Silicon-containing pulping white mud solid waste resource utilization method

Abstract

The invention relates to the related technical field of industrial solid waste resource utilization, in particular to a silicon-containing pulping white mud solid waste resource utilization method which comprises the following specific steps: firstly, washing pulping white mud by using deionized water to remove soluble inorganic salt and the like in the pulping white mud; then adding a proper amount of acetic acid and hydrochloric acid or introducing carbon dioxide into the pulping white mud, and removing silicon in the white mud according to different binding capacities of protons with silicate radicals and carbonate radicals; finally, relatively pure calcium carbonate is obtained through centrifugation or filtration, drying and other procedures, or calcium oxide can be obtained through further calcination at high temperature. According to the silicon-containing pulping white mud solid waste resource utilization method, a large amount of pulping white mud solid waste can be effectively consumed, the problems of resource waste and environmental pollution caused by a traditional pulping white mud treatment method are solved, and the method can be widely applied to the fields of chemical engineering, papermaking, building, environmental protection, food, medicine, fertilizer and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of industrial solid waste resource utilization, and particularly relates to a method for resource utilization of silicon-containing pulping white mud solid waste. BACKGROUND

[0002] As an upstream core link of the papermaking industry, the pulping industry not only provides basic raw materials for the papermaking, printing, packaging, chemical and other industries, but also drives the related downstream industry chain to create more than 100 billion economic value, and has become an indispensable part of the modern industrial system, and has an important strategic position in the national economy. However, in the alkali recovery process of the pulping industry, 0.5-0.65 tons of solid waste white mud will be produced for every ton of paper pulp. According to the data of China Paper Association, the total amount of paper pulp production in China in 2022 was 8587 tons, so the output of white mud was more than 4294 tons. The traditional landfill disposal method of solid waste white mud not only occupies land resources, but also has the environmental risk of heavy metal leachate polluting groundwater. Under the current situation of the state vigorously promoting the resource utilization of solid waste and tightening the environmental protection policy, the resource utilization of white mud is imminent and of great significance.

[0003] The main components of pulping white mud are calcium carbonate and calcium silicate, and it is particularly worth noting that the high silicon content seriously restricts the resource utilization of white mud. For example, in the existing process of preparing light calcium carbonate by calcination, the presence of silicon will cause a significant decrease in the purity of the product, and the prepared calcium carbonate filler will produce "silicon spot" defects when used in paper coating, and will appear a sharp decrease in compressive strength in cement admixture applications. Therefore, the removal of silicon in white mud is the key to the resource utilization of pulping white mud.

[0004] Silicate (SiO3 2- ) and carbonate (CO3 2- ) have significant differences in acidolysis behavior: in an acidic medium, H + preferentially combines with SiO3 2- to form H2SiO3. Therefore, under the condition of using a small amount of acid, H+ preferentially combines with SiO3 2- to form a H2SiO3 colloidal solution, while CO3 2- can still exist in the form of CaCO3. This property provides a theoretical basis for selective desiliconization - by precisely controlling the acidolysis conditions, efficient removal of silicate can be achieved while preserving the calcium carbonate matrix, thereby breaking through the technical bottleneck of high-silicon white mud difficult to high-value utilization. Based on this, the present application provides a method for resource utilization of silicon-containing pulping white mud solid waste. SUMMARY

[0005] The purpose of the present application is to provide a method for resource utilization of silicon-containing pulping white mud solid waste, to solve the problem of high-silicon white mud difficult to high-value utilization in the prior art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a method for resource utilization of silicon-containing pulping white mud solid waste, comprising the following steps:

[0007] Step 1: Removal of soluble inorganic salts: Mix the pulping mud with deionized water at a mass ratio of 1:3-5, mechanically stir for 30-60 minutes, let it stand for 2-4 hours to separate into layers, discard the supernatant, and repeat the washing process 2-3 times to ensure the removal of soluble CI. - Na + Wait until all impurities are completely removed;

[0008] Step 2, Selective Desilication Treatment: Add 0.5%–15% acetic acid or hydrochloric acid to the cleaned white mud, or introduce CO2 gas, and stir continuously for 1–2 hours to remove silicate (SiO3) ions. 2- ) and H + The resulting H2SiO3 colloidal solution is centrifuged or filtered to obtain calcium carbonate precipitate.

[0009] Step 3: Calcium carbonate refining: Dry the precipitate at 105±5℃ until the moisture content is <5% to obtain calcium carbonate with a purity ≥95%;

[0010] Step 4, High-value derivation: Calcium carbonate is calcined at 900-1100℃ for 2-3 hours to obtain calcium oxide, or it is reacted with acetic acid to generate calcium acetate solution, and calcined magnesium oxide in a molar ratio of 1:1 is added. After aging for 24 hours, it is calcined to obtain CaO / MgO composite solid alkali.

