Sodium hydroxide regeneration cycle method

Abstract

The invention relates to the technical field of regeneration cycle, in particular to a sodium hydroxide regeneration cycle method which comprises the following steps: S1, pretreating black liquor; s2, decarburizing the pretreated black liquor; step S3, preparing hydrolysate; step S4, recycling the hydrolysate; in the black liquor pretreatment process, the functionalized silica removal agent is added, and an inner core in the functionalized silica removal agent is a mixed solution of magnesium sulfate, calcium hydroxide, deionized water and absolute ethyl alcohol; according to the invention, a porous structure is obtained by chemical crosslinking of acrylamide, acryloyloxyethyl trimethyl ammonium chloride and sodium p-styrenesulfonate on the surface of the shell layer and KH-570 on the surface of the modified magnesium sulfate, and all the structures can achieve a synergistic effect, so that the silicon removal performance is improved, and the yield of sodium hydroxide is further improved.

Description

Technical Field

[0001] The present application relates to the technical field of regeneration and circulation, and more specifically, to a sodium hydroxide regeneration and circulation method. Background Art

[0002] As an important basic raw material industry, the papermaking industry, while supporting economic development, also produces a large amount of alkaline wastewater, which contains a large amount of sodium hydroxide and other chemical residues. If directly discharged, it will cause serious pollution to natural water bodies. With the enhancement of environmental awareness and the demand for sustainable development, sodium hydroxide recovery technology, as an efficient resource recycling method, not only solves the problem of environmental pollution, but also realizes the recycling and reuse of chemicals, becoming an important milestone in the green transformation of the papermaking industry.

[0003] Invention patent application CN101898770B discloses a sodium hydroxide regeneration cycle method, wherein calcium carbonate is first added to a sodium sulfate salt solution, and carbon dioxide is introduced or sulfuric acid is added to adjust the pH value of the solution, so that the sodium sulfate salt is converted into sodium bicarbonate, and gypsum and sodium bicarbonate solution are obtained by filtration, and then lime is added to the sodium bicarbonate solution for causticization, and regenerated sodium hydroxide solution and calcium carbonate are obtained by filtration, and the calcium carbonate is returned to the sodium sulfate salt conversion process for continued use. However, since papermaking wastewater contains a large amount of silicon, lime forms calcium silicate after causticization, making it difficult to recover the white mud from papermaking wastewater by calcination in a rotary kiln, which not only increases the additional processing cost of the enterprise, but also reduces the recovery rate of sodium hydroxide. Summary of the invention

[0004] The object of the present invention is to provide a method for removing a large amount of silicon from papermaking black liquor and effectively extracting sodium hydroxide from the papermaking black liquor while realizing its recycling.

[0005] The technical problem to be solved by the present invention is that the papermaking black liquor in the prior art contains a large amount of silicon, which not only makes it difficult to effectively separate sodium hydroxide from the papermaking black liquor, but also increases the processing cost of the enterprise.

[0006] A sodium hydroxide regeneration cycle method comprises the following steps:

[0007] Step S1, black liquor pretreatment: adding black liquor semi-coke to dimethyl sulfoxide, ultrasonically dispersing until fully dissolved, adjusting the pH to 6-8, adding a functionalized desiliconizer, stirring for 26-34 minutes, filtering, and drying to obtain pretreated black liquor, wherein the mass ratio of black liquor semi-coke, dimethyl sulfoxide, and functionalized desiliconizer is 4-6:80-90:0.026-0.034;

[0008] Step S2, decarbonization of pretreated black liquor: put the pretreated black liquor and nano titanium dioxide into a high-temperature tube furnace and seal it, introduce nitrogen, and when the nitrogen fills the pipeline, heat it to 845-855°C at a heating rate of 5°C / min, pump in distilled water, and keep it warm for 22-26 minutes. After the reaction is completed, stop supplying water vapor, and continue to introduce nitrogen to obtain an intermediate, wherein the mass ratio of the pretreated black liquor to the nano titanium dioxide is 3-5:0.6-1.0;

[0009] Step S3, preparation of hydrolyzate: under nitrogen protection, add the intermediate into deionized water, heat to reflux, stir to react for 12-16 minutes, cool to room temperature, filter, and obtain a hydrolyzate, wherein the mass ratio of the intermediate to deionized water is 2.8-4.6:70-80;

[0010] Step S4, recycling of hydrolyzate: the hydrolyzate prepared in step S3 can be recycled again as a cooking agent for alkaline pulping.

[0011] Preferably, in step S2, the pumping flow rate of distilled water is controlled to be 1-2 mL / min.

[0012] Preferably, the black liquor semi-coke is obtained by pyrolyzing black liquor dry powder at 580-620° C. for 10-12 hours in a nitrogen atmosphere of 99.999%.

