LABORATORY STUDIES OF EROSION-CORROSION PROCESSES UNDER OXIDIZING ANDOXIDISING SULPHIDISING CONDITIONS/

The development of advanced coal-fired power generation systems is rec eiving considerable world interest. The successful development of such systems requires that components are manufactured from appropriate ma terials, that the materials degradation modes are identified and that models exist to predict material performance. Wastage of materials due to erosion-corrosion processes has been identified as a major plant p roblem both within bubbling and circulating fluidised beds and to a le sser extent within pressurised fluidised beds, unless the pressurised system operates in an oxidising/sulphidising regime, as often found wi thin coal gasification plant. This paper presents a review of a range of laboratory test facilities that have been established to study high temperature erosion-corrosion processes and discusses how each has ai med to simulate in plant conditions, their limitations and successes. By the nature of the available Literature much of this review concentr ates on erosion-oxidation studies, although recent work under erosion- sulphidation conditions is also considered. The review is split into t hree sections; simulation of in-bed wastage condition; erosion-corrosi on within convective path components, superheaters and economisers; an d erosion-corrosion within gas turbine components as part of a coal fi red combined cycle plant. In all three systems, low wastage rates are associated with the formation of a mechanically protective surface oxi de. The inability to form such oxide glazes, or the failure of the oxi de, can lead to very high wastage rates, up to 4 mu m h(-1) for in-bed components as an example. Thus successful simulation of plant conditi ons within the laboratory depends on the ability of the laboratory rig s to duplicate the erosive wear processes, and this is discussed. Some stoichastic models capable of predicting wear patterns and wear rates are also reviewed.