Bio-generation comes naturally to Portucel Soporcel

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Bio-generation comes naturally to Portucel Soporcel

December 12, 2010 - 14:00
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BRUSSELS, Dec. 13, 2010 (RISI) -The Portucel Soporcel Group is one of Portugal's largest generators of energy from renewable forest biomass. In the years between 2000 and 2008, the group reduced its fossil CO2emissions by 58%. With a renewed focus on renewable energy, Portucel Soporcel started up two biomass-fueled power plants - one in Cacia and the other in Setúbal - that produce a net of around 167 GWh/a.
The new Andritz recovery boiler at Cacia “runs like a Swiss watch”. The two older units to the right have been decommissioned

All to the grid

What is interesting is that none of the energy generated by the boilers is used by the mills. This is not permitted, according to Portugal's directives for "green energy" credits, so the electricity is sold directly to the national grid. "Even without these boilers, we are energy self-sufficient at this mill," says José Manuel Nordeste, mill manager at the Cacia pulp mill.

The situation is a bit different at Setúbal. "The installation of a new and very large paper machine at our site requires some purchase of power," says Setúbal's pulp mill manager Óscar Monteiro Arantes. "However, the extra margin we receive for green energy still makes it attractive."

From left, Cacia project director António Gomes, Andritz agent José Henriques and mill manager José Manuel Nordeste

Value-added pulping and energy

The Portucel Soprocel Group is responsible for about 65% of Portugal's total electricity produced from renewable forest biomass. "Renewable energy is a key focus in the world," Nordeste says, "and is a major focus for us. It is important for us to be players in this industry to ensure that order is maintained in the market. Forestry resources are our lifeblood. There is a potential threat if we let others control the resource, or simply burn it, before we can add value to it."

The biomass boiler projects consisted of the supply of two identical bubbling fluidized bed (BFB) boilers with a total production capacity of 49.75 MWth. According to Jukka Kari, Andritz's project manager, the boilers are mid-size (58 tonnes/hr, 93 bar, and 472º C).

Operator at the Cacia mill’s biomass boiler to optimize performance

Portucel Soporcel's scope included the civil/structural work and part of the electrification and automation. "Andritz basically provided everything above the foundations from the fuel feeding conveyor to the main steam header in the turbine-generator plant," Kari says. Contracts were signed in February 2008 the boilers were mechanically complete in the fall of 2009.

Investments at Setúbal

The group has made considerable investments in upgrading the Setúbal mill, which started up in 1967. The Setúbal site is situated just 4 km from a port, making transportation of finished goods very efficient. The mill produces 530,000 tonnes/yr of bleached pulp, primarily from the preferred Eucalyptus globulus fiber.

Arantes estimates the total recent investment to be €550 million ($750 million) for a new paper machine, new combined heat/power plant, fiberline retrofits, and the biomass boiler.

"We use about 150,000 tonnes/yr of biomass as a fuel here at the mill," Arantes says. "About 80% of our logs are debarked before entering the mill. We use special harvesting and binding equipment to gather forest waste and put it into small bundles for transport."

In addition to providing green energy, the removal of forest waste has another large benefit: a reduction in forest fires. "By removing the waste from the forest floor, we actually reduce the risk and impact of fires," Arantes explains. "We do not remove everything however. Our forestry experts know where they can remove without damaging the soil."

As for the boiler itself, Arantes says: "Andritz kept all the contract milestones on-time or ahead of schedule. The startup was without complications, it went into service quite smoothly. The design of the boiler is good. There is good flexibility to burn different biomasses with different moistures."

Setúbal pulp mill manager Óscar Monteiro Arantes (left) with José Henriques in front of the biomass pile at Setúbal

Excellent reference at Cacia

Cacia is midway up the nation of Portugal, about 8 km from Aveiro and very close to the sea. "Cacia is in the heart of our country's eucalyptus forests," says Nordeste. "The proximity of this raw material is a key advantage for us." Cacia's production of 285,000 tonnes/yr is primarily designed for special applications such as décor papers, specialty coated papers, and tissue.

The recovery boiler at Cacia played a key role in deciding the supplier for the biomass power boiler project, according to Nordeste. "One of the strongest references for Andritz was the new recovery boiler they installed here in 2006," Nordeste says. "Our two old units were at end-of-life. We would not be able to make the other improvements to the fiber line and the rest of the mill without this new recovery boiler operating well. It works perfectly, like a Swiss watch.

"Yet power boilers are different," Nordeste adds. "You can make big mistakes in handling and burning eucalyptus bark. It comes in long, stringy strips and must be cut correctly."

Inside the BFB biomass power boiler at Setúbal

One major challenge, according to António Gomes, project director for the biomass boiler project and now Cacia's production manager, is that the mill never knows what kind and quality of biomass they will be receiving. "We see all kinds of contaminants in terms of metals, concrete, and other things," he says. "You need a very robust and reliable boiler system to handle it."

Flexibility in handling varying fuels and moistures is also key. "We needed a very flexible boiler to handle the range of biomass and the ranges of moisture," he says. "Depending upon the season, we go from 45% moisture in the spring to 60% in the winter."

As with Setúbal, the boiler project proceeded without a glitch. The boiler was mechanically complete in September 2009 and was commissioned and started up in a very smooth fashion.

"To me it is quite simple," Nordeste states. "The equipment works well. The supplier's project team knew what they were doing and the process knowledge is there. And, if something ever goes wrong, we know the supplier has the willingness and capacity to make it right."