Method and system for preparing a lean methane-containing gas stream
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Solution Overview
Problem
Existing methods for preparing lean methane-containing gas streams are costly and inefficient, requiring multiple fractionation columns and producing excess refrigerant make-up, which increases operational and capital expenses.
Innovation Solution
A method and system that involves feeding a hydrocarbon feed stream into a separator to produce a vaporous methane-enriched stream, followed by a stabilizer column to separate pentane and a fractionation unit to produce an ethane-enriched stream, allowing for a smaller fractionation unit and reducing the need for refrigerant make-up by splitting the stabilizer overhead stream, thereby minimizing energy and operational costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multiple fractionation columns are used to separate NGL, then separation completeness is improved, but device complexity and capital expenses increase
Solution Approach 1:
The separation process is divided into two distinct stages: first, a scrub column separates the feed stream into a methane-rich overhead stream and a liquid bottom stream containing NGL; second, a single fractionation column separates the liquid bottom stream into stabilized condensate and a stabilizer overhead stream. This segmentation allows each column to be optimized for its specific separation task, reducing the need for multiple full-scale fractionation columns while maintaining separation completeness.
Solution Approach 2:
The invention extracts and removes the heavy NGL components (C5+) from the feed stream in the liquid bottom stream before they can complicate the fractionation process. By taking out these heavy components first, the subsequent fractionation column only needs to handle lighter components, simplifying the overall separation system and reducing the number of columns required.
2Manufacturing precision
If conventional NGL extraction is used, then hydrocarbon separation is achieved, but energy consumption increases due to operating multiple large fractionation columns
Solution Approach 1:
The energy-intensive fractionation process is segmented into two parts: the scrub column operates at higher pressure and temperature to perform the initial separation, while the single fractionation column operates at lower pressure and temperature to complete the separation of lighter components. This segmentation reduces the total energy consumption compared to using multiple large fractionation columns operating under more demanding conditions throughout.
Solution Approach 2:
The invention changes the operating parameters between the two columns: the scrub column operates at higher pressure and temperature to maximize NGL recovery, while the fractionation column operates at lower pressure and temperature to efficiently separate the lighter hydrocarbons. These parameter changes optimize energy consumption at each stage of the separation process.
3Device complexity
If a single fractionation column is used, then device complexity is reduced, but separation completeness deteriorates
Solution Approach 1:
The separation function is segmented between two columns with different designs and operating conditions: the scrub column is optimized for removing heavy NGL components, while the fractionation column is optimized for separating lighter hydrocarbons. This segmentation allows a single fractionation column to achieve complete separation when combined with the scrub column, whereas a single standalone fractionation column would require excessive complexity to achieve the same result.
Solution Approach 2:
The scrub column performs a preliminary separation action by removing the heavy NGL components before the feed enters the fractionation column. This preliminary action prepares the stream for more efficient fractionation, allowing the single fractionation column to achieve complete separation of lighter components without requiring multiple columns in series.
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 results in significant CAPEX and OPEX savings, reduced energy consumption, and increased production efficiency by allowing the fractionation unit to be bypassed, with the duty of the fractionation unit becoming available for liquefaction, and enabling on-demand production of ethane and propane enriched streams.
Implementation Method 1
feeding a hydrocarbon feed stream into a separator, withdrawing from the separator a vaporous methane enriched overhead stream containing at least the majority of the methane from the hydrocarbon feed stream, withdrawing from the separator a liquid bottom stream
Implementation Method 2
passing the liquid bottom stream to a stabilizer column, withdrawing from the stabilizer column a stabilized condensate stream enriched in pentane
Implementation Method 3
passing the slip stream portion to a fractionation unit comprising one or more fractionation columns to obtain an ethane enriched stream
Data Source
AI summary
The invention relates to a method and system of preparing a lean methane-containing gas stream (22), comprising: —feeding a hydrocarbon feed stream (10) into a separator (100); —withdrawing from the separator (100) a liquid bottom stream (12); —passing the liquid bottom stream (12) to a stabilizer column (200); —withdrawing from the stabilizer column (200) a stabilized condensate stream (13) enriched in pentane, —withdrawing from the stabilizer column (200) a stabilizer overhead stream (14) enriched in ethane, propane and butane; —splitting the stabilizer overhead stream (14) according to a split ratio into a main stream portion (15) and a slip stream portion (16), —passing the slip stream portion (16) to a fractionation unit (300) to obtain an ethane enriched stream (17) and a bottom stream enriched in propane and butane (18).