Himawan Tri Bayu Murti Petrus

Coconut Shell Charcoal as a Bioreductor in Roasting Process of Nickel Laterite from Pomalaa, Southeast Sulawesi: Performance and Kinetics Study

In facing the scarcity of sulfide nickel ore, processing nickel laterite to form nickel pig iron becomes an important issue. Also, Indonesia inherits 10% of nickel laterite in the world, assigning as the third biggest country of nickel laterite possession in the world. Nickel pig iron is one of nickel products involving massive high-grade metallurgical coke consumption that is commonly being used as stainless steels. Consequently, high amount of carbon dioxide is also produced in this process. And so, substituting of the coke using bioreductor material – in this study, Coconut Shell Charcoal – is important. The study is done by conducting several variables. The reductors used were Coconut Shell Charcoal and Anthracite Coal. The process was conducted in 800°C and 1000°C, in a muffle furnace, and between 15 to 240 minutes of reduction time. Results from all reductors show that higher temperature indicates a better reduction process. Moreover, X-Ray Powder Diffraction (XRD) analysis data shows that there is no significant difference in the final product between two reductors. By replacing metallurgical coke using bioreductor, the carbon emission in the process can be reduced. Hence, providing a better process and environment to the next generation.

Kinetic study of nickel laterite reduction roasting by palm kernel shell charcoal

Demand to process nickel-bearing laterite ore increase as continuous depletion of high-grade nickel-bearing sulfide ore takes place. Due to its common nickel association with iron, processing nickel laterite ore into nickel pig iron (NPI) has been developed by some industries. However, to achieve satisfying nickel recoveries, the process needs massive high-grade metallurgical coke consumption. Concerning on the sustainability of coke supply and positive carbon emission, reduction of nickel laterite ore using biomass-based reductor was being studied.In this study, saprolitic nickel laterite ore was being reduced by palm kernel shell charcoal at several temperatures (800–1000 °C). Variation of biomass-laterite composition was also conducted to study the reduction mechanism. X-ray diffraction and gravimetry analysis were applied to justify the phenomenon and predict kinetic model of the reduction. Results of this study provide information that palm kernel shell charcoal has similar reducing result compared with the conventional method. Reduction, however, was carried out by carbon monoxide rather than solid carbon. Regarding kinetics, Ginstling-Brouhnstein kinetic model provides satisfying results to predict the reduction phenomenon.

Effect of Bentonite Addition on Geopolymer Concrete from Geothermal Silica

Silica scaling is one of major problems in geothermal power plant. Silica recovery is a promising method to solve this particular problem in regard to silica utilization as geopolimer concrete. In this experimental study, bentonite was used as raw alumina source. Experiments were conducted by means observing the geopolymerization through alkaline activator ratio, raw material ratio, and temperature optimization. After mixing and casting for 24 hours, samples were cured at 80°C, 100°C, and 120°C for certain period of time and kept at room temperature for 7 days before compressive strength test. The optimum curing time and temperature gained from this experiment were 120 minutes and 100°C with compressive strength of 29.16 MPa. The development of geopolymer bond and microstructure of samples were then investigated by SEM technique. Scanning electron microscopy (SEM) analysis also showed better improvement in geopolymer layer of concrete sample with increasing curing temperature.

Evaluation of shrinking core model in leaching process of Pomalaa nickel laterite using citric acid as leachant at atmospheric conditions

Most of kinetics studies related to leaching process used shrinking core model to describe physical phenomena of the process. Generally, the model was developed in connection with transport and/or reaction of reactant components. In this study, commonly used internal diffusion controlled shrinking core model was evaluated for leaching process of Pomalaa nickel laterite using citric acid as leachant. Particle size was varied at 60-70, 100-120, -200 meshes, while the operating temperature was kept constant at 358 K, citric acid concentration at 0.1 M, pulp density at 20% w/v and the leaching time was for 120 minutes. Simulation results showed that the shrinking core model was inadequate to closely approach the experimental data. Meanwhile, the experimental data indicated that the leaching process was determined by the mobility of product molecules in the ash layer pores. In case of leaching resulting large product molecules, a mathematical model involving steps of reaction and product diffusion might be appropriate to develop.

