Hydrogen energy is the most promising source of sustainable energy under development. The decomposition of cellulose suspension for hydrogen production by using a 27.12 MHz in-liquid plasma was carried out at atmospheric pressure. Various types of reagents, such as 1 mol/dm3 H2SO4, 1 mol/dm3 NaOH and 0.333 mol/dm3 Na2SO4, were used and compared as to the rate of gas production. Cellulose dispersed in acid liquids is decomposed indirectly by active radicals by the plasma. The highest hydrogen production rate was obtained by employing 1 mol/dm3 NaOH. The gasification rate of cellulose suspension was determined from the increase of C atoms in the product gas. When 1 mol/dm3 NaOH was used, the rate was 7 times greater than that for pure water. It was found that carbon atoms in the product gas is indicative of the decomposition rate of the cellulose suspension.
A huge amount of underutilised empty fruit bunches (EFB) are produced in Malaysia. The abundance of EFB has gained much attention, as they are seen as a potential resource for solid fuel production. However, EFB cannot be directly fed to existing combustion systems due to its undesirable properties. Hence, pre-treatment such as torrefaction is usually conducted to address these limitations. Torrefaction is a thermochemical pre-treatment method that upgrades biomass properties at mild temperatures. The purpose of this study is to investigate the effects of varying oxygen concentrations and temperatures on EFB (0.375 mm particle size) during the torrefaction process. The experiment was conducted at 220 °C, 260 °C, and 300 °C in oxygen concentrations ranging from 0 to 21 vol.% using a vertical tubular reactor. The torrefied EFB was found to turn dark as the torrefaction temperature and oxygen concentration increased. The density of the torrefied EFB was also seen to decrease with increasing temperature. It was also observed that the presence of oxygen lowered the density of the torrefied EFB compared to that of inert conditions. From this work, it was found that solid yield decreased with increasing temperature and oxygen concentration. The solid yield of torrefied EFB ranged from 74-89%, 63-79%, and 51-72% at 220 °C, 260 °C, and 300 °C, respectively, under different oxygen concentrations. The results also reveal an increase in heating values with increasing temperature and oxygen concentrations, ranging from 18.8 to 24.6 MJ/kg. In conclusion, oxygen torrefaction can potentially be a feasible option for biomass pre-treatment.
Reaction pathways of NOX and N2O over CaO under carbonator conditions of the calcium-looping (CaL) process were investigated using a laboratory-scale fluidized bed with calcined limestone (CaO) and inert quartz sand as bed materials. Char particles were fed to the fluidized bed to simulate char transportation to the carbonator. With char feed to the sand bed, slight reduction of NO and N2O in the feed gas was observed, but considerable CO formation was observed. When NO was fed to the CaO bed, NO was first adsorbed onto the CaO surface. The adsorbed NO was desorbed when char or gaseous CO2 was fed. Although char feed to the CaO bed decreased NO slightly, the reduction of NO was nearly equal to that in the sand bed. This reduction of NO with char feed was attributable solely to NO reduction by the char. The formation of CO from char oxidation for CaO bed was much less than that for the sand bed. These results suggest that CO was oxidized over CaO before it reduced NO. For N2O decomposition, the CaO bed had high catalytic activity. CaL process is expected as a multifunctional process of CO2 capture and N2O decomposition with low CO emissions.
Ecological footprint (EF) is a measure to evaluate the human impact on the earth recently. The purpose of this study is to evaluate prefectural EF values in 2010 from available energy and material consumption data. The prefectural EFs are calculated based on six categories; “forest area for assimilating CO2”, “cropland” “fi, shing grounds”, “forest area for product paper and/or timber”, “grazing land”, and “built-up land” according to the definition by World Wide Fund for Nature (WWF). The resulting prefectural EF values are higher in the local prefectures having heavy and chemical industries, especially in Yamaguchi, Oita, Okayama, and Hiroshima. However, the other areas relate closely to the energy and material consumption from these prefectures. Therefore, in addition, the prefectural EFs are reevaluated by employing the mean value of CO2 amount of emission from an industry section. The difference of the EF values between 47 prefectures became small and higher EF values are found in Hokkaido, Tokyo, Okinawa, and prefectures in the Tohoku and Chugoku regions.
The potential of amine-based solvents was investigated by a thermodynamic analysis for low-energy CO2 capture from the flue gas of a thermal power plant. The solubility of CO2 into the amine-based solvent was predicted by the vapor-liquid equilibrium model on the basis of absorption reactions between CO2 and amine. The model was covered for developed and developing amine-based solvents. Considering the energy consumptions of CO2 capture and compression, the power output of the coal-fired power plant with a post-combustion CO2 capture was estimated. The results showed that the solvent characteristics of high CO2 cyclic capacity and low absorption heat had an important effect on reducing the thermal energy requirement for CO2 capture. In the case of CO2 capture from a 12% CO2-containing flue gas, the lowest thermal energy requirement was estimated at approximately 2 GJ/t-CO2, and the efficiency penalty of power generation was reduced to 7.2%pt. Also, concerning the impact of CO2 capture and compression on the power generation system, 1%pt. of power generation efficiency could be recovered by lowering 0.6 GJ/t-CO2 of the thermal energy requirement of CO2 capture. These results mean that the aminebased solvents still have high capability to improve energy performance of post-combustion CO2 capture. However, lowering the regeneration temperature in the range of 90 °C to 130 °C did not have a significant advantage in reducing energy consumption. This comprehensive analysis for the CO2 capture and compression integrated with a coal-fired power plant is useful for process evaluation, and the desire will be to extend the analysis to other applications.
The surface tension of heavy oil and its temperature dependence were measured by the pendant drop method under atmospheric pressure in the temperature range of 30 to 250 °C. The surface tension was determined by fitting the numerical solution of the Young-Laplace equation to the image of a droplet hanging at the tip of a 1/16” stainless steel tube. The distillates and residues fractionated by vacuum distillation of atmospheric residue and bitumen were used as samples. The surface tensions of all samples decreased linearly with temperature. The fractionation of samples by column chromatography revealed that the samples, which were poor in saturates and rich in aromatics, had higher surface tension. In addition, a model on the basis of the principle of corresponding states was used to predict the surface tension of heavy oil. It was demonstrated that the model was capable of predicting the surface tension of the distillates with good accuracy, but it was insufficient to predict the surface tension of residue.