# Evaluation of HCl Emissions from

Boilers Firing Low- Rank Coals

By James E. Staudt, PhD Andover Technology Partners 112 Tucker Farm Road North Andover, MA 01845 (978) 683 - 9599

November 11 , 2011

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**Background** The US EPA has finalized the Utility Boiler Air Toxics Rule, which establishes emissions limits for filterable PM, mercury, and HCl. This report will discuss an effort that Ando ver Technology Partners (ATP) has been involved in to calibrate the assumptions in EPA’s analysis of the impacts of the rule. This effort relate s to t he HCl emissions from sub bituminous and lignite fired units and the potential need for add on acid gas controls (e.g., DSI) on these units.

ATP has reviewed HCl emissions data to determine if there is reason to expect the need for add - on acid gas controls, such as dry sorbent injection (DSI) or other technologies to reduce HCl emissions at sub bituminous - and lignite -fired units . These low rank coals tend have lower chlorine content than bituminous coals and the ir fly ash tends to have higher natural alkalinity . Western subbituminous coal (such as that mined in the Powder River Basin and referred to as PRB coal) and lignite coal s conta in natural alkalinity in the form of non -glassy calcium oxide (CaO) and other alkaline and alkaline earth oxides. The resulting fly ash (classified as ‘Class C’ fly ash) has a natural pH of 9 and higher and the natural alkalinity can effectively neutralize much of the HCl in the flue gas stream prior to the primary control device. Eastern bituminous coals, by contrast, tend to produce fly ash with lower natural alkalinity. Though bituminous fly ash (classified as ‘Class F’ fly ash) may contain calcium, it tends to be present in a glassy matrix and unavailable for acid - base neutralization reactions. As a result of the fly ash neutralization , HCl emissions from many of the facilities firing low rank coals are likely to be low, and may be sufficiently low enou gh to avoid the need for add - on acid gas controls . The ICR data was reviewed to examine HCl emissions and to evaluate the need for additional add - on controls .

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### Evaluation of HCl Emissions from Boilers Firing Low**- Rank Coals**  **Objectives** This effort was t o examine emissions data to characterize the HCl emissions from subbutuminous (mostly PRB) and lignite coals. Using the data in the March 16, 2011 Excel file MACT floor analysis for acid gas, there are 68 entries for subbituminous coals (this excludes blen ds of subbituminous and other fuels) and there are six entries for Lignite. **Analysis of All**  **Subbituminous Data** Table 1 shows the summary statistics for the 68 units listed as solely s ubbituminous fired. Most reported data was by electronic reporting (ERT) or using Part II protocol. Inferred fuel HCl is determined by multiplying the reported Fuel Cl by 36/35. Not every unit provided complete data. As a result, the sample sizes add up to less than 68 uni ts. In addition to reflecting standard measures (mean, median, standard deviation, and minimum), data from various sources is organized by quartiles. Representation of the data in quartiles rather than representing it in terms of average and standard devi ation is preferred because one or two data points with large measurement errors can throw off the average and the standard deviation so that these statistics become misleading. Using quartiles gives a clearer picture of what the distribution looks like. Any result greater than the proposed limit of 0.002 lb/MMBtu is highlighted in red As shown in the table , the maximum value in the third quartile of each sample is below the proposed limit of 0.002 lb/MMBtu. The median emission levels (also equal to the se cond quartile) are all below the emission limit. The reported HCl rates of 0.01 lb/MMBtu, as shown in the fourth quartile, are above the maximum inferred fuel HCl, suggesting measurement errors. The negative percent reduction also demonstrates that there are measurement errors in the data. The blue line in Figure 1 graphically represents the full data that is summarized in Table 1. As shown, 88% of the entries are at or below the limit for the rule. From this data, it can be reasonably assumed that th e majority of subbituminous coal fired units will meet the HCl emission standard without the need for additional controls. Table 2 shows similar statistics, but only for those units with only CS ESPs (i.e., no flue gas desulfurization technology such as we t scrubber or spray dryer and no fabric filters following a CS ESP). As shown, up to the third quartile is generally below the proposed limit, except when looking at the ETTS data. The fourth quartile shows emissions rates above the proposed limit. Whe n looking at the Hydrogen Chloride – min data more closely, only 2 of the 22 data points were above the proposed limit (see unit - specific data in the Appendix and Figure 1). This data is plotted as a red line in Figure 1. As a result, there is a chance that some facilities may require additional controls for HCl, but it is likely that the vast majority will not. The data for the full 22 units is shown in the Appendices.

