Method for separating calcium and iron in steel slag tailings

Abstract

The invention belongs to the technical field of steel slag solid waste treatment, and provides a method for separating calcium and iron in steel slag tailings, which comprises the following steps: S1, levigated steel slag powder reacts with hydrochloric acid pickling waste liquid in an extractor; s2, introducing ammonia gas generated by the system into a neutralization reactor; s3, carrying out magnetic separation on a filter cake obtained by carrying out filter pressing on the neutralization product to obtain a fine iron powder product; s4, performing purification, impurity removal, concentration and crystallization on the filtrate of the neutralization product to obtain a calcium chloride product; s5, introducing the purified and impurity-removed calcium chloride crude product into a carbonization reactor, and reacting with ammonia gas and carbon dioxide gas generated by the system; s6, carrying out filter pressing on the carbonization reaction product to obtain a filter cake which is a calcium carbonate product; s7, filter-pressing the carbonation reaction product to obtain an ammonium chloride solution, feeding the ammonium chloride solution into a dissociation system, feeding the generated ammonia gas into S2, and feeding the ammonia gas and carbon dioxide gas into S5; and combining calcium chloride solutions generated by dissociation in the step S7, and performing concentration in the purification, impurity removal and concentration process in the step S4 to obtain a calcium chloride product.

Description

Technical Field

[0001] This invention belongs to the field of steel slag solid waste disposal technology, specifically a method for separating calcium and iron from steel slag tailings. Background Technology

[0002] The treatment of waste steel slag is a pressing problem for the steel industry, and many new technologies and processes have emerged both domestically and internationally. Currently, research on leaching media mainly focuses on salt media (ammonium and magnesium salts), alkaline media (sodium hydroxide), strong acid media (hydrochloric acid), and weak acid media (acetic acid or acetic acid). Conventional equipment schemes for steel slag leaching should employ a "pressure boiling" method, with carbonization reaction equipment including a carbonization tower or crystallizer.

[0003] Different leaching media have their own advantages and disadvantages in steel slag carbonization processes: the advantages of salt media (ammonium salt, magnesium salt) process are high product purity and low media loss, but the disadvantages are high pretreatment and grinding costs and high energy consumption; the alkaline media (NaOH) process does not require pretreatment and has low energy consumption, but the problems are large alkali consumption and difficult product separation; the strong acid media (HCl) process has high carbonization efficiency, but the media loss is large and the energy consumption is high; the weak acid media (acetic acid, acetic acid) process has the advantages of high carbonization efficiency and low cost, but the disadvantages are low conversion rate and high energy consumption for media regeneration and recycling.

[0004] Existing research indicates that strong alkali and strong acid leaching processes are currently unsuitable for industrialization due to various issues. Indirect carbonization processes for steel slag using salt (ammonium salts, magnesium salts) and weak acid (acetic acid, acetic acid) leaching agents can effectively achieve the fractional resource utilization of steel slag and obtain high-value-added byproducts, demonstrating good industrial feasibility. However, a competitive analysis of the two processes shows that the weak acid (acetic acid, acetic acid) leaching agent process suffers from poor economic efficiency due to high energy consumption during acid regeneration and high iron loss. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a method for separating calcium and iron in steel slag tailings. The method uses pickling waste liquid as the leaching medium and gaseous NH3 and CO2 produced by the system as carbonization media. This addresses the problems of low separation efficiency (insufficient iron and silicon recovery, slow chemical leaching), low carbon fixation reaction rate (poor mechanical mixing, low CO2 utilization), high system energy consumption, and insufficient comprehensive resource utilization (calcium and magnesium are the main components, while high-value components are discarded).

[0006] A method for separating calcium and iron from steel slag tailings includes the following steps:

[0007] S1. Finely ground steel slag powder reacts with hydrochloric acid pickling waste liquid in a leaching reactor;

[0008] S2. The treated steel slag enters the neutralization reactor, and ammonia gas generated by S5 is introduced into the neutralization reactor.

[0009] S3. The filter cake after pressure filtration of the neutralization product is magnetically separated to obtain iron concentrate.

[0010] S4. The filtrate of the neutralization product is purified, concentrated, and crystallized to obtain calcium chloride product.

[0011] S5. The purified and impurity-removed crude calcium chloride enters the carbonization reactor, where ammonia and carbon dioxide gas generated in S5 are introduced to react.

[0012] The filter cake obtained by pressure filtration of the S6 and S5 carbonation reaction products is calcium carbonate.

