IECM 12.0 beta User Manual > Modules Included with the IECM > Pulverized Coal (PC) Plant > SET PARAMETERS > Base Plant >

Furnace Factors

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Inputs for the furnace factors that affect the major flow rates and concentrations of the gas and solids streams are entered on the Furnace Factors parameter screen. This screen accepts inputs for the flue gas and ash products emitted from the boiler into the flue gas and ash streams. Factors in emissions include: incomplete combustion and thermodynamic equilibrium between gas species associated with the combustion products.

This screen's inputs are needed to calculate boiler efficiency and air pollutant emissions. The emission of carbon, ash, sulfur and nitrogen are specified by the United States Government's Environmental Protection Agency's (EPA) compilation of emission factors. Also included from the compilation are the incomplete transfer percentages of solid and gaseous forms of these substances.

This screen is available for all plant configurations.

The following parameters are provided:

•Percent Ash Entering Flue Gas Stream: The default values for this parameter are a function of the fuel and boiler types and are based on the AP-42 EPA emission factors. Ash not entering the flue gas stream is assumed to be removed as bottom ash. This is also referred to as the overhead ash fraction.

•Sulfur Retained in Flyash: This parameter gives the percent of total sulfur input to the boiler that is retained in the flyash stream of a coal-fired power plant. The default values are a function of the selected boiler type and the coal rank as specified by the AP-42 EPA compilation of emission factors.

•Percent of SOx as SO3: This parameter quantifies the sulfur species in the flue gas stream. Sulfur not converted to SO2 is assumed to be converted to SO3. The default value is based on emission factors derived by Southern Company* and are a function of the selected coal.

•Preheater SO3 Removal Efficiency: Sulfuric acid (H2SO4) is created downstream of the boiler by the reaction of SO3 with H2O. A percent of the sulfuric acid is condensed on particulates in the preheater and removed from the flue gas. This parameter specifies the amount of SO3 removed from the flue gas in the preheater as a function of the coal rank. The default value is taken from the removal efficiency reported in the literature (references are below). This efficiency then determines the mass of SO3 removed from the flue gas in the collector. For more information see also:

•Hardman, R; Stacy, R; Dismukes, E "Estimating Sulfuric Acid Aerosol Emissions from Coal-Fired Power Plants", US DoE-FETC Conference on Formation, Distribution, Impact and Fate of Sulfur Trioxide in Utility Flue Gas Streams 1998 (currently available at https://web.archive.org/web/20040307161115/http://www.netl.doe.gov/publications/proceedings/98/98fg/hardman.pdf )

•Rubin, E. S. "The Importance of Sulfur Trioxide for the Toxic Release Inventory", US DoE-FETC Conference on Formation, Distribution, Impact and Fate of Sulfur Trioxide in Utility Flue Gas Streams 1998 (currently available at https://web.archive.org/web/20030416143712/http://www.netl.doe.gov:80/publications/proceedings/98/98fg/rubin.pdf)

•Nitrogen Oxide Emission Rate: This parameter establishes the level of NOx emissions from the boiler. The default values reflect the AP-42 EPA emission factors. It is a function of boiler firing method and the coal rank.

•Percent of NOx as NO: This parameter establishes the level of nitric oxide (NO) in the flue gas stream. The remainder of the total NOx emissions is assumed to be nitrogen dioxide (NO2). The default parameters reflect the AP-42 EPA emission factors and are dependent on the fuel type.

•Concentration of Carbon in Collected Ash: This parameter accounts for retention of carbon in the fly ash and bottom ash. The amount of carbon in the collected ash streams is typically known. It is used to calculate the total unburned carbon in the primary fuel, boiler efficiency and flue gas composition.

•Percent of Burned Carbon as CO: This parameter accounts for any incomplete combustion in the furnace, and is used to calculate boiler efficiency and flue gas composition. The remainder is assumed to be CO2 or unburned carbon.

* Hardman, R., R. Stacy, et al. (1998). Estimating Total Sulfuric Acid Emissions from Coal-Fired Power Plants, Southern Company Services.