Modeling Biomass Gasification Using Thermodynamic Equilibrium Approach

In this paper, the thermodynamic equilibrium models for biomass gasification applicable to various gasifier types have been developed, with and without considering char. The equilibrium models were then modified closely matching the CH₄ only or both CH₄ and CO compositions from experimental data. It is shown that the modified model presented here based on thermodynamic equilibrium and taking into account local heat and mass considerations can be used to simulate the performance of a downdraft gasifier. The model can also be used to estimate the equilibrium composition of the syngas. Depending on the gasifier type and internal fluid flow, heat and mass transfer characteristics, with proper modification of the equilibrium model, a simple tool to simulate the operation and performance of varying types of biomass gasifier can be developed.     

改进的缔合物模型优化模拟KCl-MgCl2,KCl-FeCl2熔盐体系

改进的缔合物模型中缔合平衡的求解过程被简化,使其能够同时优化更广范围的热力学数据,包括量热、emf和相图等等数据,将其应用于KCl-MgCl2和KCl-FeCl2熔盐体系,从已有的热力学数据优化出合理的溶液模型参数,由该模型推算溶液的热力学性质,结果显示改进的缔合物模型能够很好地描述熔盐体系的非理想性质.     

Nitric Acid-Air Diffusion Coefficient: Experimental Determination Using a Diffusion Cell

Abstract

Trace gaseous nitric acid was generated using a diffusion cell. The determination was made by collection in cellulose filters coated with K₂CO₃ and measuring the concentration by ion chromatography. The measured HNO₃-air diffusion coefficient was 0.0404±0.0010 cm²/s (n=21) for T=298.15 K and P=1 atm. Their dependence with the temperature, over the range from 297.15 K to 318.15 K, could be expressed by D = 10^?4.7773.T^1.366 (R²=0.9467).     

A New Investigation of Aqueous Orthophosphoric Acid Speciation Using Raman Spectroscopy

The Raman spectrum of aqueous phosphoric acid has been investigated at apparentconcentrations of 0.3 to 9.7 mol-dm^–3 at 25°C. A quantitative analysis hasbeen made over this concentration range after the determination of the responsecoefficients of the H₂PO^– ₄ and H₃PO₄ species. In the first step, the spectra wereinterpreted assuming that only two species (H₂PO^– ₄ and H₃PO₄) were present inthe system. The dissociation of phosphoric acid obtained in this case is consistentwith the values Preston and Adams⁽¹⁾ obtained, and which was also found fromRaman spectroscopy. However, a discrepancy exists between the representationsfrom spectra and experimental ones. This discrepancy can be removed if anotherspecies, the anionic dimer H₅P₂O^– ₈ is taken into account. Therefore, in the secondstep, a modified interpretation of the spectra, was used to determine theconcentrations of the H₂PO^– ₄, H₅P₂O^– ₈, and H₃PO₄ species and to deduce the correspondingdegree of dissociation of the acid, as well as the speciation of the solutions as afunction of the apparent concentration of phosphoric acid. As in the results Elmoreand co-workers,² which were deduced from pH measurements, the degree ofdissociation reaches a minimum and then increases significantly for apparentphosphoric acid concentrations greater than 1 mol-dm^–3.     

Activity Coefficients of Uranyl Nitrate and Nitric Acid in Aqueous Mixtures

The activity coefficients of nitric acid and uranyl nitrate in in aqueous mixtures are necessary to model the system H₂O-HNO₃-UO₂(NO₃)₂-TBP-diluent. Three methods have been compared in this work to determine activity coefficients based on experimental data, Pitzer's equation or Zdanovskiy's rule. Acid activities have been calculated from the data of two first methods. These results were compared with the data of third method. Errors were about 3.3.%. Activity coefficients of uranyl nitrate γ_U as a function of concentration of uranyl nitrate and nitric acid were determined in 76 mixed solutions. The equation to calculate γ_U was proposed.     

