FI118348B - The effect of temperature and alkali supply on the brightness of the pulp - Google Patents

Abstract

A method for improving pulp brightness utilizes a combination of a distributed total white liquor charge during the warm fill, hot fill and cooking stages of a batch cooking process and low cooking temperatures during the cooking stage. The high total white liquor charge ranges between 15 % AA &tilde& 35 % AA, while the cooking temperatures range between 150 &tilde& 168 DEG C._________________________

Description

, 118348 / Effect of temperature and alkali charge on pulp brightness Inverkan av tempur och alkalimatning pä massans ljushet

The present invention relates to a process for improving the final brightness of a pulp. More particularly, the invention relates to modifying both the cooking temperature and the white liquor charge in a rapid displacement heating based cooking system.

Rapid Displacement Heating ("RDH") is a low energy batch cooking process for producing sulphate pulp. The RDH method combines the inherent benefits of batch cooking with the efficient energy use of a continuous cooker by re-using the waste black liquor displaced from the already cooked cooking space to pre-treat the wood chips in the next cooking. Thus, both the chemicals in these fridges and their heat are recycled for subsequent cooking. The pretreatment of the new wood chips in the next cooking begins with low temperature liquids (about 80-130 ° C) and then proceeds with low temperature liquids · ***; higher (about 130-165 ° C) and which heat the cooker to the highest possible temperature before raising the temperatures to steam to the final cooking temperature (170 ° C).

RDH and other alkaline cooking processes produce pulp which S · · ;;; is relatively dark in color. Many applications of pulp and paper often require higher contrast, so the pulp usually needs to be bleached to high brightness to produce white pulp for writing and printing paper and board. The color of the pulp is created by changes in the lignin component of the raw material during the defibration process. Because RDH- • m · ···. the process uses high cooking temperatures and dilute S · black liquor, unfortunately the problem has been poor • 9 ·: *. * bleaching with conventional ECF and TCF bleaching processes • · ·: ... ·. High cooking temperatures and black liquor dilution seem to accelerate the condensation reactions leading to the condensation of lignin with lignin and other wood-extractable substances. As a result, the bleaching of the pulp is reduced.

Thus, an alternative method is needed in the RDH cooking process to avoid such harmful side reactions and to improve the bleaching of the pulp.

The present invention provides a method for improving the brightness of a pulp. The process of the present invention, based on the changes made to the rapid displacement heating batch cooking process, combines the steps of adding white liquor solution [% active alkaline (AA) or effective alkalinity (EA)] or Na-OH to both the warm filling step and the original hot and, on the other hand, boiling the wood chips at temperatures lower than those previously employed in batch-type operation to produce a pulp with improved pulp bleaching. Thus, in the range 15% AA to 35% AA, the total white-white batch is added to the hot and hot stages and to the cooking stage in a predetermined amount. If a cool pad is used in the practice of the invention, the cool white liquor is also added to the black liquor released from the cool liquor collector. White liquor is added as a rule • ·. ·. * · · "· woman soup at every step of the baking process.

• · * • · ·. While cooking the chips, white and * · · * “· * black liquor is present in the kettle. Cooking temperatures are low, around * · * * 150-167 ° C. The final brightness of the pulp is improved by: ** reducing white liquor with high AA or EA to low, ** ·. the cooking temperature. As a result, the amount of pollutants • * · and the consumption of bleaching chemicals in the pulp mill * i *: · 'operations are reduced.

* · • · • · ···

Figure 1 is a schematic representation of the boiler and associated apparatus used in the current RDH cooking system.

3, 118348

Figures 2A, 2B and 2C each show a profile or addition of white liquor at different stages of the RDH cooking process. In Fig. 2A, curve A shows the addition of a small amount of white liquor at the beginning of the warm filling mode. Curve B represents the cooking step and shows the presence of white liquor in the boiler during the actual cooking of the chips.

Figure 2B shows the continuous addition of white liquor to black liquor at each stage of the RDH cooking process, from the warm filling to the completion of the hot filling. The figure also shows that white liquor is also present in the boiler during the actual cooking.

Figure 2C shows the continuous addition of white liquor at each RDH step, including the addition of white liquor to the wash filtrate from the displacement tank.

ί.ί.ϊ Figure 3 shows the Stage 3 RDH system without the addition of • J * white liquor during hot and hot filling.

• · · ··· «.Vj Figure 4 shows a RDH system of step 3 with white liquor • ·,, ·. is added during hot and hot filling.

· · * · «Ί! ί

Fig. 5 is a graph showing the dependence of D1 brightness on the used. of the total chlorine charge (D100 + Dl) in the RDH mass • · ·

and in the baseline case. Curve A

• · »* ·] represents RDH mass R3 (0.225 Kappa factor). Curve B shows: T: RDH mass R4 (0.27 Kappa factor). Curve C represents RDH mass I ***: R7 (0.225 Kappa factor). Curve D represents RDH mass R8 (0.27 ·· *

Kappa factor).

Fig. 5A is a graph showing the dependence of D1 brightness on a D1 chlorine dioxide charge. Curve A represents RDH mass R3 (0.225 kappa factor). Curve B represents the RDH mass R4 (0.27 Kappa factor).

Curve C represents RDH mass R7 (0.225 Kappa factor). Curve D

represents the RDH mass of R8 (0.27 Kappa factor).

118348 4

Figure 6 shows the dependence of the D1 brightness on the total chlorine charge available in the D100 and D1 steps for all bleaches with a Kappa factor of 0.225. Curve A represents RDH mass R3. Curve B represents RDH mass R12. Curve C represents RDH mass R7.

Figure 6A shows the dependence of D1 brightness on the chlorine dioxide charge of the D1 phase. Curve A represents RDH mass R3 (0.225 Kappa factor). Curve B represents RDH mass R12 (0.225 Kappa factor). Curve C represents RDH mass R7 (0.225 Kappa factor).

Figure 7 shows the dependence of D1 brightness on the total chlorine charge available in D100 and D1 steps for all bleaches with a Kappa factor of 0.27. Curve A represents RDH mass R4. Curve B represents RDH mass R12. Curve C represents RDH mass R8.

Fig. 7A shows the dependence of D1 brightness on the chlorine charge of the D1 phase. Curve A represents RDH mass R4 (0.27 Kappa * factor). Curve B represents RDH mass R12 (0.27 Kappa factor).

· * · *. Curve C represents RDH mass R8 (0.27 Kappa factor).

• · Ϊ * t • · · * ·

The present invention provides a method for improving the bleachability of the pulp, based on this method. modifications to the known RDH cooking system for wood chips. More specifically, in this method, a white liquor charge is added from the beginning of the RDH cooking period: T: and continuing to the incremental step i "* j of the process, at which point the actual cooking begins. The method is based on: *: also using some of the comparatively lower cooking temperatures in the actual cooking compared to the cooking temperatures commonly used in the RDH defibration process.

