Derivation of the q-line equation
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Recently, while reviewing the principles of chemical engineering, I encountered problems when deriving the equation for the q-line during distillation calculations. For the distillation section: y=(L/L+D)x+(D/L+D)xD; for the stripping section: y=(Lˊ/L'-W')x-(W/L'-Wˊ)xW; and for the feed plate: L'=L+qF. How is this equation for the q-line, namely y=q/(q-1)x-1/(q-1)xF, derived? I’m completely stuck; I’m asking for help from everyone
This post was last edited by BigDreamerNewbie on 2018-9-3 at 14:53. It has been completed; the results are as follows: For the rectification section, Vy = Lx + DxD. For the stripping section, V’y = L’x – WxW. Subtracting these two equations gives (V’–V)y = (L’–L)x – (WxW + DxD), or equivalently, (V’–V)y = (L’–L)x – FxF. When deriving the q-line equation, we have L’ = L + qF and V’ = V + (q–1)F. Substituting these values yields (q–1)Fy = qFx – FxF. Then y = qx/(q-1) – XF/(q-1), which is the equation of the line