Stainless Steel TLUD Lunchbox-Retort Project

In order to avoid the problems with burners and retorts rusting away quickly I want to build (or buy) a stainless steel biochar maker.

Here is a description of my first attempt at it: The Lunchbox-retort.

Stainless steel lunchboxes can be bought at camping stores for around AU$35.- and will allow immediate biochar making if added into an existing fireplace. The three compartments allow much experimenting.

Stainless Steel TLUD Lunchbox-Retort Project

Here is a video of SS Lunchbox retort in firplace

In order to use the SS-lunchbox without having to fire the fireplace, I built an insulated TLUD , to fit around the Lunchbox-Retort. It also fits to the tripod of the Champion TLUD. The bottom and top plates can be rotated to adjust primary and secondary air volumes.

Here is a video of the first burn in full swing

All the parts before firing:

The insulation is “Superwool 607”:

Before insertion of the “Superwool”: The SS tubes are flues from a BBQ and Fireplace shop (5” for the flue, 9” for the inner wall and 11” for the outer wall). These come in 900mm length and that is enough to make three Lunchbox-TLUD’s.

Superwool installed:

The SS-Lunchbox-Retort fits upside-down into the TLUD:

Here the results of the first burn:

The whole burner and the retort got so hot that all tar deposits (from previous burns at lower temperature in the fireplace) were charred and flaking off the retort walls.

The “fuel” burned to a fine white ash:

The char in the retort that was at the top has some blue char in it – I wonder what that means. I guess it’s what happens at high temperature, but please let me know if you can explain this: