This project goes over the build of a simple gasification system that functions to produce wood gas for running a generator, a cooking stove, and for lanterns. We feed the wood chips and other materials through the opening at the top of the gasifier, the air also gets drawn in from the top. The air would drop through the wood mass, down to the reduction zone and gets collected down at the bottom of the tank through the output pipe.
STEP 1 : MATERIALS REQUIRED
The materials needed to build this downdraft style gasifier are 3 old propane tanks, old steel sheets, and wood pellets.
The first step is to make sure that propane tanks are empty. Remove the handles from the top of the 3 propane tanks and unthread the valves.
STEP 2 : STACKING THE PROPANE TANKS
Cut the top portion from 2 tanks and stack the body of the tanks on top of each other and weld it. One of the cut-out top pieces can be used a lid.
STEP 3 : ADDING REDUCTION ZONE
The bottom portion of the lower tank is cut open to create the reduction zone of the gasifier. To make the reduction point, we take the scrap steel sheet and make a five-inch wide small tube of them and weld them to the bottom third propane tank.
STEP 4 : BOTTOM OUTLET TANK
The bottom five-gallon propane tank is used as an ash bin where all the ash is going to get caught and as an outlet for all the gases coming out of the system. The top portion of this tank is cut in such a way that it fits the reduction zone collar of the secondary tank.
Make sure that both the tanks fit nicely together so that you can pull the inner chamber out of the bottom ash tank to remove it, dump the ash catch out and use it again and again.
The top of the upper tank is cut open.This acts as the feed area where all the wood pieces are dropped in.
STEP 5 : ADDING A SCREEN
We make a screen with holes using a 20mm hole saw cutter from the leftover cutouts of the propane tank. We are gonna mount this screen inside the gasifier’s lower reduction zone.
A hinge and a wire are attached to the screen so it can open and close. This gives us the ability so we can shake the screen if it plugs up with ash or other materials. The wire goes through the reactor up to the top.
STEP 6 : ADDING A PRESSURE RELIEF SYSTEM
We have a pressure relief system installed on the lid of the gasifier. If anything were to happen inside of the gasifier, the build-up pressure can be made to escape through the top lid. This is done by hooking up two springs on both sides of the lid through small loops. The springs on both sides are attached to hand levers.
STEP 7 : IMPROVING AIRFLOW
We drill 8 half-inch diameter holes just above the reduction zone area and put thick steel tubing through them to the center of the chamber. The airflow will go in and be drawn down through the center of the reduction zone which helps in the efficient burn. The pipes are curved into the chamber so that it does not interfere with any wood mass as it goes into the reduction zone. We add plugs along these 8 tubes to regulate the airflow into the system.
STEP 8 : ADDING A PELLET STOVE FAN
The next step is to add the draw fan to the gasifier. Here we use a pellet stove fan.We add a 2-inch plate over the face of the fan and a threaded pipe to seal any air going into the gasifier.
We start up the gasifier by putting some chopped wood through the top and using the fan to get the wood gas-producing out of the bottom outlet pipe.
Image Credits : MrTeslonian