Waste Incineration Environment Research Articles

Corrosion behavior and mechanism of Inconel 625 coatings in high-temperature acidic environments for waste incineration applications

This study explores the high-temperature corrosion behavior and mechanisms of laser-clad Inconel 625 coatings applied in waste incineration environments. Inconel 625 coatings were deposited on a substrate using laser cladding technology, and corrosion tests were performed in various high-temperature acidic environments. The coatings were analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and laser confocal microscopy to investigate their microstructure, composition, and corrosion products. The findings indicate that corrosion weight gain was most pronounced in HCl environments at 800 °C and HBr environments at 600 °C, underscoring the critical influence of temperature and acidity on reaction kinetics. Moreover, the corrosion morphology was closely tied to the environment, with distinct patterns observed: pitting in HCl, nodular growth in H2SO4, and cracking and spalling in HF and HBr environments. High temperatures promoted oxidation reactions, resulting in the formation of a dense oxide layer predominantly composed of Cr2O3 and NiCr2O4, which offered some degree of protection. However, pitting and cracking in acidic environments suggested that the protective oxide layer's effectiveness was compromised under extreme conditions. This study provides a comprehensive understanding of the corrosion behavior and mechanisms of Inconel 625 coatings in various acidic environments and high temperatures within waste incineration applications. It offers valuable insights into the impact of temperature and different acidic media on corrosion rates and morphologies, laying the groundwork for predicting the service life and developing protective strategies for these materials in industrial settings.

High-temperature corrosion behavior of C276 alloy, 1.4529 steel and laser-cladding 1.4529 coating under the synergistic action of deposited chloride salt and HCl-containing atmosphere

The corrosion behavior and mechanism of C276 alloy, 1.4529 steel (9 S) and its laser-cladding coating (9 C) in a simulated waste incineration environment were studied by isothermal corrosion tests. The results show 9 C and 9 S have comparable corrosion resistance to C276 at 550 °C, and they are well protected by the mixed product layer rich in Fe and Cr. A loose and porous product layer caused the corrosion resistance of C276 to be lower than expected. At 700 °C, all three materials underwent severe high-temperature electrochemical corrosion and activated oxidation, forming a Ni-rich micro-nano porous surface and multilayer corrosion products.

Insight into the corrosion resistance of Mo-added NiCrBSi coating in simulated waste incineration environment

The corrosion resistance of Ni40AA and Ni40AA-Mo coatings on 304SS substrate was evaluated in molten NaCl-Na2SO4-KCl-K2SO4 salts at 600 ℃. In the oxidizing-chloridizing environment, results showed that Cr or Cr-rich oxides would react with molten salts and generate chlorides or chromates (Na2Cr2O4; K2CrO4). After adding Mo, the dissolved Cr in soluble corrosion products was significantly reduced. Mo substituted Cr to react with molten salts and reduced the depletion of Cr, which benefited the accumulation of Cr-rich oxides. Therefore, adding Mo enhanced the corrosion resistance of Ni40AA, reducing the corrosion weight gain by approx. 50% and the thickness loss by 1/3.

Analysis of material degradation for uncoated and NiCoCrAlY cold spray coated Superfer 800H in the secondary chamber of medical waste incinerator

NiCoCrAlY coating was deposited on Superfer 800H superalloy with cold spray process to reduce the degradation rate of substrate superalloy in actual medical waste incineration environment. Erosion–corrosion performance of uncoated and cold sprayed superalloy was evaluated in the secondary chamber of medical waste incinerator. The degradation rate of the specimens was assessed by measuring the thickness loss of the specimen after cyclic exposure for 1000h in medical waste incineration environment. Average degradation rate for uncoated and cold sprayed superalloy was found to be 157.95mpy and 36.56mpy respectively. The better performance of cold spray coated specimen might be attributed to the formation of protective Al2O3 scale at the top of surface and dense structure of the deposit coating.

The effect of temperature on mechanical properties of oxide scales formed on a carbon steel in a simulated municipal solid waste incineration environment

The effect of exposure temperature on the mechanical properties of scales in a carbon steel was investigated in a simulated waste incineration environment consisting of a gas mixture (N2-O2-H2O-HCl) with samples immersed in a salt (K2SO4-Na2SO4-ZnCl2-KCl) in the temperature range of 573 to 773K. The microstructure, corrosion rate, elastic modulus (E) and hardness (H) of scales were determined by SEM, XRD, descaled weight loss and instrumented indentation technique. The results indicated that both the E and H decreased as a negative exponential function of temperature, thus obtaining a low mechanical and microstructural integrity of scales with high defect density between 673 and 773K.

