CN109024033B - Pulping method using high-concentration brine as cooking medium - Google Patents

Pulping method using high-concentration brine as cooking medium Download PDF

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CN109024033B
CN109024033B CN201810872785.XA CN201810872785A CN109024033B CN 109024033 B CN109024033 B CN 109024033B CN 201810872785 A CN201810872785 A CN 201810872785A CN 109024033 B CN109024033 B CN 109024033B
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cooking
brine
concentration brine
pulp
liquor
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CN109024033A (en
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陈夫山
王亚腾
宋晓明
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Qingdao University of Science and Technology
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Qingdao University of Science and Technology
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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
    • D21C3/00—Pulping cellulose-containing materials
    • D21C3/02—Pulping cellulose-containing materials with inorganic bases or alkaline reacting compounds, e.g. sulfate processes
    • 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
    • D21C3/00—Pulping cellulose-containing materials
    • D21C3/22—Other features of pulping processes
    • D21C3/222—Use of compounds accelerating the pulping processes
    • 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
    • D21H11/00—Pulp or paper, comprising cellulose or lignocellulose fibres of natural origin only
    • D21H11/12—Pulp from non-woody plants or crops, e.g. cotton, flax, straw, bagasse

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  • Chemical & Material Sciences (AREA)
  • Inorganic Chemistry (AREA)
  • Separation Of Suspended Particles By Flocculating Agents (AREA)
  • Paper (AREA)

Abstract

The invention provides a pulping method using high-concentration brine as a cooking medium, which comprises the following steps: adding a flocculating agent into the high-concentration brine, settling, adding alkali into the high-concentration brine, and uniformly mixing to obtain a cooking liquor; adding plant fiber raw materials into the cooking liquor, adding a catalyst into the cooking liquor, uniformly mixing, heating and cooking the mixed liquor, and extracting the pulp black liquor in the pulp to obtain the pulp black liquor and the target pulp. The pulping method using the high-concentration brine as the cooking medium can fully utilize water resources such as seawater, inland brackish water and the like, and avoids competition with domestic water and other industrial water of residents; the high-salinity wastewater generated by the RO treatment technology can be utilized, so that the problem of water resources for pulping and papermaking is solved, and the problem of wastewater treatment by the RO treatment technology is also solved.

Description

Pulping method using high-concentration brine as cooking medium
Technical Field
The invention belongs to the field of pulping and papermaking, and particularly relates to a pulping method using high-concentration brine as a cooking medium.
Background
According to the statistics of the environmental protection department in China, the total amount of water used in the papermaking industry in 2015 is 118.35 hundred million tons, wherein the fresh water amount is 28.98 million tons, and accounts for 7.5 percent of the total fresh water consumption of the industry. Huge consumption of water resources becomes a bottleneck limiting the development of the pulping and papermaking industry, many large-scale pulping and papermaking projects are limited due to overhigh water resource demand, and some coastal water-deficient areas in China limit the supply of fresh water to pulping and papermaking enterprises.
Besides the consumption of water resources, the waste water generated in the pulping and papermaking industry is a big problem restricting the development of the pulping and papermaking industry. The discharge amount of wastewater in 2015 years in the pulping and papermaking industry is 23.67 hundred million tons, which accounts for 13.0 percent of the total discharge amount of the wastewater in the national industry. The Chemical Oxygen Demand (COD) in the discharged wastewater is 33.5 ten thousand tons, which accounts for 13.1 percent of the total COD discharge amount of the national industrial wastewater. After the pulping and papermaking wastewater is subjected to conventional three-stage treatment, all indexes can meet the current discharge requirements of various levels of the country, and the pulping and papermaking wastewater is discharged into wetlands or rivers in an external drainage mode. However, some soluble salts and organic pollutants, such as ammonia nitrogen, salts and residual COD, still remain in the discharged water, and the environment is still polluted.
With the improvement of living standard and the continuous development of industry and business, the consumption of water resources by human beings is increased continuously, and in the near future, the water resource supply of the pulping and papermaking industry is predicted to become more tense, and the water quality of the used water is also deteriorated continuously. In addition, with the increasing demand for environmental protection, the wastewater discharge standard of the pulping and papermaking industry will become more stringent at that time. From these aspects, it has become an urgent need of paper industry to open up a new water source for pulp and paper industry and to increase the reuse rate of pulp and paper wastewater.
