Preparation method and application of lignin

Abstract

The invention discloses a preparation method and application of lignin, and relates to the technical field of preparation of natural organic compounds. The preparation method comprises the following steps: mixing a plant raw material containing lignin with a solution containing sulfurous acid and / or sulfite, reacting at the temperature of 100-180 DEG C under the pressure of 0.4-0.8 MPa, and performing solid-liquid separation to obtain lignin filtrate. The lignin and cellulose obtained through the preparation method are easy to separate, the lignin content in the lignin filtrate is high, the lignin filtrate is applied to zinc smelting oxygen pressure leaching, commercially available lignin can be completely replaced, the proportion of flotation tailings cannot be increased, sulfur recovery is more facilitated, and the TOC content and the chloride ion content of the oxygen pressure leaching liquid can be reduced.

Description

Technical Field

[0001] The invention relates to the technical field of natural organic compound preparation, and in particular to a preparation method of lignin and application thereof. Background Art

[0002] The oxygen pressure leaching process for hydrometallurgical zinc smelting requires the use of lignin as a dispersant to prevent sulfur wrapping, but the quality of lignin on the market varies greatly, and it is not targeted and has poor adaptability to the oxygen pressure leaching process for zinc smelting. In addition, the lignin prepared from high-chlorine plants such as corn cobs has a high chlorine content. After oxygen pressure leaching, the organic matter (TOC) and chloride ion content of the leachate are high, which affects the quality of the zinc flakes. For example, the lignin prepared from corn cob raw materials contains 2-5% chlorine, which is difficult to remove or the cost of removal is high after entering the hydrometallurgical zinc smelting system, affecting the quality of the electrolytic zinc flakes.

[0003] In order to ensure the source and quality of lignin raw materials and avoid large fluctuations in the quality of zinc flakes, the sulfite alkaline method is currently commonly used in the industry to prepare lignin for oxygen pressure leaching of wet zinc smelting. The preparation conditions are generally 85-90°C at normal pressure. The lignin obtained by this method is used for oxygen pressure leaching of zinc smelting. The TOC and chloride ion contents show a downward trend, and the zinc leaching rate is relatively high. However, the lignin content in the obtained lignin filtrate is generally 8-15g / L, which is low. A large addition volume is required when using it. According to the calculation of the unit consumption of zinc concentrate for oxygen pressure leaching of lignin, the lignin content of the lignin filtrate prepared every day is calculated at an average of 10g / L, and about 140m 3 Lignin filtrate, therefore, can only partially replace commercially available lignin in the two-stage zinc oxygen pressure leaching process. At the same time, in the process of separating lignin and cellulose prepared by the sulfite alkaline method, the pulping is serious, the filter pressing is difficult during the production process, and the cellulose and lignin are difficult to separate. The filtrate brings in a large amount of cellulose. It is used for zinc smelting oxygen pressure leaching. The weight distribution ratio of the two-stage underflow flotation concentrate and tailings of the leached slag is generally (60% to 70%): (30% to 40%), while the weight distribution ratio of the flotation concentrate and tailings of the normal commercially available lignin is (80% to 90%): (10% to 20%). It can be seen that the existing sulfite alkaline method used in wet zinc smelting oxygen pressure leaching will cause a decrease in flotation sulfur concentrate and an increase in tailings, and cannot completely replace commercially available lignin for zinc smelting oxygen pressure leaching. Summary of the invention

[0004] The present invention aims to solve at least one of the above-mentioned technical problems existing in the prior art. To this end, the purpose of the present invention is to provide a method for preparing lignin, which uses a sulfite process to prepare lignin, and the obtained lignin filtrate has a high lignin content, which can completely replace commercially available lignin for zinc smelting oxygen pressure leaching.

[0005] The second aspect of the present invention is to provide a method for preparing lignin and its application in oxygen pressure leaching in zinc smelting.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] A first aspect of the present invention provides a method for preparing lignin, comprising the following steps:

[0008] The plant raw material containing lignin is mixed with a solution containing sulfurous acid and / or sulfite, reacted at a temperature of 100 to 180° C. and a pressure of 0.4 to 0.8 MPa, and then the solid and liquid are separated to obtain a lignin filtrate.

