A sodium hydroxide regeneration cycle method

Abstract

The present application relates to the field of regeneration and circulation technology, and specifically to a sodium hydroxide regeneration and circulation method, which comprises the following steps: step S1, pretreatment of black liquor; step S2, decarbonization of pretreated black liquor; step S3, preparation of hydrolyzed liquid; and step S4, recycling of hydrolyzed liquid. The present application adds a functionalized desiliconizer during the black liquor pretreatment process, wherein the core of the functionalized desiliconizer is a mixture of magnesium sulfate, calcium hydroxide, deionized water, and anhydrous ethanol, and the shell comprises a porous structure obtained by chemical crosslinking of acrylamide, acryloyloxyethyltrimethylammonium chloride, sodium p-styrenesulfonate, and KH-570 on the surface of modified magnesium sulfate. The above structures can act synergistically to improve the desiliconization performance while further improving the sodium hydroxide yield.

Description

Technical Field

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

[0002] As a vital raw material industry, the papermaking industry, while supporting economic development, also produces large quantities of alkaline wastewater. This wastewater contains significant amounts of sodium hydroxide and other chemical residues. Direct discharge of this wastewater would cause severe pollution to natural water bodies. With growing environmental awareness and the demand for sustainable development, sodium hydroxide recovery technology, as a highly efficient resource recycling method, not only addresses environmental pollution issues but also enables the recycling and reuse of chemicals, becoming a key milestone in the papermaking industry's green transformation.

[0003] Invention patent application CN101898770B discloses a sodium hydroxide regeneration and recycling method, in which calcium carbonate is first added to a sodium sulfate solution, and carbon dioxide or sulfuric acid is added to adjust the pH of the solution to convert the sodium sulfate into sodium bicarbonate. Gypsum and sodium bicarbonate solution are filtered to obtain gypsum. Lime is then added to the sodium bicarbonate solution for causticization, and filtered to obtain a regenerated sodium hydroxide solution and calcium carbonate. The calcium carbonate is returned to the sodium sulfate 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 white mud from papermaking wastewater by calcination in a rotary kiln. This not only increases the company's additional processing costs 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, decarburization of pretreated black liquor: placing the pretreated black liquor and nano-titanium dioxide into a high-temperature tube furnace, sealing it, and introducing nitrogen. When the nitrogen fills the pipe, heating it to 845-855°C at a heating rate of 5°C / min, pumping in distilled water, and keeping it warm for 22-26 minutes. After the reaction is completed, stop supplying water vapor and continue introducing 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 and react for 12-16 minutes, cool to room temperature, filter to 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 the hydrolyzed liquid: the hydrolyzed liquid 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 6-8 hours, centrifuging, washing the precipitate, and drying 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, and treating magnesium sulfate with KH-570 to obtain modified magnesium sulfate. The modified magnesium sulfate contains hydroxyl groups that 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, nitrogen deoxygenation, and under nitrogen protection, adding a mixture a containing acrylamide, acryloyloxyethyltrimethylammonium chloride, sodium p-styrenesulfonate and initiator, controlling the dripping within 10 minutes, then adding a mixture b of naphthalene and anhydrous ethanol, controlling the dripping within 20 minutes, and continuing to stir the reaction 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, mixture a, mixture b and hydroquinone is 6-8:1-2:40-50:18-22:12-16:0.027-0.031, and in the mixture a, propylene The mass ratio of amide, acryloyloxyethyltrimethylammonium chloride, sodium p-styrenesulfonate, 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. In the mixed solution b, the mass ratio of naphthalene and anhydrous ethanol 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-styrenesulfonate serves as both a reaction monomer and a stabilizer for graft polymerization in the emulsion. At the same time, the sulfonic acid groups on the naphthalene can form hydrogen bonds with the surface hydroxyl groups of calcium hydroxide and modified magnesium sulfate to obtain a functionalized 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 achieve effective extraction of sodium hydroxide from papermaking black liquor, a functionalized desiliconizer is added in this application. The core of the functionalized desiliconizer is a mixture of magnesium sulfate, calcium hydroxide, deionized water and anhydrous ethanol. The shell layer comprises acrylamide, acryloyloxyethyltrimethylammonium chloride, sodium p-styrenesulfonate and KH-570 on the surface of modified magnesium sulfate, and the porous structure is obtained by chemical cross-linking. In the core, the magnesium ions in magnesium sulfate and the calcium ions in calcium hydroxide can react chemically 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 a dry powder prepared by atomizing and drying the black liquor produced in the wheat straw caustic soda process of Hefei Heye Paper Co., Ltd. The TiO2 used is rutile type and is purchased from DuPont with the brand 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 a frequency of 35 kHz and an ultrasonic power of 550 W for 24 minutes until uniform dispersion is achieved, the temperature is raised to 42° C., the mixture is stirred for 6 hours, the mixture 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 4:8:25:0.4;

