The methane tail gas generated within ethylene plants is typically utilized as regeneration gas and fuel for cracking furnaces. During the cryogenic separation process, excessive ethylene is lost to the tail gas, resulting in a high concentration of olefins in the tail gas, which will have adverse effects on the economy and the long-term safe and stable operation of the plant. Based on the ?Front-End Depropanizer and C₂ hydrogenation of Sinopec LECT technology, this paper analyzes that the separation efficiency of C₁ and C₂ in the high-pressure demethanizer system is the primary cause of the olefin concentration fluctuations in methane tail gas. By analyzing the influence of low methane/hydrogen ratio in the cracked gas composition on the separation efficiency of high-pressure demethanizer system, this study explores the measures for enhancing the heat exchange efficiency of the overhead condenser and controlling the amount of ethylene in the methane tail gas by optimizing the operating conditions and locally reconstructing the processes while maintaining the primary separation process unchanged. These measures include adjusting the operating conditions of the demethanizer system, increasing the circulation of methane, and recovering ethylene from tail gas. Additionally, the study compares the impact of various schemes on plant investment and operational energy consumption levels, and establishes several methods for controlling the ethylene concentration in the demethanizer system and the methane tail gas.

The 35 kt/a butadiene unit of a petrochemical company uses N-methylpyrrolidone as the extraction solvent. In the NMP method for butadiene production, the control of water content in NMP plays a crucial role in the normal production of the unit. Excessive water content can easily cause poor solvent selection performance, insufficient heat source in the solvent system, and fluctuations in pressure difference in the main washing tower. This article summarizes the experience in controlling the water content in NMP solvent of the butadiene unit.

Since the ethylene plant of a refinery was put into operation in June 2018 after overhaul, the pressure difference in the gasoline/diesel section of gasoline fractionator has gradually increased from 5.4 kPa at the initial startup to a maximum of 7.5 kPa, while the pressure difference in the pumparound section and the quench oil section remained relatively stable. In response to the increased pressure difference in the gasoline/diesel section of gasoline fractionator, relevant measures were developed to control the rising trend and stabilize the pressure difference within 6 kPa. The internal components of the tower were modified during the overhaul in 2023, successfully reducing the pressure difference to around 2.5 kPa.

During the operation of the ethylene cracking unit of a refining and chemical plant, the methane content at the top of the ethylene distillation column continuously increased. The investigation and analysis showed that it was caused by the leakage on the methane-hydrogen side of the condenser in demethanizer. After replacing the steel-aluminum transition joint with a new one, the methane content gradually decreased, meeting the production requirements. Through the operational analysis and the macro inspection, metallographic analysis, hardness testing and scanning electron microscope observations of the failed samples, it was found that the main reasons for the cracks include the improper control of the cooling and heating rates of cold box system during daily start-up and shutdown and the manufacturing defects in the steel-aluminum transition joint. By formulating strict operating procedures for cooling and heating rates, strictly refining and optimizing process operations, and optimizing the operating procedures for relevant equipment, the goal of long-term stable operation of the unit can be achieved.

This paper discusses the application of spiral wound tube heat exchangers in propane dehydrogenation process. The problems of traditional tubular heat exchangers in propane dehydrogenation process are analyzed, and the structure, working principle and characteristics of spiral wound tube heat exchangers, including high efficiency, compactness and multi-media heat exchange capacity, are expounded. Through the comparison with traditional tubular heat exchangers and the actual case analysis, the advantages of spiral wound tube heat exchangers in improving heat exchange efficiency, reducing energy consumption and carbon emissions, and improving propylene yield are demonstrated. At the same time, the application cases and process parameters of spiral wound tube heat exchangers in propane dehydrogenation process are elaborated in detail.

Cracking gas compressor is a critical unit in ethylene plants. The unplanned shutdown of cracking gas compressor due to operational failure will cause incalculable losses to the production of ethylene plants. Therefore, the good operation of cracking gas compressor is crucial for the smooth production of ethylene plants. With the extension of operating time of the cracking gas compressor unit of a company, problems emerged in various components of the compressor unit. The problems of cracking gas compressors found during the overhaul, including the serious wear of water injection nozzles, the coking in cylinder body and flow passages, and the corrosion of shaft seal gas seal, were tackled and eliminated one by one, ensuring that the “5-year overhaul” target of cracking gas compressors can be met.

Turning gear is a safety protection device for cracking gas compressor unit. During the single test of the steam turbine of a cracking gas compressor unit of an ethylene plant, the turning gear was operated normally. When the compressor unit was turned up after the combination of steam turbine and compressor through the coupling, the turning gear shook back and forth, and the compressor rotor could not rotate normally. The turning gear could not meet the turning requirements of the compressor unit. In this paper, the problems in the starting process of the turning gear of cracking gas compressor unit in ethylene plant are analyzed in depth, and a corresponding solution is put forward. By lowering the rotating speed and increasing the starting torque, the normal operation of the turning gear of compressor unit can be ensured. 

