Petroleum refinery equipment components experience varying degrees of high temperature erosion and corrosion. The erosion corrosion effects are predominant in fluidized catalytic crackers, delayed cokers, fiexicokers, thermal crackers and vacuum distillation units. Typical components affected are piping elbows, nozzles, valve seats and guides, thermowells and pump internals. Erosion corrosion assumes a more menacing dimension when coupled with higher temperature, where most structural alloys soften resulting in accelerated wear. Traditionally, high temperature erosion resistant components in refineries are manufactured from Cobalt based alloys incorporating a generous amount of Cr and W. They are used for hardfacing or making cast components.
This paper examines a whole family of new candidate materials that is expected to offer better high temperature erosion characteristics compared to the ones utilized now. The materials include a range of Co based CrMo alloys and a range of alloy-matrix-composite alloys incorporating carbides of Chromium, Titanium and Tungsten. High temperature hardness and erosion testing is used to grade and compare the various candidate materials. The effect of manufacturing techniques on the erosion and abrasion properties is also evaluated to optimize the manufacturing route for a given component. Typical refinery components, where the new materials will find application, are discussed.
High temperature erosion is a menace constantly battled by refinery operators. There is an on-going quest to develop materials that perform better in such aggressive environments. The predominant reason for this quest is refinery economics. There is a gradual increase in temperatures, pressures and velocities associated with hydrocarbon processing, in order to enable better conversions and to process feed stocks with higher sulfur, nitrogen and organic acids. This puts additional performance demands on existing materials. In order to address this challenge, several new materials have been developed in the past years-they are grouped under cobalt based alloys and alloy matrix composite materials, the latter being relatively new materials for the refinery industry. The present study deals with these new materials, their high temperatures wear properties and potential applications.
HIGH TEMPERATURE EROSION IN REFINERY EQUIPMENT
Refinery components experience varying degrees of high temperature erosion. The eroding species can be liquid, coke or in most severe cases ceramic catalyst fines. Operating temperatures vary between 300°C and 800°C.
By far, the most severe erosion is encountered in the FCC section of the refinery. The AI203 catalyst erodes most internal components of the FCC reactor and regenerator and associated piping and valves. Erosion occurs at about 500- 550°C in the reactor/stripper section and at 700-750°C in the regenerator section. The high velocity catalyst erodes components like feed nozzles, steam and air grid nozzles, standpipe slide valves, and catalyst loading valves and cyclones. The erosion problem aggravates due to the high temperatures, which soften the materials of construction of the system. It is noteworthy that, FCCU units often times serve as proving grounds for high temperature erosion solutions.
Coke is another high temperature eroding species encountered in refining and petrochemical plants. High temperature erosion due to finely divided coke particles is encountered in cokers, thermal crackers and ethylene crackers. Furnace tubes, transfer lines, return bends and thermo wells are the most affected.
Liquid impingement and erosion occurs at relatively lower temperatures like 350°C. In
