Direct steam injection (DSI) heating and use in bitumen froth treatment operations

A direct steam injection (DSI) heater for heating a process stream in a bitumen froth treatment operation, the DSI heater comprising:

• a diffuser extending into the process stream and comprising a tubular body having a proximal portion in fluid communication with a steam source and configured to receive steam therefrom, and a distal portion comprising a perforated injection section having outlets in fluid communication with the process stream for injecting the steam, the outlets being arranged in multiple side-by-side rows on respective planes that are each perpendicular to a longitudinal axis of the tubular body;
• a piston plug mounted within the tubular body of the diffuser and being configured to axially move between different positions within the tubular body, the piston plug comprising a plug body and at least a first annular seal and a second annular seal positioned at opposed ends thereof, the piston plug being controllable within the tubular body of the diffuser to provide an open area of the outlets through which steam is injected into the process stream, by axially displacing the piston plug within the tubular body between different axial positions in a stepwise fashion to selectively cover or uncover corresponding rows of outlets to provide the open area for steam injection, such that when one or more rows of outlets are completely covered:
• the first annular seal is located in between and spaced apart from adjacent rows of outlets, and abuts against inner surfaces of the tubular body, and
• the second annular seal abuts against inner surfaces of the tubular body to inhibit steam from passing beyond the second annular seal toward the covered outlets.

A process for heating a process stream flowing in a bitumen froth treatment operation, the process comprising:

• injecting steam directly into the process stream via a direct steam injection (DSI) heater comprising:
• a diffuser extending into the process stream and comprising a tubular body having a proximal portion in fluid communication with a steam source and configured to receive steam therefrom, and a distal portion comprising a perforated injection section having outlets in fluid communication with the process stream for injecting the steam, the outlets being arranged in multiple side-by-side rows on respective planes that are each perpendicular to a longitudinal axis of the tubular body;
• and
• a piston plug mounted within the tubular body of the diffuser and being configured to axially move between different positions within the tubular body, the piston plug comprising a plug body and at least a first annular seal and a second annular seal positioned adjacent opposed ends of the plug body;
• axially displacing the piston plug within the tubular body between different axial positions to selectively cover or uncover corresponding rows of outlets to provide an open area for steam injection, such that when one or more rows of outlets are completely covered:
• the first annular seal is located in between and spaced apart from adjacent rows of outlets, and abuts against inner surfaces of the tubular body;
• and
• the second annular seal abuts against inner surfaces of the tubular body to inhibit steam from passing beyond the second annular seal toward the covered outlets.