As an allotrope of oxygen, ozone is a strong oxidant with particularly active chemical properties, which is widely recognized as a highly effective disinfectant. Ozone can quickly kill bacteria and viruses in both air and water. Ozone can also kill bacteria or microorganisms that cause the generation of odors so as to achieve the effect of odor removal. Ozone is easy to decompose and cannot easily be stored. It will gradually decompose into oxygen at room temperature. So, when it is used, it needs to be generated and used on site. For more basic information about ozone, you can refer to our previous blog An Introduction of Ozone. Ozone generators are devices used to generate the gas ozone.
Ozone generators are widely used in disinfection and odor removal applications in home environment, commercial environment, ozone generation for industry use, processing and preservation of agricultural products, disinfection and sterilization in medical industry, sewage treatment, etc. Later, in this blog, we will give you a comprehensive introduction to several related aspects of ozone generators which include Ozone Generation Methods, Feed Gas Options for Generation, Ozone Generation Quantity and Concentration, their Cooling Methods, their Key Components, Ozone Water Treatment, Product Quality and Price, etc. Hopefully, this blog can improve your understanding of ozone generating equipment. Now we will go through the details in the order that described above in the following.
1. Three Ways to Generate Ozone
In the generation of ozone gas, three methods will usually be adopted. They are respectively dielectric barrier discharge, ultraviolet photolysis and water electrolysis. In the following, we will introduce these three methods.
Dielectric Barrier Discharge
Dielectric barrier discharge (DBD) method is also called corona discharge or silent discharge method. It refers to the method to generate ozone by inserting dielectric into the discharge space and ionizing air or oxygen with high voltage. This method is widely used in ozone generating equipment production industry. Ozone generators applied this method are widely used in home environment, commercial environment, industrial environment, agricultural environment, medical field, etc.
There are several advantages while applying this method. Firstly, it has high efficiency of ozone generation by adopting this method. It can satisfy the demand for large quantity of ozone gas in industrial, agricultural and water treatment fields. Meanwhile, the concentration of ozone gas produced with this method is relatively the highest compared with other methods. Secondly, ozone generators produced applying this method has a relatively longer lifespan for long period use. Thirdly, the structure of this type of ozone generators is relatively simple. It will be easy to achieve miniaturization in the design and production process, which make it possible to be used in a variety of scenarios. Then, to meet the requirements for large quantity and high concentration of ozone generation, this method will be less expensive than the ultraviolet photolysis method, which will be talked about later in this blog. What’s more, to generate the same amount of ozone gas, its power consumption will be relatively lower.
There are also some drawbacks in adopting this method to generate ozone. Firstly, it is about the feed gas. If air is used instead of oxygen as the feed gas, in the ozone generation process, nitrogen oxides will be produced as byproducts, which is harmful for human health. Then, attention should be paid to the humidity of the working condition where ozone generating equipment is being used. Excessive humidity will affect the efficiency of ozone production. Long-term use under humid environment will shorten the service life of the equipment.
Ultraviolet photolysis is the use of ultraviolet radiation on the air, so that a part of the oxygen molecules in the air will be decomposed into oxygen atoms. Then, these oxygen atoms will combine with the surrounding oxygen molecules again to form ozone molecules. With the joining of another oxygen atom, unlike one oxygen molecule who has two oxygen atoms, one ozone molecule has three oxygen atoms. As this combination continues, ozone gas is thus gradually generated and assembled.
One advantage of generating ozone with this method is that the operation of the equipment will not be affected by humidity. At the same time, no byproducts like nitrogen oxides will be generated in the process of ozone generation. But there are still several disadvantages in adopting this method. One disadvantage is that its ozone production efficiency is relatively low. Generally, the maximum efficiency of ozone generation by a UV bulb is about 2 g/h. If 10 g/h or higher efficiency is needed, its economic cost will be high. Therefore, ozone generators adopting this method can only be used in small quantity and low concentration ozone applications like air disinfection, sterilization and odor removal. This method cannot meet the requirements of water treatment industry and other applications with large quantity ozone demand. Another disadvantage in this method is that it costs more electricity to produce the same amount of ozone. In addition, the service life of an ultraviolet bulb is around half a year to a year or so. Long-term use of this method requires consideration of the cost of regular UV bulb replacement.
Water electrolysis works by electrolysis of water. Low-voltage direct current is used to produce ozone gas by oxidizing the water at the interface between the positive electrode and the solution. The advantage of this method is that the concentration of ozone generated is high and it is suitable for the preparation of high concentration ozone water. And no nitrogen oxides are formed in the process of ozone generation. The disadvantage of this method is that the water used for electrolysis must be pure. Otherwise, the chlorine atoms that may be present in the water can affect the efficiency of ozone production. Secondly, the ozone quantity produced by this method is small and not easy to collect. Thirdly, the energy consumption of ozone generation using this method is relatively large.
