Abstract: Performance of Mellapak 250Y and 350Y corrugated structured packing in distillation
applications at pressures rangingfrom 0.3 to 2.0MPa is analysed by using HTU-NTU method.
These data are obtained in a distillation column with 0.15 m diameter op-erated with n-
butane/n-pentane system at total reflux. In considering the axial backmixing effects, the
height of an overall gas phasetransfer unit, HTUOG, is divided into two parts. One part
represents the height of an overall gas phase transfer unit, withoutbackmixing,designated
asHTU*OG, and the other part, designated as the height ofa backmixing unit (HBUo), accounts
for the backmixing effects.The HTUOG is evaluated from the measured concentration profile
of n-butane in liquid phase. The HBUo obtained experimentally iscorrelated in terms of the
properties of the materials being separated and the equivalent diameter of the structured
packing. Our resultshows that HBUo varies from 0.12 to 0.34 m as pressure increases from
1.0 to 1.9 MPa. It indicates that the overall efficiency of thestructured packing decreases
gradually at high pressure, as a result of the vapor backmixing.

Key words: mass transfer, structured packing, backmixing, height of a transfer unit, high pressure

摘要： Performance of Mellapak 250Y and 350Y corrugated structured packing in distillation
applications at pressures rangingfrom 0.3 to 2.0MPa is analysed by using HTU-NTU method.
These data are obtained in a distillation column with 0.15 m diameter op-erated with n-
butane/n-pentane system at total reflux. In considering the axial backmixing effects, the
height of an overall gas phasetransfer unit, HTUOG, is divided into two parts. One part
represents the height of an overall gas phase transfer unit, withoutbackmixing,designated
asHTU*OG, and the other part, designated as the height ofa backmixing unit (HBUo), accounts
for the backmixing effects.The HTUOG is evaluated from the measured concentration profile
of n-butane in liquid phase. The HBUo obtained experimentally iscorrelated in terms of the
properties of the materials being separated and the equivalent diameter of the structured
packing. Our resultshows that HBUo varies from 0.12 to 0.34 m as pressure increases from
1.0 to 1.9 MPa. It indicates that the overall efficiency of thestructured packing decreases
gradually at high pressure, as a result of the vapor backmixing.

关键词: mass transfer;structured packing;backmixing;height of a transfer unit;high pressure