A Biomass Combustion-Gasification Model: Validation and Sensitivity Analysis

1995 ◽  
Vol 117 (4) ◽  
pp. 329-336 ◽  
Author(s):  
N. Bettagli ◽  
U. Desideri ◽  
D. Fiaschi

The aim of the present paper is to study the gasification and combustion of biomass and waste materials. A model for the analysis of the chemical kinetics of gasification and combustion processes was developed with the main objective of calculating the gas composition at different operating conditions. The model was validated with experimental data for sawdust gasification. After having set the main kinetic parameters, the model was tested with other types of biomass, whose syngas composition is known. A sensitivity analysis was also performed to evaluate the influence of the main parameters, such as temperature, pressure, and air-fuel ratio on the composition of the exit gas. Both oxygen and air (i.e., a mixture of oxygen and nitrogen) gasification processes were simulated.

2011 ◽  
Vol 317-319 ◽  
pp. 42-47
Author(s):  
Li Fang Zhang ◽  
Yong Chang Liu

By fitting the calculated transformed fraction according to developed phase-transformation model to the experimental data obtained by differential dilatometry, the kinetic characteristics of the austenitization process in T91 steels have been investigated. According to the kinetic parameters fitted, we recognize that the nucleation and growth of austenite grain are mainly controlled by the diffusion of carbon in ferritic and austenite respectively. In addition, by increasing the diffusion active energy of carbon in austenite, carbides hinder the motion of interface and thus refine austenite grain.


2012 ◽  
Vol 550-553 ◽  
pp. 2758-2762 ◽  
Author(s):  
Xi Jie Chu ◽  
Yong Gang Wang ◽  
Li Hong Zhao

The pyrolysis tests of Shenhua coal and Shenhua direct liquefaction residue have been carried out using thermogravimetric at the differential heating rate. The kinetic parameters k and E were calculated using DAEM method. Results show DAME model can describe the pyrolysis behavior of Shenhua coal within the range of 20% to 95%, the activation energy of coal pyrolysis ranges from 53.98 to 279.38 kJ/mol, and DAME model can describe the behavior of Shenhua direct liquefaction residue within the range of 10% to 80%, the activation energy of residue pyrolysis is about 170 kJ/mol. The results of which are basically consistent with the experimental data.


Author(s):  
Ryan A. Bandura ◽  
Timothy J. Jacobs

Computational fluid dynamics (CFD) is now a ubiquitous computational tool for engine design and diagnosis. It is often necessary to provide well-known initial cycle conditions to commence the CFD computations. Such initial conditions can be provided by experimental data. To create an opportunity to computationally study engine conditions where experimental data are not available, a zero-dimensional quasi-predictive thermodynamic simulation is developed that uses well-established spray model to predict rate of heat release and calculated burned gas composition and temperature to predict nitric oxide (NO) concentration. This simulation could in turn be used in reverse to solve for initial cylinder conditions for a targeted NO concentration. This paper details the thermodynamic simulation for diesel engine operating conditions. The goal is to produce a code that is capable of predicting NO emissions as well as performance characteristics such as mean effective pressure (MEP) and brake specific fuel consumption (BSFC). The simulation uses general conservation of mass and energy approaches to model intake, compression, and exhaust. Rate of heat release prediction is based on an existing spray model to predict how fuel concentrations within the spray jet change with penetration. Rate of heat release provides predicted cylinder pressure, which is then validated against experimental pressure data under known operating conditions. An equilibrium mechanism is used to determine burned gas composition which, along with burned gas temperature, can be used for prediction of NO in the cylinder. NO is predicted using the extended Zeldovich mechanism. This mechanism is highly sensitive to temperature, and it is therefore important to accurately predict cylinder gas temperature to obtain correct NO values. Additionally, MEP and BSFC are determined. The simulation focuses on single fuel injection events, but insights are provided to expand the simulation to model multiple injection events.


Author(s):  
Juncheng Li ◽  
Zhiyu Han ◽  
Cai Shen ◽  
Chia-fon Lee

In this paper, the effects of the start of injection (SOI) timing and exhaust gas recirculation (EGR) rate on the nitrogen oxides (NOx) emissions of a biodiesel-powered diesel engine are studied with computational fluid dynamics (CFD) coupling with a chemical kinetics model. The KIVA code coupling with a CHEMKIN-II chemistry solver is applied to the simulation of the in-cylinder combustion process. A surrogate biodiesel mechanism consisting of two fuel components is employed as the combustion model of soybean biodiesel. The in-cylinder combustion processes of the cases with four injection timings and three EGR rates are simulated. The simulation results show that the calculated NOx emissions of the cases with default EGR rate are reduced by 20.3% and 32.9% when the injection timings are delayed by 2- and 4-deg crank angle, respectively. The calculated NOx emissions of the cases with 24.0% and 28.0% EGR are reduced by 38.4% and 62.8%, respectively, compared to that of the case with default SOI and 19.2% EGR. But higher EGR rate deteriorates the soot emission. When EGR rate is 28.0% and SOI is advanced by 2 deg, the NOx emission is reduced by 55.1% and soot emission is controlled as that of the case with 24% EGR and default SOI. The NOx emissions of biodiesel combustion can be effectively improved by SOI retardation or increasing EGR rate. Under the studied engine operating conditions, introducing more 4.8% EGR into the intake air with unchanged SOI is more effective for NOx emission controlling than that of 4-deg SOI retardation with default EGR rate.


Author(s):  
Barnali Mandal

ABSTRACTObjectives: The aim of the study was to determine the growth kinetics of Pediococcus acidilactici using a mathematical model for large scale pediocinproduction.Methods: Growth kinetics of P. acidilactici has been studied for pediocin production in small scale batch fermenter (Erlenmeyer flask) using meatprocessing waste medium. The experiments have been conducted with varying the concentrations of glucose, protein, and lactic acid. A mathematicalmodel has been developed to describe growth rate, products (pediocin and lactic acid) formation rate, and substrates (glucose and protein) utilizationrate. Monod model for dual substrates (glucose and protein) has been used with considering lactic acid inhibition. Luedeking-Piret model has beenintroduced to describe the production of pediocin and lactic acid.Results: The values of kinetic parameters have been determined using experimental data and model equations. The model prediction has beencompared satisfactorily with the experimental data for the validation of the model.Conclusions: The developed model was satisfactorily validated to scale up the production of pediocin.Keywords: Pediococcus acidilactici, Pediocin, Meat processing waste, Monod model, Luedeking-Piret model, Kinetic parameters.


2021 ◽  
Vol 263 ◽  
pp. 03009
Author(s):  
Ilya Ovchinnikov ◽  
Vladimir Avzovin

Quite a lot of works have been devoted to the problem of modeling the behavior of thin-walled structures exposed to an aggressive environment leading to corrosive wear of their surface. Researchers have proposed a fairly large set of models of corrosive wear, taking into account the influence of various factors on the kinetics of corrosion (time, material, temperature, the nature of the corrosive environment, the stress-strain state of the structure). Moreover, different authors often propose different models for the same conditions. In the article under consideration, a rather unique comparative study of three corrosion models proposed by different authors (Dolinsky V.M., Gutman E.M., Ovchinnikov I.G.) was carried out to simulate the behavior of the same circular plate subjected to the combined action of load and corrosion wear and tear. Moreover, the identification of the models, that is, the determination of the coefficients included in them, was carried out using the same experimental data. These models were then used to simulate the behavior of plates subject to corrosive wear under various loads. The results of numerical simulation were compared with experimental data obtained during testing of corrosive plates. Interestingly, in the models used, the effect of the stress state on the kinetics of corrosion was taken into account using different invariants of the stress state: the stress intensity in V.M. Dolinsky, medium voltage in the model of E.M. Gutman, and the specific energy in the model of I.G. Ovchinnikov. The analysis showed that the difference from the experiment when using the three models considered does not exceed 9.3%. The discrepancy between the results obtained using different models is also within the acceptable range, which suggests that all three models can be used to predict the behavior of plates under corrosive wear conditions. However, it is of interest to conduct research on the predictive capabilities of models on large forecast arms that go beyond the scope of experimental studies. At the same time, carrying out numerical experiments to simulate the behavior of complex structures in a stressed state and subject to corrosive wear, using several models that allow a good description of the experimental data and the most complete consideration of the operating conditions, makes it possible to obtain a more complete and versatile picture of what is happening in design processes, in comparison with the calculations performed according to one model, even if it describes the experimental data well.


Metals ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 1131 ◽  
Author(s):  
Ono ◽  
Uchikoshi ◽  
Hayashi ◽  
Kitagawa ◽  
Yeh ◽  
...  

A versatile numerical model for hydrogen absorption into metals was developed. Our model addresses the kinetics of surface adsorption, subsurface transport (which plays an important role for metals with active surfaces), and bulk diffusion processes. This model can allow researchers to perform simulations for various conditions, such as different material species, dimensions, structures, and operating conditions. Furthermore, our calculation scheme reflects the relationship between the temperature changes in metals caused by the heat of adsorption and absorption and the temperature-dependent kinetic parameters for simulation precision purposes. We demonstrated the numerical fitting of the experimental data for various Pd temperatures and sizes, with a single set of kinetic parameters, to determine the unknown kinetic constants. Using the developed model and determined kinetic constants, the transitions of the rate-determining steps on the conditions of metal-hydrogen systems are systematically analyzed. Conventionally, the temperature change of metals during hydrogen adsorption and absorption has not been a favorable phenomenon because it can cause errors when numerically estimating the hydrogen absorption rates. However, by our calculation scheme, the experimental data obtained under temperature changing conditions can be positively used for parameter fitting to efficiently and accurately determine the kinetic constants of the absorption process, even from a small number of experimental runs. In addition, we defined an effectiveness factor as the ratio between the actual absorption rate and the virtually calculated non-bulk-diffusion-controlled rate, to evaluate the quantitative influence of each individual transport process on the overall absorption process. Our model and calculation scheme may be a useful tool for designing high-performance hydrogen storage systems.


Author(s):  
Navid Mostoufi ◽  
Ali Ghoorchian ◽  
Rahmat Sotudeh-Gharebagh

The kinetics of acetylene hydrogenation has been studied in a fixed bed reactor of a commercial Pd/Al2O3 catalyst. The experiments were carried out at 30, 50 and 70 ºC with various feed compositions at atmospheric pressure. The experiments were repeated at 70 ºC in the presence of the used catalyst to determine the effect of the catalyst deactivation where the corresponding deactivation rate constant was determined in order to predict the activity of the catalyst during each run. Two well known kinetic models were used for a nearly similar catalyst to predict the experimental data of this work and none of them were found satisfactory. A new model was then proposed to fit the experimental data. The hydrogenation reactor was also simulated at industrial operating conditions with the proposed kinetics for both plug and dispersion flows. The results of these simulations were almost close to each other in most cases.


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