Enhanced removal of DNAPL trapped in porous media using simultaneous injection of cosolvent with air: influencing factors and removal mechanisms

Factors influencing dense non-aqueous phase liquid (DNAPL) removal by concurrent injection of cosolvent and air were evaluated using micromodels and visualization techniques. Cosolvent (ethanol/water) was injected simultaneously with air into glass micromodels containing residual perchloroethylene (PCE). Impacts of the air flow rates and PCE solubility in the remedial fluid on PCE removal processes were examined. Although two major processes, immiscible displacement and dissolution, may contribute PCE removal from porous media during cosolvent-air (CA) flooding, PCE displacement occurred only in the initial flooding period and was independent of the air flow rate and ethanol content. However, faster airflow through the porous medium improved remedial fluid distribution and dynamics and resulted in enhanced dissolution of the DNAPL. Dissolution rates were directly related to PCE solubility in the remedial fluid. Enhanced contact between cosolvent and DNAPL during CA flooding was observed in a non-homogeneous micromodel with random flow paths.     

Oil mobility in a saturated water-wetted bed of glass beads

The mobilization of an oil bank in a packed bed of glass beads saturated with an aqueous phase has been studied both theoretically and experimentally. The size of the glass beads was varied in the range between 0.5 and 5mm. Two oils (hexadecane and hexane) with viscosities different for an order of magnitude and densities smaller than that of water have been used. A few more runs have been carried out using perchloroethylene (PCE), with density greater than that of water. The interfacial tension in the aqueous phase was varied in a quite large range (0.38-39.1 dyn/cm) by adding surfactants to the water. The glass assembly made it possible to follow the evolution of the dyed oily phase by the use of a digital camera. A very simple stochastic model for describing the porous structure of the packed bed made it possible to set a criterion for determining the probability of mobilization of ganglia which are produced by the fragmentation of the oil bank. The same model permits also to estimate the probability function of the velocity of a ganglion of an assigned size.     

Dissolution of a multicomponent DNAPL pool in an experimental aquifer

This paper presents the results from a well-defined, circular-shaped, multicomponent dense nonaqueous phase liquid (DNAPL) pool dissolution experiment conducted in a three-dimensional, bench scale model aquifer. The multicomponent pool is a mixture of tetrachloroethylene (PCE) and 1,1,2-trichloroethane (1,1,2-TCA); PCE was the major component and 1,1,2-TCA was the minor component. Downgradient plume concentrations were measured at five specific locations over time until the majority of the 1,1,2-TCA was depleted from the DNAPL pool source. The experimental results suggest distinct spatial-temporal plume patterns for minor DNAPL components versus major DNAPL components. The downgradient concentration varied over time for 1,1,2-TCA while a stable plume developed for PCE. A semi-analytical solution for contaminant transport resulting from dissolution of multicomponent nonaqueous phase liquid pools successfully simulated the plume structure and dynamics for both the major and minor DNAPL components.     

Stretching of a liquid layer underneath a semi-infinite fluid

Exact similarity solutions of the Navier–Stokes equation are derived describing the flow of a liquid layer coated on a stretching surface underneath another semi-infinite fluid. In the absence of hydrodynamic instability, the interface remains flat as the layer thickness decreases in time. When the physical properties of the fluids are matched, we obtain Crane’s analytical solution for two-dimensional (2D) flow and a corresponding numerical solution for axisymmetric flow. When the rate of stretching of the surface is constant in time, the temporal evolution of the interface between the layer and the overlying fluid is computed by integrating in time a system of coupled partial differential equations for the velocity in each fluid together with an ordinary differential equation expressing kinematic compatibility at the interface, subject to appropriate boundary, interfacial, and far-field conditions. Multiple solutions are found in certain ranges of the density and viscosity ratios. Additional similarity solutions are presented for accelerated 2D and axisymmetric stretching. The numerical prefactors that appear in the analytical expressions for the interface location and wall shear stress are presented for different ratios of the densities and viscosities of the two fluids.     

