At the end of this module, you will be able to:
- State the benefits of ozone bleaching (compared to other chemistries)
- Describe ozone bleaching chemistry
- Explain how ozone is generated
- Explain how ozone bleaches pulp
- Identify important ozone bleaching variables
- Identify and describe ozone bleaching processes and equipment
- Identify and describe safety hazards and safe work practices associated with ozone bleaching
The following key questions are answered in this module:
How is ozone generated?
Ozone is created by applying high voltage to a gas that contains oxygen.
What are the advantages of ozone bleaching?
Ozone provides several economical and environmental benefits over chlorine dioxide and other bleaching chemicals. It can be formed from oxygen, it is a strong oxidizer, and reacts quickly with pulp.
Does ozone bleaching require special equipment?
Yes, the equipment depends on the pulp consistency. High consistency is most popular today. A special horizontal reactor is used instead of a large conventional tower because the reaction is fast. A wash press, or similar equipment, is needed to achieve high consistency.
What process variables are important for ozone bleaching?
Temperature, pH, consistency, and mixing all impact the efficiency and selectivity of ozone bleaching.
Is ozone hazardous?
Ozone is toxic even at low concentrations and at high concentrations it can explode. The concentration of ozone gas in air must be continuously monitored.
Below is a transcript of the video sample provided for this module:
Because ozone gas is unstable and cannot be stored, it is manufactured-on-demand. Ozone is created by applying high voltage to a gas that contains oxygen. For pulp bleaching, pure oxygen is used so a high concentration, 10 to 12% of ozone can be generated. Electrons travel across a gap between electrodes. When oxygen molecules collide with the electrons, they break apart into individual oxygen atoms. The individual atoms attach to molecular oxygen and form ozone.
Use the additional resources and links below to learn more about this topic: