Fiseha Tesfaye

Thermochemical properties of selected ternary phases in the Ag–Bi–S system

Thermodynamic properties of the equilibrium phases matildite (β-AgBiS2), schapbachite (α-AgBiS2), and pavonite (AgBi3S5) with their stoichiometric variations have been studied. The ternary phase AgBiS2 was synthesized from the pure binary sulfides, and characterized by the SEM–EDS and X-ray powder diffraction techniques. Thermal analysis of the synthesized phase was done by the differential scanning calorimetry and thermogravimetry techniques. Based on the calorimetric measurements, phase transformation and melting temperatures as well as enthalpies of AgBiS2 have been determined. Thermodynamic properties of both AgBiS2 and AgBi3S5, including their stoichiometric variations at saturations of bismuth and sulfur, have been compiled and critically evaluated. Heat capacities of both phases have been estimated with two different estimation methods. The estimated results have been compared with the available experimental literature data. Despite the fact that the estimation methods are partly based on assumptions, the obtained values are generally in reasonable agreement with the available literature data. The obtained results are presented and discussed.

Thermodynamic stability of solid phases in the system Cu–O–Al2O3 by means of the EMF and DSC-TGA techniques

Thermodynamic properties of solid phases in the Cu–O–Al2O3 system were measured by means of the EMF method with oxygen concentration galvanic cells based on stabilized zirconia solid electrolytes. The standard Gibbs energies of formation of pure copper oxides and copper aluminates from their component oxides were determined. Copper aluminates were also investigated calorimetrically by the DSC-TGA combined techniques. Based on the calorimetric measurements, the enthalpies and temperatures of spinel decomposition and delafossite melting were determined. The obtained results were discussed and compared with the available literature data.

The Thermodynamics of Slag Forming Inorganic Phases in Biomass Combustion Processes

To reduce the use of fossil fuels and increase self-sufficiency in energy, nowadays, there is an increasing interest to produce heat, power and transportation fuels from renewable resources. Solid biomass is one of the most important renewable energy sources for meeting this target. However, fouling, slagging, and corrosion threaten long-term operation availability and costs of biomass power plants. Slags accumulated on the surfaces of superheaters, which decrease thermal efficiency, often constitute a considerable percentage of complex inorganic phases. However, thermodynamic properties of the complex inorganic phases and their combined effect, which will help to deal with the slag related problems during high-temperature biomass combustion processes, are not well known. In the present paper, thermodynamic properties of K-, Ca-, and Na-based inorganic phases and their mixtures under different gas conditions are both critically reviewed and experimentally studied. The obtained results are presented and discussed.

Energy Technology 2017

This collection focuses on energy efficient technologies including innovative ore beneficiation, smelting technologies, recycling and waste heat recovery. The volume also covers various technological aspects of sustainable energy ecosystems, processes that improve energy efficiency, reduce thermal emissions, and reduce carbon dioxide and other greenhouse emissions. Papers addressing renewable energy resources for metals and materials production, waste heat recovery and other industrial energy efficient technologies, new concepts or devices for energy generation and conversion, energy efficiency improvement in process engineering, sustainability and life cycle assessment of energy systems, as well as the thermodynamics and modeling for sustainable metallurgical processes are included. This volume also offers topics on CO 2 sequestration and reduction in greenhouse gas emissions from process engineering, sustainable technologies in extractive metallurgy, as well as the materials processing and manufacturing industries with reduced energy consumption and CO 2 emission. Contributions from all areas of non-nuclear and non-traditional energy sources, such as solar, wind, and biomass are also included in this volume. Papers from the following symposia are presented in the book: Energy Technologies Advances in Environmental Technologies: Recycling and Sustainability Joint Session Deriving Value from Challenging Waste Materials: Recycling and Sustainability Joint Session Solar Cell Silicon .

Valuable Metals and Energy Recovery from Electronic Waste Streams

E-waste management through traditional methods such as disposing in landfills, burning in incinerators or exporting abroad for disposal are no longer options due to the strict environmental regulations. Fortunately, the presence of valuable metals in the e-waste and increasing demand for the metals as well as complexities of the currently available primary raw materials make recycling an attractive and viable option both environmentally and economically. Moreover, it is efficient in terms of resource management by closing the loop of metals. Consequently, urban mining such as the recovery of precious metals from e-waste streams through sustainable recycling processes have emerged. The sustainable recycling practices address the scarcity of primary resources and reduce consumption of energy for metals production while managing environmental issues related to hazardous materials from the e-waste streams. In this paper, valuable metals recoveries from e-waste streams through pyrometallurgical and hydrometallurgical processes are critically reviewed. And, innovative ideas for different steps of the thermochemical processes in the valuable metals and energy recovery from the e-waste streams are discussed.

