A solid electrolyte oxygen sensor for steelmaking slags of the basic oxygen converter
- PDF / 1,177,172 Bytes
- 7 Pages / 583.28 x 777.28 pts Page_size
- 42 Downloads / 210 Views
.
of the solid electrolyte with CaO-SiO2-Fe203-FeO slag was examined in detail, and then, the oxygen sensor of quick response with a stable electromotive force was developed in laboratory scale experiments. Subsequently, the sensor was used to measure the oxygen pressure in 100,000 kg LD converter slag at the end of the blowing. The sensor dipped in the slag would give the local oxygen pressure in the slag fixed by the following reaction. 2FeO(in slag) + 1/2 O2(in slag) = FeO203 (in slag)
[ 1]
Thus, the ratio of ferric to ferrous concentration in the slag can be estimated as long as temperature and basicity are constant. Larson and Chipman, 6 and Timucin and Morris 7 measured the amounts of ferric and ferrous oxides in CaO-SiO2-Fe203-FeO slags, and derived relationships between concentrations, oxygen pressure and basicity. Mori s measured the contents of ferric and ferrous oxide in various slags under a fixed oxygen pressure to propose a new scale of slag basicity. In the present work, a simple empirical relation between the ratio of ferric to the total iron ion content and the electromotive force will be derived for the quick estimation of the ratio in the slags of industrial furnaces. II. E X P E R I M E N T A L II. 1 Cell Equations The cell equation for the oxygen sensor is expressed as M, MO/ZrO2-CaO or - M g O / F e 2+, Fe 3+ (in slag) [21 The electromotive force, E, of the cell is given as RT Po2(in slag) E = 4 F - I n Po2(M,_ MO)
[3]
where, R is gas constant, F is Faraday constant, and T
ISSN 0360-2141 /80/0911-0463500.75/0 METALLURGICAL TRANSACTIONS B 9 1980 AMERICAN SOCIETY FOR METALS AND THE METALLURGICAL SOCIETY OF AIME
VOLUME 11B, SEPTEMBER 1980--463
is the absolute temperature. The left electrode in Eq. [2] was composed either of molybdenum and its dioxide or of chromium and its sesquioxide. The oxygen pressure of the reference electrode at the experimental temperature is given by the following equations.* * These data are taken here, because they gave accurate oxygen potentials in molten steel from the EMF measurements in Refs. 9 and I0.
R T In Po2(Mo, MOO2) = -509,980 + 129.8T J/mol
[4] R T In Po2(Cr, CrzO3) = -755,200 + 171.2T J/mol
[5] II.2 Cell Construction and Procedures in Laboratory Experiments The construction and experimental setup are shown in Fig. 1. The solid electrolyte is made of either ZrO 2-11 mol pct CaO or ZRO2-9 tool pct MgO, and 8 mm~ OD • 5 mm~ ID • 100 mm in size. Nominal compositions of the tubes are shown in Table I together with apparent density and porosity. Inside, the tube contains a platinum wire and is filled with a mixture of molybdenum and its dioxide powders, which serves as the reference electrode. APt- 13 pct Rh wire is welded on the platinum wire to acfas a thermocouple. In some cases, the outside wall of the bottom part is coated with a very thin film of platinum by chemical deposition from
* About 50 to 70 mg of crushed sample was dissolved into HC1 aqueous solution under CO2 gas atmosphere. When some amount of residue was found, it could be dissolved
Data Loading...
