Control Technology Options for Boiler MACT and CISWI Compliance

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1 Control Technology Options for Boiler MACT and CISWI Compliance by Arun V. Someshwar, NCASI Northern Regional Meeting Thursday, May 9, 2013 Wausau, WI

2 Overview 12/12 Boiler MACT & CISWI Limits & Control Options for Particulate Matter, Dioxins & Furans, Carbon Monoxide, Hydrochloric Acid, and Mercury 12/12 CISWI Limits & Control Options for SO 2 and NO x Lead and Cadmium 2

3 BMACT/CISWI Limits for PM & Control Options BMACT & 0.11 lb/mmbtu for biomass stokers & FBCs; 0.04 lb/mmbtu for coal boilers CISWI 11 mg/dscm or ~0.01 lb/mmbtu for biomass and ~0.15 lb/mmbtu for coal ERUs Technologies for PM control are quite mature Meeting the 0.01 lb/mmbtu for biomass ERUs could be a challenge Note the high limits for coal ERUs 3

4 BMACT/CISWI Limits for PCDD/Fs & Control Options BMACT no limit only work practice, which involves annual tune-up of boiler CISWI 0.12 ng O 2 for biomass and ng O 2 for coal ERUs Both limits for ERUs should be easy to meet 4

5 CO Limits under Boiler MACT All Emissions in 3% O 2 Short-Term 30 day avg, CEM Stoker FBC PC Stoker FBC PC Biomass Coal

6 Meeting CO Limits under Boiler MACT Short-term CO limits for biomass stokers and FBCs (1500 and 470 ppm) should pose no concern However, these same limits for all 3 types of coal boilers (130 to 160 ppm) could be problematic A few biomass stokers equipped with CO CEMs may require optimization to meet the long-term 30 d avg CO limit of 720 ppm all the time Boiler optimization with air staging is the best solution to lower CO 6

7 When to Choose a CEM for CO Measurement? Gather sufficient short-term data on boiler, preferably under various operating conditions including conditions of fuel quality (wet, lower Btu, etc.) If these data consistently show ppm levels well below the short term limit, a CEM may not be necessary If the data show large variations, then calculate a 99 or 99.9% UPL to see if this value could potentially exceed the short-term limit If yes, explore the installation of a CEM since the 30-day averaging period will allow for boiler operations to be adjusted so a long-term avg limit can be met all the time 7

8 Some Observations on CO for Coal Boilers 3-hr avg limit for coal PC is 130 ppm, much better than the previously proposed limit of 41 ppm however, the 30 d avg CEM limit is 320 ppm - CEM limit looks far preferable Same is true for coal stokers - short-term limit is 160 ppm, and 30 d avg CEM limit is 340 ppm Similar is the case for coal FBCs - short-term limit is 130 ppm, whereas the 30 d avg CEM limit is 230 ppm 8

9 Advantages of Installing a CO CEM The components of parametric monitoring to comply with CO limits at all times are not settled, including limits for boiler O 2, locations for O 2 monitoring, applicability of O 2 trim systems for multi-fuel boilers, etc. these could hamper proper boiler operations Installing a CO CEM might avoid most of these issues CO CEMs are good indicators for gauging boiler efficiency and boiler instability CO CEMs could also be offered as useful indicators within the work practice guidelines for PCDD/Fs 9

10 Meeting CO Limits under CISWI Only short-term CO limits apply to biomass and coal ERUs no CEM-based limits 260 O 2 for biomass ERUs and 95 O 2 for coal ERUs The biomass ERU limit of 260 O 2 (or about 335 O 2 ) would be extremely difficult to meet if the ERU is of stoker design 10

11 BMACT/CISWI Limits for HCl & Control Options The 12/12 Boiler MACT HCl limit for existing and new solid fuel boilers is lb/mmbtu or between 16 and 17 O 2 - this limit can be met relatively easily by boilers equipped with some sort of wet scrubbing For boilers with dry PM controls (ESPs/FFs), HCl emissions can be controlled using dry sorbent injection (DSI) the sorbents include trona, sodium bicarbonate and hydrated lime The 12/12 CISWI MACT HCl limits for biomass and coal ERUs are 0.2 and 13 2,, resply. The biomass ERU limit is extremely challenging 11

