PPI (PULP & PAPER INTERNATIONAL) MAGAZINE: Technology networking

Is it the answer to paper production cost efficiency?

April 2007
By Geoff Sheridan

When mills feel the pressure to keep costs down, they pass that pressure onto their chemical suppliers, who are generally willing to help.

Chemicals (excluding coating chemicals) are a relatively small component of the overall paper production cost structure, as Figure 1, a cost structure for double-coated fine paper, shows.

Fig. 1 - Cost structure for double coated fine paper

However, the chemicals used have an integral part to play in the overall process from furnish to finished product in terms of their contribution. These chemicals vary from those wet end additives required for paper machine hygiene and runnability, to those needed for paper properties and functionality, to others that are applied to create added value for the final product.

With cost usually the overriding driver of the pulp and paper industry, all too often such chemicals are individually targeted for cost reduction and replacement without recognizing the implications that this may have on both cost efficiency and product quality.

To reduce costs, an important step is to identify the synergies, both positive and negative, between the functional paper chemicals that provide quantifiable paper properties and process chemicals that ensure machine hygiene and productivity.

The ability to network different technologies to the benefit of machine productivity and finished product quality should be a high priority for any chemical supplier.

What is technology networking?

The terms 'technology' and 'network' can be defined as follows:

'Technology' is the ability to combine product, industry knowledge and application skills that have practical value to the benefit of both customer and supplier. A 'network' is a system of units that are related and useful to each other.

Technology networking is therefore the knowledge and competence to understand the papermaking process and implement complementary chemical treatments to ensure minimum interference and interaction with each other and to maximize their impact on cost efficiency and paper quality.

The first step however is to recognize by segmentation those chemical treatments used and their role within the process.

Technology considerations

The role or function of the technologies used within the paper industry and how they are perceived in terms of status, process impact and purchasing criteria by the papermaker can be important in defining elements of a package that is designed to address individual application technologies or a total approach.

An understanding of the classification is essential in establishing the specific service requirement as well as the technical importance of the product involved.

Knowledge of the technologies employed within the paper industry, their role and the way they are perceived by the papermaker is critical to establishing the importance attached to them and the basis on which they are purchased. Table 1 shows the technologies used within the paper industry; Table 2 shows their role.

The value chain

It is also important to be aware of the many steps involved in the process of converting a fiber source to an acceptable finished product and understanding the value chain for this process as well as the importance placed on each segment.

All paper grades can be viewed in the same way, but a particularly good example is the consumer packaging sector, Figure 2. The image clearly shows that value increases the further the progress toward the final product. It is therefore understandable that greater attention is placed on the technologies used.

Fig. 2 - The consumer packaging value chain

If the maximum impact on the process efficiency is to be realized, one should not, however, treat each operational segment in isolation, even though in some cases they can be physically removed from each other.

Technology networking in action

As many paper grades today are made using ever older and more frequently recycled fibers, these fibers need to be rejuvenated to make them more attractive to the many functional chemicals that are used to impart hydrophobicity or strength.

BIM KEMI has developed PR and CR technologies to provide this much needed surgery.

These polymers are designed to eliminate the blemishes, smooth out the wrinkles and condition the fibers in order to make them more receptive to oppositely charged additives, such as sizing agents or dry strength polymers, or simply to enable better control of undesirable contaminants, such as pitch or stickies.

One of the most beneficial examples of technology networking is to employ the PR and CR polymers in the wet end of the process, i.e. at the beginning of the value chain to the benefit of the higher value end.

But these technologies can have a negative impact further down the chain if not properly selected or if they do not complement other chemical additives used.

System charge control example

A paper machine is a highly complex interactive process and disturbances easily lead to quality and runnability problems. So stabilizing the wet end is key. The cost of instability is poor productivity, reduced wet web strength and overall reduction in machine cleanliness.

