In this paper, the growth rate distribution of SiO2 solid film by chemical vapor deposition (CVD) under a reduced pressure of 25,000 Pa has been investigated experimentally and numerically. The activation energy of the apparent surface reaction taking no particle formation into consideration was 335 kJ/mol. For all experimental conditions, the experimental results for the growth rate of CVD could be reproduced by the calculation ones before the maximum growth rate when mass transfer could be controlled by the apparent surface reaction. On the other hand, the calculation results for the growth rate of CVD disagreed to some extent with the experimental results after the maximum growth rate when mass transfer could be controlled by diffusion. By the observation of SEM images, the mass transfer in this CVD could include not only surface reaction but also particle formation. It was also suggested that the diffusion coefficient could become the apparent diffusion coefficient with the effect of particle formation. In future work, according to the estimation of the particle formation rate by using a membrane filter, the growth rate distribution could be reproduced by numerical calculation with not only surface reaction but also particle formation.
Hydrogen (H2) is one of the most promising secondary energy resources expected to contribute to the prevention of global warming. Bio-H2, which is derived from biomass feedstock, is more environmentally friendly than hydrogen synthesized from fossil fuels. In our indirect thermochemical processes with solid-gas reactions, the effective heat transfer, which is accomplished by circulation of alumina balls acting as heat carriers (HCs), is a critical issue, and it is necessary to achieve circulation of the heat transfer medium that maximizes production efficiency. In this study, the heat transfer performance of a small-scale indirect biomass gasification process to be promoted in the near future was investigated, focusing on heating of HCs using high-temperature gas to achieve optimum heat utilization in the preheating reactor. To continuously pyrolyze cedar feedstock in the subsequent pyrolysis reactor, HCs must be heated to the desired temperature in the preheater within a residence time. Even if high-temperature gas with sufficient calorific value flows into the preheater, if the heat transfer is not completed within the residence time, the HCs will not be heated to the target temperature and the sensible heat is discharged as tail gas. Therefore, we evaluated the operating conditions that promote the heat transfer during the residence time, focusing on the hot flue gas conditions.
The use of stationary fuel cell power systems for residential applications has been expanding owing to the characteristics of energy saving and environmental friendliness. Technical Committee 105 Working Group 14 (TC105 WG14) in the International Electrotechnical Commission (IEC) proposed assessment procedures for environmental impacts of stationary fuel cell systems using the life cycle assessment (LCA) methodology. In this study, the impact of the 700 W scale of a polymer electrolyte fuel cell combined heat and power generation system (PEFC-CGS) was tested based on the proposal document of the IEC TC105 WG14. In the estimation, the aurum (Au) in the circuit board, which is a precious metal, as well as platinum (Pt) contained in the cell stack, and differences in the hydrogen fuel production paths were considered. According to our results, the factors that contributed to the environmental impact were revealed. Therefore, to improve these factors for product differentiation from environmental aspects, differences in cell performance due to the cell manufacturing method were investigated. Then, it was confirmed that the multilayer electrode reduced the abiotic depletion potential (ADP) at manufacturing by 6 or 12%, and differentiation between products could be achieved by manufacturing the catalyst layers.
This research studied dehydration of sorbitol in aqueous solution to isosorbide over heterogeneous catalysts (Amberlyst-15, Purolite CT269, and H-beta) and a homogeneous catalyst (sulfuric acid). The dehydration of sorbitol was carried out in a high-pressure reactor under a nitrogen gas atmosphere at a fixed initial pressure of 2 MPa. It was found that the Purolite CT269 catalyst gave the highest sorbitol conversion of 100% and an isosorbide selectivity of 42% after 6 h at 453 K. The results showed that an increase in the reaction temperature gave rise to sorbitol conversion. However, the solid - compound was formed during the reaction at high temperature by polymerization of the product. The high acidity could catalyze the dehydration process; however, strong acid such as sulfuric acid gave low selectivity to isosorbide. Thus, the acidity of the catalyst plays a vital role in catalytic performance for the sorbitol dehydration to isosorbide.
