Separation performance and tray efficiency of large-scale suspending downcomer trays for xylene column have been calculated by Aspen Plus. Influence on tray efficiency has been studied, considering the calculated result of gas and liquid loadings in the column. The simulation results show that the total tray efficiency can reach 72.0% under 83.4% feed loading condition; the total tray efficiency can reach 75.2% under 97.5% feed loading condition. The real gas loading in the column is over 110% of designed loading, while the liquid loading is about 113~135% of designed loading. Distribution of liquid on trays significantly affects the efficiency of suspending downcomer trays. Uneven distribution of liquid on trays may induce a lower tray efficiency under the condition of lower liquid loading. Feed distributor and directing baffles installed on tray deck can make distribution of liquid more uniform.

Aiming at the bottom design problems of vertical storage tanks, this paper compared the basis for the setting, thickness selection and width selection of the annular edge plate among different standards (GB 50341—2014, API 650—2020, JIS B 8051—2013 and BS EN 14015—2004). The results show that there are differences in the setting, thickness selection, and width selection of the annular edge plate in different standards. Among them, there are more detailed regulations on the thickness of the annular edge plate in GB 50341 and API 650. And the calculation of the width of the edge plate is basically the same in different standards. The paper also reached the following conclusions through comparative analysis: reasonable weld position, quantity, length and assembly process can reduce welding deformation effectively, which is conducive to ensuring the safe operation of the tank; adjusting the thickness of the edge plate reasonably can optimize the deformation coordination of the bottom ring tank wall and the edge plate, and improve the seismic resistance of the storage tank. However, if the edge plate is too thick, it will increase the stress level in the connection area between the bottom ring tank wall plate and the edge plate as well as in the nearby area. Therefore, it is necessary to consider the amount of deformation, tank seismic resistance, and stress level to determine the thickness of the edge plate.

This paper proposes three typical selection of charge gas compressor interstage after-coolers for ethylene plant covering double segmental baffle exchanger, X-shell exchanger and heat changer with helical baffle. Combining with the process characteristics of the interstage after-coolers, fluid fouling characteristics, optimization design of heat transfer, mechanical cleaning requirements and investment economics, this paper carries out an analysis of the advantages and disadvantages of the three types of interstage after-coolers and comprehensive comparison. Meanwhile, the preferred recommended selection sequence is given based on actual engineering experience, which provides a theoretical basis for the selection of interstage after-coolers of this system for the ethylene plant.

Design temperature is an important design parameter in the design calculation of pressure vessels. It affects the safe operation of pressure vessels directly. This paper highlights the basic principles in GB/T 150, ASME and HG/T 20580 codes for determination of the design temperature of pressure vessels. Fluid analysis method was adopted to calculate the wall temperature of the shell metal of two electric heaters with different specifications under six working conditions. Then the relationship between the metal wall temperature and the flow rate, the maximum temperature of the medium and the maximum wall temperature of the heating element was obtained. The paper also summarizes the factors affecting the metal wall temperature of the electric heater shell, and gives suggestions for determining the design temperature of the electric heater shell. This can provide reference for the structure design of electric heaters.

In one plant, the piping attached to the equipment was continuously vibrated during the operation of the plant and the local tip of its bracket was welded to vessel shell directly. After long-term operation, cracks occurred in the shell of the equipment from the stress concentration at the bracket tip, which led to leakage after the expansion of the cracks. This paper introduces the entire process of discovering medium leakage, identifying the leakage location, qualitatively analysing the causes, and repairing the shell cracks. The structural causes of the cracks were found through precise analysis of the stress distribution by using the finite element method. The paper also summarizes the relevant design and operation points, which can provide reference for the equipment with similar problems.

In this paper, the influence of different proportional loads on the reverse angle and rotating speed oscillation of the reciprocating compressor with double-acting cylinder was discussed by means of theoretical calculation of an example. The calculations show that the flow regulation method adopted in this paper can improve the reverse angle value and reduce the rotating speed oscillation under the low flow condition of the compressor. This method is beneficial to improve the rod bushing's lubricity and operation stability of the compressor, which can provide some guidance for the control of uneven load regulation of reciprocating compressor cylinder.

