• Energy Research

Abstract Fluidized bed reactor significantly intensified the shrimp shell (SS) calcination process for the preparation of high performance CaO based catalyst. A modified Shrinking-Core Model (SCM) was employed to describe the calcination process at high temperature. The activation energy of the chemical reaction controlled initial stage of the decomposition was 64 kJ mol −1 . The activation energy of the diffusional controlled subsequent stage of the decomposition was 22 kJ mol −1 . The response surface methodology (RSM) and the central composite design (CCD) were used to optimize biodiesel preparation conditions. Three critical operational parameters, calcination temperature (°C), catalyst loading (%) and methanol to oil ratio (–) were chosen as independent variables in CCD. The individual effect of the calcination temperature and the combined effect of the calcination temperature with the catalyst loading were significant to biodiesel conversion. The optimal condition for achieving the maximum biodiesel conversion was obtained: calcination temperature (800 °C), catalyst loading (3%), and the ratio of methanol to oil (10), with yield and conversion reaching 87.5% and 89%. The 0.16 h of calcination duration was achieved using fluidized bed reactor.

The use of an industry waste, brown coal fly ash collected from the Latrobe Valley, Victoria, Australia, has been tested for the post-combustion CO(2) capture through indirect minersalization in acetic acid leachate. Upon the initial leaching, the majority of calcium and magnesium in fly ash were dissolved into solution, the carbonation potential of which was investigated subsequently through the use of a continuously stirred high-pressure autoclave reactor and the characterization of carbonation precipitates by various facilities. A large CO(2) capture capacity of fly ash under mild conditions has been confirmed. The CO(2) was fixed in both carbonate precipitates and water-soluble bicarbonate, and the conversion between these two species was achievable at approximately 60°C and a CO(2) partial pressure above 3 bar. The kinetic analysis confirmed a fast reaction rate for the carbonation of the brown coal ash-derived leachate at a global activation energy of 12.7 kJ/mol. It is much lower than that for natural minerals and is also very close to the potassium carbonate/piperazine system. The CO(2) capture capacity of this system has also proven to reach maximum 264 kg CO(2)/ton fly ash which is comparable to the natural minerals tested in the literature. As the fly ash is a valueless waste and requires no comminution prior to use, the technology developed here is highly efficient and energy-saving, the resulting carbonate products of which are invaluable for the use as additive to cement and in the paper and pulp industry.

In this work, the impact of chemical additions, especially nano-particles (NPs), was quantitatively analyzed using our constructed artificial neural networks (ANNs)-response surface methodology (RSM) algorithm. Fe-based and Ni-based NPs and ions, including Mg2+, Cu2+, Na+, NH4+, and K+, behave differently towards the response of hydrogen yield (HY) and hydrogen evolution rate (HER). Manipulating the size and concentration of NPs was found to be effective in enhancing the HY for Fe-based NPs and ions, but not for Ni-based NPs and ions. An optimal range of particle size (86–120 nm) and Ni-ion/NP concentration (81–120 mg L−1) existed for HER. Meanwhile, the manipulation of the size and concentration of NPs was found to be ineffective for both iron and nickel for the improvement of HER. In fact, the variation in size of NPs for the enhancement of HY and HER demonstrated an appreciable difference. The smaller (less than 42 nm) NPs were found to definitely improve the HY, whereas for the HER, the relatively bigger size of NPs (40–50 nm) seemed to significantly increase the H2 evolution rate. It was also found that the variations in the concentration of the investigated ions only statistically influenced the HER, not the HY. The level of response (the enhanced HER) towards inputs was underpinned and the order of significance towards HER was identified as the following: Na+ > Mg2+ > Cu2+ > NH4+ > K+.

Abstract Fischer-Tropsch (FT) synthesis was carried out in a microchannel reactor using an iron-based catalyst. The performance of microchannel reactor was evaluated in the aspect of CO conversion versus time on stream, catalyst deactivation, pressure drop and gas hour space velocity. The result indicates an excellent mass and heat transfer in the microchannel reactor. The negative impact of external and internal film diffusional limitation could be avoided in this microchannel reactor at experimental conditions. The effect of reaction temperature, operational pressure, syngas ratio and space velocity upon CO conversion and hydrocarbon selectivity were extensively investigated. The kinetic modeling was conducted and the mechanisms i.e. carbide, enlic, alkyl, formate and CO insertion were extensively explored. A mechanism derived from Eley-Rideal-type mechanism was found to be the most statistical and physical relevance at the experimental conditions during FT synthesis using iron-based catalyst in this microchannel reactor.

