Different bleaching processes of paper & pulp industry

The main types of pulp bleaching processes are as follows:

1. Chlorine bleaching: This is a traditional bleaching process that uses chlorine gas or chlorine compounds (such as chlorine gas, sodium chloride) as bleaching agents. However, chlorine bleaching produces toxic organic chlorides and chlorinated compounds, causing negative environmental impacts. Therefore, it has gradually been phased out.

2. Enzyme bleaching: Enzyme bleaching uses specific enzymes to remove pigments and impurities from the pulp. This method is relatively mild and environmentally friendly, but the bleaching effect is relatively weaker.

3. Oxygen bleaching: Oxygen bleaching uses hydrogen peroxide (also known as oxygenated water) or other oxidants to bleach the pulp. This method is relatively environmentally friendly and does not produce toxic by-products, but it requires a longer time and high-temperature conditions.

4. Ozone bleaching: Ozone bleaching uses ozone gas to bleach the pulp, which has a higher bleaching effect and speed. Ozone bleaching is relatively environmentally friendly, but the generation and use of ozone have higher costs.

5. Chlorine dioxide bleaching: Chlorine dioxide bleaching uses sodium chlorate or other chlorate salts as bleaching agents. Compared to chlorine bleaching, chlorine dioxide bleaching produces fewer organic chlorides and chlorinated compounds, resulting in less environmental impact.

6.

• Hydrogen peroxide bleaching: Hydrogen peroxide bleaching uses hydrogen peroxide as a bleaching agent, which has good environmental performance. It can be combined with other bleaching agents (such as ozone) to improve the bleaching effect.

In practical applications, a combination of multiple bleaching processes is often used to achieve the desired bleaching effect and pulp quality. Additionally, the selection and adjustment of bleaching processes need to consider factors such as the type of pulp, its intended use, and environmental requirements.

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