[0009] The preparation method of the invention belongs to the sulfite method, wherein the plant raw material is subjected to high-temperature and low-pressure leaching at a specific temperature and pressure, and then the lignin and cellulose are separated by solid-liquid separation, and the obtained lignin filtrate has a high lignin content, which can solve the problems of increased flotation tailings and difficult sulfur recovery caused by the low lignin content in the lignin filtrate prepared by the traditional sulfite alkaline method, and overcomes the defect that the lignin prepared by the sulfite alkaline method cannot completely replace the commercially available lignin for oxygen pressure leaching of zinc smelting.

[0010] In some embodiments of the present invention, the plant raw material containing lignin includes at least one of bagasse, sugarcane, bamboo chips, rice husks, and sawdust.

[0011] The raw materials for preparation are widely available, and the surrounding plant resources can be directly utilized to reduce production costs.

[0012] In some embodiments of the present invention, the plant raw material is crushed and ground; the particle size of the plant raw material powder obtained by grinding is 1 to 2 mm.

[0013] In some embodiments of the present invention, the mass ratio of the plant raw material to the solution containing sulfurous acid and / or sulfite is 1:10-20.

[0014] In some embodiments of the present invention, the reaction time is 4 to 8 hours.

[0015] In some embodiments of the present invention, the reaction time is 4 to 6 hours.

[0016] In some embodiments of the present invention, the sulfite includes calcium sulfite; the sulfurous acid and / or calcium sulfite are obtained by reacting calcium hydroxide with sulfur dioxide.

[0017] In some embodiments of the present invention, the calcium hydroxide is lime water, and the sulfurous acid and calcium sulfite are obtained by reacting lime water with sulfur dioxide.

[0018] Specifically, the reaction process of lime water and sulfur dioxide is actually the absorption of sulfur dioxide by lime water and its conversion into sulfite or sulfurous acid.

[0019] In some specific embodiments of the present invention, the initial pH of the reaction of lime water and sulfur dioxide is 12-13.

[0020] In some embodiments of the present invention, the sulfur dioxide is sulfur dioxide gas produced by a workshop for preparing sulfuric acid after washing, or sulfur dioxide gas produced by the combustion of sulfur and oxygen.

[0021] In some embodiments of the present invention, the pH of the solution containing sulfurous acid and / or sulfite is 1-2.

[0022] In some embodiments of the present invention, the solid-liquid separation time is 0.1 to 0.5 h; the solid-liquid separation obtains a filter residue including cellulose and the lignin filtrate.

[0023] The time required for the solid-liquid separation of the present invention is shorter, that is, the solid-liquid separation speed is fast, which reflects that in the preparation method of the present invention, the separation of cellulose and lignin is easier, and the problem of the difficulty in separating cellulose and lignin in the traditional sulfite alkaline method can be solved.

[0024] In some embodiments of the present invention, the solid-liquid separation method includes filter pressing.

[0025] Specifically, the solid-liquid separation is carried out in a filter press.

[0026] In some embodiments of the present invention, the solid-liquid separation is preceded by a pressure relief and temperature reduction process, and after the reaction, the pressure is relieved to normal pressure and the temperature is reduced to below 100°C.

[0027] In some embodiments of the present invention, the pressure relief and temperature reduction are performed in a flash tank.

[0028] In some embodiments of the present invention, the acidic water vapor and tail gas generated during the pressure relief, temperature reduction and solid-liquid separation process are absorbed by circulating water, and the circulating water that absorbs the acidic water vapor and tail gas is used for the preparation of sulfurous acid and / or sulfite solution.

[0029] In some embodiments of the present invention, the mixing process of the plant material containing lignin and the solution containing sulfurous acid and / or sulfite is carried out in a pulping tank. This process is actually a pulping process.

[0030] In some embodiments of the present invention, the content of lignin in the lignin filtrate is 30-50 g / L.

[0031] In some specific embodiments of the present invention, the content of lignin in the lignin filtrate is 35-50 g / L.

[0032] The second aspect of the present invention provides an application of the lignin filtrate prepared by the preparation method described in the first aspect of the present invention in oxygen pressure leaching in zinc smelting.

[0033] In some embodiments of the present invention, based on the mass of zinc concentrate, the amount of the lignin filtrate is 60 to 100 L / ton of zinc concentrate.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] The preparation method of lignin provided by the present invention adopts a sulfurous acid method to leaching at high temperature and low pressure to prepare lignin. The raw materials in the preparation process are plant raw materials, which have a wide source and low cost. The preparation method of the present invention is used to easily separate lignin and cellulose during the solid-liquid separation process, and the obtained lignin filtrate has a high lignin content, which can completely replace commercially available lignin for use in zinc smelting oxygen pressure leaching.

[0036] The lignin filtrate prepared by the present invention is applied to oxygen pressure leaching in zinc smelting. Compared with lignin prepared by sulfite alkaline method, it does not cause an increase in the proportion of flotation tailings. The mass ratio of flotation concentrate to flotation tailings is in the range of (80-90): (10-20), which is more favorable for sulfur recovery. Moreover, compared with commercially available lignin, the TOC content and chloride ion content of the oxygen pressure leaching solution can be reduced. The TOC content is reduced from 100-140 mg / L to 70-90 mg / L, and the chloride ion content is reduced by 20-50 tons / year. In addition, the leaching rate of zinc in oxygen pressure leaching is high, not less than 97%. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 Schematic diagram of the process flow of an embodiment of the present invention.

[0038] right Figure 1 The annotations in are as follows:

[0039] S1-raw material preparation; S2-plant raw material crushing and pulping; S3-leaching reaction; S4-pressure relief and cooling; S5-solid-liquid separation; S6-lignin filtrate; S7-cellulose; S8-sulfur dioxide preparation; S9-sulfur dioxide absorption; S10-sulfurous acid and calcium sulfite transportation; S11-flue gas washing. DETAILED DESCRIPTION

[0040] The present invention is further described in detail below by specific examples. Unless otherwise specified, the raw materials, reagents or devices used in the examples and comparative examples can be obtained from conventional commercial sources or can be obtained by prior art methods. Unless otherwise specified, the experiments or test methods are conventional methods in the art.

[0041] The plant raw materials used in the following examples and comparative examples of the present invention are conventional bagasse, bamboo chips, rice husks, and wood chips.

[0042] The process flow of the following embodiments of the present invention is as shown in the attached drawings. Figure 1 As shown, the specific steps include:

[0043] S1. Raw material preparation: low-sugar raw materials such as bamboo chips, rice husks, and sawdust with a particle size of 1 to 5 cm are stored for 1 to 3 months and transported to the crushing silo by a conveyor belt or a transport tool; the rice husks, sawdust, bamboo chips and other low-sugar raw materials are naturally fermented and partially decomposed during the storage process, which can soften the cellulose and reduce the intensity of subsequent chemical treatment;

[0044] S2. Crushing and pulping of plant raw materials: crushing the plant block materials with a crusher, including crushing and grinding, and sieving the plant raw material powder to a particle size of 1 to 2 mm, and using a conveyor belt or a transfer tool to transfer the plant raw material powder to the pulping silo; the plant raw material powder is fed from the silo into a closed pulping tank by a spiral feeder for pulping, and the mass ratio of the plant raw material to the mixed solution of sulfurous acid and calcium sulfite during the pulping process is 1:10 to 20;

[0045] S3 leaching reaction: The slurry in step S3 is pumped into the reactor by a metering centrifugal pump for continuous leaching at a reaction temperature of 100 to 180 ° C and a pressure of 0.4 to 0.6 MPa for 4 to 6 hours, and then discharged into the filter press in step S5 through a discharge pipe;

[0046] S4. Depressurization and cooling: depressurize and cool the lignin slurry in the lignin reactor to a temperature of ≤100°C and a pressure drop to normal pressure;

[0047] S5. Solid-liquid separation: The filter press presses the lignin slurry in the flash tank to separate the S6 lignin filtrate, which is transported to oxygen pressure leaching to replace the purchased lignin, and the separated S7 cellulose, the remaining lignin is washed and sold to papermaking companies;

[0048] In step S2, the step of preparing the mixed solution of sulfurous acid and calcium sulfite includes the following steps S8 to S10:

[0049] S8. Sulfur dioxide preparation: sulfur dioxide flue gas from the sulfuric acid production workshop after washing or sulfur dioxide flue gas produced by burning sulfur and oxygen;

[0050] S9. Sulfur dioxide absorption: Use lime water spray device to absorb sulfur dioxide in the tower. When the pH of lime water is reduced from 12 to 13 to pH 1.5 to 2.0, the sulfurous acid and calcium sulfite mixture is prepared and sent to the closed storage tank of sulfurous acid and calcium sulfite mixture;

[0051] S10 sulfurous acid, calcium sulfite transport: the prepared calcium sulfite, sulfurous acid mixed solution is pumped into the pulping tank in step S3, and mixed with the crushed, ground plant material as a slurry for preparing lignin;

[0052] S11. Flue gas washing: The acidic water vapor and tail gas generated in step S4, step S5 and step S10 are absorbed in a washing tower using circulating water, and the circulating water can be used as supplementary water for the sulfur dioxide absorption process.

[0053] It should be noted that S1 to S11 do not represent an inherent order of these steps. For example, the preparation of sulfur dioxide in S8 and the crushing of plant raw materials in S2 can actually be carried out simultaneously.

[0054] The following is explained in conjunction with specific embodiments and comparative examples, and S1 to S11 of the embodiments will not be repeated in detail. Among them, the temperature and pressure in the preparation process are range values, and the pressure is the vapor pressure. The pressure can be adjusted by adjusting the temperature of cooling water or by exhausting gas during the process, so the temperature and pressure are range values. The amount of sulfurous acid and calcium sulfite mixed solution is also a range value, because this value needs to be adjusted according to the fluidity of the slurry after the plant powder is added to avoid clogging of the pipeline by the slurry.

[0055] The plant raw materials have a uniform particle size because they have been crushed into the required particle size before use. It should be understood that the particle size here is not a limitation of the preparation method of the present invention, but one of the implementation methods.

[0056] The lignin content was determined by the potassium dichromate method.

[0057] Example 1

[0058] This embodiment provides a method for preparing lignin, which adopts a sulfite method to prepare lignin, including steps S1 to S11. The specific parameters of this embodiment are as follows:

[0059] The particle size of the bagasse raw material is 2-5 cm, and after crushing and grinding, the bagasse powder with a particle size of 1-2 mm is obtained, and the dosage is 100 g; sulfur reacts with oxygen after combustion to generate SO2, which is absorbed by lime water to prepare a mixed solution of sulfurous acid and calcium sulfite, and when the pH value of the solution is 1.5-2, the mixed solution of sulfurous acid and calcium sulfite is prepared; the bagasse powder is mixed with 1000-2000 mg of the mixed solution to form a slurry, and the mixture is reacted at a temperature of 140-160° C. and a pressure of 0.4-0.6 MPa for 4 hours, and the mixture is cooled to below 100° C. after the reaction is completed, and the pressure is reduced to normal pressure at the same time; in the solid-liquid separation, cellulose and lignin are separated for 0.1-0.5 hours, and the lignin content in the obtained lignin filtrate is 44.86 g / L.

[0060] Application Example 1

[0061] This application example uses the lignin prepared in Example 1 for zinc smelting oxygen pressure leaching, including the following steps:

[0062] The lignin filtrate prepared in Example 1 was used to carry out an oxygen pressure leaching experiment of zinc concentrate, with a temperature of 145-155° C., 300 g of zinc concentrate (Zn mass content 48.52%), a pressure of 1.4-1.5 MPa, a lignin consumption of 4 kg / ton of zinc concentrate, a leaching slag containing 2.85% zinc, and a zinc leaching rate of 97.85%. The weight distribution ratio of the leaching slag flotation concentrate and tailings was 88.75:11.22, and the flotation ore sulfur foam layer was 10-20 cm.

