Oxygen Liquefier Design Phasing for Energy Efficiency
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Solution Overview
Problem
Current air separation plants face challenges in efficiently producing liquid oxygen and nitrogen in liquid form, particularly in achieving the desired flowrates and energy efficiency, especially when pumping and transporting higher pressure products.
Innovation Solution
The process involves cooling and splitting a pressurized air stream, using a main heat exchanger and distillation column, with additional refrigeration duty from a lost air compressor and expansion turbine to produce liquid oxygen and nitrogen, and utilizing a secondary turboexpander to enhance cold production and waste heat regeneration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If air separation plants produce liquid oxygen and nitrogen in liquid form, then transportation efficiency and energy efficiency are improved, but the complexity of the system increases
Solution Approach 1:
The air separation plant is divided into multiple distillation columns (first and second distillation columns) that can operate independently or in combination. Each column can produce liquid products separately, allowing flexible operation modes that optimize energy efficiency while managing system complexity through modular architecture
Solution Approach 2:
The distillation columns are designed to produce multiple liquid products (liquid oxygen and liquid nitrogen) simultaneously or separately. The system can operate in different modes (first operating mode producing both liquids, second operating mode producing primarily liquid oxygen) to accommodate varying customer demands and optimize energy efficiency
2Productivity
If the plant operates in second operating mode to produce higher flowrate of liquid oxygen, then productivity is improved, but the complexity of operation increases
Solution Approach 1:
The system allows dynamic switching between operating modes based on customer demand. The second operating mode is specifically designed to maximize liquid oxygen production when demand is high, while the control system automatically manages the complex operational parameters to maintain ease of operation despite the increased productivity requirement
3Productivity
If liquid products are pumped to higher pressure for transportation, then transportation efficiency is improved, but energy consumption increases
Solution Approach 1:
The system produces products in liquid phase which can be pumped efficiently to higher pressures for transportation. The distillation columns are designed to output liquid products directly, leveraging the favorable pumping characteristics of liquids compared to gases, thereby achieving transportation efficiency with acceptable energy consumption
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 allows for increased production of liquid oxygen and nitrogen with improved energy efficiency and waste heat utilization, enabling higher flowrates of liquid oxygen and nitrogen products while optimizing energy use and transportation efficiency.
Implementation Method 1
cooling a pressurized inlet air stream in a main heat exchanger, thereby producing a cooled inlet air stream
Implementation Method 2
expanding the warmed refrigerant air stream in an expansion turbine, thereby producing an expanded refrigerant air stream
Implementation Method 3
introducing the distillation stream into a distillation column... the distillation column produces a first flowrate of product liquid oxygen, and a first flow rate of liquid nitrogen product
Data Source
AI summary
A process for producing liquid oxygen, including, a first operating mode, and a second operating mode. During the first operating mode, the distillation column produces a first flowrate of product liquid oxygen, and a first flow rate of liquid nitrogen product. During the second operating mode, the distillation column produces a second flowrate of product liquid oxygen, and a second flow rate of liquid nitrogen product. Wherein, the second flowrate of product liquid oxygen is greater than the first flowrate of product liquid oxygen.