In the previous posting we discussed the basic components of an ozone water treatment system. In this posting we will focus on gas preparation. You can find more detailed information on feed gas systems on our website: https://www.spartanwatertreatment.com/ozone-generator-feed-gas-systems.html
To recap, employing the corona discharge process, you need oxygen (O2) to make ozone (O3). You can obtain the necessary oxygen from air or you can make or purchase oxygen. The selection of the gas preparation system depends on the requirements of the end use application and well as the economics of the process. Air fed ozone generators can only make 2-3% by weight ozone; while oxygen feed systems can make ozone at 6-12% weight percent. In a later posting we will cover why you might want to use air versus oxygen. In this posting we will just focus on the equipment needed.
If air is used it normally needs to be compressed and fully dry, -70 degrees C dew point. The degree of compression depends on the specific ozone generator and the method of drying the air. If a refrigeration system and desiccant dryer are used, the pressure might be as low as 20 psi. If a pressure swing adsorption (PSA) system is used the compressed air might need to be 100 psi.
PSA systems require higher pressure (about 10 psi) but rely on a single moving part. The system is composed of two columns filled with a material that can reversibly absorb water. Air is fed through one column while the other column is regenerated. The columns are switched every few minutes to maintain a continuous supply of dry air to the ozone generator. The only moving part is the solenoid valve used to switch the flow from one column to the other. The absorbing material is long lived and relatively inexpensive.
You can also buy oxygen, typically as a liquid (LOX). The equipment required is a cryogenic tank, evaporator and valving. This equipment is fairly expensive and you are committed to purchasing oxygen as opposed to using air which is free, but there are operational advantages to using LOX and it simplifies the system design. Industrial gas companies will provide the equipment on a long term lease basis as part of an industrial gas contract. This is normally a choice for larger systems.
The final option is to concentrate oxygen from air. This approach uses PSA. Small ozone applications can often be economically served by PSA systems. The PSA system requires compressed air at around 100 psi. A major difference with simple air drying PSA is the amount of air required. An oxygen concentration system needs 4-5 times as much compressed air as a simple PSA air dryer. Some of the smaller PSA systems come with built in compressors. You can click on the following link to learn more about these systems: https://www.spartanwatertreatment.com/ozone-generators-oxygen-concentrators.html
The use of properly pressurized dry air or oxygen is critical to the operation and maintenance of an ozone generator. If the gas is wet, it will damage the generator and result in output below specification. Poor feed gas quality is probably the major cause of ozone generator maintenance problems.