Mixed Refrigerant Precooling Control for LNG Stream Cooling
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Solution Overview
Problem
Existing methods for liquefying natural gas streams face challenges in controlling multi-component pre-cooling refrigeration cycles, leading to inefficiencies and unsatisfactory results.
Innovation Solution
A method and apparatus that involve a mixed refrigerant stream being passed through heat exchangers, with temperature and flow monitoring, and a secondary cooling stream being expanded and controlled based on the monitored values to optimize the cooling process, allowing for more precise adjustment and increased efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by stationary object
If a single component refrigerant is used to pre-cool the multi-component refrigerant, then the refrigeration load is shifted from the multi-component cycle to the single component cycle, but the control of the multi-component pre-cooling refrigeration cycle becomes unsatisfactory
Solution Approach 1:
The patent implements a control system that continuously monitors the temperature and flow rate of the cooled mixed refrigerant stream, and uses this feedback information to dynamically adjust the flow rate of the cooling stream. This closed-loop feedback mechanism enables precise control of the pre-cooling cycle, resolving the control issues while maintaining optimized refrigeration load distribution.
Solution Approach 2:
The system transitions from static control to dynamic control by continuously adjusting the cooling stream flow rate based on real-time measurements of temperature and flow of the cooled mixed refrigerant. This dynamic adjustment capability allows the system to adapt to changing operating conditions, improving both control performance and energy efficiency.
2Productivity
If the flow of cooling stream is controlled using both temperature and flow measurements of cooled mixed refrigerant, then the cooling process efficiency is enhanced and power consumption is reduced, but the system complexity increases due to additional monitoring and control requirements
Solution Approach 1:
The control system uses feedback from temperature and flow measurements to dynamically adjust the cooling stream flow rate, optimizing the cooling process efficiency and reducing power consumption through intelligent, real-time control decisions.
Solution Approach 2:
The system performs self-regulation by automatically adjusting its own operating parameters (cooling stream flow rate) based on measured process conditions, eliminating the need for complex external control mechanisms and achieving optimization through self-service 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 the efficiency of the cooling process, reduces power consumption, and allows for rapid adjustment of the refrigerant stream to match cooling duties, improving the production of liquefied natural gas.
Implementation Method 1
expanding at least a fraction of the cooling stream to provide one or more expanded cooling streams
Implementation Method 2
passing at least one of the one or more expanded cooling streams through one or more of the heat exchangers of step (b) to cool the mixed refrigerant stream
Data Source
AI summary
A mixed refrigerant stream (10) comprising a first mixed refrigerant is passed through one or more heat exchangers (12) to provide a cooled mixed refrigerant stream (20). At least a fraction of a cooling stream (30) comprising a second mixed refrigerant is expanded (14) to provide one or more expanded cooling streams (40a), at least one of which may be passed through one or more of the heat exchangers (12), to cool the mixed refrigerant stream (10) thereby providing the cooled mixed refrigerant stream (20) which is used to cool (22) a hydrocarbon stream (70). The temperature (T1) and the flow (F1) of at least part of the cooled mixed refrigerant stream (20) is monitored, and the flow (F2) of the cooling stream (30) is controlled using the flow F1 and the temperature T1.