The ethanol industry is well-established, with the first wave of plant construction largely complete. Plant owners and operators are achieving acceptable return on investment (ROI) and are taking cost-effective steps to modify production cycles and equipment as needed.

Still, many plants, particularly those in the 100 million-gallon-per-year (MGY) range, could achieve additional ROI through upgrades that debottleneck critical processes to boost overall throughput, increase yield from base throughput, or both. Our debottlenecking studies for several clients have revealed common-sense solutions to do exactly that.

These debottlenecking studies start with a regimented review of plant equipment or unit operation capacity. We follow with interviews with the operations staff, the people who have a deep understanding of how their plants are performing because they work with the equipment every day.

Following this input, we begin applying the appropriate engineering tools. Are there hidden capacities that may be uncovered with modest investments? Can other co-products be added, such as corn oil or cattle feed? Though many plants have already evaluated co-products, owners may have been hesitant because of the capital investment required. Initial studies often reveal common equipment bottlenecks at:

  • Dryers
  • Boilers
  • Cooling towers
  • Pumps

The idea is to expand capacity and yield at a reasonable cost. Operators have gained valuable years of experience in running their plants and have become proficient at identifying opportunities to gain better yields. If they ran into problems, they have been able to do their own engineering, sometimes in consultation with the original equipment vendor. For example, if capacity problems are identified at a pump, booster pumps may be an option (usually an inexpensive addition).

However, once these areas of focus are addressed, it may be time for more detailed engineering studies that provide a holistic view of all options that should be considered for further efficiency. Detailed engineering generally reveals a full range of equipment modifications or upgrades that may be needed as capacity is added for one process. For example, simply upgrading a dryer to a larger capacity unit will not achieve the full capacity possible unless other equipment is modified or upgraded.

The key is to identify the bottlenecks and then determine cost-effective steps to de-bottleneck.

For example, in the milling process, potential steps include adding mills, increasing conveyor speed, mixing screen sizes or increasing air volume through the mills. In the cooking and liquefaction process, the slurry bender may be replaced, steam heat can be reconfigured, liquefaction time can be added with a new tank or venting can be reconfigured to capture ethanol recycled from scrubber water. Fermentation can be augmented with booster pumps, expanded ferm-cooler exchangers or expanded mash/beer exchangers. The opportunities extend throughout the production train.

Debottlenecking studies can reveal other opportunities for co-product production. Oil extraction is now common in most ethanol plants. Since much of this oil is inedible, it has gone to vertical integration with biodiesel or renewable diesel assets, or sometimes sold to other biodiesel producers. Some plants have added protein and fiber products via dry grain fractionation.

Many ethanol plants have opportunities to achieve higher rates of efficiency or greater productivity, often with minimal investment.

George Baskin, Ph.D., is a senior project manager based in our St. Louis office. His experience includes helping established and startup enterprises — many in the renewable and sustainable arena — grow and expand, working with them to develop, price and schedule large capital expenditure projects.