Method for preparing H2-CO energy gas from steel slag

Abstract

The invention provides a method for preparing H2-CO energy gas from steel slag, and belongs to the field of metallurgy and solid waste treatment. The preparation method comprises the following specific preparation steps: step 1, blowing weak oxidizing gas to the liquid level of the steel slag in a molten state to oxidize FeO in the steel slag, so that hydrogen and carbon monoxide gas are generated while ferric oxide is converted into a magnetic phase which is easy to separate; and 2, separating and collecting the reacted gas. After the steps, the energy gas containing H2 and CO is finally generated for recycling. Through the treatment steps provided by the invention, (1) CO2 is absorbed and converted into CO energy gas, and carbon emission is reduced; (2) waste heat of the steel slag is utilized, water vapor is converted into clean energy H2, and the hydrogen production cost is remarkably reduced; and (3) the injection proportion of H2O-CO2 gas is regulated and controlled, and the generation rate of H2-CO is remarkably increased.

Description

Technical Field

[0001] The present invention relates to the field of metallurgy and solid waste treatment, and in particular to a method for preparing H2-CO energy gas by using steel slag, not particularly for converter steel slag with a fixed basicity and FeO content and a specific insulation temperature. Background Art

[0002] Converter slag is a solid waste discharged during the steel production process. For every ton of crude steel produced, about 100-150 kg of slag is produced, the discharge temperature reaches 1723-1923 K, and the FeO content is as high as 20-30%. At present, the slag recycling process mainly recycles part of the slag materials, and the sensible heat and latent heat (residual energy) of the slag are hardly effectively utilized. The production of green hydrogen and the reduction of carbon dioxide emissions have become key technical development directions. The government has also included the comprehensive utilization of solid waste in the important agenda, continuously improved various policies and regulations, and provided relevant incentives and preferential policies. Promote the clean and efficient use of fossil energy such as coal, promote the green transformation of industries such as steel, petrochemicals, and building materials, carry out real-time green technology innovation and tackle key problems, and carry out benchmarking and improvement actions for resource efficiency in key industries and key products. Therefore, finding a suitable slag treatment process, reducing carbon emissions and comprehensive utilization technology of slag for green hydrogen preparation are major technical problems that steel companies urgently need to solve.

[0003] The FeO content in steel slag is as high as 20-30% and has high-temperature melting characteristics. Conventional water treatment not only wastes a lot of waste heat, but also easily causes the risk of hydrogen explosion. The present invention utilizes the weak oxidizing properties of water vapor and carbon dioxide to not only convert FeO into a magnetic iron oxide phase, but also generate H2 and CO energy gases for storage and utilization, and mixes a certain amount of inert gas argon to reduce the risk of energy gas recovery, thereby achieving safe and efficient comprehensive utilization of steel slag. Summary of the invention

[0004] The problem to be solved by the present invention is not only to recover the iron-containing phase in steel slag, but also to utilize the waste heat of steel slag to convert it into H2 or CO energy gas for storage, thereby improving the comprehensive utilization efficiency of steel slag and the production efficiency of H2 or CO energy gas, and matching an appropriate amount of inert gas to ensure the stability of the H2-CO energy gas mixture and improve production safety.

[0005] The present invention proposes

[0006] A method for preparing H2-CO energy gas using steel slag, characterized in that the preparation steps are as follows:

[0007] Step 1: spraying a weak oxidizing gas onto the liquid surface of the molten steel slag to oxidize FeO in the steel slag, so that the iron oxide is converted into an easily separable magnetic phase and hydrogen and carbon monoxide gases are generated;

[0008] Step 2: Separate and collect the gas after the reaction.

[0009] Furthermore, the melting temperature of the steel slag in step 1 is 1400-1600°C.

[0010] Furthermore, the chemical composition of the steel slag in step 1 is: 50.0-36.7% CaO, 25.0-18.3% SiO2, 20.0-25% FeO, 5.0-33.0% Al2O3, and 0-20% MgO.

[0011] Furthermore, in step 1, the weak oxidizing gas is an Ar-H2O-CO2 mixed gas; the temperature of the Ar-H2O-CO2 mixed gas is between 100 and 125°C.

[0012] Furthermore, in the Ar-H2O-CO2 mixed gas in step 1, the Ar partial pressure is 0.1-0.333, the water vapor partial pressure is 0.1-0.5, and the CO2 partial pressure is 0.1-0.8.

[0013] Furthermore, the Ar-H2O-CO2 mixed gas injection intensity is 120 m 3 / (min·t).

[0014] The reaction principle of molten steel slag and weak oxidizing gas is:

[0015] 2Fe 2+ +H2O(g)→2Fe 3+ +O 2- +H2(g)

[0016] 2Fe 2+ +CO2(g)→2Fe 3+ +O 2- +CO(g)

[0017] The solution disclosed by the present invention has the following advantages:

[0018] 1. The method for generating H2-CO energy gas provided by the present invention mainly comprises the following steps: 2+ Oxidation process:

[0019] In step 1, "the slag is in a molten state", a reasonable temperature range is controlled, and the elements in the slag in the molten state exist in the form of ions;

[0020] Then, as the steps proceed, "an adjustable weak oxidizing gas is sprayed onto the liquid surface of the molten slag to oxidize the FeO in the slag", and H2O and CO2 will be converted into H2 and CO respectively.

