Model optimizacije uporabe bele žlindre pri nizkoogljičnih jeklih

Banovšek, Jure (author), Knap, Matjaž (mentor), Drofelnik, Nejc (co-mentor)

Čistost jeklene taline zahteva natančno kontrolo procesnih parametrov in poznavanje reakcij v agregatih sekundarne metalurgije. Interakcije med talino in žlindro skušamo predstaviti z uporabo teoretičnih ali empiričnih numeričnih modelov. V magistrskem delu sem analiziral nekaj obstoječih numeričnih modelov za določevanje sulfidne kapacitete in viskoznosti žlindre. Za izračun sulfidne kapacitete so predstavljeni model Sosinsky & Sommerville, Youngov in Taniguchijev model ter model KTH. Viskoznost žlindre pa sem izračunal z uporabo modelov NPL, Iidovega, Urbainovega in Razširjenega Urbainovega modela. Izbranih je bilo 32 vzorcev žlindre sistema CaO-Al2O3-SiO2-MgO. Vzorci so bili razdeljeni v dve skupini, A skupino, s 5 mas. % MgO in skupino B, z 10 mas. % MgO. Za izbrane vzorce so bili z omenjenimi modeli opravljeni izračuni sulfidne kapacitete in viskoznosti pri različnih temperaturah. Rezultate sulfidne kapacitete smo uporabili tudi za določevanje porazdelitvenega razmerja žvepla med žlindro in talino. Za določitev slednjega smo potrebovali vrednosti ravnotežne aktivnosti kisika, ki smo jih izračunali z uporabo modela Ohta & Suito ter upoštevanjem spremembe Gibbsove proste energije pri reakciji dezoksidacije med aluminijem in kisikom. V rezultatih je za posamezen model predstavljen vpliv sestave žlindre. S pomočjo izračunov je podrobneje analiziran vpliv posamezne komponente in primerjava med skupinama vzorcev žlindre A in B. Na podlagi izračunov pri 1400 °C, 1450 °C, 1500 °C, 1550 °C in 1600 °C je bila ugotovljena temperaturna odvisnost preiskovanih veličin. Izračune numeričnih modelov sem medsebojno primerjal, njihove vrednosti pa smiselno ovrednotil.

• Language: Slovenian
• Keywords: numerični modeli, sulfidna kapaciteta, porazdelitveno razmerje žvepla, viskoznost, žlindra
• Work type: Master's thesis/paper
• Organization: NTF - Faculty of Natural Sciences and Engineering
• Year: 2020
• PID: 20.500.12556/RUL-121884
• COBISS.SI-ID: 41524483
• Publication date in RUL: 05.11.2020

Secondary language

• Language: English
• Title: Model for optimizing white slag usage in low-carbon steel

Abstract

The cleanliness of steel melt requires careful control of process parameters and chemical reactions during the operation of ladle furnace. With the help of theoretical or empirical numerical models, we perform calculations based on which we can more accurately assume the interactions between melt and slag. In the present thesis work, I analyzed the existing numerical models to determine sulfide capacity and viscosity of slags. I presented the Sosinsky & Sommerville, Young, Taniguchi, and KTH model along with the NPL, Iida, Urbain, and Extended Urbain model. For experimental studies, I selected 32 slag samples of the CaO-Al2O3-SiO2-MgO system. The samples were divided into two groups, group A with 5 weight % MgO and group B with 10 weight % MgO. Using the aforementioned models, I performed sulfide capacity and viscosity calculations at different temperatures. I further used the results of sulfide capacity in determining the sulfur distribution ratio between slag and melt. To determine the latter, I calculated the equilibrium values of oxygen activity using the Ohta & Suito model and taken into account the change of Gibbs free energy in the deoxidation reaction between aluminum and oxygen. In the results, I presented the influence of slag composition for each model. With the help of calculations, I analyzed the influence of each slag component in more detail. Furthermore, I inspected the comparison between the A and B groups of samples. Based on calculations at 1400 °C, 1450 °C, 1500 °C, 1550 °C in 1600 °C, I determined the temperature dependence of the investigated quantities. Finally, I compared the calculation results between the models and evaluated their values.

• Keywords: numerical models, sulfide capacity, sulfur distribution ratio, viscosity, slag