| 1. |
- Revstedt, Johan, et al.
(author)
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Large eddy simulation of flow in stirred vessels
- 2002
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In: Chemical Engineering & Technology. - 0930-7516 .- 1521-4125. ; 25:4, s. 443-446
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Journal article (peer-reviewed)abstract
- Large eddy simulations (LES) of the flow in stirred tanks were performed. One of the advantages with LES is that it can provide details of the flow field that cannot be obtained with so-called Reynolds averaged equations and the corresponding models. Simulations were done on both single and multi-impeller systems. Both Rushton and curved-blade radial impellers were studied in both a fixed and a rotating frame of reference. The results show that the periodicity is much stronger and present in a larger part of the vessel for the Rushton turbine than for a curved-blade turbine.
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| 2. |
- Kovacs, T., et al.
(author)
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Flow and turbulence in the discharge of radial pumping turbines : Influence of the turbine type
- 2001
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In: Chemical Engineering & Technology. - 0930-7516 .- 1521-4125. ; 24:10, s. 1035-1044
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Journal article (peer-reviewed)abstract
- Velocity measurements were made in the impeller discharge of 6SRGT- and Rushton-type impellers in a 0.6 m(3) tank using, constant temperature anemometry with a direction sensitive split-film probe. The reproducibility error of the measurement system was found to be greater than 5 % for all measured properties. The main flow and turbulent parameters measured at three agitation rates in the impeller discharge are compared for the two turbines with respect to both agitation rate and the measured power input. For comparison of the flow properties in the centerline of the two turbines having different diameter and blade height, a uniform representation was used treating the impeller stream as a special kind of free jet. Using this representation, we obtained similar results for both turbines on all measured parameters. The profile measurements showed a similar main flow field for both turbines, but significant differences were found in the axial distribution of turbulent kinetic energy and the energy dissipation rate.
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| 3. |
- Skoglund, A., et al.
(author)
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Comparison between linear and nonlinear prediction models for monitoring of a paperboard machine
- 2002
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In: Chemical Engineering & Technology. - 0930-7516 .- 1521-4125. ; 25:2, s. 197-202
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Journal article (peer-reviewed)abstract
- Data from a paperboard machine were used to compare the performance of linear partial least squares (PLS) and nonlinear feed-forward neural network (FFNN) modeling of a continuous process. Fifteen selected variables were used as input parameters to the models, while the quality class of the manufactured product was the output response. The models were validated with external data different to those used in the design of the models. Evaluation with root mean square error of prediction (RMSEP) showed that the FFNN models were better for prediction than the PLS models. For monitoring, however, the PLS models detected deviations from normal settings in the paperboard machine more sensitively than the FFNN models. It is suggested that these findings have general relevance to other continuous processes in manufacturing industries too.
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| 4. |
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| 5. |
- Al-Rabiah, Abdulrahman A., et al.
(author)
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Comparative Kinetic Analysis and Process Optimization for the Production of Dimethyl Ether via Methanol Dehydration over a γ-Alumina Catalyst
- 2022
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In: Chemical Engineering & Technology. - : Wiley. - 1521-4125 .- 0930-7516. ; 45:2, s. 319-328
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Journal article (peer-reviewed)abstract
- Various kinetic models of methanol dehydration to dimethyl ether over a commercial γ-alumina catalyst were compared with a view to selecting the most appropriate model as a basis for process optimization. To achieve significant improvements in the conventional design, the Berčič-and-Levec kinetic model was employed and process intensification was applied to develop a more energy-efficient process, by enhancing the adiabatic reactor performance and maximizing the heat recovery from the highly exothermic reactor. The single-pass conversion of methanol was increased to 83 %, with an inlet temperature of 217 °C to the adiabatic reactor. Application of process intensification resulted in an improved flowsheet, which reduced the total energy requirements by 59.3 % and cut the CO2 emissions by 60.8 %.
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| 6. |
- Arjmand, Mehdi, et al.
(author)
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Energy Saving in Crude Oil Atmospheric Distillation Columns by Modifying the Vapor Feed Inlet Tray
- 2011
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In: Chemical Engineering & Technology. - : Wiley. - 0930-7516 .- 1521-4125. ; 34:8, s. 1359-1367
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Journal article (peer-reviewed)abstract
- Optimization of a typical crude oil atmospheric distillation unit and reduction of energy conservation were carried out through modifying the implementation and change in the flash zone of the tower. A conventional procedure in such units involves the combination of liquid and vapor product of the prefractionation train surge drum upon introduction to the tower. However, it is theoretically illustrated and represented by simulation means that introducing the vapor feed into the upper stages of the distillation column separately can lead to an energy saving of 12.6% in the condenser duty, an increased liquid-to-gas flow (L/G) at certain points of the column, and hence to a reduction in diameter and investment costs of new tower designs of approximately US$ 0.7 million a(-1). The proposal can be put into practice without the need of additional equipments or additional cost of difficult rerouting the streams. An industrial case study of a steadystate crude oil distillation unit is given by simulation provision of AspenHysys (TM).
