CA2069107C - Process for the preparation of cooking liquors having high sulphidity for sulphate pulp cooking - Google Patents
Process for the preparation of cooking liquors having high sulphidity for sulphate pulp cooking Download PDFInfo
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- CA2069107C CA2069107C CA002069107A CA2069107A CA2069107C CA 2069107 C CA2069107 C CA 2069107C CA 002069107 A CA002069107 A CA 002069107A CA 2069107 A CA2069107 A CA 2069107A CA 2069107 C CA2069107 C CA 2069107C
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- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
- D21H17/00—Non-fibrous material added to the pulp, characterised by its constitution; Paper-impregnating material characterised by its constitution
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- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
- D21C11/00—Regeneration of pulp liquors or effluent waste waters
- D21C11/04—Regeneration of pulp liquors or effluent waste waters of alkali lye
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Abstract
An improvement is provided in a process for preparing, under reducing conditions, cooking liquors for sulphate pulp cooking. The black liquor which is formed in the cooking process is fed, after evaporation, completely or partly to a reactor operating at increased temperature. The increased temperature is obtained by energy which is supplied from an external heat source and/or release of energy from the black liquor, thereby to form a melt of sodium sulphide. The melt then is withdrawn to be further processed to cooking liquor.
The melt, and the whole or part of at least one of sulphur-containing, sulphur-and sodium-containing materials which are present in the pulp mill including sulphur-containing, and sodium- and sulphur-containing make-up chemicals used for the total chemicals balance of the pulp mill, are fed to the reactor in such a way that the mole ratio of sodium to sulphur in the total mixture which is fed to the reactor is within the range of from 1.5 to 4.
The melt, and the whole or part of at least one of sulphur-containing, sulphur-and sodium-containing materials which are present in the pulp mill including sulphur-containing, and sodium- and sulphur-containing make-up chemicals used for the total chemicals balance of the pulp mill, are fed to the reactor in such a way that the mole ratio of sodium to sulphur in the total mixture which is fed to the reactor is within the range of from 1.5 to 4.
Description
(a) TITLE OF THE INVENTION
PROCESS FOR THE PREPARATION OF COOKING LIQUORS HAVING HIGH
SULPHIDITY FOR SULPHATE PULP COOKING
(b) TECHNICAL FIELD TO WHICH THE INVENTIfON RELATES
The present invention relates to a process for the preparation of cooking liquors having high sulphidity for the sulphate pulp industry starting from chemicals which are available in the pulp mill or make-up chemicals which are common in the pulp mill.
(c) BACKGROUND ART
Sodium sulphide and the closely-related chemical, sodium hydrogen sulphide, are often interchangeable with each other and the application thereof often differs in order to meet different sulphidity demands. In the aqueous phase, sodium sulphide hydrolyses completely or partly to sodium hydroxide and sodium hydrogen sulphide according to the equation:
Na2S + H20 ~J NaOH + NaSH (1) The concept "sulphidity in the pulp industry" is usually expressed according to the equation:
sulphidity ( % ) = 2 x NaSH x 100 NaOH - NaSH
wherein NaSH and NaOH are expressed in molar units. This means, e.g., that an aqueous solution containing sodium hydrogen sulphide and sodium hydroxide having a sulphidity of 40% contains 4 times more moles of sodium hydroxide than sodium hydrogen sulphide. In the same way the equilibrium equation (1) above expresses a solution having a sulphidity of 100 % .
Large amounts of sodium sulphide are prepared in thc: sulphate pulp industry.
When recovering the cooking chemicals, the so-called black liquor is burnt in a soda recovery unit, the lower part of which is reductive. In the lower zone of the soda recovery unit, the sulphur components of the black liquor are reduced to the sulphide state and accordingly °
~ CA 02069107 2001-06-26 convert to sodium sulphide. The sulphate pulp mills often operate within the sulphidity range of 25 to 40% (white liquor sulphidity). A major part of the sodium reacts with carbon dioxide when burning black liquor to form sodium carbonate. The mixture of sodium sulphide and sodium carbonate forms a melt at the bottom of the soda recovery unit. This melt is withdrawn and is reacted with water to form so-called "green liquor" . A
typical green liquor has the following composition:
Sodium carbonate 90 - 105 g/ 1 Sodium sulphide 20 - 50 g/1 Sodium hydroxide 15 - 25 g/ 1 (all substances calculated as sodium hydroxide).
Chemicals recovery according to the "sulphate process" (kraft) results in a relatively large amount of sulphur reaching the oxidative zone and being rejected from the soda recovery unit mainly as sodium sulphate (electrical filter ash) and sulphur dioxide. If the white liquor sulphidity exceeds 35%, problems begin to ariise, i.a., by high emissions of sulphur dioxide from the soda recovery unit. Scrubbing with an alkaline medium is therefore often used in order to eliminate or strongly reduce the sulphur dioxide emissions.
The green liquor so-obtained is converted to white liquor according to the known causticizing process. The composition of a white liquor ma.y vary from mill to mill but approximate concentration values are as follows:
Sodium hydroxide, NaOH 80 - 120 g/ 1 Sodium sulphide, Na2S 20 - 50 g/1 Sodium carbonate, Na2,CO3 10 - 30 g/ 1 Sodium sulphate, NazS04 5 - 10 g/1 (all substances calculated as sodium hydroxide).
If NazS is estimated to be fully hydrolysed according to the equation:
Na2S + H20 ~ NaOH + NaSH
PROCESS FOR THE PREPARATION OF COOKING LIQUORS HAVING HIGH
SULPHIDITY FOR SULPHATE PULP COOKING
(b) TECHNICAL FIELD TO WHICH THE INVENTIfON RELATES
The present invention relates to a process for the preparation of cooking liquors having high sulphidity for the sulphate pulp industry starting from chemicals which are available in the pulp mill or make-up chemicals which are common in the pulp mill.
(c) BACKGROUND ART
Sodium sulphide and the closely-related chemical, sodium hydrogen sulphide, are often interchangeable with each other and the application thereof often differs in order to meet different sulphidity demands. In the aqueous phase, sodium sulphide hydrolyses completely or partly to sodium hydroxide and sodium hydrogen sulphide according to the equation:
Na2S + H20 ~J NaOH + NaSH (1) The concept "sulphidity in the pulp industry" is usually expressed according to the equation:
sulphidity ( % ) = 2 x NaSH x 100 NaOH - NaSH
wherein NaSH and NaOH are expressed in molar units. This means, e.g., that an aqueous solution containing sodium hydrogen sulphide and sodium hydroxide having a sulphidity of 40% contains 4 times more moles of sodium hydroxide than sodium hydrogen sulphide. In the same way the equilibrium equation (1) above expresses a solution having a sulphidity of 100 % .
