Sri Harjanto

Behavior of dioxin during thermal remediation in the zone combustion process

In the previous study, a new process concept for the thermal remediation of particulate/powder materials contaminated by polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) has been verified. It leads to removal efficiencies of more than 99.9% in the soil contaminated by PCDD/Fs in terms of toxicity equivalent quantity (TEQ). However, details of the reactions and phenomena during the process, i.e., decomposition, vaporization, reformation and trap of PCDD/Fs and their relating compounds, have not sufficiently been clarified yet. The present study aims to examine experimentally the transport and fate of PCDD/Fs in the process. In the experiment, a laboratory-scale process simulator and a soil sample preliminary mixed with octachlorinated dibenzo-p-dioxin spiked by carbon-13 isotope (13C-OCDD) were used. The distribution of 13C-OCDD in the soil bed during the process was measured by applying a quench technique that rapidly cools-down the bed. Further, the total amount of 13C-OCDD discharged with outlet gas was measured. Using the obtained data, mass balance of 13C-OCDD in the process was estimated. The results show that about 99% of 13C-OCDD preliminary admixed with the soil was decomposed rather than released to the outlet gas. Only a trace amount of 13C-OCDD remained in the treated soil. In addition, a very small amount of other congeners having the 13C-cycles was detected in the treated soil and outlet gas although its TEQ values are not significant. These were probably formed by dechlorination reactions occurring in the process.

Stability of the beta phase in Ti-Mo-Cr alloy fabricated by powder metallurgy

A new b Ti alloy was designed and fabricated by powder metallurgy process using pure metallic powders. The addition of Mo and Cr increased the stability of the b phase. By contrast, O promoted a phase formation upon cooling. The addition of 18%Mo and 10%Cr stabilized the b phase into ambient temperature. O increased the critical cooling rate of formation of a phase due to the prediction of the continuous cooling transformation diagram calculated by the Java-based Material Properties software. Sintering and solution treatment also enhanced the alloying behavior of pure powders to their designated chemical compositions. Hardness of the alloy decreased with increasing Mo and Cr content, which led to the decrease of a phase. The Ti-18%Mo-10%Cr alloy exhibited better corrosion resistance than a commercial Ti-6%Al-4%V alloy, which is used as current biomaterial.

Formation and transport of PCDD/Fs in the packed bed of soil containing organic chloride during a thermal remediation process.

The authors previously proposed the concept of a new thermal remediation process for particulate/powder materials contaminated by polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and experimentally verified its validity on the basis of process efficiency. However, contaminees such as soils and fly ashes from waste incinerators often contain a considerable amount of other chlorides, which may act as a main source of chlorine in the formation of PCDD/Fs via thermal processes. The present study aims to examine the formation and transport of PCDD/Fs in the packed bed of soil containing a chloride during the process. Polyvinyl chloride (PVC) polymer was mixed with soil sample as an organic chloride model. A laboratory-scale apparatus was employed as a process simulator. Further, a technique to quench the process was applied to observe the concentration distribution of PCDD/Fs in the solid bed in the vertical direction. The result shows that the PCDFs tend to form dominantly in the high temperature (calcination and/or combustion) zone and are successively trapped in the low temperature (wet) zone. Especially, TeCDF is the most dominant homologue contained in the wet zone and outlet gas. Although PCDD/Fs are once trapped at the wet zone, the concentration of the remediated materials gives fairly low value (1.9 pg/g-dry, 0.04 pg-TEQ/g-dry). It signifies that organic chlorides mingled in the solid contaminee not affect the removal efficiency of PCDD/Fs in the process. Nevertheless, attention should be paid to the potential emission of PCDD/Fs in the outlet gas due to the presence of organic chloride in the soil.

Hydrogen Adsorption Behavior of Mechanically Milled and Pelletized Coconut Shell Activated Carbon

Activated carbon can be the best selection for the solid media of hydrogen storage materials because of cheap, good availability, high quantity of pore on its surface and good adsorption capacity. To obtain optimal handling of coconut charcoal-based (CSAC) without reducing its property on hydrogen adsorption capacity, the effect of mechanochemical and pelletizing process to CSAC was examined. Mechanical milling by using planetary ball mill was conducted to reduce particle size distribution and to mechanochemically process CSAC with KOH. CSAC particles reduce its particle size distribution to nano and sub micron size due to mechanical milling. After mechanochemical and pelletizing process, the surface area and pore volume of CSAC decrease to 68.5% and 61% compared with those of as received sample. However, hydrogen adsorption capacity of CSAC pellet only decrease 5 and 9% at measurement pressure and temperature of 4000 kPa, -5oC and 4000 kPa, 25oC, respectively.

Column flotation monitoring based on electrical capacitance volume tomography: A preliminary study

A preliminary study of column flotation monitoring process using electrical capacitance volume tomography (ECVT) was conducted. ECVT was one of the monitoring systems which based on the capacitance measurement. It was used to understand the phenomenon that occurs inside the column in a three-dimensional (3-D) image. A linear back projection (LBP) algorithm technique was used to reconstruct the 3-D ECVT images from all measurement data obtained in this study. As a preliminary study, the effect of gas injection in the two-phase (liquid and gas) system was conducted. This study is conducted to assess the possibility of ECVT system in the monitoring of column flotation process. The experiments were conducted by using column flotation with 5 cm diameter and 150 cm height in which a sparger was installed at the bottom of column to inject air inside the column. 32-CH rectangular ECVT sensor was installed at 13 cm above the sparger and placed around the column. The gas injection variations used were 2-7 l/min wit...

