Ozone Generator: Should I Buy One?
Everything You Need To Know About Ozone Generators!
Four Things You Need to Know to Purchase an Ozone Generator
There are several key things you need to know before you can buy an ozone generator. Before going into details, however, it is important to note that we are talking about corona discharge type ozone generators.
These are the most important type of commercial/industrial ozone generators. There are other types of ozone generators, but non corona discharge units are mostly for use in small scale applications, producing typically less than half a pound per day or less than 10 grams per hour of ozone.
This article will review the key selection factors and how it relates to various applications for ozone and the impact on the cost of an ozone generator.
The key factors include:
1. Output: This is how much ozone the machine makes, normally quoted in grams per hour or pounds per day.
2. Concentration: Ozone can be produced at different concentrations ranging from 1-12 weight percent. The concentration of ozone has an effect on most applications and also affects machine output.
3. Gas Feed: you must have a source of feed gas containing oxygen, there are three choices: dry air, oxygen concentrated from air or purchased oxygen (either as liquid oxygen (LOX) or compressed oxygen in cylinders).
4. Generator Cooling: Ozone generator create heat that must be removed, the options for removing this heat are air cooling or water cooling.
Selecting the proper combination of features depends strongly on the application. For example, in water treatment applications higher concentrations of ozone are used while in air treatment applications lower concentrations can be selected.
Ozone Generator Cooling
Every degree above the stipulated temperature results in a decrease of production. For example, for every degree increase in temperature the rate of ozone production decreases by 0.6% in some systems. So, if the machine was supposed to operate at 72 degrees and it is actually operated at 82 degrees the production would be reduced by 6%. Some generators shut themselves down completely at certain temperatures to prevent damage. So cooling is a critical issue for the generator
There are two common cooling methods, air cooling with fans and water cooling. Air cooling is less efficient and reduces the size of the ozone generator that can be built. In general, ozone generation of over 10 pound per day cannot be readily done with air cooled ozone systems.
Water cooled systems come in several variations. Closed loop systems use a water chiller to cool the water and cycle it continuously through the ozone generator. Water typically enters the ozone generator at around 60 degrees F and leaves at 70 degrees F.
Indirect cooling loops using ground water or other water sources are also used. Here a heat exchanger has one side connected to the ozone generator with a recycling loop and on the other side a once through flow of water available at the site. Often the water temperature is higher than optimum and a larger generator must be purchased to compensate for the loss of production.
The choice of the type of water cooling and the use of a chiller is based on an engineering study to balance the cost of the increased generator size with the cost of chilling the water.
Ozone Generator Gas Feed
In addition, the air must be extremely dry because moisture reduces ozone output and will damage the ozone generator. To produce a reasonable concentration of ozone, the air must have a dryness as measured by the dew point of about -100 degrees Fahrenheit.
This means that in a million parts of air there is only one part water. This level of dryness requires special dryers to remove the humidity. Refrigerated dryers found on some compressors can only reach about a dew point of -40 degrees Fahrenheit.
Using a feed gas with oxygen concentration greater than 90% allows the ozone concentration to increase to the 5-10 percent range. In addition, ozone generators produce higher outputs of ozone in terms of pounds per day or grams per hour using oxygen versus air.
Purchased oxygen typically is very dry due to the manufacturing process used. It can be purchased as a compressed gas in cylinders or as a liquid. The volume that can be stored as a compressed gas is much smaller than in liquid form. So, unless the ozone generator is being only used for short amounts of time, compressed gas is probably not a good feed gas option.
Liquid oxygen, sometimes referred to as LOX, can be supplied in small containers or delivered in truck load quantities. It must be evaporated to the gas phase prior to use. It is the most economical form of oxygen if the oxygen production plant is not too far away.
Another option is to concentrate oxygen from air in a process known as pressure swing absorption (PSA). In this process a material called a molecular sieve absorbs both water and nitrogen from air leaving mainly oxygen in the gas stream. Oxygen concentrations of 90-95% are readily achieved. The process is done in both small scale as well as large industrial systems. Small applications include portable oxygen systems for people that need supplemental oxygen for breathing.
