Brominated Sorbents for Small Cold-Side ESPs, Hot-Side ESPs and Fly Ash Use in Concrete
- Sorbent Technologies Corporation, Twinsburg, OH (United States)
This report summarizes the work conducted from September 16, 2005 through December 31, 2008 on the project entitled Brominated Sorbents for Small Cold-Side ESPs, Hot-Side ESPs and Fly Ash Use in Concrete . The project covers testing at three host sites: Progress Energy H.F. Lee Station and the Midwest Generation Crawford and Will County Stations. At Progress Energy Lee 1, parametric tests were performed both with and without SO{sub 3} injection in order to determine the impact on the mercury sorbent performance. In addition, tests were performed on the hot-side of the air preheater, before the SO{sub 3} is injected, with H-PAC sorbents designed for use at elevated temperatures. The BPAC injection provided the expected mercury removal when the SO{sub 3} injection was off. A mercury removal rate due to sorbent of more than 80% was achieved at an injection rate of 8 lb/MMacf. The operation with SO{sub 3} injection greatly reduced the mercury sorbent performance. An important learning came from the injection of H- on the hot-side of the air preheater before the SO{sub 3} injection location. The H-PAC injected in this manner appeared to be independent of the SO{sub 3} injection and provided better mercury removal than with injecting on the cold-side with SO{sub 3} injection. Consequently, one solution for plants like Lee, with SO{sub 3} injection, or plants with SO{sub 3} generated by the SCR catalyst, is to inject H-PAC on the hot-side before the SO{sub 3} is in the flue gas. Even better performance is possible by injecting on the cold-side without the SO{sub 3}, however. During the parametric testing, it was discovered that the injection of B-PAC (or H-PAC) was having a positive impact upon ESP performance. It was decided to perform a 3-day continuous injection run with B-PAC in order to determine whether Lee 1 could operate without SO{sub 3} injection. If the test proved positive, the continuous injection would continue as part of the long-term test. The injection of B-PAC did allow for the operation of Lee 1 without SO{sub 3} injection and the long-term test was conducted from March 8 through April 7, 2006. The total mercury removal for the 30-day long-term test, excluding the first day when SO{sub 3} was injected and the last day when a plain PAC was used, averaged 85%. The achievement of 85% Hg removal over the 30 days longterm test is another milestone in the history of achievement of the Albemarle Environmental f/k/a Sorbent Technologies Corporation B-PAC sorbent. A clear indication of the impact of B-PAC on opacity came at the end of the long-term test. It was hoped that Lee 1 could be operated for several days after the end of the long-term test. It took less than a day before the opacity began to increase. The discovery that B-PAC can improve ESP performance while capturing a large amount of mercury is another milestone for the B-PAC mercury sorbent. The parametric testing at the Midwest Generation Crawford Station was divided into two phases; the first using C-PAC, the concrete friendly sorbent, and the other using nonconcrete friendly materials. The first phase of the parametric tests was conducted before the long-term test. The second phase of the parametric testing was performed after the long-term test in order to avoid contaminating the fly ash containing the concrete friendly sorbents. The parametric test began with an injection rate of 1 lb/MMacf and, after a period to allow the mercury concentration to stabilize, the rate was increased to 3 lb/MMacf. The Hg removal for this test was about 60% due to sorbent and 69% total at the injection rate of 1 lb/MMacf and 80% due to sorbent and 84% total for the 3 lb/MMacf injection rate. The average total vapor phase mercury removal for the first 21 days of the long-term test was 82% at an injection rate of 4.6 lb/MMacf. The last nine days of the long-term test was used for testing different sorbents. A series of tests with different B-PAC sorbents followed the long-term test. All of the B-PAC, sorbents had similar mercury performance, achieving about 70%, 80% and 90% mercury removal due to sorbent at injection rates of 2, 4 and 6 lb/MMacf, respectively. It took 50% more of the Norit Hg LH sorbent to achieve 80% mercury removal than with the B-PAC, sorbents. The impact of C-PAC on the properties of concrete was investigated by Lafarge (the fly ash seller at Crawford), by Albemarle Environmental f/k/a Sorbent Technologies, and by Headwaters Resources, a project partner. The properties evaluated include the concrete air content, air stability, air distribution, setting time, and strength. C-PAC does not appear to deleteriously affect any of the important properties of concrete. It may even improve some properties. The finding that C-PAC does provide high levels of mercury removal without impacting the fly ash cement properties is a milestone in this project. At Crawford 7, the opacity would increase 3% to 5% over a period of hours from the time that the boiler first reached high load until the boiler load was reduced at night. For the parametric test, the opacity dropped when the C-PAC was turned on or when the injection rate was increased. As the long-term test progressed, the opacity for each successive period when at full load was lower than the previous one, so that at the end of the test the opacity at full load was averaging about 8% below that before the injection began. The finding that a gas-phase brominated mercury sorbent such as B-PAC or C-PAC can positively impact ESP performance is another milestone for this project. Midwest Generation Will County Unit 3 is equipped with a hot-side ESP and, thus, the injection temperature was about 700{degree}F. The high temperature version of C-PAC was used in the trial since it was desired to maintain the fly ash for sale for cement use. The duration of the testing at the Will County Station was reduced from that originally planned, due to a reduction in DOE funding. The biggest changes were the shortening of the baseline period and the switch from a long-term 30-day test to a short continuous injection run. The first phase of the parametric injection tests used only one sorbent (the high temperature version of C-PAC) but different injection lances. Regular lances were used in the first day of this phase of testing and the X-a-Lances on the second day. The injection of the high temperature version of C-PAC with regular injection lances provided mercury removal rates of about 30% and 45% due to sorbent at the injection rates of 3 and 5 lb/MMacf, respectively, based upon cold-side flow rates. This is very good performance considering that the injection temperature is about 700{degree]F at full load. However, the same sorbent at the same injection rates provided mercury removal rates of about 50% and 67% when the X-a-Lances were utilized. This is an improvement of about 50% relatively. As a result of these findings, the X-a-Lances were used for the rest of the test program. The standard H-PAC sorbent performed in the same manner as did the C-PAC. The performance of the Norit Hg LH sorbent was poor in this application. C-PAC did increase the foam index of the fly ash slightly, as was observed in the testing at the Midwest Generation Crawford Station, but the increase was small and predictable enough to allow for the use of the fly ash in cement. The impact of C-PAC on the properties of concrete was not investigated due to the limitation of funds. However, based upon past experience, it is highly likely that the concrete properties including the concrete air content, air stability, air distribution, setting time, and strength would have shown no impact based upon the minimal impact upon foam index.
- Research Organization:
- Sorbent Technologies Corporation, Twinsburg, OH (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- FC26-05NT42308
- OSTI ID:
- 1053787
- Country of Publication:
- United States
- Language:
- English
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