Ethanol Producers Talk Shop

Gathering eight experts from seven plants together at the 2006 FEW to answer any question thrown at them was the object of "Shop Talk I & II," where inquiries on grinding corn, drying distillers grains and almost everything in between were all fair game
By Ron Kotrba | August 01, 2006
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The 2006 FEW offered attendees an opportunity to partake in two separate but clearly correlated Q&A sessions that offered inquiring minds a better understanding of ethanol production practices. Eight qualified members of seven different ethanol plants opened themselves up to audience members' questions in Shop Talk I and II, and those in attendance consisted of a wide cross-section of current and future producers, operators, equipment vendors, academia and others.
Even though the two sessions were split up between front-end processes (I) and back-end operations (II), the two major areas of ethanol production are intimately bound to each other. So when DENCO LLC's Laboratory Supervisor Dori Coler quoted Mike Ingledew, saying, "The fermentor is not a garbage can," her intimation was that, although it is conceptually possible to separate front-end processes from those associated with the rear of the process, the quality and quantity of ethanol and distillers grains produced at any given plant are paired results intrinsically tied to each input, condition or operational adjustment made along the way.
Here's a look at some of the topics discussed.

Feedstock Preparation
Any savvy businessperson looks at all available options to develop new revenue streams. Dry fractionation is one such option for current and future ethanol producers, but several concerns about the emerging technology are still afloat. "There is a starch loss," said Stan Janson, plant manager at West Burlington, Iowa-based Big River Resources LLC, a 40 MMgy Fagen Inc./ICM Inc. plant. While Janson noted the benefits fractionation can reportedly bring to the production process—such as facilitating pumping due to less viscous mash—the high capital costs and intense maintenance requirements were relayed as prohibitive to its widespread acceptance. Janson told the audience that as the markets get tighter down the road, it's likely the industry will see more bio-refineries being developed.

For standard dry milling, everything begins with the grind. Hence, the question of "grind size" versus "cook time" was in play during the sessions. Grind size is important, Coler asserted, because enzyme effectiveness is correlated with surface area. A finer grind exposes more surface area, therefore increasing the effectiveness of the enzymes in cooking, while a courser grind exposes less of the starch's surface area. Too fine a grind, however, might lead to dough balls, she said. "You want it course enough to keep the strainers from plugging and fine enough that starch is exposed." A sieve analysis is done every week at DENCO to check the grind size. According to Coler, enzyme effectiveness in DENCO's cook process peaks at 183 degrees Fahrenheit. Concerns over the separation efficiency of centrifuges in relation to grind size were also addressed.

DENCO adjusts payments to corn producers based on higher moisture content and damage, as do other plants. DENCO's corn averages 72 percent starch, Coler said.

Kurt Koller, chemist at Badger State Ethanol LLC in Monroe, Wis., said there may come a time when ethanol plants buy grain on a starch-content basis, but right now it doesn't make sense.

Better Understanding Leads to Quality Checks
According to Koller, consistent fermentation was brought up as one of the biggest challenges to producing consistent products. Many on the panels were of like mind. "At DENCO, we always try to run as consistently as possible," Coler said. "Consistency overall is better than those highs and lows."

With yeast being the "labor" force driving the production of alcohol, healthy fermentors and good conditioning lead to a better product through more robust fermentation. Koller said his plant uses active dry yeast (ADY), which Badger State Ethanol rehydrates using a solution of water and dextrose raised to 104 degrees. He said they look for yeast cell counts in the range of 40 million to 50 million cells per milliliter, and a budding rate of 50 percent, with 80 percent viability.

As stated earlier, how the process runs in the front end of the plant affects processes further downstream. Coler, Janson and others expressively pointed this out when it was brought up more than once that if fermentation isn't running at peak capacity, sugars will be present downstream, causing problems in the evaporators, dryers and elsewhere.