The compressor & pump equipment of the units in hydro-processing service of a refining and chemical company adopts the belt transmission mode, which does not meet the relevant requirements of GB 50160-2008 Standard for fire prevention design of petrochemical enterprises (2018 edition) and there are safety risks. Based on the safety requirements, the transmission mode of the compressor & pump equipment must be revamped to ensure that the production of the enterprise complies with the law. In this paper, different transmission modes were selected for rotating equipment with different structures. And a new flywheel structure was constructed by modeling the pulley with the aid of Solidworks software. And some technical parameters of the compressor & pump equipment were corrected according to the actual production needs. After several months of operation of the revamped compressor & pump equipment, the results showed that the compressor & pump vibration, bearing temperature and noise met the requirements of the corresponding specifications; the technical performance such as flow, head, current and voltage met the use requirements and could fully meet the production requirements. These results indicated that the revamp had completely eliminated the safety hazards of this type of equipment and improved the operation efficiency of the compressor & pump, making it more energy-efficient and safe and reliable, which achieved the expected purpose. This case study can provide reference for the management and rectification of similar safety hazards in other hazardous chemicals enterprises.

As the main process equipment of PTA plant, the reliability of the mechanical seal of PTA purification crystallizer has a direct impact on the stable operation of the whole plant. This paper analyzed the causes of mechanical seal failure in the purification crystallizer of a PTA plant. And finite element software was adopted to simulate the conditions of the mechanical seal before and after the structural improvement and optimization so as to know the temperature field and deformation of the dynamic and static rings. According to the results of the simulation analysis, the structure of the mechanical seal was improved. This has effectively reduced the ambient temperature of the components, especially the dynamic and static rings, improved the seal lubrication conditions and solved the failure problem of the original mechanical seal.

The extruded granulator is the core equipment of pelletizing unit of polyolefin plant, which plays an important role in powder molding and processing. This paper mainly introduces the structure and working principle of the friction clutch of the CMP-230X type extruded granulator in polyethylene and polypropylene plants of a petrochemical company. The causes of typical failures of the friction clutch over the years are analyzed from the aspects of instrument control, mechanical construction and process operation and so forth. Meanwhile, the corresponding effective measures are formulated, which is helpful to reduce the stop times and ensure the long cycle operation of the extruded granulator.

Aiming at the visible quality defects of the inner steel tank of SF double skin oil tanks widely used in gas stations, the reasons for these defects are obtained through analysis based on the classifications including design defects, material defects, and manufacturing defects, as well as the evaluation of the impact of oil tank instability and oil tank leakage. The defects are caused by poor design ability of manufacturers and inadequate implementation of standards; weak skills of employees and outdated manufacturing processes; low-level of quality awareness and uncontrolled quality management. The lack of technical personnel or professional competence on the construction side, ambiguous technical standards in the contract, and formalistic inspection and acceptance are also partly responsible for the quality defects. Based on the provisions of relevant codes and standards and combined with the practice of project management, this paper presents the quality control measures for manufacturers and builders respectively. The research results can provide technical guidance and experience for the control of visible quality defects in the inner steel tanks of SF double skin oil tanks in gas stations.

The vertical coal mill of a coal gasification project malfunctioned during commissioning. According to the experience of installation and debugging, the fault point of the vertical coal mill is inferred to be between the connecting ring of the seal of the machine frame and the driving disc of the coal mill. In order to determine the actual wear of the fault location, it is necessary to remove or jack up the driven disc of the coal mill to see the fault location. However, the clearance here is relatively small, and the labor and machinery required for such removal is costly. After investigation and analysis of the structure of the coal mill, it is found that after the grinding roller is raised, enough operating room can be left for the thickness measurement by ultrasonic testing instrument and for the personnel to operate. Therefore, the thickness of the connecting ring and the local wear between the driving disc can be quantitatively determined by ultrasonic scanning. Based on the comprehensive analysis of problems occurred on-site, the online repair method for the coal mill was proposed. The coal mill ran smoothly after repair, and similar failures did not occur again. Practice proves that the online repair is safe, feasible, time saving and reliable. It can save the cost investment of repair and is of high application value.