[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. 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. 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 stirred for 5h, and the mixture is added to 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 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 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 a frequency of 40 kHz and an ultrasonic power of 600 W for 30 minutes until uniform dispersion is achieved, the temperature is raised to 44° C., the mixture is stirred for 7 hours, the mixture 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 4:10:28:0.5;

[0028] Step A2, calcium oxide and modified magnesium sulfate are added to deionized water, and the mixture is ultrasonically dispersed for 28 minutes at an ultrasonic frequency of 45kHz and an ultrasonic power of 650w to obtain a suspension. The pH of the suspension is adjusted to 3.5, and the mixture is heated to 48°C and deoxygenated with nitrogen. Under nitrogen protection, a mixed solution a containing acrylamide, acryloyloxyethyltrimethylammonium chloride, sodium p-styrenesulfonate, an initiator and deionized water is added dropwise, and the mixture is controlled to drip within 10 minutes. Then, a mixed solution b of naphthalene and anhydrous ethanol is added, and the mixture is controlled to drip within 20 minutes. After the dripping is completed, the reaction is stirred for 5.5 hours, and p-styrene is added. The hydroquinone was 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 was 7:1.5:45:20:14:0.029; the mass ratio of acrylamide, acryloyloxyethyltrimethylammonium chloride, sodium p-styrenesulfonate, initiator, and deionized water in the mixed solution a was 1.0:0.3:0.065:0.017:18; the initiator was 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 was 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 ultrasonically treated at a frequency of 45 kHz and an ultrasonic power of 650 W for 36 minutes until uniform dispersion is achieved, the temperature is raised to 46° C., the reaction is stirred for 8 hours, 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, calcium oxide and modified magnesium sulfate are added to deionized water, and ultrasonic frequency is 50kHz, ultrasonic power is 700w, and ultrasonication is carried out for 30min until uniform dispersion is obtained to obtain a suspension, and the pH of the suspension is adjusted to 4, then the temperature is raised to 56°C, nitrogen is passed through to deoxygenate, and under nitrogen protection, a mixed solution a containing acrylamide, acryloyloxyethyltrimethylammonium chloride, sodium p-styrenesulfonate, an initiator and deionized water is added dropwise, and the addition is controlled to be completed within 10min, and then a mixed solution b of naphthalene and anhydrous ethanol is added, and the addition is controlled to be completed within 20min. After the addition is completed, stirring and the reaction is continued 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, and 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, and the initiator is a mixture of ammonium persulfate and sodium bisulfite in a mass ratio of 1:1. In mixed solution b, the mass ratio of naphthalene and anhydrous ethanol 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 a frequency of 35 kHz and an ultrasonic power of 550 W for 24 minutes until uniform dispersion is achieved, the temperature is raised to 42° C., the mixture is stirred for 6 hours, the mixture 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-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. 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. 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 stirred for 5h, and the mixture is added to 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 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 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 a frequency of 35 kHz and an ultrasonic power of 550 W for 24 minutes until uniform dispersion is achieved, the temperature is raised to 42° C., the mixture is stirred for 6 hours, the mixture 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 4:8:25:0.4;

[0040] Step A2, calcium oxide and modified magnesium sulfate are added to deionized water, at an ultrasonic frequency of 40kHz, an ultrasonic power of 600w, and ultrasonicated for 26min until uniformly dispersed to obtain a suspension, and the pH of the suspension is adjusted to 3, 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-styrenesulfonate, an initiator and deionized water is added dropwise, and the mixture is controlled to drip within 10min, and then a mixed solution b of naphthalene and anhydrous ethanol is added, and the mixture is controlled to drip within 20min, and the dripping is completed. After the dripping is completed, the reaction is stirred for 5h, and the mixture is added to 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-styrenesulfonate, initiator, and deionized water in 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 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 a frequency of 35 kHz and an ultrasonic power of 550 W for 24 minutes until uniform dispersion is achieved, the temperature is raised to 42° C., the mixture is stirred for 6 hours, the mixture 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 4:8:25:0.4;

