摘要:

The applicability of iridium (Ir) for gasifier thermowells is investigated. Based on field tests, some promising results have been obtained; for example, no degradation was observed for the Ir specimen exposed for 104 h to the environments on the gasifier wall. Another specimen exposed in the gasifier slag tap area was damaged, partially exhibiting a fused appearance. Analysis indicated that iron reduced from coal slag decreased the melting temperature of the Ir specimen through alloying. In this paper, the performance of pure Ir in slagging gasification environments is discussed with respect to laboratory corrosion tests conducted in synthesized atmospheres. A short commentary on ceramic thermowells is also presented.

ISSN:0960-3409    

DOI:10.1080/09603409.1993.11689450

出版商:Taylor&Francis    

年代:1993

数据来源: Taylor

摘要:

Corrosion concerns for metallic materials of construction for gasifier and syngas cooler components for intermediate BTU coal gasification processes are analysed in the context of materials performance in the Shell Coal Gasification Process (SCGP). High temperature gas-phase corrosion, high temperature corrosion fatigue, dew point corrosion, and shut-down corrosion are discussed. The status of corrosion prediction and alloy selection capabilities is shown to be adequate for commercial equipment. Similarities in materials requirements and behaviour between several processes and processing conditions are pointed out. Much of the corrosion prediction and alloy selection information needed to build successful commercial plants is available without the need to develop or evaluate new alloys and has been demonstrated in an SCGP demonstration plant.

ISSN:0960-3409    

DOI:10.1080/09603409.1993.11689451

出版商:Taylor&Francis    

年代:1993

数据来源: Taylor

摘要:

For the last 10 years Hoechst AG, KEMA N. V., and EPRI have studied materials performance in raw syngas heat exchangers of coal water slurry fed gasifiers. Initial experiments were carried out in a 165 tonnes per day demonstration plant; later experiments were carried out in a commercial plant and are still in progress. Water-cooled or steam-cooled test loops were used in both plants to simulate actual heat exchanger service as closely as possible. The first test loop was operated for 5500 h at metal temperatures ranging from 320–370°C. Despite these low temperatures, the corrosion rates observed were relatively high and were ascribed to the corrosive nature of the gasified fuel, which had a high sulfur and chloride content. The second test loop is still in operation. Results on the first 3600 h of operation are reported here. Both evaporator and superheater test loops were successfully operated. Corrosion rates were generally moderate, because of the gasification of a relatively clean coal and operating procedures preventing corrosion during down time. The effects of differences in fuel quality and operating practices on alloy performance are discussed.

ISSN:0960-3409    

DOI:10.1080/09603409.1993.11689452

出版商:Taylor&Francis    

年代:1993

数据来源: Taylor

摘要:

After a short description of the present status of construction of the Demkolec Demo KV-STEG in Buggenum and some relevant details about process conditions in the gasifier/syngas cooler area, a description of the materials test exposure facilities is given. During a three year demonstration period several tests will be performed at different locations in the plant. The materials test exposure programme in the gasifier/syngas cooler area and an overview of candidate materials to be tested are given. Exposure durations of 15000 h with intermediate sampling are anticipated. The exposures will start shortly after the first successful service runs of the plant.

ISSN:0960-3409    

DOI:10.1080/09603409.1993.11689453

出版商:Taylor&Francis    

年代:1993

数据来源: Taylor

摘要:

The industrial need for a sulfidation-resistant alloy in coal combustion and conversion systems, chemical processing, petroleum refining and waste incineration is reviewed. The development of a new alloy to meet this industrial need is described. The important metallurgical factors considered during the alloy development process are discussed. This paper presents the major characteristics of this new alloy with particular reference to its resistance to high temperature corrosion relevant to coal combustion and gasification systems. The physical metallurgy, mechanical properties and fabricability of the alloy are also reviewed.

ISSN:0960-3409    

DOI:10.1080/09603409.1993.11689454

出版商:Taylor&Francis    

年代:1993

数据来源: Taylor

摘要:

On the basis of alloy 800 H and alloy AC-66, materials introduced in the 1960s and the late 1980s, respectively, two new alloys, Cronifer III-TM (alloy III-TM) and Nicrofer 45-TM (alloy 45-TM), were developed to resist high sulfur and carbon-bearing environments. Carburization behaviour was examined in the temperature range 750–1100°C for more than 1000 h in CH4/H2(ac= 0.8). The silicon-containing alloys Cronifer III-TM and Nicrofer 45-TM showed a mass gain similar to or even lower than that of the nickel-base alloy 625. Data on sulfidation resistance up to 650°C obtained in 10% SO2/N2indicated a mass loss of less than 5gm−2after 1000h for all alloys tested (800 H, AC-66, 625, III-TM, 45-TM). At 750°C alloy 800 H suffered breakaway corrosion and alloy 625 severe spallation. Alloys AC-66, III-TM and 45-TM showed superior corrosion resistance. Tests performed in a simulated coal gasification environment (1% H2S, 4% CO, 3% H20, balance H2) showed negligible mass gain for the alloys at 550°C. Results at 650°C remained satisfactory after 1000 h for alloys 800 H, AC-66, III-TM and 45-TM, with weight gains of less than 35 gm-2. Metallographic examination of the alloys, however, indicated local corrosion attack, which was lowest for 45-TM at 550°C and lowest for AC-66 at 650°C. Alloy 800 H showed the worst behaviour at all temperatures. Exposure tests in a simulated waste incineration atmosphere (2.5gm−3HC1, 1.3g−3SO2, 9% O2, balance N2) in the temperature range 550–850°C showed alloy 45-TM to have the best performance over the whole temperature range.

