Direct steam injection: An efficient petfood processing method
Benefits over indirect heating methods make DSI an efficient, cost-effective alternative
Direct steam injection (DSI) heating is a specific method used during petfood and food processing where steam is directly mixed with the process fluid that needs to be heated. This type of heating is seen as an efficient, cost-effective alternative to indirect-contact heat exchangers, which have multiple fluid flow paths that don't allow for direct mixing of the fluids.
The benefits of DSI, according to Ed Beecher of Coperion Corp., are significant. In his Petfood Forum 2014 presentation, "Innovations available for petfood extrusion processes," Beecher said the single-stage process requires no preconditioning and provides reliable production. In addition, since the process utilizes direct thermal energy input, it reduces the need for specific mechanical energy input, which results in lower energy costs than other methods of heating.
There are also more physical advantages, according to Hydro-Thermal Corp. "Both equipment expense and space requirements can be trimmed," said the company. "Direct-contact steam injection systems generally require less space than other methods of heat transfer, and they also eliminate the need for condensate return systems, which are often required for indirect heat exchangers. Additionally, maintenance costs may be significantly lower than those of other heating systems."
There are multiple types of DSI heaters currently in use, with varying abilities and limitations, including externally modulated devices such as spargers and mixing tees, and internally modulated steam injection heaters.
External modulation varies the velocity at which the steam is injected into the liquid, as well as the relationship between the steam and the…