DEVELOPMENT OF AN EXPERIMENTAL SYSTEM TO STUDY MERCURY UPTAKE BY ACTIVATED CARBONS UNDER SIMULATED FLUE GAS CONDITIONS

[摘要] Mercury is an increasing environmental concern because of its high volatility in the vapor phase in flue gas streams and the ineffectiveness of existing control technologies to remove the vapor phase mercury. Previous research has documented that activated carbon can be an effective adsorbent for vapor phase mercury in a variety of conditions. Mercury speciation has a large impact on the adsorption by activated carbon because oxidized forms of mercury (Hg2+) can be removed much more easily than elemental mercury (Hg0). An experimental system was developed in this study to test the impact of a simulated flue gas on the adsorption of mercury under more realistic process conditions. Mass flow controllers (to control gas flow rates), a water bath (to add moisture), an oil bath (to keep a steady mercury concentration), two gas washing bottles (to remove acid gases and oxidized mercury), and a Nafion dryer (to remove moisture) were utilized in the experimental system. All the components of the experimental system were verified to produce stable flue gas composition and flow rate. Analytical procedures for mercury measurement were developed and tested. It was discovered that approximately 15% of the total mercury in flue gas consists of oxidized mercury and 85% of elemental mercury.Systematic calibration and tests of analytical equipment and all components of the experimental system are critical to the proper functioning of this experiment.Two commercial adsorbents were tested for mercury uptake in a simulated flue gas. Elemental mercury capacity of both BPL and FGD carbon increased dramatically as compared to tests with the same adsorbent under nitrogen conditions. The increased capacity is likely caused by the oxidation and acidification of the carbon surface along with the oxidizing conditions within the flue gas. The exact mechanism of the reaction between the flue gas components and the carbon surface are very complex and poorly understood and were not the subject of this study. The main conclusion of this study is that the adsorbent performance in a nitrogen atmosphere is not relevant for full-scale applications where flue gas components produce numerous reactions on the carbon surface and yield drastically different mercury uptake capacity.

[发布机构] the University of Pittsburgh

[效力级别] Adsorption