Pervaporation membranes can be classified into organic and inorganic membranes. NaA zeolite membrane, as an inorganic membrane, has well-defined zeolitic pores with high hydrophilicity. The pore size of NaA zeolite membrane is 0.42 nm, which is larger than water molecule (~ 2.9 A) and less than most of organic molecular diameters. Therefore, the membrane shows excellent permselectivity and flux for separation of water from organics. Compared to organic membranes, the zeolite membranes have several advantages including higher permeation flux, higher separation factor and better thermal/chemical stability.
During the separation process, the feed solvent is introduced to the feed side of the membrane, and the H2O is removed from the permeate side. The low pressure of the permeate side is maintained by the use of a vacuum pump. Water molecules are preferentially adsorbed on the surface of the membrane, and then permeate through NaA zeolite membrane layer. The driving force of the process is the difference in the partial pressures of water across the membrane. In the feed side, the dehydrated product can be achieved on the retentate,and the H2O in the permeate side is condensed and drained.
Pervaporation process
The pervaporation process is not limited to the gas/liquid equilibrium of the solvent. It can achieve high-purity solvent with low energy consumption, and separate solvents which are difficult to be achieved by traditional separation methods such as distillation, extraction and adsorption. It has obvious advantages for separation of azeotropic or close azeotropic mixtures and dehydration of solvents with minor or trace water, which is a promising technology for substitution of traditional separation technologies. It has a promising application in energy, petrochemical industry, biological medicine, electronics, environmental protection and other fields.
Technical features
Dehydration of organics by zeolite pervaporation membranes can achieve high-purity solvent with low energy consumption, and separate solvents which are difficult to be achieved by traditional separation methods such as distillation, extraction and adsorption. It is a promising technology for replacement of traditional separation technologies. It has more obvious advantages for dehydration of solvents with minor or trace water.
High efficient & energy saving: Yield 99% energy-saving 50%
The core of pervaporation technology is based on the selective permeability of water and rejection of organics for the membranes. The separation process is especially suitable for the separation of azeotropic/close-boiling mixtures; the energy consumption could be over 50% lower than traditional distillation and adsorption technology. The yield is larger than 99%.
Environmental friendly: Without any third components
The application of pervaporation for dehydration of organics does not introduce a third component which avoid the environmental pollution. Moreover, the water enriched permeate could be treated and reused, which makes the whole process zero discharge.
Small space occupation
The pervaporation facilities have compact structure, small space occupation and high resource utilization. Compared to distillation separation plants, the space occupation of pervaporation plants could be 80 percents lower.
Safe operation: Easy operation and high safety
The pervaporation separation technology has simple flow sheet, mild operation conditions, high automaticity and high security in operation process. Therefore, it is very suitable for dehydration of flammable and explosive solvents.
Pervaporation membrane separation technology
Comparison of pervaporation technology with traditional technologies
Process
The pervaporation dehydration process includes the operating units of feed preheating, membrane permeation, vacuum pumping and product condensation. Vacuum and low-temperature condensation are applied in the membrane downstream to provide the differential vapor pressure across the membrane. The permeate vapors are vacuumed into the condenser to become liquid for recovery or drain.
Application fields
l New energies(production of fuel ethanol, fuel butanol, bio-diesel, etc)
l Petrochemical industry(purification of organic solvents)
l Environment(replacement of traditional separation technology, fulfillment of energy saving and emission reduction)
l Fine chemicals (dehydration of fine chemicals, recovery of solvents, etc)
l Biology, pharmacy(recovery of pharmaceutical solvents)
l Electronics(production & recycle of highly-pure solvent and detergent)
l Food(recovery of food solvents)
