FINAL TECHNICAL REPORT

September 1, 1994 through January 16, 1996

Project Title: MOVING BED COPPER OXIDE DESULFURIZATION AND NO_X REMOVAL PROCESS DEVELOPMENT

ICCI Project Number: 94-1/2.1A-11

Principal Investigator:  Joseph N. Darguzas, Sargent & Lundy

Other Investigators:  Henry Pennline, U. S. Department of Energy; David G. Sloat, Sargent & Lundy; Jeri Penrose, Sargent & Lundy

Project Manager:  Franklin I. Honea, Illinois Clean Coal Institute

ABSTRACT

This project supports the development of a process which removes a majority of the acid rain-causing gases, sulfur dioxide and nitrogen oxides, from the flue gases generated by burning Illinois basin coal.  The process to be examined is the moving bed copper oxide system.  The moving bed offers lower pressure drops and reduced sorbent attrition compared to the fluidized bed version.  Research done on the fluidized bed version showed the copper oxide process to be promising, however the moving bed version had not been tested.

The experimental parametric portion of this project evaluates the chemical and physical aspects of the flue gas cleanup process.  The experimental work is being conducted as part of a Cooperative Research and Development Agreement (CRADA) between Sargent & Lundy, Foster Wheeler Development Corporation, Tecogen Incorporated, and the Department of Energy's (DOE) Pittsburgh Energy Technology Center (PETC).  The experiments serve to evaluate the ability of the copper oxide sorbent to remove the SO₂ and NO_x from a flue gas stream.  The tests evaluate the process in an environment similar to that at the backend of a pulverized coal steam generator.

Parameters of the absorption process and the copper oxide regeneration process being tested include:  Absorber temperature, Inlet SO₂ and NO_x concentration, Flue gas flow rate, Sorbent flow rate, Sorbent regeneration temperature, Sorbent regeneration residence time, and Regeneration gas flow rate.  In addition, the testing identifies the impact of fly ash from coal combustion on the above process characteristics as well as pressure drop and plugging potential of the moving bed.

The economic evaluation portion of this project identifies the cost and design issues which must be addressed to make the process available for commercial use when burning Illinois Coal.  An economic analyses of the process presents levelized costs which demonstrate the commercial viability of the advanced process.  The power plant sizes examined range between 100 and 500 megawatts of electrical output.  Coal sulfurs ranged from 2% to 5%.

EXECUTIVE SUMMARY

Public pressure and regulations including the Clean Air Act Amendments (CAAA) of 1990 are requiring coal-fired facilities to greatly reduce emissions of sulfur dioxide (SO₂) and nitrogen oxides (NO_x) gases.  With expected sulfur removal efficiencies of about 95%, flue gas desulfurization (FGD) with regenerable copper oxide sorbent promises to be an economical and attractive FGD option for many utilities.  In contrast with other available FGD options, copper oxide FGD does not generate waste products and does not preclude the use of Illinois coal as a fuel supply.

The copper oxide process captures SO₂ from flue gas and converts the SO₂ to either elemental solid sulfur or liquid sulfuric acid, both of which are salable by-products.  Therefore, there is no waste generated by the desulfurization process.  The copper oxide is not consumed in the process and thus there is no daily sorbent consumption cost which would otherwise contribute to operational costs and increase the marginal costs of electric production.  Another benefit of the copper oxide process is that it combines sulfur removal with the capability to catalytically reduce NO_x with ammonia, which can bring most facilities into compliance with the CAAA for both pollutants.

The chemical relationships involving the removal of sulfur compounds from coal combustions gases utilizing copper oxide have been known since the turn of the century.  The physical development issues which must be addressed at this time are the moving bed absorber and regeneration reaction characteristics.  The moving bed configuration greatly increases the probability of commercialization for the copper oxide process by the end of the decade.  The moving bed should reduce the flue gas pressure drop across the system and should also reduce the high rate of sorbent attrition that occurs in the fluidized bed configuration.  The experimental parametric testing will help define these unknown characteristics.

The U.S. Department of Energy's (DOE) Pittsburgh Energy Technology Center (PETC) has built a test facility and has performed experimental parametric tests of a pilot scale moving bed copper oxide process.  This test facility was used to help provide the parametric design information necessary to advance the moving bed copper oxide process closer to commercialization.  This ICCI study supported a cooperative research and development agreement (CRADA) with PETC to establish how the copper oxide system can be integrated into a commercial power plant design for burning high sulfur Illinois basin coals and help usher this promising technology to commercialization.  The members of the CRADA are Sargent & Lundy, Foster Wheeler Development Corporation, Tecogen, and the DOE-PETC.

The CRADA was used to obtain parametric test data for the moving bed copper oxide system and support the design of both a larger-scale demonstration facility and a full scale commercial plant.  Both of these demonstrations are planned as part of the DOE Low Emission Boiler System project (LEBS).  The parametric tests provided data which will be used to support the design of the larger-scale demonstration project at the Illinois Coal Development Park.

Initial tests were preformed while firing natural gas in the combustor and spiking the flue gas with SO₂ and NO.  Results from the initial testing have shown SO₂ removal efficiencies of 81%, 86%, 93%, and 96% respectively, for 3240 ppm, 3060 ppm, 2240 ppm, and 1500 ppm SO₂ levels.  A 2200 ppm SO₂ concentration is roughly equivalent to the concentration from combusting a 2.8% sulfur Illinois coal.  The results indicated no significant change in efficiencies within a temperature window of 700 and 800^oF.  The tests also show a NO_x removal efficiency on the order of 95%.

Tests were also performed while firing coal.  The initial attempt to clean the flue gas during coal firing demonstrated a pluggage problem that led to high pressure drop with the initial screen design used at PETC.  The CRADA team discussed and recommended a more open screen design to avoid the plugging.  The retrofit screen was tested and the screen pressure drop and pluggage problems did not return.  The more open screen design will be included in the larger-scale demonstration planned for the LEBS project.

The experimental parametric test results were used to develop designs for the copper oxide system equipment and an economic evaluation.  Levelized costs were projected for power plant sizes ranging from 100 to 500 MW and coal sulfurs ranging from 2% to 5%.  The levelized costs for a copper oxide system (7.35 mils/kWh) compare favorably with that of a limestone FGD system which includes a selective catalytic reduction system (8.68 mils/kWh).  Actual commercial costs for the copper oxide system may be even lower as the testing and process design becomes more refined.  The cost of the catalyst has the potential to be reduced by almost 20% if produced in large quantities.  The capital cost of the system could go down by 10 to 20% as the systems design parameters are optimized.  With these optimizations the levelized cost of the copper oxide system can potentially be reduced by 20%.