Reaction mechanisms of natural gas in the HIsarna alternative ironmaking process

To tackle climate change, caused by increasing levels of greenhouse gases in the atmosphere, legislation to curb CO2 emissions have become more stringent. The steel industry is responsible for 6.5% of anthropogenic CO2 emissions. Consequently, the steel industry has been endeavouring to develop green steel production technologies with HIsarna being one of the promising alternative ironmaking technologies. HIsarna technology offers the flexibility to use reductants other than solid carbon materials. Natural gas has the potential to be used either partially or fully as an alternative to solid carbon materials in the ironmaking process. Its major component, methane, contains two reductants: elemental carbon (Carbon Black) and hydrogen. The by-product of using hydrogen in the ironmaking process is steam, resulting in reduced CO2 emissions from the overall process. This PhD research studies the reaction mechanisms of methane in the smelting reduction vessel (SRV) based on five main objectives with the aim to provide the fundamental knowledge needed to (partially) replace coal with natural gas in the HIsarna process. A static heat and mass balance model was developed for the HIsarna process to predict CO2 emissions and coal consumption. The results were validated against pilot plant data. The model was used to predict the CO2 emissions for two cases: (1) methane used as a carrier gas of coal (2) methane fully replacing coal. The research also investigated the gasification reactivity of carbon black (CB) along with its chemical-physical properties, which could potentially effect its reactivity. The reduction behaviour of the individual reductants, carbon and hydrogen, with molten HIsarna slag in conditions similar to the smelting reduction vessel (SRV) was examined. Finally, the reaction mechanism between methane and the HIsarna slag was investigated. This research has been conducted systematically and provides a fundamental understanding of the methane gas reduction behaviour in HIsarna thermal conditions

Gasification and physical-chemical characteristics of carbonaceous materials in relation to HIsarna ironmaking process

HIsarna ironmaking process is one of the emerging technologies being developed to mitigate the increasing carbon footprint from the steel making industry. This innovative process offers flexibility with the type of reductants used in the smelting reduction vessel for the conversion of iron ore to liquid hot metal. Natural gas is well known for being a relatively clean fossil fuel producing carbon black and hydrogen when it undergoes thermal decomposition. The gasification reactivity of carbon black compared to the carbonaceous materials used in HIsarna process is investigated in this work using isothermal gravimetric analysis (TGA) method at 1250˚C, 1350˚C and 1450˚C under atmospheric pressure. Furthermore, physical-chemical characteristics of the individual carbonaceous materials, which may influence the reactivity, are evaluated systematically. The experimental results show that carbon black is the least reactive followed by thermal coal and charcoal. It was found that the effect of the morphology of the carbonaceous materials on the reactivity is dominant compared to the surface area of the materials. In addition, the reactivity increases with the alkali index (AI) and the level of the amorphousness of the material’s structure. Three well-known kinetic models, i.e. the volumetric model (VM), the grain model (GM) and the random pore model (RPM) were applied to predict the gasification behaviour of the three carbonaceous materials. The random pore model best describes the gasification reaction of the selected samples due to the influence of the pore diffusion on the reaction. It is observed that the activation energy of the samples are not following the order of reactivity, this can be explained by the kinetic compensation effect

Enhancing Security with the Combination of DCT & 3DES

Information security is becoming more importantin data storage and transmission. Because of widelyused images in security process, it is the importantconfidential image data from unauthorized access.The original image was converted by using twodimensional transform and encryption 3DES withtwo keys. This system presented a transformationalgorithm based on the image cosine transformationand a well known encryption and decryptionalgorithm called 3DES. This paper also analyzed theimage encryption algorithms DCT and 3DES. Theoriginal image is encrypted after the transformationprocess. In this approach to reduce the computationalrequirements for huge volume of images andresulting high speed transformation and encryptionsystem