5, 118348

According to the present invention, the total white liquor charge in the range of about 15% AA to 35% AA is divided into hot black liquor, original hot black liquor, and cooking steps. A cool plug or cool liquor collector, if used, will also receive a white liquor charge. In addition to the use of this distributed white liquor charge, the present invention utilizes lower cooking temperatures of about 150-167 ° C. As a result, a pulp is obtained which has improved final brightness after bleaching with any combination of bleaching chemicals.

The operational steps of a typical RDH cooking system are as follows: (1) filling the chips; (2) filling with cool black liquor; (3) filling with warm black liquor; (4) hot black liquor filling; (5) temperature rise; (6) maintaining the temperature; (7) displacement; and (8) pumping out. The basic principles of RDH function are described in U.S. Patent 4,578,149, issued March 25, 1986, the entire contents of which are incorporated herein by reference. Thus, the details of RDH procedures are considered only to the extent that one skilled in the art will be able to understand the changes to the RDH cooking system that result in the pulp of whitening quality described below.

Figure 1 shows schematically the RDH used in pulping.

• • I

···, type of hardware. It is clear that this figure represents

S · I

very general features of the cooking appliance, and that changes and. modifications will be made to this system as detailed below! In the figures shown below, many tools: T: such as gauges, pressure relief connections, pumps and valves * · * are omitted to simplify the designs. Figure 1 illustrates a known RDH cooking ··· process and aims at facilitating the understanding of the improvements made to the process according to the principles of the present invention.

118348 6

Figure 1 illustrates a digester, designated 10, of the type generally used for the chemical cooking of wood chips. The boiler 10 has a cut bottom 12. The inlet valve 14 regulates the entry of various reactive liquids into the boiler 10. The contents of the boiler 10 can be heated to the final cooking temperature by pumping the soup through a heat exchanger or steam in a vented not shown.

After the wood chips have been added to the boiler 10, the cool black liquor (temperature about 70-95 ° C) from the cool broth collector 16 (tank A) 16 is pumped by a pump 18 along a line 22 controlled by a valve 22 through an inlet valve 14. Next, the warm black liquor from the hot broth collector 24 (temperature about 90-150 ° C) is pumped by pump 18 through valve 22 and through valve 14 to the bottom of the boiler 10. During the filling of this warm broth, some of the black liquor is displaced from the boiler 10 and is then returned along line 26 · · V,: to the cool broth collector 16. Then, the hot broth (temperature of about 150-168 ° C) is pumped into the hot broth. from the collector (reservoir C) 28 by a pump 32 controlled by a valve 32 to the bottom of a cooker »··· · ** '· via a valve 14. During the filling of this hot broth • ·, the black liquor is displaced from the boiler 10 and it * ··, ···, is returned to the hot broth collector 24 and the hot broth collector 28, respectively, along lines 34 and 36. In the middle stages of filling the hot liquor, the white liquor stored in the hot white liquor collector 38 is pumped out by pump 30 and connected to the hot black liquor leaving the hot liquor collector 28, whereupon these combined liquors pass through valve Γ ": 32 and further to the bottom of the cooker 10.

·· · »· · * *« «·

After completion of the hot filling, the inlet and outlet valves of the boiler 10 are closed and the temperature increase step begins. Steam is injected into the cooking pot 10 and the temperature is raised to a cooking temperature of about 170 ° C on average.

The temperature of the boiler is maintained at about this temperature until the wood chips have decomposed, depending on the white liquor charge and the H-factor.

After completion of the cooking step, 40 wash liquors (temperature about 70-85 ° C) stored in the displacement tank (tank D) are pumped into the digester 10 using a pump 42 and a valve 44. The contents are washed and the digester 10 cooled. When the washing filtrate is added to the digester 10, the waste broths are displaced and returned to the hot broth collector 24 and hot broth collector 28, respectively, along lines 46 and 48. The displacement step ends when all the wash filtrate has been used, with the amount of filtrate based on the dilution factor of the wash follower. After completion of the displacement, the cooked pulp is pumped from the boiler 10 to an outlet tank by pump 50.

The current RDH cooking system uses cooking temperatures higher than 170 ° C to achieve rapid cooking, which results in faster condensation reactions. The result is bleaching problems when the pulp is processed * ·! ί ϊ by conventional EOF and TCF bleaching methods. The present invention overcomes these problems and ··· improves the bleaching of the pulp by modifying the cooking method of I ··· wood chips. This improved RDH process utilizes higher alkalinity (or white matter).

* · *, Batch) and lower cooking temperatures. Eri-S «I

more specifically, white liquor is added during the warm and initial hot filling phase. This is in contrast to the existing RDH method, · · »* ··· *, where white liquor is only added in the middle of the» · * · '* hot-fill step. Further, when a cool plug is used in the present invention, then, val; coli broth is added to the cool black liquor leaving the cool broth collector (or A tank) M *. Thus, from the beginning of the RDH cooking process to the temperature raising step, white liquor

«I

* ... * is added to the black liquor during each step. The addition of white liquor at each step, also called white liquor 118348 8 profile, is shown in more detail in Figures 2A, 2B and 2C below.

In Fig. 2A, curve A shows the addition of a small amount of white liquor at the beginning of the warm filling as the warm black liquor leaves the B tank or the warm broth collector and flows into the boiler. White liquor can also be added to the A container or to the cool plug, if any. After completion of the hot filling, utilizing two hot broth collectors C1 and C2, the mixture of white liquor and black liquor remains in the cooking pan. Curve B represents the cooking step and shows the presence of white liquor in the boiler during the actual cooking of the chips. Black liquor is also present during cooking.

Figure 2B shows the continuous addition of white liquor to black liquor at each step of the cooking process, starting from hot filling to hot filling.

Figure 2C shows the continuous addition of white liquor at all stages, including the addition of white liquor to the wash filtrate from the displacement tank.

• * · «t t •« • | * Dissolved organic material concentration in original tv .1. the hot filling operation (Cl and C2 tanks containing black liquor) was compared to situations where added and not added! . * ty white liquor during hot and hot filling.

• 5 ·

Figure 3 illustrates the RDH system of step 3, where no white liquor was added at I · * * during warm and hot filling. Only warm black liquor leaves the warm broth collector • (B tank) 24 and flows during hot filling along line V * 56 and further to line * 20 leading to the boiler 10. Although this RDH system comprises two hot roller ** · »collector 28 (Cl tank) and 58 (C2 tank), respectively · ** so there are RDH defibration processes that use only one hot roller # ♦ · * · * broth collector. When the present invention J ... * is implemented in practice, white liquor profiling can be applied to systems regardless of the number of black liquor collectors.

As shown in Figure 3, during the initial hot filling, the hot black liquor exits the hot broth collectors 28 and 58 along lines 60 and 62, respectively, and flows to the cooking pan 10 along lines 64 and 20. In the middle stages of hot filling, the hot white liquor from hot white liquor collector 38 is mixed with the hot black liquor leaving the hot liquor collector 58 along line 66. Thereafter, the mixture flows along lines 64 and 20 to the boiler 10.

