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Alkali and alkaline earth metals (AAEM), especially sodium, make a great contribution to the formation of fine particulates during coal combustion. Extraction and loading through chemical methods have been widely used for coal pretreatment to change the occurrence and content of sodium but could not load intrinsic minerals. In this study, synthetic char was used as a mineral carrier to study the characteristic of fine particulate formation during coal combustion. The silica and alumina were added to synthetic char as intrinsic minerals to study the interaction between sodium and Si and Al compounds in coal. The results show that the inorganic water-soluble sodium is more likely to form stable fine particles, while organic sodium prefers to react with silica and alumina in the absence of chlorine. Chemical reactions and physical capture are two main ways for sodium capture by silica and alumina. The content of sodium captured through chemical reactions is 2.4 times that by the physical way.

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The control of fouling deposition on the main equipment has always been an important issue concerned by scientific research and industrial application. However, severe fouling deposits on the induced fan blade and the low-temperature economiser were found in a 1000MW coal-fired power plant with ultra-low emission. The deposit samples were collected and analyzed through X-ray diffraction spectrometer, X-ray fluorescence, elemental analyser and scanning electron microscope with energy dispersive spectrometers. The result shows that the deposits are mainly composed of tschermigite ((NH4)Al(SO4)2?12H2O), letovicite ((NH4)3H(SO4)2), calcium sulphate (CaSO4) and quartz (SiO2). The ammonium sulfate is the main component of the fouling deposits. It acts as an adhesive and makes an important contribution to the deposition. The analysis shows that the ammonia slip from denitrification system and the unreasonable temperature setting are the main reasons for fouling deposition. It is suggested that the high concentration of ammoniam slip at denitrification system and the rapid condensation of the sulphuric acid mist at heat exchanger should be paid more attention in coal-fire power plants.