Diffusion Coatings for Corrosion-Resistant Components in Coal Gasification Systems

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

SRI International

关键词: Coal Gasification;    Corrosion;    Alloys;    Flow Rate;    Heat Recovery;   

DOI  :  10.2172/887133
RP-ID  :  none
RP-ID  :  FC26-03NT41616
RP-ID  :  887133

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. In previous tests, we had frequently encountered problems with our steam generator that were exacerbated by the very low flow rates that we needed. During this period we installed a new computer-controlled system for injecting water into the steam generator that eliminated this problem. We also tested alloy coupons coated by using the improved procedures described in our last quarterly report. Most of these coatings were nitrided Ti and Ta coatings, either by themselves, or sometimes with barrier layers of Al and Si nitrides. The samples were tested for 300 h at 900 C in a gas stream designed to mimic the environment in the high temperature heat recovery unit (HTHRU). Three samples that showed least corrosion were exposed for an additional 100 h.