High Pressure Of Water Research Articles

Formation mechanical mechanism of low-angle fractures in pre-salt carbonate reservoirs: a case study from Carboniferous KT-I formation of the NT oilfield in the eastern margin of the Precaspian Basin, Kazakhstan

Fracture is an important factor that affects the oil and gas productivity of carbonate reservoirs. Much researches have been done on the origin of high-angle fractures in carbonate reservoirs, but few efforts have been made on the genetic mechanical mechanism of low-angle fractures. Based on the seismic data, core data, conventional logging data and rock mechanics experimental data, combined with three-dimensional in situ stress field simulation methods, the features, formation geological conditions and genetic mechanical mechanism of low-angle fractures (LAFs) were analyzed by applying Coulomb–Moore criterion, Griffith criterion and non-coordination criterion. The proportion of the number of shear fractures is as high as 90.2%, while that of tensile fractures is only 9.8% in the study area. Shear fractures are mainly unfilled fractures, and tensile fractures are mainly partially filled fractures. The LAFs were formed in the second tectonic movement, in which the knee-fold structure with high in the west and low in the east developed in the study area. The buried depth of most parts of the KT-I formation is 800 m when the study area develops the knee-fold structure, with a maximum depth of 1800 m and a minimum buried depth of 70 m, and the dip angle of the steepest part of the stratum is about 20°. A large number of LAFs were formed in the study area under the joint influence of tectonics and abnormally high pressure of water, including near-horizontal LAFs in the non-weak fabrics section (type I low-angle shear fractures), the LAFs having a certain angle with bedding in the non-weak fabrics section (type II low-angle shear fractures) and near-horizontal LAFs in the weak fabrics section (type III low-angle shear fractures). The formation of type I and type II low-angle shear fractures follows the Coulomb–Moore criterion. Type I low-angle shear fractures are formed in strata with a certain dip angle, while type II low-angle shear fractures are formed in near-horizontal strata. Type III low-angle shear fractures are formed under the comprehensive influence of pre-existing weak fabrics and strong horizontal extrusion, which follows the non-coordination criterion. Low-angle tensile fractures are mainly caused by abnormally high pressure and reverse faults in the study area, following Griffith’s criterion. The research in this paper not only reveals the formation mechanical mechanism of LAFs in pre-salt carbonate reservoirs but also provides guidance for the prediction of LAFs and solving the problem of water channeling caused by LAFs in oil fields.

Underwater sound-absorbing performance of composite structure under hydrostatic pressure by considering constitutive models

Underwater vessels face significant challenges as the high hydrostatic pressure of deep water affects their stealth performance. Linear models may not accurately depict the deformation of structures under hydrostatic pressure due to its non-linear properties of rubber and therefore, influence the results. This study utilized uniaxial tension and compression test data of styrene-butadiene rubber to fit four constitutive models and the optimal was selected to calculate the sound-absorbing performance under hydrostatic pressures,. Results showed that the Yeoh model fitted by uniaxial compression with r2 of 0.9928. Viscous losing, waveform conversion and locally resonance are main sound-absorbing mechanisms. The maximum sound-absorbing coefficient of structure at 0 MPa is 0.8914 at 7.6 kHz and the sound-absorbing performance mostly decreases with increasing hydrostatic pressure, Maximum reduction of 32 % was achieved at 3.2 kHz. Experiments verified the accuracy of simulation results, and the mean relative errors between the simulated results and the experimental results are 15.28 % (0 MPa), 16.91(0.5 MPa) %, 16.67 % (1 MPa) and 16.38 % (2 MPa), respectively. These findings can provide guidance for development of underwater sound-absorbing structures in hydrostatic pressure conditions.

