摘要:

The purpose of this paper is to review corrosion processes and experience related to coal-fired gas turbines. For over 40 years there have been major programmes of research directed towards burning coal in a gas turbine either directly or as a coal-derived fuel. This history is briefly reviewed, demonstrating the importance which corrosion of the hot section has had in limiting the achievements and defining the systems. The probable corrosion mechanisms are identified, and because of their synergistic interaction with corrosion, erosion and deposition are also considered. The discussion identifies pressurized fluidized bed combustion (PFBC) as the direct combustion technique most likely to be able to avoid serious corrosion problems in the immediate future. Recent results from PFBC pilot plant investigations related to turbine materials are compared, and thereby future directions for overcoming corrosion problems are proposed. MST/449

ISSN:0267-0836    

DOI:10.1080/02670836.1987.11782268

出版商:Taylor&Francis    

年代:1987

数据来源: Taylor

摘要:

Hot corrosion studies were conducted at 900°C in a simulated combustion gas atmosphere containing sulphur trioxide at a partial pressure of 750 Pa on a nickel-base super alloy (Nimocast 713) partially immersed in various ZnSO4–10wt-%NaCl–Na2SO4molten salt mixtures. Weight changes were measured thermogravimetrically with time and it was found that the overall effect of the zinc sulphate addition was to reduce the degree of hot corrosion. Quantitative scanning electron microscopy investigations revealed no evidence of zinc in the attacked zone. It is postulated that the zinc reduces the chlorine activity in the system by forming a volatile chloride, thereby reducing the corrosive effect of the gas phase/molten salt mixtures. MST/507

ISSN:0267-0836    

DOI:10.1080/02670836.1987.11782269

出版商:Taylor&Francis    

年代:1987

数据来源: Taylor

摘要:

The vanadate-induced corrosion of M Cr AIY coatings (M = Ni/Fe) on Inconel alloy 600 has been studied by using samples with preformed vanadate deposits. The samples were exposed to oxygen at 650 to 800°C for a maximum of 25 h in a thermobalance. The presence of molten vanadate ((Na2O)x·V2O5) on the surface causes accelerated corrosion. The corrosion rates increase with increasing V2O5content of the vanadates. In the presence of molten vanadate, protective scales of Cr2O3-Al2O3fail to develop; rather the oxide layer next to the coating consists of the oxides of all components in the coating and of vanadium both as vanadate and as vanadium sesquioxide. In most cases the molten vanadate phase fluxes the oxide scale and particularly the NiO phase in the oxide layer. Under these conditions the corrosion is probably governed by inward transport of oxygen (or oxygen species) in the vanadate melt. When the NiO concentration in the oxide layer next to the metal is high (as on nickel-base coatings with more than 75 wt-%Ni) a Ni3(VO4)2layer gradually develops between the oxide and the melt. This is accompanied by compositional changes in the oxide layer beneath the vanadate and results in a slow oxidation rate. MST/510

ISSN:0267-0836    

DOI:10.1080/02670836.1987.11782270

出版商:Taylor&Francis    

年代:1987

数据来源: Taylor

ISSN:0267-0836    

DOI:10.1080/02670836.1987.11782271

出版商:Taylor&Francis    

年代:1987

数据来源: Taylor

ISSN:0267-0836    

DOI:10.1080/02670836.1987.11782272

出版商:Taylor&Francis    

年代:1987

数据来源: Taylor