Advanced TAD technology for premium tissue grades (ATAD)

SOFT TISSUE, HARD ENERGY REALITY 

Through-air drying (TAD) has been celebrated in the tissue industry since the 1960s for delivering premium products with superior bulk, strength, absorbency, and softness. However, TAD's Achilles' heel has been its significantly higher energy consumption compared to conventional tissue production processes. This energy intensity has limited the technology’s adoption, particularly outside regions like North America, where energy costs are significantly higher.

ANDRITZ has tackled the TAD energy challenge head on by launching Advanced TAD (ATAD), a groundbreaking innovation designed to slash energy use in the TAD drying process by more than 20%. Crucially, the energy reduction takes place while preserving the premium quality that makes TAD so appealing. Developed through years of research and testing at the ANDRITZ state-of-the-art PrimeLine TIAC pilot plant in Graz, Austria, ATAD addresses the core challenge head-on by removing more water from the sheet before it enters the energy-intensive TAD drying section.

Paul Richards, Senior Technology Manager Tissue and Grade Owner for TAD & Hybrid technologies at ANDRITZ explains, “Since starting the TAD journey, our goal has always been to target maximum energy efficiency. That is why our standard offering for TAD includes an impingement drying hood over the Yankee. Energy efficiency has caused producers and chemical suppliers to cooperate and drive the exit solids from the TAD process downwards. Drying beyond the 65-70% level is more energy demanding using through-drying, but more efficient when using high velocity impingement drying.

“The ATAD concept is straightforward in theory: remove as much water as possible from the sheet before it reaches the first TAD drum. Although TAD technology has been around for over 30 years, the pre-TAD section dewatering has long represented a process limitation, with only one proprietary process from a major producer demonstrating a viable solution. We set out to develop an alternative that leverages ANDRITZ’s deep expertise in both tissue and broader paper industry technologies.” 

ENERGY AND EMISSIONS REDUCTION, ALONG WITH TOP QUALITY RESULTS 

The dedicated pilot machine in Graz is set up to be very flexible for various concepts. Therefore, ANDRITZ has extensively tested the ATAD concept regarding energy consumption against different TAD concepts available on the market. Boris Jancic, ANDRITZ’s Head of Operation Tissue Pilot Plant, explains, “The results of ATAD have been remarkable. Depending on the grades produced (bathroom or towel tissue), the energy savings based on steam, gas, and electrical from vacuum pumps and air system fans were measured between 6 and 16% reduced consumption.

“The 5 or 6% pre-TAD solids increase, which means solids above 30% ahead of TAD 1 drum, are not a dream, but on our pilot machine, repeatable and proven results. These results have been achieved after three years of intensive R&D activities and concept improvements. Additionally, trial results confirmed that further solids improvements are possible but testing on our pilot machine was limited by some mechanical components.”

To address concerns that the pressing of the paper sheet could have a negative impact on sheet quality, especially caliper, ANDRITZ carried out extensive laboratory work on the quality of the products produced with the ATAD concept. Jancic adds, “Final analyses showed that with the ATAD paper samples produced were equally comparable with samples produced using standard TAD processes.”

On the sustainability factors of ATAD, Franz Harrer, Director Global R&D and Pilot Plant Operations at ANDRITZ Paper & Tissue says, “CO₂ emissions in TAD are largely tied to gas consumption for heating the hot air that evaporates water in the TAD section. By removing more water mechanically upfront, less evaporation is needed, directly lowering emissions generated from use of fossil fuels. Depending on the split between gas and electricity used for drying, CO₂ reductions of up to 15% or more are achievable. We're also advancing use of electrification and heat recovery options to improve this further.” 

INSTALLATION AND OPERATION – SIMPLICITY IS KEY 

“Our primary goal with ATAD has been universal applicability,” says Richards. “While ideal for new ANDRITZ PrimeLine TAD machines, ATAD technology is designed for retrofit on existing TAD lines – even those from other OEMs. We have kept the whole concept extremely simple, using known components and processes to minimize costs and complexity.”

For operators, ATAD is straightforward: initial setup resembles any suction roll. It adds equipment, for example, an extra fabric loop, but the energy savings more than justify the additions to the process. The system reuses waste heat from the Yankee or TAD exhaust, and the steam shower simply heats the fabric-sheet-felt sandwich quickly. Controls are basic – no complex profiling is needed initially, though adaptable if required.

Richards concludes, “TAD must become more affordable and sustainable to expand beyond North America, where cheap energy has masked inefficiencies. ATAD reduces the energy load significantly, but it's part of a bigger picture. Many existing TAD machines – especially some operating without Yankee hoods – rely heavily on TAD for the final drying stages, which is inefficient. Combining ATAD's wet-end dryness gains with further energy optimizations such as impingement drying with Yankee hoods can dramatically amplify energy savings.”