Dynamic modelling of BOF process : comparison of model performance with the plant data

In a top blowing steel making process (BOF), the refining reactions of C, Si, Mn and P are related to several physicochemical phenomena occurring in different zones (e.g. slag-metal emulsion, jet impact zone, slag-bulk metal zone) inside the converter. In earlier publications, the authors have demonstrated a dynamic model, based on the fundamental approach of multiple zone reaction kinetics to simulate the refining of elements (C, Si, Mn and P) in a top blowing steelmaking process (BOF).[1,2] After successful model validation with the literature data from a 200 ton converter[3], simulations have been carried out to assess the model performance with the plant data. Off-line heat data obtained from a 330 ton converter at Tata Steel, Netherlands was used for the model validation. The BOF shop in Tata Steel operates with a wide range of operating and process conditions such as (i) different scrap mix, (ii) dynamic flux addition strategy, (iii) dynamic change in lance position and (iv) top and bottom flow rate. The model predictions of hot metal impurities were validated with the two sub-lance measurements and the simulated slag compositions were compared with the end blow measurements. The possible effect of the uncertainties associated with the measured (or reported) input variables in industrial conditions on the accuracy of the model calculations has been investigated. Further, the role of dynamic change in lance height and flow rate on the slag formation and the hot metal refining has been studied. The present study identifies the critical input variables required for the accuracy in the prediction of the dynamic model in plant conditions and provides a fundamental understanding to control the dynamic process variables in a BOF operation

Dynamic model of basic oxygen steelmaking process based on multi-zone reaction kinetics : modelling of manganese removal

In the earlier work, a dynamic model for the BOF process based on the multi-zone reaction kinetics has been developed. In the preceding part, the mechanism of manganese transfer in three reactive zones of the converter has been analyzed. This study identifies that temperature at the slag-metal reaction interface plays a major role in the Mn reaction kinetics and thus a mathematical treatment to evaluate temperature at each reaction interface has been successfully employed in the rate calculation. The Mn removal rate obtained from different zones of the converter predicts that the first stage of the blow is dominated by the oxidation of Mn at the jet impact zone, albeit some additional Mn refining has been observed as a result of the oxidation of metal droplets in emulsion phase. The mathematical model predicts that the reversion of Mn from slag to metal primarily takes place at the metal droplet in the emulsion due to an excessive increase in slag-metal interface temperature during the middle stage of blowing. In the final stage of the blow, the competition between simultaneous reactions in jet impact and emulsion zone controls the direction of mass flow of manganese. Further, the model prediction shows that the Mn refining in the emulsion is a strong function of droplet diameter and the residence time. Smaller sized droplets approach equilibrium quickly and thus contribute to a significant Mn conversion between slag and metal compared to the larger sized ones. The overall model prediction for Mn in the hot metal has been found to be in good agreement with two sets of different size top blowing converter data reported in the literature

Dynamic model of basic oxygen steelmaking process based on multi-zone reaction kinetics : model derivation and validation

A multi-zone kinetic model coupled with a dynamic slag generation model was developed for the simulation of hot metal and slag composition during the BOF operation. The three reaction zones, (i) jet impact zone (ii) slag-bulk metal zone (iii) slag-metal-gas emulsion zone were considered for the calculation of overall refining kinetics. In the rate equations, the transient rate parameters were mathematically described as a function of process variables. A micro and macroscopic rate calculation methodology (micro-kinetics and macro-kinetics) were developed to estimate the total refining contributed by the recirculating metal droplets through the slag-metal emulsion zone. The micro-kinetics involves developing the rate equation for individual droplets in the emulsion. The mathematical models for the size distribution of initial droplets, kinetics of simultaneous refining of elements, the residence time in the emulsion, dynamic interfacial area change were established in the micro-kinetic model. In the macro-kinetics calculation, a droplet generation model was employed and the total amount of refining by emulsion was calculated by summing the refining from the entire population of returning droplets. A dynamic FetO generation model based on oxygen mass balance was developed and coupled with the multi-zone kinetic model. The effect of post combustion on the evolution of slag and metal composition was investigated. The model was applied to a 200-ton top blowing converter and the simulated value of metal and slag was found to be in good agreement with the measured data. The post-combustion ratio was found to be an important factor in controlling FetO content in the slag and the kinetics of Mn and P in a BOF process

Dynamic model of basic oxygen steelmaking process based on multi-zone reaction kinetics : modelling of decarburisation

