Method for magnetizing and converting titanium-containing blast furnace slag into ilmenite

Abstract

The invention discloses a method for magnetizing and converting titanium-containing blast furnace slag into ilmenite, which comprises the following steps: (1) uniformly mixing ground titanium-containing blast furnace slag with copperas and activated carbon, and roasting at a certain temperature in an air atmosphere to convert perovskite in the titanium-containing blast furnace slag into ilmenite and calcium sulfate; (2) the obtained roasting slag can be subjected to magnetic separation to enrich ilmenite as a sulfuric acid process titanium dioxide production raw material, and magnetic separation tailing calcium sulfate can be used as a mineralization raw material, so that the comprehensive utilization of the titanium-containing blast furnace slag is realized; and meanwhile, comprehensive utilization of the sulfate process titanium dioxide byproduct copperas can be realized.

Description

Technical Field

[0002] The invention belongs to the field of comprehensive utilization of solid waste and reduction of carbon dioxide emission, and mainly relates to a method for magnetizing and converting titanium-containing blast furnace slag into ilmenite. Background Art

[0003] Since the Industrial Revolution, the use of fossil fuels has produced a large amount of CO2, which has had a serious impact on the global climate. The greenhouse effect caused by CO2 emissions has a huge impact on the global climate and ecosystem. The development of CO2 storage or reuse after the combustion of fossil fuels has become an important direction for global emission reduction. CO2 capture and storage technology is currently the most effective way to achieve carbon emission reduction. Among them, CO2 mineral storage is the use of CO2 to react with calcium-magnesium silicate minerals to store it permanently in the form of stable carbonates. Blast furnace slag is a waste slag containing calcium-magnesium-aluminum silicates. my country emits about 200 million tons each year, and its utilization rate is less than 60%, resulting in resource waste and land occupation. The rich calcium and magnesium ions in titanium-containing blast furnace slag are not only suitable for CO2 mineralization, but also can recycle important titanium resources.

[0004] Domestic scholars have conducted extensive research on the recycling of titanium in titanium-containing blast furnace slag. Patent CN201510010258.4 uses a vacuum carbon thermal reduction-acid leaching combined process. By maintaining high pressure and high temperature during the vacuum reduction process, it achieves effective separation of silicon and titanium, and finally obtains TiC products. Patent CN201710187393.5 uses Si powder as a reducing agent to reduce titanium-containing blast furnace slag, and obtains titanium-silicon intermetallic compound Ti5Si3 and glass slag by mixing Si powder and titanium-containing blast furnace slag for roasting. Patent CN201710729871.0 uses a one-step hydrochloric acid treatment of titanium-containing blast furnace slag to achieve the extraction of titanium resources and obtain titanium dioxide powder. Yan Fang et al. used a two-stage sulfuric acid leaching process to study the extraction of titanium from Panzhihua Steel's water-quenched titanium-containing blast furnace slag, achieving a high leaching rate. Liu Xiaohua et al. used a dilute sulfuric acid pressure leaching process to study and finally obtained a product with a TiO2 content of more than 90%. Chen Qifu and others used industrial sulfuric acid to treat Panzhihua Iron and Steel's titanium-containing blast furnace slag and successfully extracted titanium resources. Sun Kang and others took into account the thermodynamic reaction trend and realized a new method for separating silicon and titanium. Although there are many methods for treating titanium-containing blast furnace slag, in order to reduce energy consumption and improve economic efficiency, it is crucial to select appropriate additives and recover valuable titanium elements.

[0005] On the other hand, more than 90% of the world's titanium resources are used to produce titanium dioxide. More than 95% of my country's titanium dioxide is produced by the sulfuric acid process. In this process, 3-4 tons of green vitriol (FeSO4·7H2O) are produced as a by-product for every ton of titanium dioxide produced. The green vitriol formed by crystallization in the acidic solution gradually dehydrates during storage, seriously polluting the environment. The utilization of green vitriol has always been a problem to be solved in the titanium dioxide industry. At present, the titanium dioxide production in Panzhihua accounts for more than 30% of the national production. According to this estimate, about 11 million tons of green vitriol are discharged each year. In patent CN201510097926.1, Li Chun proposed a method for converting the titanium component in titanium-containing blast furnace slag into a ilmenite phase that can be enriched by magnetic separation. First, the titanium-containing blast furnace slag and green vitriol are roasted in an oxidizing atmosphere to obtain a primary conversion slag, and then ammonium carbonate is used in an aqueous solution to convert calcium sulfate in the primary conversion slag into calcium carbonate. Finally, the secondary conversion slag obtained by coal gas reduction is used to convert pseudobrookite into magnetic ilmenite. Although this method has achieved the extraction of titanium resources, it has the disadvantage of a lengthy process flow, and the titanium phase has undergone multiple transformations from perovskite, tialite to ilmenite. If solid waste green vitriol can be used as a roasting aid to achieve magnetic separation and enrichment of ilmenite in one step, it will greatly simplify the process flow of titanium resource recycling from titanium-containing blast furnace slag.

