Apparatus for precooling hydrogen for liquefaction using external liquid nitrogen and high pressure gaseous nitrogen
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Solution Overview
Problem
Current hydrogen liquefaction processes are inefficient and costly due to the high energy consumption required for refrigeration, particularly in the precooling stage, and the need for multiple rotating equipment such as compressors and turbine boosters.
Innovation Solution
An integrated system combining an air separation unit (ASU), hydrogen generation unit (HGU), and hydrogen liquefaction unit (HLU) that utilizes pressurized gaseous oxygen and liquid nitrogen from the ASU for primary and secondary refrigeration, minimizing the use of cycle compressors and optimizing refrigeration efficiency by vaporizing nitrogen within the precooling unit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If liquid nitrogen is injected into the precooling heat exchanger to provide refrigeration, then the hydrogen stream can be cooled to the required temperature, but large quantities of liquid nitrogen are required and the process becomes less thermodynamically efficient
Solution Approach 1:
The invention changes the thermodynamic parameters of nitrogen by compressing it to high pressure (e.g., 200-500 bara) before expansion, enabling the nitrogen to achieve much lower temperatures during Joule-Thomson expansion. This allows efficient precooling of hydrogen without requiring excessive quantities of nitrogen, thereby improving refrigeration efficiency while maintaining effective cooling.
Solution Approach 2:
The invention performs preliminary compression and cooling of nitrogen before it enters the precooling heat exchanger. By pre-compressing nitrogen to high pressure and pre-cooling it in the heat exchanger using cold hydrogen streams, the system prepares the nitrogen to deliver maximum refrigeration effect during expansion, reducing the total quantity of nitrogen needed and improving overall efficiency.
2Temperature
If a nitrogen refrigeration cycle with multiple turbines and compressors is used, then refrigeration can be provided, but the device complexity increases with multiple rotating equipment
Solution Approach 1:
The invention extracts and eliminates the need for cycle compressors and turbine boosters from the traditional nitrogen refrigeration cycle. By using high-pressure gaseous nitrogen from an external source and utilizing a single expansion turbine, the system removes the complex multi-stage compression and boosting equipment while still achieving the required refrigeration temperatures for hydrogen precooling.
Solution Approach 2:
The high-pressure gaseous nitrogen from the air separation unit serves multiple functions: it provides the working fluid for the expansion turbine, acts as a refrigerant source, and its compression is already accomplished by the ASU process. This multi-functionality eliminates the need for dedicated cycle compressors and booster turbines, simplifying the overall system.
3Temperature
If liquid nitrogen is sourced from a separate nitrogen liquefier, then refrigeration can be provided, but capital expenditure increases and the system requires additional compression equipment
Solution Approach 1:
The invention uses high-pressure gaseous nitrogen from the air separation unit as an intermediary substance. Instead of requiring a separate liquid nitrogen liquefier, the gaseous nitrogen serves as the medium that, when expanded through the turbine, provides the necessary refrigeration. This intermediary approach eliminates the need for additional liquefaction equipment and reduces capital expenditure.
Solution Approach 2:
The air separation unit itself provides the high-pressure gaseous nitrogen needed for the refrigeration process. The ASU's existing compression and separation processes generate the required nitrogen stream, making the system self-sufficient without needing external liquid nitrogen sources or additional liquefaction equipment, thereby reducing capital costs.
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 energy consumption and capital expenditure by optimizing refrigeration, achieving energy savings of about 1.24% while improving the precooling efficiency of hydrogen to approximately 80K, thus enhancing the overall hydrogen liquefaction process.
Implementation Method 1
provides refrigeration by expansion and cooling of high pressure gaseous nitrogen in a turbine
Implementation Method 2
This nitrogen stream vaporizes and is warmed to near ambient temperature as it exchanges cold with the hydrogen stream(s)
Implementation Method 3
cooled in a precooling heat exchanger to approximately -180°C to -190°C
Data Source
AI summary
An integrated industrial unit is provided, which can include: a nitrogen source comprising an air separation unit that is configured to provide pressurized gaseous nitrogen and liquid nitrogen; a hydrogen source; a hydrogen liquefaction unit, wherein the hydrogen liquefaction unit comprises a precooling system, and a liquefaction system; and a liquid hydrogen storage tank, wherein the precooling system is configured to receive the gaseous hydrogen from the hydrogen source and cool the gaseous hydrogen to a temperature between 70K and 100K, wherein the precooling system comprises a primary refrigeration system and a secondary refrigeration system, wherein the liquefaction system is in fluid communication with the precooling system and is configured to liquefy the gaseous hydrogen received from the precooling system to produce liquid hydrogen, wherein the liquid hydrogen storage tank is in fluid communication with the liquefaction system and is configured to store the liquid hydrogen received from the liquefaction system.