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102811countercurr-extrc

# 102811countercurr-extrc - Countercurrent extrac,on ...

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Unformatted text preview: Countercurrent extrac,on Absorp,on and stripping Wankat ch. 12 Natural gas liquids (C3+) recovery from natural gas CO2 capture from ﬂue gas Natural gas drying plant Absorp,on of water by ethylene glycol, followed by solvent regenera,on Objec,ves for this lecture •  Convert mole frac%ons into mole ra%os •  Derive opera,ng line equa,on for stripper column. •  Apply McCabe- Thiele analysis to mul,stage stripping using mole frac,ons •  Calculate frac,onal stage requirement •  Derive opera,ng line equa,on for absorber column •  Apply McCabe- Thiele analysis to mul,stage absorp,on using mole frac,ons McCabe- Thiele Analysis of Counter- current Stripper Column Given X0, XN, YN+1 and L/G ﬁnd N required 1. Convert VLE data to mole ra,os (unless x0 < 0.05) Note: y=x line has no use here. 3. Step oﬀ stages (use Murphree eﬃciencies if available). •(XN,YN+1) Y 2. Plot (XN, YN+1) and (X0, Y1) and draw opera,ng line. It will be below the VLE line. Note: calculate Y1 from X0 and opera,ng line equa,on (mass balance). 1 • 2 • 3 • • • •(X0,Y1) N = 3 To ﬁnd minimum stripping gas ﬂow rate (Gmin): X First ﬁnd (L/G)max, by plobng X0 on the VLE line (watch for other pinch points if VLE is curved). Lever- arm rule To es,mate frac,onal stage requirement in a packed column: Y VLE op. line (X4, Y4) • • , Y ) (X3 4 • XN X • 3 X4 • • XN X frac,onal stage = X N − X 3 requirement X 4 − X3 € McCabe- Thiele Analysis of Counter- current Absorber Column Given X0, Y1, YN+1 and L/G ﬁnd N required 1. Convert VLE data to mole ra,os (unless x0 < 0.05) Note: y=x line has no use here. 3. Step oﬀ stages (use Murphree eﬃciencies if available). • Y 2. Plot (X0, Y1) and (XN, YN+1) and draw opera,ng line. It will be above the VLE line. Note: calculate XN from YN+1 and opera,ng line equa,on (mass balance). (XN,YN+1)• • (X0,Y1)• • 3 • 1 • 2 N = 3 To ﬁnd minimum extrac,ng solvent ﬂow rate (Lmin): X First ﬁnd (L/G)min by plobng YN+1 on the VLE line (watch for other pinch points if VLE is curved). ...
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