[0013] Preferably, the functionalized silicon remover is prepared by the following steps:

[0014] Step A1, uniformly dispersing magnesium sulfate, deionized water, anhydrous ethanol and KH-570 by ultrasonication, heating to 42-46°C, stirring for reaction for 6-8h, centrifuging, washing and drying the precipitate to obtain modified magnesium sulfate, wherein the mass ratio of magnesium sulfate, deionized water, anhydrous ethanol and KH-570 is 4:8-12:25-30:0.4-0.6, treating magnesium sulfate with KH-570 to obtain modified magnesium sulfate, wherein the modified magnesium sulfate contains hydroxyl groups which can pave the way for subsequent reactions;

[0015] Step A2, adding calcium oxide and modified magnesium sulfate to deionized water, ultrasonically dispersing them uniformly to obtain a suspension, adjusting the pH of the suspension to 3-4, then heating to 42-56°C, passing nitrogen to deoxygenate, and under nitrogen protection, dripping a mixed solution a containing acrylamide, acryloyloxyethyl trimethyl ammonium chloride, sodium p-styrene sulfonate and an initiator, and controlling the dripping to be completed within 10 minutes, then adding a mixed solution b of naphthalene and anhydrous ethanol, and controlling the dripping to be completed within 20 minutes. After the dripping is completed, stirring and reacting for 5-6 hours, adding hydroquinone, filtering and drying, crushing, and sieving to obtain a functionalized desiliconizer, wherein the mass ratio of calcium oxide, modified magnesium sulfate, deionized water, mixed solution a, mixed solution b and hydroquinone is 6-8:1-2:40-50:18-22:12-16:0.027-0.031, and in the mixed solution a, acrylamide, acryloyloxyethyl trimethyl ammonium chloride, sodium p-styrene sulfonate and an initiator are 0.01-0.027-0.031. The mass ratio of amide, acryloyloxyethyl trimethyl ammonium chloride, sodium p-styrene sulfonate, initiator and deionized water is 0.8-1.2: 0.2-0.4: 0.03-0.1: 0.09-0.25: 16-20, the initiator is a mixture of ammonium persulfate and sodium bisulfite in a mass ratio of 1:1, and the mass ratio of naphthalene to anhydrous ethanol in the mixed solution b is 2-3:10. In the above reaction, under the action of the initiator, the vinyl monomer undergoes a free radical polymerization reaction, and amino groups and quaternary ammonium salt cations are introduced through the above reaction. At the same time, in the polymerization process, naphthalene is used as a pore-forming agent, and sodium p-styrene sulfonate is used as both a reaction monomer and a stabilizer for graft polymerization in the emulsion. At the same time, the sulfonic acid group on it can form hydrogen bonds with the surface hydroxyl groups of calcium hydroxide and modified magnesium sulfate to obtain a functional silicon remover with a porous structure.

[0016] In summary, this application has the following beneficial effects:

[0017] In order to remove a large amount of silicon elements in papermaking black liquor and to effectively extract sodium hydroxide from papermaking black liquor, a functionalized desiliconizer is added in the present application. The core of the functionalized desiliconizer is a mixture of magnesium sulfate, calcium hydroxide, deionized water and anhydrous ethanol. The shell layer is a porous structure obtained by chemical crosslinking of acrylamide, acryloyloxyethyltrimethylammonium chloride, sodium p-styrene sulfonate and KH-570 on the surface of modified magnesium sulfate. In the core, magnesium ions in magnesium sulfate and calcium ions in calcium hydroxide can chemically react with silicate ions to form insoluble or insoluble substances, thereby improving the desiliconization performance. The presence of the amide group can form a Hydrogen bonds enhance the binding force between the modifier and ions and promote dispersion. The presence of the quaternary ammonium salt structure can further improve the dispersibility of silicate ions through electrostatic regulation, steric hindrance and hydrophobic association. The presence of the benzene ring can prevent the silicate ion particles from approaching through its large steric hindrance effect, thereby improving its dispersion performance. The presence of the sulfonic acid group can, on the one hand, inhibit the agglomeration of silicate ions through the expansion of the double electric layer, significantly improving the dispersion stability. On the other hand, it can produce hydrogen bonds with the calcium hydroxide in the inner core and the hydroxyl groups on the surface of the modified magnesium sulfate. Through their synergistic effect, the desiliconization performance of the functionalized desiliconizer is further improved, while the yield of sodium hydroxide is increased. DETAILED DESCRIPTION

[0018] The present application is further described in detail below with reference to the embodiments.

