Diffusion Coatings for Corrosion-Resistant Components in Coal Gasification Systems

Krishnan, Gopala N. ; Malhotra, Ripudaman ; Alvarez, Esperanza ; Lau, Kai-Hung ; Perez-Mariano, Jordi ; Sanjurjo, Angel

SRI International

关键词: Coal Gasification;    Corrosion;    Particulates;    Alloys;    Scanning Electron Microscopy;   

DOI  :  10.2172/901148
RP-ID  :  None
RP-ID  :  FC26-03NT41616
RP-ID  :  901148

美国|英语

来源: UNT Digital Library

【 摘 要 】

Heat-exchangers, particle filters, turbines, and other components in integrated coal gasification combined cycle system must withstand the highly sulfiding conditions of the high-temperature coal gas over an extended period of time. The performance of components degrades significantly with time unless expensive high alloy materials are used. Deposition of a suitable coating on a low-cost alloy may improve its resistance to such sulfidation attack, and decrease capital and operating costs. The alloys used in the gasifier service include austenitic and ferritic stainless steels, nickel-chromium-iron alloys, and expensive nickel-cobalt alloys. During this period, we analyzed several coated and exposed samples of 409 steel by scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX), and report on the findings of four samples: (1) Analysis of two porous coupons after exposure to the porous metal particulate filter of the coal gasification power plant at 370 C for 2140 hours revealed that corrosion takes place in the bulk of the sample while the most external zone surface survived the test. (2) Coating and characterization of several porous 409 steel coupons after being coated with nitrides of Ti, Al and/or Si showed that adjusting experimental conditions results in thicker coatings in the bulk of the sample. (3) Analysis of coupons exposed to simulated coal gas at 370 C for 300 hours showed that a better corrosion resistance is achieved by improving the coatings in the bulk of the samples.