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All Journal Reaktor International Journal of Renewable Energy Development Journal of Engineering and Technological Sciences Journal of Engineering and Technological Sciences
Tjokorde Walmiki Samadhi
Chemical Engineering Program, Bandung Institute of Technology, Jalan Ganesha 10 Bandung 40132, Indonesia
Aerospace Engineering Automotive Engineering Chemical Engineering, Chemistry & Bioengineering Chemistry Civil Engineering, Building, Construction & Architecture Control & Systems Engineering Electrical & Electronics Engineering Energy Engineering Materials Science & Nanotechnology

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Miscibility Development Computation in Enhanced Oil Recovery by Flare Gas Flooding Samadhi, Tjokorde Walmiki; Siagian, Utjok W.R.; Budiono, Angga P.
Journal of Engineering and Technological Sciences Vol 44, No 3 (2012)
Publisher : ITB Journal Publisher, LPPM ITB

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (251.227 KB) | DOI: 10.5614/itbj.eng.sci.2012.44.3.5

Abstract

The use of flare gas as injection gas in miscible gas flooding enhanced oil  recovery  (MGF-EOR)  presents  a  potential  synergy  between  oil  production improvement  and  greenhouse  gases  emission  mitigation.  This  work  is  a preliminary evaluation of the feasibility of miscible flare gas injection based on phase behavior computations of  a model oil (43% n-C5H12 : 57% n-C16H34) and a model flare gas (91% CH4  : 9% C2H6). The computations employed the multiple mixing-cell  model  with  Peng-Robinson  and  PC-SAFT  equations  of  state,  and compared the minimum miscibility pressure (MMP) value in the cases of flare gas  injection  and  CO2  injection.  For  CO2  injection,  both  equations  of  state produced  MMP  values  close  to  the  measured  value  of  10.55  MPa.  Flare  gas injection MMP values were predicted to be 3.6-4.5 times those of CO2  injection. This very high MMP implies high gas compression costs, and may compromise the  integrity  of  the  reservoir.  Subsequent  studies  shall  explore  the  gas -oil miscibility  behavior  of  mixtures  of  flare  gas  with  intermediate  hydrocarbon gases and  CO2,  in  order to  identify  a suitable approach for rendering flare  gas feasible as an injection gas in MGF-EOR.
Synthesis of NaY Zeolite Using Mixed Calcined Kaolins Subagjo, Subagjo; Rahayu, Endang Sri; Samadhi, Tjokorde Walmiki; Gunawan, Melia Laniwati
Journal of Engineering and Technological Sciences Vol 47, No 6 (2015)
Publisher : ITB Journal Publisher, LPPM ITB

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (257.138 KB) | DOI: 10.5614/j.eng.technol.sci.2015.47.6.4

Abstract

Kaolin is one of several types of clay minerals. The most common crystalline phase constituting kaolin minerals is kaolinite, with the chemical composition Al2Si2O5(OH)4. Kaolin is mostly used for manufacturing traditional ceramics and also to synthesize zeolites or molecular sieves. The Si-O and Al-O structures in kaolin are inactive and inert, so activation by calcination is required. This work studies the conversion of kaolin originating from Bangka island in Indonesia into calcined kaolin phase as precursor in NaY zeolite synthesis. In the calcination process, the kaolinite undergoes phase transformations from metakaolin to mullite. The Bangka kaolin is 74.3% crystalline, predominantly composed of kaolinite, and 25.7% amorphous, with an SiO2/Al2O3 mass ratio of 1.64. Thermal characterization using simultaneous DSC/TGA identified an endothermic peak at 527°C and an exothermic peak at 1013°C. Thus, three calcination temperatures (700, 1013, and 1050 °C) were selected to produce calcined kaolins with different phase distributions. The best product, with 87.8% NaY zeolite in the 54.7% crystalline product and an SiO2/Al2O3 molar ratio of 5.35, was obtained through hydrothermal synthesis using mixed calcined kaolins with a composition of K700C : K1013C : K1050C = 10 : 85 : 5 in %-mass, with seed addition, at a temperature of 93 °Cand a reaction time of 15 hours.
Effect of Ethanol Addition as Extraction Solvent on The Content of Bioactive Materials in Dragon Fruit Skin Extract and Powder Shofinita, Dian; Bindar, Yasid; Samadhi, Tjokorde Walmiki; Jaelawijaya, Arwinda Aprillia; Fawwaz, Mifta
Reaktor Volume 20 No.2 June 2020
Publisher : Dept. of Chemical Engineering, Diponegoro University

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (458.061 KB) | DOI: 10.14710/reaktor.20.2.68-74

