2011 FEW Review - Track 4 Production: Tuning it Up

Multi-pronged approaches to optimization
By Susanne Retka Schill | July 20, 2011

The well-attended production track at the 2011 International Fuel Ethanol Workshop got into the nitty gritty of optimizing ethanol plants, addressing topics from yeasts and enzymes to the proper grind, efficient distillation, maximized water use and well-tuned software controls.

Christopher Richards, global sales manager, Lallemand Ethanol Technolgy, pointed out there are four steps to optimizing plants. The first is to achieve consistency. “Seventy percent of any gains come from reducing variability,” he said. A consistent plant, even one that is running poorly, is easier to optimize than a variable one. The second stage involves standard operating procedures. “Are they right? Do they need to be updated?” he asked, adding that writing, reviewing and continually updating standard operating procedures “can be an effective way of getting buy-in from shifts.”  The third stage, this fermentation expert said, is making sure there is effective dosing and that fermentation is consistent and efficient. Only when those three are in place, he said, can new ideas, products and technologies be examined. “Most people want to jump to step four,” he added.

Reducing variability was the main focus of the software experts who discussed process control. Representatives from ICM Inc., Rockwell Software and Expertune Inc. described the conceptual frameworks behind their software solutions. John Gerry, president of Expertune, explained that better base layer control in individual control loops is needed before an overall advanced process control system can be put in place. “In typical plants, 40 to 60 percent of the control loops are turned to manual mode,” he said.

Before comprehensive computerized control systems are put in place, ethanol operators are typically reacting to laboratory test results, said Maina Macharia, industry manager-biofuels for Rockwell Software. Adapted from the oil industry, multivariable predictive control (MPC) systems are used to build computer models capable of doing virtual online analysis that can then make adjustments from real-time tests. In the plant-wide MPC systems installed to date by Rockwell, the average production rate increased 9.7 percent, the average yield increase was 3.6 percent, the average natural gas used per gallon reduced 5.72 percent, for an overall margin improvement ranging from 5 to 11 cents per gallon.

MPC is useful where there are measurement that can be taken and valves can be manipulated, explained Bob Wilson, capital sales manager at ICM Inc. “Yeast and enzymes don’t have valves,” he added. ICM’s team for total optimization has developed advanced process control models to work synergistically with MPC. Advanced process control implementation at one 115 MMgy plant brought its capacity up to 120 MMgy, he said.

Other speakers during the panels in the production track addressed many other areas of plant operations, with several introducing their companies’ ideas for innovation. “The drying operation for DDGS is responsible for 30 percent of the total energy use in the plant,” said Vivek Sharma, Genencor senior applications scientist. Genencor is developing a dewatering  enzyme that reduces the water-holding capacity of whole stillage, allowing 10 to 14 percent more liquid to be sent to the evaporator and reducing the liquids in the wet cake, thus reducing the wet cake load on the dryers.

Thin stillage is the target of another technology using anaerobic digestion combined with ultrafiltration membranes developed by Biothane LLC.  Timur Dunaev,  process engineer, said anaerobic digestion can provide flexibility between using thin stillage for energy production, or sending it on the evaporators and dryers for distillers grains in favorable feed markets. Thin stillage produces 4 to 7 cubic feet of biogas for every gallon and in the process removes 98 percent of the chemical oxygen demand and 99.9 percent of total solids, making any consequent water treatment much easier.

—Susanne Retka Schill