[0019] The black liquor dry powder used in the examples and comparative examples of the present application is the dry powder prepared by atomization drying of black liquor in the wheat straw caustic soda process of Hefei Heye Paper Co., Ltd. 2 It is rutile type and purchased from DuPont with brand number R104.

[0020] Preparation Examples 1-3 and Comparative Preparation Examples 1-4 provide a functionalized silicon remover.

[0021] Preparation Example 1

[0022] This preparation example provides a functionalized desiliconizer, which is prepared by the following steps:

[0023] Step A1, magnesium sulfate, deionized water, anhydrous ethanol and KH-570 are ultrasonically treated at an ultrasonic frequency of 35 kHz and an ultrasonic power of 550 W for 24 min until they are uniformly dispersed, the temperature is raised to 42° C., the reaction is stirred for 6 h, centrifuged, the precipitate is washed and dried to obtain modified magnesium sulfate, wherein the mass ratio of magnesium sulfate, deionized water, anhydrous ethanol and KH-570 is 4:8:25:0.4;

[0024] Step A2, calcium oxide and modified magnesium sulfate are added to deionized water, and the ultrasonic frequency is 40kHz, the ultrasonic power is 600w, and the ultrasonic is carried out for 26min until the dispersion is uniform to obtain a suspension, and the pH of the suspension is adjusted to 3, and then the temperature is raised to 42°C, and nitrogen is passed through to deoxygenate. Under nitrogen protection, a mixed solution a containing acrylamide, acryloyloxyethyltrimethylammonium chloride, sodium p-styrenesulfonate, an initiator and deionized water is added dropwise, and the dripping is controlled within 10min, and then a mixed solution b of naphthalene and anhydrous ethanol is added, and the dripping is controlled within 20min. After the dripping is completed, the reaction is continued to stir for 5h, and the addition of Hydroquinone is filtered, dried, crushed and sieved to obtain a functionalized silicon remover, wherein the mass ratio of calcium oxide, modified magnesium sulfate, deionized water, mixed solution a, mixed solution b and hydroquinone is 6:1:40:18:12:0.027, the mass ratio of acrylamide, acryloyloxyethyltrimethylammonium chloride, sodium p-styrenesulfonate, initiator and deionized water in the mixed solution a is 0.8:0.2:0.03:0.09:16, the initiator is a mixture of ammonium persulfate and sodium bisulfite in a mass ratio of 1:1, and the mass ratio of naphthalene to anhydrous ethanol in the mixed solution b is 2:10.

[0025] Preparation Example 2

[0026] This preparation example provides a functionalized desiliconizer, which is prepared by the following steps:

[0027] Step A1, magnesium sulfate, deionized water, anhydrous ethanol and KH-570 are ultrasonically treated at an ultrasonic frequency of 40 kHz and an ultrasonic power of 600 W for 30 min until they are uniformly dispersed, the temperature is raised to 44° C., the reaction is stirred for 7 h, centrifuged, the precipitate is washed and dried to obtain modified magnesium sulfate, wherein the mass ratio of magnesium sulfate, deionized water, anhydrous ethanol and KH-570 is 4:10:28:0.5;

[0028] Step A2, calcium oxide and modified magnesium sulfate are added to deionized water, and the ultrasonic frequency is 45kHz, the ultrasonic power is 650w, and the ultrasonic is carried out for 28min until the dispersion is uniform to obtain a suspension, and the pH of the suspension is adjusted to 3.5, and then the temperature is raised to 48°C, and nitrogen is passed through to deoxygenate. Under nitrogen protection, a mixed solution a containing acrylamide, acryloyloxyethyl trimethyl ammonium chloride, sodium p-styrene sulfonate, an initiator and deionized water is added dropwise, and the dripping is controlled within 10min, and then a mixed solution b of naphthalene and anhydrous ethanol is added, and the dripping is controlled within 20min. After the dripping is completed, the reaction is continued to stir for 5.5h, and p-styrene is added. The hydroquinone is prepared by filtering, drying, crushing and sieving. The functionalized desiliconizer is obtained, wherein the mass ratio of calcium oxide, modified magnesium sulfate, deionized water, mixed solution a, mixed solution b and hydroquinone is 7:1.5:45:20:14:0.029; in the mixed solution a, the mass ratio of acrylamide, acryloyloxyethyl trimethyl ammonium chloride, sodium p-styrene sulfonate, initiator and deionized water is 1.0:0.3:0.065:0.017:18; the initiator is a mixture of ammonium persulfate and sodium bisulfite in a mass ratio of 1:1; in the mixed solution b, the mass ratio of naphthalene and anhydrous ethanol is 2.5:10.