The seawater and the inland bitter water are used as the sources of the water for paper-making pulping, so that the method has the following two advantages:
1) the source is rich. On the earth, the area of the sea greatly exceeds that of the land, the seawater is almost inexhaustible, the coastal land coastline of China is up to 18400km, the island coastline is up to 14000km, and the sea-water-based offshore sea-water-based sea-water-level. The reserves of the inland brackish water in China are also extremely rich, and the total area of the brackish water in China is as high as 1.6Mkm2About 16.7 percent of the area of the homeland, wherein the storage amount of slightly saline water and moderately saline water with mining value is up to 20.05 hundred million m3。
2) Is not easy to conflict with the domestic water of residents and other industrial water. Because the salt content of the seawater and the inland brackish water is high, the application value of the seawater and the inland brackish water in other industries is not high, strong competition can not be generated, and the large increase of the water cost and the limitation of water resources to the papermaking industry are avoided.
On the other hand, the RO treatment technology (i.e., reverse osmosis water treatment technology) has been developed, and by this technology, municipal sewage drainage, papermaking drainage, and the like can be desalted and these wastewaters can be recovered as fresh water. The recovered fresh water can be applied to pulping and papermaking or other production processes, some pulping and papermaking enterprises currently use the external drainage of municipal sewage as a water source, and some researches are carried out to carry out membrane technology treatment on the external drainage of papermaking and recycle the generated fresh water.
However, the RO treatment technology also has a great problem that a certain proportion of high-concentration brine is generated along with the generation of fresh water, and the treatment and the recycling of the high-salt wastewater are also a key problem to be solved urgently. If the high-concentration brine can be reused in the pulping process, the water source for pulping can be enlarged, and the development of zero discharge of the papermaking wastewater can be promoted.
In a comprehensive view, the high-salinity and high-salinity water generated by seawater, brackish water and high-salinity wastewater generated by the RO treatment technology is used as a medium to cook fiber raw materials such as straws and the like, so that a new water source can be developed for the pulping and papermaking industry, the problem of environmental pollution caused by the discharge of the high-salinity wastewater can be solved, and the method has a wide application prospect.
However, if high-concentration brine such as seawater, brackish water, and high-salinity wastewater generated by RO treatment technology is directly used as a medium to cook plant fiber raw materials such as straw, the following problems occur:
(1) the cooking is not thorough, the pulp residue rate is high, and the pulp residue rate can be reduced only by increasing the cooking temperature or prolonging the cooking time.
(2) The resulting pulp has high kappa number and high hardness, and when the pulp is used for papermaking of paper and paperboard, the optical performance and the physical performance of a finished product are influenced.
(3) Cooking chemicals, such as sodium hydroxide, sodium sulfide, etc., are used in increased amounts and at increased costs.
(4) The black liquor has high viscosity, which is not beneficial to the subsequent black liquor alkali recovery process.
Disclosure of Invention
The invention aims to provide a pulping method using high-concentration brine as a cooking medium, which aims to solve the problems of overlarge water resource consumption and difficult recovery and treatment of high-salinity wastewater in the paper-making and pulping industry.
In order to solve the above problems, the present invention provides a pulping method using high-consistency brine as a cooking medium, comprising the steps of:
(1) sequentially adding a precipitator and a flocculating agent into the high-concentration brine, uniformly mixing, then settling the high-concentration brine until the turbidity of supernatant is lower than 25FTU and the chroma is lower than 15 ℃, and removing precipitates to obtain pretreated high-concentration brine;
(2) adding alkali into the pretreated high-concentration brine obtained in the step (1), and uniformly mixing to obtain a cooking liquor;
(3) adding a plant fiber raw material into the cooking liquor obtained in the step (2), adding a catalyst into the cooking liquor, uniformly mixing, heating the mixed liquor to 115-170 ℃, cooking, and preserving heat for 15-60 min to obtain slurry;
(4) and (4) extracting the pulp black liquor in the pulp in the step (3) to obtain the pulp black liquor and the target pulp.
It should be noted that the standard unit degree of color is 1 degree when 2mg of cobalt (IV) chloride hexahydrate and 1mg of platinum (in the form of hexachloroplatinic (IV) acid) are contained in each liter of the solution.
Preferably, the pulping method using high-concentration brine as a cooking medium comprises the following steps:
the method specifically comprises the following steps:
(1) sequentially adding a precipitator and a flocculating agent into the high-concentration brine, uniformly mixing, pumping the high-concentration brine to a sedimentation tank, settling in the sedimentation tank until the turbidity of supernatant is lower than 25FTU and the chroma is lower than 15 ℃, filtering the settled high-concentration brine, and removing solid impurities to obtain pretreated high-concentration brine;
(2) adding alkali into the pretreated high-concentration brine obtained in the step (1), and uniformly mixing to obtain a cooking liquor;
(3) adding a plant fiber raw material into a digester, then adding the cooking liquor in the step (2) into the digester, and adding a catalyst into the cooking liquor; rotating the digester at the rotating speed of 2-15 rpm, mixing for 15-30 min, uniformly heating the mixed solution to 115-170 ℃ within 80-120 min, and preserving heat for 15-60 min to obtain slurry;
(4) spraying the slurry obtained in the step (3) into a spraying bin, extracting the pulp black liquor in the slurry by adopting a spiral pulp extruder to obtain the pulp black liquor and target slurry, concentrating the pulp black liquor, and sending the concentrated pulp black liquor to an alkali ash collecting section for alkali recovery; and washing the target pulp, and using the washed pulp for producing paper. The paper includes but is not limited to cardboard, cultural paper, and toilet paper.
