A method for recovering calcium element in a by-product of molecular sieve prepared from blast furnace slag

Abstract

The application discloses a method for recovering calcium element in by-product of molecular sieve prepared from blast furnace slag, which comprises the following steps: (1) dissolving ammonium sulfate in sulfuric acid, adding blast furnace slag after heating to 30-100 DEG C, stirring to obtain mixed slurry, and filtering to separate the filtrate and the residue, wherein the residue is washed, dried and ground for use; (2) using the filtrate obtained in step (1) to prepare zeolite molecular sieve; (3) dissolving ammonium carbonate in deionized water, adding the residue obtained in step (1), stirring uniformly, adding magnesium oxide to continue to react for a period of time, filtering, and separating the residue and the filtrate, drying the residue to obtain a solid containing calcium carbonate; evaporating and concentrating the filtrate, drying after crystallization, and grinding to obtain ammonium sulfate. The application realizes harmless comprehensive utilization of blast furnace slag resources, and can maximize the recovery of effective components in blast furnace slag and application in industrial production.

Description

Technical Field

[0001] This invention relates to the field of solid waste resource utilization, specifically to a method for recovering calcium from molecular sieve byproducts prepared from blast furnace slag. Background Technology

[0002] Industrial development is inseparable from steel. With the increase in steel production, problems such as the accumulation and difficulty in utilizing solid waste have become increasingly prominent. Blast furnace slag is a type of solid waste, a byproduct of steel production. It is discharged from the blast furnace during the steelmaking process and is treated in two ways: dry slag and water slag. Water-quenched slag is more common and mainly consists of SiO2, CaO, Al2O3, MgO, and other compounds such as Fe2O3, TiO2, and MnO2. In recent years, my country's steel production has continued to rise, generating approximately 300 million tons of blast furnace slag annually, of which SiO2, CaO, and Al2O3 account for over 90%.

[0003] Calcium carbonate is an essential raw material in industrial production and daily life, with applications spanning traditional building coatings, plastic fillers, artificial stone, environmentally friendly building materials, high-end packaging, and specialty building materials. However, the byproducts of producing synthetic zeolite from silicon and aluminum in blast furnace slag contain a large amount of calcium, essential for calcium carbonate production. If these byproducts are not recycled, they can cause secondary pollution. Therefore, the rational recovery and utilization of calcium from these byproducts fundamentally reduces solid waste accumulation and represents a new method for addressing the issue of blast furnace slag solid waste accumulation and achieving comprehensive resource utilization. Summary of the Invention

[0004] The purpose of this invention is to provide a method for recovering calcium from molecular sieve byproducts prepared from blast furnace slag, aiming to reduce the accumulation of solid waste and alleviate environmental pressure.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A method for recovering calcium from molecular sieve byproducts prepared from blast furnace slag includes the following steps: (1) Dissolve ammonium sulfate in sulfuric acid, heat to 30~100℃ and add blast furnace slag, stir to obtain a mixed slurry, filter to separate filtrate and filter residue, wherein the filter residue is washed, dried and ground for use; (2) Use the filtrate obtained in step (1) to prepare zeolite molecular sieves; (3) Dissolve ammonium carbonate in deionized water, add the filter residue obtained in step (1), stir evenly, add magnesium oxide and continue to react for a period of time, filter, separate the filter residue and filtrate, dry the filter residue to obtain a solid containing calcium carbonate; the filtrate is concentrated by evaporation, dried after crystals are precipitated, ground to obtain ammonium sulfate.

[0006] Further, by weight, the raw materials involved in the method include: 1-10 parts of powdered blast furnace slag, 1-20 parts of sulfuric acid, 1-20 parts of ammonium sulfate, 0.1-5 parts of magnesium oxide, 1-5 parts of ammonium carbonate, and 10-75 parts of water.

[0007] Furthermore, the concentration of sulfuric acid in step (1) is 1~3 mol / L.

[0008] Furthermore, the stirring speed in steps (1) and (3) is 5~20 r / min.

[0009] Furthermore, the stirring time in step (1) is 0.5~48h.

[0010] Furthermore, in step (3), magnesium oxide is added and the reaction continues for 3 to 48 hours.

[0011] Furthermore, the calcium carbonate content in the solid containing calcium carbonate in step (3) is 50-99%.