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| 7. |
- Azis, Muhammad Mufti, 1983, et al.
(author)
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The Effect of Bituminous and Lignite Ash on the Performance of Ilmenite as Oxygen Carrier in Chemical‐Looping Combustion
- 2013
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In: Chemical Engineering and Technology. - : Wiley. - 0930-7516 .- 1521-4125. ; 36:9, s. 1460-1468
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Journal article (peer-reviewed)abstract
- The influence of ash in chemical-looping combustion (CLC) has been studied in a lab-scale fluidized bed reactor. The oxygen carrier, ilmenite, was investigated with German lignite coal, Chinese bituminous coal, Mexican pet coke, wood char, and methane. Lignite ash and ash from gasified Chinese bituminous coal were compared in this study. Up to 50 wt % and 33.3 wt % loadings of ash from the combustion of lignite and ash from the gasification of coal were added. The gas conversion was clearly affected by the addition of ash, and very similar results were seen both for methane conversion and for CO conversion in the solid fuel tests. Thus, both ashes showed initial decrease in gas conversion with the addition of some ash due to the presence of inert/deactivating material in the ashes. At higher ash loading, a beneficial effect of ash could be seen. Furthermore, no negative effect of ash addition on the fluidizability of the bed material could be seen.
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| 8. |
- Bachinger, T., et al.
(author)
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Physiologically motivated monitoring of fermentation processes by means of an electronic nose
- 2001
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In: Chemical Engineering & Technology. - 0930-7516 .- 1521-4125. ; 24:7, s. 33-42
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Journal article (peer-reviewed)abstract
- An on-line approach of non-invasive monitoring of the physiological changes in fermentation processes is presented. In yeast batch and bacterial fed-batch fermentations it is shown that metabolic state changes can be revealed using an electronic nose. The transient responses of the gas sensors to the changes in the composition of the volatiles emitted from the cell cultures during fermentation are used to retrieve a semi-quantitative representation of the physiological state of the cultures. With the sensor responses of the electronic nose it is shown that physiological variables such as rates of growth, substrate uptake and product formation can be depicted. The non-invasive method thus seems as a pertinent alternative to conventional bioreactor monitoring methods.
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| 9. |
- Brogren, C, et al.
(author)
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Absorption of NO in an alkaline solution of KMnO4
- 1997
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In: Chemical Engineering & Technology. - : Wiley. - 1521-4125 .- 0930-7516. ; 20:6, s. 396-402
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Journal article (peer-reviewed)abstract
- A packed column has been used to study the absorption of nitrogen oxide in an alkaline solution of potassium permanganate. The reactions taking; place during the absorption have been examined and the rate constants have been estimated from experimental data. The experiments show that potassium permanganate is an excellent absorbent for nitrogen oxide. However, to avoid formation of MnO2, the hydroxide concentration has to be very high, i.e. >3 mol/l. It was found that the reaction could be expressed as first-order with respect to NO and with respect to KMnO4. The rate constant may be expressed in terms of the hydroxide concentration as follows: k(mn) = 6114.9 10(1.9208 10-4 CNaOH) m(3) mol(-1) s(-1).
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| 10. |
- Bruening, Simone, et al.
(author)
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Modeling Suspension Cultures of Microbial and Mammalian Cells with an Adaptable Six-Compartment Model
- 2017
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In: Chemical Engineering & Technology. - : WILEY-V C H VERLAG GMBH. - 0930-7516 .- 1521-4125. ; 40:5, s. 956-966
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Journal article (peer-reviewed)abstract
- Process models can be used for model-based control strategies, but model development is a time-consuming and laborious task. To reduce the modeling effort, a new structured compartment model was developed, which may easily be adapted to different cultivation processes. The proposed six-compartment model was used to describe the time courses of cultivations of bacteria, yeast, fungi, and mammalian cell lines, namely, Escherichia coli,Lactobacillus delbrueckii, Saccharomyces cerevisiae, Cyathus striatus, and a hybridoma mammalian cell line. The model can describe the time courses of important state variables and can be adapted to the cultivation processes by parameterization. This reduces the modeling effort for a new process significantly.
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