[0029] Preparation Example 3

[0030] This preparation example provides a functionalized desiliconizer, which is prepared by the following steps:

[0031] Step A1, magnesium sulfate, deionized water, anhydrous ethanol and KH-570 are subjected to ultrasonic treatment at an ultrasonic frequency of 45 kHz and an ultrasonic power of 650 W for 36 min until they are uniformly dispersed, the temperature is raised to 46° C., the reaction is stirred for 8 h, the reaction is centrifuged, the precipitate is washed and dried to obtain modified magnesium sulfate, wherein the mass ratio of magnesium sulfate, deionized water, anhydrous ethanol and KH-570 is 4:12:30:0.6;

[0032] Step A2, adding calcium oxide and modified magnesium sulfate to deionized water, ultrasonic frequency of 50kHz, ultrasonic power of 700w, ultrasonic for 30min until uniform dispersion, to obtain a suspension, adjusting the pH of the suspension to 4, then heating to 56°C, nitrogen deoxygenation, under nitrogen protection, dripping a mixture of acrylamide, acryloyloxyethyl trimethylammonium chloride, sodium p-styrene sulfonate, initiator and deionized water, controlling the dripping within 10min, then adding a mixture of naphthalene and anhydrous ethanol b, controlling the dripping within 20min, after dripping, continue stirring and reacting for 6h , add hydroquinone, filter and dry, crush and sieve to obtain a functionalized silicon remover, wherein the mass ratio of calcium oxide, deionized water, mixed solution a, mixed solution b and hydroquinone is 8:50:22:16:0.031, the mass ratio of acrylamide, acryloyloxyethyltrimethylammonium chloride, sodium p-styrenesulfonate, initiator and deionized water in mixed solution a is 1.2:0.4:0.1:0.25:20, the initiator is a mixture of ammonium persulfate and sodium bisulfite in a mass ratio of 1:1, and the mass ratio of naphthalene to anhydrous ethanol in mixed solution b is 3:10.

[0033] Comparative Preparation Example 1

[0034] This comparative preparation example provides a functionalized desiliconizer, which is prepared by the following steps:

[0035] Step A1, magnesium sulfate, deionized water, anhydrous ethanol and KH-560 are ultrasonically treated at an ultrasonic frequency of 35 kHz and an ultrasonic power of 550 W for 24 min until they are uniformly dispersed, the temperature is raised to 42° C., the reaction is stirred for 6 h, the precipitate is centrifuged, washed and dried to obtain modified magnesium sulfate, wherein the mass ratio of magnesium sulfate, deionized water, anhydrous ethanol and KH-560 is 4:8:25:0.4;

[0036] Step A2, calcium oxide and modified magnesium sulfate are added to deionized water, and the ultrasonic frequency is 40kHz, the ultrasonic power is 600w, and the ultrasonic is carried out for 26min until the dispersion is uniform to obtain a suspension, and the pH of the suspension is adjusted to 3, and then the temperature is raised to 42°C, and nitrogen is passed through to deoxygenate. Under nitrogen protection, a mixed solution a containing acrylamide, acryloyloxyethyltrimethylammonium chloride, sodium p-styrenesulfonate, an initiator and deionized water is added dropwise, and the dripping is controlled within 10min, and then a mixed solution b of naphthalene and anhydrous ethanol is added, and the dripping is controlled within 20min. After the dripping is completed, the reaction is continued to stir for 5h, and the addition of Hydroquinone is filtered, dried, crushed and sieved to obtain a functionalized silicon remover, wherein the mass ratio of calcium oxide, modified magnesium sulfate, deionized water, mixed solution a, mixed solution b and hydroquinone is 6:1:40:18:12:0.027, the mass ratio of acrylamide, acryloyloxyethyltrimethylammonium chloride, sodium p-styrenesulfonate, initiator and deionized water in the mixed solution a is 0.8:0.2:0.03:0.09:16, the initiator is a mixture of ammonium persulfate and sodium bisulfite in a mass ratio of 1:1, and the mass ratio of naphthalene to anhydrous ethanol in the mixed solution b is 2:10.

[0037] Comparative Preparation Example 2

[0038] This comparative preparation example provides a functionalized desiliconizer, which is prepared by the following steps:

[0039] Step A1, magnesium sulfate, deionized water, anhydrous ethanol and KH-570 are ultrasonically treated at an ultrasonic frequency of 35 kHz and an ultrasonic power of 550 W for 24 min until they are uniformly dispersed, the temperature is raised to 42° C., the reaction is stirred for 6 h, centrifuged, the precipitate is washed and dried to obtain modified magnesium sulfate, wherein the mass ratio of magnesium sulfate, deionized water, anhydrous ethanol and KH-570 is 4:8:25:0.4;

