Loading...
Search for:
process-synthesis
0.018 seconds
Optimization of a process synthesis superstructure using an ant colony algorithm
, Article Chemical Engineering and Technology ; Volume 31, Issue 3 , 2008 , Pages 452-462 ; 09307516 (ISSN) ; Pishvaie, M. R ; Rashtchian, D ; Sharif University of Technology
2008
Abstract
The optimization of chemical syntheses based on superstructure modeling is a perfect way for achieving the optimal plant design. However, the combinatorial optimization problem arising from this method is very difficult to solve, particularly for the entire plant. Relevant literature has focused on the use of mathematical programming approaches. Some research has also been conducted based on meta-heuristic algorithms. In this paper, two approaches are presented to optimize process synthesis superstructure. Firstly, mathematical formulation of a superstructure model is presented. Then, an ant colony algorithm is proposed for solving this nonlinear combinatorial problem. In order to ensure...
Quantitative-Based Safety Evalution in the Primarly Stages of the Project Life Cycle
, M.Sc. Thesis Sharif University of Technology ; Rashtchian, Davoud (Supervisor) ; Bozorgmehri, Ramin (Supervisor)
Abstract
Inherent safety means that the process is naturally safe and the conditions of occurrence of unsafe cases and situations are eliminated from the system so that unsafe conditions can be controlled and prevented from occurrence by means of layers of protection. In general, evaluation of inherent safety may be studied in two different conditions; the first one is associated with the units that are not completely designed and built yet. In the initial steps of developing a process, there is much freedom in the determination of materials, equipment, and designing variables. As soon as the process enters its life cycle, making changes in the process will be very difficult and expensive. Therefore,...
Inherently Safer Synthesis and Optimization of Chemical Processes
, M.Sc. Thesis Sharif University of Technology ; Rashtchian, Davoud (Supervisor)
Abstract
There are different well-established strategies for making a process plant inherently safer. The benefits of applying these strategies on reducing the overall risk inside a plant are obvious. However, some of these changes are rejected many times because they appear to be too costly. But if the effects of applying inherently safer design strategies are investigated not only on the processing costs of a plant but also on the potential accident costs, the decision would in fact be different. In this paper an optimization procedure is proposed which integrates both processing and accident costs for different design schemes. In this procedure, some of the design variables are chosen with regard...
Reactor and Heat Exchanger Network Synthesis with Genetic Algorithm
, M.Sc. Thesis Sharif University of Technology ; Farhadi, Fathollah (Supervisor) ; Bozorgmehri, Ramin (Supervisor)
Abstract
In most chemical processes, at the first stage, the feed are being treated in physical steps such as preheating. Afterward it enters reaction system to undergo chemical treatment. In the final stage, product of reaction system is physically processed to prepare them to exit the boundary of the process. There are various ways to process materials chemically. This process can be continuous, batch and even semi-batch, via a single reactor or a network of the reactors. And also it can be performed under various range of operating condition. Moreover in some cases, intermediate cooling and heating is necessary. The question is that which configuration and operating condition is the best. The goal...
Evolutionary design of optimum distillation column sequence
, Article Canadian Journal of Chemical Engineering ; Volume 90, Issue 4 , 2012 , Pages 956-972 ; 00084034 (ISSN) ; Laleh, A. P ; Svrcek, W. Y ; Sharif University of Technology
2012
Abstract
Synthesis of the optimum distillation column sequence (DCS), which incorporates a huge search space composed of both conventional and complex arrangements, is a highly complicated combinatorial problem in the field of chemical process design and optimisation. In this study, a novel procedure for the synthesis of optimum DCS proposed by Boozarjomehry et al. [Boozarjomehry et al., Can. J. Chem. Eng. 87, 477-492 (2009)] is expanded to include the complex distillation arrangements. The method is based on evolutionary algorithms, and the total annual cost (TAC) is the main criterion used to screen alternatives. Efficient procedure has been proposed for encoding mechanism to include and classify...
