查看更多>>摘要：The electricity demand is increasing rapidly with the development of society and technology.Coal-fired thermal power plants have become one of the primary sources of electricity generation for urbanization.However,coal-fired thermal power plants produce a great amount of by-product coal fly ash every year.Coal fly ash disposal in landfills requires a sizable space and has negative environmental impacts.Therefore,it is crucial to develop new technologies and methods to utilize this enormous volume of solid waste in order to protect the environment.In this review,the fundamental physical and chemical character-istics of coal fly ash are introduced,and afterward the disposal policies and utilization ways of coal fly ash are discussed to gain a comprehensive understanding of the various ways this waste.The leaching of valuable metals in coal fly ash and the extraction of metal elements in leachate under different conditions are also summarized.Furthermore,the possibility of coal fly ash to serve as a supplementary source for mineral resources is analyzed,providing a basis for its extensive use as a raw material in the metal industry in China and worldwide.
查看更多>>摘要：The Pabdeh Formation represents organic matter enrichment in some oil fields,which can be considered a source rock.This study is based on the Rock-Eval,Iatroscan,and electron microscopy imaging results before and after heating the samples.We discovered this immature shale that undergoes burial and diagenesis,in which organic matter is converted into hydro-carbons.Primary migration is the process that transports hydrocarbons in the source rock.We investigated this phenomenon by developing a model that simulates hydrocarbon generation and fluid pressure during kerogen-to-hydrocarbon conversion.Microfractures initially formed at the tip/edge of kerogen and were filled with hydrocarbons,but as catagenesis progressed,the pressure caused by the volume increase of kerogen decreased due to hydrocarbon release.The transformation of solid kerogen into low-density bitumen/oil increased the pressure,leading to the development of damage zones in the source rock.The Pabdeh Formation's small porethroats hindered effective expulsion,causing an increase in pore fluid pressure inside the initial microfractures.The stress accumulated due to hydrocarbon production,reaching the rock's fracture strength,further contributed to damage zone development.During the expansion process,microfractures preferentially grew in low-strength pathways such as lithology changes,laminae boundaries,and pre-existing microfractures.When the porous pressure created by each kerogen overlapped,individual microfractures interconnected,forming a network of microfractures within the source rock.This research sheds light on the complex interplay between temperature,hydrocarbon generation,and the development of expulsion fractures in the Pabdeh Formation,providing valuable insights for understanding and optimizing hydrocarbon extraction in similar geological settings.
查看更多>>摘要：To study the dynamic mechanical properties and failure characteristics of intersecting jointed rock masses with different joint distributions under confining pressure,considering the cross angle α and joint persistence ratio η,a numerical model of the biaxial Hopkinson bar test system was established using the finite element method-discrete-element model coupling method.The validity of the model was verified by comparing and analyzing it in conjunction with laboratory test results.Dynamics-static combined impact tests were conducted on specimens under various conditions to investigate the strength characteristics and patterns of crack initiation and expansion.The study revealed the predominant factors influencing intersecting joints with different angles and penetrations under impact loading.The results show that the peak stress of the specimens decreases first and then increases with the increase of the cross angle.When α＜60°,regardless of the value of η,the dynamic stress of the specimens is controlled by the main joint.When α ≥60°,the peak stress borne by the specimens decreases with increasing η.When α＜60°,the initiation and propagation of cracks in the cross-jointed specimens are mainly controlled by the main joint,and the final failure surface of the specimens is composed of the main joint and wing cracks.When α ≥ 60°or η≥ 0.67,the secondary joint guides the expansion of the wing cracks,and multiple failure surfaces composed of main and secondary joints,wing cracks,and co-planar cracks are formed.Increasing lateral confinement significantly increases the dynamic peak stress able to be borne by the specimens.Under triaxial conditions,the degree of failure of the intersecting jointed specimens is much lower than that under uniaxial and biaxial conditions.
查看更多>>摘要：In this study,the installation of an airlift pump with inner diameter of 102 mm and length of 5.64 m was utilized to consider the conveying process of non-spherical coal particles with density of 1340 kg/m3 and graining 25-44.5 mm.The test results revealed that the magnitude of increase in the solid transport rate due to the changes in the three tested parameters between compressed air velocity,submergence ratio,and feeding coal possibility was not the same,which are stand in range of 20％,75％,and 40％,respectively.Hence,creating the optimal airlift pump performance is highly dependent on submergence ratio.More importantly,we measured the solid volume fraction using the method of one-way valves in order to minimize the disadvantages of conventional devices,such as fast speed camera and conductivity ring sensor.The results confirmed that the volume fraction of the solid phase in the transfer process was always less than 12％.To validate present experimental data,the existing empirical correlations together with the theoretical equations related to the multiphase flow was used.The overall agreement between the theory and experimental solid delivery results was particularly good instead of the first stage of conveying process.This drawback can be corrected by omitting the role of friction and shear stress at low air income velocity.It was also found that the model developed by Kalenik failed to predict the performance of our airlift operation in terms of the mass flow rate of the coal particles.
Jiangwan HeMehdi SeratiMartin VeidtArthur De Alwis...
67-80页
查看更多>>摘要：The crack initiation stress threshold is widely used in excavation industries as rock spalling strength when designing deep underground structures to avoid unwanted brittle failures.While various strain-based methods have been developed for the estimation of this critical design parameter,such methods are destructive and often requires subjective interpretations of the stress-strain curves,particularly in rocks with pre-existing microcracks or high porosity.This study explore the applicability of non-destructive ultrasonic through-transmission methods for determining rock damage levels by assessing the changes in transmitted signal characteristics during loading.The change in velocity,amplitude,dominant frequency,and root-mean-square voltage are investigated with four different rock types including marble,sandstone,granite,and basalt under various stress levels.Results suggest the rate of signal variations can be reliably used to estimate crack closure and crack initiation stress levels across the tested rocks before failure.Comparison of the results between the conventional techniques and the new proposed methods based on ultrasonic monitoring are further discussed.