HIsarna process simulation model : using FactSage with macro facility

The HIsarna process is one of the emerging technologies for reducing the carbon footprint of the ironmaking process, which is currently in the pilot plant stage. A kinetic HIsarna process simulation model based on the effective equilibrium reaction zone concept has been developed using the FactSage macro programming facility to advance understanding of the whole process. In the model, the HIsarna process is conceptually divided into various equilibrium zones involving combustion, coal pyrolysis and gasification, gas/slag/carbon reactions, and slag/metal reaction. The model has been validated through the pilot plant data, and the results are in good agreement with the quantity and composition of hot metal, slag, and gas. The HIsarna off-gas stream with high CO2 content can potentially allow capture and storage directly for carbon mitigation. The utilization of titanium magnetite ore in the HIsarna process has also been investigated via the developed model. The injection of titanium magnetite ore which has high FeO content decreases coal consumption. Still, it increases the slag volume as higher gangue content when keeping the same productivity as the pilot plant trial. The HIsarna process shows promising potential in using low-quality high titania iron ore as feed materials, but the slag system needs to be further optimized. From the heat distribution, the off-gas sensible heat accounts for a large part of the input heat due to its high temperature but can be recovered with good efficiency. The present model is an efficient tool for understanding the HIsarna process and providing theoretical guidance for future pilot research

Kinetic study on reduction of FeO in a molten HIsarna slag by various solid carbon sources

To investigate the reduction behaviour of different reductants such as charcoal (CC), thermal coal (TC), and carbon black (CB) with HIsarna slag, a series of isothermal reduction experiments were performed in a vertical tube resistance furnace (VTF), coupled with a Quadrupole mass spectrometer (QMS) at 1450, 1475 and 1500 ˚C. The results confirm that the highest overall reduction rate was achieved by CC, followed by TC and CB. The reduction mechanism between FeO containing molten slag and the selected carbonaceous materials is determined by studying the morphology of the water quenched samples at the intervals of 1.5, 3 and 5 minutes, using optical and scanning electron microscopes. The results reveal that the overall reaction is controlled by two main mechanisms: (1) nucleation and growth of CO bubbles, proceeded by the gaseous intermediates CO and CO2; and (2) diffusion of FeO in the molten slag. The initial reduction period in which chemical reaction control is dominant, can be described by the Avrami-Erofeev model, whereas the final period is described by the three-dimensional diffusion model

Gasification and structural behaviour of different carbon sources and resultant chars from rapid devolatilization for HIsarna alternative ironmaking process

To evaluate the potential of using renewable biomass in the novel HIsarna technology, reactivity of thermal coal (TC), charcoal (CC), Bana grass char (BGC) before and after rapid devolatilization at 1500 °C in a drop tube furnace (DTF) was investigated. Thermogravimetric (TG) was used for CO2 gasification study, and high temperature confocal scanning laser microscope (HT-CSLM), Brunauer-Emmett-Teller (BET) and scanning electron microscopy (SEM) were used to characterise the morphology of all three raw carbonaceous materials and their chars produced by rapid devolatilization. CC has fastest gasification reaction before and after rapid heat treatment, and BGC raw is more reactive than TC raw but BGC 1500 °C and TC 1500 °C have very similar gasification behaviour. The reactivity index of the rapidly devolatilized char is reduced to 84.21% (BGC), 92.11% (TC) and 94.23% (CC) compared to their raw materials. This shows that BGC is more severely affected by the rapid devolatilization, and this behaviour is likely to be governed by the high ash content which will melt and cause pore blockage during heat treatment. According to HT-CSLM results the average particle sizes decreased by 28%, 24% and 20 % for TC, CC and BGC respectively. While the SEM images shown that TC has gone through significant structural changes during the rapid devolatilization, but CC and BGC maintained their parent structural shapes. The BET results indicate that TC is non-porous, but both CC and BGC contain a large number of constricted micropores with significantly larger surface area