The above is an introduction and comparison of the three methods for ozone generation. Through comparison, we can see that the method of dielectric barrier discharge is relatively the most economical, efficient, and the most feasible ozone generation method.
2. Air vs. Oxygen as Feed Gas
When ozone is generated by dielectric barrier discharge, either ordinary air or oxygen can be used as the feed gas. The following is a brief comparison of the respective characteristics of the two types of feed gases.
When natural air is chosen as the feed gas to produce ozone, the ozone generator ionizes 21% of the oxygen present in the air. The advantage of producing ozone using natural air is that the gas flow rate will not be taken into account. And you don’t need to consider the cost of oxygen machine if oxygen is chosen as the feed gas. But the drawback is that ozone generated with this method is relatively lower in concentration, and certain amount of nitrogen oxides will be produced in the process. Furthermore, components of the ozone generator using air as feed gas are vulnerable to contamination and therefore need to be cleaned regularly.
Ozone generation with oxygen as the feed gas means using oxygen as the ionizing object by an ozone generator to generate ozone gas. The only drawback to generate ozone in this way is that its oxygen flow is smaller than using air as the feed gas. Also, since oxygen is used as the feed gas, an oxygen machine will be an indispensable component of the ozone generation system. Therefore, the price of this type of ozone generators will be higher than those using air as feed gas. But its advantages are even greater. Firstly, you can get more purified ozone gas. Moreover, no nitrogen oxides will be produced in its ozone generation process. Secondly, it is the ozone quantity generated. Ozone generation using oxygen as feed gas can increase the ozone generation quantity by 2-3 times compared with using air as the feed gas. Thirdly, when oxygen is chosen as the feed gas for ozone water treatment operation, its ozone solubility in water will be higher. Also, in medical use, medical institutions prefer to use oxygen as the feed gas in order to get highly purified ozone gas. What’s more, ozone generators applying oxygen as feed gas will be less likely to be contaminated. Thus, its daily maintenance work will be less and easier.
The above is a comparison of ozone generators using two types of feed gases. Users can decide which type of ozone generator to choose according to the specific requirements of ozone generation quantity and gas purity as well as the budget.
3. Ozone Generation Quantity and Concentration
Ozone generation quantity refers to the amount of ozone generated per unit time from certain generation machine. It equals to ozone concentration times feed gas intake. The units of measurement applied are generally mg/h, g/h and kg/h. Typically, mg/h and g/h are used in small equipment, while kg/h is used in large equipment to distinguish specification and size differences.
Ozone concentration is an important index to measure the technical performance of an ozone generator or a generating system. It is used to reflect the capacity or speed of ozone generation equipment to produce ozone. There are many factors that will affect the concentration of ozone. These factors include the structure of the generating equipment, its production accuracy, its cooling method, its driving voltage and frequency, its dielectric material used, the oxygen content in feed gas, the cleanliness and dryness of feed gas, and the efficiency of power supply system, etc.
Among these factors mentioned above, the cooling method is an important factor which affects ozone concentration greatly. Ozone in the air generally has a half-life of 20-50 minutes. The higher the temperature is, the faster ozone decays. It has been estimated that around 30 ℃, around 50% of ozone will decay in 1 minute. When it is between 40-50 ℃, around 80% of ozone will decay in 1 minute. When it is over 60 ℃, ozone will decay instantly.
Gas concentration is usually measured and expressed in two ways: mass ratio and volume ratio. Mass ratio refers to the mass of the gas contained in a unit volume, usually expressed in mg/m3, g/m3, etc. While volume ratio refers to the percentage of gas volume per total volume, usually expressed as a percentage. The measurement unit PPM is widely used in the medical field to indicate gas concentration. Ppm means parts per million by volume. For ozone, since its density is 2.14 kg/m3, so 1 ppm of ozone equals to 2.14 mg/m3. Usually, we take 1 ppm = 2 mg/m3 as a generally accepted ratio.
4. Cooling Methods in Ozone Generators
Ozone generators work by ionizing air or oxygen to generate ozone. In this ionization process, the conversion of air or oxygen to ozone requires energy transfer. So, a large amount of heat will thus be generated. Since excessive heat accumulation will cause and accelerate the decay of the ozone gas generated, so effective cooling measures should be taken in the equipment. In the manufacture and use of ozone generators, the equipment often adopts air cooling, water cooling or both ways to diffuse the heat.
