Reflux Ratio within a column Still These HETPs change depending on how much liquid & vapour are flowing around them. This ratio can be described by the Reflux Ratio - the ratio of Liquid flowing down the column over the amount of distillate drawn off : R = L / D = (V-D) / D This can be easily measured if the still design is like Stone & Nixons where all the vapour is condensed separately, and you control the amount withdrawn vs returned (refluxed). Its a little harder with the Stillmaker design where the refluxing liquid is determined by the amount of cooling done by the first condensers, and you never get to single it out, but you should be able to estimate the amount of vapour from the amount of heat you apply. As the reflux ratio increases, so the HETP improves. Generally though, you can see that choosing the right packing to start with does the greatest improvement; increasing the Reflux ratio only squeezes the last extra bit out of it (at the cost of having to wait longer too). Where you will notice it is when the design is poor to start with - increasing the reflux ratio will help out quite a bit. #chem.lord
Posted on: Tue, 09 Sep 2014 15:01:17 +0000
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