Force analysis and visualization of NAPL removal during surfactant-related floods in a porous medium

Governing mechanisms of dense non-aqueous phase liquid (DNAPL) removal during surfactant and surfactant-foam (SF) flooding were studied by porous-patterned glass model experiments. Physical forces, viscous forces and capillary forces, acting on trichloroethylene (TCE) blobs were quantified to understand DNAPL removal mechanisms during the floods, simultaneously visualizing the removal mechanisms. The viscous force of the remedial fluid was intimately related to TCE removal from the porous medium. The remedial fluid with a high viscous force displaced more TCE blobs. Displacement of residual TCE by the remedial fluid began as viscous pressure of flooding was closed to the capillary pressure of the porous medium. In the region of viscous pressure less than the capillary pressure, residual TCE was either retained or solubilized, not displaced, implying that TCE solubilization was the dominant TCE removal process. Glass porous model visualization validated a dominance of the capillary forces during a surfactant flush and a dominance of the viscous forces of the displacing fluid during a SF flood.     

Liquid Viscosity of Binary Mixtures of Methanol with Ethanol and 1-Propanol from 273.15 to 333.15 K

The liquid viscosities and densities of two binary mixtures of methanol with ethanol and 1-propanol were measured in the temperature range from 273.15 to 333.15 K with a capillary viscometer and a glass pycnometer, respectively. The uncertainties in the measured viscosities were estimated to be smaller than 1.3%. The experimental viscosity values could be fitted to the Mertsch and Wolf equation within 2%.     

烯丙基咪唑离子液体的合成与溶液性能

室温离子液体氯化1-烯丙基-3-甲基咪唑被合成,利用质谱和NMR对其结构进行了表征。该离子液体与水或乙醇的二相混合液在293.2K的粘度被测定并计算了该混合体系的过量粘度,建立了过量粘度与水或乙醇的摩尔分数的关系。另外,电导率随组分及温度的变化以及电导活化能也被测定,溶液的电导率随温度的升高及溶剂量的增加而增大。     

Physical and Thermodynamic Properties of Aqueous 2-Amino-2-Methyl-1,3-Propanediol Solutions

Densities and viscosities of mixtures of 2-amino-2-methyl-1,3-propanediol (AMPD)–water were measured at temperatures of 30, 40, 50, 60, and 70°C. The solubility of N₂O in the aqueous AMPD solutions was measured at temperatures of 30, 40, and 50°C. The concentrations selected for study were 10, 20, and 30 mass% AMPD for all three temperatures. The experimental values for density and viscosity were correlated as functions of temperature. The maximum deviations were less than 0.005% for densities and 0.3% for viscosities.     

Influences of superplasticizer modification and mixture composition on the performance of self-compacting concrete at varied ambient temperatures

The fresh behaviour of self-compacting concrete (SCC) at varying temperatures differs from that of normal vibrated concrete. This is because the rheology of SCC depends not only on degree of cement hydration, but also on the adsorption of superplasticizers – mostly polycarboxylate based polymers (PCE) -, which is affected by the time and hydration progress. Due to the variety of PCEs and mixture compositions for SCC a prediction of the rheology at varying temperatures is complicated. The charge densities of PCEs as well as the water to solid ratio in the paste are identified to be the main decisive parameters for robust fresh concrete properties.Rheometric concrete investigations with different SCC mixture compositions and varied anionic charge densities of the PCE were conducted. SCC which is rich in powder components showed robust performance at low temperatures while SCC with low powder content was favourable at high temperatures. High charge density PCE pointed out to be very robust at low temperatures but at high temperatures it significantly reduced the flow retention. Low charge density PCE could not generate self-compacting properties at low temperatures but retained the flow performance over sufficiently long time. Based on considerations about particle interactions and adsorption mechanisms of PCEs, the relevant processes are explained and options for the development of robust mixture compositions for individual temperature ranges are itemised.     

染料与纤维共磨对纸浆模塑染色和强度性能的影响

目的探究深色纸浆模塑制品染色过程中出现色差的机理,研究染料与纤维共磨对染色效果和强度性能的影响,提出改善深色纸浆模塑制品染色效果与强度性能的工艺。方法在相同磨浆转数下,探究染料的加入方式对纤维形态、染色制品强度、光学性能及染料上染率的影响;将染料与纤维共磨,探究不同磨浆转数对浆料的滤水性能、染色制品的染色效果和强度的影响。结果实验证实,染料和纤维共磨有利于改善染色制品的抗张强度和耐破强度,能在显著提高染色效果的同时有效降低染色制品的正反面色差。与传统添加方式相比,染色制品的色差由2.53缩小到0.20,上染率从72.02%提高到了77.93%。显微镜图像分析显示,共磨浆料的纤维起毛现象更明显。此外,随着磨浆转数增加,染色制品的光学性能和强度性能得到提高。结论染料与纤维共磨可以提高打浆效果,改善深色纸浆模塑制品的染色效果和强度性能。     

