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The green, clean and efficient utilization of coal is an important way for the sustainable development of coal industry. Shaanxi province is rich in coal resources, which are mainly distributed in the five coal fields in the north of Shaanxi province, and the oil-rich coal resources rank first in China. In this paper, the distribution characteristics of oil-rich coal in Shaanxi Province and the geological factors affecting the tar yield of coal are discussed by collecting the previous geological exploration data and the coal core of a coal mine in Yushen mining area of northern Shaanxi Province. The results show that the Jurassic coal field in northern Shaanxi is the best oil-rich coal in Shaanxi Province, and the tar yield is distributed in the range of 7.6%-15.3%. Material composition, oil generation potential, thermal evolution degree and coal-forming environment control the size and distribution of tar yield in coal. The desmocollinite content, volatile matter content, H element content and H/C atomic ratio were positively correlated with the tar yield of coal, and the correlation coefficient was high. There is a high correlation between the hydrocarbon index and tar yield in rock pyrolysis parameters, which can be used as an index to quickly identify tar yield in coal. The tar yield of coal increases first and then decreases with the increase of thermal evolution degree, and reaches the maximum value when Ro is about 0.9%. The higher the coal tar yield value is in the peat swamp facies with micro-flow, strong reduction and shallow overlying water-micro-flow in sedimentary environment. The research results provide reference for geological prediction of oil-rich coal.

At present, the technology of embedded channels in shield tunnel segments has been applied in subway tunnels, achieving significant economic benefits. However, it has not yet been implemented in high-speed railway shield tunnels, mainly because of the strict requirements of the overhead contact system, where the embedded channel is intended solely for the contact network. The low utilization of full-ring embedded channels leads to considerable waste. This study focuses on the precise positioning and installation of embedded channels in high-speed railway shield tunnels, aiming to optimize the use of embedded channels, improve on-site construction, and enhance subsequent operation and maintenance. The research is of considerable importance. Based on the Zhanjiang Bay Submarine Tunnel Project of the Guangzhou - Zhanjiang High-speed Railway, a comprehensive technical analysis was conducted. Simplifications and standardization of the contact network anchor segment joints and suspension types were carried out. The appropriate embedded channel lengths and segment combinations were determined according to the different needs of the contact network. Assembly points and corresponding channel segment blocks that met the requirements were proposed, along with recommended assembly points. Through on-site assembly tests and expert reviews, the general suspension of individual embedded channel segments for the contact network, as well as the precise positioning and assembly of locally embedded channel segments in multiple rings for center anchoring and anchoring, and suspension anchor, were successfully validated. The feasibility of precise positioning and assembly of locally embedded channels in large-diameter shield tunnels for high-speed railways was verified. This approach was applied in the 7.55 km shield section of the entire tunnel. According to the assembly results, different types of embedded channel segments were assembled to the specified design positions, achieving a 100% assembly pass rate, and fulfilling the requirements of the contact network and relevant specifications. [ABSTRACT FROM AUTHOR]

This study investigates pore distribution and permeability behavior of tar-rich coal following high-temperature pyrolysis at 500°C using X-ray computed tomography (CT) scanning. Coal samples post-pyrolysis were CT scanned, generating 1755 cross-sectional slices for three-dimensional reconstruction. An axial algorithm extracted pore distribution features, and geometric parameters were computed. An Equivalent Pore Network Model analyzed permeability characteristics. The results show that Post-pyrolysis pore distribution in tar-rich coal exhibited nonuniformity with a significant range in pore size distribution. Pores displayed concentrated spatial patterns. Total porosity was 14.24%, with 12.34% being connected. Most pores in Representative Elementary Volume (REV) regions fell within 10-50 μιτι in width and 20-60 pm in length, constituting over 40% of the total. Pore surface area peaked between 200-100 pm2, also comprising over 40% of the total. The Pore Network Model showed distinct characteristics in two REV regions: REV-1 demonstrated an early stage of development with poor connectivity, while REV-2 displayed a well-developed network with a bimodal coordination number histogram. The study highlights nonuniform post-pyrolysis pore distribution and significant pore size variations in tar-rich coal. This study is crucial for understanding permeability behavior in tar-rich coal after high-temperature pyrolysis. [ABSTRACT FROM AUTHOR]

The world is rich in tar-rich coal resources, which have broad exploration and development prospects. At present, the academic community has relatively weak research on the impact of shock waves on the permeability of target coal bodies. This article focuses on the development technology of controllable shock waves in tar-rich coal reservoirs. Firstly, a systematic analysis was conducted on the drilling situation and physical parameters of the target coal seam. Secondly, the impact of shock waves on permeability of target coal was systematically analyzed. Thirdly, a systematic summary was conducted on the process parameters and measures of coal seam operations. Research has shown that: (a) The permeability of coal samples after shock wave action is much greater than the permeability of coal samples in their original state. (b) Under the same axial and confining pressure conditions, as the gas pressure increases, the increase in the permeability of coal under the action of shock waves shows a decreasing trend. (c) The shock wave generates a large number of crack structures inside the coal body. These cracks will undergo very obvious closure under external pressure. (d) Under different axial and confining pressures, when the gas pressure is 1 MPa, the maximum increase in permeability of coal samples under shock wave action can reach 90–200 times. When the gas pressure is 2 MPa, the increase in permeability before and after shock wave action is the smallest, reaching 30–90. • The impact of shock waves on the permeability of target coal is analyzed. • The process parameters and measures of coal seam operations is revealed. • In-situ development of oil-rich coal on-site testing operation process is discussed. [ABSTRACT FROM AUTHOR]