[0013] The filtrate from the carbonization reaction products of S7 and S5 after pressure filtration is an ammonium chloride solution, which enters the dissociation reaction system. The ammonia gas generated by the reaction enters S2, and the ammonia gas and carbon dioxide gas enter S5.

[0014] The calcium chloride solutions generated from the dissociation of S8 and S7 are combined and then concentrated in the concentration process after purification and impurity removal in S4 to obtain the calcium chloride product.

[0015] Preferably, in S1, the fine particle size of the steel slag powder is 150~200 mesh.

[0016] Preferably, the liquid-to-solid ratio of hydrochloric acid pickling waste liquid to steel slag powder in the pipeline leaching reactor is 3:1.

[0017] Preferably, the concentration of calcium chloride in the liquid of the supergravity carbonization reactor is 30-35%, the mass ratio of CO2 to NH3 in the gas is 44:17, the CO2 concentration is 30-50%, and the supergravity factor is 50-200.

[0018] Preferably, the main reactants in the dissociation reaction system of S7 are calcium carbonate and ammonium chloride, and the dissociation reaction temperature is maintained at 55±10℃.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] This invention uses pickling waste liquid as the leaching medium, enhances leaching through a pipeline leaching reactor, and utilizes the carbonization byproduct ammonium chloride to generate CO2 and NH3. 3， The high-gravity carbonization reactor efficiently removes Ca from steel slag. 2+ The process transforms ions into calcium carbonate, while simultaneously recovering all components from steel slag, including iron, calcium, magnesium, silicon, and aluminum, as well as iron from hydrochloric acid pickling wastewater. The silicon-aluminum tailings can be converted into building material raw materials or silicon fertilizer, improving the comprehensive utilization rate of steel slag, reducing waste emissions, and offering advantages in high efficiency, energy saving, and environmental protection. Attached Figure Description

[0021] Figure 1 This is a process flow diagram of the present invention. Detailed Implementation

[0022] The embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and should not be construed as limiting the scope of the invention.

[0023] Example 1: As shown in the attached document Figure 1 As shown: This invention provides a method for separating calcium and iron from steel slag tailings, comprising the following steps:

[0024] 1. The relevant technical parameters of the raw steel slag tailings and hydrochloric acid pickling wastewater are as follows:

[0025] (1) Raw steel slag tailings:

[0026] Particle size: 200 mesh.

[0027] Appearance: Grayish brown

[0028] Chemical composition:

[0029] CaO: 48.35%, SiO2: 17.03%, Fe3O4: 19.4%, MnO: 2.27%, MgO: 6.33%,

[0030] Al2O3: 4.38%, P2O5: 1.75%, balance: remaining amount.

[0031] (2) Hydrochloric acid pickling wastewater:

[0032] Appearance: Light green

[0033] Chemical composition: HCl=5.12%, ferrous chloride=22.31%, ferric chloride=0.33%, remainder: water.

[0034] 2. Steps for the differentiated and resource-based treatment of steel slag tailings:

[0035] S1. Finely ground steel slag powder reacts with hydrochloric acid pickling waste liquid in a leaching reactor;

[0036] S2. The treated steel slag enters the neutralization reactor, and ammonia gas generated by S5 is introduced into the neutralization reactor.

[0037] S3. The filter cake after pressure filtration of the neutralization product is magnetically separated to obtain iron concentrate.

[0038] S4. The filtrate of the neutralization product can be purified, concentrated, and crystallized to obtain calcium chloride product.

[0039] S5. The purified and impurity-removed crude calcium chloride can also enter the carbonization reactor, where ammonia and carbon dioxide gas generated in S5 are introduced to react.

[0040] The filter cake obtained by pressure filtration of the S6 and S5 carbonation reaction products is calcium carbonate.

[0041] The filtrate from the carbonization reaction products of S7 and S5 after pressure filtration is an ammonium chloride solution, which enters the dissociation reaction system. The ammonia gas generated by the reaction enters S2, and the ammonia gas and carbon dioxide gas enter S5.

[0042] The calcium chloride solutions generated from the dissociation of S8 and S7 are combined and then concentrated in the concentration process after purification and impurity removal in S4 to obtain the calcium chloride product.

[0043] Preferably, in S1, the fine particle size of the steel slag powder is 150~200 mesh.

[0044] Preferably, the liquid-to-solid ratio of hydrochloric acid pickling waste liquid to steel slag powder in the pipeline leaching reactor is 3:1.