It should be noted that the digester can be selected by the skilled person according to the actual situation, including batch digesters and continuous digesters, the mixing process of which is carried out in a screw feeder, or a pre-dip silo. The digester can be a rotary spherical digester.
Preferably, the high-salinity water comprises seawater, brackish water, and high-salinity wastewater generated by RO treatment. Specifically, the high-concentration brine comprises seawater, inland brackish water and salt-containing wastewater with the salt content of 0.5-5%; for example, the paper mill effluent, the effluent after the municipal wastewater treatment, the strong brine obtained by reverse osmosis of the paper mill effluent, the waste strong brine obtained by reverse osmosis of the municipal wastewater effluent, and the strong brine generated by seawater desalination.
Preferably, the flocculant is one or a mixture of PAC and PAM; the dosage of the flocculant is that the volume ratio of the flocculant to the high-concentration brine is (5-20): 1000. PAC refers to polyaluminum chloride with the chemical formula of Al2Cln(OH)6-nThe CAS number is one of 1327-41-9, 101707-17-9, 11097-68-0 and 114442-10-3. PAM is an abbreviation of Polyacrylamide, refers to Polyacrylamide, is a nonionic polymeric flocculant and has a chemical formula of C3H5NO, molecular weight 150-2000 ten thousand, with CAS registry number 9003-05-8.
Preferably, the precipitant is NaOH and Na2CO3A mixture of (a); the dosage of the precipitant is such that the mass ratio of the precipitant to the high-concentration brine is (1-8): 1000. wherein, the NaOH and Na2CO3The mixture of (1) and (b) is prepared by mixing the two according to a certain mass ratio, and the required mass ratio is determined according to the water quality of the high-concentration brine; the dosage of the precipitant is such that the mass ratio of the precipitant to the high-concentration brine is (1-8): 1000.
preferably, the base is sodium hydroxide; the mass percentage of the alkali in the cooking liquor (calculated by NaOH) is 3 wt% -8 wt%.
Preferably, the plant fiber raw material is one or a mixture of two of crop straws and grass raw materials; the crop straws comprise wheat straws, rice straws, ginger straws, corn straws, sorghum straws and millet straws; the grass raw materials comprise reed, silvergrass and Chinese alpine rush.
More preferably, when the plant fiber material contains the grass material, the step (2) further includes a step of adding sodium sulfide to the cooking liquor.
Further preferably, the mass percentage of the sodium sulfide in the cooking liquor is 0.5 wt% to 3 wt%.
Preferably, the method further comprises the step of pretreating the plant fiber, and the specific steps are as follows: taking plant fiber raw materials, cutting the raw materials to 20-50 mm, and then washing and dedusting the raw materials.
Preferably, the catalyst is an anthraquinone; the molecular formula of the anthraquinone is C14H8O2The CAS registry number is 84-65-1.
The mass of the added catalyst is 0.03-0.08% of the oven-dry mass of the plant fiber raw material. The oven-dry quality of the plant fiber raw material refers to the plant fiber raw material with water completely removed.
Compared with the prior art, the invention has the following beneficial effects:
(1) the pulping method using the high-concentration brine as the cooking medium can fully utilize water resources such as seawater, inland brackish water and the like, and avoids competition with domestic water and other industrial water of residents; in addition, the high-salinity wastewater generated by the RO treatment technology can be utilized, so that the problem of water resources for pulping and papermaking is solved, the problem of wastewater treatment by the RO treatment technology is solved, and a way is provided for zero discharge of the pulping and papermaking wastewater.
