Chemical Genius in the Pulp and Paper Industry:

    An Overview  

The pulp and paper industry is one of Canada’s most widely distributed industries. Development of this industry is owed in part to the work of chemical engineers who have succeeded in applying on a large scale the various processes conducted in laboratories by chemists. In fact, it is to the engineers that we owe the design of the huge pulp and paper mills, the ability to process logs by the hundreds, and to apply proper chemical processes to a large volume of pulp to make the desired paper. Without engineers, we would virtually have to make our paper one sheet at a time. 

To make paper, the mill uses either recycled material or virgin fibres (from wood). In the latter case, the wood is chopped and transformed into pulpwood chips before it is brought to the digester. At the digester, an aqueous mixture of sodium sulphide and hydrogen is incorporated to break down the lignin and free the cellulose. It should be noted that it is the cellulose that is used to make the paper, while the lignin must be removed. The lignin is withdrawn little by little and only the cellulose is retained. The result of this step is a pulp that will be screened (to remove the woodchips) and washed (to remove impurities). It is at the final transformation stage that this pulp is bleached to eliminate natural coloured substances and traces of lignin and resin. This process is carried out using chlorine dioxide, oxygen and ozone. A number of scientific experiments were required to find the winning combination of suitable products and appropriate concentrations. Once the pulp has been bleached, chemical additives (such as starch) are added to solidify the paper or to colour it (synthetic dyes). The final stage consists of pressing the pulp, passing it through the dryer and then cutting the sheets. 

But that is not all! Chemical engineers also look after the health of the environment and try to eliminate pollution that may be produced by the mill. Thus, with the help of technicians, they ensure that the water evacuated from the mill is not harmful. To achieve this, the engineer’s main task is to regulate the pH level of the various  effluents from the mill, depending on whether they are alkaline or acid. Adding suitable chemical products to the water neutralizes the pollution. If you would like more information about the various stages of paper production, why not visit the following user-friendly Web site: http://www.open.doors.cppa.ca/.