PPI Special Report

The Concepts

By A PPI Special Report Wed, Dec 04, 2013
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Deep Eutectic Solvents

A ground-breaking discovery: Deep Eutectic Solvents (DES), produced by plants, open the way to produce pulp at low temperatures and at atmospheric pressure. Using DES, any type of biomass could be dissolved into lignin, cellulose and hemicellulose with minimal energy, emissions and residues. They could also be used to recover cellulose from waste and dissolve ink residues in recovered paper.

How does it work?

Deep Eutectic Solvents are an adaption of a natural phenomenon known from plant metabolism. Researchers found that plants can operate even under water stress (i.e. during periods of drought or frost), using the organics in their cells to produce DES. Glucose based natural DES can dissolve wood and selectively extract – as a function of the chemical characteristics and operating conditions – lignin, hemicellulose and most probably cellulose. That is what makes them predestined to replace traditional pulping techniques. Research into DES has only just begun,and hundreds of new types of DES are yet to be discovered.

How would it work for our sector?

DES could have four key applications in the sector, based on the ability of the solvents to selectively dissolve specific components. The capacity to dissolve lignin allows Omnivorous Pulping.

DES that dissolve lignin could replace both chemical and mechanical pulping. DES pulping yields pure cellulose, lignin and hemicellulose at low cost. This has been demonstrated with wood and straw (where silica is removed by the DES). Tailor-made fibers can be obtained by adjusting the DES properties and process design.

The potential to dissolve cellulose can enable the recovery of cellulose from waste. Cellulose is soluble in DES. When developed further, this would enable the recovery of pure cellulose from papermaking residues (rejects, sludges, paper waste) in the form of clean dissolved pulp or as a basic building block for biochemicals, materials or fuels.

In the future, DES could be used for recycled fiber processing. It should be possible to find DES capable of dissolving ink residues in recovered paper.

When the solubility of cellulose in specific DES is further improved, DES-based papermaking and sheet forming could become possible. The industry could use DES to eliminate water from papermaking entirely, prepare the stock and remove contaminants.

Team Insight

How long do you think it will be before a result can be seen?

Annita Westenbroek (Royal Netherlands Paper and Board Association) on DES: Personally, I think that a first DES Omnivore pulping plant could be realised in 10 years. The potential energy and cost savings as well as new market opportunities are that large, that we foresee that research in this field will soon explode, involving all actors required for successful development and implementation. Still quite some research is needed to find the most suitable and efficient DES solvents for our application. Moreover the whole pulping process system needs to be adapted and designed to operate with the new solvents, including the recovery processes. But when joining forces, as we did in the Two Team Project, I am convinced we can do it.

Flash condensing with steam

How does it work?

The breakthrough concept is the use of vapor combined with largely dry fibers to form paper and board. It works by introducing high-consistency fibers, fillers and chemicals into highly turbulent steam. The steam carries the fibers into the forming zone, where the combination of condensing and steam expansion creates the paper sheet and enables bonding. High gas velocities make the forming section very short. Very little extra heating is required for drying, as water content after the wire is less than 30%.

How would it work for the sector?

Steam forming could be used with all kind of fibres. It could most easily be applied to production using chemically-pulped virgin pulp fibres, but it could also be employed with recycled fibres obtained through dry recycling processes and additional cleaning. It could even be applied to refine thermo-mechanically pulped ‘gluing fibres’, which are highly hydrophobic and are currently not used in conventional papermaking.

In the ideal scenario, steam forming could enable massive water savings. Rather than using 100 liters of water to dilute 1 kilo of fibers, the fibers would be suspended in 100 liters of water vapor, generated from just 0.1 liter of water. This low volume of water could easily be adsorbed and dried out of the paper sheet. The combined press and drying has to be of a new type and would rely heavily on condensing and very little extra heating as very high entrance temperatures of the fiber web could be expected.

Team Insight

Will this concept really break through?

Johannes Kappen (Papiertechnische Stiftung, PTS): Steam forming is a key enabler of dry paper making. This technology turns an old papermakers dream into reality. It would be a breakthrough indeed. Flash condensing with steam enables a completely new way of paper making and in creates opportunities for new products. The integrated approach, covering all aspects of the paper making process, can serve as a mould for the implementation of further innovations. CEPI has lit many torches. Someone has to take them up now and keep the fire burning. A platform approach is ideally suited to facilitate this. It is the involvement of the industry that is decisive. We all should have an eye on it that the fire keeps burning high throughout the next years.

