As the demand for fuel ethanol grows, technology for production of fuel ethanol becomes critical. Some of the
key considerations while selecting the right technology would be:
How futuristic is the technology so that it will remain current for a long time and you will not be required
to upgrade it constantly
How does it build upon your current facilities so that your investment in fuel ethanol plant is minimal
Does it take care of your energy bill Can the technology handle a wide spectrum of raw materials
Is the technology robust Is it truly a clean technology , with no presence of entrainers like cyclohexane The
EcoMol Molecular Sieve Plants offers you comfort on all the above factors.
The EcoMol Pressure Swing Absorption technology offers the following advantages:
Constant product quality
Lowest Energy Consumption
Maximum Alcohol Recovery
High turndown ratio
Automation and Control system
Longer Life of desiccant
EcoMol : Why is it a better Technology? Fast de-pressurization of bed during regeneration may cause the bed
to fluidize, crushing the molecular sieve beads. The MolSieve bed offered by Praj is designed for gentle
movement, thus ensuring longer desiccant life. Depending on the requirement, Praj can supply skid mounted
units for smaller capacities which are easy to install.
There are two modules available for recovering the alcohol in the regeneration stream
Mapping Fuel-Ethanol Technologies
Conventionally, azeotropic distillation has been employed in production of Fuel-Ethanol. In azeotropic
distillation, dehydration is carried out in presence of entrainer like benzene or cyclohexane.
Although benzene has been banned in several countries for its carcinogenic effect, cyclohexane is still being
employed. The distillation method is very energy intensive. A large number of plants in Brazil still run on
this technology.
To bring down energy consumption and to ensure high level of dryness in final ethanol product, Molecular
Sieve (MolSieve) has proved to be ideal. Molecular Sieve is a synthetic adsorbent. It was introduced more
than a decade ago to dehydrate ethanol. Earlier systems operated in liquid phase and used thermal swing
regeneration process, which did not make them very energy efficient. Further development on the adsorbent saw
introduction of vapor phase operation with pressure swing regeneration system. This proved to be highly
energy-efficient.
The vapor phase pressure swing regeneration system employs Molecular Sieve beds which act as adsorbent. These
beds are made of zeolite with an effective pore size opening of about 3 Angstrom.
In order to understand the process of dehydration of ethanol, consider a column packed with freshly activated
Molecular Sieve. As rectified spirit (hydrated ethanol) vapor first enters the bed, water is diffused and
adsorbed within the pores of the adsorbent structure in a thin layer. As more alcohol enters the column, it
passes through this layer to slightly lower level where another incremental amount of water is adsorbed. This
continues until a point is reached where all possible water adsorption from this slug of alcohol is
accomplished.
Transfer of water from the vapor of rectified spirit to the Molecular Sieve occurs through a zone where water
(adsorbate) content is reduced from its inlet to its outlet concentration. This finite length of bed, where
the adsorbate transfer occurs, is known as the mass transfer zone. Two beds are provided in order to make the
process continuous.
Whilst the active bed is under pressure carrying our dehydration, the regeneration bed is under vacuum. The
shift of operation (swing) from one bed to another is controlled with help of control valves and automation.
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