Figure 4 shows the RDH system of step 3, where white liquor is added during hot and hot filling. First, during warm filling, the white liquor is added to the warm black liquor leaving the warm liquor collector 24 along line 70. The warm filling flows along lines 56 and 20 to the boiler 10. During this warm filling, either cool or hot white liquor can be used. During the initial hot filling, the hot white liquor from hot white liquor collector 38 is mixed with the black liquor leaving the hot liquor collector 28 along line 72, and further mixed with the second black liquor leaving the second hot liquor collector 58 along lines 62 and 66.

• 14 ·.! · This mixture of hot white liquor and hot black liquor flows »*. *, Of these two hot broth collectors 28 and 58 lines 64

S I

·, And 20 along the stove to 10.

• · * M »t :: * The following results were obtained from this comparison: | * t · * · * Without the addition of white liquor in a hot and hot filling operation (Fig. 3) f t · «# · · * j ** '. Rest. hot Total flow, Dissolved *; ** Fill operation gal. (1) / soup organic matter,%

Cl black liquor 20799 (78724) 13.1 · ».. · C2 black liquor 8709 (32964) 14.9 10 1 1 8348

Adding white liquor to hot and hot filling (Figure 4)

White Liquid Charges: 1.5% AA in Black Cl. Black 1.5% AA in C2 Black Liquor

Rest. hot Total flow, Dissolved filling gal. (1) / soup organic matter,%

Cl black liquor 19877 (75234) 10.1 C2 black liquor 7971 (30170) 9.8 This case study clearly demonstrates that the concentration of dissolved organic compounds in the original hot fill process can be modified by adding white liquor to the hot fill line. The content of dissolved organic compounds in C1 black liquor and C2 black liquor decreases from 13.1% to 10.1% and from 14.9% to 9.8%, respectively.

To maximize the benefits of bleaching and improve lignin removal in this RDH process, warm black liquor (temperature about 70-150 ° C and concentration. 3-20 g / l AA) and hot black liquor (temperature about * * f * · *; * in the range 100-168 ° C and a concentration in the range 8-30 g / 1 AA) should • · · ·· *! enhances by any combination of white liquor or NaOH solution.

• »• * · φ · • * *

As can be seen from the above figures, hot and hot: T: black liquor can be modified using white liquor profiling. These liquids may also be modified with sodium hydroxide. (NaOH). Addition of white liquor or NaOH controls the concentration of total solids (* · · TDS) and the concentration of black liquor. * by mixing any combination of black liquor, white liquor and NaOH. The washing filtrate displacement step, where the temperature of the black liquor φ: *. * J is maintained at about 50-105 ° C and the concentration of the black liquor 118348 is maintained at 1-18 g / 1 AA, can be any combination of white liquor or NaOH solution.

The following examples further illustrate preferred embodiments of the present invention.

As shown below, in Tables 1, IA, 2, 2A, 3 and 3A

shows the fiberization results and the conditions of several soups used to prepare RDH pulps for subsequent bleaching studies. The fiberization results are summarized in Table 3B.

Table 1 RDH Defibration Conditions and Results - "Best Case"

Soup R 1 R 2 R 3 R 4 R 4 Followed by R 1 R2 trace R3 trace. R4 nasty.

H-factor 937,532,475,452 AA (TAPPI) 16.0 16.0 16.0 16 for hot fill,%

Sulphide 30.4 30 30.3 30.2 Mouth, (TAPPI),% of AA • · • * · * **. * Maximum 160 160 160 160 *: * Temperature. ,

° C

• · · • · φ ·

Time for high 16 20 17 19 • * to the lowest temperature, min • · ·

Time of mouth 130 37 60 57 at moderate temperatures, min «· ·

Kappa, 7.2 8.9 9.2 9.8 unselected · »« «· **: · 'Kappa, 7.1 8.2 8.8 9.3 · * · *: screened * ··· • * • · * 118348 12

Total- 46.3 47.3 48.2 1.7 Yield%

0.9 1.2 1.4 1.7 Boys%

Screened 45.4 46.1 46.8 46.9 Yield%

Viscous 26 39 40.7 44.9 tees, 0.5% CED, cp Residue after cooking: AA (Na 2 O), 28.2 31.6 32.9 31.6

g / L

EA (Na 2 O), 21.1 24.2 24.2 24.2

g / L

Na 2 S 14.3 14.9 17.4 14.9

(Na 2 O), g / L

TTA (Na 2 O), g / L

Solid, 14.8 15.9 16.7 16.8%

Solid, 161,173,183,185

g / L

Sulphity, 51 47.1 52.9 47.1 * · * · *% AA ··· ________ ____________

Hot Filling: · «· *

Hot 18 18 18 18: *, lye

! # · / Stakes, L

• «· V: Filling- 13 14 13 13 time, min

! ·, * Temperatures. ° C

• * *: Peak 130 127 127 128 • · ·; Pohja 145 141 141 141 • · · m · i -., 1. i i i. . .........................,, - • · * · • · · · · · · · · · · · 118348 13

Chemical conditions in the collector: AA (Na 2 O), 22.9 20.6 25.7 21.7 29.2 24.6 27.3 23.6

g / L

EA (Na 2 O), 16.1 15.1 18.1 16.1 20.2 18.3 19.8 17.9

g / L

Na 2 S 13.7 11 15.2 11.2 18 12.7 14.9 11.4

(Na 2 O), g / L

TTA (Na20), - - - - -

g / L

Sulphide, 59.4 53.4 59.1 51.6 61.6 51.2 54.9 48.3% of AA

Solids, 9.5 10.5 11.1 11.9 11.9 13.6 12.7 13.6%

Solid, 99.8 111 118 127 127 146 137 146

g / L

Elapsed time 45 43 41 42 total , min * * includes the time to heat to 145 ° C and the time at 145 ° C after the initial injection of hot black liquor and the last addition of hot ML-VL.

Table IA

Conditions and Results of RDH Defibration - "Best Case" ··· * ····.: · Soup R1 R1 R2 R3 R4 ··. ··. number Rl after R2 trace R3 trace. R4 nasty.