Large amounts of sodium sulphide are prepared in thc: sulphate pulp industry.
When recovering the cooking chemicals, the so-called black liquor is burnt in a soda recovery unit, the lower part of which is reductive. In the lower zone of the soda recovery unit, the sulphur components of the black liquor are reduced to the sulphide state and accordingly °
~ CA 02069107 2001-06-26 convert to sodium sulphide. The sulphate pulp mills often operate within the sulphidity range of 25 to 40% (white liquor sulphidity). A major part of the sodium reacts with carbon dioxide when burning black liquor to form sodium carbonate. The mixture of sodium sulphide and sodium carbonate forms a melt at the bottom of the soda recovery unit. This melt is withdrawn and is reacted with water to form so-called "green liquor" . A
typical green liquor has the following composition:
Sodium carbonate 90 - 105 g/ 1 Sodium sulphide 20 - 50 g/1 Sodium hydroxide 15 - 25 g/ 1 (all substances calculated as sodium hydroxide).
Chemicals recovery according to the "sulphate process" (kraft) results in a relatively large amount of sulphur reaching the oxidative zone and being rejected from the soda recovery unit mainly as sodium sulphate (electrical filter ash) and sulphur dioxide. If the white liquor sulphidity exceeds 35%, problems begin to ariise, i.a., by high emissions of sulphur dioxide from the soda recovery unit. Scrubbing with an alkaline medium is therefore often used in order to eliminate or strongly reduce the sulphur dioxide emissions.
The green liquor so-obtained is converted to white liquor according to the known causticizing process. The composition of a white liquor ma.y vary from mill to mill but approximate concentration values are as follows:
Sodium hydroxide, NaOH 80 - 120 g/ 1 Sodium sulphide, Na2S 20 - 50 g/1 Sodium carbonate, Na2,CO3 10 - 30 g/ 1 Sodium sulphate, NazS04 5 - 10 g/1 (all substances calculated as sodium hydroxide).
If NazS is estimated to be fully hydrolysed according to the equation:
Na2S + H20 ~ NaOH + NaSH
this means that the amount of sodium, which is bound as c<~rbonate, often amounts to more than 20 % of the sodium present as hydroxide.
It is known that the presence of sodium hydrogen sulphide is advantageous in pulp cooking according to the sulphate process. The presence of sodium hydrogen sulphide increases the selectivity of the cooking towards higher lignin release. The effect can also be expressed by saying that an increased hydrogen sulphide content makes it possible to reach a lower kappa number at the same viscosity when the conditions otherwise are comparable.
The kappa number is a measure of the lignin content and the viscosity is considered to be a measure of the strength of the cellulose fibre.
It is of interest to be able to cook the pulp to as low kappa number as possible. This especially applies if it shall be bleached to high, e.g., 90 (ISO) brightness.
For this purpose bleaching is required with chlorine-containing bleaching chemicals resulting in synthetic chlorine-carbon bonds (TOCI - total organic chlorine bound) which are a great environmental load. In order to reduce the proportion of lil;nin bleached-off with chlorine-containing bleaching chemicals, bleaching with an oxygen ;gas has also been developed.
This technique is in the process of development in, i. a. , Sweden and Japan.
In order to reduce the bleaching with chlorine chemicals it is known further to improve the selectivity of the cooking by so-called "modified cooking"
resulting in still lower kappa numbers. Modified cooking according to the present technique of the prior art is based upon the following process conditions:
1. The alkali concentration shall be as constant as possible during the course of the cooking.
2. The hydrogen sulphide concentration shall be as high as possible, particularly in the beginning of the bulk delignification phase. The hydrogen sulphide concentration can be low at the end phase of the cooking.
It is known that the presence of sodium hydrogen sulphide is advantageous in pulp cooking according to the sulphate process. The presence of sodium hydrogen sulphide increases the selectivity of the cooking towards higher lignin release. The effect can also be expressed by saying that an increased hydrogen sulphide content makes it possible to reach a lower kappa number at the same viscosity when the conditions otherwise are comparable.
The kappa number is a measure of the lignin content and the viscosity is considered to be a measure of the strength of the cellulose fibre.
It is of interest to be able to cook the pulp to as low kappa number as possible. This especially applies if it shall be bleached to high, e.g., 90 (ISO) brightness.
For this purpose bleaching is required with chlorine-containing bleaching chemicals resulting in synthetic chlorine-carbon bonds (TOCI - total organic chlorine bound) which are a great environmental load. In order to reduce the proportion of lil;nin bleached-off with chlorine-containing bleaching chemicals, bleaching with an oxygen ;gas has also been developed.
This technique is in the process of development in, i. a. , Sweden and Japan.
In order to reduce the bleaching with chlorine chemicals it is known further to improve the selectivity of the cooking by so-called "modified cooking"
resulting in still lower kappa numbers. Modified cooking according to the present technique of the prior art is based upon the following process conditions:
1. The alkali concentration shall be as constant as possible during the course of the cooking.
2. The hydrogen sulphide concentration shall be as high as possible, particularly in the beginning of the bulk delignification phase. The hydrogen sulphide concentration can be low at the end phase of the cooking.
3. The concentrations of lignin released and sodiwn ions shall be as low as possible, particularly in the last stage of the cooking.
4. The temperature shall be low, particularly in the beginning and at the end of the cooking.
Of the above-cited items, item 2 is of special interest with regard to the present invention. So far, one has been allowed to contend with the; concentration of hydrogen sulphide ions provided by the 40% sulphidity in the white liquor.
From, i.a., S. Norden et al, Tappi, Vol 62, No. 7, July 1979, p. 49; B.
Johansson et al, Svensk Papperstidning No. 10, 87 (1984), p. 30; and D. Tormund et al, Tapi, Vol. 72, No. 5, May 1989, p. 205, it is evident that a further increased content of hydrogen sulphide ions beyond 40 % sulphidity is very advantageous in the initial stage of the cooking.
In modified cooking the cooking liquor is added at two or several places. An extra high sulphidity in the cooking liquor added in the beginning of the cooking is of greatest use while the sulphidity in cooking liquors added in the final phase of the cooking may be low.
(d) DESCRIPTION OF THE INVENTION
An object of a first aspect of the present invention is to provide the important pulp mill balance between sodium and sulphur.
An object of a second aspect of the present invention is to provide such balance in cooking with high sulphidity, particularly in the so-called "modified cooking"
.
