Chlorine Dioxide Generation
Chlorine dioxide is widely used in the bleaching of kraft pulp. It reacts readily with lignin and does not significantly react with cellulose fibers, so it produces strong, stable, clean, high-brightness pulps. However, because chlorine dioxide is unstable as a gas and can only be stored in very dilute water-based solutions, it must be generated on-site.
This course covers some early commercial chlorine dioxide generation processes in addition to the processes that are currently in use. It also discusses the conditions that can cause chlorine dioxide to decompose and other safety considerations.
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Learning Objectives
By the end of this course, you will be able to:
- Define the general reaction for generating chlorine dioxide
- Identify and describe the chemicals used for chlorine dioxide generation
- Recognize the by-products of chlorine dioxide generation
- List the advantages of the R8 process over previous processes
- Identify the equipment used in the R8 process
- List the advantages of the SVP-HP and R10 processes over the R8 and SVP-Lite processes
- State the conditions that can cause chlorine dioxide decomposition
- Describe safety considerations for chlorine dioxide generators
Specs
| Course Level | Intermediate |
| Languages | English, Portuguese, French, Polish, Russian |
| Compatibility | Audio, Video, MobileReady, Responsive |
| Based on: | Industry Standards and Best Practices |
Key Questions
Why is chlorine dioxide generated on-site?
Chlorine dioxide gas is very unstable, so it cannot be transported in high concentrations. It is stored at about 1% on-site.
How is chlorine dioxide gas created?
Chlorine dioxide gas is created by the reduction of sodium chlorate in a strong acid solution.
What is the main chlorine dioxide generation process in use today?
The two main processes are called R8 and SVP-LITE. They both operate under vacuum conditions and use methanol as a reducing agent.
What are the main pieces of equipment for chlorine dioxide generation?
There are several pieces of equipment in the R8/SVP-LITE process: a circulation pump, generator, reboiler, salt cake filter, condenser, absorption tower, and a vent gas scrubber.
What is a puff?
A puff is an explosion that occurs when chlorine dioxide gas decomposes. The severity is proportional to the concentration of chlorine dioxide gas in air.
Sample Video Transcript
The reaction in the generator forms sodium sesquisulfate crystals. These crystals are pumped from the bottom of the generator to a rotary drum filter to remove water. Water is used on the filter to remove and recover reaction chemicals. The filtrate is returned to the generator, and sodium sulfate crystals are dissolved in hot water. The salt cake can then be used in the pulp mill recovery system. The R8 and SVP-Lite processes produce 40% less salt cake than the R3 and SVP processes.
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