Kraft Pulping Past Current & Future Past, Current & Future
Kraft Pulping Past Current & Future Past, 3 d Annual 3rd ua Light g t Green G ee Machine ac e Institute st tute Conference. Atlanta , 22 – 24 January 2012 A d Anders Hj Hjortt Metso Paper Sweden AB Karlstad,, Sweden
Continuous Cooking
2
© Metso
The continuous digester Past – Current - Future
Content
• The development of the continuous digester • The first generation of digesters, ca 1950 – 1980 - Conventional cookingg in single g and two vessel digesters g • Second generation, modified cooking, ca 1980 – 2000 - MCC, EMCC, ITC, BLI, etc. • Current, Current ca 2000 - ???? - Compact cooking - ImpBinTM • Modification M difi ti off old ld di digesters t
3
© Metso
The continuous digester Past – Current - Future
Content
• The development of the continuous digester • The first generation of digesters, ca 1950 – 1980 - Conventional cookingg in single g and two vessel digesters g • Generation two. Modified cooking, ca 1980 – 2000 - MCC, EMCC, ITC, BLI, etc. • Current, Current ca 2000 - ???? - Compact cooking - ImpbinTM • Modification M difi ti off old ld di digesters t
4
© Metso
Those who did it!!! The inventors of the continuous digester ~ 1950, 1950 Kamyr AB, AB Karlstad Sweden
5
© Metso
First pilot plant 1944 – Kalix, Sweden Version 1
6
© Metso
First pilot plant 1944 – Kalix, Sweden Version 2
7
© Metso
First working High Pressure Feeder
8
© Metso
Second generation High Pressure Feeder
9
© Metso
Modern High Pressure Feeder
10
© Metso
Conventional chip feeding system
11
© Metso
The continuous digester Past – Current - Future
Content
• The development of the continuous digester • The first generation of digesters, ca 1950 – 1980 - Conventional cookingg in single g and two vessel digesters g • Generation two. Modified cooking, ca 1980 – 2000 - MCC, EMCC, ITC, BLI, etc. • Current, Current ca 2000 - ???? - Compact cooking - ImpbinTM • Modification M difi ti off old ld di digesters t
12
© Metso
Digester types
Single vessel steam/liquor
Two vessel steam liquor 13
© Metso
Single vessel hydraulic
Two vessel hydraulic
First reference list
14
© Metso
Typical continuous digester 1950 – 1980 Typical operating figures:
15
•
Cross sectional load 25 – 28 admt/m2 (2.3 (2 3 – 2.6 26 2 bdst/ft )
• • • • • •
Cooking temperature soft wood 165 °C / 329 F
© Metso
Cooking temperature hard wood 160 °C C / 320 F Top pressure 7 bar(g) / (100 psig) steam phase type Top pressure 10 bar(g) / (145 psig) hydraulic type Residual alkali 6 – 8 g/l as EANaOH Wash factor 2 m3/admt (after 1960)
The continuous digester Past – Current - Future
Content
• The development of the continuous digester • The first generation of digesters, ca 1950 – 1980 - Conventional cookingg in single g and two vessel digesters g • Second generation, modified cooking, ca 1980 – 2000 - MCC, EMCC, ITC, BLI, etc. • Current, Current ca 2000 - ???? - Compact cooking - ImpbinTM • Modification M difi ti off old ld di digesters t
16
© Metso
Continuous Cooking Development
17
© Metso
The four rules – slightly modified 1. The alkali concentration should be as even as possible 2. The temperature p should be low throughout g the cook to minimise carbohydrate degradation 3. The concentration of HS- should be as high as possible 4. The concentration of dissolved lignin has no negative effect as long as the alkali concentration is sufficiently high
18
© Metso
Two vessel S/L digester with MCC Softwood example
Con current cooking 158 oC / 316 F
Counter C t currentt cooking ki 162 oC / 324 F Impregnation 125 oC / 257 F
19
© Metso
Counter current washing 135 oC / 275 F
After MCC came ITC
20
© Metso
Two vessel S/L digester with MCC and ITC Softwood example
Con current cooking 156 oC / 313 F
Impregnation 125 oC / 257 F
21
© Metso
Counter C t currentt cooking ki zone 1 156 oC / 313 F Counter current cooking zone 2 156oC / 313 F
The development from 1960 – 1990 Summary
22
© Metso
By 1990 the complexity had reached it’s peak! Single vessel hydraulic digester with MCC & ITC
23
© Metso
It was necessary to do something!!! Reduce the number of screens in the digester!
