CA2112563A1 - Method for recovery of chemicals and energy from spent liquor - Google Patents
Method for recovery of chemicals and energy from spent liquorInfo
- Publication number
- CA2112563A1 CA2112563A1 CA 2112563 CA2112563A CA2112563A1 CA 2112563 A1 CA2112563 A1 CA 2112563A1 CA 2112563 CA2112563 CA 2112563 CA 2112563 A CA2112563 A CA 2112563A CA 2112563 A1 CA2112563 A1 CA 2112563A1
- Authority
- CA
- Canada
- Prior art keywords
- gas
- particles
- reactor
- chemical
- temperature
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Classifications
-
- 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
- D21C11/12—Combustion of pulp liquors
- D21C11/125—Decomposition of the pulp liquors in reducing atmosphere or in the absence of oxidants, i.e. gasification or pyrolysis
-
- 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
- D21C11/06—Treatment of pulp gases; Recovery of the heat content of the gases; Treatment of gases arising from various sources in pulp and paper mills; Regeneration of gaseous SO2, e.g. arising from liquors containing sulfur compounds
- D21C11/063—Treatment of gas streams comprising solid matter, e.g. the ashes resulting from the combustion of black liquor
- D21C11/066—Separation of solid compounds from these gases; further treatment of recovered products
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E20/00—Combustion technologies with mitigation potential
- Y02E20/12—Heat utilisation in combustion or incineration of waste
Landscapes
- Engine Equipment That Uses Special Cycles (AREA)
- Polysaccharides And Polysaccharide Derivatives (AREA)
- Paper (AREA)
- Industrial Gases (AREA)
- Processing Of Solid Wastes (AREA)
Abstract
Abstract The present invention relates to a process for the extraction of chemicals and energy from cellulose spent liquors, preferably black liquor obtained in the sulphate cellulose process, wherein the spent liquor is introduced into a gasification reactor (1) for pyrolysis and partial incineration, wherein an energy-rich gas is formed containing particles of inorganic chemical melt, the said gas mixture is conveyed out of the reactor (1) and concomitantly cooled by injection of a finely-divided cooling medium, preferably water, in connection with the departure from the reactor (1), the said mixture of gas and non-adhesive chemical particles is led from a cooling chamber (2) arranged in connection with the gasification reactor (1) to a separating arrangement (3), preferably a cyclone, where the non-adhesive chemical particles are separated from the gas, the gas stream, essentially cleaned of chemical particles, is taken out via an upper connection on the separating arrangement (3) while the chemical particles are taken out via a lower connection on the separating arrangement (3), wherein the melt particles leaving the reactor in the gas mixture are cooled to a temperature where they have at least partially solidified and been converted to solid phase, so that the particles included in the gas mixture are non-adhesive, and that a subsequent heat exchange of the separated gas is carried out from an essentially preserved temperature level.
Description
`
21 t 2 ~
, l'itle:
E'rocess for extraction of chemicals and energy from c:ellulose spent liquor~.
llechnical background:
The present invention relates to a process for the extraction of ch~micals and ener~y from c:ellulose spent liguors, primarily for the extraction of c:hemicals and energy from the gas ~tream from a reactor ~or black liquor gasification.
State of the art:
Nowaday6 ever ~tronger demands are being made, in relation to different types of process, Ilor recoverlng 6ubstances that are integral to the E~rocess, which substance~ can be reusable chemicals and allso energy which has been added or liberated during the process. These demands have mainly arisen with regard to t~e environment and for economic rea60ns. A general problem i8 that in certain proce~se~ gas mixtures are obtained that contain both ~elt and gas phase, which gas Dlixtures are difficult to deal with in regard to the recovery of the content of chemicals and energyO In E~articular it is the melt particles that cause problems, ~ince these, in an associated heat exchange process, often settle on the convection surfaces of the heat exchanger, something which is undesirable. This problem arises during use of the known process according to SE-B-328 179.
An industrial process area where problems of this nature arise is in connection with the gasification of spent liquors from paper pulp production.
q'he gasification of spent liquor takes place in a reactor, where the content of organic substances in the ~;pent liquor is pyrolysed and partially incinerated so t:hat heat energy can be extracted and the chemical -~ 2112~3 content separated off for recovery. The invention will be described below in relation to the gasification of black liquor, in order to describe the invention in more concrete fashion, which does not, however, limit the invention to this specific area.
