Papers by Author: Jean Michel Brossard

Abstract: Damage of SiC oxide bonded refractories in waste-to-energy facilities (WtE) has been characterized. Different phenomena were observed: wear by slag phases, volume expansion of tiles and fracture in different locations. These results are in agreement with laboratory experiments. The role of gas composition and tiles temperature profile on deposit composition, on condensation of gaseous alkali chloride and on formation of liquid phase inside the porosity of the refractories has been emphasized. Gaseous alkali species are involved, not only in the formation of liquid phases, but also as a precursor of cristoballite formation around the SiC grains as well as in the rich alumina-silica matrix. On the hot face of the refractories, oxo-reduction reactions produce the formation of wollastonite. Post-mortem analysis after several thousand hours of operation point to three main corrosion mechanisms:

Abstract: Increase of the energy recovery efficiency facilities is one of the challenges fixed recently by UE to Municipal Solid Waste Incineration (MSWI) operators. To achieve this target, one option consists in optimizing the water/steam cycle to increase electrical efficiency. Nevertheless, higher steam temperature into heat exchanger tube is expected to increase the risks of fireside corrosion, particularly on superheater tubes, along with important loss of materials, frequent shutdowns for repairs and high operational costs. In this study, fireside corrosion test had been performed using an innovative laboratory-scale corrosion pilot. Effect of increase in metal temperature from 400°C to 450°C on corrosion performances of SA192 carbon steel tube and AISI 316L stainless steel had been examined. Mechanisms and corrosion rates are discussed with regards to lifetime reported for both materials after 1 year in service in the same plant.

Abstract: Fireside corrosion is since a long time the main limitation to increase efficiency of energy recovery boilers of waste to energy (W-t-E) facilities. Nevertheless, the increase of steam conditions in addition with the variation of feeding fuels composition imply greater risks of fouling and corrosion along with heat exchanger failure, loss of plant availability and high maintenance costs. Fireside corrosion mechanisms had already been widely treated in the literature and this paper will review the main critical factors that enhance fireside corrosion of superheater. Recent failure cases will be developed in regards with recent studies that provide interesting routes to predict corrosion failure and develop maintenance strategy.

Abstract: The efficiency of Waste-to-Energy (W-t-E) boilers is affected by fireside corrosion of the heat exchangers that involve unexpected shutdown of facilities for repairs and limit the increase of steam conditions used to produce electricity. The parameters governing fireside corrosion are various and mechanisms are very complex, nevertheless, they are relatively well documented in the literature. In this paper, a laboratory-scale corrosion pilot, which reproduces MSWI boilers conditions, is described. The specificity of our approach includes simultaneous simulation of the temperature gradient at flue-gas/tube interface, the velocity of flue-gas and ashes. Corrosion rates obtained on Tu37C carbon steel at a metal temperature equal to 400°C and a flue gas temperatures of 650°C and 850°C (1100 ppm HCl, 110 ppm SO2 and synthetic ashes free of heavy metals) are respectively around 1.6 2m/hour and 5.6 2m/hour. Preferential metal loss, attributed to erosion-corrosion phenomena, is also observed at low flue-gas temperature (T=650°C) on the face exposed at 90° to the flue-gas. The analysis of corrosion scales demonstrates the reproducibility of results and the reliability of corrosion mechanisms determined from experiments, with degradation observed similar to superheater tubes from EfW facilities. Thus, the corrosion pilot developed can be used as an accurate simulator of the environment encountered in MSWI.