How to Size an Oxygen Generator for Ozone Production

Introduction

Ozone is a powerful oxidant used in water treatment, air purification, and industrial processes. But ozone generators don’t just pull ozone from the air—they need a steady supply of oxygen to produce consistent, high-quality ozone.

The feed gas you choose determines your ozone output. Air-fed systems produce lower ozone concentrations. Oxygen-fed systems produce higher concentrations, better efficiency, and more reliable performance.

But feeding oxygen means you need a reliable oxygen supply. For many facilities, that means an on-site oxygen generator. And getting the generator size right is critical. Too small, and your ozone system underperforms. Too large, and you’ve wasted capital and energy.

This guide walks you through sizing an oxygen generator for ozone production—step by step.

Why Oxygen Feed Matters for Ozone Production

Before sizing, understand why oxygen is the preferred feed gas.

Ozone production basics:

Ozone (O₃) is created by passing oxygen (O₂) through a high-energy electrical discharge. The reaction is simple: 3O₂ → 2O₃. But efficiency varies dramatically with feed gas.

Air vs. oxygen feed:

Parameter	Air Feed	Oxygen Feed
Ozone concentration	1-3%	6-12%
Energy efficiency	Lower	2-3x higher
Nitrogen oxides	Produced	None
Moisture issues	Significant	Minimal
Feed gas preparation	Complex	Simpler

Why oxygen wins:

With oxygen feed, the same energy produces more ozone. Higher concentration means smaller equipment, lower energy costs, and no harmful NOx byproducts. For continuous operation, oxygen feed is the clear choice.

Purity matters:

Higher oxygen purity yields higher ozone concentration. A 93% oxygen generator produces about 10% less ozone than a 95% generator. For critical applications, every percentage point counts.

Step 1: Determine Ozone Output Requirements

Start with your ozone system’s needs.

Find your ozone production rate:

Ozone generators are rated by output—typically grams per hour (g/hr) or pounds per day (lb/day).

Common ozone applications:

Application	Typical Ozone Output
Small water treatment	10-200 g/hr
Municipal water plant	1-50 kg/hr
Wastewater treatment	1-100 kg/hr
Food processing	10-500 g/hr
Aquaculture	10-200 g/hr
Industrial	100-10,000 g/hr

Get the spec:

Check your ozone generator manual. It will list required oxygen flow rate at a given purity. If you’re planning a new ozone system, work with the manufacturer to get these numbers.

Account for duty cycle:

Is the ozone system continuous or intermittent? A system running 24/7 needs different redundancy than one used a few hours daily.

Step 2: Calculate Oxygen Flow Rate from Ozone Output

If you know ozone output, you can calculate required oxygen flow.

The conversion:

Ozone production (g/hr) = Oxygen flow (L/min) × Ozone concentration (%) × Efficiency factor

Simplified rule of thumb:

For a well-designed system:

• 1 kg/hr ozone requires approximately 8-12 Nm³/hr oxygen
• 1 lb/day ozone requires approximately 8-12 scfh oxygen

Example calculation:

Ozone requirement: 2 kg/hr

Oxygen needed: 2 × 10 = 20 Nm³/hr (approximately)

The variable:

Different ozone generators have different efficiencies. Always use manufacturer data when available. The rule of thumb is for preliminary sizing only.

Purity impact:

Oxygen purity affects ozone output. A 90% oxygen purity might require 10-15% more flow than 95% purity to achieve the same ozone output.

Step 3: Specify Oxygen Purity

Purity affects both generator size and ozone performance.

Common purity levels:

• 90-93%: Entry-level, acceptable for many applications
• 93-95%: Standard industrial grade
• 95-98%: Higher purity for demanding applications
• 98%+: High-purity for critical ozone needs

Purity vs. ozone output:

As a rough guide, ozone output increases roughly 1-2% for each 1% increase in oxygen purity. A 95% purity generator produces about 5-10% more ozone than a 90% generator at the same flow.

The trade-off:

Higher purity requires:

• Larger oxygen generator
• More compressed air
• Higher capital cost

For most applications, 93-95% oxygen is the sweet spot. It provides excellent ozone output without the premium cost of ultra-high purity.

Application-specific needs:

Application	Recommended Purity
Municipal water	90-95%
Wastewater	90-95%
Food processing	90-93%
Semiconductor	95-98%
Laboratory	95-98%

Step 4: Account for Pressure Requirements

Oxygen generators and ozone systems have pressure requirements.

Typical pressures:

• Oxygen generator output: 5-8 bar (70-115 PSI)
• Ozone generator inlet: Varies by manufacturer (typically 1-3 bar)

Pressure matching:

If the ozone generator needs lower pressure than the oxygen generator delivers, you’ll need a pressure regulator. If it needs higher pressure, you may need a booster.

Pressure drop:

Account for pressure losses in piping, filters, and valves. Oversize piping to minimize drops.