Black liquor i8 obtained as a residual product, spent liquor~ in the production of pulp according to the sulphate cellulose method. The black liquor contains alkaline chemicals, in the form of various sodium compounds, which it i~ desirable to recover for reuse in the pulp production process. The recovery process compri~e~ ~ he~ting stage, a reactor, w~here the organic molecular chains are broken down by p,yrolysis and incineration to energy-rich gas and the inorganic content ma1nly forms finely divided particles c,f chemical melt which can be recovered. ~he pyrolysis in combination with the incineration thus liberates heat e!nergy, usually the temperature is about 1000C in the reactor, and produces a combustible gas. It is desirable to extract the liberated heat and also exploit the combustible gas by mec~ns of further incineration.
SE-B-448 173 describes ~ method for the recovery of chemicals and-energy from black liquor.
According to SE-B-448 173 it has been possible to recover the sensible h~at in the gas and simultaneously avoid settling problems by means of directly allowing the gases t:o pass through a liquid bath. Besides the melt particles being taken up by the said liquid, which is green liquor, t:he gas is simultaneously cooled. The gas which leaves t:he liquid bath and which has been freed from melt particles thereby achieves a temperature which in an ~mpressurised system only amounts to the order of 80-90 C, which also corresponds to the approximate temperature in the green liquor bath. Thus, in this unpressurised -~
system, a melt-free gas flow is obtained at about 90C, clS iS a liquid bath, consisting of green liquor, at about -- 2112~3 90C. Even if the process according to SE-B-448 173 is carried out at as high a pressure as 150 bar, heat r,ecovery can at best take place by the generation of 300 C saturated steam.
From the energy recovery point o~E view t]hese temperature~ are too low to be optimal. It is t~herefore desirable to be able to transfer the heat at a higher temperature level so that it can be obtained in t~he form of superheated steam, preferably for turbine o]peration with a view to producing electrical current. In o~perating steam turbines the highest degree of e~ficiency i~s obtained when the superheated steam is delivered at high pressure and high temperature, for example 150 bar and 600C. Thus it i8 desirable to achieve heat exchange at as high a temperature as possible.
In the method described above, however, the gas is cooled down to a temperature in the region of 100-300C, which limit~ the possibility for eEficient energy recovery. It is evident from the above reasoning that it would be desirable to be able to extract the heat at a higher temperature, ~o that it can b~a recovered in the form of superheated steam.
A process is previously known from S]E-B-182 336 for the extraction of chemicals and energy from cellulose spent liquors, preferably black liguor obtained in the sulphate cellulose process, wherein the spent liquor is conducted into a gasification reactor (1) ~or pyrolysis and partial incineration, wherein an energy-rich gas is formed containing particles of inorganic chemical melt, the said gas mixture is conveyed out of the reactor (1) and is thereby cooled by injection oiE a finely-divided cooling medium (cold gas), in connection with departure from the reactor (1), the said mixture of gas and non-adhesive chemical particles is conducted from a cooling chamber (2), arranged in connection with the gasification reactor (1), where they 2~63 h,ave at least partially solidified and been transformed i.nto solid phase, so that the particles included in the gas mixture become non-adhesive, and thence to a s.eparating arrangement (3), preferably a cyclone, where the non-adhesive chemical particles are separated from the gas, ~he gas ctre.~m, which has been essentially cd eaned of chemical particles, i8 removed via an upper connection on the separating arrangement (3) while the chemical particles are removed via a lower connection on t.he separating arrangement (3), and wherein a subsequent h.eat exchange of the separated gas is performed from an essentially preserved temperature level. This known mlethod suffers, however, from certain operational and t.echnical disadvantages. ~hi8. i8 in particular the case ir the generated gas i8 to be. u~ed for gas turbine operation since the known method does not provide sufficient purity for the operation of a ~ombustion .
t.urbine. Furthermore the method lack~ a well thought out .
use of the cooling medium or the scrubber medium, which mlakes the process difficult to optimise.
~ ~ : ' ' .
Sol~tion and advantages:
A first ob~ect of the invention is thus to offer a process and an arrangement whereby it is .
plossible to make use of the heat from a gas stream containing ~oth melt particles and gas, without d.rastically lowering the temperature level of the gas h,efore the heat exchange takes place, at the same time as settling problems are avoided. An additional object of the invention is to solve this in an optimal manner, in connection with application to gas turbines and in relation to the use of a cooling or scrubbing medium.