(2) The pulping method using the high-concentration brine as the cooking medium overcomes the influence of various ions in the high-concentration brine on cooking. The invention relates to a pulping method using high-concentration brine as a cooking medium, which reduces impurities by adding a specific flocculating agent and a precipitating agentThe content of various ions, thereby saving the use amount of sodium hydroxide and sodium sulfide. The flocculating settling method is adopted, the flocculating agent is added, suspended particulate matters such as silt, seaweed and the like in the high-concentration brine are removed, so that the consumption of alkali by the impurities in the cooking process is avoided, ions such as magnesium, calcium and the like in the seawater can be removed through the precipitating agent, the ions can react with the alkali in the cooking liquid to generate precipitates, and the content of effective alkali in the cooking liquid is reduced. Particularly, the flocculating agent is PAC or PAM, and the adopted precipitating agent is NaOH and Na2CO3The flocculant and the precipitator are used in a matching way, so that the effect is more obvious;
(3) the pulping method using the high-concentration brine as the cooking medium has thorough cooking and low pulp residue rate. Because the high-concentration salt water has the characteristics of high salt content and high calcium and magnesium ions, when the plant raw materials are cooked, the calcium and magnesium ions can react with effective alkali in the cooking liquor to generate precipitates, so that the content of the effective alkali in the cooking liquor is reduced, and the problems of difficult soaking of the cooking liquor and difficult degradation of lignin are caused; the high-concentration salt water has high salt content, on one hand, a large amount of positive ions can be deposited in fiber cell walls to cause the southward effect, so that lignin is prevented from being dissolved out of the cell walls, the lignin dissolution rate is reduced, and on the other hand, the high ionic strength caused by the high salt content can also damage the charge stability of dissolved lignin colloid to cause the redeposition of the dissolved lignin. These factors can finally cause incomplete cooking and high pulp residue rate; the resulting pulp has high kappa number and high hardness; the boiling black liquor has high viscosity and is difficult to concentrate, and the alkali recovery treatment needs to additionally add additives with high calorific value such as coal, charcoal and the like, and has low combustion temperature. In the pulping method using the high-concentration brine as the cooking medium, the flocculant and the precipitator are added, so that the content of solid impurities and calcium and magnesium ions is reduced, the content of effective alkali in cooking liquor is increased, and the cooking effect is improved. Meanwhile, the removal and dissolution of lignin are accelerated by adding a catalyst, controlling the preimpregnation time, the cooking temperature and the cooking time, the problems are overcome, and the application of high-concentration brine in the pulping process is realized.
Detailed Description
Those not indicated in the examples of the present invention were carried out under the conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products commercially available. The raw materials used in the examples are all commercially available. Wherein:
the PAC is purchased from Oldey chemical trade, Inc., Changzhou;
the PAM is purchased from Suzhou constant signal environmental protection science and technology limited, and the specification/model is ZETAG-125;
the NaOH is purchased from chemical reagents of national drug group, Inc., and is chemically pure in specification;
the Na is2CO3Purchased from chemical reagents of national medicine group, limited company, and the specification/model is chemically pure;
the sodium sulfide is purchased from chemical reagents of national medicine group, and the specification/model is chemical purity;
the anthraquinone is purchased from chemical reagents of national medicine group, Inc., and has the specification of analytical purity;
the wheat straw is purchased from Shandong Guanghua paper industry group company;
the rice straw is purchased from Shandong Guanghua paper industry group, Inc.;
the ginger straw is taken from ginger straw grown in a flatness manner in Qingdao Shandong province;
the corn straws are taken from corn straws grown in Jiantai county of Zibo city in Shandong;
the sorghum straws are taken from sorghum straws grown in Fucheng county of Hebei Hengshui city;
the millet straw is selected from millet straw grown in Handan city in Hebei;
the reed is obtained from reeds grown in Anping county of Hebei Heng Heshui city;
the silvergrass is from silvergrass grown in Anping county of Hebei Heng Shui City;
the Chinese alpine rush is taken from Chinese alpine rush growing in the Hebei corridor;
it should be noted that the above are only sources of the raw materials used in this embodiment, and the raw materials of the present invention may also be other conventional products sold in the market, and the implementation of the technical solution and the implementation of the technical effect of the present invention are not affected by the raw materials of different manufacturers and models.
Example 1
The pulping method using high-concentration brine as a cooking medium comprises the following steps:
(1) adding a precipitator and a flocculating agent into the high-concentration brine, uniformly mixing, then settling the high-concentration brine until the turbidity of supernatant is lower than 25FTU and the chroma is lower than 15 ℃, and removing precipitates to obtain pretreated high-concentration brine;
wherein the high-concentration brine is seawater and comprises the following main components: the salt content of the seawater is 35.5g/kg, wherein the content of sodium element is 10.77g/kg, the content of magnesium element is 1.29g/kg, and the content of calcium element is 0.412 g/kg. The flocculant is PAC, and the dosage of the flocculant is that the volume ratio of the flocculant to the high-concentration brine is 5: 1000. the precipitant is NaOH and Na2CO3The weight ratio of the precipitant to the high-concentration brine is 5.5: 1000.
(2) adding alkali into the pretreated high-concentration brine obtained in the step (1), and uniformly mixing to obtain a cooking liquor;
wherein the alkali is sodium hydroxide, and the mass percent of the alkali in the cooking liquor is 5.0 wt%.