查看更多>>摘要：This study focuses on CO2 capture by pressure swing adsorption(PSA),with modified clinoptilolite as the adsorbent.Natural clinoptilolite is modified by roasting,by acid pickling,by a combination of acid pickling and roasting,and by ion exchange.Modification by acid pickling-roasting and by ion exchange are found to give the highest CO2 adsorption capacities,of 730 mUg and 876.7 mL/g,respectively.It is found that regeneration of clinoptilolite by a combination of vacuum desorption and heating enables recovery of as much as 89％of its previous CO2 adsorption capacity.To examine the CO2 adsorption capacity of clinoptilolite when applied to mixed gas,a simulated coking exhaust containing 12％CO2 and 4％O2 is used,and it is found that ion exchange modified clinoptilolite achieves a CO2 removal efficiency of 92.5％.A BET test reveals that acid pickling-roasting and Na+modification enhance the porosity of clinoptilolite,thereby improving its adsorption capacity.This work demonstrates the feasibility of applying modified clinoptilolite as an effective adsorbent for CO2 capture,providing a promising tool for dealing with greenhouse gases.
Igor G.DonskoyAleksandr N.KozlovMaksim V.PenzikDenis A.Svishchev...
91-100页
查看更多>>摘要：The article presents the results of experimental studies on the gasification of mixtures of brown coal and polyethylene(up to 20 wt％fraction)in a laboratory reactor.The work aims to study the agglomeration process during the heating and oxidation of the mixtures.The measurement results(gas composition,pressure drop)provide indirect information on the dynamics of thermal decomposition and structural changes in the fuel bed.We have shown that the interaction between polyethylene and a coal surface leads to the formation of dense agglomerates,in which the molten polymer acts as a binder.Clinkers form as a result of interfacial interactions between components and filtration flow rearranging.The hydrogen/carbon ratio in the solid residue of coal-polyethylene co-gasification increases from 0.07-0.2 to 1.11,indicating the formation of stable hydrocarbon compounds on the carbon surface.The conducted research makes it possible to identify possible interactions between chemical reactions and transfer processes that lead to agglomeration in mixtures of coal with polyethylene.
查看更多>>摘要：Oil transport is greatly affected by heterogeneous pore-throat structures present in shale.It is therefore very important to accurately characterize pore-throat structures.Additionally,it remains unclear how pore-throat structures affect oil transport capacity.In this paper,using finite element(FE)simulation and mathematical modeling,we calculated the hydrodynamic resistance for four pore-throat structure.In addition,the influence of pore throat structure on shale oil permeability is analyzed.According to the results,the hydrodynamic resistance of different pore throat structures can vary by 300％.The contribution of additional resistance caused by streamline bending is also in excess of 40％,even without slip length.Fur-thermore,Pore-throat structures can affect apparent permeability by more than 60％on the REV scale,and this influence increases with heterogeneity of pore size distribution,organic matter content,and organic matter number.Clearly,modeling shale oil flow requires consideration of porous-throat structure and additional resistance,otherwise oil recovery and flow capacity may be overestimated.
查看更多>>摘要：Chemical leaching of coals would be required to produce cleaner coals for some special applications where physical benefi-ciation may not be effective enough.This would also help in recovering Li and rare earth metals besides in the sequestration of CO2.About 20 Indian coals having complexly distributed moderate to high ash contents were sequentially treated with various alkali-acid such as NaOH-HCl,HF,HC1,HCl-HF,and NaOH-HCl-HF leaching.This aimed to establish and design the best stepwise sequential process for the highest degree of demineralisation through a chemical leaching process.Kinetics and process intensification studies were carried out.More than 80％demineralisation of Madhaipur and Neemcha coals was observed using the best sequential treatment designed presently.The repeated stepwise treatment of the alkali and the acid was also studied,which was found to significantly enhance the degree of demineralisation of coals.The integrated process of alkali-acid leaching followed by solvent extraction(Organo-refining)and vice versa of the treated coal was also studied for producing cleaner coals.
查看更多>>摘要：Coalbed methane(CBM)is a significant factor in triggering coal and gas outburst disaster,while also serving as a clean fuel.With the increasing depth of mining operations,coal seams that exhibit high levels of gas content and low permeability have become increasingly prevalent.While controllable shockwave(CSW)technology has proven effective in enhancing CBM in laboratory settings,there is a lack of reports on its field applications in soft and low-permeability coal seams.This study establishes the governing equations for stress waves induced by CSW.Laplace numerical inversion was employed to analyse the dynamic response of the coal seam during CSW antireflection.Additionally,quantitative calculations were performed for the crushed zone,fracture zone,and effective CSW influence range,which guided the selection of field test parameters.The results of the field test unveiled a substantial improvement in the gas permeability coefficient,the average rate of pure methane flowrate,and the mean gas flowrate within a 10 m radius of the antireflection borehole.These enhancements were notable,showing increases of 3 times,13.72 times,and 11.48 times,respectively.Furthermore,the field test performed on the CSW antireflection gas extraction hole cluster demonstrated a noticeable improvement in CBM extraction.After antireflection,the maximum peak gas concentration and maximum peak pure methane flow reached 71.2％and 2.59 m3/min,respectively.These findings will offer valuable guidance for the application of CSW antireflection technology in soft and low-permeability coal seams.
NETL
NSTL
万方数据