The response of mechanical and chemical pulps to refining

This paper reports on theoretical equations describing the flow of pulp in refiners were used to analyze the experimental results obtained in a series of pilot plant trials. Western red cedar and loblolly pine wood chips were refined in 1-3 stages at rotational speeds of 1200 and 1800 rpm to produce thermomechanical pulps (TMP). Also, sulfate semibleached and low-yield sulfite pulps were refined at low (5%), medium (12%), and high (25%) consistency. The results indicate that the number of refining stages did not affect mechanical pulp quality. At a given specific energy, increasing the rotational speed increased the specific energy per impact and decreased the total number of impacts, resulting in a faster rate of fines generation for mechanical pulps. For chemical pulps higher pulp consistency produced gentler refining and yielded a higher rate of freeness decrease.