Andritz calls it a High Energy Recovery Boiler. But you can call him HERB. The latest HERB was started up at the Holmen Group’s Iggesund Mill in Sweden. It is helping Iggesund reach its goal of being free from fossil fuel emissions. As a matter of fact, this HERB is the most energy-efficient of any recovery boiler in the world.
At 08:00 on June 12, 2012, Iggesund Paperboard’s new recovery boiler came online. For the mill, the investment was a huge vote of confidence from Holmen’s Board of Directors. For the project team, it was an opportunity to participate in helping the world’s most energy-efficient recovery boiler (in terms of power-to-heat ratio) come to life. For Andritz and everyone involved, the start-up was a major achievement and a resounding success.
STRATEGY INTO ACTION
“Having your energy strategy on paper is one thing,” says Iggesund mill manager Staffan Jonsson. “Getting the funding to implement that strategy, especially during these tough economic times, is another thing altogether. It was a real big moment for this mill and this community when the Board gave its approval.”
The Holmen Group gave the go-ahead for the Euro 238 million investment at the Iggesund Mill in 2010. In addition to the recovery boiler, the investment included a new turbine-generator plus equipment for capturing and incinerating weak, sulphur-containing gases. The investment will not lead to an immediate increase in paperboard production, but the mill’s pulp production is planned to gradually increase from 355,000 tonnes/yr to 420,000 tonnes/yr.
The start-up of HERB is a key step towards realizing the mill’s long-term development plan. “Fundamental to our sustainability are processes that use renewable raw materials, and a product (invercote paperboard) that can be recycled,” Jonsson explains. It is Iggesund’s stated goal to be a global leader in terms of air and water purity, to be self-sufficient in electricity, and to operate on 100% biofuel.
“We’re very close to our goal now,” Jonsson says. “With the new Andritz recovery boiler and the other new measures we are taking, overall environmental performance and energy performance has improved greatly. When we chose the HERB design, we chose to take a leap forward in terms of technology.”
STRENGTHENING THE HEART
“In my view, the recovery boiler is the heart of our pulp mill,” Jonsson says. “It is the most important part of a closed loop that circulates the liquor and produces the energy that keeps our machines running. When the heart is strong, the other systems can flourish.”
The old heart of the Iggesund mill was actually two hearts (two recovery boilers installed in the 1960’s). Unfortunately they were producing a fainter and fainter pulse, according to Iggesund lead Project Manager, Lennart Wanberg. “We had gone through several rebuilds. Each year we had to reduce the steam pressure to stay within boilers’ safety limits. We had to decide whether to rebuild or replace. While a new boiler is a major investment, it is also expensive to operate and maintain two old boilers.”
At the end of their useful lives, the old boilers were operating at about 62 bar steam pressure. This compares with a design of 110 bar for HERB (at 515°c).
The community of Iggesund surrounds the mill and has a symbiotic relationship with it. As Iggesund Paperboard goes, so goes the community of Iggesund. Residents take pride that Iggesund has one of the highest levels of investment for paperboard mills and aims to produce a high-quality product. In the last decade, the mill has upgraded its evaporation, recausticizing, and kiln – only the recovery boiler remained.
“In today’s market, sustainability is joining product quality in importance as a competitive tool,” Jonsson says. “I think it was quite a brave decision by the Holmen Board to make this large investment. It is proof of the confidence they place in this mill and this community.”
The investment project took about two years to complete. At its peak, 900 construction workers and specialists were on-site. Part of this was during a winter season that dumped more snow than Sweden had seen in many years.
For a project this size, considerable pre-project planning is the norm. “We looked at the technical specifications, visited references, and asked considerable questions,” Jonsson says. “In all these areas we got a very good impression of Andritz.”
The HERB design appealed to Iggesund from the beginning. “When we worked on our energy strategy, electrical power prices were high, oil prices high, and longer term we feel they will stay high,” Jonsson says. “A key factor for us was the idea of producing an additional 310 GWH/yr of electricity.”
