Decarburization Kinetics of Fe–C Melt with CO₂–O₂ Mixed Gas by Isotope Tracing Method

Abstract

The partial substitution of O 2 with CO 2 in steelmaking process is an important technology to reduce CO 2 emission and recycle. In order to improve CO 2 -O 2 decarburization utilization, the decarburization kinetics of Fe-C melt with CO 2 -O 2 mixed gas have been studied using 13 CO 2 -18 O 2 dual isotope tracing method and established the decarburization kinetic model. The results show that less than 40% of the oxygen is partially replaced by CO 2 , which improves the O 2 utilization involved in the decarburization reaction and the CO 2 utilization is still more than 80%. For the rate limiting steps, regarding O 2 , it is governed by the mixed control mechanism involving gas-phase mass transfer and interfacial chemical reaction; regarding CO 2 , with the increase of CO 2 partial pressure, the rate limiting step changes from the mixed control to gas-phase mass transfer control only. As bath temperature increase from 1723 to 1873 K, the overall decarburization rate increases; bath temperature mainly affects O 2 decarburization rates, whereas, the rates of CO 2 are not significantly affected. The apparent activation energy of CO 2 -O 2 mixed gas decarburization is 21.5 kJ•mol -1 .

Decarburization Reactions of CO₂–O₂ Mixed Gas in the Impact Zone of the Cavity for Converter by Dual Isotope Tracing Method

“…13 CO 2 -18 O 2 Dual Isotope Tracing Mechanism Using 13 CO 2 -18 O 2 dual isotope gases, the mixed gas complex reactions can be distinguished clearly in the impact zone of the cavity: I. Reactions between mixed gas and carbon on the molten surface Based on the previous work, 10) it was assumed that Q x1 , Q x2 and Q x3 (mL•min − 1 ) were the flowrates of uninvolved reaction, CO 2 formed by carbon and oxygen, and CO 2 from post combustion; Q y1 , Q y2 , Q y3 and Q y4 (mL•min − 1 ) were the O 2 consumption to form CO 2 , the O 2 consumption to form CO, the O 2 consumption to post combustion, and the O 2 uninvolved reaction; Q z1 , Q z2 and Q z3 (mL•min − 1 ) were the CO product from O 2 , the CO product from CO 2 , and the CO consumption to post combustion, respectively; Q α and Q β were the inlet gas flowrates of CO 2 and O 2 ; Q total was the overall flowrates at outlet. As for the ion currents monitored by mass spectrometer, I 28 , I 29 and I 30 were ion currents of 12…”

“…In our previous works, [8][9][10] using 13 CO 2 -18 O 2 dual isotope gases, the mixed gas complex reactions can be distinguished clearly in gas-liquid reaction interface. On the basis, the change of gas concentration in the cavity was studied by changing the injection height, and the influence of post combustion on decarburization process was also analyzed.…”

Oxygen Distribution at the Hot Spot in BOF Steelmaking

“…Carbon monoxide does not appear as reactant in the considered chemical reactions seen in Eqs. [1] to [4].…”

“…The reaction-controlled mechanism was disregarded as it was found that hot spot temperatures can exceed well over 2000 °C [11] and even at lower temperatures, these phenomena play a subservient role. [1] The total species transport to the hot spot is proportional to the area of the cavity (calculated using the model of Koria [12] ), and the specific species transport through the gaseous boundary layer (using Eq. [5]).…”

“…For high carbon contents, a literature study suggests that the rate of decarburization would prove limiting by gaseous mass transfer. [1] All models describing emulsion refining depend on assumptions regarding the FeO generation rate. The carbon-refining efficiency estimations of the emulsion are also based on these FeO-generation rates, and various proposed models have used 100 pct oxygen utilization on the hot spot.…”