Non-Carbon Sorbents for Mercury Removal from Flue Gases

Non-Carbon Sorbents for MercuryRemoval from Flue GasesGökhan O. Alptekin, Ph.D., MikeCesario, Margarita DubovikPittsburgh Coal ConferencePittsburgh, PASeptember 26, 2006TDA Research Inc. • Wheat Ridge, CO 80033 • www.tda.com

TDA Research, Inc.• Privately Owned / Began operations in 1987• 67 full-time technical staff• Primarily chemists and engineers 60% with advanced degreesWheat Ridge Facility12345-12355 W 52 nd Avenue22,000 ft 2 offices and labsSynthetic Chemistry, Catalyst/SorbentSynthesis and Testing, Machine andElectronics Shops, SEM, TOF Mass SpecGolden Facility4663 Table Mountain Drive27,000 ft 2 offices and labs27 fume hoods, Synthetic Chemistry,Catalytic Process DevelopmentTDAR e s e a r c h

TDA ProductsC60 (Ih)The first commercial (1.3 ton/day)installation of TDA’s partial oxidationtechnology (SulfaTreat DO) atBakersfield, CA .TDA built and licensed all of the reactorsfor the Frontier Carbon Corp. 40 ton/yearfullerene factory in Kitakyushu, JapanConducting polymers availablethrough Sigma-AldrichTDAR e s e a r c h

Introduction• Mercury emissions from wasteincinerators and coal-fired utilities areunder scrutiny• Mercury is designated as a “hazardous airpollutant” in the Clean Air Act Amendmentof 1990 because of its harmful effects onhumans and wildlife• Hg is associated with serious neurologicaland developmental effects• A plausible link has been shownbetween the bioaccumulation of methylmercury in fish and the emissions fromman-made sources• EPA already regulates Hg emissions from waste incinerators• More than 40 ton Hg is captured per yearSugar• Clear Sky Initiative requires control of Hg emissions fromcoal-fired plants• 45% reduction by 2010Salt• 70% reduction by 2018TDAR e s e a r c h

Cost of Mercury Removal• A preferred option of removing mercury is dry sorbent injectionbecause of its low capital cost and it is easy to retrofit• Projected costs with existing abatement technologies usingactivated carbon sorbents can be as high as $55,000 per poundof mercury removed (based on combined operating andannualized capital costs)• $4 million per year for a 250 MW power plant (Sjostrom 1997)• The cost of mercury removal at 90% removal efficiency could costto Nation from $2 to $6 billion per year• In fact, all these estimates understate the costs• The state-of-the-art carbon sorbents degrade the quality of fly ashwhich is sold as a cement substitute• Fly ash that contains carbon is not suitable for use in cement– Based on 3000:1 injection ratio, the carbon content of the flyash can exceed 6%• If the fly ash is not salable for concrete, it has no use at all, andimmediately becomes an expensive waste problemTDAR e s e a r c h

Conventional TechnologiesPhysical adsorbents• Low adsorption capacity and mass transfer limitations– Activated carbons– non-specific adsorbents– weak affinity to Hg at flue gas temperatures– Chemically modified carbons– promoters include sulfur, iodine, chlorine (Korpiel, 1997)– better capacity but higher cost (impregnated carbons cost~$1/lb, 2 times higher than $0.50/lb untreated carbon)Mercury oxidation and scrubbing(by wet FGD)• Oxidized forms of mercury arereactive and easier to remove, butoxidizing mercury is difficultMass FractionEquilibrium CalculationsHgCl 2Hg 0HgO0 300 600 900 1200Temperature, °CSenior, Boole, Morency, et. al., PSI Final Report, 1997TDAR e s e a r c h

Difficulties in Hg OxidationOxidizingCatalystsWet ScrubberSCRCoalOxidizingChemicalsRef: Srivastava, 2005Residue• Difficulties in Hg oxidation• Lower oxides of mercury are instable• Strong oxidizers are only present in low concentrations in the fluegas (e.g., Cl 2, HCl and NO 2)• Addition of oxidizers is a possibility, but the control of their emissionswill be problematic• It is also economically infeasible to install wet scrubbers solely formercury control (only 20% of the coal-based power plants use wetscrubbers for FGD, Hargrove, 1997)TDAR e s e a r c h

TDA’s Approach• TDA Research, Inc. is developing a dry injection sorbent formercury removal from flue gases• Features of the sorbent• High capacity and good utilization• Low cost• Achieve greater than 90% mercury removal efficiency• Tolerance to possible flue gas contaminants (e.g., residual SO 2 ,NO x )• Easy disposal• Stabilize mercury permanently (no leaching of mercury)• Does not alter properties of the fly ashTDAR e s e a r c h

Apparatus and Test ConditionsTypical Gas Composition(wet basis)Component Vol%CO 2 10.0%H 2 O 8.0%N 2 79.0%O 2 2.0%SO 2 10-300 ppmNOx 10-50 ppmHg Inlet= 0.01-0.2 mg/m 3Temperature = 100-320 o CPressure= 1-2 psigGHSV= 10,000 – 2,000,000 h -1• 80-150 µm sorbent particles are used in a fixed-bed reactor• All system components are Pyrex or Teflon to minimize mercury amalgamation• Mercury is introduced using permeation tubes• Tested samples are sent to an independent lab for chemical analysis (ICP-AA) toconfirm measured Hg absorption capacityTDAR e s e a r c h