24
© Metso
The continuous digester Past – Current - Future
Content
• The development of the continuous digester • The first generation of digesters, ca 1950 – 1980 - Conventional cookingg in single g and two vessel digesters g • Second generation, modified cooking, ca 1980 – 2000 - MCC, EMCC, ITC, BLI, etc. • Current, Current ca 2000 - ???? - CompactCookingTM - ImpbinTM • Modification M difi ti off old ld di digesters t
25
© Metso
Continuous cooking P hi the Pushing h lilimits i
26
© Metso
Continuous Cooking Development
27
© Metso
The four rules – slightly modified 1. The alkali concentration should be as even as possible 2. The temperature should be low throughout the cook to minimise carbohydrate degradation 3 Th 3. The concentration t ti off HSHS should h ld b be as hi high h as possible ibl 4. The concentration of dissolved lignin has no negative effect as long as the alkali concentration is sufficiently high
28
© Metso
Impregnation Relative rates for diffusion and reaction
The best Th b t impregnation i ti is i obtained by a low temperature and a long impregnation time
Cooking chemicals penetrate the chip without being consumed.
29
© Metso
CompactCookingTM™ G2 Alkali profiling
30
© Metso
A short retention time – increased temperature The H-factor contribution is increasing exponentially with an increased temperature. The increase is drastic when the temperature exceeds 165 °C
oC
31
© Metso
HS- concentration profiles
Recirculate black liquor Avoid dilution with wash liquor A high HS- concentration brings:
Increased delignification rate Decreased amount of residual phase lignin Increased cooking selectivity 32
© Metso
CompactCookingTM™ R & D had shown: • Alkali & HS- profiling is crucial • A low temperature is important for carbohydrate retention
The big question was: How do we do this?
33
© Metso
Which way to go? A two vessel system was chosen
34
© Metso
CompactCooking™
It was obvious that a two vessel digester must be used! B t how But h do d we gett the th chips hi iinto t th the di digester? t ? Customers had started to ask for production levels unheard of before!! 2000 t/d
35
© Metso
3000 t/d
4000 t/d
????
A conventional feeding line
36
© Metso
Chips
37
© Metso
Heating of chips
38
© Metso
Feeding, steaming & impregnating in one vessel??
39
© Metso
ImpBin™
40
© Metso
ImpBin™ Upper part
41
© Metso
CompactCooking™ G2 with ImpBin™
42
© Metso
CompactCooking™ G2 with ImpBin™ Typical retention times
43
© Metso
CompactCooking™ R d Reduced d reject j content d due to iimproved d iimpregnation i
44
© Metso
CompactCooking™ R d Reduced d cooking ki temperature (SW) 356 F 338 F 320 F 302 F 384 F
CompactCooking G2 Optimizes the process conditions Low cooking temperature 45
© Metso
CompactCooking™ G2 – cooking development R d Reduced d operating i and d capital i l costs
Comparison based on a HW 2500-3000 ADMT/24h cooking system.
MCC/ITC™
COMPACT COOKING™ G1
COMPACT COOKING™ G2
Rejects (%)
~1-2
~0,5-1
Continuous Cooking
2
© Metso
The continuous digester Past – Current - Future
Content
• The development of the continuous digester • The first generation of digesters, ca 1950 – 1980 - Conventional cookingg in single g and two vessel digesters g • Second generation, modified cooking, ca 1980 – 2000 - MCC, EMCC, ITC, BLI, etc. • Current, Current ca 2000 - ???? - Compact cooking - ImpBinTM • Modification M difi ti off old ld di digesters t
3
© Metso
The continuous digester Past – Current - Future
Content
• The development of the continuous digester • The first generation of digesters, ca 1950 – 1980 - Conventional cookingg in single g and two vessel digesters g • Generation two. Modified cooking, ca 1980 – 2000 - MCC, EMCC, ITC, BLI, etc. • Current, Current ca 2000 - ???? - Compact cooking - ImpbinTM • Modification M difi ti off old ld di digesters t
4
© Metso
Those who did it!!! The inventors of the continuous digester ~ 1950, 1950 Kamyr AB, AB Karlstad Sweden
5
© Metso
First pilot plant 1944 – Kalix, Sweden Version 1
6
© Metso
First pilot plant 1944 – Kalix, Sweden Version 2
7
© Metso
First working High Pressure Feeder
8
© Metso
Second generation High Pressure Feeder
9
© Metso
Modern High Pressure Feeder
10
© Metso
Conventional chip feeding system
11
© Metso
The continuous digester Past – Current - Future
Content
• The development of the continuous digester • The first generation of digesters, ca 1950 – 1980 - Conventional cookingg in single g and two vessel digesters g • Generation two. Modified cooking, ca 1980 – 2000 - MCC, EMCC, ITC, BLI, etc. • Current, Current ca 2000 - ???? - Compact cooking - ImpbinTM • Modification M difi ti off old ld di digesters t
12
© Metso
Digester types
Single vessel steam/liquor
Two vessel steam liquor 13
© Metso
Single vessel hydraulic
Two vessel hydraulic
First reference list
14
© Metso
Typical continuous digester 1950 – 1980 Typical operating figures:
15
•
Cross sectional load 25 – 28 admt/m2 (2.3 (2 3 – 2.6 26 2 bdst/ft )
• • • • • •
Cooking temperature soft wood 165 °C / 329 F
© Metso
Cooking temperature hard wood 160 °C C / 320 F Top pressure 7 bar(g) / (100 psig) steam phase type Top pressure 10 bar(g) / (145 psig) hydraulic type Residual alkali 6 – 8 g/l as EANaOH Wash factor 2 m3/admt (after 1960)
The continuous digester Past – Current - Future
Content
• The development of the continuous digester • The first generation of digesters, ca 1950 – 1980 - Conventional cookingg in single g and two vessel digesters g • Second generation, modified cooking, ca 1980 – 2000 - MCC, EMCC, ITC, BLI, etc. • Current, Current ca 2000 - ???? - Compact cooking - ImpbinTM • Modification M difi ti off old ld di digesters t
16
© Metso
Continuous Cooking Development
17
© Metso
The four rules – slightly modified 1. The alkali concentration should be as even as possible 2. The temperature p should be low throughout g the cook to minimise carbohydrate degradation 3. The concentration of HS- should be as high as possible 4. The concentration of dissolved lignin has no negative effect as long as the alkali concentration is sufficiently high
18
© Metso
Two vessel S/L digester with MCC Softwood example
Con current cooking 158 oC / 316 F
Counter C t currentt cooking ki 162 oC / 324 F Impregnation 125 oC / 257 F
19
© Metso
Counter current washing 135 oC / 275 F
After MCC came ITC
20
© Metso
Two vessel S/L digester with MCC and ITC Softwood example
Con current cooking 156 oC / 313 F
Impregnation 125 oC / 257 F
21
© Metso
Counter C t currentt cooking ki zone 1 156 oC / 313 F Counter current cooking zone 2 156oC / 313 F
The development from 1960 – 1990 Summary
22
© Metso
By 1990 the complexity had reached it’s peak! Single vessel hydraulic digester with MCC & ITC
23
© Metso
It was necessary to do something!!! Reduce the number of screens in the digester!
24
© Metso
The continuous digester Past – Current - Future
Content
• The development of the continuous digester • The first generation of digesters, ca 1950 – 1980 - Conventional cookingg in single g and two vessel digesters g • Second generation, modified cooking, ca 1980 – 2000 - MCC, EMCC, ITC, BLI, etc. • Current, Current ca 2000 - ???? - CompactCookingTM - ImpbinTM • Modification M difi ti off old ld di digesters t
25
© Metso
Continuous cooking P hi the Pushing h lilimits i
26
© Metso
Continuous Cooking Development
27
© Metso
The four rules – slightly modified 1. The alkali concentration should be as even as possible 2. The temperature should be low throughout the cook to minimise carbohydrate degradation 3 Th 3. The concentration t ti off HSHS should h ld b be as hi high h as possible ibl 4. The concentration of dissolved lignin has no negative effect as long as the alkali concentration is sufficiently high
28
© Metso
Impregnation Relative rates for diffusion and reaction
The best Th b t impregnation i ti is i obtained by a low temperature and a long impregnation time
Cooking chemicals penetrate the chip without being consumed.
29
© Metso
CompactCookingTM™ G2 Alkali profiling
30
© Metso
A short retention time – increased temperature The H-factor contribution is increasing exponentially with an increased temperature. The increase is drastic when the temperature exceeds 165 °C
oC
31
© Metso
HS- concentration profiles
Recirculate black liquor Avoid dilution with wash liquor A high HS- concentration brings:
Increased delignification rate Decreased amount of residual phase lignin Increased cooking selectivity 32
© Metso
CompactCookingTM™ R & D had shown: • Alkali & HS- profiling is crucial • A low temperature is important for carbohydrate retention
The big question was: How do we do this?
33
© Metso
Which way to go? A two vessel system was chosen
34
© Metso
CompactCooking™
It was obvious that a two vessel digester must be used! B t how But h do d we gett the th chips hi iinto t th the di digester? t ? Customers had started to ask for production levels unheard of before!! 2000 t/d
35
© Metso
3000 t/d
4000 t/d
????
A conventional feeding line
36
© Metso
Chips
37
© Metso
Heating of chips
38
© Metso
Feeding, steaming & impregnating in one vessel??
39
© Metso
ImpBin™
40
© Metso
ImpBin™ Upper part
41
© Metso
CompactCooking™ G2 with ImpBin™
42
© Metso
CompactCooking™ G2 with ImpBin™ Typical retention times
43
© Metso
CompactCooking™ R d Reduced d reject j content d due to iimproved d iimpregnation i
44
© Metso
CompactCooking™ R d Reduced d cooking ki temperature (SW) 356 F 338 F 320 F 302 F 384 F
CompactCooking G2 Optimizes the process conditions Low cooking temperature 45
© Metso
CompactCooking™ G2 – cooking development R d Reduced d operating i and d capital i l costs
Comparison based on a HW 2500-3000 ADMT/24h cooking system.
MCC/ITC™
COMPACT COOKING™ G1
COMPACT COOKING™ G2
Rejects (%)
~1-2
~0,5-1
