Papers by Keyword: Metal Dusting

Abstract: The paper summarizes the results of the analysis made on the ruptured tube of the reactor made of austenitic stainless steel in which the conversion of aniline to diphenylamine occurs at elevated temperature and pressure and in the presence of a catalyst. The tube wall perforation occurred in the piping used to measure the pressure in the reactor and a fire occurred after an aniline, ammonia and catalyst vapour leak. The material analyses carried out clearly showed that the thinning and subsequent perforation of the tube wall was due to a specific corrosion attack, so-called metal dusting, which occurs at elevated temperatures and in the presence of a carburizing atmosphere.

Abstract: Segmented carbon filaments produced by catalytic decomposition of 1,2-dichloroethane over Ni-Mo (8 wt.% Mo) self-organizing catalyst were subjected to functionalization in two different regimes. The structure, textural properties and chemical composition of surface were studied using SEM, Raman spectroscopy, adsorption (BET) and XPS. It was shown that oxidation of carbon nanomaterial in concentrated HNO₃ results in enhancement of O-containing groups concentration (from 2.2 to 6.8 wt.%), increase in specific surface area (from 224 to 280 m²/g) and slight structural disorder of graphitic material (increase of I_D/I_G ratio from 2.15 to 1.84).

Abstract: Ni-Pd alloy was prepared by a co-precipitation technique. Catalytic decomposition of a model chlorinated hydrocarbon (1,2-dichloroethane) was performed in a quartz flow-through reactor system. Both the temperature regime and the composition of the reaction mixture were varied during the experiments. Concentration of 1,2-dichloroethane was found to affect significantly the kinetics of the process, the yield of the nanostructured carbon product and its textural and morphological characteristics. In terms of optimal temperature, the maximum carbon yield was obtained within a range of 650-670 °C.

Abstract: First case describes hot temperature corrosion of 1.4841 heat resisting steel, which was caused by formation of the low melting nickel sulphide (LME effect).In the second case centrifugally cast tubes of Ø52.6 x 5.8 mm size made of 25/35 CrNi steel, which are exposed to high temperature and to severe reducing environment (carbon activity ac >> 1), are concerned. In such condition a graphitization may start, that results in the disintegration of its structure, which is called ,,metal dusting”.The third case is dealing with an attack of the 1.4301 steel pipe welds by microbiologically influenced corrosion. After short service time several leakages of water were revealed. It was proved, that failure was caused by microbiologically influenced corrosion of sulphate-reducing bacteria (SRB) and not by an improper welding technology.

Abstract: Among the high temperature damages, this paper was discussed on the cases in which the materials were damaged mainly by the effect of environmental factors. That is, high temperature oxidation, steam oxidation, molten salt corrosion, high temperature particle erosion and corrosion, high temperature sulfurization, carburizing, metal dusting, nitriding, high temperature chloride corrosion and so on were introduced using my research data. Finally, anticipation to future research of high temperature corrosion was maintained.

Abstract: The work shows the results of the tests of 9Cr-1Mo steel, which was for 10 years operated in the CCR platforming unit in Group Lotos SA in Gdańsk, and then in the laboratory was sulphidised during 166 h at a temperature of 600 °C. Sulphidation was performed in a mixture of H₂-H₂S gases at the vapour pressure of sulphur 4.1·10^-14 atm, so the order of magnitude of vapour pressure was less than that of the dissociation pressure of FeS. Although sulphidising took place in conditions which preclude any iron sulphide formation, research results have demonstrated that after 166 hour exposure in reaction mixture in 9Cr-1Mo steel produces iron and chromium sulfides. Sulphide precipitates form under a layer of fine carbides, located directly on the surface of steel. Formation of scale sulphide here is most likely caused by the penetration of hydrogen sulphide through the porous layer of carbides that increases the pressure of hydrogen sulphide. Thus the vapour of sulphur in apertures and narrow passages occurs between the layer of carbides and the rest of oversaturated carbon layer top, until its pressure value is reached allowing the formation of sulphide scaling.

