Mercury Control Technology Development in the Laboratory: International HgCEM Research and Development Applications

Transcription

1 Mercury Control Technology Development in the Laboratory: International HgCEM Research and Development Applications presented by Eric M. Prestbo, Karl R. Wilber, Gabriel D. Eiras and Kai Zhang CEM Conference May-2014, Istanbul Turkey

2 BRIEF SYNOPSIS OF ADVANCES IN CEM-BASED MERCURY FLUE GAS MEASUREMENTS, STIMULATED BY - USA REGULATIONS - PERFORMANCE EVALUATIONS IN THE FIELD - TECHNICAL ADVANCES 2

3 U.S. EPA EGU MATS and Cement MACT U.S. EPA Regulation Existing Source Standard New Source Standard Deadline for Compliance Electric Generator 1.2 lbs./t-btu Unit MATS 0.35 lbs./t-btu April 2015 Portland Cement MACT 21 lbs./mm tons clinker September lbs./mm tons clinker Summary for EGUs, mercury concentration must be really low at ~ 170 parts per trillion (v/v) = 1.5 µg/m3 for EGUs 3

4 In the USA, HgCEM Equipment Trials in Real Flue Gas Determines Acceptance Because U.S EPA Regulations are based on performance standards, there is no need to have an equivalent MCERTS or TUV certification required in the USA for HgCEM equipment. Instead there are: EPA Field Trials in Independent Research Group Performance Testing (i.e. EERC) Field Trials by Power and Cement Companies Frequent Relative Accuracy Tests (RATA) 4

5 U.S. EPA Trials Summary Relative Accuracy must be <20% Most HgCEMs did poorly, except Tekran and Thermo. Only the Tekran 3300 CEM was able to pass all USEPA Trial performance measurements. 5

6 Joint EERC, EPRI & ICCI Project Determining the Accuracy of CMMs at Low Mercury Concentrations Figures adapted from Laudal et al., 2010 NOTE: The coal result bias for the Thermo Freedom System was resolved on a second test at EERC 6

7 Reliant Energy: HgCEM Accuracy - low Hg levels wet scrubber stack Sorbent Traps (avg) = 0.59 ug/m3 Tekran with M&C (avg) = 0.56 ug/m3 Slide courtesy of Eric Roland NOTE: Reliant Energy is now NRG 7

8 Field Trials: Lessons Learned about HgCEM System Design and Operation The coal flue gas matrix is very challenging Conversion of Hg2+to Hg0 quantitatively with longterm robustness is critical for success Quantitative transport of Hg species from probe to detector requires: Dilution with dry air High temperatures for Hg2+ - no cold spots Inert surface materials 8

9 MATRIX: Accurately Measuring pptv* Levels of Mercury in Coal Flue Gas 1 µg/m3 Hg = 112 parts per trillion (v/v) Accurate measurements requires understanding and managing the many potential mercury redox reactions with halogens, sulfur oxides and water in the gas phase and on surfaces Tekran R&D spent 1998 to 2003 understanding flue gas mercury reactions in the laboratory Detectors can only measure Hg0 9 SO2 HBr NOX 0 H O Hg 2 Fe HgCl2 Se HCl Hg0

10 CONVERSION: The Challenge of Mercury and Reactive Halogens Hg0 + reactive halogen is our friend and foe: Required for Hg analysis by HgCEMs and direct thermal method for sorbent traps (30B) Helpful for Hg control and used for HgCEM performance checks Bi-directional reaction affected by Temperature Catalytic surface reactions Gas and particle matrix Bi-directional reactions HgCl2 Hg0 + Cl2 For analysis, Hg0 formation must be quantitative with no back reaction Hg0 + Br2 HgBr2 For control, HgX2 formation and capture needs to be quantitative with no back reaction to minimize release of Hg0 Simplified chemistry for illustration purposes only 10

