Exposures to Coal Fly Ash During Maintenance of Air Cleaning Devices in Power Plants

Transcription

1 Exposures to Coal Fly Ash During Maintenance of Air Cleaning Devices in Power Plants

2 Harry J Beaulieu, PhD, CIH, CSP President & Senior Scientist Industrial Hygiene Resources Boise, ID Arlen W Siert, PhD, CIH, CSP, CHMM Xcel Energy Denver, CO Stephen C Woods, MS, CIH Xcel Energy Denver, CO

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4 Project Scope 10-year exposure assessment: Coal fired electrical power plants: 4 Bituminous Coal / 4 Sub-bituminous Coal Baghouse vs. electrostatic precipitator (ESP) exposures 1,540 air contaminant exposures collected 1,036 8-hr TWA exposures determined

5 Coal Types Bituminous coal: Higher BTU; Rocky Mountain & Illinois (burned by 45% of plants), and most expensive Sub-Bituminous coal: Lower BTU; Powder River Basin (PRB) of Wyoming & Montana (burned by 40% of plants), cheaper, but harder on equipment (more rock and grit, & slags the boiler tubes)

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11 Baghouse, Bag Changing Operations Removing the old, dirty bag, and dropping the dust. Very dusty! Replacement with a new bag.

12 Baghouse Cleaning: Over-Exposures by Coal Type (B and SB) % of Samples > OEL Air contaminant Total Dust Respirable Dust Respirable Quartz Aluminum Arsenic Barium Beryllium Calcium Chromium (Cr-VI) Cobalt Iron Magnesium Manganese Vanadium Bituminous Sub-Bituminous

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14 Total Particulates Fly Ash Exposures: Baghouse Bag Changing Bituminous Coal (Western Slope, Colorado) ACGIH TLV: 10 mg/m 3 (AL: 5 mg/m 3 ) Sub-bituminous Coal (Powder River Basin (PRB), WY) Measures 8hr-TWA-mg/m 3 Measures 8hr-TWA-mg/m 3 Samples 28 Samples 23 High 1427 High 3929 High/OEL 143 High/OEL 393 Largest Conc n 9790 Largest Conc n 8690 GM / AM 70 / 255 GM / AM 200 / 420 % n >AC< TLV 14% % n >AC< TLV 0% % n > TLV 86% % n > TLV 100% % n > 50xTLV 14% % n > 50xTLV 17%

15 Respirable Particulates Fly Ash Exposures: Baghouse Bag Changing Bituminous Coal (Western Slope, Colorado) ACGIH TLV: 3 mg/m 3 (AL: 1.5 mg/m 3 ) Sub-bituminous Coal (Powder River Basin (PRB), WY) Measures 8hr-TWA-mg/m 3 Measures 8hr-TWA-mg/m 3 Samples 33 Samples 12 High 732 High 91 High/OEL 244 High/OEL 30.3 Largest Conc n 5400 Largest Conc n 94 GM / AM 9.5 / 104 GM / AM 11.2 / 23.5 % n > AL<TLV 6% % n > AL<TLV 8.3% % n > TLV 58% % n > TLV 83% % n > 50xTLV 21% % n > 50xTLV 0%

16 Respirable Silica (Quartz) Fly Ash Exposures: Baghouse Bag Changing ACGIH TLV: 25 µg/m 3 (AL: 12.5 µg/m 3 ) OSHA PEL: 100 µg/m 3 Bituminous Coal (Western Slope, Colorado) Sub-bituminous Coal (Powder River Basin (PRB), WY) Measures 8hr-TWA-µg/m 3 Measures 8hr-TWA-µg/m 3 Samples 33 Samples 12 High 39,300 (5.4% Si) High 1,260 High / TLV 1,572X High/TLV 50.4X Largest Conc n 290,000 Largest Conc n 1,300 GM / AM 182 / 3774 GM / AM 69 / 220 % n > AL<TLV 15% % n > AL<TLV 17% % n > TLV 61% % n > TLV 67% % n > 50xTLV 33% % n > 50xTLV 8%

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18 Arsenic Fly Ash Exposures: Baghouse Bag Changing Bituminous Coal (Western Slope, Colorado) OSHA PEL: 10 µg/m 3 AL: 5 µg/m 3 Sub-bituminous Coal (Powder River Basin (PRB), WY) Measures 8hr-TWA-µg/m 3 Measures 8hr-TWA-µg/m 3 Samples 32 Samples 13 High 39 High 18.3 High/PEL 3.9 High/PEL 1.8 Largest Conc n 200 Largest Conc n 30 GM / AM 0.8 / 3.1 GM / AM 4.5 / 7.0 % n < AL 88% % n < AL 54% % n > AL<PEL 6% % n > AL<PEL 15% % n > PEL 6% % n > PEL 31%

19 Beryllium Fly Ash Exposures: Baghouse Bag Changing Bituminous Coal (Western Slope, Colorado) OSHA PEL: 2 µg/m 3 (AL: 1 µg/m 3 ) Sub-bituminous Coal (Powder River Basin (PRB), WY) Measures 8hr-TWA-µg/m 3 Measures 8hr-TWA-µg/m 3 Samples 15 Samples 14 High 1.2 High 13 High/OEL 0.6 High/OEL 6.5 Largest Conc n 2.9 Largest Conc n 28 GM / AM 0.04 / 0.2 GM / AM 1.0 / 2.4 % n < AL 93% % n < AL 50% % n > AL<PEL 7% % n > AL<PEL 14% % n > PEL 0% % n > PEL 36%

