Corrosion Threat Research Articles

Determination of Optimal Corrosion Logging Frequencies for Gas Storage Fields

Summary Many of the existing wells in underground natural gas storage facilities were originally designed to extract hydrocarbons, using construction techniques and practices that differ from modern storage well drilling and completion practices used today. In addition to the age of these wells, their primary flow strings and tubulars may have been exposed to naturally occurring corrosive environments that could have degraded their wall thickness and remaining burst strength. This presents a serious risk of well failure and loss of containment for both the wells and reservoirs of these fields. To address this issue, the Pipelines and Hazardous Materials Safety Administration in its interim final rule recommended that all operators of gas storage facilities determine the reassessment intervals required to maintain the pressure rating and flow isolation properties of the flow string of all gas storage wells. This work presents a novel methodology for establishing the optimal logging frequencies required to maintain the integrity casing wall thickness of the primary flow string, which serves as the leading indicator of casing integrity. In this study, metal loss data from magnetic flux-leakage logs run on existing gas storage wells are collected, vetted, and used to derive a probabilistic distribution of linear corrosion rates. Statistical values of corrosion rate corresponding to severity levels are used to approximate the corrosion rate distribution, allowing for deterministic prediction of remaining burst strength with suitable failure criterion models. The modified ASME B31G model is used to predict casing remaining life as a function of metal loss class and average corrosion rate (ACR). The reliability criterion for establishing fitness-for-service of a corroded casing string is evaluated separately using Monte-Carlo simulation, while reassessment intervals corresponding to a particular casing condition are calculated deterministically. The modeling results with the new approach present predictions of remaining life for four commonly used casing strings as a function of metal loss class and ACR. The results show that the remaining life of a corroded casing can be reasonably estimated as a function of static corrosion rate and metal loss class. The most significant finding is that a brand-new well with an average annual corrosion rate of 1.0% initiating instantaneously upon installation will have an estimated remaining life of 28–32 years. Reassessment intervals are defined based on casing half-life as a function of metal loss class and ACR. A field case study is also presented to demonstrate the successful application of the new methodology in predicting reassessment frequency to mitigate risks from external corrosion mechanisms. The novelty of the proposed approach is in the ability to reasonably predict casing remaining life and safety target levels using derived statistical distributions of linear corrosion rates calculated from magnetic flux leakage logs. This in turn allows operators to confidently establish reassessment intervals for future casing inspection logging to identify corrosion threats in a timely manner that achieves a balance of risk mitigation and cost savings.

Study of anti-corrosion epoxy resin coatings with high corrosion resistance and mechanical performance based on quantum dots

The corrosion of steel construction in marine environments faces severe corrosion threats, and coatings based on nanofillers are an effective strategy for steel corrosion protection. However, the related studies of the anti-corrosion coatings based on quantum dots are still poor. In this work, CuS and ZnS quantum dots (QD) were initially synthesized, and epoxy resin (EP) coatings containing QD with ratios of 0.05 wt%, 0.1 wt%, 0.2 wt%, and 0.5 wt% were successfully prepared subsequently. Surface analysis, electrochemical measurements, salt spray tests, and mechanical tensile tests were performed to characterize the prepared quantum dots and study the anti-corrosion behavior and mechanism of the prepared coatings. Results indicated that the prepared CuS and ZnS quantum dots have small sizes with values of 13.8 and 8.9 nm, respectively. Compared to the pure EP coating, QD-EP coatings have a higher mechanical strength and toughness which is conducive to improving the coatings’ corrosion resistance and service life. The impedance values of all the QD-EP coatings increase by more than three orders of magnitude in contrast to pure EP coating after 60 d of testing. Furthermore, the prepared QD-EP coatings possess a long-term anti-corrosion property.

