Method for the production of air gases by the cryogenic separation of air with variable liquid production and power usage
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Solution Overview
Problem
Air separation units (ASUs) face inefficiencies when supplying oxygen to pipelines with variable pressure due to the need for constant pressure design, leading to power consumption and liquid production inefficiencies.
Innovation Solution
Implementing a method and apparatus that allows for adjustable production pressure of air gases to match pipeline pressure, using flexible equipment design and process control strategies, such as automatic adjustment of gaseous oxygen product pressure and LOX pump speed, to minimize power consumption and increase liquid production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the ASU is designed to provide oxygen gas at constant pressure above the highest expected pipeline pressure, then the ASU operates efficiently at steady state conditions, but power consumption increases and liquid production decreases when pipeline pressure is below design pressure due to pressure letdown across control valve
Solution Approach 1:
The invention applies dynamics by transitioning from constant pressure design to variable pressure operation. The ASU product pressure is dynamically adjusted to follow pipeline pressure variations, allowing the system to adapt to changing conditions rather than maintaining a fixed design pressure. This enables efficient operation across varying pipeline pressures without unnecessary pressure letdown.
Solution Approach 2:
The invention changes the pressure parameter from a fixed constant value to a variable value that tracks pipeline pressure. By adjusting the ASU product pressure setpoint dynamically based on actual pipeline pressure conditions, the system optimizes power consumption and liquid production according to real-time requirements rather than operating at a conservative constant pressure above maximum expected pipeline pressure.
2Productivity
If the ASU is designed to provide oxygen gas at constant pressure, then equipment can be sized for steady state efficiency, but adaptability to variable pipeline pressure conditions deteriorates
Solution Approach 1:
The system becomes dynamic by continuously adjusting product pressure to match pipeline pressure variations. This allows the ASU to maintain efficiency across varying operating conditions rather than being optimized for a single steady state, improving adaptability while preserving productivity through intelligent control strategies.
Solution Approach 2:
The invention makes the ASU universally adaptable to different pipeline pressure conditions. By implementing variable pressure operation with automated control, the system can efficiently serve pipelines with varying pressure requirements throughout the day, rather than being limited to operation at a single design pressure point.
3Ease of operation
If pressure letdown across control valve is used to match pipeline pressure, then pressure matching is achieved, but energy efficiency deteriorates due to throttling losses
Solution Approach 1:
The invention applies preliminary action by adjusting the ASU product pressure in advance to match expected pipeline pressure conditions. Rather than using control valves to letdown pressure after compression, the system proactively sets the product pressure to the required level, eliminating throttling losses and improving energy efficiency while maintaining ease of pressure matching.
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 power consumption and increases liquid production by matching product pressure with pipeline pressure, achieving significant power savings and additional refrigeration without altering the operating conditions of the main or booster air compressors.
Implementation Method 1
compressing air to a pressure suitable for the cryogenic rectification of air
Implementation Method 2
the cryogenic separation of air
Implementation Method 3
rectification of air to produce a compressed humid air stream
Implementation Method 4
cooling the purified air in a heat exchanger by indirect heat exchange against process streams from the cryogenic distillation column
Implementation Method 5
the liquid oxygen produced from the lower pressure column is pumped from low pressure to a higher pressure
Implementation Method 6
the liquid oxygen produced from the lower pressure column is pumped from low pressure to a higher pressure than that of the pipeline and vaporized within the heat exchanger
Data Source
AI summary
A method for the production of air gases by the cryogenic separation of air can include the steps of sending a purified and compressed air stream to a cold box under conditions effective for cryogenically separating the air stream into oxygen and nitrogen using a system of columns, wherein the purified and compressed air stream is at a feed pressure when entering the system of columns; withdrawing the oxygen at a product pressure; delivering the oxygen at a delivery pressure to an oxygen pipeline, wherein the oxygen pipeline has a pipeline pressure; and monitoring the pipeline pressure. The method can also include a controller configured to determine whether to operate in a power savings mode or a variable liquid production mode. By operating the method in a dynamic fashion, a power savings and/or additional high value cryogenic liquids can be realized in instances in which the pipeline pressure deviates from its highest value.