Canadian Consulting Engineer

AWARD OF EXCELLENCE: Weyerhaeuser Pulp & Paper Mill Wood Waste & Low Odour Project Prince Albert, Saskatchewan

Category: Project ManagementAMEC E&C SERVICESWeyerhaeuser has taken a big step towards improving the environmental and economic performance of its pulp and paper mill in Prince Albert, Saskatchewan. T...

October 1, 2001  Canadian Consulting Engineer

Category: Project Management

AMEC E&C SERVICES

Weyerhaeuser has taken a big step towards improving the environmental and economic performance of its pulp and paper mill in Prince Albert, Saskatchewan. The “Wood Waste and Low Odour” project has enabled the mill to be almost self-sufficient in terms of energy use. It has eliminated landfilling of wood waste and dramatically reduced the emission of greenhouse gases. The retrofit has also modernized the plant’s equipment and improved the efficiency of the staff.

The project involved installing a new high pressure recovery boiler to replace two old, inefficient recovery boilers, and adding a new steam turbine power generator. As well, one of the old recovery boilers was converted to a bubbling fluidized bed boiler to burn waste wood fuel. These changes significantly reduced the plant’s gas consumption — by 60%, amounting to the energy used by 15,000 Saskatchewan homes in one year.

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The fuel comes from the wood waste generated in the mill’s pulping process, from a wood waste landfill pile expected to last 10 years, and from wood waste trucked in from two nearby sawmills. One of these, the Big River sawmill, shut down its own beehive burner when the new Prince Albert boiler came into operation.

The retrofitting to a bubbling fluidized bed power boiler is relatively new technology and yields considerable air quality improvements compared to rebuilding a conventional boiler. The project resulted in a 99.3 per cent reduction of total reduced sulphur and particulate matter emissions from the plant.

Project management

The project management team adopted “No business as usual” as the project doctrine and led the participants to live by a team-centered approach. AMEC E&C Services of Vancouver managed and co-ordinated the engineering services for the large and complex project.

The key components of safety, engineering, procurement, construction, commissioning, mill operations and project management were brought together through regular stakeholder meetings. The engineering databases developed by AMEC were fully shared by construction and commissioning crews. This approach required a more flexible delivery of engineering drawings and specifications, and as a result the project was carried out with a minimum of problems.

Safety was a particularly serious concern due to the proximity of the construction trades working close to existing operating equipment. The conversion of the old recovery boiler to bubbling fluidized bed technology had to be carried out inside the existing boiler building, which involved addressing the construction workers’ exposure to asbestos, lead paint and other hazardous materials. Weyerhaeuser’s team led an awareness program and the result was 2,250,000 hours without a lost time accident — a Saskatchewan provincial record.

The impact of the construction activities on the plant’s operations was minimal. The $300 million project cost was on budget, and the 30 month schedule was achieved ahead of time by August 2000 despite some surprises. AMEC’s use of full three-dimensional design services in a computer based model for the project helped reduce construction re-work to 0.3 per cent of the contract costs, considerably exceeding the client’s target of 1.5 per cent.

Equipment

The new high pressure recovery boiler produces steam at a pressure of 8,720 kilopascals and a temperature of 482 C. The boiler is designed for a stream rate of 1,832 tonnes per day of black liquor dry solids on softwood production and 1,755 tonnes per day on hardwood production. The steam is directed to a new 40 MW back-pressure steam turbine generator. The maximum total reduced sulphur emissions from the operation have been reduced to five parts per million. A new control room was built as part of the project.

The bubbling fluidized bed power boiler burns waste wood and can incinerate mill sludge. The conversion involved completely removing the bottom of the old boiler, and the addition of an ash removal system.

A new electrostatic precipitator treats the flue gas from the recovery boiler economizer. It uses three electric fields in the direction of gas flow. Salt cake (a residual material created from the incineration of pulp mill black cooking liquors for cooking wood chips) is collected under the new boiler and transported to a salt cake mix tank. The new precipitator is designed for a collection efficiency of 99.77 per cent.

Other components of the retrofit are a stand-alone two-effect concentrator system to provide high solids black liquor as fuel to the new recovery boiler, and a new boiler feedwater system which supplies it with purified water. The system includes a demineralized water plant, condensate polishing plant, deaerator/feedwater storage tank, two boiler feed pumps, and a demineralized water storage tank. CCE

Project: Wood Waste and Low Odour Project

Award-winning firm: AMEC E&C Services, Vancouver

Project team leaders: Ron Alekson, Paul Baluch, P.Eng., Robert Takishita, P.Eng., Steve Sanders, P.Eng., Ed Tong, P.Eng., Richard Lum, Harold Sato, P.Eng., Ernst Pennink, P.Eng., Tom Soltys, P.Eng., Klaus Schmitt, P.Eng.

Owner: Weyerhaeuser Saskatchewan

Other key players: Ahlstrom Kamyr, Delta, B.C. (construction management)

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Engineering


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