Bleaching chemicals

Chlorine dioxide is widely used in modern chemical pulp bleaching. It preserves pulp yield and gives superior pulp strength compared to other oxidants, due to it attacking only the aromatic ring of the lignin and not reacting with carbohydrates.

Chlorine dioxide is the most widely-accepted bleaching agent for the environmentally-preferred ECF (elemental chlorine free) chemical pulp bleaching process. It functions via oxidative reactions, eliminating the formation of chlorinated organic compounds.

Chlorine dioxide is produced from sodium chlorate using different reducing agents, typically on-site at the pulp mill. Kemira is able to provide custom-tailored alternatives for chlorine dioxide supply, offering our customers the ideal configuration.

Kemira’s distilled peracetic acid dPAA is a delignifying and brightening agent for the production of TCF and ECF pulps. It is also an excellent product for post-bleaching of pulps, ensuring fiber quality that meets downstream needs. Kemirox DP can help you reach brightness targets when bleaching is a bottleneck in the process.

Post-bleaching of pulp with dPAA helps

• eliminate pulp brightness variation
• prevent post-bleach yellowing
• reach brightness targets
• ensure cleanliness of pulp
• improve retention of wet end chemicals
• reduce consumption of optical brighteners and biocides
• improve dewatering

Hydrochloric acid is a multipurpose raw material that is used in the pulp and paper industry but also in chemical, metal, and food industries. It is a reducing agent for the on-site production of chlorine dioxide from sodium chlorate.

Other applications for hydrochloric acid are pH adjustment, production of chlorite slats, surface treatment of metals, and recovery of ion exchangers.

Hydrogen peroxide is mainly used as an oxidative bleaching agent for chemical, mechanical, and recycled pulp. It is both a strong oxidizing agent and a reducing agent. Kemira is one of the major producers of hydrogen peroxide in the world and has wide experience in using hydrogen peroxide in bleaching applications.

Chemical pulp bleaching

• is used for the production of TCF and ECF pulps
• good alternative for delignification and bleaching in the bleaching plant

Mechanical and chemi-mechanical pulp bleaching

• achieve a wide range of brightness suitable for high grade magazine papers, boar, and tissue products

Recycled fiber bleaching

• increase brightness ceiling, decrease brightness variation and avoid yellowing of the final pulp
• use either in the deinking process or in a separate bleaching stage

KemBorino is an alkaline aqueous solution with 12% sodium borohydride and 40% sodium hydroxide. It is an easy and economical way to generate sodium dithionite for the bleaching of mechanical pulp. Kemira can supply the dithionite generation unit and provide technical service.

KemBorino can also be used together with sodium bisulphite instead of sulfur dioxide. KemBorino bleaching is a reductive technology, which can be used both in pulp brightening and color stripping of deinked pulp. The reaction is based on the combination of sodium bisulphite and KemBorino, which are dosed straight into the pulp flow, generating sodium dithionite in-situ.

Sodium bisulfite is a reducing agent that is used in similar applications as sulfur dioxide. In the pulp and paper industry, it is used as a sulfonation agent in chemical thermo-mechanical pulp production. Sodium bisulfite is also well-suited for removing residual bleaching chemicals.

Sodium bisulfite is also used together with KemBorino™ to generate sodium dithionite for mechanical pulp bleaching.

Sodium chlorate is used for the on-site generation of chlorine dioxide, the key bleaching agent for the environmentally-preferred ECF chemical pulping process. Chlorine dioxide is produced from sodium chlorate using different reducing agents, such as hydrogen peroxide, sulfur dioxide, methanol, and hydrochloric acid.

Kemira is one the largest manufacturers of sodium chlorate in the world, producing high quality sodium chlorate that is ideal for chlorine dioxide production.

Sodium hydroxide or caustic soda is a strategic raw material in various industries and applications. In the pulp and paper industry, sodium hydroxide is used in pulp cooking.

Kemira’s sodium hydroxide is produced using the environmentally friendly membrane technology. We have access to all grades of caustic soda to meet our customer demand, but the main grade of imported caustic soda is membrane as 50% solution.

Our services include also logistics services (shipping, terminal, and land transport), which allow our customers to source the product themselves and utilize the cost efficient Kemira supply chain.

Sulfuric acid is the most commonly used chemical in the world. In the pulp and paper industry, sulfuric acid is used for the on-site generation of chlorine dioxide, the key bleaching agent for the environmentally-friendly ECF chemical pulping process. It is also used for tall oil splitting and pH adjustments.

Kemira’s high quality sulfuric acid production is completed with best-in-class logistics solutions. (shipping, terminal, and lad transport), which allow our customers to source the product themselves and utilize the cost efficient Kemira supply chain.

Sulfur dioxide has strong reducing properties. It is valuable chemical in various chemical process and in the production of bleaching chemicals, for example on-site generation of chlorine dioxide and sodium dithionite.

It is also well-suited for the elimination of residual hydrogen peroxide or chlorine dioxide in the final stage in the pulp bleaching process.