Performance of Plasma Powder Welded (PPW) Layer on Ethylene Cracking Furnace Tubes- A Technical Evaluation

摘要

Ethylene production needs maximum cracking of the hydrocarbons at lowest possible coke formation and carburization, and maximum furnace run length. A number of coatings have been developed to increase the run length by decreasing coke formation. They could show only limited success because of their breakdown and/or diffusion into the base material during the aggressive operation conditions whereby very high temperature can occur due to exothermic reaction of coke with steam/air. The plasma powder welded tube provides a 2-3 mm thick overlay of Ni/Cr alloy which protects the internal surface of the full tube, including shop and field welds. The diffusion degradation, coking, carburizatrion resistance and high temperature creep were studied. The test results have demonstrated its thermal stability, negligible diffusion into the base material and no detrimental effect on the creep rupture mechanism of the tube material.