Although it is one of the world's southernmost pulp mills, distance will not make a difference for Celuloso Arauco y Constitucion's new facility in Valdivia province, Chile. The 550,000 tonne/yr market pulp mill started up on February 9, 2004. Its planned-for success is based on low costs and the use of state-of-the-art technology. Arauco is confident the mill is well situated to serve the growing Asian market.
Arauco spent more than $1 billion to build this mill, but believes sincerely that it was money well spent. Valdivia boosts Arauco to number three in the rankings of the world's leading pulp producers, with a capacity of more than 2.2 million tonnes/yr.
Approximately 25% of the capital outlay was earmarked for securing the mill's wood supply. Arauco now owns 620,000 ha of forest in Chile and 126,000 ha in Argentina. The company is the world's largest owner of radiata pine plantations. The company says it has more than enough wood on a sustainable basis: 21 million m³/yr are available.
Valdivia uses eucalyptus and radiata pine for its pulp running it in campaigns of 13 days for pine and 12 for eucalyptus. Of its total pulp production, 60% is eucalyptus, 40% is pine. It takes 5.6 m³ of pine to make one tonne of pulp and 3.9 m³ of eucalyptus. At full production, Valdivia will use 3.4 million m³/yr of wood.
There are two species of eucalyptus available: globulus and nitens. The former provides the longest short fiber, about 1 mm. Nitens fibers are very short, about 0.6-0.7 mm, but provide good smoothness and opacity properties. The cycle for Valdivia's eucalyptus is 12-13 years.
The radiata pine is described as midway between Scandinavian/Nordic pine and southern pine. The Chilean pine provides excellent tensile properties. The pine is cut at 30 years. However, this is because Arauco's sawmills also use the pine. The part of the tree with the largest diameter is destined to make plywood, the next largest piece is used for lumber and the pulp mill gets the rest as well as the sawmill chips, which provide excellent pulp making fibers. If pulp was the sole product, the pine could be cut after 14 years. Eucalyptus is used only for pulp.
The mill also uses purchased wood — roundwood and chips from company owned and private sawmills. At Valdivia, chip inventory is 135,000 m³.
There are two lines in the woodyard, one each for pine and eucalyptus. There are two Andritz PowerFeed debarkers (5.5 m diameter, 35 m long) although logs may come in already debarked. For eucalyptus logs, Andritz developed the EucaRoller to remove any remaining bark, which is quite stringy, prior to chipping.
There are two chippers — 3.36 m HHQ model, each with 16 knives. Each chipper can handle 340 m³/hr. The chip dimension target is 24 mm x 4 mm. The eucalyptus wood poses special challenges here as well, being a hard, rough wood that is acidic. Therefore, the mill used stainless steel rather than the conventional mild steel in the construction of the chipping system.
There are two longitudinal chip piles with traveling screw reclaimers. There are four different types of chips. Chips are first screened with oversize chips sent to an Andritz HQ-Sizer for processing while fines are sent to the boiler. More than 95% of chips go directly from screening to the pulping process.
For mill manager José Vivanco, quality comes above all. This starts with the wood. The mill tries to ensure its fiber is as fresh as possible with consistent quality. Therefore, there is only limited storage for logs. Thinnings are only stored in the summer and kept under water.
"We know our wood is different from other regions of the world," Vivanco says. "But if you manage your wood in an intelligent way, feeding the same quality to the process, running the mill in a balanced way, you will get good quality pulp and stable quality all the time. This is one of the most important features for customers — always receiving the same product. You can achieve (with pine) good fiber length, comparable with northern softwoods, 2.6-2.8 mm fiber length and the coarseness is close.
"We select our pine from different sources — sawmill chips, the upper and lower parts of the tree — and feed them in carefully managed ratios so we always have a homogeneous mix of wood so our pulp quality is consistent."
Arauco's research group does continual work on its pine to try to develop the characteristics its mills need from the fiber. All of Arauco's forests are plantations and the best trees are cloned.
Extra strong
Valdivia sits in a severe earthquake zone. In the early 1960s, one of the world's strongest recorded quakes (more than seven on the Richter scale) hammered the region.
Therefore, the mill had to be built strong with special reinforcement parameters designed into every piece of equipment weighing more than five tonnes. This drove up the building costs by an estimated 20-25%.
Arauco tended to go it alone in the design and engineering of the Valdivia project although it did hire a local consultant for some parts. Construction started in January 2001 and on average, 4,000 workers were on site. During peak construction times, 7,000 workers were on site.