12 Trona Injection How It Works Mill the trona to d90 <10 µm at which size it is colloidal and does not require mixing Inject the milled trona into ductwork at temperatures above 275ºF to achieve a residence time of 3.5 to 5 secs Injection prior to multiclone provides for improved mixing and better performance HCl and SO 2 removed by adsorption and reaction on the trona or bicarbonate surface with the PM removed in an ESP or FF 12

13 BMACT/CISWI Limits for Hg & Control Options BMACT Limit lb/tbtu for Solid Fuel Boilers CISWI Limits and O 2 for biomass and coal ERUs, resply., or 1.9 and 14.7 lb/tbtu Most FPI biomass boilers emit much less than 5.7 or even 1.9 lb Hg/TBtu - thus Hg control in such units may not be required Only coal boilers where the coal Hg content far exceeds the limit of 5.7 lb/tbtu will require Hg control 13

14 Control Options to Meet Coal Boiler Limit for Hg Units With Wet PM APCDs Wet particulate scrubber or wet ESP with activated carbon injection (ACI) will remove some Hg - however typically <50% removal is expected Improved removal with the presence of HCl Improved removal with halogen-impregnated carbon 14

15 Control Options to Meet Coal Boiler Limit for Hg Units With Dry PM APCDs ACI Upstream of Secondary Collector 90% Hg capture is possible with FF - same control used by MWCs ACI + ESP is also capable of high levels of control WESP Capture Less Well Understood Best removal is ACI with Baghouse 15

16 Meeting Cd and Pb Limits for Existing Biomass CISWI Units The biomass CISWI limits for Cd and Pb continue to be challenging and likely difficult to achieve in units equipped with wet scrubbers From an analysis of recent Boiler MACT-related test emissions data, it is seen that wood-fired boiler Pb and Cd emissions could far exceed these limits, especially for units equipped with wet scrubbers Also, other data show that Cd and Pb emissions do not correlate well with total PM emissions The only practical solution would be to dramatically reduce fine PM emissions, which is very difficult 16

17 Meeting SO 2 Limits for Biomass ERUs The SO 2 emission limit of 7.3 O 2 for existing and new biomass CISWI units is extremely stringent (note it is 650 ppm for coal ERUs) If biomass ERUs (>90% biomass) also burn any S- containing fuels such as coal, TDF, oil, or kraft pulp mill NCGs, they may have to install extremely efficient SO 2 removal systems Venturi scrubbers, even w/caustic addition, may be unable to meet such low levels all the time 17

18 Meeting NO x Limits for Biomass/Coal ERUs NO x emission limits for biomass and coal CISWI units are 290 and 340 O 2, resply. Both limits would be easy to meet In some cases where NO x levels are higher than these limits, a range of NO x control options such as combustion control, SNCR and SCR exist 18

19 Summary Observations The PM limit for biomass ERUs of 0.01 lb/mmbtu would be difficult to meet except with very efficient PM control Under Boiler MACT, only work practice rules apply for PCDD/F emissions, whereas the limit for coal and biomass ERUs should be met w/o any specific controls Boiler MACT HCl limits of 16 to 17 ppm should be easy to meet with wet scrubbers or with trona/bicarbonate injection for boilers with dry PM controls However, the extremely low limit of 0.2 ppm HCl for biomass ERUs would require non-detect HCl emissions 19

20 Summary Observations Hg limits for boilers are high enough (5.7 lb/tbtu) such that no Hg emissions control would be necessary However, the limit for biomass ERUs of 1.9 lb/tbtu may require Hg emissions control in certain instances Biomass ERUs would also have a difficult time meeting the limits for Cd and Pb, especially if they are equipped with wet scrubbers only Biomass ERUs will have an especially difficult time meeting the extremely low limit (7.3 ppm) for SO 2 Meeting NO x limits for CISWI units will not be a problem 20