Here we look at some developments from machine suppliers that might have the biggest impact on the tissue industry.
Perini Journal
Clearly the most important leaps in tissue making technology are centered around the production of structured tissue similar to TAD, which is today recognized as the best technology for making high quality, highly absorbent tissue in large quantities. Will it be the same tomorrow? The drawback with TAD has always been the large capital expense required to install a machine, as well as the high energy consumption needed to dry this bulky, airy tissue grade.
In addition the economies of scale dictate that a new TAD installation must be a very large size to make economic sense. Thus a large quantity of TAD will hit the market all at once, and there are very few markets in the world that, until now at least, are capable of absorbing quantities on the order of 50,000 or 60,000 tons per year.
VOITH INTRODUCES ATMOS™. ATMOS™, meaning Advanced Tissue Molding System, is the name that Voith has chosen for its new tissue technology. This was covered fairly extensively last year in the Perini Journal number 27 so all of the details will not be covered here. In fact Voith is not releasing many technical details yet but will be making a big launch of the technology at Tissue World 2007 in Nice, France.
The key points about ATMOS™ are the following claims by Voith. It is patented and was mainly developed at Voith São Paulo, in close cooperation with Voith Paper Fabrics. Voith claims that the same quality as TAD in terms of bulk and absorption can be achieved for about 60% of the overall capital cost.
The cost saving for energy depends of course on the source of the energy and the unit cost but savings of 25-30% seem realistic. The key thing, says Voith, is that ATMOS™ can get 35% dryness at the Yankee transfer, compared to around 25% dryness for TAD. In addition, Voith claims, the new configuration can run on 100% recycled fiber (RCF) at speeds typical for TAD machines. It will also operate with fairly standard Yankee release chemicals.
FIRST COMMERCIAL RUN LAST OCTOBER. The first ATMOS™ machine started up successfully at a confidential customer in October 2006 with a speed of 700 m/min.
This follows a start-up plan set up by Voith together with the customer for producing 19-g kitchen towel based on 80% RCF/20% Southern Softwood Kraft. Within three weeks after the start-up, and ahead of schedule, the machine speed was increased to 900 m/min. The measured dryness values at Yankee transfer, combined with the available drying capacity, indicate that 1,100 m/min at the end of the optimization phase is achievable for this furnish.
Kitchen towel jumbo rolls with high bulk and water absorption capacity have been produced and converted after start-up. Quality analysis shows the towel grade paper produced with the ATMOS™ technology is saving approximately 10% of fiber and achieving approximately 70% higher bulk and absorption capacity than the base sheet towel paper produced by the customer with the conventional Dry Crepe technology before the ATMOS™ machine start-up.
The ATMOS™ machine gives the possibility to run ATMOS™ and/or Dry Crepe configurations. The machine is back in Dry Crepe configuration since November 2006 (after one month of ATMOS™ operation) as originally planned. The next ATMOS™ phase is scheduled for February/March 2007, with months in-between used for process optimizations, Voith says. It will be followed closely.
STT FROM METSO. Metso has been quietly working on its STT (structured tissue technology) concept for several years and has an installation at a confidential customer since end 2005. Not much is known about how it is running because neither Metso nor the customer will confirm anything or give any details. But clearly Metso is very confident that this will be a big success.
Metso claims that it is virtually impossible to tell the difference between STT and TAD. It is identical with the structured surface of through air dried product. It says it is not a halfway solution, like the shoe press, but instead true TAD quality at much lower investment cost meaning that the capital cost per ton of production is much lower.
The STT-concept is a patented swing concept capable of producing the full range of both Conventional and Structured products. It operates in Conventional mode as an Advantage "C" wrap and to convert to Structured mode requires only limited downtime. The felt is replaced with a STT fabric, the suction pressure roll is changed for solid and the vacuum boxes are raised to engage the fabrics. The Yankee spray chemicals are changed to the STT package. The STT concept is of course suitable to make all tissue products, such as bath, facial and towel of different basis weights.