Arauco opted for Metso's SuperBatch-K pulping system. (For a full description of the pulp producing process and equipment, see PPI, November 2003) Metso also supplied the washing system, bleach plant, pulp dryer and baling line. There are 10 Super Batch digesters, each 18.1 m high with a 5.8 m diameter and a volume of 400 m³. Kappa number out of the digesters is 28 for pine and 15 for eucalyptus.
Vivanco says the decision about which pulping process to use was based mostly on cost. "Arauco always buys the most cost efficient equipment. This was it at the time."
Vivanco moved to Valdivia from another of Arauco's pulp mills that had both batch and continuous processes. "You can improve the tear in batch more so than you can with the continuous process, but the continuous process is easier to manage." He adds that the physical properties are probably slightly better from a batch process.
The washing process features two parallel lines with two Metso DC-10 screens in each. This is the DeltaCombi brownstock screening system that does knotting and fines screening in one unit, helping to save installation and operating costs.
The mill has installed nine TwinRoll presses for the brownstock and bleach plant washing stages. Discharge consistency following the last of the three TRPW model presses prior to oxygen delignification is 32%. The presses combine displacement washing and pressing in one unit.
There is a Metso OxyTrac two-stage oxygen delignification unit that achieves 57% delignification for pine pulp and 36% for eucalyptus. The system works with a low temperature and high pressure in the first stage when alkali concentration is high. This helps avoid negative effects on the fiber.
Retention time for pine is 30 minutes in the first reactor and 63 in the second. For eucalyptus, it is 27 minutes in the first reactor and 57 in the second. AGA supplied the oxygen generating plant. Outgoing kappa number is 11-12 for pine and 9-10 for eucalyptus.
The elemental chlorine free (ECF) bleach plant follows a DOEOPDD sequence and final brightness levels can be as high as 91 ISO. Metso also supplied the bleach plant while Cellchem provided the chlorine dioxide generator. There are two high-density (11%) storage towers, each capable of holding 800 tonnes of pulp. The DeltaCombi screen concept can also be used in bleached stock screening.
Prior to entering the dryer, the pulp passes through a Metso four-stage screening system and two direct cleaners and two back cleaners, which were supplied by GL&V. The wire section has a Metso MB former fourdrinier, 24.5 m long by 9.2 m wide. There are three presses: CombiPress for the first two nips and a Symbelt shoe press.
The dryer itself is massive: 43.9 m long, 12.9 m wide and 16 m high. Moisture content into the airborne dryer is 51%. It uses low-pressure steam to dry the sheet. It is divided into a dryer section and a cooler section. Outlet moisture is 90%. Trim width is 8 m. The basis weight of the pulp is 850 g/m² and each sheet is 3 mm thick.
The Metso DryWay cutter is fully automated and can produce 12 bales at a time, each 667 by 850 mm. There are two baling lines that use Metso's Robo technology rather than conventional hydraulic and pneumatic operation. The bale wrapper is made at the mill. It is produced when Valdivia is in the midst of a campaign switch from eucalyptus to pine pulp. The baled and wrapped pulp is then conveyed to the storage warehouse to await shipment.
The railroad is Valdivia's main shipping mode although some pulp goes out by truck as well. The main use for the pulp is as reinforcement in the production of printing and writing papers.
Recovery
The six-effect lamella-type evaporators from Andritz (first delivery to Chile) increase black liquor concentration from 15.6% at the start of the process to 76%. Evaporation capacity for pine is 730 tonnes/hr, for eucalyptus, 680 tonnes/hr. The evaporators feature internal segregation technology and an integrated stripper.
The softwood pulping process does produce more solids content than hardwood does. To compensate for the lighter load with eucalyptus, the mill increases pulp production to obtain a similar solids load.
The Kvaerner Recox recovery boiler has a capacity of 3,650 tonnes dry solids/day and generates 537 tonnes/hr of steam. The mill burns its concentrated gases in the recovery boiler but can also burn them in the power boiler if the need arises.
Just after startup, Valdivia was burning about 99.5% of its concentrated gases but another incinerator was added in August so all these gases are now burned. There are three electrostatic precipitators on the recovery boiler, which operate at an efficiency of 99.7%.
Originally, Valdivia did not burn the dilute gases. However, the mill added facilities to collect the dilute gases and by the end of 2004, these were being burned in the recovery boiler.
The Andritz recausticizing process produces 7000 m³/day of white liquor. The process equipment includes one green liquor tank, two X-Filters (green liquor filtration), one clarified green liquor tank, a CD-Filter (white liquor filtration), one slaker/classifier and three causticizers. The lime mud passes to the Andritz LMD lime kiln, which has a capacity of 520 tonnes/day (CaO 87%) and is equipped with a sector cooler.