(3) Adding a plant fiber raw material into the cooking liquor obtained in the step (2), adding a catalyst into the cooking liquor, uniformly mixing, heating the mixed liquor to 155 ℃, cooking, and preserving heat for 30min to obtain slurry;
wherein the plant fiber raw material is crop straw, in particular wheat straw, the water content of the plant fiber raw material is 8%, and 400g of the plant fiber raw material is added according to the oven dry mass. The adding amount of the cooking liquor is 1.20 kg; the catalyst is anthraquinone; the mass of the catalyst added was 0.05% of the oven-dried mass of the vegetable fibre raw material.
(4) And (4) extracting the pulp black liquor in the pulp in the step (3) to obtain the pulp black liquor and the target pulp.
Example 2
The pulping method using high-concentration brine as a cooking medium comprises the following steps:
(1) adding a precipitator and a flocculating agent into the high-concentration brine, uniformly mixing, then settling the high-concentration brine until the turbidity of supernatant is lower than 25FTU and the chroma is lower than 15 ℃, and removing precipitates to obtain pretreated high-concentration brine;
wherein the high-concentration salt water is brackish water and comprises the following main components: the salt content of the brackish water is 10.6g/kg, wherein the content of sodium element is 3.26g/kg, the content of magnesium element is 0.20g/kg, and the content of calcium element is 0.54/kg. The flocculant is PAM, and the dosage of the PAM is that the volume ratio of the flocculant to the high-concentration brine is 20: 1000. the precipitant is NaOH and Na2CO3The weight ratio of the precipitant to the high-concentration brine is 2: 1000.
(2) adding alkali into the pretreated high-concentration brine obtained in the step (1), and uniformly mixing to obtain a cooking liquor;
wherein the alkali is sodium hydroxide, and the mass percent of the alkali in the cooking liquor is 3.5 wt%.
(3) Adding a plant fiber raw material into the cooking liquor obtained in the step (2), adding a catalyst into the cooking liquor, uniformly mixing, heating the mixed liquor to 115 ℃ for cooking, and preserving heat for 60min to obtain slurry;
wherein the plant fiber raw material is crop straw, in particular rice straw, the water content of the plant fiber raw material is 8%, and 400g of the plant fiber raw material is added according to the oven-dry mass. The amount of the cooking liquor added was 1.0 kg. The catalyst is anthraquinone; the mass of the catalyst added was 0.03% of the oven-dried mass of the vegetable fibre raw material.
(4) And (4) extracting the pulp black liquor in the pulp in the step (3) to obtain the pulp black liquor and the target pulp.
Example 3
The pulping method using high-concentration brine as a cooking medium comprises the following steps:
(1) adding a precipitator and a flocculating agent into the high-concentration brine, uniformly mixing, then settling the high-concentration brine until the turbidity of supernatant is lower than 25FTU and the chroma is lower than 15 ℃, and removing precipitates to obtain pretreated high-concentration brine;
wherein the high-concentration brine is high-salinity wastewater generated by RO treatment, and comprises the following main components: the salt content of the high-concentration brine is 45.7g/kg, wherein the content of sodium element is 13.90g/kg, the content of magnesium element is 1.66g/kg, and the content of calcium element is 0.531 g/kg. The flocculant is formed by mixing PAC and PAM according to the mass ratio of 1:2, and the dosage of the flocculant is that the volume ratio of the flocculant to the high-concentration brine is 12: 1000. the precipitant is NaOH and Na2CO3The weight ratio of the precipitant to the high-concentration brine is 8: 1000.
(2) adding alkali into the pretreated high-concentration brine obtained in the step (1), and uniformly mixing to obtain a cooking liquor;
wherein the alkali is sodium hydroxide, and the mass percent of the alkali in the cooking liquor is 6 wt%. In the cooking liquor, the mass percent of sodium sulfide is 0.5 wt%.
(3) Adding a plant fiber raw material into the cooking liquor obtained in the step (2), adding a catalyst, uniformly mixing, heating the mixed liquor to 143 ℃, cooking, and preserving heat for 50min to obtain slurry;
the plant fiber raw materials are grass raw materials, specifically, the silvergrass and the Chinese alpine rush are mixed according to the mass ratio of 1:1, the water content of the plant fiber raw materials is 7%, and according to the absolute dry mass, 400g of the plant fiber raw materials are added. The amount of the cooking liquor added was 1.4 kg. The catalyst is anthraquinone; the mass of the catalyst added was 0.04% of the oven-dried mass of the vegetable fibre raw material.
(4) And (4) extracting the pulp black liquor in the pulp in the step (3) to obtain the pulp black liquor and the target pulp.
