Mercury reaction chemistry in combustion flue gases from experiments and theory
Abstract/Contents
- Abstract
- Emissions from coal combustion processes constitute a significant amount of the elemental mercury released into the atmosphere today. Coal-fired power plants in the United States, with the capacity of just over 300GW, are the greatest anthropogenic source of mercury emissions. Mercury exists in coal combustion flue gas in a variety of forms depending on the coal type and combustion conditions; i.e., elemental, oxidized and particulate. Particulate mercury in the flue gas can be removed using air pollution control devices such as electrostatic precipitators and fabric filters. Oxidized mercury is easily captured by wet flue gas desulfurization scrubbers, while gaseous elemental mercury passes through the scrubbers readily. Activated carbon, when injected into the gas stream of coal-fired boilers, is effective in capturing both elemental and oxidized mercury through adsorption processes. However, the mechanism by which mercury adsorbs on activated carbon is not exactly known and its understanding is crucial to the design and fabrication of effective capture technologies for mercury. The objective of the current study is to apply theoretical-based cluster modeling to examine the possible binding mechanism of mercury on activated carbon. The effects of activated carbon's different surface functional groups and halogens on elemental mercury adsorption have been examined. Also, a thermodynamic approach is followed to examine the binding mechanism of mercury and its oxidized species such as HgCl and HgCl2 on a simulated carbon surface with and without Cl. Energies of different possible surface complexes and possible products are compared and dominant pathways are determined relatively. Since different methods are employed to capture varying forms of mercury, understanding mercury speciation during combustion and how the transformations occur between different forms is essential to developing an effective control mechanism for removing mercury from flue gas. In this study, homogeneous oxidation of mercury via chlorine is examined experimentally in a simulated flue gas environment. Mercury and chlorine are introduced into a laminar premixed methane-air flame. Cooled flue gas is sampled and sent to a custom-built electron ionization quadrupole mass spectrometer specially designed for mercury measurement on the order of parts per billion (ppb) in flue gas. The use of a mass spectrometer allows for distinguishing between the different forms of oxidized mercury (Hg+, Hg+2). By directly measuring mercury species accurately, one can determine the actual extent of mercury oxidation in the flue gas, which will aid in further developing mercury control technologies.
Description
| Type of resource | text |
|---|---|
| Form | electronic; electronic resource; remote |
| Extent | 1 online resource. |
| Publication date | 2011 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Associated with | Padak, Bihter |
|---|---|
| Associated with | Stanford University, Department of Energy Resources Engineering |
| Primary advisor | Wilcox, Jennifer, 1976- |
| Thesis advisor | Wilcox, Jennifer, 1976- |
| Thesis advisor | Brown, G. E. (Gordon E.), Jr |
| Thesis advisor | Kovscek, Anthony R. (Anthony Robert) |
| Advisor | Brown, G. E. (Gordon E.), Jr |
| Advisor | Kovscek, Anthony R. (Anthony Robert) |
Subjects
| Genre | Theses |
|---|
Bibliographic information
| Statement of responsibility | Bihter Padak. |
|---|---|
| Note | Submitted to the Department of Energy Resources Engineering. |
| Thesis | Thesis (Ph.D.)--Stanford University, 2011. |
| Location | electronic resource |
Access conditions
- Copyright
- © 2011 by Bihter Padak
- License
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
Also listed in
Loading usage metrics...