Note: Descriptions are shown in the official language in which they were submitted.
METHOD OF PRODUCING SODIUM HYDROXIDE FROM AN EFFLUENT OF FIBRE
PULP PRODUCTION
The present invention relates to a method of producing sodium hydroxide from
an effluent or
waste stream of fibre pulp production.
According to such a method, an effluent comprising organic waste together with
sodium
compounds is subjected to combustion at an elevated temperature, in order to
break up the
dissolved organic material and to recover sodium. First, the effluent is
concentrated, in particular
.. to a high concentration of more than 45 weight-% dry matter, and then the
concentrated effluent
is burnt in oxidizing conditions. The combustion residue (ash) will yield
sodium hydroxide when
dissolved or suspended in water.
A mill which produces chemi-mechanical pulp, such as BCTMP (i.e. bleached
CTMP) generally
treats its effluents in separate waste water treatment plants, such as
activated sludge plants, and
burns the generated sludges mixed with the bark in bark boilers. In most
cases, the BCTMP mills
are independent mills, which produce dried baling pulp and which have their
own biological
waste water purification units. Such mills have no recovery or recirculation
of chemicals.
There are also alternative ways of treating waste water. Millar Western's
Meadow Lake factory
in Canada was the first "effluent- free" BCTMP mill in the world. At this
mill, the waste water to
be removed from the process is led into a series of internal evaporation
units, where it is
evaporated to a high dry matter percentage, and the concentrate is burnt in an
internal soda
recovery unit. After cooling, the melt from the soda recovery unit is
pclletised and stored in
.. dumping areas. The melt comprises the alkaline chemicals used in the
process, along with
inorganic salts which are dissolved from the wood. Consequently, in practice,
the mill is waste
water free ("effluent-free"), but there is neither any recovery of chemicals
nor recirculation.
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The BCTMP mills built in the 2000s by M-real at Joutseno (2001) and Kaskinen
(2005) are, for
the purpose of treating concentrate and the recovery of chemicals, integrated
with sulphate pulp
mills.
The BCTMP mills evaporate their waste water in a cascade of evaporation units
to a high dry
matter percentage (> 45 %), and from evaporation unit section the concentrate
is pumped to a
mixing zone for mixing with black liquor received from a pulp mill located in
the same mill area.
After going through the evaporation unit of the pulp mill the mixture thus
obtained is burnt in a
soda recovery unit. In the soda recovery unit, combustion of the material
generates carbon
dioxide and water (--4 CO2 + H20) and the inorganic ingredients form a melt on
the bottom of
the recovery unit. This melt is dissolved in water, which generates green
liquor (Na2CO3 + Na2S
/ main products). Consequently, the sodium, which forms part of the alkaline
chemicals used in
the BCTMP mills, is recovered as a part of the process of dissolving the melt
(green liquor) in
the soda recovery unit. The cooking chemicals used in a sulphate pulp mill are
sodium hydroxide
(NaOH) and sodium sulphide (Na2S). The conditions of the burning in the soda
recovery unit are
reductive, thus sulphur is recovered directly in sulphide form. The main
components of white
liquor are sodium hydroxide (NaOH) and sodium sulphide (Na2S).
A pulp mill uses a major part of the green liquor for manufacturing of white
liquor, but part of
the green liquor is oxidised (Na2CO3 + Na2S Na2CO3+ Na2SO4) and led to the
BCTMP mill.
Oxidising is a means of removing the sodium sulphide, which would otherwise
cause problems
at the BCTMP mill because it consumes hydrogen peroxide, which is used in
bleaching of the
pulp. Sodium sulphate (Na2SO4) is a neutral salt which passes as a "dead load"
through the
process of the CTMP mill and ends up, in the concentrate, back in the soda
recovery unit, where
it is reduced back to sodium sulphide.
Sodium carbonate is not an effective chemical for removing lignin (i.e. for
delignification) in the
cooking of chemical pulp. Consequently, green liquor is unsuitable for use in
impregnation or
cooking in the production of chemical pulp. White liquor is produced from
green liquor by
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means of lime causticising. In this process, burnt lime (CaO) is added into
green liquor, and as a
result of causticising reactions, the carbonate is precipitated as calcium
carbonate, while sodium
forms sodium hydroxide. The lime is regenerated by burning (CaCO3 ¨> CaO) in a
lime sludge
reburning kiln.
