Ozone generator feed gases, not including ambient air.
1. Dry Air
Producing “Dry Air” can be done in a few different methods; one is by purchasing a cylinder of compressed dry air which is readily available from most bottled gas suppliers. (Similar to the picture of the green oxygen cylinders below)
Another method is to use the typical air preparation components, such as an air compressor, filters, desiccant dryer, and pressure regulators.
Refrigerated air drier
The air should be clean and dry, with a maximum dew point of -60º C (-80º F) and free of contaminants. Particles greater than 1 micron and oil droplets greater than 0.05 micron should be removed by filtration (Langlais et al., 1991). Large or small particles and moisture cause arcing which damages the ozone generator dielectrics. To understand the importance of moisture which can be present in the feed-gas, read this page about the importance of dry air for ozone creation.
Oxygen as a feed- gas provides additional ozone output when compared to using Dry Air.
Producing refined oxygen can be done in a few different methods; one is by purchasing a cylinder
of compressed oxygen which is readily available from most bottled gas suppliers.
Another method is to use an oxygen concentrator, preferably one that uses the PSA or Pressure Swing Adsorption method. Pressure swing adsorption is a process whereby a special molecular sieve is used under pressure to selectively remove nitrogen, carbon dioxide, water vapor, and hydrocarbons from air, producing an oxygen rich (80–95 percent O2) feed gas. This method is similar in the quality of oxygen that would come from an oxygen cylinder. (pictured to the right above)
The two are not similar in the pressure that they can deliver. Compressed cylinders have a much higher pressure (PSI).
OXUS-8 oxygen concentrator
OX-8 oxygen concentrator
OG-15 oxygen concentrator
You can view the many different Oxygen Concentrators available or click on the displayed pictures above to view that select model.
The table below presents a comparison of the advantages and disadvantages of each gas feed system.
Commonly used equipment, such as air compressor,
desiccant dryer, filters, etc.
More energy consumed per ozone volume
Extensive gas handling equipment
Suitable for small and large
Maximum ozone concentration of 3 – 4% by
Higher ozone concentration
(8 – 16%)
Approximately doubles the ozone output for the
same ozone generator
Oxygen resistant materials
Suitable for small and large
NOTE: From the table above, you learned that “Dry Air” can give you up to 3-4% by weight of ozone gas, whereas oxygen will allow up to 16% by weight. That’s either 36.21 or 193.12 grams meter cubed. That is a big difference!
If you are asking, why is this? It is because Ambient Air contains only 19% oxygen.
Choosing the correct feed gas will also depend upon what your application is. Some applications will need High concentrations of ozone while others can be conducted with Lower ozone concentrations.
In the previous post about how ozone is made we covered the basics of a corona discharge ozone generator. In that post we pointed out that there are three main parts to a corona discharge ozone generator:
Power Supply – this edition
Ozone Generator Power Supplies
In this article we will cover the differences in power supplies used for corona discharge ozone generators. Also, the different parts that are involved in the power supply itself. While some are very simple, other may be very complicated. First, we have to cover the basics of what these power supplies do.
Corona discharge ozone generators operate on the principle of a high voltage spark across a dielectric to form a corona. The main component to any corona discharge power supply is a transformer to increase voltage from the standard 120 or 220 VAC power used to a higher voltage ranging from 500 – 20,000 volts. This high voltage will create the spark (corona) necessary for ozone generation.
Open coil, Line Frequency, 20,000 Volt Transformers. Click on image to see ozone generators this may be used in.
The voltage used by an ozone generator is mainly dependent upon the dielectric and air gap in the corona cell. If there is a larger gap for the spark/corona to jump, a higher voltage is needed. Also, thicker and various types of dielectrics will require varying voltages. We will cover dielectric and corona cell design in future installments of How Ozone is Made.
Another factor is frequency. Higher frequency ozone generators (see below for info in frequency conversions) will typically use lower voltages as this is less stress on the frequency conversion components and smaller gap ozone generators are more conducive to higher frequencies.
Oil Filled, 10,000 Volt, Line Frequency Transformer
Line frequency ozone generators may use a basic rheostat to adjust the voltage into the transformer. This will in turn, adjust the output voltage of the transformer and adjust the rate of ozone production. In these ozone generators only a transformer and rheostat are used, no other electrical devices are necessary for ozone production.
Line Frequency Ozone Generator Rheostat. The dial turns a sweeper on the bottom that will adjust input voltage to the transformer.
Medium frequency ozone generator transformer
Some transformers may use a line choke, or a series of transformers to achieve a the voltage step-up necessary. This is an example of a larger (~450 gram/hour) ozone generator transformer assembly.