“We are used to running fairly big capital projects here,” Wanberg explains. Andritz delivered the HERB unit on a mechanical turnkey basis (engineer-procure-construct excluding the civil works). Wanberg, a veteran of the mill since 1973, came to the project from heading the central maintenance activities for the mill. The appointment to lead this project was a welcome change for him. “I worked together with then project leader, Bo Skogqvist, who retired before this project was completed. This was exciting for me and I couldn’t wait to get to work each day.”
“We did very thorough planning to minimize any mistakes during the actual project,” says Mats Tegenfeldt, project manager for the recovery boiler. Construction broke ground mid-2010 with Iggesund assuming responsibility for the concrete foundations and then Andritz’s project team carried on from there.
Hannu Ylönen, Andritz project manager, was impressed with the level of pre-project thinking on the part of Iggesund. “We had many discussions with the Iggesund team to come to the final layout, functional, and degree of automation for this boiler,” Ylönen says. “You can see this in the functionality and safety of the finished unit. Details about the architecture, the placement of boiler house windows, the color schemes, the furniture in the control room were all discussed.”
Now, as you walk through the various levels in the boiler house, you are impressed with the view that the spacious windows offer over the landscape and the Gulf of Botnia. “It is a well-considered working environment for both operations and maintenance people,” Tegenfeldt says.
Facing all the usual challenges of a large capital project, Wanberg was impressed with the spirit of cooperation. Everyone on the team worked to the same target and to have the boiler ready for Holmen’s president to start it up on the appointed day. “On the erection side, there were very many critical lifts – heavy and high. Andritz was very good at coordinating and executing this, despite heavy winds at times.”
Of all the various aspects of the project, Tegenfeldt was highly complimentary of the quality of the boiler erection, which was under the supervision of Jyrki Väänänen, Andritz site manager. “It was amazing to me to witness the quality of the welding done by the Polish subcontractor to Andritz,” Tegenfeldt says. “Out of maybe 4,500 critical welds of the pressure parts, only three faults were detected during the quality tests. This is extremely good.”
MOST AUTOMATED RECOVERY BOILER?
The Iggesund team wanted this HERB to have a high level of automation. “We had a lot of discussions with the Iggesund project team about functionality, safety, and automation of this boiler,” Ylönen says. “Lennart Olsson, lead process engineer at Iggesund, and the boiler operators made a major contribution to this effort.”
Working with Iggesund’s Hans Larsson (electrification), Kåge Larsgården (instrumentation), and Åke Dehlin (automation), key members from the Andritz team built one of the most automated recovery boilers in the world. Iggesund’s Tony Andersson, a project team member, brought out the end user’s point of view, particularly when the maintainability of the plant was considered.
“Our design for Iggesund’s boiler reflects our experience from previous deliveries, including three previous HERB deliveries to Sweden,” says Ylönen. “All boilers are most efficient at high loads, but this boiler has also has excellent low load capabilities – even down to 1,300 tonnes dry solids/day. We supplied a special extension to the master distributed control system (DCS) control called Boiler ACE to optimize combustion and sootblowing at low or high loads and to minimize emissions.”
COLD TO WARM TO FIRING HOT
It took only a week in the autumn of 2011 to make all the piping and process connections that integrated the new equipment with the rest of the mill. “We can say that it was a very smooth start-up,” Jonsson says. “It was on-time, the safety record was excellent, and the project was completed within budget. I can say that we are very pleased with the results.”
Civil construction work was very challenging, considering that the winter “was one of the coldest in everyone’s memory, with lots of snow,” Ylönen says. “The construction of the foundations was supervised by Iggesund’s Magnus Carlsson, whose work was very impressive.”
Work has begun on installing a new odorous gas collection system, which was due to be ready in mid- 2013, to further reduce the mill’s emissions. The new boiler also has incorporated Andritz’s new AlE chlorine removal system, which leaches chlorine from the ash to keep it from recycling in the chemical recovery loop. With higher pressures and temperatures, this could be an important consideration to prevent eventual corrosion of the boiler’s pressure parts. “At the moment,” Tegenfeldt says, “We are in the testing phase so we have not fully implemented it yet.”