So, in summary the main feed gases for ozone are dry air, PSA oxygen or liquid oxygen. Some ozone generators can run on all three feed gas, but this is not always the case. Some ozone generator suppliers design their systems to run either on air or some form of higher concentration oxygen. It is important to know this ahead of time since it might not be possible to switch once the unit is purchased. The key point here is that if you want higher concentration, you must use oxygen feed gas system with a generator designed to use this gas.
As noted above, ozone concentration can affect both the effectiveness of ozone in a given application and the amount of ozone that can be produced from a given ozone generator. Essentially, high concentration ozone costs more, but can do more in certain applications.
Commercial corona discharge systems produce anywhere from 1 weight percent ozone to 12 weight percent ozone. Gas treatment applications typically use the 1-3 percent range while water treatment application normally use 5-10 percent.
An important aspect of ozone concentration is in comparing different ozone generators. Manufacturers use different bases for claiming the nominal output of an ozone generator. Normally, you have to read the fine print to see what concentration they use to claim a given production rate.
As an example:
Output (g/h) Concentration (%) Price
Supplier #1 60 6 $5,500
Supplier #2 60 4 $3,800
At similar concentrations the results would look different:
Supplier #2 60 6 $6,000
(g/h = grams/hour)
So, to fairly compare machines you need to know the amount of ozone produced at a concentration of interest along with the cost of the generator. This will allow you to compare ozone generators "apples to apples".
Ozone Generator Output
As a specific example, ozone is often used to reduce chemical oxygen demand (COD) in water. COD is measured in ppm (milligrams per liter - mg/l). It normally takes 2 mg of ozone per mg of COD to remove the COD. So, if we had to treat 10,000 liters per hour of water containing 50 ppm of COD we would need:
10,000 liters/hour X 50 mg/l COD x 2 mg Ozone/mg COD = 1,000,000 mg/hour
1,000,000 mg/hour = 1,000 g/hour = 1 kg/hour
So, we would need to dissolve 1 kg/h of ozone (or 52.8 pounds per day of ozone)
Less than 100% of the ozone injected in the water dissolves, so we need to know the ozone transfer efficiency. A well designed venturi injection system can dissolve at least 90% of the ozone. For the case above, you would need 1 kg/h ÷ 0.90 = 1.11 kg/h (58.7 pounds per day of ozone). This is the amount of ozone we would have to produce at the targeted concentration to dissolve the 1 kg/h of ozone into water.
Important: A given system will produce less ozone as the concentration of ozone increases. Ozone transfer efficiency, the rate at which ozone dissolves into water increases with increasing ozone concentration. Both factors will determine the final size of the machine required.
Determining the amount of ozone required, except for the simplest applications, requires laboratory or pilot studies combined with an engineering evaluation to select the proper balance between ozone dose, concentration and generator size.
Normally, an ozone generator company will not be able to provide this information. If they can help, there will be an additional cost for conducting the studies.
1. Define the application carefully to determine the amount and concentration of ozone required. If you do not know the proper amount of ozone required contract with a capable laboratory or engineering firm to carry out the necessary studies.
2. Make sure to compare ozone production of different ozone generators at the same ozone concentration to get a fair comparison of price.
3. For applications requiring greater than 5 percent ozone, oxygen will be necessary for the feed gas. This will be typical for most water treatment applications.
4. For applications requiring lower concentrations of ozone, less than 3 percent, dry air is probably the most economical solution. These would typically be applications for air treatment, such as odor control or control of air borne bacteria.
5. For applications of less than 10 pounds per day (less than 190 g/h) air cooled systems may be appropriate, but above this level water cooled systems will likely be more economical.
QUESTION #1. How Many Volts is the Power Supply!