Abstract

This study aims to produce natural pigments for food prepared from dragon fruit skin by extraction and freeze-drying and to assess the effect of additional ethanol as extraction solvent on the process yield. During extraction stage, the effect of solvent (pure water and additional ethanol) on the yield of bioactive materials was assessed. Furthermore, during freeze-drying, the effect of maltodextrin addition as carrier agent on the quality of powder has also been evaluated. It has been found that the addition of ethanol as extraction co-solvent may give a positive effect on the yield of bioactive materials in the dragon fruit skin extracts, including the contents of anthocyanin, betacyanin, and total phenolic compounds. Regarding freeze drying, it was found that high recoveries of bioactive materials (84-92%) had been achieved, which indicates that freeze-drying may be suitable for drying such heat-sensitive materials. In addition, it was found that the addition of 10% maltodextrin as carrier agent may decrease the moisture content of the powder significantly, up to 8.162.12%, which is beneficial for its storage stability.Keywords: betacyanin; food additives; dragon fruit; extraction; anthocyanin.
Thermal and Ash Characterization of Indonesian Bamboo and Its Potential for Solid Fuel and Waste Valorization Purbasari, Aprilina; Samadhi, Tjokorde Walmiki; Bindar, Yazid
International Journal of Renewable Energy Development Vol 5, No 2 (2016): July 2016
Publisher : Center of Biomass & Renewable Energy, Diponegoro University

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.14710/ijred.5.2.95-100

Abstract

Bamboo has been widely used in Indonesia for construction, handicrafts, furniture and other uses. However, the use of bamboo as a biomass for renewable energy source has not been extensively explored. This paper describes the thermal and ash characterization of three bamboo species found in Indonesia, i.e. Gigantochloa apus, Gigantochloa levis and Gigantochloa atroviolacea. Characterization of bamboo properties as a solid fuel includes proximate and ultimate analyses, calorific value measurement and thermogravimetric analysis. Ash characterization includes oxide composition analysis and phase analysis by X-Ray diffraction. The selected bamboo species have calorific value comparable with wood with low nitrogen and sulphur contents, indicating that they can be used as renewable energy sources. Bamboo ash contains high silicon so that bamboo ash has potential to be used further as building materials or engineering purposes. Ash composition analysis also indicates high alkali that can cause ash sintering and slag formation in combustion process. This implies that the combustion of bamboo requires the use of additives to reduce the risk of ash sintering and slag formation. Article History: Received May 15, 2016; Received in revised form July 2nd, 2016; Accepted July 14th, 2016; Available online How to Cite This Article: Purbasari, A., Samadhi, T.W. & Bindar, Y. (2016) Thermal and Ash Characterization of Indonesian Bamboo and its Potential for Solid Fuel and Waste Valorization. Int. Journal of Renewable Energy Development, 5(2), 95-100.http://dx.doi.org/10.14710/ijred.5.2.96-100 
Synthesis of Geopolymer from Ferronickel Aluminosilicate Waste Samadhi, Tjokorde Walmiki; Wulandari, Winny; Dwinidasari, Aya Anisa; Rahmasari, Arum
Journal of Engineering and Technological Sciences Vol. 57 No. 4 (2025): Vol. 57 No. 4 (2025): August
Publisher : Directorate for Research and Community Services, Institut Teknologi Bandung

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.5614/j.eng.technol.sci.2025.57.4.1

Abstract

The nickel industry in Indonesia generates massive volumes of ferronickel slag that may harm the environment. This research evaluates the feasibility of utilizing coal fly ash and slag from a ferronickel smelter in Obi Island in Indonesia to synthesize geopolymer, an environmentally friendly cementitious material. Compressive strength of geopolymer mortars was measured as a function of slag particle size (coarse and fine), fly ash mass fraction in the dry aluminosilicate binder precursor blends (0.4 and 0.8), and thermal curing period (24 and 48 hours). Mortar specimens were produced by mixing ash and slag with activator solution and sand. The activator solution contained Na2SiO3 and NaOH at a mass ratio of 2:1. Solid reactants to activator solution mass ratio was 3.33. After heat curing, specimens were held in ambient conditions to an age of 7 days. The compressive strength of the mortars was in the 2.1-24.8 MPa range. Geopolymer mortars were able to comply to Indonesian SNI 15-2049-2004 or US ASTM C1329-05 standards for Portland cement. FTIR and XRD characterizations confirmed the conversion of fly ash and slag into amorphous geopolymers at near ambient temperature. Finer slag particle size increased reactivity, ultimately producing higher compressive strength.
Co-Authors Angga P. Budiono Aprilina Purbasari Bindar, Yasid Dwinidasari, Aya Anisa Endang Sri Rahayu Fawwaz, Mifta Jaelawijaya, Arwinda Aprillia Melia Laniwati Gunawan Rahmasari, Arum Shofinita, Dian Subagjo Subagjo Utjok W.R. Siagian Winny Wulandari, Winny Yazid Bindar