Steam

Using more energy to use less? You read it right. Using the full power of pure steam for superheated steam drying would save energy as most heat could be recovered and recycled. Steam will then be used as fibre carrier for making and forming paper.

How does it work?

Today, heated cylinders deliver the energy required to evaporate water from paper, and large quantities of air are used to remove the water vapour. With this air and vapour mixture, large amounts of energy (latent heat) leave the dryer section at low temperature. In the ‘Steam concept’ temperature and humidity are increased towards “Pure vapour”, where superheated steam replaces air as heat carrier. This allows full recovery of heat. Next, the use of steam is expanded into the papermaking process, with steam and heat-boosted forming, pressing, sizing and coating. And finally steam spray forming and steam foam forming are put in place. Because of temperature, the new-concept paper machine should be operated by remote control, using robotics. The concept builds on expertise gained in the food sector and from a pilot plant in the panel board sector, but also on earlier work done in our industry.

How would it work for our sector?

Implementation would be expected stepwise, following the readiness of the different technologies. Steam would progressively replace air and finally also water in the papermaking process. Starting at the drying section, the rest of the process would be transformed, rebuild by rebuild, as steam filled the whole paper machine. Three logical waves could be anticipated: superheated steam drying, with the total recovery of thermal energy in an air-free drying section; steam-boosted papermaking within an air-free paper machine; and steam-based papermaking, based on completely new forming technology, leading to more material efficient products.

Team Insight

Why “Steam”?

François Julien-Saint-Amand (CTP): The first goal is to grasp the huge potential in energy saving from drying with superheated steam. Further capitalizing on existing papermaking technology, additional breakthrough would be achieved with steam boosted papermaking as steam could further replace air in a closed paper machine. The paper machine operation would be completely taken over by robotics. Steam forming would be the final breakthrough step in papermaking technology, as steam will also replace forming water. Waterless steam spray and/or foam forming are a totally new technology, which would ensure full retention. Sheet stratification and optimised use of pulps and pulp fractions in the different layers will offer new possibilities for lighter products from recycled and virgin fibres. 

DryPulp for cureformed paper

Imagine a papermaking process that uses no water. This is it. Fibres are treated to protect them from shear, and then suspended in a viscous solution at up to 40% concentration. The solution is then pressed out and the thin sheet cured with a choice of additives to deliver the end-product required.

How does it work?

In papermaking today, cellulose fibres used to make paper have to be suspended in large volumes of water to prevent them forming clumps (flocs). The innovation introduces two technologies that enable the production of paper with no water.

First, the use of DryPulp: DryPulp consist of a shear-protected fibre in a highly viscous solution. Instead of today’s water-intensive process in which cellulose fibres are suspended in water, DryPulp is a highly viscous solution, containing a high concentration of fibres. To prevent the fibres disintegrating in such a viscous solution, they are given a protective surface layer. This is a technique borrowed from nature: a penguin accelerates to escape a predator underwater by releasing air collected while on the surface and trapped within its plumage. When the air is released it forms a thin layer around the penguin where viscosity is much lower than in the water, which reduces the friction forces. The concept has also been used in Russia to develop super-fast torpedoes. A gas bubble formed around the torpedo enables the torpedo to travel 10 times faster than competing technologies (supercavitation). In papermaking, bio-based substances could be used to modify the viscosity around fibres.

The second technology is ‘cure-forming’, which allows the formation of a thin sheet. The high consistency DryPulp is pressed to remove the viscous solution. After pressing, the web contains up to 80% fibres. The sheet is then cured using processes adapted to the end-product required.

How would it work for our sector?

The combination of these two technologies would allow the sheet to be produced as a layered product, in response to demand for certain properties and with the means to add new functionalities. For example, a sheet could be composed of a bulky middle layer embedding air bubbles or sodium bicarbonate and an outer layer with resin and fillers, making coating unnecessary.

Team Insight

Cureforming?