Response characteristics of an insertion tensiometer investigated via the vacuum saturation method

Tensiometers are devices that can be used to monitor suction variation in landslides and slopes. The soil suction that can be measured with a conventional tensiometer is limited to 85 ∼ 90 kPa due to water cavitation in the tensiometer. This low measurement range of suction may be insufficient to interpret and determine the hydraulic properties of unsaturated soil, especially in semihumid and semiarid climate regions. However, in most geotechnical engineering studies, conventional tensiometers are still utilized. Although several types of high-suction tensiometers have been developed in recent decades, high suction measurements are difficult in the field because the saturation procedures for these tensiometers are complex and time consuming. Hence, the development of a simple and rapid saturation method is necessary to support their application. The vacuum saturation technique is a simple and reliable technique for saturating the porous ceramic cup of a tensiometer. However, if a high-suction tensiometer is saturated via a vacuum syringe, the measurable maximum suction is usually<200 kPa, which limits the application of tensiometers in geotechnical engineering. In this paper, we proposed a simple saturation device and a saturation method (the vacuum cylinder saturation method, VCSM) to saturate high-suction tensiometers. Soil column experiments were conducted to investigate the advantages of the VCSM and the response characteristics of insertion tensiometers. The results indicated that high-suction tensiometers could easily and steadily measure a maximum suction of 350 kPa if saturated via the VCSM. The VCSM could effectively prevent or retard the occurrence of cavitation due to the high vacuum pressure and slow progress of water filling in the tensiometer shaft. In addition, the response curve of insertion tensiometers could be divided into three stages: installing disturbance stage, delayed response stage and equilibrium stage. The extent of the disturbance caused by insertion tensiometer installation is a key factor influencing the delayed response characteristics of the tensiometer response curve. This paper also provides greater insight into the saturation method of tensiometers and the application of insertion tensiometers.

Exploring Gas-Liquid Reactions with Microjets: Lessons We Are Learning.

Liquid water is all around us: at the beach, in a cloud, from a faucet, inside a spray tower, covering our lungs. It is fascinating to imagine what happens to a reactive gas molecule as it approaches the surface of water in these examples. Some incoming molecules may first be deflected away after colliding with an evaporating water molecule. Those that do strike surface H2O or other surface species may bounce directly off or become momentarily trapped through hydrogen bonding or other attractive forces. The adsorbed gas molecule can then desorb immediately or instead dissolve, passing through the interfacial region and into the bulk, perhaps diffusing back to the surface and evaporating before reacting. Alternatively, it may react with solute or water molecules in the interfacial or bulk regions, and a reaction intermediate or the final product may then desorb into the gas phase. Building a "blow by blow" picture of these pathways is challenging for vacuum-based techniques because of the high vapor pressure of water. In particular, collisions within the thick vapor cloud created by evaporating molecules just above the surface scramble the trajectories and internal states of the gaseous target molecules, hindering construction of gas-liquid reaction mechanisms at the atomic scale that we strive to map out.The introduction of the microjet in 1988 by Faubel, Schlemmer, and Toennies opened up entirely new possibilities. Their inspired solution seems so simple: narrow the end of a glass tube to a diameter smaller than the mean free path of the vapor molecules and then push the liquid through the tube at speeds of a car on a highway. The narrow liquid stream creates a sparse vapor cloud, with water molecules spaced far enough apart that they and the reactant gases interact, at most, weakly. Experimentalists, however, confront a host of challenges: nozzle clogging, unstable jetting, searching for vacuum-compatible solutions, measuring low signal levels, and teasing out artifacts because the slender jet is the smallest surface in the vacuum chamber. In this Account, we describe lessons that we are learning as we explore gases (DCl, (HCOOH)2, N2O5) reacting with water molecules and solute ions in the near-interfacial region of these fast-flowing aqueous microjets.

Can Urea and Trimethylamine-N-oxide Prevent the Pressure-Induced Phase Transition of Lipid Membrane?