The present invention provides, in a first aspect, an vnprovement in a process for preparing, under reducing conditions, cooking liquors for sulphate pulp cooking, wherein the black liquor which is formed in the cooking process is i:ed, after evaporation, completely or partly to a reactor operating at increased temperature, the increased temperature being obtained by energy which is supplied from an external heat source and/or release of energy from the black liquor, thereby to form a melt of sodium sulphide, the melt then being withdrawn to be further processed to cooking liquor. The improvement comprises feeding, to the reactor, the melt and the whole or part of at least one of sulphur-containing, sulphur- and sodium-containing materials which are present in the pulp mill including sulphur-containing, and sodium- and sulphur-containing make-up chemicals used for the total chemicals balance of the pulp mill, in such a way that the mole ratio of sodium to sulphur in the total mixture which is fed to the reactor is within the range of from 1.5 to 4.
The present invention provides, in a second aspect, aai improved process for preparing, under reducing conditions, cooking liquors for sulphate pulp cooking, wherein black liquor which is formed in the cooking process is fed, after evaporation, completely or partly to a black liquor gasifier operating at an elevated temperature of 700° to 950°, the elevated temperature being obtained by energy which is supply from an external heat source and/or release of energy from the black liquor, to form a melt having a low sodium carbonate content, the melt being withdrawn to be further processed to cooking liquor. The improvement comprises feeding, to the black liquor gasifier, the melt and the whole or a part of at least one of sulphur-containing and sulphur- and ;>odium- and sulphur-containing materials which are present in connection with pulp production in such amounts that the mole ratio between sodium and sulphur in the total mixture which is fed to the gasifier is within the range of 1.5 to 4.
By a first variant of these first and second aspects of the present invention, the melt contains 0.25 moles/litre or less of sodium carbonate.
By a second variant of these first and second aspects of the present invention, and/or the above-recited variant thereof, the mole ratio between sodium and sulphur in the total mixture which is fed to the reactor is within the range of 2 to 3. Preferably, the mole ratio between sodium and sulphur in the total mixture which is fc~d to the reactor is within the range of 2 to 2.8 ' By a third variant of these first and second aspects of the present invention, and/or the above-recited variants thereof, the sulphur-containing and sulphur- and sodium-containing materials which are present in the pulp mill and/or are present in connection with pulp production and which are fed to the reactor partly or completely, consists of at least one of electrical filter ash, residual product from chlorine dioxide production, sodium hydrogen sulphite-containing solutions from scrubbing of sulphur dioxide, waste liquors from CTMP, NSSC or other sulphite pulp process, sulphur dioxide from roasting of copper sulphide as well as hydrogen sulphide-containing condensat:es or air streams.
By a fourth variant of these first and second aspects of the present invention, and/or the above-recited variants thereof, the sulphur-containing and sulphur- and, sodium-containing materials which are present in connection with pulp production and which are fed to the reactor partly or completely consist of sulphur-containing andlor sulphur- and sodium-containing make-up chemicals which consist of at least one of sulphur, sulphur dioxide, sulphuric acid, sodium sulphite, sodium hydrogen sulphate, sodium thiosulphate and sodium sulphate.
By a fifth variant of these first and second aspects of the present invention, and/or the above-recited variants thereof, the melt or an aqueous solution thereof is mixed with white liquor, thereby to obtain a white liquor having increased sulphidity.
By a sixth variant of these first and second aspects of the present invention, and/or the above-recited variants thereof, an aqueous solution of the melt is used in the so-called modified sulphate cooking in which cooking liquors are ch~~rged to the reactor in two steps.
Thus, it is seen that, by passing, together with black liquor, other sodium-and sulphur-containing materials which are present in the pulp mill to a reactor in such a way that the mole ratio of sodium to sulphur falls within the range 1.5 to 4, it is possible, under reducing conditions, to prepare a melt of sodium sulphide (NazS) having a lower content of sodium carbonate than in a conventional soda recovery unit melt. From a solution of this melt a cooking liquor having very high sulphidity may be prepared. At a sodium to sulphur ratio of 2 to 3, the carbonate content is so low that the solution may be used directly for cooking purposes.
In other words, it has now surprisingly been found that a process for preparing a cooking liquor having high sulphidity which is particularly suited for modified cooking according to the sulphate process is one wherein cooking liquor having high sulphidity is added in such way that, when cooking according to prior art, a pulp may be prepared with lower kappa number than normally is obtained.
More particularly, to recapitulate, the invention in a broad aspect provides a process for preparing, under reducing conditions, cooking liquors having high sulphidity for sulphate pulp cooking wherein the black liquor formed in the cooking process is passed, after evaporation, completely or partly to a reactor operating at an increased temperature which is obtained by energy supply from an external heat source and/or release of energy from the black liquor, a melt essentially consisting of sodium sulphide being formed and withdrawn to be further processed to cooking liquor. The improved process of this broad aspect of the invention comprises adding to the reactor, in .addition to the melt, the whole or part of the sulphur-containing and/or sulphur- and sodium-containing materials which are present in the pulp mill, including sulphur-containing a:nd/or sodium- and sulphur-containing make-up chemicals which are used for the total chemicals balance of the pulp mill, in such a way that the mole ratio of sodium to sulphur in the total mixture which is fed to the reactor is within the range from 1.5 to 4.
Preferably, mole ratios of sodium to sulphur in the total mixture fed to the reactor should be within the range of from 2 to 3, and most preferably should be within the range of from 2 to 2. 8. Further, it is preferred to feed; to the reactor, up to 30 % of the black liquor stream which is formed in the pulp mill.
The sodium sulphide melt which is obtained in the process according to aspects of the present invention may be dissolved in water and may be further processed to cooking liquor in a way which is know per se. According to a preferred embodiment of an aspect of the present invention, a solution of the melt is fed directly i:o the digester for optimum use of its high sulphidity in modified cooking. In an alternative process of an aspect of the present invention, a solution of the melt is mixed with part of the white liquor which has been prepared in the usual way.
In order to allow the reduction reactions in the reactor to proceed quickly, and accordingly to obtain shorter residence times and smaller rf:actor volumes, additional energy, in addition to the energy which is released from thf; black liquor in partial oxidation can be supplied to the mixing zone of the reactor by a hot gas, the heat content and oxidation potential of which are adjusted to the reduction work required.
The heat energy may, e.g.; be supplied by a gas which is heated by a plasma generator.
The very hot gas or gas mixture can also be formed directly or indire>ctly with an oxy-fuel burner.
As gas or gas mixture, use can be made of air, recirculating process gas, hydrogen gas, natural gas, carbon monoxide, etc. When using an oxy-fuel burner, the gas or gas mixture is obtained by combustion of, e.g., acetylene or liq~uified petroleum gas with oxygen-enriched air or pure oxygen gas.
A preferred process according to an aspect of the present invention is that the hot gas is fed to the reactor close to the material which is fed, which in turn must be finely divided which can be obtained by different kinds of atomization techniques known by a person skilled in the art. The reactor must be designed to be sufficiently large in order for the reaction to have time to take place, i.e., the reactor volume must ensure a certain minimum residence time.