20 Calcium Oxide Fly Ash Exposures: Baghouse Bag Changing Bituminous Coal (Western Slope, Colorado) ACGIH TLV: 2 mg/m 3 (AL: 1 mg/m 3 ) Sub-bituminous Coal (Powder River Basin (PRB), WY) Measures 8hr-TWA-mg/m 3 Measures 8hr-TWA-mg/m 3 Samples 32 Samples 14 High 41 High 565 High/OEL 4 High/OEL 57 Largest Conc n 263 Largest Conc n 1250 GM / AM 3 / 8 GM / AM 13 / 112 % n > AL< TLV 13% % n > AL<TLV 14% % n > TLV 57% % n > TLV 86% % n > 50xTLV 0% % n > 50xTLV 29%

21 Chromium VI Fly Ash Exposures: Vacuuming Ash and Baghouse Bag Changing OSHA PEL: 5 µg/m 3 AL: 2.5 µg/m 3 Fly Ash Vacuuming Bituminous coal/ Sub-bituminous coal Baghouse Bag Changing Sub-bituminous coal Measures µg/m 3 Measures 8hr-TWA-µg/m 3 [AC] Samples 2 / 4 Samples 8 Largest Conc n 0.49 / 13 High 13 2 nd Highest 0.38 / 8.2 High/PEL 2.6 Median 0.44 / 8.1 Largest Conc n 27 % [AC n] >PEL 0 / 75 GM / AM 3.6 / 4.6 Bulk Ash-Bit Bulk Ash-Sub-Bit % n < AL 25% 3.2 ppm 49 ppm % n > AL<PEL 50% 1.7 ppm 29 ppm % n > PEL 25%

22 Cobalt Fly Ash Exposures: Baghouse Bag Changing Bituminous Coal (Western Slope, Colorado) ACGIH TLV: 20 µg/m 3 (AL: 10 µg/m 3 ) Sub-bituminous Coal (Powder River Basin (PRB), WY) Measures 8hr-TWA-µg/m 3 Measures 8hr-TWA-µg/m 3 Samples 10 Samples 9 High 3 High 89 High/OEL 0.15 High/OEL 4.5 Largest Conc n 7.9 Largest Conc n 197 GM / AM 0.13 / 0.61 GM / AM 0.9 / 13.8 % n < AL 100% % n < AL 67% % n > AL 0% % n > AL 22% % n > PEL 0% % n > PEL 11%

23 Manganese Fly Ash Exposures: Baghouse Bag Changing Bituminous Coal (Western Slope, Colorado) ACGIH TLV: 0.2 mg/m 3 (AL: 0.1 mg/m 3 ) Sub-bituminous Coal (Powder River Basin (PRB), WY) Measures 8hr-TWA-mg/m 3 Measures 8hr-TWA-mg/m 3 Samples 30 Samples 14 High 0.07 High 0.56 High/TLV 0.35 High/TLV 2.8 Largest Conc n 0.49 Largest Conc n 1.48 GM / AM / GM / AM / 0.15 % n < AL 100% % n < AL 71% % n > AL 0% % n > AL 7% % n > TLV 0% % n > TLV 21%

24 ESP-Shoveling Fly Ash Dust from the Shelves

25 ESP Cleaning: Over-Exposures of Bituminous Coal % of Samples > OEL Air Contaminant Total Particulate Respirable Particulate Respirable Quartz Aluminum Barium Calcium Iron Lead Weighted-Wire ESP (Buell); Shoveling Dust off Shelves Rigid Frame ESP (Wheelabrator); Erecting Scaffolding, Pre-wash down

26 ESP Cleaning: Over-Exposures of Bituminous Coal Largest Exposures (mg/m3, or ug/m3*) Air Contaminant Total Particulate Respirable Particulate Respirable Quartz* Aluminum Barium Calcium Iron Lead* Weighted-Wire ESP (Buell); Shoveling Dust off Shelves Rigid Frame ESP (Wheelabrator); Erecting Scaffolding, Pre-wash down

27 Conclusions Cleaning of air pollution control devices results in extremely dusty exposures to maintenance workers. Quartz-bearing dust, and numerous metals Exposures affected by type of coal burned Bituminous Greater exposure to quartz (via bulks) Quartz content % Sub-bituminous Smaller exposures to quartz Quartz content % Greater metal exposures (e.g., Cr-VI 10X > Bituminous)

28 Conclusions Unique work practices results in excessive exposures in baghouses Shaking & dropping bags: High exposures Pulley method, of gently breaking ash cake, & then lowering the bags: Lower exposures

29 Recommendations Baghouse exposure reduction controls Inspect bags more frequently, replace promptly when leaks detected Lower and raise bags via pulley in lieu of shaking bags to break up ash cake in a dirty compartment Remove bags via pulley in lieu of dropping to floor in dirty compartment

30 Recommendations ESP cleaning exposure reduction controls Increase cleaning frequency as outages allow

31 Recommendations Respiratory protection, PPE, hygiene requirements Minimum level of protection should be fullface, powered air purifying respirators (PAPR) with HEPA filters Disposable protective clothing Wash hands and face prior to lunch and breaks, Shower at end of shift

32 Recommendations Hazard communication Plant workers not generally aware of fly ash inhalation hazards, & especially contract workers Communication of hazards & regulatory requirements will help: prompt companies to implement adequate exposure assessment and exposure reduction controls motivate workers to protect themselves

33 Future Studies Mercury exposure characterization Review environmental data, including stack emissions and ash characterization IH monitoring for mercury