The abovementioned objects are achieved by the heat content of the gas after the heat exchange being obtained as superheated steam and the melt particles, which leave the reactor in the gas mixture, ~ '311256-3 being cooled to a temperature not exceeding 700c and the said finely-divided cooling medium being composed of water, together with the gas being washed after the heat exchange by being conducted through a washing arrangement (5), a so-called wet Rcrubber (5), for the washing out of remaining chemicals in solid form and gas form and by the separated solidified melt particles, which are removed at the bottom (31) of the separating arrangement ~3), being conducted to a receptacle (6) in which the particles are dissolved, wherein at lea~t parts of the ~lkaline solution formed in this way are exploited for washing the gas in the said wet scrubber (5).
The abovementioned objects are achieved in an even more preferred manner with the aid of a process according to the invention for extracting chemicals and ~nergy from black liguor obtained in the sulphate cellulose process, wherein the spent liquor is conducted into a gasification reactor for pyrolysis and partial incineration, so that a gas is formed that contains m~lt inorganic chemicals, the ~aid gas is conveyed out of the reactor and is cooled by injection of finely-divided water to a temperature in the region of 500-700C in connection with departure from the reactor, the said inorganic chemical content is cooled thereby at the same time to a temperature below its solidification point, gas and solidified melt drops are led to a separating arrangement, preferably a cyclone, where the chemical particles are separated from the gas and the gas stream, largely cleaned of inorganic chemical particles, is removed in an upper connection in order to be cooled in a waste heat boiler with generation of superheated high-pressure steam, and the chemical particles, separated off in the separating device, are dissolved in water, whereby so-called green liquor is formed.
It is true that it is previously known through SE-B-363 651 that the temperature of the gas and 211~5~3 chemical melt that ha~ been obtained can be decreased by ~;praying on water in the cooling seation of the reactor.
~Iowever, this document 3~i~1eads the expert, since in this case cooling takes place down to 200c before separation occurs. This low temperature is, as has already been iLndicated, undesirable from the point of view of heat recovery.
I)escription of the figure:
The invention will be described in Dlore detail below with reference to the attached figure iLn which is shown a basic assembly of the equipment for a procedure for car3~ying out the process according to the iinvention.
Thus a reactor 1 i6 chown to which is aonducted black liquor via a first conduit lO and air via cecond conduit ll- In the reactor space 12 the black :Liquor is gasified by pyrolysis and partial incineration ~md thereby ~orms a gas/melt mixture, where the melt drops are present in finely suspended form, at a tempera-1:ure of about 1000C. Because the gasification takes place by means of substoichiometric supply of oxygen, a number of co3nbustible gases are formed such as H2, C0, CH4, etc. The melt particles contain mainly Na2C0~ and l~aS. At the reactor end comprising the reactor outlet 13 a cooling chamber 2 is arranged inside which are dis-1ributed a number of spray nozzles 14 which are fed with water and/or cooled gas via conduits 15. With the aid of 1the nozzles 14 the water and/or gas is finely divided and comes into contact with the hot exhaust gases from the reactor l. Thereby the exhaust gases are cooled to a 1temperature of about 650C. This cooling results in the melt particles being converted into solid phase and thereby becoming non-adhesive. From the cooling chamber 2, which is located in connection with the reactor l, the gas is conducted with its content of solidified chemical particles onwards through a conduit 4 which leads to a s~yclone separator 3.
In the cyclone separator 3 the solid and non-adhesive particles are separated from the gas and 1~e gas leaves the cyclone via an upper conduit 30 while 1-he crystalline particles are taken out through a lower conduit 31. The gac phase in the conduit 30 still retains a temperature of about 650C and is conducted in direct connection thereto into a heat exchanger uni~ 7 for the s~eneration of superheated ~team. Due to the purity of the gas, heat exchange can now take place without interfering cleposition on the convection ~urfaces in the heat ex-c:hanger. The heat exchanger unit 7 comprises preferably a ~;team dome 70, a first heat exchanger core 71 for feed water which leads to the steam dome 70, a second coil ~2 ior production of saturated steam which leads back to the ~;team dome 70 and a third heat exchanger core 73 for generation of superheated steam, with a temperature o~
300-600C and a pressure of 20-lS0 bar, which is taken out via a conduit 74, preferably for the generation of electrical energy in a steam turbine according to the back pressure or condensing procedure.
