Grantee Research Project Results
Control of Mercury Emissions from Coal-Fired Power Plants
EPA Grant Number: R828170Title: Control of Mercury Emissions from Coal-Fired Power Plants
Investigators: Helble, Joseph J. , Sarofim, Adel F.
Current Investigators: Helble, Joseph J. , Sarofim, Adel F. , Qiu, Joseph , Sterling, R.
Institution: University of Connecticut , University of Utah
EPA Project Officer: Hahn, Intaek
Project Period: July 1, 2000 through June 30, 2002 (Extended to September 30, 2003)
Project Amount: $224,642
RFA: Exploratory Research - Engineering, Chemistry, and Physics) (1999) RFA Text | Recipients Lists
Research Category: Water , Air , Safer Chemicals , Land and Waste Management
Description:
Coal combustion remains one of the major anthropogenic sources of ambient mercury. Mercury capture in coal combustors is inhibited by incomplete mercury oxidation. This research project will explore methods for manipulating mercury chemistry in the post-combustion zone to increase the fraction of oxidized mercury and thus enhance mercury capture in existing pollution control devices.
The objective of our proposed effort is to develop a novel, low-cost process
for mercury emissions control. Small quantities of a hydrocarbon will be
injected into post combustion gases to manipulate the radical pool and drive
mercury toward the favored Hg(II) form. Our hypothesis, supported by preliminary
calculations using kinetic models of chlorinated hydrocarbon combustion
chemistry, is that this injection will increase the concentration of oxidizing
chlorine radical species by 5-10 fold. Based upon recent studies of mercury
oxidation kinetics, it is further hypothesized that this increase in chlorine
radical species concentrations will increase the rate of mercury oxidation, thus
driving mercury speciation toward the equilibrium-favored HgCl2 form. The approach for assessing the feasibility of this process is one of combining bench scale experiments with elementary reaction kinetics modeling. Specifically, a hydrocarbon will be injected into the 700 B 1200 K post combustion gases of an existing flat flame reactor system. Gases will be doped with mercury and HCl or Cl2 as a chlorine source in concentrations comparable to those obtained from fuel lean combustion of a typical U.S. eastern bituminous coal. Mercury and chlorine species will be measured using impinger trains and atomic absorption and ion chromatography. Chlorine radical species will also be measured indirectly by injecting trace quantities of vaporized benzene into the post combustion gases downstream of the methane injection point, and measuring benzene decay both with and without supplemental fuel injection. Benzene has been observed to effectively titrate reactive chlorine under similar conditions. Potential increases in the concentrations of other species (e.g. NOx, CO) will be closely monitored both experimentally and through gas phase homogeneous kinetic modeling.
This project, if successful, will demonstrate the feasibility of changing mercury speciation in coal combustion gases through the injection of small quantities of a hydrocarbon such as natural gas. This is expected to lead to an improved and relatively inexpensive process for mercury emissions reductions in coal fired utility boilers.
Approach:
Expected Results:
Publications and Presentations:
Publications have been submitted on this project: View all 6 publications for this project
Supplemental Keywords:
heavy metals, toxics, particulate matter, air, waste reduction, RFA, Air, Scientific Discipline, Waste, Toxics, Engineering, particulate matter, HAPS, Environmental Chemistry, 33/50, Engineering, Chemistry, & Physics, Incineration/Combustion, tropospheric ozone, air toxics, Environmental Monitoring, heavy metals, mercury & mercury compounds, Benzene (including benzene from gasoline), hydrocarbons, coal fired power plants, ion chromatography, hydrocarbon, combustion emissions, stratospheric ozone, flue gas emissions, mercury speciation, benzene, chemical composition, combustion, benzene emissions, combustion byproducts, ambient emissions, particulates, Mercury Compounds, coal combustion, ambient air, anthropogenic stresses, air pollution, anthropogenic stress, methaneProgress and Final Reports:
The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.