Philips Lighting---Discussion on the function and application of ultraviolet germicidal lamp

Foreword Today, with people's living standards increasing and the demand for healthy water is increasing rapidly, there are still 1.2 billion people in the world who do not have access to safe drinking water. Untreated water can cause a range of serious diseases, and according to United Nations statistics, about 80% of diseases and deaths in developing countries are caused by unhealthy drinking water. Ultraviolet water purification source products - UV disinfection lamps, solve the worldwide problem of healthy water. The performance, features, functions and applications of UV disinfection lamps are briefly introduced.

1. Design principle of ultraviolet germicidal lamp

In actual production, the application and design of germicidal lamps mainly consider the following three factors:

A effective radiation dose (Heff)

The effective radiation dose is the product of time and effective irradiance (irradiance is the main contributor to sterilization). However, the radiation dose is limited by its ability to penetrate the medium itself. The penetrating power depends on the size of the absorption coefficient. For solids, the surface will absorb all radiation; for water, depending on its purity, the light radiation can penetrate a few millimeters to several micrometers before being absorbed by 90%.

B. The harm that these radiations may cause

Sterilizing radiation can cause conjunctivitis and skin erythema, so humans cannot be exposed to radiation above the specified maximum. In other words, this is taken into account when designing the sterilisation device.

UV sterilization can be used for the three-state substances used (gas), liquid (mainly water) and solids (surface) with a low absorption coefficient. However, by using “thin film technology” and loop design (to cycle the product), great success has been achieved even with some poor absorption coefficients.

C light source

Increasing the lamp current of the low voltage source to achieve higher light output of the same tube length, but at the expense of reducing UV radiation efficiency (UV watts / input watts); this is due to the increase in self-absorption and temperature effects. The use of amalgam instead of pure mercury in lamps can reduce the effects of these temperatures. HOK light source, medium pressure mercury lamp, produces more UV-C ultraviolet radiation than low voltage light source, but the efficiency is also lower.

2. Characteristics of ultraviolet sterilization

Ultraviolet purification has unparalleled advantages over traditional chlorine disinfection. Chlorine disinfection forms a chlorine compound in water, which is a carcinogen, and it also has a taste when the concentration of chlorine is high. If you drink raw water, it will obviously smell this strange smell. There is now another method of water disinfection: ozone. Ozone can also be sterilized, but when the concentration is high, the decomposition time of ozone is prolonged, and it is likely to be transported to a residential house through a close-distance pipeline. Ozone water is said to be able to be used for beauty and washing, but it cannot be drunk, and its taste is unpleasant. If the concentration is lowered, the bactericidal ability is reduced. In addition, ozone disinfection should also prevent leakage.

UV disinfection lamps do not need to add any chemicals. Adding chemicals often causes a bad taste or odor in the water. Even the chemicals themselves may be harmful. For example, chlorine may react with organic substances in the water to form Chloroform with a potential carcinogenic threat. And it takes time for the chemical to work, and its effectiveness is limited if it is not thoroughly mixed with the chemical before it is used. In addition, in some cases, microorganisms can develop tolerance or immunity to certain specific chemicals. These conditions do not occur with UVC radiation disinfection.

A typical complete filtration unit has a multi-layer structure including a UV light source and a conventional mechanical filter. A suitable UVC lamp is typically integrated into a complete filtration unit by a specialized filter system manufacturer. A complete filter unit has a multi-stage purification structure. In addition to the UVC tube itself, there is a conventional mechanical filter layer for removing solid impurities and an activated carbon filter layer for removing biological substances with bad taste and odor. Other impurities such as fragrance chemicals.

3. The practical application of ultraviolet germicidal lamps

3.1 method of ultraviolet germicidal lamp

Water treatment is divided into treatment objects, including wastewater treatment, urban water treatment, drinking water treatment, pure water treatment, farm water treatment; in principle, disinfection, sterilization, photolysis degradation and other actinic Reaction; from the method of using ultraviolet germicidal lamp, there is a direct discharge of the lamp into the water, called immersion; the ultraviolet lamp is used in the casing, which is called overcurrent. (This over-current method is currently used by Philips Lighting's UV germicidal lamps.)

4.1.1 Overcurrent

The working principle of the over-current device is as follows: a flow of water at a certain flow rate generated by the pump flows through the periphery of the quartz sleeve which is transparent to ultraviolet rays, and the ultraviolet light generated by the ultraviolet lamp sterilizes and sterilizes the water. It is characterized by a fast flow rate of water, generally no more than one second flowing through the quartz jacket, so the ultraviolet light intensity of the germicidal lamp is required to be high, and the surface strength is generally required to exceed 30,000 uw/cm2. To produce such high UV intensity, high-intensity and high-power UV germicidal lamps are required. If you still want to increase the disinfection effect by extending the time, you should generally use a longer lamp, make a longer device, or process the vortex rotating structure on the outer wall of the stainless steel to extend the flow of water.

4.1.2 Immersion

The immersion structure is simpler than the overcurrent type. The UV germicidal lamp is placed directly in the water. This method can be used for flowing dynamic water or static water. This kind of treatment method should pay attention to the fact that the lamp tube may be broken due to unexpected conditions; if it is treated for a long time, the surface of the lamp tube will be covered by algae and other pollutants in the water, which will seriously affect the ultraviolet light. To disinfect water bodies of different objects, it is necessary to understand the changes in water quality and the transmittance of water to ultraviolet light.

4.2 Application prospects and fields

Philips UV germicidal lamps not only have high UV light transmission, long life, negative oxygen ions when purifying air, but also kill harmful bacteria and viruses up to 99.99%.

Although ultraviolet germicidal lamps can be applied to various aspects and can achieve various purposes, its application fields can be summarized as follows: 1. Air disinfection 2, HVAC cooling coil 3, domestic water 4, industrial drinking water 5, process water (beverage) 6, wastewater 7, semiconductor and IC manufacturing 8, swimming pools, hot springs, aquariums, fish ponds, in addition to beer, beverages, water treatment, air conditioning, disinfection cabinets, hospital dynamic sterile room, Ward and so on.

5. Summary

For a long time, pollution in macro and micro environments has been receiving much attention. At present, the problem of pollution reduction has formed an industry, including improved technology to reduce primary pollution, secondary pollution, and physical, biological, and chemical cleaning. The use of UV-C ultraviolet radiation in these technologies not only plays a bactericidal role, but also an efficient sterilization method, it will probably be the most energy efficient technology.

Text / Ge Rong Philips Lighting (China) Company Special Light Source Division