After having passed through the heat exchanger unit 7 the gas has a temperature of about 200C
and is led via a further conduit 50 into a washing arrangement 5 for a final wa~h of the gas. This washing arrangement comprises a cylindrical casing 51 to which at al first level 52 is brought an alkaline solution by means of the spray nozzles in order to eliminate remaining c:hemicals from the gas, primarily H2S. This alkaline ~;olution can be obtained partly via a recirculating c:onduit 53 and partly from a receptacle 6. In the preferred case this receptacle 6 contains green liquor which has been prepared by dissolving the chemicals that were separated off in the cyclone 3 in water or so-called weak liquor. This green liquor has thus been obtained by -` 2~12~63 dissolution of the chemical particles that were recovered from the separator 3. The liquor from the last-named receptacle 6 like that from the washer 5 is led away in conduits 60 and 55 for collection in receptacles (not shown) and for further processing in a causticisation stage for the production of white liquor which is reused in the digestion process.
The gas which i8 led away via a conduit 56 at the top of the ga~ washer 5 i~ exploited for the production of steam and/or electricity via gas and/or steam turbines.
The invention is not limited by the above description but can be varied within the limits of t!he subsequent patent claims. Thus it will be evident to t,he expert that the steam which is produced in the super-h~eated section can have a variable temperature preferably b,etween 400-600C and the pre~sure can vary within a wide range up to about 160 bar.
Additionally instead of steam the heat of the gas can be u~sed to produce preheated air for the reactor.
The gas temperature after the boiler c;an also be varied, suitably within the range 150-300C.
Tlhe gas that is taken out of the top of the separator has im the preferred case a temperature of 500-700C. The t~emperature in the reactor is suitably a~ove 800C and cian reach up to 1500C. A preferred range is however 800 -1300C. Neither is the invention limited to a reactor with an outlet at the lower end of the reactor, which in c,ertain cases can create problems (in particular d,eposition problems) if the size of the melt particles varies widely. Thus, it can in certain cases be preferred to use a reactor with an upper outlet, preferably a r,eactor of the Kopper-Totzek type, resulting in larger melt particles being collected in a melt bath at the bottom of the reactor and the melt particles departing from the reactor with the gas stream being guaranteed to , ;"~" ~ ,:"~ s ~ 's ~,S s ~Ss ^` 2112~63 have a relatively small and therefore a relatively ~miform size, and there~y to ensure that all departing particles are cooled to a temperature below the s:olidification temperature. As an alternative instead of a, cyclone, a filter, appropriately a textile filter, can ~e used.
21 t 2 ~
, l'itle:
E'rocess for extraction of chemicals and energy from c:ellulose spent liquor~.
llechnical background:
The present invention relates to a process for the extraction of ch~micals and ener~y from c:ellulose spent liguors, primarily for the extraction of c:hemicals and energy from the gas ~tream from a reactor ~or black liquor gasification.
State of the art:
Nowaday6 ever ~tronger demands are being made, in relation to different types of process, Ilor recoverlng 6ubstances that are integral to the E~rocess, which substance~ can be reusable chemicals and allso energy which has been added or liberated during the process. These demands have mainly arisen with regard to t~e environment and for economic rea60ns. A general problem i8 that in certain proce~se~ gas mixtures are obtained that contain both ~elt and gas phase, which gas Dlixtures are difficult to deal with in regard to the recovery of the content of chemicals and energyO In E~articular it is the melt particles that cause problems, ~ince these, in an associated heat exchange process, often settle on the convection surfaces of the heat exchanger, something which is undesirable. This problem arises during use of the known process according to SE-B-328 179.
An industrial process area where problems of this nature arise is in connection with the gasification of spent liquors from paper pulp production.
q'he gasification of spent liquor takes place in a reactor, where the content of organic substances in the ~;pent liquor is pyrolysed and partially incinerated so t:hat heat energy can be extracted and the chemical -~ 2112~3 content separated off for recovery. The invention will be described below in relation to the gasification of black liquor, in order to describe the invention in more concrete fashion, which does not, however, limit the invention to this specific area.
Black liquor i8 obtained as a residual product, spent liquor~ in the production of pulp according to the sulphate cellulose method. The black liquor contains alkaline chemicals, in the form of various sodium compounds, which it i~ desirable to recover for reuse in the pulp production process. The recovery process compri~e~ ~ he~ting stage, a reactor, w~here the organic molecular chains are broken down by p,yrolysis and incineration to energy-rich gas and the inorganic content ma1nly forms finely divided particles c,f chemical melt which can be recovered. ~he pyrolysis in combination with the incineration thus liberates heat e!nergy, usually the temperature is about 1000C in the reactor, and produces a combustible gas. It is desirable to extract the liberated heat and also exploit the combustible gas by mec~ns of further incineration.
