Dr Priscilla Tremain

A novel slag carbon arrestor process (SCAP) was proposed to improve the heat recovery in energy-intensive steelmaking process, which typically has a low heat recovery. The proposed SCAP process introduces a tar reformer to utilise the slag - a by-product from steelmaking process - as the catalyst to convert coke oven gas and tar into hydrogen-enriched fuel gas. This is achieved by making use of the valuable carbon and/or energy contained in the coke oven gas, which otherwise being wasted, to assist in tar reforming and produce hydrogen-enriched gas. Such concept is expected to reduce the undesired tar formation in steelmaking process along with improved heat recovery efficiency and higher quality coke oven gas production. Both simulation and experimental studies on the slag carbon arrestor process were performed. The preliminary thermodynamic analysis carried out using Aspen Plus v8.4 indicates that with the tar reformer the energy content of coke oven gas was found increased from ~ 34.6 MJ/kg to ~ 37.7 MJ/kg (or by 9%). Also, with the utilisation of carbon deposition on the slag, a reduction of up to 12.8% coke usage in the steelmaking process can be achieved. This corresponds to an energy saving of 4% and a carbon emission reduction of 5.7% compared with the conventional steelmaking process. Preliminary experimental TGA-FTIR investigations revealed a reduction in the aromatic and aliphatic hydrocarbon groups and an increase in the production of CO2 and CO, attributed to the tar cracking abilities of slag.

The current work focuses on the development of a novel calcium-looping-based biomass-integrated gasification combined cycle (CL-BIGCC) process. The process is expected to improve the energy density of synthesis gas by capturing CO2 in a carbonator. Also, at the same time, the carbonator is expected to act as an ex situ tar removal unit, where tar cracking is expected to occur via catalytic reactions with CaO. The current work evaluates the feasibility of the proposed CL-BIGCC concept via thermodynamic analysis using Aspen Plus. Moreover, the tar cracking ability of CaO is demonstrated using thermogravimetric analyzer coupled to Fourier transform infrared spectrometer (TGA-FTIR) experiments. As part of the thermodynamic analysis, sensitivity analyses of the key process parameters, such as the calcium/biomass (Ca/B) ratio, steam/biomass (S/B) ratio, carbonator temperature, and calciner temperature, and their effects on net thermal-to-electricity efficiency have been studied in detail. The optimal values of key process parameters, such as a compression ratio of 5.1, an air/fuel mass ratio of 15, a Ca/B ratio of 0.53, a S/B ratio of 0.17, and carbonator and calciner temperatures of 650 and 800 °C, respectively, have been obtained. Furthermore, the CL-BIGCC process simulated in the current work was found to have a net thermal-to-electricity efficiency of ~25% based on the above optimal parameters, which is the highest among other conventional steam-based BIGCC processes. The biomass gasification (i.e., partial oxidation) experiments in a TGA-FTIR with a CaO/biomass ratio of 1:1 at different temperatures showed that CaO effectively catalyzed tar-cracking reactions.

Two Australian thermal coals were treated with four different ionic liquids (ILs) at temperatures as low as 100 °C. The ILs used were 1-butylpyridinium chloride ([Bpyd][Cl]), 1-ethyl-3-methylimidazolium dicyanamide ([Emim][DCM]), 1-butyl-3-methylimidazolium chloride ([Bmim][Cl]), and 1-butyl-3-methylimidazolium tricyanomethanide ([Bmim][TCM]). Visual comparisons were made between the raw and IL-treated coals via optical microscopy. Changes in thermal behavior of these treated coals were compared against raw coals via pyrolysis experiments in a thermogravimetric analyzer (TGA). Changes in functional group composition in the treated coals were probed via Fourier transform infrared (FTIR) spectroscopy. The recovered ILs were also analyzed via FTIR and nuclear magnetic resonance (NMR) spectroscopies to observe any changes after recovery. Low-temperature IL treatment of each of the coals resulted in fragmentation and fracturing, reducing the average particle size. An increase in mass loss in the treated coals was also observed when compared to each raw coal, indicating an increase in lower molecular weight fragments after treatment. This was corroborated by a large increase in aliphatic hydrocarbons being observed in the treated coals, along with a decrease in oxygenated functional groups and mineral matter in one coal. The recovered ILs were shown to be unchanged by this treatment process, indicating their potential recyclability. These results indicate the potential for ILs to be implemented as solvent treatments for coal conversion processes.