1983 International Symposium On
Wood and Pulping Chemistry
PYROLYSIS AND COMBUSION BEHAVIOR OF
CHLORINATED ORGANICS IN BLEACH PLANT
EFFLUENT
N. Sasaki, H. Araki, M. Suzuki and T. Nagasawa
Japan Pulp and Paper Research Institute, Inc.
5-13, Tokodai-, Toyosato-machi, Tsukuba-gun,Ibaraki-ken, 300-36, Japan

ABSTRACT
Pyrolysis of chlorinated phenolics andthiolignin was investigated to elucidate theprinciple step occurring during combustion oforganic material in bleach plant effluent.
Chlorinated phenolics found in bleach planteffluent. such as chlorophenols, chloroguaiacols,
chlorovanillins and chlorosyringaldehydes, werecompletely decomposed at 700 to 900℃ with alkali
and oxygen.
Organically bound chlorine with lignin wasely eliminated as inorganic salt by alkali
addition at low pyrolysis temperature. Without
alkali, more than 90% of chlorine was eliminatedas hydrogen chloride., the others as methyl
chloride and tar-like material. Ether-soluble
part of tar-like material contained various
chlorinated phenolics, Which were not completely
decomposed at a high temperature.
Organic matter isolated from spent alkali
extraction liquor was also pyrolyzed under acondition, which seemed to be probable in aconventional recovery furnace. Almost wholechlorine in organic matter Was recovered in solidresidue.
It was confirmed that the technique used inthis work was useful to investigate the thermal
behavior of chlorinated organics in bleach planteffluent.
1. Introduction
The reduction of pollution load in spentkraft mill effluent is one of the most concernof paper industry. particulary, it is the mostimportant to develope an effective technique forremoval of chlorinated phenolics, because thetoxicity and, bioaccumulation and direct biological effect on the environment are of paramountconcern in the world.
Although biological purification of bleachplant effluents is useful to reduce the BOD andtoxicity, the reducability seems to be rather
unpredicable if the composition of treated effluent is varied. Therefore, as a drastic approach,a concept arises that spent bleach plant liquor
is evaporated with a pertinent technique arid all
the organic substances dissolved in the bleachingprocess is burned in a furnace.
In Canada Rapson advanced a method for
operating an effluent-free kraft pulp mill1) ,which is currently being applied at the Thunder
Bay Mill of Great Lakes Forest Products Co..2)
At the Skoghall Mill of Billerund Uddeholm AB
in Sweden, the spent alkali extraction liquor
has been treated in an ion exchange system3)
In Japan, at the kraft mill of Taio Paper
Co., an ultra filtration technique is used toremove the organic matter in bleach plant effluent and the resulting concentrated liquor isintroduced into the alkali-recovery process.4)
On the application of such new techniques'a problem arises whether chlorinated organics
can be completely decomposed in a furnace.
In this work an attention has been given to
the combustion of chlorinated phenolics, themechanism whereby new harmful compounds will beproduced, and the development of information to
help the corltrol, minimization and ultimate
elimination of possible toxic compounds in emission. particular emphasis has been given topyrolysis which is one of the principle steps
occurring during combustion.
A fate of organically bound chlorine isstudied arid the optimum condition for thermal
degradation of chlorinated organics in bleachplant effluerlt is discussed in this paper.
2.Experimental
1-1.Prearation of model compounds(a) Synthesis of Chlorinated phenolics
4,5-Dichlorocatecho1,4,5-Dichloroguaiacol,
5-Chlorovanillin, 2 , 6-Dichlorosyringaldehyde,
3,4,5-Trichloro-2,6-dimethoxyphenol were preparedaccording to the procedure of Kachi et al 5).
The other chlorinated compounds were purchased from Tokyo Kasei, Japan.
(b) Chlorination of Thiolignin
Beech thiolignin isolated from the kraft
black liquor was chlorinated by using chlorinegas.
A standard method is as follows;
Fifty g of thiolignin was suspended with
100 ml of distillated water in 300 ml of threenecked round flask. Chlorine gas was bubbled
through the suspension, regulating the passing
speed at 50 ml/min, and with the agitation of
the content at 400 rpm for a defninte time.
After the reaction, chlorinated lignin wasfiltered arid washed with water until the filtrate
was neutral, and dried over P2O5 under vaccum.
Sodium salt of chlorinated thiolignin wasprepared by the dissolution of chlorinated lignin
in a aqueous solution of sodium hydroxide,evaporation, and drying over P2O5 tinder vacuum.
A molar ratio of sodium to chlorine is designatedas “Na/C1” in this paper.
1-2.Pyrolysis apparatus
Pyrolysis of chlorinated lignin was primaryly csrried out in a quarts reactor. The pyrolysisi apparatus is shown in Fig. 1
Ten g of chlorinated lignin was taken in thereactor which was connected with a receiving tube
through two series of water-cooler, a pair of dry
ice-ethanol trap and a gas collector.
The reactor was heated in a heating furnace
which was lifted up on pyrolysis, by jacking.

