A Dot on the Map

Ontario Power Generation’s Atikokan and Thunder Bay generating station conversions mark a turning point in Canadian power generation.
By Anna Simet | November 25, 2014

On a gloomy, chilly September day, the vacant coal yard that sits alongside Ontario Power Generation’s Atikokan Generating Station resembles an empty graveyard of sorts, a relic of a once-thriving industry that will soon be laid to rest in Ontario.


Idle after 28 years of operation, the coal yard and its assets are being preserved and maintained. A view from atop the main building exhibits a long, closed conveyor that stems from the old coal transfer building, a tired arm desperately grasping on to its only existing connection to the power plant. At the opposite end of the plant site, a pair of concrete pellet storage silos rival the height of the new boiler building, protecting fuel from the light rain that has begun to mist from the gray sky above.


Meanwhile, the wood pellet-fueled station hums with life, populated with an enthusiastic staff that is eager to show the world the energy feat that they’ve become an important part of. Most were directly involved in the conversion work, including station manager Wray Clement, who, in his personalized hard hat, stands ready to explain the plant’s retrofits and workings, proud to tell plant visitors that he was born and raised in Atikokan.


The town of about 1,300 was “shocked” when it received the word that AGS would close, according to Mayor Dennis Brown, as it meant “a huge loss to the community—about 90 full-time jobs and lots of spinoff jobs.” Brown’s soft-spoken and polite demeanor somewhat belies his papa-bear nature when it comes to his town, and he’s eager to share the story of how determined town officials and citizens brainstormed and stuck necks out to prevent the town from losing much-needed jobs, including taking temporary ownership of a bankrupt fiber mill until a new owner could be found.


Excitement and pride are in the air, and rightfully so. As of mid-September, Atikokan Generating Station became the largest woody biomass power station in North America, and not only that, but the first power plant to convert from coal to wood pellets. Having proved that it can indeed be done, OPG has turned the heads of energy producers throughout the U.S. and Canada. 


Plant Workings in a Nutshell


Trucks deliver fuel to the facility above five days per week depending on fuel manufacturing operations. AGS’s fuel is transported from Rentech Inc.’s Atikokan pellet plant just 11 scenic and forest-packed miles away—Ontario’s renowned canoeing paradise, Quetico Provincial Park, is just miles from both—as well as Resolute Forest Products, both of which recently finished commissioning new pellet plants. Today, a black and red Gardewine semitrailer sits in front of the AGS pellet unloading area, seemingly dwarfed into a child’s toy truck by the sheer size of the fuel storage, handling and receiving infrastructure, work that was performed by Aecon Group Inc.


Trucks take about 15 minutes to self-unload onto a feeder, explains Brent Boyko, the face of OPG’s biomass business sector. Don’t let his title fool you—Boyko knows the mechanics of the plant as well as anybody, as he worked as station manager for nearly four years prior to taking on his new role of expanding OPG’s biomass endeavors.


From the feeder, pellets are fed into a bucket elevator that lifts them to another transfer conveyor for movement into the storage silos, each 44 feet high and 68 feet around with a 5,000-ton capacity. In contrast to the simple-looking exterior, each is equipped with spiral chutes for fuel drop reduction, temperature monitoring systems, aeration, recirculation and inert gas injection systems, as well as explosion panels and dust control systems.


While serving as pellets’ first major defense against the elements, on occasion, the silos may be skipped. “There’s a bypass system belt into the unloading system, which allows us to top-load fuel directly into the process, bypassing the silos,” Boyko explains. “This has proven valuable during the commissioning phase, because it allowed us to burn wood prior to storage silos being fully complete.”
From the storage silos, a series of conveyors pull pellets into another bucket elevator that feeds a process conveyor that transports fuel into the power house. There, it enters a series of five bunkers, each with a surge capacity of 45 metric tons, replacing existing in-plant, 750-metric-ton bunkers.


