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Year 2011

Volume 2, Issue 1 January - March 2011

Abstract: Immobilized Candida rugosa lipase acts as a biocatalyst for interesterification of used cooking oil with methyl acetate in a packed bed reactor. Reactants and products are analyzed using HPLC, and the effect of residence time and operational stability are also investigated. The results indicate that this biocatalyst can convert 71.5% fatty acid from triglyceride in used palm oil for 5.5 h of residence time. Stability test results show that the immobilized biocatalyst retains good activity for 50 hours without appreciable loss in substrate conversion. The largest conversion obtained from this study was 87.09%, achieved during the stability testing under optimum operating conditions. Furthermore, the kinetic models based on the Ping Pong Bi Bi mechanism are applied to the experimental data to describe the reaction behavior. The fitted results show that the Model C gave the smallest error and fairly described the reaction behavior.

Keywords: Biodiesel, used cooking oil, candida rugosa lipase, interesterifcation, non-alcohol route, kinetics.
(283 K)
Abstract: Carbon nanotubes (CNTs) are tubular carbon molecules with superior mechanical, chemical, optical, and electrical properties. These unique properties make CNTs potentially valuable as hydrogen storage, superconductors, drug delivery and other end-use applications. Catalytic decomposition of methane is a promising method for producing hydrogen and CNTs simultaneously for several reasons: economic, high yield of products, and ease of control. Unfortunately, the presence of a metal catalyst in the CNTs product after reaction causes a negative impact on the quality of CNTs including reducing the electrical resistivity, density, tensile strength and structural properties of the nano tubes which can lead to the reduction of CNTs performance in many applications. Process optimization is needed to produce hydrogen and CNTs with the best quality by varying the reaction time to observe the influence of reaction time on the quality of the CNTs produced through the catalytic decomposition of methane.
Production of CNTs was performed in a Gauze reactor at 700°C, 1 atm with methane as a feed was about 315 ml/min. A Stainless steel-wire mesh coated with a Ni-Cu-Al catalyst prepared by the dip-coating method as a spot for carbon deposition. The catalytic performance of the Ni-Cu-Al catalyst and the quality of carbons produced were discussed based on the X-ray diffraction (XRD) results and the Scanning Electron Micrograph (SEM) Image of the used catalysts. The diameter of CNTs produced by a longer reaction time were greater, and it can be concluded that the longer the time reaction, the worse the quality of the CNTs produced. The best of CNTs, which have a smaller diameter was given at 20 minutes reaction time. The crystal diameter of CNTs increased with increasing reaction time ranging from 5.93 nm for 20 minutes reaction to 7.33 nm for 240 minutes reaction.

Keywords: Carbon Nanotubes, Hydrogen, Purification, Quality, Reaction time
(621 K)
Abstract: Waste from stems can be utilized as alternative energy source by turning into a charcoal briquette. The nicotine content in the tobacco stem can be removed by several extraction processes using many types of solvent such as n-hexane, ethanol, kerosene and steam. The goal of this research was to develop charcoal briquette from waste of tobacco stem. The variables studied were type of solvent for extraction; temperature, time and pressure of pyrolysis, and pressure of briquetting. The indicators of the briquette quality were calorific value and gas emission resulting from the burning of the charcoal briquette. Our results showed charcoal briquette had a maximum calorific value at a pyrolysis temperature of 300°C and 90 min while the load for pressuring the briquette was 4 ton. The calorific maximum value was 5438.9 cal/g or 22.8 MJ/kg. The gas emissions consisted of 0.03% carbon monoxide, 2.7% carbon dioxide, 18% oxygen the rest of the gas were nitrogen.
(174 K)
Abstract: The surfactant-water mixture generated from the industrial biodiesel (methyl ester) production washing process generates wastewater that is usually treated in a sludge pond by the addition of bacteria prior to being discharged into water courses. Nonetheless, the treatment is inadequate and it poses an ecological threat to the environment. Treatment of this mixture can take the form of conventional treatment methods for surfactant-water emulsions such as chemical, mechanical and thermal treatments. However, the disadvantages of such methods are low removal efficiency, operational difficulties and high operation cost. An ultra-filtration membrane can be used to separate water from the mixture, in spite of membrane fouling problems and a relatively low permeating flux. In this study, the membrane performances, inclusive of moisture contents in the recovered methyl ester, due to the types of membrane (hydrophobic or hydrophilic), cross-flow velocity and trans-membrane pressures are compared. The surfactant-water mixture used in this work was obtained from washing the palm-derived methyl ester (PME) with water during the product purifying processes from the biodiesel transesterification catalyzed with sodium hydroxide.

