This paper discusses the insufficient refrigeration capacity of ternary refrigeration compressor in summer caused by light cracking raw materials and the high energy consumption during LPG vaporization, and uses Aspen HYSYS to calculate the amount of heat released by LPG vaporization and the energy consumption during the cooling of ternary refrigeration system. The results show that the amount of heat released by LPG vaporization can meet the demand of ternary refrigeration system. Through technological transformation, the production bottlenecks in summer can be solved, and the energy consumption and ethylene loss can be reduced, achieving significant economic benefit.

The product delivery plan for ethylene plant in rundown case is usually considered at the beginning of design. Different rundown cases have diverse and significant impact on the refrigeration system. Rundown case is the critical case for the design and selection of refrigeration compressor. Taking a 1.0 Mt/a ethylene plant as an example, this paper compares the effects of two rundown cases on refrigeration system from the aspects of compressor power, utilities consumption, energy consumption and equipment investment. Setting rundown cases can ensure the continuous and stable operation of ethylene plant, but the energy consumption and equipment investment will increase accordingly. Multi-faceted analysis and comparison should be made during planning and decision-making.

The caustic wash tower in ethylene plant is used to remove the acid gas such as CO₂ and H₂S in cracking gas. During its operation, the increased accumulation of polymer at the bottom of caustic wash tower resulted in poor acid gas removal effect and over high CO₂ in the overhead cracking gas. The CO₂ formed dry ice in equipment for cryogenic operation and blocked the equipment and pipelines, affecting the normal operation of the plant and producing off-spec ethylene product. This article discusses the modification of caustic wash tower, the causes of the operational problems and the measures taken. Through adjustment, the operation of caustic wash tower was greatly improved, ensuring the stable operation and on-spec product of the ethylene plant. 

To make full use of refinery dry gas, ethane in refinery dry gas is cracked in a small cracking furnace, crude separation of the cracked gas is carried out, and dilute ethylene to ethylbenzene technology is used to produce ethylbenzene and then styrene. This can not only utilize the ethane and ethylene in refinery dry gas, but also promote the transformation from refining to chemical and improve the economic benefit of the enterprise. Based on a 120 kt/a ethylene plant, this article compares the energy consumption of benzene absorption process and intercooling separation process through simulation to explore a better process.

Aspen Plus software was used to simulate an ethylene tower system before and after the modification of a 1.1 Mt/a ethylene plant. Aiming at the high ethylene loss at the bottom of ethylene tower during production, the heat load of heat exchanger was analyzed from a process point of view, and the hydraulic model of ethylene tower was analyzed from an equipment point of view. Combined with the actual operation on site, some optimization measures were proposed. The flooding in distillation section can be solved by reducing the middle boiling and increasing the bottom boiling. By lowering the liquid sampling point in condensate tank D-410, appropriately raising the outlet pressure of the 4^th stage of ethylene refrigeration compressor or appropriately reducing the temperature of hot stream to strengthen the phase change heat transfer, the flow rate of hot stream can be increased, thus meeting the required heat load.

Since January 2019, the dilution steam generation of the 330 kt/a ethylene plant in Daqing has gradually decreased, resulting in the increased flow of outsourcing medium pressure steam. By comprehensively investigating the dilution steam system, it was confirmed that the decrease of dilution steam generation was caused by the reduced heat exchanger capacity of dilution steam system and the leakage in the liquid level control valve of furnace water recovery tank. By carrying out high pressure water cleaning of the heat exchanger and replacing the leaked valve, the dilution steam generation increased, and energy saving and emission reduction were achieved.

Lubricating oil system is an important part of compressor unit. The cleanliness of oil pipeline system will directly affect the long period operation of compressor unit. The oil flushing efficiency is directly determined by the quality of lubricating oil, the temporary measures taken in oil flushing stage and the operation means in oil flushing stage. In this paper, some rectification suggestions are given according to the problems emerged during the oil flushing of compressor unit, and the improvement measures are analyzed. The improvement measures are proved effective by the subsequent oil flushing of two refrigeration compressors.

