DEVELOPMENT OF METALLIC HOT GAS FILTERS

The 16th Annual Conference on Fossil Energy Materials

I. E. Anderson ; B. Gleeson ; R. L. Terpstra

Others  :  http://www.netl.doe.gov/publications/proceedings/02/materials/Anderson.pdf
PID  :  28791

来源: CEUR

【 摘 要 】

The use of metallic filters for trapping fine (1-20µm) particulate from hot (850ûC) coal combustion exhausts can offer improved toughness and extended life over ceramic filters.Promising yield strength (200 MPa at 850ûC), ductility, permeability, and corrosion resistance were obtained in porous (70% dense) samples that were vacuum sintered from tap-densified spherical powders of a Ni-Cr-Al-Fe alloy. To further improve the corrosion/oxidation resistance of the Ni-Cr-Al-Fe alloy, additional Al was added to enhance formation of the protective Al2O3 scale and to increase the reservoir of Al for extended filter life.Two new Ni-Cr-Al-Fe alloys consisting of up to three times the Al content, relative to the base Ni- Cr-Al-Fe alloy, were developed and tested.The corrosion resistance of these aluminum-enriched alloys was evaluated, in both Òas-receivedÓ and Òpre-oxidizedÓ conditions, utilizing an oxidizing/sulfidizing gas environment designed to simulate a typical pressurized fluidized bed combustion (PFBC) process. An asymmetrical four-point bend (AFPB) test was used to determine the yield strength of these alloys, in cast form, at room temperature, 600°C, and 850 °C.Based on the results obtained, a Ni-Cr-Al-Fe alloy containing twice the aluminum content as the Ni-Cr-Al-Fe base alloy was selected as a viable filter alloy and was atomized using the Ames Laboratory high pressure gas atomizer for the purpose of further testing in filter form.The Ni-Cr-2xAl-Fe powder was sieved to the desired size of 25 Ð 45 microns and sintered to produce 0.5 mm thick porous sheets.Resistance welding trials were performed on the porous Ni-Cr-Al-Fe and Ni-Cr-2xAl-Fe sheets, tracking microstructural changes in the heat-affected zone (HAZ) of the weld due to different welding conditions.The successful outcome of this work resulted in the ability to produce a resistance spot welded porous cylinder of the Ni-Cr-2xAl-Fe alloy, suitable for extended exposure tests in a PFBC facility.