This work investigates the deposition precipitation, pore volume impregnation and hydrothermal methods of synthesizing activated carbon monolith supported metal oxide adsorbent (Co3O4/ACM). The hydrothermally synthesized Co3O4 activated carbon monolith adsorbent (Hm-Co3O4/ACM) demonstrate better adsorption capacity (SO2 is 123.1, NOx is 130.2 mg/g) than the adsorbents synthesized by the other methods. The adsorbent displayed high affinity to NOx adsorption where this influence was associated to operation conditions, physical and chemical properties of the adsorbent which were expressed in the plot of the breakthrough curve. Moreover, the surface properties (BET), thermal decomposition (TGA), functional groups (FTIR), chemical composition (XRD) and surface morphology (FESEM) of the adsorbent were investigated. The Langmuir adsorption isotherm fitted the experimental results meanwhile, the thermal regeneration of the adsorbent over two cycles showed an average regeneration efficiency of 94.4% for SO2 and 94.8% for NOx. Finally, the post regeneration characterization analyses were discussed.
Air gasification of Napier grass (NG) was studied with the target of producing combustible synthesis gas to be used in direct combustion for power generation. A small-scale autothermal bubbling fluidized bed gasifier was used to investigate the effect of reactor temperature, equivalence ratio (ER), and static bed height (SBH) on gasification performance and combustibility of the producer gas. The main generated species in syngas were identified through gas chromatography (GC) analysis. Minimum fluidization conditions were determined at different levels of SBH. Experiments carried out with two intentions of first, to achieve the highest composition of combustible species to ensure the maximum Lower Heating Value (LHV) of syngas and second, to obtain a high performance process with maximum yield of syngas and minimum residues. The results showed that the temperature and ER have significant effects on syngas yield and composition. SBH was found have a substantial effect on the production of H2 and CO. The results from this study was compared to other gasification studies from literature which have evaluated biomass gasification in bubbling fluidized bed reactors with different scales but almost similar method of experimentation. The purpose of verification was to demonstrate the effect of different reactor scales and heating characteristics on the results.
In this work, we employed a computational fluid dynamics (CFD)-based model with a Eulerian multiphase approach to simulate the fluidization hydrodynamics in biomass gasification processes. Air was used as the gasifying/fluidizing agent and entered the gasifier at the bottom which subsequently fluidized the solid particles inside the reactor column. The momentum exchange related to the gas-phase was simulated by considering various viscous models (i.e., laminar and turbulence models of the re-normalisation group (RNG), k-ε and k-ω). The pressure drop gradient obtained by employing each viscous model was plotted for different superficial velocities and compared with the experimental data for validation. The turbulent model of RNG k-Ɛ was found to best represent the actual process. We also studied the effect of air distributor plates with different pore diameters (2, 3 and 5 mm) on the momentum of the fluidizing fluid. The plate with 3-mm pores showed larger turbulent viscosities above the surface. The effects of drag models (Syamlal–O’Brien, Gidaspow and energy minimum multi-scale method (EMMS) on the bed’s pressure drop as well as on the volume fractions of the solid particles were investigated. The Syamlal–O’Brien model was found to forecast bed pressure drops most consistently, with the pressure drops recorded throughout the experimental process. The formation of bubbles and their motion along the gasifier height in the presence of the turbulent flow was seen to follow a different pattern from with the laminar flow.
Due to the adverse effects of SO 2 /NO x on humans and the environment, environmental regulations necessitate the control of their emission. In this study, an activated carbon monolith was synthesized with cobalt oxide (ACM-Co 3 O 4 ) for the purpose of simultaneous SO 2 /NO x removal from flue gas generated by coal combustion. Average regeneration efficiencies of 92.7 and 94.2 % were obtained for SO 2 and NO x , respectively. The Langmuir model can adequately describe the experimental results of the ACM-Co 3 O 4 adsorbent in SO 2 and NO x removal. The key regeneration parameters were optimized by using the response surface methodology (RSM). The RSM results revealed that the statistical prediction and experimental results were in agreement.
Coal combustion is a primary source of acid gases such as sulfur dioxide (SO2) and nitrogen dioxide (NOx); meanwhile, their effects are detrimental to man and the environment. In this work, three different adsorbents were developed by loading Co3O4 on monolith using pore volume impregnation, deposition precipitation, and hydrothermal methods (HMs) of synthesis.The breakthrough study in the simultaneous SO2 and NOx removal from flue gas revealed that the performance of the adsorbent developed by HM was better than the adsorbents developed by the other methods. Therefore, the characterization analysis and optimization of the variables that affect the adsorption capacity on the best performed adsorbent by response surface methodology were carried out. The model prediction and the experimental results for the adsorption capacity of SO2 are 134.5 and 132.9 mg/g while 152.1 and 151.6 mg/g were obtained for NOx. Furthermore, the optimized independent variables comprising amount of adsorbents, airflow rate, and temperature are 1 mg, 400 mL/min, and 100°C. The regression coefficient of 0.9934 for SO2 and 0.9991 for NOx was obtained which indicates that the interaction between the independent variables and the adsorption capacity of SO2 and NOx is very significant. These results confirmed the suitability of the model for the prediction of the process behavior and the performance of the adsorbent at low temperature with high adsorption capacity emerged as a new finding.
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