Abstract: A direct contact steam injection heater body is placed directly in line and allows axial flow of stock (i.e. liquid or slurry) through a pipe. The steam injection heater includes a Mach diffuser having a plurality of steam diffusion holes. The Mach diffuser is mounted transverse to the axial flow of stock through the pipe and the heater body. High velocity steam is injected from the plurality of steam diffusion holes into the stock flowing through the heater body. An adjustably positionable cover in the Mach diffuser modulates the amount of steam added to the flowing stock by exposing a desired number of steam diffusion holes. Modulation is accomplished at constant steam pressure by an actuator that rotates the cover. The arrangement is able to efficiently heat large flows of viscous stock, such as slurries having suspended materials that tend to flocculate. The upstream surface area of the Mach diffuser is preferably free of steam diffusion holes to eliminate unnecessary plugging.

Abstract: A direct contact steam injection heater includes a Mach diffuser having a plurality of steam diffusion holes in lieu of a coaxial steam nozzle. High velocity steam (i.e. choked flow) flows radially through the plurality of steam diffusion holes into a high velocity axial flow of liquid through a combining tube within the heater. An adjustably positionable cover over the steam diffusion holes in the Mach diffuser modulates the amount of steam added to the liquid by exposing the proper number of steam diffusion holes. This modulation is done at constant steam pressure without the use of an external steam control device. The arrangement facilitates thorough mixing of steam and liquid within the combining region. It also discourages the generation of relatively large steam bubbles within the mixture, even when heating liquids that promote the generation of relatively large steam bubbles such as liquids without a significant number or nucleation points or without sufficient surface tension.