John Rosemeier of Heartland Corn Products, a 50 MMgy ethanol plant in Winthrop, Minn., said he played a significant role in configuring Heartland Corn Products' current setup. He described a time prior to his employment at the plant, when the facility produced black DDGS for a week because of the high sugar concentrations left in the beer after fermentation. Rosemeier mentioned that ethanol plant designers ought to configure these plants in such a way that pockets of mash can't be hidden during cycling.

Rosemeier said when contamination or other problems begin to surface at a plant, indicators alert personnel to the problem; the signals need to be read, though. At DENCO, Coler said starch tests and cell counts are logged, and each batch is profiled. Basic models are produced at DENCO to give plant personnel a three-hour reading on the percent of alcohol and sugar content in the fermentors to "know where you are," she said.

Contamination and Yeast Nutrition
When ethanol plant personnel talk about cooking, yeast and fermentation, the topics of variant wild yeast and bacterial contamination never stray far behind.

One member of the audience asked what the benefits and drawbacks are of running a hydroheater. Koller said hydroheaters run at 225 degrees Fahrenheit, the benefit of which is killing any bacteria found in the grain. Even though Rosemeier agreed that there is a sanitation aspect to using hydroheaters, he said the direct injection steam is an issue with mechanical sheer and increased water consumption. "Is it worth running without it?" Coler asked. All things considered—bacterial population, the cost of antibiotics, possible downtime—would the costs negate the benefits of steam going in? Coler said, "[Without a hydroheater,] you're still adding water but not killing the bugs," which helped DENCO decide to keep its hydroheater.

Rosemeier said at the 50 MMgy Heartland Corn Products, the cook water heater being used by the plant was problematic, but when the company expanded the plant's production capacity, water consumption was a concern. He said hydroheaters take almost one-third more water than other types of heat transfer devices. With that in mind, Heartland Corn Products chose to stick with heating the slurry (218 degrees to 220 degrees) rather than injecting steam in the tanks, and had the right heat exchanger installed to do the job.
Lost production time means lost money, one participant said. So if an ethanol plant gets hit with an infection, a "safe bet" would be to hit it with as much as possible everywhere—meaning overdose with antibiotics. The panel was asked what the optimal dosage rates are for antibiotics in the presence of contamination. The answer, of course, depends on many factors. "It could be one part per million or one part per billion, depending on what product [is going to be used] and tank capacity," among other things, Coler said. "Overdosing won't hurt. Start with doubling the dose and add [another bag of] yeast. … If you can get the yeast in there healthy and moving, the bacteria won't be able to compete."

Like all living organisms, yeast needs proper nutrition to maintain robustness and optimal health. The producers were asked what forms of nitrogen are typically added to the fermentors. At Badger State Ethanol, Koller said it uses 250 parts per million to 300 parts per million of nitrogen using urea. He said lactic acid counts at his plant consistently run at approximately 0.3 percent to 0.4 percent. "We look for jumps in lactic acid," he said. More than 0.8 percent lactic acid is bad; acetic acid levels above 0.05 percent are also undesirable. According to Koller, micro counts follow acetic numbers. Panel members also mentioned Aquamonia and anhydrous ammonia as sources of nitrogen.

Backset was a topic of brief discussion, too. DENCO is using an evaporator designed for a 15 MMgy plant even though it currently produces 24 MMgy. "We [average] anywhere between 42 [percent] and 58 percent backset," Coler said. "We're running a lot of solids when available. … Our centrifuges are overloaded. … If you start a plant with clean water, it doesn't run that well. [But add] some backset, and it works better." Big River Resources runs between 40 percent and 50 percent backset, Janson said.

The Practice of Cleaning
The interconnectedness of fuel-alcohol production processes was illuminated once again when the issue of cleanliness and maintenance was aroused. As stated earlier, sugars unconsumed in the fermentors get pushed through to distillation, dehydration, evaporation and, ultimately, the DDGS. Not only are the product streams of ethanol and DDGS affected by incomplete fermentation or any other sub par process implementation, but the increased wear-and-tear on a plant's equipment, the loss of efficiencies and potentially more downtime of production could also result from inadequate front-of-the-plant procedures.