 Affected by the changes in raw material structure, the 150 kt/a ethylene plant at PetroChina Jilin Petrochemical Company had problems such as N factor increase of cracking gas compressor, coking in discharge line and cavity, increased discharge pressure at the second stage and over high speed and vibration of cracking gas compressor. By injecting dispersed scale inhibitor, the operation could be maintained for a period of time. However, with the worsening of coking, the unit was forced to be shut down for maintenance. By studying the polymerization mechanism, this paper puts forward that the optimization of cracking raw materials and the control of compressor inter-stage temperature are the key to prevent polymerization.

 As a typical mechanical equipment in petrochemical plant, reciprocating compressor is mainly used for pressurizing the gas for delivery through piston reciprocating motion. Due to the intermittent working way, vibration inevitably happens in the piping system of compressor and the suction and discharge lines connected. Therefore, a reasonable piping layout and piping support design can effectively reduce the vibration to an acceptable level, thus guaranteeing the safe operation of the whole system. Based on the characteristics of equipment and piping layout and piping support design for reciprocating compressor, this paper compares and analyzes the differences between vertical and horizontal cylinder compressors in equipment layout, piping layout and maintenance characteristics.

With the improvement in management and technology in recent years, the operation cycle of ethylene plant is generally more than five years. It becomes more difficult for an ethylene plant to operate at full capacity at the end of its run cycle. Fouling is one of the main problems in cracking gas compressor and heat exchanger system. In the 5^th year of operation of an ethylene plant, high DP problem occurred in the heat exchanger at the outlet of the fourth stage of compressor. After fully evaluating the risks of heat exchanger damage and compressor surge, this problem was successfully solved by isolating a single group of heat exchangers for offline cleanup. A bottleneck of ethylene plant at the end of its run cycle was eliminated, enabling the plant to operate at full capacity in the 6^th year.

In recent years, with the strengthening of national regulation on environmental protection, enterprises pay more and more attention to the low emission of ethylene plant. During the startup and shutdown of ethylene plant, optimizing startup steps, shortening startup and shutdown time and reducing material loss during startup and shutdown while ensuring the safety of personnel, plant and equipment are the goals of ethylene plant, and over the years, various enterprises have accumulated rich experience. The ethylene cryogenic separation unit has the highest material loss during the startup and shutdown of ethylene plant. Based on the original optimization measures, the 220 kt/a ethylene separation unit of Dushanzi Petrochemical conducted new researches and analysis on the problems including low cooling speed and high material loss of the system. Through the implementation of targeted technical transformation measures, the startup time was greatly shortened and the material loss during startup and shutdown was reduced.

This paper introduces the operation and the problems in the circulating water heat exchanger in the 1 300 kt/a ethylene plant at SINOPEC SABIC Tianjin Petrochemical Co., Ltd. Through the analysis of the quality of circulating water and the material of heat exchanger with internal leakage, the main reasons for the internal leakage of circulating water heat exchanger were found, and corresponding measures were formulated to alleviate the internal leakage of circulating water heat exchanger.

The No.2 reboiler of dilution steam generator in an ethylene plant is a U-tube heat exchanger. Since November 2019, the tube bundle of heat exchanger has been leaking frequently. The leaked tube was sampled, and the leakage reasons were analyzed by means of macroscopic inspection, material analysis, electron microscope and energy spectrum analysis. The results show that the main cause of tube bundle leakage is the alkali corrosion caused by local alkali concentration due to the evaporation of process water. In addition, acid corrosion is formed when pH control is unstable. Various protective measures were taken to reduce the leakage frequency of heat exchanger.

During the normal production of a company, the bearing of fan was broken, and a series of physical and chemical performance tests, such as chemical composition analysis, hardness test and metallographic examination, were carried out on the bearing, roller, pin roller and support frame by field sampling to preliminarily determine the causes of bearing failure. Through the experimental analysis of damaged parts and undamaged parts and the comparison of experimental and analytical data, it is concluded that the machining defects, uneven distribution of microstructure and improper heat treatment of the cage and roller in manufacture result in the bearing fracture during operation.