SE-B-448 173 describes ~ method for the recovery of chemicals and-energy from black liquor.
According to SE-B-448 173 it has been possible to recover the sensible h~at in the gas and simultaneously avoid settling problems by means of directly allowing the gases t:o pass through a liquid bath. Besides the melt particles being taken up by the said liquid, which is green liquor, t:he gas is simultaneously cooled. The gas which leaves t:he liquid bath and which has been freed from melt particles thereby achieves a temperature which in an ~mpressurised system only amounts to the order of 80-90 C, which also corresponds to the approximate temperature in the green liquor bath. Thus, in this unpressurised -~
system, a melt-free gas flow is obtained at about 90C, clS iS a liquid bath, consisting of green liquor, at about -- 2112~3 90C. Even if the process according to SE-B-448 173 is carried out at as high a pressure as 150 bar, heat r,ecovery can at best take place by the generation of 300 C saturated steam.
From the energy recovery point o~E view t]hese temperature~ are too low to be optimal. It is t~herefore desirable to be able to transfer the heat at a higher temperature level so that it can be obtained in t~he form of superheated steam, preferably for turbine o]peration with a view to producing electrical current. In o~perating steam turbines the highest degree of e~ficiency i~s obtained when the superheated steam is delivered at high pressure and high temperature, for example 150 bar and 600C. Thus it i8 desirable to achieve heat exchange at as high a temperature as possible.
In the method described above, however, the gas is cooled down to a temperature in the region of 100-300C, which limit~ the possibility for eEficient energy recovery. It is evident from the above reasoning that it would be desirable to be able to extract the heat at a higher temperature, ~o that it can b~a recovered in the form of superheated steam.
A process is previously known from S]E-B-182 336 for the extraction of chemicals and energy from cellulose spent liquors, preferably black liguor obtained in the sulphate cellulose process, wherein the spent liquor is conducted into a gasification reactor (1) ~or pyrolysis and partial incineration, wherein an energy-rich gas is formed containing particles of inorganic chemical melt, the said gas mixture is conveyed out of the reactor (1) and is thereby cooled by injection oiE a finely-divided cooling medium (cold gas), in connection with departure from the reactor (1), the said mixture of gas and non-adhesive chemical particles is conducted from a cooling chamber (2), arranged in connection with the gasification reactor (1), where they 2~63 h,ave at least partially solidified and been transformed i.nto solid phase, so that the particles included in the gas mixture become non-adhesive, and thence to a s.eparating arrangement (3), preferably a cyclone, where the non-adhesive chemical particles are separated from the gas, ~he gas ctre.~m, which has been essentially cd eaned of chemical particles, i8 removed via an upper connection on the separating arrangement (3) while the chemical particles are removed via a lower connection on t.he separating arrangement (3), and wherein a subsequent h.eat exchange of the separated gas is performed from an essentially preserved temperature level. This known mlethod suffers, however, from certain operational and t.echnical disadvantages. ~hi8. i8 in particular the case ir the generated gas i8 to be. u~ed for gas turbine operation since the known method does not provide sufficient purity for the operation of a ~ombustion .
t.urbine. Furthermore the method lack~ a well thought out .
use of the cooling medium or the scrubber medium, which mlakes the process difficult to optimise.
~ ~ : ' ' .
Sol~tion and advantages:
A first ob~ect of the invention is thus to offer a process and an arrangement whereby it is .
plossible to make use of the heat from a gas stream containing ~oth melt particles and gas, without d.rastically lowering the temperature level of the gas h,efore the heat exchange takes place, at the same time as settling problems are avoided. An additional object of the invention is to solve this in an optimal manner, in connection with application to gas turbines and in relation to the use of a cooling or scrubbing medium.
The abovementioned objects are achieved by the heat content of the gas after the heat exchange being obtained as superheated steam and the melt particles, which leave the reactor in the gas mixture, ~ '311256-3 being cooled to a temperature not exceeding 700c and the said finely-divided cooling medium being composed of water, together with the gas being washed after the heat exchange by being conducted through a washing arrangement (5), a so-called wet Rcrubber (5), for the washing out of remaining chemicals in solid form and gas form and by the separated solidified melt particles, which are removed at the bottom (31) of the separating arrangement ~3), being conducted to a receptacle (6) in which the particles are dissolved, wherein at lea~t parts of the ~lkaline solution formed in this way are exploited for washing the gas in the said wet scrubber (5).
