Distribution of dissolved and colloidal substances in the forming and press sections of a paper machine

We measured the concentration of dissolved and colloidal substances (DCS) along a paper machine by collecting whitewater samples at eight locations and analyzing them, together with water used to rinse the machine, for concentrations of fines, ash, carbohydrates, lignin compounds, fatly and resin acids and a variety of ions. The results show that the carbohydrates and lignin compounds in DCS follow a similar trend: their concentration varies little from the headbox to the formation zone but, subsequently, their concentration increases in the whitewater extracted by the first and second presses and decreases in the whitewater removed from the sheet by the third press. This behaviour can be explained by two opposing trends: increasing desorption of DCS from fines in the whitewater and an increase in DCS adsorption on fibres in the sheet along the machine.