During pyrolysis, low volatile arid watersoluble products were collected with the watercoolers. They were marked as “condensate”
fraction.
High volatile and water-insoluble products,
passing through the first trapping system, werecollected in dry ice-ethanol traps which were
packed with glass beads. A tar-like product inthe trap was washed with ether and acetone
successively. They were respectively marked as“Ether-soluble” and “Acetone-soluble” fraction.
The gaseous products were collected in a gas
collector at the final part of the apparatus
They were marked as “pyrolysis Gas” fraction.
Gas collection was carried out with an electromagnetic value, which was regulated by using amonometer. In the reactor black porous material
like char was left. It was maked as “SolidResidue”.
chlorinated phenolics were pyrolyzed with acurie Point Pyrolyzer (Nihon Bunseki, ModelJHP-2) conbined with GC (Shlmazu, Model GC-7A) 1-3 Analytical procedure
Chlorine content was determined by theargentimetric titration after Shoniger combustion.
GC and GC-MS analysis of “Ether-soluble”
and ”Pyrolysis Gas” fractions were carried outwith a Shimazu Model GC-7A with FID and JEOL
Model JMSD300. For analysis of inorganic gas,
glass columns packed with Porapak QS (3.0 mm idx 4 m, 80/100 mesh) was used. The temperature wasprogramed from –50℃ to 0℃ at 4℃/min and 0℃
to 200℃ at 8℃/min, using N2 and He (50 m1/min)as carrier gases.
For the analysis of chlorinated phenolics,
PEG-20M capillary column (0.2 mm id x 50m) wasused. The temperature was programed from 70℃
to 200℃ at 5℃/min, using N2 (3 m1/min) as acarrier gas. For the quantitative estimation ofchlorinated phenolics, glass columns Packed with
10% FFAP on Chromosorb W (AW-DMCS) was used
(2.0 mm x 2 m, 80/100 mesh). The temperature
was from 50℃ to 220℃ at 5℃/min, using N2 (50ml/min) as a carrier gas. Calibration curves
were made by using authentic chlorinatedphenolics and 2,6-Dibromophemol as a internalstandard.
MS analysis was carried out under a condition such as 23 eV, He as a carrier gas.

3. Results and Discussion
3-1 Pyrolysis of chlorinated phenolics
Seven chlorinated phenolics, which were
found in bleach plant effluent and its relativecompounds, were pyrolyzed with a Curie Point
Pyrolyzer.
The first pyrolysis was carried out under arelatively mild conditior1 (590℃, Na/C1 = 1.0
under nitrogen) to elucidate degradation
products, especially chlorinated compounds.
Main products Were shown in Table 1. All ofstarting materials still remained as unreacted
and many Chlorinated phenolics were newly
produced under such a mild condition An
elimination of chlorine from a starting material
was one of the main reactions. Further additionof chlorine to products was also a main reaction,for example, Di-and Trichlorobenzene from pChlorophenol and Trichloroveratrole from 4, 5Dichloroguaiacol.
An interesting result was that products
nethYlated on phenolic hydroxyl groups, wereproduced, like chlorinated veratrole and anisolefrom 4,5-Dichloroguaiaco1, methylated derivatives
from 5-Chlorovanillin and 4.6-Dichlorosyringaldehyde. As a radical reaction is a main reaction in pyrolysis of organic compounds6) ,chlorine-addition and methylation may be takenplace via radical reactions.

starting material completely, thermally stablechlorophenolics and its condensation products
would be produced. To elucidate such a possibility, effect of alkali and oxygen addition on
pyrolysis was investigated. Thermal degradabi1ity of chlorinated phenolics was shown in Fig.
3-(a) to (f).
On pyrolysis of 4,5-Dichloroguaiaco1. morethan 5% of the starting material still remained
as unreacted even at 900℃ if alkili arid oxygen
were lacking. However, if added alkali wasenough (Na/C1> 1.0), more than 99% wasdecomposed at 650℃. The decomposition ratio
under alkali and oxygen didn't decrease accompanying the drop of temperature. A similareffect on decomposition was observed in the caseof oxygen addition without alkali( Fig.3-(a)).

As shown in Fig. 3-(b), almost 100% of 4,5,6Trichloroguaiacol was decomposed with enoughalkali (Na/C1 = 1.0) and oxygen, even at a lower
temperature, 490℃. Without alkali or oxygen on
pyrolysis, it was more stable than 4,5-Dichloroguaiacol.

Furthermore, none-chlorinated condensation
products such as naphtharene and anthracene werealso detected. As unknown chlorinated condensatiorl products, mono-. di- and trichlorobiphenyl
compounds were also detected.
These results indicate that, unlesspyrolysis condition is enough to decompose a

5-Chlorovanillin was completely decomposed
at 650℃with alkali (Na/C1 = 1.0) and oxygen.
On the other hand. it was relatively Stablewithout oxygen. The 3% was left as undecomposed
at a higher temperature, 920℃( Fig- 3-(c) ).
2, 6-Dichlorosyringaldehyde was much degradable, as shown in Fig. 3-(d). More than 93%of the compound was decomposed at a lower temperature, 490℃ under nitrogen without alkali.
2,4,6-Trichlorophenol Was decomposed at
760℃ with enough alkali and oxygen, but muchstable at lower pyrolysis temperature( Fig- 3-(e)).
p-chlorophenol was also stable at lowertemperature( fig- 3-(f)).

To compare thermal degradability of chlorinated phenolics, the ''Complete Decomposition
Ternperature” was estimated by extrapolation of
the decomposition curves in Fig. 3 to 100%
decomposision. The complete decomposition meansthat the peak of starting material was disappeared on a gaschromatogram of the pyrolysis reaction
mixture. Although this definition is useful tocompare relative stability of chlorinatedphenolics, it is not enough to express the “real”.
degradability because some products will survive
for a longer time than the starting material. As
shown in Fig. 4, chlorinated phenolics with lesser
or simpler functional groups are more stable. In
general chlorinated phenolics in bleach plant
effluerlt will be completely decomposed at 700℃
to 900℃ with enough alkali and oxygen.

3-2 pyrolysis of chlorinated lignin
chlorinated thiolignin was pyrolyzed withthe pyrolysis apparatus. The reason why chlorinated thiolignin was used as a model compound,
were (1) chlorine content was easily Selectedand (2) pyrolysis products from carbohydratecomponent can be neglected.
The chlorine distribution in pyrolysis
products were shown in Fig. 5. Alkali and oxygenwere not added in this case.
At every temperature level, more than 90% of
total chlorine was recovered as hydrogen chloride.
About 10% was present as methyl chloride, and 2
to 5% as solid residue. Chlorine content ofRher-soluble was less than 1% and almost
constant. Chlorine distributed to Acetonesoluble fraction was kept in about 1% at everytemperature level.

