热力法开采天然气水合物的模拟实验研究

在天然气水合物一维开采模拟系统上进行了模拟热力法开采天然气水合物的实验研究.使用甲烷气体与NaCl溶液在一定温度和压力条件下形成水合物.通过以不同速率注入不同温度的热水,研究了热力法开采水合物过程中含水合物沉积物的温度分布以及甲烷气体、水生产规律.结果表明,在整个分解过程中,气体生产速率随时间增加而增加,直到达到最大值后开始下降,而水生产的速率几乎保持恒定.通过对实验结果的能量分析表明,热力开采的能量效率在0.38～2.59之间.注入热水的温度、速率以及沉积物中水合物的饱和度对热力法开采水合物的能量效率有重要影响.

甲烷水合物分解的Raman、NMR光谱原位检测

从水合物分解热力学、分解动力学和分解机理几个方面对甲烷水合物拉曼和核磁共振光谱分析的最新进展进行了综述。分解热力学方面介绍了基于拉曼和核磁共振光谱技术的水合物分解条件的原位观测;分解动力学方面主要介绍了水合物分解速率的拉曼光谱原位检测及基于检测结果构建的分解模型;水合物微观分解机理方面着重介绍了水合物分解在分子水平上是由两步构成的及分解过程中大、小孔穴保持着相同的分解速率。针对目前拉曼和核磁共振光谱法研究水合物存在的问题,对未来的发展方向和重点提出了建议。

Temperature-Induced Unfolding Pathway of Staphylococcal Enterotoxin B:Insights from Circular Dichroism and Molecular Dynamics Simulation

In this study,circular dichroism(CD)and molecular dynamics(MD)simulation were used to investigate the thermal unfolding pathway of staphylococcal enterotoxin B(SEB)at temperatures of 298–371 and 298–500 K,and the relationship between the experimental and simulation results were explored.Our computational findings on the secondary structure of SEB showed that at room temperature,the CD spectroscopic results were highly consistent with the MD results.Moreover,under heating conditions,the changing trends of helix,sheet and random coil obtained by CD spectral fitting were highly consistent with those obtained by MD.In order to gain a deeper understanding of the thermal stability mechanism of SEB,the MD trajectories were analyzed in terms of root mean square deviation(RMSD),secondary structure assignment(SSA),radius of gyration(R_(g)),free energy surfaces(FES),solvent-accessible surface area(SASA),hydrogen bonds and salt bridges.The results showed that at low heating temperature,domain Ⅰ without loops(omitting the mobile loop region)mainly relied on hydrophobic interaction to maintain its thermal stability,whereas the thermal stability of domain Ⅱ was mainly controlled by salt bridges and hydrogen bonds.Under high heating temperature conditions,the hydrophobic interactions in domain Ⅰ without loops were destroyed and the secondary structure was almost completely lost,while domain Ⅱ could still rely on salt bridges as molecular staples to barely maintain the stability of the secondary structure.These results help us to understand the thermodynamic and kinetic mechanisms that maintain the thermal stability of SEB at the molecular level,and provide a direction for establishing safer and more effective food sterilization processes.

Non-isothermal thermal decomposition kinetics of high iron gibbsite ore based on Popescu method

The thermal decomposition kinetics of high iron gibbsite ore was investigated under non-isothermal conditions.Popescu method was applied to analyzing the thermal decomposition mechanism.The results show that the most probable thermal decomposition mechanism is the three-dimensional diffusion model of Jander equation,and the mechanism code is D3.The activation energy and pre-exponential factor for thermal decomposition of high iron gibbsite ore calculated by the Popescu method are 75.36 kJ/mol and 1.51×10-5 s-（-1）,respectively.The correctness of the obtained mechanism function is validated by the activation energy acquired by the iso-conversional method.Popescu method is a rational and reliable method for the analysis of the thermal decomposition mechanism of high iron gibbsite ore.

