Bleaching of Cellulose

Optimisation of the Bleaching Process in Pulp and Paper Production

The bleaching process can be tailored and optimised to meet the specific requirements of the final paper or board product. Some paper grades require a gentler bleaching sequence to preserve fibre integrity and prevent over-bleaching, while others may require a more intensive treatment to achieve the desired brightness and whiteness level.

A comprehensive understanding of the bleaching process, together with appropriate adjustments and optimisations, enables the production of high-quality paper products with tailored properties and long-term durability. This approach not only fulfils customers' specifications and performance expectations, but also supports environmentally responsible practices and promotes sustainable production methods.

Sampling and Analysis

Systematic sampling and analysis procedures before, during and after the bleaching process are important to evaluate the process efficiency and production quality as well as to compare with the customer's existing production line. A detailed description of the procedure is given below:

• Initial sampling: Samples are taken from the raw material (usually wood chips or pulp after the cooking phase) before bleaching.
• Bleaching sequence: The bleaching process is carried out according to predefined steps, adapted to the desired final product characteristics.
• Sampling between steps: after each individual bleaching step, samples are collected to assess the impact of the specific step on the pulp.
• Laboratory cooking and bleaching trials: Complementary cooking and bleaching trials are carried out using laboratory-scale equipment to simulate industrial conditions.
• Comparative Analysis: Samples before and after bleaching are compared with material from the customer's production line to identify similarities, differences and potential areas for improvement. This comparative approach provides a deeper understanding of the material's reaction to bleaching and makes it easier to detect process deviations.

Process Variables and Equipment

The bleaching process is highly customisable and the result is influenced by key variables such as pulp consistency, pressure, temperature and the choice of bleaching chemicals. These parameters can be fine-tuned to suit a range of pulp types and end product specifications:

• Pulp Consistency
• Pressure
• Temperature
• Bleaching Chemicals: A wide range of commercially used bleaching agents can be used, including chlorine-based compounds, oxygen, hydrogen peroxide and ozone.
• Bleaching Equipment: RISE uses different types of equipment, such as Quantum mixers, autoclaves and conventional water baths, to perform bleaching under controlled and repeatable conditions.
• Sample Sizes: Experiments can be performed on sample sizes ranging from small-scale laboratory batches (around 0.5 kg) to larger volumes (5-10 kg), enabling simulation of industrial processes and optimisation for full-scale production.

Capability and Scope

RISE is equipped to perform bleaching experiments on a variety of pulp types, including chemical pulps (such as kraft and dissolving grades), pre-hydrolysed kraft pulp for dissolving, mechanical pulps and plant-based fibres. By replicating factory conditions in a laboratory environment, the results generated are directly applicable to industrial operations, ensuring relevance and reliability in process development and optimisation.

Bleaching Capabilities and Expertise

RISE has the capacity to use all commonly used bleaching chemicals in its pilot equipment. These include:

• Chlorine dioxide
• Hydrogen peroxide
• Peracetic acid
• Hypochlorite
• Oxygen
• Ozone

These chemicals are used under controlled conditions to simulate industrial processes and to evaluate their effects on pulp quality, bleaching efficiency and environmental impact.

Expertise in Bleaching and Pulp Processing

RISE has a long tradition of research and technical support in pulp processes and bleaching. The organisation's multidisciplinary team of scientists and engineers has extensive expertise in a wide range of bleaching techniques, including chlorine-based bleaching, oxygen delignification and other advanced oxidative and reductive methods.

This deep knowledge enables RISE to support the development and optimisation of bleaching processes tailored to specific fibre types, product requirements and sustainability goals. Through both experimental work and process evaluation, RISE contributes to promoting efficient, high-performance and environmentally responsible pulp production.

Deliveries

RISE provides a report containing data in Excel format with associated images and graphs. The report is carefully compiled using standardised methods appropriate to the analyses performed.

If a more detailed report is required, RISE can deliver a comprehensive scientific report based on the results obtained and the background information provided by the client. This extended report is available on request and is subject to quotation.