The effects of post combustion and post combustion gases in the electric arc furnace.

摘要

In order to decrease energy consumption and increase scrap melting and productivity, post combustion (PC) technology is being implemented in several steelmaking processes, including bath smelting, the BOF and the EAF. In order to get the full benefit from this technology, the principles that govern it and the effects, both beneficial and adverse, must be determined. To this end, the CISR has been investigating two PC processes in the. EAF, the foamy slag approach and free space approach and the oxidation of scrap by post combustion gases. The free space approach, which is the subject of this work, consists of injectors blowing PC oxygen into the upper portion of the furnace. Air Liquide is developing an example of this system. Post Combustion consists of two sets of reactions: (1) the combustion of CO with oxygen and (2) the oxidation of scrap, liquid iron and C by the CO₂ (the “de-post combustion” reactions). This project consists of two parts investigating both types of reactions. A computer simulation of a free space PC system is being developed and the kinetics of the oxidation of solid iron by CO ₂ are being measured at high temperatures.; Initial work included computer simulations of the process assuming a two-dimension geometry. These two dimension models were beneficial in gaining experience with the computer software package and provided some insights into the PC process. However, they could not adequately describe the conditions in the furnace. Therefore, a three-dimension model has been developed. Computer simulations including the post combustion reaction of CO and O₂ combining to form CO₂ and the de-post combustion reaction between CO₂ and the carbon present in the bath have been conducted. It was found that the post combustion ratio (PCR) increased with increasing exhaust temperatures and with an increase in oxygen flow rate. Also, when the oxygen was injected at a lower flow rate with an angle, bands of temperature and composition results with the highest temperatures, and the highest concentration of CO₂, occurred in a band near the injector. Finally, the temperatures near the bath surface increased as the injectors were placed closer to the bath surface. Where as the present model had several limitations and did not take into account all major factors, it did give useful insights and showed that this type of modeling is beneficial.; The oxidation rate of solid iron by CO₂, was measured using thermo-gravinometric analysis in conjunction with the impinging jet design to reduce the effects of gas phase mass transfer. Experiments were conducted in the temperature range of 1000–1500°C with a reacting gas mixture ranging from 50% CO₂–80% CO₂ (remainder CO) and a dilute mixture of 800%Ar, 10% CO₂ and 10% CO. The calculated kinetic rate constants were consistent with those found by previous researchers at lower temperatures. The calculated activation energy of 39.7 kcal/mole is in reasonable agreement with the published quantity of 44.3 kcal/mole, calculated by Grabke. The technique used in the present study allowed for a more accurate determination of the chemical rate at high temperatures.