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**Table 1**  **.** Fuel Chlorine and HCl Emissions Statistics for All 100% Subbituminous Fueled Boilers Reporting ICR **Fuel_Cl lb/MMBtu**  **Inferred fuel**

**HCl_lb/MMBtu Hydrogen** 

**Chloride -**  **ERT Hydrogen** 

**Chloride -**  **ETTS Hydrogen** 

**Chloride -**  **Part II Hydrogen** 

**Chloride -**  **min % red’n**  **average** 9.88E - 03 1.02E - 02 6.41E - 03 2.63E - 02 5.90E - 04 4.47E - 03 60.90% **median** 2.47E - 03 2.54E - 03 4.87E - 04 3.92E - 04 3.97E - 04 4.10E - 04 74.17% **standard dev** 2.02E - 02 2.08E - 02 2.33E - 02 6.79E - 02 6.51E - 04 1.91E - 02 47.69% **Min imum**  6.08E - 04 6.25E - 04 2.17E - 05 1.48E - 04 2.60E - 05 2.17E - 05 - 127.61% **Max -**  **1 st**  **quartile** 1.14E - 03 1.17E - 03 1.47E - 04 2.30E - 04 2.53E - 04 1.52E - 04 54.52% **Max -**  **2 nd**  **quartile** 2.47E - 03 2.54E - 03 4.87E - 04 3.92E - 04 3.97E - 04 4.10E - 04 74.17% **Max -**  **3 rd**  **quartile** 8.39E - 03 8.63E - 03 9.41E - 04 1.42E - 03 5.88E - 04 1.00E - 03 91.00% **Max -**  **4 th**  **quartile** 8.33E - 02 8.57E - 02 1.02E - 01 1.80E - 01 2.16E - 03 1.02E - 01 99.41% **Sample size** 32 32 37 7 20 56 56 ERT – reported by Electronic Reporting Tool as part of ICR ETTS – Collected with EPA’s Emission Tracking System Part II – reported using Part II Reporting Protocol prior to ICR 

### Table **2 .**  Fuel Chlorine and HCl Emissions Statistics for Subbituminous Fueled Boilers with CS ESPs Reporting ICR **Fuel_Cl lb/MMBtu**  **Inferred fuel**

**HCl_lb/MMBtu Hydrogen** 

**Chloride -**  **ERT Hydrogen** 

**Chloride -**  **ETTS Hydrogen** 

**Chloride -**  **Part II Hydrogen** 

**Chloride -**  **min %**  **red n**  **Average** 4.99E - 03 5.14E - 03 1.40E - 03 2.78E - 01 6.25E - 04 1.06E - 03 55.37% **Median** 1.90E - 03 1.96E - 03 6.65E - 04 2.78E - 01 4.02E - 04 6.21E - 04 62.74% **standard dev** 6.62E - 03 6.81E - 03 2.09E - 03 3.91E - 01 5.71E - 04 1.61E - 03 26.66% **Min imum**  8.35E - 04 8.59E - 04 1.62E - 04 1.18E - 03 3.00E - 04 1.62E - 04 - 12.67% **1 st**  **quartile** 1.34E - 03 1.38E - 03 6.16E - 04 1.39E - 01 3.20E - 04 3.98E - 04 51.49% **2 nd**  **quartile** 1.90E - 03 1.96E - 03 6.65E - 04 2.78E - 01 4.02E - 04 6.21E - 04 62.74% **3 rd**  **quartile** 6.67E - 03 6.86E - 03 1.10E - 03 4.16E - 01 5.75E - 04 8.88E - 04 67.94% **Max –**  **4 th**  **quartile** 2.18E - 02 2.24E - 02 7.88E - 03 5.54E - 01 2.16E - 03 7.88E - 03 82.93% **Sample size** 26 26 12 2 10 22 22 ERT – reported by Electronic Reporting Tool as part of ICR ETTS – Collected with EPA’s Emission Tracking System Part II – reported using Part II Reporting Protocol prior to ICR

