Redrop – an Efficient Monte-carlo Method for Simulating Extraction Columns

Due to increase in the price of fossil fuels and the decrease in their reserves, renewable raw materials are industrially used more and more frequently. Therefore extraction, as an energy-saving unit operation has gained additional importance. Precise design methods for technical columns are required for the future. So far, pilot-plant experiments are carried out as a basis for equipment design. These cost-intensive experiments can be minimized or even avoided by simulating the behavior of extraction columns. The simulations have to account for drop movement, axial dispersion, mass transfer, coalescence and drop breakage. The key to a successful simulation is solving the droppopulation balances. A large number of researchers have tried to numerically solve the system of equations. A great disadvantage of this procedure is the increase in numerical efforts if additional properties of the drop population have to be regarded. An alternative approach solving the population balances is using the Monte-Carlo method. ReDrop (Representative Drops) is a simulation program which can successfully predict the behavior of pilot-plant columns. Because different internal types (random packing, regular packing, sieve tray) can be modeled with ReDrop, simulations can reveal which kind of internal is the best for the interested material system. Also the dimension of the internals as well as the operating conditions can be optimized If the design of the technical column is based on pilot-plant experiments, a type of internal has to be chosen in a early design of the design procedure. A later change of the internals is cost-intensive. In this paper, ReDrop is explained in detail and results are compared to experimental values in literature. Finally, an outlook is given on the extensions of ReDrop which are currently treated.