• · · • * - - -------------

White * · * · 'lye: • · * «· J ..... ..........' '-—

White 6.04 5.65 5.53 5.52 lye

,. ·. contribution, L

• · · ···

Hot M / V 5 4.13 5.5 5.8; * · *: Incremental 11 11 9 9 "... time, min t:

Temperature, ° C

• ♦ • • • · · • 14 14 1 14 1 1 8348

Peak 140 139 140 139

Bottom 141 141 144 143

Chemical conditions in the collector: (TAPPI) AA (Na 2 O), 98 99.2 10.2 101.5

g / L

EA (Na 2 O), 83.1 84.3 85.8 86.2

g / L

Na2S - -

(Na 2 O), g / L

TTA (Na 2 O), g / L

Sulphide, 30.4 30.3 30.2% AA

Chip & Liquor:

Chip, g 3,700 3,500 3,500 3,500

37.3 37.3 37.3 37.3 Moisture of Chips,% O.D. solids 62.7 62.7 62.7 62.7 ingredients,% Warm filling: Warm 24.7 24 24 24 * 1 lye

/ V input, L

Output pH, 12.8 13.5 13.3 13.3 · 1 · 1 · beginning • · ·· .: 1.1 · increment 15 15 15 15 time, min I · 1

Temperature, ° C

Top 100 104 102 100 • ·

Pohja 113 112 111 112 • »· —im -« i i. ! · Ι i - m · 'i i i • «1 • · · m • · ·! : • · «• · 1 • · · • • • • t1 • 1 • t ··« 118348 15

Chemical conditions in the collector: AA (Na 2 O), 23.6 16.4 26.4 17.7 25.7 19.2 28.5 21.1

g / L

EA (Na 2 O), 16.4 10.5 17.4 11.5 18 12.4 18.6 13.6

g / L

Na 2 S 14.3 11.8 18 12.4 15.5 13.6 19.8 14.9

(Na 2 O), g / L

TTA (Na20), --------

g / L

Sulphide, 60.8 71.7 68.3 70.2 60.3 71 69.5 70.6% of AA

Solid, 9 9.25 13.6 12.4 14.3 13.1 14.1 13.1%

Solid, 94.3 96.4 147 131 155 141 152 141

g / L

Elapsed time 40 31 34 33 total, min *

Override:

The displacement- 32 32 32 32

volume, L

Addition time, 26 26 26 26 min • Y · Chemical conditions in the collector: (TAPPI) * · ./j* AA (Na20), 9.5 10.1 9 10.1

'G / L

····: * · *: EA (Na20), 9.5 10.1 9 10.1

I g / L

/; ·. Na2S - -

(Na 2 O), g / L

TTA (Na20), - -

g / L

• · · - ''

Sulphide, o 0 o 0% AA ·· tmii - "* * includes fill time, time to heat to 120 ° C, and time to 120 ° C after warm filling.

• · • · »« · 16 1 1 8348

Table 2 RDH Leaching Conditions and Results - "Basic Case"

Soup R 1 R 2 R 3 R 4 R 4 Followed by R 1 R2 trace R3 trace. R4 nasty.

H-factor 116.1 765 831 832 AA (TAPPI) 10.0 10.0 10.0 10.0 for hot fill,%

Sulfide 30.2 30.3 30.3 30.2 Mouth, (TAPPI),% AA

Highest 170 170 170 170 temperatures,

° C

Time to mouth temperature 23 27 21 21, min

Time 62 62 41 42 at moderate temperature, min

Kappa, 7.6 9.7 9.5 8.9 * Un Screened ·· «.,, Kappa, 7.2 9.1 8.9 8.8 Screened • ·» »i * Total- 47.3 48 , 3 48.6 49.1 Yield,% ♦ ·· * · * '*' Total 1.1 1.1 1.7 1.4 Deletion,%

Screened 46.2 46.7 46.9 47.7 Yield% · · '*. · *: ·. viscous- 19.5 33.2 33.3 32.2 * · ** teet, 0.5% CED, cp * · · · · · · · · · 17 1,18348 Residue after cooking: AA (Na 2 O), 27.9 25.4 26 25.4

g / L

EA (Na 2 O), 19.2 18 17.4 17.4

g / L

Na 2 S 17.4 14.9 17.4 16

(Na 2 O), g / L

TTA (Na 2 O), g / L

Solid, 19 19.1 19.2 19.1%

Solids, 210 211 213 210

g / L

Sulphide, 62.4 58.3 66.2 63% AA

Hot Fill:

Hot 18 18 18 18 lye

contribution, L

Filling 12 '13 12 13 Time, min

Temp. 0 C

. * · *: Peak 135 137 137 135 • · .. *.! * Bottom 153 153 154 155 * ------- - ----- * a «··· * Chemical conditions in collector: t * • tt AA (Na20), 30.4 23.6 26 21.1 26.7 20.5 26.4 20.5

g / L

* ϊ * · * · * * EA (Na20), 22.3 16.2 18.6 14.3 18 13.6 18.3 13.6

g / L

*

Na 2 S 16.1 14.9 14.9 13.6 17.4 13.6 16.1 13.6 .f. (Na20), * · *.

g / L

a * · V! TTA (Na 2 O) -. - - - ::: = ^ a «· *:: * a ··· • * 9 f a ·· l8 1 1 8348

Sulphide, 53.3 63.6 56.9 64.5 65.2 67.3 61.4 67.3% AA

Solid, 16.7 17 17.2 17.1 17 17.3 17 16.9%

Solid, 183 185 189 187 187 189 186 184

g / L

Elapsed time 46 44 45 44 total, min * * includes time to heat to 155 ° C and time at 155 ° C after initial injection of hot black liquor and last addition of hot ML-VL.

Table 2A

RDH Defibration Conditions and Results - The "Basic Case"

Soup R5 R6 R6 R7 R8 number R5 after. R6 nasty R7 nasty. R8 nasty.

White liquor:

White 3.47 3.45 3.46 3.47 lye

contribution, L

Hot M / V 5.4 7 5.6 5

Incremental 9 9 9 9 ** · * time, min ···

Temperature, ° C

«

Peak 151 152 151 151 * *

Bottom 149 147 145 144 .......- ..... ........................

Chemical conditions in the collector: (TAPPI). AA (Na 2 O), 100.8 101.4 101.2 100.8

I: Ϊ g / L

«·· - * 'f # * v: EA (Na20), 85.6 86 85.9 85.6

Λ. g / L

»E · r · f • • f f: ti · t • · ·! *: • * ·· t · • ·

III

1 1 8348 19

Na2S -

(Na 2 O), g / L

TTA (Na 2 O), 121.6 122.8 123.1 120.6

g / L

Sulphide, 30.2 30.3 30.3 30.2% AA

Chip & Liquor:

Chip, g 3,500 3,500 3,500 3,500

37.3 37.3 37.3 37.3 Moisture of Chips,% O.D. solids 62.7 62.7 62.7 62.7 ingredients,% Warm filling: Warm 24.4 25 25.2 24 liquor

contribution, L

Output pH, 13.1 13.3 13.5 13.3 at start

Incremental 15 15 15 15 time, min

Temperature, ° C

Top 109 109 106 106 ·

Bottom 121 120 118 116 • * · ·

Chemical conditions in the collector: (TAPPI) «· l i *, AA (Na 2 O), 28.1 19.2 27.9 18.6 26.7 19.2 26.7 19.7

g / L

v · «| ? · · '' EA (Na 2 O), 18.3 12.4 18 11.2 18 11.8 18.6 12.1

g / L

Λ v ..: Na2S 19.6 13.6 19.8 14.9 17.4 14.9 16.1 15.1 ΓΓ; (Na20),

\ g / L

«M • * ·

Sulphity, 69.8 70.8 71 79.6 65.2 77.1 60.7 77.2% of AA • f · va 9 · f »m * ***» · * «» ·· 20 1 1 8348

Solid, 14.5 15.4 15 16 14.7 15.5 14.6 15.9%

Solid, 157,167,164,173,159,168,158,172

g / L

Elapsed time 35 33 31 30 total , min *

Discrimination:

The displacement- 32 32 32 32

volume, L

Added time, 26 26 26 26 min

Chemical conditions in the collector: AA (Na 2 O), 4.3 4.31 4.3 4.3

g / L

EA (Na 2 O), 3.7 3.7 3.7 3.5

g / L

Na 2 S 1.24 1.24 1.24 1.74

(Na 2 O), g / L

Sulphide, 27.9 27.9 27.9 27.9% AA

Solid, 9.7 10.6 10.4 10.3%

Solids, 102 112 109 108

* ··; · g / L

• * · _ * -------------- * "*. T * includes fill time, time to heat to 120 ° C, and time to 120 ° C after warm filling .

