Molecular Sieve Dehydration

Most efficient and easy to operate system.

Ethanol dehydration with molecular sieves

Water and ethanol form an azeotrope that limits how much water can be extracted by conventional distillation.

The Vogelbusch molecular sieve system allows the dehydration of ethanol past 95 percent purity. It removes water from the ethanol/water vapor mixture that exits the rectification column to gain a dehydrated product. The dryness of this product can be tailored to meet specifications - anywhere from bioethanol with a water content of 0.5% to super dry ethanol for pharmaceutical or industrial applications with a water content of 0.01% or less.

Design options

Depending on the condition of hydrous ethanol feedstock and the presence of an alcohol distillation plant, there are two different design options for the dehydration unit: integrated or stand-alone.  

2-dehydration integrated
Integrated units for vaporous feed

are linked to a distillation and receive hydrous ethanol vapors directly from the rectification column. The regeneration, or purge, stream is returned to the distillation for recovery of ethanol.

The greatest advantage of the integrated system is a considerable reduction in energy consumption when compared to uncoupled systems. The energy-efficient heat integration of dehydration with distillation/rectification/evaporation - a proprietary system introduced by Vogelbusch - also minimizes capital costs.

Feed requires a minimum pressure of 0.5 barg.

2-dehydration standalone
Stand-alone units for liquid feed

are used for hydrous ethanol liquid from storage. The hydrous ethanol is vaporized in a small recycle column. The regeneration, or purge, stream is returned to the recycle column for recovery of ethanol.

The energy consumption of the unit is minimized by an optimal design of heat recovery under consideration of feedstock and utility conditions.

Process principle

Molecular sieve dehydration employs an adsorption process using synthetic zeolite, a crystalline, highly porous material. The process is based on the principle that zeolite's affinity for water changes at different pressures. The water loading of the zeolite depends on the partial pressure of the water in the feed which can be influenced by altering the pressure.

2 molsieve beds
PSA - Pressure swing adsorption process

The molecular sieve bed is fed with superheated vapor so that no condensation will occur. Water vapor is adsorbed into the pores of the zeolite, and ethanol vapor passes through the bed.

Once the molecular sieve bed is saturated with water, it has to be regenerated: the water is desorbed from the zeolite by reducing the pressure applied to it.

Continuous production is realized by utilizing a pressure swing adsorption system with two molecular sieve beds. One bed is in dehydration service, while the other bed is regenerated under vacuum. During regeneration, bed pressure is lowered and the desorbed water is swept out of the bed with product vapors from the other bed in dehydration service. This regeneration, or purge, stream is then condensed and pumped to distillation for recovery of ethanol.

The process is is fully automated.

2 zeolites
Zeolite testing

For best quality selection we examine molecular sieve materials of various manufacturers. In a standardized quick test developed by Vogelbusch, the key performance parameters are analyzed and compared. This quick test is done on every batch of molecular sieve material before it is loaded into a commercial molecular sieve unit.

Skid-mounted installation

For ease of installation, and reduced field erection time and costs, Vogelbusch can supply prefabricated molecular sieve units. They are compact to ship and easily reassembled on site.

Read more about skid-mounted solutions

2 molsieve tharaldson

Double set of molecular sieve beds with a daily dehydration capacity of 1.3 million liters ethanol.

Showcase projects including dehydration units

Dehydration Unit for Gibraltar
CEPSA - San Roque, Gibraltar

CEPSA (Compañía Española de Petróleos, S.A.U.) ordered a molecular sieve dehydration unit from VOGELBUSCH to purify ethanol which subsequently is to be processed to ETBE. The 12,000 liter per day unit has been prefabricated and skid-mounted in Austria and transferred to Gibraltar by truck to be integrated in the San Roque...

