Method for preparing high-purity nano calcium carbonate and nutrient soil by utilizing coal ash and biomass ash to synergistically mineralize CO2

Abstract

The invention relates to a method for preparing high-purity nano calcium carbonate and nutrient soil by utilizing coal ash and biomass ash to synergistically mineralize CO2, which comprises the following steps: adding a prepared succinimide composite solution and coal ash into a leaching reaction kettle to carry out Ca < 2 + > leaching reaction, and then filtering and separating coal ash leaching residues and Ca < 2 + > leaching liquid; conveying the Ca < 2 + > leachate to an indirect mineralization reaction kettle, introducing CO2, and stirring to obtain calcium carbonate crystal mush; filtering the calcium carbonate crystal mush, separating out a filter cake and filtrate, drying the filter cake to obtain nano calcium carbonate, and recycling the filtrate to a leaching reaction kettle; the method comprises the following steps: adding biomass ash and water into a direct mineralization reaction kettle, introducing CO2, and stirring to obtain plant ash slurry; uniformly mixing and stirring the coal ash leaching residues and the plant ash slurry to obtain the nutrient soil. The method is simple in process, the preparation cost can be reduced, efficient storage of CO2 is achieved, calcium carbonate with the purity higher than 98% can be obtained, the alkalinity of biomass ash can be reduced, and the carbon sequestration effect can be improved.

Description

Technical Field

[0001] This invention relates to the field of solid waste resource utilization and carbon dioxide sequestration technology, specifically to a method for preparing high-purity nano-calcium carbonate and nutrient soil by synergistic mineralization of CO2 using fly ash and biomass ash. Background Technology

[0002] Utilizing CO2 to mineralize industrial solid waste is an effective way to achieve the resource utilization of industrial solid waste, and it can produce high-value-added nano-calcium carbonate. However, current research on CO2 mineralization technology mainly focuses on the mineralization of single solid wastes, and the added value of the products is low, lacking multi-material synergistic processing systems.

[0003] Numerous studies have explored the use of CO2 to mineralize fly ash. Patent CN202510254488.9 discloses a method for preparing monodisperse nano-calcium carbonate from calcium-containing industrial solid waste. This method involves mixing calcium-containing solid waste with an ammonium salt solution, reacting the mixture, passing CO2 through the filtrate, and adding a crystal form control agent to prepare nano-calcium carbonate. Patent CN202510250787.5 discloses a process for preparing high-settling-volume lightweight calcium carbonate. Using calcium carbonate slurry prepared under specific process conditions as seed crystals and ammonium chloride leaching solution from calcium-containing industrial waste as raw material, a high-settling-volume (2.4 mL / g~6.5 mL / g) lightweight calcium carbonate product is obtained through a carbonation reaction. Biomass ash has high alkalinity. Although it contains metal elements such as Ca, Mg, and K required for plant growth, its high alkalinity damages the soil when applied directly, and the Ca, Mg, and K elements cannot be effectively utilized. It requires acidification treatment before it can be used as fertilizer. CN119161880B discloses a method for preparing a soil conditioner and its application. The method uses biomass ash as part of the raw materials and adds fulvic acid crosslinked chitosan, bentonite, fly ash, earthworm castings, and humic acid. The soil conditioner is prepared by mixing them evenly in proportion and can achieve the effect of long-term improvement of soil properties.

[0004] However, the fly ash leaching residue from the aforementioned studies failed to be effectively treated and still poses an environmental impact. Furthermore, research on preparing soil conditioners from biomass ash requires the addition of multiple substances, resulting in complex processes, high costs, and a narrow range of applications. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing high-purity nano-calcium carbonate and nutrient soil by synergistic mineralization of CO2 using fly ash and biomass ash. This method is simple, can reduce preparation costs, achieves efficient CO2 sequestration, and can also obtain calcium carbonate with a purity of over 98%, reduce the alkalinity of biomass ash, and improve carbon fixation effect.

[0006] To achieve the above-mentioned objectives, this invention provides a method for preparing high-purity nano-calcium carbonate and nutrient soil by synergistic mineralization of CO2 using fly ash and biomass ash, comprising the following steps:

[0007] S1. Preparation of succinimide composite solution: Add succinimide as the main leaching agent, water as the solvent, triethanolamine as the activator, n-butanol as the particle size control agent, and sodium dodecylbenzenesulfonate as the crystal form control agent according to the mass fraction. Mix evenly and set aside for use.

[0008] S2. Add the succinimide composite solution prepared in step S1 to the leaching reactor, then add fly ash and stir to generate Ca. 2+ Leaching reaction;

[0009] S3. The slurry after reaction in the leaching reactor is transported to the solid waste separation unit, where a plate and frame filter press separates the fly ash leaching residue and Ca. 2+ The leachate is then used to wash the fly ash leaching residue with water in the separation unit. After washing, the fly ash leaching residue is transported to a mixing and stirring tank for later use.

[0010] S4. The Ca obtained from step S3 2+ The leachate is transported to an indirect mineralization reactor. CO2 gas is introduced into the indirect mineralization reactor until the pH inside the reactor drops to 6.5. A back pressure valve is used to maintain the CO2 pressure inside the indirect mineralization reactor at atmospheric pressure. At the same time, the reactor is continuously stirred at a certain speed to obtain calcium carbonate slurry.

[0011] S5. The calcium carbonate slurry obtained in step S4 is transported to the solid waste separation unit, where the filter cake and filtrate are separated by a plate and frame filter press. The filter cake is dried to obtain nano-calcium carbonate, and the filtrate is recycled and transported to the leaching reactor in step S2.

[0012] S6. Add biomass ash and water to the direct mineralization reactor in proportion, introduce CO2 gas into the direct mineralization reactor, maintain the pressure inside the direct mineralization reactor at atmospheric pressure using a back pressure valve, and continuously stir at a certain speed. After the reaction is completed, transport the wood ash slurry in the reactor to the mixing and stirring tank in step S3.

[0013] S7. Stir the fly ash leaching residue and wood ash slurry in the mixing tank at 500 rpm for 30 minutes until they are evenly mixed to obtain nutrient soil.

[0014] Preferably, in step S1, the succinimide composite solution comprises the following components in parts by mass: 3-5 parts succinimide, 90-95 parts water, 3-5 parts n-butanol, 1 part sodium dodecylbenzenesulfonate, and 2-4 parts triethanolamine.

[0015] Preferably, in step S2, the fly ash is pulverized and ball-milled to a thickness of less than 0.075 mm; and Ca is generated by stirring at 500 rpm and 30-70℃. 2+ The leaching reaction was carried out for 30 minutes before the reaction was terminated.

[0016] Preferably, in step S2, the mass ratio between fly ash and succinimide composite solution is (0.05-0.2):1.

[0017] Preferably, in step S3, the amount of water used is 5 to 10 times the mass of the fly ash leaching residue.

[0018] Preferably, in steps S4 and S6, the reaction temperature is 30°C, and the mixture is stirred continuously at 500 rpm for 30 min.

[0019] Preferably, in step S6, the mass ratio between biomass ash and water is (0.05-0.2):1.

[0020] Preferably, in step S7, the mass ratio between fly ash leaching residue and wood ash slurry is 1:2.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] (1) In this invention, succinimide composite solution is used as the Ca in fly ash. 2+ Leaching agent, to extract Ca 2+ High-purity nano-calcium carbonate was prepared by leaching and mineralization, with a purity of over 98% and a particle size of less than 500 nm. Fly ash can be 100% utilized as a resource. The fly ash leaching residue is rich in pores and can slowly release residual succinimide (<0.2%), which can be used as the main raw material for nutrient soil to promote plant growth.

[0023] (2) After the biomass ash of the present invention is directly mineralized by wet process, the strong alkaline CaO, MgO and K2O in it are converted into pH neutral or weakly alkaline CaCO3, MgCO3 and K2CO3, which reduces the alkalinity of the biomass ash, which is beneficial to plant absorption and seals CO2, resulting in significant carbon fixation effect.

[0024] (3) The slurry of biomass ash wet direct mineralization is mixed evenly with porous fly ash leaching residue to obtain a slow-release nutrient soil rich in Ca, Mg and K mineral elements; the nutrient soil prepared by mixing has a high water content and strong fluidity. After adding grass seeds, it can be sprayed under high pressure to directly cover the area that needs greening, which is beneficial to improving the environment around mines and power plants.

[0025] In summary, this invention utilizes fly ash and biomass ash to mineralize CO2 and prepare nano-calcium carbonate and slow-release nutrient soil. This not only achieves 100% resource utilization of fly ash and biomass ash but also enables large-scale CO2 fixation, improving the environment. The prepared nano-calcium carbonate has high economic value, combining economic and environmental benefits, and offering multiple advantages such as pollution reduction, carbon reduction, quality improvement, and efficiency enhancement. Furthermore, the process of this invention is simple, the raw materials are inexpensive and readily available, and the preparation cost is low, making it suitable for large-scale application to improve the ecological environment around mines and power plants. Attached Figure Description

[0026] Figure 1 This is a process flow diagram of the present invention;

[0027] Figure 2 The image shows a SEM image of the nano-calcium carbonate prepared in Example 1. Detailed Implementation

[0028] The present invention will be further described in detail below with reference to specific embodiments.

[0029] Example 1

[0030] like Figure 1 As shown, a method for preparing high-purity nano-calcium carbonate and nutrient soil by synergistic mineralization of CO2 using fly ash and biomass ash includes the following steps:

[0031] S1. Preparation of succinimide composite solution: Add succinimide as the main leaching agent, water as the solvent, triethanolamine as the activator, n-butanol as the particle size control agent, and sodium dodecylbenzenesulfonate as the crystal form control agent according to the following mass parts, mix evenly and set aside; the succinimide composite solution includes the following components in the following mass parts: 3 parts succinimide, 95 parts water, 3 parts n-butanol, 1 part sodium dodecylbenzenesulfonate, and 2 parts triethanolamine.

[0032] S2. Add the succinimide composite solution prepared in step S1 to the leaching reactor. Then, add fly ash at a solid-liquid ratio of 50g fly ash / kg succinimide composite solution. The fly ash is ball-milled to a thickness of less than 0.075mm. Stir at 500rpm and 30℃ to generate Ca. 2+ Leaching reaction, reaction time 30 minutes;

[0033] S3. The slurry after reaction in the leaching reactor is transported to the solid waste separation unit, where a plate and frame filter press separates the fly ash leaching residue and Ca. 2+ The leachate is then used to wash the fly ash leaching residue with water in the separation unit. The amount of water used is 5 times the mass of the fly ash leaching residue. After washing, the fly ash leaching residue is transported to a mixing and stirring tank for later use.

[0034] S4. The Ca obtained from step S3 2+The leachate was transported to an indirect mineralization reactor. CO2 gas was introduced into the indirect mineralization reactor at 30°C until the pH inside the reactor dropped to 6.5. The CO2 pressure inside the indirect mineralization reactor was maintained at atmospheric pressure using a back pressure valve. At the same time, the reactor was continuously stirred at 500 rpm for 30 minutes to obtain calcium carbonate slurry.

[0035] S5. The calcium carbonate slurry obtained in step S4 is transported to the solid waste separation unit, where a plate and frame filter press separates the filter cake and filtrate. The filter cake is dried to obtain high-purity nano-calcium carbonate, and the filtrate is recycled and transported to the leaching reactor in step S2. The microstructure (SEM) of the nano-calcium carbonate is shown below. Figure 2 As shown in the figure, the prepared calcium carbonate is a cake-shaped nano-calcium carbonate with a particle size of less than 500 nm, and has good dispersibility.

[0036] S6. Add biomass ash and water to the direct mineralization reactor at a solid-liquid ratio of 50g biomass ash / kg water. Introduce CO2 gas into the direct mineralization reactor at 30℃. Maintain the pressure inside the direct mineralization reactor at atmospheric pressure using a back pressure valve. Stir continuously at 500rpm for 30min. After the reaction is completed, transfer the wood ash slurry in the reactor to the mixing and stirring tank in step S3.

[0037] S7. Stir the fly ash leaching residue and wood ash slurry (mass ratio of 1:2) in the mixing tank at 500 rpm for 30 minutes until they are evenly mixed to obtain nutrient soil.

[0038] Example 2

[0039] like Figure 1 As shown, a method for preparing high-purity nano-calcium carbonate and nutrient soil by synergistic mineralization of CO2 using fly ash and biomass ash is described. In this method, only step S2 is "fly ash is added according to the solid-liquid ratio of 200g fly ash / kg succinimide composite solution". All other steps are consistent with those in Example 1.

[0040] Example 3

[0041] like Figure 1 As shown, a method for preparing high-purity nano-calcium carbonate and nutrient soil by synergistic mineralization of CO2 using fly ash and biomass ash is described. In step S1 of this method, "the succinimide composite solution comprises the following components in parts by mass: 4 parts succinimide, 92 parts water, 4 parts n-butanol, 1 part sodium dodecylbenzenesulfonate, and 3 parts triethanolamine"; in step S2, "fly ash is added according to a solid-liquid ratio of 200g fly ash / kg succinimide composite solution". All other steps are consistent with those in Example 1.

[0042] Example 4

[0043] like Figure 1As shown, a method for preparing high-purity nano-calcium carbonate and nutrient soil by synergistic mineralization of CO2 using fly ash and biomass ash is described. In step S1 of this method, "the succinimide composite solution comprises the following components in parts by mass: 5 parts succinimide, 90 parts water, 5 parts n-butanol, 1 part sodium dodecylbenzenesulfonate, and 4 parts triethanolamine"; all other steps are consistent with those in Example 1.

[0044] Example 5

[0045] like Figure 1 As shown, a method for preparing high-purity nano-calcium carbonate and nutrient soil by synergistic mineralization of CO2 using fly ash and biomass ash is described. In step S1, "the succinimide composite solution comprises the following components in parts by mass: 5 parts succinimide, 90 parts water, 5 parts n-butanol, 1 part sodium dodecylbenzenesulfonate, and 4 parts triethanolamine"; in step S2, "fly ash is added according to a solid-liquid ratio of 200g fly ash / kg succinimide composite solution", and other steps are consistent with those in Example 1; in step S6, "biomass ash and water are added to a direct mineralization reactor according to a solid-liquid ratio of 200g biomass ash / kg water", and other steps are consistent with those in Example 1.

[0046] Adding grass seeds to the nutrient soil prepared in Examples 1-5, mixing them evenly, and then spraying them under high pressure onto areas such as the slope protection around mines and power plants can effectively improve the environment.

[0047] The carbon sequestration amounts of fly ash indirect mineralization and biomass ash direct mineralization in Examples 1-5 are shown in Table 1 below.

[0048] Table 1. Carbon sequestration and calcium carbonate yield from indirect mineralization of fly ash

[0049]

[0050] In summary, this invention achieves 100% resource utilization of fly ash, producing high-value-added, high-purity nano-calcium carbonate. Its porous leaching tailings can be further used to produce slow-release sprayed nutrient soil. The fly ash leaching residue contains a small amount of succinimide residue (0.1%), which can slowly diffuse into the soil, promoting plant growth. After wet direct mineralization, the pH of the biomass ash decreases from 12 to 8, which is beneficial for plant absorption and does not damage the soil. The abundant potassium carbonate, magnesium carbonate, and calcium carbonate minerals provide nutrients for plant growth. The combination of indirect fly ash mineralization and wet direct biomass ash mineralization significantly increases carbon sequestration. Based on Example 1, the carbon sequestration per ton of fly ash is 45.35 kg, producing 103.07 kg of nano-calcium carbonate; the carbon sequestration per ton of biomass ash is 62.37 kg.

Claims

1. A method for preparing high-purity nano-calcium carbonate and nutrient soil by synergistic mineralization of CO2 using fly ash and biomass ash, characterized in that, Includes the following steps: S1. Preparation of succinimide composite solution: Add succinimide as the main leaching agent, water as the solvent, triethanolamine as the activator, n-butanol as the particle size control agent, and sodium dodecylbenzenesulfonate as the crystal form control agent according to the mass fraction. Mix evenly and set aside for use. S2. Add the succinimide composite solution prepared in step S1 to the leaching reactor, then add fly ash and stir to generate Ca. 2+ Leaching reaction; S3. The slurry after reaction in the leaching reactor is transported to the solid waste separation unit, where a plate and frame filter press separates the fly ash leaching residue and Ca. 2+ The leachate is then used to wash the fly ash leaching residue with water in the separation unit. After washing, the fly ash leaching residue is transported to a mixing and stirring tank for later use. S4. The Ca obtained from step S3 2+ The leachate is transported to an indirect mineralization reactor. CO2 gas is introduced into the indirect mineralization reactor until the pH inside the reactor drops to 6.

5. A back pressure valve is used to maintain the CO2 pressure inside the indirect mineralization reactor at atmospheric pressure. At the same time, the reactor is continuously stirred at a certain speed to obtain calcium carbonate slurry. S5. The calcium carbonate slurry obtained in step S4 is transported to the solid waste separation unit, where the filter cake and filtrate are separated by a plate and frame filter press. The filter cake is dried to obtain nano-calcium carbonate, and the filtrate is recycled and transported to the leaching reactor in step S2. S6. Add biomass ash and water to the direct mineralization reactor in proportion, introduce CO2 gas into the direct mineralization reactor, maintain the pressure inside the direct mineralization reactor at atmospheric pressure using a back pressure valve, and continuously stir at a certain speed. After the reaction is completed, transport the wood ash slurry in the reactor to the mixing and stirring tank in step S3. S7. Stir the fly ash leaching residue and wood ash slurry in the mixing tank at 500 rpm for 30 minutes until they are evenly mixed to obtain nutrient soil.

2. The method for preparing high-purity nano-calcium carbonate and nutrient soil by synergistic mineralization of CO2 using fly ash and biomass ash according to claim 1, characterized in that, In step S1, the succinimide composite solution comprises the following components in parts by mass: 3-5 parts succinimide, 90-95 parts water, 3-5 parts n-butanol, 1 part sodium dodecylbenzenesulfonate, and 2-4 parts triethanolamine.

3. A method for preparing high-purity nano-calcium carbonate and nutrient soil by synergistic mineralization of CO2 using fly ash and biomass ash according to claim 1 or 2, characterized in that, In step S2, the fly ash is pulverized and ball-milled to a thickness of less than 0.075 mm; Ca is generated by stirring at 500 rpm and 30-70℃. 2+ The leaching reaction was carried out for 30 minutes before the reaction was terminated.

4. A method for preparing high-purity nano-calcium carbonate and nutrient soil by synergistic mineralization of CO2 using fly ash and biomass ash according to claim 1 or 2, characterized in that, In step S2, the mass ratio between fly ash and succinimide composite solution is (0.05-0.2):

1.

5. A method for preparing high-purity nano-calcium carbonate and nutrient soil by synergistic mineralization of CO2 using fly ash and biomass ash according to claim 1 or 2, characterized in that, In step S3, the amount of water used is 5 to 10 times the mass of the fly ash leaching residue.

6. A method for preparing high-purity nano-calcium carbonate and nutrient soil by synergistic mineralization of CO2 using fly ash and biomass ash according to claim 1 or 2, characterized in that, In steps S4 and S6, the reaction temperature is 30°C, and the mixture is stirred continuously at 500 rpm for 30 minutes.

7. A method for preparing high-purity nano-calcium carbonate and nutrient soil by synergistic mineralization of CO2 using fly ash and biomass ash according to claim 1 or 2, characterized in that, In step S6, the mass ratio of biomass ash to water is (0.05-0.2):

1.

8. A method for preparing high-purity nano-calcium carbonate and nutrient soil by synergistic mineralization of CO2 using fly ash and biomass ash according to claim 1 or 2, characterized in that, In step S7, the mass ratio between fly ash leaching residue and wood ash slurry is 1:2.

Images