Synthesis of NiCrAlY nano-scale powder by high-energy ball milling process for thermal spray coating application

These days, during the issues of climate change, there has been a shift in the energy industry from using fossil fuels to more environmentally friendly fuels such as biomass fuels. Biomass fuel is considered CO2 neutral because the carbon produced during combustion in the form of CO2 emissions can be used for new plant growth. However, besides the advantages of using biomass fuel, a problem arises when biomass fuel contains a high concentration of corrosive agents, which can be released along with hot fuel gas. These corrosive agents can damage the boiler components. Coating technology is one of the solutions to protect components that work at high temperatures against the corrosion threat. One type of coating that can be used in high-temperature applications is NiCrAlY coating by the high-velocity oxide (HVOF) process. One interesting topic that people are developing is using nano-scale coating to increase the coating’s resistance against hot corrosion and cracking. Nano-scale powder feedstock is needed to produce nano-scale coating material. In this research, top-down method is used to synthesis nano-scale powder. One of top down method, the high-energy ball milling processs, is a promising method to synthesize nano-scale powder material. Therefore, in this research, the ball milling process is used to prepare nano-scale product. The results showed that this method was successful to make the nano-scale powder. The nano-scale powder was characterized by several methods to investigate the morphology and properties of the powders. However, there are still many challenges in producing nano-scale powder that meets HVOF feedstock powder requirements. In the long run, it is expected that this research can answer those challenges so that at the end, the good quality of nano-scale powder can be achieved

Bio-inspired self-healing and anti-corrosion waterborne polyurethane coatings based on highly oriented graphene oxide

In the face of ubiquitous corrosion threats, the development of high-performance elastomer protective materials with active self-healing functions is extremely challenging and significant. We propose an approach by combining WPU elastomer with GO to create the multifunctional pearl layer structured polymers with interface hydrogen bonds. By crosslinking the polycaprolactone diol (PCL) chain with a hydrogen bond array, the elastomer with high mechanical strength, extensibility, elasticity, excellent damage resistance, and healing properties was successfully synthesized. The elastomer exhibits remarkable mechanical properties, including a tensile strength of 39.89 MPa, toughness value of 300.3 MJ m−3, and fracture energy of 146.57 kJ m−2. The enhanced damage resistance of the elastomer can be attributed to the decomposable hydrogen bond array as well as the strain-induced crystallization of PCL fragments, which effectively dissipate energy. Importantly, due to the reversibility of the hydrogen bonding array, the fractured WPU can easily heal and restore its original mechanical properties when subjected to heating at 50 °C. Moreover, the photothermal properties of GO enable the biomimetic polymer coating to achieve damage recovery after being irradiated with NIR for 30 s. The obtained biomimetic coating exhibits a highly oriented lamellar structure, thereby greatly enhancing physical barrier performance and anti-corrosion performance. Electrochemical impedance spectroscopy (EIS) shows that the impedance modulus is one order of magnitude higher than that of the blank coating. Additionally, scanning vibrating electrode (SVET) confirmed that the self-healing performance and protection effect of the biomimetic coating in 3.5 wt% NaCl solution were also reliable. This highly reliable biomimetic coating presents a revolutionary solution for creating multi-functional, high-performance smart material in harsh environments.

Faster RSTRENG: A More Efficient Effective Area Method Algorithm for Corrosion Assessment

AbstractCorrosion is one of the major threats to the safety and structural integrity of oil and gas transmission pipelines. The corrosion threat is usually managed by regular in-line inspection (ILI). The effective area method (RSTRENG) is the most popular corrosion assessment model to convert the measured corrosion size to predicted burst pressure. Given a detailed corrosion measurement profile, the effective area method involves an iterative process to find the minimum burst pressure. As stated in ASME B31G, “for a corroded profile defined by n measurements of depth of corrosion including the end points at nominally full wall thickness, n!/2(n − 2)! iterations are required to examine all possible combinations of local metal loss with respect to surrounding remaining material,” the widely used effective area algorithm has at least an order of n-square time complexity (O(n2)). As n increases, the computation time increases nonlinearly. This paper reviewed the traditional RSTRENG algorithm first, and demonstrated that it is not necessary to always loop through all the combinations and check the corresponding burst pressure one by one. Because some combinations with shallower and shorter corrosion size are certainly not the final critical combination corresponding to the minimum burst pressure. A more efficient algorithm (Faster RSTRENG) is proposed and presented in this paper, which can reduce the algorithm computation time significantly.