Solid fly ash waste from the sugar industry was treated by HCl and then carbonized under N2 at 900 °C for 1 h. The resulting carbon was used as an adsorbent for the removal of colored dyes from wastewater generated in the silk dyeing process. The untreated fly ash and commercial activated carbon were also used as adsorbents for comparison. Porous properties of all adsorbents were characterized by nitrogen adsorption/desorption at 77 K. The kinetics and equilibrium data were obtained from batch experiments with varying adsorption times (1–12 h) and initial concentrations (50–1,000 mg/L) of conventional commercial dye in wastewater, Dark Red 34. The adsorption isotherms and kinetics were studied for all three samples. The adsorption kinetics were analyzed using pseudofirst order, pseudo-second order and intra-particles diffusion models. The adsorption equilibrium data was analyzed by using Langmuir and Freundlich models. Results showed that the surface area of the treated fly ash increased from 26 to 239 m2/g after acid and carbonization treatments. Equilibrium adsorption was reached in 4 h for all samples. The experimental data indicated that the adsorption kinetics were well described by the pseudo-second order model. While isotherms fitted well with the Langmuir equation. The maximum adsorption capacities for the dye removal were 1258, 1156 and 666 mg/g for treated fly ash, activated carbon and untreated fly ash, respectively. Therefore, treated fly ash from the sugar industry shows its high potential as an adsorbent for the color removal of wastewater from silk dyeing process.
A solid waste is generated in the production of biodiesel from the leaves of the Dipterocarpus alatus tree. This waste was hydrolyzed by oleaginous yeast and was employed as the precursor for preparing activated carbon by chemical activation. This work investigated the effect of types of chemical agent i.e. acid (H3PO4 and HNO3), base (KOH and NaOH) and chloride (ZnCl2 and FeCl2) on the porous properties of the resulting activated carbons. The dry leaves prior to hydrolysis were also used for comparison. The experiment was conducted as an activator to a biomass impregnation ratio of 1:2 for 1 h, followed by carbonization at 500 °C for 1 h. The raw materials and activated carbons were analysed using proximate analysis and the porous properties by using nitrogen adsorptiondesorption isotherms and thermogravimetric analysis (TGA). According to proximate analysis, fixed carbon contents of 9.27 and 16.25 dry wt% were found for the hydrolyzed material and dry leaves, respectively. This indicated that both materials served as good precursors to produce carbons. The results of porous properties show that the maximum surface area of 456 m2/g was produced using ZnCl2 activation. The prepared carbons from hydrolyzed leaves had surface areas comparable with carbons prepared from dry leaves for ZnCl2, H3PO4, HNO3 and NaOH activation. However, activation of hydrolyzed leaves with FeCl2 and KOH gave activated carbons with a lower surface area than dry leaves. Moreover, Dipterocarpus alatus leaf activated carbons had a higher surface area than several other literature examples of activated carbons. Therefore, hydrolyzed Dipterocarpus alatus leaves are a good precursor for the preparation of economical activated carbon.
A simple method for synthesizing tannin foam (TF) from tannin resole (TR) was studied. Tannin was used as a substitute for phenol with a 10 wt% substitution ratio to form TR. The mixture of TR was dehydrated to get the TR with a solid content of 80% using a hot air oven. The dehydrated TR was used as an essential component for the formation of the TF. The functional groups, density, and compressive strength of the synthesized TF were tested by using an FTIR, ASTM D1622, and ASTM D1621, respectively. From the FTIR spectra, it was found that functional groups of TF were similar to phenol foam (PF). The addition of tannin increased the density and compressive strength of the TF. The density of tannin foam was 90.92 kg/m3, and the compressive strength of tannin foam was 0.25 MPa. Using tannin resole to make synthesized tannin foam proved to be a simpler method in dehydrating resole by hot air oven as compared with the conventional method. Moreover, the thermal performance of the TF was performed, and it was found that the TF showed a similar thermal performance to the PF.