Application of Model of Ideal Solution of Interaction Products and Thermodynamic Modeling

The essence of the ideal solution of interaction products (ISIP) model for systems involving strong interactions of the components is described. With the help of this model and thermodynamic simulation methods, the activities of the components and partial and integral thermodynamic characteristics of Fe-Si solutions at 1873–2003 K in an initial Ar atmosphere and at a common pressure of 1 atm were calculated. The compositions and structures of Fe-Si solutions according to the ISIP model are determined as statistical mixtures of [Fe], [Si] and the clusters [FeSi], [FeSi₂], [Fe₃Si] and [Fe₅Si₃]. The calculated values of activities, thermodynamic characteristics, compositions and structures of Fe-Si solutions agree satisfactorily with reliable experimental data. The thermochemical and thermodynamic properties of the compounds FeSi, FeSi₂, Fe₃Si and Fe₅Si₃ were revised. The temperature dependences of the activities of the components, and also the influence of temperature elevation on the composition of Fe-Si melts are discussed.     

Thermodynamic Insight into Protein Aggregation Using a Kinetic Ising Model

In this work, we present a kinetic analysis for protein aggregation using the kinetic Ising model, which serves as a new application of a previously proposed model [Liang et al., J. Chin. Chem. Soc.­ 2003 , 50, 335]. Considering protein as a single spin unit, we map two states of a unit to the aggregation‐prone (AP) and the fibril (F) states. This work shows that the model can successfully capture the nucleation‐growth features of protein aggregation from experiments, which offers thermodynamic interpretations of aggregation properties, such as lag‐time and fibril stability.     

Electrolysis of Nitric Acid by Using a Glassy Carbon Fiber Column Electrode System

The electrochemical redox behavior of nitric acid was studied using a glassy carbon fiber column electrode system, and its reaction mechanism was suggested and confirmed in several ways. Electrochemical reactions in less than 2.0M nitric acid was not observed. However, in more than 2.0M nitric acid, the reduction of nitric acid to nitrous acid occurred and the reduction rate was slow so that the nitric acid solution had to be in contact with an electrode for a period of time long enough for an apparent reduction current of nitric acid to nitrous acid to be observed. The nitrous acid generated in more than 2.0M nitric acid was rapidly and easily reduced to nitric oxide by an autocatalytic reaction. Sulfamic acid was confirmed to be effective to destroy the nitrous acid. At least 0.05M sulfamic acid was necessary to scavenge the nitrous acid generated in 3.5M nitric acid.     

Modeling of Thermodynamic Properties of Amino Acids and Peptides Using Additivity and HKF Theory

Relative densities, , and heat capacity ratios, of aqueous L-histidine, L-phenylalanine, L-tyrosine, L-tryptophan, and L-2,3-dihydroxyphenylalanine (L-dopa) have been measured at 15, 25, 40, and 55°C and 0.1 MPa. Apparent molar volumes, V _2,, apparent molar heat capacities, C_P2,, partial molar volumes at infinite dilution, , and partial molar heat capacities at infinite dilution, , have been calculated from these measurements and compared to available literature values. The partial molar properties at infinite dilution for these systems have been added to those previously obtained for amino acids and peptides in water and the combined set used as input to a novel additivity analysis. The model we develop is based upon the equations of state of Helgeson, Kirkham, and Flowers (HKF) and has been constructed with additive parameters. The model may be used to predict thermodynamic properties of many aqueous biochemicals over an extended temperature range. Group contributions to the parameters in our model and effective Born coefficients are reported for 24 aqueous amino acid and peptide systems. Our results are compared to data previously published in the literature.     

