably more efficient and cleaner than single stage burning where the smoke is allowed to exit carrying particulates and toxic gasses. Also with my furnace design gas can be used by passing the smoke through a hot gas flame to burn particles and toxic gasses internally. This gets the user two uses for the gas. One is the thermal heat value and the other is cleaner combustion of dirty fuels.

Scrubbers, filters and other off-the-shelf emissions abatement technologies can be incorporated as needed.

Overall emissions and efficiencies in my system (like all systems) will vary with the composition of the fuels being used and with the type of heat recovery system being used and with the quality of the installation of the system, and with the way the system is being managed. Thus there are too many variables for me to go into here to any great extent.

I am seeking contact with a city or cities that is/are interested in trying out a concept where each city block or selected city blocks would agree to install a central heating system that is fed wood and household trash that has been selected for inclusion and where all other components are kept separate. This concept would allow all the residents in that block to pool their dry trash and process it in a central system that is equipped with suitable pollution abatement technology and has a taller stack than homes normally do. Each residence in that block would agree to not have a woodstove but could if they wanted connect to underground pipes and use heat from the central system to heat spaces and/or water supplies. One or more persons could be assigned to manage the system or a rotational schedule could be adopted. A ten foot long aluminum flue pipe is shown on my webpages on top of a ten foot tall furnace, and this provides an outlet 20 feet above ground level. A 20 foot section of pipe gives a stack height of 30 feet. 

The use of wire support is usually recommended for flue pipes extending over 30 feet above ground level.

Les Blevins
AAEC

  ----- Original Message ----- 
  From: Jonathan Reeves 
  To: Les Blevins 
  Sent: Saturday, February 11, 2006 7:26 AM
  Subject: emissions


  Hi Les, 

  Been watching with interest the recent threads on bioconversion....

  Just a question about your system.....I have spoken to a few people here who have had experience of the outdoor burn anything furnaces (and i'm not putting your furnace in this category) and there is a general concern about emissions (i am sure that this is a hot topic on stove lists)..but the reality is that legislation (EPA?) will be put in place in the US and Canada to ensure that these burning devices operate within defined efficiencies and emissions.  This is currently a great concern in Laval (north of montreal) which has one of the most polluted winter air qualities within North America simply due to the high proportion of wood burning stoves in this city.  This was my initial knee jerk reaction when you mentioned burning a variety of agricultural and domestic waste products...unless this is done at extremely high temperatures (maybe dual stage) there will surely be a zone of destruction down wind.  What kind of emissions and efficiencies do you obtain with your system with various different fuels?  Also have you looked at the compostion of the ash produced for various different fuels and considered the appropriate method of disposal for each?


  Jonathan