ISSN:0960-3409    

DOI:10.1080/09603409.1993.11689455

出版商:Taylor&Francis    

年代:1993

数据来源: Taylor

摘要:

The development and breakdown of scales formed on Fe—25Cr and Fe—25Cr—20Ni alloys have been studied in O—S environments, mainly at 700°C. The chromia scales formed on Fe-25Cr were markedly more effective than the scales formed on Fe-25Cr-20Ni. A major difference was that the protective scales formed on the FeCr alloy were predominantly M2O3type, with low levels of Fe, whereas those that led to inferior protection on the FeCrNi alloy were predominantly M3O4type, with higher levels of Fe in the nominally protective scale. The influence of small additions of Y, Hf, Ce, Nb, Mn, Pt, A1 and Si on the formation of protective scales on these alloy bases was investigated. Only Si, and possibly small additions (2%) of Al, as well as Al2O3or Y2O3dispersions appeared to exert any obvious beneficial effect. Additions made through ion implantation did not result in improved protective behaviour in any of the alloys. It was postulated that alloy modifications that can minimize the Fe content of the scale, probably by promoting the exclusive formation of M2O3−type scales, should enhance the sulfidation resistance.

ISSN:0960-3409    

DOI:10.1080/09603409.1993.11689456

出版商:Taylor&Francis    

年代:1993

数据来源: Taylor

摘要:

Research was done to develop a candidate syngas cooler tube for installation in coal gasification plants. Laboratory tests were conducted to develop alloy compositions with resistance to high temperature corrosion and down-time corrosion in simulated environments of coal gasification plants. 25Cr—30Ni—2Mo—2.5Si—1.5A1—Fe was the best composition, which showed excellent resistance to both types of corrosion. However, since ductility was substantially degraded during high temperature ageing, the developed alloy cannot be utilized for stress components. Therefore, the commercial product form for the developed alloy was a dual-wall tube. The dual-wall tube billet was manufactured by hot isostatic pressing compaction of the developed alloy powder with a hollow billet of type 347H steel. Hot extrusion was employed for the tube-forming process. Welding and bending tests were performed to evaluate the fabricability of the material.

ISSN:0960-3409    

DOI:10.1080/09603409.1993.11689457

出版商:Taylor&Francis    

年代:1993

数据来源: Taylor

摘要:

A chromium coating of 25μm depth was physically deposited on two iron substrates differing mainly in their respective carbon content: pure iron and iron containing 0.3 wt% of carbon (Fe0.3C). After oxidation, the oxidized layer was thin and consisted mainly of Cr2O3. In the case of Cr on Fe0.3C, carbon was located in the deeper part of the oxide, and A1 showed a strong enrichment both in the very outer part of the oxide scale and in its inner zone. With the help of successive oxidations in16O2, then18O2, it was observed that the carbon-enriched zone in the oxide layer on the Cr coating of the Fe0.3C sample behaves as a good barrier against oxygen inner diffusion. On pure iron, the carbon-enriched layer does not prevent oxygen diffusion into the Cr coating and both a cationic and an anionic mechanism occur for the growth of the oxide layer. The oxygen diffusion parameter in Cr2O3is the same for the two substrates: 10−14cm2s−1.

ISSN:0960-3409    

DOI:10.1080/09603409.1993.11689458

出版商:Taylor&Francis    

年代:1993

数据来源: Taylor

摘要:

A new alloy containing 26.5% Cr, 39% Ni, 3.5% V, 0.3% Nb and 0.02% N was developed for heat exchangers of coal gasification power plants. This alloy is expected to be resistant to both high temperature sulfidation and aqueous corrosion during down time. Laboratory-melted alloys of various compositions were prepared to optimize the alloy composition with respect to mechanical properties. The Greeble test, tensile test, creep rupture test, Charpy impact test for aged materials, and the Trans-Varestraint test were performed. Changes in the microstructure of the alloys upon ageing were investigated by optical and electron microscopy, along with chemical analyses of the precipitates.

ISSN:0960-3409    

DOI:10.1080/09603409.1993.11689459

出版商:Taylor&Francis    

年代:1993

数据来源: Taylor