MID-YEAR TECHNICAL REPORT

December 1, 1997, through May 31, 1998

Project Title: CORRELATE COAL/SCRUBBER PARAMETERS WITH Hg

REMOVAL AND Hg SPECIES IN FLUE GAS

ICCI Project Number: 97-1/5.1A-8(2)

Principal Investigators: Matthew S. DeVito and W. A. Rosenhoover

CONSOL Inc., Research & Development

Other Investigators: Subhash B. Bhagwat, Illinois State Geological Survey

Project Manager: Ron Carty, ICCI

ABSTRACT

This project is a continuation of the ICCI project to correlate mercury (Hg) and acid gas (HCl and HF) removal data with coal properties and scrubber operating parameters for FGD-equipped utility boilers. The project team completed two field measurement programs as part of the Phase 1 project. The tests established the total Hg reductions of 60% to 70%. However, after including these data into the existing data base, there still are insufficient data to correlate Hg removal with coal/scrubber parameters. Because the data base on mercury and acid gas removal in scrubbers remains limited, the project team will determine the Hg removal at two additional boilers equipped with flue gas desulfurization processes firing Illinois coal. The Illinois State Geological Survey will incorporate these data with the Phase 1 data and statistically analyze the data and other existing data (from the U.S. DOE and EPRI air toxics assessment programs) to determine the correlation between coal properties, scrubber operating parameters, and mercury and acid gas removal. CONSOL will conduct the field sampling programs at the two additional test sites. The objectives of the field sampling program are:

1) to determine Hg and acid gas removal as a function of FGD operating parameters at two scrubbed boilers firing Illinois coal,

2) to utilize the state-of-the-art Hg sampling methods being developed by DOE, and

3) to characterize the fixated scrubber sludge and gypsum generated products in the wet SO₂ scrubber.

EXECUTIVE SUMMARY

CONSOL R&D and the Illinois State Geological Survey are continuing the ICCI Phase 1 program to: 1) determine the flue gas mercury (Hg) and acid gas (HCl and HF) removal at two additional Illinois-based coal-fired utilities equipped with wet FGD scrubbers; 2) to correlate mercury removal with coal properties and scrubber operating parameters; 3) utilize "state-of-the-art" flue gas speciation methods currently being developed by DOE and EPRI; and 4) characterize the FGD scrubber sludge.

In 1996, the project team contacted the owner/operators of all the scrubber-equipped boilers operating in Illinois. Four of the owners agreed to participate in the program. Two units were sampled in 1996-97. CONSOL will conduct a mercury and acid gas sampling program at two additional sites in June and July 1998. CONSOL has negotiated site access agreements with both test sites.

CONSOL conducted site surveys at both locations to identify site-specific sampling and safety requirements. A site-specific sampling plan is being prepared for each plant. The field sampling program will be conducted in June and July of this year. All Hg impinger chemical analyses will be completed within the EPA required time (25 days). The results will be tabulated, and material balances will be calculated for selected major elements (iron, silica, or calcium) and mercury. The Hg, HCl, and HF removal will be determined.

In the current program, the Illinois State Geological Survey (ISGS) has completed a literature search to identify all available trace element sampling data. The data base was searched to identify FGD-equipped boilers. The data set was evaluated to determine if the data met the project quality requirements (i.e., material balance closure or reproducibility). The data that passed these screens was correlated against coal properties (i.e., ash content, percent chloride, percent sulfur), mercury speciation in the flue gas (i.e., oxidized mercury, elemental mercury), and scrubber operating parameters (i.e., pH, L/G, percent oxidation). The literature search yielded limited useful information. Because of the data base limitations, a rigorous statistical analysis could not be completed. Therefore, additional FGD mercury removal information must be obtained. The data obtained from the 1996-1997 ICCI program and a previous program completed by CONSOL R&D were added to the existing data base. Data from the 1998 test program will be used to augment this database. Data from these two additional scrubbers would increase the size of the data base by about 40-50%. The project team also is negotiating with the U. S. Department of Energy (DOE) to gain access to draft data obtained at one additional site in 1996.

After reviewing the literature, it remains clear that the flue gas total mercury concentration and the oxidized/elemental mercury fractions cannot be reliably determined. The U.S. DOE, a project co-funder, is currently evaluating a new sampling train for these measurements. The project team, after consulting with the U.S. DOE, will use the state-of-the-art Ontario Hydro Method in this test program. This method has undergone rigorous pilot plant testing and is capable of providing flue gas Hg speciation.