Technology

The Impulse Drying Technology

The paper making process has been known and used for millennia but has only seen minor optimizations in the past century. During the past few decades the paper industry has dwindled to only 40 percent of its original grandeur thanks to IT technology and plastics among others. The two major inhibitors to the paper industry are the energy consumption and the process time when making sheets or molded articles. Both the sheet and molded article industries have scaled their way out of the process time issue and have produced absolutely massive facilities with huge outputs. However, the energy issue has not yet been solved.

Paper is made in much the same way, whether it is sheets or molded articles. The processed fibers are suspended in water to produce a pulp. The solids content ranging from 0,1 to 2 %. The fibers are then collected in a net using either vacuum or the sheer force of a jet spraying the pulp on the net. Excess water can be removed by mechanically pressing it out of the fibre substrate. However, only some of the water between the fibers can be removed this way, and not the water within the fibers themselves. This leaves a water content in the fibre substrate of about 40%. The only way to remove this water is by evaporation, which in itself is a significant energy consuming process. In a paper machine, up to 90% of the overall energy consumption is located in the dryer.

In the 1930’s an idea grew that potentially could solve both morphine the energy and time issue. It was an idea incorporating a very hot surface pressed onto the fibre substrate from only one side leaving the other side free. The idea was to make the water evaporate quickly creating a steam front that could displace the rest of the water out through the fibers. The idea did not work but was not dropped. Many people have been working on the idea since then and a lot of different perspectives have emerged.

It was found that subjecting the paper to pressure during the heating step would allow for a super heating of the water in the substrate much like in a pressure cooker. Upon release of the pressure the superheated water, now again subject to atmospheric pressure, would flash evaporate and create an impulse that drove the steam front out through the paper displacing liquid water in front of it, resulting in a significant drop in energy consumption.

 

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The process, however, was not easy to implement in a paper machine because of the way it is built. The paper passes through giant rollers that compresses and dries the paper, but it passes between the rollers so quickly that they only are in contact for around 20ms. Upon release of the mechanical load, there is nothing to guide the generated pressure in the right direction, and the steam escapes in all directions resulting in the paper being blown apart and rendered useless.

In ecoXpac we use a technology called thermoformed fibre. Here the wet paper substrate is likewise collected on a net and subsequently dried. However, it is dried in a closed mould comprised of a male and female part, one being hot and the other being porous, allowing for sustained pressure and a more controlled process. While pressurizing the closed mould from both sides and only heating from one side the water in the paper closest to the hot surface becomes superheated. When the right amount of superheating has taken place the pressure is released from the cold and porous side. Once the pressure gradient passes though the paper and reaches the superheated water, the flashing to steam occurs. While the mould is still closed, and the fibers are still compressed the steam has only one way to go and will displace most of the liquid water in front of it into the porous mould leaving an almost dry fibre substrate behind.

The Impulse Drying Technology makes ecoXpac able to revive a dying trade and give it new wings, resulting in a whole range of new and exciting products. The Impulse Drying Technology allows us to produce intricate shapes and even closed containers like bottles and jugs in a sustainable and biodegradable material, quickly and with a much reduced energy consumption compared to existing molded fibre techniques and methods. A single line will have an output of around 600 units an hour with the potential of scaling, and will cut the energy consumption with up to half or even three quarters compared to existing industry. The production methods developed in ecoXpac also allow us to produce interesting and ground breaking mechanical properties in the paper, creating sturdy and durable products with unrivalled functional surface properties and strength. All based on fibers from several organic sources. E.g wood pulp.