Thermal decomposition of ammonium hexafluoroaluminate and preparation of aluminum fluoride

The thermal decomposition process of （NH4）3AlF6 was studied by DTA-TGA method and the related thermodynamic data were obtained. The results show that AlF3 is obtained after three-step decomposition reaction of （NH4）3AlF6, and the solid products of the first two decomposition reactions are NH4AlF4 and AlF3（NH4F）0.69, respectively. The three reactions occur at 194.9, 222.5 and 258.4 ℃, respectively. Gibbs free energy changes of pertinent materials at the reaction temperatures were calculated. Enthalpy and entropy changes of the three reactions were analyzed by DSC method. Anhydrous aluminum fluoride was prepared. The XRD analysis and mass loss calculation show that AlF3 with high purity can be obtained by heating （NH4）3AlF6 at 400 ℃ for 3 h.

Properties and characterization of 1-methy-4,5-dinitroimidazole

X-ray diffraction （XRD）, differential scanning calorimeter （DSC） and impact sensitivity instrument were used to characterize the properties of 1-Methyl-4, 5-dinitroimidazole （MDNI）. Furthermore, specific heat capacity, thermal kinetic parameters, thermal decomposition reaction rate constant, critical explosion temperature and the drop height for impact initiation of MDNI were calculated and analyzed. The results show that MDNI is well-crystallized. The melting point of MDNI is about 74 ℃, and the specific heat capacity of MDNI is 9. 314 4 J/（g · K） and 10. 596 0 J/（g · K） when the temperature is 60 ℃ and 90 ℃, respectively. The apparent activation energy and pre-exponential factor of MDNI are calculated as 81.62 kJ/mol and 6. 78×10^7 s^-1 , respectively. The relationship between thermal decomposition reaction rate constant of MDNI and temperature is logk=7.83-4268.11/T. The critical temperature of MDNI thermal explosion is 234. 86℃. The drop height for impact initiation of MDNI is 95.3 cm.

新近的低公害型破岩法

《提要》随着世界各国经济建设及城市人口不断增长需要,城市土木工程的破碎开挖量与日俱增,而人们的环保意识也相应在日显严格化,故各种非炸药爆破类破岩方式应运而生,本文所述是日本新近研制开发出的一些非炸药类的破岩方法。

Assessment of the Stability of Cefazolin Sodium in Solids by TGA Decomposition Kinetics

\ According to the analysis of the residual products by thermogravimetric analysis (TGA), the thermal decomposition process of cefazolin sodium (CEZ·Na) was thought to be similar to the degradation in solid state in its storage time. This laid a foundation for estimating the relative chemical stability of the drug by determination of its decomposition kinetics using TGA. Although the observed thermal decomposition kinetics of CEZ·Na was complex, a conversion level of 1% was chosen for evaluation of the stability of CEZ·Na crystalline since the mechanism here was more likely to be that of the actual product failure. The evaluation results suggested that the α form of CEZ·Na had the best stability and the amorphous one was the least stable one among α form, dehydrated α form and amorphous form.

Pyrolysis Characteristics and Thermal Kinetics of Degradable Films

Developing degradable films is an important means for resolving the problem of film pollution; however, in recent years, there have been only few studies related to the thermal analysis of degradable plastic films. This research detailed the composition and pyrolysis of one kind of ordinary and three kinds of degradable plastic films using the differential thermal analysis （DTA） technique. The results showed that degradable films and ordinary film had similar DTA curves, which reflected their similar compositions; however, small differences were measured, which were due to the added constituents of the degradable films. The pyrolysis reaction orders of each film were about 0.93. The pyrolysis activation energies and pre-exponential factors followed the order of ordinary film 〉 photodegradable film 〉 photodegradable calcium carbonate film 〉 biodegradable film. The results of this research laid the foundation for new theories for harnessing soil pollution caused by plastic films.

Research on thermal decomposition of 1,3,5-trinitro-1,3,5-triazinane based on differential scanning calorimetry

In order to test the thermal decomposition of 1,3,5-trinitro-1,3,5-triazinane(RDX),the linear temperature rise experiment of RDX was carried out by differential scanning calorimeter under different heating rate conditions.The kinetic calculation of RDX thermal decomposition curve was carried out by Kissinger and Ozawa methods,respectively,and the thermal analysis software was used to calculate the parameters such as self-accelerating decomposition temperature.The results show that the initial decomposition temperature range,decomposition peak temperature range,and decomposition completion temperature range of RDX are 208.4-214.2,225.7-239.3 and 234.0-252.4℃,respectively,and the average decomposition enthalpy is 362.9 J·g^-1.Kissinger method was used to calculate the DSC experimental data of RDX,the apparent activation energy obtained is 190.8 kJ·mol^-1,which is coincident with the results calculated by Ozawa method at the end of the reaction,indicating that the apparent activation energy calculated by the two methods is relatively accurate.When the packaging mass values are 1.0,2.0 and 5.0 kg,respectively,the self-accelerating decomposition temperatures are 97.0,93.0 and 87.0℃,respectively,indicating that with the increase of packaging mass,the self-accelerating decomposition temperature gradually decreases,and the risk increases accordingly.