Oil filled, Medium frequency ozone generator operates at 1,000 Hz and ~600 volts
Many ozone generators used what is basically a car coil to increase voltage in an ozone generator. When ozone generator design was still new there were very few choices for transformers that could endure the abuse of 1,000 Hz, elevated voltage, and changing variables inside a corona cell. Today, transformer options are greater and the use of a basic car coil is becoming less common.
High Frequency Ozone Transformer
Most high frequency transformers are much smaller, open coil type transformers. This image is very typical for what may be used inside a higher frequency ozone generators. This same style transformer is used in some medium frequency ozone generators.
The spark inside an ozone generator is generated from high voltages created by the transformer, these voltages are all AC (alternating current). This means the electrical current alternates direction. This reversal of electrical current occurs at a constant speed we call frequency. This is measured with Hz (hertz). Here in the USA typical electrical power is delivered at 120 VAC 60 Hz. This means the voltage is 120 volts of alternating current, that alternates 60 times per second. In other countries power may be delivered at 220 VAC 50 Hz.
This explanation is all to understand that the spark or corona inside the ozone generator with no frequency conversion would occur 50 or 60 times every second. Many of the earlier ozone generators, and some still today operate at line frequency, an unaltered frequency. This is generally referred to as a line frequency ozone generator.
Other ozone generators use a higher frequency to increase ozone output. Higher frequencies would create more spark/corona every second. There are three main types of ozone generators:
Line Frequency – 50-60Hz
Medium Frequency – 100 – 2,000 Hz
High Frequency – 5,000 – 30,000 Hz
Medium frequency ozone generator power supply provides ~1000 Hz output
This circuit board is the driver board for a car coil type transformer as seen in the image above. This is a great example of how simple the circuitry may be in a typical medium frequency ozone generator.
High Frequency ozone generator power supply, up to 30,000 Hz output
This is the power supply for a larger (up to 450 gram/hour) high frequency ozone generator. This power supply can supply an output of up to 30,000 Hz, or as low as 1,000 Hz. As you can see this power supply is much more circuitry and components are used to achieve these higher frequencies and flexibility.
Medium frequency ozone generator power supply provides ~1,000 Hz output
This power supply is for a larger (up to 400 gram/hour) medium frequency ozone generator.
Putting it all together
There are many different types of ozone generator power supplies for many different applications. Each serves a unique purpose in the ozone generation world. Each has advantages and disadvantages.
Line Frequency Ozone Generators (50-60 Hz)
Line frequency ozone generators commonly use larger transformers and voltages from 10,000 – 20,000 volts. The only other electrical component for operation is a rheostat as pictures above. These are very simple and reliable setups that perform well for many years. Absolutely nothing beats the reliability of a line frequency ozone generator.
As the components on most line frequency ozone generators are larger to achieve the same ozone output the costs for the transformer and rheostat are higher than the costs for the smaller transformers and simple printed circuit boards used for medium frequency ozone generators. Also, line frequency ozone generators cannot achieve near the performance as the higher frequency ozone generators.
Medium Frequency Ozone Generators (100 – 2,000 Hz)
Medium frequency ozone generator transformer, with driver board.
Medium frequency ozone generators are most common today. These ozone generators may produce 1 gram/hour to thousands of pounds/day of ozone. The image above is a simple printed circuit board to increase line frequency to about 1,000 Hz, this board is attached right to the transformer that increase voltage to about 1000 volts. This is an older design with a oil filled automotive style coil. however this is a good example of the typical size of power supply for a 5 – 20 gram/hour ozone generator. There may be multiple power supplies powering multiple corona cells in one ozone generator to produce more ozone. This is a very compact, cost effective, and efficient method to produce ozone.
While medium frequency ozone generators are fairly simple there are still more components than a line frequency ozone generator. This means there are more things to fail and cause problems. Due to the elevated frequency these generators also produce more heat, both in the electronics and corona cell. Heat is the enemy of ozone.
Medium frequency ozone generators are also louder than others. While this may not be a large concern in every application, at some frequencies there is a high pitched whine that is not acceptable in some occupied spaces.
High Frequency Ozone Generators (5,000 – 30,000 Hz)
High Frequency ozone generator power supply with transformer
High frequency ozone generators offer very compact designs due to smaller transformers and corona cells. As the spark/corona is occurring up to 30,000 times per second the need for a large air gap and high voltage are alleviated. In return the electronic circuit board becomes the largest, and most expensive component of some high frequency ozone generators. This is illustrated very well in the above image. This shows 3 power supply circuit boards with the small transformer mounted right to the circuit board!
High frequency ozone generators may be very energy efficient and compact in size allowing for a very flexible platform to either use multiple cells for redundancy or other configuration changes. Many high frequency ozone generators are very cost effective as the large parts that carry a higher price (transformer and corona cell) are smaller, while the circuit board and electronics are more elaborate.
