Types and Selection of Ozone Generators

Based on the method of ozone generation, there are currently three main types of ozone generators: high-voltage discharge type, ultraviolet irradiation type, and electrolysis type.

High-voltage discharge generators use a high-voltage current of a certain frequency to create a high-voltage corona electric field, causing oxygen molecules within or around the electric field to undergo an electrochemical reaction, thereby producing ozone.

This type of ozone generator has advantages such as mature technology, stable operation, long service life, and high ozone output (up to 1 kg/h per unit), making it the most widely used ozone generator in related industries both domestically and internationally.

High-voltage discharge ozone generators are further divided into the following types:

1. Based on the frequency of the high-voltage current, there are three types: power frequency (50-60Hz), medium frequency (400-1000Hz), and high frequency (>1000Hz). Power frequency generators, due to their large size and high power consumption, have been largely phased out of the market. Medium and high frequency generators, with their advantages of small size, low power consumption, and high ozone output, are currently the most commonly used products. 2. Based on the gaseous raw material used, ozone generators are classified into two types: oxygen-based and air-based. Oxygen-based generators typically use oxygen cylinders or oxygen concentrators to supply oxygen. Air-based generators typically use air (such as compressed air) as the raw material. Since ozone is produced from oxygen, and air contains only 21% oxygen, air-based generators produce a relatively low concentration of ozone and also generate nitrogen oxides. Bottled or machine-generated oxygen has a purity of over 90%, resulting in a higher ozone concentration in oxygen-based generators. Air-based generators are generally used for environmental disinfection. For water treatment, oxygen-based generators should be given priority. However, if the generator needs to be used in conjunction with an older ozone mixing tower for drinking water disinfection, then only air-based generators can be used.

3. Based on the cooling method, ozone generators are classified into water-cooled and air-cooled types. Ozone generators generate a large amount of heat during operation and require cooling; otherwise, ozone will decompose simultaneously due to the high temperature. Water-cooled generators offer better cooling, stable operation, no ozone decay, and can operate continuously for extended periods, but they have a more complex structure and are slightly more expensive. Air-cooled generators are not ideal, resulting in significant ozone decay. Large generators or those used in critical locations are typically water-cooled. Air cooling is generally only used in generators with lower ozone output or in locations with less stringent performance requirements. When selecting a generator, water-cooled models should be chosen whenever possible.

4. Based on dielectric material, common types include quartz tubes, ceramic plates, ceramic tubes, glass tubes, and enamel tubes. Quartz tubes are most commonly used in high-performance ozone generators due to their high dielectric constant, uniform wall thickness, good ellipticity, high temperature resistance, and moisture resistance. Ceramic plates are brittle and only suitable for small generators. Ceramic tubes are difficult to control in terms of wall thickness and ellipticity, leading to uneven discharge, so they are not widely used. Glass tubes and enamel tubes have low dielectric constants, poor high-temperature resistance, and are prone to cracking, and are only used in some low-end generators.

5. Based on the structure of the ozone generating components, there are closed-loop and open-loop types. The structural feature of a closed-loop ozone generator is that the sealed body itself is the electrode, allowing for concentrated ozone production, such as in water treatment. In contrast, the electrodes of an open-loop generator are exposed to the air, preventing concentrated ozone production. It is typically used only for air purification in smaller spaces or for disinfecting small surfaces. Closed-loop generators can be used in place of open-loop generators. However, closed-loop generators are significantly more expensive than open-loop generators. It is worth noting that some people now rigidly enclose open-loop generators to pass them off as closed-loop generators. This results in significant heat buildup, severe ozone decay, and rapid generator burnout.

Ultraviolet (UV) ozone generators use ultraviolet light of a specific wavelength (185nm) to irradiate oxygen molecules, causing them to decompose and produce ozone. Due to the large size of the UV lamp, low ozone production, and short lifespan, this type of generator has a narrower range of applications and is commonly used in dish sterilizers.

Electrolytic ozone generators typically produce ozone by electrolyzing pure water. This type of generator can produce high-concentration ozone water, has low manufacturing costs, and is simple to use and maintain. However, due to drawbacks such as limited ozone production capacity, short electrode lifespan, and difficulty in ozone collection, its applications are restricted. Currently, this type of generator is only used in some specific small-scale equipment or certain specific locations, and it does not meet the criteria to replace high-voltage discharge generators.

In summary, the following factors should be prioritized when selecting an ozone generator: medium-high frequency high-voltage discharge type, quartz dielectric tube structure, water cooling, oxygen type, and closed-loop design.