An ozone generator creates ozone by creating an electrical spark that splits oxygen in the air. In order to accomplish this feat, you have to create a high voltage electrical spark. A simple rule I've observed in the lab and well recognized in the ozone industry is that a 3000 volt transformer can produce around 3000 mg/h of ozone per hour when attached to a high voltage ozone element or six or more MICA plates at 40% humidity or less.
Each Mica plate can produce a maximum of about 400 milligrams of ozone per hour IF it is properly installed due to the weak electrical spark it is capable of generating from the wire mesh. If you own a MICA plate ozone generator, view the plate in the dark. It won't light up very bright, very dimly as a matter of fact.
The types of ozone plates that turn bright purple in the dark are called "High Voltage Ozone Elements" and they can produce around 3000-4000 mgh per plate when fed with a 3000-4000 volt power transformer. These types of plates glow purple, almost like UV lamp, in the dark. They create a very strong electrical spark that is much more efficient at producing ozone vs the old fashioned MICA plates.
As a matter of fact a 4000 volt transformer and ozone element only uses about 35 watts of electricity, now that's efficient! Therefore, Tip #1 is to ask the vendor to e-mail you in writing the exact voltage, amps, and watts used by their power transformers and how many and which type of ozone plates their machines use.
If a vendor claims for instance their machine produces 16 to 20 thousand milligrams of ozone per hour but their machine only uses one 5000 volt transformer, then you'll things just don't add up.
QUESTION #2. What type of ozone element does the ozone machine use?
Believe it or not, some vendors will try and convince you that the ozone elements in their machines are "permanent" and will last forever. Folks, there's no such thing as a permanent ozone plate! If used in 90-100% humidity, even the expensive high voltage ozone plates will only last 20-40 hours. Ozone generators are not made to be used in 90% plus humidity! In humid areas, you must run the air conditioning or a dehumidifier in order to perform a shock treatment.
Tip #2 therefore is to think twice before buying an ozone generator from a vendor who doesn't offer replacement ozone plates or makes a machine that utilizes "MICA" plates.
Once you have those answers in writing, save the e-mail in case you need to use it to obtain a refund in the future.
When you receive your ozone generator, have a local electrician friend of the family (or hire someone) to open your ozone generator and give it the once over and test the strength (in volts) of the power transformer.
If you discover the stated voltage doesn't match the advertised voltage, ask for a refund. After all, what you're buying when you buy an ozone generator are high voltage power transformers, not a slick sales pitch! The honest vendors will clearly state their machines specifications on their websites and via e-mail if asked.
They'll also provide you with a picture of the inside of their units and disclose the amount of plates, type used, etc. You should be weary of vendors who hold this information close to the vest or refuse to go on the record with this information.
Now you know what questions to ask an ozone machine vendor before making a purchase. I want to close out this "Ozone Generator Buying Guide" by giving you a few tips on how to save money on your purchase:
Tip #1. Ask the vendor if they sell any used units or any "bare bones" ozone generators
Many ozone generator vendors will have spare parts on hand from returned or fixed units they can sell "on the down low" for a mere pittance of the retail price.
Others might be able to sell you a "bare bones ozone generator" without any of the bells and whistles you can easily use to make your own ozone generator, especially if you're the "do-it-yourself" type.
You might also want to check eBay to see if anyone is selling high voltage power transformers in the 3000-12,000 volt range or high voltage ozone elements that can be easily attached to the power transformer.
Some ozone vendors want $1000 or more for their ozone generators, however, the fact of the matter is that ozone machines are pretty basic electronic components and they shouldn't cost as much as a used car, especially if you buy the main components and "Do It Yourself."
Tip #2. Don't buy an ozone generator with too many "bells and whistles"
Ozone as I've already mentioned is very corrosive over time to all metals except stainless steel. Unfortunately, all electronic switches, relays, etc needs to use regular metal in order to be conduce electricity. What we have therefore is a dilemma. The solution? Don't buy an ozone generator with all the bells and whistles!
This would include an internal timer, ozone output dial (to turn the ozone up and down), etc. Just realize that if you do buy an ozone generator with these parts that eventually the ozone is going to destroy those parts and all it takes to shut down an ozone generator is to have one of the electrical components fail. If you want a timer, buy an external timer for $5 at Lowe's.
