[Stoves] separate primary and secondary air controls

[Gordon West]

Following up on Paul’s discussion on the evolution of TLUD’s, Bill Knauss has created a design of a forced draft stove with separately controlled primary and secondary air controls. The adjustments are not scientifically sophisticated as to monitoring and managing the chemistry of the combusted gases, but they are able to adjust the pyrolysis rate and temperature within a range, and to eliminate visible smoke. I have been using one of the units for over a year to grill with and we (The Trollworks) are currently wrapping up a second limited production run of the latest version.

Primary air is fed into the bottom of the pyrolysis canister from a computer fan controlled by a voltage control Secondary air mixing is accomplished from another computer fan that pushed air into the sealed cabinet surrounding the pyrocanister. Through a combination of a simple venturi and “corner” effect to induce turbulence and eddying upon the entry of the wood gas into the combustion chamber. The secondary air is introduced immediately at the top of the pyrocanister, before the mixing zone. There is also a flame spreader plate near the bottom of the combustion chamber that adds more turbulence. There is no visible smoke from lighting up until the pyrolysis is complete when the feedstock is within moisture and particle conformation spec.

Most of our feedstock experience is with pecan shells, wood chips, and wood pellets of 15% MC. The density of the feedstock has made little difference to the proper working of the stove. What is different is that the density has a linear relationship to the rate of pyrolysis and the Btu output; 1# of pecan shells = 1# of wood chips = 1# of wood pellets.

Gordon West
The Trollworks
503 N. “E” Street
Silver City, NM 88061
575-537-3689

An entrepreneur sees problems as the seeds of opportunity.




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