Abstract

The apparatus includes a reaction chamber which in operation uses an organic fuel input, typically in the form of substantially uniform-sized pellets, to produce a tar-free fuel gas. Prior to initiating operation, the lower end of the reaction chamber is filled with a charge of charcoal, forming a charcoal bed. A portion of the charcoal bed is then ignited, typically near the top, with air from the atmosphere being drawn substantially uniformly down through the reaction chamber by a pump on the outlet line leading from the reaction chamber, creating a thin pyrolysis zone near the top of the charcoal bed. The substantially uniform-size fuel pellets are added to the top of the charcoal bed, and are pyrolized as they move down through the pyrolysis zone. Since the fuel pellets are substantially uniform in size, and since the air-flow down through the chamber is substantially uniform, the temperature profile over the cross-sectional area of the pyrolysis zone is substantially uniform, and a homogeneous pyrolysis zone is created, without hot spots or channels. Such an arrangement results in self-regulating, self-sustaining operation over a relatively wide demand range, with rapid start-up and response characteristics. Air may also be directed into the reaction chamber through an inlet beneath the charcoal bed, which results in the reaction of the devolatilized charcoal to form additional fuel and an ash residue. Thus, the production and consumption of the charcoal within the apparatus may be exactly balanced.