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Drying feed stock
The moisture content of chipped wood that we were dealing with was around 50 percent or more. To dry the wood chips to the recommended moisture content it is advised that you sort out the feedstock. This will decrease drying time and volume. Woodchips coming out of the chipper produces about 50% usable feedstock depending on wood type and chipper. Fines can be used as a fuel source for cook stove batch gasifiers or as mulch.
The cheapest way to dry is in natural sunlight with air movement threw thin layers of sorted feedstock. This can be accomplished by laying out fine screen over pallets
and turning feedstock up to expose bottom layer. This method only works if the humidity is bellow 35%. The more sun the better. In 26 degrees C with humidity in range of 35% feed stock can dry in this system in about two days of sunshine. This drying set-up can dry about 128 gallons of feedstock in an area of 7.5 ft by 16 ft.A similar system for areas that have high humidity can have a rain cover over this drying area and use a heat source to aid in drying off moisture. The heat given off of the Gek radiator along with the air movement would be ideal. Once feed stock has reached desired moisture content then fuel should be sealed up to prevent re-absorption of moisture in humid environments.
Particle size
They way we are sifting our wood chips is by a shaker screen on a slight angle. This version uses a motor with a counter balance to cause the shaking action. The shaker screen dimensions are 61 cm by 244 cm and have the capability of sifting through 2 yards in 1 hr 20mins with prep time with forklift. The feed stock falls threw the coarse wire screen (2.5cm), which then get caught in the fine screen (1.5cm). This allows the fine material to fall threw and discharged into a separate bag. The large material falls over and out, and then feedstock tumbles over the fine screen in the feedstock bag.
Video link shaker screen in action Here is a picture of the fine material that needs to be sorted out of the wood chips.
This is the ideal feedstock for the Gek, and is ready to be dried.
Looking into other options of sifting and drying is a rotary tumbler. In the summer months the tumbler could be set down parallel to the ground and uses as a solar tumble dryer. For higher humidity environments this unit could be ducted to a heat source, say the heated air stream from exhaust or radiator. This system could be constructed of barrels and the same diameter screen described above for internal smaller drums for sifting. A hand crank or a small solar powered motor can accomplish the rotary motion.
Similar to this rotary soil sifter