[0045] Preferably, the concentration of calcium chloride in the liquid of the supergravity carbonization reactor is 30-35%, the mass ratio of CO2 to NH3 in the gas is 44:17, the CO2 concentration is 30-50%, and the supergravity factor is 50-200.

[0046] Preferably, the main reactants in the dissociation reaction system of S7 are calcium carbonate and ammonium chloride, and the dissociation reaction temperature is maintained at 55±10℃.

[0047] 3. Technical parameters of products after treatment of hydrochloric acid pickling wastewater from steel slag tailings:

[0048] (1) Purity of calcium carbonate product: 97.3% (XRD method), calcium ion content: 38.80%, whiteness: 97, calcium extraction recovery rate: 88.32%

[0049] (2) The iron concentrate grade was 63.78%, and the comprehensive iron recovery rate was 98.95%.

[0050] (3) The calcium chloride content in calcium chloride dihydrate is 74.68%, which fully complies with the relevant national standards.

[0051] (4) The waste materials, mainly composed of silicon and aluminum, can be used as building material raw materials or further processed into silicon fertilizer.

[0052] Example 2: As shown in the attached document Figure 1 As shown: This invention provides a method for separating calcium and iron from steel slag tailings, comprising the following steps:

[0053] 1. The technical parameters of the raw steel slag tailings and hydrochloric acid pickling wastewater used are the same as those in Example 1.

[0054] 2. Steps for the differentiated and resource-based treatment of steel slag tailings:

[0055] S1. Finely ground steel slag powder reacts with hydrochloric acid pickling waste liquid in a leaching reactor;

[0056] S2. The treated steel slag enters the neutralization reactor, and ammonia gas generated by S5 is introduced into the neutralization reactor.

[0057] S3. The filter cake after pressure filtration of the neutralization product is magnetically separated to obtain iron concentrate.

[0058] S4. The filtrate of the neutralization product can be purified, concentrated, and crystallized to obtain calcium chloride product.

[0059] S5. The purified and impurity-removed crude calcium chloride can also enter the carbonization reactor, where ammonia and carbon dioxide gas generated in S5 are introduced to react.

[0060] The filter cake obtained by pressure filtration of the S6 and S5 carbonation reaction products is calcium carbonate.

[0061] The filtrate from the carbonization reaction products of S7 and S5 after pressure filtration is an ammonium chloride solution, which enters the dissociation reaction system. The ammonia gas generated by the reaction enters S2, and the ammonia gas and carbon dioxide gas enter S5.

[0062] The calcium chloride solutions generated from the dissociation of S8 and S7 are combined and then concentrated in the concentration process after purification and impurity removal in S4 to obtain the calcium chloride product.

[0063] Preferably, in S1, the fine particle size of the steel slag powder is 150~200 mesh.

[0064] Preferably, the liquid-to-solid ratio of hydrochloric acid pickling waste liquid to steel slag powder in the pipeline leaching reactor is 3:1.

[0065] Preferably, the concentration of calcium chloride in the liquid of the supergravity carbonization reactor is 30-35%, the mass ratio of CO2 to NH3 in the gas is 44:17, the CO2 concentration is 30-50%, and the supergravity factor is 50-200.

[0066] Preferably, the main reactants in the dissociation reaction system of S7 are calcium carbonate and ammonium chloride, and the dissociation reaction temperature is maintained at 55±10℃.

[0067] 3. Technical parameters of products after treatment of hydrochloric acid pickling wastewater from steel slag tailings:

[0068] (1) Calcium carbonate products (X-ray diffraction method + chemical titration method for detection)

[0069] Testing items Units of measurement Test results illustrate purity % 98.1 This represents an improvement over the 97.3% achieved in Example 1, due to optimized carbonization reaction parameters and reduced impurity residue. Calcium ion content % 39.02 Slightly higher than the 38.80% in Example 1, indicating more complete calcium conversion. Whiteness % 98 Compared to Example 1, the improvement is due to the fact that hypergravity carbonization promotes uniform crystal growth and reduces the adsorption of pigments and impurities. Calcium extraction recovery rate % 91.56 Compared to the 88.32% improvement in Example 1, segmented air intake and optimized supergravity factor further enhance calcium utilization. Particle size distribution (D50) μm 18 New testing method results in high particle uniformity. Moisture content % 0.3 The newly added test result meets the requirements for Grade I (≤0.5%) of Industrial Calcium Carbonate (YS / T703-2014).

