INTERIM FINAL TECHNICAL REPORT

July 1, 1996, through August 31, 1997

Project Title: THE ECONOMIC EVALUATION OF USING DEEPLY CLEANED COAL IN PC UTILITY BOILERS

ICCI Project Number: CRG27-1-96

Principal Investigator: David B. Kehoe, CQ Inc.

Other Investigators: John Molberg, Argonne National Laboratories David Akers, CQ Inc.

Project Manager: Dr. Ken Ho, ICCI

ABSTRACT

The purpose of this project is to evaluate the economics of using "deeply" cleaned Illinois coal in PC utility boilers. Task 1 of the project is an initial literature search to collect recent work in quantifying the effects of ash content on power plant costs and performance. Subsequent to the assessment of the current capabilities for predicting these effects, calibrated computer models of Illinois Power's Wood River Units 4 and 5 are being constructed. Wood River was chosen because ash performance and cost effects are highly plant specific, the units were manageable size, some CQIM boiler modeling work had already been done, and Illinois Power had already undertaken a program of monitoring maintenance costs on these units. The model is being constructed using the Coal Quality Expert (CQE). The performance and costs of burning a low ash coal would be projected using this calibrated model, and compared to actual performance determined in a short full scale test burn. Long term projections of the effect of low ash content on mill internal components, burners, and boiler tube wear would be calculated from bench scale abrasion and erosion tests. The project team will use the resultant calibrated model to establish the power plant benefits of low ash coal. An advanced physical and an advanced chemical cleaning process have been selected and simulated, and laboratory-size samples are being produced. These samples will be analyzed, and the results used in CQE. The project team will then use the power plant benefits along with estimates of coal cleaning cost and estimates of the cost of flue gas treatment to determine the most cost effective compliance option.

In the current reporting period, the initial literature search has been completed. The one-week test burn of the Rend Lake coal was performed at Wood River power plant, and performance data for the plant using this low-ash coal was collected. Previous computer models of Wood River Units 4 and 5 were obtained from Illinois Power, modified, and incorporated into CQE. Raw coal has been received from the Rend Lake mine, but the delay of receipt of raw coal has caused delays in the progress of the coal cleaning evaluation. Coal washability analysis has been done, and a cleaning scheme formulated.

The project is behind schedule, largely because of delays in receiving raw coal from the Rend Lake mine. A five month, no cost extension to the project was granted by ICCI; the project will conclude in December of 1997.

EXECUTIVE SUMMARY

Complying with clean air legislation while remaining cost competitive is the largest challenge in the electric power industry today. Utilities are faced with a complex decision involving alternatives such as coal cleaning, post-combustion flue gas treatment, and allowance purchase. The best economic decision often involves speculation on future legislation (such as HAPs limits) and the future cost of sulfur allowances. For complying with existing legislation, most utilities have chosen to coal switch to cleaner coals. The effect of switching to these better quality coals has been difficult to determine, therefore, it has also been difficult to determine the economic trade-off between increased coal cost and power plant benefits.

Because of the sulfur content of Illinois coals, very few of these coals can be burned as-is, and either require extensive cleaning, flue-gas scrubbing or purchase of sulfur emission allowances. Very little of the Illinois basin coals can be cleaned to compliance levels using conventional technology. However, advanced technologies are becoming available that may allow far greater utilization of Illinois basin coals.

The economics of using cleaned Illinois coal as the primary compliance option depend on the cost of the cleaning technology and the benefit to the power plant of using the higher quality coal that results. This project directly addresses this question. By obtaining the best commercially available coal, and deeply cleaning it, this project will establish the lower boundary of advanced physical coal cleaning. In addition, this project will estimate the economics of advanced chemical cleaning as a compliance strategy.

Task 1 of the project is an initial literature search to collect recent work in quantifying the effects of ash content on power plant costs and performance. A series of conferences under EPRI sponsorship probably provide the best source of directly relevant information. These conferences have grown out of the EPRI interest in development of the CQIM and CQE. To date, four conferences have been held, most recently in 1995. In addition, an extensive literature on coal-fired plant operability exists that often identifies coal characteristics as they relate to operations. While more difficult to access and evaluate, this literature will be included in the survey.

Subsequent to the assessment of the current capabilities for predicting these effects, calibrated computer models of Illinois Power's Wood River Units 4 and 5 are being constructed. Wood River was chosen because ash performance and cost effects are highly plant specific, the units were of manageable size, some CQIM boiler modeling work had already been done, and Illinois Power had already undertaken a program of monitoring maintenance costs on these units. The model has been constructed using the Coal Quality Expert (CQE). This program was an essential extension and integration of R&D projects performed in the past under U.S. DOE and EPRI sponsorship and it expanded the available database of coal quality and power plant performance information. In addition to cosponsoring this project, EPRI contributed its background research, data, and computer models.

In Task 2 the performance and costs of burning a low ash coal will be projected using this calibrated model, and compared to actual performance determined in a short full scale test burn. Long term projections of the effect of low ash content on mill internal components, burners, and boiler tube wear would be calculated from bench scale abrasion and erosion tests. The project team will use the resultant calibrated model to establish the power plant benefits of low ash coal.

In Task 3 of this project, an advanced physical and an advanced chemical cleaning process have been selected and simulated, and laboratory-size samples will be produced. These samples will be analyzed, and the results used in CQE. The project team will then use the power plant benefits along with estimates of coal cleaning costs and estimates of the cost of flue gas treatment to determine the most cost effective compliance option. Raw coal was received from the Rend Lake mine, although the delay in receiving coal has caused delays in the progress of the coal cleaning evaluation. A review of advanced physical and chemical cleaning technologies was performed to select the best physical and the best chemical process for Illinois coal. The best physical process was identified as column flotation in combination with gravity separation and possibly grinding for liberation. This combination of technologies has been evaluated by researchers at Southern Illinois University. The best chemical process was identified as supercritical water leaching. This technology has been evaluated by the University of North Dakota. UND has been contacted to provide a cost estimate to clean the same pre-cleaned coal that will be sent to SIU.

In the current reporting period, the literature search was completed. The baseline maintenance costs at Wood River power plant were collected, and performance data for the plant using their normal coal blend were collected. Bench-scale tests of the coal from the low-ash coal test were performed at Babcock & Wilcox, and the Rend Lake coal was shown to be extremely low in coal and ash abrasiveness.

Previous computer models of Wood River Units 4 and 5 were obtained from Illinois Power, modified, and incorporated into CQE. Calibration of the computer models will began in January, after Illinois Power's data collection program on Unit 4 is complete, and a bug in CQE's maintenance calculation method was fixed.