Fouling and clean in place (CIP) measures were discussed during both sessions. Koller reiterated a running theme by mentioning how sticky the back-end systems could get if unfermented sugars reside in the mash yet get pushed through. With some dissent, it was generally accepted that a 3 percent to 5 percent caustic wash worked best to clean fermentor buildup. Rosemeier, however, said he wasn't convinced that caustic wash is best for fermentors. "In the beverage industry, it's different," Coler said, but for a fuel ethanol producer, she said, it's all about removing the chunks and getting the sticky corn mash to peel off. "Caustic is cheap, and it works," she stated. For the evaporators, however, Keith Wetzel, plant supervisor at DENCO, told the audience that an acid solution does a better job. "We acid wash every two weeks and hydroblast every eight to nine weeks," he said. Rosemeier said Heartland Corn Products in Wisconsin hydroblasts only once a year with periodic CIPs as needed, like when syrup solids drop off or pH levels rise to 10.5 or 11. Eric Dorn, production manager at Chief Ethanol Fuels of Hastings, Neb., said his plant does a shutdown and CIP with a strong, hot, caustic solution. He said newer plants using vacuum distillation have less fouling though. Keith Kor, general manager of Corn Plus—a unique 45 MMgy plant in Winnebago, Minn., which burns its solubles—said Corn Plus uses pressure distillation, and the degree of fouling is monitored via changes in pressure. "When we see a 4 to 5 [pounds per square inch] pressure drop, [we know] it's time to do a CIP."
Big River Resources has dual heat exchangers, according to Janson, so his plant shuts one down for an eight-hour CIP while the other keeps the plant going.

Uptimes and downtimes for preventative and reactionary maintenance are questions every proposed plant should ask its design/build team. "The Fagen/ICM protocol allows for 12 days a year for plant maintenance and downtime," Janson said. "You need to ask that when you're building a plant."

Dryer Differentiation and Distillers Grains
New Energy Corp., a more than 20-year-old plant now producing 100 MMgy, is a coal-fired plant that's out of the ordinary. Not only may it have been one of the few initial ethanol plants to use azeotropic distillation until it finally upgraded to molecular sieve technology, but being coal-fired allows it to economically run steam-tube dryers. Russ Abarr is the production manager at the South Bend, Ind.-based plant. According to him, the advantage of running steam-tube dryers is reducing a plant's energy costs (contingent on if a plant is coal-fired or not). Steam-tube dryers don't get as hot as those that are fired by natural gas, which Dorn said results in less VOCs. He said if a plant is drying grains with steam-tube dryers, it really doesn't need a thermal oxidizer of any kind, and if the plant is being designed with an RTO, it could reduce its boiler use—or eliminate it altogether. But where some see energy savings, others see increased maintenance costs.

"[Steam-tube dryers can be] problematic from a maintenance perspective," said Dorn, Chief Ethanol Fuels' production manager. Chief Ethanol is another plant burning coal; it also operates steam-heated dryers. Located in Nebraska, where there are plenty of feedlot cattle within trucking distance of Chief Ethanol Fuels, the 62 MMgy plant dries only 20 percent of its grains.

"Today, most go with natural gas dryers," said Janson, who's worked with both types of dryers. "I prefer natural gas dryers." Steam-tube dryers are more expensive because they require more stainless steel, he said, and they cost more to maintain.

One audience member said one manufacturer claims rotary drum dryers will not catch fire, but panelists were skeptical. Dryer fires are often caused by buildup, Abarr said. "With our steam-tube driers, we've had very few [fires]." Janson said most dryer fires were either maintenance- or operator-related.

With Corn Plus' ability to burn its syrup as energy in its fluidized bed reactor, which was designed and engineered by Von Roll and integrated into the plant via Harris Mechanical, Kor said his plant has seen fewer dryer fires.

The panel was asked whether or not the lower-heat steam-tube dryers affect DDGS quality. Abarr responded by saying all the distillers grains produced at his 100 MMgy plant are dried with steam-tube equipment. Any differences in the grains would be insignificant, he said, and if a plant was differentiating its DDGS from others using the same technology, it would simply amount to a technique in marketing.

