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Adding profitability and quality to biorefining

The growing shortage of forest resources and the abundance of nonwood resources – together with growing paper consumption, increasing waterborne pollution in Asia, and rising levels of CO2 emissions – have created an ideal set of opportunities for Chempolis' innovative pulping process.

Good profitability and high end-product quality were two of the key priorities for Chempolis in developing its advanced pulping process, alongside a high level of environmental compatibility underpinning all aspects of the production chain.

The Chempolis process is chlorine-free and completely safe for the environment.

The Chempolis process functions as a biorefinery at the heart of this chain, designed to increase the added value of end-products, enable production to be self-sufficient in terms of energy, facilitate the production of new green chemicals, and utilise the full range of nutrients contained in raw ­materials.

The resulting technology is ideally suited to the needs of papermakers in China and elsewhere in Asia, where paper consumption is growing rapidly and forest resources are either limited or their use is likely to become so for environmental reasons.

The high quality of both the Chempolis process and the products it produces is based on the use of sulphur- and chlorine-free chemicals – in the shape of formic acid and hydrogen peroxide – and the fact that they do not result in any toxic residue being passed into the environment. They also make it possible to create closed chemical and water cycles, and to use a biorefinery capable of making the maximum use of raw material and by-product inputs. This type of potential for added value simply does not exist with methods based on conventional alkaline cooking chemicals.

High-quality paper and green chemicals

Residues generated in agricultural production represent a valuable source of short-fibre raw material for papermaking. Short-fibre pulp is ideal for many types of printed products, as its forms a smooth, strong base for printing.

A key advantage of the Chempolis process is that it can enhance the only real weakness associated with straw-derived fibres: dewatering. It does this by regulating the solubility of hemicellulose during cooking, thanks to its use of acidic cooking chemicals. A lower level of hemicellulose in the resulting pulp improves dewatering performance on the paper machine, as well as the runnability of machines.

The hemicellulose contained in the vegetable matter used as input for the Chempolis process is broken down into sugars, and from sugars into green chemicals: acetic acid, formic acid, and furfural.

The fact that acetic acid and furfural can be produced in excess of the amount needed by the process itself enhances profitability, as they command a higher price than the main product: pulp.

A distillation unit lies at the heart of the Chempolis biorefinery, which is used to concentrate the formic acid and acetic acid recovered from the pulp washing stage. The water recovered here is then recycled for use in pulp washing. The concentrated acid is re-used in the cooking stage of the process.

The furfural separated from the concentrated cooking liquor during distillation can be sold on as a chemical for use in industry.

The distillation unit can produce between 100 and 200 kilograms of furfural and acetic acid per tonne of pulp, depending on the properties of the raw material input used.

Self-sufficient in energy

The energy self-sufficiency of the Chempolis process is based on the fact that the dry solids content of the lignin extracted from the cooking liquor can be increased to over 90%, thanks to the organic cooking chemicals and acidic conditions employed.

Formic acid does not dissolve silicates, which is the key to efficient chemical recovery. This is in sharp contrast to conventional alkaline nonwood processes, where high viscosity and silicate precipitation mean that the dry solids content of the lignin fraction remains under 50%, requiring the use of bought-in fuel.

In the Chempolis process, lignin represents a new type of biofuel, which can be combusted as such or gasified for producing traffic fuel or various green chemicals.

Good for the environment

In addition to energy self-sufficiency and chemical and water recycling, the key underlying benefit of the Chempolis process lies in its highly efficient use of raw material nutrients.

In conventional processes, nutrients end up in a plant's inorganic cooking chemical cycle, creating their own set of special problems. These nutrients remain in the lignin fraction in the Chempolis process and can be recovered in the form of ash and used to produce fertilizer.

Thanks to its technological, financial, and quality-related advantages, pulp produced using the Chempolis process and nonwood raw materials is very well-placed to become a major product in countries that have small forest resources and limited amounts of timber that can be used for papermaking.

Technology from Chempolis will enable an increasing proportion of the world's paper to be produced from agricultural residues in the future.

Current wood plantation levels are typically insufficient, and it will be impossible to develop sufficient extra plantations to meet consumer needs in the immediate future due to the time needed. There is an abundance of nonwood resources, in contrast, and the logistics infrastructure for using these materials is already in place.

All in all, therefore, the future for a significant proportion of future pulping lies with nonwood resources and technologies – such as the Chempolis process – that can make the best use of them.

> Esa Rousu
(Published in High Technology Finland )