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IN THE FRONT LINES OF PULPING RESEARCH

Author

Johan Bryntesson

Company

Kvaerner Pulping AB, Sweden

Keywords

pulping, fibreline, design, research, pulp quality, profitability, environmental factors

 

 

 

 

INTRODUCTION

Pulp manufacturers worldwide are continuously facing increasing demands from customers, owners and environmental agencies. The ability of implementing new technology is an important factor of how successfully pulp manufacturers cope with these challenges.

This paper will give ideas of how to improve pulp quality, increase profitability and to improve environmental parameters, objectives of interest to every person involved in fiberline operations. In addition, the paper will also give a historic perspective of how the fiberline design has changed throughout the last decades, a view of where future R&D activities are heading and what type of technology that has been implemented in some recently built fiberlines.

R&D drivers

R&D activities in the pulp and paper industry have traditionally mainly been done by universities, institutions, manufacturer´s own corporate R&D facilities and suppliers. During the last years there is trend that manufacturers in general focus less on R&D efforts into the field of pulp technology. This means that the R&D activities of the other actors, not least the suppliers, have become more important.  

Drivers for R&D work are:

  • Product quality improvements
  • Reduction of investment, operation and maintenance costs
  • Meet environmental demands/standards
  • Scale of economy / Larger capacity

Historic perspective of fiberline design

The following three illustrations show the differences between three fiberlines started-up in 1978, 1992 and 1997. When they were built they were all in the front line regarding technology at that time.

Figure 1

Picture 1. Fiberline started up 1978

Figure 2

Picture 2. Fiberline started up 1992

Figure 3

Picture 3. Fiberline started up 1997

When analysing the three fiberline systems it can be concluded that new technology has had impact on fiberline design in the following aspects:  

  • Modified cooking processes have been introduced.
  • Use of oxygen delignification system is considered to be industry standard. The first installations were one-stage systems but now there seems to be a preference for multiple stage systems.
  • Introduction of oxygen delignification systems puts focus on efficient post-oxygen washing systems.
  • Omissions of the use of elemental chlorine in the bleaching process
  • Technology shift in type of washers used.
  • Bleach sequences are shortened.

Examples of recent fiberline innovations

The already mentioned drivers for R&D activities do also fit very well in a list of R&D objectives. Simplicity is another objective that should be added to the same list. Below follow examples of recent innovations to be used in fiberlines. 

COMPACT FEED

Figure 4

Picture 4. Conventional and Compact Feed

The compact feed is a simplified chip feeding system to be used in continuous cooking systems and requires less equipment and less building space than the conventional chip feeding system. The HP-feeder and the liquor circulations are modified.  The system enables also a higher filling degree in the HP-feeder, which means an increased capacity for the feeder.

DUALOX

Figure 4a

Picture 4a

It is well known that the oxygen delignification process is characterised by an initial phase followed by a bulk phase. Having this knowledge the challenge is to create optimal process conditions for each of the different phases to achieve the best overall performance of the oxygen delignification system. This is what is done in the Dualox system. An enhanced oxygen delignification process and simple process design are the main features.

Figure 5

Picture 5. Oxygen delignification development

DualD

Since brightness and brightness stability are important pulp properties for HW pulp producers the phenomenon of yellowing haunts many ECF HW pulp producers. When analysing the components of normal kappa number HW pulp entering the bleach plant a relatively large part of Hexenuronic acids is found. These acids play an important role for the yellowing of pulp.  This process  minimizes the yellowing problem. Other advantages with the process is lower chlorine dioxide consumption and higher brighness ceiling.

Figure 6

Picture 6. Analysis of hardwood pulp components

COMPACT PRESS

The overall washing efficiency of a fiberline is of great importance for a mills environmental impact, the pulp quality produced and the mills operation cost. For this reason it is fundamental to keep the washing equipment in good order.

A few years ago this new type of wash press, was introduced. When starting the R&D work main objectives were:

  • High washing efficiency
  • High outlet consistency
  • Maintenance friendly
  • Easy to operate
  • Ingoing consistency from screen room to medium consistency applications.

All objectives have been met and today these units are operating in most fiberline applications at mills in five different continents.

Figure 7

Picture 7. COMPACT PRESS units at Ripasa Mill, Brazil

Future development focus

As a global partner to the pulp industry we have good insight of what current and future needs and requirements are. This knowledge serves as a base when deciding in what direction the R&D work should be headed. The following subjects are currently in focus:

  • Continued focus on reducing investment, operation and maintenance costs
  • Fiber property/quality issues
  • Simplicity

Recent fiberline projects for hardwood pulp

Three fiberlines for eucalyptus pulp have recently been started up or are under construction. They are located in Americana, Brasil, Hainan, China and Richards Bay, South Africa. An interesting reflection is that they all have in common they use Compact Cooking, Compact feed, DualD and Compact Press technology.

Figure 8

Picture 8. Mondi Richards Bay

  • Sources: Innovations and trends in fiberline technology, Stig Andtbacka, Håkan Dahllöf, Sven Lundgren, Kvaerner Pulping AB, Asian Paper 2004, Singapore

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