Journal of Chemical Engineering and Energy Materials

Abstract Corrosion presents a significant challenge in the operation and maintenance of refinery units, particularly in the ISOMAX unit, which is essential for upgrading gasoline quality through isomerization of light hydrocarbons. This study investigates the corrosion behavior within the ISOMAX unit by analyzing the factors influencing corrosion rates, the prevalent corrosion mechanisms, and potential mitigation strategies. The ISOMAX unit operates under high temperature and pressure conditions with feedstock containing sulfur compounds, chlorides, and traces of water, all of which contribute to a corrosive environment. Corrosion assessment was conducted using in-situ corrosion probes, metallurgical examinations, and chemical analyses of process fluids. The results showed an average corrosion rate of approximately 0.15 mm/year in carbon steel components, with localized pitting corrosion observed near weld zones due to chloride accumulation. Sulfur-induced corrosion products such as iron sulfides were also identified, confirming the chemical attack on metallic surfaces. Hydrogen embrittlement was found to be minimal, indicating effective hydrogen control in the system. To mitigate corrosion, recommendations include pretreatment of feedstock to reduce impurities, employing corrosion-resistant materials in critical areas, using corrosion inhibitors, and maintaining optimized operational parameters. Implementing these strategies can significantly reduce corrosion impact, improve equipment longevity, and ensure safer and more efficient operation of the ISOMAX unit. This study underscores the importance of continuous monitoring and proactive maintenance to manage corrosion risks in refinery isomerization processes.

Abstract Catalytic Reforming Units (CRUs) are essential components in petroleum refineries, producing high-octane gasoline and aromatic hydrocarbons through the transformation of naphtha under high-temperature and hydrogen-rich conditions. However, these operational environments are highly conducive to several corrosion mechanisms, including chloride-induced corrosion, sulfidation, and stress corrosion cracking (SCC). This study investigates corrosion phenomena in CRUs by analyzing five years of operational and inspection data from a refinery in southern Iraq. Key variables such as temperature, chloride and sulfur concentrations, and hydrogen-to-hydrocarbon ratios were examined in relation to corrosion rates observed in critical areas like reactor effluents, heaters, and separators. The results reveal a progressive increase in corrosion rates from 0.18 mm/year in 2016 to 0.39 mm/year in 2021, primarily correlated with rising chloride content and operational temperatures. Notable equipment failures, including tube ruptures and cracking near welds, were directly linked to under-deposit corrosion and SCC. Regression analysis showed a strong correlation (R² = 0.86) between chloride levels and corrosion severity. Based on the findings, the paper proposes a set of mitigation strategies including material upgrades (e.g., Alloy 625), improved water washing systems to control chlorides, enhanced corrosion monitoring, and chemical treatments. The study emphasizes the importance of proactive corrosion management to extend equipment life, prevent unscheduled outages, and reduce operational risks in CRU operations.

Abstract Corrosion in Liquefied Petroleum Gas (LPG) units poses significant challenges to the safety, reliability, and efficiency of refining and petrochemical operations. These units operate under high pressure and varying temperature conditions, exposing metallic equipment to aggressive environments containing corrosive agents such as hydrogen sulfide (H₂S), carbon dioxide (CO₂), moisture, and trace acidic compounds. The interaction of these substances with carbon steel and other commonly used materials leads to various corrosion phenomena, including uniform corrosion, localized pitting, and stress corrosion cracking. Sweet corrosion, primarily driven by CO₂, results in the formation of iron carbonate protective scales under certain conditions, while sour corrosion induced by H₂S forms brittle iron sulfide layers that exacerbate metal degradation. Additionally, microbiologically influenced corrosion (MIC) caused by sulfate-reducing bacteria further complicates corrosion management in LPG storage facilities. Effective corrosion control requires a multifaceted approach involving material selection, chemical inhibitors, protective coatings, and rigorous operational monitoring. Electrochemical techniques such as Electrochemical Impedance Spectroscopy (EIS) and Linear Polarization Resistance (LPR) are widely employed for real-time corrosion rate assessment. Despite advancements in mitigation strategies, corrosion remains a critical concern due to its impact on operational costs, safety hazards, and equipment lifespan. Continued research and development are essential to optimize corrosion prevention methods and enhance the durability of LPG processing and storage infrastructure.