In a previous study by the authors (Rout et al.[1]) a dynamic model for the BOF, employing the concept of multi-zone kinetics was developed. In the present work, the kinetics of decarburisation reaction is investigated. The jet impact and slag-metal emulsion zones were identified to be primary zones for carbon oxidation. The dynamic parameters in the rate equation of decarburisation such as residence time of metal drops in the emulsion, interfacial area evolution, initial size and the effect of surface active oxides have been included in the kinetic rate equation of the metal droplet. A modified mass transfer coefficient based on the ideal Langmuir adsorption equilibrium has been proposed to take into account the surface blockage effect of SiO2 and P2O5 in slag on the decarburization kinetics of a metal droplet in the emulsion. Further a size distribution function has been included in the rate equation to evaluate the effect of droplet size on reaction kinetics. The mathematical simulation indicates that decarburization of the droplet in the emulsion is a strong function of the initial size and residence time. A modified droplet generation rate proposed previously by the authors has been used to estimate the total decarburization rate by slag-metal emulsion. The model prediction shows that about 76 pct of total carbon is removed by reactions in the emulsion, and the remaining is removed by reactions at the jet impact zone. The predicted bath carbon by the model has been found to be in good agreement with the industrially measured data

Conceptual Design of a Novel CO₂ Capture Process Based on Precipitating Amino Acid Solvents

Amino acid salt based solvents can be used for CO₂ removal from flue gas in a conventional absorption–thermal desorption process. Recently, new process concepts have been developed based on the precipitation of the amino acid zwitterion species during the absorption of CO₂. In this work, a new concept is introduced which requires the precipitation of the pure amino acid species and the partial recycle of the remaining supernatant to the absorption column. This induces a shift in the pH of the rich solution treated in the stripper column that has substantial energy benefits during CO₂ desorption. To describe and evaluate this concept, this work provides the conceptual design of a new process (DECAB Plus) based on a 4 M aqueous solution of potassium taurate. The design is supported by experimental data such as amino acid speciation, vapor–liquid equilibria of CO₂ on potassium taurate solutions, and solid–liquid partition. The same conceptual design method has been used to evaluate a baseline case based on 5 M MEA. After thorough evaluation of the significant variables, the new DECAB Plus process can lower the specific reboiler energy for solvent regeneration by 35% compared to the MEA baseline. The specific reboiler energy is reduced from 3.7 GJ/tCO₂, which corresponds to the MEA baseline, to 2.4 GJ/tCO₂, which corresponds to the DECAB Plus process described in this work, excluding the low-grade energy required to redissolve the precipitates formed during absorption. Although this low-grade energy will eventually reduce the overall energy savings, the evaluation of DECAB Plus has indicated the potential of this concept for postcombustion CO₂ capture

Anti-mullerian hormone is a sensitive serum marker for gonadal function in women treated for Hodgkin's lymphoma during childhood

Purpose: The aim of this study was to evaluate the long-term effects of combination chemotherapy treatment for girls with Hodgkin's lymphoma ( HL) on gonadal function using anti-Mullerian hormone ( AMH) and inhibin B as ovarian reserve parameters. Patients and Methods: LH, FSH, inhibin B, and AMH were measured in 32 women treated from 1974 to 1998 for pediatric HL with chemotherapy, with the intention to avoid radiotherapy. All patients [ median age 25.0 yr ( range 19.2-40.4 yr)] were in complete remission with a median follow-up time of 14.0 yr ( range 5.7-24.5 yr) after therapy. All patients were treated with combination chemotherapy doxorubicin, bleomycin, vinblastine and dacarbazine ( ABVD) or EBVD with or without mechlorethamine, vincristine, procarbazine, and prednisone ( MOPP). Because of incomplete remission or relapse, involved field radiotherapy was needed in seven of 32 women. Results were compared with a healthy control group. Results: Patients treated with six or more cycles of MOPP combination chemotherapy had significantly higher levels of FSH and lower serum levels of inhibin B and AMH, compared with healthy women [ FSH, 17.0 vs. 6.0 U/liter ( P <0.05); inhibin B, 23.0 vs. 112.5 ng/ liter ( P <0.01); AMH, 0.39 vs. 2.10 mu g/ liter ( P <0.01)]. AMH was also significantly lower, compared with women treated without MOPP ( median 0.39 vs. 1.40 mu g/ liter; P = 0.01). Conclusions: Women treated during childhood for HL with MOPP seem to have a distinctly lower ovarian reserve as measured by lower AMH values at early adulthood, compared with healthy women. Moreover, AMH seems to be the only predictor that is sufficiently sensitive to detect this decrease in ovarian reserv