TECHNICAL REPORT

June 1, 1998, through August 31, 1998

Project Title: FURTHER DEVELOPMENT OF A COPPER OXIDE DESULFURIZATION AND NO_x REMOVAL SYSTEM

ICCI Project Number: 96-1/2.1A-5

Principal Investigator: David G. Sloat, Sargent & Lundy

Other Investigators: Joseph N. Darguzas, Sargent & Lundy; Raj Gaikwad, Sargent & Lundy; Jeri C. Penrose, Sargent & Lundy

Project Manager: Herman F. Feldmann, ICCI

ABSTRACT

This work supports continued development of the copper oxide process for controlling emissions of sulfur dioxide and nitrogen oxides from coal combustion. This advanced process utilizes a moving bed of regenerable sorbent to capture sulfur oxides from hot flue gas and recover the collected sulfur as a saleable by-product such as fertilizer, elemental sulfur, or sulfuric acid instead of producing large quantities of solid waste requiring disposal. At the same time, the sorbent catalytically reduces nitrogen oxides. Previous pilot studies have confirmed the process is capable of high removal efficiencies for both pollutants while firing high-sulfur Illinois coal; and previous economic studies have shown the process is an attractive alternative to conventional flue gas desulfurization technologies.

The current project builds on the successful pilot testing performed to date by continuing to test additional process parameters and includes testing at the Illinois Coal Development Park at a scale an order of magnitude larger than previous pilot scale work. This work is part of a total development program, and other copper oxide development activities are ongoing through the U.S. Department of Energy LEBS program.

The current study includes investigation of three areas:

1. Evaluation of byproduct generation options

2. Assessment of the possibility of PCB formation with copper oxide

3. Characterization of SO₃ removal efficiencies for copper oxide

In general, this work addresses technical issues peripheral to the main process which has been the focus of development efforts to date. These issues are necessary steps toward eventual commercial acceptance of the process, and concurrent work in these areas in parallel with ongoing process development will hasten commercialization of the technology.

EXECUTIVE SUMMARY

Any user that expects to fire Illinois Basin coal will either need to install an FGD system or, if a utility, acquire SO₂ allowances for the plant to operate from year-to-year or possibly both. FGD technology and other flue gas cleanup technologies have advanced since the first systems were installed in the 1970's. The advances have improved reliability and reduced costs.

The copper oxide process promises to be an economical and attractive flue gas desulfurization process for Illinois coals with medium to high sulfur content. The process uses a regenerable sorbent in a moving bed to simultaneously capture sulfur dioxide and catalytically reduce nitrogen oxides in flue gas. Regeneration of the sorbent then releases the sulfur dioxide in a concentrated stream for recovery. The sulfur dioxide is recovered as a byproduct such as fertilizer, elemental sulfur, or sulfuric acid for sale rather than generating large quantities of waste products as with some other FGD options.

The U.S. Department of Energy (DOE) Pittsburgh Energy Technology Center (PETC) has performed pilot scale parametric testing of the process which showed sulfur dioxide removals greater than 93% when firing a 2.6% sulfur Illinois coal. Over 90% NO_x removal has also been realized. A series of tests established performances for varying flue gas flow rates, sulfur concentrations, adsorber operating temperatures, and sorbent flow rates. Tests also defined sorbent regeneration parameters including regeneration temperatures, sorbent residence times, and regeneration gas flow rates. These results validated the process model and provided a basis for continued process development. Economic analysis indicated the process is competitive with other FGD technologies, particularly when NO_x removal is required.

The next step in the continued development of the copper oxide process is being performed in an ongoing pilot program at the Illinois Coal Development Park (ICDP) test facilities. In this program, existing facilities have been modified to combust either pulverized Illinois coal or fuel oil to produce flue gas for testing. A medium-scale copper oxide pilot plant has been constructed and will treat the flue gases from the test facility to remove SO₂ and NO_x. This pilot plant is an order of magnitude larger than the pilot plant at PETC and is one-tenth the size anticipated for commercial adsorber modules.

This project consists of three smaller studies:

1. Evaluation of byproduct generation options including more detailed characterization of the concentrated SO₂ stream from the process and engineering evaluation of conversion of the recovered SO₂ to sulfuric acid, elemental sulfur, or ammonium sulfate byproducts for sale

2. Examination of the potential for PCB formation in the copper oxide adsorption bed

3. Characterization of SO₃ removal efficiencies for copper oxide and determination of resulting acid dew points in the desulfurized flue gas.

To date, it has been necessary to make a number of modifications to the ICDP pilot plant in order to operate the process at conditions required for consistent regeneration of the sorbent. These modifications allow the regenerator to operate at a higher temperature and should improve steady-state sorbent performance. In addition, a byproduct recovery system installed to convert SO₂ in the regeneration acid gas to ammonium sulfate is being modified in order to work properly. These plant modifications have delayed the project and it is currently projected that experimental work in the pilot plant will provide the information required to complete this project by November 1998.

Characterization of SO₃ removal concurrent with SO₂ removal was performed at the PETC pilot plant. Measurement of inlet and outlet flue gas levels indicate that the copper oxide process also reduces SO₃ concentrations to less than 2 ppm. This results in a lowering of the clean flue gas acid dew point to approximately 250 degrees F, a 50 degree F reduction, and enables improved flue gas heat recovery.