Fuel gas conditioning
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Solution Overview
Problem
Existing methods for conditioning rich natural gas to lean gas for use in internal combustion engines are inefficient, as they either incur high costs with mechanical refrigeration or produce emulsified byproducts with Joule Thompson systems, leading to engine knock, reduced lifespan, and increased maintenance.
Innovation Solution
A fuel gas conditioning process that splits rich natural gas into two streams, where one stream is used as a cooling gas to pre-cool the fuel gas in a heat exchanger, followed by separation in a scrubber, allowing for efficient removal of natural gas liquids without depressurization and emulsification, thereby reducing BTU content and improving engine compatibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If mechanical refrigeration is used to condition rich natural gas, then the gas can be cooled to remove NGL, but the system becomes bulky, difficult to move, and cost-effective only for large volumes
Solution Approach 1:
The system uses a portion of the rich natural gas itself as the cooling medium. The gas is compressed, cooled in a heat exchanger, and then expanded through a valve to create cold gas that cools subsequent batches of rich natural gas. This eliminates the need for external mechanical refrigeration systems, making the unit compact, movable, and cost-effective for small volumes.
2Temperature
If Joule Thompson systems are used to condition rich natural gas, then cooling and NGL removal can be achieved, but an emulsified NGL/water byproduct is produced that is difficult to sell
Solution Approach 1:
The system extracts and separates the NGL and water from the natural gas stream before final cooling. By removing these components first, the subsequent cooling process does not create emulsified byproducts. The separated NGL and water can be handled and sold independently rather than as a difficult-to-market emulsion.
3Productivity
If rich natural gas is used directly in compression engines, then no additional processing is needed, but the engines knock, operate at higher temperatures, and experience reduced lifespan
Solution Approach 1:
The system performs preliminary conditioning of the rich natural gas by compressing it, cooling it to remove NGL, and separating the liquids before the gas is used as fuel. This pre-treatment reduces the BTU content and removes contaminants that cause knocking and overheating, allowing the engine to operate reliably at full capacity without additional processing downstream.
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 process effectively converts rich natural gas into a lean fuel suitable for engines, reducing engine knock and maintenance costs by separating natural gas liquids without emulsification, thus extending engine life and improving throughput.
Implementation Method 1
Joule Thompson systems are commonly used but have the drawback of producing an emulsified NGL/water byproduct that is difficult to sell
Implementation Method 2
The cooling gas stream is expanded to pre-cool the fuel gas in a first heat exchanger
Data Source
AI summary
Compressed rich natural gas is divided into a cooling gas stream and a fuel gas stream. The cooling gas stream is depressurized. The cooling gas and the fuel gas are then heat exchanged to provide a first cooling step to the fuel gas. The cooled fuel gas continues into a second cooling step in a second heat exchanger, and then flows into a separator vessel where liquids are removed from the bottom of the separator and conditioned fuel gas exits the top of the separator. The conditioned fuel gas from the separator and produced from its influent is depressurized and heat exchanged to provide the second cooling fluid for the second heat exchanger.