Daniel Söderberg (Innventia): When cure forming would be industrially implemented it would totally change the paradigm of modern papermaking. Although the production capacity (volume!) is clearly lower the need for capital for producing paper products will be significantly lower and a paper machine could produce a wide range of products. It may even be integrated with the converting operations. It would transform the industry from being capital intensive with huge volumes of few products to being much more product focused and flexible. The concept requires research & development starting in fundamental science of biopolymers and fluid physics over technology development and pilot activities to industrial implementation. An estimate is that this would take 10 years until the first components of the concept are implemented industrially and maybe five more years until the full concept is available.

Supercritical CO2

Neither gas nor liquid but somewhere in between, Supercritical CO2 (scCO2) is widely used in many applications, to dry vegetables, fruits and flowers, extract essential oils or spices. Suppliers for NIKE, Adidas and IKEA use it to dye textiles. Coffee and tea have been decaffeinated with scCO2 since the early 80s. We could use it to dry pulp and paper without the need for heat and steam, and why not dye paper or remove contaminants too, while we’re at it?

How does it work?

CO2 in supercritical state takes on many of the properties of both gas and liquid. With small changes in temperature and pressure a large variation in solvent properties can be achieved. The liquid-like characteristics and the combination of pressure and temperature allow paper to be dried with scCO2 in place of water before the scCO2 is removed with a simple change of pressure. Second, the gas-like characteristics provide ideal conditions for extracting contaminants in the process. The proof of concept can be seen in other sectors. CO2 is widely available. Little energy is required to take it to a supercritical state.

How would it work for our sector?

A first application for supercritical CO2 lies in “extraction drying”. The current drying section with steam-heated cylinders would to a large extent be replaced by two autoclaves. Lab tests showed wet paper with 50%-60% moisture content can be completely dried using this process, with minimal impact on paper quality and using much less energy than today’s drying section. Supercritical CO2 could first be tested in moulded fiber processes, in tissue and specialty mills and then in graphic paper and packaging machines.

Supercritical CO2 has great potential to remove contaminants such as waxes and stickies in the recycling process, improving runnability in papermaking. The use of scCO2 in recycling processes can create fractionated fiber on demand, fit for purpose. Moreover, lab tests have shown that scCO2 can remove mineral oils, a key issue today. Waxes and stickies could be removed and the process would lead to certified ‘clean’ – and most important– dry recycled fluff pulp.

The key challenge of current Deinked Pulp Mills, the transport of wet deinked pulp, can be tackled this way. The process could also be used to remove adhesives, allowing papers containing these to be brought into the recycling process. Ultimately, the system could be used to produce products directly in scCO2.

Team Insight

What will supercritical CO2 do for the Industry?

Robert Miller (Buckman Laboratories): Supercritical CO technology offers savings by revolutionising the drying of pulp and paper. Heat and steam would no longer be needed. Treating recycled paper by separating the pulp into different fibre grades would enable purchasers to buy only the exact type of fibre for their needs,including recycled fibre free from contaminants. This would enable greater production from the available fibre in Europe. The upcycling instead of recycling would increase material efficiency in the mill.

100% electricity 

Shifting pulp and paper production to energy-efficient technologies using electricity rather than fossil fuel power to generate heat will cut all CO2 emissions as the power sector shifts to renewable energy. The sector would also provide a buffer and storage capacity for the grid, storing energy as hydrogen or pulp.

How does it work?

The breakthrough consists in the optimal management of energy demand. It would decarbonise papermaking through the adoption of more efficient technologies that use electricity rather than fossil fuels to generate heat.

The sector could also provide a buffer and storage capacity for electricity, offering a means to store cheap surplus energy from the grid generated from intermittent renewable energy sources such as solar and wind power. It would do this by using electricity when it is cheap to produce and store Thermo-Mechanical Pulp (TMP) and hydrogen(H2),using the latter to generate power during periods of high electricity prices or selling it to external users.

How would it work for our sector?

The concept allows for a step-wise implementation. The industry could first replace gas-fired boilers with electric boilers (almost 100% efficiency, compared to 70-90% efficiency for coal or gas-fired boilers).

In subsequent stages it could replace the drying section in the pulp process and later the drying section of the paper machines. Various technologies exist for high-efficiency drying which are available but not yet widely used. These include ultrasonic drying, impulse drying, Condebelt drying, microwave drying, infrared drying and osmotic drying.

