This study reports the results of laboratory investigations in pressurized high-temperature carbon-rich environments simulating operations in syngas production and root cause failure analysis and laboratory analysis simulations in refinery platformer operations. The results rank a variety of stainless steels and Ni alloys.
Coking is carbon deposition from a gas phase that is encountered in many reforming, cracking and other high temperature processes. An experimental high temperature coking atmosphere was constructed and used to evaluate the effects of temperature, time and metal surface roughness on the carbon deposition of an alumina forming alloy.
Sweet (CO2) and sour (H2S) corrosion have continuously been a challenge in oil and gas production and transportation. Yet, some key issues are still not well understood, especially at high temperature production conditions. A CO2/H2S ratio of 500, which has been used (often inaccurately) to determine which corrosion mechanism is dominant, is probably even less valid at high temperature. The nature of the corrosion products forming at high temperature in CO2/H2S environments and their effects on the corrosion rate are not known. Finally, the impact on pipeline integrity of environmental changes between sweet and sour production conditions (simulating reservoir souring) has not been well documented. CO2, H2S, and CO2/H2S corrosion experiments were conducted at 120oC to investigate corrosion mechanisms and corrosion product layer formation at high temperature. The results show that the corrosion products were still clearly dominated by H2S under the pCO2/pH2S ratio of 550. Formation of Fe3O4, FeCO3, and FeS corrosion product layers had a direct impact on the measured corrosion rates and was dependent on the gas composition and on the sequence of exposure (CO2 then H2S and vice versa). Compared with H2S corrosion alone, the presence of CO2 could retard Fe3O4 formation in CO2/H2S mixture environment. No obvious change in steady state corrosion rate was observed when the corrosion environment was switched from CO2 to H2S and vice versa.
Weld overlay has been successfully used to mitigate high temperature corrosion issues in coal-fired boilers since the1990s, such as in waterwall and superheater/reheater area. Weld overlay is typically applied in shop or field by using Gas Metal Arc Welding (GMAW) process for boiler waterwall application, and the overlay welding is performed in vertical down welding mode (3G welding position) in subcritical and supercritical boiler waterwall applications. With the rapid development of coal-fired boiler market in China, ultra-supercritical boilers are becoming the dominated boiler type which often has spiral waterwall design. Most of ultra-supercritical coal-fired boiler waterwall consists of CrMo steel tubes, which could suffer severe high temperature corrosion attack after the installation of low NOx burners. It is expected that weld overlay could provide a long-term high temperature corrosion protection for ultra-supercritical boiler waterwall based on previous weld overlay study and application experience. However, for the spiral waterwall with inclined tube design, its field overlay welding is highly challenging and significantly different from typical vertical boiler waterwall overlay welding. The challenge and difference include welding position, welding sequence, welding parameters, and overlay properties, etc. This paper presents a successful field application of 309L stainless steel and 622 Ni-based alloy weld overlay on the spiral waterwall of an ultra-supercritical coal-fired boiler, including the welding development, simulation, and experience of overlay welding on the inclined tubes, along with the characterization of the weld overlay applied.
UNS S31400 stainless steel was tested as a reactor material for a thermal cracking process of agricultural, silvicultural, industrial and anthropogenic resources containing HCl. This material was chosen as it offers proper corrosion resistance in hot gases besides a good price and a high availability.