Preliminary Techno-Economic Considerations of the Sisal Process - Closing Materials Loops through Industrial Symbiosis

Philipson, Harald; Blandhol, Kjell; Engvoll, Krister; Djupvik, Veronika; Wallin, Maria; Tranell, Gabriella; Haarberg, Torstein

doi:10.2139/ssrn.4116381

Cited by 5 publications

(23 citation statements)

References 8 publications

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“…A significant increase in the reduction of SiO2 and CaO occurs from 1550 °C to 1600 °C. The results at 1600 °C and 1650 °C correspond to results in published work [8,9,19,20], indicating that local equilibrium or partial equilibrium is established instantly at these temperatures. The only obvious overall trend with time was seen for 1550 °C, where Al2O3 tends to increase and SiO2 and CaO decrease.…”

Section: Al Alloy Compositionsupporting

confidence: 86%

“…By assuming that the measured Al alloy compositions in Figure 7 were in contact with pure CaAl 4 O 7 , it was possible to calculate the equilibrium shown in Table 3 The concentrations in the product bulk slag in contact with the Si alloy droplets are shown in Table 4. A significant increase in the reduction of SiO 2 and CaO occurs from 1550 • C to 1600 • C. The results at 1600 • C and 1650 • C correspond to results in published work [8,9,19,20], indicating that local equilibrium or partial equilibrium is established instantly at these temperatures. The only obvious overall trend with time was seen for 1550 • C, where Al 2 O 3 tends to increase and SiO 2 and CaO decrease.…”

Section: Al Alloy Compositionsupporting

confidence: 86%

“…The weights and composition were used to calculate the average stoichiometry to 0.977 ± 0.007 g based on the molar relationship of Equation ( 2). This chosen metal/slag ratio and the composition of reacting materials can be seen to represent the "middle values" of previous experiments [8,20] that have shown reactions with different stoichiometry and compositions of Al metal and slag. The stoichiometric value was subsequently input for thermodynamic equilibrium calculations in FactSage 8.1 [38].…”

Section: Methodsmentioning

confidence: 98%

“…This production method offers several benefits: (i) it can effectively utilize challenging industrial by-products and offers flexibility in raw material selection, thereby mitigating the risk of potential supply shortages; (ii) it operates at relatively low temperatures, resulting in reduced electricity consumption; (iii) by substituting the conventional carbon reductant with secondary Al, direct CO 2 emissions are eliminated; and (iv) the process yields calcium aluminate (CaO-Al 2 O 3 ) slag alongside Si, providing a valuable raw material for Al 2 O 3 production. Recent pilot-scale studies [7,8], conducted under the European-funded SisAl Pilot project, have demonstrated the technical and economic viability of the aluminothermic reduction of calcium silicate slag, showcasing its potential as a multi-product production method for metallurgical-grade silicon (MG-Si) and high-alumina (Al 2 O 3 ) slag.…”

Section: Introductionmentioning

confidence: 99%

“…The CaO-SiO 2 slag, under these conditions, reduces to yield typical weight percentages of 48-52% Al 2 O 3 , 40-45% CaO, and 3-13% SiO 2 [7,9]. The silicon alloy can undergo further refinement to produce metallurgicalgrade silicon (MG-Si), while the slag can be subjected to hydrometallurgical treatment to produce either metallurgical-grade alumina (MGA) or high-purity alumina (HPA) [8,[10][11][12][13][14][15].…”

Section: Introductionmentioning

confidence: 99%

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Investigation of Liquid–Liquid Reaction Phenomena of Aluminum in Calcium Silicate Slag

Philipson,

Wallin,

Einarsrud

2024

Materials

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To achieve better process control of silicon (Si) alloy production using aluminum as a reductant of calcium silicate (CaO-SiO2) slag, it is necessary to understand the reaction phenomena concerning the behavior of formed phases at the metal-slag interface during conversion. The interfacial interaction behavior of non-agitated melt was investigated using the sessile drop method for varying time and temperature, followed by EPMA phase analysis at the vicinity of the metal–slag interface. The most remarkable features of the reaction were the accumulation of solid calcium aluminate product layers at the Al alloy–slag interface and spontaneous emulsion of Si-alloy droplets in the slag phase. The reduction is strictly limited at 1550 °C due to the slow transfer of calcium aluminates away from the metal-slag interface into the partially liquid bulk slag. Reduction was significantly improved at 1600–1650 °C despite an interfacial layer being present, where the conversion rate is most intense in the first minutes of the liquid–liquid contact. A high mass transfer rate across the interface was shown related to the apparent interfacial tension depression of the wetting droplet along with a significant perturbed interface and emulsion due to Kelvin–Helmholtz instability driven by built-up interfacial charge at the interface. The increased reaction rate observed from 1550 °C to 1600–1650 °C for the non-agitated melt was attributed to the advantageous physical properties of the slag phase, which can be further regulated by the stoichiometry of metal–slag interactions and the composition of the slag.