Automatic design of conventional distillation column sequence by genetic algorithm
, Article Canadian Journal of Chemical Engineering ; Volume 87, Issue 3 , 2009 , Pages 477-492 ; 00084034 (ISSN) ; Pourahmadi Laleh, A ; Svrcek, W. Y ; Sharif University of Technology
2009
Abstract
Synthesis of the optimum conventional (with non-sharp separations) distillation column sequence (DCS) is a challenging problem, in the field of chemical process design and optimization, due to its huge search space and combinatorial nature. In this paper, a novel procedure for the synthesis of optimum Conventional Distillation Column Sequence is proposed. The proposed method is based on evolutionary algorithms. The main criterion used to screen alternative DCS's is the Total Annual Cost (TAC). In order to estimate the TAC of each DCS alternative all columns that exist in the DCS are designed using short-cut methods. The performance of the proposed method and other alternatives are compared...
Synthesis and spectral properties of Nd-doped glass-ceramics in SiO 2-CaO-MgO system prepared by sol-gel method
, Article Journal of Rare Earths ; Volume 31, Issue 6 , 2013 , Pages 595-599 ; 10020721 (ISSN) ; Zohreh, H ; Ali, N ; Sharif University of Technology
2013
Abstract
SiO2-CaO-MgO glass and glass-ceramic powder doped with Nd 3+ were synthesized with sol-gel method. Tetraethylorthosilicate (TEOS), Ca(NO3)2·4H2O, Mg(NO 3)2·6H2O, Nd(NO3) 3·6H2O, ethanol, distilled water, and HNO 3 were used as starting materials. The synthesized powder's properties were examined with simultaneous thermal analysis (STA), X-ray diffraction (XRD), photoluminescence (PL) and scanning electron microscopy (SEM) analysis. The STA curves showed that the softening point and crystallization temperatures were shifted to higher temperatures with increasing dopant content. Regarding XRD patterns of glass samples, Nd was found to act as an intermediate oxide in glass matrix. The XRD...
Room temperature synthesis of highly crystalline TiO2 nanoparticles
, Article Materials Letters ; Volume 92 , February , 2013 , Pages 287-290 ; 0167577X (ISSN) ; Radiman, S ; Azmi Abdul Hamid, M ; Mahshid, S ; Rahmani, S ; Sharif University of Technology
2013
Abstract
Hydrolysis of titanium isopropoxide alcoholic solution has been used to prepare the crystallized TiO2 nanoparticles at low temperature. Concentration ratio was used to control the pathway of sol-gel process and change the physical characteristics of TiO2 nanopowders. The crystallinity, morphology and size of aged TiO2 nanopowders were studied by X-ray diffraction and Scanning Electron Microscopy (SEM). FTIR and, Thermo-Gravimetric (TG) analysis were used to identify the functional groups and thermal behavior of prepared samples. Experimental results have shown that high crystalline TiO2 nanomaterial with anatase polymorph can be obtained at room temperature. It has been found that the...
Influence of hydrogen reduction on growth of tungsten oxide nanowires
, Article Journal of Experimental Nanoscience ; Volume 7, Issue 6 , 2012 , Pages 597-607 ; 17458080 (ISSN) ; Khosravi, P ; Moshfegh, A. Z ; Sharif University of Technology
2012
Abstract
A simple method for synthesising W17O47 nanowires on tungsten oxide thin films deposited by sol-gel method on mica substrate has been reported. After thermally annealing thin films at 700 C in H2 ambient for different durations and subsequently in N2 ambient for 60 min, single-crystalline W17O47 nanowires along h0 01i direction were formed on the surface. Experimental results revealed that annealing under H2 ambient has an important effect on the growth of W17O47 nanowires. According to scanning electron microscopic observations, the synthesised nanowires have ∼70 nm in width and a few microns in length after annealing under H2 ambient for 30min and subsequently under N2 ambient for 60min. A...
The decoration of TiO2/reduced graphene oxide by Pd and Pt nanoparticles for hydrogen gas sensing
, Article International Journal of Hydrogen Energy ; Volume 37, Issue 20 , 2012 , Pages 15423-15432 ; 03603199 (ISSN) ; Ghasemi, S ; Irajizad, A ; Akhavan, O ; Gholami, M. R ; Sharif University of Technology
Elsevier
2012
Abstract
Reduced graphene oxide (RGO) was used to improve the hydrogen sensing properties of Pd and Pt-decorated TiO2 nanoparticles by facile production routes. The TiO2 nanoparticles were synthesized by sol-gel method and coupled on GO sheets via a photoreduction process. The Pd or Pt nanoparticles were decorated on the TiO2/RGO hybrid structures by chemical reduction. X-ray photoelectron spectroscopy demonstrated that GO reduction is done by the TiO2 nanoparticles and Ti-C bonds are formed between the TiO2 and the RGO sheets as well. Gas sensing was studied with different concentrations of hydrogen ranging from 100 to 10,000 ppm at various temperatures. High sensitivity (92%) and fast response time...
