The growth trend of ethylene capacity and the advantages of large-scale ethylene plant are introduced in this paper. Large-scale schemes for ethylene plant are preliminarily discussed combined with key equipment in ethylene plant such as cracking furnace, charge gas compressor, refrigerant compressor, large column, heat exchanger, and large valve. The main control points are pointed out based on the current technology level and design and manufacturing capabilities. The current status of large-scale ethylene plants at home and abroad is briefly summarized, and the construction methods and considerations are proposed.

 Based on the practical production experience of a domestic petrochemical unit, an in-depth analysis found that the fluctuation of CO content is mainly due to the fluctuation of average COT during the feeding and discharging of cracking furnace, the rapid rise of single group COT, the water entrainment in DS system, the changes in dilution steam flow rate, and the insufficient pre-sulfurization of furnace tube. A series of precise and effective countermeasures were proposed to address the above issues, including optimizing feeding, side burning and other operations to stabilize COT, strengthening DS system management, and ensuring sufficient pre-sulfurization of cracking furnace tubes. At the same time, comprehensive preventive measures have been proposed to address the acetylene leakage in the CO₂ hydrogenation reactor.

The spent caustic oxidation unit in a 1.1 Mt/a ethylene plant adopts wet oxidation process. During 15 years of operation, there have been many operation problems such as excessive COD in high saline sewage, leakage of acid injection point elbows, and frequent blockage of the inlet filter of air compressor, which have seriously affected the long-term and stable operation of the spent caustic oxidation unit. This paper analyzes the problems in the operation of spent caustic oxidation unit, and puts forward some improvement and preventive measures. Meanwhile, based on the consumption of various working media in the spent caustic oxidation unit and combined with production and operation experience, a series of optimization measures for energy saving and consumption reduction are proposed to reduce the cost of spent caustic treatment. In combination with the current environmental protection requirements, the odor of the spent caustic oxidation unit is reduced through technological transformation measures, so as to achieve the goal of a win-win situation for long-term operation and environmental protection.

The ethylene plant of a petrochemical company has improved its ethylene yield by increasing the processing ratio of light feedstocks since June 2023, especially by introducing a large amount of pure ethane for the first time. However, the system has encountered production bottlenecks such as insufficient quench oil, SS and methane production, and overloaded operation of compressors, demethanizer, deethanizer and ethylene distillation tower, which have affected the normal operation of the plant. Through process modification of the cracking furnace, compressors, and C₁, C₂ cycle process, as well as the optimization of operation parameters of the quench system, cooling capacity distribution, demethanizer, deethanizer and ethylene distillation tower, the impact of these bottlenecks on production has been weakened or eliminated. Through a series of modifications and optimizations, the ethylene yield of the ethylene plant has been significantly improved, contributing to the energy conservation, consumption reduction, cost reduction, and efficiency improvement of the enterprise.

The access design for petrochemical plant is closely related to future production, maintenance, firefighting, and operational activities. A good access design can guide and standardize production workflows, enhancing production efficiency while indirectly ensuring safety. During the design process, access should be intentionally planned. This can not only effectively check the compliance and rationality of access, but also enable the end-users to fully understand the access design at the design stage.

Circulating cooling water (CW) system is a critical component of utility systems in ethylene plants. Its design rationality directly affects the stability, safety, and economic performance of ethylene plants. Based on a case study of a 1.0 Mt/a ethylene plant in China, this paper systematically elaborates on the design principles for CW networks. Key design aspects such as the branched/looped network layouts and the integration of secondary water systems are discussed. The application of PIPENET software in hydraulic modeling, pipe diameter optimization, and diagnosis of flow distribution issues is also described in detail. Scientific hydraulic calculation methods and dynamic adjustment strategies can significantly enhance the energy efficiency of the system while reducing both the capital investments and operational costs of ethylene plants.

The study on reaction area layout is a core and crucial aspect of polyethylene plant design. Taking the design of the reaction area of a domestic gas-liquid polyethylene plant as an example, this paper systematically introduces the process flow of the reaction area in such plants, focusing on the establishment of equipment layout plan for the reaction area and the design ideas of important piping systems such as feeding system, discharging system, terminator system, condensate system, and circulating gas system. At the same time, this paper refers to previous design experience of such plants, compares the characteristics of different schemes, and provides references for the subsequent design and optimization of the reaction area in similar plants.

Polymers produced by the self-polymerization of butadiene is a key factor affecting the long-term safe production of butadiene extraction units, and this problem has not been solved for a long time. Affected by the self-polymerization of butadiene, the two butadiene extraction units of a petrochemical company have had production cycles ranging from 3 months to 1 or 2 years since their startup. The frequent cleaning of the filter and tower kettle reboiler as well as the leakage of some equipment due to the runaway polymerization of butadiene posed great hidden dangers and risks to the long-term safe production of the units. The "dead angle theory" for anti-polymerization was put forward, and some corresponding anti-polymerization measures were taken under the guidance of this theory. The application results show that these measures have achieved remarkable effects, and the operation cycle of the units has been successfully extended to 5 years.

Flow measurement is a frequent and critical task in petrochemical production. A wide variety of flow measuring instruments are available, each offering distinct features and suitability for specific operating conditions. This paper introduces six commonly used flow instruments in petrochemical units, including differential pressure flow meters, rotameters, electromagnetic flow meters, vortex flow meters, mass flow meters, and ultrasonic flow meters. For each type, the measurement principles, typical composition, key characteristics, and applicable selection criteria are discussed, offering practical guidance for engineering designers in the type selection of flow meters.

Lithium bromide absorption chillers utilize low-grade waste heat as the thermal source to generate low-temperature cooling source that meets industrial requirements, making them suitable for comprehensive waste heat recovery and utilization in large-scale chemical plants to achieve overall optimization, energy saving, and consumption reduction. This paper presents the application and operational optimization of a lithium bromide absorption chiller shared by three polypropylene units in a petrochemical company, discusses the operating conditions of the chiller, analyzes the causes of crystallization and poor cooling performance, and proposes some operation methods to prevent crystallization, enhance cooling efficiency, save energy, and reduce consumption.

High outlet pressure of the fourth section of cracked gas compressor in ethylene plant can easily cause the safety valve of the discharge tank of the fourth section to jump, leading to fluctuations in production operation. Yanshan Petrochemical started to periodically use cracked kerosene as feedstock in this operation cycle, and a continuous increase in outlet pressure and temperature of the cracked gas compressor was observed at the end of the operation, which led to a continuous decrease in the outlet flow rate of the fifth section, seriously affecting the smooth operation of the plant. Through partial maintenance, it was determined that serious coking inside the high-pressure cylinder of the compressor led to the seal failure of balance disk, allowing the leakage of process gas from high-pressure section to low-pressure section, which was the main reason for the high outlet pressure of the fourth section. Some optimization and improvement measures were put forward to ensure the smooth operation of the ethylene plant for a long period of time.