[0012] Furthermore, the ammonium sulfate obtained in step (3) has a purity of 85-99% and is used for recycling calcium carbonate.

[0013] Compared with the prior art, the beneficial effects of the present invention are: (1) This invention uses dilute sulfuric acid, ammonium sulfate and blast furnace slag to mix and heat the reaction. Through dissolution and displacement, the difficult-to-separate oxides such as silicon, aluminum and calcium can be effectively separated in the form of solution and precipitate, laying the foundation for the subsequent preparation of products of different elements.

[0014] (2) In the process of preparing molecular sieves from blast furnace slag and recovering calcium from by-products, this invention uses magnesium oxide and ammonium carbonate as separation aids. The process is simple to operate, produces low waste emissions, and yields products with high purity. Although magnesium oxide is widely used as a flocculant in conventional reactions, it is not fully utilized in blast furnace slag because it already contains magnesium oxide. Therefore, those skilled in the art would not have thought of adding magnesium oxide as an additional flocculant. This invention achieves efficient reuse of endogenous components in waste slag. This method has the advantages of strong practicality, high utilization rate of blast furnace slag, environmental friendliness, and high product purity. Attached Figure Description

[0015] Figure 1 This is a flowchart of the method for recovering and utilizing calcium from molecular sieve byproducts prepared from blast furnace slag according to the present invention.

[0016] Figure 2 This is a SEM image of the calcium carbonate prepared in an embodiment of the present invention.

[0017] Figure 3 This is a SEM image of the molecular sieve product of this invention. Detailed Implementation

[0018] To make the content of this invention easier to understand, the technical solution of this invention will be further described below with reference to specific embodiments, but this invention is not limited thereto.

[0019] Unless otherwise specified in the examples, the procedures should be performed under standard conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0020] Example 1

[0021] This embodiment provides a method for recovering and utilizing calcium, a byproduct of zeolite molecular sieve preparation from blast furnace slag. The raw materials, by weight, include: 1 part powdered blast furnace slag, 7 parts 2 mol / L sulfuric acid, 1.8 parts ammonium sulfate, 1.5 parts ammonium carbonate, 2 parts magnesium oxide, and 15 parts deionized water. All stirring speeds are 10 r / min. The blast furnace slag is sourced from Sanming Sansteel Group (containing 6.15 wt% Mn, 38.98 wt% SiO2, 20.04 wt% CaO, 4.99 wt% MgO, 18.94 wt% Al2O3, with the remainder being trace elements).

[0022] The following steps are used to recover and utilize calcium from blast furnace slag: (1) Dissolve ammonium sulfate in sulfuric acid, heat to 50°C and add blast furnace slag. Stir for 30 minutes to obtain a mixed slurry. After filtration and washing, collect the filtrate and filter residue separately for later use.

[0023] (2) The filtrate obtained in step (1) is rich in silicon and aluminum elements and can be used to prepare zeolite molecular sieves (the preparation method of molecular sieves is not described in detail in this embodiment, which is a conventional preparation method for those in the art). (3) Dissolve ammonium carbonate in deionized water, add dried and ground filter residue, stir and react for 24 hours, add magnesium oxide and continue stirring for 1 hour, filter to obtain filter residue and filtrate rich in ammonia, dry filter residue to obtain calcium carbonate solid with a purity of more than 75%, evaporate, concentrate and cool to crystallize filtrate to obtain ammonium sulfate crystals, grind to obtain ammonium sulfate with a purity of 85-99%, which can be used to recycle calcium carbonate.

[0024] Example 2

[0025] This embodiment provides a method for recovering and utilizing calcium, a byproduct of zeolite molecular sieve preparation from blast furnace slag. By weight, the raw materials include: 1 part powdered blast furnace slag, 7 parts 2mol / L sulfuric acid, 1.8 parts ammonium sulfate, 1.2 parts ammonium carbonate, 1 part magnesium oxide, and 12 parts deionized water; all stirring speeds are 10 r / min.

[0026] Except for the heating temperature of 60°C in step (1), the calcium element recovery and utilization process is the same as in Example 1. The purity of the obtained calcium carbonate solid can reach more than 80%, and the purity of ammonium sulfate is 88~99%.

