吸热式氮基气氛与钢复杂平衡体系的热力学计算(Ⅱ)

本文用自由能最小化法对吸热式氮基气氛与碳钢间的多元反应复杂平衡体系进行了热力学计算,得到了有关方程式.计算了体系中各组份在不同温度下的平衡组成和碳势,以及不同氮含量时气氛的碳势.结果表明,在一定温度下气氛的碳势随CO_2浓度的增加而减小;在一定CO_2含量时,炉温越高则气氛的碳势越低.此结论与用独立组元法处理得到的结果相符.     

热等离子体法裂解碳氢化合物制备炭黑的热力学研究

用Gibbs自由能最小法计算了在不同温度下,不同体系的碳氢化合物裂解的平衡组成。考察了不同压力和温度下,以甲烷、乙烷和苯为原料时系统中主要组分的浓度随反应条件的变化;改变了等离子体工作气的种类,考察了工作气对平衡组分的影响。计算结果表明:低温裂解碳氢化合物有利于生成固体的碳,在很高温度下,体系中仅有气相碳、氢自由基等组成,容易形成纳米碳管和纳米碳球;热裂解时使用氮等离子体将产生大量的毒气,而使用空气等离子体可以适当减少毒气的生成,但是纳米碳球和纳米碳管的产率下降。     

不同温度下复杂反应体系平衡计算方法的探讨

对多个反应的复杂体系,难于导出体系中各物种的平衡组成随温度变化的函数关系式,我们采取的方法是在计算一定条件下复杂反应体系平衡组成程序外嵌套温度循环,对不同温度逐点进行计算,进而绘制出平衡温度随温度变化的关系曲线。此方法可用于大部分复杂反应体系不同温度下平衡组成的计算,具有通用性的特点。该方法成败的关键是运用较好的计算平衡组成的方法以及温度循环步长的选定。     

不同甲烷气氛下煤自燃指标气体及活化能研究

针对不同氧浓度下煤自燃特性的研究大多只考虑不同氧氮比气氛,而对不同甲烷气氛下煤低温氧化规律研究较少的问题,利用程序升温氧化和热重分析实验,对不同甲烷气氛下煤自燃指标气体和活化能进行了研究。结果表明:随着CH_4体积分数的增大,产生CO和CO_2的初始温度显著升高;在煤氧化初始阶段,不同CH_4气氛下CO和CO_2生成量均随着温度的升高而缓慢增加;在煤加速氧化阶段,CO和CO_2生成量随温度的升高呈指数函数形式增加,且CH_4体积分数越低(O_2体积分数越高),CO和CO_2生成量越大,表明温度越高,CH_4对煤氧化的抑制作用越明显;随着CH_4体积分数的增大,煤低温氧化活化能增大、指前因子降低,说明CH_4体积分数的增大对于煤自燃具有较好的抑制作用。     

制备四氯化钛过程中加碳氯化反应热力学

反应热力学对研究二氧化钛加碳氯化反应具有指导作用。运用HSC软件通过计算对二氧化钛加碳氯化的CO／CO2比值、配碳比等进行了讨论,结果表明低温下加碳氯化反应的相关产物为CO2,而高温下为CO。产物TiCl4含量在整个温度范围内保持稳定。当配碳比较高时,碳的反应不完全,存在过量;较低时,不利于TiO2的完全反应。通过对工业TiCl4生产CO／CO2 比值研究,发现CO／CO2比值不完全与平衡态下的CO／CO2比值一致。同时对低价钛氧化物的生成进行了探讨,计算表明在温度低于1 100℃时不会生成低价钛氧化物。通过以上研究为进一步优化加碳氯化反应提供了依据。     

甲烷部分氧化合成燃气过程能量耦合工艺的研究

从反应温度、压力和进料量(CH_4、CO_2、H_2O和O_2)等6个变量中固定任意5个,优化剩下的一个变量的方案,研究甲烷部分氧化合成燃气含水蒸气、二氧化碳重整的能量耦合工艺(即平衡时体系的热效应为零)。建立为能量耦合的双层优化模型,即内层通过求解吉布斯自由能的最低限度得到平衡组成;外层通过改变进料组成实现体系的能量耦合。结果表明:0．1 MPa下反应体系的最佳操作温度范围为1 050～1 150 K;固定其他条件,总可通过优化O_2的量使反应体系实现能量耦合,且平衡时加入的O_2可以反应完全;平衡组分中H_2/CO比值主要取决于进料中H_2O/CO_2比值,与O_2量关系不大;另外还得出了能量耦合时变量间的关系和消炭条件。石英管反应器的热中性温度下的实验结果与本文计算结果基本一致。     

催化裂化装置再生烟气析碳反应的热力学模拟计算

采用吉布斯自由能热力学平衡算法,建立了催化裂化装置烟气析碳反应模型,该模型验证了析碳发生的可能性,其计算结果与生产实际相吻合。结合典型实际生产工况,利用该模型分别考察了烟气温度、压力、空气配比、水蒸气配比和氧气含量等对烟气碳析模型中析碳量的影响。计算结果表明:烟气温度300℃～550℃容易发生析碳,增大空气配比可以显著减弱析碳反应的发生,烟气压力在0MPa～0.32MPa、水蒸汽含量在0wt%～8wt%范围内对于析碳无显著影响。     

吸附强化乙醇水蒸气重整制氢工艺分析

以CaO为吸附剂,利用Aspen Plus对吸附强化乙醇水蒸气重整制氢工艺进行了模拟,结果显示,当乙醇进料量为100kmol/h,水醇比为6,CaO进料量为200 kmol/h,反应温度和压力分别为500℃、1 atm时,所得产品气中H_2量为579.19 kmol/h,CO_2和CO量均小于0.001 kmol/h,氢气摩尔含量达99.1%,CH_4摩尔含量小于1%,模拟结果与文献实验值吻合较好。在此基础上,对CO_2吸附强化前后效果进行了讨论,结果表明,经吸附强化后的乙醇水蒸气重整工艺较传统工艺所得重整气中H2含量提高116%,CH_4、CO_2和CO等摩尔含量降低至接近于零。讨论了重整反应温度、水醇比及CaO用量对产品气组成影响,得出,吸附强化使得重整反应可在较低温度条件下进行,减少了能源消耗;当水醇比为8,CaO量与乙醇进料量之比为2时,CH_4、CO_2和CO含量趋近于零,H_2含量接近于1。分析了不同水醇比下该工艺所需外加水量,得出,在较高的水醇比条件下,外加水量占重整反应器进料水量的比例较低,而循环水占有较大比例。     

浆态床法合成二甲醚的模拟研究

对于直接以合成气作为原料，使用Cu-Zn-Al和γ-Al2O3构成的双重催化剂、采用浆态床法合成二甲醚的反应体系，使用全混流反应器模型结合化学反应动力学进行模拟。组分方程使用超松弛迭代方法并结合C 编程进行求解，编制了计算机程序。通过模拟计算，讨论了压力、温度、空速、催化剂配比、反应气中不同氢碳比以及CO2含量对反应收率、DME选择性的影响，并讨论了在不同氢碳比下对CO转化率和CO与H2总转化率的影响，从而寻找合适的反应条件，为工业化生产提供参考。     

气相反应产物中固相沉积始现的反应温度点计算

许多气相反应不希望出现固相产品,如燃烧过程不希望有积碳。本文研究气相反应产物在什么条件下出现固体。根据Gibbs自由能最小等热力学原理,提出1种将化学反应平衡和固体饱和蒸汽压数据相结合,求气相反应产物中固相沉积始现的反应温度点的计算方法。举出氯硅烷氢化等7个体系的算例。结果表明:本法与传统的Gibbs自由能最小法结果相同;在同样的进料条件下,每个体系均存在1个固相沉积的温度范围。本文确定的这种温度范围对探讨气体反应的固相沉积现象具有很好的指导意义,所选算例得出:SiHCl_3氢化等4个体系有2个沉积温度点(TD_1,TD_2),即这些平衡体系有2个沉积的温度转折点,如果不希望有沉积,就必须使进料温度小于TD_1或者大于TD_2;而CH_4部分氧化等3个体系只有1个沉积温度点TD,此类平衡体系如果不希望有沉积,进料温度就应大于TD。     