In the production of chemi-mechanical pulp, such as CTMP, lignin is not
removed in the wood
chip-impregnation stage by using alkaline treatment (impregnation), instead
the lignin is softened
and carbohydrates (hemicellulose) are treated in advance of the following
refining stage
(defibring of wood chips). The pH value of the impregnation solution or
impregnation liquor is
lower (pH value 9-12) than in the production of chemical pulp (pH value 14).
Consequently, it is
possible also to use sodium carbonate for the impregnation of wood chips in
the production of
chemi-mechanical pulp.
In integrated BCTMP processes, oxidised green liquor from the pulp mill and
lye (NaOH), which
is typically bought from external suppliers, are used in the impregnation of
hardwood. The alkali
used in the peroxide bleaching is lye. In impregnation of softwood, sodium
sulphite is primarily
used.
Besides using an integrated solution, it is also possible to carry out a
separate recovery of sodium
chemicals at CTMP mills. According to one embodiment, namely the one known as
the Alrec
process (Alkali recovery process), the waste liquor which is concentrated to a
dry matter
percentage of approximately 65 % is burnt by using "drop burning" under
oxidising conditions
(oxygen excess) and at a temperature of 1000-1200 C.
In the Alrec burning, in contrast to burning in a soda recovery unit, the
conditions throughout the
combustion chamber area are oxidative (excess oxygen). In Alrec burning, the
percentage of
oxygen in the combustion gas is 4-6 volume-%. In the burning in a soda
recovery unit, the
burning conditions are regulated, by introducing air, in phases, into
different parts of the unit in
such a way that the conditions for instance in the stack are reductive.
Therefore
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COD (= dissolved organic material) is destroyed CO2+ H20), and
sodium of the waste liquor is recovered as sodium carbonate (Na2CO3).
It is possible to recirculate the sodium carbonate which is to be used in
impregnation of the wood
chips and in bleaching of the CTMP pulp, where it also can be used, besides
lye, as a source of
alkali.
In the high-temperature process described above, the sodium in the waste water
concentrate,
which is bound to the organic material, is evaporated into its gaseous phase,
where it is partly in
the form of Na2O and partly as elementary sodium (boiling point of sodium is
883 C). The lag
or residence time in the Alrec process is only a few seconds at a burning
temperature of 1000-
1200 C, after which period the combustion gases from the combustion chamber
are rapidly
cooled to 600 C. In this case, the gaseous sodium compounds are desublimate
directly as solid
powdery sodium carbonate. This prevents the generation of sticky molten sodium
carbonate and
thus any fouling of the walls.
The solid sodium carbonate (ash) generated in the process is dissolved in
water, impurities are
removed by filtering and the Na2CO3 solution is recirculated to the
impregnation of wood chips
and bleaching of pulp.
The process described above is reported in more detail in International
Published Patent
Application No. WO 2005/068711 (Rinheat Oy).
There are limitations associated with the known technology. In our experiments
we have
discovered that when lye (sodium hydroxide) is replaced during the
impregnation stage by
sodium carbonate, the pH value of the impregnation solution is lowered and
impregnation and
softening of hardwood chips are diminished, which tends to increase the
specific energy
consumption during refining. If the specific energy generated during refining
increases, this
limits the usability of the recovered alkali in the impregnation stage, i.e.
the 100 % sodium
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carbonate solution. Our test runs suggest that the effect of carbonate on the
specific energy of
refining depends at least on what quality of the CTMP to be produced
(technical properties of
paper) is desired and possibly on the proportions of wood species
(birch/aspen).
.. The sulphite in sodium sulphite (Na2S03), which is used in softwood-CTMP
production, oxidises
during the above-described, oxidative Alrec burning process to a neutral
sulphate compound
(Na2SO4). Sodium sulphate is a neutral salt and is not suitable as an alkaline
chemical in
impregnation or bleaching. Consequently, the Alrec process is not suitable for
recovery and
recirculation of sodium sulphite, without separate procedures for the
regeneration of sulphite.
There are also limitations associated with the use of sodium carbonate as
alkali in peroxide
bleaching. Without the presence of lye, the pH value remains low which reduces
the bleaching
effect.