[0044] Step A2, calcium oxide and modified magnesium sulfate are added to deionized water, and ultrasonic frequency is 40kHz, ultrasonic power is 600w, and ultrasonic is carried out for 26min until uniform dispersion is obtained to obtain a suspension, and the pH of the suspension is adjusted to 3, 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 with stirring 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, p-styrene, initiator, and deionized water in 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 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 a frequency of 35 kHz and an ultrasonic power of 550 W for 24 minutes until uniform dispersion is achieved, the temperature is raised to 42° C., the mixture is stirred for 6 hours, the mixture 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 4:8:25:0.4;

[0048] Step A2, calcium oxide and modified magnesium sulfate are added to deionized water, and the mixture is ultrasonically controlled at an ultrasonic frequency of 40kHz and an ultrasonic power of 600 for 26 minutes until uniformly dispersed to obtain a suspension. The pH of the suspension is adjusted to 3, and the mixture is heated to 42°C and deoxygenated with nitrogen. Under nitrogen protection, a mixture a containing acrylic acid, acryloyloxyethyltrimethylammonium chloride, sodium p-styrenesulfonate, an initiator and deionized water is added dropwise, and the mixture is controlled to be dripped within 10 minutes. Then, a mixture b of naphthalene and anhydrous ethanol is added, and the mixture is controlled to be dripped within 20 minutes. After the dripping is completed, the reaction is stirred for 5 hours, and p-styrene is added. The hydroquinone was 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 was 6:1:40:18:12:0.027; the mass ratio of acrylic acid, acryloyloxyethyltrimethylammonium chloride, sodium p-styrenesulfonate, initiator, and deionized water in the mixed solution a was 0.8:0.2:0.03:0.09:16; the initiator was 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 was 2:10.

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

[0050] Example 1

[0051] This 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 40 kHz and the ultrasonic power to 600 W, ultrasonicating for 30 minutes until fully dissolved, adjusting the pH to 6 with a 0.6 M sodium hydroxide aqueous solution, adding the functionalized silicon remover prepared in Preparation Example 1, stirring at a speed of 5000 rpm for 26 minutes, 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 10 hours under a nitrogen atmosphere of 99.999%;

[0053] Step S2, decarburization of pretreated black liquor: The pretreated black liquor and nano-titanium dioxide were placed in a high-temperature tube furnace and sealed, and nitrogen was introduced. When the nitrogen filled the tube, the temperature was increased to 845°C at a rate of 5°C / min, and distilled water was pumped into the furnace. The temperature was kept at this temperature for 22 minutes. After the reaction was completed, the water vapor supply was stopped, and nitrogen was continued to be introduced to obtain an intermediate.

[0054] Step S3, preparation of hydrolyzate: under nitrogen protection, the intermediate was added to deionized water, the temperature was raised to reflux, the reaction was stirred at a speed of 650 rpm for 12 minutes, the reaction was cooled to room temperature, and the hydrolyzate was obtained by filtering, wherein the mass ratio of the intermediate to deionized water was 2.8:70;

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

[0056] Example 2

[0057] This 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 45 kHz and the ultrasonic power to 650 W, ultrasonicating for 35 minutes until fully dissolved, adjusting the pH to 7 with a 0.8 M sodium hydroxide aqueous solution, adding the functionalized silicon remover prepared in Preparation Example 2, stirring at a speed of 550 rpm for 30 minutes, 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 11 hours under a nitrogen atmosphere of 99.999%;

[0059] Step S2, decarburization of pretreated black liquor: placing the pretreated black liquor and nano-titanium dioxide into a high-temperature tube furnace, sealing it, and introducing nitrogen. When the nitrogen fills the pipe, the temperature is increased to 850°C at a rate of 5°C / min, and distilled water is pumped into it. The temperature is kept at this temperature for 24 minutes. After the reaction is completed, the water vapor supply is stopped, and nitrogen is continued to be introduced 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, the intermediate was added to deionized water, the temperature was raised to reflux, the reaction was stirred at a speed of 700 rpm for 14 minutes, the reaction was cooled to room temperature, and the hydrolyzate was obtained by filtering, wherein the mass ratio of the intermediate to deionized water was 3.7:75;