Non-uniform corrosion characteristics of the steel pipe pile exposed to marine environments

Steel pipe piles are commonly used as structural members in offshore construction steel trestles, and they may be imposed with serious corrosion threats. This study examines the corrosion characteristics of steel pipe piles which have been existing in the East China Sea for about five years. Nine samples were collected from the splash, tidal, and immersion zones, and cleaned and scanned by a laser scanner. Then they were reverse-modelled, 3D coordinates of the surfaces were generated, and the remaining thickness was calculated. Based on the surface height data, the waviness component was filtered while the roughness component was retained for each surface, and the topographic parameters were calculated and compared. The results reveal that the remaining thickness and the roughness of the steel pipe pile both showed non-uniform features. The steel pipe pile experienced double-sided corrosion in the splash and tidal zones, whilst it only experienced one-sided corrosion on the outer surface in the immersion zone. The severest corrosion damage was observed in the splash zone. Besides, the extreme value analysis results indicated that the minimal values of the remaining thickness in all zones conformed to the generalized extreme value distribution.

Effects of Thiophene Degradation on the Corrosiveness of Oil and the Properties of Oil–Paper Insulation in the Oil-Immersed Transformers

As a non-corrosive inactive sulfur, thiophene is one of the most common sulfides in mineral oil, which are retained in oil and used for improving the oxidation stability of the oil. However, thiophene may be decomposed and form low-molecular sulfide with strong corrosiveness because of rapid energy accumulation under operating conditions of the oil-immersed power transformer. Thus, this study explored the effect of thiophene degradation on the corrosiveness and properties of insulating oil under thermal and electrical aging conditions, including a case investigation of sulfur corrosion of a 500-kV electric reactor and the accelerated aging experiments of oil–paper insulation. The results showed that the degradation and pyrolysis of thiophene depend on energy accumulation induced by thermal and electric fields in the oil-immersed transformers. Under the premise of thiophene without degradation and transformation, thiophene can still delay the deterioration of insulating oil due to its high oxidation resistance. The continuous energy accumulation induced by thermal and electric fields may cause the molecular chains of thiophene molecules to break and form some corrosive low-molecular sulfides, thereby resulting in the increase of the corrosiveness of oil, the decrease of the properties of oil–paper, and posing a huge corrosion threat to the oil-immersed transformer.

Assessment of Rainfall Erosivity Index using Lombardi Method for Amritsar, Punjab, India

The erosivity thing with inside the conventional soil loss equation (USLE) affords a powerful approach ofcomparing the erosive energy of rainfall. This study estimated the erosivity factorbased on monthly and yearly periodic rush rainfall data of Amritsar, Punjab State covering a period of 45 year from1971 to 2015using Lombardi system (EI = 1.03 Vd1.51). It was found that early arrived rainfall led high erosive index.The data of seasonal distribution of precipitation illustrated that the most ferocious erosion imminence inthe area can be anticipated in August, especially in the areas that aren’t defended by foliage cover, whichmight be due to climatic change. The average periodic erosivity indicator for the megacity during theperiod of study was 744.6 MJ mm/ hr. The correlation between periodic erosivity indicator andaverageperiodic rush was expressed as Y = 0.0002x + 0.8873. The R2 of 0.79 shows that rush alone contributed 79 %of the corrosion threat within the study period. The knowledge of impact of rainfall on erosivity is essentialin soil erosion threat assessment and for soil and water conservation planning. The information on effect ofprecipitation on erosivity is important in soil disintegration threat evaluation and for planning of waterand soil conservation.

