Analysis and prevention of metallurgical failures at a major direct coal liquefaction pilot plant

Abstract

The H-Coal Pilot Plant in Catlettsburg, KY was the largest-capacity direct coal liquefaction project operating in the United States. Since the start of operations, performance of its components was carefully monitored and occasional failures were examined and documented. The results of the examinations were used to develop remedial steps and improve the design of scale-up units. In this paper, the metallurgical aspects of the following incidents will be described: 1) stress corrosion cracking of martensitic stainless steel bolting on the waterside of a heat exchanger; 2) stress corrosion cracking of a superalloy seal ring; 3) brittle failure of a low alloy nut in a block valve body; 4) corrosion damage in the fractionator and side stripper; 5) erosion/corrosion of a coal liquid transfer line in the atmospheric fractionation area; 6) pitting corrosion in a deaerator carbon steel inlet pipe; 7) brittle failure of a martensitic stainless steel ball in a block valve handling coal liquids; and 8) cracking of cobalt-base alloy seat rings in block valve applications. In addition, remedial steps and preventive measures leading to successful performance after repair will be briefly described.