The hydrocracking unit is a Class A fire hazard device, which can be susceptible to fire and explosion accidents due to equipment failure. Therefore, it is essential to identify and quantitatively analyze the risk factors. In this paper, qualitative HAZOP, steady-state simulation, dynamic simulation and FTA are combined. Taking process flow of the absorbing-stabilizing system of an actual hydrocracking unit in a refining company as an example, and the quantitative risk analysis is carried out for the deviation of "high column pressure" of the absorption and desorption column and "high column temperature" of the naphtha stabilisation column. With the help of Aspen Plus software, the steady-state and dynamic simulation under dangerous conditions is carried out, and the probability of the consequences of the dangerous accident is calculated by FTA method. The results show that this method can help experts understand the propagation process of the accident, master the safety response time of the personnel, which is conducive to the prevention and timely treatment of accidents, and effectively improve the intrinsic safety level of the hydrocracking units.
ZnO has a strong UV absorption capacity, but also has a high photocatalytic performance, which limits its application in the field of UV shielding. In order to explore the possibility of ZnO's application in the field of ultraviolet shielding, this article uses VASP to construct a ZnO/CeO2 heterojunction and performs electronic and optical simulation calculations on it. Then lignin is used to combine with the synthesized ZnO/CeO2 heterojunction to prepare lignin-modified nano-ZnO/CeO2 heterojunction. Through the FT-IR, XRD, SEM, UV-Vis-DRS means the characterization of samples. The UV shielding properties of the synthesized samples were investigated with methylene blue as the protection object. The results show that the light absorption performance of the samples at 280～420 nm is better than that of ZnO/CeO2 samples. The retention rate of methylene blue for 70 min under UV irradiation was 77.92%, indicating that the synthesized sample was a UV shielding material with high UV shielding properties and low photocatalytic activity.
Protected amino acid compounds are often widely used as intermediates of drug molecules and functional material intermediates. The high efficiency of Boc-protected amino acid esters provides an important prerequisite for their subsequent conversion in the entire process. Boc-tert-butyl phenylalanine was selected as the raw material, and the process of selectively removing the Boc protecting group while retaining the protecting group of tert-butyl ester to generate tert-butyl phenylalanine hydrochloride was studied. Under room temperature or low temperature conditions, the yield of about 82% can be achieved by deprotection under acidic conditions, and the reaction conditions are simple and mild, and the cost of process equipment is low, which realizes simple operation, economical benefits and environmental protection.
Glass fiber (GF) reinforced nylon 6 (PA6) composites were prepared with a twin-screw extruder. The effects of GF mass fraction on the mechanical properties, thermal properties, density, water absorption and processability of PA6/GF composites were systematically investigated. The results show that the impact strength, tensile strength, flexural strength, flexural modulus, density and thermal deformation temperature of the composites increased with the increase of glass fiber content, while the water absorption and melt flow rate decreased with the increase of glass fiber mass fraction. The morphology showed that the GF was effectively wrapped and dispersed in the PA6 matrix when the GF mass fraction was increased up to 30%.
A novel organic-inorganic hybrid material [Ag(DPPE)2]2[Mo4O10(CH3O)6]·2CH3OH (1) has been prepared by using [Mo4O10(CH3O)6]2- in polyoxometalate (POMs) as inorganic building block, 1,2-bis(diphenylphosphine)ethane (DPPE) as an organic ligand and silver nitrate as a silver source, through the means of a combination of solvothermal and conventional synthesis and via the self-assembly process. X-ray single crystal diffraction analysis shows that compound 1 is formed by electrostatic interaction with polyanion [Mo4O10(CH3O)6]2- and [Ag(DPPE)2]+ cationic units. In addition, the structure of the compound was analyzed by X-ray powder diffraction and fourier transform infrared spectroscopy. The stability was determined by thermogravimetric analysis, the band gap was determined by solid UV-visible diffuse reflection test, and the fluorescence spectra in methanol solution were measured. It was found that compound 1 showed good photocurrent response.
At present,most oil fields in China have entered the high water cut period,and the flow characteristics of produced fluid have changed, so it is possible to reduce the temperature of gathering and transportation.However,there are relatively few studies on the influence of pipeline materials on low-temperature gathering and transmission characteristics. Therefore, the characteristics of low-temperature gathering and transportation of high water content crude oil in steel pipe and fiberglass pipe are studied.The results show that the wellhead back pressure rises and the oil temperature at the end of pipeline drops slowly after the water content of the pipeline is reduced. The wellhead back pressure rises differently under different water content.When the water content is the same, the temperature of fiberglass pipe is lower than that of steel pipe, and the minimum water content of fiberglass pipe for low-temperature gathering and transportation is lower than that of steel pipe under the same condition.Based on the experimental data of viscosity wall temperature,the calculation models of different pipe materials are obtained,and the calculation results are accurate, which has a guiding significance for the feasibility judgment and safe operation management of the oil field in the high water cut period.