Identifying, Predicting and Preventing Localized Corrosion in Kr-85 Storage Canisters from the Reprocessing of Nuclear Fuel

During the reprocessing of nuclear fuel radioactive gases are released from the fuel matrix. These gases need to be separated and stored to prevent release into the environment. It is proposed that certain risk factors, which are elucidated herein, caused accelerated corrosion of the interior canister walls breaking containment of legacy storage canisters. The main risk factor of concern is the effect of Rb-85. Rb-85 is produced from the radioactive beta minus decay of Kr-85. The main question is whether an environment containing Rb as a decay product causes corrosion of the canister materials at an accelerated rate. If this does occur, the the corrosion threat will grow with time as more rubidium is produced.Based on the environment within the canister, and the risk factors of the system, a corrosion lifecycle has been developed and is briefly discussed. Stage 1 represents the canister at high temperature of 600°C after it has been sealed and hot isotactic pressed (HIP) for 4 hours. In this stage it is possible for oxides to form on the canister walls due to the residual oxygen in the canister from loading. It is possible that the presence of Rb will interact with the canister material and disrupt the formation of iron and chromium oxides. These Rb oxides, if present, may not inhibit corrosion thus causing an increase in the corrosion rates. Stage 2 represents the canister cooling from 600°C to ambient. In this stage wet thermal oxides will form on the canister walls as the temperature drops below the deliquescence point and water droplets appear, setting up the conditions for aqueous corrosion, like stage 1 the possible formation of RbxCryOzwhich may not be as protective as other oxides, can cause an increase in corrosion rates. Stage 3 represent oxide and environmental interactions. In this stage the environmental risk factors, such as the presence of cathodic reactants oxygen, hydron and peroxide, will create conditions to enable aqueous corrosion. Stages 4 through 8, describe the stages of pitting, uniform corrosion, and galvanic corrosion. Because the material chosen for the canister is 4130 low alloy steel, and the welding material used was 304 stainless steel, there is the possibility of galvanic corrosion. This can increase the uniform corrosion rate, and lead to more pitting events causing depassivation of the surface, or deeper pit penetration. The chosen canister materials are also at risk of pitting attack, the risk of which is increased as the canister is likely driven to alkalinity from the products of the cathodic reaction. Pitting is especially dangerous to the canister which needs to maintain containment for 100 years.This work looks to test the risk factors and develop a mechanistic understanding of the canister’s corrosion process with the goal of recommending a material that will be able to maintain containment for the needed 100 years if nuclear fuel were to start being repressed in the United States.

Copper corrosion inhibition in nitric acid solution by 2-(1,3-dihydrobenzimidazol-2-ylidene) -3-oxo-3-(pyridin-3-yl) propanenitrile: Gravimetric, Quantum chemical and QSPR studies

The metal corrosion threat in the metallurgical industry is becoming increasingly important. So in this work, the inhibition properties of 2-(1,3-dihydrobenzimidazol-2-ylidene)-3-oxo-3-(pyridin-3-yl) propanenitrile for copper corrosion in 1 M nitric acid medium were evaluated by mass loss technique, density functional theory (DFT) and quantitative structure-property relationship (QSPR) model. The results show that this compound was excellent anticorrosive properties with a maximum inhibition efficiency of 89.39 % for a concentration of 0.2 mM at 323 K. The inhibition efficiency increases with increasing temperature and inhibitor concentration. Adsorption isotherms reported that the molecule adsorbs on copper surface according to Langmuir isotherm. Thermodynamic adsorption and activation parameters were determined and analyzed. They revealed spontaneous adsorption and a strong interaction between the molecule and copper surface. DFT calculations at the B3LYP level with 6-31G(d,p) and 6-311G(d,p) basis set permitted to explain the electronic exchanges between molecule and copper, thus justifying the experimentally obtained inhibition efficiency values. A local reactivity study of molecules indicated that N (29) and C (7) atoms are the likely sites for nucleophilic and electrophilic attacks, respectively. In addition, QSPR model was used to correlate experimental inhibition efficiency with the descriptor parameters of the studied molecule, and it is found that the calculated inhibition efficiencies are close to experimental inhibition efficiencies. Finally, this study showed a good correlation between theoretical and experimental data.