[0063] Example 2

[0064] This embodiment provides a method for preparing lignin, which adopts a sulfite method to prepare lignin, including steps S1 to S11. The specific parameters of this embodiment are as follows:

[0065] The bamboo chips raw material has a particle size of 2 to 5 cm, and after being crushed and ground, the bamboo chips powder with a particle size of 1 to 2 mm is used in an amount of 100 g; sulfur reacts with oxygen after combustion to generate SO2, which is absorbed by lime water to prepare a mixed solution of sulfurous acid and calcium sulfite, and when the pH value of the solution is 1.5 to 2, the mixed solution of sulfurous acid and calcium sulfite is prepared; the bamboo chips powder is mixed with 1000 to 2000 mg of the mixed solution to form a slurry, and the mixture is reacted for 4 hours at a temperature of 140 to 160 DEG C and a pressure of 0.4 to 0.6 MPa, and after the reaction is completed, the mixture is cooled to below 100 DEG C, and the pressure is reduced to normal pressure; in the solid-liquid separation, cellulose and lignin are separated for 0.1 to 0.5 hours, and the lignin content in the obtained lignin filtrate is 49.1 g / L.

[0066] Application Example 2

[0067] This application example uses the lignin prepared in Example 2 for zinc smelting oxygen pressure leaching, including the following steps:

[0068] The lignin filtrate prepared in Example 2 was used to carry out an oxygen pressure leaching experiment of zinc concentrate, with a temperature of 145-155° C., 300 g of zinc concentrate (Zn mass content 48.52%), a pressure of 1.4-1.5 MPa, a lignin consumption of 4 kg / ton of zinc concentrate, a leaching slag containing 2.72% zinc, and a zinc leaching rate of 97.98%; the weight distribution ratio of the leaching slag flotation concentrate and tailings was 86.19:13.81, and the flotation ore sulfur foam layer was 5-10 cm.

[0069] Example 3

[0070] This embodiment provides a method for preparing lignin, which adopts a sulfite method to prepare lignin, including steps S1 to S11. The specific parameters of this embodiment are as follows:

[0071] This embodiment provides a method for preparing lignin, which adopts a sulfite method to prepare lignin, including steps S1 to S11. The specific parameters of this embodiment are as follows:

[0072] The husk raw material has a particle size of 2 to 5 cm, and after being crushed and ground, it becomes husk powder with a particle size of 1 to 2 mm, and the dosage is 100 g; sulfur reacts with oxygen after combustion to generate SO2, which is absorbed by lime water to prepare a mixed solution of sulfurous acid and calcium sulfite, and when the pH value of the solution is 1.5 to 2, the mixed solution of sulfurous acid and calcium sulfite is prepared; the husk powder is mixed with 1000 to 2000 mg of the mixed solution to form a slurry, and the mixture is reacted for 4 hours at a temperature of 140 to 160 DEG C and a pressure of 0.4 to 0.6 MPa, and after the reaction is completed, the mixture is cooled to below 100 DEG C, and the pressure is reduced to normal pressure; in the solid-liquid separation, cellulose and lignin are separated for 0.1 to 0.5 hours, and the lignin content in the obtained lignin filtrate is 45.39 g / L.

[0073] Application Example 3

[0074] This application example uses the lignin prepared in Example 3 for oxygen pressure leaching in zinc smelting, including the following steps:

[0075] The lignin filtrate prepared in Example 3 was used to carry out an oxygen pressure leaching experiment of zinc concentrate, with a temperature of 145-155° C., 300 g of zinc concentrate (Zn mass content 48.52%), a pressure of 1.4-1.5 MPa, a lignin consumption of 4 kg / ton of zinc concentrate, a leaching slag containing 3.10% zinc, and a zinc leaching rate of 97.75%. The weight distribution ratio of the leaching slag flotation concentrate and tailings was 88.31:11.69, and the flotation ore sulfur foam layer was 5-10 cm.

[0076] Example 4

[0077] This embodiment provides a method for preparing lignin, which adopts a sulfite method to prepare lignin, including steps S1 to S11. The specific parameters of this embodiment are as follows:

[0078] The particle size of the sawdust raw material is 2-5 cm, and after crushing and grinding, it becomes sawdust powder with a particle size of 1-2 mm, and the dosage is 100g; sulfur reacts with oxygen after combustion to generate SO2, which is absorbed by lime water to prepare a mixed solution of sulfurous acid and calcium sulfite, and when the pH value of the solution is 1.5-2, the mixed solution of sulfurous acid and calcium sulfite is prepared; the sawdust powder is mixed with 1000-2000 mg of the mixed solution to form a slurry, and the mixture is reacted at a temperature of 140-160° C. and a pressure of 0.4-0.6 MPa for 4 hours, and after the reaction is completed, the mixture is cooled to below 100° C., and the pressure is reduced to normal pressure; in the solid-liquid separation, cellulose and lignin are separated for 0.1-0.5 hours, and the lignin content in the obtained lignin filtrate is 36.8g / L.