Team Insight

Why would you electrify the industry?

Thorsten Becherer (SCA Hygiene Product): ‘100% Electricity’ is a holistic concept with a breakthrough impact even beyond the pulp and paper industry. “Flame-free” means a change of mindset in the industry, similar to the change from combustion engines to electrical motors in the automotive industry. 100% Electricity will eliminate emissions in the pulp & paper industry completely (not only CO2, but also NOx and others). Onto pit creates synergies with the power sector and helps to overcome the existing technology barriers on the way towards 100% renewables.

Functional surface

The key to unlocking greater added value from fewer resources depends on a shift to producing more lightweight products, and selling surface area and functionality rather than weight. Advances in sheet formation and new cocktails of raw materials will lead the way to the lightweight future.

How does it work?

The idea is to make breakthroughs in the material composition and the formation of paper, to offer greater functionality while reducing the weight of paper products. It is about developing technology that allows full control over the paper sheet structure, reducing the amount of material by 30% per square metre.

It would meet customer expectations by increasing the physical-mechanical characteristics of the paper (tensile, compression, printability, bending, bulk, etc.) and/or adding new features (electrical properties, optical characteristics, hygroscopic behaviour, etc.).

How would it work for our sector?

Achieving this concept would require breakthroughs in two subconcepts. The first, innovative sheet formation, requires modified headbox designs or new components distribution technologies. Secondly, modification of raw material composition, or using different cocktails of raw materials − fillers, starches, pigments etc. – to improve a product’s performance or help develop new products with enhanced functionalities, for example building materials. Alternative cost-effective raw materials could even replace a proportion of the pulp in papermaking, offering considerable energy savings. 

Team Insight

Why is “Functional surface” a Breakthrough Technology?

Miguel Pelayo Guillen (SAICA):During the last 1800 years, humankind has been using paper by taking advantage of his inherent strong points: smoothness, strength, opacity ... and bypassing the weak ones: moisture sensibility, viscoelastic behaviour ... The “Functional surface” concept tries to develop ways of controlling and managing these features, and even of adding new ones permitting to expand the use of paper products to new business areas. I think those are real breakthroughs in paper technology. 

The Toolbox to replicate 

What about the great ideas that never make it? Put together a combination of process, material and equipment innovations as a toolbox of stepping stones to 2050 and the pathway becomes clearer, boosting sector and investor confidence.

How does it work?

In this concept there is no single breakthrough. There is a combination of breakthroughs and a direction in which to combine them. The toolbox shows an overview of the current best, so far unused technologies within and outside the sector (stepping stones), and a vision of a future production system that could be realised by applying these technologies. The stepping stones are divided into time segments for 2025, 2035 and 2050. The direction of breakthrough for pulping is to go smaller – from tree to fibre, from fibre to chemical, from chemical to molecule. The direction for processing is to use the last technologies in layering, forming and 3, 4 and 5D printing. Products become customised and allow a range of specific characteristics.

How would it work for our sector?

On one hand, the sector would progressively replace equipment with the most advanced technologies, once the pilot proof has been demonstrated. On the other, based on the latest material science and advanced manufacturing, biomass would be separated into all valuable streams, and used with the new manufacturing technologies to produce improved products. The technologies for this are already within sight. By 2025, the combination of new raw material processing and papermaking technologies will allow lightweight products, sandwich layers and limited customisation of products.

3D printing could play an important role between process and products. By 2035 the combination of stepping stones in the toolbox would result in even thinner layers, manipulation of layers and customization down to parts of end products. By 2050 production sites would become custom-designed, able to make fully customized products using locally available raw materials.

The concept is intended to become an innovation system for the sector. If the sector agrees to fill the toolbox with new technologies and put in place a system for this and for piloting, new combinations will become available. The toolbox would ideally be updated every so many years.

Team Insight

How did you get to a toolbox?

Petri Vasara (Pöyry Management Consulting): Innovation is also about combining things in a new and unexpected way. In “The Toolbox”, we see the paper industry able to manipulate fibre and materials at a smaller and smaller scale, down to the molecular level - which is definitely breakthrough technology, and a major change in the whole industry. We accomplish this by combining different new technologies along the chain from raw material via process to product finishing.

The OMNIVORE Pulp Mill

The OMNIVORE Pulp Mill

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