Organisms dwelling in ocean trenches are exposed to the high hydrostatic pressure of ocean water. Increasing pressure can alter the membrane packing density and fluidity and trigger the fluid-to-gel phase transition. To combat environmental stress, the organisms synthesize small polar solutes, which are known as osmolytes. Urea and trimethylamine-N-oxide (TMAO) are two such solutes found in deep-sea creatures. While TMAO stabilizes protein, urea induces protein denaturation. These solutes strongly influence the packing density and membrane fluidity of the lipid bilayer at different conditions. But can these solutes affect the pressure-induced phase transition of the lipid membrane? In the present work, we have studied the effect of these two solutes on pressure-induced fluid-to-gel phase transition based on the all-atom molecular dynamics (MD) simulation approach. A high-pressure-stimulated fluid-to-gel phase transition of the membrane is seen at 800 bar, which is consistent with previous experiments. We have also observed that in the low-pressure region (1-400 bar), urea slightly increases the membrane fluidity where TMAO decreases the same. However, the phase transition pressure remains almost unchanged on the addition of urea while TMAO shifts the phase transition toward a lower pressure. We have found that the hydrogen (H)-bond interaction between lipid and urea plays an important role in preserving the fluidity of the membrane in the low-pressure zone. However, at a higher pressure, both water and urea are excluded from the membrane surface. TMAO is also excluded from the interfacial region of the membrane at all pressures. Exclusion from the membrane surface further triggers the phase transition of the lipid membrane from the fluid to gel phase at a high pressure.

Numerical Modeling of Soil Erosion with Three Wall Laws at the Soil-Water Interface

In the area of civil engineering and especially hydraulic structures, we find multiple anomalies that weakens mechanical characteristics of dikes, one of the most common anomalies is erosion phenomenon specifically pipe flow erosion which causes major damage to dam structures. This phenomenon is caused by a hole which is the result of the high pressure of water that facilitate the soil migration between the two sides of the dam. It becomes only a question of time until the diameter of the hole expands and causes destruction of the dam structure. This problem pushed physicist to perform many tests to quantify erosion kinetics, one of the most used tests to have logical and trusted results is the HET (hole erosion test). Meanwhile there is not much research regarding the models that govern these types of tests. Objectives: In this paper we modeled the HET using modeling software based on the Navier Stokes equations, this model tackles also the singularity of the interface structure/water using wall laws for a flow turbulence. Methods/Analysis: The studied soil in this paper is a clay soil, clay soil has the property of containing water more than most other soils. Three wall laws were applied on the soil / water interface to calculate the erosion rate in order to avoid the rupture of such a structure. The modlisitation was made on the ANSYS software. Findings: In this work, two-dimensional modeling was carried of the soil.in contrast of the early models which is one-dimensional model, the first one had shown that the wall-shear stress which is not uniform along the whole wall. Then using the linear erosion law to predict the non-uniform erosion along the whole length. The previous study found that the wall laws have a significant impact on the wall-shear stress, which affects the erosion interface in the fluid/soil, particularly at the hole's extremes. Our experiment revealed that the degraded profile is not uniform. Doi: 10.28991/cej-2021-03091742 Full Text: PDF

Kinetic Study of Subcritical Water Extraction of Carbohydrate from Microalgae Nannochloropsis sp.

Microalgae contain a significant amount of carbohydrates that can be converted further to produce valuable compounds. To extract carbohydrates from microalgae, sub-critical water extraction (SWE) is a viable and novel method. Compared to other existing chemical and biological extraction methods, SWE is more economical, effective, and efficient in terms of process conditions. This process uses high temperature and pressure of water at just below supercritical conditions to keep water at a liquid state. This study aims to investigate the factors that affect the extraction yield of carbohydrates from microalgae Nannochloropsis sp. using the SWE process. The extraction was carried out at a temperature of 160 – 320 oC, a duration of 5 – 25 min, and microalgal biomass loading of 5 - 25% w/v. The kinetics study was conducted in an extraction time of 5 – 25 min at 200 oC and 5% (w/v) biomass loading. A simplified kinetic model based on a consecutive reaction was used to describe carbohydrate production and decomposition via SWE. It was found that the maximum yield of total carbohydrate was 18.04 g/100 g which was obtained at 200 oC, 10 min, and 5% (w/v) microalgal biomass loading. The carbohydrate concentration was decreased as the temperature, extraction time and microalgal biomass loading increased. This result indicated that the SWE is a promising extraction method for carbohydrate recovery from microalgae, and the factors investigated here had a significant effect on the extraction process. The proposed kinetic model was also able to capture the experimental data well within the range of operating conditions studied in this work.

