Ethanol Dehydration

Ethanol Dehydration

Many of the world’s ethanol plants have been designed to use Zeochem molecular sieves. Zeochem’s Z3-03 is the product of choice for use in the ethanol dehydration market providing excellent performance and long life.

Our Z3-03 molecular sieve is designed for targeting only water molecules in the feed stream while minimizing the co-adsorption of ethanol and other smaller molecules. The proprietary manufacturing process produces this adsorbent with superior mechanical strength and much longer service life – approaching 20 years in some plants.

The bead crush strength and attrition properties of Z3-03 are among the best in the industry. The spherical shape of our beads means that the physical forces applied during use are only compressive in nature, as compared to the tensile forces acting on extruded (rod or pellet) shapes which make them more susceptible to breakage. The smooth, hard outer surface resists attrition, thus minimizing dust formation and bead weakening. As a result, Z3-03, as packaged, contains very low dust and generates very little dust during loading.

Feed ethanol with high water content causes fast rates of water adsorption and a resulting rapid temperature rise in the adsorbent bed, all of which can be detrimental to the physical integrity of the sieve. Z3-03 is designed to withstand these extreme conditions, and test results confirm low particle breakup over the range of operating temperatures.

A feed with high water content also requires quicker operating cycles than experienced in other services. Z3-03 maintains its capacity and stability over hundreds of thousands of operating cycles. In addition, its 3 angstrom pore openings allow only water molecules to be adsorbed, reducing co-adsorption of ethanol, sieve coking and carbon deposition which shortens the adsorbent’s life.


Applications

The use of cleaner and greener fuel alternatives is on the rise worldwide, and, as such, the use of ethanol in fuel is growing.

The majority of ethanol used in fuel is blended with gasoline. For the blend to be stable, water must be removed, yet because ethanol and water form an azeotrope, not enough water can be removed from the ethanol solution using simple distillation. When ethanol purity above 95% is required, molecular sieves are the best technical choice.

By partnering with engineering companies that have built, and still build, the majority of all ethanol plants worldwide, we have developed and continue to supply Z3-03, the best 3A type molecular sieve for ethanol dehydration.

Ethanol is used in a wide range of industrial and pharmaceutical products. These range from solvents and cleaning products to cosmetics and medicines. For many of these uses, very high ethanol purity is required. Z3-03 has a proven track record of removing moisture to meet these demanding specifications.

While beverage-grade ethanol is produced by much the same fermentation methods as other grades of ethanol, the finished product has one of the highest purity standards in the industry. Our molecular sieves are consistently chosen for their ability to meet these strict operational standards.

  • Extra neutral alcohol
  • Very low impurity levels
  • Z3-03 fulfills most international food contact regulations
  • No GMO or organic compounds

Custom Solutions

Our experienced technical support and design team can design new dehydration systems and perform process assessments to troubleshoot existing plants, thus ensuring your molecular sieve is always running at optimal performance.

Related Products

Products similar to Z3-03 include other 3A molecular sieves, also designed for preferentially adsorbing water molecules. Those applications include water removal from natural gas, petrochemical and other hydrocarbon streams.

3A

3A is made by ion-exchanging the sodium in type 4A zeolite with potassium. The 3A molecular sieve will exclude most molecules except water, making it very selective.


Frequently Asked Questions

It is recommended to discuss with Zeochem theproposed changes so that a system review and design simulations can be run to determine if any operating changes are necessary or recommended. Zeochem can further check to make sure that all changes fall within recommended operating guidelines, and propose alternatives ifchanges may be problematic.

Beads are round and smooth, strong and durable, exhibiting low dusting characteristics and potential breakage. The spherical shape results in only compressive forces, while pellets (extrusions) undergo compression as well as tension, making breakage more likely. The ends of the pellets also have angled edges, making them subject to chipping and breakage. In addition, beads naturally dense load for optimum loading density without the use of dense phase loading equipment.

When beds are adsorbing in parallel and there is more flow restriction in one vessel than the others, the flow will automatically balance between the beds to achieve an equivalent pressure drop. If it is minor, then it is ordinarily not an issue. If the flow imbalance is large enough, early breakthrough on the vessel with the high flow rate (lowest pressure drop restriction) can occur. In order to better balance the flow rate between the vessels, feeds must be adjusted. This is normally done by adjusting (partially closing) valves, either manual shutoff valves or the valve travel of automatic valves. It can be a trial and error process to achieve balance so it should occur as a series of small adjustments until the operation noticeably improves. In cases where this is not possible, adjustment of the cycles and/or conditions may be possible to prevent breakthrough. When all else fails, the inlet feed rate must be reduced until breakthrough no longer occurs.

