A thermal processing apparatus and a thermal processing method where the vessel with interconnected chambers in which the solid material is thermally processed is suspended in a heat exchange medium while it is rotated, which reduces the energy to rotate the vessel, increases heat transfer surface area, increases the turbulence of the heat exchange medium around the vessel and improves the movement of solid particles relative to each other and relative to the heat exchange surface. These features combine to increase the heat transfer rates within a compact vessel size.

A surround hot air slow drying device and a three-stage baking method for pet food processing are provided. The surround hot air slow drying device for pet food processing includes a drying box. A hot air drying unit is provided at an inner bottom of the drying box, a circulating conveying unit is provided inside the drying box, a plurality of drying frames are evenly distributed on the circulating conveying unit, a material turning mechanism is provided inside the drying frames, and a positioning component is provided inside the drying box. The material turning mechanism cooperates with the positioning component to turn the raw materials in the drying frames.