Generation of supersonic jets from underwater electrical explosions of wire arrays

Underwater electrical explosion experiments of cylindrical or conical wire arrays accompanied by the generation of fast (up to ∼4500 m/s) water jets are presented. In these experiments, a pulse generator with a stored energy of up to ∼5.7 kJ, current amplitude of up to ∼340 kA, and rise time of ∼0.85 μs was used to electrically explode copper and aluminum wire arrays underwater. Streak and fast framing shadow imaging was used to extract the space–time resolved velocity of the ejected jet from the array while it propagates in air. The jet generation occurs due to high pressure and density of water formed in the vicinity of the array axis by the imploding shockwave. It was shown that the velocity of the jet ejected from the array depends on the array geometry and the thickness of the water layer above the array. The results suggest that ≥50% of the energy deposited into the array is transferred to the kinetic energy of this jet and the axial waterflow.

Design and analysis of deepwater tension sensors for ice drill application

AbstractMonitoring the tension in cables is significant in some ice drill and deepwater applications. Take our RECoverable Autonomous Sonde (RECAS) for example. It is able to melt a hole to the bottom of ice sheet and is able to move upwards. A winch is installed inside RECAS to release and recover the cable, whose tension needs to be monitored in real time in order to control the behavior of the winch. The high pressure of deep water and limited installation space pose great challenges in sensor development. In this paper, two editions of newly designed deepwater tension sensors are proposed. The first edition is based on a fresh hydraulic load module that operates in high pressure environment and the second edition tension, which aims to improve the accuracy, applies a newly designed watertight load module. Detailed force transmission and characteristic analysis of the sensors are carried out. The sensors have got through a series of experiments, including calibration experiments, pressure experiments and field experiments. The resultant accuracy of the second edition sensor, which has a better performance, is over 2% under the measuring range of 1000 kg and the dimension of the final sensor is as compact as 150 mm × 137 mm × 86 mm.

Application of electrospun nanofibrous amphiphobic membrane using low-cost poly (ethylene terephthalate) for robust membrane distillation

Although with great potential, membrane distillation (MD) is still far from satisfaction due to deficiency of ideal membranes with low cost and high performance. In this work, electrospun nanofibrous membranes (ENMs) fabricated using polyethylene terephthalate (PET) derived from recycled Coca Cola plastic bottles were evaluated in direct contact (DC) MD application. Heat-pressing was used to tune physicochemical properties of PET ENMs to get them better qualified for MD. Effect of heat-pressing on membrane structure and properties was emphasized. The preferred PET ENMs with nanofiber diameter of 517 nm exhibited high porosity of 77 %, high hydrophobicity with contact angle of ≥130°, and high liquid entry pressure of water (LEPw) of 49.8 kPa. The optimized PET ENMs displayed permeation of about 11−23 L m−2 h-1 (LMH) with varied temperature differences and salt rejection of 99.9 %. Stable permeation was noticed in the long-run membrane operation without significant permeation loss. Finally, 1H, 1H, 2H, 2H-perfluorodecyltriethoxysilane (FAS) was used to modify the surface of membrane to enhance their antiwetting capability against the oil. Surface modification rendered excellent endurance to the membrane even with addition of 0.3 M Sodium Dodecyl Sulfate (SDS, a model surfactant) while the pristine membrane failed to work once the SDS was added. This work paves the way for developing a low-cost and acceptable industrial-grade membrane with great potential in DCMD applications.

Thermal characteristics of dry cooling tower reconstructed from obsolete natural draft wet cooling tower and the relevant thermal system coupling optimization

Natural draft dry cooling tower is attractive in recent decades with its superiority of zero water loss. Some old thermal power plants are under high pressure of waste water reducing emission, thus the natural draft wet cooling tower is obsoleted. Reconstructing natural draft wet cooling tower into natural draft dry cooling tower is attractive for the saving of capital expenditure. But it has not been researched before, this study aims to fill this gap. Based on an actual reconstruction case, the operation mode of reconstructed dry cooling system is established and relevant MATLAB programming is realized, which is validated by literature data. The reconstructed system consists of two reconstructed natural draft dry cooling towers, a usual natural draft dry cooling tower and two 660 MW power units. The cooling capacity of reconstructed natural draft dry cooling tower is lower through thermal characteristic comparison with the usual natural draft dry cooling tower. In order to realize the optimal operation, different water distribution schemes are presented and several operation parameters are analyzed. Under the optimized reconstruction design, the annual water saving and annual cost are discussed. The annual water saving is about14.49 million metric tons that is about 8.86 million dollars and the minimum annual cost is about 181.47 million dollars, which brings great economic and environmental benefits.

