Temperature control for pervaporation 1

[ridge2481]

Hello,

I have few questions related to pervaporation process.

1)Can pervaporation experiments be conducted at isothermal process? If so how?

2) I am using a polymeric membrane to separate water from alcohol at a temperature of 60C. But during the process of experiments the temperature rises and falls + or - 1C. I also see variation in flux. Can you please suggest possible reasons for this temperature variations.

3) Also, how is the life of a polymer membrane judged? By performance and observation of its flux values?

Thanks in advance
RW

 

[PierreSTRAUCH]

Hi RW,

your 1. - the isothermal process is called "vapour permeation", a combination of evaporation (in a column or with an evaporator) + isothermal water removal along an hydrophilic membrane.

your 2. pervaporation or vapour permeation with a temperature lower than 90°C won't work or at least will not be economical. higher T° = higher flux

your 3. - 3 years with (liquid) pervaporation, 5 years for vapour permeation.

hope it helps,

pierre.strauch@orelis.de

http://www.orelis.de

 

[PVmem]

RW,
1. The only possibility to run pervaporation (liquid feed) at constant temperature is installing the system in an oven (especially for theoretical experiments). PS is right with vapor permeation, but the swelling and thus fluxes with vapor are different (= lower)
2. 60 °C is not the optimal temperature for dehydration, commercial membranes resp. industrial units run with temperatures between 95 and 115 °C (with polymeric membranes). The temperature drop you see comes from the energy to evaporate the water passing the membrane - the heat is taken from the sensitve heat of your feed mixture. Depending on the feed flow rate you might both have temperature and concentration polarisation effects leading to different fluxes. Additionally, the permeate flux directly depends on the water content in the feed.
3. Judgement of membrane lifetime is not easy - it especially depends on the purity of the feed and on the operation of the units.

Regards & good luck