How to optimize operating parameters using the known tower diameter
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This post was last edited by zj88812 on 2010-3-3 at 14:40. I am currently working on a project related to the distillation of ethanol and water; I am using simulations based on the known diameter of the tower in order to determine parameters such as the reflux ratio and the number of trays. I tried using the Radfrac model – after entering the tower diameter, it required me to input data such as the number of passes, weir heights, start stage, and tray type. I don’t have this information, but it is necessary to enter it anyway； I’ve watched many tutorials, all of which focus on designing the tower diameter; there are very few that explain how to calculate values such as N and R based on the known tower diameter. I’m stuck at this point, so I hope everyone can offer some advice
The tower diameter is related to the processing capacity, while the theoretical number of theoretical plates is related to the substance being processed
The teacher didn’t provide the processing volume; instead, they gave only the tower diameter and the fact that the feed composition contained about 15% ethanol. They also specified requirements for the top and bottom of the tower, and asked me to use Aspen to optimize N and R values as well as the feed location, in order to determine a rough range for the feed amount. However, Aspen required the feed amount to be entered from the beginning. When using Aspen for simulations earlier, I just set the feed rate arbitrarily; it didn’t seem right. I wonder if it’s possible to calculate an approximate feed rate using a tower diameter of 160X4200, and then use that value in Aspen for simulation and optimization?
1. Once you have an approximate value for the feed rate, you can use sensitivity analysis tools to examine the relationship between the feed rate and the tower diameter. Tray sizing. 2. For Tray rating, it is indeed necessary to enter the tray parameters. \"Number of passes\" indicates the number of channels; \"Weir heights\" refers to the height of the weirs. \"Start stage\" is the number of initial trays in the tower, which is usually 2; the condenser counts as 1. \"Tray type\" denotes the kind of tray used, such as bubble trays or Koch-Glisch trays – there are relatively few types available. 3. There is no need to use tray calculations (since you don’t have the necessary parameters). What your teacher means is to determine an approximate range for the feed flow rate based on the tower diameter, and then optimize N&R directly using that flow rate.
Oh, I see. I’ll give it a try, thanks
The flow rate can be estimated based on the tower diameter and the empty tower velocity, right?
I made a mistake earlier; the term for it in a packing tower should be packing sizing. I’d like to ask about this
Sensitivity analysis tools can be used to examine the relationship between the feed rate and the tower diameter. Tray sizing. I was wrong before; it should be a packed tower, and packing sizing should be used. Here, the starting stage for the packing section should be set to 2, and the ending stage (which should be the number of trays minus 1) also needs to be entered. The sheet thickness, as well as the type of packing and HETP, must also be specified. I have decided on the type of packing. Do the theoretical tray height and sheet thickness need to be calculated and then entered? Was it obtained through other simulations for the input as well?
The packing is the same as the tray. It’s just that 1 meter of packing is equivalent to one theoretical plate. So, several meters of packing correspond to several theoretical plates. For example, a 4-meter high packed tower. The number of theoretical plates is 4, plus 1 condenser and 1 reboiler. The total number of theoretical plates is 6. So, in the tower settings, enter 6 for Number of stages. In the Packing sizing design, the starting stage is 2 (1 if there is no condenser), and the end stage is not -1 but 5. Additionally, the sheet thickness only needs to be entered when using Sulzer-type packing; other types do not require this parameter. It is a packing parameter that can only be entered and cannot be simulated.
The plate height of HETP, etc., is a function of the packing and the material. Similar to the plate efficiency of trays. A value of around 0.75-0.8 is generally chosen. Or if you have experimental data, just enter it directly.