[0011] Preferably, in step two, the amount of acid added is based on n(H) + ):n(SiO3 2- The ratio is 2.2 to 3.8:1 (assuming complete acid dissociation) for precise control, or by introducing excess CO2.

[0012] Preferably, in step four, the calcination process employs segmented heating: 5℃ / min before 300℃, 8℃ / min in the 300~900℃ stage, and 3℃ / min above 900℃.

[0013] Preferably, the obtained calcium carbonate product meets the following requirements: silicon residue <1%, whiteness >90%, specific surface area 8-12 m² / g, and is suitable for paper coating.

[0014] Preferably, the pulping sludge is silica-containing sludge produced by a non-wood pulping process.

[0015] Compared with the prior art, the beneficial effects of the present invention are:

[0016] 1. By precisely controlling the acidolysis conditions, H+ preferentially reacts with SiO3. 2-The combined properties achieve a silicon removal rate of >60% while maintaining a calcium retention rate of ≥75%, fundamentally solving the problems of "silicon spots" and strength degradation in the application of high-silica white mud in papermaking, cement and other fields.

[0017] 2. The obtained calcium carbonate can be directly used in high-value-added fields such as paper coating and flue gas desulfurization.

[0018] 3. After removing silicon, the calcium carbonate obtained can be dehydrated to obtain pure calcium carbonate solid. Calcium carbonate can be used directly in industrial production, such as papermaking, or it can be used to produce other calcium-containing industrial raw materials, such as calcium oxide obtained after calcination, which can be used for alkali recovery in the pulping process or industrial desulfurization. Attached Figure Description

[0019] Figure 1 This is a schematic diagram illustrating the preparation of a method for resource utilization of silicon-containing pulping white mud solid waste according to the present invention. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] Please see Figure 1 The present invention provides a technical solution: a method for resource utilization of silicon-containing pulping white mud solid waste, comprising the following steps:

[0022] Step 1: Removal of soluble inorganic salts: Mix the pulping mud with deionized water at a mass ratio of 1:3-5, mechanically stir for 30-60 minutes, let it stand for 2-4 hours to separate into layers, discard the supernatant, and repeat the washing process 2-3 times to ensure the removal of soluble CI. - Na + Wait until all impurities are completely removed;

[0023] Step 2, Selective Desilication Treatment: Add 0.5%–15% acetic acid or hydrochloric acid to the cleaned white mud, or introduce CO2 gas, and stir continuously for 1–2 hours to remove silicate (SiO3) ions. 2- ) and H + The resulting H2SiO3 colloidal solution is centrifuged or filtered to obtain calcium carbonate precipitate.

[0024] Step 3: Calcium carbonate refining: Dry the precipitate at 105±5℃ until the moisture content is <5% to obtain calcium carbonate with a purity ≥95%;

[0025] Step 4, High-value derivation: Calcium carbonate is calcined at 900-1100℃ for 2-3 hours to obtain calcium oxide, or it is reacted with acetic acid to generate calcium acetate solution, and calcined magnesium oxide in a molar ratio of 1:1 is added. After aging for 24 hours, it is calcined to obtain CaO / MgO composite solid alkali.

[0026] Furthermore, in step two, the amount of acid added is calculated according to n(H) + ):n(SiO3 2- The ratio is 2.2 to 3.8:1 (assuming complete acid dissociation) for precise control, or by introducing excess CO2.

[0027] Furthermore, in step four, the calcination process adopts a segmented heating method: 5℃ / min before 300℃, 8℃ / min in the 300~900℃ stage, and 3℃ / min above 900℃.

[0028] Furthermore, the resulting calcium carbonate product meets the requirements of silicon residue <1%, whiteness >90%, and specific surface area of ​​8-12 m² / g, making it suitable for paper coating.

[0029] Furthermore, the pulping sludge is silica-containing sludge produced by a non-wood pulping process.

[0030] Example 1: Place the pulping mud in an excess of water and stir to dissolve the soluble impurities in the mud. Then let the washed mud stand until it separates into layers. Remove the supernatant of the solution. Add an appropriate amount of dilute acetic acid or hydrochloric acid (or introduce carbon dioxide) to the washed pulping mud and mix well. Then let it stand and separate into layers. Separate the supernatant and precipitate, remove the silicon, filter and dry the precipitate to obtain relatively pure calcium carbonate solid.

[0031] Calcium carbonate is a widely used industrial raw material with applications in multiple fields, such as the building materials industry to improve material performance; the paper industry to improve paper whiteness, smoothness, and opacity; agriculture to improve soil quality and fertilizer nutrients; and the environmental protection and energy industries to remove sulfur from flue gas and participate in carbon capture and storage.

[0032] Example 2: Place the pulping mud in an excess of water and stir to dissolve the soluble impurities in the mud. Then, let the washed mud stand until it separates into layers. Remove the supernatant of the solution. Add an appropriate amount of dilute acetic acid or hydrochloric acid (or introduce carbon dioxide) to the washed pulping mud and mix well. Then, let it stand and separate into layers. Separate the supernatant and precipitate, remove the silicon, filter and dry the precipitate, and finally calcine it in a muffle furnace to obtain solid calcium oxide.

[0033] Calcium oxide is hygroscopic, strongly alkaline, and highly reactive, and is widely used in many industries, such as pulping to regenerate alkali (NaOH), reduce production costs, and enable the recycling of calcium oxide; construction to improve foundation strength and water resistance; metallurgy to lower the melting point of ores in steelmaking and ironmaking; chemical industry as a raw material for various experiments; and food industry as a desiccant and purifying agent.

[0034] Example 3: The pulping mud was placed in an excess of water and stirred to dissolve the soluble impurities in the mud. The washed mud was then allowed to stand until it separated into layers. The supernatant of the solution was removed. An appropriate amount of dilute acetic acid was added to the washed pulping mud and mixed evenly. After standing and separating into layers, the supernatant and precipitate were separated to remove the silicon. An appropriate amount of dilute acetic acid was added to obtain a calcium acetate solution. Calcined magnesium oxide was added, stirred and aged, and finally dried and calcined to obtain a CaO / MgO solid alkali.

[0035] Solid alkalis are widely used in many fields, especially in the chemical industry. Common types of solid alkalis include elemental solid alkalis, composite solid alkalis, supported solid alkalis, and molecular sieve solid alkalis. They can be used in biomass and renewable energy conversion, organic chemical reaction catalysis, environmental protection and waste treatment, petroleum refining and heavy oil processing, chemical and building materials production, and many other aspects.

[0036] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for the resource utilization of silicon-containing pulping white mud solid waste, characterized in that, Includes the following steps: Step 1: Removal of soluble inorganic salts: Mix the pulping mud with deionized water at a mass ratio of 1:3-5, mechanically stir for 30-60 minutes, let it stand for 2-4 hours to separate into layers, discard the supernatant, and repeat the washing process 2-3 times to ensure the removal of soluble CI. - Na + Wait until all impurities are completely removed; Step 2, Selective Desilication Treatment: Add 0.5%–15% acetic acid or hydrochloric acid to the cleaned white mud, or introduce CO2 gas, and stir continuously for 1–2 hours to remove silicate (SiO3) ions. 2- ) and H + The resulting H2SiO3 colloidal solution is centrifuged or filtered to obtain calcium carbonate precipitate. Step 3: Calcium carbonate refining: Dry the precipitate at 105±5℃ until the moisture content is <5% to obtain calcium carbonate with a purity ≥95%; Step 4, High-value derivation: Calcium carbonate is calcined at 900-1100℃ for 2-3 hours to obtain calcium oxide, or it is reacted with acetic acid to generate calcium acetate solution, and calcined magnesium oxide in a molar ratio of 1:1 is added. After aging for 24 hours, it is calcined to obtain CaO / MgO composite solid alkali.

2. The method for resource utilization of silicon-containing pulping white mud solid waste according to claim 1, characterized in that, In step two, the amount of acid added is calculated according to n(H). + ):n(SiO3 2- The ratio is 2.2 to 3.8:1 (assuming complete acid dissociation) for precise control, or by introducing excess CO2.

3. The method for resource utilization of silicon-containing pulping white mud solid waste according to claim 1, characterized in that, In step four, the calcination process adopts a segmented heating method: 5℃ / min before 300℃, 8℃ / min in the 300~900℃ stage, and 3℃ / min above 900℃.

4. The method for resource utilization of silicon-containing pulping white mud solid waste according to claim 1, characterized in that, The resulting calcium carbonate product meets the requirements of silicon residue <1%, whiteness >90%, and specific surface area 8-12 m² / g, making it suitable for paper coating.

5. The method for resource utilization of silicon-containing pulping white mud solid waste according to claim 1, characterized in that, The pulping sludge is silica-containing sludge produced by a non-wood pulping process.

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