Aiming at the leakage case of the tube joint of high-pressure air cooler in a diesel hydrogenation unit during prevulcanization, this paper conducts macroscopic inspection, chemical composition analysis, metallographic structure analysis, fracture analysis and hardness test on the failure sample combining with two working conditions of production operation and presulfurization. It is confirmed that excessive hardness of the weld and heat-affected zone of the tube plate side of the air cooler is the main reason for the wet hydrogen sulfide stress corrosion cracking. And it is concluded that the wet hydrogen sulfide stress corrosion cracking is more likely to occur under presulfurization condition. Meanwhile, the paper also analyzes the welding process of the pipe joint of high-pressure air cooler and puts forward the improvement measures.

Waste heat boiler for Claus furnace is the core equipment of sulfur recovery unit and its stable operation is crucial for the sulfur recovery unit. This paper describes the inspection of heat exchanger tube and corrosion products by scanning electron microscope (SEM), energy spectrum analysis (EDS) and X-ray diffraction (XRD) after corrosion perforation occurred in the heat exchanger tube of waste heat boiler for Klaus furnace in a company's 140 kt/a sulfur recovery unit. It analyzes the corrosion causes based on the results of the inspection. The results show that the oxygen corrosion of the heat exchanger tubes due to excessive dissolved oxygen content in deoxygenated water is the main cause of corrosion perforation of heat exchanger tubes. By raising the operating temperature of the deaerator and installing additional chemical deoxidizing facilities, the dissolved oxygen content in the deoxidized water has been effectively reduced, and the recurrence of the above situation can be avoided.

The upper and lower shell of the diaphragm accumulator are connected by an electron beam welding structure with a gasket. The structure is small and the depth-width ratio is large, so the welding process is prone to produce incomplete penetration defect at the root. In order to improve the defect detection rate of electron beam welding of diaphragm accumulator, the experimental study was carried out using phased array technique. Firstly, the structure model of the accumulator was established by CIVA ultrasonic simulation software, and the typical incomplete penetration defects at the root were analyzed. Then, the accumulator containing the artificial incomplete penetration defects at the root was made for the experiment and research and the detection process was developed according to the research results. The characteristic image of the defects was obtained as well. Finally, a batch of diaphragm accumulators produced by the accumulator manufacturer was tested for engineering application, and one incomplete penetration defect at the root was detected. And the precise location of the defect and its own height were determined, which verified the accuracy and reliability of the inspection process. The research results provide a reliable method for the welding quality inspection of electron beam welding of accumulator products in the actual production process.

Data in corrosion monitoring systems for petrochemical transportation is generally in distributed storage. Although there exist a variety of cloud-based data hosting solutions, most of the data confidentiality methods rely only on algorithmic encryption. And how to ensure the credibility of the third party is a very worrying problem. Therefore, an improved Practical Byzantine Fault Tolerance (PBFT) consensus algorithm (referred to as improved PBFT algorithm) that combines trust mechanism with data interaction system is designed in the corrosion monitoring data sharing system. The system ensures data traceability by providing reliable data delivery without relying on third-party platforms. In the simulation test experiments, the improved PBFT algorithm and the traditional PBFT consensus algorithm (referred to as the traditional PBFT algorithm) are compared, and the results show that the improved PBFT algorithm outperforms the traditional PBFT algorithm in data stability and reliability tests. The system solves the difficult problems of non-traceability and vulnerability to attacks in monitoring data sharing, and lays the foundation for further promoting the development of block chain technology in the corrosion monitoring informatization of petrochemical transportation.