Membrane Distillation - Science method

There have been tremendous advances in membrane distillation (MD) since the concept was introduced in 1961: new membrane designs and process configurations have emerged, and its commercial viability has been evaluated in several pilot-scale studies. However, its high energy consumption has hindered its commercialization. One of the most promising ways to overcome this obstacle is to develop more energy-efficient membrane modules.

hi. it will be solved simultaneously

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If the pumping power is sufficient for your setup, it could work. But not guaranteed.

Foroogh,

From:

It's a Hyundai Vacuum Pump 0.5 Hp, (HCPSP0.5-1 × 1IN)

Looks like a plain rotary pump.

What type of membrane distillation do you want to do? I have been working on direct contact MD and I do not use a spacer/mesh. The DCMD module has a rubber gasket on each side and the membrane is set in place by that and never sticks to the surface of the module. If you want/need to use the spacer/mesh, I suggest doing short experiments without it, with it on the permeate side and finally with it on the retentate side. After, you can analyze the system performance and characterize the membrane, and with that reach a better conclusion on the best approach. If your membrane has some type of support (I use a PTFE membrane with a PE support), the support faces the permeate side of the module.

You will have to try several for your particular powder and fluid to see which works best. Sigma-Aldrich sells several types of Zonyl(TM) fluorosurfactants. Best wishes for success.

Dear Jincai Su,

I worked on a pilot-scale flat sheet PVDF membrane project for many years. I checked all of the drying methods.

It seemed that freeze drying is not scalable. Accordingly, I tested solvent exchange using alcohols.

Generally, simple drying is not suitable for polymeric membranes, especially for PVDF membranes as PVDF is hydrophobic. Simple drying causes membrane structure collapse that makes many dead-end pores and reduces the permeability and increases the pressure difference.

Hope it helps.

Best wishes

Dear Souri,

Good luck

Dear Foroogh Khodadadi:

You can benefit from these valuable Links about your topic:

@https://www.researchgate.net/topic/Membrane-Distillation

@https://youtu.be/GWX7grT-DhI

I hope it will be helpful ...

Best wishes ...

DCMD membrane cell can be used in VMD cell on condition that sealing one end of the cold side.

noted and thank you so much Tijjani El-badawy

Dear Mohamed Khedawy,

Thank you so much for your reply and time.

My main question is about the Membrane Distillation process. There are some types of configurations like DCMD, VMD, AGMD, etc.

And I want to know which of them is more common in the industrial section.

Regards

You can read:

and

Dear Foroogh Khodadadi, the essential key is the hydrophobicity of the polymer matrix. It seems that polysulfone copolymers and composites are the most favored. Please have a look at the following documents. My Regards

Good day! That is pretty complex question. In our works we have used copolymer PVDF-TFE membranes because of hydrophobicity, thermal resistance and ability to be reused after cleaning and pore declogging. Also, we have used home-made pilot plant. Please follow the next references:

The requirement for such a plant are quite general: silicone tubes with foam thermoisolation, high speed pumps, the shortest runway for concentrate on the tubes, and steel cell. Some annotations may be dedicated to cell establishing - try plan your module in such a way to avoid blind spots in your cell by forming pathways. Please, feel free to correct me if I was mistaken, and also feel free to share your expertise.

Good day! We are waiting our research paper entitled "Technological improvement of Sorghum saccharatum syrup production by membrane technologies" to be published in Oct 2022 in Journal of Water and Plant Development. It will be dedicated to clarification and concentration of high fructose-glucose juices by means of ultrafiltration and DCMD, so maybe this field will be perspective for you. Also, I wanted to write some review on these theme, so we may cooperate there. Best regards.

Moreover, see the link https://www.mdpi.com/2073-4441/12/10/2841/pdf

Plz see this site:

https://www.google.com/search ei=A_NuXfSnFIiDhbIP19eP4AI&q=Which+membrane+can+be+used+for+solvents+distillation&oq=Which+membrane+can+be+used+for+solvents+distillation&gs_l=psy-ab.12...115502.115502..117089...0.4..0.217.217.2-1......0....2j1..gws-wiz.......0i71.K9k9Ce8RzPY&ved=0ahUKEwi0tdac47XkAhWIQUEAHdfrAywQ4dUDCAs

Please Ref : E Haaz 2019 ( on line available).

