A diffusion-controlled mullite formation reaction model based on tracer diffusivity data for aluminium, silicon and oxygen

2007 ◽  
Vol 87 (1) ◽  
pp. 111-127 ◽  
Author(s):  
P Fielitz ◽  
G Borchardt ◽  
M Schmücker ◽  
H Schneider
Keyword(s):  
Reaction Model ◽  
Mullite Formation ◽  
Tracer Diffusivity ◽  
Formation Reaction ◽  
Model Based ◽  
Diffusion Controlled

Combustion characteristics of biomass and bituminous coal co-firing in non-isothermal and isothermal conditions

BioResources ◽  
2020 ◽  
Vol 15 (4) ◽  
pp. 9490-9506
Author(s):  
Meijing Chen ◽  
Baojun Yi ◽  
Zhigang Li ◽  
Qiaxia Yuan
Keyword(s):  
Bituminous Coal ◽  
Reaction Model ◽  
Combustion Characteristic ◽  
Thermogravimetric Method ◽  
Characteristic Index ◽  
Isothermal Conditions ◽  
Diffusion Controlled ◽  
Chemical Reaction Model ◽  
Stage 1 ◽  
Model Diffusion

A thermogravimetric method was used to study the combustion of bituminous coal (BC), diverse biomass (wood chips: WC, chaff: CH), and their blends under non-isothermal conditions and isothermal conditions. A higher blending amount of WC or CH under non-isothermal conditions resulted in a lower ignition temperature, burnout temperature, and a greater comprehensive combustion characteristic index. Meanwhile, the co-combustion of BC, WC, and CH all showed inhibiting effects. The inhibition effect was prominent when the blending ratio of WC was below 30%. Under isothermal conditions, with the increase of oxygen concentration and blending amount, the combustion performance of BC improved gradually. The synergistic effect between BC and biomass dominated, and the interaction was more distinct when WC content exceeded 50%. Under both non-isothermal and isothermal conditions, the interaction between CH and BC did not vary at diverse blending ratios. The dynamic results suggested that the chemical reaction model O1 was suitable for stage 1 of the co-combustion of WC and BC, the model diffusion controlled D4 controlled the co-combustion of CH and BC and stage 2 of the co-combustion of WC and BC. The blending ratio of WC or CH with the lowest activation energy was 50%.

scholarly journals The Development and Implementation of Model-Based Control Algorithm of Urea-SCR Dosing System for Improving De-NOx Performance and Reducing NH3-Slip

2011 ◽  
Author(s):  
Soo-Jin Jeong ◽  
Woo-Seung Kim ◽  
Jung-Kwon Park ◽  
Ho-Kil Lee ◽  
Se-Doo Oh
Keyword(s):  
Control Algorithm ◽  
Catalytic Reduction ◽  
Fluid Model ◽  
Nox Reduction ◽  
Reaction Model ◽  
Urea Solution ◽  
Model Based Control ◽  
Model Based ◽  
Nh3 Emission ◽  
Scr System

The selective catalytic reduction (SCR) system is a highly-effective aftertreatment device for NOx reduction of diesel engines. Generally, the ammonia (NH3) was generated from reaction mechanism of SCR in the SCR system using the liquid urea as the reluctant. Therefore, the precise urea dosing control is a very important key for NOx and NH3 slip reduction in the SCR system. This paper investigated NOx and NH3 emission characteristics of urea-SCR dosing system based on model-based control algorithm in order to reduce NOx. In the map-based control algorithm, target amount of urea solution was determined by mass flow rate of exhaust gas obtained from engine rpm, torque and O2 for feed-back control NOx concentration should be measured by NOx sensor. Moreover, this algorithm cannot estimate NH3 absorbed on the catalyst Hence, the urea injection can be too rich or too lean. In this study, the model-based control algorithm was developed and evaluated based on the analytic model for SCR system. The channel thermo-fluid model coupled with finely tuned chemical reaction model was applied to this control algorithm. The vehicle test was carried out by using map-based and model-based control algorithms in the NEDC mode in order to evaluate the performance of the model based control algorithm.

scholarly journals ACTIVITY OF PROPYL p-BENZOYLOXYBENZOATE AS A GLUTATHIONE S-TRANSFERASE(S) INHIBITOR: THE COMPARISON BETWEEN COMPUTATIONAL CHEMISTRY APPROACH AND EMPIRICAL OBSERVATION