Consistency in distillers grains products is the livestock industry's biggest concern. "DDG quality has to do with a lot of areas in the plant, not just the dryers," he said, referring back to excess sugars in the grains left over from off-peak fermentation, which caramelize in the dryers—not only turning DDGS dark but also requiring more frequent dryer maintenance.
Base loss numbers, or the content of remnant alcohol detected in the DDGS, were thrown around at the request of an audience member seeking an acceptable range. According to Abarr, a 0.01 percent base loss is typical. Janson said 0.05 percent base loss is OK.

Automation, Production Costs and More
Perhaps one of the most compelling questions asked of the Shop Talk panelists was, "Do we have enough automation at the plants, or do we rely too much on operators?"
According to Rosemeier, while fementor CIP procedures at several plants follow user-prompt schedules, evaporator CIP is a highly manual, interactive process of valving and bypassing, so the evap CIP process should be more automated.

"It would be nice if computers could make decisions," Coler said. With trending, it's sometimes easy to miss the need for a certain action. "It would be helpful if we could see the data condensed," she added.

"[Operators] need to take an active role in seeing what information is on the [control] screen," Rosemeier insisted. Instruments, control systems, sub systems, air compressors and more could be tied into the distributed control system. For example, the air compressor could gather information on voltage, run-time and speeds "to make it easier for the operators." Operators also can use real-time data to increase process efficiencies.

Abarr believes the industry needs to move more toward the direction of increased automation. "[Ethanol production] can and should be a highly automated process," he said.
"Automation is good," Kor told the audience. "It makes running a plant simpler." But he said it's appropriate that plant personnel actually go out and look at whether or not a valve is working. "Sometimes people get too attached to automation, so if the plant were to crash, what do we do?"

An efficient, balanced hybrid between manual and automated operations is the way to go, according to Janson. "If you see a [straight-line trend], you know that's not right, so go and check it out," he instructed.

When panelists were asked whether yield or productivity was more important, the consensus was clear. When ethanol prices are high, productivity is king. When ethanol prices are low, yield reigns.

One attendee asked how much it costs to produce a gallon of ethanol. Abarr responded with, "Every day the cost to make ethanol changes." Corn and energy costs, in that order, are the two most expensive inputs needed to produce ethanol. Outside of good futures contracts, corn costs are hard to control. If a plant gets corn from a region with a high basis, it'll cost more to make ethanol; if corn is bought from a region with a low basis, it'll cost less, Janson said. He told the listeners that it's safe to say a dollar per gallon is a commonly used figure representing the average production costs associated with making ethanol. Much of the energy used at a plant is consumed to run the backend operations. "The back-end energy hogs are distillation, evaporation and drying," Dorn said. "So the back-end has a profound effect on the [plant's energy use]."

Cogeneration was discussed, which Kor said Corn Plus is considering. Others certainly expressed the novelty of cogeneration, but most panelists thought it could distract producers from the core competency of making alcohol. Dorn summed up most feelings by stating, "You need to decide whether you want to run an ethanol plant or a mini power plant."

Lastly, the question asked of the panel that perhaps got the funniest responses queried what they would do at their plants if money were no object. After responses about how everything is economically based and the question isn't realistic, answers surfaced.

Big River Resources would make good use of an effective lightning deterrent system after being struck once too often. Dorn said Chief Ethanol could use new grain handling and dryer systems. At New Energy, Abarr said the liquefaction system could use modification.

"We'd like to be energy independent," Kor said about, Corn Plus. The plant may be getting wind towers to generate electricity. He said it always seems as if anytime there is a disruption in power, the power company tells him that a raccoon or squirrel must have gotten on the lines and caused an outage. After being told this numerous times, he called the power company and said, "Don't tell me it's a raccoon or squirrel again because they're all dead by now!"

Ron Kotrba is an Ethanol Producer Magazine staff writer. Reach him at rkotrba@bbibiofuels.com or (701) 746-8385.