In the historical process of transformation and upgrading of intelligent manufacturing in refining and chemical industry at home and abroad, Tarim ethane to ethylene project, as a national demonstration project, carries out the planning and design of intelligent factory, explores the application of intelligent technology in the whole process of production, and builds the foundation of intelligent factory through the deep integration of industrial technology and information technology. It continuously explores the construction of refining intelligent factory with intelligent optimization technology application, and finds a way to build an intelligent factory which is suitable for the business development and reform of ethane to ethylene plant, keeps up with the development trend of advanced technology, and effectively uses and continuously improves the advanced technologies with a unified digital factory platform and technology development system as the important guarantee.

With the rapid development of the new generation of information technology, the fourth industrial revolution with green intelligence as the core is quietly emerging, bringing great challenges and opportunities for the traditional petrochemical industry. The construction of intelligent plant is the way to transform and upgrade petrochemical enterprises. The strategic goal of automation of production, informationization of management and intelligence of enterprise can be achieved and digital transformation and intelligent development can be realized by building refining intelligence capability in the aspects of comprehensive perception, safety control, production intelligence, plant-wide optimization and efficient operation. Combining with the construction example of the intelligent plant of Changqing ethane to ethylene project, this paper discusses the digital application in the construction of intelligent plant in petrochemical enterprises.

Quench oil circulating pump is the key equipment to ensure the safe and stable operation of ethylene plant. To solve the rolling bearing failure problem of quench oil circulating pump in the ethylene plant of SINOPEC Beijing Yanshan Petrochemical Company, the causes of the failure are systematically analyzed and demonstrated from the aspects of bearing design, installation and maintenance, environmental impact and maintenance management. It is found that the direct cause is the fatigue damage of rolling bearing and the root cause is the inadequate implementation of management measures.

The spent caustic in ethylene plant has high concentrations of COD and sulfide and is difficult to be treated. This paper introduces the application of wet oxidation technology for spent caustic in ethylene plant, summarizes the actual operation and the problems emerged, analyzes the problems, and puts forward some corresponding solutions to optimize the operation of the plant. After modification, the spent caustic with high COD and high sulfide produced by ethylene plant is treated as high salt wastewater with low COD and low sulfide.

Compressor unit is an important core component of ethylene plant. During the operation of the compressor unit at SINOPEC Zhongyuan Petrochemical Corp. Ltd., some problems such as the high vibration of ethylene compressor turbine and the failure of self-operated valve in the filter switching process of propylene compressor oil station occurred. An effective solution was put forward to solve the problems affecting the long-term stable operation of the compressors. This paper also introduces the experience in management of the compressors, so as to ensure the long-term operation of the compressor unit and improve the economic benefit of the plant.

To solve the problems in the operation of the static container attached to quench oil hydraulic cyclone system in the ethylene plant of SINOPEC-SK (Wuhan) Petrochemical Company Limited, such as small perforated mesh, insufficient strength, poor coke discharge and short operation cycle, some measures including equipment transformation and operation optimization were taken. The operation cycle of the static container attached to quench oil hydraulic cyclone system can reach 90 days, and good economic benefit can be achieved.

The 1,000 kt/a ethylene plant in Dushanzi adopts front-end deethanization and front-end hydrogenation process, and isothermal tubular reactor is selected for C₂ hydrogenation process. The reactor has the advantages of long operation cycle and service life, good catalyst selectivity, and basically no or little green oil produced, but it has the operation characteristics of long start-up time and great difficulty. The plant was started up with new catalyst after four rounds of overhaul, and four risks existed in the start-up with new catalyst were identified including reactor pressurization and filling operation, methanol boiling control, CO concentration control and operation adjustment for on-spec acetylene at outlet. According to the identified risks, some mitigation measures were implemented and the start-up operation mode was fixed to ensure the safety and efficiency during the start-up of C₂ hydrogenation reactor and reduce the production of off-spec ethylene products.

In order to make efficient use of the steam condensate of system, a mixed ion exchanger was added to the desalted water unit, and the condensate was treated with ion exchange to produce refined water for external supply. After the new mixed ion exchanger was put into use, problems such as resin loss and pipeline blockage appeared successively. In order to ensure the efficient recovery of condensate, the faults were checked during several maintenance and the causes were analyzed item by item. Some treatment methods were put forward, and the faults were treated correspondingly. The results show that the reasonable modification of the internals of mixed ion exchanger can effectively prevent the resin from blocking the pipe and from running away, so as to ensure the long-term and stable operation of the ion exchanger.

