Two years ago, CMPC started up a new 32,000 ton/yr Voith tissue machine at its Talagante mill in Santiago, raising mill capacity to 62,000 tons on two machines. A year later, and after extensive modifications, the machine restarted as the world’s first tissue machine using the innovative Voith ATMOS technology.
The origin of the project to install ATMOS technology goes back to 2004. Some months after ordering a conventional turnkey tissue machine from Voith, CMPC was approached by the machine supplier to explain its new development to make structured tissue. This had already been demonstrated on pilot machine. Now Voith wanted to modify the Talagante project to accommodate the first full-scale installation of ATMOS.
A market survey indicated to Voith that the Talagante mill was the best site for the first ATMOS line. Talagante not only had the new Voith machine. It also had a product portfolio for which the ATMOS process
is ideal. Moreover, Talagante is owned by CMPC, the leading tissue producer in Latin America, and is one of a group of mills in Chile, Argentina, Peru, Mexico and Uruguay.
The Talagante machine has a 15-foot diameter yankee cylinder and a 500°C dryer hood. It can reach operating speeds on the ATMOS mode of 1000-1300 m/min producing two-ply 19 g/m2 towel paper with a furnish of high recycled fibre content. Following start-up, the machine ran in the ATMOS configuration for one month and then switched to dry crepe production for three months before returning to the ATMOS settings for a further two runs in 2007.
ATMOS machines with bigger Yankee (18’) can reach 1300-1400 m/min with virgin fibre furnish and producing towel paper, and 1400-1500 m/min when producing 18 g/m2 toilet tissue from virgin fibre.
The data from the ATMOS machine in Talagante has confirmed, at industrial scale , the results that Voith had previously obtained from its pilot machine trials, making the process suitable for full scale production, making products equal to those made in TAD machines but with lower energy and capital costs, and with high contents of recicled fibre.
THE ATMOS TECHNOLOGY
Voith believes that ATMOS is the ideal technology for the dominant tissue grades – the toilet papers and kitchen towels which account for by far the greatest volume of tissue production. Bulk, structural softness and handfeel are the leading requirements for toilet tissue, while water absorption is the most important attribute of towel tissue.
Voith states that the ATMOS machine, when producing ATMOS towel tissue, achieves an absorption capacity of up to 16-18 gH20/g fibre from a mixture of virgin fibers. This is the highest absorption value in the market, matching the best TAD tissue and surpassing the 7-9 gH20/g fibre of standard dry crepe.
When producing towel grades from 100% recycled fibre, ATMOS towel paper achieves an absorption value of 12.5-13.0, which matches the conventional TAD paper available in the market. In terms of bulky toilet tissue, the top performer is an ATMOS grade made from 70% hardwood and 30% softwood pulp with a bulk of 13-15 cm3/g. The nearest TAD grade has a bulk of 12.0, while the best dry crepe grade is 8.5.
Since bulkiness is the property which imparts softness and handfeel to tissue, ATMOS did well in consumer tests carried out by three panelists. They compared two ATMOS grades with the best TAD tissue, all three having the same basis weight and tensile strength, and found that:
- ATMOS made from 70% hardwood and 30% softwood pulp was slightly softer than the best TAD, scoring +4
- ATMOS made from 60% hardwood and 40% was softer with a score of +3.
- On a scale of 1-9: 1 signifies no difference; 5 is slightly softer and 9 is much softer
- ATMOS technology offers a mill the following advantages over through-air-drying, according to Voith:
- It permits the use of 100 % secondary fibre while achieving the premium quality and speed of a commercial TAD machines.
- Up to 40 % less capex because less machinery is required and building, erection and manufacturing costs are lower.
- Dry-crepe tissue machines can be retrofitted with ATMOS technology and they can swing between yankee cylinder mode and ATMOS mode in response to market developments.
- Up to 35 % lower energy costs, and also lower overall costs for raw materials (stock, chemicals) labour, fabrics, maintenance, and auxiliaries.
- User-friendlier operation and maintenance, and higher productivity.
CMPC COMMENTS
“Even when there is basically no market today in South America for the higher cost structured tissue, the facts that the design permitted the machine to swing very rapidly from conventional to ATMOS, and vice versa, and that CMPC competes in its markets with multinationals who have the capability of eventually placing TAD products in their markets, made it it interesting for the company to cut a deal with Voith that considered placing the machine at their disposal for a number of days to develop the process at full scale,” said a spokesman for CMPC.
He continued: “Today, a little over a year after start-up, the machine has run in ATMOS configuration for a total of 80 days in three runs. Being a complete new technological concept, to make it operational, in such a short time has represented a big challenge that has required a true team work between Voith, Voith Fabrics, the chemical supplier Buckman, the converting machine supplier Fabio Perini (Brazil and Italy), and the Talagante plant people.
“After the third run, the results predicted on the pilot machine have been confirmed on the full-size operation. It has also been proven, that with some upgrades in converting lines (more sophisticated tension controls), the products can be converted with no special difficulties in commercially available converting lines.
