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Cogen at Weyerhaeuser Resolves Wood Residuals and Electrical Requirements


November 1, 2004
By Pulp & Paper Canada

The partnership with the North American energy company, Trans Canada, which was aimed at partially using wood waste to generate power for something other than internal operations, is a first for Weyerhaeuser.

The partnership with the North American energy company, Trans Canada, which was aimed at partially using wood waste to generate power for something other than internal operations, is a first for Weyerhaeuser.

For many years even in a regulated environment, some Alberta industries were using energy such as steam to generate onsite power. Weyerhaeuser, in fact, was operating its own internal 34-megawatt power plant for many years at its Grande Prairie site. Power deregulation makes it economical for power generated at one site to be dedicated to support a company’s other operations in the province. It also allows them to sell excess electricity on the open market.

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Weyerhaeuser continues to operate its internal steam powered, 34-megawatt turbine. It needs to produce steam as part of the pulp manufacturing process. The plant operates three different steam headers, operating at 900, 170 and 55 psi.

Prior to the new TransCanada power plant coming on stream, the company was importing an additional 18 megawatts of power to meet its needs. Now it has sufficient internal power generation capacity and is helping to generate the additional 18 megawatts of power needed to meet the needs of its facilities in Drayton Valley, Edson, Claresholm and Slave Lake.

“Up until the point of deregulation, we didn’t really have that opportunity,” says Weyerhaeuser Grande Prairie project development manager, Grant Bourree. “We could have generated enough power to be self-sufficient, but in terms of putting it out on the grid and then taking it into our other plants, that opportunity didn’t exist on an economic basis.”

By generating its own power and sharing it with its other plants, Bourree says that takes Weyerhaeuser’s load off the power grid, thereby making more power available to other users in the province.

While the 80-megawatt power plant at Weyerhaeuser’s Grande Prairie site is owned and operated by TransCanada, Weyerhaeuser is providing about two-thirds of the steam required to operate the power plant’s steam generator.

The power plant achieves 80 megawatts two ways. One way is through operation by TransCanada of a Rolls Royce Trent natural gas powered turbine engine, with an output of 50 megawatts. However, the company has designed a very energy efficient plant, putting every ounce of potential energy to use generating power. For example, the exhaust gas from the gas turbine contains a significant amount of heat energy. That exhaust gas is used to heat water in a waste heat recovery boiler, which generates steam that is co-mingled with the steam transported from the adjacent pulp plant. The steam power generator produces 30 megawatts, for a total plant output of 80 megawatts.

There are also two other benefits to construction of the TransCanada cogeneration power plant in Grande Prairie.

First, generating the steam needed for Weyerhaeuser’s pulp manufacturing process and the new steam generator is consuming 40,000 to 50,000 tonnes of sawdust, bark, and planer shavings annually. This is 100% consumption of waste wood residuals generated at both Weyerhaeuser’s Grande Prairie pulp mill and sawmill, which are located next to each other.

The recent expansion of the sawmill would have generated more residual wood than was being burned to produce steam in the company’s existing steam generator. The excessive wood waste would probably have been disposed of in a landfill had the new power plant not been built.

“We are now making sure that everything that can be made into waste wood fuel is generated into waste wood fuel so that it can be used in our power boiler,” says Bourree.

The pulp facility is also venting less steam into the environment. Although steam venting does not have any significant environmental impact, a potential source for power generation was simply being wasted.

“It was painful to watch,” says Bourree. Realizing the power generating potential from the vented steam and that the company was generating surplus wood residuals, he says that Weyerhaeuser developed a concept of using its residual wood in a power-generating boiler. Once the regulatory environment had changed so that power generated on site could be shared economically with its other operations, the company began approaching a number of energy developers regarding their interest in a partnership.

“TransCanada appeared to be a very good partner,” he says. “They were certainly in the energy development business, so it was a very good fit. We’ve been very pleased to have them on board.”

TransCanada spokesman, Glen Herchak, says the company has identified this model of developing smaller to medium scale cogeneration plants in the 40 to 160 megawatt range as having significant business potential.

“TransCanada has become expert in building these types of cogeneration facilities,” he says, “that is, where we utilize the existing facility of a host site — a large industrial or commercial customer such as the one that we have with Weyerhaeuser — and use a synergistic approach where we can develop a facility directly on site with them to meet their power and steam needs.”

Power deregulation in Alberta and the level of large industrial activity in the province makes that a particularly attractive market. The company sees many other opportunities for similar power generating partnerships, particularly with companies active in mining the province’s oil sands. Right now, it is building a cogeneration power facility at Petro-Canada’s MacKay River site near Fort MacMurray.

However, its sights are not limited to Alberta. It has built what is called a ‘combined cycle’ power plant using wood residuals near Hearst, ON, and has purchased another one in Williams Lake, BC.

