Ahmet Turan

Optimization of Li4SiO4 synthesis conditions by a solid state method for maximum CO2 capture at high temperature

The aim of this research work is to optimize the synthesis of Li4SiO4 by a solid state method to maximize CO2 capture. This includes evaluating the main characteristics of the synthesised material which enhance the CO2 uptake performance. Starting from Li2CO3 and SiO2 pure reagents, the effect of the sintering process conditions (heating rate, synthesis temperature and holding time) of the previously mixed powders has been studied. The samples were characterized by N2 physisorption, particle size distribution and X-ray diffraction. The evaluation of the CO2 uptake performance of the samples has been carried out at 600 °C using a thermobalance under a flow of almost pure CO2. Unreacted Li2CO3 is present at low synthesis temperatures, and its content in the synthesised material decreases when higher temperatures are used, so complete conversion to Li4SiO4 is reached at 900 °C. At this temperature, the maximum CO2 uptake was found to be 20%, although it was yet far from the stoichiometric CO2 uptake value of 36.7%. The holding time at a synthesis temperature of 900 °C was then varied and a maximum CO2 uptake of 30.5% was obtained for a holding time of 2 h. Finally, under the optimised synthesis temperature and holding time conditions, the heating rate was varied. A value of 5 °C min−1 was found as the optimum one as the use of either lower or higher heating rates has a negative effect on the CO2 uptake performance. As crystalline phases, the particle size and BET surface area were very similar among all the prepared samples at 900 °C; the crystal size was identified as the main physical property that could explain the CO2 uptake performance of the samples, i.e., the lower the crystal size, the higher the CO2 uptake.

Effect of Reductant Type on the Metallothermic Magnesium Production Process

Abstract This paper is a contribution to the theoretical and quantitative understanding of the processes for the production of magnesium metal by metallothermic process in vacuum (Pidgeon Process). In the present study, effects of reductant type and amount were investigated. CaC2 is a low-cost alternative to FeSi (ferrosilicon) which is the common reductant in the Pidgeon Process. CaC2 slightly decreases the Mg recovery ratios but it remarkably decreases the process cost. The experimental study, conducted with the change of mass % FeSi–CaC2 ratio at 1,250 °C for 360 min, the optimum Mg recovery was measured as 94.7 % at 20 % CaC2 addition. Also aluminum, as a reductant, allows conducting the process at lower temperatures than that of FeSi. For the experiments conducted with Al addition, the highest Mg recovery ratio was measured as 88.0 % in the conditions for 300 min process duration and 100 % stoichiometric Al addition at 1,200 °C.

Self-propagating High Temperature Synthesis of TiB2

Abstract Self-propagating high temperature synthesis (SHS) is a very important technique for the synthesis of high technology ceramics, metals and alloys. SHS parameters of TiB2 were carried out in this study. Mg stoichiometry as reductant, process atmosphere and addition of NaCl and MgSO4·7H2O additives were investigated. HCl leaching was applied to SHS products to purify their TiB2 contents. Stoichiometrically 100% Mg addition ratio and Ar atmosphere were determined as the optimum parameters. NaCl addition was also positively affected the specific surface area values. 11.78 m2/g specific surface area value was measured for 5.0% NaCl addition ratio.

The effecT of Iron And oxIdIzIng flux AddITIon on The fIre AssAy of low grAde PyrITIc refrAcTory gold ores

In this study, experiments were conducted to understand the effects of different quantities of additional iron and oxidizing flux (Na2O2) on the direct fire assay of low grade pyritic refractory gold ores instead of performing any pre-treatment like roasting before fire assay. A portion of the pyritic ore was primarily roasted using a rotary kiln to remove sulphur content for the comparison of the results obtained from direct fire assay of the pyritic ore. Then, fire assay process was performed to the roasted ore and gold and silver content in the ore was determined. Unroasted ore specimens were fused by using fluxes and PbO, which accumulates the precious metals, with various quantities of iron. Correlation between the quantity of additional iron and the recovery of gold-silver were investigated. Various quantities of Na2O2, as an oxidizing flux, were added to the smelting charge with iron additions, from which the highest gold and silver recoveries were obtained from previous experiments. From the results, it was clear that the increase in additional iron and Na2O2 quantities was the reason for the increase in the recovered amounts of lead, gold and silver during the process.

Optimization of Exothermic Riser Sleeve Design Parameters

Exothermic riser sleeves are important tools to increase solidification duration, particularly for iron-steel casting. Increasing the time to solidus improved casting product quality by minimizing cavities. Therefore, process costs were significantly reduced. In comparison with the use of unsleeved risers, exothermic riser sleeves retain up to 30–35% of the heat and increase the duration to solidus by nearly 50%. Exothermic riser sleeves are a mixture of metallothermic-based exothermic and insulating materials that are manufactured in different sizes and shapes. Various suppliers produce these sleeves in different compositions. However, the designers must clearly understand the thermochemical and thermophysical properties. The purpose of the present study was to experimentally determine the effects of varying experimental parameters such as reaction duration, flammability and temperature change etc. on selected exothermic sleeves. The results were compared with thermodynamical simulations which were performed using the contents and the corresponding thermophysical properties of exothermic sleeves.