Artificial-Intelligence and Machine-Learning Technique for Corrosion Mapping

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 202801, “Automated Corrosion Mapping AI and Machine Learning,” by Marc Majors and Travis Harrington, Occidental, and Eric Ferguson, Abyss Solutions, et al. The paper has not been peer reviewed. The complete paper discusses risk reduction and increased fabric-maintenance (FM) efficiency using artificial-intelligence (AI) and machine-learning (ML) algorithms to analyze full-facility imagery for atmospheric corrosion detection and classification. With this tool, a comprehensive and objective analysis of a facility’s health is achievable in a matter of weeks from the time of data collection. This application of AI and ML is a novel approach aimed at gaining a comprehensive understanding of facility-coating integrity and external corrosion threats. Introduction Atmospheric corrosion is the most-significant asset-integrity threat in the Gulf of Mexico (GOM). Offshore facilities require constant inspection and FM—and the significant financial obligation of these activities—to stay ahead of rapid equipment degradation. In general, regulatory codes in the GOM require a visual inspection of pressure equipment and piping on a 5-year frequency at minimum. A common approach is to inspect 20% of the facility per year, with a rolling 5-year inspection plan, to balance the inspection work through time. As a result, in a 5-year inspection cycle, the owner or operator of the facility will not see the condition of the piping or equipment for the 4 years between inspection cycles. Considering the complexity, high areas, overwater, and other difficult-to-inspect areas, gathering data for inspection can be costly and time-consuming and can yield a variable quality of results. An effective asset-integrity program requires full visibility of asset and equipment condition. Prioritizing areas for nondestructive examination (NDE) on high-consequence equipment and piping allows for effective risk reduction and FM planning. To that end, AI and ML are being harnessed to detect, classify, quantify, and report the condition of piping and equipment in the GOM.

The Virtual Corrosion Engineer

The conventional corrosion management process consists of defining the expected process conditions, identifying potential corrosion threats, and estimating their likely rate, then using that information to develop mitigation plans and inspection schedules. The Virtual Corrosion Engineer (VCE) project aims to improve this process by utilizing online monitoring data to automate the running of the best available corrosion models and provide a continuously updated dashboard in real time. This paper provides an overview of the VCE, together with a brief discussion of the underlying models for two exemplar damage mechanisms, High-Temperature Hydrogen Attack (HTHA) and Under Deposit Corrosion (UDC) in steam generators.

Efficacy of glutaraldehyde enhancement by D-limonene in the mitigation of biocorrosion of carbon steel by an oilfield biofilm consortium.

Microbiologically influenced corrosion (MIC) is one of the major corrosion threats in the oil and gas industry. It is caused by environmental biofilms. Glutaraldehyde is a popular green biocide for mitigating biofilms and MIC. This work investigated the efficacy of glutaraldehyde enhancement by food-grade green chemical D-limonene in the biofilm prevention and MIC mitigation using a mixed-culture oilfield biofilm consortium. After 7 days ofincubation at 37°C in enriched artificial seawater in 125mL anaerobic vials, the 100ppm (w/w) glutaraldehyde + 200ppm D-limonene combination treatment reduced the sessile cell counts on C1018 carbon steel coupons by 2.1-log, 1.7-log, and 2.3-log for sulfate reducing bacteria, acid producing bacteria, and general heterotrophic bacteria, respectively in comparison with the untreated control. The treatment achieved 68% weight loss reduction and 78% pit depth reduction. The 100ppm glutaraldehyde + 200ppm D-limonene combination treatment was found more effective in biofilm prevention and MIC mitigation than glutaraldehyde and D-limonene used individually. Electrochemical tests corroborated weight loss and pit depth data trends.

