Desenvolvimento do sensor baseado em eletrólito sólido de β-alumina para monitoramento de enxofre na indústria siderúrgica
Abstract
Electrochemical sensors provide real time information of chemical
compositions of molten metal. They can be used to improve the control of
various metallurgical processes. One of the most successful and widely used
electrochemical sensors is the oxygen sensor, based on zircônia solid
electrolyte, usually used in steel making. Sensors are being developed for
measurement of other chemical elements, but it is very costly and complicated
to be produced. In order to solve this problem, in this work synthesis and
assembly of β-alumina and β-alumina based on solid electrolyte sensors
were studied. For this, the phase of interest was prepared by the mixing of
oxides, and characterized. Traditional ceramic forming processes, isostatic and
slip casting, were used to produce the prototypes and their ceramic
characteristics were evaluated. Both compositions did not present high density
after sintering at 1600°C, reaching 90% theoretical density. This fact could be
responsible for the break down during the application of the sensors. The Na-β-
alumina sensor produced did not present a satisfactory performance for
measuring the dissolved sulphur in liquid pig iron. On the other hand, the β-alumina sensor, despite of the secondary phase, showed good behavior in
terms of response time (between 5 and 8 seconds) for measuring the dissolved
sulphur in liquid pig iron at temperatures from 1440°C to 1460°C, with
La2O2SO4 auxiliary electrode and three different reference electrodes. The
signal response of EMF between 54 mV and 174 mV was measured in a
measuring level from 32 ppm (weight) to 432 ppm (weight) of sulphur dissolved
on the metal bath