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Potential mercury and hydrochloric acid emissions from wood fuels.

Abstract

The forest products industry has a large number of wood-fired boilers that will have to meet new EPA emission limits for mercury and hydrochloric acid (HCl). The emission standards are 9 lb./[10.sup.12] Btu heat input for mercury and 0.09 lb./[10.sup.6] Btu heat input for HCl, although boilers built after January 2003 have to meet more stringent limits of 3 lb./[10.sup.12] Btu for mercury and 0.02 lb./[10.sup.6] Btu for HCl. Demonstrating compliance with these limits requires fuel analysis and stack testing. However, stack testing is not necessary if it can be shown that the fuel has sufficiently low concentrations of mercury and chlorine such that emission limits would be met even if all the mercury is emitted and all the chlorine is emitted as HCl upon combustion of the fuel. Analysis of bark and stemwood samples collected at 30 locations across the United States gave averages of 1.42 lb./[10.sup.12] Btu and 0.28 lb./[10.sup.12] Btu for mercury in bark and stemwood. Based on these results, bark and stemwood fuels have potential mercury and HCl emissions considerably lower than the EPA limits for existing boilers.

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The U.S. Environmental Protection Agency (EPA) published Maximum Achievable Control Technology (MACT) emission standards for industrial boilers and process heaters on September 13,2004 (Federal Register 2004). These standards include specific emission limits for mercury and hydrochloric acid (HCl) for boilers that burn solid fuels such as coal or wood. The mercury limit is 9 lb./[10.sup.12] Btu heat input for existing units, and 3 lb./[10.sup.12] Btu for new units. The HCl limits are 0.09 lb./[10.sup.6] Btu for existing units, and 0.02 lb./[10.sup.6] Btu for new units.

Operators of industrial boilers subject to this standard must determine the amount of mercury and chlorine in the "worst-case" fuel, i.e., the fuel or fuel mixture with the highest anticipated level (in lb./[10.sup.6] Btu) of mercury and chlorine. Results from these analyses can then be used to estimate worst-case emissions, i.e., emissions assuming 100 percent pass through of the mercury in the fuel and assuming all the chlorine in the fuel is emitted as HCl. If the calculated emissions exceed the limits, then stack testing must be performed while the worst-case fuel is being burned in order to verify that actual emissions are not exceeding the limits.

Previously published studies indicate that mercury ranges from 2.7 ppb (Pang 1997) to 170 ppb (Huhn 1995) in bark and from 0.20 ppb (Pang 1997) to 37 ppb (Zhang et al. 1995) in stemwood. Published chlorine concentrations range from 56 ppm (NCASI 2001) to 190 ppm (DeGroot 1989) for bark and from 12 ppm (NCASI 1994) to 1148 ppm (DeGroot 1989) for stemwood.

This paper presents the findings of a study of the mercury and chlorine contents of bark and stemwood in the continental United States. A more comprehensive explanation of the study is available in NCASI Technical Bulletin 875 (2004).

Methodology

A total of 30 pulp and paper and wood products facilities participated in the study; see Figure 1 for locations. Each facility collected samples according to the requirements listed in Section 63.7521 (c)(1) of the final rule (Federal Register 2004). A portion of each sample was dried in a 60[degrees]C drying room and ground to 1 mm using a Wiley mill equipped with hardened steel knives. Eight bark samples and one stemwood sample from each facility were submitted for analysis.

[FIGURE 1 OMITTED]

[FIGURE 2 OMITTED]

Higher heating value was determined by ASTM D 2015 (2000). The rinsate from the BTU (higher heating value) determination was collected, and total chlorine was then determined as total chloride using ion chromatography by EPA method 300.0M (1993). This approach is procedurally equivalent to applying EPA Method 5050 (1994). For the determination of total mercury, stemwood and bark samples were digested and mercury determined in the digestate by EPA Method 1631E (2001, 2002). The potential emission rate for each sample was calculated by dividing the pollutant concentration by the heat content.