A first-principles microkinetic study on the hydrogenation of carbon dioxide over Cu(211) in the presence of water

The hydrogenation of carbon dioxide (CO2) is one of important processes to effectively convert and utilize CO2, which is also regarded as the key step at the industrial methanol synthesis. Water is likely to play an important role in this process, but it still remains elusive. To systematically understand its influence, here we computationally compare the reaction mechanisms of CO2 hydrogenation over the stepped Cu(211) surface between in the absence and presence of water based on microkinetic simulations upon density functional theory (DFT) calculations. The effects of water on each hydrogenation step and the whole activity and selectivity are checked and its physical origin is discussed. It is found that the water could kinetically accelerate the hydrogenation on CO2 to COOH, promoting the reverse water gas shift reaction to produce carbon monoxide (CO). It hardly influences the CO2 hydrogenation to methanol kinetically. In addition, the too high initial partial pressure of water will thermodynamically inhibit the CO2 conversion.

Effect of High Temperature and High Pressure of Water on Micro-Characteristic and Splitting Tensile Strength of Gritstone

To investigate the role of gritstone after hydro-thermal treatment on the mechanical properties and deformation failure behavior, the Brazilian test are carried out on gritstone specimens. Using load–displacement curves, the peak load and peak displacement of the gritstone specimens are analyzed in detail. The mechanical parameters are closely related to the high temperature, high pressure of water and the cooling down methods. The static splitting tensile strength (STSS) of specimens are decreasing with the increase of water pressure. In the cooling down group, the STSS and peak displacement of specimen WP1 are the lowest one. While, the STSS of specimen W1 is the biggest one. The differences in mechanical properties of the gritstone specimen are mainly caused by the ablation effect in the microscale under different HTHP and cooling down conditions. The surface deformation characteristics of the tested gritstone specimens are investigated by analyzing the full strain field and the local strain concentration. In the gritstone specimen, the major principal strain is first concentrated in the bottom or the top of gritstone specimens where the crack is initiated. The small jump of local strain means crack initiation and propagation, while the fracture of strain gauge leads to strain mutation. The SEM results are discussed to describe the fracture mechanism of brittle gritstone after HTHP treatment.

Hydrothermally Treated SnO2 as the Electron Transport Layer in High‐Efficiency Flexible Perovskite Solar Cells with a Certificated Efficiency of 17.3%

AbstractPerovskite solar cells (PSCs) are one of the most promising solar energy conversion technologies owing to their rapidly developing power conversion efficiency (PCE). Low‐temperature solution processing of the perovskite layer enables the fabrication of flexible devices. However, their application has been greatly hindered due to the lack of strategies to fabricate high‐quality electron transport layers (ETLs) at the low temperatures (≈100 °C) that most flexible plastic substrates can withstand, leading to poor performances for flexible PSCs. In this work, through combining the spin‐coating process with a hydrothermal treatment method, ligand‐free and highly crystalline SnO2 ETLs are successfully fabricated at low temperature. The flexible PSCs based on this SnO2 ETL exhibit an excellent PCE of 18.1% (certified 17.3%). The flexible PSCs maintained 85% of the initial PCE after 1000 bending cycles and over 90% of the initial PCE after being stored in ambient air for 30 days without encapsulation. The investigation reveals that hydrothermal treatment not only promotes the complete removal of organic surfactants coated onto the surface of the SnO2 nanoparticles by hot water vapor but also enhances crystallization through the high vapor pressure of water, leading to the formation of high‐quality SnO2 ETLs.

