- There is a limited set of solvents and solvent mixtures available, if the mixture you need is not in the list, don't use the gas cleaning package. There are two ways round this. The first is to ask Aspentech if they happen to have a property package for your system, just might be lucky. The second is to use Aspen Plus and starting from the package that is closest to what you need, add the missing component(s). This should work reasonably well if you have a mixture for which there are existing packages to the individual components. You will be missing some interactions, but the result should still be reasonable. We (BPT) would be happy to do this for you (for a fee of course).
- You MUST specify the column geometry. A lot depends on the liquid and vapour residence time and the interfacial area, you only get correct values with a correct geometry.
The gas cleaning package relies on three complex phenomena. At the hart is an electrolyte thermodynamics package that accounts for "normal" vapour / liquid equilibrium, but also for dissociation of various molecules into ions. The second part is that some of the reactions that take place are not infinitely fast, so you have to account for reaction kinetics. The third factor is the mass transfer where the two film theory is used to calculate the transfer rates from one phase to the other. In some cases it get's really complex because the reaction rates are really fast, but not fast enough to consider equilibrium. In those cases, the film in which the reactions occur must be split up into multiple slices.
There are elements in the user interface of the column that give you and idea of the complexity and allow you to do some tuning if needed. After having installed a gas cleaning fluid package you can install the absorber column. When all the basic configuration is done, go to the Parameters tab / Acid Gas page. Let's stick to the efficiency model, the other model goes even more complex. On this page you specify the geometry of the column.