• · • · · • * * »• · * • · ·. ···. Table 3 * · * * RDH Leaching Conditions and Results - "Best Feasible Case"

Soup R9 RIO R11 R12 R * *] 'number R9 RIO nasty. Rll crap. R12 nasty.

• · · v: H-factor 484 558 483 494 • · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · ··· · 9 16.0 16.0 16 for hot fill,%

Sulfide 30.6 30.2 29.8 30.4 Mouth, (TAPPI),% AA

Maximum 160 160 160 160 temperature,

° C

Time to 20 to 20 18 16 to the worst temperature, min

Time 60 60 62 62 63 at moderate temperatures, min

Kappa, 9.1 8.9 9.6 10 unselected

Kappa, 8.1 8.5 9.2 9.3 screened

Total- 48.1 48.1 49.1 49.1 Yield%

Overall 1.1 1.1 1.5 1.5 1.3 Boys%

Screened 47 46.9 47.6 47.8 Yield,% · »·» ·· 1 2 3 Viscous 33.5 33 39.3 32.1 ”1: teet, • 0.5% CED, cp • - '------ - .....-.......

• · · * ·: 1 'Residue after cooking: t · · AA (Na 2 O), 37.6 32.8 34.1 33.5

g / L

* • · · EA (Na 2 O), 28.6 25.3 25.9 25.3

* · 1.1: ': g / L

; 1.1: Na 2 S 17.9 15.2 16.4 16.4

(Na 2 O), g / L

M · • · · • ♦ • · · 1 • · 2 • · 3 22 118348

Solid, 18.8 19.1 19.2 19.3%

Solid, 210,212,215,214

g / L

Sulphide, 47.9 45.7 48.1 49% AA

Hot Fill:

Hot 18 18 18 18.7 lye

contribution, L

Filling 13 13 13 13 time, min

Temp. ° C

Peak 129 132 132 132

Bottom 145 147 147 145

Chemical conditions in the collector: AA (Na 2 O), 27.8 25.9 27.3 25.3 27.1 24.6 26.5 23.4

g / L

EA (Na 2 O), 19.9 18.9 19.9 18.3 20.2 18.3 19.57 17

g / L

Na 2 S 15.8 13.4 14.9 13.9 13.9 12.6 13.9 12.6 (Na 2 O),

S / L

• · · * «* TTA (Na20), _____

· 1 g / L

• · * *: *; Sulphity, 56.8 54.1 54.2 55.3 50.9 51.2 52.3 54.7 • \ ·% AA

Solid, 16.2 16.1 16.7 16.7 17 17.2 17.3 17% • · · ° *

Solid, 177 176 182 183 187 189 190 186

. . ·. g / L

• · · • · a

Elapsed time 42 42 42 3 9 total, min * • · a • • a —— Il '»*" aa · * includes time to heat to 145 ° C and time to 145 ° C for hot black liquor after the initial injection and the last addition of the hot ML-VL mixture.

a ·· • a • a • a · 23 118348

Table 3A

RDH Defibration Conditions and Results - "Best Feasible Case"

Soup R9 RIO R12 R12 R12 Number R9 RIO nasty. Rll crap. R12 nasty.

White-lye:

White 6.17 5.81 5.79 5.6 Alkaline

contribution, L

Hot M / V 4.8 5.2 5.0 6.4

Incremental 10 10 10 9 time, min

Temperature, ° C

Peak 139 140 139 141

Bottom 139 145 140 144

Chemical conditions in the collector: (TAPPI) AA (Na 2 O), 107.3 96.4 96.7 100

g / L

EA (Na 2 O), 90.8 81.8 82.3 84.8

g / L

Y: TTA (Na 2 O), 125.8 115.6 117.8 120.9

g / L

Φ · · · · · ·

Sulphity, 30.6 30.2 29.8 30.4% of AA • · • · · ____ ._ • t · ----------- ^ _ - - ------ ---------

Chips & Liquor: • · · • · ·

Chip charge, g 3,500 3,500 3,500 3,500,. ·, Moisture of chips 37.3 37.3 37.3 37.3,% • · · • · * '*! * O.D. solid- 62.7 62.7 62.7 62.7 substances,% • · * '• __________________ • · * i: • · · • »· • · · ♦ • 1 • * • · ··· 24 118348 Warm Fill: Warm 24.5 24.3 23.9 24.2 Alkaline

contribution, L

Output pH, 13.3 13.2 13.2 13 at the beginning

Incremental 15 15 15 15 time, min

Temperature, ° C

Peak 108 106 104 108

Bottom 121 117 116 118

Chemical conditions in the collector: (TAPPI) AA (Na 2 O), 27.1 21.1 26.5 21.1 26.5 20.8 25.9 20.8

g / L

EA (Na 2 O), 20.5 14.5 18.9 14.1 18.3 13.3 17.7 13.3

g / L

Na 2 S 13.3 13.3 15.2 14.1 16.4 15.2 16.4 15.2

(Na 2 O), g / L

Sulphide, 48.7 62.6 57.4 66.4 61.9 72.1 63.3 72.1% of AA

Solid, 14.3 14.9 14.8 15.8 15.6 16.1 15 15.6% • · Φ · · • f «*! Solids, 155 161 162 171 170 176 163 170

.. '. R g / L

·· »·"! Elapsed time 30 30 31 30: ***: total, min1 i «• ^“ 1 ““ p— • I ·

Elimination: • ·· * · · * Elimination 32 32 32 32

volume, L

t 1 1 '· "··' Increment Time, 26 26 26 26 min · · 1 · * · · · · · t: M» * • · · ♦ ♦ ♦ · 1 • • 1 1 1 1 1 1 1 25 118348

Chemical conditions in the collector: (TAPPI) AA (Na 2 O), 9.5 9.8 8.8 11.4

g / L

EA (Na 2 O), 8.2 9.2 8.2 10.7

g / L

Na 2 S 2.5 1.3 1.3 1.3

(Na 2 O), g / L

Sulphide, 31.7 13 14.6 13.1% AA

Solid, 10.3 10.6 11.2%

Solid, 109,112,118

g / L

* includes fill time, time to heat to 120 ° C, and time to 120 ° C after warm filling.

