Method and apparatus for cooling hydrogen
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Solution Overview
Problem
Existing hydrogen liquefaction processes face challenges in efficiently cooling equipment during startup, particularly in systems without internal cold sources, where sensitive components are prone to rapid or disproportionate temperature changes.
Innovation Solution
The proposed hydrogen cooling process utilizes a two-stage heat exchanger system with an intermediate fluid, where liquefied or vaporized natural gas warms up an intermediate fluid to a temperature below -50 °C, which is then cooled further in a second heat exchanger or through relaxation in a turbine. This process allows for controlled cooling of hydrogen without condensation, optimizing temperature regulation during startup.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the heat exchanger and equipment are cooled rapidly from ambient temperature to steady-state operating temperature during startup, then the cooling process is faster, but the equipment is damaged due to rapid temperature drops
Solution Approach 1:
The patent applies preliminary action by introducing a startup mode that operates before the normal hydrogen cooling mode. During this preliminary phase, the system uses supercritical natural gas or pre-cooled gas to gradually cool the heat exchanger and intermediate fluid without yet introducing hydrogen. This preparatory cooling action prevents thermal shock to the equipment while establishing the necessary temperature conditions for subsequent hydrogen cooling operations.
2Temperature
If the compressor compression ratio is maintained at normal levels during startup, then the cooling capacity is sufficient, but the compressor inlet temperature becomes too low causing operational issues
Solution Approach 1:
The patent applies dynamics by making the compression ratio variable based on operational mode. During startup, the compression ratio is reduced to prevent the compressor inlet temperature from dropping too low, ensuring reliable operation. Once the system reaches steady-state and hydrogen cooling begins, the compression ratio increases to provide sufficient cooling capacity. This dynamic adjustment of the compression ratio allows the system to adapt to different operational requirements and maintain reliability across all phases.
3Productivity
If the intermediate fluid molar flow rate is maintained at normal levels during startup, then the cooling efficiency is high, but the system cannot properly cool the heat exchanger without hydrogen
Solution Approach 1:
The patent applies partial action by reducing the intermediate fluid molar flow rate during startup to less than 80% of the normal operating flow rate. This reduced flow rate is sufficient to allow the heat exchanger to be cooled by supercritical natural gas or pre-cooled gas without requiring the full cooling capacity needed for hydrogen. This partial operation allows the system to function adequately during startup while preventing the intermediate fluid from becoming too cold before hydrogen is introduced.
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 effectively regulates the cooling of hydrogen liquefaction systems, preventing damage to sensitive equipment by gradually reducing temperatures during startup, while also improving the efficiency of hydrogen liquefaction by utilizing existing equipment with minimal additions.
Implementation Method 1
cooled by introducing it at this temperature into a second heat exchanger where it cools by indirect heat exchange
Implementation Method 2
by expansion in a turbine, possibly driving a compressor of the process, or a valve
Implementation Method 3
Either liquefied natural gas or vaporized natural gas, the vaporized natural gas being at a temperature below -50°C, is heated by indirect heat exchange in a first heat exchanger with an intermediate fluid flow
Implementation Method 4
a gas flow derived from the intermediate fluid cooled in step a) and/or b) is heated in the second heat exchanger to a temperature between -90°C and -150°C, is withdrawn from the exchanger at this temperature and compressed in a compressor
Data Source
Figure 1
Figure 2
AI summary
In a hydrogen cooling process during a start-up mode, supercritical natural gas (1,2) is sent to a first exchanger (E1) to cool it and exchanges heat there with an intermediate fluid flow (5) of a cycle at a pressure between 3 and 70 bar abs which cools, the intermediate fluid flow (5) cooled in the first exchanger is sent directly to the inlet of a compressor (C, C1) which compresses it with a compression ratio lower than that of the first mode, the molar flow of the intermediate fluid (13) being less than 80% of the molar flow of intermediate fluid sent to the compressor during the steady operation and the intermediate fluid (15, 17) compressed in the compressor is returned to the first exchanger as the cycle fluid.