COGENERATION: Bark biomass supplies energy for Domtar
By Pulp & Paper Canada
By Pulp & Paper Canada
The difference in the count of the cogeneration project life at Windsor is this: ten years in consideration but three years in the actual planning and construction phase. And the result: the simultane…
The difference in the count of the cogeneration project life at Windsor is this: ten years in consideration but three years in the actual planning and construction phase. And the result: the simultaneous production of heat and power, with the fuel source supplied by easily-available bark biomass. It seems such a natural (in both senses of the word) way to go for a pulp and paper mill.
The project has a long history, dating back to 1991. Domtar had initially considered a 200 MW-capacity installation, in conjunction with Hydro-Qubec, but then scaled it down to a more manageable 25 MW. In 1999, Domtar signed a contract with Hitachi who, in turn, chose SNC-Lavalin as the EPC partner. Eight months later, the first shovel of earth was overturned for the construction phase.
Andr Beland, a 25-year veteran of Domtar, was chosen as the Domtar project manager. Roger Benoit was the manager of the SNC-Lavalin team. Approximately 20-25 people from Domtar and SNC-Lavalin worked on the project, both in Montreal and the Windsor mill. The construction effort required 50-75 people at its peak.
“I’m very satisfied with the team approach established by Domtar,” said Roger Benoit. “The quality and dedication of the people was the key to the success.”
Manufacturing the steam turbine took a full year, starting in January 2000. Andr and mechanical engineer Franois Hon went to Japan to inspect the final stages of the production of the turbine at the Hitachi’s forging and casting facility, 200 km north of Tokyo facing the Pacific Ocean. There Andr and Franois witnessed the balancing and testing of the generator and validated how the tests were performed. They admit being perturbed at their initial sight of the turbine, still in pieces on the floor of the shop with one month left to crate and prepare it for transport. Only then did they note with amazement how quickly the Hitachi team worked and it was reassuring, shortly after their return home to Windsor, that they received confirmation that the turbine had set sail. The route took it through from Japan through the Panama Canal to Baltimore, MD, and then by truck to Windsor, to be reassembled on site. It took approximately 10-11 trucks to carry the entire load. The generator, the biggest piece, weighed 73 metric tons. The entire trip lasted over a month.
“Working with Hitachi was a very rich and good experience,” Andr says now of the fact that worrying about the delivery had been needless. “When they say that they will do something, they do it.”
Looking back, Andr says that the project would even have been quicker to implement had there not been an unavoidable delay in the actual production of the turbine because of the high demand for this type of product world-wide.
One of the challenges for SNC-Lavalin had been to accept responsibility for the programming of the overall turbine control system, a job usually done by the supplier, in this case, General Electric, since this was judged to be more competitive. The software program was designed by Hitachi, working closely with personnel from GE. The necessary integration was done by SNC-Lavalin, with the help of the Domtar team. Protective relays were supplied by ABB.
“I do not know of any other project done like this,” stated Roger. “It was something special and it worked.”
An important milestone was the steam blow on April 12, 2001. Out of concern for nearby residents, Domtar sent out a notice to the homes in the area to advise the people of the noise which almost equated the sonic boom of a jet airplane.
The actual start-up did not affect the operation of the plant at all. “We did not disturb the mill’s operations once,” said Andr with satisfaction. “Nobody even noticed. It was that smooth.”
The cogeneration plant is fully-automated, with synchronisation at the push of a button. No one needs to be on duty at the turbine station or start-up room as the information is accessible from other control rooms. The equipment is very reliable and needs few people for operation. Andr envisions general maintenance to be performed on a yearly basis. The generator, explains Andr, works in a slave mode and responds to the need of the process. In case of any discrepancy in the power supplied and a perceived need, there is a load sharing between Hydro-Qubec and the mill power generation. The turbine is equipped with three safety systems and a battery-operated back-up for lubrication of the bearings and hydraulic controls.
The existing steam boilers are used to generate the steam required for the cogeneration plant. No additional boilers were purchased and no changes were made to the existing ones.
The investment driver was to reduce the electrical energy costs and that was achieved. The project respected the budgets, according to Melynda Normandeau of the Domtar Communications office at Windsor. The cogeneration plant now supplies one-third of the total electricity used by the mill, with a negligible cost attached to the small amount of natural gas needed as auxiliary fuel. Since the system uses more bark than is supplied as a by-product of the mill, additional supply has to be purchased, approximately 40 000 to 50 000 dry metric tonnes per year of anhydrous bark biomass.
Usage of the bark biomass provides an additional benefit: it contributes to solving waste disposal problems by eliminating the need for landfills. In fact, the entire project was a prime example of Domtar’s commitment to environmental management.
The final result: smooth operation and cost-efficient energy production.