Study On The Mechanism Of Slagging And High Temperature Corrosion Of Coal-Combustion Boiler

The high temperature corrosion and slagging on heat exchange tubes of coal-fired boiler affect all phases of boiler design and operation. The problem is seriously in our country due to the varying of coal quality. The boiler capacity and heat efficiency of combustion are reduced by 20% and 2.5% respectively because of slagging. More than 80% coal-fired boilers are influenced by high temperature corrosion. So it's important to study the mechanism of slagging and high temperature corrosion.Several typical slagging and high-temperature corrosion samples were collected from some coal-fired power plants. The mineralogy, chemical composition, and microstructure of them were determined by X-ray diffraction spectrometry (XRD), X-ray fluorescence spectrometry (XRF), optical microscopy, and field scanning electron microscopy equipped with energy-dispersive X-ray spectrometry (FSEM-EDX), respectively. The pore size distribution of them were analyzed by a nitrogen adsorption specific surface area analyzer.The results show that, the mainly components of corrosion are iron sulfide and iron oxide. This indicates that the corrosion is a typical sulfide corrosion. The iron oxide content increase and the aluminosilicate component content decrease from inside to outside of corrosion product. The outer layer of corrosion product is loose and porous, the pore size show a typical bimodal distribution, which mainly concentrated in 50 nm and 150 nm. The main composition of the slag include iron oxide and aluminosilicate, the iron oxide content decrease from inside to outside of slag product, which may be refer to the selective deposition. Finally, the mathematic models about the formation of slag and high temperature corrosion were developed combine with the experiment analysis.