Artificial neural networks application to predict the ultimate tensile strength of X70 pipeline steels

The paper presents some results of the research connected with the development of new approach based on the artificial neural network (ANN) of predicting the ultimate tensile strength of the API X70 steels after thermomechanical treatment. The independent variables in the model are chemical compositions (carbon equivalent), based upon the International Institute of Welding equation (CE_IIW), the carbon equivalent, based upon the chemical portion of the Ito-Bessyo carbon equivalent equation (CE_Pcm), the sum of the niobium, vanadium and titanium concentrations (VTiNb), the sum of the niobium and vanadium concentrations (NbV), the sum of the chromium, molybdenum, nickel and copper concentrations (CrMoNiCu), Charpy impact energy at ?10 °C (CVN) and yield strength at 0.005 offset (YS). For purpose of constructing these models, 104 different data were gathered from the experimental results. The data used in the ANN model is arranged in a format of seven input parameters that cover the chemical compositions, yield stress and Charpy impact energy, and output parameter which is ultimate tensile strength. In this model, the training, validation and testing results in the ANN have shown strong potential for prediction of relations between chemical compositions and mechanical properties of API X70 steels.     

氧化还原平衡智能处理系统(OREICS)的开发

以Visual Basic为工具,结合数据库技术,开发了氧化还原平衡智能处理系统(OREICS)。该软件针对氧化还原平衡涉及的有关问题,提供了标准电极电势查询、电极电势计算、氧化剂／还原剂强弱判断、电池反应方向判断、计算反应平衡常数,以及元素电势图的自动生成和歧化反应判断等功能。软件界面友好,使用方便,可作为处理氧化还原平衡问题的强有力的工具。     

Calculation of constrained equilibria by Gibbs energy minimization

The Gibbs energy minimization encompasses active use of the chemical potentials (partial molar Gibbs energies) of the constituents of the system. Usually, these appear at their equilibrium values as a result of the minimization calculation, the mass balance constraints being the necessary subsidiary conditions. Yet, there are several such physico-chemical circumstances where the system is also constrained by other factors, such as surface effects, potential fields or even by chemical reaction kinetics. In this paper a particular method is presented by which constrained chemical potentials can be applied in a multi-phase Gibbs energy minimization. The constrained potentials arise typically from work-related thermodynamic displacements in the system. When Gibbs energy minimization is performed by the Lagrange method, these constraints appear as additional Lagrangian multipliers. Examples of the constrained potential method are presented in terms of the electrochemical Donnan equilibria in aqueous systems containing semi-permeable interfaces, the phase formation in surface-energy controlled systems and in systems with affinities controlled by chemical reaction kinetics. The methods have been applied successfully in calculating distribution coefficients for metal ions together with pH-values in pulp suspensions, in the calculation of surface tension of alloys, and in thermochemical process modeling involving chemical reaction rates.     

Using Vmax to estimate changes in the sodium membrane conductance in cardiac cells

Relative changes in the sodium conductance of the resting cardiac cell membrane are often estimated from relative changes in the maximum rate of rise of the action potential (Vmax). This approach has given rise to some controversy and it has not been possible so far to test it directly on an experimental basis. We have examined here the validity of this estimation using three different Hodgkin-Huxley representations of the cardiac membrane sodium current. The two basic requirements are a constant membrane capacitance and a negligible relative value of the nonsodium membrane currents at the time of Vmax. It is shown further that the approach leads to a satisfactory estimation only when the latency of Vmax is kept constant and a correction factor for the sodium driving force is applied to Vmax measurements. This conclusion applies either to a nonpropagated action or to an action potential propagated at constant velocity, provided that the membrane is not too strongly depolarized. It is valid for a wide range of sodium equilibrium potentials and a range of maximum sodium conductances limited to about 50% of the nominal value.     

