The intersecting mixer paddle design insures a thorough blending of dust and moisture, producing a uniform distribution prior to discharge. The low speed mixer operates at a constant 30 rpm to minimize paddle wear and control mixer residence time. Precise timing between the two shafts is maintained by twin spur gears enclosed in an oil tight case. During operation, a stationary layer of material forms along the interior of the tub, protecting it from wear. As the ash is mixed by the inter-leaving paddles, it is conveyed forward at a controlled rate, thus establishing a constant residence time and mixer efficiency. Precise changes to mixer paddle angle and shaft speed are possible to suit individual process requirements. Alternate paddle materials are available to address wear, corrosion, or material build-up. Mixer drive components, bearings, and shaft seal systems are external-mounted for ease of maintenance and inspection.