[0027] Example 3

[0028] This embodiment provides a method for recovering and utilizing calcium, a byproduct of zeolite molecular sieve preparation from blast furnace slag. By weight, the raw materials include: 1 part powdered blast furnace slag, 8 parts 2mol / L sulfuric acid, 1.85 parts ammonium sulfate, 1.5 parts ammonium carbonate, 0.5 parts magnesium oxide, and 15 parts water; all stirring speeds are 10 r / min.

[0029] Except for the heating temperature of 70°C in step (1), the calcium element recovery and utilization process is the same as in Example 1. The purity of the obtained calcium carbonate solid can reach more than 80%, and the purity of ammonium sulfate is 90~99%.

[0030] Example 4

[0031] This embodiment provides a method for recovering and utilizing calcium, a byproduct of zeolite molecular sieve preparation from blast furnace slag. By weight, the raw materials include: 1 part powdered blast furnace slag, 7.5 parts 2mol / L sulfuric acid, 1.85 parts ammonium sulfate, 1.2 parts ammonium carbonate, 0.1 parts magnesium oxide, and 15 parts water; all stirring speeds are 10 r / min.

[0032] Except for the heating temperature of 80℃ in step (1), the calcium element recovery and utilization process is the same as in Example 1. The purity of the obtained calcium carbonate solid can reach more than 85%, and the purity of ammonium sulfate is 90~99%.

[0033] The calcium carbonate content of the solid samples prepared in Examples 1-4 was determined using energy-scattering X-ray spectroscopy (EDX), and the results are shown in Table 1. Table 1. Calcium carbonate content of samples prepared in Examples 1-4

[0034] As shown in Table 1, when the reaction temperature was increased to 80℃, and the ratio of dilute sulfuric acid to ammonium sulfate, the reaction time, and the subsequent addition of ammonium carbonate were appropriately optimized and controlled, the purity of the obtained calcium carbonate samples was significantly improved. Among them, the product of Example 4 had the best performance, the highest calcium carbonate content, and the zeolite molecular sieve prepared under this condition had a more regular structure. Figure 3 Electron micrographs of the prepared molecular sieves.

[0035] The above results indicate that calcium can be efficiently extracted from zeolite molecular sieve byproducts prepared from blast furnace slag through targeted chemical reactions, transforming the calcium component, which was originally prone to large-scale stockpiling and low-value emissions, into a high-value chemical product, thus realizing the resource utilization of valuable components in blast furnace slag.

[0036] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for recovering calcium from a byproduct of molecular sieve preparation using blast furnace slag, characterized in that: Includes the following steps: (1) Dissolve ammonium sulfate in sulfuric acid, heat to 30~100℃ and add blast furnace slag, stir to obtain a mixed slurry, filter to separate filtrate and filter residue, wherein the filter residue is washed, dried and ground for use; (2) Use the filtrate obtained in step (1) to prepare zeolite molecular sieves; (3) Dissolve ammonium carbonate in deionized water, add the filter residue obtained in step (1), stir evenly, add magnesium oxide and continue to react for a period of time, filter, separate the filter residue and filtrate, dry the filter residue to obtain a solid containing calcium carbonate; the filtrate is concentrated by evaporation, dried after crystals are precipitated, ground to obtain ammonium sulfate.

2. The method according to claim 1, characterized in that: By weight, the raw materials involved in the method include: 1-10 parts of powdered blast furnace slag, 1-20 parts of sulfuric acid, 1-20 parts of ammonium sulfate, 0.1-5 parts of magnesium oxide, 1-5 parts of ammonium carbonate, and 10-75 parts of water.

3. The method according to claim 2, characterized in that: The concentration of sulfuric acid in step (1) is 1-3 mol / L.

4. The method according to claim 1, characterized in that: The stirring speed in steps (1) and (3) is 5-20 r / min.

5. The method according to claim 1, characterized in that: The stirring time in step (1) is 0.5-48h.

6. The method according to claim 1, characterized in that: In step (3), magnesium oxide is added and the reaction continues for 3-48 hours.

7. The method according to claim 1, characterized in that: The calcium carbonate content in the solid containing calcium carbonate in step (3) is 50-99%.

8. The method according to claim 1, characterized in that: The ammonium sulfate obtained in step (3) has a purity of 85-99% and is used for recycling calcium carbonate.

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