Why does feed gas selection matter in an ozone system?
The choice of feed gas is one of the main design decisions in an ozone generation system. It influences the ozone concentration that can be produced, the required gas flow, specific energy consumption, the size of downstream equipment and the overall operating strategy of the plant.
For water treatment applications, the three main alternatives are:
Liquid oxygen (LOX)
On-site oxygen generation by PSA
Treated dry air
None of these options is universally better. The appropriate solution depends on the required ozone production, operating profile, site utilities, oxygen availability, logistics, redundancy requirements and lifecycle cost.
What does the feed gas affect?
Feed gas selection can influence:
Achievable ozone concentration.
Gas flow required for a given ozone production.
Energy consumption of the complete ozone system.
Ozone transfer and contact-system design.
Off-gas volume and destruction requirements.
Equipment footprint and auxiliary systems.
Maintenance requirements.
Dependence on external oxygen supply.
CAPEX and OPEX over the project lifecycle.
The feed gas should therefore be selected as part of the complete ozonation process, not as an isolated utility decision.
A technically sound comparison between LOX, PSA and dry air must consider both ozone generator performance and the impact of each alternative on the rest of the plant.
LOX: when is liquid oxygen the right choice for an ozone system?
Liquid oxygen (LOX) is supplied to the site as a cryogenic liquid, stored in an insulated tank and vaporized before being fed to the ozone generation system as gaseous oxygen.
Because the oxygen is supplied externally, the plant does not need an on-site oxygen generation process such as PSA. This simplifies the feed-gas preparation equipment installed at the ozone plant, although it introduces dependence on oxygen deliveries, storage infrastructure and local supply logistics.
Main advantages of LOX for ozone generation
LOX can be particularly attractive when:
High ozone production capacity is required.
High-purity oxygen is readily available from a reliable local supplier.
The site has space and permits for cryogenic oxygen storage.
Minimizing the complexity of on-site oxygen generation is desirable.
Continuous or high-load ozone operation makes oxygen supply logistics economically viable.
Redundancy can be supported through appropriate tank sizing and delivery planning.
Using oxygen as feed gas allows the ozone generator to operate at higher ozone concentrations than a dry-air system, reducing the total gas flow required for a given ozone production.
What must be considered when using LOX?
LOX is not simply an equipment choice; it creates an external supply chain that must be included in the project design.
The evaluation should consider:
Local oxygen price and long-term supply conditions.
Delivery frequency and tanker access.
Required storage autonomy.
Tank and vaporizer sizing.
Site safety distances and applicable regulations.
Pressure regulation and oxygen distribution.
Backup strategy in the event of delayed deliveries.
Variation of oxygen demand with ozone plant operating load.
For sites with reliable oxygen logistics, LOX can provide a technically simple and robust feed-gas solution. In locations where deliveries are difficult, expensive or strategically undesirable, on-site PSA generation may offer greater operational independence.
The correct comparison should therefore be based on the total lifecycle cost and operational requirements of the complete ozone plant, rather than on oxygen price or generator energy consumption alone.
PSA: when is on-site oxygen generation the right choice for an ozone system?
A PSA (Pressure Swing Adsorption) oxygen system generates oxygen on site from compressed air, reducing or eliminating dependence on external liquid oxygen deliveries.
For ozone applications, PSA can be an attractive solution when the plant requires operational independence, when LOX logistics are difficult or expensive, or when the site prefers to generate its own oxygen continuously.
Main advantages of PSA for ozone generation
PSA can be particularly suitable when:
Reliable LOX supply is not available or is logistically complex.
The plant wants to reduce dependence on external oxygen deliveries.
Continuous operation justifies investment in on-site oxygen generation.
The site has sufficient electrical power and space for the PSA system and its auxiliaries.
Redundancy can be incorporated through compressors, dryers, oxygen generators or storage capacity.
Long-term operating conditions favour on-site generation over purchased oxygen.
Like LOX, PSA provides an oxygen-rich feed gas that allows ozone generators to operate at significantly higher ozone concentrations than dry-air systems.
What equipment does a PSA system require?
A PSA oxygen plant is more than the oxygen generator itself. Depending on the design and scope, the system may include:
Air compressors.
Air treatment and drying equipment.
Filtration.
PSA oxygen generation units.
Buffer or receiver tanks.
Oxygen quality monitoring.
Pressure regulation and distribution.
Control, alarms and safety interlocks.
These auxiliary systems must be considered when comparing PSA with LOX because they contribute to CAPEX, electrical consumption, maintenance requirements and overall system availability.
What must be considered when selecting PSA?
The design should evaluate:
Required oxygen flow and ozone production.
Operating hours and plant load profile.
Electrical energy cost.
Compressor efficiency and redundancy.
Air treatment requirements.
Ambient conditions.
Maintenance resources available on site.
Space and ventilation.
Required oxygen storage or backup capacity.
Lifecycle cost compared with purchased LOX.
PSA can provide a high degree of operational autonomy, but that autonomy comes with additional equipment and energy consumption. The most appropriate choice therefore depends on whether the project values independence from oxygen deliveries more than the simplicity of an externally supplied LOX system.
For large ozone installations, both LOX and PSA can be technically suitable. The final selection should be based on site-specific economics, utilities, logistics, redundancy requirements and long-term operating strategy.
Dry air: when is air-fed ozone generation the right choice?
Ozone can also be generated from treated dry air, without using LOX or an on-site oxygen generation system.
This configuration can be appropriate for certain ozone capacities and operating conditions, particularly when the project wants to avoid oxygen storage or oxygen-generation equipment and the required ozone production can be achieved efficiently with an air-fed system.
