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Particulate Matter Speciation

Coal-Fired Boiler PM10

Recommendations for modeling the particulate matter (PM10) speciation for seven types of Pulverized Coal-Fired (PC) boilers (Dry Bottom with Fabric Filter (FF); Dry Bottom with Electrostatic Precipitator (ESP); Dry Bottom with Flue Gas Desulfurization (FGD) system and ESP; Dry Bottom with FGD system and FF; Dry Bottom with Wet Scrubber (WS); Wet Bottom with FGD and ESP; Wet Bottom with ESP) are contained in the Excel workbooks available in the Highlights box. Also included are recommendations for two Cyclone Furnace1 boilers (PM10 controlled by ESPs and with and without FGD), four Spreader Stokers (with ESPs and with Multicyclones with and without flyash reinjection), and one Circulating Fluidized Bed (CFB) boiler. Instructions for using the workbooks are available below.

The derivation of these values is based on data from AP-42, Section 1.1 (Coal Combustion), as described below. Any individual source may deviate from these recommendations with the conditional approval of the Federal Land Manager (FLM) and the Regulatory Authority. Applicants seeking approval of an alternate speciation profile should submit stack testing data or other documentation supporting use of a different profile for the source in question. Where a different speciation profile is approved, the FLMs may request that the Regulatory Authority include emissions testing requirements in the source’s permit to confirm the validity of the alternate profile.

The filterable PM10 represents the emissions captured using the Method 5 "front-half" filter and the condensable PM10 represents the emissions captured using the Method 202 "back half" method. Filterable emissions consist of mostly fine and coarse ash from combustion, plus some unburned carbon from the fuel. In modern coal boiler systems, the fuel combustion should be nearly complete, so it can be assumed that most of the filterable PM10 will be inorganic flyash material.

Filterable PM10 mass is speciated as follows2. Filterable PM10 size speciation data are given in AP-42 Tables 1.1-6, 1.1-7, 1.1-8, and 1.1-9. Filterable mass sized 2.5 microns or less falls into the fine PM10 category when calculating light extinction with the CALPUFF system. Although most of the fine PM10 has a light extinction coefficient (Bext) of 1.0, the FLMs will assume that a nominal 3.7% of the fine PM10 emissions is unburned elemental carbon (Bext of 10) contained in the flyash3. The remainder of the filterable PM10 is coarse PM10 which has a light extinction coefficient (Bext) of 0.6.

For the condensable PM10 emissions4, AP-42 Table 1.1-5 separates the condensable PM10 into "inorganic" and "organic", with 80% of the condensable PM10 listed as inorganic and 20% listed as organic for PC boilers without FGDs and for Spreader Stoker boilers. The organic/inorganic breakout is believed to be based on the fraction of the condensable PM collected in the "solvent extractable" portion of Method 202. The apportionment of condensables between inorganic and organic components for boilers with FGDs was assumed to be the same 80/20 split as for PCs and spreader-stoker boilers without FGDs.

It is assumed that the "organic" condensable PM10 (CPM OR) is comprised of Secondary Organic Aerosols (SOA) with a light extinction coefficient of 4.0. The "inorganic" condensable PM10 (CPM IOR) is assumed comprised of sulfate (SO4) with a light extinction coefficient of 3.0 * f (RH), which accounts for the hygroscopic growth of sulfate aerosol in the presence of water vapor. This growth in particle size increases the light-scattering abilities of the sulfate aerosols5.

The recommended PM10 speciation should be applied to the PM10 emission rate estimated for the source. Ideally, both the "filterable" and "condensable" PM10 emissions would be provided. Also, for modeling of visibility impacts and 24-hour PM10 NAAQS and PSD increments, the PM10 emission rate input to CALPUFF should not represent a compliance averaging time of longer than 24-hours.

Using the Workbooks

PLEASE NOTE: These workbooks are not "recyclable". Depending upon how you use them, certain links may be broken that would be essential for a different application. Download the workbook, rename the workbook before beginning any calculations, and use a new workbook for each application.

