Rob Lerner, May, 2010

From Rob's Biochar Blog: http://biocharlog.blogspot.com/
Also take a look at his Captioned Slideshow: http://picasaweb.google.com/bajarob/RockinRocketRetort#.

We were thrilled with our first firing! The rocket stove enables ramping up temperatures gradually, which could be a big advantage when working with high moisture content feedstocks. The cross-over from distillation to pyrolysis was fairly tender. Directing all of the gasses into the stove's fuel chamber resulted at first in an over-temperature condition, which was alleviated by diverting pyrolysis gasses out the vinegar condenser pipe--at one point flames were shooting out two meters (very dramatic!)--stimulating conversation on the various uses to which these surplus combustible gasses could be put.


The 55 gallon drum--durable, affordable, widely available, easily handled--is at the heart of the design. A removable-lid drum stuffed with wood mill scrap serves as the retort. To prime the kiln, I had been considering scaling up one of the newer innovative biomass stove designs, but felt stymied by the challenge of refueling and controlling output. On a suggestion from stover-friend Charlie Sellers, I looked into the Rocket Stove (www.rocketstove.org/), a versatile design that addressed my emissions, fuel feed, and control concerns. The rest of the hardware fell into place after a bit of "outside the drum" thinking: Create fire chamber and insulating jackets (two total) by cutting ends off drums, slitting open, and welding inserts cut from a third drum. The tricky bit was opening the slit drums evenly to maintain the roundness of the now-larger cylinders. The nesting Russian doll cylinders rest on staircase ledges in the modified rocket stove base. Each cylinder is topped by a shallow cone-shaped lid with a central exhaust vent made by cutting a sliver wedge out of a sheet metal disc and welding the cut edges together.

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