### 5 www.AndoverTechnology.com **Figure 1.** HCl Emissions for Subbituminous Units with CS ESPs, from ICR data

(see Appendix for raw CS ESP data)

**Analysis of Lignite**  **Data** Because there were so few lignite data points, the data is displayed in Table 3 as in the database. As shown, generally high levels of HCl reduction are achieved with the lignite units, with all units reporting below the proposed limit. Every one of the units had a fabric filter, and some were scrubbed. This is a limited database however. Significantly, it does not include ND or MT lignite fired units.

**Table 3**  **.** ICR data for HCl emissions from Lignite Fired Units

**Plant Name state**  **Unit Number**  **Boiler_type Control**  **summary Fuel_Cl** 

**_lb/MMBtu Hydrogen** 

**Chloride -**  **ERT Hydrogen** 

**Chloride -**  **ETTS Hydrogen** 

**Chloride -**  **Part II Hydrogen** 

**Chloride -**  **min %** 

**reduction** Sandow Station TX 5A Fluidized bed firing FBC,

SNCR, ACI, DFGD, FF 9.24E - 05 2.12E - 05 2.12E - 05 Sandow Station TX 5B Fluidized bed firing FBC,

SNCR, ACI, DFGD, FF 3.02E - 05 2.55E - 05 2.55E - 05 Oak Grove TX OG1 Tangential firing SCR, ACI,

FF, WFGD 1.18E - 02 1.20E - 04 2.27E - 04 1.20E - 04 98.98% Red Hills Generating Facility MS 002 Fluidized bed firing FBC, FF 3.38E - 02 3.67E - 04 3.67E - 04 98.92% Red Hills Generating Facility MS 001 Fluidized bed firing FBC, FF 3.38E - 02 3.67E - 04 3.67E - 04 98.92% Monticello TX 2 Tangential firing SNCR, ACI,

FF, ESP 7.49E - 04 7.49E - 04 ERT – reported by Electronic Reporting Tool as part of ICR ETTS – Collected with EPA’s Emission Tracking System Part II – reported using Part II Reporting Protocol prior to ICR

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

1.0E - 05 1.0E - 04 1.0E - 03 1.0E - 02 1.0E - 01 1.0E+00**p e** **r c** **e n** **t a** **t o** **r b** **e l** **o w** **v a** **l u** **e**

**HCl, lb/MMBtu**all subbituminous subbituminous w/ CS ESP 

### Limit, 0.002 lb/MMBtu

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**Examination of fuel Database** The possible differences between ND or MT lignite and TX lignite were explored using the reported coal data from the 2001 ICR first quarter, which included over 10,000 coal samples. Figure 1 shows coal Cl content in lb/MMBtu (dry basis) , which was estimated from the reported Cl content in ppm and the reported coal heating value (dry basis) in Btu/lb. Wet basis values would be somewhat higher, depending upon moisture level. As expected, the highest Cl contents are in Illinois Basin and Northern Appalachian coals. Texas lignite showed a median concentration of 0.042 lb/MMBtu, which is in the same range as some of the lignite coals shown in Tabl e 3. The lowest Cl levels are in PRB, Montana - ND lignite and Western Bituminous coals. As a result, Montana and North Dakota lignite coal fired boilers would likely have lower HCl emissions rates than units firing Texas Lignite. **Figure 2**  **.** Distribution o f Cl Content for Different Coals