High frequency ozone generators contain many components that may fail. They also produce a great deal of heat due to the high frequency. However, with the very high frequency there is no audible sound from the ozone generators, they are the most silent of all types. Many manufacturers have just begun implementing more high frequency components in the last 5 years. Expect big changes in the future in this area of ozone generation.
This covers the basics of ozone generator power supplies. I promise the following editions of How Ozone is Made will be shorter and less technical.
The next edition of How Ozone Is Made will cover Corona Cell design in Corona Discharge Ozone Generators.
If you have any questions about ozone generators, or what may be best for you, call our application engineers today! We are glad to answer questions, dispel myths, and be a general information source for your ozone related questions.
About a week ago we posted about how ozone is made. That original post gave the fundamentals of how ozone is produced in nature and the basics of how ozone is produced within ozone generators, both UV ozone generators and corona discharge ozone generators. It was pointed out then that most (almost every) industrial ozone generator uses corona discharge to produce ozone. This 2nd installment is dedicated to informing you the reader about ozone generation from corona discharge.
The fundamentals are simple. A spark (corona discharge) is used to split the diatomic oxygen molecule into valant oxygen atoms. These oxygen atoms have a negative charge and will bond quickly with another oxygen molecule to produce ozone! For each split oxygen molecule 2 ozone molecules are produced.
Ozone Generation from Corona Discharge
A power supply is used to produce an electrical discharge across a dielectric, and an air gap. The dielectric is used to diffuse the discharge across a large area as opposed to single point like a normal spark. The oxygen molecules passing through the air gap are exposed to the electrical discharge and are split into ozone (at least that is the hope). A great deal of heat is generated from this process and is removed from the electrodes as shown.
Corona Discharge Tube
This image shows a more complete picture of a very typical ozone generation corona cell. The dielectric is a tube allowing the air gap to flow around the outside of the dielectric, with the electrode around the outside. This allows heat to be dissipated to the outside of the electrode efficiently.
This video shows a great example of ozone production from corona discharge.
There are three main factors when generating ozone from corona discharge:
Tube – cylindrical style
When generating ozone from corona discharge there are a few factors that will affect performance that must be evaluated.
Cooling of the corona cell
I will try to cover some of these fundamentals and why one may be better than another for your specific application in future installments of “how ozone is made“
Ozone is produced naturally through sparks and UV-Light, ozone is also produced commercially for many uses. This will outline a few methods ozone is produced.
Ozone is Produced Naturally from Lightening During Thunderstorms.
Ozone is Produced Naturally from UV Light from the Sun
These same methods of ozone generations can be used commercially for industrial ozone applications. Great advancements have been made in the ozone industry to produce ozone more reliably and efficiently.
Ozone Production from Corona Discharge
Oxygen flowing between an electrode and cathode produces ozone from a spark, more commonly referred to as Corona Discharge.
Ozone Production from UV Light
Ozone can be produced from a UV light tuned to the proper wavelength inside an enclosed chamber.
Ozone can also be produced directly in water using an electrolytic cell. This method uses a current within the water to split the oxygen and hydrogen atoms, then converts the oxygen directly into ozone. This is a fairly new commercial ozone generation method that may show great promise in the future. At this time, this application has very limited application.
Commercial Ozone Generation
Corona Discharge (electrical discharge field)
High voltage spark at medium to high frequencies
Creates ozone at medium – high concentrations (up to 22%)
Most commonly used
UV Ozone Generation (photochemical)
Low concentration ( max 2% concentration)
Small ozone outputs
Currently only small outputs
Ultra pure water is necessary
The most common method of ozone generation is corona discharge. Due to the low operation costs, and improved reliability this will be the main method of ozone generation for many years to come, for more information on ozone generation watch for future installments of “How Ozone is Made“
This Ozone Journal is a blog managed by the employees of Ozone Solutions. The purpose of this blog is to inform and educate the readers about the world of Ozone, provide news about the ozone industry, and have an easy opportunity to inform about new ozone products.
Check back often, ask questions, and let us know if there is anything you would like to hear about.
What is ozone?
Ozone is an oxidant. Ozone (O3), sometimes called “activated oxygen", or "triatomic oxygen", contains three atoms of oxygen rather than the two atoms we normally breathe. Ozone is the second most powerful oxidant in the world and can be used to destroy bacteria, viruses, and odors.
Ozone is a gas at ambient temperatures and pressures with a strong odor. Ozone can be produced as a gas from oxygen in air, or concentrated oxygen. This ozone gas can be dissolved into water, or used in the gas phase for a variety of applications discussed in this Journal.