.. The purpose of the present invention is to achieve a completely new
solution of recovering alkali
in chemi-mechanical and mechanical pulp production. Another purpose of the
present invention
is, for instance, to extend the usability of alkaline chemicals which are
recovered by using the
Alrec process.
.. The present invention is based on the concept of producing sodium hydroxide
from a waste
stream or effluent of a fibre pulp production process. The stream used
typically comprises
organic waste and sodium and sodium compounds which are bound to the waste.
Thus, to a
waste stream or impregnation solution, borate or a corresponding boron-bearing
material (in the
following also called a "boron compound") is added. The addition of the boron
compound
.. renders it possible to generate sodium hydroxide, which is formed of sodium
and sodium
compounds, through a borate-autocausticising reaction and subsequent
hydrolysis.
Autocausticising is a reaction which was described in literature already in
the 1970s (see Jan
Janson, "The Use of Unconventional Alkali in Cooking and Bleaching ¨ Part 1. A
New
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Approach to Liquid Generation and Alkalinity", Paperi ja Puu 59 (6-7), pp. 425-
430 (1977),
"The Use of Unconventional Alkali in Cooking and Bleaching ¨ Part 2. Alkali
cooking of wood
with the use of borate". Paperi ja Puu 59 (9), pp. 546-557 (1977) and US
Patent No. 4,116,759.
According to Janson's observations, a conventional separate causticising which
uses burnt lime
could even be avoided entirely during sulphate cooking by adding borate to the
cooking liquor,
which through the causticising reaction generates sodium hydroxide in
association with the
dissolving of the melt, i.e. production of green liquor. However, mill tests
carried out by Enso
Gutzeit in 1982 did not confirm initial expectations about the profitability
of the process.
Approximately 20 years later, Honghi Tran examined borate autocausticising
reactions anew and
showed that the lye yield from borate was double that which Janson had
described. According to
the reaction formulas presented by Tran, one mole of tetraborate (Na2B407)
generates 8 moles of
lye (NaOH), rather than 4 moles as Janson assumed. (Tran, H.; Mao, X.;
Cameron, J.; Bair,
.. C.M., Pulp and Paper Canada 1999, 100(8), 35-40). This discovery had a
substantial effect on
the profitability of borate autocausticising, because it demonstrated that
only half the original
borate dosage was required. Tran's studies have resulted in borate
autocausticising being partly
applied at some sulphate pulp mills.
In an article titled "Borate autocausticizing: a cost effective technology"
(Pulp & Paper Canada
103: 1 1 (2002), pp. 16-22, J. M. A. Hooddenbagh et al. describe two mill
tests, which were carried
out 15 years after the Enso tests and in which an autocausticising reaction
was used both in
recovery and in bleaching of chemicals. On the basis of the results, alkali
which is produced by
using the borate autocausticising process can possibly be used in the
bleaching of CTMP and
replace sodium hydroxide bought from external suppliers.
Incorporation of borates into a pulp production process, for instance in order
to generate boron-
bearing alkaline cooking liquors, has recently been described in the patent
literature, as
exemplified by International Published Patent Application No. WO 2004/025020.
That document
discloses a process, in which borate-carbonate cooking is integrated with the
recovery of
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chemicals in the production of chemical pulp of eucalyptus. This solution is
at least partly based
on autocausticising, during which part of the cooking chemicals, which are
regenerated by using
autocausticising, are used for cooking and/or oxygen delignification or during
alkaline bleaching
stages, such as peroxide bleaching without conventional causticising.
Anthrachinon is used as the
.. delignification catalyst.
US Published Patent Application No. 2005/0155730 describes a high-yield
process in which
chemical softwood pulp is produced by using quinone catalyst in the stage of
wood chips
impregnation, in which the pH value is at least occasionally below 7, or in a
cooking liquor
which has a low sulphidity level and which comprises mainly borate, sodium
hydroxide and
sodium carbonate. An alkaline cooking liquor is prepared without separate
causticising by using
calcium oxide or calcium compounds.
Two International Published Patent Applications Nos. W099/63152 and W099/63151
describe
how the efficiency of a calcination reaction is improved by using borate.
In the present invention, we have unexpectedly discovered that
autocausticising reactions take
place also during burning carried out under conditions of oxidization and high
temperatures, such
as the conditions prevailing during a burning process of the Alrec type.
The solution is implemented, according to the new technology presented, in
such a way
that the autocausticising reaction is carried out by burning an effluent in a
combustion chamber
under oxidising conditions and at a temperature which is high enough to
vaporize at least part of
the sodium (boiling point of sodium is 883 C).
In particular, the operation is carried out at a temperature in which sodium
is vaporized and
primarily present in oxide (Na2O) form. By subjecting the sodium and its
compounds, which
during the burning are released from organic material, to a reaction with
borate mainly in
gaseous phase, it is possible to produce sodium hydroxide when the ash which
typically contains
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sodium orthoborate is, during a dissolution step, dissolved or suspended in
water. The effluent of
this reaction can be used as an impregnation solution for instance in a BCTMP
process or other
chemi-mechanical defibring, and as a source of alkali in peroxide bleaching.
It is possible to use the present method for recovering alkaline sodium
compounds, which are at
least partly in the form of sodium hydroxide, and which compounds are suitable
for the
production process of fibre pulp.
More specifically, the method according to the present invention is a method
of producing
sodium hydroxide from an effluent stream of a fibre pulp production process,
which effluent
stream comprises organic waste and sodium compounds which are bound to said
organic waste,
said method comprising the following steps:
i) concentrating the effluent stream;
ii) incorporating into the effluent stream borate or a compound which
forms borate either before or after the concentration step;
iii) burning the concentrated effluent stream in oxidizing conditions to
decompose the organic waste and the sodium compounds and to produce a
combustion residue;
and
iv) dissolving the residue in water to produce sodium hydroxide;
characterized in that the step of burning the concentrated effluent stream
comprises
subjecting the effluent stream to a two stage burning treatment, in which an
autocausticising
reaction occurs in the first stage at a temperature at or above 1000 C, after
which the combustion
gases which are generated in the first stage are rapidly cooled in a second
stage to a temperature
at or below 600 C to desublimate the sodium compounds from their gaseous phase
directly to
their solid phase.
Considerable advantages are achieved with the present invention. Thus, the
invention is
generally suitable for use in burning processes in which, typically, waste
liquor which is
concentrated to a relatively high dry matter percentage, is burnt under
oxidising conditions (i.e.
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in excess oxygen). The temperature is preferably at least approximately 950
C. In particular, at
least a part of the sodium carbonate is converted to sodium hydroxide which
improves the
usability of alkali which is recovered for instance during the Alrec process.
This, in turn, lowers
the costs of chemicals and reduces energy consumption required in the
defibring of wood chips,
which is subsequent to impregnation. The usability of this alkali in peroxide
bleaching is
improved.
The present invention makes it possible to operate an independent (not-
integrated) BCTMP mill
and a mechanical pulp mill, which is waste water- free, and has the means of
recovery of alkaline
chemicals and cost-effective recirculation.
Thermal energy which is generated during the burning of organic waste is used
as steam in the
process.
In the following, the present invention will be examined in more detail with
the help of a detailed
explanation and the accompanying drawing. The process flowchart shown in the
drawing
represents one embodiment of the present technology.
In the present context, the terms "effluent" and "waste water" will be used
largely synonomus to
designate a stream containing organic residues and sodium compounds withdrawn
from a
process for producing fibrous pulp.
As described above, in the present technology, autocausticising and burning at
a high
temperature are combined to form a process in which sodium which is bound,
typically
.. chemically bound, to the organic material of an effluent (waste water), is
subjected to, in gaseous
phase and under oxidising conditions, a reaction with a boron compound. It
would seem that at
such conditions, sodium is reacted at least to some extent directly with
borate, or another boron
compound, probably instead of with carbon dioxide. As a result, a mixture of
lye (NaOH) and
sodium carbonate (Na2CO3) is generated during the dissolution of the ash,
which is recovered in
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the process. It should be pointed out that the present invention is not
restricted to this explanatory
model described here.
According to one embodiment of the present invention, metaborate or compounds
that form
metaborate are incorporated into the effluent, and the sodium and sodium
compounds which are
released during the processing, are reacted with the borate at a temperature
which is high enough
to vaporize sodium which then is present mainly in oxide form (Na2O). There
may be some
elemental sodium present as well. It is possible to incorporate the borate
compounds into the
effluent by adding them directly into this stream or by adding them for
instance into an
impregnation stream of chemi-mechanical or mechanical defibring, along with
which they are
carried through the process and form part of the effluent of the defibering
(i.e. the waste stream).
Preferably, the effluent is first concentrated to a high dry matter
concentration. According
to one embodiment, the dry matter percentage of an effluent, which is
subjected to
autocausticising, is at least 45 weight-%, preferably at least 55 weight-%,
most suitably at least
60 weight-%, in particular at least 63 weight-%, or even at least 65 weight-%.
According to another embodiment, the waste water concentrate is dried to a
powder, which is fed
into the burning as dry matter.
Preferably, an effluent which is concentrated to a high dry matter percentage
of for instance at
least approximately 60 weight-%, especially at least approximately 63 weight-%
or at least 65
weight-%, is burnt in the presence of oxygen and borate or a compound that
forms borate (a
"boron compound"), at a temperature of at least 950 C.
Typically, the dry matter of the waste comprises both an organic and an
inorganic part. The
weight ratio between these can vary within broad ranges, generally it is
approximately 3:1...1 :1,
although these are no absolute limits.
CA 2767903 2017-09-06
According to a preferred embodiment, autocausticising is carried out at a
temperature of at least
1000 C, preferably 1000-1250 C.
Here, "oxidising conditions" mean that during the entire or essentially entire
burning process
there is an excess of oxygen in order to prevent reductive conditions
occurring in any part of the
combustion chamber. The oxygen is in excess in respect of oxidizable compounds
in the
processed stream.
Most suitably, the quantity of borate or other boron compound added into the
waste water or
impregnation solution before burning is large enough to ensure that the Na:B
molar ratio of the
waste stream is at least 3:1. Preferably, the Na:B molar ratio is
approximately 3:1...50:1, most
suitably approximately 5:1...35:1.
When using borate, at least a major part of the inorganic borate is added as
sodium metaborate or
sodium tetraborate or as hydrates thereof. Other boron compounds are possible,
too.
According to the present invention, the effluent stream to be treated is
typically generated as
waste water from fibre pulp production which takes place under alkaline
conditions. In
particular, the waste water stream comprises the effluent from an impregnation
step, i.e.
impregnating, of the raw material of chemi-mechanical or mechanical pulp
production, or the
waste stream of alkaline peroxide bleaching of fibre pulp, or a combination
thereof. Thus, the
waste stream can be sourced from the production of, for instance, groundwood
pulp, pressure
groundwood, refiner pulp or chemi-mechanical refiner pulp.
The waste stream which is subjected to burning comprises mainly organic
compounds which are
dissolved in pulp production, and sodium which is chemically bound to these
compounds.
Consequently, the sodium is sourced from sodium-bearing chemicals which are
used in
impregnation of raw materials or alkaline peroxide bleaching or both, such as
sodium carbonate,
sodium hydroxide and/or oxidised green liquor or oxidised white liquor which
come from
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chemical pulp production.
According to one embodiment, the burning treatment of an (organic) waste
stream which
comprises borate or to which borate is fed, is carried out in two stages, in
which case the actual
burning takes place in the first stage under oxidising conditions and at a
temperature of over
1000 C, after which the combustion gases generated in the burning, containing
sodium in oxide
and elemental form, are rapidly cooled to a temperature below 600 C, in order
to desublimate
the sodium compounds from their gaseous phase directly into solid phase
(sodium carbonate and
in particular borate compounds, such as Na3B03).
The ash, which is generated from the burning of the waste stream, is recovered
and dissolved in
water in order to produce sodium hydroxide. At the same time, the metaborate
(NaB02) is
regenerated.
Typically, after the action described above, the ash contains a percentage of
(calculated) sodium
hydroxide which ¨ depending on the organic material and the percentage of
sodium in the waste
water ¨ is approximately 1-75 %, most suitably approximately 5-70 %,
especially approximately
10-50 %, of the dry matter weight.
Autocausticising is carried out under conditions of excess oxygen, in which
oxidising conditions
prevail throughout the combustion chamber. Typically, the percentage of the
oxygen in the
exiting combustion gas is 4-6 volume-%.
Oxygen is conducted to the burning stage as a gas stream comprising oxygen,
such as air or air
enriched with oxygen.
It is possible to carry out the burning as drop-burning, in which case the
waste water concentrate
which is subjected to autocausticising is dispersed to form droplets. The
average drop size can be
for instance approximately 0.1-5 mm, preferably < 1 mm and more preferably
<0.1 mm.
