The TORBED reactor and the rotary kiln are both gas–solid contacting thermal processing technologies, but they operate on fundamentally different principles, and this leads to noticeably different physical scales for the same processing duty.
A rotary kiln is a slowly rotating, inclined cylinder. Material is fed in at the upper end and gradually tumbles along the length of the tube while hot gases pass through. The bed only partially fills the cross-section, and heat is transferred to the solids by a combination of wall conduction, radiation from the freeboard, and convection from the gas. Because these mechanisms are relatively slow, residence times are typically in the range of tens of minutes to several hours. To accommodate this, industrial rotary kilns are generally large pieces of equipment, mounted on substantial supports and fitted with drive systems, seals, and refractory linings. They are widely used in cement, lime, and metallurgical processes, where their ability to handle high tonnages and variable feed sizes is a significant advantage.
The TORBED takes a different approach. High-velocity gas is injected through angled stator blades, creating a toroidal bed in which particles recirculate rapidly while suspended in the gas stream. This produces intense gas–solid contact and high convective heat and mass transfer rates, allowing residence times to be measured in seconds or a few minutes rather than hours. The reactor is vertically oriented and has no moving internal parts.
The practical consequence is that, for an equivalent thermal duty, a TORBED reactor is markedly more compact than an industrial rotary kiln, while the rotary kiln retains advantages in scalability to very large throughputs and in tolerating a wide range of feed materials.
For specific dimensional comparisons, vendor data should be obtained, as actual sizing depends on feed properties, temperature, and product specification.