4. Steam Building

The once through steam generators (OTSG) housed in the Steam Building use hot boiler feed water from the heat recovery system to generate steam. There are two standard oil field duty units with a heat duty of 50,000,000 BTUs per hour and a capacity of 500 m3/d cold water equivalent and 480 m3/d dry steam per unit.

The OTSG is a forced draft unit with a blower to feed combustion air into it. Hot boiler feed water from the heat recovery system first enters the unit at the top of the convection section right beneath the exhaust stack. It flows down countercurrent to the heat flow, comes off the bottom of the convection section and then enters the bottom of the radiant section. The water flows through long coils running parallel to the flame path and makes its way in parallel passing around the unit to the outlet, also located at the bottom of the radiant section.

The boiler feed water is treated before it enters the OTSG in order to eliminate scale within the boiler tubes, which shortens the run life of the boiler. Scale is created with iron, divalent cations (such as calcium and magnesium) and heat. Source water filters eliminate solids and precipitate from the water used for boiler feed water. Potassium permanganate is injected into the source water to create the precipitation reaction of the iron and manganese. Filters remove the iron to minimal levels and softeners reduce the level of ions to practical minimal levels.

There are two 100 per cent filter units, one running and one on standby. The filters are special dual-bed units, designed to deal with source water wells that may be particularly muddy or murky early in their run life.

Filtered water then flows through the water softening system much like a system at home. The softening process is a standard strong acid cation softening system to eliminate scale creation within the boiler tubes.

Moving further down the Steam Building, we arrive at the brine tank, which is used for softener regeneration. Bulk salt is unloaded by truck into the tank and then saturated with water.

The OTSG generates 80 per cent quality steam, but the SAGD wells require 100 per cent quality steam. To accomplish this, the large steam separator vessel separates the 80 per cent steam and the 20 per cent steam condensate into 100 per cent steam for use in the wells.

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