[0006] Based on the above, the present invention proposes a method for directly converting titanium-containing blast furnace slag into ilmenite by magnetization. The specific route is: the titanium-containing blast furnace slag, the solid waste green vitriol and activated carbon (as a reducing agent) which are by-products of the production of titanium dioxide by sulfuric acid process are roasted in an air atmosphere at a certain temperature, the perovskite and low-valent titanium oxide in the titanium-containing blast furnace slag are sulfated and oxidized respectively, the titanium-containing component is magnetized and converted into ilmenite, and the calcium and magnesium elements are converted into sulfates for mineralizing CO2. This is a method of "treating waste with waste" and simultaneously utilizing titanium-containing blast furnace slag and green vitriol as resources. The process uses industrial solid waste green vitriol as a sulfation aid to avoid its recycling problem. This route realizes the comprehensive utilization of titanium-containing blast furnace slag, and can also realize the comprehensive utilization of green vitriol which is a by-product of titanium dioxide by sulfuric acid process. Summary of the invention

[0007] Aiming at the problems of extracting titanium from titanium-containing blast furnace slag as solid waste and treating titanium dioxide industrial solid waste, the present invention provides a method for magnetizing and converting titanium-containing blast furnace slag into ilmenite.

[0008] The method for converting titanium-containing blast furnace slag into ilmenite by magnetization of the present invention uses titanium-containing blast furnace slag, green vitriol and activated carbon as raw materials, and the process steps are as follows:

[0009] 1. Sulfated titanium-containing blast furnace slag

[0010] The titanium-containing blast furnace slag finely ground to less than 200 μm is uniformly mixed with green vitriol and activated carbon, and the mass ratio of the titanium-containing blast furnace slag to the green vitriol is controlled to be 1:0.5-6, and the mass ratio of the titanium-containing blast furnace slag to the activated carbon is controlled to be 1:0.1-1; the mixture is roasted at 500-800° C. for 10-240 min to obtain a solid product;

[0011] 2. Magnetic separation of ilmenite

[0012] Utilize magnetic separation technology to extract and enrich ilmenite from the roasting slag obtained from the first step of sulphate roasting; 3. Mineralization of calcium-rich tailings

[0013] The ore pulp containing calcium sulfate after magnetic separation in step 2 is introduced into CO2 at a certain temperature to generate calcium carbonate to achieve mineralization of CO2.

[0014] Compared with the prior art, the present invention has the following advantages: (1) The process uses green vitriol, a by-product of titanium dioxide, as an auxiliary agent, thereby avoiding the high-energy consumption auxiliary agent recovery and circulation process in the mineral sealing process; (2) The raw material of the process is green vitriol, a solid waste of titanium dioxide, which has a wide source, thereby achieving effective utilization of waste, reducing environmental pollution and saving production costs; (3) The reaction conditions of the process are mild and the CO2 storage capacity is large; (4) The present invention uses green vitriol and activated carbon to modify titanium-containing blast furnace slag to form and enrich it into ilmenite; (5) The process of the present invention is simple, easy to operate, has no waste slag discharge, will not cause secondary pollution, has low production costs, and has prospects for industrial application. DETAILED DESCRIPTION

[0015] The present invention is described in detail below in conjunction with the embodiments, but the protection scope of the present invention is not limited to the following embodiments.

[0016] The main chemical composition (mass percentage) of the titanium-containing blast furnace slag used in the following examples is 30.38% CaO, 18.36% TiO2, 26.11% SiO2, 11% Al2O3, 7.14% MgO, and 1.86% Fe2O3. Figure 2 As shown, the XRD analysis results show that the main phase in the titanium-containing blast furnace slag is perovskite CaTiO3. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is the process flow chart of the present invention

[0018] Figure 2 This is the XRD pattern of titanium-containing blast furnace slag

[0019] Embodiment 1

[0020] (1) uniformly mixing titanium-containing blast furnace slag finely ground to less than 200 μm with green vitriol and activated carbon, controlling the mass ratio of titanium-containing blast furnace slag to green vitriol to be 1:0.5; the mass ratio of titanium-containing blast furnace slag to activated carbon to be 1:0.2; roasting the mixture at 500° C. for 240 min to obtain a solid product;

[0021] (2) using magnetic separation technology to separate ilmenite from the roasting slag obtained from the sulphate roasting step 1, wherein the titanium dioxide content in the ilmenite reaches 45.3%;

[0022] (3) To the ore pulp containing calcium sulfate after magnetic separation in step 2, NaOH is added to raise the pH value of the mother liquor to 12, and the solution temperature is controlled to be 50° C. CO2 is introduced, and the reaction is carried out for 30 minutes to obtain a turbid solution, which is filtered to obtain a mineralized product containing calcium carbonate, thereby achieving CO2 mineralization, and the mineralization efficiency reaches 176 kg CO2 / t titanium-containing blast furnace slag.

