Once-Through Steam Generator with 100% Quality Output
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Solution Overview
Problem
Traditional once-through steam generators (OTSGs) for Steam Assisted Gravity Drainage (SAGD) are limited to 80% steam quality, leading to severe deposition and tube rupture due to high Total Dissolved Solids (TDS) concentration, resulting in the wastage of 20% blowdown water that cannot be used for steam generation.
Innovation Solution
A system comprising a once-through steam generator with a steam-water separator, superheater, and desuperheater, where the separated steam is superheated and used to vaporize blowdown water, achieving 100% steam quality by utilizing a multi-stage separator and Venturi-type desuperheater with a non-stick ceramic coating to prevent deposition and remove solid particles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If steam quality is increased above 80% in traditional OTSGs, then more water is converted to steam, but severe deposition occurs on tube surfaces causing overheating and tube rupture
Solution Approach 1:
The system divides the steam generation process into separate stages: a radiant section for initial evaporation, a superheater section for steam heating, and a desuperheater section for blowdown vaporization. This segmentation allows each section to operate at optimized conditions, preventing deposition while maximizing steam quality.
Solution Approach 2:
The patent introduces a steam-water separator as an intermediary device between the radiant section and superheater. This separator removes water droplets from the steam before it enters the superheater, preventing TDS deposition on tube surfaces while allowing continued high-efficiency steam generation.
2Reliability
If steam quality is limited to 80% to prevent deposition, then tube reliability is maintained, but 20% blowdown water must be wasted
Solution Approach 1:
The patent converts the harmful blowdown water, which must traditionally be discarded, into a useful resource by vaporizing it in the desuperheater section using superheated steam. This transforms waste water into additional steam, eliminating blowdown loss while maintaining tube reliability.
Solution Approach 2:
The system utilizes phase transition of water to steam in the desuperheater section. Blowdown water is injected into the desuperheater where it undergoes phase change from liquid to vapor by absorbing heat from superheated steam, converting waste into useful steam product.
3Reliability
If a steam-water separator is added to achieve 100% steam quality, then deposition is prevented, but device complexity increases
Solution Approach 1:
The superheater section serves multiple functions: it superheats the separated steam to generate driving force for water-vaporization in the desuperheater, and simultaneously provides the heat source for converting blowdown water to steam. This multi-functionality reduces the need for additional separate heating devices.
Solution Approach 2:
The patent merges the blowdown vaporization function with the existing superheater and convection section. The desuperheater is integrated into the flue gas pathway, utilizing the same flue gas heat source that heats the water tubes, thereby combining multiple heating functions into a unified system.
4Productivity
If blowdown water is vaporized using superheated steam, then 100% steam quality is achieved, but energy consumption increases
Solution Approach 1:
The system uses its own superheated steam to vaporize the blowdown water in the desuperheater. The superheated steam serves dual purpose: maintaining its own temperature and providing the energy source for blowdown vaporization, making the system self-sufficient without requiring external energy input.
Solution Approach 2:
The flue gas continuously flows through the convection section, providing uninterrupted heat to both the water tubes and the desuperheater. This continuous heat availability ensures that blowdown vaporization occurs simultaneously with steam generation, maximizing energy utilization efficiency.
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 system effectively converts 100% of blowdown water to superheated steam, reducing erosion and increasing steam quality, thereby enhancing operational efficiency and reducing waste, while ensuring the steam is clean and free from solid particles for SAGD applications.
Implementation Method 1
a radiant section containing furnace tubes that are exposed to radiant flame heat of the burner... whereby a feed water stream flowing through said convection and furnace tubes undergoes partial conversion to steam
Implementation Method 2
a convection section having a flue gas inlet for admission of said flue gas from said radiant section into said convection section for travel therethrough... convection tubes situated between said flue gas inlet and said flue gas outlet in fluid communication with the flue gas pathway for exposure of said convection tubes to said flue gas travelling therethrough
Implementation Method 3
a steam-water separator connected to said radiant tubes in downstream relation thereto to receive a two-phase steam-water flow resulting from said partial conversion of the feed water stream, and perform separation of said two-phase steam-water flow into blowdown water and dried steam
Implementation Method 4
superheater tubes installed in said convection section in fluid communication with the flue gas pathway for exposure to said flue gas travelling therethrough, said superheater tubes being connected to a steam outlet of said steam-water separator in downstream relation thereto to receive the dried steam and convert the dried steam to superheated steam using the heat of the flue gas
Implementation Method 5
a desuperheater connected to the superheater tubes in downstream relation thereto to receive the superheated steam therefrom at a steam inlet of said desuperheater, and also connected to a blowdown outlet of said steam-water separator to receive the blowdown water therefrom, the desuperheater being configured to vaporize said blowdown water using the superheated steam from the superheater tubes
Data Source
AI summary
A system for deriving 100% quality steam for steam assisted gravity drainage (SAGD) injection or other applications features a once through steam generator (OTSG), a steam-water separator connected downstream of the OTSG's radiant tubes to separate steam and water from a two-phase flow received therefrom, superheater tubes installed in the convection section and connected to a steam outlet of the steam-water separator in downstream relation thereto to receive and heat dried steam therefrom to a superheated state, and a desuperheater connected downstream of the superheater tubes to receive the superheated steam therefrom and use same to vaporize blowdown water from the steam-water separator, whereby the vaporized blowdown water and the superheated steam collectively form a superheated steam output for the intended application, typically after additional separation of solid particles therefrom for optimal steam quality.