In an ethylene plant which only takes naphtha as the cracking feedstock, naphtha was gradually replaced by ethane while maintaining the ethylene output unchanged. Through the whole process simulation of separation system, it was found that the loads in quench area, compression zone and hot zone decreased, and bottlenecks first appeared in the passes of hydrogen and circulating ethane in cold box and the stripping section in ethylene rectifier. For compressors, bottlenecks successively appeared in low pressure methane compressor, methane refrigerator and ethylene refrigerator. Replacing no higher than 10% of the naphtha can be achieved by optimizing the operation, and replacing no higher than 20% of the naphtha can be achieved via partial modification..

The influence of excessive oxide in cracking raw materials on the ethylene plant at a petrochemical company in Shandong is analyzed in detail. The excessive oxide in cracking raw materials produces methanol, organic acid, carbon monoxide, carbon dioxide and other oxides at high temperature in cracking furnace. These impurities seriously affect the stable operation of C₂ hydrogenation reactor, resulting in the low pH value of quench water and condensate between sections of cracking gas compressor, increased equipment corrosion and quench water emulsification, shorter service life of furnace tube, off-spec propylene product, increased grease production in caustic tower, poor adsorption capacity of molecular sieve of dryer and the pollution of pyrolysis gasoline, thus affecting the quality of C₄ and C₅ products.

This paper mainly studies the anti-corrosion design of chemical concentrated sulfuric acid pipelines in the petrochemical industry and the corrosion performance of concentrated sulfuric acid on carbon steel pipeline materials, analyzes the key corrosion parts of the concentrated sulfuric acid pipelines based on the test and the collection of relevant data, and compares the corrosion of two concentrated sulfuric acid pipelines. The reasons for the difference in corrosion rates of carbon steel pipelines in different parts under different conditions are analyzed, and the key rules for anti-corrosion are found out to reduce the leakage caused by the corrosion of concentrated sulfuric acid pipelines.

During the construction of refining and petrochemical projects, project construction is carried out after project planning, site selection, pre-feasibility study and feasibility study. Each company should determine its quality objectives, formulate specific quality assurance plans and related measures and specify the implementation contents, construction methods and completion effect according to its own conditions and engineering characteristics. The construction quality management personnel should organize the design hand-over and the joint review of construction drawings, deal with the problems, organize the geotechnical investigation scheme and results review, organize the review of basic design documents and the review of design documents, and supervise the issuance and use of construction drawings. This project adopts IPMT+ supervision +EPC management mode, and has completed single commissioning, cold commissioning, mechanical completion and hot commissioning.

As one of the important components of ethylene plant, debutanizer system directly affects the long-term, safe and stable operation of ethylene plant and downstream production units. This paper mainly introduces the influence of different tower pressures on debutanizer system. It is very important to select appropriate tower pressure for the operation and energy saving of tower system. The specific effects of different feeding positions on debutanizer system are further studied, and reasonable suggestions on the optimal feeding position are given. At the same time, the influencing factors of system operation are analyzed in detail, which is helpful to realize the long, stable and optimal operation of ethylene plant, realize intrinsic safety and improve market competitiveness.

During the start-up of an ethylene plant, the failure of reboiler in the demethanizer resulted in ultra-low temperature in the bottom of the tower, exceeding the design temperature of pipelines, and a series of secondary fluctuations during reboiling recovery such as the excessively high overhead temperature of the tower and the component disorder. The causes of these problems were analyzed, some improvement plans were proposed and technical modification was carried out to ensure the safe and stable operation of the plant. In view of the insufficient driving force of overhead condenser in the demethanizer, an optimization and improvement plan was proposed. After implementation, the overhead temperature reached the standard, the heat exchange effect was obviously improved, the ethylene loss at the top of the tower was significantly decreased and the ethylene recovery was improved.

Ethylene is an important basic raw material for petrochemical industry, and CO will be generated during ethylene cracking. Excessive CO in cracking gas will lead to the poisoning of C₂ hydrogenation catalyst and the leakage of acetylene, resulting in unqualified ethylene products or even the interlock shutdown of the plant and affecting normal ethylene production. This paper discusses the generation process of CO in steam cracking unit, and systematically analyzes the causes of the excessive CO in cracking gas according to the actual production conditions of the plant. The main reasons for the excessive CO in cracking gas are the over high COT in cracking furnace, the reduced sulfur content of cracking raw material and the incomplete passivation of furnace tube before feeding. Some corresponding countermeasures are proposed according to the reasons for the excessive CO.