“From there, it’s run through a feeder and calibrated to control the amount of fuel based on the power we want to generate,” Boyko says. From the feeder, pellets drop into one of five massive, cylindrical MPS-type pulverizers, which have been modified to increase velocity and reduce classification. Each pulverizer is equipped with a white canister, Clement points out, an explosion suppression system that injects sodium bicarbonate into the chamber.


Pellets are ground to the consistency of saw dust, and blown into 15 purpose-built Doosan Mark III biomass burners. “At that point, the fuel is combusted and produces steam that spins a turbine, which connects to the grid and produces electricity,” Boyko says.


Besides Aecon and Doosan, OPG’s other major contractor was Nordmin Engineering Ltd., which provided controls system integration services for an extensive overhaul on all control systems in the facility, replacing the old panel system that was installed in the late ‘80s when the plant was first commissioned. “One thing we did was put in a hardwire panel, so that if there’s a problem with programming, one can physically hit a stop button,” says Clement.


In all, the plant takes about five hours to transition from a cold shut-down to full operations.
While AGS has received the bulk of attention, OPG has another conversion project underway 130 miles east of Atikokan, one that will also utilize pellets, but not traditional white pellets.


Thunder Bay


Quietly waiting in Thunder Bay next to the Lakehead Region Conservation Authority’s Mission Island Marsh is the Thunder Bay Generating Station, another of OPG’s plants that previously burned coal and has since ceased.  The plant won’t quite see the glamorous conversion and restart AGS did, but it will also make a name for itself through utilization of an innovative pellet fuel.


In its prime, the 306-MW facility burned low-sulfur, Powder River Basin subbituminous coal. Braving the elements where previous fuel was piled sits a small mountain of black pellets that from a distance very much resembles coal, but upon examination of a handful can leave one guessing—something left in the oven far too long, perhaps.


Project engineer Steve Carlson explains that the station, which went into service in the 1980s, burned its last load of coal in April. “In the fall of last year, we began looking at bringing advanced biomass fuel on site, and in order to do that, we had to understand the characteristics of the fuel,” he says, which included material handling tests and explosivity tests. “We compared dusting capabilities to PBR coal and found that it is pretty similar—almost exactly the same—the only difference being the ignition sensitivity of the fuel,” Carlson says.


All of the testing cultivated modifications to the material handling system, dust collection capabilities and fuel storage bunkers, followed by more fuel testing that resulted in temporary modifications of two pulverizers. “We were able to achieve full-blown throughput on those two pulverizers,” he says.


Following those trials, last fall, OPG brought in 300 tons of advanced biomass—steam-treated pellets—from two different suppliers. “In January, when it was 40 degrees [Fahrenheit] below zero with lots of snow, we wanted to see how it would handle in cold and extreme weather. There were no problems, we just pushed them with snow plows, if you can believe that,” he says, motioning to the pile of pellets that sits in the fuel yard. “That pile has been on the property for well over a year—we’re measuring water uptake and self-heating characteristics, all in an effort to understand how it will do on the ground for an extended period of time.”


As Carlson speaks, less than five miles away, a boat at the Port of Thunder Bay’s Keefer Terminal is unloading 1,200 tons of advanced wood pellets sent from Zilkha Biomass Energy. “Delivered, it has about 2 percent fines in it,” Carlson says. “We’ll use this new fuel for commissioning and capacity check tests.”


He adds that on a Btu-per-pellet basis, the cost paid for the advanced biomass pellets is very similar to that the white wood pellets used at AGS.


With study work and initial testing complete, OPG has deemed Thunder Bay a viable capital project, so the next objective is to minimalize additional investment in the facility. The capital budget for this conversion project is $5 million, according to Carlson, and what remains to be done includes an enhancement of the dust suppression and collection system at some transfer points, addition of belt metal and heat detectors, and addition of safety equipment inside the power house.


Once fully converted, the Thunder Bay station will be used as a peaking unit and come on line when it is called upon.


