Utilization of Rubber Tree Bark for Reduction of Mill Scale at 1550 °C: Implication for Sustainable Wastes Recycling in Steelmaking Process

Utilization of local-based waste materials can be a challenge due to the resource’s limitations. This study investigated the utilization of rubber tree bark (RTB) as a reductant for mill scale. RTB was blended with coal into five ratios, namely RTB#1–RTB#5. The blends were heated at 1000 °C under argon for 1 h. The char was mixed with scale to produce a carbon-mill scale composite pellet (CCP) with a 1.5 C/O molar ratio. The reduction of CCP was carried out in a tube furnace at 1550 °C for 30 min under argon flowing at 1 L/min. The reduced Fe droplets separate clearly from the residues. The CCP produced from blends RTB#1–RTB#5 shows better reduction with metal of 35.28–39.82 wt%. The degree of metallization (DOM) ranges between 75.25–84.51%, which is two times higher than that of coal. RTB#3 shows the optimum condition with the highest DOM. CaO in RTB plays a role in forming an ash layer on the metal surface and reacting with Fe2O3 to form a new phase. Utilization of our local-based biomass, such as RTB as a reductant for mill scale, is possible. The consumption of fossil fuel in the process could be decreased by 30%, thus also the production cost.

Structure evolution of a magnetite iron ore/carbon composite pellet during solid-state reduction under microwave heating

In the present study, the structure evolution under direct reduction of a Minh-Son magnetite iron ore/carbon composite pellets in a microwave-heating kiln under different microwave wattage of 60 and 90 % (with the firing time from 15 to 120 min.) was investigated. The microstructure of the pellets was characterized by scanning electron microscopy coupled with energy dispersive spectroscopy and X-ray diffraction (XRD). The phase formation was indexed using MDI Jade from the peaks matching the reference sample. At the microwave’s wattage of 60 %: the wustite (FeO) has appeared after firing time of 60 min., the metallic iron and fayalite have appeared in the reduced samples after firing time of 90 min. to 120 min. with retained phases of Fe203, Fe304, FeO and Si02– While at the microwave’s wattage of 90 %, the metallic iron has appeared in the reduced samples after firing time of 30 min. to 120 min and fayalite has appeared in the reduced samples after firing time of 60 min. to 120 min. The final reduced pellet, under microwave’s wattage of 90 % and firing time of 120 min., shows the only phases of metallic iron and fayalite according to the XRD resolution. The present work could provide a scientific understanding to illustrate iron ore/carbon composite pellet behavior during solid-state carbothermic reduction under a microwave-heating.

Comparative Study on the Kinetics of the Isothermal Reduction of Iron Ore Composite Pellets Using Coke, Charcoal, and Biomass as Reducing Agents

The kinetics of the isothermal reduction of iron ore–coke, iron ore–charcoal, and iron ore–biomass (straw) composite pellets were studied at 900–1200 °C. Compared with the other two composite pellets, the composite pellet using biomass as a reducing agent showed a more rapid reduction rate at a relatively low temperature. With an increase in the temperature, the reduction rates of the three different composite pellets tended to be equal. The reducing reactions of the three different composite pellets were all mainly controlled by gasification diffusion. The reduction rates can be described by the interface reaction kinetic model ([1−(1−m)1/3]2=kt). The apparent activation energies of the gasification diffusion of coke, charcoal, and biomass composite pellets at 900–1200 °C were calculated using the Arrhenius equation, and they were 95.81, 71.67, and 58.69 kJ/mol, respectively. The biomass composite pellets exhibited a lower apparent activation energy than the composite pellets with other reduction agents.

Preparation and Structural Stability of LiFePO4|Ga-LLZO Composite Cathode Material Heat-Treated at Intermediate Temperatures

In this study, cathode and lithium-ion conducting solid electrolyte composite pellet with 1:1 wt. % composition of LiFePO4 and Li7-3XGaxLa3Zr2O12 (x = 0.1) (LiFePO4|Ga-LLZO) was prepared via solid-state reaction. The aim of the study is to investigate the phase stability between LiFePO4 cathode and Ga-LLZO solid electrolyte material when heat treated at 400 to 600 °C. The as-mixed LiFePO4|Ga-LLZO composite was characterized by TG/DTA and the heat treated sample was then analyzed for its structure using XRD and compared to the just as-mixed composite. XRD patterns of the heat treated composite pellet showed that it retains its as-mixed phases of LiFePO4 and Ga-LLZO when sintered below 500 °C under Ar gas flow environment. However, upon heat treatment at 600 °C, the sample already reacted and decomposed with the formation of other phases.