The reactor is preferably a closed reaction vessel and the temperature in the reactor shall be at least the temperature at which the sodium sulphide is formed under otherwise prevailing conditions. A person skilled in the art may establish such temperature from case to case, e.g., by routine experiments. The temperature is preferably not below 700°C.
The pressure in the reactor is preferably atmospheric pressure. However, the process may be effected at an increased pressure, e.g., in order to reduce the reactor volume.
In Swedish Patent SE 8501465-2 there is disclosed a process to relieve the soda recovery unit by means of plasma gasification of a partial stream of the black liquor. This makes it possible to increase the pulp production in a mill having too small a soda recovery unit capacity, or, e.g., to introduce oxygen gas bleaching a:nd/or modified cooking in a mill restricted in soda recovery unit capacity without losing production capacity.
Of essential importance for the process of aspects of the present invention is that the mole ratio of sodium to sulphur in the total mixture fed to the reactor be below 4 and be within the range from 1.5 to 4, preferably from 2 to 3. This adjustment of the sodium to sulphur ratio is effected by means of sulphur-containing and/or sulphur- and sodium-containing materials which are present in the pulp mill, including sulphur-containing and/or sodium- and sulphur-containing make-up chemicals which acre used for the total chemicals balance of the pulp mill.
The make-up chemicals which are used in order to adjust the mole ratio of sodium to sulphur correctly may consist of sulphur, sulphur dioxide, sulphuric acid, sodium hydrogen sulphate, sodium sulphate, sodium sulphite, sodium hydrogen sulphite and sodium thiosulphate.
Among sulphur-containing and/or sulphur- and sodium-containing materials which are present in the pulp mill, the following can be mentionedl:
" CA 02069107 2001-06-26 a. Residual acid from chlorine dioxide production, A mixture of sulphuric acid and sodium sulphate having NaIS ratio of <_ l may be obtained from so-called Mathieson plants. In other common processes of so-called R-8 type, sodium sesquisulphate (Na3H(S04)2) having a Na/S ratio of 1.5 is formed. The deposition of the residual acid is generally a problem. It often has to be dumped.
b. So-called electrical filter ash which mainly consists of sodium sulphate.
There are normally formed from 60 to 125 kg electrical filter ash per ton of pulp which are recirculated to the combustion zone of the soda recovery unit. The Na/S ratio is __<2.
c. Sulphate-containing solutions from soda recovery unit scrubber. The Na/S
ratio is 2.
d. A process is disclosed in EP 87850238.4 wherein a partial stream of the sodium hydrogen sulphide of the white liquor is reacted with copper oxide, sodium hydroxide and copper sulphide being formed. The copper sulphide is roasted to form sulphur dioxide and copper oxide. The sulphur dioxide formed is a sodium-free sulphur source.
Further, elemental sulphur may be used or any other sulphur-containing chemical having a Na/S ratio being equal to or below 4.
By suitable combinations of the whole or part of the lblack liquor stxeam and one or more of the above-stated products, an indefinite amount of .cooking liquor having high sulphidity can be prepared.
(e) AT LEAST ONE MODE FOR CARRYING OUT 7CHE INVENTION
The invention is further illustrated by means of the following working examples.
Example 1 The following material streams were fed continuously per hour to a reactor operating at atmospheric pressure.
620 kg black liquor (65 % dry substance contenl;) containing 129 kg sodium (Na) and 35 kg sulphur (S) per ton of black liquor.
A residual acid mixture from chlorine dioxide production according to the Mathieson process containing 80 kg H2S04 and 62 kg NazS04.
800 kg Na2S04 in the form of electrical filter ash.
The above material streams were mixed with an oxygen-containing gas and passed to a reaction chamber. The oxygen-containing gas was heated to 750°C in a plasma generator.
Energy was released by partial oxidation of the black liquor, the temperature in the reaction chamber being maintained at 950°C.
The process gas evolved at the partial oxidation was cooled. After any final oxidation, heat recovery as well as scrubbing, the gas may be released to the atmosphere.
Alternatively, a major part of the energy content of the liquor may be released by partial oxidation, whereby it is not necessary to preheat the oxygen-containing gas in a plasma generator.
Incoming sulphur compounds are reduced in the reaction chamber essentially to sodium sulphide (NazS), thereby forming a melt phase which is withdrawn from the system.
Owing to the high partial pressure of sulphur in the reaction chamber and the higher affinity of sulphur to sodium compared to carbon dioxide at the prevailing reaction conditions, the formation of sodium carbonate is suppressed in the inorganic melt phase.
A 4.0 molar solution with regard to the sodium is prepared containing 1.85 moles of NaOH, 1.85 moles NaSH and 0.15 moles NaZC03 per litre from the melt prepared.
In preparation of experiments with modified two-step pulp cooking where 70 %
of the cooking chemicals were charged in step 1 and the residual 3~0 % in step 2, the following cooking liquors were prepared.
One (1) part of the liquor obtained above according to aspects of the present invention was mixed with 4.63 parts of ordinary cooking liquor (white liquor) containing 2.8 moles of NaOH and 0.7 moles of NaSH per litre solution. The cooking liquor thus prepared having a sulphidity amounting to 51 % was charged in the first cooking step, whereas the normal white liquor having a sulphidity of 40 % was charge in step 2.
Example 2 The following material streams were fed continuously per hour to a reactor operating at atmospheric pressure, namely:
566 kg black liquor (65 % dry substance content:) containing 129 kg sodium (Na) per ton and 35 kg sulphur (S) per ton, 48 kg sulphur dioxide, 80 kg NazS04 in the form of electrical filter ash and 25 kg of Na2S04 as make-up.
One proceeded in exactly the same way as in Example 1 and obtained a melt phase which was withdrawn from the system.
The sulphur dioxide which was added had been generated by roasting according to the process for preparation of sulphide-free liquor disclosedl in EP
87850238.4. A 4.0 molar solution was prepared with regard to sodium containiing 1.75 moles of NaOH, 1.75 moles of NaSH and 0.25 moles of Na2C03 from the melt.
In preparation of experiments with modified two-step pulp cooking where 70 %
of the cooking chemicals were charged in step 1 and the residual .30 % in step 2, the following cooking liquors were prepared.
According to the same charging process as in Example l, in mixing 1.0 part of the liquor prepared above with 1.14 parts of ordinary cooking liquor (white liquor) (40 sulphidity) one obtained a cooking liquor having a sulphidity of 68 % . This liquor was charged in the first cooking step.
In the other step, use was made of the sulphide-free liquor prepared according to EP
87850238.4.