Table 3B

SUMMARY OF THE FIBER TEST

Soup number

Best Soup: New RDH Cooking Method R3 R4 • · • * · • .......... I II I .........

. ·. Basic Soup: Old RDH Cooking Procedure R7 R8 vt · * 1 1 *

• · V

«···«: Best Practice Soup:, Modified New RDH Cooking Procedure R12 ··· i ...............

Cooking conditions R3 R4 R7 R8 R12 I * * "'' '· Warm filling • · · _ EA (g / 1) 18 18.6 18 18.6 17.7

Na20 * .na • · · * ... * · Solid,% 14.3 14.1 14.7 14.6 15 M · • · · • t v · ··· * · a · ··· 26 118348

Hot Fill EA (g / l) Na 2 O 20 19.8 18 18.3 19.6

Solid,% 11.9 12.7 17 17 17.3

Cooking Stage AA Charge,% 16 16 10 10 16 H-factor 475 452 831 832 494

Highest Temperature, 160 160 170 170 160

° C

Discrimination EA (g / l) 9 10.1 3.7 3.5 10.7

Na20 na

Solid,% 0 0 10.4 10.3 10

Example 1

The following final pulps were prepared for the bleaching study:

Case Soup no. Kappa Brightness, KILL

; * · *: "Paras" R3 8.8 45.3 * I R4 9.345.0 • · t "Perus" R7 8.9 4 0.6 ···! R8 8.8 41.3 • ·

• · I

• * .p "Best Implemented RIO 8.5 41.5" Rii 9.2 4 0.8 R12 9.3 41.5 e

Five RDH pulps (R3, R4, R7, R8 and R12) were bleached using the order (O) (D100) (EO) (D). However, for each of these five RDH- · · * · masses, the lignin was first removed with oxygen: t:! stirring reactors using the! ***: conditions shown in Table 4 below.

* • e · i *: e · e ♦ • · ·· · 27 118348

Table 4

Conditions for oxygen-depleted lignin removal

Best Case Basic Case Best Available Case Sample R3 R4 R7 R8 R12

Species Aspen Aspen Aspen Aspen Aspen

Cooking- RDH RDH RDH RDH RDH

way

Kappa 8.8 9.2 8.9 8.8 9.3

Viscosity 40.7 44.9 33.3 32.2 32.1 bond, mPa. s

Whiteness 45.3 45 40.6 41.3 41.5 Semen Brightness,% 0 Phase: 95 psig, 99 ° C, Pit. 12%

NaOH,% 2 2 2 2 2 02 time, 60 60 60 60 60 min final 12.8 12.9 12.5 12.5 12.3

ϊ ^ ϊ nen pH

Kappa 4.7 5.2 4.7 4.5 5 I · * *; *: viscose 14.4 13.8 12.6 13.6 12.5 µm,. . ·, MPa. s «« t »··

Kappa 46.6 43.5 47.2 48.9 50 factor decrease,, *. % * · · «··: *: ': Yield 95.2 95.8 94.3 98.8 94.4 of crude * * ·': *%

Ml ΐ i: • · · M · ♦ · · • * ♦ · • · 9 • · ··· 28 118348

For bleaching studies, using a Kappa factor of 0.225, the chlorine dioxide charge in the D100 step was calculated for R3, R7 and R12. A Kappa factor of 0.27 was used for the masses R4, R8 and R12. Tables 5 to 10 below show the conditions for (D100) (Eo) (D) bleaching and the results obtained from these oxygen-free, lignin-free pulps. The concentration of the chlorine dioxide solution was changed by a factor of 0.92 to compensate for the loss of chlorine dioxide during the filling of reactors and polyethylene bags during bleaching.

Table 5

D-bleaching of optimal RDH pulp (O) (D100) (Eo)

Factor = 0.225 Sample R3

Kind of Aspen

Cooking method RDH

02 mass, Kappa 4.7

Viscosity, mPa.s 14.4 D-100 phase: 30 min, 68 ° C, Pit. 4,2%

Chlorination factor 0.23 C102, available as Cl2 1.06 * * · *. ' Actual C102, used as 1.15 · * · as available Cl2 **** Replacement,% 100 µl H2SO4,% 1.5, V, Final pH 2 s · * Residual, g / L used- 0 , 14; Ϊ *; Cl2 in the presence of E2-phase: 60 min, 74 ° C, l.p. 10%

NaOH,% 0.8: 02 pressure, psig 25 • Y * t 02 time, min 15 V i Final pH 12.4 K (25 mL) 2.3 V: Viscosity, mPa.s 13.7, ··, Raw Material Yield,% 93.5 * · · · · · · · · · · · · · · · · · · · · · * »* 29 118348 Phase D: 74 ° C, 210 min, Pit. 10% Sample no. # 1 # 2 # 3 # 4 # 5 # 6 # 7 # 8 C102 as C102, 0.1 0.3 0.5 0.7 0.9 1.1 0.9 1.1% *

Actual 0.11 0.33 0.54 0.76 0.98 1.2 0.98 1.2 C102,% C102

NaOH,% 00 0.09 0.16 0.25 0.3 0.33 0.42 H2SO4,% 0.1 0.05 0 0 0 0 0 0

Final pH 4.1 3.4 3.3 3.3 2.9 2.6 3.6 3.7 Residue form 0.02 0.01 0.01 0.02 0.02 0.02 0 0 in C102, %

Brightness, 89.7 90.4 91.2 91.5 91.6 92 91.1 91.3

%BIG

Viscous 13.1 - - 11.2 - - 9.2 teet, mPa.s * True C102 Pit. x 0.92 Table 6

D-Bleaching of Optimum RDH Mass (O) (D100) (Eo) Gross Factor = 0.27

v V

V. * Sample R4 .:. Species Aspen

••• j Cooking method RDH

* j * 02 mass, Kappa 5.2

Viscosity, mPa.s 13.8 D-100 phase: 30 min, 68 ° C, Pit. 4.2%; · T M »: chlorination factor 0.27 C102, available as 1.4 C ^ ma * i · '; Actual C102, used as 1.53 available Cl2: Replacement,% 100.:. H2SO4,% 2 *, · · Final pH 1.9 Residual, g / L used- 0.09 '· *' in Cl2: ao r4: · »♦» 11 11 30 118348 EO- Phase: 60 min, 74 ° C, Pit. 10%

NaOH,% 0.8 O2 pressure, psig 25 O2 time, min 15

Final pH 12.5 K (25 mL) 2

Viscosity, mPa.s 13.3

Raw material yield,% 92.8 D phase: 74 ° C, 210 min, Pit. 10% Sample no. # 1 # 2 # 3 # 4 # 5 # 6 # 7 # 8