AbstractHerein, the production of biohydrogen by dark fermentation was optimized using a novel hybrid approach that combines ANNs (artificial neural networks) with RSM (response surface methodology). Using the limited numbers of data (15 runs) as training data set together with one cross‐out method for validation, the complete 29 runs of well‐established data matrix were created from ANNs for RSM statistical analysis in order to correlated the critical process parameters with hydrogen production performance. This methodology was found to be robust, cost‐effective, reliable, and can be extensively analyzed the critical operational parameters, that is, carbon sources (obtained from potato peel wastes and starchy wastes), metal cofactor Fe0, pH, and dose levels of microbes on the hydrogen production, along with concentrations of other metabolites, such as acetic acid, propionic acid, butyric acid, valeric acid, and ethanol. The established ANNs‐RSM model using Box–Behnken design indicates the significant changes caused by the variations of a few critical operation parameters. The resultant model shows an exceptionally good result in terms of nonlinear noisy processes. Both single and multiple objective optimizations for dark hydrogen fermentation can achieve by using the established hybrid ANN‐RSM system. The optimal operating conditions (starch 6.2 kg/m3, pH 6.7, Fe0 11.7 g/m3, sludge 24.6 g/m3) could lead to the generation of hydrogen with a yield of 106.2 (cm3/g) and metabolites, that is, propionic acid (2.8 kg/m3), butyric acid (2E−2 kg/m3), valeric acid (4E−4 kg/m3) acetic acid (1.9 kg/m3), and ethanol (0.1 kg/m3) simultaneously.

The basic oxygen furnace slag (SL) was selectively leached by NH4Cl. Response surface methodology and the central composite design (CCD) were employed in determining the optimal condition. The process parameters such as leaching duration, NH4Cl concentration, liquid solid ratio (LSR), and leaching temperature were chosen as independent variables in CCD. The quadratic model was developed for process optimization and statistical experimental designs. It is found that the leaching duration, NH4Cl concentration and liquid solid ratio are significant to the extraction of Ca2+ and Mg2+. The optimal conditions with setting maximum extraction of calcium and magnesium cations from SL are as following: 68 min (X1), 1.8 mol/L NH4Cl (X2), LSR 12 mL/g (X3), 53°C (X4), with the predicted Ca2+ and Mg2+ concentration reaching 13.3 and 3.2 g/L, respectively. The proposed simplified leaching mechanism indicates a two‐stage leaching. The prone leachable MgFe2O4 and Ca2Fe2O5 are extracted in the fast stage, while the extraction of CaO occurs throughout slow stage. © 2016 American Institute of Chemical Engineers Environ Prog, 35: 1387–1394, 2016

Abstract Fluidized bed efficiently intensifies thermal decomposition of Mg(OH)2 for fast preparation of porous MgO. The shrinking core model is found to well describe the decomposition process. The initial stage of decomposition is controlled by chemical reaction with activation energy being 104 kJ/mol and the subsequent stage is then controlled by diffusion with activation energy being 15 kJ/mol. The response surface methodology (RSM) and the central composite design (CCD) are employed for determining optimal conditions to prepare adsorbent with maximum CO2 removal capacity. The operational parameters such as dehydration temperature (°C), duration (min) and FR-flow rate (Nm3/h) are chosen as independent variables in CCD. The statistical analysis indicates that the effects of dehydration temperature and combined effect of temperature and duration are all significant to the CO2 removal capacity. The optimal condition for achieving the maximum CO2 adsorption capacity is obtained as the following: temperature (480 °C), duration (42 min), FR (13.8 Nm3/h) with CO2 removal capacity reaching 33 mg/g. The employment of fluidized bed in process intensification significantly reduces the thermal treatment duration down to 0.7 h.

AbstractActivated carbon was produced by K2CO3 chemical activation of furfural production waste. The results showed that the product is essentially microporous carbon whose BET surface area and pore volume when the carbon was activated at 800°C were 2218 m2/g and 1.04 cm3/g, respectively. The potential usefulness of resultant carbons for gas storage is closely investigated. The hydrogen adsorption study showed that all the carbons exhibited a fast adsorption rate and the carbon activated at 800°C had the largest amount of adsorbed hydrogen due to its greater specific surface area and micropore volume. The hydrogen adsorption capacity of the carbon activated at 800°C can reach 1.7 wt % at 77K 1 atm and 0.48 wt % at 298K 6 MPa, respectively. The isosteric heat of adsorption with zero loading of hydrogen on carbon with the largest specific surface area can be 5 kJ/mol. The adsorption model based on Tóth equation together with Benedict‐Webb‐Rubin (BWR) equation of state is proposed for this carbon in adsorbing hydrogen under high pressure. © 2010 American Institute of Chemical Engineers Environ Prog, 2010.