133 research outputs found
Transformable building structures: Design for dissassembly as a way to introduce sustainable engineering to building design & construction
No full textArchitectur
Dynamic chemical process modelling and validation: Theory and application to industrial and literature case study
No full textDynamic chemical process modelling is still largely considered an art. In this thesis the theory of large-scale chemical process modelling and validation is discussed and initial steps to extend the theory are explored. In particular we pay attention to the effect of the level of detail on the model simulation and optimisation performance. We investigate the liquid-filled tubular reactor, HIDiC and optimize the start-up from the cold state of part of a (open literature) plant. Furthermore, an industrial plant was modelled and validated for which model building times are reported.Chemical EngineeringApplied Science
Building construction in the Netherlands 1940 - 1970: Continuity + changeability = durability
No full textThe built environment is continuously changing and such changes are particularly important when regenerating buildings. These changes add something to existing buildings and make new programmes possible. The existing buildings - history - determine continuity and form a clear additional, time-dependent layer. In general, the large number of buildings built between 1940 and 1970 cannot be listed as national monuments and are therefore essentially unprotected. Furthermore, buildings from this period in particular are currently being considered for regeneration or threatened with demolition. Apart from studying relevant literature and other sources I also studied seven buildings for this project. This resulted in the Construction Engineering Research method and my work was guided by the following themes: 1. Observation - with an engineers eye. 2. Research analysis. 3. Regenerative conclusions. I drew up a list of 63 buildings, 21 of which I subjected to a summary analysis. I then studied seven of these 21 buildings in greater detail and described them in the relevant subsections of this thesis. These subsections form an integral part of the general sections of this thesis, but could also be read in isolation. The 7 subsections are: 1. Rijksverzekeringsbank Amsterdam, 2. Groothandelsgebouw Rotterdam, 3. Provinciale Bibliotheek Leeuwarden, 4. Jeruzalem Frankendaal Amsterdam, 5. Stationspostkantoor Amsterdam, 6. Paleis Van Justitie Arnhem en 7. Medische Faculteit Rotterdam. The work for this thesis should not only result in relevant conclusions, but also in a research method which can be applied to the subjects covered by the Faculty of Architecture of Delft University of Technology and in the design efforts of architectural practices.Architectur
Earth, Wind & Fire: Natuurlijke Airconditioning
No full textCollaboration between the Universities of Technology in Delft and Eindhoven has resulted in the development of a new concept for natural air conditioning of buildings. According to the so-called Climate Responsive Architecture developed in this research, the design of the indoor climate system, building physics, and services are linked to an architectural assignment. In this concept, no fans or air handling units are utilized; instead, air conditioning is accomplished by the employment of the free, available environmental energy in earth mass, wind, and the sun. The energy use for air conditioning of office buildings can, therefore, be substantially reduced. To make this possible, three responsive architectural elements have been developed: the Ventec-Roof, the Climate Cascade and the Solar Chimney by which the architect can play a significant role as technical and artistic co-designer of the climate system. The intensive cooperation between architect and HVAC engineer will, in principle, result in an improved building air quality at reduced failure costs. Ben Bronsema is an experienced consulting engineer in sustainable building services and the design of HVAC systems.Architectural Engineering + TechnologyArchitectur
Continuous-Flow Sunlight-Powered CO<sub>2</sub> Methanation Catalyzed by γ-Al<sub>2</sub>O<sub>3</sub>-Supported Plasmonic Ru Nanorods
No full textPlasmonic CO2 methanation using γ-Al2O3-supported Ru nanorods was carried out under continuous-flow conditions without conventional heating, using mildly concentrated sunlight as the sole and sustainable energy source (AM 1.5, irradiance 5.5–14.4 kW·m−2 = 5.5–14.4 suns). Under 12.5 suns, a CO2 conversion exceeding 97% was achieved with complete selectivity towards CH4 and a stable production rate (261.9 mmol·g−1 Ru·h−1) for at least 12 h. The CH4 production rate showed an exponential increase with increasing light intensity, suggesting that the process was mainly promoted by photothermal heating. This was confirmed by the apparent activation energy of 64.3 kJ·mol−1, which is very similar to the activation energy obtained for reference experiments in dark (67.3 kJ·mol−1). The flow rate influence was studied under 14.4 suns, achieving a CH4 production plateau of 264 µmol min−1 (792 mmol·g−1 Ru·h−1) with a constant catalyst bed temperature of approximately 204◦C.ImPhys/Optic