VISCONIP: SOFT ON ENERGY COSTS AND THE EDGES. Metso Paper also has recently patented and launched the new Advantage ViscoNip press which uses a multi-chamber polyurethane ‘pillow’ which effectively delivers the nip pressure against the Yankee dryer. In this manner, the press conforms to the Yankee rather than the other way around.
Energy savings of around 20-30%, improved bulk that is as good or better than the shoe press and an incredibly flat dryness profile are claimed as the most important benefits. In addition, fiber savings of up to 10% are possible if the tissue maker chooses higher bulk.
The press consists of hydraulically-loaded polyurethane chambers which are positioned parallel to each other in the cross-machine direction. The chambers apply pressure to a belt which in turn presses the sheet. Cost savings for energy are clearly one of the biggest advantages of the new press. Pilot trials at Metso show a possible after-press dryness of almost 47%. Considering current energy prices, the potential for savings is enormous, says Metso, as a dryness increase of 5%, drops the energy needed for drying by more than 25%.
A clear advantage is that the press conforms to the shape of the Yankee to give a uniform nip load over a very wide range of linear loads. Thus it delivers the pressure where it is needed, in a uniform manner. It also eliminates the classic “edge effect” as the edges have always been the place where the most problems occur when using a shoe press or a suction roll.
Operating results from the first installation at Intertissue in Wales should be available soon and are anxiously awaited. First reports have been very good.
ANDRITZ INTRODUCES PRIMETAKEOFF FOR FEWER BREAKS, HIGHER SPEEDS. Andritz is known for making the extremely fast tissue machines and recent innovations continue that tradition. The most recent breakthrough is the patented Prime TakeOff.
Tissue machine speeds have steadily increased to a record 2110 mpm along with the demand for softer products with lower strengths and higher bulk. These factors make superior sheet support between the creping doctor and reel essential. Improved sheet support and better web stability means fewer sheet breaks, fewer wrinkles and higher production from the machine.
The Prime TakeOff is located under the sheet at the creping blade and immediately stabilizes the web as the sheet changes direction and leaves the Yankee Dryer. The effect of this instant support and stability is seen in the sheet through the downstream sheet path in the form of a flat and steady sheet throughout the rest of the machine.
The Prime TakeOff is retractable for sheet threading and creping blade changes. It is applicable on both rigid and flexible doctor blade holders and is beneficial for rebuilds and new machines. The Prime TakeOff has proven results on several installations on various grades including an installation in France, where the machine speed was increased 100 m/min from one day to the next.
A NEW ENTRY IN OVER’S HEADBOX FAMILY. OVER has introduced a new Dynaflo-C2 hydraulic double layer headbox for high speed tissue machines. It is partially based on the well-known Dynaflo headbox family, from which both the geometry and hydraulics of the rectifying section are taken. Other than that, all parts are new from the feeding system of the headbox, whose headers for the two layers are separated from the body itself to reduce the volumes and the overall loads on the framing.
The headers are joined to the headbox through special flexible pipes with appropriate pitch, connected to the first two explosion chambers by means of transition pieces designed to accelerate/decelerate the stock, without generating separation points. The rectifying section based on the Dynaflo concept, gives excellent sheet formation and fiber orientation.
The layer separation inside the slice area is maintained beyond the nozzle, thanks to a rigid separation blade, whose wedge can be easily removed for maintenance. By maintaining the separation of the layers as close as possible to the impingement of the jet on the wire, a good layer purity will be achieved. For the Dynaflo-C2, the free jet length is less than 100 mm. The rigid separation blade offers moreover the possibility to work with different consistencies (lip opening) in each layer, an advantage that a headbox with internal lamellas does not make possible.
PMP ADDS LOWER CAPACITY MACHINE TO INTELLI-TISSUE PROGRAM. PMP, which has in recent years been providing its Intelli-TissueTM Making Systems, has recently added a lower capacity machine to its product program. Thus it now includes the Crescent former machines with capacity starting from 34 up to 135 t/d and can be run with both virgin pulp (12-42 gsm @reel) and recycled waste papers (15.5 – 40 gsm @reel).
