Air Pollution Control Innovations

Ethanol Scrubbers Discussed at 2009 Fuel Ethanol Workshop & Expo

Posted by Andy Bartocci on Mon, Aug 17, 2009 @ 06:00 AM

Back in June I mentioned that I was getting ready to head to the 2009 International Fuel Ethanol Workshop and Expo, which was held June 15-18 in Denver, CO.  I had the opportunity to present a new ethanol scrubber design during the emissions abatement optimization session in the energy & environment track.  My presentation dove- tailed well with other topics of the co-presenters, given below.  Ethanol Scrubber






Track 2: Energy & Environment
Emissions Abatement Optimization

  • Moderator: Monty McCoy, Technical Manager, US Water Services
  • New Ethanol Scrubber Reduces Plant Capital and Operating Costs
    Andrew Bartocci, National Sales Director, Envitech Inc.
  • Fail-Safe Scrubber Emissions Compliance for Ethanol Biorefineries
    Monty McCoy, Technical Manager, US Water Services; and Bob Elliott, Environmental Field Manager, American Engineering Testing Inc
  • VOC, CO, and NOx Abatement and Optimization with RTO's
    Andy Rodger, Engineer, Pro-Environmental Inc.
  • Air Emissions Permit Compliance and Pollution Control Device Optimization Using Advanced Measurement Techniques
    Thomas Dunder, GE Energy

I discussed a new ethanol scrubber used to recover ethanol from the fermentation and other vent streams.  These streams contain CO2, ethanol and low concentrations of various volatile organic compounds (VOC's).  Chilled water is commonly used to recover the ethanol, however, many of the VOC's (acetaldehyde, etheyl acetate, acrolein, and acetone) are highly insoluable in water and do not scrub out well.  Post processing is often required to meet emission limits, which adds costs.  I introduced a new, 2-stage scrubber design that uses re-circulated ethanol in the bottom stage and once-through chilled water in the top stage.  Ethanol is an excellent solvent for the residual VOC's and it is readily available at ethanol plants.  This approach eliminates the need for post processing and significantly reduces the plants capital and operating costs. 

The presentations by Monty McCoy of US Water Services, Bob Elliot of American Engineering Testing, Inc., and Thomas Dunder of GE Energy showed test data from various ethanol scrubbers which illustrate how water flow rate, water temperature, and  bisulfate injection rates impacts scrubber performance.  The data also showed how the emission rate changes throughout the fermentation process.

Other issues of ethanol scrubber performance were discussed including channeling and fouled mist eliminators. Channeling is related to non uniform liquid to gas (L/G) ratio. When a limited amount of water is applied to the packing in a tall, narrow tower, uniform distribution of the water is critically important. If there are parts of the packed section where the L/G is lower than the average value, gas passing through those parts of the packing will not be scrubbed as efficiently.  If any water runs down the tower walls, it won't spend as much time in contact with the gas and will absorb less ethanol than water trickling over the packing.  A properly design scrubber should have internals that help maintain uniform distribution.

Fouled mist eliminators can result in excessive pressure drop.  This can be caused by improper selection of the type of mist eliminator or from not having a proper wash system to keep the mist eliminators clean during operation. It's important to not view the fermentation scrubber as a simple can with packing in it.  There are nuances to the scrubber design that enable it to operate at optimum performance with minimum maintenance.

To download the presentation click the icon below.

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Ethanol Scrubber






photo credit: stefanie says

Topics: ethanol scrubber, ethanol, fermentation scrubber

New Ethanol Scrubber Reduces Plant Capital & Operating Costs

Posted by Andy Bartocci on Mon, Jun 22, 2009 @ 11:00 AM

I'm making plans to head to Denver for the upcoming 2009 International Fuel Ethanol Workshop and Expo, June 15-18 in Denver, CO.  Envitech has a booth at #1241.  I'll be giving a talk on our new, patent-pending ethanol scrubber which reduces capital and operating costs. 

The new Envitech ethanol scrubber reduces total organic carbon compounds (TOC) in the exhaust gases to acceptable levels without requiring thermal oxidation or chemical transformation.  The scrubber uses ethanol as a light alcohol solvent for the other, non-ethanol organic carbon compounds.  While these compounds have low solubility in water, they have high solubility in ethanol.  Because ethanol is readily available from the plant, it is an ideal solvent for these difficult to remove compounds. 

My talk is at:
1:30 pm to 3:00 pm, Wednesday, June 17th
Track 2: Energy & Environment
Emissions Abatement Optimization
New Ethanol Scrubber Reduces Plant Capital and Operating Costs

Topics: ethanol scrubber, Announcements, Product Information