To the Editor:
Regarding the March 2007 article entitled “Comparing Emissions: PC, CFB and IGCC” by Robynn Andracsek, Burns & McDonnell.
It appears the goal of the referenced article was to provide a comparison of actual emissions data for PC, CFB and IGCC technologies on a Lb/MMBTU basis. The article’s data was all derived from NOX, SO2, CO2, particulate matter and heat input data reported to the EPA. The IGCC plants mentioned are the Polk Power Station, Tampa, Fla.; and the Wabash River Power Station, Terre Haute, Ind.
We wish to point out that the reported heat input data used for the article does not result in an accurate emissions comparison. The reported heat input data for both of the IGCC plants is that of the syngas to the combustion turbine, not that of the feed coal to the plant as is the case for PC and CFB systems. For IGCC, 65 to 75 percent of the coal’s heating value is converted to syngas heating value while most of the remainder is converted to heat used to generate steam for the combined cycle’s steam turbine. Consequently, all of the article’s IGCC emission rates (NOX, SO2, PM, and CO2 expressed on a Lb/MMBTU basis) are overstated by approximately 40 percent. This is a significant discrepancy which leads to erroneous conclusions about the relative emissions among the technologies.
Consistent heat input data must be used for an accurate emissions comparison. Note that if this is done, CO2 emissions (without carbon capture) would be identical on a fuel input basis for all technologies using the same fuel, since all the fuel’s carbon is converted to CO2 (excluding the small fraction which may be retained in the ash or slag). However, since the efficiency of IGCC units is typically better than existing PC units, the CO2 emissions per megawatt hour can be as much as 20 percent lower.
Mark J. Hornick
General Manager, Polk Power Station
Tampa Electric Company
Vice President – Power Production
Wabash Valley Power
Robynn Andracsek replies: Heat input data for the IGCC feed coal would provide a more accurate comparison, however this data is not measured on short term basis (hourly, daily). The data that is measured (weekly, monthly) is not publicly available or required to be reported; therefore, regrettably, a comparison using feed coal heat inputs cannot be made.
Since I’ve lived through most of the history of nuclear power, I can relate to those horror stories of infinite outages and NRC “ratchet” requirements after TMI (“Nuclear Power’s History Has Role in Its Future,” Power Engineering, March 2007).
One comment I do want to make about your article is that you seem to buy into the myth that TMI-2 caused the hiatus in nuclear plant construction in this country. That is not exactly true; while it certainly did not help the program, utilities had begun cancelling orders long before the accident ever happened. The real reason was that the industry had overprojected power demand for a number of years and suddenly realized that it did not need all the plants that were either on the boards or under construction at the time. President Ford projected during his administration that we would have over 1,000 nuclear plants by the turn of the century.
What is also not widely known is that coal-fired plants experienced the same kind of hiatus; it was just easier for them to pick up again once demand increased. Since those plants could pick up the load, there wasn’t a lot of incentive to rev up the nuclear industry until relatively recently.
Meanwhile, you made a good case in the article for how much the industry has improved. Now that the licensing process has been streamlined and economies of scale will be better utilized, there is a lot of promise. Even some of the old anti-nukes are realizing that we either will get on the train or be left at the station.
Mike Cohen, Senior Contract Administrator
Northrop Grumman Newport News
Good job on your “Nuclear Reactions” page (Power Engineering, March 2007) reminding us of the industry’s nuclear power up-rate successes. It brings to mind a giga-statistic side note to your column.
The contribution of the total of the up-rates (10 GWs) at the several U.S. nuclear plants to the nation’s grid and energy security is a story that needs to be expanded and unapologetically bragged about. The 10 GWs gained nationwide from the up-rates listed in the same article, when added to the 20 GW gained nationwide from the more efficient operation of the 100 existing plants (from 70 percent capacity factors in the 1970s to the 90 percent capacity factors in 2007) equate to 30 GW added to the grid over the past 30 years without building any new plants. This is the equivalent of 30 new, 1000 MWe nuclear power plants serving the needs of the nation without any environmental problems associated with new plant siting.
Our nuclear plant operating personnel are doing a fantastic job.
Power Engineering magazine welcomes letters from its readers. Send e-mail letters to firstname.lastname@example.org. Send surface mail letters to Letters to the Editor, Power Engineering, PennWell Publishing, 1421 S. Sheridan, Tulsa, OK 74112. Please include your name, title, company and a phone number or email address so we may contact you.