Keywords: Biodiesel-water separation, surfactant-water emulsion, hydrophilic, hydrophobic, micro-filtration membrane, ultra-filtration membrane, biodiesel oil, methyl ester
pdf (193 K)
Abstract: The direct and indirect heat load through enclosure materials, internal load (sensible and latent heat) plays an important role in the building life cycle energy. This paper evaluates the effect of Indonesian building regulation for building envelopes and predicts the possible future electricity demand scenarios as well as policy improvement.
A building simulation program (ECOTECTTM) is used to simulate the cooling load scenarios based on different buildings envelope materials. Due to the competitive price and simple production processes concrete block is a very appealing material for Indonesian buildings; its Overall Thermal Transfer Value (OTTV) is lower than the current walls material (brick). The result for the hottest month the cooling load effect shows a concrete blocks reached 5,617 Wh/m2 compared to 2,363 Wh/m2 for bricks.
The result on alternatives materials as well as codes improvement then applies on the electricity supply-demand scenarios planning. The development on scenarios planning based on the information from economic analysis (using Granger-causality test) in order to find out the influence on economic growth in electricity consumption in Indonesia. The potential of electricity cost reduction then calculated by using LEAP (Long-range Energy Alternative Planning) an integrated modelling tool.
The building codes standard OTTV based is beneficial particularly on the skin load-dominated buildings (single landed) in non-humid ambient condition whereas most of the residential high rise buildings in tropical countries are internal load-dominated. The results show that low OTTV values do not directly reduce the electricity consumption in high-rise buildings, however higher OTTV value means higher electricity consumption in single landed buildings. The future electricity demand in Indonesia mainly consumed by industrial sectors however based on the prediction the room for improvement in residential sector is high. The improvement through material improvement and policy improvement will reduce the electricity consumption up to 40 per cent and up to 30 per cent less cost.

Keywords: Buildings, policy, electricity demand, Indonesia.
pdf (222 K)
Absract: Recently, several strategies to produce the visible-light-active TiO2 by doping of TiO2 with transition metal and nonmetal dopants such as C, N and S were proposed. Among them, carbon doping was reported to be effective to improve the photocatalytic activity. In this study, we applied a microwave heating to produce the carbon-modified TiO2 photocatalyst. This technique is very simple and rapidly produces the visible-light-active carbon-modified TiO2 due to the nature of microwave heating. In addition, we have investigated optical properties of the microwave-treated TiO2, and proposed a several new approaches to evaluate its optical properties by uses Mid-Infrared Free Electron Laser (MIR-FEL).
(200 K)
Abstract: The objective of this study is to develop a mathematical model for the effective utilization of renewable energy sources in a developing country like India. Decentralized energy planning (DEP) is in the interest of efficient utilization of resources. DEP is
one of the options for meeting the rural and small scale energy needs in a reliable, affordable and environmentally sustainable way.
The main aspect of the energy planning at a decentralised level would be to prepare an area-based DEP to meet energy needs and development of alternate energy sources at least-cost to the economy and environment. The geographical coverage and scale reflects the level at which the analysis takes place, which is an important factor in determining the structure of models. DEP planning involves multiple objectives and different kinds of constraints. The kinds of objective functions and constraints which have to be included in the DEP have been presented in the current work. The model developed here has been applied to a typical Indian block unit, Kunigal, which comprises several villages. Based on the analysis made in the present work, it is found that biomass-based energy systems have the potential to meet all the energy needs of Kunigal block.

Keywords: Decentralized Energy Planning; Energy planning; Goal Programming; Scenarios; Sustainable Energy Development Scenario.
(189 K)

ISSN: 1906-4918
Frequency: Quartery
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