While the initial driver of both the Thunder Bay and the Atikokan Generating Station was a 2009 provincial law that requires all coal-fired power stations to convert or shut down, the impact of the stations’ transitions from coal to renewable fuel will likely reach far beyond the towns of Atikokan and Thunder Bay, much further than the borders of Ontario and Canada. Turning the heads and engaging the attention of utilities around North America that are mapping out their plans for the future, Ontario Power Generation has proven out a concept that undoubtedly be replicated elsewhere.



Author: Anna Simet
Managing Editor, Biomass Magazine
asimet@bbiinternational.com
701-738-4961

 

Catching up with Aecon


With 280 of its employees and subcontractors on site during peak construction, Aecon Inc. made its debut into the pellet world with the design and construction of AGS’s fuel handling and storage system. The company employs 12,000-plus people and has a presence mostly in the mining, fertilizer, coal power, steel and iron ore sectors, performing a great deal of conveyor work.  Besides its first pellet project, the AGS conversion marks Aecon’s first material handling and storage engineering, procurement and construction contract, according to Jason Smith, project engineer.  “We took what we knew from EPC deliveries in the past and material handling work that we’ve done, and brought the two together,” he says.


On main differences between other work Aecon has done, Smith says the risk around wood dust and the potential for explosions was a new factor for consideration. “While we were in the design phase, there were a couple of wood facilities in British Columbia that experienced fires and explosions, so a lot of work and attention went into preventing creation of dust, trying to minimize and extract it.” Aecon used Jenike & Johannson to define flow characteristics of the wood pellets and particles to optimize the design of the conveyors, chutes and silos, and researchers at Dalhousie University helped define the explosive parameters of the wood particles.


While safety design was top of mind—for both employees and asset protection—another aspect that posed a challenge was scheduling of the project, Smith adds. “A lot of attention went into that [scheduling] so we weren’t executing civil work in the winter months—we tried to minimize that. When your temperatures reach minus 35 degrees Celsius, it becomes very costly to do construction in the winter, and it also affects the quality of work.”


A final key concept of Aecon’s fuel infrastructure work at AGS was designing a very compact footprint to keep the overall capital cost competitive, according to Smith. Aecon was also awarded a traditional construction contract to complete retrofitting work in the plant, he added, which included retrofitting each of the boiler’s 15 3.5-metric-ton burners.

 

CBI'S Conversion Contribution


Rentech Inc., one of Atikokan Generating Station’s fuel suppliers, has completed a conversion of its own by transforming a wood processing facility previously owned by Fulghum Fibers into a 100,000-ton-per-year pellet plant. At the same time, it is also converting a similar facility in Wawa, Ontario, to produce 450,000 tons of pellets.


At the front end of the conversions are atypical raw material sizing systems. The flail debarkers and chippers supplied by Continental Biomass Industries produces microchips in a single pass as a first step, rather than the traditional, two-step method of chip production followed by grinding. CBI has installed a single-line flail chipper in Atikokan, and at Wawa, a flail chipper and a standalone chipper, said Matt Skinner, stationary systems manager.


“At Atikokan, we start with a 50-foot-long chain infeed conveyor that takes logs inside of the building—it sticks out about 40 feet outside the enclosed building—and conveys the logs into the two-roll flail that debarks the logs, and directly behind that is our 8400 chipper,” he explains. “We bypass one whole grinding step by going directly from the round wood coming in to debarking, chipping, and then straight to the dryer.”


Start up at Atikokan was scheduled for the week of Oct. 27, and the crew at CBI was ready to make the final touches. “Everything mechanically is already set into place, but we will load the controls program and test all wiring on machines,” says CBI CEO Anders Ragnarsson. “We can’t run those big motors in our New Hampshire shop; we have to wait until their permanently wired on site.”


What is done at the shop is complete equipment assembly, according to Ragnarsson. “We engineer these systems to be transportable in the largest modules possible,” he explains. “Everything is prefit and preassembled. Then we break it apart into the biggest modules we can. It keeps assembly and rigging at a minimum and we ensure everything fits—it saves time.”