Fuel Quality and MATS for Coal- Fired Plants: The Ripple Effect

Transcription

1 Fuel Quality and MATS for Coal- Fired Plants: The Ripple Effect Connie Senior & Greg Filippelli EUEC, February 3-5, 2014

2 ADA-ES Emission Control Products

3 Mercury & Air Toxics Compliance: Almost Here Mercury Study Report to Congress 1997 Clean Air Mercury Rule (later vacated) 2005 Various state rules for EGUs Mercury & Air Toxics Standards for EGUs ICI Boiler MACT, CISWI, Portland Cement Compliance Begins CAIR/CSAPR, Regional Haze Rule, too

4 The Ripple Effect You ve put in a DSI system for MATS compliance How are your future fuel choices going to affect performance and cost of operation?

5 Ground Rules Dry Sorbent Injection (DSI) means different things at different plants So let s make sure we know the ground rules WHY? HCl control (low-sulfur coal) SO 2 control (low-sulfur coal) SO 3 control to improve ACI system performance (highsulfur coal) Blue plume control during the heating season and SCR use

6 Ground Rules HOW? Dry Sorbent Injection (DSI) means different things at different plants So let s make sure we know the ground rules SO 3 Sodium bisulfite (SBS) Limestone Mg(OH) 2 MgO Hydrated lime - Ca(OH) 2 Trona sodium sesquicarbonate Sodium bicarbonate (SBC) HCl SO 2

7 Coal Quality: Sulfur % S (dry) ICR2 (1999) data Source: Quick, USGS

8 Coal Quality: Chlorine Cl (mg/kg, dry) < ICR2 (1999) data Source: Quick, USGS

9 Know Your Sorbent How will your sorbent respond to changes in coal composition? Hydrated lime % Control HCl SO 3 Used for HCl and SO 3 control Injected at relatively low temperatures SO 2 capture typically <20% Changes in coal sulfur have relatively: SO 2 Minor impact on HCl control Temperature Proportionate impact on SO 3 control Source: L Hoist, 2011

10 Know your sorbent How will your sorbent respond to changes in coal composition? Sodium Sorbents Effective for HCl and SO 3 control (varying utilization) Injected at relatively high ( 1500 o F) temperatures Changes in coal sulfur may have: Minor impact on HCl control Proportionate impact on SO 3 control Source: Solvay, 2012 Measurable impact on sorbent use rate

11 Ripples Will changing DSI rates affect anything else? ESP performance Bag cleaning rates Hg control with activated carbon injection (ACI)

12 Resistivity, ohm cm Ripples 1.E+12 1.E+11 1.E+10 1.E+09 Will changing DSI rates affect anything else, like PM emissions? 1.E Source: Mastropietro, 2010 Temperature, F 90% EBit/ 10% Ca(OH) 2 Eastern Bituminous 90% EBit/ 5% Ca(OH) 2 / 5% CaSO 4 Bituminous Coal Hydrated lime addition can increase fly ash resistivity (lab data) Reduction in SO 3 in flue gas also increases resistivity Depending on the size and condition of the ESP, use caution in increasing hydrated lime rates in response to higher sulfur coal

13 Ripples 1.E+13 Will changing DSI rates affect anything else, like PM emissions? Subbituminous Coal Resistivity, ohm cm 1.E+12 1.E+11 1.E+10 1.E Temperature, F Source: Mastropietro, % PRB/ 5% Ca(OH) 2 / 5% CaSO 4 90% PRB/ 10% Ca(OH) 2 PRB Hydrated lime might increase resistivity (lab data) Native resistivity is already so high that that flue gas conditioning system might already be in place, depending on size and condition of ESP More flue gas conditioning agent may be required

14 Resistivity, ohm cm Ripples 1.E+13 1.E+12 1.E+11 1.E+10 Will changing DSI rates affect anything else, like PM emissions? 1.E Temperature, F Source: Mastropietro, 2010 PRB 90% PRB/ 10% trona Subbituminous Coal Sodium sorbents tend to lower resistivity of fly ash (lab data) Sodium-based DSI could improve ESP performance, depending on size and condition of ESP

15 Ripples Will changing rates affect anything else, like the ACI system performance? Hg removal across ESP 100% 80% 60% 40% 20% 0% MRC Results: 10 lb/mmacf, injection upstream of APH APH Inlet: 627 F; APH outlet: 300 F (assume 1 ppm baseline SO 3 ) Brominated PAC #1 Brominated PAC # ppm SO 3 Source: Pollack, Air Quality VII, 2009 When DSI is used for SO 2 control, two potential effects on ACI for Hg control: High temperature (pre-aph) injection could remove halogens in flue gas before they have a chance to react with Hg: reduced effectiveness of nonbrominated PAC Increasing DSI sorbent also decreases SO 3 concentration: increased effectiveness of PAC

16 Ripples Will changing rates affect anything else, like the ACI system performance? Hg Emission, lb/tbtu % PRB (no DSI) % PRB (trona, 0.76 NSR) % PRB (sodium bicarbonate, 0.85 NSR) PAC Injection, lb/mmacf Source: Rogers et. al, 2013 EUEC Example: Mercury stack emissions at St. Clair Unit 3 100% PRB, with additional halogen added to coal Non-brominated PAC injected downstream of air preheater and trona or sodium bicarbonate injected upstream of air preheater Production of NO 2 reduced the effectiveness of PAC for Hg control

17 Example Objective: HCl control, target to achieve <0.002 lb/mmbtu Air Pollution Control: Cold-side-ESP Trona injection for HCl control 100% PRB Coal sulfur content, wt% 0.28 Coal chlorine content, wt% 0.01 Higher Heating Value, Btu/lb 8,960 SO 2 at Injection Location, lb/mmbtu Milled Trona, Expected Injection Rate, lb/hr ,085

18 Example Objective: HCl control, target to achieve <0.002 lb/mmbtu Air Pollution Control: Cold-side-ESP Trona injection for HCl control 100% PRB 85% PRB-15% Bituminous Coal sulfur content, wt% Coal chlorine content, wt% Higher Heating Value, Btu/lb 8,960 9,952 SO 2 at Injection Location, lb/mmbtu Milled Trona, Expected Injection Rate, lb/hr ,085 7,900

19 Put A Plan Together 1. Compile composition data for coals to be considered 2. Compile data on APCD operating constraints 3. Compile data on unit performance with respect to fuel options 4. Process coal data to assess corresponding expected sorbent consumption (alkaline and carbon sorbents) 5. Assess predicted sorbent loading impacts on APCD and emissions 6. Model optimized fuel composition ranges to meet operational and compliance objectives

20 Questions? If you have questions, please contact: