CN1264771A - Pulping technology without discharge of concentrated black liquid and process for reclaiming its black liquid - Google Patents
Pulping technology without discharge of concentrated black liquid and process for reclaiming its black liquid Download PDFInfo
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- CN1264771A CN1264771A CN 99115265 CN99115265A CN1264771A CN 1264771 A CN1264771 A CN 1264771A CN 99115265 CN99115265 CN 99115265 CN 99115265 A CN99115265 A CN 99115265A CN 1264771 A CN1264771 A CN 1264771A
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- lignin
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Abstract
A pulping technology without discharge of concentrated black liquid and a process for reclaim the black liquid are disclosed. It features that the traditional technological condition for pulp digestion is such weakened that alkali dosae is reduced to 3-5% and the temp is lowered to 100 deg.C and after digested, the grass material is mechanical broken for fully separation of cellulose and lignin from carbonhydrate to obtain qualified pulp. All the black liquid is reclained. The lignin can be physicochemically separated from concentrated black liquid and the filtrate can be added with chemical and then pumped back to digister.
Description
The present invention relates to a kind of chemical machinery production technology of non-wood pulps such as straw, wheat straw, reed, Chinese alpine rush and process for reclaiming of black liquor thereof of comprising.
Use non-wood material papermaking, traditional method mainly contains chemical method and half chemical method.
So-called chemical method is meant with NaOH and makes corrosive agent that make the cellulose in the grass as raw material under High Temperature High Pressure, hemicellulose separates with inorganic matter with lignin and other organic matters.Chemical pulp fiber fineness height contains lignin in the paper pulp and carbohydrate is less, but pulping rate is low.The paper mill that is raw material with Chinese northern wheat straw is an example, and the ratio of over dry wheat straw and oven dry stock is 2.8: 1, and promptly pulping rate is 38%.
Half chemical method is plant material to be corroded under acidity, neutrality or alkali condition with sulfurous acid or sulphite.Be that with the difference of chemical method under the condition of half chemical method, the lignin of institute's stripping and other organic matters are few than chemical method from plant material, therefore the non-fiber composition of staying in the paper pulp is more, thereby pulping rate is higher than chemical method.
No matter be chemical pulping or semichemical pulping technology, under the High Temperature High Pressure conditions of cooking, non-cellulose compositions such as the lignin in the raw material are dissolved in a large number in the cooking liquor and produce black liquid or red liquid.Also have quite a few cellulose and hemicellulose to be dissolved in the cooking liquor simultaneously.Black liquor is the main pollution composition of paper waste.Lignin accounts for about 50% in the solid content of black liquor, is starch secondly, the hydrolysate and the inorganic salts of carbohydrate, pectin etc.The general effective residual alkali that also has near 1% concentration in the utilizing black pulp liquor.
The method of traditional improvement black liquor is that black liquor vaporizing is concentrated, and makes that the concentration of solid content reaches about 50% in the black liquor, and spray burning in combustion furnace is then reclaimed alkali lye from the ashes with causticizing process again.
For straw pulp black liquor, the black liquid of wheat straw, reed, Chinese alpine rush etc. for example, because wherein component contents such as lignin, pectin, silica are higher, the evaporation and concentration difficulty, therefore the relative timber black liquor of fuel value of concentrated black liquid is on the low side, and easily flame-out during spray burning, the heavy oil consumption amount is big, and alkali recovery is on the low side, generally has only about 50%.The papermaking straw pulp factory of a 5-10 ton, last its construction investment of cover soda recovery unit is more than 100,000,000 yuans.
Be subjected to the pressure of national environmental protection policy and the constraint of business economic condition, the road of administering black liquor with biochemical process and physico-chemical process is being explored in the paper mill of many 1-5 tons.
Biochemical process is earlier black liquor to be carried out the anaerobic hydrolysis fermentation process, makes organic matter wherein be transformed into lower fatty acid, mainly is acetate, and acetate further is converted into methane and carbon dioxide again.All can not be up to standard through black liquor COD and colourity that Anaerobic Treatment is crossed, also to pass through Aerobic Process for Treatment, aerobic main employing activated sludge process and biomembrance process.Have only 15% monomer to be degraded by microorganisms owing to account for the lignin of black liquor China shape thing about 50%, all the other major parts are still excellent after anaerobic-aerobic is handled.Therefore administering black liquor with biochemical process must be with the lignin in acid-precipitation method or the physico-chemical process removal black liquor in a certain improvement operation, and so, the improvement running cost of black liquor still can be in any more, and non-alkali liquor is recyclable again.
