Figure - available from: Advances in Materials Science and Engineering
This content is subject to copyright. Terms and conditions apply.
Source publication
In this study, a new coal-dust polymer composite material (CP) was fabricated to improve the borehole gas drainage effect and address the limitations of traditional sealing materials. This material used coal dust generated during underground drilling construction as filler, amino resin as binder, and also some other additives. Based on the orthogon...
Citations
... Over the last few decades, polymer-carbon composites have gained wide popularity in scientific and industrial societies. As a result, the methods for their production were continuously improved [4][5][6][7][8], and the scope of their application expanded [9][10][11][12][13]. ...
... Commonly used carbon fillers are carbon fibers, carbon black, and graphite. It was found that carbon fibers significantly enhance the mechanical strength of composites [10,11] and the carbon black additive improves their thermal properties [8,9], while graphite has a positive impact on the mechanical, thermal, and electrical properties of composites [2,12,14]. Less frequently, the fillers based on fossil coals, both raw coals and processed coal products, were used to reinforce polymer matrices [2,[15][16][17][18][19][20][21]. ...
The effect of particle size and oxidation degree of new carbon microfillers, based on coal pitch (CP) and petroleum pitch (PET) cokes, on the structure as well as thermal, mechanical, and electrical properties of the composites based on ultrahigh molecular weight polyethylene (UHMWPE) was investigated. The composites studied have a segregated structure of filler particle distribution in the UHMWPE matrix. It was found that composite with smaller CP grain fraction has the highest Young’s modulus and electrical conductivity compared to the other composites studied, which can be the result of a large contribution of flake-shaped particles. Additionally, conductivity of this composite turned out to be similar to composites with well-known carbon nanofillers, such as graphene, carbon black, and CNTs. Additionally, the relationship between electrical conductivity and Young’s modulus values of composites studied was revealed, which indicates that electrical conductivity is very sensitive to the structure of the filler phase in the polymer matrix. In general, it was established that the properties, especially the electrical conductivity, of the composites studied strongly depends on the size, shape, and oxidative treatment of CP and PET filler particles, and that the CP coke of appropriately small particle sizes and flake shape has significant potential as a conductive filler for polymer composites.
... 6 The wax fraction of lignite is industrially extracted and refined to obtain montan wax which, among other uses, is applied as matting agent or dispersing aid in coatings. 7,8 The use of coal itself as filler has been proposed, 9 optionally in a partly extracted state that allows effective hydrogen bonding to polymers, 10 as has the application of coal as a raw material for fillers such as carbon black, 11 carbon fiber 4,12 or graphene oxide. [13][14][15] Most coal-derived products applied today stem from coal tar, a by-product of the coking process to produce coke for the steel industry. ...
Solvent extraction of subbituminous coal at mild conditions (360°C) provides solid extracts that consist of numerous organic molecules that can be utilized in the synthesis of polymeric coatings. We describe the extraction process as well as the application of the resultant materials, which bear phenolic groups as the main reactive functionality, for the synthesis of polyurethane and epoxy coatings. The respective reactions of coal extract with isocyanates or epoxides were validated by 13C-NMR. By combining 50–67% coal extract with suitable, flexible co-reactants and co-resins, we formulated coatings with excellent wet adhesion to aluminum, flexibility, and corrosion protection with the same quality as reference coatings. The work is an advancement toward the goal of developing economic and resource-efficient routes from coal to polymers with attractive properties, where coal extracts can compete with petrochemically derived raw materials.
... The CBM in China ranks third in the world with 3:68 × 10 12 m 3 of reserves at depths < 2000 m [5]. The total potential CBM includes considerable amounts of onshore conventional natural gas resources and provided 7.26 billion m 3 of energy in 2018 [6]. ...
The effective radius of methane extraction after high-pressure water jet slotting is the most important parameter for borehole optimization and extraction time planning. We applied a steady flow model and thermal-hydrological-mechanical (THM) coupling model to calculate the effective radius after high-pressure water jet slotting. Field measurements at the Zhongliangshan coal mine show that both the steady flow model and the THM coupling model can accurately represent the effective radius, and the THM coupling model provides further information regarding extraction time. After that, a variety of factors, including extraction time, coal burial depth, slot radius, initial permeability, and initial methane pressure, are discussed. The effective radius of a slotted borehole is 1.94 times larger than that of a conventional borehole.
... Compared with cement mortar, it had superior expansibility and good water retention ability within 30 h. Li et al. [85] used coal dust as a filler, amino resin as a binder and other additives to synthesize a composite polymer material (CP). Amino resin is a linear polymer, which connects coal particles to play a role in stress transfer. ...
... Sealing performance of composite polymer material (CP): (a) High fluidity and super sealing ability; (b) good combination with coal mass; (c) adapt to the deformation of borehole[85]. ...
Safe mining is the premise and guarantee of sustainable development of coal energy. Due to the combination of excellent properties of polymers and traditional soft matters, polymer-containing soft matters are playing an increasingly important role in mine disaster and hazard control. To summarize the valuable work in recent years and provide reference and inspiration for researchers in this field, this paper reviewed the recent research progress in polymer-containing soft matters with respect to mine dust control, mine fire control, mine gas control and mine roadway support. From the perspective role of polymers in a material system, we classify mine polymer-containing soft matters into two categories. The first is polymer additive materials, in which polymers are used as additives to modify fluid-like soft matters, such as dust-reducing agents (surfactant solution) and dust-suppressing foams. The second is polymer-based materials, in which polymers are used as a main component to form high performance solid-like soft matters, such as fire prevention gels, foam gels, gas hole sealing material and resin anchorage agent. The preparation principle, properties and application of these soft matters are comprehensively reviewed. Furthermore, future research directions are also suggested.
