Bleaching of Cellulose

Purpose

Bleaching of cellulose is a central process in the paper and pulp industry, where the aim is to remove unwanted colorants and impurities from raw materials such as wood pulp or recycled paper. The process is crucial for producing paper and paperboard with high quality and desired brightness.

Bleaching can be carried out through various methods, including chemical bleaching and more environmentally friendly alternatives such as oxygen compounds and hydrogen peroxide. The most common chemical bleaching agents include chlorine, chlorine dioxide, and alkaline peroxide.

During the bleaching process, colorants and other impurities are broken down or removed from the cellulose fibres. This is achieved by breaking down the cellulose structure and oxidizing or chemically modifying colorants to reduce their visibility. The result is a cleaner and brighter pulp suitable for the production of high-quality paper products.

The bleaching process can be customized and optimized depending on the requirements for the final paper or paperboard. Some types of paper require a gentler bleaching to preserve fibr strength and avoid over-bleaching, while others require a more aggressive bleaching to achieve the desired brightness and whiteness.

Effective and accurate monitoring of the bleaching process is crucial to ensure desired results are achieved. This includes regular analysis of samples to monitor the degree of bleaching, control the effectiveness of bleaching agents, and identify any deviations or issues in the process.

By understanding the bleaching process and making necessary adjustments and optimizations, the paper and pulp industry can produce high-quality products with desired properties and durability. This not only helps meet customer requirements and expectations but also reduces environmental impact and promotes sustainable production methods.

Performing sampling and analysis before and after the bleaching process is crucial to assessing the effectiveness and quality of bleaching, as well as comparing with the customer's existing process. Here is a more detailed description of the process:

Sampling Phase: Before the bleaching process begins, samples are taken from the raw material (usually chips or pulp after cooking). These samples represent the original state of the material and are used as a baseline to assess changes that occur during bleaching.

Bleaching Process: After the samples are taken, the bleaching process is carried out according to the planned bleaching stages. This may include different bleaching agents and reaction conditions depending on the desired degree of bleaching and final product quality.

Sampling Step after Each Bleaching Stage: After each bleaching stage, samples are taken from the bleaching process to assess the effect of that specific bleaching stage. This allows for monitoring and adjustment of bleaching parameters to achieve the desired degree of bleaching and product quality.

Cooking and Bleaching Trials in Relevant Equipment: After the bleaching process is complete, corresponding cooking and bleaching trials are performed in relevant equipment. This could be equipment similar to that used by the customer or typical of the industry. By replicating the process in relevant equipment, it ensures that the results are comparable to the customer's line.

Comparison with Customer's Line: The analyzed samples before and after bleaching are compared with samples from the customer's line to assess similarities and differences. This provides a deeper understanding of how the bleaching process affects the material and enables identification of any deviations or areas for improvement that may need to be addressed.

By following this rigorous methodology, it ensures that the bleaching process is effective and that the product meets the desired quality requirements. This is crucial for producing high-quality paper products and meeting customer expectations and requirements.

Variations in conditions such as pulp consistency, pressure, temperature, and different bleaching chemicals enable a versatile bleaching process that can be tailored to different types of pulp and desired outcomes. Here is a more detailed description of the variables that can be adjusted and the different bleaching equipment used:

Pulp Consistency: Pulp consistency, or the density of the pulp, can be varied to adjust the bleaching process to specific needs. By changing the consistency, factors such as bleaching degree and reaction rate can be affected.

Pressure: Variations in pressure can be used to regulate the temperature in autoclaves and thereby influence the bleaching reactions. Pressure can also be used to increase the reaction rate and improve bleaching results.

Temperature: Temperature is a crucial factor in the bleaching process as it affects the speed and efficiency of bleaching reactions. By varying the temperature, the desired bleaching degree and quality of the final product can be achieved.

Bleaching Chemicals: All commercially used bleaching chemicals can be used in the bleaching process to achieve different results and properties in the final product. This may include chlorine bleaching, oxygen bleaching, peroxide bleaching, and ozone bleaching.

Bleaching Equipment: RISE uses various bleaching equipment such as Quantum mixers, autoclaves, and conventional water baths to perform bleaching experiments under controlled conditions. These equipments enable different bleaching methods and parameters that can be tailored to specific needs.

Sample Size: The sample size can vary from small amounts (0.5 kg) for laboratory experiments to larger batches (5-10 kg) to simulate production conditions and optimize the process for industrial scale.

RISE can therefore carry out bleaching of various types of pulps, including chemical pulps (wood pulp and dissolving cellulose), pre-hydrolyzed sulfate cellulose for dissolving, mechanical pulps, dissolving, and plant fibers. By applying the same conditions in the laboratory as in the factory environment, RISE ensures that the results obtained are relevant and transferable to the production process

Methods and Expertise

RISE has the capability to use all common bleaching chemicals in its pilot equipment for bleaching. These chemicals include:

Chlorine dioxide: Chlorine dioxide is a powerful bleaching agent used to bleach cellulose-based materials. It is effective in removing colorants and other impurities from pulp and typically provides a high degree of bleaching.

Hydrogen peroxide: Hydrogen peroxide is another common bleaching chemical used to bleach cellulose-based materials. It is a milder bleaching method compared to chlorine dioxide and is often used to preserve the strength of pulp and the integrity of fibers.

Peracetic acid: Peracetic acid is a chemical used as an alternative to hydrogen peroxide for bleaching pulp. It provides effective bleaching and can be used in combination with other bleaching chemicals to achieve desired results.

Hypochlorite: Hypochlorite is a chemical compound containing chlorine and used for bleaching various materials, including pulp. It is an effective bleaching chemical but can be aggressive towards fibers if not used correctly.

Oxygen: Oxygen or oxygen-based bleaching is an environmentally friendly bleaching method that uses oxygen to bleach cellulose materials. It is a milder bleaching method that does not produce as much waste as other chemical bleaching agents.

Ozone: Ozone is another environmentally friendly bleaching method that uses ozone molecules to bleach cellulose-based materials. It is a fast and efficient bleaching method that leaves no residual by-products.

By using these different bleaching chemicals in pilot equipment, RISE can evaluate their effectiveness, compare their performance, and optimize the bleaching process for different types of pulp and other cellulose-based materials. This allows for tailoring the bleaching process to achieve desired results in terms of bleaching efficiency, paper quality, and sustainability.

Expertise:

In bleaching and pulp processing, RISE has a long history of conducting research and providing expertise. Our team of researchers and engineers possess broad and deep knowledge of various bleaching methods and pulp processes, including chlorine bleaching, oxygen bleaching, and other advanced techniques used to produce quality paper and pulp.

Our high expertise in bleaching and pulp processing is reflected in our successful collaborations with companies in the paper and pulp industry and their contributions to the development of sustainable and environmentally friendly production methods. With a strong track record of groundbreaking research and practical application, RISE is a respected authority in this field.

Deliveries

RISE offers a report that includes data in Excel format and relevant images and diagrams. It is carefully compiled using standard methods for the conducted analyses. The report also includes an assessment of measurement uncertainty to ensure the reliability of the presented results. All relevant parameters significant to the specific analysis are included to provide a comprehensive picture of the situation. Additionally, detailed comments and explanations are provided to offer further insight and understanding of the presented data.

Standard Report (Quotation):

RISE provides a comprehensive report where results are presented in a clear manner through concise but informative sections with clear diagrams and tables. This report structure is designed to make it easy for customers and stakeholders to quickly grasp the presented results without having to delve into extensive texts.

In-depth Report (Quotation):

If desired, there is an option for a more detailed report on quotation where RISE has the capacity to create a more detailed scientific report based on the results and background information provided by the customer. This report may include an in-depth analysis of data, extensive discussions on methodology and results, as well as a thorough assessment of relevant factors and contexts. By utilizing the latest research and expertise in the field, RISE can provide a thorough understanding of the observed results and their implications.