Molecular Sieve Dehydration Units (MSDU)

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Drying Liquids and Gases

Alcohols (Methanol, Ethanol, Isopropyl, etc.) and other solvents (Toluene, etc.)

Most alcohol dehydration for production is based on distillation with packed or trayed columns which include reflux condensers and re-boilers.  Depending upon the starting concentrations and final requirements, the column design is determined by the number of theoretical plates (column height), versus the amount of reflux and reboiling (energy input).  Although there are limits with azeotropic mixtures (ie. ethanol water azeotrope), distillation has been a standard in the processing industry for many years.  However, because this is a thermal separation process, the energy consumption is a major factor in the operation. 

When the water content is below 15% and there is a very dry requirement, utilizing molecular sieves (or mole sieves) are an attractive alternative to distillation. Molecular Sieve adsorption has proven to provide a very dry (even anhydrous) product, while drastically reducing energy cost with minimal operator supervision. Molecular Sieves can offer significant energy savings (up to 40%) compared to distillation, especially when a very dry result is required. 

Azeotropes leave the equation

For alcohol azetropes such as the ethanol-water azetrope or IPA-water, or solvent azeotropes such as MEK-water, simple distillation is no longer an option and more complicated 'azeotropic distillation' methods are required to dehydrate past the azeotrope. Carcinogenic entrainers have been a common but risky solution. Wintek's MSDU adsorbs water past the azeotrope level (if required) and eliminates the added complexity and concerns with azeotropic distillation. Molecular Sieve Diagram

Because certain molecular sieves preferentially adsorb water, water is adsorbed in to the sieve as vapor or liquid passes thru a column. As the vapor or liquid continues to move through the column, more water is removed, resulting in a dryer alcohol until it is fully dehydrated.  Over time, the column will reach a saturation limit, at which point the flow is diverted to a second (dry) column, and the first column is then regenerated.

When properly designed, a molecular sieve system can selectively separate water from other molecules such as alcohols (methanol, ethanol, IPA, etc) and other solvents (Ethyl Acetate, Toluene, etc). The water holding capacity of the molecular sieve is dependent upon several variables, but typically has a maximum capacity of 22 wt% water per unit weight of mole sieve.

(MSDU) Gas Phase Molecular Sieve Adsorption with pressure/vacuum (PSA/VSA) swing desorption (Inquiry Form)

Molecular Sieve Dehydration Unit This design passes the wet alcohol (or solvent) stream in vapor state at a controlled pressure through a column filled with molecular sieve beads.  As the vapors pass through the bed of molecular sieve beads, water is drawn into the internals of the beads by polar attraction, leaving the remaining vapors dehydrated as they exit the column.  After a period of time, the gas flow is diverted to a second column to allow the process vapors to be continuously dehydrated, while the first column is regenerated.

Regeneration in this case is accomplished by reducing the pressure and/or by pulling a vacuum on the column, while using a purge gas to help strip the water out of the molecular sieve beads. Some designs utilize a portion of the dehydrated alcohol as the purge gas, which can be as high as 30% with some competitors, which is then required to be reprocessed through distillation or simply wasted. 

Wintek’s Patented MSDUs are high efficiency designs providing:
  • Recovery rates of 90-95% 
    • Low Energy Use
  • Molecular Sieve Dehydration Unit
  • Minimal Labor/operator intervention 
  • Designed to handle a wide variation in feed concentrations (0-10% water, 15% possible).
  • High Purity: 
    • Standard Dryness: 99.5% dehydration  
    • Extra Dry: 99.9% 
    • Ultra Dry: 99.95%
  • Process from ½ gpm to over 25 gpm of wet alcohols/solvents
  • Packaged Units, fully piped, wired
  • Basic process is very simple, reducing labor and training.

(MSDUL) Liquid Phase Molecular Sieve Adsorption with thermal regeneration

This design passes a liquid stream of wet alcohol or solvent through a column filled with molecular sieve beads.  As the liquid passes through the bed of sieve beads, the water molecules are sucked into the beads due to polar attraction.  As the bulk liquid continues through the column, more and more of the water is adsorbed onto the internal surfaces of the molecular sieve, until essentially all of the water is removed and the dried alcohol(or solvent) exits the column.  This process continues until the sieve becomes saturated with water, at which time the sieve must be changed, or regenerated. Regenerating the sieve typically involves 1) draining the liquid, 2) heating the sieve beads , 3) gas purging either at pressure or vacuum, and lastly,  4) cooling the sieve.

Heating the mole sieve beads is done either by circulating a hot gas(externally-heated design), or utilizing a vessel design with heating elements built into the vessel(internally-heated design).  During the heating and purging process, the water is desorbed along with any residual liquids that have remained after the draining step.  Due to the time and energy required for the regeneration process, this design is most suitable when the starting water content is 1wt% or less.

Click here for the inquiry form on our various Molecular Sieve Dehydration Units. 

For additional information, Call: (973) 252-8200, Fax: (973) 252-8233, or Email Sales at Wintek-Corp.com