AbstractTar-rich coal has the features of high tar yield and great potential for oil production. The underground in-situ pyrolysis technology is an effective way to accomplish the green and efficient utilization of tar-rich coal resources. The pore structures of coal seam have great change in the actual in-situ pyrolysis process. Hence, the physical properties of coal seam also vary with pyrolysis temperature, which affects the heat transfer performance of coal seam. However, previous studies on heat transfer characteristics of coal seam have been seldom paid attention to the physical property dynamic change during the in-situ pyrolysis, which possibly causes deviation between the simulated heat transfer characteristics and the actual performance. It is still unclear whether the deviation is acceptable in practical engineering practice at present. In this article, a modification scheme for the physical property dynamic change of coal seam was proposed. The effects of physical property dynamic change on heat transfer characteristics of coal seam during in-situ pyrolysis of tar-rich coal were analyzed using numerical simulation approach. In addition to single factor correction, the effects of three-factor coupling modification on heat transfer performance of coal seam were also systematically investigated. The simulation results indicated that both the average temperature and the effective heating area of the coal seam increased after the specific heat capacity was corrected individually. Whereas, the heat transfer of coal seam was weakened after the endothermic effect of pyrolysis and the thermal conductivity coefficient were modified, respectively. When the three factors were coupled for correction in the single well and single fracture mode, the correction factor that played a leading role was the thermal conductivity coefficient, accounting for 90%. However, an increase in the number of cracks enhanced the heat transfer, resulting in the specific heat capacity was dominant among the three correction factors. The present study can offer theoretical guidance and technical support for realizing large-scale in-situ pyrolysis of tar-rich coal. [ABSTRACT FROM AUTHOR]

AbstractA large amount of pyrolysis residue is left in the coal seam after the in-situ pyrolysis of tar-rich coal, which contains rich heat energy. However, there are few numerical simulations on waste heat utilization from in-situ pyrolysis of tar-rich coal at present. This paper mainly focused on the temperature field distribution and heat transfer characteristics of the coal seam in the process of waste heat utilization of tar-rich coal in large spatial scale and over a long period. The effects of cooling medium type, cooling fluid velocity, cooling fluid temperature, fracture distribution and well pattern on temperature field distribution and heat transfer performance of tar-rich coal seam were analyzed by Fluent numerical simulation. The present study can offer theoretical guidance and technical support for large-scale utilization of residual heat from pyrolysis residue of tar-rich coal. [ABSTRACT FROM AUTHOR]

The separation of low-temperature coal tar (LTCT) containing solid particles by vacuum distillation is essential in various applications, such as in-situ pyrolysis. However, the separation characteristics of solid-containing LTCT using vacuum distillation have yet to be fully understood. Therefore, explorations were conducted with variations in pressure and solid particle concentration by analyzing pitch with Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The FTIR demonstrated that the organic constituents exhibit greater regularity at higher temperatures, leading to a 2 % reduction in the tightly bound cyclic OH tetramers, an intricate hydrogen bonding. The structural parameters indicate a 2 % decrease in f ar H, alongside a decline in AR from 0.332 to 0.293. This suggests that the low-pressure distillation conditions contribute to an increased retention of aromatic hydrocarbons in pitch, potentially complicating its subsequent utilization. The reduction in F from 2.273 to 2.029 signifies a shorter aliphatic chain, indicative of an intensified degradation effect. The elevated content of solid particles results in a more rigid texture of pitch in micromorphology. This study examined LTCT pitch to clarify the separation mechanism of solid-containing LTCT, offering insights into appropriate vacuum distillation conditions for LTCT separation and aiding in the effective utilization of pitch products. [Display omitted] • Analyzing pitch using FTIR and SEM reveals the LTCT vacuum distillation procedure. • Elevated distillation temperatures lead to deeper deoxygenation of the pitch. • Organic components are arranged more regularly at elevated temperatures. • Too low distillation pressure results in aromatic hydrocarbons remaining in pitch. • Increasing solids content makes the pitch harder and less friable texture. [ABSTRACT FROM AUTHOR]

Background: Data on viral kinetics and variants affecting the duration of viral shedding were limited. Our objective was to determine viral shedding in distinct severe acute respiratory syndrome coronavirus 2 variants, including Omicron BA.4/5 and BF.7, and to identify the relevant influencing factors., Methods: We carried out a longitudinal cohort study at Beijing Xiaotangshan Fangcang shelter hospital from May to June 2022 (Omicron BA.4/5) and from November to December 2022 (Omicron BF.7). Nucleocapsid protein (N) and open reading frame (ORF) genes were considered as the target genes of the reverse transcription PCR. The daily results of cycle threshold (CT), including lowest ORF1ab-CT values for days 1-3 post-hospitalisation and lowest N-CT values for days 1-3 post-hospitalisation (CT3minN) and demographic and clinical characteristics were collected., Results: 1433 patients with coronavirus disease 2019 (COVID-19) were recruited from the Fangcang shelter hospital, in which 278 patients were diagnosed with Omicron BA.4/5 and 1155 patients with Omicron BF.7. Patients with BF.7 infection showed a longer duration of viral shedding. The duration of viral shedding was associated with the variants age, alcohol use, the severity of COVID-19 and CT3minN. Moreover, the nomogram had excellent accuracy in predicting viral shedding., Conclusions: Our results indicated that patients with Omicron BF.7 had a longer period of contagiousness than those with BA.4/5. The duration of viral shedding was affected by a variety of factors and the nomogram may become an applicable clinical instrument to predict viral shedding. Furthermore, we developed a new COVID-19 viral shedding predicting model that can accurately predict the duration of viral shedding for COVID-19, and created a user-friendly website to apply this prediction model (https://puh3.shinyapps.io/CVSP_Model/)., Competing Interests: Conflict of interest: The authors declare that they have no conflict of interest., (Copyright ©The authors 2024.)