As a rule, the particles/fibers/fillers in a stock suspension carry a negative (anionic) charge and the majority of chemical additives carry a positive (cationic) charge. It is essential to know these charges when assessing the reaction and retention mechanisms in fiber and filler suspensions. In many applications, the electric charge is the key criterion for the behavior of additives. Generally speaking, particles of opposite charges attract each other - a mechanism that enables the reaction of a wet strength agent or retention aid with fibers.

Electrical charges on the surface of fibers and other materials in a papermaking furnish have profound but subtle effects on both the process and the finished product. Because "charges" are invisible, they are sometimes overlooked as a source of operational problems and variability. The balance of charges within a paper machine system can directly affect the performance of other chemicals.

Low or variable retention of materials during paper formation can lead to other problems, for instance with dewatering rates, sizing efficiency, and deposit control.

The cost of this instability is poor productivity, reduced wet web strength and an overall reduction in machine cleanliness.

A major problem is water-soluble organic material, often referred to as 'anionic trash' because it impairs the performance of

all chemical additives and reduces paper quality. Control of this material is critical to the cost and efficiency of many important functional additives. All raw fiber material carries anionic trash - at different levels and from different sources.

The colloidal charge reflects the amount and variability of anionic trash, which can have a major impact on the papermaking process. Therefore, charge levels need to be stabilized.

If the wet end is under control then more functional charged technologies such as sizing agents, wet- and dry-strength polymers, optical brighteners, etc. will be much more effective and easier to apply.

Case study: Tissue

Tissue mill in western Europe producing 28,000 tonnes/yr.

Fiber: DIP

Problem: Stickies deposition on the wire was producing holes in the sheet and breaks in converting. Machine had to stop 2-3 times/day for cleaning

Solution: BIM CR 9070 introduced at 1.2 kg/tonne at the machine chest

Result: Cleaning reduced to once/week, no unscheduled downtime in converting and a more stable wet end chemistry

Benefits:
• Increased productivity
• 6% fiber cost savings
• Improved sheet properties
• Better wet strength retention
• Lower clarification polymer chemical cost
• ROI - 98%.

Case study: Newsprint

Newsprint mill in western Europe producing 60,000 tonnes/yr.

Fiber: 100% DIP

Problem: Holes, spots and breaks caused by stickies deposits were creating unscheduled downtimes

Solution: Add BIM PR 9030 to the DIP chest to stabilize charge demand

Result: No breaks caused by stickies or stoppages for cleaning

Benefits:
• Increased productivity
• Improved sheet properties
• Cost reduction because of talc removal
• Cost reduction because of reduced consumption of retention chemicals
• ROI - 112%.

Sum of the parts

It is crucial for both mill and supplier to be increasingly aware that performance and final overall cost should be the focus, not individual chemical costs.

Evidence for this can be found in all grades where the use of wet end additives, if chosen correctly for their compatibility and complementary functionality with other chemical treatments, can help achieve desired value-added properties as well as make the most economical use of the machine's productivity.

Technology networking can ensure that by understanding the influence such treatments may have on other wet end additives (such as sizing or strength agents or even other process improvement additives) any interaction will not have a negative effect on runnability, cost and paper quality.

The principle of technology networking is to recognize that each treatment, no matter how insignificant it might seem in terms of cost or function, should be carefully selected in relation to others and the next step in the production process.

What this demands from the supplier is a thorough auditing of the operation from furnish to finished product together with the papermaker before selecting best practice technologies for application.

If this is diligently observed then the small cost of chemicals can have a beneficial impact and overall contribution on the cost structure.

The ability of both supplier and producer to quantify the relevant areas of paper manufacture that are affected by certain technology programs and to clearly understand their cost and contribution value should make concerns about expenditure on wet end chemical treatments a thing of the past.

Geoff Sheridan is market development manager, BIM. For more information email: Geoff.Sheridan@bimkemi.se, or telephone: +44 1204-366997

Pulp & Paper International is FREE to qualified subscribers. Click here to find out more.