2010 ◽  
Vol 6 (1) ◽  
pp. 88-93
Author(s):  
Enade Perdana Istyastono ◽  
Agnes Nora Iska Harnita ◽  
Sudibyo Martono
Keyword(s):  
Computational Chemistry ◽  
Quantitative Structure Activity Relationship ◽  
Reaction Model ◽  
Glutathione S Transferase ◽  
Qsar Study ◽  
Anticancer Compounds ◽  
Empirical Observation ◽  
Formation Reaction ◽  
Multifunctional Enzymes ◽  
The Difference

The activity of propyl p-benzoyloxybenzoate as a glutathione S-transferase(s) (GSTs) inhibitor has been examined through computational chemistry based theoretical approach and laboratory experiment. This research was related to the nature of GSTs as multifunctional enzymes, which play an important role in the detoxification of electrophilic compounds, the process of inflammation and the effectivities of anticancer compounds. Quantitative Structure-Activity Relationship (QSAR) study, which was established on curcumin and its derivatives using computational chemistry approach, was used to examine the theoretical activity of p-benzoyloxybenzoate as a GSTs inhibitor. Empirical observation on GSTs inhibition was examined using formation reaction model of GS-CNB conjugate through conjugation of 1-chloro-2,4-dinitrobenzene (CDNB) and glutathione (GSH) with GSTs (prepared from rat's liver) as catalysts. The result showed that the difference between the activities of propyl p-benzoyloxybenzoate as a GSTs inhibitor obtained from the computational chemistry approach and the empirical observation were not statistically significant at 95% level of confidence.   Keywords: Propyl p-benzoyloxybenzoate, inhibitor,  glutathione S-transferase (GSTs), QSAR

scholarly journals A model of the growth of hydrogen bubbles in the electrolysis of water

2021 ◽  
Vol 927 ◽  
Author(s):  
F.J. Higuera
Keyword(s):  
Current Density ◽  
Electrode Surface ◽  
Reaction Model ◽  
Supersaturated Solution ◽  
Average Current Density ◽  
Hydrogen Bubbles ◽  
Diffusion Controlled ◽  
Dilute Aqueous Solution ◽  
Average Current ◽  
And Migration

The growth of attached bubbles during the electrochemical evolution of hydrogen at a horizontal cathode at the base of a quiescent, dilute aqueous solution is analysed using a simple model of the process that includes the Butler–Volmer reaction model, the diffusion and migration of electroactive species and a symmetry condition that approximately accounts for the presence of periodically spaced bubbles on the electrode surface. The diffusion controlled growth of a bubble approximately follows a $t^{1/2}$ law when the spacing of the bubbles on the electrode is large, departing slightly from it due to the non-uniformity of the concentration of dissolved hydrogen in the supersaturated solution into which the bubble grows, and approaches a $t^{1/3}$ law when the spacing decreases. The space- and time-averaged current density increases exponentially with the applied voltage for an alkaline solution when the consumption of water in the reaction is not taken into account. For an acidic solution, the average current density saturates to a transport limited value that depends on bubble spacing. For a given voltage, the presence of attached bubbles increases the average current density due to the decrease of the concentration overpotential caused by the bubbles. The spacing of the bubbles on the electrode surface decreases when the voltage increases if the maximum supersaturation at the electrode is imposed to be constant. The result suggests that coalescence of attached bubbles will occur above a certain voltage.

Kinetic mechanisms for mullite formation from sol-gel precursors

1990 ◽  
Vol 5 (9) ◽  
pp. 1963-1969 ◽  
Author(s):  
Dong X. Li ◽  
William J. Thomson
Keyword(s):  
Activation Energy ◽  
Reaction Kinetics ◽  
Single Phase ◽  
Sol Gel ◽  
Mullite Formation ◽  
X Ray Diffraction ◽  
X Ray ◽  
Diffusion Controlled ◽  
Kinetic Mechanisms ◽  
Kinetics Of

The reaction kinetics for the formation of mullite (3Al2O3 · 2SiO2) from sol-gel derived precursors were studied using dynamic x-ray diffraction (DXRD) and differential thermal analysis (DTA). The reaction kinetics of diphasic and single phase gels are compared and different reaction mechanisms are found for each gel. Mullite formation in the diphasic gel exhibits an Avrami type, diffusion-controlled growth mechanism with initial mullite formation temperatures of about 1250 °C and an activation energy on the order 103 kJ/mole. On the other hand, mullite formation from the single phase gel is a nucleation-controlled process with an initial formation temperature of 940 °C and a much lower activation energy of about 300 kJ/mole.

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