The abovementioned objects are achieved in an even more preferred manner with the aid of a process according to the invention for extracting chemicals and ~nergy from black liguor obtained in the sulphate cellulose process, wherein the spent liquor is conducted into a gasification reactor for pyrolysis and partial incineration, so that a gas is formed that contains m~lt inorganic chemicals, the ~aid gas is conveyed out of the reactor and is cooled by injection of finely-divided water to a temperature in the region of 500-700C in connection with departure from the reactor, the said inorganic chemical content is cooled thereby at the same time to a temperature below its solidification point, gas and solidified melt drops are led to a separating arrangement, preferably a cyclone, where the chemical particles are separated from the gas and the gas stream, largely cleaned of inorganic chemical particles, is removed in an upper connection in order to be cooled in a waste heat boiler with generation of superheated high-pressure steam, and the chemical particles, separated off in the separating device, are dissolved in water, whereby so-called green liquor is formed.
It is true that it is previously known through SE-B-363 651 that the temperature of the gas and 211~5~3 chemical melt that ha~ been obtained can be decreased by ~;praying on water in the cooling seation of the reactor.
~Iowever, this document 3~i~1eads the expert, since in this case cooling takes place down to 200c before separation occurs. This low temperature is, as has already been iLndicated, undesirable from the point of view of heat recovery.
I)escription of the figure:
The invention will be described in Dlore detail below with reference to the attached figure iLn which is shown a basic assembly of the equipment for a procedure for car3~ying out the process according to the iinvention.
Thus a reactor 1 i6 chown to which is aonducted black liquor via a first conduit lO and air via cecond conduit ll- In the reactor space 12 the black :Liquor is gasified by pyrolysis and partial incineration ~md thereby ~orms a gas/melt mixture, where the melt drops are present in finely suspended form, at a tempera-1:ure of about 1000C. Because the gasification takes place by means of substoichiometric supply of oxygen, a number of co3nbustible gases are formed such as H2, C0, CH4, etc. The melt particles contain mainly Na2C0~ and l~aS. At the reactor end comprising the reactor outlet 13 a cooling chamber 2 is arranged inside which are dis-1ributed a number of spray nozzles 14 which are fed with water and/or cooled gas via conduits 15. With the aid of 1the nozzles 14 the water and/or gas is finely divided and comes into contact with the hot exhaust gases from the reactor l. Thereby the exhaust gases are cooled to a 1temperature of about 650C. This cooling results in the melt particles being converted into solid phase and thereby becoming non-adhesive. From the cooling chamber 2, which is located in connection with the reactor l, the gas is conducted with its content of solidified chemical particles onwards through a conduit 4 which leads to a s~yclone separator 3.
In the cyclone separator 3 the solid and non-adhesive particles are separated from the gas and 1~e gas leaves the cyclone via an upper conduit 30 while 1-he crystalline particles are taken out through a lower conduit 31. The gac phase in the conduit 30 still retains a temperature of about 650C and is conducted in direct connection thereto into a heat exchanger uni~ 7 for the s~eneration of superheated ~team. Due to the purity of the gas, heat exchange can now take place without interfering cleposition on the convection ~urfaces in the heat ex-c:hanger. The heat exchanger unit 7 comprises preferably a ~;team dome 70, a first heat exchanger core 71 for feed water which leads to the steam dome 70, a second coil ~2 ior production of saturated steam which leads back to the ~;team dome 70 and a third heat exchanger core 73 for generation of superheated steam, with a temperature o~
300-600C and a pressure of 20-lS0 bar, which is taken out via a conduit 74, preferably for the generation of electrical energy in a steam turbine according to the back pressure or condensing procedure.
After having passed through the heat exchanger unit 7 the gas has a temperature of about 200C
and is led via a further conduit 50 into a washing arrangement 5 for a final wa~h of the gas. This washing arrangement comprises a cylindrical casing 51 to which at al first level 52 is brought an alkaline solution by means of the spray nozzles in order to eliminate remaining c:hemicals from the gas, primarily H2S. This alkaline ~;olution can be obtained partly via a recirculating c:onduit 53 and partly from a receptacle 6. In the preferred case this receptacle 6 contains green liquor which has been prepared by dissolving the chemicals that were separated off in the cyclone 3 in water or so-called weak liquor. This green liquor has thus been obtained by -` 2~12~63 dissolution of the chemical particles that were recovered from the separator 3. The liquor from the last-named receptacle 6 like that from the washer 5 is led away in conduits 60 and 55 for collection in receptacles (not shown) and for further processing in a causticisation stage for the production of white liquor which is reused in the digestion process.