Yes dry (warm) air gives the same results.

Dear Dorsa Mousavi You can take advantage of the link below

Regards

Dear Amir,

You can use cross-linked PVA membrane for removing glycerol , glycerol carbonate, potassium carbonate salt and water. Do not use poly(acylonitrile)[PAN] membrane in alkaline media. The -CN group of PAN will hydrolyze to -COOH in alkaline medium. PAN also degrade in highly alkaline medium.

I hope that this answer will be helful for you.

Regards,

Sanjay

Thank you Mr. Amjad an Mr. Silva for the reply. I changed the velocity and now my process is working! Thanks a lot!

Hello _{^{Nhi Võ I think that the below reference is useful for you}}

Characterization of membrane distillation modules and analysis of mass flux enhancement by channel spacers

Water temperature difference across the MD module can not become very large in large scale MD. It may increase slightly more than the temperature difference between the water inlet and outlet of the small/lab scale membrane distillation (MD).

Look at the following attached files

I just completed a thesis on "Forward osmosis for wastewater treatment and energy recovery: A technoeconomic analysis," in which I determined the cost of forward osmosis treatment for municipal wastewater. I am happy to send you the .pdf file if you are interested in my results.

Thank you very much for the answer to my question

Membrane distillation is a simultaneous process which involves both heat and

mass transfer processes. There are two approaches for modeling MD. The

first one concerns the modeling of the transport mechanism through the hydrophobic

membrane. The second concerns with the overall modeling for predicting the permeate flux at given operation conditions. A linear relationship between the mass flux (Jm) and the water vapor pressure difference ∆Pv across the membrane was suggested to describe the water vapor transport in MD. Therefore, you have to check your equations, especially the Antoine equation, where the vapour pressure increases exponentially with temperature ..

Ask supplier about temperature stability also. At higher temperature swelling of Acrylic may observed. But if you want to use water only than it is good.

                                                MSF                     MED                  RO

 

Capital cost ($/m3/J) :          1100-1600            900-1250            700-1000

Operation cost ($/m3/J):         1,5 - 1,8               1,0 - 1,5              0,5 - 1,0

In simple terms:

1. Right application. Full knowledge of water analysis (Composition of ionic as well as non-ionic impurities, organics, silica, suspended solids, hardness, etc. RIGHT PRETREATMENT WILL BE THE KEY

2. Bench tests with actual wastewater

3. Pilot studies, 3-6 months in the field, complete with pretreatment

4. Feasibility study including CAPEX and OPEX analysis

5. Full knowledge of MD membrane chemistry, membrane configuration, membrane flux with given conditions,

6. Full cooperation between MD supplier, engineer and Owner

Membrane Distillation (MD) is most certainly a viable technology, and compete with more traditional technologies such as Seawater RO and Multi-Effect Distillation (MED) plants. Membrane Distillation is a newer technology, has more companies entering the market but still lacks large number of commercial installation. Companies such as Memsys from Germany has Membrane Distillation product, has sold large systems in China, and has done pilot plant work in the USA.

Based on my evaluation, MD technology should be considered for desalination of non-traditional sources of wastewater including reject streams from Cooling towers, Air scrubbers blowdown streams and coal pile runoff from power plants, RO reject streams, etc. If waste heat is available (Example, condensate loop or air stack for power plants) then the technology could be more affordable, will require less power.

Most Membrane Distillation technologies are made with the materials that can be exposed to wide pH range, wide range of chemicals, oxidizing environment, etc.

Best regards,

Ken Pandya

Office 001 972 733 4404

Dear Khaled, maybe this helps:

best regards

Johannes

I couldn't agree with Prof Hassan and Dr Lijo more on the potential of MD for water desalination with the readily availability of waste heat on site. As demonstrated in our recent publications, electrical energy consumption of seawater MD desalination is by far lower than that of RO, thus MD can be arguably an energy saving alternative to RO when waste heat can be utilized.