In its power boiler, a Kvaerner Hybex bubbling fluidized bed model, Valdivia can generate 120 tonnes/hr of steam at a pressure of 85 kg/cm². It can burn bark, sawdust, sludge and non-condensible gases. The mill also has two turbines (MAN), one backpressure and one condensation. Inlet steam pressure is 85 bar at a temperature of 485°C. The two generators can produce 70 MW each. Vivanco says the mill has a power surplus of 50 MW when producing softwood pulp and 36 MW when running a hardwood campaign.
Emerson Process supplied most of Valdivia's control system using its DeltaV System. There are more than 3,000 Foundation Fieldbus devices, 1,500 Rockwell E3 and E3+ motor starters, 15 Siemens and Rockwell PLCs communicating to the DeltaV.
Emerson provided the project management for the control system, system engineering and configuration, Foundation Fieldbus consulting and commissioning.
Effluent
The mill has extensive water treatment facilities, both incoming and outgoing. Fresh water is obtained from the nearby Rio Cruces.
The treatment plant consists of two coagulation and two flocculation chambers. The water then flows through sand and anthracite filters. The mill uses 32 m³ of water per tonne of pulp (softwood) and 29 m³/tonne (hardwood).
Valdivia operates a three-stage effluent treatment plant. The 40 m diameter primary clarifier is more a settling basin. The effluent then passes through a cooling tower and into the biological secondary treatment phase. There are two lagoons and two clarifiers in secondary treatment, each capable of processing 25,000 m³ of effluent.
Once the organic and inorganic oxygen demand (BOD, COD) are controlled, the mill needs to control the color, which is where the tertiary treatment phase comes in. Color is controlled with aluminum sulfate. The clean water is then put back into the Rio Cruces.
Sludge from the primary and secondary treatment processes is burned as it is composed mainly of organic content. Sludge from the tertiary phase, mainly chemical, is landfilled although future plans call for composting.
Valdivia's process generates about 4 kg of solid effluent per tonne of pulp, or 23 m³ of liquid effluent per tonne. The COD load to the treatment plant is 140 mg/L; BOD load is 25-50 mg/L. The normal chlorophenolic load is 0.02 mg/L.
"Far from the world"
A normal year's operation calls for one 10-day maintenance shutdown per year as well as one half-day shutdown every six months. The mill operates 354 days/yr.
Maintenance is carried out by the mill's own workforce. Contractors will be hired for the major shutdowns. Vivanco says he does not think that Arauco will opt for a long-term maintenance contract offered by the major suppliers. This is due to costs. However, he adds, "If it is cost effective, we will seriously look at it."
Vivanco points out that Arauco's mills' uptime is normally 96%. "Suppliers must show me that their maintenance services will improve on that for us to consider (their offers)."
Therefore, being as self-sufficient as possible is important. Still, being a remote mill means this is a difficult task. As Vivanco says, "We are far from the world." One ace in the hole that the mill has is the local tradesmen. "Close by, we have some very good workshops." He describes one incident when the mill had a major problem with a turbine. Arauco considered sending the equipment back to Germany, which would have necessitated a long shutdown. A local shop was able to solve the problem in 10 days.
Training
Building a greenfield pulp mill in a remote location meant that many employees would be new to the industry. The mill employs a total of 259 people: 140 in production (engineering, technical and operations); 93 in engineering and maintenance; 26 in administration.
Of the 259, only 80 came from other Arauco mills. Vivanco is proud of the training effort. "We did a good job. We used mostly our own engineers to train the operators. We had many who had never been in a pulp mill before."
For the most part, the mill created its own training manuals. Valdivia also purchased an IDEAS simulation package from Andritz.
Running since February, the mill can still be considered in a "learning process", particularly when it comes time to switch pulp production from softwood to hardwood. There is still a lot of fine tuning needed when making the switch. Small shutdowns in the washing and screening process are needed. "We still need time to learn how to properly tune up the process," Vivanco said in October.
Still, the start-up curve is very complimentary of the mill's efforts. From start-up through July 2003, the mill exceeded its production targets. August and September were slightly below budget. In October, mill reached 108% of design capacity as the monthly average, just 8.75 months after startup.
Thus far, Valdivia's customers are "very happy" with the pulp they are receiving, according to Vivanco. "We are offering a bright, clean and uniform product. This is what they want."
Vivanco also holds out hope that markets will improve. "It is still a cyclical thing and it is swinging more than before but for shorter periods. To compete in bad times, you need to be very efficient." This is the key to Arauco's (and Valdivia's) eventual success: stable and homogeneous quality, low-cost production tied in to the use of new technology and mills that are "strategically" located.
