Safety risk control in engineering design serves as the foundational guarantee for production safety in the refining and chemical industry. This paper summarizes the inherent safety risks associated with materials, operating conditions and external environments in refining and chemical units. It outlines the three-tier technical framework comprising inherent safety design, risk prevention and control and emergency response. It also clarifies the key control points throughout the entire design lifecycle. It is considered that compared to the regulatory standard systems of Europe and the United States, China's system exhibits differences in concepts and methodologies, academic foundations, and enforcement effectiveness. The paper identifies significant gaps in standard coverage within China's refining and chemical engineering safety risk governance framework in areas such as aging process units, extreme operating scenarios, emerging technology implementations, and intelligent safety management at the facility level. In response to these issues, the paper proposes recommendations for improving relevant regulations and standards.

Based on computational fluid dynamics (CFD) simulation technology, this paper conducts an optimization study on the agitated crystallizer in the lactide flash crystallization process. By establishing a gas-liquid-solid three-phase Eulerian model, the effects of key parameters including inlet vapor fraction (10%~30%), impeller diameter (600~900 mm), rotational speed (80~110 r/min) and the addition of bottom-sweeping impellers on crystallizer flow field distribution were investigated systematically. Research findings indicate that maintaining the inlet vapor fraction at 20% not only prevents excessive liquid phase entrainment by the gas phase, but also ensures effective flash separation efficiency; increasing the impeller diameter to 800 mm and adding a bottom-scraping impeller can effectively reduce solid-phase deposition at the bottom; an impeller rotational speed of 90 r/min achieves uniform suspension of the solid phase. Comparative analysis between CFD simulation results and calculated value based on the empirical formula for power number shows a small deviation, confirming the reliability of the model. This research provides critical design guidance and support for the industrial scale-up of lactide crystallizers.

Targeting the operational issues in quench heat exchangers of ethylene cracking furnace, this paper systematically analyzes the key factors affecting the long-term operation with focused research on reducing coking rates, minimizing the damage of inlet heat exchanger tube and significantly decreasing leakage probability in the high-pressure water circuit. Based on the findings, effective optimization and improvement scheme is put forward from the aspects of design, operation and maintenance so as to ensure safe and stable operation of the quench heat exchanger, thereby providing robust support for long-term stable operation of ethylene cracking furnaces.

Storage tanks serve as critical equipment for energy storage and are widely utilized in the petrochemical industry. Damage accidents caused by overpressure of medium in storage tank occur from time to time. Accurate prediction of the pressure at the roof-to-shell junction is critically important for ensuring weak roof-to-shell attachment failure occurs during overpressure scenarios. Therefore, this paper took a dome-roof tank as the research object and the failure pressure at its roof-to-shell junction using method and simulation method respectively. It conducted a analysis of the failure pressure assessments at the tank roof-to-shell junction, evaluating elastic failure versus elastoplastic failure under varying stress evaluation criteria. The calculation results indicate that the failure pressure at the roof-to-shell junction progressively decreases with increasing tank diameter; the analytical method yields the lowest failure pressure, amounting to only half of that from numerical simulation; and the failure pressure values calculated using the linear elastic strength failure assessment method are 1.2 times those obtained from the elastoplastic yield failure assessment method. The research findings can provide references for the estimation of failure pressure at the tank roof-to-wall junction and for weak roof-to-shell attachment design.

Automatic control of the drying process is a crucial means of achieving drying objectives. It plays a vital role in ensuring uniform moisture content of the discharged material, improving material quality, reducing labor intensity and optimizing dryer performance. Aiming at the control requirements of dryers for material drying, a temperature control scheme for the dryer was proposed and optimized. Meanwhile, based on in-depth research on the fuzzy PID control algorithm, a temperature control system for ribbon dryers based on fuzzy PID control was designed, and the overall dryer control system was implemented through a PLC system. This solution can ensure material drying quality while enhancing equipment automation and production efficiency, delivering superior control performance. The research outcome facilitates determining optimal process parameters for material production, improving product consistency and quality.

