Studies on Beech Wood Semichemical Pulp. II

Experiments on operating variables in the refining procedures (2)

Abstract

According to the information of the Japan Tappi, in Japan, there are three systems for the refining procedures in semichemical pulping. These systems are as follows :
1. Single-pass refining system.
2. Double-pass refining system.
3. Fiberizing and refining system.
This paper deals with the results of studies on the effects of fiberizing or refining variables ineach system for refining procedure.
In these experiments, beech wood chips cooked by the neutral sodium sulphite solution were refined in a 12 in. single-rotating mill (Spraut Waldron refiner).
The following results were obtained.
1. In the single-pass refining system and the primary refining step at the double-pass refining system, it was found that the unit refining energy was dependent on the refining temperature. The screenings were influenced by the plate separation and the refining temperature. When the operation was treated at high refining temperature, unit refining energy was decreased, but the screenings were increased. But then, screenings were decreased by the narrow plate separation at high refining temperature.
2. In the fiberizing and refining system, it was found that the total energy consumption per unit of feed was dependent on the feeding rate at the refining step, and the unit refining energy was dependent on the plate separation, the refining consistency, and the feeding rate at the refining step.
3. In the fiberizing and refining system, the freenesses and screenings of refined pulps were influenced by the following factors : plate separation, feeding rate, and refining consistency at the refining step. Therfore, refining at the narrow plate separation, low feeding rate, and low refining consistency made it possible to reduce freeness and screenings of refined pulps.
4. In the fiberizing and refining system, the physical properties of refined pulps were influenced by the plate separation at the refining step. As the plate separation was decreased, the physical properties of refined pulps were improved.
5. From these relationships (2, 3, 4), it was clear that there were constant relationships among the unit refining energy, freeness of refined pulps, and physical properties of refined pulps.
As the unit refining energy was increased, the freenesses of refined pulps decreased. The bulk density, bursting strength, and tensile strength of these pulps rose as the freeness was decreased.
6. The physical properties of refined pulp were improved by beating except the tear strength.
7. It was not distinguished that the physical properties of beaten pulps differed with the beating methods except the fiberlength distribution, bulk density, and specks in a hand sheet.