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80**P e** **r c** **e n** **t a** **t o** **r b** **e l** **o w** **C l** **c o** **n c** **e n** **t r** **a t** **i o** **n**

**Coal Cl Content, lb/MMbtu** Northern Appalachian Illinois Basin Powder River Basin Texas Lignite Western Bituminous Montana - ND Lignite



### Dry basis

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**Conclusions regarding HCl emissions from low rank coals**  The analysis of the ICR data and the fuel data shows that:

 The majority of subbituminous fueled units are expected to meet the proposed HCl limit as they are currently operating; however, some may not and therefore may choose to install add - on acid gas controls (such as DSI or other FGD technology) to account for fuel heterogeneity and to provide for fuel flexibility . So, while most subbituminous fire d units equipped with CS ESPs are likely to avoid the installation of add - on acid gas controls, there is some uncertainty about how many would choose to do so .  The data suggests that lignite -fired units are expected to comply with the proposed limit without any additional controls; however, no data was available for lignite units with only an ESP and the data that was available was limited in number. Review of c oal Cl data suggests that ND and MT lignite should be more likely than TX lignite to meet the proposed limit without additional controls due to the lower Cl concentration in the coal.

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# Appendices **HCl emissions from Subbituminous**  **Units with CS ESPs**

### 9 www.AndoverTechnology.com **Hydrogen Chloride**

**Plant Name state**  **Unit Number**  **Boiler**

**type MWe**  **Fuel_Cl**

**_lb/MM Btu**  **ERT -**  **ETTS Part**  **II min**  **% reduction** Whelan NE 1 Tang 84 1.62E - 04 1.62E -04 Montrose MO 2 Tang 188 3.00E -04 3.00E -04 Montrose MO 1 Tang 188 3.00E -04 3.00E -04 Montrose MO 3 Tang 188 3.00E -04 3.00E -04 Quindaro KS Unit 1 Cycl 77 3.80E -04 3.80E -04 Hudson NJ HUDU2 Wall 660 3.94E -04 3.94E -04 Nearman Creek KS N1 Wall 257 4.10E -04 4.10E -04 Newton IL 002 Tang 620 1.30E - 03 4.87E - 04 4.87E -04 62.52% Prairie Creek IA Unit 2 Stoker 221 5.00E -04 5.00E -04 Joliet 9 IL Cycl 326 1.20E - 03 5.41E - 04 5.41E -04 54.74% Prairie Creek IA Unit 1 Stoker 221 6.00E -04 6.00E -04 Joppa Steam IL 1 Tang 183 1.73E - 03 6.41E - 04 6.41E -04 62.97% Vermilion 002 Tang 110 6.41E - 04 6.41E -04 Vermilion 001 Tang 72 6.41E - 04 6.41E -04 Hoot Lake MN 2 Tang 61 2.24E - 03 6.88E - 04 6.88E -04 69.29% La Cygne KS 2 Wall 685 1.47E - 03 7.31E - 04 9.00E -04 7.31E -04 50.40% Waukegan IL WK8 Tang 383 8.35E - 04 9.41E - 04 9.41E -04 - 12.67% Pulliam WI 8 Wall 138 2.07E - 03 1.18E - 03 1.18E -03 42.97% Gallatin TN 2 Tang 300 9.13E - 03 1.56E - 03 5.54E - 01 1.56E -03 82.93% Bridgeport CT BHSEMU3 Tang 403 8.14E - 03 1.90E - 03 1.90E -03 76.68% Hudson NJ HUDU2 Wall 660 2.16E -03 2.16E -03 R.M. Schahfer IN R.M.0014 Cycl 468 2.18E - 02 7.88E - 03 7.88E -03 63.88% ERT – reported by Electronic Reporting Tool as part of ICR ETTS – Collected with EPA’s Emission Tracking System Part II – reported using Part II Reporting Protocol prior to ICR 

### D **ata for HCl emissions from Subbituminous**  **Units with CS ESPs**