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

[0062] Example 3

[0063] This 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 50 kHz and the ultrasonic power to 700 W, ultrasonicating for 40 minutes until fully dissolved, adjusting the pH to 8 with a 1.0 M sodium hydroxide aqueous solution, adding a functionalized desiliconizer, stirring at a speed of 6000 rpm for 34 minutes, 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 12 hours under a nitrogen atmosphere of 99.999%;

[0065] Step S2, decarburization of pretreated black liquor: placing the pretreated black liquor and nano-titanium dioxide into a high-temperature tube furnace, sealing it, and introducing nitrogen. When the nitrogen fills the tube, the temperature is raised to 855°C at a heating rate of 5°C / min, and distilled water is pumped into it. The temperature is kept at this temperature for 26 minutes. After the reaction is completed, the water vapor supply is stopped, and nitrogen is continued to be introduced 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, the intermediate was added to deionized water, the temperature was raised to reflux, the reaction was stirred at a speed of 750 rpm for 16 minutes, the reaction was cooled to room temperature, and the hydrolyzate was obtained by filtering, wherein the mass ratio of the intermediate to deionized water was 4.6:80;

[0067] Step S4, recycling of the hydrolyzed liquid: the hydrolyzed liquid 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 hydrolyzed solutions 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 speed of 550 rpm for 10 min until uniform, the temperature was raised to 80° C., the speed was maintained constant, 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 the mixture was 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 spectrometry (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) in green liquor obtained without adding silicon remover, W b is the silicon content (ppm) in the hydrolyzate obtained by adding the silicon removal agent;

[0081] 2. Sodium hydroxide content: The analysis method adopted is GB / T 4348.1-2013 "Sodium hydroxide for industrial use - 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 in Examples 1-3 and Comparative Examples 1-4

[0084]

[0085]

[0086] As shown in Table 1, compared with Comparative Examples 1-4, the sodium hydroxide prepared in Example 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 non-creative modifications to the present embodiment as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

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 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; Step S2, decarburization of pretreated black liquor: The pretreated black liquor and nano-titanium dioxide are placed in a high-temperature tube furnace and sealed, and nitrogen is introduced. When the nitrogen fills the pipe, the temperature is increased to 845-855°C at a heating rate of 5°C / min, and distilled water is pumped into the furnace. The temperature is kept at this temperature for 22-26 minutes. After the reaction is completed, the water vapor supply is stopped, and nitrogen is continued to be introduced to obtain an intermediate; Step S3, preparation of hydrolyzate: under nitrogen protection, add the intermediate into deionized water, heat to reflux, stir and react for 12-16 minutes, cool to room temperature, and filter to obtain a hydrolyzate; Step S4, hydrolyzed liquid recycling: the hydrolyzed liquid prepared in step S3 can be recycled again as a cooking agent for alkaline pulping; The functionalized silicon remover is prepared by first modifying magnesium sulfate with KH-570 to obtain modified magnesium sulfate, and then reacting the modified magnesium sulfate with acrylamide, acryloyloxyethyltrimethylammonium chloride and sodium p-styrenesulfonate under the initiation of an initiator through free radical polymerization.

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

034.

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

0.

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

5. sodium hydroxide regeneration cycle method according to claim 1, is characterized in that, 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 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, purging with nitrogen to deoxygenate, and under nitrogen protection, dropwise adding a mixture a containing acrylamide, acryloyloxyethyltrimethylammonium chloride, sodium p-styrenesulfonate, an initiator, and deionized water. The addition is controlled to be complete within 10 minutes, and then adding a mixture b of naphthalene and anhydrous ethanol. The addition is controlled to be complete within 20 minutes. After the addition is completed, stirring and reacting for 5-6 hours, adding hydroquinone, filtering and drying with suction, crushing, and sieving to obtain a functionalized desiliconizer.

6. sodium hydroxide regeneration cycle method according to claim 5, is characterized in that, 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. sodium hydroxide regeneration cycle method according to claim 5, is characterized in that, In 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. In mixed solution a, the mass ratio of acrylamide, acryloyloxyethyltrimethylammonium chloride, sodium p-styrenesulfonate, 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. In mixed solution b, the mass ratio of naphthalene and anhydrous ethanol is 2-3:

10.

8. sodium hydroxide regeneration cycle method according to claim 1, is characterized in that, 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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