The effects of hydration activity of calcined dolomite (HCD) on the silicothermic reduction process

Abstract:In this paper, the theoretical and industrial definitions of metallic calcium production by the metallothermic process in a vacuum atmosphere were investigated. In the experiments, Al is the only reductant used for metallothermic calcium production. The effects of Al stoichiometry, time variances, and temperature changes were investigated. The experiments were carried out at 1200 • C, 1250 • C, and 1300 • C, and with 100% Al, 125% Al, and 150% Al stoichiometry to produce metallic calcium from the residue of metallic magnesium production. Both the raw materials and the residue phases were characterized by atomic absorption spectrometry (AAS), X-ray diffraction (XRD) spectrometry, and chemical analysis techniques. Experimental results were investigated to determine the highest efficiency of reduction conditions. From the results of the experiments, reaction kinetics and activation energy were calculated. According to the experimental results, the highest recovery rate parameters for the reduction of calcium are 150% stoichiometric Al for 480 min at 1300 • C, with 72% recovery.

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“…where k is the rate constant, t is the time (hour), and α is the calcium recovery fraction [22,23]. during the reduction.…”

Section: Resultsmentioning

confidence: 99%

“…where k is the rate constant, t is the time (hour), and α is the calcium recovery fraction [22,23]. The slope of the graph gives the value of the activation energy, which was calculated from Arrhenius Equation (5): during the reduction.…”

Section: Resultsmentioning

confidence: 99%

Reduction Conditions of Metallic Calcium from Magnesium Production Residues

Tasyürek

Buğdaycı

Yücel

2018

Metals

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“…Proses dekomposisi dolomit menjadi MgO dan CaO sudah banyak dilakukan baik secara isothermal maupun non-isothermal [7][8][9][10][11][12]. Variabel proses sangat berpengaruh terhadap pembentukan kurva dan puncak fasa MgO dan CaO.…”

Section: Pendahuluanunclassified

Pengaruh Suhu Kalsinasi Pada Proses Dekomposisi Dolomit

Royani¹,

Sulistiyono²,

Sufiandi³

2018

jsmi

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Proses dekomposisi dolomit menjadi MgO dan CaO merupakan proses penting mengingat kedua oksida tersebut banyak digunakan dalam berbagai aplikasi. Untuk melihat pengaruh suhu proses kalsinasi terhadap dekomposisi dolomit menjadi MgO dan CaO, maka dilakukan kalsinasi. Proses kalsinasi menggunakan tungku Muffle furnace dengan suhu sebesar 500 o C, 600 o C, 700 o C, 800 dan 900 o C. Sebanyak kurang lebih 100 gram/sampel dolomit dimasukkan dalam tungku dan dipanaskan dengan laju pemanasan 10 o C/menit pada berbagai suhu yang kemudian ditahan masing-masing selama 1 jam, 2 jam, 3 jam, 4 dan 5 jam. Produk kalsinasi kemudian ditimbang dan dikarakterisasi dengan X-Ray Diffraction (XRD) dan Scanning Electron Microscope (SEM). Hasil percobaan menunjukkan kalsinasi dolomit semakin meningkat seiring dengan kenaikkan suhu kalsinasi. Proses kalsinasi dolomit optimum tercapai pada suhu 900 o C selama 4 jam dengan pengurang berat mencapai 46,74 %. Berdasarkan perhitungan stoikiometri pengurangan berat 46,74 % menunjukkan bahwa 97,78 % dolomit terdekomposisi menjadi MgO dan CaO. Pembentukan fasa MgO dan CaO dari dolomit melalui dua tahapan yaitu tahapan pembentukan fasa MgO-CaCO 3 pada suhu 700 o C dan tahapan pembentukan CaO pada suhu 800 o C-900 o C. Kesimpulan yang didapatkan dari proses kalsinasi dolomit ini adalah peningkatan suhu kalsinasi dapat meningkatkan proses dekomposisi dolomit menjadi fasa MgO dan CaO.

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“…Zhang et al have combined calcination and reduction steps to study the kinetics of a one-step Mg reduction by experiment and simulation. They obtained a result that the one-step Mg reduction production process can reduce reduction time and save energy [10][11][12][13]. Fu et al studied the thermodynamics and kinetics of the integration process of calcination and reduction and found that canceling the calcination process can greatly save energy [14][15][16][17][18].…”

Section: Introductionmentioning

confidence: 99%

Nucleation and Condensation of Magnesium Vapor in Argon Carrier

Han

Guo

et al. 2020

Metals

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The nucleation and condensation of Magnesium (Mg) vapor carried by argon gas (Ar) were examined. The condensation of Mg vapor at a heat source temperature of 1273–1473 K and Ar flow rate of 0.1–0.4 m3/h was analyzed. The result indicated that the condensation temperature is affected by the heat source temperature and Ar flow rate, and the condensation temperature of Mg vapor was 1013.3 K at a heat source temperature of 1473 K and Ar flow rate of 0.2 m3/h. The effects of Mg vapor partial pressure and temperature of the condensation zone on the nucleation and condensation of Mg vapor carried by Ar were calculated and analyzed in terms of atomic collisions and critical nucleation radius. Increased vapor oversaturation and decreased condensation temperature were favorable for liquid nucleation growth. The Mg condensation products in Ar flow rate of 0.2 m3/h at a heat source temperature of 1473 K were analyzed by XRD, SEM, and EDS, which indicated that the condensed product was of high purity and not easily oxidized in Ar flow. In this paper, the quality of Mg vapor condensation was controlled, which provided the theoretical and experimental basis for a continuous Mg production process.

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The effects of hydration activity of calcined dolomite (HCD) on the silicothermic reduction process

Cited by 19 publications

References 12 publications

Reduction Conditions of Metallic Calcium from Magnesium Production Residues

Reduction Conditions of Metallic Calcium from Magnesium Production Residues

Pengaruh Suhu Kalsinasi Pada Proses Dekomposisi Dolomit

Nucleation and Condensation of Magnesium Vapor in Argon Carrier

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