190 research outputs found
A kinetic modelling study of ethane cracking for optimal ethylene yield
No full textCurrent generation steam cracking plants are considered to be mature. As a consequence it is becoming more and more important to know whether the underlying mechanistic cracking process offers still scope for further improvements. The fundamental kinetic limits to cracking yields have recently been researched in detail for different feed stocks with a new synthesis reactor model, d-RMix, incorporating a large scale mechanistic reaction scheme, SPYRO® [M.W.M. van Goethem, S. Barendregt, J. Grievink, J.A. Moulijn, P.T.J. Verheijen “Model-based, thermo-physical optimisation for high olefin yield in steam cracking reactors”, Chemical Research and Engineering Developments 88 (2010) 1305–1319]. Mathematical optimization revealed for ethane cracking a maximum ethylene yield of about 67 wt%. with a linear-concave optimal temperature profile along the reaction coordinate with a maximum temperature between 1200 and 1300 K. Further mechanistic analysis of these results showed that the linear-concave shape not only suppresses the successive dehydrogenation and condensation reactions of ethylene, but mainly reduces the role of the ethane initiation reaction to form two methyl radicals
A Design Procedure and Predictive Models for Solution Crystallisation Processes
No full textApplied Science
On the design of chemical processes with improved controllability characteristics
No full textTraditionally, process design and control system design are carried out sequentially. The premise underlying this sequential approach is that the decisions made in the process design phase do not limit the control design. However, it is generally known that incongruent designs can occur quite easily. In the literature two different classes of approaches are being described that consider the control performance of the design alternatives from the earliest design stages: (i) Anticipating sequential approaches where process design and control system design are still carried out sequentially, but in anticipation of the control design the controllability properties of the process are taken into account during the process design phase. (ii) Simultaneous approaches. In the simultaneous approach the process design and the control system design are carried out simultaneously. This work is focused on the first approach. Tools and methods are presented that can assist the process designer in designing processes that are well controllable. The control system design still needs to be carried out afterwards, but the process designer has already anticipated on it. The methods and tools presented in this thesis are aimed at the different stages of the conceptual process design phase: formulation, synthesis, analysis and evaluation. Primarily the synthesis and the analysis phases will be addressed to overcome some of the limitation of the anticipating sequential approaches. Since most industrially scale processes operate in a steady state this mode of operation has been the reference for this research. However as dynamic modes of operation are becoming more important, an exploration was made of the potential of periodic operation of Fischer Tropsch synthesis.Applied Science
A structured approach to heat exchanger network retrofit design
No full textProcess plants have high energy consumption. Much energy can be saved by a proper design of the heat exchanger network, which contains the main heat transferring equipment of the plant. Existing plants can often be made more energy-efficient by a retrofit: the (physical) modification of the equipment and piping in the heat exchanger network. This also allows application of new heat transfer equipment types that have enhanced heat transfer efficiency. Effective retrofit design requires dedicated design methods to handle the complex trade-offs, the large number of constraints and the lack of data. This thesis contains a new practical retrofit design framework and various new design methods for heat exchanger networks. It especially addresses the optimal application of alternative heat exchanger types. The thesis gives an extensive description of the design problem. It reviews the existing methods for the heat exchanger network performance analysis, for the targeting and optimisation of the key quantities for network design and for the actual elaboration of the conceptual retrofit design. It explains how these methods fit within the design framework. Besides, it gives a new network analysis tool, the Auxiliary Heat Flow Curves and various new design methods, based on pinch technology. These design methods take into account more effectively any practical constraints, like physical and logical units in the plant. They include Structural Targeting with Integrity Zones and the Retrofit Exchanger Shifting Procedure. The new design methods aim for simple modifications of the network and a maximum of independent saving options. They have proven to be effective for a number of case studies that have been executed, including an industrial case.Applied Science
Designing reactive distillation processes with improved efficiency
No full textIn this dissertation a life-span inspired perspective is taken on the conceptual design of grassroots reactive distillation processes. Attention was paid to the economic performance of the process and to potential losses of valuable resources over the process life span. The research was cast in a set of goal-oriented engineering and specific scientific design questions. The scientific novelty of this work is based around four key aspects of reactive distillation process design: (i) the formulation of an extended design problem in reactive distillation achieved by refreshing it in the wider context of process development and engineering and in a more relevant way regarding sustainability; (ii) the definition of an integrated design methodology achieved by analyzing current design methodologies and bridging the gaps between them; while we suggest this methodology as a way to beat the design complexity by decomposition, it requires the mastery of many tools and many concepts; (iii) the improvement of design tools achieved by exploring and extending current techniques and systematically applying them to the reactive distillation case; (iv) the definition of performance criteria that can be used to account for the process performance from a life-span inspired perspective, as well as applications of them.Applied Science
Design and analysis of suspension crystallisers: Aspects of crystallisation kinetics and product quality
No full textApplied Science
Chemische procesontwerpen aan de TU Delft 1920-2000 in TU Delft Repository
No full textDelftChemTechApplied Science
Process Design in a Changing Environment - Identification of Quality Demands Governing the Design Process
No full textTechnology, Policy and Managemen
Model Reduction in Chemical Engineering: Case studies applied to process analysis, design and operation
No full textDuring the last decades, models have become widely used for supporting a broad range of chemical engineering activities, such as product and process design and development, process monitoring and control, real time optimization of plant operation or supply chain management. Although tremendous advancements continue to take place in the development of numerical techniques and the acceleration of the computing speed, these advancements have been outpaced by the tendency to make rigorous models of much more complicated and extensive systems. Such rigorous models cannot always be effectively used for design and optimisation. A reduction of the model size and complexity is required to make a model-based solution practical. Many current numerical approaches in systems engineering apply order-reduction to a model in its entirety, without preserving the underlying network structure of the process or its multi-scale decomposition. Retaining these meaningful structural features of a process in a reduced model is a necessity for numerous applications. This is the motivation for the research and the results presented in this thesis. The novelty of this thesis is in systematizing and exploiting the essential structural features of a process in model reduction. The model reduction approach aims first at simplifying the physical and the behavioural structure, as well as the systemic level of the chemical process in the model. Only then additional mathematical and numerical (scheme) reductions are selectively applied to individual compartments or units. In the following step, the reduced models of the individual units are connected at system level and the reduced model of the full process is obtained. In this way, the model reduction procedure is able to preserve the essential structural features of the process. Moreover, the physical meaning of the variables and equations is kept as much as possible. The feasibility and the advantages of the approach are presented for two types of applications: (1) the iso-butane alkylation process, an example of a complex process with relatively simple (one-phase) products; and (2) the freezing step in ice cream manufacture, an example of a single process unit with a complex product. The model reduction procedures works well for the cases considered. The resulting models are solved in acceptable amounts of time. Moreover, they are successfully used for applications such as assessment of the plantwide control structures and the dynamic optimization of the plant operation for the iso-butane alkylation process, and the sensitivity analysis of the model’s parameters in the case of the ice cream freezing process. However, the issue of the optimality with respect to the level of the multi-scale decomposition when developing the reduced model is still open.Chemical EngineeringApplied Science
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