Hydrocarbon Stream Cooling via Dynamic Refrigerant Expansion
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Solution Overview
Problem
Existing methods for liquefying natural gas, such as those described in U.S. Pat. No. 3,763,658, require substantial condensing duty in propane exchangers, which reduces their cooling ability for other streams and limits the efficiency and capacity of hydrocarbon cooling processes.
Innovation Solution
A method and apparatus that involve heat exchanging a hydrocarbon stream with a refrigerant stream, compressing and dynamically expanding the refrigerant stream to reduce enthalpy, and further cooling it to achieve partial condensation, thereby reducing the heat load on subsequent cooling stages and increasing the cooling capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If substantial condensing duty is provided in propane exchangers to achieve partial condensation of refrigerant, then the refrigerant can be condensed, but the cooling ability for other hydrocarbon streams is reduced
Solution Approach 1:
The condensation process is divided into two separate stages: first, high-pressure compressors compress the refrigerant and ambient coolers cool it; second, dynamic expanders expand the cooled compressed refrigerant to achieve partial condensation. This segmentation allows the propane exchangers to focus on cooling hydrocarbon streams while condensation occurs in the expander stage.
Solution Approach 2:
The refrigerant is pre-cooled by ambient coolers before entering the dynamic expander. This preliminary cooling action reduces the temperature of the compressed refrigerant, enabling more efficient condensation during expansion and reducing the cooling burden on propane exchangers.
2Power
If two-stage compression with intercooler and aftercooler is used to compress refrigerant, then compression is achieved, but substantial condensing duty is required which reduces cooling ability
Solution Approach 1:
Dynamic expanders are introduced as an intermediary device between compression and condensation. These expanders take the cooled compressed refrigerant and use dynamic expansion to achieve partial condensation, serving as a bridge that reduces the energy burden on the cooling system.
Solution Approach 2:
The patent utilizes phase transition during dynamic expansion of the refrigerant. By expanding the cooled compressed refrigerant through dynamic expanders, the refrigerant undergoes phase change from gas to liquid, achieving condensation without requiring additional cooling capacity from propane exchangers.
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 heat load on refrigerant heat exchangers, allowing for more efficient cooling of hydrocarbon streams and increased capacity in hydrocarbon cooling processes, such as natural gas liquefaction, by extracting work from the ambient-cooled compressed refrigerant stream during dynamic expansion.
Implementation Method 1
heat exchanging the hydrocarbon stream against a first refrigerant stream to provide a cooled hydrocarbon stream and an at least partly evaporated refrigerant stream
Implementation Method 2
compressing the at least partly evaporated refrigerant stream using one or more compressors to provide a compressed refrigerant stream
Implementation Method 3
cooling the compressed refrigerant stream, after one or more of the compressions, against ambient to provide a cooled compressed refrigerant stream
Implementation Method 4
dynamically expanding the cooled compressed refrigerant stream of step (c) to provide an expanded refrigerant stream
Implementation Method 5
further cooling the expanded refrigerant stream to provide an at least partially condensed refrigerant stream
Data Source
AI summary
Method of cooling a hydrocarbon stream (10) such as natural gas, the method at least comprising the steps of (a) heat exchanging the hydrocarbon stream (10) against a first refrigerant stream (20) to provide a cooled hydrocarbon stream (30) and an at least partly evaporated refrigerant stream (40); (b) compressing the at least partly evaporated refrigerant stream (40) using one or more compressors (14, 16, 18) to provide a compressed refrigerant stream (50, 60, 70); (c) cooling the compressed refrigerant stream (50, 60, 70) after one or more of the compressors against ambient to provide a cooled compressed refrigerant stream (70a); (d) dynamically expanding the cooled compressed gaseous refrigerant stream (70a) to provide an expanded refrigerant stream (80); and (e) further cooling the expanded refrigerant stream (80) to provide an at least partially condensed refrigerant stream.