D|D for Cellulosic Ethanol Plant in Hugoton
SYNATA BIO (Abengoa) - Hugoton, Kansas, USA

The commercial-scale, cellulosic ethanol facility in Hugoton utilizes Abengoa’s own enzymatic hydrolysis technology to produce 25 million gallons of ethanol and 21 megawatts of electricity from 300,000 tons of biomass per year. Implemented in 2014, Vogelbusch USA provided process design for the distillation and molecular sieve dehydration areas and also supplied...

4 promaiz
Bioethanol Plant in Alejandro Roca
PROMAÍZ - Alejandro Roca, Córdoba Province, Argentina

With a nameplate capacity of 420,000 liters per day, Promaíz is the largest bioethanol production facility in Argentina. The plant processes bioethanol from corn which is used as fuel additive in the local markets. Besides the technology package for the complete plant and detailed planning of piping and vessels, Vogelbusch has...

Dehydration Unit in Pointe-a-Pierre
ETHYLCHEM - Pointe-a-Pierre, Trinidad, West Indies

Hydrous ethanol imported from Brazil is the feedstock for a molecular sieve dehydration facility set up by EthylChem at the Pointe-a-Pierre refinery in Trinidad. It has a production capacity of 1,082,000 litres per day (100 MMGY) of fuel ethanol with a purity of over 99.9 per cent that is intended...

Ethanol dehydration in Osaka
COSMO OIL - Sakai-City, Osaka, Japan

Cosmo Oil produces 140,000 liters per day (12 MMGPY) of low moisture ethanol (300 ppm) utilizing process design by Vogelbusch USA. The skid-mounted unit was installed as part of a larger project to retrofit an existing MTBE production facility at their Sakai Refinery for ETBE production.

Tharaldson distillation dehydration
Bioethanol Plant in Casselton
THARALDSON ETHANOL - Casselton, North Dakota, USA

Tharaldson Ethanol started up their state-of-the-art fuel ethanol facility located in Casselton, North Dakota in 2009. The plant utilizes technology licensed by VOGELBUSCH USA, including the VOGELBUSCH Multicont continuous fermentation process, and is currently operating at a capacity of 1,300,000 liters per day, making it one of the largest dry corn...

2G Demonstration Plant in Kalundborg
INBICON - Kalundborg, Denmark

Inbicon, a subsidiary of DONG Energy, has developed a proprietary process for the conversion of wheat straw. Complementing this biomass conversion process Inbicon has opted for sound and energy efficient technology from Vogelbusch for part of ethanol fermentation as well as the distillation, dehydration and stillage evaporation. The 17,000 liter per...

Bioethanol Plant in Beinheim
ROQUETTE - Beinheim, France

As part of a wet milling complex, this plant is designed to utilize wheat starch and optionally milled grain. It has a daily capacity of 400,000 liter ethanol and was put into operation in 2008. Vogelbusch provided the know-how and technology package for the process plant and supplied key equipment for distillation...

4 penford2008
Bioethanol Plant in Cedar Rapids
INGREDION (Penford) - Cedar Rapids, Iowa, USA

Penford Products Company successfully started up their state-of-the-art fuel ethanol facility in May 2008. The plant utilizes technology licensed by VOGELBUSCH USA and has a nameplate capacity of 450,000 liters per day. Corn hydrolysate from the company’s existing wet corn milling operation is used as feedstock. Tom Malkoski, Penford’s President and...

4 agroetanol
Distillation|Dehydration in Norrköping

The bioethanol plant of Lantmännen Agroetanol AB utilises process technology licensed by Vogelbusch for distillation and dehydration. The proprietary Multipressure system considerably reduces the steam consumption compared to traditional distillation systems and optimum thermal integration further improves the energy-saving properties of the plant.   The facility, which is Agroetanol’s second production...

Bioethanol Plant in Cloverdale
POET BIOREFINING (Altra Indiana) - Cloverdale, Indiana, USA

Altra Indiana reached design capacity in June 2008 at its facility in Cloverdale, Indiana. The plant was built using know-how provided by VOGELBUSCH USA, including the VOGELBUSCH Multicont continuous fermentation process, and has a nameplate capacity of 908,000 liters per day. The facility uses 32 million bushels (813,000 metric tons)...

