| dc.description.abstract | Cold cathode fluorescent lamp (CCFL) is a primary component of thin-film transistor liquid-crystal display (TFT-LCD) that is major back light module for faceplate. Each CCFL contains about 3.0mg mercury. The market share of CCFL produced in Taiwan has reached to 26.5%. According to statistics for the display search, the numbers of CCFL products are 21 millions. The result could result in a great number of waste mercury. The wasted mercury in environment possibly is converted to other type via microbes or concentrated. Alkyl mercury, high toxic chemical, is formed via chemical or photochemistry reaction to lead to acute or chronic response.
Mercury recovery technology (MRT) from Sweden was frequently used for the waste mercury treatment. The targets treated using the technology are high mercury content lamps include exposure lamp, UV lamp and fluorescent lamp. Recovery of mercury for the lamps exceeds 99.99%. However, recovery and treatment for CCFL only reach to 81.24%, which is relatively lower among these lamps. A number of investigators presented the desorption of pure fluorescent powder obtained from waste CCFL could use a tube furnace under 200oC to generate low residual mercury. The above operation temperature is different from temperature of mercury release in the realistic plant.
In this study, mercury recovery equipment in the realistic plant was applied to run the experiment of mercury desorption from the CCFL. The controlled parameters include heating temperature, heating time, condense temperature and vacuum pressure to investigate the dominant factors on the mercury recovery. Moreover, the best operation parameters can be obtained in this study. The result indicated average treatment rate was 75.44% under 400oC. This approach could recover largely mercury. Another high desorption efficiency was found in temperature of 500~700oC that similar to boiling point of mercury oxide. The result is thought to oxygen reacts with mercury in the CCFL to form mercury oxide. This lead to a higher temperature for the mercury desorption. By examining the different operation parameters, it can be found that the heating temperature of 850 oC, the condense temperature of -6oC, the heating time of 12hours, the vacuum pressure of 15mbar are selected as the most appropriate operation parameters. The rate of recovery and treatment for mercury reached to 99.53% under the above conditions. In addition, fluorescent powder containing mercury for five types of CCFL was treated using realistic plant equipment under the appropriate operation condition to run the experiment of the mercury desorption. The result indicates the efficiency of recovery and treatment about 80.58% for alone and composite sample is similar.
The surface of CCFL is examined via scanning electron microscope (SEM) and energy dispersive spectrometer (EDS). A significant change can be found in the surface of the electrode after the CCLF was lighted. In the time, the weight percent of mercury on the surface of electrode is about 10.53%. It can be concluded that the surface of electrode for CCFL in lighting under 1000 K would excite the electron to result in that Ni alloyed with Hg on the surface. If efficiency for the screen of pretreatment is low, the approach can increase temperature of the mercury desorption in a distillation system. Thus, it was assumed that the efficiency will increase significantly, if targets that was the fluorescent powder separated from CCFL were treated. | en_US |