Just want to add that MD can be an ideal candidate for small-scaled seawater desalination in remote coastal areas where RO is restricted due to the lack of infrastructure, pre-treatment facilities, chemicals, and expertise.

Dear Asma

Azeotropic mixtures may often be effectively separated by distillation by adding a third component, called entraine.In chemistry azeotropic distillation[s any of a range of techniques used to break anazeotropein distillation In chemical engineering, azeotropic distillation usually refers to the specific technique of adding another component to generate a new, lower-boiling azeotrope that is heterogeneous (e.g. producing two, immiscible liquid phases), such as the example below with the addition of benzene to water and ethanol. This practice of adding an entrainer which forms a separate phase is a specific sub-set of (industrial) azeotropic distillation methods, or combination thereof. In some senses, adding an entrainer is similar to extractive distillation. Separation of azeotropic mixtures is a topic of great practical and industrial interest. Most liquid mixtures of organic components form nonideal systems. The presence of some specific groups, particularly polar groups (oxygen, nitrogen, chlorine and fluorine), often results in the formation of azeotropes. Azeotropic mixtures may often be effectively separated by distillation by adding a liquid material (entrainer) to the system.

In most cases, azeotropic mixtures require special methods to facilitate their separation. There is a need to search for a separating agent other than energy, and this agent might be a membrane material for pervaporation or an entrainer for extractive distillationy adding a liquid material (entrainer) to the system. Entrainer completely miscible with the original components . Entrainer may (or not) form additional azeotropes with the original components . The distillation is carried out in a sequence of columns .The addition of the entrainer results in a residue curve map promising for separation. Both original components must belong to the same distillation region .e.g.

When the positive deviations from ideality are sufficiently large, the mixture is said to form a minimum-boiling azeotrope. The Figures below show the constant temperature phase diagram (Above) and constant pressure phase diagram plus equilibrium curve (Below) for a minimum-boiling azeotropic mixture of carbon disulfide (CS2) and acetone. The characteristic of such mixture is that the total pressure goes through a maximum (constant temperature phase diagram), and therefore the temperature goes through a minimum (constant pressure phase diagram), shown as point L.At point L, the concentration in the vapour phase is the same as the concentration in the liquid phase ( y = x ), and a = 1.0. This concentration is known as the azeotropic composition (0.61 mole fraction CS2). At this point, the mixture boils at a constant temperature (39.25 oC under 1 atm) and without change in composition. On the equilibrium diagram, it can be seen that at this point, the equilibrium curve crossed the 45o diagonal.

regards,

Prem Baboo

Dear Tarik Eljaddi,

Whats your expected active membrane area?

Simple question - but complex answer. Just some hints there.

Wettability is not trivial - it depends on (i) the liquid considered, and the composition of the solution - since some contaminants may adsorb and favour wetting ("fouling") and (ii) the material surface energy, pore size and roughness.

To reduce wetting typically - get membranes with the right pore size to limit/prevent capillary diffusion in the pores at your feed or permeate liquid working hydrostatic pressure. Then depending on your feed solution - but typically increase roughness and tune surface energy of your materials. Obviously low surface energy for water, may vary for oil based feeds depending n the oil. Very tricky - but feasible for mixed solvents (ethanol/water etc...).

There are quite a number of studies looking at the impact of multiple of individual parameters involving surface wettability etc... check our review on MD (Water - MDPI).

You´re right, but it is quite usual to focus on the process benefits more than on the real fact behind

Suggested reading:

ADNAN, S., HOANG, M., WANG, H. & XIE, Z. 2012. Commercial PTFE membranes for membrane distillation application: Effect of microstructure and support material, Desalination 284: 297-308

Yes. RO and MD can be coupled

So far, MD has not been commercialized yet due to the cost of heat needed for the feed. Solar heating was attempted but it is rather expensive. Most MD companies are now trying to create market for this technology in niche applications involving free (waste) heat. The examples of that are many.

In addition, low flux membranes and fouling issues have also proven to be significant.