Administer black liquor with physico-chemical process, mainly be in black liquor, to add acid and inorganic salts or high polymer coagulant, lignin separated, with solid-state form after press filtration, acid clear liquid can mix capable biochemical materialization with middle section water again to be handled, but alkaline filtrate blowback rotary spherical digester reuse after regulating basicity.
Physico-chemical process can produce more acid or alkaline lignin filter residue, and at present the comprehensive utilization technique and the achievement of lignin is popularized, and therefore, physico-chemical process is administered black liquor also the higher and secondary residue pollution problem of cost.
In sum, no matter administer black liquor with existing any method, all once the property investment is big, the problem that operating cost is high.Therefore, the improvement of black liquid has become a key factor of restriction China medium and small paper mill survival and development.
From above-mentioned consideration, the present invention proposes a kind of reduction conditions of cooking, make the lignin chemical mechanical slurry systeming process of stripping and the reuse improvement method of black liquor stage by stage.Principle of the present invention is described below.
No matter be machinery pulping, chemical pulping or semichemical pulping, its purpose all is the string that obtains certain-length, rugosity, intensity and purity, and then through bleaching, adds filler and makes the paper of various uses and class.
For the straw paper making raw material, wheat straw for example, there is one deck cuticula on its wheat straw surface, the fiber of wheat straw is separated, this layer cuticula must be removed, the amount that adds chemical agent when this just makes boiling will increase, and boiling temperature will improve, the result is in lignin and a large amount of dissolvings of other non-fibrous carbon hydrates, and hemicellulose also is dissolved in the black liquor in a large number.Cellulosic in addition performance also suffers damage, and influences paper quality.Therefore producing paper with wheat straw, reed, generally all is low and middle-grade paper, mainly is writing paper.For increasing strength of paper, generally to mix the wood pulp about 20%.And hemicellulose helps improving the composition of paper strength just.Therefore, when utilizing grass as raw material slurrying such as wheat straw, reed, its purpose should be under the prerequisite that does not influence paper quality, keeps cellulose and hemicellulose as much as possible, to improve pulping rate, reduces the papermaking cost.
In existing grass as raw material chemical pulping process, the consumption of NaOH is 13～16%, and its expense accounts for 50% of paper pulp (magma) cost of material.But in digestion process, really the alkali that consumes on dissolved lignin has only 3～4%, during all the other alkali more than 10% are consumed and and the organic acid that generates of the dissolving of the carbohydrate in grass as raw material back mutation.Use sulfite pulping, the consumption situation and the alkaline process of auxiliary agent are similar.But carbohydrate is water-soluble more much better than lignin, do not need very strong conditions of cooking they just constantly stripping enter in cooking liquor and the cleaning and rinsing water.Therefore, the primary and foremost purpose of reinforcement conditions of cooking is the stripping lignin.
The color of the black liquor that produces in chemical pulp and the semi-chemical pulp production process is mainly caused by lignin.
As previously mentioned, because no matter therefore lignin administer the black liquor pollution problem with which kind of method to anaerobe and aerobic microbiological quite stable all, what at first will consider is the lignin of how handling in the black liquor.
Lignin is aromatic polymer, and its molecule is the tridimensional network-like structure molecule of paniculate tool, is unbodied.About 70% is lignin between the cellular layer of ligneous plant, and it makes plant have rigidity as the filler of intercellular adhesive and cell membrane.Exist connecting of chemical bond between lignin and hemicellulose.Therefore, lignin be separated from plant material, must be caused the reduction of lignin molecular weight, destroy connecting of the chemical bond that exists between lignin and hemicellulose.For this reason, we must understand following some fundamental characteristics of lignin:
1, the color of lignin is different and different with separation method, and separation method relaxes more that then color is more shallow.The color of lignin itself is white or fawn, then changes dark brown, black and redness in the process of pulping by cooking into.