Rheological Characterization of Hydroxypropylcellulose Gels

The present paper describes the rheological properties of hydroxypropylcellulose (HPC) gels formulated in propylene glycol (PG), water, ethanol, and mixtures of these components. The effects of molecular weight, polymer concentration, and solvent composition on the apparent viscosity and flow characteristics have been studied by continuous shear rheometry. The HPC gels are shear thinning and do not exhibit significant yield or hysteresis in their rheograms. The apparent viscosity increases with increasing molecular weight and concentration of the polymer, as expected. Although not so pronounced at lower concentrations (≤ 1.5%), HPC gels tend to become increasingly non-Newtonian with increasing molecular weight at higher polymer concentrations (3%). A mathematical model has been proposed for the prediction of viscosities of HPC gels. There exists a high degree of dependence on molecular interactions between various solvent molecules in the prediction of mixture viscosities in ternary systems. The effects of solvent composition on the viscoelastic behavior of these gels have also been examined by dynamic mechanical analysis. The HPC gels are highly viscoelastic and exhibit greater degrees of elasticity with increased PG content in ternary solvent mixtures with water and ethanol. The study also suggests that dynamic mechanical analysis could prove to be a useful tool in the determination of zero-shear viscosities, viscosities that are representative of most realistic situations.     

小麦醇溶蛋白膜力学性能与吸湿性研究

采用小麦醇溶蛋白的乙醇/水(70/30(v/v))溶液制备了醇溶蛋白膜,分析了交联剂用量与pH值对膜的拉伸性能、吸水性及透湿性的影响.结果表明,适度交联的醇溶蛋白膜具有最大拉伸强度与较高的断裂伸长率.随交联剂用量增加,膜的吸水率稍有下降,而透湿性显著增大.酸碱处理能显著提高膜的拉伸强度,但使吸水性稍有增大.     

Densities and Kinematic Viscosities of One Quinary Regular Liquid System and Its Five Quaternary Sub-Systems at Temperatures (293.15 and 298.15) K

The densities and kinematic viscosities of the quinary liquid regular system octane(1)–hexane(2)–ethylbenzene(3)–cyclohexane(4)–toluene(5) and its five quaternary subsystems were measured at 293.15 K and 298.15 K. Pure component properties are in excellent agreement with their corresponding literature values. The kinematic viscosity data were employed to test some literature viscosity prediction models.     

An excess function method to model the thermophysical properties of one-phase secondary refrigerants

This paper describes an easy-to-use and accurate method to calculate some of the thermophysical properties of aqueous solutions which are used as secondary refrigerants. This method is based on the correction of the ideal behaviour of aqueous solutions by excess functions. This method allows to determine the following properties: freezing points, densities, heat capacities, thermal conductivities and dynamic viscosities. As an illustration, it is applied to aqueous solutions of (i) ethyl alcohol, (ii) ammonia, (iii) sodium chloride, (iv) ethylene glycol and (iii) propylene glycol.     

Experiments and simulations of liquid imbibition in aqueous foams under microgravity

We describe the capillary motion of liquid into aqueous foams under microgravity. Experiments in which a constant input of liquid is added to a foam under a variety of controlled experimental conditions (bubble size, cell geometry, bubble interfacial properties) have been performed in parabolic flights and in the MAXUS 6 sounding rocket. For comparison, we also performed numerical simulations, based on the foam drainage equations in which the gravitational contributions are removed. The agreement between these simulations and the experimental data is good, and the quantitative adjustment between them enables us to estimate foam permeabilities and surface shear viscosities.     

Measurements of the viscosity of compressed gaseous and liquid nitrogen + methane mixtures

The shear viscosity coefficients of three compressed gaseous and liquid nitrogen + methane mixtures have been measured at temperatures between 100 and 300 K and at pressures to about 30 MPa (4350 psia) with a piezoelectric quartz crystal viscometer. The precision of the measurements ranges from about 0.5% at high densities to about 1% at low densities. The estimated experimental error ranges from about 2% at high densities to about 4% at densities near the critical density and at supercritical temperatures near the critical temperature. The measurements have been compared with an extended corresponding states model, previously proposed for calculating the viscosities of fluid mixtures. Differences between the measured and calculated viscosities are discussed.     

