Red liquor. Green power.
The new ANDRITZ SulphitePower recovery boiler improves production costs and environmental performance at Tembec in Canada while providing steady, long-term revenue for green electricity.
Canadian forest products company, Tembec, supplies value-added niche products from its sulphite mill in Temiscaming, Québec: tailor-made dissolving pulps (ethers, acetates, nitrocellulose, and microcrystalline cellulose), chemicals (lignosulfonates), and coated bleached board. To stabilize production and have room for capacity expansion, the mill needed a new chemical recovery boiler to replace three old converted coal-fired boilers and one boiler that had been shut down.
As Paul Cousineau, Corporate Manager of Major Projects, explains, “Our old boilers had reached the end of their useful life. Fouling was one of the biggest issues. Plus, we wanted to reduce our SO2 emissions considerably.”
In addition, there was the potential to create a steady stream of revenue generating power for the Provincial utility through a 25-year supply contract, according to Paolo Dottori, Vice President of Environment, Engineering, and Procurement.
Green electricity project
Tembec’s new boiler and turbine-generator is now producing steam for mill processes and generating power for the Provincial utility. The centerpiece of the investment is an ANDRITZ SulphitePower boiler and electrical turbine with a generating capacity of just over 60 MW. Once fully optimized, the new equipment will reduce the mill’s SO2 emissions by 70%.
Best available technology
The Temiscaming mill produces “red liquor,” a co-product of its ammonia-based sulphite pulping process. “The last recovery boilers in North America for sulphite mills were installed in the late 1970s,” Cousineau says. “ANDRITZ has done considerable work since then, installing sulphite recovery units around the world. We believe the ANDRITZ design is the best available technology.”
“We continue to develop our technology,” explains Bernd Zuschin, ANDRITZ Project Manager. “For example, this is the first ammonium sulphite boiler we have ever built. Our deliveries up to this point have been for magnesium-based sulphite processes.”
Simplified operations and maintenance
“This was a relatively fast-track for delivery, especially considering the sea transports, but we made all of the milestones,” says Christoph Gruber, ANDRITZ Commissioning Manager. The boiler started up early 2015.
Trevor Turner and Dan Guénette, now both Head Operators, were involved with the project from the beginning. “The SO2 emissions from any sulphite mill must be tightly controlled,” they say. “This boiler does that superbly. Life for our operators is now simplified. The boiler runs well and stabilizes quickly. We can adjust liquor flows and air ratios based on pulp mill needs, with most of the operation in automatic mode.”
Fouling is considerably reduced, according to Michel Monet, Steam Plant Superintendent. “The arrangement of the heat transfer surfaces in the SulphitePower boiler allows my operators to optimize temperatures in specific zones to reduce fouling and potential corrosion,” he says.
Dottori knows his team made a lot of very good decisions in terms of equipment selection. “Our digesters and the board machine are performing better because of the solid and stable steam supply we are delivering to them,” he says. “The boiler is big and robust, with spare capacity, and it burns difficult liquors quite effectively. We’re still optimizing, but overall we are happy.”
Cousineau agrees. “I would definitely do another project with ANDRITZ,” he says. “That’s the bottom line.”