Journal
FUEL PROCESSING TECHNOLOGY
Volume 198, Issue -, Pages -Publisher
ELSEVIER
DOI: 10.1016/j.fuproc.2019.106234
Keywords
Zhundong coal; Initial fouling; Ash deposition; Layer structure
Funding
- National Key Research and Development Program of China [2018YFB0605105]
- National Natural Science Foundation of China [51676076]
- Analytical and Testing Centre at HUST
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Sodium, calcium, sulfur and chlorine in the flue gas of coal-fired boilers are the main cause of ash deposition/fouling in heat exchangers. However, there are still many debates on the mechanism of ash deposition/fouling due to the lack of direct micro evidence. This paper aims to clarify the initial deposition/fouling characteristics of a high-alkali coal by computer-controlled scanning electron microscopy (CC-SEM). The results demonstrate that temperature has an influence on the deposition/fouling compounds. The crystalline compounds in the samples at 900 degrees C were mainly CaSO4 and Ca2Al2SiO2, while the compounds in the samples at 500 degrees C were mainly NaCl. Sulfur had a significant adsorption effect on sodium and calcium at 900 degrees C, while chlorine had a significant adsorption effect on sodium at 500 degrees C. A 3-layer microstructure of deposition/fouling was found after the samples were stripped by molecular force. Additionally, deposition/fouling could be divided into three stages: the formation of sodium salt precursors, the growth of loose structural aluminosilicates and the adhesion of particulates on the surface. Sulfates, especially Na2SO4 and CaSO4 formed a precursor for the initial deposition/fouling of high-alkali coal.
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