Chlorine Dioxide Bleaching
Chlorine dioxide is an excellent bleaching chemical because it is very selective for lignin. Because of this, its use has expanded greatly over the last few decades. This course discusses the purpose of chlorine dioxide bleaching and the basics of chlorine dioxide bleaching chemistry. It also describes the equipment used in chlorine dioxide bleaching, as well as the typical ECF bleaching sequences such D0, D1, and D2 along with their differences.
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Course Details
Learning Objectives
• Describe the purpose of chlorine dioxide bleaching
• Describe the basics of chlorine dioxide bleaching chemistry
• Explain how pH affects chlorine dioxide bleaching
• Explain how temperature affects chlorine dioxide bleaching
• Identify and describe equipment used for chlorine dioxide bleaching
• Identify typical ECF bleaching sequences
• Identify and describe differences between D0, D1, and D2 stages
• Describe modification required for hardwood bleaching
• Describe the safety hazards and safety guidelines for chlorine dioxide
Specs
Frequently Asked Questions
Why is chlorine dioxide generated onsite?
What is ECF bleaching?
What is the best pH for a D0 stage?
How should chlorine dioxide be distributed among the different D stages.
What are some safety concerns with using chlorine dioxide?
Sample Video Transcript
Chlorine dioxide is an excellent bleaching chemical because it is very selective for lignin. However, it is relatively expensive, so chlorine dioxide was originally used in later bleaching stages where there is low lignin content to produce pulp with a high, stable brightness without compromising strength. Over the last few decades, the use of chlorine dioxide has expanded. At first, chlorine dioxide was used to protect pulp strength by replacing 5% to 10% of the chlorine. It was later found that substituting up to 50% chlorine dioxide improved the delignification efficiency. To reduce the environmental impact of using elemental chlorine, chlorine dioxide has essentially replaced chlorine and become the foundation of elemental chlorine-free, or ECF bleaching. Because chlorine dioxide reacts much differently with pulp than chlorine, the production of harmful dioxins is less than 2% of that created by chlorine.
