High-energy substances like effect propellant and propellant are used in fireworks. In the process of manufacture, transportation, and use, heat can easily get out of control. The emulsifier polyisobutene succinimide (T152) is frequently used to emulsify explosives. Given the thermal safety of the propellant in fireworks, this paper used the emulsifier T152 to emulsify the propellant. Thermogravimetric Fourier-transform infrared spectrometry and differential scanning calorimetry were used to analyze and test the propellant. In addition, several methods of thermokinetic calculation were used to calculate thermal stability. The thermal stability of the propellant before and after adding T152 was compared and analyzed. The test results indicate that the apparent activation energy of the propellant increases with the addition of T152. The emulsifier improved the thermal stability of the propellant. The research results can provide relevant data and suggestions for the thermal reaction of pyrotechnic propellants, thereby reducing the potential risks of the fireworks industry. Full article

Process industries often use B-ring self-tightening sealing structures and rely on interference assembly to meet the initial sealing requirements. Therefore, determining reasonable B-ring material, size and interference is crucial to ensure the sealing performance of the structure. In this paper, based on elastic deformation analysis, the deformation co-ordination equation of a B-ring sealing structure was established, and a sealing contact pressure calculation formula was obtained, with discussion of the main factors affecting sealing performance. With the finite element method, transient temperature field analysis was carried out for startup and shutdown load cases, and contact analysis was carried out for interference assembly, startup and shutdown. Based on the evaluation criteria of sealing performance with proposed sealing rate and leakage parameters, the effects of material properties, interference, B-ring size, etc., on sealing performance were investigated, revealing that although a B-ring with high material yield stress can meet the sealing requirements, both the B-ring and the sealing surface of a reactor body will yield plastic deformation. B-rings with a low material yield stress exhibit obvious plastic deformation during startup and leak during shutdown. However, leakage parameters can be minimized by smaller interference and moderate wave radius. Full article

A prediction method applicable to erosion-prone areas of fluorine chemical pipelines is herein proposed. By summarizing the common working conditions in the fluorine chemical industry, a computational fluid dynamics (CFD) model for industrial pipelines is established, and three-dimensional numerical calculations of the flow field in the pipelines are carried out to analyze the characteristics of the hydrodynamic parameters and phase distribution in the flow field, as well as the erosion rate distribution in different areas of the pipelines. The areas in the pipeline that are susceptible to erosion are predicted based on the results. The method has universal applicability and has been applied in many large petrochemical companies. It achieves the function of predicting the areas of severe pipeline erosion in a scientifically sound manner. This paper also details the application of the method in a distillation oil and gas pipeline of a large oil and gas company in western China. Full article

The Zn-5%Al-rare earth alloy coating has been used in High-Vanadium Full-Locked Cable (HVFLC) that is made in China. This application has shown excellent protective performance. However, during practical use, the coating may appear to be deteriorated in various degrees, which may further worsen the corrosion resistance and mechanical properties of the cable. This paper focuses on High-Vanadium Full-Locked Cable (HVFLC). Firstly, different types of prefabricated defect treatments have been applied into the wires of the cable, followed by corrosion paste accelerated corrosion test and mechanical tensile properties test. The aim of this act is to figure out the effects on the corrosion resistance and mechanical properties of the wire due to different types of defects in alloy plating. The results show that the corrosion resistance of the wires has been greatly affected because of the solder joint defects. Furthermore, the tensile strength of the wire indicates a drop of about 40%. This research makes up the gap in the related fields in China. In addition, basic data has been provided for the development of the HVFLC in China. Full article

A new type of high elastic polyurea protective coating reinforced by nano silica is prepared by filler composite in order to avoid both the leakage of fluorine chemical pipelines containing highly toxic and dangerous media as well as the damage to fluorine chemical pipelines under impact loads. The aim is to improve the intrinsic safety of fluorine chemical pipelines and ensure the safety of the ecological environment, life and property. The effects of different processes and process parameters on the properties of polyurea coating were studied. The polyurea coating was blended and strengthened with nano silica modified by silane coupling agent KH-550. The suitable stirring speed, material addition sequence and nano silica concentration of the new polyurea material were put forward to prepare a new polyurea coating with excellent properties. The properties of the polyurea coating were characterized, including curing time, tensile strength, elongation at break and impact resistance. Then, by using the numerical simulation method, the protection law of polyurea coating on fluorochemical pipelines with or without polyurea coating under the impact of small balls with different speeds was studied, and the equivalent stress mitigation and energy absorption mechanism of polyurea coating were analyzed from the perspective of macro and micro mechanisms. The results show that silane coupling agent KH-550 has successfully modified nano silica, and the optimal filling concentration of modified nano silica is 4 wt%. At this time, the tensile strength of filled reinforced polyurea coating is increased to 15.7 MPa, the elongation at break is 472%, the hardness is 61 HA, and the impact resistance of the matrix material is increased by 9.7 kJ/m². This shows that the polyurea reinforced by nano silica has excellent mechanical properties and impact resistance. The simulation results show that the polyurea coating can slow down the impact caused by the equivalent stress of small balls at different speeds. When the ball speed is 5 m/s, the equivalent stress of polyurea coating slows down to 49.3%, and the percentage of reduction of the impact caused by the equivalent stress of the polyurea coating decreases gradually with the increase of ball impact speed. Full article

Leakages of bolted pipe flange connections of water-containing hydrofluoric acid pipelines were frequently reported by the extraction section in the fluorine chemical industry. Water-containing hydrofluoric acid can cause severe injuries to human beings due to its strong causticity. The water-containing hydrofluoric acid pipe was a short lined pipe, so a lot of flange connections and supports were adopted in the pipeline. In this paper, the finite element models of the pipeline were established to analyze the internal force of the pipeline under conditions including internal pressure, temperature, self-weight, and so on. Based on this, the equivalent design pressure of the flange connections was determined. The results of the stress analyses of the pipeline showed that leakages were mainly caused by a large bending moment, due to the unreasonable layout of the piping supports under self-weight. When the pipeline was supported on the beam of the pipe gallery, which is not necessarily beneficial to reduce the bending moment of the pipeline, and the flange connection was close to the supporting beam at the same time, leakages frequently occurred in this flange connection. To support the pipeline reasonably, the flange connection should be placed at zero bending moment positions. Therefore, the positions with zero bending moments of the pipeline with equal and unequal spacing supports were obtained under gravity load, to provide a basis for the rational support of lining piping. Full article

This study focused on heavy gas dispersion under the terrain conditions of street canyons. The effects of street aspect ratio and height ratio were investigated, and the influence of environmental wind speed in the typical ideal street canyon terrain was explored. The results indicated that the surrounding flow field distributions in street terrains were dominated by higher buildings. In addition, when the building height was held constant, the flow field was affected by the joint influence of the two isolated buildings. The interception effect of the street canyon on upstream pollutants declined with the decrease in the street canyon’s aspect ratio. In addition, when the height ratios were different, a large quantity of upstream pollutants accumulated on the windward side of higher buildings. The relative concentration per unit area inside the canyon was affected by the air circulation inside and outside the canyon and the size of the dispersion space. The increase in the environmental wind speed promotes the entry of pollutants into the street while aggravating the overall dispersion of the pollutants. Therefore, the emergence of the most unsafe wind speeds caused most of the pollutants to gather in the street canyons. Full article

Traditional hazard and operability analysis (HAZOP) is one of the most widely applied methods for process safety management in process enterprises. Due to its principles based on the conservative and qualitative judgment, it often leads to too conservative risk identification results for the fluorine chemical industry usually with high-risk processes to keep the continuity of production. Most of improved quantitative and semi-quantitative methods are based on the layer of protection analysis (LOPA) to resolve the over-conservative problem of traditional HAZOP with the database of LOPA. However, the improved model, taking LOPA as the main line and HAZOP only as the provider of scenarios and influencing factors, is limited to the fact that LOPA can only analyze complete and independent protection layers (IPLs). Therefore, in order to realize the quantitative or semi-quantitative analysis of disaster causes and consequences, a new semi-quantitative HAZOP method takes HAZOP as the main line to integrate LOPA, F&EI (fire and explosion index) for quantitatively calculating the reduction factors, probability on failure demand (PFD) of general protection layers (GPLs) and PFD of IPLs. With the case comparison of fluorine chemical industry, it is proved that this new method can effectively improve the problem that traditional HAZOP are too conservative in complex scenarios. Full article

Hydrogen fluoride (HF) is a typical dangerous gas in the fluorine chemical industry. Its leakage is one of the most common types of accidents in this industry, and it poses a serious threat to personnel safety and health, environmental sanitation, and social stability. In this paper, the process and consequences of an HF leakage accident in a fluorine chemical plant were simulated by using computational fluid dynamics (CFD) simulation software, and hazardous areas (lethal area, severe injury area, light injury area, and maximum allowable concentration area) of HF diffusion were determined according to the HF concentration corresponding to the degree of personal injury. Moreover, the effects of wind speed and height on hazardous areas were analyzed. The research results of this paper provide model support for similar enterprises to predict the consequences of harmful gas leakage accidents, and give suggestions on emergency evacuation and rescue work, which have practical application significance. Full article

In 2005, a 60 kt/a alkylation (ALK) unit began to resume production in the Second Oil Refinery Plant of Beijing Yanshan Petrochemical Company. There have been many leak cases from pipeline welds, valve body, flange, etc. After a half-year period of operation, production process is stable. However, the operation of the hydrofluoric (HF) acid ALK unit has been suffered from corrosion problems. There are no clear answers and references to the following problems. What types of corrosion are currently in the main equipment for HF acid ALK unit? What does cause equipment corrosion? What are the main influencing factors for corrosion? What measures can be taken to reduce the corrosion of HF acid? In this paper, considering the acid-related conditions of the ALK unit, the damage mechanism and damage rate analysis were carried out to calculate the safety risk of the static equipment of the ALK unit. Based on the damage mechanism and failure history, the material suitability of the ALK unit was investigated. The anti-corrosion measures and recommended materials for important corrosion parts of the ALK unit were proposed. It is meaningful for reducing the number of shutdowns of ALK units and maintaining safe and stable operation of the unit. Full article

Backlash is a commonly non-linear phenomenon, which can directly degrade the control accuracy of a pneumatic control valve. To explain the cause and law of backlash error, and to propose an effective method, many research works on the modeling of a pneumatic control valve system have been carried out. The currently model of a control valve system can be classified as a physical model, data-driven model, and semi-physical model. However, most models only consider the force-displacement conversion process of a pneumatic diagram actuator in a pneumatic control valve system. A physical model based on the whole workflow of the pneumatic control valve system is established and a control method to eliminate the backlash error is proposed in this paper. Firstly, the physical model of the pneumatic control valve system is established, which is composed of three parts: pneumatic diaphragm actuator model, nozzle-flapper structure model and electromagnetic model. After that, the input–output relationship of the pneumatic control valve system can be calculated according to the established physical model, and the calculation results are consistent with the experimental result. Lastly, a self-calibration PID (SC-PID) control method is proposed for backlash error elimination. The proposed method can solve valve stem oscillation caused by backlash during valve control. Full article