Åke Nordlander and Mark Lockie
Dec. 1, 1998
When it comes to creating environmental landmarks in the pulp industry, Aspa Bruk is in the premier league. They were first in the world to install oxygen delignification technology in the 1970s and were the pioneers of totally chlorine-free technology at the end of the 1980s. Now the plant is two thirds of its way through a SEK 410 million ($54 million) three-stage plan, which it hopes will bring them closer to bleach plant closure than any other mill.
The target is to increase capacity from its current level of 140,000 ton/yr up to 200,000 tons/yr and reduce impact on the environment. The Aspa 200,000 project has helped raise the quality of its pulp already, with improved strength and cleanliness.
Out of the SEK 410 million, some SEK 150 million will be spent on boosting the capacity and the remaining SEK 260 million is dedicated for prescheduled investments. Up until now the mill has spent almost SEK 250 million.
One of the main reasons for the mill's extraordinary environmental track record is its idyllic location next to Lake Vättern in the center of Sweden. According to the managing director at the mill, Bengt Unander-Scharin, "There are also stringent regulations. We have been told that if we want to increase production, we will have to reduce our effluent by half."
Anders Lindqvist, left, production manager at Aspa Bruk, together with mill managing director, Bengt Unander-Scharin, in front of their new pressurized white liquor filter
At present the mill has one pulp line and three products - 15% unbleached pulp, and TCF and ECF pulp produced in equal proportions. Its main markets are Scandinavia, western Europe, where Germany is the principal market, and Japan. Stage one of the project did not actually raise capacity of the plant because of bottlenecks elsewhere in the process, explains the production manager at the mill, Anders Lindqvist, but it did update very old equipment at the mill in the recausticizing area. Recausticizing is a very important link in Aspa's overall vision to eliminate emissions and represents a significant portion of the total project cost in step one at about SEK 65 million.
There were primarily four main components to the new installation. As Lindqvist points out, "We chose a completely new technology - comprising a pressurized green liquor filter of cassette type, a pressurized white liquor filter, a recausticizing vessel, a lime mud filter and a slaker."
The green liquor filter replaced a clarifier, while the pressurized white liquor filter replaced an open filtering process. According to Lindqvist, "We were forced to modernize. These were both bottlenecks and the equipment was old and worn out. The new plant produces very clean green and white liquor with a sludge content less than 20 mg/l - far below the old equipment."
Lower sludge contents are now helping the site's digester achieve better results. Before the new plant was installed, sludge built up in the digester and could only be kept in check through regular acid washing of its heat exchanger. This, in turn, led to a drop in production. Lindqvist believes that the site will be able to remove these problems completely in the future.
Essentially stage one saw the implementation of a kidney using a new pressurized technique for recycling and cleaning digester chemicals. In simple terms Aspa's latest development could be termed a mixing plant. Kvaerner Pulping was the chosen supplier for this stage.
According to Unander-Scharin, "The background to the investment goes as far back as 1972 when we commissioned the world's first oxygen stage. At the time, the focus on recausticizing was neglected and we have suffered from this on the digester side ever since. The lack of an upgrade in 1972 has dogged us until now. It became a very urgent investment for us and constituted stage one in our focus, Aspa 200,000."
According to Lindqvist the mill has a separate working-environmental group to take into account the internal environmental parameters. They drew up special environmental requirements, which the suppliers then studied and followed up after installation. One result the mill is proud of is the noise level in the recausticizing plant, which has fallen below 80 dB through extra insulation of noise-emitting machinery. The mixing plant is also extremely clean and the mill claims that it is not a problem to have a conversation right by the machines.
Many mills see running at the forefront of environmental technology as a risk. But as Unander-Scharin points out, "It is our only option as a small niche mill, although of course we realize the risks. We feel that it is important to focus on new technology in parallel with tested technology. In Aspa 200,000, there are several different sections with innovations. These may prove to be extra added value for us in the future."
Stage one was in operation by 1997 and stage two by the middle of 1998. After stage two has been implemented, capacity will be increased to 160,000 tons. It won't be until stage three is implemented that capacity will be taken up to 200,000 tons.
The new diffusion washer
from Kvaerner Pulping.
The second step needed a three and a half week shutdown in May 1998. It involved the expansion and modernization of the recovery boiler, evaporation plant, cooking plant and a new screening room. Suppliers for this stage included Kvaerner Pulping, which was in charge of the digester and evaporation plant, Ahlstrom, which rebuilt the recovery boiler, Sunds Defibrator, which took care of the new screening room and ABB, which delivered a completely new DCS (distributed control system) system for the entire mill.
Stage three is perhaps the most exciting prospect from an environmental standpoint. Not only will the final stage allow production to rise to 200,000 tons, but it could also allow the mill to make significant strides towards closure - perhaps even allowing it to jump into the lead on the world stage.
The work involves rebuilding the oxygen delignification and bleaching plants and according to Lindqvist, the mill will probably modernize the existing drying plant, which is very antiquated and requires constant attention. A decision for stage three is expected soon and this could lead to the new equipment being installed by 2000.
Bearing in mind the current industry recession, which has seen prices for northern bleached softwood kraft plummet to $460/ton, CIF, it would be understandable if the mill were to shelve its project until the market improves. But according to the mill, its objective is to finalize all investments during the current industry recession to become competitive at the 200,000 ton/yr level by the time the market turns upward once more.
Aspa Bruk is now in the design, evaluation and proposals stage for step three. The major modernization of the bleach plant will further reduce effluents. According to Unander-Scharin, "When I look at the proposed figures they are very good. We will achieve very low water consumption levels and a very low COD (chemical oxygen demand) in the effluent. Some other mills have come very close to closure. We won't be closed completely, but we hope to have the best record in the world. We are working very closely with our suppliers."
The key is to remove the non-process elements in the closed loop. As Lindqvist explains, "In some way we must either recycle or remove residual products as further closing increases the pressure on the kidney. But we are well equipped with the technology we have at present."
The technology to do this will be the new recausticizing plant, where the green liquor will be filtered. "It's all a question of how we arrange the process for the entire mill, but for now all the details have yet to be decided," Lindqvist says.
At present, the mill has a limit of 20 tons/day of COD. This is set to change dramatically, as Lindqvist says, "COD must be reduced to 10 tons/day according to the environmental regulations."