11 Tekran 3300Xi HgCEM Converter Flue Gas Converter/Conditioner (patented) Proprietary thermal converter material set at 700 degrees C DI water injected into tail of thermal converter to fix Hg0 from potential back reactions and eliminate interferences Gas is rapidly chilled, water condenses and removes reactive compounds 11

12 TRANSPORT: HgCEM design to minimize transport reactions and losses 30:1 dilution with dry zero air (can be higher) Filter element and related surfaces made with inert coatings and frequent system blowbacks (hourly) For umbilical lines, must use fluoropolymer tubing (PFA, FEP), heat to 180 C, no cold spots Thermal converter catalyst material is robust and surface chemistry has been characterized and is known Inject fresh DI water after the thermal converter and rapidly drop the temperature, to chemically fix Hg0 and prevent Hg(II) re-formation by back reactions with reactive halogens or other compounds (Tekran only) In effect, a mini wet-scrubber with chilled coalescing filter 12

13 MERCURY CONTROL RESEARCH, EQUIPMENT AND EXAMPLE RESULTS 13

14 Tekran 3300RS (Research Systems) 3300RS-Dual Probe 3300RS Upstream Injection 14

15 Schematic of Johnson Matthey Catalyst Testing Equipment Simulated Power Plant Exhaust gas Tekran 3300RS Dual Port system Heated Reactor with catalyst FTIR analysis SO3 analysis Reactor Outlet 15 Slide courtesy of Michael Nash at Johnson Matthey

16 Johnson Matthey 3300RS Dual Port System and Test Rig Configuration Slide courtesy of Michael Nash at Johnson Matthey 16

17 Example data from Johnson Matthey Conversion of Hg0 to Hg2+ across a catalyst Online measurement of flue gas components during simulated power plant conditions. Condition 1: a low halogen bituminous condition Condition 2: a high halogen bituminous condition Slide courtesy of Michael Nash at Johnson Matthey 17

18 Mercury Research Configuration at Shanghai Jiaotong University Tubular Furnace Sorbents Computer Oil Bath Tekran mercury analysis system Reactor and sorbent performance evaluation with controlled Hg source and Tekran 3300RS Unit Slide courtesy of Professor Yan NaiQiang at Shanghai Jiaotong University 18

19 Example Mercury Research Results from Shanghai Jiaotong University Conversion of Hg0 to Hg2+ Good mass balance Good recovery to zero Hg no memory effect Slide courtesy of Professor Yan NaiQiang at Shanghai Jiaotong University 19

20 U. of Ningbo-Nottingham Hg Control Technology Configuration with 3300-RS Slide courtesy of Dr. Tao Wu s Research Lab at the U. of Ningbo-Nottingham

21 Cormetech Micro-Reactor Schematic Mainly used for parametric studies of both fresh and deactivated catalyst The reactor is a fully automated and continuous system capable of injecting a wide variety of gaseous and aqueous species Capable of measuring DeNOx, SO2 oxidation, and Hg0 oxidation over a single layer Slide courtesy of Cormetech 21

22 Cormetech Reactor & Tekran 3300RS Unit This Tekran 3300RS was designed to provide known upstream input of Hg0 and Hg2+ using a custom injection module Installed in a vented enclosure 22 Slide courtesy of Cormetech

23 Cormetech Example of an Hg0 Trend for a Continuous Hg Test Reactor is fully automated, using pre-defined testing sequence and stability criteria Automated allows many factors to be tested Factors affecting Hg0 oxidation are temperature, AV, and Hg0, NH3, SO2, CO, HCl, and HBr concentrations Slide courtesy of Cormetech 23

24 Conclusions Full Speed Ahead for USA Hg Emission Regulations after long run of HgCEM equipment performance trials For research and monitoring, the HgCEM design must deal with the flue gas matrix, Hg2+to Hg0 conversion and transport challenges in order to get accurate results In the mercury control research laboratory, there are now custom HgCEM units to help develop and commercialize control technology 24