Chemical reaction engineering
The core task is the design of the following properties of chemical reactors :
- the operating mode ( continuous , discontinuous )
- the type, size and material
- the operating conditions (pressure, temperature, concentration, catalysts, purity of the starting material).
Before production begins on a larger scale, the implementation is first tested in smaller laboratory or pilot plants. The exam requires basic knowledge of the chemical reactions used in the reactors .
It is necessary that the material balance is clearly clarified by the stoichiometry . In addition to the main chemical reaction, changes in pressure or temperature can also result in by-products from side reactions such as parallel and subsequent reactions ( reaction network ). It is important to understand these side reactions.
The energy balance is also important . While the heat in the reaction vessel plays a rather subordinate role in reactions on a laboratory scale , in large reactors the amount of heat supplied or given off by a chemical reaction can no longer be neglected. Chemical thermodynamics provide the basis for heat calculations .
The third important factor is the time balance of a chemical reaction. Here the chemical kinetics , i.e. H. the changed reaction rate with regard to temperature and concentration play an important role. For example, the daily production volume of a chemical product in an appropriately sized system can be calculated using the time balance.
The objective is to determine the optimal reactor design, whereby in addition to the lowest possible investment and operating costs , in particular costs for raw materials and energy, boundary conditions must also be taken into account, such as safety-related issues or the effects of by-products on subsequent process steps.
The operating costs are essentially determined by the energy requirement (heat balance of the reactor) and the specific product output that can be achieved in the reactor . If one only considers the material side of the optimization, then one can also postulate that the highest possible specific product output should be obtained in the reactor - this is synonymous with a minimal space-time . The optimization of the specific product performance is fundamentally characterized by the properties of the chemical reaction and can be achieved with the means of concentration control and material flow control and, of course, indirectly also temperature control.
The investments depend - apart from economic aspects - very strongly on the reactor volume and the complexity of the equipment. With the optimization of the specific product performance, however, a minimization of the reactor volume is automatically linked (minimized space-time ). To solve the tasks presented, the reaction engineer must apply knowledge in the following areas:
- Chemical reaction kinetics and especially the kinetics of more complex reactions (reaction networks) as well as fundamental knowledge of reaction mechanisms .
- Chemical catalysis , homogeneous and heterogeneous catalysis ( micro- and macrokinetics of heterogeneous catalytic reactions). About 80% of the reactions carried out in the chemical industry are catalytic.
- Basic types of chemical reactors, ideal reactors , circuits of ideal reactors
- Micro and macro mixing in the reaction apparatus , residence time , real behavior
- Optimization of the specific product performance through concentration management: sales-oriented optimization, adapted concentration management; Material flow control in heterogeneous reactions
- Heat balance of the reactor adiabatic reactors, isothermal reactors, polytropic reactors, autothermal mode of operation. Coupling of substance and heat balance.
This is also the content of the subject of chemical reaction engineering in technical chemistry.
- J. Hagen: Chemical reaction engineering, an introduction with exercises. VCH-Verlag, Weinheim 1992.
- A. Löwe: Chemical reaction engineering with MATLAB and SIMULINK. Wiley-VCH, Weinheim, ISBN 3-527-30268-9 .
- K. Dialer, U. Onken, K. Leschonsky: Basic features of process engineering and reaction engineering. Hanser-Verlag, Munich 1984.
- M. Jakubith: basic operations and chemical reaction engineering, introduction to technical chemistry. Wiley-VCH-Verlag, Weinheim 1998, ISBN 3-527-28870-8 .
- O. Levenspiel: The Chemical Reactor Omnibook. Osu Publishing, Oregon 1993.
- K.-H. Reichert: Basics of technical chemistry I - reaction technology -, lecture script at the Institute of Technical Chemistry at the TU Berlin. Edited by Dipl. Chem. H.-U. Moritz. 1982.
- E. Fitzer, W. Fritz, G. Emig: Technical chemistry, introduction to chemical reaction engineering. Springer-Verlag, Berlin / Heidelberg 1995
- M. Baerns, H. Hofmann, A. Renken: Chemical reaction engineering. 2nd Edition. Georg Thieme Verlag, Stuttgart 1987.