The structure of small and medium-sized ozone generating equipment is relatively simple, and the power consumption of the equipment is relatively low. Therefore, this kind of equipment usually adopts air cooling method to meet the needs of heat diffusion. Compared with small and medium-sized ozone generating equipment, large ozone generating equipment produce significantly more heat during operation in large amount ozone generation applications. Therefore, water cooling method with better heat diffusion effect is often adopted by this kind of large equipment. When the equipment needs to be cooled by water flow, there will always be water flowing by the high voltage modules of the equipment to carry heat away. Therefore, the design and manufacture of heat diffusion pipes in large ozone generating equipment should be properly handled to avoid potential safety hazards.
5. Key Components
A typical ozone generator adopting dielectric barrier discharge method usually consists of several components. Among these components, the most important ones are the dielectric material and electrode material used in the equipment. In the following, we will have a brief introduction of these two components and their material composition.
The dielectric component is used within an ozone generator to isolate the positive and negative electrodes. Common dielectric materials used include glass tubes, ceramic sheets and quartz tubes, etc.
Glass Tube: Structurally, an ozone generator using a glass tube has an electrode placed inside a glass tube, known as the inner electrode. The other electrode is wrapped around the outside of the glass tube, known as the outer electrode. Thus, an ozone generating module that can discharge high voltage electricity along the glass surface is formed. The advantage of using glass tubes is that the cost of glass material is relatively low. But the main problem with glass tubes is that they tend to have a shorter service life. Moreover, glass is prone to crack when the temperature changes rapidly. In addition, glass material is not impact resistant. Therefore, ozone generators using glass tubes are also more prone to be broken during product transportation.
Ceramic Plate: Ceramic plates are commonly used as dielectric components in ozone generators. In the manufacturing process of this type of equipment, the ceramic plate is first covered with a layer of metal powder which is about 1mm thick. Then, by being sintered at a high temperature, the metal powder on the ceramic plate melts and attaches itself to the surface of the ceramic, forming two electrodes respectively on each side of the ceramic plate. After this treatment, the ceramic plate between the two electrodes becomes the dielectric component. Ceramic plates are widely used in small and medium-sized ozone generators. The main advantages of ozone generators using ceramic plates lie in its mature production technology, large ozone generation quantity and stable performance. While the disadvantages of this type of ozone generators are mainly reflected in their large power consumption and inadaptation to humid environment. Another advantage in this type of ozone generators is in its transportation process. Compared with products with glass or quartz tubes, this type of ozone generators has a lower probability of damage during transportation.
Quartz Tube: The structure of an ozone generator using quartz tubes is quite similar to that of a device using glass tubes. Compared with glass tubes, quartz tubes’ advantage comes from its better material consistency than glass. In addition, quartz tubes also have the characteristics of higher temperature and humidity resistance. Ozone generators using quartz tubes are also less prone to deposit formation. So, they are easier to be cleaned. Quartz material can be made into many shapes. So, this can provide more flexibility for the design of dielectric components. But just like these ozone generators using glass tubes, equipment using quartz tubes are more likely to be damaged in their transportation process.
In a variety of ozone generating products, the materials used in their electrodes are usually aluminum, stainless steel, titanium, etc. Here are some basic characteristics about each material:
Aluminum: Aluminum electrodes are widely used in the production of ozone generators. Aluminum has good thermal conductivity and resistance to ozone, which can help reduce the production of nitrogen oxides in the process of ozone generation.
Stainless Steel: Stainless steel is also a widely used electrode material in ozone generators. It has a good resistance against ozone oxidation. But its disadvantage is that its thermal conductivity is not so good as aluminum materials.
Titanium: In the production of some ozone generators, their electrode material will first be coated with titanium before being used later. The purpose of titanium coating treatment is to make use of its great antioxidant properties in titanium. The electrodes after the treatment will provide a good compromise between its oxidation resistance and thermal conductivity.
The above is a brief introduction of the dielectric components and electrode components that have been widely used in ozone generators, as well as their characteristics of respective materials.
Here, there is still one more detail that needs to be noted. In ozone generators, loosening of the connections between electrode and wire may sometimes occur if they are not properly treated. Usually, loose wire connections only lead to poor contact failures at low voltage electric appliances. But there is high voltage current in ozone generators when they are working. When high voltage current passes through a loose connection between the wire and the electrode, there will easily be sparks produced there. The high temperature generated by the sparks will lead to the rapid oxidization of the material at the connection, which will further aggravate the poor contact. To avoid this kind of situation and ensure good contact between the wire and the electrode, the connection should be fixed with silica gel. This takes advantage of silica gel’s excellent oxidization and high temperature resistance properties. The use of silica gel can not only ensure the proper contact between the wire and the electrode, but also avoid the oxidization of the connection to a certain extent.
