Benjapon Chalermsinsuwan

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.

Epoxidation of waste used-oil biodiesel: Effect of reaction factors and its impact on the oxidative stability

Epoxidation of waste used-oil biodiesel (WUO-B) was performed to test the feasibility of properties improvement. The effects of the reaction temperature (30–50 °C) and time (2–12 h), molar ratio of H2O2: HCOOH (1: 7 to 1: 1) and the stirring rate (100–300 rpm) on the level of unsaturated carbon bond conversion and the epoxy compound selectivity were identified using a 2k (two levels) factorial design. Besides epoxy biodiesel as the main product, only one by-product, hydroxyl-biodiesel, was generated. The conversion of unsaturated carbon bonds was positively affected by the molar ratio of H2O2: HCOOH and the stirring rate, while the reaction temperature and time had no significant affect (in the investigated ranges). In contrast, with respect to the epoxy compound selectivity, the stirring rate had a positive effect, while both the reaction temperature and time each had a negative effect. The oxidative stability (OS) of the epoxy waste used-oil biodiesel (EWUO-B) revealed a linear relationship to the unsaturated carbon bond conversion level, but no significant relationship to the epoxy compound selectivity. EWUO-B prepared from a 1: 1 molar ratio of H2O2: HCOOH at 50 °C with stirring at 300 rpm for 12 h exhibited a higher OS (around 37.85 h) than that of the WUO-B. Except for the cold flow properties and methyl ester content, all other key properties of the EWUOB were within the specifications of the EN14214 standard set by the Department of Energy Business.

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.

Effect of Biomass Compositions on Combustion Kinetic Parameters using Response Surface Methodology

Abstract The aim of this research is to find the correlation between chemical compositions of biomass, including cellulose, hemicelluloses and lignin, and kinetic rates of biomass combustion. The combustion behavior of biomass constituent was studied by thermogravimetric analyzer. The correlations were generated by means of using Response Surface Methodology based on Simplex-Lattice experimental design. The results obtained from statistical analysis can be used to generate mathematical models and also contour plots which exhibited the relationship between biomass composition and its combustion kinetic. From the observation, the models and contour plots indicated the complexity of combustion mechanism. The correlations proposed by this research were expected to be potentially used to predict combustion behavior in case of real biomass.

Factorial design analysis of parameters for the sorption-enhanced steam reforming of ethanol in a circulating fluidized bed riser using CFD

The sorption-enhanced steam reforming of ethanol (SESRE) has recently been reported as a novel process for hydrogen (H2) production. SESRE can operate well on a Ni-based catalyst with dolomite as a sorbent in packed-bed reactors. In this study, the circulating fluidized bed (CFB) concept was proposed to obtain higher productivity and continuous operation of SESRE. Particular focus was directed to the design and selection of suitable operating conditions of the CFB riser. Two-dimensional transient models using the Euler–Euler approach and the kinetic theory of granular flows were applied to investigate the H2 production performance from a pilot-scale riser. The 2k full factorial design method was utilized to examine the significances of five specific parameters, namely, the riser diameter, inlet temperature, catalyst-to-sorbent ratio, solid flux, and inlet gas velocity on two response variables, namely, H2 purity and H2 flux. From the ANOVA results, either the main effect or the interactions of each parameter were shown to be significant on both the H2 purity and the H2 flux, particularly the riser diameter and the solid flux. For optimizing the operation and reaction parameters, the best case was the system with riser diameter of 0.2 m, inlet temperature of 600 °C, catalyst-to-sorbent ratio of 2.54 kg kg−1, solid flux of 200 kg m−2 s−1, and gas velocity of 3 m s−1, obtaining H2 purity of 91.30% on a dry basis with a significantly high H2 flux of 0.147 kg m−2 s−1. The hydrodynamics showed that SESRE reached breakthrough within the bottom dense zone. However, incomplete conversion occurred in the core of the riser because of the very dilute bed.

Two-Dimensional CFD Simulation of Reducing Operating Pressure Effect on the System Hydrodynamics in a Downer Reactor

The effect of the system hydrodynamics in a circulating fluidized bed downer (CFBD) reactor with a reducing operating pressure and solid mass flux on the hydrodynamics in a downer reactor were evaluated using a two-dimensional computational fluid dynamics simulation. Five low operating pressure conditions (0.90 to 0.99 atm) and four different solid mass fluxes (250 to 1,000 kg/m2 s) were explored. The simulation results demonstrated that the CFBD reactor had a higher mean free path when operated with a low solid mass flux than with a high solid mass flux. Moreover, a large difference between the operating and atmospheric pressures induced a high system turbulence or oscillation. The CFBD reactor with hydrodynamic fluctuation showed a good solid circulation between the gas and solid particles, as reflected by the solid volume fraction and velocities and granular temperature. These phenomena will be suitable for the chemical reaction systems. Therefore, a suitable solid mass flux was in the range of 500 to 750 kg/m2 s for all operating pressures under study because of the appropriate solid particle amount and the mixing in the system.

Effects of ZnO Addition on Fe2O3/Al2O3 Oxygen Carriers on CH4 Reduction for Chemical Looping Combustion

Fe2O3/Al2O3/ZnO oxygen carriers with small content ZnO (5 wt% to 10 wt%) were prepared by physical mixing method and were evaluated its capability as an oxygen carrier in a chemical looping combustion. The combustion was conducted by using CH4 as a fuel gas. The reduction process of Fe2O3/Al2O3/ZnO oxygen carrier was carried out in a fixed bed reactor. The solid reduction products were characterized by X-ray diffraction (XRD) and Scanning Electron Microscope with EDS Attachment (SEM-EDS). The results show that the reactivity of Fe2O3/Al2O3/ZnO oxygen carriers is greater than that of Fe2O3/Al2O3 which is implied the synergetic effect between ZnO and Fe2O3. XRD results show that the iron oxide in the oxygen carriers is reduced to metallic iron. SEM-EDS also shows that the iron agglomeration is prevented. Consequently, the suitable content of ZnO in oxygen carriers is ranged from 5 wt% to 10 wt%.