盐卤硼酸盐化学XXVLi2O—B2O3—H2O过饱和溶液20℃结晶动力学研究

Ｌｉ２Ｏ·３Ｂ２Ｏ３—Ｈ２Ｏ及Ｌｉ２Ｏ·４Ｂ２Ｏ３—Ｈ２Ｏ）过饱和溶液２０℃结晶过程均只有一个阶段。前者结晶析出Ｌｉ２Ｂ４Ｏ７·３Ｈ２Ｏ，后者结晶析出ＬｉＢ５Ｏ８·５Ｈ２Ｏ。本文探讨了这两种固相的结晶机理并拟合出结晶动力学方程，结果表明两个结晶过程均受控于单核表面反应。     

Comparison of alternative upscaled model formulations for simulating DNAPL source dissolution and biodecay

This paper compares the performance of analytical and numerical approaches for modeling DNAPL dissolution with biodecay. A solution derived from a 1-D advective transport formulation (“Parker” model) is shown to agree very closely with high resolution numerical solutions. A simple lumped source mass balance solution in which with decay is assumed proportional to DNAPL mass (“Falta1” model) over- or underpredicts aqueous phase biodecay depending on the magnitude of the exponential factor governing the relationship between dissolution rate and DNAPL mass. A modification of the Falta model that assumes decay proportional to the source exit concentration is capable of accurately simulating source behavior with strong aqueous phase biodecay if model parameters are appropriately selected or calibrated (“Falta2” model). However, parameters in the lumped models exhibit complex interdependencies that cannot be quantified without consideration of transport processes within the source zone. Combining the Falta2 solution with relationships derived from the Parker model was found to resolve these limitations and track the numerical model results. A method is presented to generalize the analytical solutions to enable simulation of partial mass removal with changes in source parameters over time due to various remedial actions. The algorithm is verified by comparison with numerical simulation results. An example application is presented that demonstrates the interactions of partial mass removal, enhanced biodecay, enhanced mass transfer and source zone flow reduction applied at various time periods on contaminant flux reduction. Increasing errors that arise in numerical solutions with coarse discretization and high decay rates are shown to be controlled by using an adjusted decay coefficient derived from the Parker analytical solution.     

川东北飞仙关组鲕滩气藏天然气运聚效率

设计进行了封闭体系下原油裂解成气的模拟实验, 建立并标定了原油裂解成气及其碳同位素分馏的化学动力学模型, 以罗家寨气田罗家7井为例分别进行了地质应用.生烃动力学研究发现, 飞仙关组古油藏具备“高效气源灶”的特点, 原油在中晚侏罗世172~151Ma约20Ma时期内裂解殆尽, 且原油裂解气的生成与其运聚成藏作用具有良好的时空匹配关系, 由此可促成飞仙关组气藏天然气的高效运聚.碳同位素分馏动力学研究证实甲烷成藏参与率达87%.利用生烃动力学与碳同位素分馏动力学结合的方法对天然气的运聚效率进行探讨是一个新的有效途径.      

Combustion Kinetics of Athabasca Bitumen from 1D Combustion Tube Experiments

There are two basic requirements for heavy-oil recovery processes: first, mobilize the bitumen, and second, have a drive mechanism deliver the mobilized bitumen to a production wellbore. In situ combustion has the potential to be an important heavy-oil recovery method. Before design of in situ combustion recovery processes can start, it is necessary as a first step to understand the kinetics of various complex chemical reactions and determine kinetic constants associated with the reactions. Even with modern reservoir simulation capabilities, this is a significant challenge. In this research, an Athabasca bitumen combustion tube experiment, conducted by the ISC Research Group at the University of Calgary, was history matched by using a reservoir thermal simulator to determine a set of kinetic parameters as well as the transport parameters for the system. The main results of the history match was a match of air injection rate, bitumen and gas production volumes, average product gas compositions, temperature profiles along the tube through time, and pressure. Gridding sensitivities were examined to determine if the derived kinetic and transport parameters were dependent on gridblock size. The results revealed that the grid was refined enough to sufficiently capture thermal, mass transfer, and reaction length scales. After this single match was achieved, the same constants were used to successfully predict several other combustion tube experiments. The results suggest that the fuel (coke) for high-temperature oxidation (HTO) originates mainly from low-temperature oxidation (LTO) and not from thermal cracking. This implies that the major control on HTO is upstream oxygen transfer into the LTO region. If LTO does not occur, then a relatively small amount of coke is deposited in the matrix due to thermal cracking and this may be insufficient to start or sustain HTO.     