2, lignin itself is water insoluble, only in lignin hydrolysis, cracking and could be soluble in water after the mutation.Lignin can produce basic hydrolysis and alkaline bleach liquor cleavage under alkali condition:
Following formula is the model of lignin alkaline bleach liquor cleavage, and constantly the result of cracking makes the lignin brisement be very little fragment, and degraded all produces a new phenolic hydroxyl group at every turn, has increased the solubility of lignin fragment.
Lignin and the effect of NaOH cooking liquor, main reaction is:
(1) basic hydrolysis of β-alkyl-aryl ether reduces the lignin molecule, and introduces new phenolic group and make the lignin molecule be dissolved in solution.
(2) under the high basicity of high temperature, alpha-alkyl ether also can hydrolysis.
(3) demethoxylation generates methyl alcohol, and has increased the hydroxyl in the lignin molecule.
(4) oxidation partially and generate hydroxyl also helps the dissolving of this element.
3, meanwhile, under alkali condition, condensation reaction also can take place in lignin, is promptly become big molecule by micromolecule.The condensation lignin only could be by the basic hydrolysis stripping under higher temperature.
4, lignin is except the characteristics with alkali fusion, also can with Na
2The S reaction generates the sulfur-bearing lignin and stripping.
SH is introduced in the α position
-After, make the beta-aromatic ether bond rupture in the lignin molecule and the lignin molecule torn to fragmentate, help the stripping of lignin.Condensation reaction does not take place in the sulfur-bearing lignin simultaneously, can prevent the lignin condensation effectively.The condensation lignin is difficult to stripping owing to molecular weight increases, and the condensation lignin darkens.The dark color of black liquor is mainly caused by the condensation lignin.
5, short molten reaction can take place with chlorine in lignin
Chlorine and lignin effect, by replace, hydrolysis makes the lignin dissolving, and producing more phenolic hydroxyl group, that lignin is easy to is soluble in water.
6, the oxidation reaction of lignin
The lignin decapacitation makes it outside the stripping with hypochlorite, also have on the industrial production a series of oxidant can with the lignin effect, making it oxicracking is the stripping of lignin fragment, or destroys colorific group in the lignin, and reaches the purpose of bleached pulp.
7, lignin (70～110 ℃) under higher temperature occurs softening and viscosity increase phenomenon.
According to the analysis of lignin character as can be known, if the reduction conditions of cooking, then the color of dissolved lignin can shoal in the black liquor; Add auxiliary agent, can stop the generation of lignin condensation reaction, the black liquor color can shoal because of the minimizing of condensation lignin equally.Since lignin can with chlorine and other oxidant reactions, can on purpose allow a part of lignin in the bleaching stage stripping.
According to above analysis, the present invention proposes a kind of reduction pulping and digesting condition, and direct reuse boiling dope increases the pulping process of mechanical pulping defibrination operation and the process for reclaiming of black liquor.
The present invention realizes by following step.
1, reduction conditions of cooking
A. no matter be soda pulping process or sulfite pulping, the consumption of its chemicals accounts for 10～16% of over dry raw material weight.In the method for the invention, the lower limit of chemical dose such as caustic soda or sulphite can reduce to 3～5%.The purposes of opening according to the papermaking of paper pulp institute with require differently, the consumption of NaOH or sulphite accounts for forage oven dry weight percentage and can change between 3-10% during boiling.
B. boiling temperature can be reduced to 70～120 ℃ from about 150 ℃, and pressure also descends thereupon.
2, increase the pulverising mill slurry process
Under low concentration chemistry medicament and relatively low temperature, pressure condition, the lignin in the slurry and other carbohydrate all are in half dissolved state, promptly are in like molten but not molten state.Though so-called half dissolved state be meant lignin major part be hydrolyzed oxidation and become soluble sodium salt, but because non-lignin carbohydrate is deadlocked on fibre bundle with the lignin sodium salt because of the conditions of cooking change is in " being boiled " state, though the fiber of this moment is separated from each other on microstate, because it is not soluble in water fully to connect their lignin and the big portion of carbohydrate, so cellulose is also by gluing and involving mutually.
For cellulose, hemicellulose are separated fully with lignin, carbohydrate, method of the present invention is carried out the pulping wet-milling to forage after boiling.
