Natural Gas Splitter Column Recirculation for High C2+ Recovery
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Solution Overview
Problem
Existing methods for producing methane-rich and C2+ hydrocarbon-rich fractions from natural gas are inefficient when the feed natural gas is rich in heavy hydrocarbons like ethane, propane, and butane, particularly at high inlet temperatures, requiring excessive cooling and additional energy consumption, which is not feasible in all facilities, especially floating ones.
Innovation Solution
A method involving the formation of multiple recirculation streams that are dynamically expanded in turbines to produce frigories, which are then reintroduced into the process to enhance the separation efficiency and reduce energy consumption by optimizing the heat exchange and compression stages within the splitter column system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional cooling cycles with propane are used to separate C2+ hydrocarbons from natural gas, then separation efficiency is improved, but energy consumption increases and the system becomes too complex and dangerous for floating plants or urban regions
Solution Approach 1:
The invention extracts the heavy fraction (C2+ hydrocarbons) directly from the cooled natural gas stream in a separator flask, eliminating the need for complex propane-based cooling cycles. The heavy fraction is separated by density differentiation after simple cooling, achieving separation efficiency without the energy-intensive traditional cooling method.
Solution Approach 2:
The invention changes the operating parameters by using a single-stage cooling process followed by gravitational separation, rather than the traditional multi-stage propane cooling cycle. This parameter change reduces energy consumption while maintaining separation efficiency for facilities where traditional methods are impractical.
2Quantity of substance
If the feed natural gas has high ethane, propane and butane content, then the C2+ hydrocarbon fraction becomes more valuable, but the cooling requirements increase excessively
Solution Approach 1:
The invention applies partial cooling action - cooling the feed natural gas to a temperature sufficient for heavy fraction separation but not as extensively as traditional methods. The cooled stream is then separated in a flask, achieving C2+ recovery without excessive cooling requirements that would be needed for high C2+ content gases using conventional methods.
3Device complexity
If a single expansion turbine is used in the splitter column, then the device complexity is reduced, but the productivity and selectivity of C2+ hydrocarbon recovery decreases
Solution Approach 1:
The invention segments the expansion process by using multiple expansion turbines at different locations in the splitter column. The first expansion turbine processes the light fraction, while the second expansion turbine processes the heavy fraction. This segmentation enables independent optimization of each expansion stage, achieving high C2+ recovery rates (above 99% ethane recovery) without excessive system complexity.
4Reliability
If the C2+ hydrocarbon fraction is recovered using conventional distillation methods, then the process is well-established, but the selectivity and ethane recovery rate drops when feed gas has high inlet temperature
Solution Approach 1:
The invention applies preliminary cooling action before the separation process. The feed natural gas is cooled in a heat exchanger before entering the splitter column, ensuring that the cooling and separation conditions are optimized from the start. This preliminary action maintains high selectivity and ethane recovery rates even when the feed gas has high inlet temperature, while keeping the process stable and reliable.
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 method achieves high selectivity and efficiency in recovering C2+ hydrocarbons, maintaining ethane recovery rates above 99% while reducing energy consumption, even with high C2+ hydrocarbon content in the feed gas, and is applicable in facilities where traditional cooling cycles are impractical.
Implementation Method 1
dynamically expanding the turbine input flow in a first expansion turbine
Implementation Method 2
cooling the feed natural-gas stream advantageously at a pressure greater than 40 bars in a first heat exchanger
Implementation Method 3
separating the cooled natural-gas stream in the separator flask and recovering an essentially gaseous light fraction and an essentially liquid heavy fraction
Implementation Method 4
compressing this stream in at least one first compressor coupled with the first expansion turbine and in a second compressor
Data Source
AI summary
A method comprising the cooling of the feed natural-gas (15) in a first heat exchanger (16) and the introduction of the cooled feed natural-gas (40) in separator flask (18). The method further comprising dynamic expansion of a turbine input flow (46) in a first expansion turbine (22) and the introduction of the expanded flow (102) into a splitter column (26). This method includes sampling at the head of the splitter column (26) a methane-rich head stream (82) and sampling in the compressed methane-rich head stream (86) a first recirculation stream (88). The method comprises the formation of at least one second recirculation stream (96) obtained from the methane-rich head stream (82) downstream from the splitter column (26) and the formation of a dynamic expansion stream (100) from the second recirculation stream (96).