Therefore there are now four basic types of lines offered by PMP: Intelli-TissueTM 900, 1400, 1800 and 2100. The division was made taking the speed factor into account with 900 an entry level solution that reduces capital cost & risk to a minimum, 1400 an economical solution that is a unique combination of simplicity and technology, 1800 an optimum cost solution that utilizes proven technology and user-friendliness and 2100 a high-tech solution that gives high output with attractive return on investment.
PMT ITALIA WORKS ON SAVING ENERGY AND FIBERS. At PMT Italia recent developments of the last few years have been focused on the following issues: reduction of the energy cost in the whole process (from stock preparation to tissue machine), improvements in the quality of the paper produced, increasing efficiency of the machines, and advances in the maintenance, safety and environmental performances of the machines.
As far as the energy and fibers savings, improvements are going in the following direction:
• Producing pulpers working with medium consistency with the appropriate impeller design;
• Improved refining by installing disks more appropriate to the type of treated fibers and working on the no-load power values and on the control loop of the installation;
• Installation of motors with inverters, the positioning of appropriate control instruments, the optimisation of the process design;
• Headboxes with higher consistency, at the same quality, to save energy in the approach flow. Also offering headboxes with Consistency Profiling allows the papermakers to save fibers;
• New pressing methods to produce paper with similar qualities of the TAD products;
• Optimising the felt run design for a longer felt run and felt conditioning with a subsequent energy and maintenance cost reduction;
• Energy savings on the drying process, optimisation of the transfer system between creping blade and reel, winding at low nip loads on the reel in order to maintain bulk on the paper.
STEEL YANKEE DRYER FROM TOSCOTEC MOVES AHEAD. Toscotec has several new developments, including a multi-layer headbox and a large diameter suction press roll. It is also further developing its steel Yankee dryer (SYD). The new multi-layer headbox, available with slice widths up to 6000 mm, is said to optimize the fiber positioning in the tissue web. The main difference compared to other headboxes is the possibility to easily retrofit the headbox with a dilution control system, with the HB requiring no major modifications and the upgrade done with a very short production downtime.
A second new development is the Large Diameter Suction Press Roll whose unique characteristic is to provide a larger nip compared to conventional suction press rolls.
Maintaining improved uptime, lower capital cost and lower maintenance cost of a conventional suction press roll, this unit provides higher softness and bulk without the problems arising from the installation of a shoe press. Toscotec has advanced with its Steel Yankee Dryer (SYD), incorporating experience from conventional steel dryers with modern FEM analysis. The first SYD to be installed (ø 2500 mm) was started up in April 2000. Since then, Toscotec got the approval for ASME and EC (PED) to manufacture Steel Yankee Dryers up to 4572 mm (15 foot) in diameter with maximum steam pressures of 10 bar (145 psig). The use of high-quality steel plate instead of cast iron results in a 20 to 25% higher heat transfer coefficient. On a machine with an even drying split between Yankee and hood, the overall drying rate is 10 – 12% higher. Moreover, the same paper production can be achieved with lower steam pressures or higher SYD drying contribution, with consequent energy benefits.
For a rebuild, the SYD provides an additional feature: the ability to dry a wider sheet inside the grooves of the Yankee dryer. Many papers have illustrated the difficulties in running a tissue sheet that is wider than the ribs due to the differences in heat transfer rate at the edges. The SYD is also 30 – 35% lighter than an equivalent diameter cast iron cylinder, so the resulting civil and installation costs are lower. Toscotec recently started a 3660 mm diameter (12 foot) SYD for a confidential major multi-national tissue company and, in late 2006, started-up the first 4572 mm diameter (15 foot) dryer. This cylinder, together with other two Steel Yankee Dryers in order, will add to 10 units already successfully running in the field.•