Transcript Document

7th International Symposium
„Chosen Processes at the Wood Processing“
Slovakia 2007
ENVIRONMENTALLY
FRIENDLY METHODS FOR
PULP BLEACHING
Inese Sable
Latvian State Institute of Wood Chemistry
Today:
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Cl2
NaOCl
Ca(OCl)2
ClO2
NaClO2
Cl2O
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Na2S2O4
ZnS2O4
NaHSO3
H2O2
Na2O2
O2
O3
SO2
CH3COOH
CaS2O4
Al2(S2O4)3
KMnO4
Chlorine and its compounds harmful for the environment
Future:
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Na2S2O4
ZnS2O4
NaHSO3
H2O2
Na2O2
O2
O3
SO2
CH3COOH
CaS2O4
Al2(S2O4)3
KMnO4
New method:
(based on method of determination of cellulose)
Pulp bleaching by ammonium persulphate
First stage - oxidation:
Treatment with (NH4)2S2O8 in acidic medium (using
H2SO4, HNO3, HCl, CH3COOH) in 80oC 4 hours
2. Second stage - reduction:
Treatment with NaBH4, Na2S2O4, Na2SO3, NaH2PO2 for
alkaline medium (2% NaOH) in 80oC 40 minutes
1.
(NH4)2S2O8 in acid medium gives:
O2
H2O2
H2SO5
H2S2O8
O3
Mechanisms of lignin
destructurization by Caro’s acid
O
H2SO5
OH2
O
COOH
OH
+
H
O
O
O
OH2
OH
COOH
+
H
+ H2SO5
OMe
-CH3OH
OH
OMe
O
O
OH
O
H2SO5
O
O
O
O
+ H2SO4
O
2
+OH
+
H
COOH
COOH
Soda pulp samples
Spruce (Picea abies )
13,5 %
Aspen tree (Populus
tremula )
3,8 %
Grey alder
(Alnus incana )
2,2 %
Rapid- Kothen
Sheet Former
Test methods
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Brightness - TAPPI Test Method T 452 om02 with Carl Zeiss Elrepho No.19986;
Mechanical properties - LVS EN ISO 19242:2001 and EN ISO 12625-4:2005 with a
vertical Frank Prufgerate Tensile Tester
Vertical Frank Prufgerate Tensile
Tester
OH
60
CH
3C
O
65.9
HC
l
HN
O3
40
H2
SO
4
Un
ble
ac
he
d
Brigtness, %ISO
80
71.8
54.4
28.6
24.4
20
0
CH
3C
O
OH
40
HC
l
HN
O3
60
H2
SO
4
Un
ble
ac
he
d
Tensile index, (N*m)/g
80
55.9
42.3
32.8
20
11.2
0
0
68.6
Na
H2
PO
2
71.8
Na
2S
2O
4
80
Na
2S
O
3
65.8
4
60
40
Na
H2
PO
2
64.5
Na
BH
Un
bl
ea
ch
ed
Na
2S
2O
4
65.9
Brigtness, %ISO
80
60
Na
2S
O
3
4
40
20
0
Na
BH
Un
bl
ea
ch
ed
Brightness, %ISO
H2SO4
54.8
28.6
HNO3
66.8
63.0
28.6
20
0
18.3
Na
H2
PO
2
Na
2S
2O
4
60
Na
2S
O
3
4
28.3
Na
BH
40
20
Na
H2
PO
2
29.3
Un
bl
ea
ch
ed
40
Tensile index, (N*m)/g
60
Na
2S
2O
4
80
Na
2S
O
3
4
20
Na
BH
Un
bl
ea
ch
ed
Tensile index, (N*m)/g
H2SO4
55.9
30.5
0
0
HNO3
80
42.3
16.5
19.9
0.0
0
Conclusions
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Methods for pulp bleaching with ammonium
persulphate in an acidic medium have been
developed
The highest quality indices for the pulp are
reached in the case of realising the bleaching in
the sulphuric acid medium; in the nitric acid
medium, the mechanical indices of the
handsheets are somewhat inferior; the reaction
practically does not occur in nitric acid and
acetic acid.
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Applying the offered method, it is recommended
to obtain paper fibres with the average
brightness and average mechanical strength
Using Na2S2O4, Na2SO3 and NaH2PO2 as
reduction agents, the obtained handsheets show
lower quality indices.
Thank you!
Please your questions on email:
[email protected]
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