[0040] Step A2, calcium oxide and modified magnesium sulfate are added to deionized water, and the ultrasonic frequency is 40kHz, the ultrasonic power is 600w, and the ultrasonic is carried out for 26min until the dispersion is uniform to obtain a suspension, and the pH of the suspension is adjusted to 3, and then the temperature is raised to 42°C, nitrogen is passed through to deoxygenate, and under nitrogen protection, a mixed solution a containing acrylamide, ethyl acrylate, sodium p-styrene sulfonate, an initiator and deionized water is added dropwise, and the dripping is controlled within 10min, and then a mixed solution b of naphthalene and anhydrous ethanol is added, and the dripping is controlled within 20min. After the dripping is completed, the reaction is continued to stir for 5h, and the addition of Hydroquinone is filtered, dried, crushed and sieved to obtain a functionalized silicon remover, wherein the mass ratio of calcium oxide, modified magnesium sulfate, deionized water, mixed solution a, mixed solution b and hydroquinone is 6:1:40:18:12:0.027, the mass ratio of acrylamide, ethyl acrylate, sodium p-styrene sulfonate, initiator and deionized water in the mixed solution a is 0.8:0.2:0.03:0.09:16, the initiator is a mixture of ammonium persulfate and sodium bisulfite in a mass ratio of 1:1, and the mass ratio of naphthalene to anhydrous ethanol in the mixed solution b is 2:10.

[0041] Comparative Preparation Example 3

[0042] This comparative preparation example provides a functionalized desiliconizer, which is prepared by the following steps:

[0043] Step A1, magnesium sulfate, deionized water, anhydrous ethanol and KH-570 are ultrasonically treated at an ultrasonic frequency of 35 kHz and an ultrasonic power of 550 W for 24 min until they are uniformly dispersed, the temperature is raised to 42° C., the reaction is stirred for 6 h, centrifuged, the precipitate is washed and dried to obtain modified magnesium sulfate, wherein the mass ratio of magnesium sulfate, deionized water, anhydrous ethanol and KH-570 is 4:8:25:0.4;

[0044] Step A2, calcium oxide and modified magnesium sulfate are added to deionized water, and ultrasonic frequency is 40kHz, ultrasonic power is 600w, ultrasonic for 26min until uniform dispersion is obtained to obtain a suspension, and the pH of the suspension is adjusted to 3, and then the temperature is raised to 42°C, nitrogen is passed through to deoxygenate, and under nitrogen protection, a mixed solution a containing acrylamide, acryloyloxyethyltrimethylammonium chloride, p-styrene, initiator and deionized water is added dropwise, and the dripping is controlled within 10min, and then a mixed solution b of naphthalene and anhydrous ethanol is added, and the dripping is controlled within 20min. After the dripping is completed, the reaction is continued to stir for 5h, and p-styrene is added. Hydroquinone is filtered, dried, crushed and sieved to obtain a functionalized silicon remover, wherein the mass ratio of calcium oxide, modified magnesium sulfate, deionized water, mixed solution a, mixed solution b and hydroquinone is 6:1:40:18:12:0.027, the mass ratio of acrylamide, acryloyloxyethyltrimethylammonium chloride, p-styrene, initiator and deionized water in the mixed solution a is 0.8:0.2:0.03:0.09:16, the initiator is a mixture of ammonium persulfate and sodium bisulfite in a mass ratio of 1:1, and the mass ratio of naphthalene to anhydrous ethanol in the mixed solution b is 2:10.

[0045] Comparative Preparation Example 4

[0046] This comparative preparation example provides a functionalized desiliconizer, which is prepared by the following steps:

[0047] Step A1, magnesium sulfate, deionized water, anhydrous ethanol and KH-570 are ultrasonically treated at an ultrasonic frequency of 35 kHz and an ultrasonic power of 550 W for 24 min until they are uniformly dispersed, the temperature is raised to 42° C., the reaction is stirred for 6 h, centrifuged, the precipitate is washed and dried to obtain modified magnesium sulfate, wherein the mass ratio of magnesium sulfate, deionized water, anhydrous ethanol and KH-570 is 4:8:25:0.4;