Of the above-cited items, item 2 is of special interest with regard to the present invention. So far, one has been allowed to contend with the; concentration of hydrogen sulphide ions provided by the 40% sulphidity in the white liquor.
From, i.a., S. Norden et al, Tappi, Vol 62, No. 7, July 1979, p. 49; B.
Johansson et al, Svensk Papperstidning No. 10, 87 (1984), p. 30; and D. Tormund et al, Tapi, Vol. 72, No. 5, May 1989, p. 205, it is evident that a further increased content of hydrogen sulphide ions beyond 40 % sulphidity is very advantageous in the initial stage of the cooking.
In modified cooking the cooking liquor is added at two or several places. An extra high sulphidity in the cooking liquor added in the beginning of the cooking is of greatest use while the sulphidity in cooking liquors added in the final phase of the cooking may be low.
(d) DESCRIPTION OF THE INVENTION
An object of a first aspect of the present invention is to provide the important pulp mill balance between sodium and sulphur.
An object of a second aspect of the present invention is to provide such balance in cooking with high sulphidity, particularly in the so-called "modified cooking"
.
The present invention provides, in a first aspect, an vnprovement in a process for preparing, under reducing conditions, cooking liquors for sulphate pulp cooking, wherein the black liquor which is formed in the cooking process is i:ed, after evaporation, completely or partly to a reactor operating at increased temperature, the increased temperature being obtained by energy which is supplied from an external heat source and/or release of energy from the black liquor, thereby to form a melt of sodium sulphide, the melt then being withdrawn to be further processed to cooking liquor. The improvement comprises feeding, to the reactor, the melt and the whole or part of at least one of sulphur-containing, sulphur- and sodium-containing materials which are present in the pulp mill including sulphur-containing, and sodium- and sulphur-containing make-up chemicals used for the total chemicals balance of the pulp mill, in such a way that the mole ratio of sodium to sulphur in the total mixture which is fed to the reactor is within the range of from 1.5 to 4.
The present invention provides, in a second aspect, aai improved process for preparing, under reducing conditions, cooking liquors for sulphate pulp cooking, wherein black liquor which is formed in the cooking process is fed, after evaporation, completely or partly to a black liquor gasifier operating at an elevated temperature of 700° to 950°, the elevated temperature being obtained by energy which is supply from an external heat source and/or release of energy from the black liquor, to form a melt having a low sodium carbonate content, the melt being withdrawn to be further processed to cooking liquor. The improvement comprises feeding, to the black liquor gasifier, the melt and the whole or a part of at least one of sulphur-containing and sulphur- and ;>odium- and sulphur-containing materials which are present in connection with pulp production in such amounts that the mole ratio between sodium and sulphur in the total mixture which is fed to the gasifier is within the range of 1.5 to 4.
By a first variant of these first and second aspects of the present invention, the melt contains 0.25 moles/litre or less of sodium carbonate.
By a second variant of these first and second aspects of the present invention, and/or the above-recited variant thereof, the mole ratio between sodium and sulphur in the total mixture which is fed to the reactor is within the range of 2 to 3. Preferably, the mole ratio between sodium and sulphur in the total mixture which is fc~d to the reactor is within the range of 2 to 2.8 ' By a third variant of these first and second aspects of the present invention, and/or the above-recited variants thereof, the sulphur-containing and sulphur- and sodium-containing materials which are present in the pulp mill and/or are present in connection with pulp production and which are fed to the reactor partly or completely, consists of at least one of electrical filter ash, residual product from chlorine dioxide production, sodium hydrogen sulphite-containing solutions from scrubbing of sulphur dioxide, waste liquors from CTMP, NSSC or other sulphite pulp process, sulphur dioxide from roasting of copper sulphide as well as hydrogen sulphide-containing condensat:es or air streams.
By a fourth variant of these first and second aspects of the present invention, and/or the above-recited variants thereof, the sulphur-containing and sulphur- and, sodium-containing materials which are present in connection with pulp production and which are fed to the reactor partly or completely consist of sulphur-containing andlor sulphur- and sodium-containing make-up chemicals which consist of at least one of sulphur, sulphur dioxide, sulphuric acid, sodium sulphite, sodium hydrogen sulphate, sodium thiosulphate and sodium sulphate.
By a fifth variant of these first and second aspects of the present invention, and/or the above-recited variants thereof, the melt or an aqueous solution thereof is mixed with white liquor, thereby to obtain a white liquor having increased sulphidity.
By a sixth variant of these first and second aspects of the present invention, and/or the above-recited variants thereof, an aqueous solution of the melt is used in the so-called modified sulphate cooking in which cooking liquors are ch~~rged to the reactor in two steps.
Thus, it is seen that, by passing, together with black liquor, other sodium-and sulphur-containing materials which are present in the pulp mill to a reactor in such a way that the mole ratio of sodium to sulphur falls within the range 1.5 to 4, it is possible, under reducing conditions, to prepare a melt of sodium sulphide (NazS) having a lower content of sodium carbonate than in a conventional soda recovery unit melt. From a solution of this melt a cooking liquor having very high sulphidity may be prepared. At a sodium to sulphur ratio of 2 to 3, the carbonate content is so low that the solution may be used directly for cooking purposes.
In other words, it has now surprisingly been found that a process for preparing a cooking liquor having high sulphidity which is particularly suited for modified cooking according to the sulphate process is one wherein cooking liquor having high sulphidity is added in such way that, when cooking according to prior art, a pulp may be prepared with lower kappa number than normally is obtained.
More particularly, to recapitulate, the invention in a broad aspect provides a process for preparing, under reducing conditions, cooking liquors having high sulphidity for sulphate pulp cooking wherein the black liquor formed in the cooking process is passed, after evaporation, completely or partly to a reactor operating at an increased temperature which is obtained by energy supply from an external heat source and/or release of energy from the black liquor, a melt essentially consisting of sodium sulphide being formed and withdrawn to be further processed to cooking liquor. The improved process of this broad aspect of the invention comprises adding to the reactor, in .addition to the melt, the whole or part of the sulphur-containing and/or sulphur- and sodium-containing materials which are present in the pulp mill, including sulphur-containing a:nd/or sodium- and sulphur-containing make-up chemicals which are used for the total chemicals balance of the pulp mill, in such a way that the mole ratio of sodium to sulphur in the total mixture which is fed to the reactor is within the range from 1.5 to 4.
Preferably, mole ratios of sodium to sulphur in the total mixture fed to the reactor should be within the range of from 2 to 3, and most preferably should be within the range of from 2 to 2. 8. Further, it is preferred to feed; to the reactor, up to 30 % of the black liquor stream which is formed in the pulp mill.
The sodium sulphide melt which is obtained in the process according to aspects of the present invention may be dissolved in water and may be further processed to cooking liquor in a way which is know per se. According to a preferred embodiment of an aspect of the present invention, a solution of the melt is fed directly i:o the digester for optimum use of its high sulphidity in modified cooking. In an alternative process of an aspect of the present invention, a solution of the melt is mixed with part of the white liquor which has been prepared in the usual way.
In order to allow the reduction reactions in the reactor to proceed quickly, and accordingly to obtain shorter residence times and smaller rf:actor volumes, additional energy, in addition to the energy which is released from thf; black liquor in partial oxidation can be supplied to the mixing zone of the reactor by a hot gas, the heat content and oxidation potential of which are adjusted to the reduction work required.
The heat energy may, e.g.; be supplied by a gas which is heated by a plasma generator.
The very hot gas or gas mixture can also be formed directly or indire>ctly with an oxy-fuel burner.
As gas or gas mixture, use can be made of air, recirculating process gas, hydrogen gas, natural gas, carbon monoxide, etc. When using an oxy-fuel burner, the gas or gas mixture is obtained by combustion of, e.g., acetylene or liq~uified petroleum gas with oxygen-enriched air or pure oxygen gas.
A preferred process according to an aspect of the present invention is that the hot gas is fed to the reactor close to the material which is fed, which in turn must be finely divided which can be obtained by different kinds of atomization techniques known by a person skilled in the art. The reactor must be designed to be sufficiently large in order for the reaction to have time to take place, i.e., the reactor volume must ensure a certain minimum residence time.
The reactor is preferably a closed reaction vessel and the temperature in the reactor shall be at least the temperature at which the sodium sulphide is formed under otherwise prevailing conditions. A person skilled in the art may establish such temperature from case to case, e.g., by routine experiments. The temperature is preferably not below 700°C.
The pressure in the reactor is preferably atmospheric pressure. However, the process may be effected at an increased pressure, e.g., in order to reduce the reactor volume.
In Swedish Patent SE 8501465-2 there is disclosed a process to relieve the soda recovery unit by means of plasma gasification of a partial stream of the black liquor. This makes it possible to increase the pulp production in a mill having too small a soda recovery unit capacity, or, e.g., to introduce oxygen gas bleaching a:nd/or modified cooking in a mill restricted in soda recovery unit capacity without losing production capacity.
Of essential importance for the process of aspects of the present invention is that the mole ratio of sodium to sulphur in the total mixture fed to the reactor be below 4 and be within the range from 1.5 to 4, preferably from 2 to 3. This adjustment of the sodium to sulphur ratio is effected by means of sulphur-containing and/or sulphur- and sodium-containing materials which are present in the pulp mill, including sulphur-containing and/or sodium- and sulphur-containing make-up chemicals which acre used for the total chemicals balance of the pulp mill.
The make-up chemicals which are used in order to adjust the mole ratio of sodium to sulphur correctly may consist of sulphur, sulphur dioxide, sulphuric acid, sodium hydrogen sulphate, sodium sulphate, sodium sulphite, sodium hydrogen sulphite and sodium thiosulphate.
Among sulphur-containing and/or sulphur- and sodium-containing materials which are present in the pulp mill, the following can be mentionedl:
" CA 02069107 2001-06-26 a. Residual acid from chlorine dioxide production, A mixture of sulphuric acid and sodium sulphate having NaIS ratio of <_ l may be obtained from so-called Mathieson plants. In other common processes of so-called R-8 type, sodium sesquisulphate (Na3H(S04)2) having a Na/S ratio of 1.5 is formed. The deposition of the residual acid is generally a problem. It often has to be dumped.
b. So-called electrical filter ash which mainly consists of sodium sulphate.
There are normally formed from 60 to 125 kg electrical filter ash per ton of pulp which are recirculated to the combustion zone of the soda recovery unit. The Na/S ratio is __<2.
c. Sulphate-containing solutions from soda recovery unit scrubber. The Na/S
ratio is 2.
d. A process is disclosed in EP 87850238.4 wherein a partial stream of the sodium hydrogen sulphide of the white liquor is reacted with copper oxide, sodium hydroxide and copper sulphide being formed. The copper sulphide is roasted to form sulphur dioxide and copper oxide. The sulphur dioxide formed is a sodium-free sulphur source.
Further, elemental sulphur may be used or any other sulphur-containing chemical having a Na/S ratio being equal to or below 4.
By suitable combinations of the whole or part of the lblack liquor stxeam and one or more of the above-stated products, an indefinite amount of .cooking liquor having high sulphidity can be prepared.
(e) AT LEAST ONE MODE FOR CARRYING OUT 7CHE INVENTION
The invention is further illustrated by means of the following working examples.
Example 1 The following material streams were fed continuously per hour to a reactor operating at atmospheric pressure.
620 kg black liquor (65 % dry substance contenl;) containing 129 kg sodium (Na) and 35 kg sulphur (S) per ton of black liquor.
A residual acid mixture from chlorine dioxide production according to the Mathieson process containing 80 kg H2S04 and 62 kg NazS04.
800 kg Na2S04 in the form of electrical filter ash.
The above material streams were mixed with an oxygen-containing gas and passed to a reaction chamber. The oxygen-containing gas was heated to 750°C in a plasma generator.
Energy was released by partial oxidation of the black liquor, the temperature in the reaction chamber being maintained at 950°C.
The process gas evolved at the partial oxidation was cooled. After any final oxidation, heat recovery as well as scrubbing, the gas may be released to the atmosphere.
Alternatively, a major part of the energy content of the liquor may be released by partial oxidation, whereby it is not necessary to preheat the oxygen-containing gas in a plasma generator.
Incoming sulphur compounds are reduced in the reaction chamber essentially to sodium sulphide (NazS), thereby forming a melt phase which is withdrawn from the system.
Owing to the high partial pressure of sulphur in the reaction chamber and the higher affinity of sulphur to sodium compared to carbon dioxide at the prevailing reaction conditions, the formation of sodium carbonate is suppressed in the inorganic melt phase.
A 4.0 molar solution with regard to the sodium is prepared containing 1.85 moles of NaOH, 1.85 moles NaSH and 0.15 moles NaZC03 per litre from the melt prepared.
In preparation of experiments with modified two-step pulp cooking where 70 %
of the cooking chemicals were charged in step 1 and the residual 3~0 % in step 2, the following cooking liquors were prepared.
One (1) part of the liquor obtained above according to aspects of the present invention was mixed with 4.63 parts of ordinary cooking liquor (white liquor) containing 2.8 moles of NaOH and 0.7 moles of NaSH per litre solution. The cooking liquor thus prepared having a sulphidity amounting to 51 % was charged in the first cooking step, whereas the normal white liquor having a sulphidity of 40 % was charge in step 2.