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Section: Al Alloy Compositionsupporting

confidence: 86%

Section: Al Alloy Compositionsupporting

confidence: 86%

Section: Methodsmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Investigation of Liquid–Liquid Reaction Phenomena of Aluminum in Calcium Silicate Slag

Philipson,

Wallin,

Einarsrud

2024

Materials

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Pilot-Scale Aluminothermic Production of Silicon Alloy and Alumina-Rich Slag

Zhu,

Philipson,

Blandhol

et al. 2024

ACS Sustainable Chem. Eng.

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As global demand for silicon (Si) and alumina continues to surge, the significance of developing more sustainable production methods has intensified. The SisAl process represents a path-breaking approach to producing Si and alumina by utilizing side streams from the silicon and aluminum industries. In the present work, a comprehensive series of pilot-scale trials was conducted to assess the scalability and validity of the SisAl process. The influences of reductant raw materials, charging methods, input material ratios, and other processing parameters were also investigated. On coupling between thermodynamic calculations and experimental results, it was demonstrated that the SisAl process is stable and controllable at a pilot scale. The typical composition of the produced Si alloy ranges from 70 to 75 wt % Si, 15–18 wt % Ca, and 8–10 wt % Al. The produced CaO-Al 2 O 3 -based slag has a composition of 48–57 wt % Al 2 O 3 , 40–45 wt % CaO, and 3–13 wt % SiO 2 . Furthermore, various reductants, including Al blocks, dross, and scraps, were evaluated in the pilot trials, yielding comparable outcomes, with alloy composition differences only within approximately 3 wt % under the same parameter conditions, demonstrating the versatility of raw materials selection in the SisAl process. Moreover, it was found that acidic slag exhibited better features for future upscaling than the neutral slags, with a 5 wt % higher Si content in the alloy and a 4 wt % increase in Al 2 O 3 content in the slag phase. Additionally, the chemical composition of the products was shown to be controllable by adjusting the stoichiometry of the input materials (Al/SiO 2 ratio). As the charged stoichiometry increases from 1 to 1.2, the Si content in the alloy significantly decreases from 73 to 63 wt %, while the Al content correspondingly increases from 9 to 18 wt %. Further investigation into processing parameters, such as charging method, slag prefusion, and stirring methods, has also revealed valuable insights toward the continued upscaling of the SisAl process to a potentially innovative, sustainable, low-carbon industrial process.

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Separation Time of Aluminothermic Reduction Products for Sustainable Silicon Production

Bullón,

Crego,

Ferrín

et al. 2024

Open Res Europe

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Background This work was carried out within the framework of the SisAl Pilot project, which is devoted to the environmentally friendly production of silicon. This new method relies on the aluminothermic reduction of quartz in slag, offering a more sustainable alternative to the traditional reduction of silica with carbon in submerged arc furnaces. Methods The process takes place in a rotary kiln producing silicon (Si) and alumina slag (actually, a CaO – Al2O3 slag), which must be separated at the end to extract the silicon. This separation process is analyzed through mathematical modelling and numerical simulation, as it is of industrial interest to know how much time it takes for Si and CaO – Al2O3 slag to separate once the process has ended. Generally, a multiphase flow model is used to estimate the separation time of the two components once aluminothermic reduction has ended. Results Several scenarios are considered for the numerical simulation of the separation time, namely different initial configurations and material properties of both fluids are covered. Moreover, the separation times obtained with two distinct multiphase flow models -VOF (volume of fluid) and Eulerian- are compared. Conclusions The separation times resulting from simulations using the multiphase Eulerian model are more realistic compared to those from the VOF model, which clearly tends to underestimate separation times. Furthermore, apart from the selected multiphase flow model, the density difference between silicon and alumina slag plays a critical role in determining the separation time.

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Preliminary Techno-Economic Considerations of the Sisal Process - Closing Materials Loops through Industrial Symbiosis

Cited by 5 publications

References 8 publications

Investigation of Liquid–Liquid Reaction Phenomena of Aluminum in Calcium Silicate Slag

Investigation of Liquid–Liquid Reaction Phenomena of Aluminum in Calcium Silicate Slag

Pilot-Scale Aluminothermic Production of Silicon Alloy and Alumina-Rich Slag

Separation Time of Aluminothermic Reduction Products for Sustainable Silicon Production

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