Recent Updates on DP28W™: Metallurgical Study on Welding Joint Properties and Successful Experiences in Commercial Plants

摘要

Sumitomo Metal Industries, Ltd (SUMITOMO) and Toyo Engineering Corporation (TOYO) are the pioneers who have paved the way to apply duplex stainless steels to synthesis loop of urea process since 1980's. The latest version of their duplex stainless steel, DP28W™ has been used in commercial urea plants since early 2000's and its excellent corrosion resistance in urea carbamate solution has been confirmed. A noticeable advantage of DP28W™ is to keep excellent corrosion resistance even in weld metal and heat affected zone because of optimized alloying design of base metal and welding material. In this paper, results of metallurgical study on welding joints and successful experiences in commercial plants are reviewed. In the meantime DP28W™ has superior passivation property with little oxygen concentration, which achieves to operate urea plant with less amount of passivation air. Because of those advantages, DP28W™ can be used for refurbishment of old urea reactors lined-with titanium and internal parts. In this paper, advantages of refurbishment of old urea reactors using DP28W™ and replacement of internal parts using DP28W™ are reviewed.