聚乙烯亚胺的抑膨促渗机理

为解决风化壳淋积型稀土矿(WCE-DREO)原地浸出过程中出现的滑坡和浸出速度慢等问题,研究了聚乙烯亚胺(PEI)对蒙脱石(MMT)和风化壳淋积型稀土矿的抑膨性能及作用机理。随着聚乙烯亚胺浓度的增加,聚乙烯亚胺对蒙脱石和风化壳淋积型稀土矿的抑膨效果逐渐增强。由0.4%聚乙烯亚胺和2%硫酸铵组成的复合浸出剂与单独使用2%硫酸铵相比,稀土的浸出效率从93.94%提高到95.24%,浸出时间缩短了约33%。聚乙烯亚胺可通过水解产生大量-NH_(3)^(+),从而中和黏土矿物夹层和表面的负电荷,减少静电排斥,削弱黏土矿物的水化和膨胀。PEI可在黏土颗粒上形成一层聚合物膜,改变颗粒表面的亲水性,减少水的侵入。小颗粒在长链PEI的包裹和桥联作用下发生团聚,从而增大了颗粒尺寸,有利于浸出剂的渗入。PEI骨架还能嵌入黏土夹层并挤出夹层水,从而抑制黏土矿物的膨胀。

Prediction of landslide displacement with dynamic features using intelligent approaches

Landslide displacement prediction can enhance the efficacy of landslide monitoring system,and the prediction of the periodic displacement is particularly challenging.In the previous studies,static regression models(e.g.,support vector machine(SVM))were mostly used for predicting the periodic displacement.These models may have bad performances,when the dynamic features of landslide triggers are incorporated.This paper proposes a method for predicting the landslide displacement in a dynamic manner,based on the gated recurrent unit(GRU)neural network and complete ensemble empirical decomposition with adaptive noise(CEEMDAN).The CEEMDAN is used to decompose the training data,and the GRU is subsequently used for predicting the periodic displacement.Implementation procedures of the proposed method were illustrated by a case study in the Caojiatuo landslide area,and SVM was also adopted for the periodic displacement prediction.This case study shows that the predictors obtained by SVM are inaccurate,as the landslide displacement is in a pronouncedly step-wise manner.By contrast,the accuracy can be significantly improved using the dynamic predictive method.This paper reveals the significance of capturing the dynamic features of the inputs in the training process,when the machine learning models are adopted to predict the landslide displacement.

A Numerical Gas Fracturing Model of Coupled Thermal,Flowing and Mechanical Effects

Gas fracturing,which overcomes the limitation of hydraulic fracturing,is a potential alternative technology for the development of unconventional gas and oil resources.However,the mechanical principle of gas fracturing has not been learned comprehensively when the fluid is injected into the borehole.In this paper,a damage-based model of coupled thermal-flowing-mechanical effects was adopted to illustrate the mechanical principle of gas fracturing.Numerical simulation tools Comsol Multiphysics and Matlab were integrated to simulate the coupled process during the gas fracturing.Besides,the damage evolution of drilling areas under several conditions was fully analyzed.Simulation results indicate that the maximum tensile stress,which occurs in the upper and lower of the injection hole,decreases with the increase of the tectonic stress coefficient(TSC).As the TSC increases,shear fractures increase,a crushed area is gradually formed and the seepage area increases rapidly.The influence of TSC on fracture expansion is concluded as follows:with the decrease of TSC,the relative width of fractures decreases whilst the depth increases.It indicates that thermal stress and pore pressure promote the expansion of tensile fractures but restrain the expansion of shear fractures.Therefore,a relatively lower injection gas pressure is required to obtain the same degree of fracturing with a coupled thermal gradient.

Simulation of the interaction of methane,carbon dioxide and coal

Gas adsorption has an important influence on gas flow in a coal body.Research on the characteristics of coal and gas adsorption is the theoretical basis for studying gas flow in coal.In this paper,the interaction between methane,carbon dioxide and surface molecules of anthracite was simulated using the quantum chemistry method.Adsorption energy and adsorption configurations of different quantities of gas molecules absorbed on the coal surface were calculated.The results show that adsorption between coal and the two kinds of gas molecules is a physical adsorption process and there is an optimal configuration.Gas molecules are more easily adsorbed in the hydroxyl-containing side chain,while it is difficult for them to be adsorbed at the position of the benzene ring.Besides,carbon dioxide molecules are more readily adsorbed on the coal surface than methane molecules.The findings have an important significance in revealing the nature of gas adsorption in coal.

Novel oxygen-enrichment method using annular air curtain for single-head roadway of plateau mine

The low-oxygen environment restricts the exploitation of mineral resources on plateaus and affects miner’s safety.This paper proposes an oxygen-enrichment method using an annular air curtain.Through numerical simulation and experiments,it was confirmed that the proposed method improves the breathing environment in the single-head roadway of a plateau mine.Computational fluid dynamics(CFD)was used to investigate the oxygen-enriching effect and oxygen spatial distribution regularities after using the proposed oxygen-enrichment method in the single-head roadway of a plateau mine.The reliability of the CFD model was confirmed by experiment.Orthogonal testing was conducted to investigate the influence degree and optimal level combination of factors influencing oxygen enrichment.The results demonstrate that the annular air curtain effectively prevented oxygen loss,thus forming a local oxygen-rich space and improving the effective utilization rate of oxygen.Oxygen supply concentration and velocity are positively correlated with the oronasal oxygen mass fraction through a linear function,while the air curtain outlet wind velocity is negatively correlated with the oronasal oxygen mass fraction through a linear function.The annular air curtain diameter and oronasal oxygen mass fraction do not have an obvious functional relationship.When the annular air curtain diameter was greater than 0.9 m,the oronasal oxygen mass fraction was stable at approximately 25.30%.The influencing factors of the novel oxygen-enrichment method are,in descending order,as follows:oxygen supply concentration,annular air curtain diameter,air curtain outlet wind velocity,and oxygen supply velocity.The optimal level combination is oxygen supply concentration of 100%,oxygen supply velocity of 11 m/s,air curtain outlet wind velocity of 1.5 m/s,and annular air curtain diameter of 0.9 m.