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ANDRITZ delivered a turnkey pulp drying line which includes the approach flow system, pulp machine, airborne sheet dryer, densification press, cutter/layboy, and automated baling line. The pulp machine (above) features twin wire forming technology and a PrimePress X shoe press.
Sappi Saiccor is the world’s largest producer of chemical cellulose (dissolving) pulp for textiles and specialty markets. According to Alan Tubb, Saiccor Chief Executive, dreams of expanding the Saiccor mill began in 2005, with an increase in market demand and the successful completion of a debottlenecking project which was Amakhulu’s forerunner. In addition to increased capacity, a major motivator was to leverage opportunities to reduce the mill’s emission volumes and reliance on fossil fuels.
“By investing in the best technology, we have managed to increase our profit margin while decreasing our environmental impact,” explains Tubb. The mill has reduced its dependency on fossil fuels significantly and has seen a substantial reduction of effluent dissolved solids. Saiccor has also managed to maintain the same water consumption despite the additional 200,000 tonnes pulp capacity.
ANDRITZ’s contribution to AmakhuluProject Director and Sappi Group Head of Technology, Andrea Rossi, explains that ANDRITZ’s involvement in the Mkomazi expansion project in 1993-1994 proved a major motivator in choosing the company again as major supplier for the woodyard, bleaching, drying, and evaporator deliveries for Amakhulu. “ANDRITZ has a very good local technical presence,” Rossi says. The local office hired site, safety, quality, purchasing and scheduling personnel, and the office sourced many of the materials, platforms, supports, piping, tanks, and vessels as well as the local mechanical and piping erection contractors.
“ANDRITZ offers a basket of technology,” says Gary Bowles, Sappi Saiccor General Manager, “that makes our interfacing far more streamlined.”
The contribution went beyond technology. Backed with the financial support of ANDRITZ and other EPC suppliers and contractors, Saiccor set up a training school in the local community. Combined with the 1000 temporary and permanent jobs offered by the project, living conditions were improved for many of the local population.
New woodyard technology for SappiANDRITZ supplied a turnkey woodyard – incoming log receiving deck, log washing system, chipper, chip belt stacking system, chip reclaiming, and conveyors. With it, the mill is able to take on a larger volume of logs of up to 6 m in length. The HHQ-Chipper™, the first of its kind in South Africa, handles large diameter logs.
When asked why it has taken South African mills this long to invest in horizontally-fed chipping technology, Tony Neave, Saiccor’s Plant Manager for Pulp Preparation, explains that it is always hard to move away from proven technology. However, since taking the plunge, Saiccor has achieved a chipping rate 10% higher than the original design rate. In terms of general runnability, the chipper is less problematic than Saiccor’s existing chippers and far more user-friendly.
Surpassing design targets in the bleach plant and drying lineThe ANDRITZ technology includes the delivery of fine screening, oxygen stage, and four-stage ECF bleach plant. The plant is based principally on the mill’s Bleaching Plant 3, delivered by ANDRITZ in 1994-1995, including six conventional vacuum filters for brownstock washing and the bleach plant. The new bleach plant has been operating at 1020 admt/d – already surpassing its design target.
ANDRITZ also installed a turnkey pulp drying line which includes the approach flow system, pulp machine, airborne sheet dryer, a densification press, a cutter/layboy, and automated baling line. Most impressive in ANDRITZ’s delivery is the twin wire forming technology (a new technology for Saiccor) and the inclusion of a PrimePress X shoe press from ANDRITZ Küsters in the press section. The PrimePress X reduces Saiccor’s operating costs through its increased moisture extraction, necessitating less steam in the drying plant.
Next in line is the ANDRITZ airborne sheet dryer with a heat recovery system. Following the dryer, an ANDRITZ Küsters PrimeCal Hard calender is utilized as a densification press to flatten the density profile prior to the cutter. ANDRITZ delivered the cutter/layboy and automated baling line (baling, bale storage, and bad bale treatment), including the BaleMatic™ control system.
“This was a challenging project for us,” says Bernd Asbeck, ANDRITZ’s Project Manager for the drying plant. “The drying of dissolving pulp was a new process for us,” Asbeck says. “The physical design was significantly influenced by the low pH of the stock. We had to redesign the entire machine to make the engineering suitable for manufacturing with the special materials required for the corrosive environment.”
Skyrocketing stainless steel prices formed a major financial drain for the Amakhulu project. “We were competing not only with international demand for materials, but also a strong local demand with the 2010 Soccer World Cup construction beginning,” explains Rossi.