Example 4
The pulping method using high-concentration brine as a cooking medium in the embodiment specifically comprises the following steps:
(1) adding a precipitator and a flocculating agent into the high-concentration brine, uniformly mixing, pumping the high-concentration brine to a sedimentation tank, settling in the sedimentation tank until the turbidity of supernatant is lower than 25FTU and the chroma is lower than 15 ℃, filtering the settled high-concentration brine, and removing solid impurities to obtain pretreated high-concentration brine;
wherein the high-concentration brine is high-salinity wastewater generated by RO treatment, and comprises the following main components: the salt content is 9.6g/kg, wherein the content of sodium element is 3.26g/kg, the content of magnesium element is 0.37g/kg, and the content of calcium element is 0.44/kg. The flocculant is PAC, and the dosage of the flocculant is that the volume ratio of the flocculant to the high-concentration brine is 5: 1000. the precipitant is NaOH and Na2CO3The weight ratio of the precipitant to the high-concentration brine is 2.5: 1000.
(2) adding alkali and sodium sulfide into the pretreated high-concentration brine obtained in the step (1), and uniformly mixing to obtain a cooking liquor;
wherein the alkali is sodium hydroxide, and the mass percent of the alkali in the cooking liquor is 8 wt%. The mass percent of sodium sulfide in the cooking liquor is 3 wt%.
(3) Cutting plant fiber raw materials to 20mm, and then washing and dedusting; adding a plant fiber raw material into a digester, then adding the cooking liquor in the step (2) into the digester, and adding a catalyst into the cooking liquor; rotating the digester at the rotating speed of 2rpm, mixing for 15min, uniformly heating the mixed solution to 160 ℃ within 100min, and preserving heat for 30min to obtain slurry;
the plant fiber raw material is a grass raw material, specifically is reed, the moisture content of the reed is 8%, and the plant fiber raw material with the oven dry mass of 400g is added according to the oven dry mass. The adding amount of the cooking liquor is 1.6 kg; the catalyst is anthraquinone; the mass of the catalyst added was 0.08% of the oven-dried mass of the vegetable fibre raw material.
(4) Spraying the slurry obtained in the step (3) into a spraying bin, extracting the pulp black liquor in the slurry by adopting a spiral pulp extruder to obtain the pulp black liquor and target slurry, concentrating the pulp black liquor, and sending the concentrated pulp black liquor to an alkali ash collecting section for alkali recovery; and washing the target pulp, and using the washed pulp for producing paper.
Example 5
The pulping method using high-concentration brine as a cooking medium in the embodiment specifically comprises the following steps:
(1) adding a precipitator and a flocculating agent into the high-concentration brine, uniformly mixing, pumping the high-concentration brine to a sedimentation tank, settling in the sedimentation tank until the turbidity of supernatant is lower than 25FTU and the chroma is lower than 15 ℃, filtering the settled high-concentration brine, and removing solid impurities to obtain pretreated high-concentration brine;
wherein the sedimentation tank is an inclined plate sedimentation tank or an inclined plate sedimentation tank; the high-concentration brine is high-salinity wastewater generated by RO treatment, and comprises the following main components: the salt content is 5.3g/kg, wherein the content of sodium element is 1.76g/kg, the content of magnesium element is 0.11g/kg, and the content of calcium element is 0.26 g/kg. The flocculant is PAM, and the dosage of the PAM is that the volume ratio of the flocculant to the high-concentration brine is 20: 1000. the precipitant is NaOH and Na2CO3The weight ratio of the precipitant to the high-concentration brine is 1: 1000.
(2) adding alkali and sodium sulfide into the pretreated high-concentration brine obtained in the step (1), and uniformly mixing to obtain a cooking liquor;
wherein the alkali is sodium hydroxide, and the mass percent of the alkali in the cooking liquor is 7 wt%. The mass percent of sodium sulfide in the cooking liquor is 1.5 wt%.
(3) Cutting plant fiber raw materials to 50mm, and then washing and dedusting; adding a plant fiber raw material into a digester, then adding the cooking liquor in the step (2) into the digester, and adding a catalyst into the cooking liquor; rotating the digester at a rotating speed of 15rpm, mixing for 30min, uniformly heating the mixed solution to 170 ℃ within 120min, and preserving heat for 30min to obtain slurry;
the plant fiber raw material is crop straw, specifically sorghum straw and millet straw which are mixed according to the mass ratio of 1: 1; the water content of the vegetable fiber raw material is 9 percent, and the vegetable fiber raw material with oven dry mass of 400g is added according to the oven dry mass. The amount of the cooking liquor added was 1.2 kg. The catalyst is anthraquinone; the mass of the catalyst added was 0.06% of the oven-dried mass of the vegetable fibre raw material.
(4) Spraying the slurry obtained in the step (3) into a spraying bin, extracting the pulp black liquor in the slurry by adopting a spiral pulp extruder to obtain the pulp black liquor and target slurry, concentrating the pulp black liquor, and sending the concentrated pulp black liquor to an alkali ash collecting section for alkali recovery; and washing the target pulp, and using the washed pulp for producing paper.