Forage after the new method boiling is carried out the pulping wet-milling, can directly use beater disintegrating machine.Because the fiber in the forage separates with lignin and other compositions on chemical constitution at this moment, other materials that just are in colloidal state are implicative of each other, therefore only need a little external force it can be torn separation, and do not need as the timber mechanical jordaning, to lean on hard sharp projection that it is stripped down from whole timber.
Therefore, use beater disintegrating machine can reduce cellulosic loss, improve pulping rate.
Pulverize in the process of wet-milling at the boiling material, the part lignin, carbohydrate and inorganic salts continue soluble in water, and defibrination rinse water color also can not deepen, in follow-up sewage disposal process, all make COD and colourity up to standard easily with existing biochemical process, physico-chemical process.Consider that lignin has characteristic softening and that viscosity increases in the time of 70～110 ℃, the temperature when suitably improving pulping helps cellulosic separation.
3, black digestion liquid fully recovering
As previously mentioned, different along with paper pulp purposes and subsequent treatment condition, factors such as cooking liquor concentration, temperature, pressure, time all can change in by a larger margin.The steaming slurry that is produced under the conditions of cooking of reduction relatively can obtain 70～90% black liquor after extruding, all the other 10～30% quilts steam slurry and bring the comminution slurry process into.The concentrated black liquid of extruding through black liquor can be used to forage is carried out pre-soaking, and also directly the blowback rotary spherical digester repeats boiling.
With the black liquor that traditional digesting technoloy produces, the color relation to paper pulp can impact after 40% when the reuse black liquor surpasses, and brings difficulty to bleaching.
Method proposed by the invention, when the scope of NaOH dosage 3～5%, its U.S. concentration of the black digestion liquid through being repeatedly used all about 6, does not have influence to the paper pulp color substantially.
When the Baume concentration of black liquor surpasses after 6, can remove wherein part lignin, carbohydrate and inorganic salts with physico-chemical process, black liquor Baume lowering of concentration is reused.
4, suitably increase bleaching oxidant consumption, make the lignin content of bleached pulp reach the papermaking standard-required.
When producing bleached pulp, oxidant further decomposes the residual lignin in the paper pulp and dissolves in the water, so that paper pulp reaches required whiteness after becoming paper.Because the relative traditional handicraft of lignin of new technology stripping when boiling and when pulverizing will be lacked, and therefore, should suitably increase the oxidant consumption when bleaching, shows that the paper pulp totle drilling cost is still far below traditional handicraft but test.
As previously mentioned, utilize the method for reduction straw pulp conditions of cooking proposed by the invention, can make lignin in the forage and carbohydrate, inorganic salts etc. be in dissolving and half dissolved state, chemical bonding force between the cellulose changes mechanical deadlocked power into, utilize the mechanical force of pulping fiberizer to make the fibre bundle in the slurry tear pulverizing then, obtain meeting the thick slurry of papermaking and the requirement of other purposes.Because the reduction of conditions of cooking, the condensation trend of lignin weakens, and the lignin color is more shallow relatively, and the leachable during boiling reduces, and the organic concentration of black liquor and colourity all significantly descend, for black liquor repeatedly reuse created condition.
The rare black liquor and the middle section water that produce in pulp preparing process proposed by the invention, because condensation lignin wherein is less, color is more shallow, no matter is can more easily make it qualified discharge with biochemical process or physico-chemical process therefore.
The reclamation rate of black liquor is 70%～90%, and lignin when the reuse boiling in the old black liquor and carbohydrate can more easily be changed into gas form discharges such as carbon dioxide by further oxidation Decomposition.Therefore, utilize the reuse black liquor to steam slurry, the organic matter in the black liquor is not to increase exponentially, and test shows, reuse once, the gravity Baume of black liquor increases the 1-2 degree, but along with the reinforcement of conditions of cooking, organic concentration can increase comparatively fast in the reuse black liquor.
