Diffusion Coatings for Corrosion-Resistant Components in Coal Gasification Systems Quarterly Technical Progress Report: Number 10 (open access)

Diffusion Coatings for Corrosion-Resistant Components in Coal Gasification Systems Quarterly Technical Progress Report: Number 10

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 …
Date: June 1, 2006
Creator: Krishnan, Gopala N.; Malhotra, Ripudaman; Alvarez, Esperanza; Lau, Kai-Hung & Sanjurjo, Angel
System: The UNT Digital Library
Diffusion Coatings for Corrosion-Resistant Components in Coal Gasification Systems Quarterly Technical Progress Report: Number 9 (open access)

Diffusion Coatings for Corrosion-Resistant Components in Coal Gasification Systems Quarterly Technical Progress Report: Number 9

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 tested coated alloy coupons under conditions designed to mimic the conditions in the filter unit after the high-temperature heat recovery unit (HTHRU). The filter unit is another important area where corrosion has caused unscheduled downtime, and the remedy has been the use of sintered metal tubes made of expensive alloys such as inconel. The objective of our test was to determine if those coatings on 400-series steel that were not able to withstand the harsher conditions of the HTHRU, may be sufficiently resistant for use in the filter unit, at the reduced temperatures. Indeed, most of our coatings survived well; the exceptions were the coated porous samples of …
Date: January 1, 2006
Creator: Krishnan, Gopala N.; Malhotra, Ripudaman; Alvarez, Esperanza; Lau, Kai-Hung & Sanjurjo, Angel
System: The UNT Digital Library