The effect of wood extractives composition, pH and temperature on pitch deposition

A study of the effects that wood extractive composition has on pitch deposition was conducted using model solutions of a resin acid, fatty acid and triglyceride. The deposition behaviour was investigated under various conditions of pH and temperature. Statistical pitch deposition models were developed through the use of general multiple linear regression analysis techniques to relate total pitch deposited to the concentration of the various components present in the pitch before deposition. The models show that resin acid is the major, but not the only component contributing to pitch deposition. The models also allow the effect of pH and temperature shocks on the system to be determined. The differences in deposition behaviour at the different pH and temperature conditions can be explained by the chemical and physical properties of the components. Suitable control strategies are proposed for the various pH and temperature conditions.