Theoretical analysis on expansion mechanism in carbon dioxide expander

The expansion mechanism inside carbon dioxide expander is analyzed theoretically in this paper.The mechanism analysis of metastable equilibrium indicates that there is a potential barrier during phase change process.That is to say energy is required to overcome the potential barrier when the new interface is formed from primary phase.The superheat of liquid is the impetus of phase change and has an exponential decrease with the increase of the saturated temperature of fluid.The analysis also indicates that ...     

Solubility of CO2 in aqueous ammonia solution at low temperature

The solubility of carbon dioxide in aqueous ammonia solution with concentrations of 1.13, 2.18, 3.83, 6, and 8.11 molal was measured at atmospheric pressure and a range of temperatures from 268.15 to 288.15 K. The results showed that the solubility of carbon dioxide in ammonia aqueous solution increased with increasing temperature. The UNIQUAC-NRF model is applied to the experimental data for the present work. This modified model is used to calculate carbon dioxide solubility in aqueous ammonia solution at a range of temperatures from 268.15 to 288.15 K and atmospheric pressure. The results of AAD% (Absolute Average Deviation) show that the UNIQUAC-NRF model can accurately correlate the solubility of experimental data of carbon dioxide in aqueous ammonia solution over a wide range of low temperatures.     

林地开垦后对不同质地红壤碳氮和磷库的影响

林地开垦农用后,土壤有机C和总N、P的浓度及在各团聚体粒级中的分布可发生较大的变化。对亚热带山地两类不同质地的红壤研究表明,林地开垦为旱地和茶园后,有机质和全N明显下降,全P呈轻微下降。下降量壤质土壤(黄泥土)大于粘质土壤(黄粘泥)。表土(0～15cm)的有机C和总N、P下降大于亚表土(15～30cm)。在三个团聚体粒级中,砂粒中有机C和总N、P的下降幅度最大,并随粒径变细下降幅度逐渐变小,表明与砂粒和粉砂结合的有机C和N、P易受利用方式的改变而变化。从林地到茶园、旱地,各团聚体粒级中有机P及有机P占总P的比例趋向下降。砂粒和粉砂中Olsen-P也呈下降的趋势。     

A general-purpose coarse-grained molecular dynamics program

In this article, we describe a general-purpose coarse-grained molecular dynamics program COGNAC (COarse Grained molecular dynamics program by NAgoya Cooperation). COGNAC has been developed for general molecular dynamics simulation, especially for coarse-grained polymer chain models. COGNAC can deal with general molecular models, in which each molecule consists of coarse-grained atomic units connected by chemical bonds. The chemical bonds are specified by bonding potentials for the stretching, bending and twisting of the bonds, each of which are the functions of the position coordinates of the two, three and four atomic units. COGNAC can deal with both isotropic and anisotropic interactions between the non-bonded atomic units. As an example, the Gay-Berne potential is implemented. New potential functions can be added to the list of existing potential functions by users. COGNAC can do simulations for various situations such as under constant temperature, under constant pressure, under shear and elongational deformation, etc. Some new methods are implemented in COGNAC for modeling multiphase structures of polymer blends and block copolymers. A density biased Monte Carlo method and a density biased potential method can generate equilibrium chain configurations from the results of the self-consistent field calculations. Staggered reflective boundary conditions can generate interfacial structures with smaller system size compared with those of periodic boundary conditions.     

Peat fires detected by the BIRD satellite

Tropical peat swamp forests store huge amounts of carbon, which is released to the atmosphere as carbon dioxide during fires. Recurrent peat swamp forest fires are local catastrophic events that can have a serious impact on the global carbon balance. Urgent tasks in this regard are the provision of information on the fire locations and magnitude of the carbon emissions. The experimental Bi-spectral InfraRed Detection (BIRD) satellite enables early detection of peat swamp forest fires and retrieval of their quantitative characteristics, such as the effective fire temperature, area and radiative energy release. The combination of ground truth measurements and data obtained by BIRD can improve the accuracy of estimates of carbon emissions into the atmosphere and related trace gas composition.