Utilize reduction conditions of cooking proposed by the invention, increase the method slurrying of mechanical crushing, because repeatedly reuse of black liquor can obtain following effect significantly:
1, reduces the consumption of chemicals such as NaOH and sulphite, made the papermaking cost descend;
2, improved pulping rate, in average raising 10%, then paper output also improves 10%;
3, because repeatedly reuse of black liquor declines to a great extent the waste water control expense;
4, since in the digestion process condensation lignin reduce, the improvement that the lignin color shoals to middle section water brings convenience;
5, when bleaching increases oxidant and the proper extension bleaching time slightly increases bleaching or this, but totle drilling cost still has and declines to a great extent.The forage pulping process condition of one of the object of the invention is as follows:
1, conditions of cooking
NaOH or sulphite 3～10%
Auxiliary agent A 0.05～0.1%
Auxiliary agent B 0.5～1%
70 ℃～120 ℃ of temperature
Operating pressure normal pressure～3kg/cm
2
Liquor ratio 3～6: 1
Time 2～6h
The product of boiling speed and time is a constant in the above-mentioned conditions of cooking, and the promptly so-called H factor that is to say that drug dosage, boiling temperature and digestion time are three variable factors in a total amount.
2, defibrination condition
Earlier use the pulverizer pulping, carry out secondary defibrination, pulping defibrination temperature when being necessary again: room temperature to 100 ℃.
Two the steaming slurry black liquor recovery improvement method of the object of the invention is as follows:
When the black liquor gravity Baume surpassed more than 8 °, available physico-chemical process was handled black liquor, and flocculant prescription and application process that the present invention proposes are as follows:
(1) No. 1, the flocculant prescription
Lime (quick lime white lime or carbide slag all can) 2～6%
Ferrous sulfate 0.05～0.2%
Magnesium sulfate 0.2～0.5%
Bittern or calcium chloride 0.05～0.1%
Agent 50～the 100PPM of flocculating polymer
(2) application process
Earlier milk of lime will be added in the black liquor, fully stir, the saturated aqueous solution that adds ferrous sulfate, magnesium sulfate, bittern or calcium chloride then respectively fully stirs, and adds concentration at last and be 1 ‰ polyacrylamide solution, stir, sink clear, filter with filter press, clear liquid can continue reuse, also can enter middle section water and handle, filter residue can with coal mixed combustion, also in the phosphoric acid and after make the organic calcium magnesium-phosphorus fertilizer.
Embodiments of the invention are as follows:
1, utilize wheat straw to produce chemi-mechanical pulp
A. raw material
Dried wheat straw 1000kg
NaOH 10kg
Digesting assistant A 0.1kg
Digesting assistant B 10kg
Water 5000kg
B. conditions of cooking
110 ℃ of temperature
4 hours time
C. pulping: common beater disintegrating machine
D. paper pulp: pulping rate 50%, promptly amount to oven dry stock 500kg, writing paper whiteness 80 degree are processed in bleaching, and other indexs are all qualified.
E. black liquor; Behind 5 ° of the once boiling black liquid wave hairdressings, reuse 6 times is 7 °.Black liquor pH value 8.
2, utilize reed slurrying
A. the dried reed 60 of raw material restrains
NaOH 6 grams
Auxiliary agent A 0.05%
Auxiliary agent B 0.1%
300 milliliters in water
B. conditions of cooking:
Temperature 110～～120 ℃
4 hours time
C. defibrination: household soy milk machine
D. paper pulp: pulping rate 50%, float back 75 ° of whiteness of pattern (not adding brightening agent).
E. black liquor: pH value 7.5,5 ° of Baume concentration are 10 ° after the reuse 6 times.
3, the reed pulp black liquor is handled
Repeatedly the reuse black liquid wave hairdressing is 8 °, adds the black liquor delignification agent by following prescription:
Lime 3 ‰
Ferrous sulfate 0.5 ‰
Magnesium sulfate 2 ‰
Bittern 0.5 ‰
High polymer coagulant 100PPM
The flocculation of lignin and part carbohydrate is separated out and is filtered 1 ° of back clear liquid gravity Baume, PH11, fully recovering, filter residue and coal mixed combustion after stirring.
Claims (5)
1, the present invention relates to a kind of process for reclaiming that does not have black liquor discharging pulping process and black liquor thereof, it is characterized in that, reduction straw pulp conditions of cooking, slurry is aided with mechanical crushing after steaming again, make the forage chemi-mechanical pulp, cooking liquor carries out repeatedly reuse, with physico-chemical process concentrated black liquid is carried out delignification where necessary and handles, the reuse again of filter back clear liquid is to realize the low pollution and the low-cost production of paper pulp.