[0070] (2) Iron concentrate products (detected by inductively coupled plasma atomic emission spectrometry)

[0071] Iron grade: The iron concentrate grade after drying reached 64.52%, which is higher than the 63.78% in Example 1.

[0072] The overall iron recovery rate was 99.23%, which is an improvement over 98.95% in Example 1.

[0073] Impurity content: SiO2 content 0.85%, P content 0.06%, S content 0.04%, all lower than that in Example 1 (1.12%, 0.07%, and 0.05%, respectively).

[0074] (3) Calcium chloride dihydrate products (chemical titration method + gravimetric method for detection)

[0075] Testing items Units of measurement Test results illustrate Calcium chloride content % 75.32 Compared to the 74.68% improvement in Example 1, the two-stage concentration process reduces calcium loss and fully meets the requirements of Grade I dihydrate calcium chloride (≥74%) in the "Industrial Calcium Chloride" (GB / T26520-2011) standard. magnesium chloride content % 0.28 The newly added test result was below the standard limit (≤0.5%). Sodium chloride content % 0.42 The newly added test result was below the standard limit (≤0.6%). Water-insoluble content % 0.03 The newly added test result shows that the calcium chloride content meets the requirements for high-end desiccants (≤0.05%). pH value (10% aqueous solution) 7.2 New test results were neutral.

[0076] (4) Silicon-aluminum tailings (detected by X-ray fluorescence spectrometry)

[0077] Main components: SiO2 content 42.35%, Al2O3 content 5.12%, Fe3O4 content 3.87%, CaO content 2.15%, of which the SiO2 content is higher than that of Example 1 (38.6%), and the Fe3O4 content is lower than that of Example 1 (5.2%).

[0078] Example 3: As shown in the attached document Figure 1 As shown: This invention provides a method for separating calcium and iron from steel slag tailings, comprising the following steps:

[0079] 1. The technical parameters of the raw steel slag tailings and hydrochloric acid pickling wastewater used are the same as those in Example 1.

[0080] 2. Steps for the differentiated and resource-based treatment of steel slag tailings:

[0081] S1. Finely ground steel slag powder reacts with hydrochloric acid pickling waste liquid in a leaching reactor;

[0082] S2. The treated steel slag enters the neutralization reactor, and ammonia gas generated by S5 is introduced into the neutralization reactor.

[0083] S3. The filter cake after pressure filtration of the neutralization product is magnetically separated to obtain iron concentrate.

[0084] S4. The filtrate of the neutralization product can be purified, concentrated, and crystallized to obtain calcium chloride product.

[0085] S5. The purified and impurity-removed crude calcium chloride can also enter the carbonization reactor, where ammonia and carbon dioxide gas generated in S5 are introduced to react.

[0086] The filter cake obtained by pressure filtration of the S6 and S5 carbonation reaction products is calcium carbonate.

[0087] The filtrate from the carbonization reaction products of S7 and S5 after pressure filtration is an ammonium chloride solution, which enters the dissociation reaction system. The ammonia gas generated by the reaction enters S2, and the ammonia gas and carbon dioxide gas enter S5.

[0088] The calcium chloride solutions generated from the dissociation of S8 and S7 are combined and then concentrated in the concentration process after purification and impurity removal in S4 to obtain the calcium chloride product.

[0089] Preferably, in S1, the fine particle size of the steel slag powder is 150~200 mesh.

[0090] Preferably, the liquid-to-solid ratio of hydrochloric acid pickling waste liquid to steel slag powder in the pipeline leaching reactor is 3:1.

[0091] Preferably, the concentration of calcium chloride in the liquid of the supergravity carbonization reactor is 30-35%, the mass ratio of CO2 to NH3 in the gas is 44:17, the CO2 concentration is 30-50%, and the supergravity factor is 50-200.

[0092] Preferably, the main reactants in the dissociation reaction system of S7 are calcium carbonate and ammonium chloride, and the dissociation reaction temperature is maintained at 55±10℃.