Waste incineration corrosion processes: Oxidation mechanisms by electrochemical impedance spectroscopy

AbstractMolten chloride mixtures are formed in waste incineration plants during waste firing and energy production. These mixtures are responsible for degradation processes like hot corrosion. In order to evaluate the damage of molten salt mixtures in waste incineration environments, the alloys 625 and 617 were exposed beneath a molten KCl‐ZnCl2 mixture at 650 °C in air. The corrosion process was monitored by electrochemical impedance spectroscopy (EIS). An extensive microscopy analysis has been done in order to correlate the electrochemical results, and to establish an electrochemical mechanism for such high temperature corrosion processes.

Materials performance in simulated waste combustion environments

Combustion of waste for power generation gives increased fouling and corrosion compared to fossil fuels, and leads to higher operating and maintenance costs. New materials solutions to increase lifetime include austenitic stainless steels, nickel base alloys, coatings and weld overlaying. In this work a simulated waste incineration environment with regularly renewed deposits of KCl–ZnCl2 has been used to evaluate the performance of candidate materials and to elucidate the operative degradation mechanisms.

Hot Corrosion Monitoring of Waste Incineration Corrosion Processes Using Electrochemical Techniques

In order to evaluate the damage of molten salt mixtures in waste incineration environments, the alloy 625 was exposed to a molten KCl-ZnCl2 mixture at 650 °C for 200 hours. The corrosion process was monitored by electrochemical impedance spectroscopy (EIS). After exposure the corrosion products were analyzed by X-ray diffraction and SEM. Two different electrochemical impedance models were found to describe the electrochemical processes. In the early stages of corrosion the alloy developed a protective Cr2O3 scale which turned into a porous spinel oxide scale after 100 hours.

Effect of Alloying Elements on Corrosion Resistance of Ni-Base Cast Alloys in Waste Incineration Environments

After examining practical structural materials for use in the high-temperature environments of waste incinerators, it was found that a Ni-Cr-W casting alloy is promising. However, the corrosion reaches its peak in the vicinity of 900°C. This peak is related to the behavior of chlorides that form in the interior of the alloy. As the chlorides continuously generate and decompose, the Cl recycles, accelerating corrosion. It is thought that when the temperature rises, the chlorides vaporize outside the alloy, suppressing Cl recycling and thus reducing the amount of corrosion. Adding Al to the alloy generates highly volatile AlCl3, making it possible to prevent the accumulation of chlorides in the vicinity of 900°C and lower the corrosion peak. As a result of conducting exposure testing for a year at an actual incinerator, it was demonstrated that adding Al is an effective way to improve corrosion resistance.

High temperature corrosion of metallic materials in simulated waste incineration environments at 300–600 °C

AbstractThe durability of the materials employed in waste incineration plants is affected by different factors that together result in severe degradation of the materials. The effects of alloying elements, as well as deposit composition and temperature range are investigated in this work. Different alloys were exposed in laboratory experiments to a specifically simulated waste incineration atmosphere N2 – 8 vol.% O2 – 2000 vppm HCl – 15 vol.% H2O – 200 vppm SO2 at 300–600 °C. The samples are covered with different salt mixtures especially chlorides and sulphates. Experiments with PbCl2‐KCl‐ZnCl2 at 450 °C, which is molten, showed catastrophic corrosion, but this was not observed in the case with KCl, which is solid. Mixtures of five different sulphates did not cause significant mass losses at 600 °C, but sulphate‐chlorided mixtures caused bigger mass losses. The presence of Al and Si in the alloys decreased mass change effects, the presence of Mo in alloys tested showed a negative effect.

Analysis of locally starting corrosion phenomena using mass change measurements

This paper describes a mathematical approach for the evolution with time of area-specific mass changes when locally starting enhanced corrosion processes occur simultaneously with general corrosion. For the formation of a single corrosion pit in a surface of limited size, the approach yields an analytical expression which qualitatively predicts the characteristic features of mass change versus time curves over the whole time range. Steps towards the mathematical description and numerical simulation of complex pitting situations, including pit coalescence, are outlined. The benefit from a mathematical analysis of mass changes in cases of local corrosion is exemplified using discontinuously measured mass changes of high-alloyed iron- and nickel-base materials after exposure to a simulated waste incineration environment.