Optimization of gold ore Sumbawa separation using gravity method: Shaking table

Most of artisanal small gold mining in Indonesia has been using amalgamation method, which caused negative impact to the environment around ore processing area due to the usage of mercury. One of the more environmental-friendly method for gold processing is gravity method. Shaking table is one of separation equipment of gravity method used to increase concentrate based on difference of specific gravity. The optimum concentration result is influenced by several variables, such as rotational speed shaking, particle size and deck slope. In this research, the range of rotational speed shaking was between 100 rpm and 200 rpm, the particle size was between -100 + 200 mesh and -200 + 300 mesh and deck slope was between 3° and 7°. Gold concentration in concentrate was measured by EDX. The result shows that the optimum condition is obtained at a shaking speed of 200 rpm, with a slope of 7° and particle size of -100 + 200 mesh.Most of artisanal small gold mining in Indonesia has been using amalgamation method, which caused negative impact to the environment around ore processing area due to the usage of mercury. One of the more environmental-friendly method for gold processing is gravity method. Shaking table is one of separation equipment of gravity method used to increase concentrate based on difference of specific gravity. The optimum concentration result is influenced by several variables, such as rotational speed shaking, particle size and deck slope. In this research, the range of rotational speed shaking was between 100 rpm and 200 rpm, the particle size was between -100 + 200 mesh and -200 + 300 mesh and deck slope was between 3° and 7°. Gold concentration in concentrate was measured by EDX. The result shows that the optimum condition is obtained at a shaking speed of 200 rpm, with a slope of 7° and particle size of -100 + 200 mesh.

IR spectral similarity studies of geothermal silica-bentonite based geopolymer

The geopolymer structures are formed through polymerization of silicate and aluminate species. The resulted structure is predicted to be similar with zeolite. In this study, geopolymer samples were made from mix powder of geothermal silica and bentonite, then activated with sodium hydroxide and sodium silicate. The effect of silica content, NaOH molarity and curing temperature effect were investigated on geopolymer IR spectra and compared with 3A zeolite IR spectra. Pearson correlation value (r) and spectral similarity correlation (Corr) were used to assess spectra similarity between geopolymer samples and zeolite. The development of geopolymer bond and microstructure of samples were then investigated by FTIR technique. IR spectra of geopolymer samples show that Si-O-Al absorption bands are formed around 900-1300 cm-1 and 400-800 cm-1. The optimum of silica contents, NaOH molarity and curing temperature obtained from the experiment were 140 grams, 10 M and 80°C with Corr value of 922 and compressive strength of 7,59 MPa. Corr value is proven to have relation with material strength. Higher Corr value is identified to have higher aluminosilicate species which contributes to higher compressive strength.The geopolymer structures are formed through polymerization of silicate and aluminate species. The resulted structure is predicted to be similar with zeolite. In this study, geopolymer samples were made from mix powder of geothermal silica and bentonite, then activated with sodium hydroxide and sodium silicate. The effect of silica content, NaOH molarity and curing temperature effect were investigated on geopolymer IR spectra and compared with 3A zeolite IR spectra. Pearson correlation value (r) and spectral similarity correlation (Corr) were used to assess spectra similarity between geopolymer samples and zeolite. The development of geopolymer bond and microstructure of samples were then investigated by FTIR technique. IR spectra of geopolymer samples show that Si-O-Al absorption bands are formed around 900-1300 cm-1 and 400-800 cm-1. The optimum of silica contents, NaOH molarity and curing temperature obtained from the experiment were 140 grams, 10 M and 80°C with Corr value of 922 and compressive stren...

Simultaneous Hydrolysis and Fermentation of Sweet Sorghum Varieties (FS501 and KCS105) into Bioethanol Using Saccharomyces steineri – A Kinetics Study

In this study, kinetics of bioethanol production by fermentation of three different substrates, which were artificial substrate and the juice of two sweet sorghum varieties (FS501 and KCS105) using Saccharomyces steineri, were examined using two proposed models by assuming that simultaneous hydrolysis and fermentation occurred. Fermentation of the substrate of FS501 and KCS105 juices showed better data fitting by using the modified version of the kinetics model while the fermentation of artificial substrate which was free of any other components followed Philippidis’s kinetics model. This difference was caused by the change of the yeast behavior in the form of the reduction of both the rate of fructose and/or glucose consumption by the yeast and the rate of fructose and or glucose conversion into ethanol during lag phase. As the consequence, sucrose hydrolysis seems very dominant in the FS501 and KCS105 juices fermentation during the lag phase. The change of behavior of the yeast was estimated being caused by the existence of “impurities” such as acetic acid, glycerol, nitrogen, phosphor, and potassium in the FS501 and KCS105 juices. From statistical analysis using correlation coefficient (between kinetics parameters and “impurities”), acetic acid was the most influential component to change the behavior.