This approach is sometimes called the Ponchon-Savarit Method. Working on the Hx diagram is more general than a McCabe-Thiele construction, because it. Ponchon – Savarit Method Presentation by. Prof. K. V. Rao Programme Director Department of Petroleum Engineering & Petrochemical Engineering. Lever Arm. Modified versions of the Ponchon-Savarit and McCabe-Thiele methods are presented which incorporate a correct analysis of the feed region in the case of partly.
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Ponchon Savarit Method
These were then paired with the equilibrium savari, which relates the composition of liquid on a stage to the vapor leaving the stage. The steady-state enthalpy balance for a distillation column is: This graphical method uses both material and energy balances to determine the number of theoretical stages required to achieve a specific separation.
The intersection is the point L 1 liquid on tray 1. The operating lines will connect the point representing the liquid on a stage with coordinates x nh n to methoe point representing the adjusted enthalpy at ponchpn appropriate end of the column. For an adiabatic process, the feed and products will be colinear on an Hx diagram.
Once the overall enthalpy line is crossed, construction continues, but operating lines are now drawn between the L i point and the B’ point instead of the D’ point.
Consequently, there are 5 ideal stages required for this separation — with a partial reboiler, that means 4 ideal trays. Construction continues until L 5 which is almost directly on top of x B. Distillation calculations can be performed graphically on an enthalpy-concentration Hx diagram. MaylisApr 22, The operating lines are developed from enthalpy balances on the rectifying and stripping sections just as in the McCabe-Thiele approach operating metgod were developed from the equivalent component balances.
No, create an account now. You can set values for the feed quality and feed, distillate, and bottom compositions to obtain the corresponding Ponchon—Savarit graphical construction and the number of column stages. I personally understand it this way: This has been used before if you have used lever arm principles.
RMP Lecture Notes
A reflux ratio of 1. Metnod this modification, the system is adiabatic, so a line can be drawn through the feed point, F, and the points x Dh Dp and x Bh Bp. This approach is sometimes called the Ponchon-Savarit Method.
If the saturation curves show significant changes in curvature or separation, it suggests that to assume equimolar overflow will introduce error. MaylisApr 21, Eitherway you could actually compute for the number of stages using M-T while incorporating the enthalpy balances I think you know that as wellbut personally I find P-S method faster than M-T incorporating such balances because at least with P-S you just have to continually draw savwrit lines without having to worry about recomputing the operating and stripping lines every single time, lol.
Join Physics Forums Today! This line represents the system enthalpy balance, and so is called the overall enthalpy line.
The H- and h- enthalpy versus composition for both the liquid and gas phases are represented by the red and blue curves, respectively. Your second stage and onwards that Download free CDF Player.
Ponchon-Savarit Graphical Equilibrium Stage Method – Wolfram Demonstrations Project
The reflux is a saturated liquid and feed enters the column at the optimum stage. The D’ point on the Hx diagram can then be placed at 0. While doing constructions on the yx diagram, a “pinch” was defined as the intersection point between the equilibrium curve and the operating curve.
Yes, my password is: The Ponchon—Savarit graphical construction allows the rigorous computation of the number of equilibrium stages in the case of the separation of a binary mixture composed of -hexane and -octane.
My understanding is that the McCabe Thiele method assumes that the liquid and vapor svaarit flow rates are constant in each section of the column. The very shape of the Hx diagram provides a clue as to the importance of the energy balances.
Apr 21, 5. The Ponchon Savarit method does not make this simplifying assumption, so it is more accurate. If the dew point and bubble point lines are more or less straight and roughly parallel, it indicates that the latent heat of vaporization is basically constant with respect to composition.
In that diagram the light-blue lines are the stages. The “pinch point” also expands, resulting in a single line where the operating and tie lines overlap. Your first stage is drawn correctly.
These values and the reflux ratio can be used to find the enthalpy coordinate for the D’ point, H Dp. A similar procedure can be followed on an Hx diagram, except instead of using component balances, enthalpy balances are used. A feed containing 40 mole percent n- hexane and 60 percent n- octane is fed to a distillation column. Continue the construction, alternating between tie lines and and operating lines until you have moved to the left of the overall enthalpy line at point L 3.
Al-Baghli, and Brian G. You need to begin dropping your line from the vapor curve, not from the liquid curve it would be pointless, it’d look like you’re calculating the maximum reflux I’ll whip up a Paint diagram for you. Points for the feed and product can be located on the Hx diagram; for our purposes we’ll call them the F, D, and B points.
Minimum reflux still corresponds to a pinch at the feed conditions, so to determine the minimum reflux a line must be constructed so that the overall enthalpy line coincides with the tie line that runs through the feed point.