Sacrificial Liner Shortening for Underground Coal Gasification

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Solution Overview

Problem

In underground coal gasification, the growing gasification cavity moves the hot reaction zone away from the injection point of oxidant gases, reducing efficiency and product quality, as existing methods require significant surface-operated equipment for repositioning the injection point.

Innovation Solution

A sacrificial liner linkage system that automatically shortens the injection well liner by using sacrificial liner portions made of materials that melt or disintegrate at lower temperatures than the steel liner, allowing the hot zone to draw up and reposition the injection point without surface-operated devices.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the injection well liner is shortened by cutting or withdrawing it using surface-operated equipment, then the injection point can be repositioned to maintain gas quality, but the device complexity and operational difficulty increase significantly

Engineering Contradiction:

Improvegas qualityVSAvoidsurface equipment requirements

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The liner system performs self-shortening through the differential thermal expansion mechanism. The stainless steel liner expands more than the carbon steel casing when exposed to hot gases, causing the liner to detach from the casing and effectively shorten the injection point without requiring any surface-operated equipment or complex mechanical systems.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The invention utilizes temperature as a controlling parameter to trigger the shortening action. By designing the liner and casing with different thermal expansion coefficients, the system automatically responds to temperature changes from the hot gases, causing the liner to expand differentially and detach from the casing, thereby repositioning the injection point.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If the liner is withdrawn or cut to reposition the injection point, then the coal face migration is tracked, but the loss of time and operational efficiency increase

Engineering Contradiction:

Improveinjection point positioningVSAvoidrepositioning operation time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The system automatically tracks the coal face migration by using the thermal energy from the hot gases itself to drive the shortening mechanism. The differential thermal expansion occurs continuously as hot gases flow through the liner, causing progressive detachment and shortening that naturally follows the migration of the gasification front without requiring periodic intervention.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The shortening mechanism operates continuously as long as hot gases are flowing through the liner. The thermal expansion process is ongoing and automatic, allowing the injection point to continuously track the coal face migration without interruption or downtime associated with manual repositioning operations.

Inventive Principle:

Principle #20Continuity of useful action

3Ease of operation

If a sacrificial liner linkage system is used for automatic shortening, then the need for surface equipment is reduced, but the manufacturing complexity of the liner system increases

Engineering Contradiction:

Improveautomatic shortening operationVSAvoidliner linkage system fabrication

Core Design Contradiction:

Ease of operationVSEase of manufacture

Solution Approach 1:

The design incorporates different material compositions (stainless steel vs. carbon steel) with distinct thermal expansion coefficients. This material parameter differentiation enables the differential thermal expansion mechanism that drives automatic shortening, transforming a complex operational requirement into a materials science solution.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The liner system uses composite construction with inner stainless steel liner and outer carbon steel casing. This composite structure leverages the different thermal properties of the two materials to create the differential expansion effect, where the stainless steel liner expands more than the carbon steel casing when heated, causing automatic detachment and shortening.

Inventive Principle:

Principle #40Composite materials

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

Maintains high syngas quality by automatically moving the injection point with the coal face, reducing the need for surface equipment and logistic operations, thus enhancing the efficiency and adaptability of the gasification process.

Implementation Method 1

sacrificial liner portions made of materials that melt or disintegrate at lower temperatures than the steel liner

Methodology Applied

Scientific EffectMelting: Melting

Implementation Method 2

the hot zone of gasification moves away from the injection point

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Data Source

PatentUS9976403B2Method for shortening an injection pipe for underground coal gasification

Publication Date: 2018.05.22 CARBON ENERGY

AI summary

A method for automatically shortening an injection well liner for underground coal gasification is provided in which portions of the injection well liner melt during the underground coal gasification process to shorten the injection well liner.