[0079] Application Example 4

[0080] This application example uses the lignin prepared in Example 4 for zinc smelting oxygen pressure leaching, including the following steps:

[0081] The lignin filtrate prepared in Example 4 was used to carry out an oxygen pressure leaching experiment of zinc concentrate, with a temperature of 145-155° C., 300 g of zinc concentrate (Zn mass content 48.52%), a pressure of 1.4-1.5 MPa, a lignin consumption of 4 kg / ton of zinc concentrate, a leaching slag containing 3.19% zinc, and a zinc leaching rate of 97.52%. The weight distribution ratio of the leaching slag flotation concentrate and tailings was 85.21:14.79, and the flotation ore sulfur foam layer was 5-10 cm.

[0082] Example 5

[0083] This embodiment provides a method for preparing lignin, which adopts a sulfite method to prepare lignin, including steps S1 to S11, but not including a grinding step. The specific parameters of this embodiment are as follows:

[0084] The particle size of the bagasse raw material is 2-5 cm, and the amount is 100 g without grinding; sulfur and oxygen react to generate SO2 after combustion, and lime water is used to absorb and prepare a mixed solution of sulfurous acid and calcium sulfite. When the pH value of the solution is 1.5-2, the mixed solution of sulfurous acid and calcium sulfite is prepared; bagasse is mixed with 1000-2000 mg of the mixed solution to form a slurry, and the mixture is reacted for 4 hours at a temperature of 140-160° C. and a pressure of 0.4-0.6 MPa. After the reaction is completed, the mixture is cooled to below 100° C. and the pressure is reduced to normal pressure; cellulose and lignin are separated for 0.1-0.5 hours in solid-liquid separation, and the lignin content in the obtained lignin filtrate is 46.8 g / L.

[0085] Example 6

[0086] This embodiment provides a method for preparing lignin, which adopts a sulfite method to prepare lignin, including steps S1 to S11, but excluding a crushing step. The specific parameters of this embodiment are as follows:

[0087] The bamboo chips raw material has a particle size of 2 to 5 cm and is used in an amount of 100 g without being ground; sulfur reacts with oxygen after combustion to generate SO2, which is absorbed by lime water to prepare a mixed solution of sulfurous acid and calcium sulfite, and when the pH value of the solution is 1.5 to 2, the mixed solution of sulfurous acid and calcium sulfite is prepared; bamboo chips powder is mixed with 1000 to 2000 mg of the mixed solution to form a slurry, and the mixture is reacted for 4 hours at a temperature of 140 to 160° C. and a pressure of 0.4 to 0.6 MPa, and after the reaction is completed, the mixture is cooled to below 100° C. and the pressure is reduced to normal pressure; cellulose and lignin are separated for 0.1 to 0.5 hours in solid-liquid separation, and the lignin content in the obtained lignin filtrate is 47.6 g / L.

[0088] The preparation conditions of the lignin in the above Examples 1 to 6 and the lignin content in the lignin filtrate are summarized in Table 1 below.

[0089] Table 1 Preparation conditions of Examples 1 to 6 and lignin content in lignin filtrate

[0090]

[0091]

[0092] The lignin content of Examples 5 and 6 is comparable to that of Examples 1 to 4, but since the plant raw materials are not ground, the slurry is prone to block the pipeline during the preparation process.

[0093] Comparative Example 1

[0094] This comparative example provides a method for preparing lignin, which is the same as Example 1, except that:

[0095] The bagasse size is 2 to 5 cm and is not ground; the reaction temperature with the mixed solution of sulfurous acid and sulfite is 85 to 95° C., the pressure is normal pressure, and the reaction time is 4 hours; the lignin content in the lignin filtrate is 9.38 g / L.

[0096] Comparative Example 2

[0097] This comparative example provides a method for preparing lignin, which is the same as comparative example 1, except that:

[0098] The sugarcane bagasse was replaced with bamboo chips; the lignin content in the lignin filtrate was 8.37 g / L.