Thermodynamic Properties of Magnetic Semiconductors Ag 2 FeSn 3 S 8 and Ag 2 FeSnS 4 Determined by the EMF Method

Phase equilibria and thermodynamics in the Ag2SnS3–SnS–Sn2S3–FeS system were investigated using differential thermal analysis, X-ray diffraction, and EMF methods. Determined phase relations were used to express the forming chemical reactions for compounds Ag2FeSn3S8 and Ag2FeSnS4. The forming chemical reactions were performed by applying electrochemical cells of the types: (–) C | Ag | Ag3GeS3I glass | Ag2FeSn3S8, SnS, Sn2S3, FeS | C (+) and (–) C | Ag | Ag3GeS3I glass | Ag2FeSnS4, SnS, Ag2FeSn3S8, FeS | C (+). Based on the measured EMF versus temperature relations, experimental thermodynamic data of the quaternary phases Ag2FeSn3S8 and Ag2FeSnS4 were derived for the first time.

The K 2 SO 4 –CaSO 4 System and Its Role in Fouling and Slagging During High-Temperature Processes

Currently, there is an increasing interest to produce energy mainly from renewable sources such as biomass. However, fouling, slagging and corrosion threaten long-term operation availability and costs of biomass power plants. Alkali metal elements in the biomass fuel and the ash fusion behavior are the two major origins contributing to slagging during high-temperature biomass combustion. Accumulated slags decrease thermal efficiency of superheaters. These slags often constitute a considerable percentage of complex inorganic phases such as K2Ca2(SO4)3. However, thermodynamic properties of these inorganic phases and their combined effect, which would help to solve the fouling, slagging and high-temperature corrosion related problems in biomass combustion processes, are not well known. In the present work, thermodynamics and phase equilibria of selected phases in the K2SO4–CaSO4 system were both critically reviewed and experimentally studied. The obtained results are presented and discussed.

A Sustainable Methodology for Recycling Electric Arc Furnace Dust

In a race to save the planet of its rapidly depleting natural resources, the use of Secondary Raw Materials (SRMs) as replacements in several processes is currently intensively pursued. In fact, this is currently one of the European Union (EU)’s mandates. Valorization of SRMs is consistent with circular economy, where resource efficiency is maximized for the benefit of both businesses and the environment. In line with this mandate, this paper focuses on investigating process phenomena related to hydrometallurgical recycling of Electric Arc Furnace (EAF) dust. In the experimental study, selective dissolution of zinc and other metals is investigated to acquire a recyclable leach residue. Based on the experimental and theoretical investigations, zinc could be extracted from the EAF dust and a recyclable leach residue produced, having chemical composition suitable as a feed material into electric arc furnace.

High-temperature oxidation of bismuth- and antimony-based sulfosalts

ABSTRACT In this article, oxidation processes of Ag-Bi-Sb-based phases were investigated. Synthesized AgBiS2 and AgSbS2-Sb2S3-Sb samples were thermally analyzed in synthetic air by applying the simultaneous DSC-TGA analysis technique. The oxidation processes at PO₂=0.2 atm and T<1173 K were observed to take place in many-step sequence of various reactions with an overall reaction 2AgMeS2 + 5.5O2(g) ⇄ 2Ag + Me2O3 + 4SO2(g), where Me=(Bi,Sb). Oxidations of AgBiS2, Sb2S3, and AgSbS2 were observed to begin above 549±2K, 610±2K, and 733±2K, respectively. Furthermore, oxidation processes of AgBi3S5 and Ag3SbS3 were estimated, and thermodynamic functions for the overall oxidation reactions were calculated and discussed.

Phase Equilibria and Thermodynamics of Selected Compounds in the Ag–Fe–Sn–S System

Polythermal sections in the vicinity of the quaternary compounds Ag2FeSnS4 and Ag2FeSn3S8 have been modeled. The mechanism of formation of these quaternary compounds and their thermal stability have been investigated. Measurements of electromotive force allowed calculations of the standard thermodynamic functions ΔG°, ΔH°, and S° of the Ag2FeSnS4 and Ag2FeSn3S8 compounds. Based on calorimetric measurements, the enthalpies of phase transitions of the selected compounds were determined. Furthermore, the heat capacities of both quaternary compounds were estimated by applying different calculation methods. Thermodynamic properties of the quaternary compounds, which are regarded as functional magnetic materials, were analyzed and are discussed in detail.