Examples and Results

A selection of the results published by Kazi and Chornet [56]were used to evaluate

the impregnation model and to calculate D at the given impregnation conditions.

Axial impregnation with a 2.3 mol L–1 NaOH solution was calculated for two different

conditions:

_ Conditions A: Pressure 200 kPa, Temperature 75 °C, time 15 min.

_ Conditions B: Pressure 1480 kPa, Temperature 100 °C, time 15 min.

The concentration profiles obtained from model and experimental results are

depicted in Fig. 4.15.

Figure 4.16 shows the radial profiles for the same impregnation conditions as

in Fig. 4.15, under conditions B.

The calculated diffusion coefficients, D, at the given conditions are summarized

in Tab. 4.14.

0 10 20 30 40

0,0

0,2

0,4

0,6

0,8

1,0 Hardwood Axial Impregnation

P = 200 kPa; T = 348 K, t = 15 min

P = 1480 kPa; T = 373 K, t = 15 min

Experiment

Model

NaOH concentration ratio

Axial Position, Z, mm

Fig. 4.15 Profiles of concentration ratio for axial impregnation

with 2.3 mol L–1 NaOH at specified conditions A and B

(see text). Wood sample length Z = 150 mm; radius a = 25 mm

(data from Kazi and Chornet [56]).

4.2 Kraft Pulping Processes 155

0,0 0,1 0,2 0,3 0,4 0,5

0,0

0,2

0,4

0,6

0,8

1,0

Hardwood Radial Impregnation

P = 1480 kPa; T = 373 K, t = 60 min

Experiment

Model

NaOH Concentration ratio

Radial Position, (R-r)/R

Fig. 4.16 Profile of concentration ratio for radial impregnation

with 2.3 mol L–1 NaOH; impregnation pressure = 1480 kPa;

temperature = 100 °C. Wood sample length Z = 150 mm;

radius a = 25 mm (data from Kazi and Chornet [56]).

Tab. 4.14 Conditions of selected impregnation experiments [56]

and calculated diffusion coefficients, D, by numerical solution

(see Section 4.2.3.8).