Schedule the change out well ahead of time, preferably during an already scheduled shutdown or turn around. Order and have all needed products and supplies on site well ahead of time to avoid any delays. Make sure all contractors, plant personnel, and equipment will be ready to begin the morning of the scheduled start, with any necessary orientation, training, etc. completed in advance. Follow the Zeochem guidelines and recommendations for unloading and reloading the sieve to streamline the process and avoid delays. Have contingency plans in place should there be weather or unexpected delays that occur.

The water capacity is the percent by weight that the sieve adsorbs. At equilibrium, the adsorption is basically driven to completion to determine the absolute maximum amount of potential adsorption. This is most often used as a general baseline measure of the sieve’s quality and ability to adsorb water. Dynamic capacity is the working capacity that is expected from the sieve to avoid breakthrough of water in an actual process. The design simulation determines this capacity based upon the feed and regeneration stream compositions and conditions, and the water concentration, as well as the concentration of other contaminants. It involves not only the equilibrium capacity, but calculation of the mass transfer zone, effects of other contaminants, andaging of the sieve over time. All of these factors contribute to the difference between achievable water adsorption in service and the theoretical maximum water loading for the sieve.

For short term shutdowns of less than 1 day, especially in warm climates, the vessels can be locked in under full pressure and simply restarted from the point of stoppage. In cold climates or wintertime conditions, 6-12 hours could be a downtime limitation due to more rapid cooling. In such cases, depressurizing or partial depressurizing of the vessels and surrounding piping and equipment would be recommended in order to avoid condensation and liquids during the shutdown. For upstream pipelines and equipment that cannot be depressurized, low point drains should be checked to make sure any collected liquids are drained off before restarting. For long term shutdowns of more than 1 day, it is recommended to regenerate all the beds first, depressurize down to 5-10 psig while maintaining a blanket of dry inert gas in each vessel. Check the vessel pressures periodically in order to maintain positive pressure to avoid air ingress. Note that any beds in a regeneration heating cycle should be completed prior to shutdown in order to avoid repeating the regeneration heating step from the beginning.

Bead dusting and breakupis a common cause of pressure drop increase. This is often caused by upsets such as rapid pressure swings, liquids carryover, regeneration refluxing, and flow channeling. Rapid pressure swings can cause movement of the sieve orthe entire bed in some cases. When severe enough it can lead to flow channeling in the bed and early breakthrough in addition to increased pressure drop. Liquids carryover eventsin which liquids slam into the bed can cause sieve breakup, especially for repeated occurrence when it is a chronic problem. Regeneration refluxing occurs when liquids rain down on the sieve bed due to cooling and condensing at the top of the vessel early in the heating cycle while simultaneouslyliquids are being vaporized and driven from the sieve bed.It creates a rolling boil that can breakdown the sieve over time. In general, even under the best of circumstances, the pressure drop across the sieve bed normally goes up by 1.5-2 times over the life of the sieve due to bed settling and compaction, coke and carbon buildup on the sieve, anddust and particulate matter that collects in the bed.

Common upsets include feed water concentration spikes, pressure and temperature swings, flow changes or disruptions, changes in pressure drop, and operating control issues. It is recommended to immediately call ZeochemTechnical Service once the upset is discovered. After review of the details and the current operation, Zeochem will provide a technical assessment and makerecommendations to return the plant to normal operation. In many cases the unit can be lined out, however, sometimes the molecular sieve is damaged to the point where the adsorption capability is compromised. In these cases a reload of fresh sieve may be required. Our Technical Service team can help determine if that is necessary. It is also very important to identify the source and the cause of the upset so that measures can be taken to prevent it from happeningagain in the future.

Make sure all bed loading materials, supplies, equipment, and manpower are accounted for and ready to go ahead of the start date.Keep the sieve as dry as possible prior to loading by storing appropriately. In the field, stage the product for each bed so that all the materials to be loaded in a bed are present and ready to be loaded. Do not place packaging directly on the ground (keep on pallets) and cover with tarps when needed to keep packaging and the sieve dry. Maintained sealed packaging until time to loadinto the vessel or hopper (when applicable). Avoid loading in the rain whenever possible. Sieve readily adsorbs water from the air and the wetter the environment, the more water the sieve will adsorb during the loading.