Banca de QUALIFICAÇÃO: BÁRBARA DA SILVA ROCHA

Uma banca de QUALIFICAÇÃO de MESTRADO foi cadastrada pelo programa.
STUDENT : BÁRBARA DA SILVA ROCHA
DATE: 15/02/2022
TIME: 08:00
LOCAL: Virtual
TITLE:

Thermodynamic study of the gas-solid reduction of niobium oxides.

KEY WORDS:

chemical equilibrium, thermodynamics, niobium, methane, carbon monoxide.

PAGES: 74
BIG AREA: Engenharias
AREA: Engenharia Química
SUMMARY:

The majoritive of niobium reserves worldwide are located in Brazil. This metal’s excellent physical and mechanical properties make it attractive to the industry. Niobium is commonly obtained through carbothermic and metalothermic reduction. This work aimed to understand the thermodynamics behind niobium oxides reduction by gaseous reducing agents, such as methane and carbon monoxide. The equilibrium constants of the independent representative reactions of each system were calculated and the temperatures at which the reactions are more feasible were selected. Equilibrium composition was calculated by the Gibbs energy minimization method in Microsoft Excel spreadsheets using the Solver supplement. Taking NbO as the solid reactant, the reduction by pure CH 4 as well as by a gas mixture of CH 4/ H 2 with compositions of 62.5%, 12.5% and 12.5% of methane was investigated. The effect of the initial number of moles of the solid was also studied. The results showed that CO is not a feasible choice for niobium oxides reduction. Reactions with CH 4 tend to form carbide, but at lower compositions and at high temperatures (above 2000 K) it was possible to form metallic niobium. Increasing the initial number of moles of NbO to 1.2 moles yield a complete conversion at 2.5% composition and 2150 K. Applying these optimal conditions in the reduction of NbO 2 by CH 4 lead to a complete conversion to NbO at 2100 K. Under any conditions, methane is capable of reducing Nb 2 O 5 to NbO 2 . Thus, from a thermodynamic point of view, methane was shown to be a promising reducing agent for niobium oxides.

BANKING MEMBERS:
Presidente - 349801 - CARLSON PEREIRA DE SOUZA
Interno - 2929066 - ANDRE LUIS LOPES MORIYAMA
Externo ao Programa - 345842 - UILAME UMBELINO GOMES
Externa à Instituição - MARIA JOSÉ SANTOS LIMA - UFRN