Low Temperature Sunlight-Powered Reduction of CO<sub>2</sub> to CO Using a Plasmonic Au/TiO<sub>2</sub> Nanocatalyst
No full textSunlight-powered reduction of CO2 to fuels and chemicals is a promising strategy to close the carbon loop and facilitate the energy transition. In this research, we demonstrate that Au nanoparticles supported on TiO2 are an efficient plasmonic catalyst for the sunlight-powered reverse water-gas shift (rWGS) reaction. A maximum CO production rate of 429 mmol ⋅ gAu−1 ⋅ h−1 with a selectivity of 98 % and an apparent quantum efficiency of 4.7 % were achieved using mildly concentrated sunlight (1.44 W ⋅ cm−2 equals 14.4 sun). The CO production rate showed an exponential increase with increasing light intensity, suggesting that the process is mainly promoted by a photothermal effect. Thermal reference experiments with the same catalysts promoted CH4 formation, dropping the CO selectivity to 70 %. Thus, mildly concentrated sunlight can efficiently and selectively enhance the promotion of the rWGS reaction without using external heating.ImPhys/Optic
Optimization of the reactor section of a catalytic ethyleneglycol plant
No full textA reactor network design is being given for the catalytic manufacture of ethyleneglycol. This relatively new process has a potential for major cost savings above the common, industrially applied, hydration of ethyleneoxide at high temperatures. To generalize the design of the plant, the reactor section of the catalytic ethyleneglycol plant is optimized by postulating a reactor network superstructure, which embeds all possible structural and operadonal configuradons. Because of the presence of fixed-bed reactors, the mathematical formulation of the superstructure results in a system of algebraic and differential equations, which are discretized by the method of orthogonal collocadon on finite elements. Hence, the reactor network synthesis problem that is formulated based upon this superstructure is a large-scale non-linear programming problem. Inequality constraints are added to comply with prescribed requirements and the objecdve function is formulated to balance both the operating and the capital costs associated with the reactor secdon. The mathematical formulation of the superstrucmre is optimized with the optimization package GAMS. The optimal reactor section of the catalytic ethyleneglycol plant features two recycle reactors in series followed by a plugflow reactor and a flasher, whose top-stream is recycled to the first reactor in the serial configuration. The characteristics of this configuration are proven to be physically logical. The optimal reactor section offers a 16 % higher yearly profit when compared to the heuristic design. The costs associated with the use of the catalyst are the main cost determining factor, while the maximum temperature limit in the reactors is the major restrictive constraint. Apart from the ethylene glycol reactor section, the GAMS-model is able to optimize reactor networks for any kinetic mechanism and for any objective function (with or without a flasher), without requiring any extra programming effort to change the number of reactors. This work is significant in that it is an attempt to combine an efficient synthesis tool based entirely on mathematical programming techniques with technological assumptions to produce a structurally as well as an operationally optimal design.Process Systems EngineeringDelftChemTechApplied Science
Dynamic modeling for startup and shutdown of a coupled reactor and distillation column
No full textCompeting in a global market place forces chemical industry to be flexible and cost-effective in production. To optimize production the processes are modeled before they are built. Normally these models show the steady-state behavior. This, however, will be insufficient to show the flexibility of the process and guarantee safety and environmental constraints are met under all circumstances. Dynamic models are useful to give extra insight in the operability, flexibility and profitability of a process. The goals of this project are to build a model that will describe startup and shutdown behavior of a process and perform a simplified optimization of a specific startup procedure. For these goals a model has been constructed in gPROMS, which gives a representation of the dynamic behavior of a glycolether process. This process consists of a reactor, distillation column and recycle. The model consists of over 15 000 equations, which include the physical