[Emission Concentration and Characteristics of Particulate Matter and Water-Soluble Ions in Exhaust Gas of Typical Combustion Sources with Ultra-Low Emission].

A self-developed direct condensation sampling system and monitoring method for total particulate matter (TPM) in ultra-low-emission and high-humidity exhaust gas were applied to the emission monitoring of particulate matter in flue gas from three typical combustion sources with ultra-low emissions in Beijing. The emission levels and composition characteristics of particulate matter and water-soluble ions in the exhaust gas of typical combustion sources with ultra-low emissions were analyzed and evaluated. The interaction and influencing factors of filterable particulate matter (FPM) and condensable particulate matter (CPM) and their water-soluble ions were explored. The results showed that the emission concentration of FPM in the exhaust gas of the coal-fired boiler with ultra-low emissions was between 1.04 mg·m-3 and 1.11 mg·m-3 in standard smoke oxygen content, and that of TPM was between 3.82 mg·m-3 and 8.69 mg·m-3, which all met the national ultra-low emission limit (10 mg·m-3). However, the TPM emission concentration of the coal-fired power plant exceeded the emission limit of Beijing (5 mg·m-3). The emission concentrations of CPM and its total water-soluble ions from the coal-fired heating boiler were 3.05 mg·m-3 and 1.30 mg·m-3, respectively, which were significantly lower than those of the coal-fired power plant, and were related to the higher load and flue gas temperature of the coal-fired power plant. Furthermore, the emission concentrations of CPM and its total water-soluble ions from the coal-fired power plant boiler were 2.2 to 2.4 times and 1.7 to 2.2 times greater than those of the coal-fired heating boiler, respectively. The emission concentrations of TPM and its total water-soluble ions from the gas power plant were 1.99 mg·m-3 and 1.44 mg·m-3, respectively, which were significantly lower than those from the coal-fired boiler. CPM was the main form of particulate matter in the exhaust gas of the combustion source. The contribution of CPM to TPM in the ultra-low-emission boiler flue gas increased significantly, and increased with the increase in the flue gas temperature, ranging from 72.6% to 88.1% for the coal-fired boiler and 93.1% for the gas power plant. Total water-soluble ions made up 66.1% to 94.2% of the CPM. The flue gas temperature had a significant impact on the existing forms, removal efficiencies, and emission concentrations of particulate matter and water-soluble ions. SO42- was the main characteristic water-soluble ion of particulate matter in the coal-fired boiler, and its emission concentration ranged from 0.98 mg·m-3 to 1.18 mg·m-3, accounting for 27.7% to 49.6% of the total water-soluble ion emissions, which originated from flue gas desulfurization. F- was another characteristic water-soluble ion of particulate matter in the coal-fired power plant, and its emission concentration ranged from 1.91 mg·m-3 to 2.32 mg·m-3, accounting for 54.4% to 56.1% of the total water-soluble ion emissions, which might have been related to the high F content of fuel coal. NH4+ was the main characteristic water-soluble ion of particulate matter in the gas power plant, and its emission concentration was 0.92 mg·m-3, accounting for 64.2% of the total water-soluble ion emissions, which originated from the escape of NH3 in the process of selective catalytic reduction. The emission concentration of NH4+ was significantly higher than that of the coal-fired boiler; this might have been related to the synergistic removal effect of the gas-fired power plant, which lacked other purification facilities.

[Emission Characteristics of Water-Soluble Ions in Fumes of Coal Fired Boilers in Beijing].

Selecting coal fired boilers with typical flue gas desulfurization and dust extraction systems in Beijing as the study objects, the issues and characteristics of the water-soluble ions in fumes of coal fired boilers and theirs influence factors were analyzed and evaluated. The maximum mass concentration of total water-soluble ions in fumes of coal fired boilers in Beijing was 51.240 mg x m(-3) in the benchmark fume oxygen content, the minimum was 7.186 mg x m(-3), and the issues of the water-soluble ions were uncorrelated with the fume moisture content. SO4(2-) was the primary characteristic water-soluble ion for desulfurization reaction, and the rate of contribution of SO4(2-) in total water-soluble ions ranged from 63.8% to 81.0%. F- was another characteristic water-soluble ion in fumes of thermal power plant, and the rate of contribution of F- in total water-soluble ions ranged from 22.2% to 32.5%. The fume purification technologies significantly influenced the issues and the emission characteristics of water-soluble ions in fumes of coal fired boilers. Na+ was a characteristic water-soluble ion for the desulfurizer NaOH, NH4+ and NO3+ were characteristic for the desulfurizer NH4HCO3, and Mg2+ was characteristic for the desulfurizer MgO, but the Ca2+ emission was not increased by addition of the desulfurizer CaO or CaCO3 The concentrations of NH4+ and NO3- in fumes of thermal power plant were lower than those in fumes of industrial or heating coal fired boilers. The form of water-soluble ions was significantly correlated with fume temperature. The most water-soluble ions were in superfine state at higher fume temperature and were not easily captured by the filter membrane.

[Left lower first premolar with 3 root canals: a case report].

3 root canals were found when a left lower first premolar, which preoperative radiograph showing root canal variety, was treated and were verified by postoperative radiograph. The root canal variety of lower premolars should be paid more attention to prevent root canal from losing.