 In the ethylene plant of PetroChina Dushanzi Petrochemical Company, 5C Ⅱ centrifugal compressor is the key equipment of air separation unit, and the fluctuations in compressor unit directly affect the stability of air separation unit. This paper introduces the maintenance of Level 3 vibration anomaly of 5C Ⅱ compressor unit to reversely infer the reasons for the abnormal vibration of compressor unit, comprehensively discusses the operation, process analysis and maintenance treatment of the compressor unit, and puts forward the operation bottlenecks of 5C Ⅱ compressor in use, such as the accuracy of inlet air filter core, the internal inspection of intermediate heat exchanger, and the processes of inspection, maintenance and re-commissioning.

This paper mainly analyzes the reasons for the increased axial displacement in the turbine of propylene refrigeration compressor, summarizes the problems emerged since the startup of propylene refrigeration compressor after overhaul, and puts forward some solutions to the increased axial displacement in turbine. Relevant technical optimization and transformation were carried out. Through constant exploration and test, the continuously increased axial displacement in the turbine of propylene refrigeration compressor was effectively controlled.

During the operation of propylene compressor unit in the ethylene plant of SINOPEC Shanghai Petrochemical Co., Ltd., the bearing bush temperature at the governor side of steam turbine remained high and fluctuated frequently. After analyzing the operation of bearing bush and the quality of lubricating oil, some corresponding measures were taken. Without shutting down the compressor unit, a certain proportion of the five groups of base oil was added into the oil tank to solve the high bearing bush temperature problem of steam turbine and improve the reliability of long-term operation of key compressor units.

In view of the frequent speed fluctuation problem of a single compressor unit under the parallel operation mode of two cracking gas compressor units, the components such as electro-hydraulic converter, self-excited valve, speed probe, pilot valve, and valve disc and valve seat of main stop valve were checked respectively during two rounds of shutdown inspection, and no abnormality was found. Based on the characteristics of the influence of ambient temperature on speed fluctuation and the different characteristics of three or four sections of fluctuation curve, it was found that liquid was accumulated in the overhead return pipeline of gasoline stripper, and the speed fluctuation problem was eliminated by adding thermal insulation and heat tracing.

Pyrolysis gasoline is one of the by-products in the pyrolysis of hydrocarbons to produce ethylene. In industrial production, unsaturated groups of benzene ring branched chains in pyrolysis gasoline are usually saturated by two-stage adiabatic fixed bed catalytic hydrogenation. The first-stage hydrogenation mainly saturates dienyl groups such as conjugated dienyl under low-temperature liquid phase conditions, and the second-stage hydrogenation saturates monoenyl groups under high temperature. According to the removal sequence of C₅ components, pyrolysis gasoline hydrogenation unit can be divided into front-end depentanization and back-end depentanization, namely middle distillate hydrogenation and full hydrogenation. At present, most chemical enterprises adopt front-end depentanization, while some enterprises use back-end depentanization. In this paper, the factors influencing the operating cycle of second-stage catalysts in full hydrogenation unit of pyrolysis gasoline are analyzed, and some corresponding solutions are put forward.

The ethylene cracking furnace in the 1,000 kt/a ethylene plant at PetroChina Dushanzi Petrochemical Company was designed to use dimethyl disulfide (DMDS) to inhibit the catalytic reactions in furnace tubes, but the coking in furnace tubes could not be slowed down. The operation cycle of gas phase light hydrocarbon furnace was generally around 55 days, affecting the ethylene capacity of the plant. A coking inhibitor was used. It can be decomposed at 400 ℃, has lower decomposition temperature than other organic sulfides, is easy to play the anti-coking function, and has the advantages of low flash point and high boiling point. After the application of this coking inhibitor, the amount of coking was significantly reduced, the surface temperature of furnace tube was significantly decreased, the absolute pressure ratio and outlet temperature of quenching heat exchanger grew slowly, and the operation cycle of light hydrocarbon furnace was greatly prolonged. It also helps slow down the carburization of furnace tube and extend the service life of furnace tube.

The radiation tubes in the No.8 cracking furnace in the megaton ethylene plant of PetroChina Dushanzi Petrochemical Company were replaced by furnace tubes with enhanced heat transfer elements (raindrop shaped inner wall distribution) during the overhaul in 2019. Up to now, six operation cycles have been completed. The first cycle is 68 days from October 3, 2019 to December 10, 2019, and the second cycle is 94 days from December 16, 2019 to March 19, 2020. The operation after the modification with new radiation tube shows that the application of this new technology is one of the effective ways to increase production and reduce consumption.