FURNISH OPTIMIZATION

A: SUMMARY

This paper deals with the principles of optimization of pulp furnishes for homogeneous tissue products. The major arguments developed are that the most important properties of tissue paper, softness, bulk, and water absorptive capacity can be determined for pure individual pulps, and that these characteristic pulp values, every bit as real as the more familiar breaking length and specific volume, can be combined through the use of the weight average law of mixing to calculate similar values for pulp mixtures. These facts and relevant cost information can be used to optimize a multi-component furnish system. In addition to giving applicable algebraic relationships, a simple, easily visualizable graphical method is introduced. The results show that in the majority of cases a 2-component system is optimum; adding more components invariably decreases the optimum. The concept of universal paper machine is presented, based on the fact that, with respect to these properties, paper machines are similar. Through such universality, a single set of values, established on a single paper machine, can be used to calculate optimum furnish composition for any other machine or technology. A new, density-based proportional softness scale is discussed to facilitate parallel treatment of the three properties discussed. The graphical method also provides a simple way of determining realistic pulp pricing, as well as providing a way to quantify the benefits of stratification. Finally, a new pulp testing method, more appropriate for tissue products, is suggested.