PULP AND PAPER PROCESSES: LINDE'S OXYGEN DELIGNIFICATION & EXTRACTIVE OXIDATION
What is Oxygen Delignification?
Delignification is the act of processing the chemical structure of lignin so that it can be dissolved in the paper production process. With chlorine gradually being phased out of the bleaching process, and oxygen being the least expensive bleaching chemical in the mill, oxygen delignification offers significant operating cost advantages over delignification processes that use bleaching agents such as chlorine dioxide and hydrogen peroxide.
Savings earlier in the production process
Oxygen delignification offers significant operating cost advantages and is a recognized way to enhance yield in bleached pulp production. An important environmental impact of oxygen delignification is the reduction or elimination of adsorbable organic halides (AOX). Other benefits include lower biochemical/chemical oxygen demand. Linde provides technical support for the oxygen delignification application and will work with you to help select the appropriate system for your mill’s unique operating situation.
There are two types of oxygen delignification:
High Consistency Oxygen Delignification (HCOD) and Medium Consistency Oxygen Delignification (MCOD)
Selecting the appropriate type of delignification system involves careful consideration of each mill's unique operating situation and the balance between installation and operating costs.
Benefits of Oxygen Delignification:
- After the initial cost, lower overall bleaching and cooking chemical requirements
- AOX is reduced or eliminated from the pulping process
- Lower biological oxygen demand/chemical oxygen demand and less color in the effluent
- Better yield than extended cooking
- An important step toward total chlorine-free or elemental-free pulp production and mill closure
- Removes lignin with excellent efficiency
- Suits the production of hardwood pulps, as well as the production of softwood pulps
Reinforcing Extraction with Oxygen and Peroxide
Because the process conditions during the extraction stage are optimal for the addition of oxygen and hydrogen peroxide, Linde also offers oxygen- and oxygen-and-peroxide-reinforced extraction as an application related to delignification. Adding these components during the alkaline extraction stage reduces the chemical demand of chlorine dioxide in subsequent stages. While the addition of hydrogen peroxide improves product brightness, the addition of oxygen selectively reduces the lignin content of the pulp. Both types of extraction are applicable to all bleaching sequences.