Method and apparatus for cooling a hydrocarbon stream
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Solution Overview
Problem
Current methods for liquefying natural gas in LNG plants are inefficient due to high power consumption in NGL recovery processes, particularly because they require additional cooling bundles and divert cooling duty from the main methane stream, reducing liquefaction efficiency.
Innovation Solution
A method and apparatus that involve passing an initial hydrocarbon stream through a separator to create an overhead stream and a mixed feed stream, cooling and liquefying the overhead stream, separating C1, C2, C3, and C4 streams, and further cooling a fraction of these streams by admixing with the C1 stream, thereby maintaining pressure and avoiding the need for expansion or compression devices, which reduces power consumption and capital expenditure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional NGL recovery methods are used with additional cooling bundles, then NGL separation is achieved, but cooling duty is diverted from the main methane stream and power consumption increases
Solution Approach 1:
The invention extracts the C1 overhead stream from the mixed hydrocarbon feed stream and processes it separately through a dedicated cooling path. This separation allows the C1 stream to be cooled and liquefied independently without requiring additional cooling bundles in the main heat exchanger, thereby preserving cooling duty for the main methane stream and reducing overall power consumption.
Solution Approach 2:
The C1 overhead stream serves its own cooling needs by being admixed with cooled fractions of C2, C3, and C4 overhead streams. This self-cooling mechanism eliminates the need for external refrigeration or additional cooling bundles, allowing the system to recover NGLs with minimal power consumption while maintaining efficient cooling of the main hydrocarbon stream.
2Quantity of substance
If additional cooling bundles are installed in the main heat exchanger, then NGL cooling capacity is increased, but device complexity and capital expenditure increase
Solution Approach 1:
The invention extracts the C1 overhead stream from the main hydrocarbon feed stream and processes it through a separate cooling path using a fraction of the already-cooled C2, C3, and C4 overhead streams. This eliminates the need for additional cooling bundles in the main heat exchanger, thereby reducing device complexity and capital expenditure while maintaining adequate NGL cooling capacity.
Solution Approach 2:
The invention recovers cooling capacity by utilizing a fraction of the C2, C3, and C4 overhead streams that have already been cooled in the main heat exchanger. Instead of discarding this cooling potential, it is reused to cool the C1 overhead stream, eliminating the need for additional cooling bundles and reducing capital expenditure.
3Stress or pressure
If expansion or compression devices are added to the cooling process, then pressure control is improved, but power consumption and capital expenditure increase
Solution Approach 1:
The cooling process is designed to operate at substantially constant pressure by directly admixing the C1 overhead stream with cooled fractions of C2, C3, and C4 overhead streams. This self-regulating approach maintains pressure balance without requiring expansion or compression devices, thereby eliminating additional power consumption and capital expenditure while achieving adequate pressure control.
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 enhances liquefaction efficiency by minimizing power consumption and avoiding the need for additional cooling bundles, allowing for more efficient cooling of the main hydrocarbon stream while maintaining pressure, thus reducing operational and capital expenses.
Implementation Method 1
cooling at least a fraction of at least one of the group comprising: the C2 overhead stream, the C3 overhead stream and the C4 overhead stream; with the C1 overhead stream
Implementation Method 2
further cooling the cooled stream against at least a fraction of the cooled, preferably liquefied, hydrocarbon stream
Data Source
AI summary
A method and apparatus for cooling a hydrocarbon stream such as natural gas. An initial hydrocarbon stream is passed through a first separator to provide an initial overhead stream and a mixed hydrocarbon feed stream. The initial overhead stream is cooled to provide a cooled hydrocarbon stream such as LNG, and at least a C1 overhead stream and one or more C2, C3 and C4 overhead streams are separated from the mixed hydrocarbon feed stream. At least a fraction of at least one of the group comprising: the C2 overhead stream, the C3 overhead stream and the C4 overhead stream is cooled with the C1 overhead stream to provide a cooled stream, which is further cooled against at least a fraction of the cooled, preferably liquefied, hydrocarbon stream to provide an at least partly liquefied cooled stream.