Results

In order to obtain some measure of the overall variability, blind duplicates of 10 percent of the samples were submitted to the laboratory. In addition, one sample was submitted (blind) five times, once with each batch of samples shipped to the laboratory. The mean relative percent difference (RPD) between the mercury duplicates was 18 [+ or -] 16 percent (n = 27), and the mean RPD between the chlorine duplicates was 14 [+ or -] 9 percent (n = 27). The relative standard deviation (RSD) obtained from the five blind replicate analyses was 5 percent for mercury and 14 percent for chlorine. These data indicate that grinding to 1 mm was sufficient to give homogeneous analytical samples.

Summaries of the sample results are provided in Table 1 and Figure 1 for mercury and in Table 2 and Figure 2 for chlorine.

Conclusions

The potential emissions of mercury and HCl from the barks and stemwoods sampled in this study are, in all cases, much lower than the emission limits for existing solid fuel boilers set by EPA in its recently issued MACT emission standards (9 lb. Hg/[10.sup.12] Btu heat input and 0.09 lb. HCl/[10.sup.6] Btu heat input). However, a few of the bark samples showed potential emissions higher than the EPA limits for new solid fuel boilers (3 lb. Hg/[10.sup.12] Btu and 0.02 lb. HCl/[10.sup.6] Btu).
Table 1.--Summary of mercury results.

 Bark
 Concentration Potential emissions
Facility code State Wood type Max. Min. Avg. Max. Min. Avg.
 (ppb, dry basis) (lb./[10.sup.12] Btu)

 CAM AL Mix 24.9 10.7 15.8 2.75 1.34 1.79
 SAS AL HW 10.8 4.9 8.0 1.28 0.61 0.97
 AAD AR Mix 11.6 6.2 8.8 1.33 0.75 1.05
 MAG AR SW 17.6 14.2 15.7 1.95 1.58 1.75
 YCT CA SW 30.4 13.7 19.3 3.48 1.47 2.10
 PFB FL SW 13.9 <1.0 8.4 1.50 <0.12 0.94
 PFI FL Mix 10.1 6.0 7.6 1.14 0.70 0.86
 AGI GA HW 14.5 8.3 11.8 1.71 1.03 1.44
 MIR ID SW 20.8 13.2 17.6 2.29 1.59 1.96
 WKM KY HW 11.1 5.5 9.0 1.41 0.70 1.12
 FLB LA SW 22.1 13.6 16.5 2.44 1.49 1.81
 JMI ME Mix 10.3 5.3 7.5 1.16 0.60 0.85
 LML ME HW 12.5 5.4 9.2 1.41 0.66 1.03
 EMM MI Mix 17.6 8.9 13.4 2.06 1.04 1.56
 MMT MI HW 6.7 4.3 5.6 0.80 0.51 0.66
 IMB MN HW 12.3 6.7 8.6 1.42 0.76 0.99
 NMG MS SW 14.7 2.2 11.1 1.69 0.26 1.23
 GNW SW NC 19.4 4.9 15.0 2.06 0.53 1.61
 GNF NY Mix 12.2 5.0 8.0 1.45 0.63 0.98
 MOB OR SW 22.4 9.9 17.9 2.43 1.13 1.92
 POG OR SW 37.4 22.2 29.2 4.01 2.43 3.14
 WOW OR SW 30.7 10.0 24.5 3.38 1.11 2.72
 SPG PA Mix 14.7 8.7 11.3 1.71 1.03 1.35
 BSW SC Mix 17.4 9.0 15.4 1.95 1.08 1.75
 SSP SD SW 12.4 8.4 9.6 1.34 0.91 1.04
 PTT TX SW 18.6 8.2 14.4 2.17 0.89 1.59
 CVM VA Mix 10.0 2.8 7.4 1.22 0.34 0.88
 KWB WA SW 15.0 8.6 11.4 1.63 0.97 1.23
 TWP WI HW 6.6 3.9 4.9 0.76 0.45 0.57
 MWG WV Mix 15.8 5.2 12.0 1.96 0.65 1.49
Overall 37.4 <1.0 12.5 4.01 <0.12 1.42