Example 2 The following material streams were fed continuously per hour to a reactor operating at atmospheric pressure, namely:
566 kg black liquor (65 % dry substance content:) containing 129 kg sodium (Na) per ton and 35 kg sulphur (S) per ton, 48 kg sulphur dioxide, 80 kg NazS04 in the form of electrical filter ash and 25 kg of Na2S04 as make-up.
One proceeded in exactly the same way as in Example 1 and obtained a melt phase which was withdrawn from the system.
The sulphur dioxide which was added had been generated by roasting according to the process for preparation of sulphide-free liquor disclosedl in EP
87850238.4. A 4.0 molar solution was prepared with regard to sodium containiing 1.75 moles of NaOH, 1.75 moles of NaSH and 0.25 moles of Na2C03 from the melt.
In preparation of experiments with modified two-step pulp cooking where 70 %
of the cooking chemicals were charged in step 1 and the residual .30 % in step 2, the following cooking liquors were prepared.
According to the same charging process as in Example l, in mixing 1.0 part of the liquor prepared above with 1.14 parts of ordinary cooking liquor (white liquor) (40 sulphidity) one obtained a cooking liquor having a sulphidity of 68 % . This liquor was charged in the first cooking step.
In the other step, use was made of the sulphide-free liquor prepared according to EP
87850238.4.
Claims (9)
1. In a process for preparing, under reducing conditions, cooking liquors for sulphate pulp cooking, wherein the black liquor which is formed in the cooking process is fed, after evaporation, completely or partly to a reactor operating at increased temperature, said increased temperature being obtained by energy which is supplied from an external heat source and/or release of energy from the black liquor, thereby to form a melt of sodium sulphide, said melt then being withdrawn to be further processed to cooking liquor, the improvement comprising: feeding, to said reactor, said melt and the whole or part of at least one of sulphur-containing, sulphur- and sodium-containing materials which are present in the pulp mill including sulphur-containing, and sodium- and sulphur-containing make-up chemicals used for the total chemicals balance of the pulp mill, in such a way that the mole ratio of sodium to sulphur in the total mixture which is fed to the reactor is within the range of from 1.5 to 4.
2. In a process for preparing, under reducing conditions, cooking liquors for sulphate pulp cooking, wherein black liquor which is formed in the cooking process is fed, after evaporation, completely or partly to a black liquor gasifier operating at an elevated temperature of 700 ° to 950 °, said elevated temperature being obtained by energy supply from an external heat source and/or release of energy from the black liquor, to form a melt having a low sodium carbonate content, said melt being withdrawn to be further processed to cooking liquor, the improvement comprising: feeding, to said black liquor gasifier, said melt and the whole or a part of at least one of sulphur-containing and sulphur-and sodium-and sulphur-containing materials which are present in connection with pulp production in such amounts that the mole ratio between sodium and sulphur in the total mixture which is fed to the gasifier is within the range of 1.5 to 4.
3. The improved process according to claim 1 or claim 2, wherein said melt contains 0.25 moles/litre or less of sodium carbonate.
4. The improved process according to any one of claims 1 to 3, wherein the mole ratio between sodium and sulphur in the total mixture which is fed to the reactor is within the range of 2 to 3.
5. The improved process according to claim 4, wherein the mole ratio between sodium and sulphur in the total mixture which is fed to the reactor is within the range of 2 to 2.8
6. The process according to any one of claims 1 to 5, wherein said sulphur-containing and sulphur- and sodium-containing materials which are present in the pulp mill and/or are present in connection with pulp production and which are fed to the reactor partly or completely consists of at least one of electrical filter ash, residual product from chlorine dioxide production, sodium hydrogen sulphite-containing solutions from scrubbing of sulphur dioxide, waste liquors from CTMP, NSSC or other sulphite pulp process, sulphur dioxide from roasting of copper sulphide as well as hydrogen sulphide-containing condensates or air streams.
7. The process according to any one of claims 1 to 5, wherein said sulphur-containing and sulphur- and, sodium-containing materials which are present in connection with pulp production and which are fed to the reactor partly or completely consist of sulphur-containing and/or sulphur- and sodium-containing make-up chemicals which consist of at least one of sulphur, sulphur dioxide, sulphuric acid, sodium sulphite, sodium hydrogen sulphate, sodium thiosulphate and sodium sulphate.
8. The process according to any one of claims 1 to 7, wherein said melt or an aqueous solution thereof is mixed with white liquor, thereby to obtain a white liquor having increased sulphidity.
9. The process according to any one of claims 1 to 8, wlherein an aqueous solution of said melt is used in so-called modified sulphate cooking in which cooking liquors are charged to the reactor in two steps.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| SE8903953A SE465039B (en) | 1989-11-23 | 1989-11-23 | MADE TO MAKE SUBSTANCES WITH HIGH SULFIDITY BEFORE SULFAT PREPARATION |
| SE8903953-1 | 1989-11-23 | ||
| PCT/SE1990/000751 WO1991008337A1 (en) | 1989-11-23 | 1990-11-21 | A process for the preparation of cooking liquors having high sulphidity for sulphate pulp cooking |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2069107A1 CA2069107A1 (en) | 1991-05-24 |
| CA2069107C true CA2069107C (en) | 2002-04-09 |
Family
ID=20377574
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002069107A Expired - Lifetime CA2069107C (en) | 1989-11-23 | 1990-11-21 | Process for the preparation of cooking liquors having high sulphidity for sulphate pulp cooking |
Country Status (18)