[0099] Comparative Example 3

[0100] This comparative example provides a method for preparing lignin, which adopts a sulfite alkaline method to prepare lignin, comprising the following steps:

[0101] The sugarcane bagasse is 2 to 5 cm in diameter and has a particle size of 1 to 2 mm after grinding, and the dosage is 100 g; 20 g of sodium sulfite and 20 g of lime are added to 1000 to 2000 mg of water to form a mixed solution, and the ground sugarcane bagasse is reacted with the mixed solution at a temperature of 140 to 160° C., a pressure of 0.4 to 0.6 MPa, and a time of 4 hours. After the reaction is completed, cellulose and lignin are separated for 4 to 8 hours during the solid-liquid separation process, and the lignin filtrate content is 9.24 g / L.

[0102] The grinding equipment, reaction equipment and solid-liquid separation equipment used in this comparative example are the same as those in Example 1.

[0103] Comparative application example 1

[0104] Comparative Application Example 1: The lignin prepared in Comparative Example 3 is used in zinc smelting oxygen pressure leaching, and the specific steps are as follows:

[0105] The lignin filtrate prepared in Comparative Example 3 was used to carry out an oxygen pressure leaching experiment of zinc concentrate, with a temperature of 145-155° C., 300 g of zinc concentrate (Zn mass content 50.32%), a pressure of 1.4-1.5 MPa, a lignin consumption of 4 kg / ton of zinc concentrate, 3.39% zinc in the leaching slag, and a zinc leaching rate of 97.57%; the weight distribution ratio of the leaching slag flotation concentrate and tailings was 83.26:16.74, and the flotation ore sulfur foam layer was 10-20 cm.

[0106] Comparative Examples 4 to 18

[0107] Comparative Examples 4 to 18 provide a method for preparing lignin, wherein the lignin is prepared by a sulfite alkaline method, and the steps are the same as those of Comparative Example 3, and the differences are shown in Table 2.

[0108] Among them, in Comparative Examples 7 to 18, the amount of plant raw material used is 50 g, sodium sulfite 10 g, lime 10 g, and water 1000 mL.

[0109] Comparative Application Examples 2 to 12

[0110] Comparative Application Examples 2 to 12 respectively use the lignin prepared in Comparative Examples 4 to 14 for oxygen pressure leaching in zinc smelting. The specific steps are the same as those in Comparative Application Example 1, except that the mass content of zinc in the zinc concentrate is different, see Table 3 for details; the differences in the leaching effects are shown in Table 4.

[0111] Table 2 Preparation conditions of comparative examples 1 to 18 and lignin content in lignin filtrate

[0112]

[0113] Combining the above Table 1 and Table 2, we can see that:

[0114] In the lignin filtrate obtained by the sulfite method at high temperature and low pressure leaching of the present invention, the lignin content is not less than 35 g / L. Although the sulfite method is used in Comparative Examples 1 and 2, the reaction temperature is low and the reaction is carried out at normal pressure. The lignin content in the obtained lignin filtrate does not exceed 10 g / L. The lignin content is low and it cannot completely replace the commercially available lignin for zinc smelting oxygen pressure leaching in production.

[0115] Comparative Examples 3 to 18 are all traditional sulfite alkaline methods. Whether it is conventional atmospheric pressure leaching or high temperature and low pressure leaching in the embodiment, the lignin content in the obtained lignin filtrate does not exceed 22 g / L, and the time required for its solid-liquid separation is longer, that is, the separation process of cellulose and lignin is difficult. At the same time, in the unseparated mixed solution, the lignin content is only in the range of 10 to 22 g / L. Obviously, the traditional sulfite alkaline method is poor for preparing lignin, and the lignin content is low. It is applied to zinc smelting oxygen pressure leaching. Because the required added volume is larger, it can only replace part of the commercially available lignin.

[0116] The following is a summary of the mass content of zinc in the zinc concentrates and the oxygen pressure leaching effects of zinc smelting in Examples 1 to 4 and Comparative Application Examples 1 to 12, as shown in Tables 3 and 4.

