Wyniki wyszukiwania - BazTech

Ograniczanie wyników

Znaleziono wyników: 2

Liczba wyników na stronie

Wyniki wyszukiwania

Wyszukiwano:
w słowach kluczowych: reformer tube

Sortuj według:

Ogranicz wyniki do:

Evaluation of reformer tubes degradation after long term operation

Łabanowski J.

Journal of Achievements in Materials and Manufacturing Engineering

2010

Vol. 43, nr 1

244-251

Purpose of this paper is to show the effect of long-term service at elevated temperatures on microstructural changes of cast steel reformer tubes made of the alloy IN-519 (24%Cr, 24%Ni, Nb). The relationship between mechanical properties and microstructure degradation is discussed. Design/methodology/approach: Investigations were performed on five tubes taken from ammonia reformer furnace. Tubes worked at temperature of 880şC and 3.2 MPa pressure. The operation time varied from 24000 to 95000 hours. Microstructure of the material has been examined with the use of light optical microscopy and scanning electron microscopy (SEM). The energy dispersive X-ray analysis (EDX) was used for phase identification. The mechanical properties have been evaluated in static tensile tests at room temperature. Findings: Metallographic investigations of IN-519 cast steel catalytic tubes show that structural changes occur in non-monotonic way with operating time at elevated temperatures. For this reason the evaluation of tube degradation can not be based only on the microstructure examinations. The presence of a good correlation between mechanical properties of the catalytic tubes and service conditions, i.e. temperature, time, and internal stress was confirmed. Research limitations/implications: The surface condition of the tubes walls like carburization and oxidation is not considered in this study. Practical implications: The method for assessing the current degradation level and for predicting residual lifetime of creep-resistant tubes has been established. The method uses elongation values as the main factor characterizing structural degradation of catalytic tubes. It respects all degradation mechanisms involved in tubes degradation, and can give reliable information on reformer tube condition through almost whole period of operation. Originality/value: Microstructure transformations occur in the IN-519 cast steel tubes during long-term operation in the reformer furnace were revealed and described

Degradacja materiału rur katalitycznych

Jasiński W.

Problemy Eksploatacji

2004

nr 2

125-132

W zakładach chemicznych wodór do syntezy amoniaku otrzymywany jest w procesie termiczno-katalitycznego rozkładu metanu z parą wodną pod ciśnieniem do 4 MPa w staliwnych austenitycznych rurach wypełnionych katalizatorem niklowym. W warunkach eksploatacji następują zmiany strukturalne i fazowe w materiału rury, prowadzące do istotnych zmian właściwości mechanicznych. Stabilna odlewnicza mikrostruktura dendrytyczna ulega zanikowi. Wydzielają się fazy międzymetaliczne wywołujące kruchość stopu i następuje inicjacja procesu pełzania.

The hydrogen to ammonia synthesis in the chemical plants is received in process of endothermic thermal-catalytic decomposition of methane with water steam. The process is carried out in reformer tubes made of austenitic cast steel with nickel catalyst under pressure up to 4,0 MPa. The long-lasting influence of raised temperature causes the precipitation of the intermetallic needle-shaped s phases in alloyed austenite matrix. The stable cast dendrite microstructure disappears. This results in decrease of the mechanical properties of the pipe material as well as in the intensification of the creeping.