2,, it is characterized in that the straw pulp conditions of cooking after reduction is as follows according to claim 1;
(1) 3～10% of the consumption point over dry raw material of NaOH or sulphite, the best is 3～6%, suitably adds digesting assistant simultaneously;
(2) boiling temperature is 70 ℃～120 ℃, best about 100 ℃;
(3) digestion time is 2～6 hours, best about 4 hours;
(4) liquor ratio is 3: 1～6: 1, and as steaming slurry with rotary spherical digester, liquor ratio is taken off limit, steams slurry with vertical digester or boiling pond, and liquor ratio can be greatly.
3, according to claim 1, it is characterized in that forage steams the back and carries out pulping with hammer leaf or blade pulverizer, and forage is pulverized, tears, separated, cellulose and lignin and carbohydrate, inorganic salts are separated, also can be aided with the defibrination operation when being necessary;
4, according to claim 1, it is characterized in that steaming disposed slurry and earlier reach 70%～90% with the special-purpose machinery extruding black liquor, black liquor after joining alkali and making up a prescription fully recovering in immersion forage or directly pump into the rotary spherical digester steamer;
5, according to claim 1, it is characterized in that the concentration of reuse black liquor is controlled with the way that adds flocculant, the dispensing ratio is as follows:
Lime 3～6 ‰
Ferrous sulfate 0.5～1 ‰
Magnesium sulfate 1～3 ‰
Bittern 0.2～0.5 ‰
High polymer coagulant 50～100PPM
Dispensing is stirred the back and is isolated the lignin filter residue with plate and frame filter press, and clear liquid is through joining alkali and make up a prescription back blowback rotary spherical digester reuse, filter residue can with coal mixed combustion, also the phosphoric acid neutralization makes the organic farming fertilizer of calcium magnesium phosphorus.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 99115265 CN1264771A (en) | 1999-02-23 | 1999-02-23 | Pulping technology without discharge of concentrated black liquid and process for reclaiming its black liquid |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 99115265 CN1264771A (en) | 1999-02-23 | 1999-02-23 | Pulping technology without discharge of concentrated black liquid and process for reclaiming its black liquid |
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| Publication Number | Publication Date |
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| CN1264771A true CN1264771A (en) | 2000-08-30 |
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| CN 99115265 Pending CN1264771A (en) | 1999-02-23 | 1999-02-23 | Pulping technology without discharge of concentrated black liquid and process for reclaiming its black liquid |
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2005052247A1 (en) * | 2003-11-28 | 2005-06-09 | Xiangwu Cheng | Catalyzer for clean pulping and process for using the same |
| CN111549552A (en) * | 2020-05-25 | 2020-08-18 | 广西大学 | High-yield chemi-mechanical pulp making method for recycling alkali in waste water |
| CN114150522A (en) * | 2021-08-10 | 2022-03-08 | 天津科技大学 | Low-energy-consumption pulping method for quickly dissolving out hemicellulose |
| CN115821618A (en) * | 2022-12-28 | 2023-03-21 | 广西大学 | Black liquor resource utilization method by combining cyclic cooking of fiber raw materials and evaporative combustion |
-
1999
- 1999-02-23 CN CN 99115265 patent/CN1264771A/en active Pending
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2005052247A1 (en) * | 2003-11-28 | 2005-06-09 | Xiangwu Cheng | Catalyzer for clean pulping and process for using the same |
| US7264690B2 (en) | 2003-11-28 | 2007-09-04 | Xiang Wu Cheng | Catalyzer for clean pulping and process for using the same |
| CN111549552A (en) * | 2020-05-25 | 2020-08-18 | 广西大学 | High-yield chemi-mechanical pulp making method for recycling alkali in waste water |
| CN114150522A (en) * | 2021-08-10 | 2022-03-08 | 天津科技大学 | Low-energy-consumption pulping method for quickly dissolving out hemicellulose |
| CN114150522B (en) * | 2021-08-10 | 2024-01-05 | 天津科技大学 | Low-energy-consumption pulping method for rapidly dissolving hemicellulose |
| CN115821618A (en) * | 2022-12-28 | 2023-03-21 | 广西大学 | Black liquor resource utilization method by combining cyclic cooking of fiber raw materials and evaporative combustion |
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