[0117] Table 3 Mass content of zinc in zinc concentrate of application examples 1 to 4 and comparative application examples 1 to 12

[0118]

[0119] Table 4 Zinc smelting oxygen pressure leaching effect of application examples 1 to 4 and comparative application examples 1 to 12

[0120]

[0121]

[0122] Wherein, zinc leaching rate = (zinc mass content - slag rate × slag zinc content) / (zinc mass content);

[0123] Slag rate = dry weight of slag after oxygen pressure leaching / weight of zinc concentrate;

[0124] The method for detecting zinc content in slag is: dissolving with aqua regia, EDTA titration and measuring with energy spectrometer.

[0125] Combining Table 1, Table 2 and Table 4, it can be seen that the lignin prepared by the sulfite method of the present invention is used in zinc smelting oxygen pressure leaching, the zinc leaching rate is high, the leaching residue is subjected to two-stage underflow sulfur flotation, and the ratio of flotation concentrate to tailings is 80-90:10-20. In the comparative example, if solid-liquid separation is performed, the separation is difficult, and the lignin content in the obtained lignin filtrate is only about 10g / L. Although the ratio of flotation concentrate to tailings is also in the range of 80-90:10-20, it cannot be used to replace commercially available lignin; if solid-liquid separation is not performed, although the lignin content is increased, when it is in the range of 15-22g / L, the tailings increase in the corresponding comparative application examples 5-8, and it cannot be used to replace commercially available lignin.

[0126] In addition, for Application Example 1, the TOC content and chloride ion content of the oxygen pressure leaching solution were compared with those of conventional commercially available lignin when used in zinc smelting oxygen pressure leaching. It was found that compared with the commercially available lignin, the TOC content of Application Example 1 was reduced from 100-140 mg / L to 70-90 mg / L, and the chloride ion content was reduced by 20-50 tons / year.

[0127] In summary, the preparation method of lignin provided by the present invention adopts the sulfite method to leach lignin at high temperature and low pressure, the raw material source is wide, the cost is low, the obtained lignin is easy to separate from cellulose, the solid-liquid separation is fast, and the lignin content in the lignin filtrate is high. It is applied to zinc smelting oxygen pressure leaching, which can not only completely replace the commercially available lignin, but also will not cause an increase in the proportion of flotation tailings, which is more beneficial for sulfur recovery, and can reduce the TOC content and chloride ion content of the oxygen pressure leaching solution.

[0128] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A method for preparing lignin, characterized in that: The steps include: The plant raw material containing lignin is mixed with a solution containing sulfurous acid and / or sulfite, reacted at a temperature of 100 to 180° C. and a pressure of 0.4 to 0.8 MPa, and then the solid and liquid are separated to obtain a lignin filtrate.

2. The preparation method according to claim 1, characterized in that: The plant raw material containing lignin includes at least one of bagasse, sugarcane, bamboo chips, rice husks, and sawdust; And / or, the plant raw material is crushed and ground; the particle size of the plant raw material powder obtained by grinding is 1 to 2 mm.

3. The preparation method according to claim 1 or 2, characterized in that: The mass ratio of the plant raw material to the solution containing sulfurous acid and / or sulfite is 1:10-20.

4. The preparation method according to claim 1, characterized in that: The reaction time is 4 to 8 hours.

5. The preparation method according to claim 1, characterized in that: The sulfite includes calcium sulfite; the sulfurous acid and / or calcium sulfite is obtained by reacting calcium hydroxide with sulfur dioxide.

6. The preparation method according to claim 1 or 5, characterized in that: The pH of the solution containing sulfurous acid and / or sulfite is 1-2.

7. The preparation method according to claim 1, characterized in that: The solid-liquid separation time is 0.1 to 0.5 hours; the solid-liquid separation obtains filter residues including cellulose and the lignin filtrate.

8. The preparation method according to claim 1, characterized in that: The content of lignin in the lignin filtrate is 30-50 g / L.

9. Use of the lignin filtrate prepared by the preparation method according to any one of claims 1 to 8 in oxygen pressure leaching for zinc smelting.

10. The use according to claim 9, characterized in that: Calculated based on the mass of zinc concentrate, the dosage of the lignin filtrate is 60-100 L / ton of zinc concentrate.

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