The higher biodiesel content blended into diesel fuel gives the lower calorific value that may affect the fuel economy. To determine the effect of using 30% biodiesel mixed in diesel fuel (B30) compared to B20, especially on fuel economy in automotive vehicles, a road test was conducted using 4 brands of passenger vehicles for 50,000 km. The daily route of this road test consisted of 10.6% of general road, 49.9% of climbing-downhill road, and 39.5 % of highway road, which covers a distance of 560 km per day. The method used in this study for fuel economy analysis is the full-to-full method, by comparing the fuel consumption of B30 and B20 in two vehicles in each brand (8 cars in total). Based on the test results, statistically, in testing the fuel economy with full to full method, population of data used has been normally distributed and homogeneous. In Passenger1 and Passenger4 vehicles, the average fuel economy value of B30 is 6.7% and 3.7% higher than the B20’s, while in vehicles Passenger2 and Passenger3, the average fuel economy value of B20 is 1.5% and 3.9% higher than those of B30. In addition, the results of the one way ANOVA test on data of passenger vehicles B20 and B30 shows p–value <0.05, which states the average value of fuel economy in each passenger vehicle is different based on statistical analysis. However, based on the difference of engine technology, the fuel consumption of B30 and B20 does not have a significant difference.
Clinker formation was a serious problem that prevented continuous operation of more than a week in cocurrent up-flowing moving bed gasifiers operated for pellets from Japanese cedar. In this work we investigated the clinker formation characteristics in gasifiers of this particular type by analyzing the pellets fed to and the clinker samples collected from gasifiers of the Oobae-Kuroshio Power Plant. We found that the major compounds of the clinkers were lime, CaCO3, K2CO3, KAlO2, and Larnite, and identified that they were formed with the CaCO3-K2CO3 melt as an adhesive. The pellet ash had a deformation temperature (DT) of over 1300 °C in an oxidizing atmosphere, but around 770 °C in a reducing atmosphere (CO 60%-CO2 40%). In the gasification atmosphere with high CO2 partial pressure, a melt consisting of CaCO3-K2CO3 is supposed to form from 735 °C due to eutectic of the CaCO3-K2CO3 system, which should be the main cause of clinker formation. Furthermore, we observed a trace of foaming with gas bubbles in low viscosity melts on the ash samples. On the other hand, we found that the DT of ash from pellets commercially available in Germany measured in both oxidizing and reducing atmospheres was above 1200 °C showing no foaming phenomenon in reducing atmospheres of 750- 800 °C, indicating completely different ash formation characteristics from Japanese cedar pellets case, which cannot be detected by conventional method assigned by ISO.
In order to suppress clinker formation in the co-current up-flowing biomass pellet gasifier, first we investigated the reaction processes of mineral matters in Japanese cedar from a fundamental view point. We found that the eutectic point of the CaCO3-K2CO3 system was the dominant factor in clinker formation in the gasifier where the CaCO3 phase is stable due to a high CO2 partial pressure. Then we tested an aluminum oxide additive, which is harmless and inexpensive, for pellet preparation and found that it was effective in inhibiting the melt formation in the CaCO3-K2CO3 system. In the CaCO3-K2CO3-Al2O3 system where Al2O3 coexists, we confirmed that the CaCO3-K2CO3 melt migrates compounds with structures similar to those of complex compounds such as Fairchildite and KAlO2. The formation of these compounds suppressed the formation of melt together with foaming around 800 °C, and the deformation temperature (DT) was confirmed to be above 1300 °C. By using Japanese cedar pellets with an aluminum hydroxide additive in the Oobae Kuroshio Power Plant and the Uchiko Biomass Power Plant, the average continuous operating hours of 689 hours and 658 hours, respectively, were achieved satisfying the originally planned power generation scheme.