Superheater fireside corrosion mechanisms in MSWI plants: Lab-scale study and on-site results (original) (raw)
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Materials and Corrosion, 2019
In this study, a field-returned superheater tube of carbon steel 16Mo3 (1.5415) was analyzed in detail. In addition to cross-section analysis, different scales were investigated layer by layer using microscopic, diffraction, and spectroscopic techniques. The corrosion products can be divided into three layers: The layer adjacent to the metallic tube surface was an iron-and chlorine-rich scale, followed by an FeS layer present at the gas flow side, and the outermost layer was an iron oxide scale consisting of Fe 3 O 4 and α-Fe 2 O 3. The different mechanisms responsible for the structure of such scale formation and the different corrosion products formed at the tube are discussed. Furthermore, the root cause for the disability to form a protective scale under such conditions was identified by comparison with results from laboratory tests. K E Y W O R D S carbon steel, chlorine corrosion, field-returned superheater tube, high temperature, waste incineration This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. How to cite this article: Krumm L, Galetz MC. Corrosion of 15Mo3 carbon steel superheater tubes in waste incineration plants: A comparison between a field-returned tube and laboratory tests.
2021
The combustion of coal and biomass fuels in power plants generates deposits on the surfaces of superheater / reheater tubes that can lead onto fireside corrosion. This type of materials degradation can limit the lives of such tubes in the long term, and better methods are needed to produce predictive models for such damage. This paper reports on four different approaches that are being investigated to tackle the challenge of modelling fireside corrosion damage on superheaters / reheaters: (a) CFD models to predict deposition onto tube surfaces; (b) generation of a database of available fireside corrosion data; (c) development of mechanistic and statistically based models of fireside corrosion from laboratory exposures and dimensional metrology; (d) statistical analysis of plant derived fireside corrosion datasets using multi-variable statistical techniques, such as Partial Least Squares Regression (PLSR). An improved understanding of the factors that influence fireside corrosion is ...
Scientific reports, 2017
Municipal solid waste (MSW) incineration is widely adopted as a waste management strategy and for the energy production. However, this technology experience grave deposition and corrosion of the boiler tubes due to high chlorine (~1.09wt.%) and alkali metal (Na, K) content in MSW. Little is known about the concentration profile of these corrosive elements in the deposits at different boiler locations. Therefore, a full-scale experimental investigation was conducted to determine the concentration profile of Cl, K, Na, S, and Ca in the deposits at pre-protector and compare with those at 3rd superheater during MSW combustion at a 36 MWe waste incineration plant (WIP) in Chengdu, China. The deposit samples were analyzed using wet chemical techniques, scanning electron microscope coupled with energy dispersive spectroscopy (SEM/EDS), and X-ray diffraction (XRD). The concentrations of Na, K, and Cl were high in the deposits at pre-protector while S and Ca concentrations were high on the 3...
Development of a Laboratory-Scale Pilot for Studying Corrosion on MSWI Heat Exchangers
Materials Science Forum, 2008
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.
2021
The heterogeneous nature of the ash chemistry of biomass fuels gives rise to challenges in predicting the deposit melting, sintering, and enrichment of corrosive ash species. An experimental method has been developed to study the evolution of ash deposit chemistry and morphology in temperature gradients simulating the conditions of real superheater deposits. The method is based on applying synthetic ash mixtures on an air-cooled corrosion probe, which is inserted into a tube furnace. The focus has been on how the melting behavior of alkali salt-rich deposits, i.e., KCl-K2SO4-NaCl-Na2SO4 mixtures, affects the chemistry and morphology. Intradeposit vaporization-condensation of alkali chlorides has been of interest. The interaction of reactive gas components (H2O+SO2), with the deposits, was also studied. The vaporization-condensation mechanism leads to enrichment of alkali chlorides in crevices and voids within deposits, leading also to build-up of chlorides on the steel surface, whic...