 Stemwood
Facility code Concentration Potential emissions
 (ppb, dry basis) (lb./[10.sup.12] Btu)

 CAM 3.6 0.43
 SAS 1.0 0.12
 AAD 3.6 0.43
 MAG 2.7 0.31
 YCT 1.4 0.17
 PFB 1.6 0.18
 PFI 2.0 0.24
 AGI 2.0 0.24
 MIR 3.0 0.35
 WKM 1.5 0.18
 FLB 3.2 0.35
 JMI 1.2 0.23
 LML 2.0 0.35
 EMM 2.9 0.33
 MMT 2.9 0.34
 IMB 2.2 0.27
 NMG 2.0 0.22
 GNW 2.1 0.24
 GNF 1.2 0.15
 MOB 1.6 0.19
 POG 2.5 0.29
 WOW 2.8 0.32
 SPG 4.0 0.46
 BSW 2.2 0.26
 SSP 1.5 0.18
 PTT 3.4 0.40
 CVM 3.2 0.38
 KWB 1.5 0.31
 TWP 2.1 0.24
 MWG 2.5 0.29
Overall 2.3 0.28

Table 2.--Summary of chlorine results.

 Bark
 Concentration Potential emissions
Facility code State Wood type Max. Min. Avg. Max. Min. Avg.
 (ppb, dry basis) (lb./[10.sup.6] Btu)

 CAM AL Mix 150 89 122 0.017 0.011 0.014
 SAS AL HW 81 53 68 0.010 0.007 0.009
 AAD AR Mix 111 71 92 0.014 0.009 0.011
 MAG AR SW 124 77 93 0.015 0.009 0.011
 YCT CA SW 210 56 97 0.024 0.006 0.011
 PFB FL SW 97 57 77 0.012 0.006 0.009
 PFI FL Mix 105 76 90 0.012 0.009 0.011
 AGI GA HW 99 64 84 0.012 0.008 0.011
 MIR ID SW 105 65 79 0.013 0.007 0.009
 WKM KY HW 121 70 86 0.016 0.009 0.011
 FLB LA SW 155 90 111 0.018 0.010 0.013
 JMI ME Mix 118 73 91 0.014 0.009 0.011
 LML ME HW 130 62 89 0.014 0.008 0.010
 EMM MI Mix 115 77 96 0.014 0.009 0.012
 MMT MI HW 110 <40 67 0.013 <0.006 0.008
 IMB MN HW 112 70 86 0.013 0.008 0.010
 NMG MS SW 134 68 105 0.015 0.008 0.012
 GNW NC SW 122 83 101 0.013 0.009 0.011
 GNF NY Mix 94 59 68 0.012 0.007 0.008
 MOB OR SW 273 46 93 0.034 0.005 0.010
 POG OR SW 99 71 90 0.011 0.008 0.010
 WOW OR SW 170 72 121 0.020 0.008 0.014
 SPG PA Mix 162 76 101 0.020 0.010 0.013
 BSW SC Mix 114 75 92 0.013 0.009 0.011
 SSP SD SW 96 60 71 0.011 0.007 0.008
 PTT TX SW 117 87 102 0.013 0.010 0.012
 CVM VA Mix 101 68 81 0.012 0.008 0.010
 KWB WA SW 87 68 77 0.010 0.008 0.009
 TWP WI HW 109 59 89 0.013 0.007 0.011
 MWG WV Mix 132 74 91 0.017 0.009 0.012
Overall 273 <40 90 0.034 0.005 0.011

 Stemwood
Facility code Concentration Potential emissions
 (ppb, dry basis) (lb./[10.sup.6] Btu)