Influence of Oxygen on Microstructures of Ti-Mo-Cr Alloy

In this study, the effect of oxygen addition on the microstructures of Ti-18%Mo-10%Cr alloy was investigated. The alloy was fabricated by a powder metallurgy method. The samples were subjected to sintering at 1300°C for 4 hours and furnace cooling. A Bo-Md method was initially applied for predicting stable phase. Calculation using the Bo-Md method showed that Ti-18%Mo-10%Cr alloy have bcc (β) phase at ambient temperature. All samples with various oxygen contents exhibited needle-like structures within equiaxed grains. The increase of oxygen content promoted formation of porosity in the α phase. Calculation of phase stability using JMatProTM showed that the decrease of β phase’s stability was not due to formation of the α phase on sintering, but due to promotion of nucleation and grain growth of diffusional α phase upon furnace cooling. It was also shown that vol.% of porosity of the alloy slightly increased with increasing oxygen content. Therefore, the increase of oxygen concentration could accelerate the formation of α phase and reduce the alloy’s density. The hardness increased as the oxygen concentration increased. The increase of the hardness might be due to combination of the solid solution hardening of oxygen and the precipitation hardening of α phase.

Reduction of Composite Pellet Containing Indonesia Lateritic Iron Ore as Raw Material for Producing TWDI

Blast furnace process is still an important process for producing pig iron. The process needs high grade iron ore and coke. The two materials can not be found easily. In addition blast furnace process needs cooking and sintering plant that produces polluted gases. Utilization of composite pellet for pig iron production can simplify process. The pellet is made of iron ore and coal. In addition the pellet can be made from other iron source and coal. This paper discusses the evolution of phase during reduction of composite pellet containing lateritic iron ore. Fresh iron ore and coal were ground to 140 mesh separately. They were mixed and pelletized. The quantity of coal added was varied from 0 %, 20 % and 29 % of pellet weight. Pellets were heated with 10 °C/minute to 1100 °C, 1200 °C, 1300 °C and 1350 °C in a tube furnace and temperature was held during 10 minutes. Heated pellets were analyzed with XRD equipment. XRD of reduced pellets showed that iron phase change with coal and temperature. Lack of coal during heating results the re-oxidation of iron phases. This process is due to replacement of reductive atmosphere by oxidative atmosphere.

Optimizing the Nanostructural Characteristics of Chemical Bath Deposition Derived ZnO Nanorods by Post-Hydrothermal Treatments

Zinc oxide (ZnO) is an inorganic semiconductor material which has been widely studied due to its various potential applications. Over the past decades, one-dimensional (1-D) nanostructures such as nanowires and nanorods have stimulated significant scientific interests because of their unique properties in comparison to bulk materials. For the application of dye sensitized solar cell (DSSC), 1-D ZnO nanostructures are more desired than the spherical nanoparticles since the former provides ballistic effect leading to faster electron transfer which in turn can increase the device performance. Motivated by this consideration, in the current study ZnO nanorods were deposited on ITO glass substrate via chemical bath deposition (CBD) process where the seeding solution was prepared at 0°C. In order to increase their crystallinity and optical properties, the as-deposited ZnO nanorods were subjected to post-hydrothermal treatment at 150°C for 3, 6 and 9 hours. The scanning electron microscope (SEM) analysis revealed that the ZnO nanorods were successfully grown as vertically-aligned hexagonal structure, while the X-ray diffraction (XRD) study showed that the intensity of (002) crystal plane is the highest peak for all nanorod samples. The optical study by UV-Vis spectroscopy showed that the absorption edge of the as-deposited sample was slightly red-shifted to visible region after post-hydrothermal treatment. The ZnO nanorods sample derived from post-hydrothermal treatment for 6 hours provided the optimum nanostructural characteristics with an average diameter of 228 nm, crystallite size of 27.97 nm and the band gap energy, Eg, of 3.12 eV.

Properties of Fe-Mn-C Alloy as Degradable Biomaterials Candidate for Coronary Stent

The development of biomaterial has reached biodegradable stage. Biodegradable means it can be degraded after certain period of time after implantation and cause no harm for the system. Degradable Biomaterial has the potential to be used as Coronary Stent to minimize the risk from thrombosis issue. Thrombosis is a symptom of body defense where will be a clots blood effect around stent area. The formation of clots blood will disturb a blood flow in artery and it will result a restenosis effect.

Corrosion Behavior of Fe-Mn-C Alloy as Degradable Materials Candidate Fabricated via Powder Metallurgy Process

Fe-Mn alloys are prospective degradable materials for coronary stents. Several methods and strategies are investigated to produce excellence properties for this application, such as addition of alloying elements. The study is focused on the corrosion behavior of novel Fe-Mn alloys, i.e. Fe-25Mn-1C and Fe-35Mn-1C fabricated by powder metallurgy process. Addition of carbon is intended to obtain the phase that has ability to easily degradable without compromising its mechanical properties. The results show that austenite phase formed from this process and corrosion rate increased in proportion with the manganese addition from 32.2 mpy (Fe-25Mn-1C) to 43.7 mpy (Fe-35Mn-1C) using polarization methods. The presence of porosity, which cannot be extinguished by sintering, makes the degradation favorable. The results of this study indicate that these alloys have prospective properties to be applied as degradable biomaterials.