Chemical & Process Technology: Internal heat integrated distillation columns

Sunday, June 6, 2010

Internal heat integrated distillation columns

Process Intensification (PI) is an approach to develop an innovate systems and practices offer a drastic reduction in chemical and energy consumptions, improvements in process safety, decreased equipment volume and waste formation and increased conversions and selectivity towards desired product(s). More detail discussion on PI has been presented by P.J. Lakhapate in "Process Intensification".

Another approach was introduced by R.S.H. Mah and co-workers is internal heat integrated distillation columns (iHIDiCs). It is common known that distillation is an energy intensive separation in particular those mixtures with very llow relative volatilities. Typical mixture systems are propylene-propane, ethyl benzene-styrene systems, etc. Several method such as thermal coupling, heat integration, vapor recompression and heat pumps were used to reduce energy consumption and improve distillation efficiency .

In vapor recompression designs, the vapors leaving the top of the distillation column are compressed and then are condensed in the reboiler of the same column, providing the heat needed for vapor generation. Internal heat integrated distillation columns (iHIDiCs) are further intensifications of vapor recompression principle. These columns combine the advantages of both direct vapor recompression and adiabatic operation and can have significantly lower energy demands than common vapor recompression distillation columns or heat pumps.

A systematic design hierarchy was proposed for iHIDiCs, including thermodynamic and hydraulic approaches. Starting from a conventional design, a full iHIDiC design can be achieved by performing basic design assumptions to conventional data. Temperature profiles are a key for heat integration, while hydraulic calculations are necessary to quantify the ability of a column design to place heat panels.

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