“Specifically, the industrial scale operation has confirmed the swing capability of the machine, the product quality, which is for all purposes equal to standard TAD, the ability to make 19 g/m2 paper at up to 1200 m/min, and the forecast energy consumptions, which are clearly lower than TAD while anyway higher than conventional tissue.
“The fact that energy costs in Chile have tripled since the go-ahead decision on the ATMOS project, added to the strong demand that CMPC is having for its conventional tissue products, doesn´t make it feasible right now for the company to launch those structured products at high scale to replace conventional consumer grades, except for some niches in which TAD products are marketed today by our competitors, such as Away from Home dispenser towels for even higher fiber savings, while maintaining the premium quality.
“The ATMOS process is a sound one and we are happy to have been able to help Voith develop the technology in an industrial scale. We are also happy that Voith chose CMPC as a key partner for this project, giving us the possibility to make those structured products in a more economic way if the market requires them in the future or if our competitors decide to introduce them in our market area,” the source concluded.
ATMOS BACKGROUND
The inventors of ATMOS – Rogério Berardi, Luiz Carlos da Silva and Thomas Scherb – are based at the Voith Tissue Process Technology Centre in São Paulo, Brazil. They set out to develop an economical alternative to the TAD tissue which has dominated the premium market for 30 years, having 100% more bulk and 90% more absorption capacity than standard dry crepe tissue.
TAD produces a soft, bulky tissue because is dried largely by hot air and with a minimum of the mechanical pressing which has a negative impact on bulk and softness. At the Yankee cylinder, only 25% of a TAD sheet is exposed to pressing pressure, compared with the 100% exposure of the dry creping process.
For more than 30 years, this premium tissue has been the domain of the big tissue producers because of the high capex and opex required for through-air-drying. Capital costs and energy consumption are 200-250% higher than those of dry creping.
The São Paulo team set out produce a sheet of TAD quality but at greatly reduced production costs. It should, like TAD, be 75% unpressed and should have a dryness of 35% after the ATMOS process and before thermal drying. At the yankee cylinder, the R&D strategy called for higher efficiency and a uniform moisture profile.
The development work was carried out on the Voith pilot tissue machine at São Paulo, in close co-operation with Buckman Laboratories (chemicals), Perini (converting) and Voith Paper Fabrics.
The solution involves a wet moulding process on dedicated moulding fabrics, immediately after the forming section. A permeable belt is used to pass hot air and steam into the sheet at the vacuum roll and raise the dryness level to 35%. At the yankee cylinder, another 60% of the water content is removed with minimum pressing contact.
By 2006, the research effort had produced ATMOS, a process “which achieves the same bulk and absorption as TAD for 35% less total mill investment cost and 30-35% less energy consumption,” according to Thomas Scherb.
Comparisons of pilot results from ATMOS with the those of TAD clearly put ATMOS in the premium sector, even though secondary fibre is used in the furnish.
BESPOKE CHEMICALS
Buckman Laboratories International has developed a range of chemicals for use on ATMOS lines: the MAGNOS chemistries and application technologies. The MAGNOS range is the result of two years of R&D work in close cooperation with Voith. It includes creping adhesives and adhesive extenders, film forming additives such as PVP and PVOH products, modifiers created specifically for this new technology, speciality process chemicals and water treatment products.
The Buckman coating package is designed to ensure improved sheet transfer and uniform adhesion to the yankee cylinder surface, fine-tuned creping control and better machine runnability. Additional product categories and new products are being developed.
Voith and Buckman have formed a cooperative business agreement, whereby:
- Voith will promote and support Buckman as the preferred supplier for the process chemicals needed to operate ATMOS and will urge all their customers to choose Buckman
- Buckman will provide process chemistry personnel for the startup of ATMOS machines and machine conversions.
CMPC - THE BIGGER PICTURE
CMPC is South America’s leading producer of tissue with around 250,000 tons/yr capacity today, which will rise to well over 300,000 tons in 2008. But tissue is only part of the group’s activities.
CMPC is also a major pulp producer, with a capacity of 2 million tons in three Chilean mills. It supplies some 200 customers in Europe, Asia, and America with long and short-fibre market pulp.
In Chile, the company has over 420,000 hectares of pine and eucalyptus plantations. Another 100,000 ha of taeda and elliotti pine are being developed in the north-east of Argentina
Chile itself has 15.6 million ha of forests, of which 2.1 million ha are industrial plantations, the main species being radiata pine, eucalyptus globulus and eucalyptus nitens.
Radiata pine, a native of southern California, has very high growth rates in Chile – just 20-24 years from planting to harvesting compared with 50-80 years in the northern hemisphere.
Eucalyptus is native to Australia but growth rates are much higher in many other countries, from Brazil to Indonesia, Portugal to Thailand. In Chile, it takes around 12 years from planting to harvesting. TW
