Pornpote Piumsomboon

Biofuel production from crude palm oil with supercritical alcohols: comparative LCA studies.

A recent life cycle assessment (LCA) reported that biodiesel production in supercritical alcohols (SCA) produces a higher environmental load than the homogeneous catalytic process because an enormous amount of energy is required to recover excess alcohol. However, the excess alcohol could be dramatically reduced by increasing the operating temperature to 400°C; although the product would have to be considered as an alternative biofuel instead of biodiesel. A comparative LCA of the biodiesel production in two SCA at 300°C (C-SCA) and novel biofuel production in the same two SCA at 400°C (N-SCA) is presented. It was clear that the N-SCA process produces a dramatically reduced environmental load over that of the C-SCA process due to a lower amount of excess alcohol being used. The N-SCA process could be improved in terms of its environmental impact by changing from fossil fuel to biomass-based fuels for the steam generation.

Catalytic steam reforming of biomass-derived tar for hydrogen production with K 2 CO 3 /NiO/ γ -Al 2 O 3 catalyst

A major problem of using Ni-based catalysts is deactivation during catalytic cracking and reforming, lowering catalytic performance of the catalysts. Modification of catalyst with alkali-loading was expected to help reduce coke formation, which is a cause of the deactivation. This paper investigated the effects of alkali-loading to aluminasupported Ni catalyst on catalytic performance in steam reforming of biomass-derived tar. Rice husk and K2CO3 were employed as the biomass feedstock and the alkali, respectively. The catalysts were prepared by a wet impregnation method with γ-Al2O3 as a support. A drop-tube fixed bed reactor was used to produce tar from biomass in a pyrolysis zone incorporated with a steam reforming zone. The result indicated that K2CO3/NiO/γ-Al2O3 is more efficient for steam reforming of tar released from rice husk than NiO/γ-Al2O3 in terms of carbon conversion and particularly hydrogen production. Effects of reaction temperature and steam concentration were examined. The optimum temperature was found to be approximately 1,073 K. An increase in steam concentration contributed to more tar reduction. In addition, the K2CO3-promoted NiO/γ-Al2O3 was found to have superior stability due to lower catalyst deactivation.

Optimum condition of membrane electrode assembly fabrication for PEM fuel cells

The aim of this research was to study the effect of fabrication factors on the performance of MEA of a PEM fuel cell. The MEA was prepared by using 5 cm2 of porous electrodes with Pt loading 1 mg/cm2 and Nafion 115 membrane from Electrochem Co. Ltd. The studied factors were temperature, pressure and time of compression in the range of 130–150 ‡C, 50–100 kg/cm2 and 1–5 minutes, respectively. A 2k factorial design was conducted in this study. The results showed that interaction between pressure and temperature and interaction between temperature and time of compression have significant effects on the performance of the MEA. With low pressure, but high temperature and long compression time, current density is increased. The results showed that the optimum condition was 65 kg/cm2, 137 ‡C and 5.5 min of compression time. It was also found that the force of 69 kg-cm for assembling the single cell gave the best performance.

Parametric studies on catalytic pyrolysis of coal-biomass mixture in a circulating fluidized bed

Pyrolysis is an efficient way of thermally converting biomass into fuel gas, liquid product and char. In this research, pyrolysis experiments were carried out in a circulating fluidized bed reactor with a riser diameter of 25 mm and height 1.65 m. The biomass used was corn cobs. The experiments were conducted systematically using two level factorial design with temperature ranging from 650 to 850 degree Celsius, corn cobs and catalyst contents in feed ranging from 0 to 100%, and from 1 to 5 wt%, respectively, and Ni loaded on catalyst ranging from 5 to 9 wt%. The results showed that when temperature and catalyst contents in feed and Ni loaded on catalyst increased, the percent of hydrogen and carbon monoxide increased. The amount of corn cobs was found to have an effect only on the composition of hydrogen. Carbon dioxide was also observed to increase slightly. On the other hand, the percent of methane was considerably decreased. The optimum conditions were 850 degree Celsius, corn cob content in feed of 100%, catalyst content in feed of 5% and Ni loaded on catalyst of 9%. At this condition the percentages of hydrogen and carbon monoxide were 52.0 and 18.0, respectively.

Evaluation of biomass component effect on kinetic values for biomass pyrolysis using simplex lattice design

We evaluated the correlation between the biomass constituents and their kinetic values. To simplify the models and indicate the effect of each constituent, pure biomass components and their mixtures were used as biomass model. The experiments were set up based on simplex-lattice design. The pyrolysis of synthesized biomass was performed by non-isothermal thermogravimetric analyzer. Several kinetic models in the literature, including Kissinger-Akahira-Sunose, Ozawa-Flynn-Wall and analytical method were used to determine kinetic values for each experiment. The generated regression models and predicted kinetic values from those methods were compared. The results obtained from analytical model (for n≠1) showed a good agreement (R2>0.95) with those obtained from experiments. This study also provide contour plots for all cases in order to observe the behavior of biomass pyrolysis at different component ratio.