Assessment of microbiologically influenced corrosion in oilfield water handling systems using molecular microbiology methods

The monitoring, prediction and control of microbiologically influenced corrosion (MIC) are common challenges in the oil industry. This paper aims to optimize monitoring of souring and corrosion threat in oil field water handling systems using latest developments in molecular microbiological methods. Microbial quantification was performed using quantitative polymerase chain reaction (qPCR) method. Microbial population structure fingerprinting was done using next generation sequencing (NGS). The findings were compared with the corrosion rates and most probable number (MPN) values obtained from conventional serial dilution methods. The results show that molecular microbiology methods provide faster and optimum corrosion mitigation strategies.

Techno-commercial Assessment of Concurrent Municipal Brown Field Reclamation Procedures: A Pivotal Case study of Jawahar Nagar Dump Site

Techno-commercial Assessment of Concurrent Municipal Brown Field Reclamation Procedures: A Pivotal Case study of Jawahar Nagar Dump Site

Corrosion risk assessment using adaptive bow-tie (ABT) analysis

Corrosion is a major threat to safety and asset integrity in oil and gas production and processing facilities. This paper proposes a simple, yet practical model for quantitative corrosion risk assessment from safety and economic perspectives. This includes an Adaptive Bow-Tie (ABT) model for the corrosion risk with a specific focus on microbiologically influenced corrosion, along with corrosion economic risk profile. The ABT model is logically tested using corrosion science and statistically verified using a pipeline corrosion database, including cases of corrosion-induced failures. The ABT model also provides opportunities to run root-cause contribution (RCC) analysis and to estimate the probability of corrosion, corrosion-induced failures, and highly probable sequences leading to failure. The model application is demonstrated using a crude oil transportation pipeline system. The study identifies and quantifies parameters that helps to prioritize the actions needed to prevent and control corrosion and avoid failures. The proposed model can serve as an important mechanism to identify, assess, and manage corrosion threat to an asset.

Evaluation of 475 °C embrittlement in UNS S32750 super duplex stainless steel using four-point electric conductivity measurements

One of the consequences of the 475 °C embrittlement of duplex stainless steels is the reduction of the resistance to localized corrosion. Therefore, the detection of this type of embrittlement before the material exhibits significant loss in toughness, and corrosion resistance is important to ensure the structural integrity of critical components under corrosion threats. In this research, conductivity measurements are performed using the alternating current potential drop (ACPD) technique with using a portable four-point probe as a nondestructive evaluation (NDE) method for detecting the embrittlement in a 2507 (UNS S32750) super duplex stainless steel (SDSS) aged at 475 °C from as-received condition to 300 h. The electric conductivity results were compared against two electrochemical tests namely double loop electrochemical potentiokinetic reactivation (DL-EPR) and critical pitting temperature (CPT). Mechanical tests and the microstructure characterized using scanning electron microscopy (SEM) imaging are conducted to track the progress of embrittlement. It is shown that the electric conductivity correlates with the changes in impact energy, microhardness, and CPT corrosion tests result demonstrating the feasibility of the four-point probe as a possible field-deployable method for evaluating the 475 °C embrittlement of 2507 SDSS.

Technical Note: Monitoring X65 Steel Internal Corrosion in Humidified N2-Containing H2S Using Membrane-Based Electrochemical Sensors