Example 6
The pulping method using high-concentration brine as a cooking medium in the embodiment specifically comprises the following steps:
(1) adding a precipitator and a flocculating agent into the high-concentration brine, uniformly mixing, pumping the high-concentration brine to a sedimentation tank, settling in the sedimentation tank until the turbidity of supernatant is lower than 25FTU and the chroma is lower than 15 ℃, filtering the settled high-concentration brine, and removing solid impurities to obtain pretreated high-concentration brine;
wherein the sedimentation tank is a conventional sedimentation tank; the high-concentration brine is high-salinity wastewater generated by RO treatment, and comprises the following main components: the salt content is 21.6g/kg, wherein the content of sodium element is 7.88g/kg, the content of magnesium element is 0.52g/kg, and the content of calcium element is 1.19/kg. The flocculant is prepared by mixing PAC and PAM according to the mass ratio of 1:5, and the dosage of the flocculant is that the volume ratio of the flocculant to the high-concentration brine is 12: 1000. the precipitant is NaOH and Na2CO3The weight ratio of the precipitant to the high-concentration brine is 5: 1000.
(2) adding alkali and sodium sulfide into the pretreated high-concentration brine obtained in the step (1), and uniformly mixing to obtain a cooking liquor;
wherein the alkali is sodium hydroxide, and the mass percent of the alkali in the cooking liquor is 3 wt%.
(3) Cutting plant fiber raw materials to 35mm, and then washing and dedusting; adding a plant fiber raw material into a rotary spherical digester, then adding the cooking liquor obtained in the step (2) into the rotary spherical digester, and adding a catalyst into the cooking liquor; rotating the rotary spherical digester at the rotating speed of 9rpm, mixing for 23min, uniformly heating the mixed solution to 150 ℃ within 80min, and preserving heat for 15min to obtain slurry;
wherein the plant fiber raw material is crop straw, in particular ginger straw; the water content of the vegetable fiber raw material is 9 percent, and the vegetable fiber raw material with oven dry mass of 400g is added according to the oven dry mass. The amount of the cooking liquor added was 2 kg. The catalyst is anthraquinone; the mass of the catalyst added was 0.05% of the oven-dried mass of the vegetable fibre raw material.
(4) Spraying the slurry obtained in the step (3) into a spraying bin, extracting the pulp black liquor in the slurry by adopting a spiral pulp extruder to obtain the pulp black liquor and target slurry, concentrating the pulp black liquor, and sending the concentrated pulp black liquor to an alkali ash collecting section for alkali recovery; and washing the target pulp, and using the washed pulp for producing paper.
Comparative example 1
The pulping process of this comparative example, with highly concentrated brine as cooking medium, is completely identical to the process of example 1, except that: no flocculant is added in step (1).
Comparative example 2
The pulping process of this comparative example, with highly concentrated brine as cooking medium, is completely identical to the process of example 1, except that: no precipitant is added in step (1).
Comparative example 3
The pulping process of this comparative example, with highly concentrated brine as cooking medium, is completely identical to the process of example 1, except that: no flocculant or precipitant is added in step (1).
Comparative example 4
The comparative example uses high-concentration brine as cooking mediumThe pulping process of (a) is completely identical to the process of example 1, with the only difference that: the precipitating agents added in the step (1) are NaOH and Na2CO3Mixing according to the mass ratio of 1: 1.
Comparative example 5
The pulping process of this comparative example, with highly concentrated brine as cooking medium, is completely identical to the process of example 1, except that: no catalyst was added in step (3).
Comparative example 6
The pulping process of this comparative example, with highly concentrated brine as cooking medium, is completely identical to the process of example 1, except that: the mass of the catalyst added in the step (3) is 0.10 percent of the oven-dried mass of the plant fiber raw material.
Examples of Effect test
Taking the target pulp prepared in the examples 1-6 and the comparative examples 1-6, numbering 1-12, respectively screening the obtained pulp by using a flat screen, wherein a screen plate is a slit screen, the width of a screen slit is 0.15mm, the screened pulp is fine pulp, measuring the moisture of the obtained fine pulp according to GB/T462 and 2008, and further calculating the oven dry mass of the obtained fine pulp, wherein the ratio of the oven dry mass of the fine pulp to the original oven dry mass is the yield of the fine pulp; the ash content is measured according to the method in the national standard GB/T742-2008; the kappa number is determined according to the method in the national standard GB/T1546-2004; the viscosity is measured according to the method in the national standard GB/T1548-2016; the beating degree is measured according to the method in the national standard GB/T3332-2004; the tensile index is measured according to the method in the national standard GB/T12914-2008; the tear index was determined according to the method in the national Standard GB/T455-2002.
