Membrane Assisted Distillation

Separation processes account for about half of the energy consumed in the process industries. Distillation is the most widely used separation technology and also the highest energy demanding separation unit operation. The membrane-assisted distillation (hybrid) processes have been proved to be a sustainable alternative to the conventional ternary and pressure swing distillation, traditionally used for splitting azeotropic mixtures. Alternatively, the hybrid system can increase the capacity of an existing distillation process for the same amount of energy, while still meeting the financial challenges of the retrofitting project. Pervaporation hydrophilic membranes are able to selectively remove water and methanol from organic solvents, requiring only the enthalpy corresponding to the fraction of water that permeate through the membrane. Different configurations are possible for the membrane-assisted distillation, for example the pervaporation section can be integrated into the distillation to reduce the number of trays and decrease the reflux ratio, it can be introduced in front of the distillation process to split the azeotropes before distillation or it can be installed on the top or on the bottom to achieve final product specification.

The benefits of pervaporation-based hybrid processes are known since long time, however more robust and reliable membranes, developed in the recent years, made the hybrid distillation technologies economically more attractive, because of lower membrane replacement cost. In this presentation we will introduce industrial applications for the dehydration of alcohols, ethers and the ability of the membrane to separate methanol from other organic solvents. The cases studies will show how pervaporation / vapour permeation hybrid process contributed to the process intensification strategy, by bringing significant improvement in decreasing equipment size, increasing production capacity, reducing energy consumption and enhance process plant modularization.