Quantitative comparison of iron and cobalt based catalysts for the Fischer-Tropsch synthesis under clean and poisoning conditions

Abstract Quantitative data comparing iron and cobalt based catalysts for the Fischer-Tropsch synthesis (FTS) are scarce due to the fact that these two kinds of catalysts typically utilize different process conditions. This paper focuses on studying the catalytic behavior of two highly active iron and cobalt based research catalysts at clean conditions and during poisoning with common syngas contaminants. The catalyst activity and selectivity at identical conditions, the CO conversion effect, and the effect of poisons on iron and cobalt catalysts were systematically explored in a quantitative manner. At a set of identical FTS conditions, the cobalt catalyst was 2.5 times as active as the iron catalyst with higher CH4 and C5+ selectivities but much less olefins and lower CO2 selectivity. Cobalt based catalysts are more susceptible to deactivation by oxidation at high CO conversions (e.g. > 80%) due to the high partial pressure of water (PH2O) in the reactor, while the iron catalyst can be stabilized at a high conversion level. Under clean FTS conditions, the cobalt catalysts displayed a more pronounced CO conversion effect on stability and selectivity; on the other hand, a combination of effects (i.e. from CO conversion and the nature of the catalyst) were observed for the iron catalysts. The sensitivities of the Fe and Co catalysts to the typical contaminants (i.e., H2S and NH3) present in the syngas derived from coal, natural gas or biomass were compared. Iron and cobalt catalysts exhibited similar resistance to the H2S poison (i.e. threshold levels 25–50 ppb), but the iron catalyst was found to be much more resistant to ammonia than the cobalt catalyst (i.e., threshold levels of 80 ppm and 45 ppb, respectively). Co-feeding 150–200 ppm ammonia lowered CH4 selectivity and 2-olefin content (suppressing secondary reactions of 1-olefin) on both types of catalysts. In contrast, co-feeding up to 1 ppm H2S significantly increased CH4 formation only on cobalt catalysts but had a minor effect on CH4 selectivity with iron catalysts. It increased 2-olefin content (enhanced secondary reactions of 1-olefin) regardless of catalyst type. H2S and NH3 have different impacts on H2, CO adsorption, and the formation of sulfur and nitride compounds have been proposed to explain these dissimilar effects.

Potential use of real-time dissolved oxygen sensors for oxygen scavenging feedback control

The North Sea oil and gas sector has been operational since the 1970’s and the natural pressure in the reservoirs has been gradually decreasing, which has led to an increased use of water injection to facilitate the required pressure for oil and gas extraction. This involves high pressure and flow of sea water, which is transported through the offshore facilities and due to the corrosive environment, it introduces corrosion. One of the main culprits is dissolved oxygen, which the offshore operators actively remove with vacuum and chemical oxygen scavengers. The vacuum deaerators have a removal limit, after which the dissolved oxygen concentration is decreased using chemical oxygen scavengers most often sodium sulfite, but this adds a cost. The main expense is not the chemical itself, but the side product of the chemical reaction, which leaves sulfates, that feed sulfate reducing bacteria, leading to a production of Hydrogen sulfide which leads to sour corrosion. One solution to reduction in dissolved oxygen and oxygen scavenger is proper control of the facilities. This work investigates the potential for feedback control of the facilities using an online dissolved oxygen instrument, where an experimental study of three commercial dissolved oxygen instruments has been performed, with good results.

Fabrication and Characterization of Graphene Microcrystal Prepared from Lignin Refined from Sugarcane Bagasse.

