Boiler Briquette Coal versus Raw Coal: Part I—Stack Gas Emissions

ABSTRACT

Stack gas emissions were characterized for a steam-generating boiler commonly used in China. The boiler was tested when fired with a newly formulated boiler briquette coal (BB-coal) and when fired with conventional raw coal (R-coal). The stack gas emissions were analyzed to determine emission rates and emission factors and to develop chemical source profiles. A dilution source sampling system was used to collect PM on both Teflon membrane filters and quartz fiber filters. The Teflon filters were analyzed gravimetrically for PM₁₀ and PM_2.5 mass concentrations and by X-ray fluorescence (XRF) for trace elements. The quartz fiber filters were analyzed for organic carbon (OC) and elemental carbon (EC) using a thermal/optical reflectance technique. Sulfur dioxide was measured using the standard wet chemistry method. Carbon monoxide was measured using an Orsat combustion analyzer.

The emission rates of the R-coal combustion (in kg/hr), determined using the measured stack gas concentrations and the stack gas emission rates, were 0.74 for PM₁₀, 0.38 for PM₂₅, 20.7 for SO₂, and 6.8 for CO, while those of the BB-coal combustion were 0.95 for PM₁₀, 0.30 for PM_{2 5}, 7.5 for SO₂, and 5.3 for CO. The fuel-mass-based emission factors (in g/kg) of the R-coal, determined using the emission rates and the fuel burn rates, were 1.68 for PM₁₀, 0.87 for PM₂₅, 46.7 for SO₂, and 15 for CO, while those of the BB-coal were 2.51 for PM₁₀, 0.79 for PM_2.5, 19.9 for SO₂, and 14 for CO. The task-based emission factors (in g/ton steam generated) of the R-coal, determined using the fuel-mass-based emission factors and the coal/ steam conversion factors, were 0.23 for PM₁₀, 0.12 for PM_2.5, 6.4 for SO₂, and 2.0 for CO, while those of the BB-coal were 0.30 for PM₁₀, 0.094 for PM_2.5, 2.4 for SO₂, and 1.7 for CO. PM₁₀ and PM_2.5 elemental compositions are also presented for both types of coal tested in the study.