Mixed Refrigerant Injection for Uniform LNG Heat Exchanger Evaporation
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Solution Overview
Problem
Existing methods for liquefying natural gas face challenges due to nonuniform distribution of liquid and gas phases in cooling streams, leading to inefficient heat exchange and potential damage to compressor components from incomplete evaporation.
Innovation Solution
A method that involves introducing a cooling stream into a heat exchanger, expanding it into biphasic streams at different pressures, separating phases, and adjusting the flow rate based on temperature differences to ensure uniform evaporation and prevent incomplete evaporation, thereby maintaining efficient heat exchange and apparatus integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a biphasic cooling stream is introduced into the heat exchanger, then the heat exchange efficiency is improved, but the uniform distribution of liquid and gas phases deteriorates
Solution Approach 1:
The cooling stream is divided into multiple separate streams, each introduced into different passages of the heat exchanger. This segmentation ensures that each passage receives a controlled mixture of liquid and gas phases, improving uniformity while maintaining heat exchange efficiency.
Solution Approach 2:
The liquid and gas phases are mixed before introduction into the heat exchanger passages. This preliminary mixing action ensures that the phases are uniformly distributed before entering the heat exchange process, resolving the distribution issue while maintaining efficiency.
2Productivity
If the flow rate of cooling stream is increased, then the liquefaction productivity is improved, but the risk of incomplete evaporation and compressor damage increases
Solution Approach 1:
The temperature of the cooling stream at the outlet of the heat exchanger is measured and used as feedback to control the flow rate of the cooling stream. When the temperature approaches the dew point (indicating incomplete evaporation), the flow rate is automatically reduced, preventing compressor damage while allowing high productivity during normal operation.
3Use of energy by moving object
If the cooling stream is expanded to multiple pressure levels, then the heat exchange performance is improved, but the device complexity increases
Solution Approach 1:
Multiple cooling streams at different pressure levels are merged into a single combined stream before introduction into the heat exchanger. This merging approach maintains the performance benefits of multi-level expansion while simplifying the overall device architecture by reducing the number of separate introduction points and control systems.
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 ensures uniform distribution of phases, enhances energy performance, and prevents damage to compressor components by ensuring complete evaporation of the cooling stream, simplifying the architecture of the liquefaction plant and maintaining its integrity.
Implementation Method 1
the cooling stream is expanded, forming a liquid phase and a gaseous phase
Implementation Method 2
the cooling stream introduced into the exchanger in a biphasic state is evaporated therein against the hydrocarbon stream, which undergoes liquefaction
Implementation Method 3
employing at least one cooling stream which evaporates in a heat exchanger against the hydrocarbon stream to be liquefied
Data Source
AI summary
A method for liquefying a stream of hydrocarbons from a feed stream, including introducing the feed stream and a first cooling stream into a first heat exchanger, extracting a plurality of partial cooling streams obtained from the first cooling stream from the heat exchanger via separate outlets, introducing each partial cooling stream into an expansion element to produce a plurality of biphasic cooling streams at different pressures, introducing each biphasic cooling stream into a phase separator element to produce a gaseous cooling stream which is diverted from the first exchanger and a liquid cooling stream which is introduced into the first exchanger via respective inlets, evaporating each liquid cooling stream by heat exchange with at least the feed stream and the first cooling stream so as to extract a cooled hydrocarbon stream at the outlet from the first heat exchanger and to extract a plurality of evaporated cooling streams.