• Energy Research

{"references": ["J. Gao, Y. Wang, Y. Ping, D. Hu, G. Xu, F. Gu and F. Su, RSC Adv. 2 (2012) 2358-2368. doi:10.1039/c2ra00632d"]} Full Changelog: https://github.com/ChemRxnEngLab/GibbsEnergyMinimizationModel/commits/v0.1.0

ABSTRACT This work aims to develop and validate a model based on chemical equilibrium to predict the composition of syngas produced by gasification of woody biomass (sawdust). The model uses Gibbs Energy minimization to evaluate the composition of the system in chemical equilibrium. The results are validated by comparison between experimental data from a gasification experiment and those of other similar models in the literature. The study shows good agreement among experimental results and elucidates the role of solid unburned carbon in such systems, which is present in considerable amount. It can be concluded that equilibrium models can be used to predict carbon conversion in gasification systems.

Gibbs free energy minimization has been used to estimate the hydrogen production potential of air gasification of the wet organic fractions of municipal solid waste available in the Bergen region in Western Norway. The aim of this work was to obtain an upper limit of the amount of hydrogen that could be produced and to estimate of the number of vehicles: passenger ferries and cars that could be supplied with an alternative fuel. The hydrogen production potential was investigated as function of waste composition, moisture content, heat loss, and carbon conversion factor. The amount of hydrogen annually available for both gasification and gasification combined with water-gas-shift-reaction was calculated for different scenarios. Up to 2700 tonne H2 per year could be produced in the best case scenario; which would, if only utilised for maritime operations, be enough to supply nine ferries and ten fast passenger boat connections in the Hordaland region in Western Norway with hydrogen.

ABSTRACT The introduction of solution databases into the F*A*C*T system will be discussed from the point of view of use in mass-constrained Gibbs energy minimization computations using an advanced version of the SOLGASMIX program. Examples will be shown illustrating various treatments of solution thermodynamics including those applicable to metallic solutions, slags, molten salts and aqueous solutions. Special features of the interactive program will be emphasized.

Kaedah peminimuman jumlah tenaga Gibbs sangat berguna untuk menganalisis kemungkinan penukaran metana kepada hidrokarbon dan syngas pada suhu dan tekanan tertentu secara teoritikal. Keputusan numerik menunjukkan penukaran metana meningkat dengan peningkatan kepekatan oksigen dan suhu tindak balas. Bagaimanapun, kehadiran oksigen merencat pembentukan hidrokarbon tinggi yang kebanyakannya mengandungi aromatik, tetapi menggalakkan pembentukan hidrogen. Apabila tekanan sistem bertambah, hasil aromatik, olefin dan hidrogen berkurang, tetapi hasil parafin meningkat. Karbon monoksida menjadi produk mengandungi oksigen yang utama daripada pengoksidaan metana sementara hampir tiada H2O, CH3OH and HCOH yang dikesan walaupun sejumlah kecil karbon dioksida terbentuk pada suhu yang agak rendah dan tekanan tinggi. Kata kunci: Keseimbangan kimia termodinamik, peminimuman jumlah tenaga Gibbs, penukaran metana, hidrokarbon tinggi The total Gibbs energy minimization method is useful to theoretically analyze the feasibility of methane conversion to higher hydrocarbons and syngas at the selected temperature and pressure. Numerical results showed that the conversion of methane increased with oxygen concentration and reaction temperature, but decreased with pressure. Nevertheless, the presence of oxygen suppressed the formation of higher hydrocarbons that mostly consisted of aromatics, but enhanced the formation of hydrogen. As the system pressure increased, the aromatics, olefins and hydrogen yields diminished, but the paraffin yield improved. Carbon monoxide seemed to be the major oxygen-containing equilibrium product from methane oxidation whilst almost no H2O, CH3OH and HCOH were detected although traces amount of carbon dioxide were formed at relatively lower emperature and higher pressure. Key words: Thermodynamic chemical equilibrium, Gibbs energy minimization, methane conversion, higher hydrocarbons

The article deals with the thermodynamic approach for describing chemical processes and phenomena. It is shown that the Gibbs energy minimization method is successfully used to assess the possibility of a spontaneous reaction in isobaric-isothermal conditions. The author analyzes ways to implement this thermodynamic method for studying chemical processes. In order to disclose the content of a scientific concept “isobaric potential of formation of a substance”, an algorithm for constructing this definition is proposed, which is based on detailing of all its components.

Prediction of pathways of radionuclides, heavy metals and other harmful components isolated in cementitious matrices is considered critical in geochemical studies related to hazardous waste disposal [1-3]. Hence, rigorous multi-phase multi-aggregate thermodynamic models with appropriate kinetic and metastability constraints can be very helpful in solving this difficult problem. In a companion contribution [4], we demonstrate that usage of the Gibbs energy minimization (GEM) algorithms permits direct calculation of solid solution – aqueous solution (SSAS) equilibria which adequately describe the solubility data. The suggested "core" thermodynamic dataset can be extended and tuned on the basis of solubility, mineralogical and petrographical studies of fresh, aged and doped cements.

Computation of chemical equilibria in multiphase systems by Gibbs free energy minimization under constraints set by the material balance has increasing interest in many application fields, including materials technology, metallurgy and chemical engineering. The results are utilised in multi-phase equilibrium studies or as parts of equilibrium-based process simulation. Yet, there exist a number of practical problems where the chemical system is influenced by other constraining factors such as surface energy or electrochemical charge transport. For such systems, an extended Gibbs energy method has been applied. In the new method, the potential energy is introduced to the Gibbs energy calculation as a Legendre transformed work term divided into substance specific contributions. The additional constraint potential is then represented by a supplementary undertermined Lagrange multiplier.In addition, upper bounds on the amounts of products can be set, which then limit the maximum extents of selected spontaneous chemical reactions in terms of affinity. The range of Gibbs energy calculations can then be extended to new intricate systems. Example models based on free energy minimisation have been made e.g. for surface and interfacial systems, where the surface, interfacial or adsorbed atomic or molecular layers are modeled as separate phases. In an analogous fashion the partitioning effect of a semi-permeable membrane in a two-compartment aqueous system can be modeled. In such system the large ions, not permeable through the membrane, cause an uneven charge distribution of ionic species between the two compartments. In this case, the electrochemical potential difference between the two aqueous phases becomes calculated for the multi-component system. The calculated results are consistent with the Donnan equilibrium theory; however the multi-phase system may also include the gas phase and several precipitating phases, which extends the applicability of the new method. Finally, similar constraints can also be set to extents of reaction advancements, allowing usage of Gibbs energy calculations in dynamic reaction rate controlled systems.

This article contains the research results of thermodynamic modelling of the chemical interaction of iron phosphides ( Fe 3 P, Fe 2 P, FeP and FeP 2 ) with ferrosilicon FeSi 2 . The results were received by a method of the full thermodynamic analysis using the program HSC-5.1 of the Finnish metallurgical company Outokumpu, which was developed on a principle of the Gibbs energy minimization. The article considers the experimental results concerning to kinetics of the phosphorus extraction from electrothermal ferrophosphorus using ferrosilicon of a grade FS65. In addition, optimum technological parameters of the phosphorus extraction from the industrial ferrophosphorus, containing 26,4 % of phosphorus, and manufacture of a ferroalloy were determined.