“Cogeneration in general, natural gas fired cogeneration plants and wood waste plants like the one in Grande Prairie, are something that we continue to be interested in developing for a variety of different reasons,” Herchak says, “but obviously the environmental benefit is certainly one of them.”

Putting the necessary infrastructure in place at the Grande Prairie site took a substantial investment by both Weyerhaeuser and TransCanada.

For its part, Weyerhaeuser invested $13 million to upgrade its power boiler and upgrade its waste wood supply system so that it could physically transport the additional waste wood fuel from the wood room in the pulp mill and sawmill to the power boiler. The bark boiler burns about 40 tonnes per hour of waste fuel. The bark and sawdust are burned separately. The bark is burned on a bed, while the fines are burned in suspension, much like a pulverized coal-type boiler. Bourree says that planer shavings are also consumed at the bark boiler.

As part of its investment, Weyerhaeuser also launched a number of conservation projects to free up additional steam to send to the new steam turbine in the cogeneration plant.

TransCanada made an $80 million investment in the power plant. Plant manager Paul Isaak describes its design as rather unique in the power generating industry, and a significant benefit to the Alberta power grid.

Over the last 10 to 20 years, there has been growing demand for electricity in the northwest part of Alberta fuelled by natural gas exploration and development. Yet during that period of time, there has been almost no new power generation facilities added. Therefore power is being imported into the area on transmission lines.

“By having our facility in this part of the country, it reduces the tie line flow considerably,” says Isaak, “and it makes the whole grid much more stable and reliable.”

Construction began in 2001 and was completed in about a year. The plant went through a start up phase and reached full design capacity in April, 2003.

Given Weyerhaeuser’s positive experience with this project, Bourree says he is quite certain that other companies may also consider using this template to develop cogeneration projects of their own.

“If you look around the countryside, certainly there’s a lot of teepee burners still out there and other incinerators that are burning waste wood fuel,” he says. “Perhaps there
is some opportunity for them to do something similar.”

On the other side

There is also considerable interest in thermal power generation using wood residue in Quebec, Canada’s second largest producer of forest products. Quebec private power producer, Boralex Inc., with ownership in various types of power plants in Canada, the US and France, began investing in wood residue power generating plants in 1998. The company now owns seven thermal power generating plants using wood residue as the feedstock. Two are in Quebec and five are in the American northeast. These plants now represent two-thirds of the company’s total power generating capacity.

In addition to its 28 megawatt power plant in the Lac St. Jean area north of Quebec City at Dolbeau, and a new 34 megawatt plant near Val D’Or in northwestern Quebec at Senneterre, it recently purchased two thermal power generating facilities using wood residue feedstock in Maine.

“Our motivation was certainly to try to upgrade the use of bark, which in most cases was landfilled,” says Boralex Board of Directors member, Yves Rheault. Furthermore, forestry companies faced considerable transportation costs taking the wood residue to landfills.

Boralex Inc’s focus is on large thermal power installations. Its criteria for constructing greenfield installations or investing in existing power plants are feedstock availability, close proximity to the wood residue feedstock, coincidental use of steam heat generated from the thermal power generation process in a co-generation application with a forestry facility, and close proximity to the power transmission grid.

Rheault says that about 200,000 tonnes of wood residue is required annually for a 20-megawatt power plant. He adds that Boralex is definitely in growth mode given current market conditions.

“We would be certainly interested to look at potential projects in Ontario, Alberta and British Columbia — no doubt about that,” he says.

Forest industry consultant and owner of McMillan Management headquartered in Boyle, AB, Don McMillan, says it’s the co-generation aspect of thermal power generation using wood residue that really brings cost competitiveness in line. He has 30 years experience advising forest product producers in the areas of financial analysis, operating analysis, design, modernization, productivity, and production efficiencies.

“That ‘co’ part is a very important part of the power generation process with wood residue,” he says.

He is elated at the technological advances and economic viability now being demonstrated in the use of wood residue in the generation of power. This has been an issue of concern since the mid-1980s, when the public began complaining about the build up of wood residue on Vancouver Island and Vancouver, as well as the problem of emissions from burners.

“It has always been an irritant for me personally that this energy has been vented to the atmosphere,” he says. “I don’t know anybody in the industry who hasn’t looked at that plume coming from the top of a burner or any wood fired system and thinking, my God, look at the energy going out of that! Why isn’t there a way we can turn this into something valuable, at least, if nothing else, at least to pay for itself. Industry has been working on the wood residue issue for years.”

Over the years, he has witnessed constant improvement in wood utilization. At one point, companies were only using 40% of logs and wood chips were considered a useless by-product. Today, utilization in many cases is up to 80%. Using the remaining 20% in power generation will bring wood utilization very close to 100%.

He concludes that companies interested in generating power and/or heat using wood residue should ensure they investigate options before jumping in.

“It is not a simple solution by any means, and you need specific expertise in the field to marry the right technology with the right fuel source,” he says. “But is it there? Yeah, most definitely, and it is proven.”


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