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Technology of thermal membrane distillation

The memsys technology is based on vacuum multi effect membrane distillation, which is a highly efficient thermal process for thermal separations in a modular concept. These memsys modules consist of flat sheet membranes combined with an innovative plate and frame design made of Polypropylene. The patented construction allows to form all functionalities for the process and therefore transforms traditional heavy industry engineering into a unique monolithic industrial design. For detailed information view our Markets page.

General technical information

memsys has succeeded in combining the advantages of the most efficient thermal multi effect processes with membrane distillation to a very small modular configuration. The name of this new process is V-MEMD and stands for Vacuum - Multi Effect Membrane Distillation.

Membrane Distillation (MD) is a unit operation that uses hydrophobic membranes which vapor can pass only. Generally vapor pressure is the driving force. For the memsys process negative pressure and temperature differences facilitate an optimum flux.

Most of today existing MD are based on MSF (multi stage flash) process. Key to the memsys success is the use of the superior ME (multi effect) process which reduces feed volume for energy supply significantly. By this mechanical stress to membrane is reduced which is important as life time of membranes is crucial for economical success of membrane driven processes.

The basic principle of standard MD is simple: Hot feed water flows into a channel bordered by a micro-porous, hydrophobic membrane. Due to surface tension the liquid cannot enter the membrane. Different temperature and vapor pressure on both sides of the membrane force the evaporating vapor to pass the membrane. Condensation of distillate occurs on the other side. Non-volatiles stay in the feed and are rejected with the brine. Temperature and pressure levels are reduced from stage to stage.

Hygiene aspects

Common to all distillation processes is the very high quality of the water purified. No minerals, bacteria or viruses can pass the vapor phase. Even raw water with a mineral contend of more than 50.000 mg/l TDS can be purified to a level of less than 1 – 2 mg/l TDS (< 10 µS/cm = mikro Siemens per cm) in a single step of distillation process. This high quality of separation can be achieved for all mineral parts and organic elements including dangerous elements like Boron and Arsen which can pass mechanical filtration processes like reverse osmosis.
A sterile environment has to be warranted by simple measures like high enough temperatures in the process.

Energy consumption

The biggest obstacle of MD is seen traditionally in the high thermal energy consumption for his process. One more major advantage of memsys ME distillation is that it can be powered by temperatures below 70°C. This allows combination of cheap and/or environmental friendly heat sources like waste heat from industrial processes or diesel generators or solar energy from thermal solar collectors. Therefore up to 90% of the required energy can be substituted.

Materials

All components needed for the memsys process are made from food approved plastic. This has a massive impact on costs, weight and reliability as no corrosion occurs. Raw materials are PP and PTFE only which are cheap, easy for further processing and recyclable. Frames and stacks are produced in established automotive production processes which stay for highest quality standards and high outputs.
Due to moderate temperatures and low process pressure all pipework and pumps can be made of plastic as well.

Environment

Environmental issues become increasingly important for modern processes. Especially seawater desalination has been reviewed for environmental impact of pretreatment used. The memsys process is noncritical towards raw water quality. Non-polar surfaces of used materials prevent scaling and fouling. Low process temperatures are also prohibitive for scaling. If bio-fouling occurs it can be removed by maintaining the system with regular short process runs with high temperatures. If any pretreatment is needed due to bad raw water quality it will be on a very environmental friendly base.

Engineering

memsys presents the first modular thermal separation process. Different customer requests regarding volumes or thermodynamic set-ups can be realized by adding memsys modules without costly engineering. A wide scalability is granted.

FAQ – frequently asked questions to memsys thermal separation

You will find answers to the following questions about the memsys process of thermal membrane distillation in the PDF download below:

  • What are the process requirements?
  • What are typical concentrations and recovery rates?
  • What is the relation of flux and temperature delta?
  • What are the relations of distillate production and membrane area?
  • What is the relation of TDS and flux?
  • What is the energy consumption of the process?
  • What is the footprint of MD compared to other technologies?
  • What are scaling experiences?
  • What chemicals are critical for the modules or the membrane?
  • What are fouling experiences?
  • What is the demand for pretreatment?
  • What are life time experiences?