Liquid nitrogen generator and process
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Solution Overview
Problem
Conventional cryogenic air separation plants require a booster air compressor and nitrogen recycle compressor, leading to complex and costly compressor assemblies, and often necessitate pre-cooling the air before purification, increasing equipment complexity and operating expenses.
Innovation Solution
A method and apparatus that produces liquid nitrogen without a booster air compressor, utilizing a lost air turbine for additional refrigeration and optimizing turbine operations to enhance refrigeration capacity, with a single Main Air Compressor as the sole compression means, and eliminating the need for pre-cooling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a booster air compressor and nitrogen recycle compressor are used in conventional cryogenic air separation plants, then the nitrogen production capacity is improved, but the device complexity and equipment cost increase
Solution Approach 1:
The invention extracts and eliminates the booster air compressor and nitrogen recycle compressor from the conventional system. By using a single main air compressor operating at elevated pressure (10-50 bar) combined with expansion turbines for refrigeration, the system achieves nitrogen production without the complex multi-compressor arrangement, directly resolving the contradiction between productivity and device complexity
Solution Approach 2:
The invention changes the operating pressure parameter of the main air compressor to elevated levels (10-50 bar), which enables the system to function without additional booster compressors. This parameter change allows the expansion turbine to provide sufficient refrigeration capacity while maintaining nitrogen production, thereby simplifying the compressor assembly while preserving productivity
2Manufacturing precision
If pre-cooling is applied before purification in conventional systems, then the purification efficiency is improved, but the device complexity and operating expenses increase
Solution Approach 1:
The invention performs preliminary cooling of the compressed air stream before it enters the purification unit. By cooling the air to a lower temperature (e.g., from ambient to near 0°C or below) prior to purification, the system improves purification efficiency while avoiding the need for complex pre-cooling equipment, as the cooling is integrated into the existing compression and expansion process
Solution Approach 2:
The system uses its own expansion turbine refrigeration capacity to provide the pre-cooling function. The expansion turbine, which generates refrigeration for liquefaction, also cools the air stream before purification, making the system self-sufficient and eliminating the need for separate pre-cooling equipment, thereby reducing device complexity while maintaining purification efficiency
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
Achieves higher efficiency and reduced equipment costs by optimizing refrigeration capacity, minimizing heat transfer losses, and simplifying the compressor system, resulting in 3-4% lower power consumption and significantly lower equipment costs.
Implementation Method 1
expanding a first portion of the compressed air in a cold turbine to form an expanded fluid
Implementation Method 2
expanding a first portion of the compressed air in a cold turbine to form an expanded fluid
Implementation Method 3
a lost air stream is warmed and expanded to less than 2 bar(a) in a warm turbine
Implementation Method 4
The compressed air is cooled in a heat exchanger
Implementation Method 5
purifying a feed air in a purification unit
Data Source
AI summary
A process for producing liquid nitrogen utilizes a distillation system comprising higher-pressure and lower-pressure columns, a first condenser in the lower-pressure column bottom, and a second condenser disposed on top of the lower-pressure column. Feed air is compressed in a main air compressor above 15 bar(a) and cooled in a main heat exchanger. A first cooled air portion is expanded in a cold turbine before separation in the higher-pressure column. A second cooled air portion is liquefied before entering the higher-pressure column. Liquid nitrogen streams condensed by both the first and second condensers are combined to yield the final product. Another feature involves warming and expanding a lost air stream (e.g., from the cold turbine outlet and/or higher-pressure column) to below 2 bar(a) in a warm turbine.