Schematic of the Test SystemTDAR e s e a r c h

Typical Test Profile0.12T= 140 o C, Hg Inlet Conc.= 0.12 mg/m 3 , GHSV= 180,000 h -1Hg Absorbed Hg = 0.172 = mg, (0.108 wt% wt% loading) loading) - (1085- (1085 micro g micro Hg / g Sorbent) g Hg / g Sorbent)FeedAnalysisFeedAnalysis0.09BreakthroughHg Concentration, mg/m 30.060.030.000 500 1000 1500 2000 2500Run Time (min)• Feed analysis through [O2] a reactor Absorption Started by-pass Absorbtion is Over: performed Start of Regeneration in most mg/m3 cases Hg at thebeginning, in the middle and at the end of each test to ensure stable Hg inletconcentrationTDAR e s e a r c h

Sorbent Performance at High Temperature40Hg Inlet= 80 µg/m 3 , Simulated Flue Gas, GHSV= 120,000 h -13530----- 618-90A, T= 245 o C, GHSV= 120,000 h -1 , Hg Inlet= 80 ug/m 3 , Capacity @ breakthrough = 341 ug/g----- 618-90A, T= 165 o C, GHSV= 120,000 h -1 , Hg Inlet= 80 ug/m 3 , Capacity @ breakthrough = 2,833 ug/gHg Concentration (µg/m 3 )252015105T=245 o CT=165 o C00 1000 2000 3000 4000 5000 6000 7000 8000 9000Run Time (min)• We observed a high Hg capacity at 165 o C (0.29% wt.)• Hg capacity decreases at higher temperatures (at 245 o C, thesorbent achieved 0.034% wt.)TDAR e s e a r c h

Effect of Hg Inlet ConcentrationT= 245 o C, Hg Inlet= 20-80 µg/m 3 , Simulated Flue Gas, GHSV= 120,000 h -1403530----- 618-90A, T= 245 o C, GHSV= 120,000 h -1 , Hg Inlet= 80 ug/m 3 , Capacity @ breakthrough = 341 ug/g----- 618-90A, T= 245 o C, GHSV= 120,000 h -1 , Hg Inlet= 20 ug/m 3 , Capacity @ breakthrough = 152 ug/gHg Concentration (µg/m 3 )252015105Hg Inlet= 80µg/m 3 Hg Inlet= 20µg/m 300 600 1200 1800 2400 3000Run Time (min)• We observed a higher Hg capacity at higher Hg inlet• The sorbent achieved 341 µg/g and 152 µg/g at 80 and 20 µg/m 3 Hg inletconcentrationsTDAR e s e a r c h

Performance Comparison with AC SorbentsHg absorption capacity of AC sorbentsTest Site InformationMercury Capture, %Test SiteCoalParticulateControlACI TestResultsTest DurationPG&EBrayton Point,Unit 1Low-sulfur bituminous,Hg = 0.03 ppm,Cl = 2000-4000 ppmTwo ESPsin series94.5ACI for two 5-dayperiods; 10 lb/mmacfPG&ESalem Harbor,Unit 1Low-sulfur bituminous,Hg = 0.03-0.08 ppm,Cl = 206 ppmESP90ACI for one 4-dayperiod; 10 lb/mmacfWisconsinElectricPleasantPrairie, Unit 2Subbituminous,Hg = 0.11 ppm,Cl = 8 ppmESP66ACI for one 5-dayperiod; 11.3 lb/mmacfAlabamaPowerGaston, Unit 3Low-sulfur bituminous,Hg = 0.14 ppm,Cl =169 ppmESP +smallFFSource: Srivastava, 200590.6 (78)ACI for one 9-dayperiod; 1.5 lb/mmacf• AC sorbents requirements range from 1.5 to 11.3lb/MMacf• Bench-scale tests shows that TDA’s sorbent is capable of:• 0.3 lb/MMacf at T=165 o C• 4.1 lb/MMacf at T=245 o CTDAR e s e a r c h

Economic Feasibility• The major cost item in dry sorbent injection systems is the costof the sorbent• TDA estimates the cost of its sorbent cost around $1-2/lb• Although it costs more than AC ($0.5/lb) and is somewhat moreexpensive impregnated ACs (e.g. $1/lb Br-AC), TDA’s sorbent hashigher capacity than conventional sorbents especially at elevatedtemperatures• Key benefit is lower sorbent usage and the absence of carboncontamination of fly ash• As a result our sorbent has minimal impact on the propertiesof fly ash• Based on the fixed-bed test results, sorbent replacement cost canbe lowered to $1,000-$2,000/lb Hg• Even with the annualized cost of capital for the injection systemand cost of parasitic losses, it is possible to greatly reduce cost ofmercury removalTDAR e s e a r c h

Future Work• Once the screening is completed, the operating conditions will beoptimized• The impact of impurities in the flue gases needs to be determined• HCl and SO 3are of particular interest• The fate and stability of the mercury adsorbed on the sorbent has to bedetermined• Leachability studies• The impact of the non-carbon sorbent on fly ash properties needs to beassessed• The impact of the Hg system on the plant efficiency, operational flexibilityneeds to be assessed• The sorbent performance needs to be demonstrated at large-scale in arepresentative test• All data to date are limited to fixed-bed bench-scale testing, while thesorbent performance should be measured in injection mode• In collaboration with Apogee Scientific, Inc. the sorbent performance willbe demonstrated in the injection mode at Excel Energy’s Pawnee PowerPlantTDAR e s e a r c h

Acknowledgments• The funding for this work is provided by anEPA SBIR Phase II Grant (Contract No. EP-D-06-043) and DOE SBIR Phase I GrantTDAR e s e a r c h