The Steam box: A (Re)Discovered Technology to Optimize Paper Production

Paper manufacturing is an energy-intensive process, especially at the drying stage. But when used properly, a well-calibrated steam box can reduce the amount of energy needed to dry the paper and even speed up the process. In this article, you’ll learn how you can take advantage of a steam box to increase productivity and reduce the energy requirements of a paper machine.

An effective principle when properly applied

Placed at the output end of the forming table, just before the presses, a steam box increases the temperature of the sheet of paper, which decreases the viscosity of the water and therefore reduces the moisture content of the paper, so less energy is needed for the drying process. At least that’s the basic principle of how the technology works.

But as Éric Émond, Senior Energy Consultant at Énergir’s DATECH Group, notes, “Many steam boxes were misused and eventually removed because they did not produce the expected results.”

So the question is, how do you properly use a steam box to improve how sheets of paper are dried?

The devil is in the details

The first thing to understand is that the steam pressure and temperature settings, as well as the distance from the sheet, must be set very precisely. “Typically, you want to release a flow of steam heated to an additional 5°C to 10°C that condenses on the surface of the sheet—not before or after. This is where the increase in temperature of the sheet is at a maximum,” says Éric Émond. It’s this temperature gain that makes it easier and more efficient to extract water from the paper and ensure the sheet contains less moisture as it enters the drying machine. A properly calibrated steam box does not let any steam escape. It all condenses on the sheet.

Reducing needs twice instead of once

What’s more, modern steam boxes have numerous control zones in the crosswise direction of the machine, making it possible to flatten (or to balance) the moisture profile of the sheet. This feature allows for a second energy gain, since a sheet with an irregular moisture profile generally needs to be overdried, which takes extra energy. Some paper machines then have to rewet the sheet to adjust the final moisture level. An efficient steam box eliminates this energy-intensive practice.

The profiling function is made possible by the many actuators that distribute the steam efficiently across the sheet. While in the past these actuators were somewhat hit or miss, new technologies have since been developed to make them much more reliable. But proper maintenance of the actuators and the steam box is still essential to maintain optimal efficiency.

Less energy, more profitability

In the past, steam boxes may have been given bad press (!), but today they are valuable allies of paper manufacturers when used properly. And that includes using the right settings. An efficient steam box produces a dryness gain of 1% and a speed gain of up to 5%, as well as a reduction in the variability of the moisture profile of each sheet. Given the considerable amount of energy required to produce paper, these advantages can lead to increased savings and/or profitability in a highly competitive market—especially since the acquisition cost can pay for itself in under six months, in some cases.

To learn more about this technology, its advantages and how it can be applied in your company, don’t hesitate to contact the DATECH team at [email protected].

Éric Émond.
Senior Advisor, Energy expertise

DATECH Group