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It is possible to use the method described above generally for recovering
alkaline sodium
compounds, which are used in the fibre pulp production process, at least
partly as sodium
hydroxide.
In the production of chemi-mechanical pulps, such as BCTMP, ash, which is
partly causticised in
the production, is dissolved in water, the insoluble inorganic oxides (dregs)
are removed by
filtering or centrifuging, and the alkaline solution generated can be used
directly, without further
treatment with traditional lime causticising, as a source of alkali for
impregnation and peroxide
bleaching.
The present invention can be implemented for instance in equipment arranged as
shown in the
drawing. The equipment comprises a combustion chamber 1 and a cooling chamber
2, which
according to the drawing are arranged one below the other in such a way that
it is possible to
lead the combustion gases, which are generated in the combustion chamber, to
the cooling
chamber, in which it is possible to cool them with the aid of cooling gas,
such as cooling air or
circulated combustion gas, which is led into the cooling chamber. The
combustion chamber is
equipped with a nozzle 3 for feeding the waste water concentrate to be burnt,
through which
nozzle it is possible to feed the concentrate for instance as a mist which
comprises small droplets
which are dispersed by using steam.
The cooling gas can be conducted into the cooling chamber 2 through an inlet
nozzle 4. The
bottom of the cooling chamber is equipped with an outlet nozzle 5 for removing
carbonate, and
with an outlet nozzle 6 for removing cooling gases and cooled combustion
gases.
Effluent which is removed from a process and which comprises metaborate or
boron compound
that forms metaborate, is evaporated in an internal process evaporation unit
preferably to achieve
a dry matter percentage of at least 45 %. After that, it is conducted through
feeding nozzle 3 into
the combustion chamber 1, where it is burnt for instance at a temperature of
over 1000 C.
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The burning process is described in more detail in the International Published
Patent Application
No. WO 2005/068711 (Rinheat Oy).
The residence time in the combustion chamber 1, at a high temperature, is only
a few seconds
and the combustion gas coming from the combustion chamber is rapidly cooled in
the cooling
chamber 2 to below 600 C, in which case the sodium compounds are desublimated
directly to
solid material and can be removed as ash.
When the ash is dissolved in water, the sodium orthoborate (trisodiumborate)
which is generated
reacts with water, in which case it forms sodium hydroxide and, at the same
time, the metaborate
regenerates according to formulas (1) and (2).
(1) Na2CO3 + NaB02 --> Na3B03 + CO2
metaborate orthoborate
(2) Na3B03 + H20 ¨> 2 NaOH + NaB02
Borates are completely water-soluble compounds and regenerated metaborate is
transferred in
the impregnating solution to the impregnation step and from there further on,
in the effluent of
the impregnation together with waste water, through the evaporation unit, back
to oxidising
burning. The percentage of borate in the waste water which goes to the
evaporation unit is kept at
a constant level, by adding make-up.
As pointed out before, the burning is carried out in the combustion chamber in
excess oxygen, in
order to ensure that the burning conditions in all parts of the chamber are
those of oxidation.
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It is also possible to carry out the dissolution of the ash in the cooling
chamber 2. In that case,
water is fed into the cooling chamber via inlet nozzle 4. The water thus fed
can be either clean
water or an aqueous solution, such as a solution generated from the
recirculation. With the aid of
water, a liquid film can be formed on the surface of the chamber, in which
film it is possible to
dissolve the alkali metal carbonate comprised in the cooled combustion gases.
Example
A concentrate from an evaporation unit, which concentrate has an organic
material percentage of
.. 52 cYo and an inorganic material percentage of 48 % of the dry matter, was
burnt with excess air
in laboratory conditions. The burning temperature was 1100 C. Before burning,
sodium
metaborate was mixed into the concentrate.
Table
Na2CO3 pH value of Titrated
Ash yield percentage of ash aqueous NaOH percentage
mg/g ash solution of ash mg/g ash
Concentrate 43.1 719 11.8 40
Concentrate+NaB02 48.4 109 12.9 385
Na/B mole/mole =
3:1
The Na2CO3percentage of ash was determined by a TOC carbon analyser.
The percentage of lye in the aqueous solution of ash was determined by
titration, which was
based on the standard SCAN-N 30:85.
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