REFINER PULP FROM P RADIATA.

In the reported pilot plant experiments, using a refiner with a twin screw feeder mechanical pulps have been made in a single stage with 0. 5 percent 0. 006 cut shive burst index 2. 6, tear index 8. 7, and breaking length 3800 metres and a wet rupture energy of 5. 2 at 100 Csf at a power input of 2250 KWh/tonne over dry pulp. These strengths are equal to those reported in North America and Scandinavia for T. M. P. pulps. Fibre classification indicated a higher percentage of long fibre in these pulps than for overseas T. M. Pulp. The stock concentration ex the plates was between 35 and 45 percent oven dry and the fluctuation in motor load as low as plus or minus 3 percent of full motor load. Presteaming the chips at 130 degree C for ten minutes prior to refining gave increases of up to 10 percent in tear index and 5 percent in burst index at a cost of 5-7 percent increase in power consumption. Treatment of the chips with chemicals prior to steaming gave marginal increases in strength again at the cost of increase in power consumption. The role of dams in plates and the cause of high power usage in refining is discussed. A refining theory is offered. Extensive experimental data are included. 11 refs.