| Country | Link |
|---|---|
| EP (1) | EP0502052B1 (en) |
| JP (1) | JP2815701B2 (en) |
| CN (1) | CN1030003C (en) |
| AR (1) | AR243947A1 (en) |
| AT (1) | ATE112595T1 (en) |
| AU (1) | AU662882B2 (en) |
| BR (1) | BR9007837A (en) |
| CA (1) | CA2069107C (en) |
| DE (1) | DE69013159T2 (en) |
| ES (1) | ES2062569T3 (en) |
| FI (1) | FI103902B1 (en) |
| MX (1) | MX173408B (en) |
| MY (1) | MY104532A (en) |
| NO (1) | NO176109C (en) |
| RU (1) | RU2067637C1 (en) |
| SE (1) | SE465039B (en) |
| WO (1) | WO1991008337A1 (en) |
| ZA (1) | ZA909337B (en) |
Families Citing this family (14)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5326433A (en) * | 1991-02-06 | 1994-07-05 | Ahlstrom Recovery Inc. | Multi-level sulfide content white liquor production and utilization in cellulose pulping |
| US5213663A (en) * | 1991-07-22 | 1993-05-25 | The Foxboro Company | Method for controlling the sodium carbonate concentration of green liquor in the dissolving tank |
| FI92725C (en) * | 1991-09-09 | 1994-12-27 | Ahlstroem Oy | Process for preparing boiling liquid |
| FI914586A (en) * | 1991-09-27 | 1993-03-28 | Ahlstroem Oy | FOERFARANDE FOER FOERMINSKNING AV ASKLASTEN AV EN CELLUFABRIKS PANNANLAEGGNING |
| SE9103707L (en) * | 1991-12-16 | 1993-02-15 | Chemrec Ab | SET TO MAKE HIGH SULFIDITY COOKIES |
| SE9300199L (en) * | 1993-01-25 | 1994-07-26 | Kvaerner Pulping Tech | Method for recycling cellulosic liquids |
| US6030493A (en) | 1994-11-04 | 2000-02-29 | Kvaerner Pulping, Ab | Process for recovering chemicals and energy from cellulose spent liquor using multiple gasifiers |
| SE518735C2 (en) * | 1999-10-13 | 2002-11-12 | Chemrec Ab | Process and apparatus for the extraction of chemicals in connection with gasification of residues from pulp production |
| CN1087045C (en) * | 2000-03-17 | 2002-07-03 | 中国科学院生态环境研究中心 | Cyclic process for treating black paper-making liquid of alkali pulping to recover useful resource |
| CL2010001609A1 (en) * | 2010-12-29 | 2011-03-18 | Univ De Concepcion 50% | Process for obtaining tall oil util that comprises the reaction between a solution of sodium sesquisulfate and tall oil soap. |
| CN103510418B (en) * | 2012-06-25 | 2016-03-30 | 北京英力生科新材料技术有限公司 | A kind of without black liquor chemical pulping process |
| CN103726375A (en) * | 2013-12-30 | 2014-04-16 | 中冶美利纸业股份有限公司 | Sulfite pulping process of salix mongolica |
| CN103726376A (en) * | 2013-12-30 | 2014-04-16 | 中冶美利纸业股份有限公司 | Intermittent low-temperature quick pulping process for broad-leaf wood |
| FI130066B (en) * | 2019-02-13 | 2023-01-31 | Andritz Oy | A method of replacing sodium losses in a pulp mill, and a method of producing bleached cellulosic pulp |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4098639A (en) * | 1975-06-17 | 1978-07-04 | Mo Och Domsjo Aktiebolag | Process for reducing the requirement of fresh chemicals without increasing emissions in the pulping of cellulosic material |
| SE447400B (en) * | 1985-03-26 | 1986-11-10 | Skf Steel Eng Ab | SET AND DEVICE FOR CHEMICAL EQUIPMENT OF MASS WASTE IN CONVENTIONAL SODAPANNA |
| IL80678A (en) * | 1985-11-19 | 1999-05-09 | Schering Biotech Corp | Human interleukin-4 |
| JPS62166881A (en) * | 1986-01-16 | 1987-07-23 | Michio Matsuhashi | Periplasmic protein-secreting variant strain of escherichia coli |
| AU589540B2 (en) * | 1986-08-14 | 1989-10-12 | Alby Klorat Ab | A process for the preparation of sulphide-free alkali liquor |
| JPS63237790A (en) * | 1987-03-27 | 1988-10-04 | Toyo Jozo Co Ltd | Human superoxide dimustase using ompa signal peptide and extracellular secretion by gram negative bacterium |
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1989
- 1989-11-23 SE SE8903953A patent/SE465039B/en not_active IP Right Cessation
-
1990
- 1990-11-21 AT AT90917424T patent/ATE112595T1/en not_active IP Right Cessation
- 1990-11-21 CN CN90109309A patent/CN1030003C/en not_active Expired - Fee Related
- 1990-11-21 AR AR90318435A patent/AR243947A1/en active
- 1990-11-21 JP JP3500321A patent/JP2815701B2/en not_active Expired - Fee Related
- 1990-11-21 ZA ZA909337A patent/ZA909337B/en unknown
- 1990-11-21 MX MX023395A patent/MX173408B/en unknown
- 1990-11-21 MY MYPI90002045A patent/MY104532A/en unknown
- 1990-11-21 RU SU905052326A patent/RU2067637C1/en active
- 1990-11-21 BR BR909007837A patent/BR9007837A/en not_active IP Right Cessation
- 1990-11-21 ES ES90917424T patent/ES2062569T3/en not_active Expired - Lifetime
- 1990-11-21 CA CA002069107A patent/CA2069107C/en not_active Expired - Lifetime
- 1990-11-21 DE DE69013159T patent/DE69013159T2/en not_active Expired - Fee Related
- 1990-11-21 WO PCT/SE1990/000751 patent/WO1991008337A1/en active IP Right Grant
- 1990-11-21 EP EP90917424A patent/EP0502052B1/en not_active Expired - Lifetime
- 1990-11-21 AU AU68836/91A patent/AU662882B2/en not_active Ceased
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1992
- 1992-05-19 NO NO921962A patent/NO176109C/en unknown
- 1992-05-20 FI FI922288A patent/FI103902B1/en active
Also Published As
| Publication number | Publication date |
|---|---|
| AU662882B2 (en) | 1995-09-21 |
| EP0502052A1 (en) | 1992-09-09 |
| RU2067637C1 (en) | 1996-10-10 |
| DE69013159D1 (en) | 1994-11-10 |
| MY104532A (en) | 1994-04-30 |
| JPH05502274A (en) | 1993-04-22 |
| JP2815701B2 (en) | 1998-10-27 |
| CN1030003C (en) | 1995-10-11 |
| WO1991008337A1 (en) | 1991-06-13 |
| DE69013159T2 (en) | 1995-03-09 |
| NO921962D0 (en) | 1992-05-19 |
| NO921962L (en) | 1992-05-20 |
| NO176109B (en) | 1994-10-24 |
| NO176109C (en) | 1995-02-01 |
| CA2069107A1 (en) | 1991-05-24 |
| AU6883691A (en) | 1991-06-26 |
| ZA909337B (en) | 1991-09-25 |
| CN1051953A (en) | 1991-06-05 |
| FI922288A0 (en) | 1992-05-20 |
| ES2062569T3 (en) | 1994-12-16 |
| MX173408B (en) | 1994-03-01 |
| EP0502052B1 (en) | 1994-10-05 |
| SE465039B (en) | 1991-07-15 |
| SE8903953L (en) | 1991-05-24 |
| FI103902B (en) | 1999-10-15 |
| SE8903953D0 (en) | 1989-11-23 |
| FI103902B1 (en) | 1999-10-15 |
| FI922288A (en) | 1992-05-20 |
| ATE112595T1 (en) | 1994-10-15 |
| AR243947A1 (en) | 1993-09-30 |
| BR9007837A (en) | 1992-08-25 |
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