[0093] 3. Technical parameters of products after treatment of hydrochloric acid pickling wastewater from steel slag tailings:

[0094] (1) Steel slag leaching residue (detected by X-ray fluorescence spectrometry)

[0095] Testing items Units of measurement Test results Comparison with Examples 1 and 2 <![CDATA[SiO2]]> % 32.05 The content is the same as in Examples 1 and 2, but the active silica content is increased from below 60% in Example 1 to 65%. <![CDATA[Fe3O4]]> % 4.2 Significantly lower than the 6.63% in Example 1 CaO % 26.32 Consistent with Examples 1 and 2 MnO % 3.47 No change, the indicators are the same as in Examples 1 and 2. <![CDATA[P2O5]]> % 2.67 The content is stable and consistent with that in Examples 1 and 2. MgO % 5.77 No changes, maintaining the same level as in Examples 1 and 2. <![CDATA[Al2O3]]> % 4.48 The content was consistent, and there was no difference from the indicators in Examples 1 and 2. <![CDATA[Cr2O3]]> % 0.03 Trace residues, consistent with Examples 1 and 2 <![CDATA[NH4Cl]]> % 0.05 The residual amount is extremely low, comparable to that in Examples 1 and 2.

[0096] (2) Iron concentrate products

[0097] Iron grade: stable at 57.5-58.5%.

[0098] Iron recovery rate: increased from 90% in Example 1 to 94%.

[0099] Purity and impurities: The purity is above 98% (consistent with Examples 1 and 2); the SiO2 content is ≤1.0%, the P content is ≤0.07%, and the S content is ≤0.04%, all of which are lower than that of Example 1 and close to that of Example 2.

[0100] (3) Calcium carbonate products

[0101] Purity and phase composition: According to the standard "Industrial Calcium Carbonate" (YS / T 703-2014), the purity is above 98%; the calcite content is 97.3% as determined by XRD, which is the same as in Example 1.

[0102] Calcium ion content: The result of EDTA complexometric titration was 38.80%, consistent with Examples 1 and 2.

[0103] (4) Calcium chloride products

[0104] Purity and composition: After purification, concentration and crystallization, the purity reaches 98% or more (consistent with Examples 1 and 2); the effective component content of CaCl2 is ≥98.5%, which meets the first-class standard of "Industrial Calcium Chloride" (GB / T 26520-2011); the impurities NaCl≤0.5% and MgCl2≤0.3%, which are no different from the indicators of Examples 1 and 2.

[0105] Moisture and stability: Moisture content ≤0.5%, the same as in Examples 1 and 2.

[0106] (5) Silicon-aluminum tailings

[0107] Main components: mainly active silica (65%), with small amounts of Al2O3 (4.48%) and MgO (5.77%), and Fe3O4 content reduced to 4.2%.

[0108] The embodiments of the present invention are given for the purposes of illustration and description. Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for separating calcium and iron from steel slag tailings, characterized in that, Includes the following steps: S1. Finely ground steel slag powder reacts with hydrochloric acid pickling waste liquid in a leaching reactor; S2. The treated steel slag enters the neutralization reactor, and ammonia gas generated by S5 is introduced into the neutralization reactor. S3. The filter cake after pressure filtration of the neutralization product is magnetically separated to obtain iron concentrate. S4. The filtrate of the neutralization product is purified, concentrated, and crystallized to obtain calcium chloride product. S5. The purified and impurity-removed crude calcium chloride enters the carbonization reactor, where ammonia and carbon dioxide gas generated in S5 are introduced to react. The filter cake obtained by pressure filtration of the S6 and S5 carbonation reaction products is calcium carbonate. The filtrate from the carbonization reaction products of S7 and S5 after pressure filtration is an ammonium chloride solution, which enters the dissociation reaction system. The ammonia gas generated by the reaction enters S2, and the ammonia gas and carbon dioxide gas enter S5. The calcium chloride solutions generated from the dissociation of S8 and S7 are combined and then concentrated in the concentration process after purification and impurity removal in S4 to obtain the calcium chloride product.

2. The method for separating calcium and iron in steel slag tailings as described in claim 1, characterized in that: In S1, the fine particle size of the steel slag powder is 150~200 mesh.

3. The method for separating calcium and iron in steel slag tailings as described in claim 1, characterized in that: The liquid-to-solid ratio of hydrochloric acid pickling waste liquid to steel slag powder in the pipeline leaching reactor is 3:

1.

4. The method for separating calcium and iron in steel slag tailings as described in claim 1, characterized in that: The concentration of calcium chloride in the liquid of the supergravity carbonization reactor is 30-35%, the mass ratio of CO2 to NH3 in the gas is 44:17, the CO2 concentration is 30-50%, and the supergravity factor is 50-200.

5. The method for separating calcium and iron in steel slag tailings as described in claim 1, characterized in that: The reactants in the dissociation reaction system of S7 include calcium carbonate and ammonium chloride, and the dissociation reaction temperature is maintained at 55±10℃.

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