The gas which i8 led away via a conduit 56 at the top of the ga~ washer 5 i~ exploited for the production of steam and/or electricity via gas and/or steam turbines.
The invention is not limited by the above description but can be varied within the limits of t!he subsequent patent claims. Thus it will be evident to t,he expert that the steam which is produced in the super-h~eated section can have a variable temperature preferably b,etween 400-600C and the pre~sure can vary within a wide range up to about 160 bar.
Additionally instead of steam the heat of the gas can be u~sed to produce preheated air for the reactor.
The gas temperature after the boiler c;an also be varied, suitably within the range 150-300C.
Tlhe gas that is taken out of the top of the separator has im the preferred case a temperature of 500-700C. The t~emperature in the reactor is suitably a~ove 800C and cian reach up to 1500C. A preferred range is however 800 -1300C. Neither is the invention limited to a reactor with an outlet at the lower end of the reactor, which in c,ertain cases can create problems (in particular d,eposition problems) if the size of the melt particles varies widely. Thus, it can in certain cases be preferred to use a reactor with an upper outlet, preferably a r,eactor of the Kopper-Totzek type, resulting in larger melt particles being collected in a melt bath at the bottom of the reactor and the melt particles departing from the reactor with the gas stream being guaranteed to , ;"~" ~ ,:"~ s ~ 's ~,S s ~Ss ^` 2112~63 have a relatively small and therefore a relatively ~miform size, and there~y to ensure that all departing particles are cooled to a temperature below the s:olidification temperature. As an alternative instead of a, cyclone, a filter, appropriately a textile filter, can ~e used.
Claims (8)
1. Process for the recovery of chemicals and energy from cellulose spent liquors, preferably black liquor obtained in the sulphate cellulose process, wherein the spent liquor is introduced into a gasification reactor (1) for pyrolysis and partial incineration, wherein an energy-rich gas is formed containing particles of inorganic chemical melt, the said gas mixture is conveyed out of the reactor (1) and is concomitantly cooled by injection of a finely-divided cooling medium in conjunction with the departure from the reactor (1), the said mixture of gas and non-adhesive chemical particles is conducted from a cooling chamber (2), arranged in connection with the gasification reactor (1), where they have at least partly solidified and been converted to solid phase, so that the particles included in the gas mixture become non-adhesive, and onwards to a separating arrangement (3), preferably a cyclone, where the non-adhesive chemical particles are separated from the gas, the gas stream, which has essentially been cleaned of chemical particles, is removed via an upper connection on the separating arrangement (3) while the chemical particles are removed via a lower connection on the separating arrangement (3), and wherein a subsequent heat exchange of the separated gas is carried out from an essentially preserved temperature level, characterised in that the heat content of the gas after the heat exchange is obtained as superheated steam and the melt particles leaving the reactor in the gas mixture are cooled to a temperature not exceeding 700°C and that the said finely-divided cooling medium is composed of water and also that the gas is washed after the heat exchange by being conducted through a washing arrangement (5), a so-called wet scrubber (5), for washing out remaining chemicals in solid form and gas form and that the separated solidified melt particles which are removed from the bottom (31) of the separating arrangement (3) are conducted to a receptacle (6) in which the particles are dissolved, wherein at least parts of the alkaline solution formed in this way are utilised for washing the gas in the said wet scrubber (5).
2. Process according to Claim 1, characterised in that the gas mixture before the heat exchange is cooled to a temperature which is not lees than 500°C.
3. Process according to Claim 1, characterised in that the gasification takes place at a temperature exceeding 700°C preferably at 800°-1500°C most preferred 800°-1300°C.
4. Process according to any one of the preceding claims, characterised in that the gasification takes place at atmospheric pressure.
5. Process according to any one of the preceding claims, characterised in that the gasification takes place at increased pressure.
6. Process according to Claim 1, characterised in that the gas at the inlet to the wet scrubber has a temperature of 100°-300°C.
7. Process according to any one of the preceding claims, characterised in that the superheated steam is conducted to a steam turbine in the condensing or back pressure procedure.
