Microstructural Characteristic of Montmorillonite and Its Thermal Treatment Products

The montmorillonite was studied by differen t methods, such as chemical analysis, DAT, TG, X RD, IR, AFM and MAS NMR. The experimental results show that the hydroxyl in octa hedra sheets begins dehydrating when the thermal treatment temperature reaches 659℃, but th e layer structure remains the same,and the corresponding Al(Ⅵ) is turned into Al(Ⅳ) in octahedra sheets. When the temperature reaches 900℃, the layer struct ure of montmorillontite is destroyed, and the new mineral phase μ-cordierite i s found. When the temperature reaches 1200℃, the μ-cordierite phase loses its stability, and decomposes into cristobalite phase and mullite phase.Meanwhile, the recrystallization phenomenon in thermal treatment products is obvious. There is a small quantity of Al Ⅵ signal in MAS NMR spectrum, corresponding to Al of mullite. When the temperature reaches 1350℃, the cristobalite and mullite phases reduce slightly, and more Fe-cordierite phase appears, corresponding to Fe-cordierite spectrum in XRD and MAS NMR.

Establishment and evaluation of a co-effect structure with thermal concentration-rotation function in transient regime

The advanced heat flux manipulating structures inspired by TO-based spatial mapping have aroused wide interests owing to huge potential in high-efficient thermal energy utilization.However,most researches are limited to the realization of single function in one specific structure and appropriate evaluation of the energy transfer process is relatively lacking.In this work,based on time-dependent two-dimensional heat conduction equation,a co-effect structure capable of accomplishing concentration and rotation functions simultaneously is established and validated by finite element simulations compared with the conventional single concentrator and singe rotator.In addition,from the perspective of thermodynamics,the transformed local entropy production rate and total entropy production are theoretically derived and applied to evaluate the quality of energy transfer processes.The proposed co-effect structure can help to explore other potential mass/flux manipulating devices and the evaluation method is valuable for the further manufacturing as well as optimization of these devices in engineering applications.

Heavy Oil Reservoir Seismic Characteristics during Thermal Production:A Case Study

Most production methods of heavy oil involve thermal production.However,it is challenging to delineate the thermal-affected zone due to complex reservoir conditions.With steam injected,the heavy oil viscosity drops;the reservoir density and velocity decrease accordingly,causing changes to seismic impedance.Moreover,the oil-and-water viscosity ratio and permeability show the difference with changing temperature,indicating that the reservoir’s ability to transmit seismic waves would also be temperature-dependent.Therefore,the seismic responses and attenuation characteristics of the steam chamber can be helpful to monitor the steam-affected zone.We introduce an improved viscoelastic model to approximate the heavy oil reservoir during thermal production,and use the frequency-space domain finite difference algorithm to simulate the seismic wave-fields.Numerical results demonstrate that this model is applicable to a wide temperature range,and can effectively reveal the seismic characteristics of the steam chamber.Through analyzing the propagation differences of seismic waves under different temperatures,it is concluded that the attenuation coefficient,root-meansquare amplitude difference and amplitude ratio of PP-wave and PS-wave under different conditions can reveal the temperature variation in the steam chamber,with which it is possible to detect the steam chamber spatial distribution.

Investigation of low-molecular weight organic acids and their spatiotemporal variation characteristics in Hongfeng Lake,China

The identities and concentrations of low-molecular-weight organic acids （LMWOAs） were determined by ion chromatography throughout a 20-m water column in Hongfeng Lake, China. The spatiotemporal variations of LMWOAs and their contributions to dissolved organic matter （DOM） in a research period of 24 hr were also investigated. The results demonstrated that five LMWOAs （lactic, acetic, pyruvic, sorbic, oxalic acid） were detected, and their total concentration and proportion in DOC were 6.55 μmol/L and 7.47%. Their average levels were 2.50, 0.65, 2.35, 0.96 and 0.09 μmol/L, respectively. LMWOAs were higher during daytime （10：00-18：00 on Jun 13, 2008） than nighttime （21：00-6：00 the next morning）, in particular 4.99 μmol/L high in the epilimnion （ 1 m water depth）, reflecting the fact that direct import from terrigenous sources and photochemical production from humic materials were dominant during LMWOAs＇ origin and accumulation. The same factors caused LMWOAs to be 0.63 μmol/L in the epilimnion higher than in the hypolimnion. The rapid decrease of total organic acid （TOA） up until 18：00 mainly resulted from bio-uptake and mineralization in the hypolimnion （〉1 m water depth）. Pyruvic acid increased with time in the epilimnion and decreased in the hypolimnion, largely related to the two contrary processes of continuous degradation and synthesis of macromolecular organic matter during life materials＇ cycle mediated by organisms. Simultaneously, plankton behavior and thermal stratification played a pivotal role in LMWOAs＇ behavior in the water column, causing decreasing and increasing profiles. The distribution of LMWOAs represents an interesting resource for biogeochemical research of DOM in aquatic ecosystems.