Abstract The integration of renewable energy sources into modern power grids has significantly increased the operational demands on synchronous generators. Among various fault conditions, loss of excitation (LOE) presents a critical threat, causing under-excitation, instability, and potential damage to generators. Traditional protection schemes often rely on electromechanical relays and conventional sensors, which may not respond optimally under the variable operating conditions of renewable energy systems. This article explores the potential of smart materials—including piezoelectric, magnetostrictive, and shape memory alloys—to enhance LOE protection schemes. These materials can be integrated into sensing and actuation systems to provide rapid, adaptive, and precise responses to excitation loss. A comprehensive review of material properties, sensor integration strategies, modeling approaches, and experimental validations is presented. The findings indicate that smart-material-based schemes improve the detection speed, reliability, and fault-tolerant performance of synchronous generators while enabling seamless compatibility with distributed renewable energy systems. The paper concludes with a discussion of challenges and future directions, including material durability, system scalability, and cost-effective implementation.

Abstract The present study examines and introduces the network method as a numerical method for solving the groundwater equation. The use of network models has grown significantly over the past decade. These models have been widely used in the fields of petroleum and environmental engineering. The application of the network model in recent years has not been limited to cases such as calculations related to two-phase flow or permeability calculations. New applications of this type of model include the study of three-phase flow, the effect of hysteresis, wettability, and mass transfer between different phases, which were mentioned in detail in the research background chapter. The purpose of this research is to use the network model as a numerical method for solving the groundwater equation in the saturated state, meaning that the problem in question is divided into different nodes using the network model and instead of solving the partial differential equation governing the problem, the equation governing the network model is solved. According to the equations obtained for homogeneous and homogeneous aquifers, the coefficients of different nodes depend only on their distance from the node in question and are proportional to the inverse of their distance. In the section investigating the effect of heterogeneity and asymmetry, the coefficients obtained, in addition to being proportional to the inverse of their distance, were also proportional to the fourth power of the pipe diameter. In order to be able to attribute the coefficients of the nodes only to the length in all cases, whether homogeneous and homogeneous or inhomogeneous and non-homogeneous porous media. The advantage of using equivalent length is that all node coefficients will be a function of their distance from the desired node only.

Abstract The study of biological removal of volatile inorganic compounds has been widely conducted. Most studies have focused on H2S and other sulfur or nitrogen-containing compounds such as sulfides, mercaptans, methane thiol, or ammonia. The removal of H2S from wastewater treatment plants was investigated in 1923, and the oldest recorded article is from 1934. In various studies that have been conducted so far to remove pollutants including H2S, different biological systems have been used. As mentioned earlier, these biological systems include bio filters, trickling bio filters, and biological scrubbers. The use of bio filters with organic substrates is more commonly used for biological treatment of volatile inorganic compounds. Since microorganisms grow as biofilms on packing materials and absorb, decompose, and convert pollutants into non-harmful substances. Therefore, the selection of the appropriate microorganism in biological treatment will play an important role. For the removal of sulfur-containing compounds in bio filters, microbial species of the genera Thiobacillus and Hyphomicrobium are often considered very desirable decomposers. Volatile organic compounds can also be treated by specialized microorganisms. These compounds include halogenated aliphatic and other halogenated and aromatic pollutants. The dominant microorganisms in VOC-purifying bio filters are heterotrophs that require an organic carbon source and are unable to use carbon dioxide as the sole carbon source. Removal capacity, which indicates the rate of pollutant removal at a given mass load and is defined as the mass of pollutant removed per unit bed volume per unit time, is an important parameter in biological removal processes. This parameter for different pollutants in the biological treatment of VIC can vary from a few grams to more than 200 grams per cubic meter per hour of inlet gas with a removal efficiency of over 90%, and this parameter has been reported as one of the main parameters in various articles