In some areas of Xinjiang, the dip angle of coal seams can reach 50 °. Unlike horizontal coal seams, fluids in high dip coal seams are severely affected by gravity, and the pressure propagation law of coalbed methane wells has special characteristics. The optimal drainage and extraction well position needs to be optimized. This article considers the gravity effect of formation water and establishes a pressure propagation model for single-phase drainage in steep coal seam, and verifies the correctness of the model.Then, the water production of fractured wells in the inclined reservoir is calculated under stable seepage conditions, and the optimal drainage well position is optimized. Finally, numerical simulation methods are used to study the pressure propagation laws of single wells and well groups in heterogeneous bounded inclined reservoirs. The results show that in a high dip coal seam with an inclination angle of 45 °, the position where the distance ratio between the drainage well and the upper and lower boundaries is 3
Infrared thermal imaging technology is widely used in the study of precursor characteristics and early warning methods of rock failure. However, infrared radiation precursory features have many forms, so it has certain influence on the accurate early warning of rock instability. The failure and instability of rock are closely related to the evolution of strain energy, and the infrared radiation information of rock is related to the dissipation and release of strain energy. If the strain energy is combined with infrared radiation information, the rock failure and instability can be monitored and warned accurately. Based on this, in this paper, the release time of elastic energy is determined by the cusp mutation theory based on the energy evolution characteristics, which is combined with the infrared radiation anomaly information to determine the precursor of rock failure and instability. The results show that with the sudden drop of the elastic energy curve, the infrared radiation synchronization appears abrupt change. The elastic energy release time of sandstone predicted by constructing the sharp point mutation model can be divided into two situations: leading and lagging the first mutation time of infrared radiation. Taking the elastic energy release time as the standard, the infrared radiation mutation near the sandstone can be regarded as the precursor of sandstone failure. The results can provide a new idea for mine disaster monitoring and early warning.
A model of a micro-texture tool featuring various textures such as micro-pits, parallel grooves, vertical grooves, and oblique grooves was developed. The impact of these micro-texture tools on the turning process of titanium alloy was investigated using the finite element analysis software ABAQUS. Through an examination of cutting force, friction coefficient, cutting temperature, and surface residual stress for micro-texture tools with distinct morphologies, the optimal micro-texture morphology was determined. The findings reveal that micro-texture tools can effectively reduce the cutting force, friction coefficient, and cutting temperature while transforming surface residual stress from tensile to compressive on the workpiece. Furthermore, with increasing cutting speed, cutting force and cutting temperature rises, friction coefficient decrease, and the residual stress on the workpiece surface shifts from compressive to tensile stress, exhibiting an ascending trend.
To investigate the influence of ordered micro texture design on the dynamic pressure effect of dry gas seal T‐groove, based on the principle of gas film lubrication, finite difference method was used to study the effects of ordered micro texture variables such as micro texture arrangement spacing, micro texture length, T‐shaped groove base length and width, and micro texture gradient inclination angle on sealing parameters. The design variables of four types of micro textures were compared. The results show that the micro texture of the T‐shaped groove can change the dynamic pressure effect of the groove itself, just like the structural parameters of the T‐shaped groove, but it does not change the dynamic law of the dry gas seal groove itself. The influence of microtexture variables on the opening force of T-shaped grooves in dry gas seals: microtexture gradient inclination angle>microtexture arrangement spacing>microtexture length and width>T-shaped groove base length and width amplification; The impact on leakage rate: microtexture length and width>microtexture arrangement spacing>T-shaped groove base length and width amplification>microtexture gradient inclination angle. The research results have certain reference value for the optimization and design of bi‐directional rotating end face gas film seals.
The defect detection of non-woven fabrics can help enterprises improve production efficiency and save costs. Due to the local characteristics of the convolution kernel, the object detection algorithms based on CNN lack the global modeling of the image, and the detection effect is not ideal for defect detection with a large range of scale changes. Therefore, a non-woven fabric defect detection method is proposed based on the combination of Swin Transformer and YOLOv5, which encodes and decodes features through its powerful self-attention. The network can obtain a larger receptive field and fully relate to the context. The layered construction based on the feature pyramid of Swin coincides with the design of the neck of YOLOv5. It can help the network predict the target on the multi-scale feature map. On this basis, CBAM attention mechanism is introduced to help the network focus on important information. Through Mosaic and MixUp data augmentation, the data distribution is enriched and the robustness is increased. Finally, the anchor size of the prediction target frame is fine-tuned to make the regression prediction more accurate. The effectiveness of the proposed method is verified on the self-made data set, and the detection performance of non-woven fabrics is improved.
The combination of remote sensing image information extraction and artificial intelligence algorithms is an important technical tool for land use status survey, monitoring and management in land resources and environmental departments.Aiming at the problems of insufficient spatial information localization and inaccurate multi-scale target feature segmentation generated by U-net in remote sensing image extraction, a CA-Res2-Unet model incorporating an attention module into the head of Res2Net to replace the coding part of U-net is proposed, which aims to enhance the spatial localization and multi-scale feature information segmentation capability of U-net.Experiments were carried out on mainstream networks and improved models through the WHDLD public data set and the self-made data set of Shenfu New District. The results show that compared with the basic model, OA, MIoU and F1
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