Search

Graphical Abstract:

With an aim to utilize the local-based waste materials, this research investigated the production of mill scale - biomass pellet (MBP) as an alternative charged material for EAF steelmaking. Rubber tree bark (RTB) is one of the major biomasses in Thailand, consisting of carbon and hydrogen as the main compositions. The carbon derived from RTB was mixed with coal into five different ratios. Pure coal and RTB were employed for comparison. Seven carbonaceous samples were blended with mill scale at a C/O molar ratio of 1:1 to produce MBP, namely Coal, blend#1 – blend#5 and RTB. The reduction of MBP was investigated in a horizontal tube furnace under argon atmosphere at 1550°C for 15 and 30 minutes. The obtained products were iron droplets and residual black powder of unreacted oxides. Quantities of reduced iron from the MBP of blend#1 – blend#5 was about 58 – 61 wt% after 30 minutes, while it was 62 wt% and 57 wt% for coal and RTB, respectively. Degree of metallization (DOM) for blend#1 – blend#5 was between 78.1 – 81.7%, while it was 82.7% and 83.3% for coal and RTB. This research offers the possible method to utilize mill scale and RTB biomass toward circular economy.

Ferrosilicon alloy has been commercially produced in an electric furnace at 1700 - 1750 °C, using quartz as a silica source. With an aim to reduce production cost, rice husk ash (RHA) had been introduced to the process as a silica source. The present study reports an in-depth investigation on the ferrosilicon alloy formation at 1550 °C via carbothermic reduction using RHA with coal and graphite. Blend A: RHA/Fe2O3/Coal and B: RHA/Fe2O3/Graphite were prepared according to the C/O molar ratio of 1/1. The well-mixed samples were compacted into a pellet and then heated at 1550 °C in the tube furnace for 30 and 60 minutes while the argon flowing at the rate of 1 L/min. XRD and SEM results show that the bulk metal mainly composes of FeSi phase, while SiC and other slag phases adhere at the surface of the droplet. Characteristics of the carbonaceous materials, especially ash oxides content affect the kinetic of ferrosilicon formation. Silicon concentration in the produced metal droplets was measured using an ICP technique. For blend A, Si content in the metal was 18.3 wt% and 81.9 wt% after 30 and 60 minutes, respectively. While, Si recovery in the metal for blend B reached 88.4 wt% since 30 minutes. The experimental results show that the production of ferrosilicon alloy from RHA can be produced at 1550 °C, which the temperature lower than that of the commercial method by 150-200 °C. The finding in this research is beneficial for ferrosilicon and agricultural industries and thus promotes the sustainable steelmaking industry.

Aluminium dross is a waste from aluminium melting process, containing approximately 70 wt% of Al2O3. Disposal of dross in landfill causes soil and ground water pollutions, leading to the difficulty of waste management. This work aims to utilize aluminium dross as a source of Al2O3 for the synthesis of hercynite (FeAl2O4). Aluminium dross was heated at 1200°C for 1 hour in air and then compacted into a substrate using a hydraulic press. The substrate was brought into contact with two different types of iron chip at 1550°C in air for 6 hours. Pure iron chip and iron chips containing 0.8 wt% carbon were employed in this experiment in order to investigate the effect of carbon content in the iron chip on the formation of hercynite. The samples after reactions were characterized using XRD, SEM and EDS techniques. It was found that the final product is hercynite having a dark grey solid phase. The formation of hercynite was due to the interaction of Al2O3 in the dross with Fe and/or FeO in the system. FeO came from the oxidization of iron chip due to the excess of oxygen in the system. Carbon content in the iron was found to effect the formation of FeO in the system, which in turn effect the formation of hercynite. This research is one of the possible way to recycling aluminium dross instead of bury in a landfill.

Rice husk is one of the major agricultural wastes in Thailand, which predominately consist of silica up to 90 wt%. Rubber tree bark (RTB) is an agricultural waste from the harvesting of natural rubber, composed of cellulose and rubber parts, which is a carbon-based material. This research aims to investigate the possibility of using rice husk and rubber tree bark as a silica and carbon resources for producing ferrosilicon alloy. Three different types of carbon were used for the investigation: Coal, RTB and Coal-RTB blend. Rice husk ash, iron ore and carbon were blended homogeneously according to their molar ratios. The prepared samples were heated at 1550 °C in argon atmosphere for 30 minutes and thus the metal droplets were produced. The silicon contents in the produced metal droplets were analyzed by using Inductive coupled plasma (ICP). The results show that the metal produced by this method are ferrosilicon alloy with the highest silicon contents in the metal droplets was 45.32 wt% for RTB, while it was 18.25 wt% for coal. This research unlocks the potential of utilization of agricultural waste in steelmaking industry.