The butadiene twin screw compressor of a petrochemical company is a critical unit that directly affects the safe and stable production of the unit. During previous maintenance processes, the seal on the compressor's outlet side has leaked multiple times. After the maintenance in July 2024, the leakage rate of the seal on the compressor's outlet side was approximately 48 L/h, far exceeding the allowable leakage standard for mechanical seal (0.02 L/h). Due to the high cost of oil film mechanical seal spare parts, the conventional maintenance strategy of simply replacing the spare parts during maintenance is not only expensive but also fails to fundamentally solve the leakage problem of the compressor unit. In response to the above problems, the reasons for the mechanical seal leakage of this equipment were analyzed, and some treatment methods were developed.

This paper systematically introduces the piping design of a 150 kt/a single-chamber cracking furnace. Taking the piping design of a cracking furnace in a domestic ethylene plant as a practical case study, it focuses on the determination of planar layout scheme for the cracking furnace area, the support structure and positioning design of vertical quench heat exchangers, the piping design strategies for cracked gas conveying system and riser/downcomer, as well as the design principles for column spacing in front-furnace pipe racks and the layout schemes for feed pipe valve groups. Through feasibility verification of standardized design for critical equipment selection and core piping system configuration in the cracking furnace, this study proposes standardized layout solutions with engineering practical value.

This paper introduces the sources of “three wastes” (wastewater, waste gas, and solid waste) in ethylene plants, and discusses the control measures for organized and unorganized emission sources of "three wastes". Furthermore, targeted waste reduction measures are proposed to ensure that the emissions of “three wastes” comply with the national regulations for discharge of pollutants from the petrochemical industry, providing valuable references for the environmental protection and control of ethylene plants.

The cracking furnace of the ethylene plant of a petrochemical company increases the processing capacity of light hydrocarbons, reducing the production of mixed C₄ to 8.5 t/h, which can be used to produce about 4 t/h of butadiene in the butadiene plant. The requirement of butadiene feed for the full-load operation of two lines in butadiene rubber plant is 5.4 t/h, with a gap of about 1.2 t/h. With a high TBC concentration, the butadiene product from the new area cannot be directly used by the butadiene rubber plant in the old area, so it needs to be recycled to the butadiene plant of the ethylene plant No.2 for re-refining to ensure its reaction performance. At present, the butadiene with high TBC concentration from the butadiene plant of the ethylene plant No.1 is sent to the butadiene storage tank of the ethylene plant No.2, and then 1.2 t/h of butadiene with high TBC concentration is recycled via the re-refining line into butadiene distillation tower for TBC removal to meet the butadiene demand of the butadiene rubber plant. Therefore, a recycled stream of butadiene feed is added to the conventional distillation system. The storage temperature of butadiene product tank not only affects the consumption of freezing liquid, but also affects the heat balance of butadiene distillation tower and the load of tower kettle reboiler. In this paper, by controlling the temperature of Tank T-902A during the re-refining of 1,3-butadiene product with high TBC concentration from the new area, the energy consumption of the plant can be reduced, and cost reduction, efficiency increase and high quality development can be achieved.

Quality management is the core of the production of petrochemical products, significantly impacting the performance, safety, and reliability of the products. The PDCA cycle and Statistical Process Control (SPC) are important tools in quality management, playing a crucial role in improving product quality and enhancing enterprise competitiveness. This article takes the butadiene products from a company as an example to explore how to effectively apply the PDCA cycle and SPC in practical production, thereby improving the quality of butadiene, reducing the quality risks of products, avoiding product quality defects, and ensuring the quality of butadiene products.

According to the production and operation characteristics of ethylene plants, emergency operation cards were prepared and improved for emergencies such as fire and explosion, hydrocarbon leakage, equipment failure and utilities, and the concept of "one-minute emergency response" was consistently followed, highlighting the criticality, accuracy measures and key points of emergency response. At the same time, effective measures, such as assessing the emergency response principles of the shift supervisor team, carrying out emergency drills for shifts, strengthening training on the use of safety protection facilities and fire fighting facilities for the staff on duty, and developing an annual cyclic drill plan for shifts, were taken to improve the emergency response skills of the staff on duty. As a result, rapid and stable emergency response of the staff on duty was achieved in various emergency events such as steam interruption, avoiding significant load reduction or even shutdown of the unit, ensuring the rapid recovery and smooth operation of the unit, and significantly improving the emergency management capabilities.

During the implementation of engineering projects, pipeline welding construction accounts for more than 50% of the total installation workload of the plant, and the quality of pipeline construction directly affects the safe operation of the entire plant. Pipelines are assembled by welding multiple pipe segments together, and the construction process is complex, involving a wide variety of pipeline materials, extensive work areas, numerous participating parties, long construction periods, and large amounts of documentation. The management of welds and the compilation of documentation have always been the pain points and challenges in project construction. To standardize the pipeline welding workflow, achieve the full-process control of construction process and data information transparency, enhance lean and standardized construction management, and reduce the repetitive work on construction sites, this project innovatively constructed and applied a 4D pipeline lean construction management system during construction, which realized dual application on both PC and mobile APP platforms. By using information technology to solve the problems in traditional construction, the precision of process pipeline welding management was improved while reducing management complexity.