Consistency matters:

Ozone generators perform best with stable pressure. Fluctuations affect ozone output and consistency. A buffer tank (Step 5) helps stabilize pressure.

Step 5: Consider Storage and Buffering

Ozone systems often have variable oxygen demand.

Why buffer tanks matter:

• Ozone generators may cycle on and off
• Oxygen generators run most efficiently at steady output
• A buffer tank decouples production from demand

Sizing the buffer tank:

A simple rule: size the tank to hold 10-20 minutes of oxygen at average consumption.

Example:

• Oxygen consumption: 20 Nm³/hr (0.33 Nm³/min)
• Desired buffer: 15 minutes
• Tank capacity needed: 0.33 × 15 = 5 Nm³

Storage location:

Place the buffer tank between the oxygen generator and the ozone system. This ensures the ozone system has immediate supply while the generator runs steadily.

For critical applications:

Consider a larger buffer or redundant generators. If ozone is essential for your process, a few hours of stored oxygen can bridge maintenance or generator issues.

Step 6: Factor in Redundancy and Reliability

Ozone systems often operate 24/7. Oxygen supply must be reliable.

Redundancy options:

Option	Description	Best For
Single generator	Lowest cost	Intermittent use, backup oxygen source available
N+1	One extra generator	Continuous operation, maintenance coverage
Dual 100%	Full redundancy	Critical applications, no downtime tolerance
Liquid backup	Tank of liquid oxygen	Emergency backup, peak demand coverage

Spare parts:

Keep critical spares on hand: filters, sensors, and maybe a spare generator head for smaller units.

Monitoring:

Remote monitoring with alarms can alert you to problems before they interrupt ozone production.

Step 7: Calculate Total Oxygen Demand

Bring all the pieces together.

Sizing worksheet:

1. Ozone output: ____ kg/hr (from application)
2. Oxygen flow: ____ Nm³/hr (from ozone generator spec)
3. Purity target: ____ % (from application requirements)
4. Pressure: ____ bar (from ozone generator spec)
5. Buffer storage: ____ Nm³ (10-20 minutes of flow)
6. Redundancy: (single, N+1, or dual)

Final generator size:

Select an oxygen generator rated for the required flow at your target purity and pressure. Add 10-20% margin for future growth or efficiency losses.

Example:

• Ozone output: 2 kg/hr
• Oxygen flow: 20 Nm³/hr at 93% purity
• Pressure: 3 bar
• Buffer: 5 Nm³ tank
• Redundancy: Single generator with liquid backup
• Generator size: 20 Nm³/hr + 20% margin = 24 Nm³/hr

FAQ

Q1: How much oxygen does an ozone generator need?

A1: It depends on ozone output and generator efficiency. A typical rule: 8-12 Nm³ of oxygen per kg of ozone per hour. Check your ozone generator manufacturer for exact requirements.

Q2: What oxygen purity is best for ozone production?

A2: For most applications, 90-95% oxygen is sufficient. Higher purity increases ozone output but also increases generator cost. 93-95% is the common sweet spot for industrial ozone systems.

Q3: Can I use a membrane oxygen generator for ozone?

A3: Yes. Membrane generators produce 90-95% oxygen—perfect for most ozone applications. They’re simple, reliable, and low-maintenance. For higher purity (95%+), PSA may be required.

Q4: How much does an oxygen generator for ozone cost?

A4: Costs vary widely based on capacity. A small unit for 100 g/hr ozone might cost $5,000-$10,000. A large system for 50 kg/hr ozone could be $50,000-$200,000. Get quotes based on your specific needs.

Q5: Do I need a buffer tank with my oxygen generator?

A5: Yes, for most applications. A buffer tank lets the oxygen generator run steadily while the ozone system cycles, ensuring consistent oxygen availability. Size for 10-20 minutes of average flow.

Q6: What happens if oxygen purity drops?

A6: Ozone output decreases proportionally. A 5% drop in purity might reduce ozone production by 5-10%. For critical applications, monitor oxygen purity and alarm on deviation.

Q7: How long does an oxygen generator for ozone last?

A7: With proper maintenance, 10-15 years. Sieves (for PSA) or membranes may need replacement at 5-10 years. The compressor is often the limiting factor—choose a quality unit sized for continuous duty.

Conclusion

Sizing an oxygen generator for ozone production is about matching your ozone system’s needs with the right oxygen supply. Start with ozone output, calculate required oxygen flow, specify purity, consider pressure, add buffer storage, and plan for reliability.

Get it right, and you’ll have a system that produces consistent, high-quality ozone with optimal efficiency. Get it wrong, and you’ll struggle with low output, unstable operation, or unnecessary capital cost.

The investment in proper sizing pays back in better ozone performance, lower energy costs, and reliable operation.

At MINNUO, we help customers size oxygen generators for ozone applications—from small water treatment to large municipal systems. We focus on getting the numbers right so your ozone system performs as designed. Because we know that when your ozone runs, your process runs.