properties of the system. Further features of the model are the use of an equilibrium tray model, inclusion of liquid flows over the weir and dumping through the holes, inclusion of vapor flows through the holes and through the downcomer, addition and purge of inert, and a dynamic, single phase, plug-flow reactor of the shell-and-tube-type operating under turbulent flow conditions. All trends in the profiles of the model and ASPEN follow each other nicely and the steady state is estimated to be 5-10% accurate compared to ASPEN. The model is capable of describing a shutdown, as long as vapor escapes through the downcomer from the reboiler. It is also capable of describing a startup in which the column is heated, inerts are purged, the reactor is heated and the steady-state is reached. All this is done without an external heat source, using only the heat generated by the reboiler. The results have not been verified experimentally. Several errors were made in modeling the process, such as an incorrect excess of MeOH in the reactor, incorrect surface areas for heat loss on the tray and in the reboiler, small reset rates for controllers in the condenser, large setpoint changes and high rates of temperature rise in the system. Their influences, however, are small, or can be corrected with longer calculation times. Drawbacks of the model are the long calculation times (2.5 hours) and numerical instabilities. Also, the model developed is not completely generic, but could be adapted for other systems. During a simplified optimization by factorial design of the startup-schedule used, only four optimization steps were needed to reduce the loss at the end-point by 28%, while only considering three variables. Though the absolute gain is only Hfl. 781, this demonstrates that optimization can lead to significant increases in profitability. Overall the model provides valuable insight in the processes that take place during dynamic operation of an interconnected reactor and distillation system.Process Systems EngineeringDelftChemTechApplied Science
Modeling of Complex Reaction Systems: Steam Cracker
No full textSteam pyrolysis of ethane and naphtha is an important chemical bulk process. It produces ethylene and propylene, which are important base chemicals. In order to be competitive, crackers have to be operated at near optimal conditions. Hence, a simulation program of the process, particularly of the pyrolysis is very helpful. KTI uses and licenses such a program called SPYRO*. Development of this program has started over 20 years ago. Consequently, it uses a closed model. It has been the objective of this study to investigate the feasibility of the development of an open version of SPYRO. Here open means that the equations are written in residual form .This enhances the flexibility of the program very much. For our studies we have used the model of Froment for ethane cracking because the documentation to make an open SPYRO model was insufficient. This Froment model has been modified as to improve the modeling of the bends. It has been checked, whether the solution of this model would pose any problems. It was found that the index might become more than 1 during integration. As yet no sound physical explanation has been found for this phenomena. It also follows from investigation of the index that a start-up problem of the numerical integration exists for the original set of differential equations. We have found a more elegant method to circumvent this problem than Froment. Moreover, we were able to solve the set of equations for bad initial conditions (equal to the boundary conditions). The ordinary differential equations of the model are turned into algebraic equations using orthogonal collocation on finite elements. This allows the model to be solved with an equation solver. The results were compared with various commercial numerical integrators. Excellent agreement was found for limited numbers of sections and collocation points. The speed of solution of the linearized set of modal equations depends on the size, the sparsity and structure of the Jacobian. The latter has an enormous effect on the fill-in of the L and U decomposition matrices. We found a very satisfying structure by modification of the equations and proper arrangement in the Jacobian. On the basis of the above results we may draw the following conclusions regarding the feasibility of the development of an Open SPYRO model. Unfortunately we had to use a simple model of Froment rather than the SPYRO equations themselves. Nevertheless, we have concluded that such a development is feasible. Within a reasonable time an accurate solution will be found even with bad starting values. The computation time can be further reduced with a smart initialization procedure.Chemical EngineeringApplied Science
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