Preparation of basic magnesium carbonate and its thermal decomposition kinetics in air

The thermal decomposition process of basic magnesium carbonate was investigated. Firstly, Basic magnesium carbonate was prepared from magnesite, and the characteristics of the product were detected by X-ray diffraction （XRD） and scanning electron microscopy （SEM）. Subsequently, the thermal decomposition process of basic magnesium carbonate in air was studied by thermogravimetry-differential thermogravimetry （TG-DTG）. The results of XRD confirm that the chemical composition of basic magnesium carbonate is 4MgCO3·Mg（OH）2·4H2O. And the SEM images show that the sample is in sheet structure, with a diameter of 0.1-1 μm. The TG-DTG results demonstrate that there are two steps in the thermal decomposition process of basic magnesium carbonate. The apparent activation energies （E） were calculated by Flyrm-Wall-Ozawa method. It is obtained from Coats-Redfem＇s equation and Malek method that the mechanism functions of the two decomposition stages are D3 and A1.5, respectively. And then, the kinetic equations of the two steps were deduced as well.

Thermal Decomposition Kinetics of Abietic Acid in Static Air

The thermal decomposition of abietic acid in air was investigated under non-isothermal condition using thermogravimetric analysis-differential thermal analysis （TGA-DTA） technique with heating rates of 5, 10, 15 and 25 K.min-~. The non-isothermal kinetic parameters were obtained via the analysis of the thermogravimetric and differential thermogravimetric （TG-DTG） curves by using Flynn-Wall-Ozawa method and Kissinger method. The thermal decomposition mechanism of abietic acid was studied with four integral methods （Satava-Sestak, MacCallum-Tanner, ordinary integral and Agrawal）. The results show that the thermal decomposition mechanism is nu- cleation and growth, and the mechanism function is Avrami-Erofeev equation with n equates 1/2. The activation energy and the pre-exponential factor are 64.04 kJ.mol^-1 and 5.89×10^5 s^-1, respectively.

Thermal Stability and Thermal Decomposition Kinetics of 1-Butyl-3-methylimidazolium Dicyanamide

Thermal stability and thermal decomposition kinetics of 1-butyl-3-methylimidazolium dicyanamide ([bmin+][N(CN) ]2-) were investigated using both isothermal and non-isothermal thermogravimetric analyses (TGA) under high pure nitrogen as carrier gas. The long-term thermogravimetric studies revealed that the highest temperature used should be 110 °C, at which [bmin+][N(CN)2-] lost less than 10% by mass in 10 hours. The non-isothermal activation energy values determined using Friedman and ASTM methods were (150±13) and (147±2) kJ·mol –1 , respectively. Multivariate non-linear-regression methods showed that expanded Fn and CnB models were the best fit models with highest correlation coefficient of 0.9994, and the apparent activation energies were consistent with iso-conversional methods.

Theoretical analysis and experimental verification of thermal decomposition mechanism of CuSe

Experiments on the thermal decomposition of CuSe were carried out by using a thermogravimetric analyzer(TGA)at different heating rates.The kinetic parameters and mechanisms were discussed based on model-free and model-based analyses.The decomposition rate and decomposition behavior of CuSe were investigated by using a vacuum thermogravimetric furnace.The results showed that the R3 model was identified as the most probable mechanism function under the present experimental conditions.The average values of activation energy and the pre-exponential factor were 12.344 J/mol and 0.152 s^(−1),respectively.The actual decomposition rate of CuSe was found to be 0.0030 g/(cm^(2)·min).