6. Ozone Generators vs. Ozone Water Treatment Equipment
Ozone generators and ozone water treatment equipment are two of the most common types of ozone applications. They both make use of ozone’s strong oxidization to achieve disinfection and odor removal effect. Based on their respective characteristic and operation method, they are differentiated in specific applications.
Ozone generators are widely used in space sterilization, odor removal, industrial oxidization treatment, food processing and preservation, sewage treatment, and medical disinfection and sterilization, etc. Since ozone is in the form of gas at room temperature, so, for attics or basements in a home where cannot be easily treated with traditional disinfection methods, ozone sterilization will be more efficient and thorough.
For home use, ozone generators can broadly be applied for sterilization and odor removal in all rooms in a family, especially in kitchens and bathrooms where odor problems are almost inevitable. They can also be applied for furniture, clothing and pet odor removal. For deep-rooted smoke smell, their removal performance can be magical. Not only for home interior application, under appropriate control of ozone concentration and time, they are also good companions for car odor removal. Furthermore, for chemical odors which come up once in a while, their removal effect is also amazing.
Ozone generators are widely used in commercial, industrial and agricultural fields. They are quite common in hotels, laundries, car services and many other industries. In addition, for post-disaster restoration use after fire and flood, ozone has significant disinfection and odor removal effects. In industrial production, ozone has been using for long time in food preparation industry. When used for industrial environment disinfection, compared with the use of ultraviolet lights with the problem of area being blocked, ozone generators will be better choices with their full-scale coverage ability. In agricultural production, for the planting and irritation of grains and vegetables, ozone water has a direct killing effect on almost all types of microorganisms, such as fungi, bacteria and viruses. Moreover, with ozone’s great effect being gradually learnt, its application scope is still expanding.
Ozone water treatment makes use of ozone’s strong oxidation to disinfect and sterilize all kinds of polluted water bodies. Ozone water treatment has been widely popularized and used in Europe and America for many years. It can be used not only for industrial and sanitary sewage treatment, but also for natural water disinfection and sterilization to make it suitable for drinking purpose.
In daily life, one of the best applications of ozone is to install ozone water treatment equipment to water pipes. By doing this, tap water will easily be converted to ozone water. When there is ozone water ready for use, it can be used to scrub everywhere you want in your home. This is another way to use ozone for sterilization instead of ozone generators. Also, you don’t need to send everybody out to empty the room for ozone sterilization when an ozone generator is used. Furthermore, this method will be much milder than using ozone generators, which can avoid the potential damage to certain items by the strong oxidization effect from ozone generators.
The use of ozone water treatment equipment can also add more convenience to life. For instance, if washing machines use ozone water to wash clothes, there is no need to use disinfectant any more when the washing is finished. Also, if ozone water is used to wash fruits and vegetables, then the use of other wash products is not necessary any more. In addition, if you want to use ozone to disinfect your car interior or for odor removal purpose, then scrubbing with ozone water will be the best solution. This is true since there is a lot of leather and rubber materials used inside a car. Frequent use of ozone generators for sterilization will accelerate the aging of these materials. But scrubbing the interior with ozone water will not cause that problem.
There are other cautions need to be noticed in the use of ozone generating equipment. First, since ozone’s strong oxidization will accelerate the aging of rubber, so, it is not recommended to use ozone generating equipment frequently in garages. Then, during the use of ozone water treatment equipment, heat will be generated when it is working. When it stops working, the machine will cool down gradually. As the machine cools, the reduction of air pressure inside the machine might cause the flowing back of water into the machine. This often leads to the damage to the machine. Therefore, to prevent this kind of situation, it is strongly suggested that a check valve should be installed to the pipe in case of water flowing back.
7. Quality vs. Price
Like other commodities in our daily life, when selecting an ozone generator, we also need to consider its cost performance and future economic cost in the long-term use.
Low-price products have the problems of poor reliability and poor compatibility of accessories. Their components are also not easy to get in the market. These products can sometimes be considered if they are intended to be used in short term test without the requirement of long-term stability.
However, if the long-term stability of the product is considered, users should choose the products with higher cost performance. Even if the purchase price of these products will be slightly higher, their stable performance will prove that they are worth your money. Moreover, the universality of the accessories in high-quality products can enhance the use and maintenance experience of the end users. This will also reduce the time and labor cost to a certain extent in the purchaser’s customer service in the future.
In the above, we have introduced ozone generators and ozone water treatment equipment from several related aspects. Hopefully this will provide you with some valuable advice when you are choosing ozone generators and other related equipment.