Underground Coal Gasification with Pressurized Conduit Containment
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Solution Overview
Problem
Conventional underground coal gasification systems suffer from low product gas yield and hydrogen recovery due to oxidant and product gas dispersion beyond the reaction region, leading to increased costs and contamination.
Innovation Solution
Incorporating a system of conduits around the UCG reaction region to form a primary fluid region that contains oxidant and product gases, maintaining higher pressure than the reaction region to inhibit migration and enhance gas utilization and extraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional UCG systems are used without containment structures, then device complexity is reduced, but product gas yield and hydrogen recovery deteriorate due to gas dispersion
Solution Approach 1:
The coal seam is divided into distinct functional zones: a reaction region where gasification occurs and a containment region surrounded by conduits that captures dispersed gases. This segmentation allows the system to address gas dispersion problems without requiring complete enclosure of the entire reaction zone, thereby improving productivity while limiting the increase in device complexity to specific containment structures rather than the entire system.
Solution Approach 2:
Conduits act as intermediary structures injected into the coal seam to serve as gas capture channels. These conduits intercept dispersed oxidant and product gases before they can escape the containment region, transferring gases from the reaction zone to production wells. This intermediary mechanism improves gas recovery efficiency without requiring direct modification of the reaction zone itself.
2Productivity
If oxidant is injected without containment structures, then ease of operation is improved, but hydrogen recovery deteriorates due to oxidant dispersion
Solution Approach 1:
Conduits are pre-injected into the coal seam surrounding the reaction region before oxidant injection begins. This preliminary containment structure establishment ensures that when oxidant is subsequently injected, the dispersed oxidant is immediately captured by the pre-positioned conduits, preventing hydrogen loss through oxidation of surrounding coal. This preliminary action maintains operational simplicity while significantly improving hydrogen recovery.
Solution Approach 2:
The conduits serve as intermediary pathways that intercept dispersed oxidant gases, preventing them from contacting and oxidizing the surrounding coal seam. By using these intermediate structures, the system maintains the simplicity of oxidant injection operations while achieving high hydrogen recovery through the intermediary gas capture mechanism.
3Object-affected harmful factors
If no containment region is formed, then device complexity is reduced, but contamination increases due to gas migration
Solution Approach 1:
The coal seam is segmented into a reaction region and a containment region separated by conduits. This segmentation creates a barrier that prevents product gases from migrating into and contaminating the surrounding coal seam. The segmented approach addresses contamination issues by localizing gas dispersion to a controlled region rather than requiring complete system enclosure, thereby limiting the increase in device complexity to specific containment structures.
Solution Approach 2:
Conduits serve as intermediary structures that act as gas barriers between the reaction region and the surrounding coal seam. These conduits intercept and contain dispersed product gases, preventing them from migrating into the coal seam and causing contamination. The intermediary conduit structures provide an effective contamination barrier without requiring complex complete enclosure systems.
4Productivity
If pressure is increased to contain gases, then gas containment improves, but energy consumption increases
Solution Approach 1:
The system uses pneumatic injection of fluids (water, steam, or gas) into the coal seam to create and maintain the containment region. By injecting these fluids under pressure through the conduits, the system creates a pressure differential that contains gases without requiring excessive pressure buildup. The pneumatic approach allows for controlled gas containment while managing energy consumption through efficient fluid injection rather than high-pressure compression.
Solution Approach 2:
The system changes physical parameters of the coal seam by injecting fluids that alter pore pressure, permeability, and fluid distribution. These parameter changes create a containment zone through modified coal seam properties rather than relying solely on high external pressure. By changing the physical state and properties of the coal seam matrix through fluid injection, the system achieves effective gas containment with more moderate pressure requirements, thereby reducing energy consumption.
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
Improves product gas yield and hydrogen recovery by containing gases within the reaction region, reducing costs and minimizing contamination.
Implementation Method 1
delivering a primary fluid to an area of the coal seam that is outward of the UCG reaction region to form a pressurized region
Implementation Method 2
supplying an oxidant and, if required, water and/or steam to an underground coal seam in order to ignite coal and sustain the gasification process
Implementation Method 3
when the oxidant gas disperses from the injection well within the coal seam
Data Source
AI summary
Methods and systems for gasifying coal are disclosed herein. In some embodiments, a representative coal gasification system can comprise (i) an injection well extending from a ground surface to an underground coal gasification (UCG) reaction region of a coal seam; (ii) a production well spaced apart from the injection well and extending from the ground surface to the UCG reaction region, and (iii) conduits each extending from the ground surface to areas of the coal seam. End portions of the conduits within the coal can be laterally peripheral to the UCG reaction region. The conduits are configured to deliver a primary fluid from the ground surface to the primary region, the injection well is configured to deliver an oxidant gas to the UCG reaction region, and the production well is configured to deliver the product gas from the UCG reaction region to the ground surface.