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"The use of waste cooking oil (WCO) as feedstock and in microwave heating technology helps to reduce the cost of biodiesel. In this study, a continuous flow transesterification of waste cooking oil (WCO) by microwave irradiation for biodiesel production using calcium oxide (CaO) as aheterogeneous catalyst, calcined from cockle shells, is used. The catalyst was packed inside a plastic perforated container mounted on a stirrer shaft and inserted inside the reactor. The thermocouple inside the reactor was connected to a temperature controller and microwave power input to maintain the temperature. Response surface methodology (RSM) was employed to study the relationships between power input, stirrer speed and liquid hourly space velocity (LHSV) on the WCO methyl ester (WCOME) conversion at a fixed molar ratio of methanol to oil of 9 and a reaction temperature set at 65oC. The experiments were developed using the Box-Behnken design (BBD) for optimum conditions. The transesterification of the WCO was produced at 72.5% maximum WCOME conversion at an optimum power input of 445 W, stirrer speed of 380 rpm and LHSV of 71.5 h-1 . The energy consumption in a steady state condition was 0.594 kWh for the production of 1 litre WCOME, for this heterogeneous catalyst is much faster than conventional heating."

"Thermal decomposition of fish bones to obtain calcium oxide (CaO) was conducted at various temperatures of 400, 500, 800, 900, 1000, and 1100 °C. The calcium oxide was then characterized using X-ray diffractometer, FTIR spectrophotometer, and SEM analysis. The calcium oxide obtained from the decomposition at 1000 °C was then used as a catalyst in the production of biodiesel from waste cooking oil. Diffraction pattern of the calcium oxide produced from decomposition at 1000 °C showed a pattern similar to that of the calcium oxide produced by the Joint Committee on Powder Diffraction Standard (JCDPS). The diffractions of 2q values at 1000 °C were 32.2, 37.3, 53.8, 64.1, and 67.3 deg.

The FTIR spectrum of calcium oxide decomposed at 1000 °C has a specific vibration at wave-length 362 cm-1, which is similar to the specific vibration of Ca-O. SEM analysis of the calcium oxide indicated that the calcium oxide's morphology shows a smaller size and a more homogeneous structure, compared to those of fish bones. The use of calcium oxide as a catalyst in the production of biodiesel from waste cooking oil resulted in iod number of 15.23 g/100 g KOH, density of 0.88 g/cm3, viscosity of 6.00 cSt, and fatty acid value of 0.56 mg/KOH. These characteristic values meet the National Standard of Indonesia (SNI) for biodiesel."

"Permintaan global akan ferokrom terus meningkat dikarenakan kebutuhan bahan baku untuk produksi baja tahan karat. Produksi baja tahan karat terus meningkat setiap tahun. Pada tahun 2021, produk baja tahan karat meningkat hingga sebesar 13% dibandingkan dengan tahun sebelumnya. Di Indonesia, kebutuhan baja nasional terus meningkat dan diperkirakan akan mencapai 100 juta ton pada tahun 2045. Namun, industri baja nasional masih menghadapi masalah utilisasi kapasitas produksi nasional yang sangat rendah, yakni rata-rata 54%. Peristiwa ini disebabkan oleh tingginya jumlah produk baja impor yang masuk ke Indonesia, padahal potensi mineral kromit sebagai bahan baku pembuatan ferokrom cukup besar. Pemerintah Indonesia kemudian menetapkan bahwa proses pengolahan mineral kromit dalam negeri harus dilakukan untuk meningkatkan nilai tambah dengan kandungan kromium (Cr) minimum 60%. Oleh karena itu, proses benefisiasi pada mineral kromit kadar rendah asal Indonesia perlu dilakukan sebelum proses peleburan menjadi ferokrom. Pada penelitian ini, proses reduction roasting pasir kromit dilakukan untuk menentukan pengaruh jumlah aditif CaO dan CaSiO3, temperatur reduksi, dan jumlah reduktor batubara terhadap peningkatan kadar dan rasio pasir kromit kadar rendah asal Kabupaten Morowali, Sulawesi Tengah. Bahan baku yang digunakan, yaitu pasir kromit, batubara, bentonit, kalsium oksida, dan wollastonite dicampur serta dipeletisasi menggunakan air sebagai aktivator bentonit. Proses reduction roasting dilakukan menggunakan muffle furnace pada variabel temperatur 1000oC, 1100oC, 1200oC, dan 1300oC dengan jumlah aditif, yaitu 0%, 5%, 10%, 15%, dan 20% serta jumlah reduktor, yaitu 0%, 1%, 2%, 3%, 4%, dan 5%. Setelah itu, proses pemisahan magnetik dilakukan untuk memisahkan kromium yang bersifat paramagnetik dengan logam besi yang bersifat feromagnetik. Hasilnya menunjukkan bahwa penambahan aditif CaSiO3 memiliki pengaruh yang lebih baik dibandingkan dengan aditif CaO. Penambahan aditif CaSiO3 menurunkan titik leleh senyawa membentuk fase cair yang memiliki efek positif dalam kemudahan pemisahan partikel logam besi. Sedangkan, aditif CaO membatasi kontak antara kromit dengan reduktor yang memiliki pengaruh dalam membantu proses reduksi besi secara karbotermik melalui gasifikasi karbon sebagai reduktor oksida besi. Temperatur yang lebih tinggi memberikan energi yang lebih besar kepada atom-atom untuk bergerak mengakibatkan migrasi dan difusi partikel logam besi yang meningkatkan pertumbuhan dan penggabungan partikel. Selanjutnya, hasil terbaik dari reduction roasting yang dilanjutkan dengan magnetic separation diperoleh melalui proses reduksi roasting pada temperatur 1300oC dengan aditif CaSiO3 sebesar 15% dan reduktor batubara sebanyak 5% yang menghasilkan kadar Cr sebesar 23,37% dan rasio Cr/Fe sebesar 2,55.

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Global demand for ferrochrome continues to increase due to the need for raw materials in stainless steel production. Stainless steel production has been growing annually. In 2021, stainless steel products increased by 13% compared to the previous year. In Indonesia, national steel demand continues to rise and is estimated to reach 100 million tons by 2045. However, the national steel industry still faces the issue of very low national production capacity utilization, which averages 54%. This situation is caused by the high number of imported steel products entering Indonesia, despite the significant potential of chromite mineral as a ferrochrome raw material. The Indonesian government has then established that domestic chromite mineral processing must be carried out to increase added value with a minimum chromium (Cr) content of 60%. Therefore, beneficiation of low-grade chromite minerals from Indonesia needs to be performed before the smelting process into ferrochrome. In this research, reduction roasting of chromite sand was conducted to determine the influence of CaO and CaSiO3 additive amounts, reduction temperature, and coal reductant quantity on increasing the grade and ratio of low-grade chromite sand from Morowali Regency, Central Sulawesi. The raw materials used, namely chromite sand, coal, bentonite, calcium oxide, and wollastonite were mixed and pelletized using water as the bentonite activator. Reduction roasting was performed using a muffle furnace at temperature variables of 1000oC, 1100oC, 1200oC, and 1300°C with additive amounts of 0%, 5%, 10%, 15%, and 20%, and reductant quantities of 0%, 1%, 2%, 3%, 4%, and 5%. Subsequently, magnetic separation was conducted to separate paramagnetic chromium from ferromagnetic iron. The results showed that CaSiO3 additive has a better influence compared to CaO additive. CaSiO3 additive lowers the melting point of compounds, forming a liquid phase that has a positive effect on the ease of iron metal particle separation. Meanwhile, CaO additive limits contact between chromite and reductant which influences the assistance of iron reduction through carbothermic process via carbon gasification as iron oxide reductant. Higher temperatures provide greater energy for atoms to move, resulting in migration and diffusion of iron metal particles that increase particle growth and agglomeration. Furthermore, the best results from reduction roasting followed by magnetic separation were obtained through the reduction roasting process at 1300°C with 15% CaSiO3 additive and 5% coal reductant, which produced a Cr content of 23.37% and Cr/Fe ratio of 2.55."