Shipboard Membrane Air Separation for Dry Utility Air and Inert Gas
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Solution Overview
Problem
Existing marine systems for producing utility air and inert gas are inefficient, costly, and pollutant-intensive, as they rely on compressing ambient air and using diesel fuel in inert gas generators that produce corrosive combustion gases and generate pollution.
Innovation Solution
A system that compresses ambient air, cools it with seawater, dries it using a moisture separator and polymeric dehydration membrane, and separates it into nitrogen-rich inert gas using an air separation membrane, eliminating the need for diesel fuel and reducing energy consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If inert gas generators use combustion gas from diesel fuel burning, then inert gas with low oxygen content is produced, but the system becomes expensive and generates corrosive combustion gas and pollution
Solution Approach 1:
The system converts the harmful combustion process into a beneficial separation process. Instead of burning diesel fuel to produce inert gas, the system uses a membrane separator to physically separate nitrogen from oxygen in ambient air. The membrane module selectively allows nitrogen to pass through while retaining oxygen, converting the previously harmful combustion method into a clean, non-polluting separation process that produces the same inert gas effect without corrosive byproducts
Solution Approach 2:
The system replaces the chemical combustion mechanism with a physical membrane separation mechanism. The inert gas generator previously relied on chemical reactions (diesel combustion) to consume oxygen and produce inert gas. The new system uses a polymeric membrane that selectively transports nitrogen molecules through its structure based on size and solubility differences, substituting a clean physical separation process for the polluting chemical combustion process
2Reliability
If utility air is produced by compressing ambient air and passing it through refrigeration dryers and filters, then dry utility air is obtained, but the system requires significant energy and has high maintenance needs
Solution Approach 1:
The system replaces the mechanical refrigeration drying system with a membrane-based separation system. Instead of using refrigeration dryers that require compressors, condensers, and expansion valves to remove moisture, the system uses a polymeric membrane that selectively allows water vapor to pass through while retaining dry air components. This substitution eliminates the need for complex mechanical refrigeration equipment and significantly reduces energy consumption
Solution Approach 2:
The system extracts and removes only the necessary component (moisture) from the compressed air stream using the membrane separator. The membrane selectively extracts water vapor molecules from the compressed air based on their smaller size and higher solubility in the polymeric membrane material, allowing the dry air components to pass through. This targeted extraction approach is more energy-efficient than using refrigeration dryers that must cool the entire air stream to condense and remove moisture
3Reliability
If inert gas generators burn diesel fuel to produce inert gas, then low oxygen content gas is achieved, but the system requires significant fuel consumption and generates pollution
Solution Approach 1:
The system replaces the chemical combustion mechanism with a physical membrane separation mechanism. The inert gas generator previously relied on chemical reactions (diesel combustion) to consume oxygen and produce inert gas. The new system uses a polymeric membrane that selectively transports nitrogen molecules through its structure based on size and solubility differences, substituting a clean physical separation process for the polluting chemical combustion process
Solution Approach 2:
The system converts the harmful combustion process into a beneficial separation process. Instead of burning diesel fuel to produce inert gas, the system uses a membrane separator to physically separate nitrogen from oxygen in ambient air. The membrane module selectively allows nitrogen to pass through while retaining oxygen, converting the previously harmful combustion method into a clean, non-polluting separation process that produces the same inert gas effect without corrosive byproducts
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
The system produces dry utility air and inert gas at reduced cost and energy usage, with minimal moving parts and reduced pollution, while extending the life of membrane modules and minimizing maintenance.
Implementation Method 1
The compressed air passes through a heat exchanger, into which sea water from outside the vessel is directed. The sea water absorbs heat from the hot compressed air
Implementation Method 2
The cooled compressed air is dried, first by passing it through a moisture separator and one or more coalescing filters, and by then passing it through a polymeric dehydration membrane
Implementation Method 3
The remaining filtered dry air passes through an air separation membrane module, which produces a nitrogen-rich stream suitable for use as an inerting gas
Data Source
AI summary
A shipboard system provides dry, oil-free utility air and inert gas for use on a marine vessel. A compressor converts ambient air into a pressurized air stream. The air stream is cooled by heat exchange with sea water in the vicinity of the vessel. The air stream is then dried in a dehydration membrane module, and some of the product of the dehydration module is taken for use as utility air. The remainder of the dried air is passed through an air separation module which includes a polymeric membrane. The product of the air separation module includes a nitrogen-enriched gas which is used as an inert gas on the vessel. The compressor is the only mechanically moving component of the system.