[0048] Step A2, calcium oxide and modified magnesium sulfate are added to deionized water, and the ultrasonic frequency is 40kHz, the ultrasonic power is 600, and the ultrasonic is performed for 26 minutes until the dispersion is uniform to obtain a suspension, and the pH of the suspension is adjusted to 3, and then the temperature is raised to 42°C, and nitrogen is passed through to deoxygenate. Under nitrogen protection, a mixed solution a containing acrylic acid, acryloyloxyethyl trimethyl ammonium chloride, sodium p-styrene sulfonate, an initiator and deionized water is added dropwise, and the dripping is controlled within 10 minutes, and then a mixed solution b of naphthalene and anhydrous ethanol is added, and the dripping is controlled within 20 minutes. After the dripping is completed, the reaction is continued to stir for 5 hours, and p-styrene is added. The hydroquinone is prepared by filtering and drying, crushing and sieving to obtain a functionalized silicon remover, wherein the mass ratio of calcium oxide, modified magnesium sulfate, deionized water, mixed solution a, mixed solution b and hydroquinone is 6:1:40:18:12:0.027; in the mixed solution a, the mass ratio of acrylic acid, acryloyloxyethyltrimethylammonium chloride, sodium p-styrenesulfonate, initiator and deionized water is 0.8:0.2:0.03:0.09:16; the initiator is a mixture of ammonium persulfate and sodium bisulfite in a mass ratio of 1:1; in the mixed solution b, the mass ratio of naphthalene and anhydrous ethanol is 2:10.

[0049] Examples 1-3 and Comparative Examples 1-4 provide a method for preparing a sodium hydroxide regeneration cycle method.

[0050] Example 1

[0051] The present embodiment provides a preparation method of a sodium hydroxide regeneration cycle method, comprising the following steps:

[0052] Step S1, black liquor pretreatment: adding black liquor semi-coke to dimethyl sulfoxide, controlling the ultrasonic frequency to 40kHz, the ultrasonic power to 600w, ultrasonicating for 30min until fully dissolved, adjusting the pH to 6 with a 0.6M sodium hydroxide aqueous solution, adding the functionalized silicon remover prepared in Preparation Example 1, stirring at a speed of 5000rpm for 26min, filtering, and drying at 65°C to constant weight to obtain pretreated black liquor, wherein the mass ratio of black liquor semi-coke, dimethyl sulfoxide and functionalized silicon remover is 4:80:0.026, and the black liquor semi-coke is obtained by pyrolyzing black liquor dry powder at 580°C for 10h under a nitrogen atmosphere of 99.999%;

[0053] Step S2, decarbonization of pretreated black liquor: put the pretreated black liquor and nano-titanium dioxide into a high-temperature tube furnace and seal it, introduce nitrogen, and when the nitrogen fills the pipe, heat it to 845°C at a heating rate of 5°C / min, pump in distilled water, and keep it warm for 22 minutes. After the reaction is completed, stop supplying water vapor, and continue to introduce nitrogen to obtain an intermediate;

[0054] Step S3, preparation of hydrolyzate: under nitrogen protection, add the intermediate into deionized water, heat to reflux, stir and react for 12 min at a controlled speed of 650 rpm, cool to room temperature, filter, and obtain a hydrolyzate, wherein the mass ratio of the intermediate to deionized water is 2.8:70;

[0055] Step S4, recycling of hydrolyzate: the hydrolyzate prepared in step S3 can be recycled again as a cooking agent for alkaline pulping.

[0056] Example 2

[0057] The present embodiment provides a preparation method of a sodium hydroxide regeneration cycle method, comprising the following steps:

[0058] Step S1, black liquor pretreatment: adding black liquor semi-coke to dimethyl sulfoxide, controlling the ultrasonic frequency to 45kHz, the ultrasonic power to 650w, ultrasonicating for 35min until fully dissolved, adjusting the pH to 7 with 0.8M sodium hydroxide aqueous solution, adding the functionalized silicon remover prepared in Preparation Example 2, stirring at a speed of 550rpm for 30min, filtering, and drying at 70°C to constant weight to obtain pretreated black liquor, wherein the mass ratio of black liquor semi-coke, dimethyl sulfoxide and functionalized silicon remover is 5:85:0.030, and the black liquor semi-coke is obtained by pyrolyzing black liquor dry powder at 600°C for 11h under a nitrogen atmosphere of 99.999%;

[0059] Step S2, decarbonization of pretreated black liquor: put the pretreated black liquor and nano titanium dioxide into a high-temperature tube furnace and seal it, introduce nitrogen, and when the nitrogen fills the pipe, heat it to 850°C at a heating rate of 5°C / min, pump in distilled water, and keep it warm for 24 minutes. After the reaction is completed, stop supplying water vapor, and continue to introduce nitrogen to obtain an intermediate, wherein the mass ratio of the pretreated black liquor to the nano titanium dioxide is 4:0.8;

[0060] Step S3, preparation of hydrolyzate: under nitrogen protection, add the intermediate into deionized water, heat to reflux, stir and react for 14 min at a controlled speed of 700 rpm, cool to room temperature, filter, and obtain a hydrolyzate, wherein the mass ratio of the intermediate to deionized water is 3.7:75;

[0061] Step S4, recycling of hydrolyzate: the hydrolyzate prepared in step S3 can be recycled again as a cooking agent for alkaline pulping.

