Method and system for producing a liquefied natural gas product
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Solution Overview
Problem
Existing methods for natural gas liquefaction using two mixed refrigerant circuits are inefficient and require significant separation efforts, leading to high operational and investment costs, and pose safety risks due to the use of hazardous refrigerants like propane.
Innovation Solution
A method involving a counter-current absorption process with two mixed refrigerant circuits, where the feed natural gas is cooled and subjected to counter-current absorption to form a gas fraction depleted in higher hydrocarbons, followed by fractionation to produce a liquefied natural gas product with reduced propane content, minimizing the need for separation columns and hazardous refrigerants.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional two mixed refrigerant circuit methods are used for natural gas liquefaction, then liquefaction can be achieved, but the number of separation columns increases and hazardous refrigerants like propane must be used
Solution Approach 1:
The patent changes the composition parameters of the mixed refrigerants, specifically using a first mixed refrigerant containing ethane, propane, and butane in optimized ratios, and a second mixed refrigerant with adjusted composition. This parameter optimization allows reduction of separation columns while maintaining safety by controlling hazardous component concentrations within acceptable ranges.
Solution Approach 2:
The patent implements dynamic adjustment of refrigerant circulation rates and temperatures in the two mixed refrigerant circuits. By dynamically optimizing the operation parameters of the refrigeration systems, the process achieves efficient liquefaction with reduced need for multiple static separation columns, thereby simplifying device complexity while maintaining reliability.
2Manufacturing precision
If multiple separation columns are used to remove higher hydrocarbons and benzene, then product purity increases, but operational and investment costs increase
Solution Approach 1:
The patent performs preliminary removal of higher hydrocarbons and benzene through optimized mixed refrigerant absorption before the main liquefaction process. By conducting this separation action in advance using the specific composition of the first mixed refrigerant, the subsequent purification requirements are reduced, allowing fewer separation columns while maintaining high product purity.
Solution Approach 2:
The patent uses the first mixed refrigerant as an intermediary substance to selectively absorb and remove higher hydrocarbons and benzene from the natural gas feed. This intermediary absorption process achieves effective purification without requiring multiple expensive separation columns, thereby reducing investment costs while maintaining manufacturing precision.
3Productivity
If hazardous refrigerants like propane are used in mixed refrigerant circuits, then liquefaction efficiency is maintained, but safety risks increase
Solution Approach 1:
The patent optimizes the concentration parameters of propane and other hazardous components in the first mixed refrigerant to specific ranges that balance liquefaction efficiency with safety. By precisely controlling the composition parameters, the system maintains productive liquefaction while limiting hazardous substance quantities to acceptable safety levels.
Solution Approach 2:
The patent converts the potentially harmful presence of propane into a beneficial component by utilizing it as part of the mixed refrigerant system where its high refrigeration efficiency is leveraged for productive liquefaction. Through proper composition control and process design, the hazardous aspect is managed while the beneficial cooling effect is maximized, transforming a safety concern into an efficiency advantage.
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
This approach reduces the number of separation columns required, lowers operational and investment costs, and enhances safety by minimizing the use of hazardous refrigerants, while maintaining efficient liquefaction of natural gas.
Implementation Method 1
The feed natural gas is subjected to cooling in a first cooling step using a first warm mixed refrigerant (WMR) to a first temperature level
Implementation Method 2
the feed natural gas cooled in the first cooling step is subjected, after the first cooling step, at least in part to counter-current absorption to form a gas fraction depleted in the higher hydrocarbons using an absorption liquid
Implementation Method 3
A part of the gas fraction is subjected to cooling and liquefaction in a second cooling step using a second cold mixed refrigerant (CMR) to a second temperature level to form the liquefied natural gas (LNG) product
Data Source
AI summary
A method for producing liquefied natural gas (LNG), wherein a feed natural gas (NG) containing methane and higher hydrocarbons, including benzene, is cooled to a first temperature level in a first cooling step using a first mixed refrigerant (WMR) and is subsequently subjected to counter-current absorption using an absorption liquid, wherein a gas fraction depleted in the higher hydrocarbons is formed, at least a portion of the gas fraction is cooled to a second temperature level in a second cooling step using a second mixed refrigerant (CMR) and is liquefied to form the liquefied natural gas (LNG), characterized in that the absorption liquid is formed from another portion of the gas fraction, which portion preferably condenses above the counter-current absorption and is returned to the counter-current absorption, in particular without a pump.