Continuing its years-long investigation of whether torrefied biomass could extend its life, Boardman Power Station is prepping to undergo a substantive test burn.
Trial by Fire
Boardman Power Station is feeling the heat. The last operating coal-burning power station in Oregon, the relatively young, 550-MW plant has faced much pressure and scrutiny regarding its ultimate fate, which must be decided and underway by 2020. While several potential options have been ruled out—including a half billion-dollar pollution control equipment upgrade, and repowering with natural gas and wood pellets—one option has remained on the table since Portland General Electric began exploring possibilities: replacing Powder River Basin coal with torrefied biomass.
After years of research and tests, the project, which has garnered attention from energy stakeholders of all kinds, has reached a new level: a full-scale, 24-hour test burn using 100 percent torrefied biomass. Besides wood, torrefied energy crops such as arundo donax will be fired, as the utility has been growing and harvesting energy crops on test plots around the plant the past several years.
An exact date for the test hasn’t been nailed down yet, but it will happen before the end of the year, and may occur relatively suddenly. Spokesman Steve Corson explains the time has to be just right—not only because the 8,000 tons of torrefied material required for the burn has to be on-site and ready for consumption by the plant’s Rankine cycle coal boiler, but Boardman remains a working plant that still plays an important role in the utility’s power supply. “We need to time the test to occur during a window when generation from the plant is optional for us to meet our customers’ needs—for example, when we’re not experiencing extreme weather that could drive peak loads, and when other generating resources are available to meet demand.”
In these days leading up to the test burn, plant staff and expert consultants are working to determine the most effective execution. “This includes examining the safety implications of a new fuel, coal transport testing, pulverizer grinding performance and ash characteristics,” Corson says. “And included in this will be test instrumentation, coupled with plant instrumentation to assess the burn performance.”
Those engaging in the test burn will assess overall plant stability as the plant burns the biomass, according to Corson. “We believe the test can be completed without undue risk,” he says. “We already confirmed that the plant’s existing equipment can handle torrefied biomass, with our cofiring test burn last year. Nevertheless, there’s uncertainty involved in any unusual procedure of this sort, so we need to account for that uncertainty and minimize it through careful planning.”
Though torrefied biomass has characteristics very similar to coal and tests to date has shown compatibility with the plant’s mechanics, PGE wouldn’t escape having to make changes—capital investments—to accommodate the fuel switch. “Part of the attraction here is that the conversion could be completed with minimal modifications to the existing plant, to the conveyors, silos, pulverizers, burners and boiler,” Corson says. “There are also advantages from an emissions standpoint, with little or minimal sulfur dioxide or mercury emissions expected, for instance. That said, we’d expect the plant to need additional emissions controls for oxides of nitrogen, so an SCR (selective catalytic reduction) [system] would likely be required, and thus is part of the math in deciding if the conversion will make sense.”
Even though the test burn will be the most extensive to date, Corson emphasizes that even a full-day test burn won’t answer all of PGE’s questions. At least, not yet. “It will give us some additional information about the plant’s emissions profile when fueled by biomass, plant chemistry, and how the plant’s equipment handles the fuel,” he says. “Presuming all goes well, that will point us toward areas where we need to focus our attention in future test burns, and will begin to give us a more complete picture of what will be required if we decide to proceed with a conversion.”
By the time that happens—likely 2020 or sooner—Oregon Torrefaction, the company PGE has hired to supply the fuel needed for the upcoming test burn, hopes to see a more developed torrefied biomass market in the country. Working with the utility to determine if the potential is real, and whether the long-term operation of Boardman on biomass could be feasible and economic, could help grease the track.
Building a Market
Oregon Torrefaction has been working on the fuel-gathering project for PGE for about a year and a half, according to Matt Krumenauer, CEO. “We’re working to produce and procure the torrefied material, and we’ve got a number of facilities working with us,” he says, explaining that the company isn’t manufacturing torrefied material itself, but to churn out the 8,000 tons needed, has brought on board several companies with a variety of technologies, including New Biomass Energy in Mississippi, Airex Energy in Quebec and Reklaim in Boardman. “We’ve also borrowed a mobile torrefaction system from Idaho National Energy Lab—we’ve moved that to Boardman and its producing material for us,” Krumenauer says. “Then, we’re densifying it in a cuber that we are contracting another company to run for us. We’ve got a number of different efforts going on, to really see if this is a viable opportunity and whether it will perform technically at the power plant.”
Krumenauer highlights the variety of torrefaction technologies involved, all of which result in end products with similar characteristics. “We have a rotary kiln—a pretty standard type of torrefaction system, the Reklaim system is a Wyssmont Turbodryer, which is a fairly standard thermal treatment application, and Airex has its own propriety technology, as does New Biomass Energy,” he says. “Not only do we have a range of different technologies, but we’re also using many different types of woody biomass.”
In Oregon, the company is sourcing 100 percent of its material from national forest restoration treatments and stewardship contracts, small-diameter biomass, and plans are to test some of PGE’s purpose-grown energy crops. On the task of delivering the material PGE needs in the desired timeframe, Krumenauer says things are on track to deliver by the year’s end, and the process is going fairly well. “We’re learning a lot—this is a fairly large proof-of-concept run, and we’re going to be completing a full economic analysis after the burn is completed, and hopefully help PGE determine if this is a viable opportunity.”
Related to the initiative is a consortium Oregon Torrefaction has formed, the Consortium for Advanced Wood to Energy Solutions, an effort by the U.S. Endowment for Forestry Communities, the U.S. Forest Service and a number of different academic institutions and private sector companies that are working to help advance torrefaction in a precompetitive manner. “The point is to help advance the market,” Krumenauer says. “That’s the mission-driven aspect behind this effort—to create and advance a market for these low-value biomass residuals, primarily from national forests. Our hope is that if this is successful, and we’re able to help PGE and other utilities, it will open up opportunities for companies like Airex and New Biomass Energy. We don’t view it at all as competitive, we view it as something that will help break that chicken-and-egg scenario.”
Meanwhile, the focus after delivering the torrefied material to Boardman will be to analyze the test burn results. “Immediately after, we have to evaluate the technical aspects, the economic aspects, and the feedstock sustainability aspects to really understand what the true cost would be, to try to supply a facility the size of Boardman,” Krumenauer says. “Our next steps will really be analysis-based. After that, I think we will look at helping supply larger, longer-duration test burns, and sharing this information with the broader industry. There are other power plants that could certainly cofire or convert.
While the Boardman’s potential conversion investigation is taking a great deal of time, excitement is building, Krumenauer adds. “I have to give PGE a lot of credit for sticking with this. It’s been a long, hard path, but we’re getting there. We’re going to get through this test burn—I’m certain it will be successful, it’s just a lot of work—and we’ll see what comes after that.”
Source : Anna Simet, Biomass Magazine. « Trial by Fire », BBI International, Biomass Magazine, Released November 29, 2016