[0062] Example 3

[0063] The present embodiment provides a preparation method of a sodium hydroxide regeneration cycle method, comprising the following steps:

[0064] Step S1, black liquor pretreatment: adding black liquor semi-coke to dimethyl sulfoxide, controlling the ultrasonic frequency to 50kHz, the ultrasonic power to 700w, ultrasonicating for 40min until fully dissolved, adjusting the pH to 8 with 1.0M sodium hydroxide aqueous solution, adding a functionalized desiliconizer, stirring at a speed of 6000rpm for 34min, filtering, and drying at 75°C to constant weight to obtain pretreated black liquor, wherein the mass ratio of black liquor semi-coke, dimethyl sulfoxide and functionalized desiliconizer is 6:90:0.034, and the black liquor semi-coke is obtained by pyrolyzing black liquor dry powder at 620°C for 12h under a nitrogen atmosphere of 99.999%;

[0065] Step S2, decarbonization of pretreated black liquor: put the pretreated black liquor and nano titanium dioxide into a high-temperature tube furnace and seal it, introduce nitrogen, and when the nitrogen fills the pipe, heat it to 855°C at a heating rate of 5°C / min, pump in distilled water, and keep it warm for 26 minutes. After the reaction is completed, stop supplying water vapor, and continue to introduce nitrogen to obtain an intermediate, wherein the mass ratio of the pretreated black liquor to the nano titanium dioxide is 5:1.0;

[0066] Step S3, preparation of hydrolyzate: under nitrogen protection, add the intermediate into deionized water, heat to reflux, stir and react for 16 min at a controlled speed of 750 rpm, cool to room temperature, filter, and obtain a hydrolyzate, wherein the mass ratio of the intermediate to deionized water is 4.6:80;

[0067] Step S4, recycling of hydrolyzate: the hydrolyzate prepared in step S3 can be recycled again as a cooking agent for alkaline pulping.

[0068] Comparative Example 1

[0069] Comparative Example 1 is the same as Example 1, except that the functionalized silicon remover in Example 1 is replaced by the functionalized silicon remover prepared in Comparative Preparation Example 1.

[0070] Comparative Example 2

[0071] Comparative Example 2 is the same as Example 1, except that the functionalized silicon remover in Example 1 is replaced by the functionalized silicon remover prepared in Comparative Preparation Example 2.

[0072] Comparative Example 3

[0073] Comparative Example 3 is the same as Example 1, except that the functionalized silicon remover in Example 1 is replaced by the functionalized silicon remover prepared in Comparative Preparation Example 3.

[0074] Comparative Example 4

[0075] Comparative Example 4 is the same as Example 1, except that the functionalized silicon remover in Example 1 is replaced by the functionalized silicon remover prepared in Comparative Preparation Example 4.

[0076] Performance Testing

[0077] The following performance tests were performed on the hydrolyzates obtained in Examples 1-3 and Comparative Examples 1-4:

[0078] 1. Silicon content: A mixture of nitric acid and hydrogen peroxide was added dropwise to the hydrolyzed solution, and the addition was completed within 15 min. After the addition was completed, the mixture was stirred at a rotation speed of 550 rpm for 10 min until uniform, the temperature was raised to 80° C., the rotation speed was maintained unchanged, and the reaction was stirred for 15 min. The temperature was then raised to 120° C. and stirred for 24 min. The temperature was raised to 180° C. and allowed to stand for 26 min. The mixture was cooled to room temperature to obtain a sample to be tested. The silicon content of the samples prepared in Examples 1-3 and Comparative Examples 1-4 was tested in turn by inductively coupled plasma atomic emission spectroscopy (ICP-AES), and the silicon removal rate was calculated. The calculation formula for the silicon removal rate is shown in formula (1):

[0079]

[0080] In formula (1), W a is the silicon content (ppm) of green liquor obtained without adding silicon remover, W b is the silicon content (ppm) of the hydrolyzate obtained by adding the silicon removal agent;

[0081] 2. Sodium hydroxide content: The analysis method adopted is GB / T 4348.1-2013 "Industrial sodium hydroxide - Determination of sodium hydroxide and sodium carbonate content" to measure the sodium hydroxide content;

[0082] The above specific test results are shown in Table 1 below:

[0083] Table 1 Performance parameters of sodium hydroxide obtained from Examples 1-3 and Comparative Examples 1-4

[0084]

[0085]

[0086] It can be seen from Table 1 that, compared with Comparative Examples 1-4, the sodium hydroxide prepared in Examples 1-3 not only has a higher yield, but also has better silicon removal performance.