ClO2 as ClO2, 0.1 0.3 0.5 0.7 0.9 1.1 0.9 1.1% *

Actual 0.11 0.33 0.54 0.76 0.98 1.2 0.98 1.2 C102,% C102

NaOH,% 00 0.09 0.16 0.25 0.3 0.33 0.42 H2SO4,% 0.1 0.05 0 0 0 0 0 0

Final pH 4.3 3.4 3.4 3.2 2.8 2.7 3.7 3.5 Residue form 0.01 0.01 0.01 0.02 0.01 0.01 0 0 C102,%

Brightness,% ISO 89.8 90.5 91.2 91.5 91.8 91.8 91.4 91.5

Viscosity 12.5 - - 11.6 - - - 9.8 * Actual ClO2 Pit. x 0.92 • · • · · · · · · · · · · · · · · · · · · · ·; D-bleaching basic RDH pulp (O) (D100) (Eo)

Gross factor = 0.225 • · · Sample R7. La j i Aspen

: .i .: Cooking method RDH

02 mass, Kappa 4.5 * \ Viscosity, mPa.s 13.6 • · · *. ' * D-100 Phase: 30 min, 68 ° C, Pit. 4.2% • * ·:: * "Chlorination factor 0.23 C102, available as Cl2 at 1.01 * .. * 31 318348

Actual C102, Used as 1.1 Cl2 Replacement,% 100 H2SO4,% 2

Final pH 2.7 Residue, g / L of 0.01 in Cl2 EO-phase: 60 min, 74 ° C, Pit. 10%

NaOH,% 0.8 O2 pressure, psig 25 O2 time, min 15

Final pH 12.3 K (25 mL) 2.3

Viscosity, mPa.s 13.3

Yield from crude material,% 97 D-phase: 74 ° C, 210 min, Pit. 10% Sample no. # 1 # 2 # 3 # 4 # 5 # 6 C102 as C102, 0.1 0.3 0.5 0.7 0.9 1.1% *

Actual 0.11 0.33 0.54 0.76 0.98 1.2 C102,% C102

NaOH,% 00 0.08 0.2 0.33 0.42 H2SO4,% 0.10.050 0 0 0. . Final pH 4 3.5 3.4 3.4 3.4 3.8 • · * • · · · * Residual form 0 0 0 0 0 0 ··· dossa C102,% ·· *

Brightness,% ISO 87.6 88.7 89, 7 90.3 90.3 90.6 • · • ·. . *. Viscose Set 12.6 - - 11.4 - 9.6 • · · r '' • · · ________ _____: * Actual C102 Pit. x 0.92 • · *

Table 8 • · · * # ·

D-bleaching of basic RDH pulp (O) (D100) (Eo) • * · • * · ···. Gross factor = 0.27 h · * »« Sample R8; Type V Aspen

. ***. Cooking method RDH

··· 32 1 1 8348 02-Mass, Kappa 4.7

Viscosity, mPa.s 12.6 (D-100) step: 30 min, 68 ° C, Pit. 4,2%

Chlorination factor 0.27 C102, available at 1.27 C ^ ma *

Actual C102, Used as 1.38 Cl2 Replacement,% 100 H2SO4,% 2

Final pH 1.9 Residual, g / L of 0.07 in Cl2 EO-phase: 60 min, 74 ° C, Pit. 10%

NaOH,% 0.8 O2 pressure, psig 25 O2 time, min 15

Final pH 12.2 K (25 mL) 2.1

Viscosity, mPa.s 12.6

Yield from crude material,% 94.2 Phase D: 74 ° C, 210 min, Pit. 10% Sample no. # 1 # 2 # 3 # 4 # 5. # 6 C102 as Cl02, 0.1 0.3 0.5 0.7 0.9 1.1% *: V: Actual 0.11 0.33 0.54 0.76 0.98 1.2 C102 ,% C102 • · »· ·: · NaOH,% 0 0 0.08 0.2 0.33 0.42 ·» · * * H2S04,% 0.1 0.05 0 0 0 0 «* * · * · "* Final pH 3.6 3.1 3.1 3.1 3.2 3.6 3.6 Residual form 000000 in C102,% • · · *“ / / Brightness,% ISO 87 88 , 7 89.3 90.1 90.5 90.5 * · · • * ·

Viscosity, 12.2 - 11.2 - 9.5 mPa.s * · · · .. .. * True C102 Pit. x 0.92 • · · • · · * * t · »» · • * • · ·· * 33 1 1 8348

Table 9

D-bleaching of the best achievable RDH pulp (0) (D100) (Eo)

Factor = 0.225 Sample R12

Kind of Aspen

Cooking method RDH

02 mass, Kappa 5

Viscosity, mPa.s 12.5 D-100 phase: 30 min, 68 ° C, Pit. 4,2%

Chlorination factor 0.03 C102, available as 1.13 Cl2 *

Actual ClO2, Used as 1.22 Available Cl2 Replacement,% 100 H2SO4,% 1.5

Final pH 2 Residue, g / L of 0.04 in Cl2 EO-phase: 60 min, 74 ° C, Pit. 10%

NaOH,% 0.8 O2 pressure, psig 25 O2 time, min 15

Final pH 12.7 K (25 mL) 2.3

Viscosity, mPa.s 11.9 '· * · * Raw material yield,% • · · ", D-phase: 74 ° C, 210 min, Length 10% Sample # 1 # 2 # 3 # 4 # 5 # 6 • · C102 as C102, 0.1 0.3 0.5 0.7 0.9 1.1 • · *% «kt · * I φ * •

Actual 0.11 0 # 33 0.54 0.76 0.98 1.2 C102,% C102 «* · • · ·. * ·. ·. NaOH,% 0 0 0.08 0.2 0.33 0.42 • · * Φ H2SO4,% 0.1 0.05 0 0 0 0 • a · l ***: Final pH 4.1 3.7 3,4 3,4 3,4 3,3 * · · Residual form 0.01 0.01 0.01 0.01 0.01 0.01 • · 'dossa C102,% • * • φ φ φ φ 34 118348

Brightness,% ISO 88.9 90 90.8 91 91.6 91.8

Viscosity 11/9 - - 10.5 - 9.4 * Actual C102 Pit. x 0.92

Table 10

D-bleaching of the best achievable RDH pulp (0) (D100) (Eo)

Factor = 0.27 Sample R12

Species Aspen

Cooking method RDH

02 mass, Kappa 5

Viscosity, mPa.s 12.5 D-100 phase: 30 min, 68 ° C, Pit. 4,2%

Chlorination factor 0.03 C102, available as 1.35 Cl2 = *

Actual C102, Used as 1.47 Available Cl2 Replacement,% 100 H2SO4,% 2

Final pH 2.3 Residue, g / L available in 0.08 Cl2: Y: E0 step: 60 min, 74 ° C, Pit. 10% • · ..II * NaOH,% 0.8 02 pressure, psig 25; * j 02 time, min 15: *: Final pH 12.6 K no. (25 Ml) 2.2 '.ί. * Viscosity, mPa.s 12.2 j * · *; Yield from crude material,% m D-phase: 74 ° C, 210 min, Pit. 10% Sample no. # 1 # 2 # 3 # 4 # 5 # 6 Φ · • · · * \ * C102 as C102, 0.1 0.3 0.5 0.7 0.9 1.1 • · · o, * · «-¾ • *» »" *: Actual 0.11 0.33 0.54 0.76 0.98 1.2 · «* 1 l» l * / C102,% C102 ·· · · · • ♦ * ... \ NaOH,% 0 0 0.08 0.2 0.33 0.42 • · ·· * 4 35 1 1 8348 H2S04,% 0.1 0.05 O 0 0 0