This paper will report on a new membrane-based electrochemical sensor that may provide an important utility in monitoring and characterizing internal corrosion of natural gas pipelines. Using this sensor, the corrosion rate of X65 steel exposed to H2S in humidified environments up to 60°C has been measured. Consistent with the authors’ earlier CO2 study, the membrane’s conductivity did not change when exposed to H2S-containing acidic gas. Introducing H2S consistently increased the measured corrosion rate between testing conditions, though corrosion rates were typically less than 2 μm/y. At 30°C, the corrosion rate doubled from 7.3 nm/y to 14 nm/y below a relative humidity of 30%, and it increased by an order of magnitude (0.19 μm/y to 1.9 μm/y) at 55% relative humidity, showing that the influence of H2S on corrosion increases dramatically with greater humidity. Trends with relative humidity match industry expectations: the corrosion rate is low (<0.25 μm/y) without the presence of a condensed aqueous phase, but it increases as the water content of the system increases. The membrane-based electrochemical sensor (MBES) was therefore able to capture relevant corrosion trends, even while the corrosion rates would not have presented a serious threat to any natural gas pipeline. As such, the MBES can be used to detect the onset of emerging corrosion threats before they occur. Field emission scanning electron microscopy and energy-dispersive x-ray spectroscopy confirmed that H2S reacted with the metal covered by the membrane phase, showing evidence of sulfur-rich sites on the X65 surface. In addition, finite element analysis (FEA) confirmed that electrochemical measurements and data analysis techniques could be successfully used for this membrane-based sensor, despite its unconventional cell geometry.

Alternative approach for efficient hole transporting electrode by depositing MWCNT layer on CZTS-MWCNT material for perovskite solar cell application

Abstract Metal electrode contact (i.e., Al, Ag, and Au) used for charge collection at perovskite solar cells (PSCs) needs an alternative replacement due to their expensive processing cost. Chemically reactive organic hole-transporting material (HTM) easily exposes corrosion threat to these metal electrode contacts at the Metal/organic-HTM junction. Including these two critical factors, PSC also faces a challenging issue of interface instability at perovskite/organic HTM junction. Therefore, in this work, metal contact has been replaced by Multi-wall Carbon Nanotube (MWCNT) with a simple drop-casting deposition process, and inorganic semiconductor material Cu2ZnSnS4 (CZTS) has been applied as HTM by spin coating technique. However, to improve the efficiency of PSC, CZTS-MWCNT composite has been used here as HTM due to its significant optoelectronics properties. These materials CZTS, MWCNT, and CZTS-MWCNT composites have been synthesized and characterized by XRD, FESEM, TEM, UV–Vis, and Raman spectroscopy, respectively. The fabrication process of the regular (n-i-p) structured PSCs has been described, and the photovoltaic performances have been investigated by their current-voltage characteristics. It has been observed that MWCNT embedded composite HTM (i.e., CZTS-MWCNT) has not only successfully delivered 7.60% PCE but also improved the stability of the PSC.

A kinetic evaluation on NO2 formation in the post-flame region of pressurized oxy-combustion process

Pressurized oxy-combustion is a promising technology that can significantly re-duce the energy penalty associated with first generation oxy-combustion for CO2 capture in coal-fired power plants. However, higher pressure enhances the production of strong acid gases, including NO2 and SO3, aggravating the corrosion threat during flue gas re-circulation. In the flame region, high temperature NOx exists mainly as NO, while conversion from NO to NO2 happened in post-flame region. In this study, the conversion of NO ? NO2 has been kinetically evaluated under representative post-flame conditions of pressurized oxy-combustion after validating the mechanism (80 species and 464 reactions), which includes nitrogen and sulfur chemistry based on GRI-MECH 3.0. The effects of residence time, temperature, pressure, major species (O2/H2O), and minor or trace species (CO/SOx) on NO2 formation are studied. The calculation results show that when pressure is increased from 1 to 15 bar, NO2 is increased from 1 to 60 ppm, and the acid dew point increases by over 80?C. Higher pressure and temperature greatly reduce the time required to reach equilibrium. With increasing pressure and decreasing temperature, O plays a much more important role than HO2 in the oxidation of NO. A higher water vapor content accelerates NO2 formation in all cases by providing more O and HO2 radicals. The addition of CO or SO2 also promotes the formation of NO2. The NO2 formation in a pressurized oxy-combustion furnace can be over 10 times that of an atmospheric air-combustion furnace.