A Fundamental Equation for Calculation of the Thermodynamic Properties of Ethanol

A formulation for the thermodynamic properties of ethanol (C₂H₅OH) in the liquid, vapor, and saturation states is presented. The formulation is valid for single-phase and saturation states from 250 to 650K at pressures up to 280MPa. The formulation includes a fundamental equation and ancillary functions for the estimation of saturation properties. The experimental data used to determine the fundamental equation include pressure-density-temperature, ideal gas heat capacity, speed of sound, and vapor pressure. Saturation values computed from the ancillary functions were used to ensure thermodynamic consistency at the vapor-liquid phase boundary. Comparisons between experimental data and values computed using the fundamental equation are given to verify the uncertainties in the calculated properties. The formulation presented may be used to compute densities to within ±0.2%, heat capacities to within ±3%, and speed of sound to within ±1%. Saturation values of the vapor pressure and saturation densities are represented to within ±0.5%, except near the critical point.     

Rheological characterization of hydroxypropylcellulose gels

The present paper describes the rheological properties of hydroxypropylcellulose (HPC) gels formulated in propylene glycol (PG), water, ethanol, and mixtures of these components. The effects of molecular weight, polymer concentration, and solvent composition on the apparent viscosity and flow characteristics have been studied by continuous shear rheometry. The HPC gels are shear thinning and do not exhibit significant yield or hysteresis in their rheograms. The apparent viscosity increases with increasing molecular weight and concentration of the polymer, as expected. Although not so pronounced at lower concentrations (≤ 1.5%), HPC gels tend to become increasingly non-Newtonian with increasing molecular weight at higher polymer concentrations (3%). A mathematical model has been proposed for the prediction of viscosities of HPC gels. There exists a high degree of dependence on molecular interactions between various solvent molecules in the prediction of mixture viscosities in ternary systems. The effects of solvent composition on the viscoelastic behavior of these gels have also been examined by dynamic mechanical analysis. The HPC gels are highly viscoelastic and exhibit greater degrees of elasticity with increased PG content in ternary solvent mixtures with water and ethanol. The study also suggests that dynamic mechanical analysis could prove to be a useful tool in the determination of zero-shear viscosities, viscosities that are representative of most realistic situations.     

Combined effect of Bond and capillary numbers on hydrocarbon mobility in water saturated porous media

The mobilization of an oil bank under the combined effect of Bond (N(B)) and capillary (N(C)) numbers, in a packed bed column of glass beads saturated with water, has been investigated. In order to reach the irreducible saturation the experiments have been run with sweeping water velocities outside the range of validity of the Darcy's law. The size of the glass beads was varied in the range between 2 mm and 5 mm. The oils used for the tests are hexadecane and hexane with viscosities different for an order of magnitude and densities smaller than that of water, and alpha-methylnaphthalene, which has a density very close to that of water, in order to single out the effect of the capillary number on the mobilization process. The plots of oil saturation as function of the trapping number (N(T)), which is the vectorial sum of N(B) and N(C), are reported and a mobilization diagram is drawn. Furthermore, a few tests in a basin, simulating an aquifer at a laboratory scale, have proved that the results obtained in the packed column are useful for determining the fate of a spill of oil above an aquifer. For these experiments also perchloroethylene (PCE), which has a density greater than that of water, has been used.     

Cationization of cotton for industrial scale salt-free reactive dyeing of garments

Reactive dyeing of cotton garments involves two stages, namely exhaustion and fixation of dyes. The exhaustion stage in reactive dyeing requires high quantity of salt. After dyeing process, the highly saline coloured effluent is discharged and the treatment of this effluent at present is not economically viable and making industries look for other alternatives for usage of salt. Cationization of cotton is one of the effective alternatives to overcome the usage of the salt. The present work focuses on the exhaust method of cationization of garments at an industrial scale using 3-chloro-2-hydroxypropyl trimethylammonium chloride as a cationic agent. Two commercially popular reactive dyes namely Navy Blue and Green dyes were chosen for dyeing the garments at 10% shade. The results of dyeing were evaluated on the basis of colour strength, dyeing levelness and colour fastness. The uniformity of dye on the fabrics was evaluated based on dyeing levelness and was found to be good for cationized cotton dyed garments. The fastness properties of dyed fabrics to washing and light were good. The dye utilization in the cationized cotton dyed garments was twice as that of the conventionally dyed cotton garments. The environmental hazard posed by the highly saline coloured effluent could be easily mitigated by the salt-free reactive dyeing process.