4 GreenP2007
Ethanol Dehydration in North Sitra
GREEN POWER - North Sitra, Kingdom of Bahrain

Some 400,000 lpd of crude industrial alcohol from a refinery in Saudi Arabia are processed in the Bahrain unit. After entering the plant, the feed is purified in a rectification column where low-boiling substances such as diethylether and acetaldehyde are separated before being dehydrated by molecular sieve technology to achieve...

Bioethanol Plant in Ravenna
KAAPA ETHANOL (Abengoa) - Ravenna, Nebraska, USA

Abengoa Bioenergy successfully started up their state-of-the-art fuel ethanol facility located in Ravenna, Nebraska in September 2007. The plant utilizes technology licensed by Vogelbusch USA, including the Vogelbusch Multicont continuous fermentation process, and has a nameplate capacity of 88 million gallon per year (950,000 lpd). The facility uses 32 million...

Chief Ethanol Hastings
Bioethanol Plant in Hastings
CHIEF ETHANOL FUELS - Hastings, Nebraska, USA

The Chief Ethanol Fuels facility is utilizing Vogelbusch-licensed technology. In 2007, a third molecular sieve drying system was designed and installed, raising operating capacity to 832,000 l/d. The cooperation first started in 1983 when Chief Ethanol Fuels set up af 120,000 l/d plant. Vogelbusch process design included continuous fermentation, multi-pressure distillation,...

4 lexington0
Bioethanol Plant in Lexington
CHIEF ETHANOL FUELS (Cornhusker) - Lexington, Nebraska, USA

Vogelbusch USA Inc started up the ethanol plant of Cornhusker Energy in spring 2006, with a production capacity of 450,000 litres/day of bioethanol from corn. The plant employs a state of the art Vogelbusch continuous fermentation process. An energy integrated distillation, evaporation and dehydration system ensures maximum efficiency. In 2016, Chief Ethanol...

4 euroethyl
Alcohol Dehydration Unit in Alfatar
EURO ETHYL - Alfatar, Bulgaria

Euro Ethyl’s molecular sieve system was supplied preassembled by Vogelbusch USA and the performance test was successfully completed in November 2006. The plant has a rated capacity of 120,000 litres of dehydrated alcohol per day. The integration of the molecular sieve with the existing plant required additional distillation equipment to increase...

4 cropernergies
Bioethanol plant in Zeitz
CROPENERGIES - Zeitz, Germany

The 800,000 litre/day plant of CropEnergies,  a unit of German Südzucker group,  is designed for multiple grain sources together with by-products of beet sugar processing. The plant and is highly advanced in terms of energy saving and environmental protection. Vogelbusch contributed process design for the raw material processing, continuous fermentation,...

4 pekin
Bioethanol Plant in Pekin
PACIFIC ETHANOL (Aventine) - Pekin, Illinois, USA

In March 2004 the molecular sieve unit at the Aventine Renewable Energy plant was brought on stream. With a rated capacity of 1.2 million liters per day (110 mm gallons/year) anhydrous alcohol, at that time the largest capacity molecular sieve alcohol dehydration unit in the world. The molecular sieve unit replaced...

Bioethanol Plant in Jilin

Located in Jilin City in Northeast China, this production line for bioethanol was officially commissioned in November 2003 after an implementation period of 22 months. The plant produces 300,000 tonnes of fuel alcohol annually from maize. The product is used as a 10% petrol additive.  Process design by Vogelbusch provided for...

Neutral Alcohol Plant in Harbin
HARBIN WINERY - Harbin District, PR China

The fine alcohol plant of Harbin Winery, a Chinese producer of potable alcohol from corn, was upgraded by Vogelbusch in several steps. The client required specifically high alcohol quality in terms of organoleptic and analytical criteria and in particular with regard to methanol separation. The facility was designed to set...


