**3.2 Kraft pulping properties**

**Figure 4** shows the graphs and equations established to mathematically determine the alkali charge to obtain the kappa number ±18. **Table 4** presents these corresponding values, as well as other technological parameters calculated for the target kappa. Clones decrease the kappa number at an average range rate of 8% (clone D) to 13% (clone A). In the pulp delignification degree for Kappa ±18, the wood from the five genotypes produced pulps with distinct characteristics, except for pulp yield which did not significantly differ between them with values ranging from 51.3–52.8%. Clone C used the lowest alkali to obtain a kappa number ± 18 (23.2%), significantly differing between clones A and B. Consumed alkali ranged between 32.0–40.6 g L−1, with the lowest value for clone D, and with no significant difference between clone E. Clone C obtained the lowest residual effective alkali value (13.3 g L−1), while clones B and D showed the highest values for this parameter (20.0 and 20.3 g L−1, respectively). Clones A, D and E presented the lowest wood specific consumption, with values close to 3.5 m3 t−1, and clone E showed the best performance in terms of pulp productivity (MAIpulp = 19.8 t h−1 yr−1).

### **Figure 4.**

*Kappa number curves as a function of the active alkali applied to the five* Eucalyptus *spp. clones. Adjustedregression for higher correlation coefficient.*

*Wood Quality and Pulping Process Efficiency of Elite* Eucalyptus *spp. Clones Field-Grown… DOI: http://dx.doi.org/10.5772/intechopen.106341*


*REA–residual effective alkali; WSC–wood specific consumption; MAIpulp–mean annual increment of pulp. Means followed by the same letter in the same column do not differ from each other by the Tukey test (p > 0.05).*

### **Table 4.**

*Kraft pulping characterization for Kappa number ± 18 of the five* Eucalyptus *spp. clones.*

### **3.3 Principal components analysis**

**Figure 5** shows the ordering of eigenvectors and the measures of similarity between *Eucalyptus* spp. clones. Clones were preserved in their characteristics but showed proximity between them. Regarding the study parameters, MAIpulp, consumed alkali, fiber lumen width and wood specific consumption are those which represented the largest variances in the analysis, determining the distribution of clones and variables. Three main groups of variables were formed: group 1 containing fiber diameter (FD), alkali charge (AC) and fiber lumen width (FLW), negatively related

### **Figure 5.**

*Principal component analysis of the fiber dimensions, basic density and kraft pulping parameters of the five*  Eucalyptus *spp. clones. FL–fiber length; FD–fiber diameter; FWT–fiber wall thickness; FLW–fiber lumen width; BD- basic density; AC–Alkali charge; CA–consumed alkali; WSC–wood specific consumption and MAIpulp–mean annual pulp increment (significant variables according to Boot N x 10.000 criteria and their percentage of variance; MAIpulp −69.9%; CA – 45.2%; FLW- 42.7%; WSC – 37.5%).*

to clone D; group 2 formed by consumed alkali (CA) and specific wood consumption (WSC) directly related to clone B, and inversely to clone D; and group 3 formed by yield, fiber wall thickness (FWT) and basic density (BD) directly related to clones D, and negatively to clone B.