Integration of computational fluid dynamics simulation and statistical factorial experimental design of thick-wall crude oil pipeline with heat loss

CFD with statistics was developed for flow simulation in a thick-wall pipeline.Crude oil temperature decreased along pipeline length and radius.Heat transfer coefficient and ambient temperature were the effect parameters.Increasing heat transfer coefficient decreases the wax appearance distance.Increasing ambient temperature increases the wax appearance distance. The aim of this study was to explore the heat transfer behavior between convection and conduction in the thick wall crude oil pipeline with laminar unsteady state flow using integration of developed computational fluid dynamics model and statistical experimental design. The governing equations were employed to investigate the effects of wall thickness, wall thermal conductivity, surrounding heat transfer coefficient and ambient temperature on transport profile using statistical experimental design and to locate an origin point where wax precipitate in the pipeline (wax appearance distance) by using response surface methodology (RSM). A good agreement between the model and literature experimental data suggests that the proposed numerical scheme is suitable for simulating the transport profile in pipeline and predicting the phenomena for any other conditions. From the statistical analysis, it was found that, surrounding heat transfer coefficient and ambient temperature were the major effect parameters on the wax appearance distance.

Characterization of fluidization regime in circulating fluidized bed reactor with high solid particle concentration using computational fluid dynamics

The hydrodynamics inside a high solid particle concentration circulating fluidized bed reactor was investigated using computational fluid dynamics simulation. Compared to a low solid particle reactor, all the conventional fluidization regimes were observed. In addition, two unconventional fluidization regimes, circulating-turbulent and dense suspension bypassing regimes, were found with only primary gas injection. The circulating-turbulent fluidization regime showed uniformly dense solid particle distribution in all the system directions, while the dense suspension bypassing fluidization regime exhibited the flow of solid particles at only one side system wall. Then, comprehensive fluidization regime clarification and mapping were evaluated using in-depth system parameters. In the circulating-turbulent fluidization regime, the total granular temperature was low compared to the adjacent fluidization regimes. In the dense suspension bypassing fluidization regime, the highest total granular temperature was obtained. The circulating-turbulent and dense suspension bypassing fluidization regimes are suitable for sorption and transportation applications, respectively.

Comparisons of particle cluster diameter and concentration in circulating fluidized bed riser and downer using computational fluid dynamics simulation

The information of particle cluster dynamics is necessary for improving the performance of a circulating fluidized bed system. The main objective of this study is to compare the particle cluster diameters and concentrations from computational fluid dynamics simulation results between circulating fluidized bed riser and downer. The calculation methodologies are based on the concept of kinetic theory of granular flow and statistics. The mathematical model was verified by using the experimental dataset from literature and used for computing the particle cluster dynamics. In the circulating fluidized bed riser and downer, a dense and dilute core-annulus flow structures were obtained, respectively. The particle cluster in the circulating fluidized bed riser possessed more heterogeneity movements than that in the circulating fluidized bed downer. This can be explained by the system flow direction. About the particle cluster dynamics, the particle cluster diameters and concentrations in the circulating fluidized bed riser were higher than the ones in the downer. The calculated values were comparable to the empirical correlations. This confirms the validity of the calculation methodologies. Particle cluster dynamics and its example application inside circulating fluidized bed riser and downer were also discussed.

Effect of Regeneration Temperature on the Composition and Carbon Dioxide Sorption Ability of a K2CO3/Al2O3 Solid Sorbent in a Bubbling Fluidized Bed Reactor

The effect of the regeneration temperature (150°, 250°, and 350°C) during multiple CO2 cyclic sorption-regeneration cycles of a K2CO3/Al2O3 solid sorbent in a bubbling fluidized bed reactor was evaluated in terms of the CO2 capture capacity and chemical composition of the solid sorbent. The CO2 capture capacity after regeneration at 150° and 250°C decreased with increasing cycle numbers, reaching approximately 57 and 78%, respectively, and 19.0 and 39.3%, respectively, of the original capacity after one and five regeneration cycles. This decline in the CO2 capture capacity was due to the accumulation of KHCO3 (at 150°C) and KAl(CO3)2(OH)2 (150° and 250°C) from their incomplete degradation back to the K2CO3/Al2O3 solid sorbent. When regenerated at 350°C, the CO2 capture capacity remained essentially constant in each cycle number because of complete desorption (no residual KHCO3 and KAl(CO3)2(OH)2). The formation mechanism of complex structure occurred similar to the one in a fixed bed reactor/thermogravimetric analyzer with lower regeneration temperature. The general operation conditions for K2CO3/Al2O3 solid sorbents are summarized.

Synthesis of polyaniline-wrapped carbon nanotube-supported PtCo catalysts for proton exchange membrane fuel cells: activity and stability tests

A series of the polyaniline (PAN)-wrapped carbon nanotube (CNT)-supported PtCo (PtCo/xPAN–CNT) catalysts was prepared for the oxygen reduction reaction (ORR) in a proton exchange membrane (PEM) fuel cell. The effect of the PAN content wrapped around the multiwall CNTs in the range of 0–15 wt% on the activity and stability of the PtCo catalysts was explored. Increasing the PAN content on the CNT surface did not significantly affect the Pt : Co ratio and catalyst loading on the CNT surface, while it positively affected the electrode conductivity, crystallite size, average particle size and the electrochemical surface area (ESA) as well as the hydrophilic property of the PtCo catalyst. Among all the prepared PtCo catalysts, PtCo/10PAN–CNT exhibited the highest catalytic activity towards the ORR, with a kinetic current density of 36.9 mA cm−2 in 0.5 M H2SO4 and a current density of 407 mA cm−2 at 0.6 V (244 mW cm−2) in a PEM fuel cell under a humidified H2/O2 environment at 60 °C and ambient pressure. The presence of PAN on the CNT surface can reconfigure the catalyst-support interaction, resulting in an increased catalyst stability.