2.5 Purging char ash
In the course of the reduction reactions, the charcoal pieces are consumed to produce CO gas
and shrink and break apart until they pack densely and are rich in ash and minerals, inhibiting
the flow of gases through the hearth. These small pieces must be purged to restore gas flow.
The Power Pallet’s pressure sensors detect this condition, and automatically actuate the grate
shaker to shake the grate basket until the smallest pieces of char-ash fall onto the bottom of
the gas cowling, which is cleared by the scroll plate. The purging of these small char pieces
restores the flow of gases. The ash collection scroll then pushes the char-ash to the ash-out
auger, which pushes it into an external collection vessel that extends off the skid and resides
alongside the Power Pallet. The grate basket is the boundary of the flow of gas and the flow of
solids in the gasifier; the remaining char-ash solids are conveyed to the ash collection vessel