Analytical solution for functionally graded anisotropic cantilever beam under thermal and uniformly distributed load

The bending problem of a functionally graded anisotropic cantilever beam subjected to thermal and uniformly dis-tributed load is investigated,with material parameters being arbitrary functions of the thickness coordinate. The heat conduction problem is treated as a 1D problem through the thickness. Based on the elementary formulations for plane stress problem,the stress function is assumed to be in the form of polynomial of the longitudinal coordinate variable,from which the stresses can be derived. The stress function is then determined completely with the compatibility equation and boundary conditions. A practical example is presented to show the application of the method.

Study on the thermal decomposition kinetics of nano-sized calcium carbonate

This study of the thermal decomposition kinetics of various average diameter nano-particles of cal-cium carbonate by means of TG-DTA(thermogravimetry and differential thermal analysis) showed that the thermal decomposition kinetic mechanisms of the same crystal type of calcium carbonate samples do not vary with decreasing of their average diameters ; their pseudo-active energy Ea; and that the top-temperature of decom-position Tp decreases gently in the scope of micron-sized diameter, but decreases sharply when the average di-ameter decreases from micron region to nanometer region. The extraordinary properties of nano-particles were explored by comparing the varying regularity of the mechanisms and kinetic parameters of the solid-phase reac-tions as well as their structural characterization with the variation of average diameters of particles. These show that the aggregation, surface effect as well as internal aberrance and stress of the nano-particles are the main reason causing both Ea and Tp to decline sharply with the decrease of the average diameter of nano-particles.

Study on co-cracking performance of different hydrocarbon mixture in a steam pyrolysis furnace

Co-cracking is a process where the mixtures of different hydrocarbon feedstocks are cracked in a steam pyrolysis furnace, and widely adopted in chemical industries. In this work, the simulations of the co-cracking of ethane and propane, and LPG and naphtha mixtures have been conducted, and the software packages of COILSIM1 D and Sim CO are used to account for the cracking process in a tube reactor. The effects of the mixing ratio, coil outlet temperature, and pressure on cracking performance have been discussed in detail. The co-cracking of ethane and propane mixture leads to a lower profitability than the cracking of single ethane or single propane. For naphtha, cracking with LPG leads to a higher profitability than single cracking of naphtha, and more LPG can produce a higher profitability.

Integrability of N-Component Bariev Model Under Open Boundary Conditions

N-component Bariev model for correlated hopping under open boundary conditions in one dimension is studied in the framework of Bethe ansatz method. The energy spectrum and the related Bethe ansatz equations are obtained.

Thermal stress distribution around a thermally-insulated polygonal cutout in graphite/epoxy composite laminates under heat flux

In this study,the effect of influencing parameters on the stress distribution around a polygonal cutout within a laminated composite under uniform heat flux was analytically examined.The analytical method was developed based on the classical laminated plate theory and two-dimensional thermo-elastic method.A mapping function was employed to extend the solution of a perforated symmetric laminate with a circular cutout to the solution of polygonal cutouts.The effect of significant parameters such as the cutout angular position,bluntness and aspect ratio,the heat flux angle and the laminate stacking sequence in symmetric composite laminate containing triangular,square and pentagonal cutouts was studied.The Neumann boundary condition was used at the edges of the thermally insulated polygonal cutout.The laminate was made of graphite/epoxy(AS/3501) material with two different stacking sequences of [30/45]sand[30/0/-30]_(s).The analytical solutions were well validated against finite element results.

Suspension roasting process of vanadium-bearing stone coal:Characterization,kinetics and thermodynamics

The thermodynamics,kinetics,phase transformation,and microstructure evolution of vanadium-bearing stone coal during suspension roasting were systematically investigated.Thermodynamic calculations showed that the carbon in the stone coal burned and produced CO_(2) in sufficient oxygen during roasting.The mass loss of stone coal mainly occurred within the temperature range from 600 to 840℃,and the thermal decomposition reaction rate increased to the peak at approximately 700℃.Verified by the Flynn−Wall−Ozawa(FWO)and Kissinger−Akahira−Sunose(KAS)methods,the thermal decomposition reaction of stone coal was described by the Ginstling−Brounshtein equation.The apparent activation energy and pre-exponential factors were 136.09 kJ/mol and 12.40 s^(−1),respectively.The illite in stone coal lost hydroxyl groups and produced dehydrated illite at 650℃,and the structure of sericite was gradually destroyed.The surface of stone coal became rough and irregular as the temperature increased.Severe sintering occurred at the roasting temperature of 850℃.