Fatigue assessment of pressure vessel welded joints is a critical process to ensure the long-term safe operation of the equipment. With the release and implementation of the GB/T 4732.1~4732.6—2024 (hereinafter referred to as GB/T 4732) standard, China's fatigue design methods for pressure vessels has made significant progress based on the ASME standard system. However, it still differs notably from the European EN 13445—2021 (hereinafter referred to as EN 13445) standard in welded joint assessment. Based on existing theoretical research, this study systematically compared the technical differences between GB/T 4732 and EN 13445 in fatigue assessment of welded joints, focusing on design methods, stress calculation and engineering applicability of the assessment results. Using tank welds as a case study, the computational results showed that the allowable cycle count for identical welded joints assessed under EN 13445 was significantly higher than that under GB/T 4732. By further analyzing the reasons for this discrepancy, the study has revealed the technical characteristics of different standard systems and provided references for standard selection and design optimization in engineering practice.

Concerning the abnormal increase in corrosion rates in the dehydrogenation tail gas system of a styrene unit, which has threatened the safe and stable operation of the unit, this paper conducts an analysis of the corrosion mechanism and research on the innovations for long-term operation. Corrosion in the dehydrogenation tail gas system of the styrene unit primarily occurs in areas such as the inlet pipelines, shell heads and outlet condensate pipelines of the tail gas cooler, exhibiting typical localized CO₂ corrosion morphologies like pitting, groove-like and plateau-like features. Mechanism analysis reveals that the corrosion is primarily induced by electrochemical corrosion resulting from carbonic acid formation when CO₂ in the medium dissolves in water. The corrosion rate is influenced by the coupling of multiple factors including temperature, pressure, CO₂ content, precipitate alkalinity, water composition and flow conditions. This paper focuses on discussing the effects of medium temperature, CO₂ partial pressure, and impact of medium flow velocity on the CO₂ corrosion rate. Based on the results of the corrosion mechanism analysis, a series of modification measures have been proposed and implemented covering the addition of a quencher and a salt cooler to reduce the medium temperature, CO₂ partial pressure and flow velocity. After the modifications, the corrosion rates in the tail gas system's heat exchangers and pipelines significantly decreased. No significant signs of corrosion were observed after two years of full-load operation, indicating that CO₂ corrosion in the system has been effectively controlled. This research has achieved safe and stable operation of the dehydrogenation tail gas system and effectively extended the operational cycle of the unit. It provides a reference for addressing corrosion protection issues in similar units.

Hydrogenation units are core facilities for crude oil processing at refineries. With the increasing inferior quality of feedstocks (high sulfur, nitrogen, and chlorine content) and increasingly severe operating conditions, corrosion risks and failure hazards have been significantly intensified. Among these challenges, the corrosion-induced failures in high-pressure air coolers have become a critical industry-wide challenge. This paper analyzes the impact of increased nitrogen content in the feedstock of a refinery's wax oil hydrotreating unit on the air cooler of the hot high-pressure separator. Through systematic corrosion assessment and calculation, it conducts comprehensive corrosion control design encompassing material selection, process corrosion prevention and corrosion monitoring/inspection. The paper proposes effective anti-corrosion strategies. This integrated approach provides robust support for ensuring the long-term safe and stable operation of high-pressure air coolers in hydrogenation units.

With the acceleration of urbanization and industrialization in China and the increasing demand for environmental protection, the natural gas industry is developing rapidly and the utilization of LNG cold energy has become an important research direction. However, the utilization of cold energy is often constrained by various factors such as small scale and low utilization rate. To address this situation, this paper explores an innovative model for large-scale and long-distance cold energy coupling utilization by examining a case study of the thermal energy interchange station jointly established by a Sinopec LNG receiving terminal and an ethylene project. The project LNG cold energy for cooling petrochemical units and product separation, achieving cascading energy coupling. Technically, the approach employs as an intermediate medium for long-distance cold energy transportation and as a high-precision heat exchange medium, enabling cold energy application across temperature grades. This facilitates the full integration of LNG cold energy with waste heat from petrochemical units. Operational results demonstrate that the project implementation only reduced production costs for the LNG receiving terminal, also effectively lowered the overall energy consumption and carbon dioxide emissions of the ethylene project. It has achieved world's largest-scale utilization of LNG cold energy with long-distance cold energy transportation, significantly expanding the cold energy service radius. This provides reference value for advancing large-scale cold energy coupling development.