To solve the problems of pipeline corrosion and quench water emulsification in the quenching system of ethylene plant during industrial application, technical modifications were carried out including adding new injection points for corrosion inhibitor, replacing the type of corrosion inhibitor and introducing automatic pH control system. The problems were effectively solved, and the safe, stable, long-term, full-load and optimum operation of the ethylene plant was ensured.

This paper analyzes the feasibility of reducing the operating pressure in the debutanizer system of an 800 kt/a steam cracking unit which is operated at a high load with heavy feedstock, finds the best operating pressure under the current working conditions, and achieves the goals of slowing down the material polymerization in tower bottom and reboiler, extending the operation cycle of reboiler, optimizing the quality of overhead and bottom products, reducing the energy consumption of the system and improving the economic benefits.

In this paper, the causes of the excessive dissolved oxygen in boiler feed water in the methanol unit of olefin plant at PetroChina Dushanzi Petrochemical Company are analyzed. The internal leakage of boiler feed water sampler, the compliance of boiler feed water sampling, the leakage at static sealing points of sampling system and the upstream water sources were systematically investigated. According to the investigation results, some plans were made including adjusting the dissolved oxygen of deaerator, standardizing the sampling process, carrying out the trial test of deoxidizer and checking the filler of the deaerator. These adjustment measures solved the problem of excessive dissolved oxygen in boiler feed water.

This paper introduces the failure mechanism of TP304H pipe, and compares its high temperature performance with those of several typical heat-resistant steel. Combined with the working condition characteristics of high temperature steam pipes in convection coil of cracking furnace, the material selection method and principle are proposed. The specific working conditions of P91 replacing 304H are provided.

This paper introduces the equipment, facilities and related technologies of the cracking furnace of the 200 kt/a ethylene plant in Tianjin. Through the analysis of the transfer line valve, low NOx emission technology and the advanced control system of the cracking furnace, some improvement measures are put forward combined with the operation of the ethylene cracking furnace in Tianjin, and the design ideas and principles of new equipment, facilities and technologies of cracking furnace are explored, which is conducive to improving the intelligent application level and operation stability of cracking furnace, so as to achieve the purposes of energy saving, consumption reduction and emission reduction and to reduce the labor intensity of the staff.

Based on the investigation of the differences in process parameters such as crossover temperature and furnace tube temperature during the operation of the No. 6 cracking furnace in the old area of PetroChina Dushanzi Petrochemical Company, it was found that the bellows of four expansion joints of diluent steam pipelines were overstretched and seriously exceeded the design scope. At the same time, the draft tube was seriously deformed and blocked the pipeline, which not only affected the flux of the pipelines, but also led to the fracture and material leakage at the expansion joints if it cannot be found in time, seriously affecting the smooth operation of the plant. In order to completely solve the influence of expansion joint on the operation of cracking furnace, the expansion joint was replaced by straight pipe section by re-calculating the stress of process pipelines and adding part of spring hanger and support, thus eliminating the hidden trouble caused by the deformation of expansion joint of cracking furnace.

The coal-to-olefin (MTO) process is currently the most popular coal deep processing process. The analysis of the existing process flow shows that it is still possible to further optimize the details of the upstream and downstream layout of the material and excavate considerable economic benefits, so as to achieve energy saving and consumption reduction during the operation. 

 Ethylene and propylene are the main basic products of petrochemical industry and dominate the petrochemical industry. Ethylene yield and ethylene and propylene yields are important economic and technical indicators of ethylene plant. The cost of ethylene raw materials accounts for more than 70％ of the production cost. Improving the ethylene and propylene yields of the plant and reducing the raw material consumption per unit product can greatly reduce the cost per unit product, thereby enhancing the competitiveness of the enterprise. The ethylene yield and the ethylene and propylene yields can be effectively improved by means of using light raw materials, optimizing the operation of cracking furnace and quenching system and adopting CCC control for compression system, and the processing energy consumption of the plant can be greatly reduced. While improving the ethylene yield, the plant encountered some problems such as low quench oil temperature and excessive fuel gas output, which became the bottleneck restricting the further reduction of energy consumption. How to effectively solve the bottleneck problem becomes the key direction of the next step.