Study on hydrogen smelting reduction behaviour in synthetic molten HIsarna slag

The reduction behaviour of hydrogen with FeO in synthetic molten HIsarna slag has been investigated using two experimental methods: (1) Blowing 5% or 10% H2-Ar onto the molten slag at 1450, 1475, 1550 ˚C respectively; and (2) Injecting 10% H2-Ar into the molten slag at the flowrates of 0.5, 1.0, 1.5 L/min. In the case of blowing the gas onto the melt, the reaction is controlled by gas phase diffusion in the initial stage and then liquid phase diffusion becomes dominant. The reaction rate is significantly improved by injecting the gas into the molten slag; bubbles are generated during the gas injection resulting in ample surface area between the gas and liquid slag. The overall reduction is controlled by the liquid phase mass transfer of FeO in the injection case; described by the penetration theory. Furthermore, an increased number of bubbles are generated with increasing flow rate, which in turn increases the reaction rate in the case of hydrogen injection

Assessment of the Association of Vitamin D and the Risk of Tuberculosis among End-Stage Kidney Disease Population

We investigated the role of vitamin D in the risk of tuberculosis (TB) among patients with end-stage kidney disease (ESKD). The retrospective cohort was conducted with data of 20,985 patients with kidney disease and 20,985 controls without kidney disease (1:1 matching on age of cohort entry and sex) in the duration of 1997–2010 from the Taiwan National Health insurance database. Then, by a case–cohort study, among 20,985 kidney disease, 3194 ESKD patients were identified with matched 3194 non-ESKD patients. Multivariate analyses revealed a significant association between kidney disease and tuberculosis (adjusted incidence rate ratio (IRR) 1.57 (1.33–1.86)), and the risk increased after 3 years of follow-up the (adjusted IRR 3.79 (2.55–5.62)), but after more years of follow-up no significance was observed. We also found that ESKD increases the risk of tuberculosis (adjusted IRR 3.67 (2.27–5.93)). However, vitamin D usage was not related with the tuberculosis risk in ESKD patients (p > 0.1783). Our study showed increased risk of tuberculosis in kidney disease and ESKD patients, and vitamin D was not beneficial in ESKD

Herpes Zoster Risk in Patients with Rheumatoid Arthritis and Its Association with Medications Used

Rheumatoid arthritis (RA) was associated with the risk of incident herpes zoster (HZ), which might be influenced by medication use by RA patients. We aimed to investigate the association of RA with the risk of incident HZ and how the HZ risk effected by RA medications in CIC RA patients. We conducted an observational study including population-based representative insurance claims data of 19,673 patients with RA and 39,346 matched patients without RA during 1997–2010 from the Taiwan National Health Insurance Research Database; we identified 1651 patients with catastrophic illness-certified (CIC) RA and 11,557 matched patients with non-CIC RA. Exploratory analyses assessed the association between RA/CIC RA and risk of incident HZ and its complications. The association of prescribed medications with HZ risk in CIC RA patients was also estimated. The incidence rates of HZ were higher in CIC RA patients and non-CIC RA than in the matched people without RA (21.95 and 14.03 vs. 7.36 events per 1000 person-years, respectively). The adjusted incidence rate ratio (95% confidence interval (CI)) for HZ was 1.74 (1.65–1.84) in RA patients vs. matched non-RA and 1.65 (1.44–1.89) in CIC RA patients vs. non-CIC RA. For HZ complications, RA had a 2.85-fold higher risk than non-RA, and CIC RA had a 1.78-fold higher risk than non-CIC RA. Moreover, in CIC RA patients, prednisolone use was associated with incident HZ risk compared with prednisolone nonuse (adjusted odds ratio 1.48, 1.08–2.03); prolonged prednisolone use (approximately 5 years) increased the risk (adjusted odds ratio 2.16, 1.46–3.19). Our results suggested that RA was positively associated with HZ risk, particularly in RA patients with prednisolone use