A high-sulfur gas field is equipped with four natural gas purification processing units, each unit having two Claus blowers with one of them driven by steam turbine. The steam turbine-driven Claus blower serves as a critical energy-saving and environmentally friendly device within the sulfur recovery unit. However, its steam turbine has repeatedly experienced trips during startup and operation due to excessive vibration triggering the high-high interlock. Steam turbine maintenance is both time-consuming and complex, and these unexpected trips severely disrupt the normal production of the unit, as well as the regular use and maintenance of the equipment. This paper analyzed vibration trip data during steam turbine startup, along with on-site pipeline routing and mechanical operation conditions. The analysis confirmed that the primary cause of the trips was misalignment in the steam inlet and outlet pipelines of the steam turbine. To address the root cause of the turbine trips, improvements were implemented focusing on five key aspects: installing additional valves to the steam outlet pipeline, retrofitting steam turbine inlet and outlet pipelines, adding pipeline chain block, reinforcing pipe elbow supports and optimizing the types of pipeline supports. These modifications have effectively resolved the issue of unit trips caused by vibration, thereby ensuring the stable operation of the natural gas purification processing units.

The mechanical seal of the axial flow pump in the loop reactor of a high-density polyethylene unit underwent modifications due to a series of failures including blackening of the seal oil, the presence of bubbles within the seal chamber, elevated pressure in the seal oil tank, and seal face wear caused by axial movement of the pump shaft. The sealing system was modified from a double mechanical seal with PLAN 32+PLAN 52 flush scheme to a triple mechanical seal with PLAN 32+PLAN 53C+PLAN 52 flush scheme. This paper compares the structure and operating principles of these two sealing schemes, expounds the advantages of triple mechanical seals and their potential leakage risks. Based on this analysis, it proposes routine maintenance and failure prevention measures for the modified mechanical seals.

Failure-induced leakage occurred at the downstream spool of the AIC2502 primary valve in the catalyst regeneration system of an aromatics complex, which affected its safe operation. To prevent unplanned shutdowns or safety incidents caused by similar equipment failures, a systematic failure analysis was conducted through macroscopic examination, thickness gauging, process medium analysis, spectrographic analysis, material hardness testing and metallographic examination. The analysis results indicate that the primary damage mechanism involved welding-induced material degradation. Grooving corrosion and cracks were observed in the heat-affected zones (HAZ) of weld joints at both pipe ends, where stress concentration at welded regions facilitated further crack propagation. Based on the analytical conclusions, the paper proposes recommended measures such as material upgrades and welding process optimization to ensure the long-term safe operation of the aromatics complex.

In petrochemical industry, storage tanks are key equipment for storing crude oil, natural gas and other petrochemical feedstocks. Among all tank components, the bottom plate endures the most severe environmental conditions and bears the greatest pressure, making it more prone to developing defects. Consequently, it is one of the most critical parts in tank defect detection. Eddy current testing has the advantages of high detection accuracy, easy operation and no need to detect media. So it is widely used in defect detection of oil and gas pipelines, storage tanks and other equipment. However, due to the skin effect, conventional eddy current testing cannot be directly applied to ferromagnetic materials, such as those commonly used in storage tank bottom plates. This paper proposes utilizing finite element simulation to determine magnet parameters, thereby achieving pre-magnetization of ferromagnetic materials and thus addressing the skin effect problem. This method subjects the ferromagnetic materials to pre-magnetization treatment, causing it to enter saturation state.. Meanwhile, relevant experiments were conducted to validate the detection effectiveness of this method. The results demonstrate that under pre-magnetization conditions, the capability of pulsed eddy current testing to detect defects on the lower surface of ferromagnetic materials is significantly improved.