Furthermore such a possibility will be increased
if chlorinated organics in bleach plant effluent
is burned in a furnace, because temperaturelevel and alkali concentration in a recovery
furnace are disproportioned, and oxygen concentration is shortened at the many parts.
The emission of such pyrolysis products
would occur new pollution problem to circumstances.
Methyl chloride is seemed to be produced
via radical reactions of chlorine radicals withmethyl radicals from methoxyl groups. This wassupported by model experiments that, at 760℃
without alkali under nitrogen, methyl chlorides
were produced in 4.48 mole % from 4,5,6-Trichloroguaiaco1, 11.52 mole % from 3,4,5-Trichloro2,6-dimethoxypheno1, and trace amount from 2,4,6Trichlorophenol.
With alkali, chlorine distribution was
remarkably changed. As shown in Fig. 6, chlorine
content in Solid residue fraction enhanced to 99%
with the increase of Na/Cl ratio to 1.0, andlevelled off after that. On the contrary
hydrogen chloride decreased rapidly. As wholechlorine in the Residue was washed out with hotwater, it can be said that produced hydrogenchloride was converted to sodium chloride. It
is interesting that methyl chloride and chlorine
in Ether-soluble arid Acetone-soluble fractions
also increased rapidly on addition of alkali as
Na/Cl ratio>1.0.
Although the 99% of chlorine can be eliminated as sodium chloride on pyrolysis with enoughalkali, it is possible. that small amount but
many kinds of chlorinated.phenolics and its
condensation products would be produced.

Chlorinated phenolics, which were detectedon pyrolysis without alkali under nitrogen, wereshown in Table 2.

Total chlorinated phenolics detected by MassSpectroscopy, were about 20 to 30 at every
temperature level. Total yield of detectedchlorophenolics attained to maximum at 470℃, anddecreased accompanying increase of temperature.
Main product; detected were 4-Chlorocatechol,2,4,6-Trichlorophenol, 3 ,4 ,5-Trichlorophenol and
3,4,5-Trichloro-2,6-dimethoxyphenol. It is worth
noting that these products are found in bleachplant effluent arid possible to be converted to
toxic chlorinated compounds unless pyrolysis
condition is enough.
On the other hand, with alkali (Na/C1 = 1.0)
at 500℃ under nitrogen, only four chlorinatedphenolics were detected in trace amount. This
indicates that organically bound chlorine withlignin molecules are more unstable than thosewith chlorinated phenolics. Accordingly there
will be a very slim chance that chlorinatedphenolics is produced from chlorinated lignin,on pyrolysis with enough alkali.
To confirm the feasibility of our experimental method and the appliability of these results
to pyrolysis of bleach plant effluent, organic
matter isolated from spent alkali extraction
liquor, was pyrolyzed under the same condition
as chlorinated lignin pyrolysis.

As shown in Table 3, distributions ofchlorine and products of the isolated organic
matter were similar to those of chlorinatedthiolignin. Accordingly it can be said that thetechnique for pyrolysis and products-detection inthis work is useful to investigate the thermal
behavior of material in bleach plant effluent.
However, for a future study to simulate afull-scale combustion of bleach plant effluent,
new technique and apparatus, in which action ofaqueous vapor oxygen distribution, and state ofmaterial are considered, must be developed.
4. Conclusion
Chlorinated phenolics and thiolignin werepyrolyzed under several conditions to elucidate
the thermal behavior of organic matter in bleachplant effluent.
Some chlorinated phenolics found in bleachplant effluents and its relative compounds canbe completely decomposed at 700 to 900℃ withenough alkali and oxygen. Chlorinated phenolics
with lesser arid simpler functional groups arethermally more stable.
Organically bound chlorine with lignin canbe easily eliminated as sodium chloride by alkali
addition at a low pyrolysis temperature, 500℃.
However, many kinds of chlorinated phenolics areproduced under the condition lacking of alkali.
A part of chlorinated phenolics is possible to beconverted to condensation products.
It was confirmed that the present techniques
for pyrolysis and products-detection were useful
to investigate the thermal behavior of organic
matter in bleach plant effluent.