Adsorption kinetics, isotherm, and thermodynamic studies of adsorption of pollutant from aqueous solutions onto humic acid

In the present study,humic acid was used as an adsorbent for the investigation of the adsorption kinetics,isotherms,and thermo-dynamic parameters of hexavalent chromium from aqueous solution at varying pH,temperatures,and concentrations.Adsorption isotherms and equilibrium adsorption capacities were determined by the fittings of the experimental data to three well-known iso-therm models:Langmuir,Freundlich,and Redlich-Peterson.The results showed that the Langmuir and Redlich-Peterson models appear to fit the adsorption better than did the Freundlich adsorption model for the adsorption of chromium onto humic acid.The equilibrium constants were used to calculate thermodynamic parameters such as the change of free energy,enthalpy,and entropy.The derived adsorption constants (logaL) and their temperature dependencies from Langmuir isotherm have been used to calculate the corresponding thermodynamic quantities such as the free energy of adsorption,heat,and entropy of adsorption.The thermo-dynamic data indicate that Cr (VI) adsorption onto humic acid is entropically driven and characterized by physical adsorption.     

Comments on “Two-dimensional concentration distribution for mixing-controlled bioreactive transport in steady-state” by O.A. Cirpka and A.J. Valocchi

In this comment we present a re-analysis of the analytical solution presented by Cirpka and Valocchi for steady-state concentrations of dissolved bioreactive compounds and bacterial biomass in porous media. We discuss the validity range of the analytical solution. In particular, the criterion used to determine the sustainability of biomass is revisited. This re-analysis shows that the ω$\omega$ criterion used by Cirpka and Valocchi is only a necessary but not a sufficient criterion to determine the bioreactive zones. As a consequence, the analytical solution does not provide the exact distribution of compounds throughout the domain, but can serve as upper or lower boundaries for species concentrations at a given location. These conclusions are supported by the simulation results obtained from an established reactive transport model.     

Performance of A Combination Process of UV/H2O2/Micro‐Aeration for Oxidation of Dichloroacetic Acid in Drinking Water

The decomposition of dichloroacetic acid (DCAA) in water using a UV/H₂O₂/micro‐aeration process was investigated in this paper. DCAA cannot be removed by UV radiation, H₂O₂ oxidation or micro‐aeration alone, while UV/H₂O₂/micro‐aeration combination processes have proved effective and can degrade this compound completely. With initial concentrations of about 110 μg/L, more than 95.1% of DCAA can be removed in 180 min under UV intensity of 1048.7 μW/cm², H₂O₂ dosage of 30 mg/L and micro‐aeration flow rate of 2 L/min. However, more than 30 μg/L of DCAA was left after 180 min by UV/H₂O₂ combination process without micro‐aeration with the same UV intensity and H₂O₂ dosage. The effects of applied UV radiation intensity, H₂O₂ dose, initial DCAA concentration and pH on the degradation of DCAA have been examined in this study. Degradation mechanisms of DCAA with hydroxyl radical oxidation have been discussed. The removal rate of DCAA was sensitive to operational parameters. There was a linear relationship between rate constant k and UV intensity and initial H₂O₂ concentration, which indicated that a higher removal capacity can be achieved by improvement of both factors. A newly found nitrogenous disinfection by‐product (N‐DBP)‐DCAcAm, which has the potential to form DCAA, was easier to remove than DCAA by UV/H₂O₂ and UV/H₂O₂/micro‐aeration processes. Finally, a preliminary cost comparison revealed that the UV/H₂O₂/micro‐aeration process was more cost‐effective than the UV/H₂O₂ process in the removal of DCAA from drinking water.     

