ANDRITZ CircleToZero: technologies to reduce carbon emissions in tissue production

Step-by-step to carbon footprint reduction

ANDRITZ offers solutions to reduce a tissue mill’s carbon footprint in the categories of energy, fiber, water, biochemicals and digitalization. By our calculations (Figure 1) we estimate that a “typical” tissue machine using conventional technologies (e.g. suction press rolls and cast Yankee) and producing 200 t/d emits just over 47,000 tons per year of CO2eq. This is for the stock preparation system and the machine itself, and not for other upstream or downstream processes. Some of our technology modules which reduce kW/t, and therefore CO2eq/t, are shown in Figure 2. Implementing these modules, each of which has its own ROI benefits, makes it possible to reduce kW/t by up to 17% and CO2eq/t by about 15%. These are significant reductions.

Flexible and reliable tissue machines that incorporate both experience and innovation

• Modifying the approach flow system(double dilution) to reduce the energy consumed by the fan pump and screen by about 10%.
• Insulating the heads of the Yankee to reduce energy losses and to reduce steam consumption by about 5%.
• Utilizing vacuum blowers instead of water ring pumps to save about 25% energy in the main motors. The exhaust from the blowers is hot enough to be used in different heating systems and less fresh water is required to operate them.
• Installing a Rebel high-performance roll cover on the tissue suction roll can improve sheet dryness after the press of 1% and more, allowing a machine speed increase or energy savings in the drying section between 50-100 kWh/t of paper produced. The Rebel can operate without water cooling, permitting energy savings up to 25%
  of the initial roll driving power requirement.
• Installing a PrimePress XT Evo shoe press (Figure 3) to reduce fiber consumption and/or save energy. The shoe press is loaded by two pressurized hoses, allowing a mill to fine-tune the nip profile for maximum dryness, or maximum bulk, or somewhere in-between. If the goal is high dryness, the PrimePress XT Evo offers about a 6% after-press dryness gain compared to a conventional suction roll – meaning thermal energy savings of up to 24%. If the goal is high bulk at a target same dryness, basis weight or fibers can be reduced up to 10% – reducing the corresponding CO2eq emissions.
• Installing a PrimeDry YES heat recovery steam generator system (Figure 4). Our solution is to use exhaust air from a gas-fired Yankee hood and condensate from the Yankee with a steam generator (heat exchanger) to produce 15% of the steam required for the Yankee, saving up to 5% in thermal energy consumption.
  Installing a larger diameter PrimeDry Steel Yankee in combination with a steam-heated PrimeDry Hood. Steam generated with biomass is used in both systems resulting in a drying system with zero CO2eq emissions.
• Another possibility is to use biomass to generate renewable bio-syngas to replace fossil fuels when firing the Yankee burners. Sofidel, a major European tissue producer, entered into a long-term collaboration with Meva Energy to build and operate a syngas generation plant at Sofidel’s Kisa, Sweden mill, utilizing biomass as the feedstock. This will enable the mill to reduce CO2eq emissions by 8500 t/a. ANDRITZ Novimpianti air and energy and ANDRITZ burner experts are collaborating in the project, which also involves the Department of Energy of Pisa University.
• Some tissue producers are considering on-site cogeneration of electricity, especially when there are no fossil-free sources for purchased electricity. ANDRITZ offers the option to use hot air from the turbine exhaust to heat the Yankee hood, allowing conventional hood burners to be switched off (Figure 5).
• Hydrogen (either purchased or produced on-site via electrolysis) can replace natural gas and significantly reduce CO2eq emissions. Hydrogen can be used to replace 100% of the fuel used to heat the Yankee hood while also partially replacing the fuel used in a cogeneration system. Combustion of hydrogen provides a direct reduction of CO2eq and CO emissions by about 15%.

For mills located in regions where CO2eq emissions are restricted, but there is increasing consumer interest in higher quality products, a new technology PrimeLineTEX machine may be worthy of consideration. The PrimeLineTEX produces a “textured” sheet with quality much better than dry-crepe and close to TAD. The required energy is slightly higher than dry-crepe, but about one-half that of TAD. The higher quality of the TEX products, opens the possibility to substantially reduce (up to 30%) the fiber input compared to dry-crepe.

Current lab trials at the ANDRITZ Tissue Innovation and Application Center (PrimeLineTIAC) in collaboration with a global leader in chemical supply to develop sustainable and state-of-the-art bio-chemicals for tissue production. These bio-renewable products will contribute to overall carbon emissions reductions. Any tissue mill can benefit from digitalization to improve efficiencies and repeatability. Digital solutions such as ANDRITZ Metris are well suited to optimize production while minimizing a tissue mill’s total GHG emissions.