Fireside corrosion of selected alloys by ash recovered from coal-water slurry combustion
Fuel Processing Technology, 1997
The corrosion behavior of five selected stainless steels was evaluated in a simulated fireside corrosion atmosphere for a coal-water slurry system. Two types of ash, generated from actual combustion tests of coal-water slurries, were used as the fireside test deposits. The ashes differed in the amount of unburned carbon in each. The alloys selected were Types 304, 316, 321. 347 stainless steels and high-nickel 800 M. Tests were conducted for 48 h at temperatures of 600, 700, 800°C in a simulated flue gas, representative of the atmosphere expected in coal-water slurry combustion, and at 1000°C in inert atmosphere. Analyses of the test coupons after removal from the furnace included scanning electron microscopy, optical microscopy, and weight-loss measurements. Scanning electron microscopy showed the presence of fused corrosion deposits, proving that liquid phases were involved in the corrosion process. Microprobe analysis of selected samples detected no sulfur in the corrosion products, suggesting that complex sulfates were not being formed. The low-carbon ash was more corrosive toward the alloys than the high-carbon ash. The high-carbon ash tended to shift the temperature of maximum corrosion toward higher temperatures. Type 316 stainless steel showed the highest corrosion losses among the five alloys tested with the low-carbon ash at 600-800°C. For tests with the high-carbon ash, the corrosion losses for all the alloys, except for Type 347, were low. The differences in corrosion losses between the types of ashes relate to the differences in carbon and calcium contents of the two ashes. The overall corrosion losses were small when compared to literature values for fireside corrosion losses in pulverized coal combustion. Published by Elsevier Science B.V.
Corrosion in waste-fired boilers: A thermodynamic study
Fuel, 2009
ABSTRACT A twofold study using thermodynamic equilibrium calculations was carried out to study corrosion in MSW incinerators. Corrosion was associated with the amount of alkalis and trace metals gaseous chlorides. Firstly, a two-level factorial experimental design combined with a data analysis were used to determine the main and interaction effects for various alkalis and trace metals gaseous chlorides responses. The factors studied were Na, K, S and Cl concentrations. The results provided a picture of the controlling parameters and insight about the processes taking place. Secondly, the efficiency of two corrosion-fighting additives (ammonium sulphate and silica) was investigated. Calculations confirmed experimental results and brought further insight on differentiated results for Na, K, Pb and Zn but also on capture mechanisms.
Journal of Engineering for Power, 1960
After burning 25 to 30 per cent Pana coal in 1957 (the same amount as during the first 18 months of operation), the corrosion rate remained low, 5 to 10 per cent, instead of returning to the higher rate of 50 per cent as might be expected if Pana coal were the major factor. The abrupt reduction in corrosion is more likely to have been due to the reduced metal and gas temperatures in the platens resulting from the installation of furnace-screen surface. Also, the use of higher excess air and the installation of 25-20 clad tubes have undoubtedly been beneficial in reducing corrosion. The use of additive and the shift of soot blowers seem to have been helpful, but the role they played was not decisive in the overall effort.
Fireside Corrosion of Heat Exchanger Materials for Advanced Solid Fuel Fired Power Plants
Oxidation of Metals
To address the challenge of climate change, future energy systems need to have reduced greenhouse gas emissions and increased efficiencies. For solid fuel fired combustion plants, one route towards achieving this is to increase the system’s steam temperatures and pressures. Another route is to co-fire renewable fuels (such as biomass) with coals. Fireside corrosion performance of two candidate superheater/reheater alloys has been characterised at higher heat exchanger surface temperature. Samples of the alloys (a stainless steel, Sanicro 25 and a nickel-based alloy, IN740) were exposed in fireside corrosion tests at 650 °C, 700 °C and 750 °C, in controlled atmosphere furnaces using the ‘deposit recoat’ test method to simulate superheater/reheater exposure for 1000 h. After exposure, the samples were analysed using dimensional metrology to determine the extent and distributions of corrosion damage in terms of surface recession and internal damage. At 650 °C, the stainless steel and n...