If you want to be able to turn the ozone output up and down, buy a "repeat cycle timer" that can turn your ozone generator on for a few seconds ever x amount of minutes, and repeat that cycle indefinitely. Both of those items can be connected via an extension cord in another room to your ozone generator. Less is more when it comes to longevity in shock treatment ozone generators.
Tip #3. Don't over do it when performing shock treatments!
There is a reason the trained professionals that administer ozone shock treatments command thousands of dollars to perform shock treatments; they know what they're doing and how to safely and effectively perform a shock treatment without leaving your home smelling like ozone for weeks after the shock treatment!
Besides being an ozone generator manufacturer, I also run a restoration business that employs ozone in some of our work. For mold remediation, ozone only plays a small role in riding the house of toxic mold for instance. Sheet rock has to be taken down and replaced, super high CFM air cleaners make sure the mold, when disturbed, isn't re-distributed throughout the structure.
Wet wood has to be dried. Leaky pipes have to be fixed, etc etc. Yes, shock levels of ozone will kill the mold, but that's just a small part of mold remediation, regardless of what some ozone vendors might advertise to help hawk their units.
The main mistake I see homeowners make when doing a shock treatment is not properly removing or covering all petroleum based products such as carpet foam, sofa cushions, etc. We use Kevlar to cover carpets and foam filled sofas, mattresses, etc. Kevlar is ozone resistant and will keep the foam from interacting with the ozone.
Ozone will oxidize foam and rubber and cause a chemical-ozone smell that can linger for weeks. So tip #3 is to not over do it with an ozone shock treatment! One or two hour shock treatments in furniture filled homes is advisable.
You might have to perform several such shock treatments, but it's better to be safe than sorry when shocking a furniture filled home. Some vendors tell their clients to just turn the ozone generator on and let it run for a few days. I strongly advise against that practice.
WHAT EXACTLY IS OZONE?
The short answer is three oxygen atoms that make up the o3 molecule known as ozone. In nature, ozone is created in our atmosphere up high to create an "ozone lawyer" to protects us from the harmful rays of the sun.
Down low near earth, ozone is created to oxidize and remove man made pollution from the air we breathe. I know, I know. The EPA's spin is that ozone is in and of itself "smog". The directory of the EPA was quoted saying that she hopes someday "we can eliminate all ground ozone all together". That would be great, but to do that we'd all have to drive bikes, live in tee-pees, refrain from making any fires to cook or food, and refrain from using electricity.
In other words, even during the pre-man era there was ozone in the air from fires, and if by chance her dream came true, we'd all die because we can't stop naturally occurring forest fires and without ozone to break down the smoke, we'd all eventually die. Besides, if there was no pollution in the air, mother nature wouldn't come to the rescue and create ozone to clean up our mess! Let me put this another way. If there is a lot of pollution, there will be a lot of ozone.
Ozone is a blue gas, smog from industry and buses, cars, trucks, etc is a black-brown nasty color. Why call poor little Ms Ozone, the hard working cleaner that she is "smog" and not call the nasty brown and black "smog" emitted by industry smog instead? I know, I know, that's a novel idea, but I'm sure that wouldn't sit well with the Board of Directors of the major industries that are polluting our air, industries that feature former Presidents of the United States on their board of directors. If instead of "ozone alters" we were told exactly which toxic byproduct of industry was filling our air, and from which source, do you think that would put pressure on those polluters to clean up their act?
Sure it would! But that would cost a lot of money, and make things more expensive, and make us less competitive around the world and lord knows we are already running an unsustainable national trade deficit.
So ostensibly the powers that be met a long long time ago and came up with a plan to vilify ozone in order to draw attention away from the actual pollution culprits in order to protect those vital industries from any public outrage. Not cool, but the people behind this misinformation do what they have to do to protect our big industries which after all are the backbone of our economy in the final analysis, for better or for worse.