B&W Kraft Recovery Operations Shortcourse

Tall Oil Soap Recovery TAPPI Kraft Recovery Short Course

C.D. Foran, Arizona Chemical Co., Savannah GA

Slide 1

Tall oil soap is a mixture of the sodium salts of rosin acids, fatty acids and neutrals that separates from kraft black liquor.

Composition of Crude Tall Oil

Acid Number Resin Acids % Fatty Acids % Neutrals %

Southern USA

Northern

New

USA &

Zealand &

Canada Scandinavia Chile

165

135

132

158

41

30

23

43

51

55

57

40

8

15

20

14

1

Slide 2

How Much Tall Oil Can Be Recovered ?

Region

Piedmont Coastal Canada Southwestern West of Cascades

Tall Oil kg/1000 kg OD Wood

24

26

11.5

31.5

7.5

Tall Oil lb/ ODT Wood

48

52

23

63

15

NZ & Chile Finland

Sweden

12

24

18.5

37

25

50

Tall Oil Loss

Lb. CTO/ODT Pine Wood

kg CTO/ODt Pine Wood

Soap Recovery

52

26

51

25.5

50

25

49

24.5

48

24

47

23.5

46

23

45

22.5

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Average

100%

Impact of Storage Time on Tall Oil Loss

80%

60%

40%

20%

0% 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 Storage Time (weeks)

Outside Chips Roundwood Chips

Slide 3

Why Should Tall Oil Soap Be Recovered ?

?To improve pulp and paper mill operations ?To reduce the toxicity of pulp mill effluents, ?To reduce accidents due to slips and falls. ?To increase mill revenue

2

Slide 4

Tall Oil Soap Should Be Recovered To Improve Pulp and Paper Mill Operations :

1. Reduce evaporator fouling, 2. Increase evaporator uptime, 3. Increase recovery boiler

solids burning capacity, reduction efficiency

4. Reduce paper machine foaming,

5. Reduce bleaching costs,

Heat Transfer Coefficient (of Initial Maximum)

Impact of Improved Soap Removal on Evaporator Overall Heat Transfer

110%

100%

90%

80%

70%

60% 0

10

20

30

40

Hours Running

No Soap Recovery Poor Soap Recovery Good Soap Recovery

Availability Fraction of Maximum Evaporation Rate

Slide 65

Influence of Skimmer Outlet Residual on:

Evaporator Time On-Line

100% 98% 96% 94% 92% 90% 88% 86% 84% 82% 80% 0.5 0.7 0.9 1.1 1.3 1.5 1.7 1.9 2.1

Skimmer Outlet Soap Residual (% CTO on a Solids Basis)

Evaporation Rate

100%

98%

96%

94%

92%

90%

88% 0.5 0.7 0.9 1.1 1.3 1.5 1.7 1.9 2.1

Skimmer Outlet Soap Residual (% CTO on a Solids Basis)

3

Slide 6

How Soap Skimming Affects Evaporator Performance Overall

Good Poor

Skimming Skimming

Skimmer Residual (%) 0.6

1.1

Downtime (hr./month)

45

75

Evaporation Rate (Mkg/hr)

323

315

Production (Tonnes)

Unbleached

34500

32100

Change 0.5 30 -8

-2400

Bleached

24700

23000

-1700

Slide 7

Tall Oil Soap Should Be Recovered To Reduce Pulp Mill Effluent Toxicity

1. Fatty Acids, Resin Acids and Phenols affect both the toxicity to fish and the taste and color of fish.

2. Sodium soaps of resin acids account for 80% of the effluent toxicity.

3. Sodium soaps of unsaturated fatty acids account for 20% of the effluent toxicity.

4. Toxicity is independent of oxygen demand.

4

SlSidliede8 9

What causes soap to separate from black liquor ?

? Increased liquor solids, ? Decreased liquor temperature, ? Residual effective alkali above 6 gpl, ? Increased fatty acid to resin acid ratio ? Decreased hardwood liquor content.

Soap Solubility

Slide 9

Tall Oil % of Liquor Solids

3.5

3.0

PAST

2.5

2.0

1.5

NOW

1.0

0.5

0.0 10 15 20 25 30 35 40 45 50 55

Black Liquor Total Solids (%)

160 F 71 C 120 F 49 C 80 F 27 C

At washer filtrate temperatures, soap begins to come out of solution at about 8% solids. Minimum solubility occurs at 25 ? 30% solids.

5

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