Mathematische Modellierung des MDEA-Absorptionsprozesses

In chemical engineering, absorption processes are used in many cases for the purpose of selective separation of one or more gas components from a multicomponent gas stream. Compared to adsorption, which uses large solid surfaces, absorption has one main advantage: i.e. a countercurrent flow of both gas stream and scrubbing liquid can be obtained easily. Thus the gas loaded liquid leaving the absorption column can directly be recycled in a desorber and used for absorption again in a continuous process. For this reason absorption processes are very widespread in industry. Absorption uses the effect that gases are soluble in liquids. Different interactions between the soluble gases and solvent components lead to different solubilities and selectivities. E.g. polar gases dissolve very well in polar solvents but non-polar gases do not. Some scrubbing liquids contain agents, which react chemically with one or more of the dissolved gas components. A process using these kinds of agents is called "chemical absorption". Because dissolved gases are partially transformed to reaction products the capacity of the solvent for these reacting components is increased significantly. Thus in chemical absorption processes, typically a high selectivity is observed. So chemical absorptions are used frequently for many kinds of industrial purposes. Aqueous alkanolamine solutions are well suited for the selective absorption of sour gases like hydrogen sulfide and carbon dioxide. Alkanolamines are mainly used to clean fuel gas or synthesis gas. The most important field for the application of alkanolamines is the purification of natural gas. In case of using the alkanolamine of type N-methyldiethanolamine (MDEA) the absorption of carbon dioxide is strongly hindered owing to a slow chemical reaction. So, MDEA is an alkanolamine especially suited for the selective removal of hydrogen sulfide from gases where the co-absorption of carbon dioxide is not economical. This is a constraint for many industrial applications. To project and optimise a chemical process effectively, the use of a mathematical simulation model is a reasonable tool. Such a simulation model helps in building a plant, revamping an existing one or calculating how an existing plant should be operated if process constraints have to be changed. In most absorption processes fast changes in composition or gas flow are quite rare. Hence for the reason of planning or optimization of absorption plants stationary process models are adequate. Equilibrium models are well known and often used in process simulation. But the use of equilibrium models is only sensible for processes, where the state variables do not differ much compared to those in case of the thermodynamic equilibrium. On the other hand for processes, where strong kinetic effects hinder the system's way to equilibrium, the classic equilibrium model fails. A special kind of these processes is the sour gas absorption with aqueous MDEA solutions, which is the example process used in this work. Because of the fast development of computer performance in the last years, the application of highly complex models is now possible. For the purpose of process simulation of a reactive separation process, the use of models with different degrees of complexity can be adequate. Usually, complex models will take more time for computing and have more difficulties in achieving the convergence. Thus the quest for a simple model, which gives good prediction, is extremely important. All the included correlations for the properties of the occurring fluids, apparatus and kinetic effects show a significant influence on the simulation results. For a proper comparison of different process models the use of exact identical correlations and properties of substances are essential. In this work, different complex process models for sour gas absorption with MDEA solutions are shown and used for simulation of plants, for which complete sets of experimental data are available. For the purpose of validation the simulation results with experimental data have to be compared.

Grantor dc:publisher

Publikationsserver der RWTH Aachen University

Year dc:date

2004

Author dc:creator

• Giesen, Ralf

Contributors dc:contributor

• Lucas, Klaus

• info:eu-repo/classification/ddc/620
• Gaswäsche
• Schwefelwasserstoff
• Absorption
• Methyliminodiethanol <N-Methyl-2,2-iminodiethanol>
• Prozessmodell
• Ingenieurwissenschaften
• Prozesssimulation
• Thermodynamik
• Methyldiethanolamin
• Thermische Trennverfahren
• Sauergaswäsche

Statement dc:rights

• info:eu-repo/semantics/openAccess

Language dc:language

ger

Identifier

https://publications.rwth-aachen.de/search?p=id:%22RWTH-CONV-120383%22

OAI identifier oai:identifier

oai:publications.rwth-aachen.de:58506