Formation of Submicron Particulates (PM1) from the Oxygen-Enriched Combustion of Dried Sewage Sludge and Their Properties
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- 作者：Lian Zhang ; Megumi Masui ; Hiroharu Mizukoshi ; Yoshihiko Ninomiya ; Chikao Kanaoka
- 刊名：Energy & Fuels
- 出版年：2007
- 出版时间：January 2007
- 年：2007
- 卷：21
- 期：1
- 页码：88 - 98
- 全文大小：858K
- 年卷期：v.21,no.1(January 2007)
- ISSN：1520-5029
文摘
The dried sewage sludges were pulverized and combusted in an oxygen-enriched atmosphere to investigatethe emission of particulate matter smaller than 1.0 
m (PM1). Combustions were conducted at 1200 
C in adrop tube furnace with the oxygen content varying from 10% to 30% and 50% in the gas atmosphere. Thecollected PM1 was characterized including its concentration, particle size distribution, and the size-dependenceof the elemental composition and chemical species. The results indicate that, after the complete combustion ofsludges, the PM1 formed accounts for about 1~7% on the basis of total ash, which is influenced significantlyby the oxygen content in the gas atmosphere as well as the sludge type. In general, because of the improvementon the temperature of char particles and their breakage, the amount of PM1 is increased exponentially with theincreasing of the oxygen content. With regard to PM1 formation mechanisms, the refractory elements withinit, including Si, Al, Ca, Fe, and Mg, undergo two pathways for their transformation: vaporization-condensationfor their presence in the particulates 
0.1 m (PM0.1) and direct liberation of the inherent fine minerals fortheir presence in those >0.1 m. Their modes of occurrence in raw sludge play an important role in thevaporization. At 10% oxygen content, decomposition of the organically bound fraction is the main waycontributing to their presence in PM0.1. With the oxygen content increases, more of the inorganic speciesvaporizes too. Direct liberation of the refractory metals is also determined positively by the oxygen content inthe gas atmosphere, which is due to the breakage of char particles at an elevated oxygen content. With regardto the volatile elements in PM1, including P, S, Na, K, Zn, Cl, and Mn, they were mainly generated by thevaporization-condensation mechanism. Vaporization of S, Cl, Na, and K is significantly obvious at 10%oxygen, and hence, sulfates and chlorides are favored. With the oxygen content increases, the vaporization ofP and Zn becomes significant. The amounts of Na and K are almost unchanged; meanwhile, S and Cl decreasesomewhat. Formation of the phosphates is facilitated, owing to the high partial pressure of P. A portion of Naand K is possibly captured by Al silicates. Zn is also possibly captured by apatite and iron oxide to form thecomplex compounds. The toxicity of these species needs a detailed evaluation.
m (PM1). Combustions were conducted at 1200 C in adrop tube furnace with the oxygen content varying from 10% to 30% and 50% in the gas atmosphere. Thecollected PM1 was characterized including its concentration, particle size distribution, and the size-dependenceof the elemental composition and chemical species. The results indicate that, after the complete combustion ofsludges, the PM1 formed accounts for about 1~7% on the basis of total ash, which is influenced significantlyby the oxygen content in the gas atmosphere as well as the sludge type. In general, because of the improvementon the temperature of char particles and their breakage, the amount of PM1 is increased exponentially with theincreasing of the oxygen content. With regard to PM1 formation mechanisms, the refractory elements withinit, including Si, Al, Ca, Fe, and Mg, undergo two pathways for their transformation: vaporization-condensationfor their presence in the particulates 0.1 m (PM0.1) and direct liberation of the inherent fine minerals fortheir presence in those >0.1 m. Their modes of occurrence in raw sludge play an important role in thevaporization. At 10% oxygen content, decomposition of the organically bound fraction is the main waycontributing to their presence in PM0.1. With the oxygen content increases, more of the inorganic speciesvaporizes too. Direct liberation of the refractory metals is also determined positively by the oxygen content inthe gas atmosphere, which is due to the breakage of char particles at an elevated oxygen content. With regardto the volatile elements in PM1, including P, S, Na, K, Zn, Cl, and Mn, they were mainly generated by thevaporization-condensation mechanism. Vaporization of S, Cl, Na, and K is significantly obvious at 10%oxygen, and hence, sulfates and chlorides are favored. With the oxygen content increases, the vaporization ofP and Zn becomes significant. The amounts of Na and K are almost unchanged; meanwhile, S and Cl decreasesomewhat. Formation of the phosphates is facilitated, owing to the high partial pressure of P. A portion of Naand K is possibly captured by Al silicates. Zn is also possibly captured by apatite and iron oxide to form thecomplex compounds. The toxicity of these species needs a detailed evaluation.