Skid-mounted system for recovery of ethanol
01 Jun 2017

Report on ethanol drying system published in Biofuels International Magazine May/June 2017.


Frequently asked questions on the installation of a molecular sieve unit:

All users
For Investors
For Technicians
  • Which is the minimum capacity for economic production?

    The economic minimum capacity of a dehydration unit is around 10,000 liters per day.

  • And the investment for such plant?

    Capital expenditure always depends on plant capacity and configuration as well as local conditions. Costs for the process plant (excluding building, auxiliaries, infrastructure) are in the range of euro 500,000 to several millions.

    This figure is for general reference only since each project has its own particularities that need consideration. 

  • Which maximum water content can be handled?

    Hydrous alcohol with a water content up to 15% can be economically processed in the molecular sieve. 

    Feedstocks with higher water contents can be processed if a rectification column is added to the system.

  • Why select an integrated unit?

    Integrating a molecular sieve dehydration unit with the ethanol plant saves both energy and investment cost. Firstly, the heat of condensation of dehydrated ethanol can be used in the process, e.g. for pre-heating of mash or operation of an evaporation effect. Secondly, the regeneration, or purge, stream can be reprocessed in the existing rectification column and thus it is not necessary to add a recycle column. 

  • Why select a standalone unit?

    Standalone units are the choice for dehydrating purchased ethanol or for central processing of hydrous ethanol from several sources. They may also be an option if the available space within an ethanol plant is limited or if dehydration is carried out infrequent.

  • How about adding dehydration to a potable alcohol plant?

    For super dry ethanol for pharmaceutical or industrial applications a standalone solution is recommended.

    For the production of bioethanol, the potable alcohol plant can be adapted by adding an integrated dehydration unit. Concentrated ethanol vapor with sufficient pressure will be fed to the dehydration from a rectification or repurification column. The product specification of bioethanol allows to reduce the efforts for the removal of by-products compared to potable alcohol production, thus the rectification system will have some spare capacity to recycle the regeneration stream of the dehydration unit. The heat of product condensation can be used in an additional column reboiler for reduction of steam consumption.

  • What are the advantages of skid mounted units?

    Our compact skid-mounted designs include all process equipment within a structural steel framing.

    They are easy to install and require minimum field connections thus reducing field erection time and costs.

  • Up to which capacity are skid-mounted units recommended?

    We have supplied complete dehydration plants in skid modules with capacities up to 400,000 liters ethanol per day.

    For larger capacities it is possible to have selected process components mounted on skids, including vessels, pumps and smaller heat exchangers, plus the interconnecting piping.

  • What are zeolites?

    Zeolites are crystalline, highly porous materials made up of alumino silicates. These synthetic crystals are characterized by a three-dimensional pore system. The pores can be adjusted to precisely determined uniform openings, allowing for molecules smaller than its pore diameter to be adsorbed while excluding larger molecules - therefore they are referred to as molecular sieves.

    Synthetic zeolites are available with openings in a range from 3 to 10 Angstroms (Å). In ethanol dehydration, 3Å zeolites (= with  a pore diameter of 3Å) are used to separate water from ethanol. The small water molecules with a diameter of 2.5Å are retained by adsorption within the crystals, but the larger ethanol molecules (4Å) cannot enter and, therefore, pass through the bed.

  • What is the service life of zeolites in dehydration?

    With well selected zeolite quality and considerate material handling - our process design keeps mechanical abrasion at a minimum - our customers report life spans of 15 years and longer.

  • What are the selection criteria for zeolites?

    Zeolites need to be mechanically stable and have to show a characteristic property profile, which is tested in our laboratories before loading of the vessels.

    Our most important selection criteria for zeolites are high adsorption capacity of water and low co-adsorption of ethanol respectively high selectivity for water in the separation water/ethanol.