In addition to the technical challenges, Asbeck and his team met the usual project challenges. “The biggest challenge was time,” Asbeck says. “We were on a tight schedule, with installation beginning in May 2007 and start-up one year later. We were doing the full erection of the drying line systems, not just erection supervision. We focused on finding the right quality-minded sub-suppliers, inside and outside of South Africa, and documenting their QA programs.”
In addition, “real estate” inside the mill was at a premium. “There were only small areas for laydown and erection preparation because the mill was in full operation during our construction and installation work,” Asbeck recalls. Despite being placed under tight deadlines and in an even tighter geographical location with limited access for civil construction, the drying line was finished two days ahead of schedule. Since the production of the first bale on the 13th of May 2008, the pulp drying line has “exceeded many expectations,” says Krish Naidu, Mill Area Manager for Bleaching and Drying. “We have a very good working relationship with ANDRITZ. They are team-driven and customer-oriented in terms of satisfying our needs.”
Conquering the large evaporatorANDRITZ also supplied Saiccor’s newest evaporator, which is currently the largest of its kind for magnesium sulphite applications. The plant concentrates incoming black liquor (12.5% dry solids) to 58% dry solids content before firing in the recovery boiler.
The units are especially constructed for the magnesium sulphite cooking process, with special emphasis on the production of clean reusable condensates. The plant is equipped with a methanol liquefaction system for stripping volatile gases which are then combusted in the boiler. The ANDRITZ technology is very different from Saiccor’s existing mechanical vapor recompression evaporators – a switchover motivated by the increased reliability of a multi-effect evaporator. The existing evaporators require frequent shutdowns to mechanically clean scale build-up, while the new evaporators have internal heat surface washing in the sulphite liquor stages.
The evaporator transport and erection was a challenge. “It certainly forced ANDRITZ to think out of the box, which they did without complaint,” reflects Rossi. Five of the evaporator’s effects were transported whole, while South Africa’s weight restrictions on national roads forced the biggest effect to be dismantled, rebuilt into smaller pieces, and then transported by road. The vessels were positioned in place with a 450-tonne crane – one of the biggest in South Africa.
The evaporator plant has yet to be commissioned, although it has run successfully for short periods of time. A delay in the digester plant was induced when a leak of sulphur dioxide gas from a newly commissioned pipeline was detected in October, according to Colin Reddy, Mill Area Manager for Evaporation and Recovery. Although the malfunction was quickly isolated by the technical staff, the digesters subsequently had to undergo a shutdown while a more thorough investigation was made.
“Dynamic simulation is the way to go”Included in the delivery is an I.D.E.A.S. Simulator from ANDRITZ Automation, which allows Saiccor to perform logic and loop testing – and operator training – for its chemical recovery and boiler processes. Colin Reddy and his team were able to isolate and remove problems with the DCS configuration before the start-up. The simulator has been invaluable in training 200 new and existing staff at the mill. “I.D.E.A.S. has been extremely helpful for the start-up and training of operators,” says Rossi. “With skills levels as they are in South Africa, dynamic simulation is the way to go.”
Project challengesAcross the board, the biggest challenge to the expansion project was the resulting congestion and logistical dilemmas of expanding a brownfield site. With over 3000 people on site during peak construction, tremendous effort was placed on safety training. This certainly paid off, with an injury frequency rate of just 0.2% and a Lost Time Frequency Index of 0.18 for the eight million man-hours worked throughout the project.
With mills around the world forced to close their doors, one would have thought that the global recession would have been a major challenge to Amakhulu. However, the expansion was almost finished before South Africa was impacted by the recession. Although the plant was forced to run at approximately 70% of capacity for a number of months due to project-related aspects, “It is currently ramping back up to full capacity,” says Bowles.
The support of ANDRITZ has eased Sappi Saiccor’s upgraded mill into its first successful production runs. As Rossi explains, “We are extremely happy to have worked with all the ANDRITZ team members. They have had a very positive attitude and were willing to find the solutions to ensure we met performance requirements.”
The ANDRITZ scopeWoodyard. Turnkey delivery of eucalyptus processing line and the first horizontal feed HHQ-Chipper™ in South Africa. Designed for 300 m³ sub/h.
Fiberline. Fine screening, oxygen delignification, and ECF bleach plant for magnesium sulphite cooking process. Designed for 870 admt/d.
Recovery. Turnkey delivery of a 6-effect evaporator (largest in world for magnesium sulphite process) with condensate stripping and methanol liquefaction. Designed for 370 t/h evaporation.
Pulp Drying. Turnkey delivery of approach flow, pulp dewatering, drying, and baling line. 4.06 m working width. Designed for 930 t/d. PrimePress X shoe press from ANDRITZ Küsters
Simulation. I.D.E.A.S. Simulator for chemical recovery processes