Longking NLO ozone generators can be configured for both oxygen-fed and dry-air operation, allowing the feed-gas concept to be adapted to the requirements of the project.
Main advantages of dry-air ozone systems
Dry-air operation can be attractive when:
Ozone production requirements are moderate.
The plant wants to avoid LOX storage and deliveries.
On-site PSA oxygen generation is not justified.
Suitable compressed-air infrastructure is available or can be integrated into the project.
Operational simplicity and independence from external oxygen supply are important.
The complete lifecycle cost is favourable for the required duty.
Dry-air systems can therefore be a practical solution for municipal and industrial applications where the operating conditions do not require the higher ozone concentrations typically associated with oxygen-fed generation.
Why must the air be properly treated?
Ambient compressed air cannot normally be fed directly to an industrial ozone generator.
The air must be properly conditioned to provide stable operating conditions, typically including:
Compression.
Filtration.
Moisture removal and drying.
Pressure regulation.
Monitoring of the relevant gas conditions.
Maintaining sufficiently dry feed gas is particularly important for stable ozone production and for protecting the ozone generation system.
For this reason, the compressor and air-treatment package should be engineered as part of the ozone plant rather than considered as a separate utility.
How does dry air compare with oxygen-fed ozone generation?
Compared with oxygen-fed systems, dry-air ozone generation generally operates at:
Lower ozone concentration.
Higher total gas flow for the same ozone mass production.
Higher specific energy demand for ozone generation.
Greater dependence on the performance of the air-compression and drying system.
These differences can also affect downstream equipment such as piping, ozone injection systems, contact chambers and off-gas treatment.
This does not mean that dry air should automatically be rejected. The correct choice depends on the required ozone production, operating hours, site utilities, logistics, capital cost and long-term operating strategy.
A dry-air system may be the most appropriate solution for one project, while PSA or LOX may provide better lifecycle performance for another.
LOX vs PSA vs Dry Air: which feed gas should you choose for an ozone system?
There is no single feed-gas solution that is optimal for every ozone installation. The correct choice depends on ozone production, operating hours, local utilities, oxygen logistics, redundancy requirements and lifecycle cost.
As a general engineering guide:
Choose LOX when
Reliable liquid oxygen supply is available locally.
Ozone demand is medium to high.
The plant wants to minimize on-site oxygen-generation equipment.
Storage space and cryogenic installation requirements can be accommodated.
Delivery logistics and oxygen pricing are predictable.
LOX generally offers a simple oxygen-fed configuration at plant level, but it creates dependence on external oxygen supply.
Choose PSA when
The plant requires greater independence from external oxygen deliveries.
Continuous operation can justify investment in on-site oxygen generation.
Electrical power, space and maintenance resources are available.
Oxygen logistics are difficult, expensive or unreliable.
The project can incorporate appropriate redundancy and backup capacity.
PSA provides on-site oxygen autonomy, but requires additional compression, air treatment, electrical consumption and maintenance.
Choose dry air when
Required ozone production is compatible with air-fed operation.
The plant wants to avoid both LOX storage and PSA oxygen generation.
Proper compressed-air treatment and drying can be provided.
Lower ozone concentration and higher gas flow are acceptable within the overall process design.
The complete lifecycle evaluation favours a dry-air solution.
Dry air can provide a practical and independent feed-gas solution, although it generally requires more gas flow and higher specific energy demand than oxygen-fed ozone generation.
Quick comparison
LOX
Best suited to: medium and large ozone systems where reliable oxygen logistics are available.
Main advantage: high-quality oxygen without on-site oxygen production.
Main consideration: dependence on deliveries and cryogenic storage.
PSA
Best suited to: continuous installations seeking on-site oxygen autonomy.
Main advantage: oxygen generated directly at the plant.
Main consideration: additional equipment, electrical consumption and maintenance.
Dry Air
Best suited to: applications where air-fed ozone generation is technically and economically appropriate.
Main advantage: no external oxygen supply or PSA system required.
Main consideration: lower ozone concentration and higher gas flow compared with oxygen-fed systems.
The final decision should therefore be based on the complete ozone plant, not only on the ozone generator itself. Feed-gas preparation, ozone concentration, energy consumption, gas–liquid transfer, off-gas handling, redundancy, maintenance and oxygen logistics should all be evaluated together.
How should the feed gas for an ozone system be selected?
The selection between LOX, PSA and dry air should be made during the engineering stage of the ozone plant, considering the complete system rather than the ozone generator in isolation.
The main parameters to evaluate include:
Required ozone production in kg O₃/h.
Operating hours and expected load profile.
Required ozone concentration.
Local electricity cost and available power.
Availability and cost of liquid oxygen.
Site accessibility and oxygen delivery logistics.
Space available for storage or oxygen-generation equipment.
Required redundancy and backup philosophy.
Maintenance capabilities at the plant.
Impact of gas flow on ozone transfer and off-gas treatment.
Expected CAPEX and OPEX throughout the system lifecycle.
For some projects, LOX provides the simplest and most competitive solution. For others, PSA offers greater operational independence. In specific applications, properly treated dry air can remain a technically and economically appropriate alternative.
Longking EnTech ozone systems can be engineered for oxygen-fed or dry-air operation, allowing the feed-gas strategy to be adapted to the technical and operational requirements of each installation.
The objective should not be to select the cheapest oxygen source in isolation, but to identify the configuration that provides the best overall technical and lifecycle performance for the complete ozone system.
For more information, explore our NLO ozone generator systems and our engineering capabilities for ozone diffusion, contact and complete ozone treatment systems.