Abstract: The high temperature oxidation behaviour of Ni-Cr-B-Si coatings with a higher Si-content was investigated in order to evaluate the suitability of such materials especially for novel applications concerning highly aggressive environments like metal dusting. Metal dusting is a corrosion phenomenon that occurs in reducing-, carbon-supersaturated (a_c>1) gaseous atmosphere, containing CO, H₂, CO₂ and H₂O, at elevated temperatures between 400 and 800°C. Metal dusting reactions can be classified into two types. The first one concerns Fe-alloys, where Fe₃C is growing on the surface. The second one is related to the reaction of Ni, Co and their alloys, where the destruction takes place through inward growth or direct ingrowth of graphite, without forming the metastable Fe₃C. Regarding to the literature, metal dusting is typically encountered in industrial furnaces, but mainly in the chemical or petrochemical industry. The way to suppress metal dusting is to stop the dissociation of the carbon source or to stop the carbon ingress in the material. One possibility in order to avoid the carburization of Fe, Ni, Co and their alloys is to preoxidize the samples. Based on the reducing atmosphere, where metal dusting occurs, the isothermal outsourcing for the formation of a protective Al-, Cr- or Si-oxide layer on the samples in air is mostly necessary. The role of a stable Al₂O₃ and Cr₂O₃-layer on the sample as a diffusion barrier against the carbon ingress, based on their low solubility for carbon, has already been investigated and proved by many scientists. The formation of a protective and thermodynamically very stable SiO₂ scale was also investigated. Within the scope of this work, the influence of a higher Si-content (4,5 wt%) in NiCrBSi-alloys, depending on the temperature, was analyzed. For this purpose the samples were oxidized in air at 600, 700 and 800°C respectively. The surface morphology and the phase composition of the grown oxide scales were characterized by means of scanning electron microscopy combined with energy dispersive X-ray (SEM/EDX) and by X-ray diffraction (XRD) technique. The experimental results demonstrate the importance of silicon content on the coatings properties, respectively on the stability of the formed oxide scale (free of micro cracks, no spallation). This element is able to form beside chromium, a dense oxide layer on the sample surface, protecting it against further degradation induced by the atmosphere in different high temperature applications. Moreover, the increased chromium content of the feedstock powder (from 10 wt% in previous work to 12,5 wt%) demonstrated that the Ni-Cr-B-Si coatings exposed at 600°C, 700°C as well as at 800°C were not susceptible to internal oxidation.

Abstract: Laboratory metal dusting test of several Ni binary alloys containing the representative element was conducted in a simulated syngas atmosphere at 650°C for 100h. The Ni alloys containing element belonging to Group 14 and 15 in the periodic series exhibited excellent metal dusting resistance, while those containing Group 13 did not. This behavior was able to be reasonably interpreted from the Blyholder mechanism and the concept of Pauling’s electronegativity.

Abstract: The kinetics and mechanism of metal dusting corrosion of 9Cr-1Mo steel, commonly used in CCR platforming units, have been studied as a function of temperature (773 – 1173 K) in propane-butane atmosphere, being the mixture of 70 vol. % of propane and 30 vol. % of butane with the total pressure equal 105 Pa. The kinetics of corrosion have been studied thermogravimetrically in the apparatus enabling the mass changes of corroded sample to be followed continuously with the accuracy of the order of 10-6 g. It has been found that metal dusting corrosion in this atmosphere, modeling in some way industrial environments in petrochemical industry, is complex and two-stages of linear kinetics may be distinguished. In the first stage, which may be considered as an incubation period, the reaction proceeds with rather low rate, which increases dramatically in the second stage, the beginning of which depends strongly on temperature. Linear course of reaction indicates that chemical reactions and not diffusion processes determine the rate of corrosion. This conclusion is confirmed by the fact, that the layer of corrosion products is not compact but considerably porous.

Abstract: Metal dusting behaviour of alloy800H was investigated in a laboratory-pressurized reactor where CO-H2-CO2-H2O gas mixtures flowed continuously, simulating the gas environments in actual syngas production plant. Four test conditions, having a variety of gas pressures and H2O contents, were conducted for a long rod specimen that was imposed thermal gradient of 777°C to 454°C in a longitudinal direction. After an exposure of 100h at high pressure, metal dusting has initiated with a bell-shape distribution on the test specimens at temperatures between 600°C and 700°C. Gas pressure has accelerated metal dusting even if the gas atmospheres had the same gas composition. On the contrary, metal dusting has been alleviated with increasing the H2O content in the test gas. Oxide scale characterisations were analyzed by using Raman spectroscopy and XPS at the test specimen surfaces exposed at different temperature. The ratio of a protective Cr2O3 scale to spinel oxides such as FeCr2O4 and MnCr2O4 has increased with increasing the exposure temperature, with reducing the gas pressure, and with lowering the H2O content. These behaviours have been interpreted from thermodynamic indices: carbon activity ac and the oxide scale integrity related to oxygen potential Po2 as a function of temperature.