(473e) Mercury Removal From Coal by Leaching with Sulfur Dioxide

The objective of this research is to develop a standard method to reduce the mercury emissions from coal-fired power plants. This research focuses on pretreatment of coal to remove mercury prior to coal combustion. The purpose is to determine whether this pretreatment can replace the adsorption process of mercury vapor from the flue gas stream using activated carbon.The minute amount of mercury in Pittsburgh No. 8 coal (0.177 ppm) was removed by flowing a gas stream containing 10% oxygen and 1000 ppm SO2 into a coal water slurry at 30 ml/s. A total of 50 g of 35x65 mesh coal was leached each time in 500 ml of solution. The temperature was varied from 50 to 80 °C, and the initial solution pH varied at 5.7, 1.8, and 1.5. It was found that the mercury removal increased from 44.2% at 50 °C to 88.6% at 75 °C at the pH 5.7 (pH of distilled water) and after 3 hours of reaction time. The pyrite conversions were much lower than those of mercury. Both the mercury and pyrite removals increased as the pH decreased at 71 °C.Mercury removal percentages increased as high as 99% at pH 1.5 and at a temperature of 71 °C. Mercury removal was high enough to consider the application of this technology to a commercial process.