The Future of Paper Drying… with Today’s Technologies

The paper industry is continuously working on new and better ways to improve the complete papermaking process, especially as demands grow for CO₂ savings and sustainability. This means that paper will always be a product for the future.

Fig. 1: Shipping of produced rolls/dryer cans from Shanghai, China, to Atlanta, GA, results in lower CO₂ emissions than a comparable route from Saarland, Germany, to Atlanta. Routes to Sao Paulo, Brazil, are also compared.

Drying is a main area of interest. Different scientific organizations work on the concept of “producing drier paper,” saying the amount or percentage of water going with the fiber onto the “wet section” must be reduced significantly. This would be a game changer for paper production technology, but it remains unclear when it will be ready for large-scale production or widely adopted by paper mills. This research could take decades. Nevertheless, such a change would revolutionize paper mill design and reshape the business models of machineries and suppliers.

THE HYDROGEN ALTERNATIVE

As an alternative, there are conventional and more immediately applicable commercial, off-the-shelf technologies available to help paper mills reduce their CO₂ emissions. One promising solution is the use of hydrogen as an energy carrier for central boilers or steam houses. This is already being discussed, but it is essential that the hydrogen is “green”, meaning it is produced only using renewable energy. The second challenge, perhaps the greater one, is hydrogen distribution. In Germany, paper mills are preparing their boiler houses for multi-gas operation with natural gas and hydrogen. This technology won’t change paper production itself.

In October, 2024, the German government released the overall National Hydrogen Strategy (Nationale Wasserstoffstrategie), which lays out the master plans for a hydrogen pipeline network in Germany. This network will not be able to supply all industries; there will still be industry areas with no access to hydrogen, either due to insufficient hydrogen capacity or because the mill is too far off the main pipeline, making an access point impractical.

GOING ELECTRIC

Another alternative approach is to fully electrify paper machines, including energy supply for steam production or drying. The authors are aware of at least one tissue machine that was set to start operating with this technology by the end of 2024.

The claim of “zero-emissions” is only valid if the electricity used is coming 100 percent from renewable sources. This strategy of retrofitting tissue lines could serve as a blueprint for other paper grades. Energy availability remains a critical discussion point, as this also holds a mirror to discussion about energy availability in various societies and nations. Norway generates more than 90 percent of its electricity from hydropower, which provides a stable, controllable supply. In Southern Europe, solar power is a key resource, but energy storage for continuous 24/7 operation must still be addressed.

Two contrasting examples stand out: Germany, which stopped using nuclear power in April, 2023, and plans to also shut down coal-fired power plants, aims to lead by example for other industrial countries. Meanwhile, tech companies in the US are investigating whether to start or restart nuclear power plants to provide CO₂-neutral power, especially for the growing demand from AI-applications. There is possibly no wider spread of the interpretation of CO₂-free electric power supply.

Other technical solutions—such as de-centralized, heated dryer cans—may never make it into the machine hall, or at least not until the industry develops a completely new papermaking process; some new paper drying technologies must wait for new paper process technologies. In general, no one technology is likely to satisfy all the needs of politicians, environmentalists, papermakers, and consumers. Mills may be forced to have different options available to run the line.

THE CASE FOR STEEL DRYERS

As long as steam is the energy for paper drying, the drying section must operate at the highest possible level. The well-known demands to the drying section will not change; they will only become of greater importance.

The use of casted dryers is like racing NASCAR with a carburetor from the 1970s. We strictly recommend that new PM lines and rebuilds use steel dryers at all positions, as they ensure 7-10 percent improvement in drying performance. The benefit of a significant increase in drying capacity is often discussed and proven. The full machine layout becomes leaner, cheaper, and less resource intensive. It is interesting to note that productivity, costs, and sustainability work together in the same direction.

In addition to energy supply solutions, it becomes crucial to minimize emissions from the production of papermaking materials, machinery, and equipment when further optimization of the process itself is no longer possible. Tracking the product CO₂ footprint helps papermakers identify where major emissions occur, which is especially relevant for the paper industry when investing in new equipment.

Analyzing emissions during the manufacturing process of drying cylinders—including raw material extraction (steel), preprocessing, production, and logistics—reveals that European manufacturers generally have a smaller CO₂ output compared to regions in Asia. This difference is largely attributed to a more sustainable steel production process. Studies by German authorities have shown that German steel production has a 20 percent lower CO₂ output compared to Asian production, primarily due to stricter environmental regulations and more efficient supply chains.

Additionally, the CO₂ footprint can be further reduced due to shorter transport distances within Europe. For example, Germany’s highly developed logistics network provides low-emission transport options, and the supply chains are generally more transparent, ensuring a reliable flow of information.

Using the ISO 14083 standard, which establishes a framework for calculating and comparing emissions across transportation modes and routes, transport emissions were calculated for a 20.000 kg shipment (see Fig. 1). Shipping from Shanghai, China, to Atlanta, GA, results in approximately 3.900 kg of CO₂ emissions, whereas a comparable route from Dillingen in Germany to Atlanta generates around 2.400 kg. This demonstrates the environmental benefits of shorter transport distances and production within Europe. Political measures, such as support programs for sustainable technologies and the introduction of CO₂ prices, support these efforts and promote more environmentally friendly practices in the industry.

It is important to note that while these emissions analyses are valuable, they could be somewhat overshadowed by the fact that the energy used throughout the lifetime of the drying process will likely exceed the emissions associated with the material production.

COMPARING TCO

While these discussions address one-time costs, total cost of ownership (TCO) considerations are often overlooked. Lighter steel dryers, for example, reduce bearing loads, require less drive energy, and minimize additional screen load on towed cylinders. In addition, the lower mass saves steam in heating the cylinders, allowing the machine to resume production more quickly after a shutdown, increasing overall availability.

Another key step in the evolution of drying technology is the requirement that dryers be “ready-for-and-fitted-with” heat insulation to reduce heat losses over the headplates. There is no other equipment in the drying section that offers an opportunity for such a rapid ROI.

For instance, losses at the cylinder heads are reduced significantly (Fig. 2) with the Energy and Safety Device #ESD, introduced by German roll maker KRAFFT Walzen. The energy of the expensive high-pressure steam stays in the cylinder and does not dissipate into the hood, where there is usually enough warm air already.

Despite the advanced technologies discussed here, even something as simple as metal sheets for heat insulation can help save 2-5 percent of energy costs (see Fig. 3). Assuming a five percent reduction of losses, the annual saving could top US$100 thousand and help reduce CO₂ emissions by about 3,500 tpy.

To illustrate the benefit, imagine turning off steam on Christmas Eve and your system is still producing dry paper on New Year’s morning. This highlights the significant energy-saving potential of modern insulation techniques and benchmark dryers.

The German supplier Carl KRAFFT & Söhne has delivered more than 300 of its #KSD steel dryer systems to mills in the US. All these dryers follow this example of the best steel with the lowest CO₂ footprint, most efficient supply chains, and lightweight systems with the highest drying efficiency and lowest energy losses. Driven by design that has already been established, these concepts are ready for the future, as they allow papermakers to fulfill the latest sustainability demands.