[0087] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make modifications to the present embodiment without any creative contribution as needed, but such modifications are protected by the patent law as long as they are within the scope of the claims of the present application.

Claims

1. A sodium hydroxide regeneration cycle method, characterized in that, The following steps are involved: Step S1, black liquor pretreatment: adding black liquor semi-coke into dimethyl sulfoxide, ultrasonically dispersing until fully dissolved, adjusting the pH to 6-8, adding a functionalized desiliconizer, stirring for 26-34 minutes, filtering, and drying to obtain pretreated black liquor; Step S2, decarbonization of pretreated black liquor: put the pretreated black liquor and nano-titanium dioxide into a high-temperature tube furnace and seal it, introduce nitrogen, and when the nitrogen fills the pipe, heat it to 845-855°C at a heating rate of 5°C / min, pump in distilled water, and keep it warm for 22-26 minutes. After the reaction is completed, stop supplying water vapor and continue to introduce nitrogen to obtain an intermediate; Step S3, preparation of hydrolyzate: under nitrogen protection, add the intermediate into deionized water, heat to reflux, stir to react for 12-16 minutes, cool to room temperature, filter, and obtain a hydrolyzate; Step S4, recycling of hydrolyzate: the hydrolyzate prepared in step S3 can be used as a cooking agent for alkaline pulping and then recycled again; The functional silicon remover is firstly prepared by modifying magnesium sulfate with KH-570 to obtain modified magnesium sulfate, and then undergoing free radical polymerization reaction with acrylamide, acryloyloxyethyl trimethyl ammonium chloride and sodium p-styrene sulfonate under the initiation of an initiator to obtain the functional silicon remover.

2. The sodium hydroxide regeneration cycle method according to claim 1, wherein In the step S1, the mass ratio of black liquor semi-coke, dimethyl sulfoxide and functionalized desiliconizing agent is 4-6:80-90:0.026-0.

034.

3. Sodium hydroxide regeneration cycle method according to claim 1, is characterized in that, In the step S2, the mass ratio of the pretreated black liquor to the nano-titanium dioxide is 3-5:0.6-1.

0.

4. The sodium hydroxide regeneration cycle method according to claim 1, wherein In the step S3, the mass ratio of the intermediate to deionized water is 2.8-4.6:70-80.

5. The sodium hydroxide regeneration cycle method according to claim 1, wherein The functionalized silicon remover is prepared by the following steps: Step A1, uniformly disperse magnesium sulfate, deionized water, anhydrous ethanol and KH-570 by ultrasonication, raise the temperature to 42-46° C., stir and react for 6-8 hours, centrifuge, wash and dry the precipitate to obtain modified magnesium sulfate; Step A2, adding calcium oxide and modified magnesium sulfate into deionized water, ultrasonically dispersing them uniformly to obtain a suspension, adjusting the pH of the suspension to 3-4, then heating to 42-56° C., passing nitrogen to deoxygenate, and under nitrogen protection, dripping a mixed solution a containing acrylamide, acryloyloxyethyltrimethylammonium chloride, sodium p-styrenesulfonate, an initiator and deionized water, controlling the dripping to be completed within 10 minutes, then adding a mixed solution b of naphthalene and anhydrous ethanol, controlling the dripping to be completed within 20 minutes, and after the dripping is completed, continuing to stir and react for 5-6 hours, adding hydroquinone, filtering and drying by suction, crushing, and sieving to obtain a functionalized desiliconizer.

6. The sodium hydroxide regeneration cycle method according to claim 5, wherein In the step A1, the mass ratio of magnesium sulfate, deionized water, anhydrous ethanol and KH-570 is 4:8-12:25-30:0.4-0.

6.

7. The sodium hydroxide regeneration cycle method according to claim 5, wherein In the step A2, the mass ratio of calcium oxide, modified magnesium sulfate, deionized water, mixed solution a, mixed solution b and hydroquinone is 6-8: 1-2: 40-50: 18-22: 12-16: 0.027-0.031, the mass ratio of acrylamide, acryloyloxyethyl trimethyl ammonium chloride, sodium p-styrene sulfonate, initiator and deionized water in the mixed solution a is 0.8-1.2: 0.2-0.4: 0.03-0.1: 0.09-0.25: 16-20, the initiator is a mixture of ammonium persulfate and sodium bisulfite in a mass ratio of 1:1, and the mass ratio of naphthalene to anhydrous ethanol in the mixed solution b is 2-3:

10.

8. The sodium hydroxide regeneration cycle method according to claim 1, wherein The black liquor semi-coke is prepared by pyrolyzing black liquor dry powder at 580-620° C. for 10-12 hours in a nitrogen atmosphere of 99-99.999%.

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