Production of Iron Based Alloys from Mill Scale through Metallothermic Reduction

Abstract Mill scale (MS) has a potential to use as an iron source because of its high iron content. MS mainly consists of a mixture of iron oxides, metallic iron and other base metal oxides. MS is formed on the surfaces of steel ingots during continuous casting as a waste material. In this study, the use of MS as an iron source for the production of carbon-free iron containing alloys (unalloyed iron, Fe-Ni, Fe-Cr-Ni, Fe-Cr-Ni-Mo) via a metallothermic reduction process was investigated. Thermodynamic calculations and the experimental studies were performed on the basis of 100 g of MS. The effects of different stoichiometric amounts of MS and aluminum (Al) powders (as reductant) were investigated for the production of unalloyed Fe. While, different amount of metal oxide ratios and their effects on metal recoveries, compositions and microstructure of final alloys were studied during Fe-based alloys production. The highest iron recovery during unalloyed Fe production was obtained as 95.14 % by using 100 g of MS and 100 % stoichiometric Al (28.6 g) containing mixture. In Fe-based alloys production series, the highest metal recovery values were reached up to 95.0 % for Fe, 95.1 % for Ni, 68.3 % for Cr and 77.2 % for Mo, respectively.

Production of ZrB2-B4C Composite Materials via SHS Process

ZrB2 and B4C are one of the most significant advanced ceramics. They are being used in various industrial areas from space technology to nuclear industry owing to their physical properties such as high melting point, high thermal/electrical conductivity and low density. Present study was conducted in two main stages: Self-propagating high-temperature synthesis (SHS) reactions and leaching. ZrO2, Carbon black, B2O3 were used as starting material to produce ZrB2-B4C powders by SHS. Also Mg powder was used as the reductant. The reaction mixtures (approximately 100 g) were mixed thoroughly 15 minutes in a turbula mixer and charged into Cu crucible and compacted. W (tungsten) wire was placed at the top of copper crucible and the reaction realized by passing current through the wire. After initiation, a highly exothermic reaction became in a self-sustaining mode and propagated throughout the SHS mixture. The samples were characterized by using AAS and X-Ray Diffraction.

An Investigation on Antimony Production by Using Niederschlag Process

Niederschlag process is commonly used to produce metallic antimony. The process is a metallothermic process which is conducted in one step for metallic antimony production. Using this method Sb2S3 is mixed with coal and metallic iron and subjected to reduction. During heating, antimony sulfide is decomposed and sulphur combines with iron to form the matte phase. Metallic antimony is collected at the bottom of the crucible. In this study, evaluation of Sb2S3 concentrate, extracted and obtained from West Anatolian Region of Turkey was investigated by using Niederschlag process. The reductant stoichiometry, reduction temperature and duration were carried out in the experiments. Chemical analysis methods by using atomic absorption spectrometry (AAS) and X-ray diffraction spectrometry (XRD) techniques were used for the characterization of the concentrate, metallic nuggets and matte phases.

Effect of the Reductants on the Production of Iron Based Alloys from Mill Scale by Metallothermic Process

In this study, iron based alloys (Fe, Fe-Cr-Ni-Mo, etc.) were produced by using metallothermic methods starting from Mill Scales obtained continuous casting processes. During the process, the combustion was realized by ignition and the produced wave propagates throughout the reactant mixture yielding the desired product. In this work, Mil scale used as an iron source, which includes +2, +3 values iron oxides. Aluminum, Magnesium and Silicon were used as reductants. In these metallothermic experiments, different ratios of reductants were examined, and their effects on the metal recovery and alloy compositions were investigated. The samples were characterized by using chemical analysis (AAS), XRD and XRF techniques.

Effects of Functional Additives on the SHS of Boron Carbide

SHS (Self-propagating High-temperature Synthesis) is one of the important methods to synthesize B4C powders. The process contains the reaction of boron oxide powders (B2O3) with magnesium reducing agent and carbon black carburizer. SHS products are leached in HCl media to purify synthesized B4C powders in the following step. In the present study, effects of various functional additives (KClO3, KHSO4, MgSO4.7H2O, NaCl, MgO and Na2SO4) in the SHS stage were carried out. Various proportions of the additives were mixed with the initial SHS charge mixtures. Two different molar ratios were employed in the initial SHS mixtures as 1:3:0.8 B2O3:Mg:C and 1:2.5:0.8 B2O3:Mg:C. After the SHS step, HCl leaching process was applied to the SHS products. Filter cakes were dried and characterized by using X-Ray Diffraction Spectroscopy, BET and chemical analysis techniques.