Elevated fixed-grate apparatus for use with multi-fuel furnaces

A refractory brick of an elevated fixed-grate apparatus for use in a furnace for combusting residual wood waste product with a wide range of moisture content, said refractory brick comprising:

• a solid refractory core formed as an arcuate segment of less than a complete circle;
• a pair of lateral ribs located on the bottom of the brick at opposite edges of said solid refractory core, said pair of lateral ribs formed integrally with said solid refractory core;
• a central rib centrally located on the bottom of each said solid refractory core;
• and each said rib being oriented radially arcuate segment sector forming said solid refractory core, said central rib formed integrally with said solid refractory core;
• said refractory brick includes a first number of refractory bricks that are capable of forming a first circular course and an additional number of bricks beyond the first number of bricks that are used to form more than one subsequent circular course, said first and subsequent circular courses together isolating underfire air located below said refractory bricks from overfire air located above said refractory bricks;
• said first circular course and each said subsequent circular course are stacked one atop another in a concentric manner so as to form a contiguous stepped top surface which includes an opening in a topmost one of said subsequent courses from which said residual wood waste product is supplied, said contiguous stepped top surface being solid in its horizontal direction and supporting said residual wood waste product during combustion thereof, each said subsequent circular course having an outer peripheral dimension smaller than an immediately preceding circular course upon which said subsequent circular course is placed, each said circular course having an inner peripheral dimension such that an inner cavity is formed by said courses being stacked one atop another;
• each said rib extends completely across a bottom surface of each said solid refractory brick and is dimensioned in a manner sufficient to provide vertical spacing of said solid refractory cores of each said subsequent circular course from said solid refractory cores of said immediately preceding circular course, said vertical spacing providing a horizontally arranged air passage between each said course, said horizontally arranged air passage enabling transfer of underfire air from below said solid refractory bricks to above said solid refractory bricks.