Thermodynamic Modeling of Polymer Solution Interface

A new method is presented to characterize the interfacial concentration field and interfacial tension between equilibrium polymer solution phases, using readily accessible equilibrium concentration data. The new method is tested and validated using experimental data from different polystyrene solutions and it consists of i) calculation of a universal expression for the concentration gradient coefficient based on the Cahn‐Hilliard model and the Wolf interfacial tension master equation, and ii) development of a highly accurate algebraic function (Kappa distribution) that, for a given equilibrium polymer concentration set, yields the essentially exact interfacial profile predicted by the classical gradient theory for polymer solutions.

     

非理想气体的逸度因子和非理想溶液的活度系数

对单组分非理想气体,推导了它的逸度因子的微分方程式。对多组分非理想气体,推导了各组分逸度因子满足的微分方程式,定义了一个总逸度因子,并找到了总逸度因子和各组分逸度因子之间的关系。同样,对非理想溶液,推导了各组分活度系数满足的微分方程式,定义了非理想溶液的总活度系数,并找到了两者满足的关系。最后分析了逸度因子和活度系数之间的异同点。     

Photocatalytic Synthesis of Gold Nanoparticles Using Preyssler Acid and Their Photocatalytic Activity

Preyssler acid H14[NaP5W30O110] was used as reducing agent and stabilizer for the synthesis of gold nanoparticles by photolysis of Au(III)/Preyssler acid/propan-2-ol solution.Preyssler acid plays both the role of transferring electrons from propan-2-ol to Au(III) and stabilizing the nanoparticles.Propan-2-ol was used as sacrificial reagent for the photoformation of reduced Preyssler acid.Gold nanoparticles (Au NPs) were characterized by UV-Vis spectroscopy,transmission electron microscopy (TEM),and particle size distribution (PSD) measurements.The synthesized Au NPs had a uniform hexagonal morphology and their size was about 17 nm.The catalytic performance of these NPs for photodegradation of methyl orange (MeO) was investigated in aqueous solution.UV-Vis studies showed that Au NPs can catalyze photodegradation of this azo dye.The pseudo-first-order rate constants were also calculated for this reaction.     

Thermodynamic Modeling of KF-CrF3 Binary System

A comprehensive thermodynamic model of KF-CrF₃ system was established. The intermediate phases K₂Cr₅F₁₇, KCrF₄, K₂CrF₅ and K₃CrF₆ were described by the stoichiometric compound model and the liquid phase by associated solution model. All the model parameters were optimized by the experimental phase equilibria data assisted by the first-principles prediction within the framework of the calculation of phase diagram(CALPHAD) method. It is demonstrated that the calculated results are fairly consistent with the experimental data, thus we obtained a set of self-consistent and reliable thermodynamic parameters which could well describe the phase equilibria and thermodynamic properties of KF-CrF₃ system.     

Oxidation of Diethylene Glycol with Nitric Acid

Russian Journal of Organic Chemistry -     

Extraction of Nitric Acid from Chloride-Nitrate Solutions

The extraction of nitric acid from chloride-nitrate solutions simulating solutions that result from eudialyte breakdown with hydrochloric acid after extractive recovery of rare-earth elements was studied. A general flowsheet was suggested for the extraction of rare-earth elements from chloride solutions and utilization of nitrate ions as concentrated solutions of nitrates used in recycling.     

ThMn12型金属间化合物YFe10-xSix有序化行为的热力学研究

采用四亚晶格热力学模型,辅助以第一性原理总能计算,研究了具有ThMn12原型结构的YFe10-xSix金属间化合物中元素的占位有序化行为.结果表明,YFe10.2Si1.8和YFe10Si2化合物中稀土元素Y占据2a亚晶格,Fe占据全部8i亚晶格和部分8j,8f亚晶格,Si占据部分8j,8f亚晶格,且Si更倾向于占据8f亚晶格.随温度的变化,YFe10-xSix化合物中各元素的占位有序化行为并不发生改变.本文预测结果与近期文献报道的实验结果相当吻合,间接证明了成分为YFe10Si2的化合物以ThMn12型结构的YFe10.2Si1.8相和α-(Fe,Si)固溶体相的共存形式更为合理.