Abstract: A process for reinjecting flown-off particles into a solid fuel fire box of a boiler or furnace of the "projector with back grid" type, in which particulate fuel is projected from a fuel source adjacent a first zone to a grid, with the fuel burned along its trajectory from the first zone to a second zone on the grid. Means are provided for separately collecting both large and small fuel particles thrown off during combustion along the trajectory to the grid, and reinjecting the collected particles with the fine particles continuously reinjected at a rate approximately proportional to the boiler load at said second zone by means of a particle conveying air stream.

Abstract: An apparatus for reinjecting flown-off particles into a solid fuel fire box of a boiler or furnace of the "projector with back grid" type, in which particulate fuel is projected from a fuel source adjacent a first zone to a grid, with the fuel burned along its trajectory from the first zone to a second zone on the grid. Means are provided for separately collecting both large and small fuel particles thrown off during combustion along the trajectory to the grid, and reinjecting the collected particles with the fine particles continuously reinjected at a rate approximately proportional to the boiler load at said second zone by means of a particle conveying air stream.