Production of Iron Nuggets from the Akpafu-Todzi Iron Ore and Artisanal Ferrous Slag using Post Consumer Thermosets (Waste Electrical Sockets) as Reductants

Post-consumer thermosets are difficult to recycle because, unlike thermoplastics, they cannot be remoulded to create other items as a result of the extensive cross-linkages in their structure. The increased production of thermoset blends and composites in recent years has greatly increased the amount of waste materials. However, higher levels of carbon and hydrogen present in thermosets make them a potential reductant in the iron extractive industries. In this research work, postconsumer thermoset was transformed into carbon resource through a charring process. The resulting carbonaceous material from the thermoset was used as reductant in the production of metallic iron from the Akpafu-Todzi iron ore and artisanal slag using the microwave technology through the composite pellet approach at varying firing times. Analyses by XRF, XRD and SEM/EDS showed that the Akpafu Todzi iron ore is comprised of the iron oxides hematite (Fe2O3) and wustite (Fe0.942O), while the artisanal slag was predominantly fayalite (Fe2SiO4). Complete reduction of the ore was attained after 120 min reduction but the maximum extent of reduction was 78.84% for the slag, demonstrating the potential of postconsumer thermosets to function effectively as a reductant in the iron extractive industry. Keywords: Reduction; Akpafu-Todzi Iron Ore; Post Consumer Thermosets; Waste Electrical Sockets

Kinetics of the Volume Shrinkage of a Magnetite/Carbon Composite Pellet during Solid-State Carbothermic Reduction

The volume shrinkage evolution of a magnetite iron ore/carbon composite pellet during solid-state isothermal reduction was investigated. For the shrinkage, the apparent activation energy and mechanism were obtained based on the experimental results. It was found that the volume shrinkage highly depended on the reduction temperature and on dwell time. The volume shrinkage of the pellet increased with the increasing reduction temperature, and the rate of increment was fast during the first 20 min of reduction. The shrinkage of the composite pellet was mainly due to the weight loss of carbon and oxygen, the sintering growth of gangue oxides and metallic iron particles, and the partial melting of the gangue phase at high temperature. The shrinkage apparent activation energy was different depending on the time range. During the first 20 min, the shrinkage apparent activation energy was 51,313 J/mol. After the first 20 min, the apparent activation energy for the volume shrinkage was only 19,697 J/mol. The change of the reduction rate-controlling step and the automatic sintering and reconstruction of the metallic iron particles and gangue oxides in the later reduction stage were the main reasons for the aforementioned time-dependent phenomena. The present work could provide a unique scientific index for the illustration of iron ore/carbon composite pellet behavior during solid-state carbothermic reduction.

IDENTIFIKASI PERUBAHAN MINERAL SELAMA PROSES PEMANASAN PELET KOMPOSIT NIKEL DENGAN ANALISIS DIFRAKSI SINAR X ( IDENTIFICATION OF MINERAL CHANGES DURING HEATING OF NICKEL COMPOSITE USING X-RAY DIFFRACTION ANALYSIS )

Logam nikel didapat dari proses pengolahan bijih nikel yang salah satunya adalah saprolit. Pada penelitian ini proses reduksi pelet komposit yang merupakan masa campuran bijih nikel serta batubara kadar rendah dan bahan tambahan dilakukan dalam tungku tabung. Proses reduksi dilakukan pada temperatur 450 °C, 700 °C serta 1100 °C selama 0 jam. Proses reduksi juga dilakukan pada temperatur yang lebih tinggi yaitu 1300 °C namun dengan pemanasan terlebih dahulu pada temperatur 700 °C dan ditahan pada 1 jam dan 2 jam. Produk pelet komposit dianalisis dengan metode difraksi sinar X untuk mengetahui kandungan mineralnya. Hasil menunjukkan bahwa pemanasan pelet komposit menyebabkan terjadinya perubahan warna dari warna coklat menjadi abu-abu. Pemanasan juga menyebabkan terjadinya perubahan komposisi mineral dari masing-masing pelet. Mineral-mineral yang terdapat dalam pelet komposit dan produknya adalah antigorit, klinoklor, kuarsa, enstatit, forsterit,gutit, hematit, magnetit, nikel dan besi. Pemanasan pelet pada temperatur rendah yang lebih lama akan menghasilkan jumlah logam besi yang lebih rendah. Nickel is obtained from saprolite through nickel ore processing. In this study, reduction of composite pellet has been done in a tube furnace. The pellet comsist of nickel ore, coal and additive. The reduction process carried out at 450˚C, 700˚C and 1100˚C for 0 hour. Moreover the reduction is also carried out at 700 °C during 1 and 2 hours followed by heating at 1300˚C for 2 and 1 hours. Reduction product was analyzed by X-Ray diffraction to determine the mineral content. The results indicate that the heating causing color changes from red brown to gray. Heating changes the mineral composition of the pellet. The minerals are antigorite, clinoclore, quartz, enstatite, forsterite, goethite, hematite, magnetite, nickel and iron. Heating the pellets at low temperature longer will produce lower iron.