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排序方式: 共有134条查询结果,搜索用时 546 毫秒
31.
32.
Bruins EE Bauer TS den Bok HW Duif CP van Hoek WC de Lange DJ Misiejuk A Papandreou Z Sichtermann EP Tjon JA Willering HW Yeomans DM Reike H Durek D Frommberger F Gothe R Jakob D Kranefeld G Kunz C Leiendecker N Pfeiffer G Putsch H Reichelt T Schoch B Wacker D Wehrmeister D Wilhelm M Jans E Konijn J de Vries R Furget C Voutier E Arenhövel H 《Physical review letters》1995,75(1):21-24
33.
The mathematical optimization of a continuous alcoholic fermentation process combined with a flash column under vacuum was
studied. The objective was to maximize % yield and productivity in the fermentor. The results using surface response analysis
combined with modeling and simulation were compared withy those obtained when the problem was written as a nonlinear programming
problem and was solved with a successive quadratic programming (SQP) technique. Two process models were evaluated when the
process was optimized using the SQP technique. The first one is a deterministic model, whose kinetic parameters were experimentally
determined as functions of the temperature, and the second is a statistical model obtained using the factorial design technique
combined with simulation. Although the best result was the one obtained using the rigorous model, the values for productivity
and % yield obtained using the simplified model are acceptable, and these models can be used when the development of a rigorous
model is excessively difficult, slow, or expensive. 相似文献
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35.
Biodiesel Production from Integration Between Reaction and Separation System: Reactive Distillation Process 总被引:1,自引:0,他引:1
Nívea de Lima da Silva Carlos Mario Garcia Santander César Benedito Batistella Rubens Maciel Filho Maria Regina Wolf Maciel 《Applied biochemistry and biotechnology》2010,161(1-8):245-254
Biodiesel is a clean burning fuel derived from a renewable feedstock such as vegetable oil or animal fat. It is biodegradable, non-inflammable, non-toxic, and produces lesser carbon monoxide, sulfur dioxide, and unburned hydrocarbons than petroleum-based fuel. The purpose of the present work is to present an efficient process using reactive distillation columns applied to biodiesel production. Reactive distillation is the simultaneous implementation of reaction and separation within a single unit of column. Nowadays, it is appropriately called “Intensified Process”. This combined operation is especially suited for the chemical reaction limited by equilibrium constraints, since one or more of the products of the reaction are continuously separated from the reactants. This work presents the biodiesel production from soybean oil and bioethanol by reactive distillation. Different variables affect the conventional biodiesel production process such as: catalyst concentration, reaction temperature, level of agitation, ethanol/soybean oil molar ratio, reaction time, and raw material type. In this study, the experimental design was used to optimize the following process variables: the catalyst concentration (from 0.5 wt.% to 1.5 wt.%), the ethanol/soybean oil molar ratio (from 3:1 to 9:1). The reactive column reflux rate was 83 ml/min, and the reaction time was 6 min. 相似文献
36.
Adriano Pinto Mariano Caliane Bastos Borba Costa Maria Regina Wolf Maciel Francisco Maugeri Filho Daniel Ibraim Pires Atala Dejanira de Franceschi de Angelis Rubens Maciel Filho 《Applied biochemistry and biotechnology》2010,160(8):2424-2448
In this work, mathematical modeling was employed to assess the dynamic behavior of the flash fermentation process for the
production of butanol. This process consists of three interconnected units as follows: fermentor, cell retention system (tangential
microfiltration), and vacuum flash vessel (responsible for the continuous recovery of butanol from the broth). Based on the
study of the dynamics of the process, suitable feedback control strategies [single input/single output (SISO) and multiple
input/multiple output (MIMO)] were elaborated to deal with disturbances related to the process. The regulatory control consisted
of keeping sugar and/or butanol concentrations in the fermentor constant in the face of disturbances in the feed substrate
concentration. Another objective was the maintenance of the proper operation of the flash tank (maintenance of the thermodynamic
equilibrium of the liquid and vapor phases) considering that oscillations in the temperature in the tank are expected. The
servo control consisted of changes in concentration set points. The performance of an advanced controller, the dynamic matrix
control, and the classical proportional-integral controller was evaluated. Both controllers were able to regulate the operating
conditions in order to accommodate the perturbations with the lowest possible alterations in the process outputs. However,
the performance of the PI controller was superior because it showed quicker responses without oscillations. 相似文献
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39.
de Souza RF De Giovani WF 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2005,61(9):1985-1990
The synthesis, electrochemical and spectral (UV-vis, 1H NMR, IR, fluorescence) properties as well as thermal behaviors of Al(III) and Zn(II) complexes with the flavonoids quercetin (H2L(1)), rutin (H2L(2)) and galangin (HL(3)) are presented. The complexes may be formulated as [Al2(L(1))(H2O)8]Cl4, [Al3(L(2))2(H2O)12]Cl5, [Al(L(3))(H2O)4]Cl2, [Zn2(L(1))(H2O)4]Cl2, [Zn3(L(2))2(H2O)6]Cl2 and [Zn(L(3))(H2O)2]Cl. The higher fluorescence intensities of the complexes related to the free flavonoids, are attributed to the coordination of the ligands to the small, highly charged Al(III) and Zn(II) ions. The coordination effectively increases the rigidity of the ligand structure and increases the fluorescence quantum yield by reducing the probability of non-radiative energy dissipation process. Antioxidant activities of the compounds were also investigated under an electrochemical point of view. The cyclic voltammetric data show a considerable decrease of the oxidation potentials of the complexes related to that of the free flavonoids. Thus, the flavonoid-metal complexes are more effective antioxidants than the free flavonoids. 相似文献
40.
Lime Pretreatment of Sugarcane Bagasse for Bioethanol Production 总被引:2,自引:0,他引:2
Sarita C. Rabelo Rubens Maciel Filho Aline Carvalho Costa 《Applied biochemistry and biotechnology》2009,153(1-3):139-150
The pretreatment of sugarcane bagasse with lime (calcium hydroxide) is evaluated. The effect of lime pretreatment on digestibility was studied through analyses using central composite design (response surface), considering pretreatment time, temperature, and lime loading as factors. The responses evaluated were the yield of glucose from pretreated bagasse after enzymatic hydrolysis. Experiments were performed using the bagasse as it comes from an alcohol/sugar factory (non-screened bagasse) and bagasse in the size range from 0.248 to 1.397 mm (screened bagasse) (12-60 mesh). It was observed that the particle size presented influence in the release of fermentable sugars after enzymatic hydrolysis using low loading of cellulase and β-glucosidase (3.5 FPU/g dry pretreated biomass and 1.0 IU/g dry pretreated biomass, respectively). 相似文献