ごみ焼却環境における耐熱鋳鋼SCH2の粒界腐食に及ぼすNb添加の影響

ごみ焼却環境における耐熱鋳鋼SCH2の粒界腐食に及ぼすNb添加の影響

廃棄物焼却ボイラの高温腐食に及ぼす応力の影響

廃棄物焼却ボイラの高温腐食に及ぼす応力の影響

Influence of Surface Preparation on the Corrosion of Steels in Simulated Waste Incineration Environments

In order to study the corrosion behaviour of stainless steels on the base of Fe-18Cr-10Ni were conducted in a simulated waste incineration atmosphere discontinuous exposures. Especially the influence of surface preparation and also the influence of alloying elements on the corrosion were of interest. Therefore different surface preparations as sandblasting, grinding and electropolishing were applied to the samples before exposure. The experiments were carried out in a N 2 -5%O 2 -2.5%H 2 O-0.05%HCl-0.05%SO 2 atmosphere at 600 °C with the samples embedded in fly ash from a waste incineration plant. In addition thermogravimetric experiments were conducted in a He-5%O 2 -0.05%HCl atmosphere at 600 °C without fly ash using a microbalance. Analysis of the corrosion products was performed after the experiments by scanning electron microscopy with EDX and X-ray analysis. The metal losses of the samples were determined after removing the corrosion scale.

Stability of protective oxide films in waste incineration environment—solubility measurement of oxides in molten chlorides

Solubility measurements of several oxides in molten NaCl–KCl and NaCl–KCl–Na 2SO 4–K 2SO 4 were conducted in three different levels of basicity. The dissolution behavior of the oxides showed almost the same tendency as that shown by the dissolution behavior of the oxides in molten Na 2SO 4 in literature. In a waste incineration environment, a protective Cr 2O 3 film easily dissolves in molten chlorides as CrO 4 2− because pO 2− of the molten chlorides tends to have a small value due to the effect of water vapor contained in the combustion gas. From the result of the solubility measurement, the addition of molybdenum and/or silicon was expected to improve the corrosion resistance of alloys. Laboratory corrosion tests confirmed this expectation. However, the scale analysis suggested that the effect of molybdenum could not be explained completely by only the mechanism derived from the result of the solubility measurement.

High temperature corrosion mechanisms and effect of alloying elements for materials used in waste incineration environment

Corrosion products on two typical materials, SA213-T12 steel and alloy 625 exposed to the actual combustion gas, were analyzed in addition to laboratory tests for penetration of corrosive matter. It has been clarified that corrosion products of oxides containing a little chlorides and sulphides show lamellar structures and that at the alloy–scale interface, chlorination, sulphidation, and oxidation occur under a low P O 2 –high P Cl 2 condition. The formation of scale structures and the effect of corrosion-resistant alloying elements can be explained according to the stability tendencies of metals, chlorides, and oxides in the M–Cl–O equilibrium diagrams. The severity of corrosion environments at the interface is influenced by the penetration extent of corrosive matters through deposits and scales, and the protective effects of oxide films derived from alloying elements play an important role in preventing the corrosion. On the other hand, it has been shown that thermal fluctuation characterized in this kind of environment makes the lamellar scale structures and sometimes breaks and peels off the scale, and thus accelerates the corrosion. On the basis of the above mentioned knowledge, a new corrosion model is presented.

廃棄物燃焼環境で材料耐食性の高精度評価を実現する熱勾配高温腐食試験法の開発

廃棄物燃焼環境で材料耐食性の高精度評価を実現する熱勾配高温腐食試験法の開発

Corrosion Behavior of IN-800 Superalloy in Waste-Incineration Environments: Hot Corrosion by Molten Chlorides

The corrosion resistance of the IN-800superalloy in contact with a molten mixture of (52-48)mol.% PbCl2-KCl, similar to that found inwaste-incineration plants, has been studied. Thecorrosion kinetics have been analyzed using continuous-currentelectrochemical techniques and electrochemical-impedancespectroscopy (EIS). Studies were performed to determinethe influence of temperature and of the presence of carbon in the salt on the corrosion rate.Scanning electron microscopy (SEM) and electron probemicroanalysis (EPMA) were used as additional techniquesto analyze the corrosion products in order to elucidate the corrosion mechanism.

Corrosion Behavior of 12CrMoV Steel in Waste Incineration Environments: Hot Corrosion by Molten Chlorides

The corrosion resistance of a 12CrMoV alloy incontact with a molten mixture of (52-48)mol.%PbCl2-KCl, similar to that found inwaste incineration plants, has been studied. Thecorrosion kinetics have been analyzed using continuous-currentelectrochemical techniques and electrochemical impedancespectroscopy (EIS). Studies were performed to determinethe influence that temperature and the presence of carbon in the salt have on the corrosion rate.Scanning electron microscopy (SEM) and electron-probemicroanalysis (EPMA) were used as additional analyticaltechniques to analyze the corrosion products in order to elucidate the corrosionmechanism.

交流インピーダンス法による廃棄物燃焼環境における材料の耐食性評価

交流インピーダンス法による廃棄物燃焼環境における材料の耐食性評価