From unknowns to benefits

Why are stock preparation and wet end processes often challenging?

In a word, variation. Raw materials change all the time, which means stock preparation must constantly adapt. Take fiber length, for example. This often differs from one pulp batch to another, impacting machine runnability and strength properties.

This in itself is difficult, and it makes the already complex wet end that follows stock preparation even more challenging. These variations cause instability in board and paper machines, leading to interruptions, inefficiencies and off-spec quality. This is true for both integrated and non-integrated mills.

Changing stock characteristics directly impact wet end stability. The wet end is more complex than other parts of the mill because of the chemistry involved. Operators must manage multiple chemicals to ensure steady web formation.

If you get that chemistry wrong, the whole wet end destabilizes. This can cause poor retention, excessive energy consumption in drying due to poor dewatering, and higher costs due to machine cleaning and unplanned shutdowns.

What can Valmet offer to help solve such challenges?

Valmet is unique in the sense that it can supply the entire mill package, from machines to measurements and automation control systems. We bring deep knowledge of board and paper making measurement technology and process machinery to the table.

Model Predictive Controls (MPC) are key here – like our unique retention control, which we have worked on since the 1990s. We know the process, all the possible interactions, and the technology that measures and controls them.

It helps tremendously that we have hands-on knowledge of machine dynamics. This process expertise helps us build the right controls to manage process behaviors.

The understanding we have gained from decades of working with these processes and measurements has allowed us to develop highly sophisticated controls. These controls assess multiple variables to determine which action to take.

However, we can’t exaggerate just how important the analyzers are to this story. Valmet has spent decades developing the most accurate, reliable and high-frequency industrial measurements for a reason. Great measurements are the foundation of everything else.

What benefits do customers gain from Valmet’s solutions?

The variables in stock preparation and wet end are constantly interacting and changing process conditions. When something goes wrong – say, the board isn’t strong enough – it’s difficult to find the root cause without real-time measurements.

So to avoid those situations, mills run with high safety margins – over-dosing chemicals or adding more expensive fibers, for example. The excess margins increase costs and can have negative side effects like foaming, which reduces runnability and decreases end-product quality.

Valmet delivers all the fundamental building blocks for stabilizing both stock preparation and wet end sub-processes, enabling mill-wide optimization. Real-time online data feeds advanced algorithms to precisely control each process variable.

In practice, this means customers not only get stable processes, but if something unexpected does occur, the Valmet systems react immediately to get the process back on track, eliminating production delays. With reliable processes, customers can reduce safety margins, save chemicals, energy, and water, and run machines confidently at higher speeds.

The return on investment is measured in months once the Valmet analyzer and control systems are in place. It’s easy to confirm the impact too. With real-time data, you see immediately how conditions change if a control is disabled. Enabling the control stabilizes process values almost instantly.

While we focus on a rapid return on investment, Valmet plans products for the long term. Our customers get a great deal of transparency with our solutions. They know what they’re getting now, and they have a clear view of the entire solution lifecycle through our long-term product planning and continuous customer dialogue. 

Text Randel Wells