Patent ID: 7533632

Claim:
A gravity feed, natural circulation boiler for an SAGD process using low quality feedwater for carbonatious material recovery, comprising: a single steam drum having an inside diameter; a plurality of downcomer pipes connected to the steam drum for discharging water from the stream drum; a single furnace having a plurality of individually replaceable membrane wall modules, each module comprising at least one upper header, a membrane roof connected to and first sloping downwardly away from the upper header, a membrane wall connected to and descending from the membrane roof, a membrane floor connected to and sloping downwardly from the membrane wall and subsequently connected into a lower header without any subsequent bends; the roof, the wall and the floor together defining a fire box having an inlet end and an outlet end, and the furnace including a membrane front wall connected to the upper and lower headers and being at the inlet end of the fire box; means defining a windbox upstream of the front wall; at least one burner at the inlet end of the firebox for heating the firebox; a plurality of riser pipes connected between the steam drum and the upper header for supplying steam to the steam drum when the firebox in heated, the downcomer pipes being connected to the lower header for supplying water from the stream drum under gravity feed so that each module defines a single circuit; a rear wall screen at the outlet of the firebox, connected between the downcomer pipes and the riser pipes; at least one steam generator bank downstream of the screen and also connected between the downcomer pipes and the riser pipes; a stack connected to the firebox outlet downstream of the bank; and an economizer.