It should also be noted that these workbooks were developed primarily for application to existing boilers for which there may be no explicit limits on pollutants such as H2SO4. However, for new boilers for which information may be available on multiple PM10 constituents, the workbooks can be modified to incorporate that additional data.

Select the Excel workbook that most closely resembles the boiler in question. The bold values in the magenta cells in row five of the spreadsheets are dummy values for coal quality (heating value, % sulfur, % ash)6, and heat input; the user should substitute actual values for coal quality. Because PC boilers are very sensitive to coal sulfur content, care should be taken to enter the correct value for % sulfur for these units. (You can ignore the f(RH) value which is included to test the effect of humidity on relative light extinction of the various species.) Except as indicated, the bold values in the body of the spreadsheets represent data that were entered directly and originated in either AP-42 Table 1.1-5, 1.1-6, 1.1-7, 1.1-8, and 1.1-9, or, in the case of the "3.7% of Fines" value for elemental carbon, from Table 6 of EPA’s January 2002 DRAFT "Catalog of Global Emissions Inventories and Emission Inventory Tools for Black Carbon". Unless entering "custom" values, do not change any value in a cell that is not both bold and colored magenta, orange, or yellow.

Based upon the emissions data available (total or filterable PM10 in lb/hr or lb/mmBtu), enter the emission rate into the appropriate (orange or yellow) cell with a corresponding dummy value. Corresponding emission rates for filterables and condensables will show up in the green cells, and emission rates for each species of condensables will appear in the blue cells–use these values. All condensable PM10 is considered to be submicron.

In order to separate filterable PM10emissions by size, the AP-42 Tables 1.1-5, 1.1-6, 1.1-7, 1.1-8, and 1.1-9 size fractions for the appropriate boiler and controls were used. The resulting charts show filterable PM10 emissions in lb/hr for size ranges modeled by CALPUFF. Match the proper species with the correct size range. The assumption is made that coarse PM10 is between 2.5 and 10 micron, and the corresponding emission rates are shown in the blue cells in the "PM Size" table. It is assumed that elemental carbon represents 3.7% of the fine PM10 and is all in the smallest CALPUFF size range (magenta cells). The remaining fine soil was assigned to the size range below 2.5 micron, and the results are shown in the darker blue cells (in g/sec). Please note that the smallest CALPUFF size range (magenta cells) has been split to show entries for fine soil and elemental carbon.

Neither the filterable PM10 speciation spreadsheet nor its associated charts will work unless the correct value is calculated for total filterable PM10 emissions (in lb/hr). There are several ways to do this, depending upon the type of emissions data initially input:

  • If you enter Total PM10 in lb/hr (into orange cell C27), everything is calculated automatically for you.
  • If you enter Total PM10 in lb/mmBtu (into orange cell C34), you need to make sure that you have also entered the heat input rate into (magenta) cell J5; then, everything is calculated automatically for you.
  • If you enter Filterable PM10 in lb/hr (into yellow cell E46), the spreadsheet will calculate Total PM10 (in lb/hr) in cell C46. Transfer that value to (orange) cell C27, and everything is calculated automatically for you.
  • If you enter Filterable PM10 in lb/mmBtu (into yellow cell E52), the spreadsheet will calculate Total PM10 (in cell C52) in lb/mmBtu. Transfer that value to (orange) cell C34, and everything is calculated automatically for you, provided that you have entered the heat input rate into (magenta) cell J5.

Or, you can enter the Filterable PM10 emission rate (in lb/hr) directly into (yellow) cell E26 of the "PM (Size)" table.

If you have questions, comments, or suggestions, please contact Don Shepherd at the National Park Service, Air Resources Division in Denver at 303-969-2075 or contact us through the Webmaster link at the bottom of the page.

updated on 03/29/2006  I   http://www.nature.nps.gov/air/permits/ect/ectCoalFiredBoiler.cfm   I  Email: Webmaster