Application of CO2 for paper mill production optimisation
We can find different phases in the paper production line where the use of CO2 for pH safe acidification leads to a relevant improvement by upgrading the drainage or recovering chemicals.
Lower the pH of the pulp to improve drainage.
Replaces the strong acids to provide more consistent control.
CO2 can be used at the pH control of the pulp at two different points.
Replace part of the compressed air with CO2 as a carrier gas during flotation.
CO2 is used to produce precipitated calcium carbonate for the production of printing paper.
pulp to have better
draining.
factor.
black solids.
After bleaching with peroxide and NaOH, the CO2 is injected to adjust the pH level to values around 7.0 to avoid brightness reversion.
CO2 is used for the pH control of the pulp near the head box of the paper machine. This pH control provides a better draining performance at the wire in the paper machine.
Flotation System
CO2 is used in effluent treatment in flotation system to replace part of the compressed air used as a carrier gas during flotation (primary treatment of fiber recovery).
As CO2 has more affinity with the liquid phase than the air, so along the process it creates small bubbles, and improves flotation during the process, improving the flotation. Efficiency can be increased by around 15%. Usually, CO2 replaces from 40 to 60% of the total compressed air used.
PCC production
CO2 is used for PCC (Precipitated
Calcium Carbonate); production,
PCC is used as a filler in the alkaline sizing papers production (print paper).
Kraft pulp pH control tower.
CO2 is used to replace strong acids (HCO2 SO4 ), and aluminium sulphate providing a smoother control, it avoids great variation at the CO2 .
It's used before or after the refining process, aiming a thin adjustment of the pH level, and consequently, a reduction of the consumption of aluminium sulphate or sulfuric acid dosed for pH control, which is, total or parcial to neutral / alkaline sizing of paper.
CO2 control to press high consistency
Special packaging paper Bags.
(bags of cement, multi-wall bags).
CO2 is used to eliminate aluminium sulphate providing a smoother control, and avoiding great variation of pH values. CO2 is used in high consistency press, aiming adjustment of the pH and, consequently improve the pulp drain-ability. The consistency expected is around 30%. A reduction on the consumption of aluminium sulphate dosed for pH control is significant. The mechanical properties of this type of paper are improved. This is very important for tear resistance of paper bags.
Testing
Nippon Gases releases Sustainability Report 2023 - 25/07/2023
Nippon Gases Europe releases its Sustainability Report for the fiscal year ending March 2023