Air ioniser
The metallic comb or saw Ionizer (also ionizer ) are called low-power devices that produce ions by means of high voltage. The oxygen ions have a natural origin and are generated by electrical ionization of atoms or molecules.
- 2.1 Elimination of static electricity
- 2.2 corona treatment of plastic surfaces
- 2.3 Air Cleaner
- 2.4 ionizers in domestic electrical appliances
- 3.1 Electrical safety
- 3.2 contamination
Types and construction methods
Ionizers are parts for the partial ionization of air. If this ionized air is blown into space or directly on surfaces, materials can be charged or discharged. The resulting free radicals promote chemical degradation processes, which can be used for odor removal and disinfection.
Ionizers work with high voltage, usually of several thousand volts and an electrical discharge at tips or contain sources of ionizing radiation (ultraviolet emitters, radioactive isotopes). The achievable currents usually be about 1 uA, which corresponds to several billion ions per second.
Ionizers with corona discharge
Such metallic ionizers have high voltage supplied conductive tips that generate corona discharge and field emission in the immediate vicinity ions. There are designs that unregulated continuously produce ions, and others in which the electric field is controlled by measuring and targeted adjustment of the high voltage ( controlled ionizer ).
Regulated and unregulated ionizers are used both for the construction of defined charges as well as for the disposal of unwanted charges (prevention of electrostatic charging and ESD).
To achieve that the ionizers can be placed further away from the unloaded material ( up to about 2 m ), they are also offered with blown air or attached to existing nozzles. Wherein the ions are blown out together with the air executed to active site (e.g., in printing presses ).
Sawtooth ionizers are often formed as a thin comb-like strips. They are fed with DC or AC voltage. For ac all comb tips are commonly connected to the voltage source. When the direct voltage close to each other arranged metal tips are alternately positively and negatively charged.
Among others in Xerox copiers and laser printers will work with AC voltage superimposed DC voltage. Here the ionizers of non-contact electrostatic charging of the drum before exposure serve.
Ion generation by radiation
Ultraviolet radiation and any other ionizing radiation ( alpha, beta, X-ray and gamma radiation ) also generates ions. Ultraviolet lamps were formerly used in continuous operation in hospitals for disinfection. Today they are found in drinking water treatment as well as for curing of paints, resins and plastics. The main effect is not created by this ion.
Radioactive isotopes ( radionuclides ) are used inter alia in ionisation to detect ions absorbing substances ( fumes, aerosols ). In this case, the ionization caused by conductivity of the air is measured. This conductivity decreases in the presence of organic gases or aerosols.
Applications
Elimination of electrostatic charges
An application of ionizers is the elimination of electrostatic charges (risk of electrostatic discharge, fire hazards, personal protection ). It is used when the charged parts can be unloaded only by inadequate grounding.
Electrostatic discharge is a threat to installations where electrical insulating products are moved ( film production, film packaging, paper making, printing machinery, textile manufacturing, grain mills, bottling ). Here is a fire and possibly an explosion. With charge dissipation or using ionizers weakly conductive -made air is also prevents the process material due to electrostatic charging each other or stick to the transport paths, which would hinder the transport. Furthermore, as the attraction of unwanted particles can be prevented. In the paper sheets -processing machines electrostatic bonding with the separation of the sheets from the stack, with ionizers prevented during transport of the sheet within the machine during stacking as well as at the end of the machine. In sheet-fed offset printing machines is prevented by ionization that color drops prematurely skip from the impression cylinder to the sheet of the impression cylinder.
At workplaces for production and processing of electronic devices (wafer, circuits, light emitting diodes, laser diodes, PCB assembly ) ionizers are used on the one hand to ensure the ESD protection of the components and on the other hand to prevent pollution by electrostatically attracted dust particles.
To check the effect of ionizers used for ESD protection, there is the so-called Charged Plate Monitor ( CPM), an instrument by which the charge field can be determined as a reflection of charge between two defined plates.
Corona treatment of plastic surfaces
Corona treatment is the superficial roughening and activating non-conductive surfaces by corona discharges, mostly to improve the bondability or liability. After such treatment, the plastic surface may be ( in some plastics) in the first laminated or coated or better.
Purifier
Devices for ionization of room air is available as a small low-power devices. The beyond the dust-binding effect effects of appliances for domestic use ( increasing well-being, fresher indoor air ), which are based on the generation of anions are not scientifically proven and are controversially discussed.
The water formed in an air - ionization ozone causes a splitting of many odor-causing molecules.
However involve the breakdown products of nicotine and cigarette smoke, in addition to the ozone itself, high health risks, so that eg the German Lung Foundation warns to eliminate the bad smell smoky rooms with ozone generating air cleaners.
When ionization occurs even at today's devices ozone. This reactive gas acts as a disinfectant, antiseptic and exhausted at very low concentrations, the respiratory tract. The health department of the city of Zurich also warns against harmful decay products in indoor air, which are caused by ozone.
Considerations effect and toxicological relevance of NTP air cleaning devices revealed that the use of non- thermal plasma can not be recommended. In particular, to warn against the use in rooms where people are present.
Ionizers in domestic electrical appliances
Commercially Hair dryers, vacuum cleaners and notebooks with ionizers are available, which promise an antistatic effect.
So-called water ionizers for household are supposed to improve the quality of drinking water.
Security
Electrical Safety
The operating voltages of corona ionizers constitute no hazard when properly insulation or a leakage circuit breakers. The currents in laser printers and copiers are usually too small to cause damage to health by touch.
Since the electric fields to be disposed of by many factors such as natural ion clouds, open moving water, open fire, humidity, etc. are affected, they occur in practice completely unpredictable. For example, completely the same treated material to be processed the same batch be charged differently. Even the same process material may be loaded differently on repeated processing. DC voltage superimposed ionizers for electrostatic discharge can functionally tip over and then take charge to discharge under these circumstances. The distance between the peaks and the applied voltage, if necessary air flow and pulse times, so must be coordinated.
Contamination
Due to the ion production, free radicals that lead to chemical reactions and, inter alia, to the formation of ozone, nitrogen oxides and other pollutants. The ozone produced can affect the human respiratory system and promotes corrosion.