Final pH 3.9 3.4 3.3 3.3 3.3 3.3 Residue form 0.01 0.01 0.01 0.01 0 0.01 dossa C102,%

Brightness,% ISO 88.9 90 90.8 91.1 91.5 91.8

Viscosity, 12.4 - 10.7 - 9.5 mPa. s * Actual ClO2 Pit. x 0.92

As seen in Figures 5 and 5A, the use of a higher Kappa factor did not appear to reduce the need for chlorine dioxide in the D1 stage. The best case RDH masses (R3 and R4) produced a brightness of 1.5-2 points higher than the baseline RDH masses (R7 and R8) using equivalent chlorine dioxide charges.

Figures 6 and 6A show that the brightness achieved with the RDH mass (R12) corresponding to the most feasible case was average, i.e. between the brightness of the best case RDH mass (R3) and the base case RDH mass (R7).

• * • · ♦ • · ·

Figures 7 and 7A show that the brightness achieved with the RDH mass (R12) corresponding to the most feasible case "* | t" was average, i.e., the RDH mass of the best case (R4) and the RDH mass corresponding to the base case. pulp (R8) between the whites.

• ·· t:: «

Table 11 below summarizes the results obtained from pulp bleaching studies. The pulps which were bleached: T: The easiest were the pulps corresponding to the best case. The most difficult to bleach were the masses of the base case, and the bleachability of the most feasible case was i: "* between the two classes. The results showed that a high degree of alkalinity (adding white liquor to warm and hot fill): ***: work and cooking stage, AA contribution in the range 15-35% AA) ··· 36 118348 combined with low cooking temperature (about 150-167 ° C) improves the whiteness of the pulp and thus the final brightness of the pulp. during cooking should be kept.

Table 11

SUMMARY OF THE BLEACHING STUDY

Soup number

Best Soup: New RDH Cooking Method R3 R4

Basic soup: Old RDH cooking method R7 R8

The most realistic soup:

Modified new RDH cooking procedure R12

Bleaching results

Kappa at 0.225 D (100% C102 substitution) factor e · „ii * Final brightness,% IS0 * · · · · · · · · · · · · · · · · · · · · · · · ·020202 Cl02 contribution in the last D step,% *. 0.1 0.3 0.5 0.7 0.9 1.1 ::: _ ·: *. R3 89.7 90.4 91.2 91.5 91.9 92 · * * (Best soup) R12 88.9 90 90.8 91 91.6 91.8. ·:% (Parh.

• · · \ tot.

existing) »· · •» 1: R7 87.6 88.7 89.7 90.3 90.3 90.6 * 1 * (Basic) «· · • · · - '- 111 e * \ t: Captive ... 1 factor in 0.27 D (100% C 10 2 substitution) 37 118348

Final brightness,% ISO

C102 input in final D step,% 0.1 0.3 0.5 0.7 0.9 1.1 R4 89.8 90.5 91.2 91.5 91.8 91.8 (Best soup) R12 88.9 90 90.8 91.1 91.5 91.8 (Best Available) R8 87 88.7 89.3 90.1 90.5 90.5 (Basic)

It will be appreciated that the presently preferred embodiments described herein may be subject to obvious changes and modifications by one skilled in the art. These changes and modifications can be made without departing from the spirit and purpose of the present invention and without adversely affecting the benefits obtained. Accordingly, the appended claims are intended to cover these changes and modifications.

a · »·» * · · • · · · · · ···························································· · «• • · · ♦ ♦ ♦ mi mi mi mi mi::::::: 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 i 1 1 1 i i 1 1 1. ·

Claims (9)

38 118348 A batch cooking process using rapid displacement heating to produce a lignin-free pulp, in which the waste liquor generated by the cooking of the cellulosic material in the boiler (10) is displaced and collected in the collectors (24, 28, 58). as a warm black liquor to retain and use the heat contained in this waste liquor to heat another batch of cellulosic material in pre-treatments of the hot black liquor and hot black liquor displacement type, always with hotter waste liquors prior to cooking, characterized in that: to black liquor during the pre-treatment steps with hot black liquor and to the cooking liquor during the cooking step * · ·· -, white liquor a decentralized added to the total input ·· * e *, · in the range of about 15% of the active alkalinity of 35 * ·]% active alkalinity; and • · - • e - ··· ϊφϊ the temperature of the cooking liquor is raised to about 150-167 ° C for the cooking step. Process according to claim 1, characterized in that the white liquor solution is added to the warm black liquor (temperature between 90-150 ° C) and the hot black liquor (temperature range 150-167 ° C) in a predetermined amount. . * e * ··· * The process of claim 1, characterized in that the white liquor is added to the cool black liquor (heats up at a temperature between 70 ° C and 90 ° C) and that the cellulosic material 39 118348 is pre-treated with this coolant. black liquor with added white liquor before pre-treatment with warm black liquor. Process according to claim 1, characterized in that the preferred total amount of white liquor is> 20% AA. Process according to claim 1, characterized in that the preferred cooking temperature is between 155 ° C and 167 ° C. A process for producing a bleachable pulp by the process of claim 1, comprising the steps of: (a) placing the chips in a boiler (10); (b) pretreating the wood chips with a mixture of warm black liquor and white liquor at a temperature below the boiling point; ···· ·· * (c) displacing the mixture from the cooking pot (10) by at least one • M1 * '**' mixture of hot black liquor and hot white liquor; Y (d) raising the temperature of the boiler (10) to the cooking temperature; (e) maintaining the temperature until the chips have decomposed; (f) displacing the contents of the digester (10) with the filtrate fluid obtained from pulping; and »·· (g) the contents of the boiler (10) are emptied by applying gas pressure or pumping the contents of the ♦ * ··· boiler (10) out. The process according to claim 6, characterized in that it comprises the step of pretreating the chips with a mixture of cool black liquor and white liquor (or NaOH solution) prior to the pretreatment step with warm black liquor. 40, 118348 Process according to Claim 6, characterized in that the total charge of the white liquor used is between 15% AA and 35% AA. Method according to Claim 6, characterized in that it comprises the step of displacing the contents of the boiler (10) by any combination of washing filtrate and white liquor (or NaOH solution). • · * · • 9 9 «• 99 • • 11« 9 * 9 9999 99 9 • 9 9 9 9 9 9 9 - 9 9 999 9 9 9 9 • · • · · ··· • 9 99 9 9 999 999 * 9 9 9 999 9 9 • * 9 9 9 9 * 9 9 · • 41 118348