[0023] Embodiment 2

[0024] (1) uniformly mixing titanium-containing blast furnace slag finely ground to less than 200 μm with green vitriol and activated carbon, controlling the mass ratio of titanium-containing blast furnace slag to green vitriol to be 1:3; the mass ratio of titanium-containing blast furnace slag to activated carbon to be 1:0.5; roasting the mixture at 600° C. for 60 min to obtain a solid product;

[0025] (2) using magnetic separation technology to separate ilmenite from the roasting slag obtained from the sulphate roasting step 1, wherein the titanium dioxide content in the ilmenite reaches 44.8%;

[0026] (3) To the ore pulp containing calcium sulfate after magnetic separation in step 2, NaOH is added to raise the pH value of the mother liquor to 13, and the solution temperature is controlled to be 70° C. CO2 is introduced, and the reaction is carried out for 90 minutes to obtain a turbid solution, which is filtered to obtain a mineralized product containing calcium carbonate, thereby achieving CO2 mineralization, and the mineralization efficiency reaches 187 kg CO2 / t titanium-containing blast furnace slag.

[0027] Embodiment 3

[0028] (1) uniformly mixing titanium-containing blast furnace slag finely ground to less than 200 μm with green vitriol and activated carbon, controlling the mass ratio of titanium-containing blast furnace slag to green vitriol to be 1:5; and the mass ratio of titanium-containing blast furnace slag to activated carbon to be 1:0.5; calcining the mixture at 650° C. for 120 min to obtain a solid product;

[0029] (2) using magnetic separation technology to separate ilmenite from the roasting slag obtained from the sulphate roasting step 1, wherein the titanium dioxide content in the ilmenite reaches 45.7%;

[0030] (3) Adding NaOH to the ore pulp containing calcium sulfate after magnetic separation in step 2 to raise the pH value of the mother liquor to 12, and controlling the solution temperature to 60° C. to introduce CO2 for 60 min to obtain a turbid solution, which is filtered to obtain a mineralized product containing calcium carbonate, thereby achieving CO2 mineralization, with a mineralization efficiency of 216 kg CO2 / t titanium-containing blast furnace slag.

[0031] Embodiment 4

[0032] (1) uniformly mixing titanium-containing blast furnace slag finely ground to less than 200 μm with green vitriol and activated carbon, controlling the mass ratio of the titanium-containing blast furnace slag to green vitriol to be 1:6; and the mass ratio of the titanium-containing blast furnace slag to activated carbon to be 1:1; calcining the mixture at 800° C. for 90 min to obtain a solid product;

[0033] (2) using magnetic separation technology to separate ilmenite from the roasting slag obtained from the sulphate roasting step 1, wherein the titanium dioxide content in the ilmenite reaches 46.8%;

[0034] (3) Adding NaOH to the ore pulp containing calcium sulfate after magnetic separation in step 2 to raise the pH value of the mother liquor to 13, and controlling the solution temperature to 60° C. to introduce CO2 for 60 min to obtain a turbid solution, which is filtered to obtain a mineralized product containing calcium carbonate, thereby achieving CO2 mineralization, with a mineralization efficiency of 182 kg CO2 / t titanium-containing blast furnace slag.

Claims

1. A method for converting titanium-containing blast furnace slag into ilmenite by magnetization, characterized in that: The steps include: Step 1: uniformly mix titanium-containing blast furnace slag finely ground to less than 200 μm, green vitriol (FeSO4·7H2O) and activated carbon in a certain mass ratio and roast them in an air atmosphere at a certain temperature to obtain a solid product; Step 2: Using magnetic separation technology to extract and enrich ilmenite from roasted slag; Step 3: The ore pulp containing calcium sulfate after magnetic separation in step 2 is introduced into CO2 at a certain temperature to generate calcium carbonate to realize the mineralization of CO2.

2. The method for converting titanium-containing blast furnace slag into ilmenite by magnetization according to claim 1, characterized in that The mass ratio of the titanium-containing blast furnace slag to the green vitriol in step 1 is 1:0.5-6.

3. The method for converting titanium-containing blast furnace slag into ilmenite by magnetization according to claim 1, characterized in that The mass ratio of the titanium-containing blast furnace slag to the activated carbon in step 1 is 1:0.1-1.

4. The method for converting titanium-containing blast furnace slag into ilmenite by magnetization according to claim 1, characterized in that The material mixture of step 1 is calcined at a temperature of 500 to 800° C. and a calcination time of 10 to 240 minutes.

Images