Effect of the Devolatilization Process on PM₁₀ Formation during Oxy-fuel Combustion of a Typical Bituminous Coal

Abstract

The devolatilization process has important influence on the formation of PM 10 (particulate matter with an aerodynamic diameter of ≤10.0 μm) in oxy-fuel combustion of pulverized coal but has been explored little. A bituminous coal was devolatilized in either CO 2 or N 2 at 1573 K on a drop-tube furnace (DTF) to produce CO 2 -char and N 2 -char. Coal and its char samples were burned at 1573 K and in 29 vol % O 2 /71 vol % CO 2 . PM 10 was collected and segregated into 13 size fractions, which were subjected to subsequent analysis. The results show that the particle mass size distributions of PM 10 from coal and chars have similar peak and trough sizes, suggesting that the devolatilization process has insignificant influence on the major pathways of PM 10 formation. Three particle modes can be identified, i.e., ultrafine mode (<0.5 μm, PM 0.5 ), central mode (0.5− 2.5 μm, PM 0.5−2.5 ), and coarse mode (2.5−10 μm, PM 2.5−10 ). Coal combustion produces more PM 0.5 and PM 0.5−2.5 than char combustion, suggesting that the devolatilization process has important influence on the production of PM 0.5 and PM 0.5−2.5 . In contrast, the PM 2.5−10 yield is insignificantly affected by the devolatilization process under the investigated conditions. In addition, the combustion of CO 2 -char generates more PM 0.5 and PM 0.5−2.5 than that of N 2 -char, indicating that the devolatilization in CO 2 favors the formation of PM 0.5 and PM 0.5−2.5 .

Characteristics of Fly Ash under Oxy-Fuel Circulating Fluidized Bed Combustion

“…The lower alkaline metal was caused by the higher vaporization degrees under oxy-fuel combustion mode. A fast combustion rate and reduction atmosphere on the surface of the char particle may result in the higher vaporization degrees under oxy-fuel combustion mode. , The vaporization of alkaline metals was harmful for coal combustion, which form the PM2.5 emission and aggravate deposition and slag . In our study, the concentrations of alkaline earth metals in the fly ash were relatively higher.…”

Correlation of the Sub-micrometer Ash Yield from Pulverized Coal Combustion with Coal Ash Composition

“…It may be attributed to two reasons. First, in addition to the vaporization of refractory oxides/metals during char combustion, the release of organically bound metals associated with coal devolatilization may also play a substantial role in PM 1 formation. ,− , As the volatile matter content of the coal increases, therefore, more organically bound metals are likely to release during devolatilization to contribute in PM 1 formation. , Additionally, a coal with a higher rank index value generally produces the char with a higher reactivity during pulverized coal combustion . The resulting char may burn at a relatively higher temperature, favoring the vaporization of refractory oxides/metals to form more sub-micrometer ash.…”

“…The data used to examine the correlations between the PM 1 yield from pulverized coal combustion and the coal and ash composition were collected from the literature. ,− ,,,,,− ,− The criterion for data collection is the experimental work reporting the data, including the PM 1 yield, analytical composition of the parent coal, and elemental composition of coal inorganic matter or laboratory ash. Of the data, the yield of PM 1 or fine mode ash was determined by burning a pulverized coal in a laboratory combustor, mostly a DTF, under well-defined conditions.…”

Fouling and Slagging Characteristics during Co-combustion of Coal and Biomass

“…The sampling probe was water-cooled with diluted nitrogen gas at the probe tip to prevent any secondary reactions of the char and ash. The details of our DTF system can be found elsewhere (Wen et al 2013(Wen et al , 2014 To ensure complete burning and reduce the impact of the unburned carbon, the primary air and secondary air were heated to 200 °C before entering the furnace. For each experiment, the stable combustion lasted 1 h or more with a continuous-feeding system, and the on-line flue gas analyzer was used to monitor the contents of O2 and CO in the flue gas.…”