Through determination, the following experimental results are obtained:
Figure GDA0001795915860000131
Figure GDA0001795915860000141
from the above results, it is understood that the pulping method using a high-consistency brine as a cooking medium according to the present invention can completely realize alkaline pulping of a plant fiber material using a high-consistency brine as a cooking medium. Although the experimental data of the groups 1-6 are different due to the different selection of the plant fiber raw material, the group 1 and the groups 7-12 use wheat straw as the plant fiber raw material and are all pulped under the same condition, and the comparison of the data of the groups 1 and 7-12 shows that: through the selection of the flocculating agent, the precipitating agent and the catalyst, the pulping effect is obviously influenced.
It should be understood that the above examples are only for clarity of illustration and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications can be made without departing from the scope of the invention.

Claims (8)

1. A pulping method using high-concentration brine as a cooking medium is characterized by comprising the following steps:
(1) sequentially adding a precipitator and a flocculating agent into the high-concentration brine, uniformly mixing, then settling the high-concentration brine until the turbidity of supernatant is lower than 25FTU and the chroma is lower than 15 ℃, and removing precipitates to obtain pretreated high-concentration brine;
the flocculant is one or a mixture of PAC and PAM; the dosage of the flocculant is that the volume ratio of the flocculant to the high-concentration brine is (5-20): 1000, parts by weight;
the precipitant is NaOH and Na2CO3A mixture of (a); the dosage of the precipitant is such that the mass ratio of the precipitant to the high-concentration brine is (1-8): 1000, parts by weight;
(2) adding alkali into the pretreated high-concentration brine obtained in the step (1), and uniformly mixing to obtain a cooking liquor;
(3) adding a plant fiber raw material into the cooking liquor obtained in the step (2), adding a catalyst into the cooking liquor, uniformly mixing, heating the mixed liquor to 115-170 ℃, cooking, and preserving heat for 15-60 min to obtain slurry;
the catalyst is anthraquinone; the mass of the added catalyst is 0.03-0.08% of the absolute dry mass of the plant fiber raw material;
(4) and (4) extracting the pulp black liquor in the pulp in the step (3) to obtain the pulp black liquor and the target pulp.
2. A pulping process using highly concentrated brine as cooking medium according to claim 1, characterized by comprising the following steps:
(1) sequentially adding a precipitator and a flocculating agent into the high-concentration brine, uniformly mixing, pumping the high-concentration brine to a sedimentation tank, settling in the sedimentation tank until the turbidity of supernatant is lower than 25FTU and the chroma is lower than 15 ℃, filtering the settled high-concentration brine, and removing solid impurities to obtain pretreated high-concentration brine;
(2) adding alkali into the pretreated high-concentration brine obtained in the step (1), and uniformly mixing to obtain a cooking liquor;
(3) adding a plant fiber raw material into a digester, then adding the cooking liquor in the step (2) into the digester, and adding a catalyst into the cooking liquor; rotating the digester at the rotating speed of 2-15 rpm, mixing for 15-30 min, uniformly heating the mixed solution to 115-170 ℃ within 80-120 min, and preserving heat for 15-60 min to obtain slurry;
(4) spraying the slurry obtained in the step (3) into a spraying bin, extracting the pulp black liquor in the slurry by adopting a spiral pulp extruder to obtain the pulp black liquor and target slurry, concentrating the pulp black liquor, and sending the concentrated pulp black liquor to an alkali ash collecting section for alkali recovery; and washing the target pulp, and using the washed pulp for producing paper.
3. A pulping process with high-consistency brine as cooking medium according to claim 1 or 2, characterized in that the high-consistency brine comprises seawater, brackish water, high-salinity wastewater from RO treatment.
4. A pulping process with highly concentrated brine as cooking medium according to claim 1 or 2, characterized in that the alkali is sodium hydroxide; the alkali accounts for 3-8 wt% of the cooking liquor.
5. The pulping method using high-concentration brine as a cooking medium according to claim 1 or 2, wherein the plant fiber raw material is one or a mixture of two of crop straws and grass raw materials; the crop straws comprise wheat straws, rice straws, ginger straws, corn straws, sorghum straws and millet straws; the grass raw materials comprise reed, silvergrass and Chinese alpine rush.
6. The method for producing pulp using high-consistency brine as a cooking medium according to claim 5, wherein the step (2) further comprises a step of adding sodium sulfide to the cooking liquor when the plant fiber material contains the grass material.
7. A pulping process with highly concentrated brine as a cooking medium according to claim 6, characterized in that the mass percentage of sodium sulfide in the cooking liquor is 0.5-3 wt%.
8. A pulping process using high consistency brine as cooking medium according to claim 5, further comprising the step of pretreating the plant fibers, the specific steps being as follows: taking plant fiber raw materials, cutting the raw materials to 20-50 mm, and then washing and dedusting the raw materials.
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