Characterization of Fly Ash and a Protective Coating for Brazilian Thermal Power Plant Boilers

Abstract

Thermoelectric power plants that use mineral coal show high wear in heat exchanger due to the action of several damage mechanisms associated with the impact of hard particles from the residue of burnt coal, the ashes. The employment of coatings should be given into consideration particularly for critical components, which are subject to severe erosive conditions is one of the solutions. However, the choice of material will depend on several factors, including the properties of aggressive ashes. This paper aims to characterize ashes generated by a Brazilian coal-based power plant and a FeCrNbNi-based metallic coating obtained by the electric arc spraying process. No trace of sulfur content was found in fly ashes and it was defined that wear is mainly related to the impact and energy of hard particles are the leading causes of degradation in coal-fired boiler equipment. According to the assessment, applied coating showed (5 ± 2)% by volume of pores and cracks, with 1.6% of oxides after the spraying process and hardness 35% greater than ash particles. Preliminary results in field operation suggest that the material showed relatively low wear compared to the original substrate and showed great applicability in controlling material deterioration for this purpose.

Determination of the Metallic Coating Properties Obtained by Thermal Spraying and Analysis of its Influence on the Heat Transfer Efficiency in the Thermoelectric Power Plant Boiler Tubes

“…The same procedure was performed to determine the microhardness of the substrate and the region of interface between substrate / coating. The coating microhardness was approximately 3 times higher than that of the substrate and 11% lower than the hardness of coal ash used in a Brazilian thermoelectric power plant, which is 825 HV [32]. The high hardness of coatings is a contributing factor to the longevity of the pipeline.…”

Avaliação do Desempenho no Ambiente de uma Caldeira de Revestimento Metálico de Liga à Base de Ferro Obtido por Aspersão Térmica a Arco Elétrico

“…Uma liga Fe-Cr-Nb-Ni-B foi depositada pelo processo de aspersão térmica a arco elétrico sobre uma chapa de aço carbono com dimensões de 1 x 1 m com 8 mm de espessura, com composição química conforme a Tabela 1. Tubos de caldeiras costumam ser fabricados em aço ASTM A516 grau 60, cujos teores de carbono e manganês estão de acordo com os da chapa utilizada [28].…”

“…Gomes et al [28] também estudaram o mesmo revestimento objeto de avaliação deste trabalho. Eles mostraram que ele apresentava alguns defeitos típicos, tais como partículas parcialmente fundidas, óxidos, trincas, microtrincas e porosidades.…”

Numerical Analysis of the Erosion Mechanism inside the Tube Sockets of Main Steam Thermometers in a Coal-Fired Power Plant

“…In order to alleviate the damage caused by erosion, scholars are committed to create coatings with dense microstructure, high hardness and excellent resistance performance to erosion [14]. Many experiments had proved that the coatings were able to effectively improve the safety and economy of power plant equipment [15][16][17][18][19][20].…”