8. Process according to any one of the preceding claims, characterised in that the washed gas is utilised as a fuel for the production of electricity and steam in a steam turbine unit or a combined gas turbine/steam turbine cycle.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| SE9102186-5 | 1991-07-16 | ||
| SE9102186A SE470066B (en) | 1991-07-16 | 1991-07-16 | Extraction of chemicals and energy from cellulose wastes by gasification |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2112563A1 true CA2112563A1 (en) | 1993-02-04 |
Family
ID=20383335
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2112563 Abandoned CA2112563A1 (en) | 1991-07-16 | 1992-06-29 | Method for recovery of chemicals and energy from spent liquor |
Country Status (9)
| Country | Link |
|---|---|
| EP (1) | EP0660896A1 (en) |
| JP (1) | JPH07500150A (en) |
| AU (1) | AU655063B2 (en) |
| BR (1) | BR9206271A (en) |
| CA (1) | CA2112563A1 (en) |
| FI (1) | FI940145A0 (en) |
| NO (1) | NO940149D0 (en) |
| SE (1) | SE470066B (en) |
| WO (1) | WO1993002249A1 (en) |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| SE500263C2 (en) * | 1993-03-11 | 1994-05-24 | Chemrec Ab | Process for separating sulfur compounds from a carbon dioxide and hydrogen sulfide-containing gas stream |
| SE505249C2 (en) * | 1994-11-04 | 1997-07-21 | Kvaerner Pulping Tech | Recovery of bleach filtrate by using the filtrate in a gas cooling system in a gasification plant |
| DE19642162A1 (en) * | 1996-10-12 | 1998-04-16 | Krc Umwelttechnik Gmbh | Process for the regeneration of a liquid resulting from the power process for the digestion of wood with simultaneous production of energy |
| DE19718131C2 (en) * | 1997-04-29 | 1999-10-14 | Krc Umwelttechnik Gmbh | Method and device for the regeneration of a liquid obtained in the power process for the digestion of wood by gasification |
| US20110226997A1 (en) * | 2010-03-19 | 2011-09-22 | Air Products And Chemicals, Inc. | Method And System Of Gasification |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3073672A (en) * | 1959-04-15 | 1963-01-15 | Stora Kopparbergs Bergslags Ab | Method of gasifying sulphurous cellulose waste liquors |
| US3323858A (en) * | 1964-08-21 | 1967-06-06 | Lummus Co | Process for recovering the alkali metal content of spent pulping liquor |
| SE363651B (en) * | 1969-06-03 | 1974-01-28 | Svenska Cellulosa Ab | |
| SE448173B (en) * | 1985-06-03 | 1987-01-26 | Croon Inventor Ab | PROCEDURE FOR THE RECOVERY OF CELLULOSA DISPOSAL CHEMICALS BY PYROLYSIS |
-
1991
- 1991-07-16 SE SE9102186A patent/SE470066B/en not_active IP Right Cessation
-
1992
- 1992-06-29 EP EP92915696A patent/EP0660896A1/en not_active Withdrawn
- 1992-06-29 BR BR9206271A patent/BR9206271A/en not_active Application Discontinuation
- 1992-06-29 JP JP5502439A patent/JPH07500150A/en active Pending
- 1992-06-29 CA CA 2112563 patent/CA2112563A1/en not_active Abandoned
- 1992-06-29 WO PCT/SE1992/000477 patent/WO1993002249A1/en not_active Application Discontinuation
- 1992-06-29 AU AU23327/92A patent/AU655063B2/en not_active Ceased
-
1994
- 1994-01-12 FI FI940145A patent/FI940145A0/en not_active Application Discontinuation
- 1994-01-14 NO NO940149A patent/NO940149D0/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| NO940149L (en) | 1994-01-14 |
| AU655063B2 (en) | 1994-12-01 |
| SE470066B (en) | 1993-11-01 |
| AU2332792A (en) | 1993-02-23 |
| EP0660896A1 (en) | 1995-07-05 |
| SE9102186D0 (en) | 1991-07-16 |
| JPH07500150A (en) | 1995-01-05 |
| SE9102186L (en) | 1993-01-17 |
| NO940149D0 (en) | 1994-01-14 |
| FI940145A (en) | 1994-01-12 |
| FI940145A0 (en) | 1994-01-12 |
| BR9206271A (en) | 1995-10-10 |
| WO1993002249A1 (en) | 1993-02-04 |
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