Rice Husk Ash as a Low Cost Adsorbent for the Removal of Methylene Blue and Congo Red in Aqueous Phases

Adsorption is of significant importance for effluent treatment, especially for the treatment of colored effluent generated from the dyeing and bleaching industries. Low cost adsorbents have gained attention over the decades as a means of achieving very high removal efficiencies to meet effluent discharge standards. The present article reports on batch investigations for color removal from aqueous solutions of Methylene Blue (MB) and Congo Red (CR) using Rice Husk Ash (RHA) as an alternative low cost adsorbent. The performance analysis was carried out as a function of various operating parameters, such as initial concentration of dye, adsorbent dose, contact time, shaker speed, interruption of shaking and ionic concentration. Performance studies revealed that a very high percentage removal of color was achievable for both dyes. The maximum percentage removal of MB was 99.939%, while 98.835% removal was observed for CR. These percentage removals were better than existing systems. Detailed data analysis indicated that adsorption of MB followed the Temkin isotherm, while CR followed the Freundlich isotherm. These isotherms were feasible within the framework of experimentation. Batch kinetic data, on the other hand, indicated that pseudo second order kinetics governed adsorption in both cases. Sensitivity analysis further indicated that the effects of initial dye concentration, shaker speed, pH and ionic strength had no noticeable effect on the percentage dye removal at equilibrium. Batch desorption studies revealed that 50% acetone solution was optimum for CR, while desorption of MB varied directly with acetone concentration.     

A Study of the Thermodynamics and Kinetics of Copper Adsorption Using Chemically Modified Rice Husk

The use of rice husk as a low cost adsorbent for the removal of copper from wastewater has been explored in a laboratory scale experiment. The rice husk used for the study was treated with alkali to increase the sorption properties. The influence of metal ion concentration, weight of biosorbent, stirring rates, temperature and pH were also evaluated, and the results are fitted using adsorption isotherm models. From the experimental results it was observed that almost 90–98% of the copper could be removed using treated rice husk. The Langmuir adsorption isotherm, Freundlich isotherm and Tempkin isotherm models were used to describe the distribution of copper between the liquid and solid phases in batch studies, and it was observed that the Langmuir isotherm better represented the adsorption phenomenon. The experimental rate constant, activation energy, Gibbs free energy, enthalpy and entropy of the reaction were calculated in order to determine the mechanism of the sorption process.     

Assessment of generation temperatures of crude oils

Biological marker maturity parameters were used to estimate the minimum HC generation temperatures of crude oils from Eastern Hungary. More than 50 oils and oil shows were analysed. Molecular- and homologous-ratios of biological marker compounds (triterpanes, steranes, mono- and triaromatic steroid hydrocarbons) were used as maturation parameters. The oils have at least five maturity stages, i.e. they have been generated under different thermal conditions. The highest reservoir temperature in each group was chosen as the best estimate of the groups' temperature just below the generation temperature, i.e. reservoirs of the group might be expected to be at shallower depths (lower temperatures) than those of the generation zone due to vertical migration into pools. For each maturation level, a threshold temperature range for genesis was inferred from reservoir temperatures; they are from 130–135°C for the least mature oils to 210–215°C for the most mature oils. In the least mature oils cracking was not observed, hence carbon–carbon cracking reactions had not taken place during their genesis. The most mature oils are intensively cracked oils; they are almost condensates. Two major genetic groups (families) of oils were found in the area. Both are present in each maturation level. The effects of migration were checked, and no influence on maturation was found. A number of the oils are in overpressured reservoirs within, or just above, the zone of the present-day active oil generation, hence the present-day temperatures of the pools must have been maximum temperatures. Contrary to the traditionally accepted temperature range for petroleum generation–maturation reactions (50–150°C), there is strong evidence from this study that the onset of oil generation requires temperatures higher than 130°C and is still proceeding above 215°C.