 CAM 77 0.009
 SAS 53 0.006
 AAD 52 0.006
 MAG 65 0.008
 YCT 67 0.008
 PFB 51 0.006
 PFI 65 0.008
 AGI 72 0.009
 MIR 50 0.006
 WKM 52 0.006
 FLB 72 0.008
 JMI 60 0.007
 LML 64 0.008
 EMM 91 0.011
 MMT 53 0.006
 IMB 61 0.008
 NMG 54 0.006
 GNW 61 0.007
 GNF 57 0.007
 MOB 77 0.009
 POG 62 0.007
 WOW 57 0.007
 SPG 62 0.007
 BSW 62 0.008
 SSP 73 0.009
 PTT 57 0.007
 CVM 51 0.006
 KWB 57 0.007
 TWP 79 0.009
 MWG 58 0.007
Overall 62 0.007


Literature cited

American Society for Testing and Materials (ASTM). 2000. Standard test method for gross calorific value of coal and coke by the adiabatic bomb calorimeter. ASTM D 2015. ASTM, West Conshohocken, PA.

DeGroot, W.F. 1989. Methyl chloride as a gaseous tracer for wood burning? Environmental Sci. and Tech. 23(3):252.

Environmental Protection Agency (EPA). 1993. Methods for the determination of inorganic substances in environmental samples. Method 300.0M. EPA/600/R-93/100. EPA, Washington, DC.

________. 1994. Bomb preparation method for solid waste. Method 5050. SW-846. www.epa.gov/epaoswer/hazwaste/test/pdfs/5 050.pdf.

________. 2001. Appendix to Method 1631: Total mercury in tissue, sludge, sediment, and soil by acid digestion and BrCl oxidation. EPA/821/R-01/013. EPA, Washington, DC.

________. 2002. Mercury in water by oxidation, purge and trap, and cold vapor atomic flourescence spectrometry. Method 1631E. EPA/821/R-02/09. EPA, Washington, DC.

Federal Register. 2004. National emission standards for hazardous air pollutants for industrial, commercial, and institutional boilers and process heaters. Final rule. FR 69 (176) 55218-55286. www.gpoaccess.gov/fr/index.html.

Huhn, G., H. Schulz, H. Stark, R. Tolle, and G. Schuurmann. 1995. Evaluation of regional heavy metal deposition by multivariate analysis of element contents in pine tree barks. Water, Air and Soil Pollution 84(3-4): 367-383.

National Council for Air and Stream Improvement, Inc. (NCASI). 1994. A study of kraft recovery furnace hydrochloric acid emissions. Tech. Bull. No. 674. NCASI, New York.

________. 2001. Emissions of sulfuric, hydrochloric, and hydroflouric acids from combination bark boilers. Tech. Bull. No. 849. NCASI, Research Triangle Park, NC.

________. 2004. Nationwide evaluation of mercury and chlorine levels in bark and stemwood. Tech. Bull. No. 875. NCASI, Research Triangle Park, NC.

Pang, S. 1997. Mercury in wood and wood fuels. MS thesis. Dept. of Civil Engineering, Univ. of Minnesota, St. Paul, MN.

Zhang, L., Q. Jun-Long, and D. Planas. 1995. Mercury concentration in tree rings of black spruce (Picea Mariana Mill. B.S.P.) in boreal Quebec, Canada. Water, Air and Soil Pollut. 81(1-2): 163-173.

The authors are, respectively, Research Associate, NCASI, 402 SW 140th Terrace, Newberry, FL 32669; Vice President of Air Quality, NCASI, PO Box 13318, Research Triangle Park, NC 27709-2218; and Senior Research Chemist, NCASI, PO Box 458, Corvallis, OR 97333. The authors would like to thank Jeff Christian of Columbia Analytical Services in Kelso, WA, for his assistance with the analysis portion of the study and John Beebe of NCASI in Kalamazoo, MI, for providing the maps. This paper was received for publication in August 2004. Article No. 9919.
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Title Annotation:TECHNICAL NOTE
Author:Mentz, Karen; Pinkerton, John; Louch, Jeff
Publication:Forest Products Journal
Date:Feb 1, 2005
Words:2562
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