The effective method of mine gas control and efficient development is gas extraction technology. The sealing effect of grouting material on borehole directly affects the efficiency of gas extraction. The new type of rich-watered sealing material with suitable mechanical strength and significant plastic characteristics was developed based on the addition of accelererant, alkali activator, expansion agent and reinforcing agent to Portland cement for mining. The effect of reinforcing agent on the mechanical properties of materials under different w/c ratios was tested by RMT. By means of X-ray diffraction (XRD), scanning electron microscopy (SEM) and other test methods, the microstructure evolution of grouting materials and its influence mechanism on macroscopic mechanics were revealed. The results show that the crystal structures of hydration products AFt, Ca(OH)2 and C-A-H regulate the development of mechanical strength of materials. The uniaxial compressive strength of rich-watered grouting materials can reach 3.5–5.6 MPa and the residual strength is greater than 3 MPa in the range of rich-watered ratio of 0.9–1.3. The new rich-watered grouting material developed has significant plastic deformation characteristics under high rich-watered ratio conditions, which can greatly adapt to borehole deformation and reduce the gap width of slurry-coal interface, and can meet the technical requirements of long-term sealing of gas extraction boreholes.
In order to improve the efficiency of gas extraction in coal mines, a data-driven fine-management and control method for gas extraction is proposed. Firstly, the accurate prediction of coal seam thickness and gas content was used to evaluate the gas reserves. Based on the time relationship between mining activities and gas extraction, the calculation model of borehole distance in different extraction units is established, and the differential borehole design is realized. Then, a drilling video-surveillance system and drilling trajectory measurement device are used to control the drilling process and the construction effect. Finally, the model of extraction data-correction and the identification of failed boreholes is established, then the failed boreholes are repaired. The technology method provided in the paper has realized the fine control of gas-extraction borehole design, construction, measurement, and repair, and formed a more scientific gas-extraction borehole control technology system, which provides new thought for efficient gas extraction.
The quality of borehole sealing is closely related to the sealing materials. As a kind of sealing material, how polymer materials improve the sealing quality has not been deeply analyzed. This paper based on the analyses of the dynamic contact state between polymer material and borehole wall, taking borehole, polymer material and their contact surface as the research object, this paper analyzes the changes of air leakage channel after sealing, the internal particles of foaming material, and the structure characteristics of contact surface. From multi-angle to obtain the sealing mechanism of polymer material. The results are: (1) the reduction rate D equation of the air leakage channel is derived. It positively relates to the expansion support force of sealing material. (2) Polymer materials could reduce the stress and deformation of coal surrounding borehole by 2.3 ~ 4.5% and 15.2% ~ 19.9% respectively, to narrow the air leakage range outside the hole. (3) The unusual structure of polymer foam particles can be well bonded and fixed with the borehole wall, improve the borehole stability, and reduce the air leakage inside the hole. (4) Polymer sealing material can maintain an average gas concentration of 44.90% within 60 days, not less than 30%, and ensure the extraction effect.
The poor sealing effect of gas extraction boreholes causes low efficiency of gas extraction. As a consequence, the requirements of coal mine safety production are often not attained. The sealing effect of boreholes depends not only on the sealing material itself but also on the combination degree between the material and the hole wall and the structural change characteristics of the material during operation. Our theoretical analysis shows that the amount of liquid leakage increases with the gap width Δh in a cubic law, decreases with the sealing hole viscosity in a hyperbolic form, increases linearly with the diameter of the borehole, and increases with the eccentricity in a quadratic function. We have developed a PD sealing material that has good compactness and sealing effects, excellent water retention performance, and an expansion rate of 1.29. The material can generate secondary expansion through microscopic development, which is beneficial to improve the quality of the sealing hole. HV-CMC has good stability in plugging mucus. In addition, the manual pump has been redeveloped to be portable and also to overcome the blockage of the suction valve of the original device. In addition, the auxiliary device for drilling and sealing has been invented. The field application demonstrates that the gas concentration and flow pressure difference of the new sealing borehole can be maintained at a high level in a short period of time and then decrease slowly with time. The resulting improved sealing effect demonstrates that our new approach has important theoretical and practical significance for mine gas drainage.
To compare the differences between new CF drilling sealing materials and ordinary cement, the author considered to conduct experimental research from the aspects of permeability, pore size and fluidity. Based on experiments conducted on samples simulating coal in an underground coal mine, the permeability around sealed boreholes was studied using scanning electron microscopy and low field nuclear magnetic resonance. In addition, the pores in the two kinds of grout used were studied quantitatively by mercury injection porosimetry and carbon dioxide gas adsorption. The experimental results show that the new CF seal slurry has better fluidity, average pore size, porosity and permeability than ordinary cement. This indicates that the new CF drilling sealing material has better grouting performance than ordinary cement due to its microscopic pore structure. This experimental study provides a better choice of sealing material for coal seam gas extraction drilling, which can improve the sealing quality of the sealing hole, improve the extraction efficiency, avoid the emission of toxic and harmful gas, and provide guarantee for the safety production of coal mine.