Graphene microcrystal (GMC) is a type of glassy carbon fabricated from lignin, in which the microcrystals of graphene are chemically bonded by sp3 carbon atoms, forming a glass-like microcrystal structure. The lignin is refined from sugarcane bagasse using an ethanol-based organosolv technique which is used for the fabrication of GMC by two technical schemes: The pyrolysis reaction of lignin in a tubular furnace at atmospheric pressure; and the hydrothermal carbonization (HTC) of lignin at lower temperature, followed by pyrolysis at higher temperature. The existence of graphene nanofragments in GMC is proven by Raman spectra and XRD patterns; the ratio of sp2 carbon atoms to sp3 carbon atoms is demonstrated by XPS spectra; and the microcrystal structure is observed in the high-resolution transmission electron microscope (HRTEM) images. Temperature and pressure have an important impact on the quality of GMC samples. With the elevation of temperature, the fraction of carbon increases, while the fraction of oxygen decreases, and the ratio of sp2 to sp3 carbon atoms increases. In contrast to the pyrolysis techniques, the HTC technique needs lower temperatures because of the high vapor pressure of water. In general, with the help of biorefinery, the biomass material, lignin, is found to be qualified and sustainable material for the manufacture of GMC. Lignin acts as a renewable substitute for the traditional raw materials of glassy carbon, copolymer resins of phenol formaldehyde, and furfuryl alcohol-phenol.

Hydrophobic alumina hollow fiber membranes for sucrose concentration by vacuum membrane distillation

Hydrophobic alumina hollow fiber membranes were first used for sucrose concentration in a vacuum membrane distillation (VMD) system. The alumina hollow fiber membranes were prepared using the combined phase inversion and sintering method and then grafted with FAS to impart hydrophobicity. The as-prepared hydrophobic alumina hollow fiber membrane had a high mechanical strength of 191 MPa, a high water contact angle of 140° and a high liquid entry pressure of water of 5.0 bar. Fifty-two hydrophobic alumina hollow fibers were packed into a shell-and-tube module. To evaluate the sucrose concentration performance of the prepared membrane module, the effects of various parameters on the permeate flux, such as the feed flow rate, temperature, vacuum pressure and concentration, were investigated in the VMD system. In the batch sucrose concentration tests, an 8 L 10°Brix sucrose solution was successfully concentrated to 50°Brix by removing 6.4 L of water using the VMD system. At a feed flow rate of 5 L/min and temperature of 70 °C, the permeate flux remained as high as 35.1 and 19.0 kg/m2 h when the sucrose solution was concentrated to 10°Brix and 50°Brix. Furthermore, the permeate flux could be recovered in a new concentration cycle after the membrane module was washed with pure water. The results revealed that the hydrophobic alumina hollow fiber membranes are promising and feasible for concentration processes in a VMD system.

Research of the geological factors of coal deposits in the south of the Far East by electrical exploration methods

Coal deposits in the south of the Far East are characterized by complex geological factors, which is due to the inclined occurrence the enclosing layers and coal seams, high pressure of underground water, the presence of water-bearing sandy-pebble and gravel-pebble sediments, the presence of numerous faults and various inclusions, the presence of island permafrost. In the exploration of deposits, the low efficiency of previously used electrical exploration methods, including electrical sounding and profiling, was noted. In this paper, it is shown that increasing efficiency in the solution of some mining and geological tasks is associated with the use of the electrical tomography method. This method has advantages in the conditions of weak differentiation of rock resistivity due to the high density of obtained parameters. With the use of electrical tomography, the tasks in the allocation of tectonic disturbances and coal seams uplift under quaternary sediments, estimation of the landslide slopes structures on the coal pit edges have been solved. Successful results were obtained in isolating the weathered layer of the bedrock, sandstone outcrops under the soil-vegetative layer in the upper part of the section, the bedrock surface on the deposit’s flanks and the covers of effusive rocks on the surface.

Effects of Water Related Factors on Pre-grouting in Hard Rock Tunnelling

Water control is highly concerned for underground facilities, and rock grouting has been used over decades to reduce the water inflow. The performances of grouting are influenced by many factors such as rock type, joint distribution and grouting materials. In this paper, the effects of water related factors are focused, from the engineering perspective. The observed volume of water inflow from the probe drilling hole often serves as the base for judgment of grouting needs. The allowable limit of water inflow varies for underground facilities of different purposes. For similar underground facilities, such limit may also differ substantially in different regions. High pressure of underground water would increase difficulty for grouting. The water appearance may give indication on whether the fillings of joints or the weakness zones have been eroded. In the coastal area, the inflow water can be saline, and this needs to be taken into consideration to eliminate corrosion on electrical installations underground.