Fast two-step microwave-activated synthesis of Mn doped ZnS nanocrystals: Comparison of the luminescence and doping process with thermochemical approach
, Article Journal of Luminescence ; Volume 131, Issue 4 , April , 2011 , Pages 721-726 ; 00222313 (ISSN) ; Hajisalem, G ; Taghavinia, N ; Houshiar, M ; Sharif University of Technology
2011
Abstract
In this work we report a fast two-step microwave activated synthesis of the ZnS:Mn nanocrystals. Zn(NO3)2 and Na2S 2O3 were used as the precursors and Mn(NO 3)2 was employed as the source of the impurity. The aqueous synthesis was based on the heat sensitivity of Na2S 2O3, which releases some S species on heating. Consequently, the reaction was well activated under microwave irradiation resulting in formation of ZnS:Mn nanocrystals. Thioglycerol (TG) was also used as the capping agent and the catalyst of the reaction. The synthesis process was done in two steps, i.e. 1 min irradiation without TG and then injection of TG and continuation of irradiation. ZnS:Mn nanocrystals were quickly formed...
Synthesis of titania/carbon nanotube heterojunction arrays for photoinactivation of E. coli in visible light irradiation
, Article Carbon ; Volume 47, Issue 14 , 2009 , Pages 3280-3287 ; 00086223 (ISSN) ; Abdolahad, M ; Abdi, Y ; Mohajerzadeh, S ; Sharif University of Technology
2009
Abstract
TiO2/multi-wall carbon nanotube (MWNT) heterojunction arrays were synthesized and immobilized on Si(0 0 1) substrate as photocatalysts for inactivation of Escherichia coli bacteria. The vertically aligned MWNT arrays were grown on ∼5 nm Ni thin film deposited on the Si by using plasma enhanced chemical vapor deposition at 650 °C. Then, the MWNTs were coated by TiO2 using dip-coating sol-gel method. Post annealing of the TiO2/MWNTs at 400 °C resulted in crystallization of the TiO2 coating and formation of Ti-C and Ti-O-C carbonaceous bonds at the heterojunction. The visible light-induced photoinactivation of the bacteria increased from MWNTs to TiO2 to TiO2/MWNTs, in which the bacteria could...
The ODYSSEY approach to early simulation-based equivalence checking at ESL level using automatically generated executable transaction-level model
, Article Microprocessors and Microsystems ; Volume 32, Issue 7 , 2008 , Pages 364-374 ; 01419331 (ISSN) ; Hessabi, S ; MohammadZadeh, N ; Zainolabedini, N ; Sharif University of Technology
2008
Abstract
Design technology is expected to rise to electronic system-level (ESL). This necessitates new techniques and tools for synthesizing ESL designs and for verifying them before and after ESL synthesis. A promising verification strategy for future very complex designs is to initially verify the design at the highest level of abstraction, and then check the equivalence of the lower level automatically generated models against that initial golden model. We present one such approach to simulation-based functional verification implemented in our ESL design methodology called ODYSSEY. Our ESL synthesis tool generates a transaction-level model (TLM) at TLM level 2 (i.e., design with partial timing)...
Role of precursors and coating polymers in sol-gel chemistry toward enhanced selectivity and efficiency in solid phase microextraction
, Article Analytica Chimica Acta ; Volume 742 , 2012 , Pages 45-53 ; 00032670 (ISSN) ; Piri Moghadam, H ; Ahdi, T ; Sharif University of Technology
Elsevier
2012
Abstract
To evaluate the selectivity and efficiency of solid phase microextraction (SPME) fiber coatings, synthesized by sol-gel technology, roles of precursors and coating polymers were extensively investigated. An on-line combination of capillary microextraction (CME) technique and high performance liquid chromatography (HPLC) was set up to perform the investigation. Ten different fiber coatings were synthesized in which five of them contained only the precursor and the rests were prepared using both the precursor and coating polymer. All the coatings were chemically bonded to the inner surface of copper tubes, intended to be used as the CME device and already functionalized by self-assembly...