Dissolving wood pulp
The facility in Lenzing, Austria, is the largest integrated dissolving wood pulp and fiber production site in the world.
Integrated dissolving wood pulp production not only offers exceptional economic benefits, it is also a method of production with many ecological advantages. Lenzing boasts double the savings of non-integrated mills. For instance, it saves on transportation because of the short distances involved and it eliminates altogether the need for the energy-intensive drying and packaging of dissolving wood pulp.
Biorefinery of #wood
In addition, waste heat from processing and heat from the incineration of bark and residual materials from the integrated production process are carefully used as resources and reintroduced into the production cycle.
The production of co-products such as acetic acid, furfural and xylose likewise helps to increase the total yield from the #wood as well as value creation.
The Lenzing site produces the dissolving wood pulp needed for fiber production itself. This pulp production is exemplary (“bio-refinery”). Traditionally, the base materials for the dissolving wood pulp made at the Lenzing site comprise a mix of mainly red beech but also ash and maple.
Material utilization in an optimum way
The logs are barked, chipped and dissolved in a cooking liquor of magnesium bisulfite at a temperature of about 150 °C. The cellulose – nearly 40% of the #wood – is separated off as raw pulp in the process. The raw pulp is then bleached in a completely chlorine-free process using oxygen, ozone and hydrogen peroxide and processed into pulp sheets or flakes.
The other #wood components remain in what is called the thin liquor together with the other cooking chemicals. Marketable spin-off products (co-products) such as acetic acid, furfural and xylose are obtained in further processing steps.
In recent years, the use of wood substance has increased to such an extent that about half of the #wood is now transformed into products. The cooking chemicals are recovered from the remainder. The components in what is called the thick liquor that are unfit to be used as material (such as lignin) are used for producing energy. It is the most important source of energy at this facility.
Pulp production process
chemical cycles, co-products, utilization
Lenzing site - simplified description
*) Oxygen, hydrogen peroxide, ozone
Pulp production at the Lenzing site is not only self-sufficient in terms of meeting its energy needs; it actually produces a surplus of energy. The Lenzing site utilizes the surplus heat (steam) and the surplus electricity for fiber production. The production of fibers from pulp using the viscose process is a chemical-technological process that proceeds in multiple steps. Closed-loop production processes are provided with recovery facilities. A substantial portion of the chemicals can be recycled as a result.