Natural Circulation Boiler for SAGD with Membrane Wall Modules
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Solution Overview
Problem
Current Steam Assisted Gravity Drainage (SAGD) boiler technologies face issues with sub-ASME feedwater quality, leading to tube failures, poor steam quality, high pumping power, and high costs due to the presence of volatile and non-volatile organic components and high silica levels, which are not effectively managed by existing Once Through Steam Generator (OTSG) boilers.
Innovation Solution
A natural circulation boiler design with a steam drum, membrane wall modules, and a selective catalytic reduction module, capable of operating with sub-ASME feedwater quality, featuring a gravity feed system, riser pipes, and an economizer, to produce high-quality saturated steam while managing feedwater impurities through conservative design principles and water treatment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Once Through Steam Generator (OTSG) boiler technology is used, then steam generation capability is provided, but tube failures occur due to poor boiler feedwater quality
Solution Approach 1:
The boiler is divided into multiple independent membrane wall modules, each with its own circulation circuit. This segmentation allows isolated maintenance and reduces the impact of feedwater quality variations on the entire system, preventing widespread tube failures while maintaining steam generation capability.
Solution Approach 2:
A steam drum is introduced as an intermediary component between the membrane wall modules and the feedwater system. The drum provides a buffer zone that allows for steam-water separation and provides a reservoir to mitigate the impact of poor feedwater quality, protecting the tubes from direct exposure to contaminants.
2Manufacturing precision
If OTSG technology is used, then steam generation is achieved, but steam quality is poor
Solution Approach 1:
The natural circulation system provides inherent feedback mechanisms where steam and water continuously circulate through the membrane walls. This feedback loop ensures that steam quality is continuously monitored and adjusted, maintaining high-quality saturated steam while preserving generation efficiency through the self-regulating circulation pattern.
Solution Approach 2:
The system utilizes controlled phase transitions of water to steam within the membrane wall modules. The phase change process naturally separates steam from water, producing high-quality saturated steam while the continuous circulation maintains efficient heat transfer and steam generation rates.
3Power
If OTSG technology is used, then steam generation capability is provided, but pumping power and condensate handling costs increase
Solution Approach 1:
The boiler employs natural circulation where steam and water flow through the membrane wall modules driven by density differences and gravity. This self-service mechanism eliminates the need for external pumps to maintain water circulation, significantly reducing pumping power consumption while preserving steam generation capability through the natural thermodynamic cycle.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The boiler effectively operates with low-quality feedwater, reducing tube failures, improving steam quality, and lowering operational costs by using a conservative design that minimizes heat flux, maximizes turbulence, and incorporates advanced water treatment to manage impurities, ensuring reliable and efficient heavy oil and bitumen recovery.
Implementation Method 1
a furnace having a plurality of individually replaceable membrane wall modules, each module comprising an upper header, a membrane roof connected to and 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
Implementation Method 2
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
Implementation Method 3
the downcomer pipes being connected to the lower header for supplying water from the stream drum under gravity feed
Implementation Method 4
A natural circulation boiler design with a steam drum, membrane wall modules, and a selective catalytic reduction module
Data Source
AI summary
A gravity feed, natural circulation boiler for an SAGD process using low quality feedwater for carbonatious material recovery, has a large diameter steam drum with downcomers. A furnace of the boiler has individually replaceable membrane wall modules, each with upper and lower headers and membrane roof, wall and floor parts connected to the drum and defining a fire box having an inlet end and an outlet end. The furnace includes a membrane front wall connected to the drum with a windbox upstream of the front wall. Burners at the inlet end of the firebox heat the firebox and riser pipes are 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. Furnace outlet screen bank and subsequent generating banks each with upper and lower headers and associated feeder and riser tubes complete the boiler.