Formation and growth mechanisms of ultrafine particles in sludge-incineration flue gas

Abstract

Atmospheric particulate matter with diameter < 2.5 μm now makes up much of the air pollution in China, but it is the ultrafine particles (UFPs) with diameter < 90 nm that are of particular interest. This is because UFPs are strongly linked with human health for two reasons: they contain a variety of hazardous substances and they can deeply penetrate human respiratory systems. Therefore, scanning electron microscopy combined with X-ray dispersive energy spectrometry was used to characterize the morphology and surface texture, as well as the elemental composition of 60 UFPs. The UFPs was generated in a sewage sludge-incineration power plant in Zhejiang Province. This was done to determine the microstructure of the ultrafine particles and to follow the evolution of particle surface elemental composition with increasing particle size. Then, a comparison of the characteristic time for nucleation, condensation and coagulation was done to estimate the dominant mechanism. The results show that the UFPs have generally irregular shapes (cotton-like, irregular balls, sheets, etc.) and that they usually aggregate to form a mass. With increase in the size of a UFP, the mass fraction of the elements presents clearly changed: Na, K and Fe gradually decreased; while Ca, Si and Al, as well as the heavy metals Cu, Zn and Ni increased. Characteristic time estimation is a convenient and effective tool for identifying the predominant mechanisms during combustion. In this study, calculations of characteristic time were used to reveal a mechanism of vaporization, nucleation, condensation and coagulation, which drives the formation and growth of ultrafine particles.

Cadmium Stabilization by Sewage Sludge Incineration Ash

“…[21] Owing to the high content of aluminum and silicon, the residues from incineration of sewage sludge may be reused as ceramic raw materials in stabilizing cadmium-laden waste. [22][23][24][25] The following achievements can be made. Firstly, cadmium was incorporated in ceramic system with matrix rich in aluminum and silicon to achieve stabilization.…”

Desulfurization using limestone during sludge incineration in a fluidized bed furnace: Increased risk of particulate matter and heavy metal emissions

“…Coarse particles are mostly generated from the inorganic minerals by fragmentation and agglomeration, which can be captured by conventional bag filters or electrostatic precipitators [4] . Produced by coagulation and condensation, fine particles are often defined as submicron particles, which are more challenging to capture in conventional emission control systems and can be emitted to the atmosphere [5] [6] . In addition, those fine particles can contain many kinds of hazardous trace elements and can be inhaled into human lungs and be harmful to human health.…”