Carbon dioxide (CO2) is an effective, easy way to regulate the pH in the wet end and improve pH stability. In addition, it eliminates the safety hazards and risk of corrosion associated with mineral acids, and is easier to handle.
Our environmentally friendly ACTICO® pH control solution provides total control over pH in the wet end, also eliminating the risk of pH shocks. Through a sophisticated combination of automation and carbon dioxide (CO2) injection systems, the ACTICO pH control technology can be tailored to individual paper machines to support process-specific parameters. It can also be deployed at different positions on the paper machine for maximum flexibility. Many of our customers prefer to regulate pH in the headbox, for instance, by dosing CO2 in the short circulation.
Benefits in general
• Tighter control over pH values and greater self-buffering capacity
• Less dissolution of calcium carbonate (CaCO3) (if solid CaCO3 is present)
• Quality gains with fewer spots and holes in the paper
• Process improvements to minimise scaling, deposits/precipitation and breaks
• Improved brightness as a result of reduced yellowing
• Reduced need for paper chemicals (retention aids, optical brightening agents (OBA), etc.)
Benefits compared with mineral acids:
• Ease of handling
• Less maintenance with lower risk of corrosion
• Safety benefits as CO2 is less hazardous than mineral acids
• Simplified process equipment with smaller footprint
Depending on the individual process flow, additional benefits are also feasible. Reference customers who switched from sodium bisulfite (NaHSO3) to CO2 for acidification of peroxide-bleached mechanical pulp reported a significant drop in costs in addition to the usual stabilisation of pH and an end to pH excursions. Another customer also reported significant cost savings after switching from sulfuric acid to CO2 as OBA was no longer needed for pulp and the lower pH reduced pulp yellowing. And a specialty fine paper mill found that switching to CO2 halved their alum requirements for rosin sizing, also significantly reducing CaCO3 dissolution and resolving problems with plugging of the holes in the suction roll and felt filling (both in the press section).
Experience has also shown that ACTICO pH control, when combined with ADALKA® process stabiliser, can adjust process water hardness to fresh water level, while reducing paper spots (by up to 80%), deposits, OBA needs and energy requirements – all with increased productivity.
To maximise the efficiency of our ACTICO pH control application, we developed bespoke ACTICO injectors and dissolving systems. In conjunction with our ACTICO flow control unit for optimum CO2 dosing, they ensure that the CO2 is homogenously dissolved in the process water.