Multi-Circulation HRSG Steam Drum Partitioning for SAGD
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Solution Overview
Problem
Existing heat recovery steam generators (HRSGs) for Steam Assisted Gravity Drainage (SAGD) and enhanced oil recovery (EOR) face challenges with poor boiler feedwater quality, leading to tube failures and inefficiencies due to high levels of contaminants and silica, as well as high pumping power and condensate handling costs.
Innovation Solution
A multi-circulation HRSG design with an internally partitioned steam drum and separate 'clean' and 'dirty' circulation loops, where boiler water with lower dissolved solids circulates in high heat flux zones and higher solids in low heat flux zones, reducing contaminant deposition and operating costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional single-circulation HRSG design is used, then simpler structure and lower cost, but poor feedwater quality causes tube failures and inefficiencies
Solution Approach 1:
The single circulation system is segmented into two separate circulation loops: a clean water loop and a dirty water loop. Each loop has its own steam drum, heat exchanger banks, and downcomer pipes. This segmentation allows the clean loop to protect against tube failures from contaminants while the dirty loop handles contaminated feedwater, resolving the contradiction between reliability and complexity.
Solution Approach 2:
A blend water system acts as an intermediary between the clean and dirty loops. Contaminated water from the dirty loop is blended with clean water before being reintroduced into the system, serving as a mediator that prevents direct contamination of the clean circulation loop while maintaining overall system functionality and reducing the need for complex external treatment systems.
2Productivity
If conventional HRSG operates with high contaminants and silica, then higher steam production capacity, but increased tube fouling and operating costs
Solution Approach 1:
The heat exchanger banks are segmented into clean and dirty sections, with the dirty section specifically designed to handle contaminated feedwater. This segmentation concentrates fouling in designated areas while protecting the clean section and steam generation areas from contamination, allowing high steam production capacity without proportional increase in tube fouling.
Solution Approach 2:
The system converts the harmful effect of contaminants into a beneficial separation process. Contaminated water is deliberately routed through the dirty circulation loop where contaminants are concentrated and managed, while the clean loop maintains high-quality water for efficient heat transfer and steam generation. This transforms the problem of contamination into a controlled separation that maintains productivity while minimizing fouling in critical areas.
3Productivity
If conventional HRSG uses high pumping power, then faster water circulation and heat transfer, but higher operational costs
Solution Approach 1:
The circulation system utilizes natural convection currents and density differences between heated and cooled water to create circulation loops. The steam drums are positioned at strategic heights, and downcomer pipes are configured to allow gravity-assisted flow. This equipotential design reduces reliance on high-power pumps while maintaining effective water circulation and heat transfer through balanced hydraulic gradients.
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 multi-circulation HRSG design enhances steam quality, reduces tube fouling, and operates efficiently with lower-quality feedwater, lowering emissions and operational costs while maintaining desired efficiencies in SAGD and EOR processes.
Implementation Method 1
The steam drum typically uses centrifugal force generated through either tangential entry of the two-phase fluid into cyclones or through stationary propeller-type or torturous path devices. The centrifugal action literally 'squeezes' the steam out of the steam-water mixture.
Implementation Method 2
When hot gas passes between and around the tubes of a boiler bank, depending on whether water or steam is flowing through the boiler bank, the water is converted to steam or the steam is superheated.
Implementation Method 3
The boiler water is fed from the clean side partition of the drum to the dirty side partition of the drum via natural head differential.
Data Source
AI summary
A multi-circulation heat recovery steam generator (HRSG) for steam assisted gravity drainage (SAGD)/Enhanced Oil Recovery (EOR) processes comprises a steam drum internally partitioned to provide a clean side and a dirty side. The clean side downcomer pipe supplies water to one or more generating banks as part of a clean circuit located in a high heat flux zone of the boiler. Boiler water is fed from the clean side of the drum to the dirty side of the drum via natural head differential. Water is then fed through a corresponding downcomer to a dirty generating bank, which is located in a low heat flux zone of the boiler.