CARBIDE PRECIPITATE GROWTH ANALYSIS OF KHR35CT – ASTM A297 HP-MOD MATERIAL

• Main Author: Bastian, Maulidin
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/33901
• Institution: Institut Teknologi Bandung

Reformer furnaces is used to produce hydrogen rich gas from a mixture of sulfur- free hydrocarbons and steam at high temperature. Endhotermic reaction occurred in nickel catalyst at 443-455 psig and 400-900oC. KHR35CT catalyst tube is manufactured based on ASTM A297 HP-Mod standard and designed using API 530 code to avoid creep. This thesis is intended to understand the relationship between service time and temperature of catalyst tubes on the growth of carbide precipitates, material hardness, and predicting the tube remaining life. Examination of microstructure by optical microscope and SEM was performed on new tubes and tubes that have been used for 17,500, 96,300 and 113,800 hours at normal operating temperature (850°C). Temperature data for tube examination was obtained from thermographic examination, burner design and DCS unit. Sampling variations from the top to bottom of the tube were used to understand the relationship of temperature for the growth of carbide precipitate and material hardness. New tube carbide volume fraction was 7.72% and increased to 10.95% after it was serviced for 113,800 hours. Furthermore, it was found that at the lower segment of the tube, where the exothermic reaction temperature is more dominant than the skin temperature, the carbide volume fraction was increased up to 10.46% and it was occurred at ±850°C. After 113,800 hours of service, the hardness was decreased from 191 BHN to 173 BHN. The decrement in material hardness was most likely due to the coarsening and agglomeration of carbide precipitates in the catalyst tube material. Moreover, the alterations in catalyst tube hardness were more influenced by the service life than temperature of service.