[0021] Finally, a mixed gas containing H2 and CO is obtained after gas analysis and collection.

[0022] 2. The H2-CO preparation method provided by the present invention significantly improves the overall gas generation rate and the H2O-CO2 participation reaction rate. After separation treatment, it can be used as energy gas for steel production. Compared with the current commonly used hydrogen production method, this method uses solid waste for preparation, greatly reduces waste gas emissions and saves energy. The oxidized steel slag can also be recycled after magnetic separation treatment, which plays a role in reducing the amount of steel slag solid waste.

[0023] 3. The weak oxidizing gas control range provided by the present invention not only improves the comprehensive utilization rate of steel slag, but also appropriately reduces the volume concentration of H2 and CO by mixing a certain amount of inert gas argon, so that it is not within the explosion limit range of hydrogen and carbon monoxide, thereby improving production safety. DETAILED DESCRIPTION

[0024] The technical solution of the present invention will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0026] Example 1

[0027] In this embodiment, steel slag with a mass of 5 g is selected. The contents of each component in the steel slag are shown in Table 1. Among them, CaO is 2.5 g; SiO2 is 1.25 g; FeO is 1.25 g. Argon gas is sprayed at 200 mL / min, water vapor is 160 mL / min, and carbon dioxide is 240 mL / min. The steel slag is melted in an argon atmosphere using a tubular furnace, and the reaction temperature is 1600 °C.

[0028] 5 g of slag was selected and melted at 1600 °C, and the mixed gas (Q Ar =200 mL / min, Q H2O =160 mL / min, Q CO2=240 mL / min), and oxidized FeO in the steel slag. During the oxidation process, the quadrupole online gas mass spectrometer analyzed the changes in gas composition, and the average generation rate of H2-CO mixed gas was 8.73×10 -6 mol / s, of which the average generation rate of CO can reach 6.61×10 -6 mol / s, the average generation rate of H2 can reach 2.12×10 -6 mol / s. After the reaction, the steel slag product was rapidly cooled at a cooling rate of 100 °C / min. The cooled steel slag was crushed, and the Fe content in the slag phase was determined by XRF and titration analysis. 2+ and Fe 3+ The content changes, the iron grade is 20.42%, Fe 2+ The content is 13.64%, Fe 3+ The content is 6.78%. To analyze whether the energy gas concentration is within the safe range, considering that water vapor is easy to condense, the calculated generated gas is analyzed with Ar-CO2-CO-H2 mixed gas, and the CO concentration is 2.01% and the H2 concentration is 0.64%. Both gases are below their respective explosion limits (explosion limit range CO: 12.5~74.2%, H2: 4.0~75.6%).

[0029] In this embodiment, the definitions of specific parameters are as follows:

[0030] 1. Gas generation rate: the molar amount of gas generated per unit time, mol / s;

[0031] 2. Iron grade: the total iron content in the slag, i.e. TFe;

[0032] 3. Fe 2+ Content: the mass fraction of iron in slag in the form of 2+ valence, i.e. the content of divalent iron;

[0033] 4. Fe 3+ Content: the mass fraction of iron in slag in the form of 3+ valence, i.e., trivalent iron content;

[0034] Example 2

[0035] Embodiment 2 is substantially the same as Embodiment 1, except that:

[0036] The mixed gas (Q Ar =200 mL / min, Q H2O =240 mL / min, Q CO2 =60 mL / min), and the FeO in the steel slag was oxidized. During the oxidation process, the gas composition was analyzed by a quadrupole online gas mass spectrometer, and the average generation rate of the H2-CO mixed gas was 5.52×10-6 mol / s, of which the average generation rate of CO can reach 1.82×10 -6 mol / s, the average generation rate of H2 can reach 3.70×10 -6 mol / s. After the reaction, the steel slag product was rapidly cooled at a cooling rate of 100°C / min; the cooled steel slag was crushed, and the Fe content in the slag phase was determined by XRF and titration analysis. 2+ and Fe 3+ The content changes, the iron grade is 21.77%, Fe 2+ The content is 16.64%, Fe 3+ The content is 5.14%.

[0037] Example 3

[0038] Embodiment 3 is substantially the same as Embodiment 1, except that:

[0039] After the steel slag with CaO content of 43.33%, SiO2 content of 21.67%, FeO content of 25%, and MgO content of 10% was kept melted at 1550℃, the mixed gas was sprayed onto the surface of the molten steel slag. After analysis by a quadrupole online gas phase mass spectrometer, the average generation rate of the H2-CO mixed gas was 9.02×10 -6 mol / s, the generation rate of CO can reach 7.90×10 -6 mol / s, the generation rate of H2 can reach 1.11×10 -6 mol / s. After the reaction, the steel slag product was rapidly cooled at a cooling rate of 100°C / min; the cooled steel slag was crushed, and the Fe content in the slag phase was determined by XRF and titration analysis. 2+ and Fe 3+ The content changes, the iron grade is 21.1%, Fe 2+ The content is 10.94%, Fe 3+ The content is 10.16%.

[0040] Comparative Example

[0041] In this comparative example, a method of blowing a weak oxidizing gas water vapor was adopted. The blowing gas was argon 200 mL / min and water vapor 400 mL / min. The average generation rate of H2 was 4.81×10 -6 mol / s. Due to the condensation of water vapor, only Ar and H2 exist in the gas phase. The concentration of hydrogen is 3.23%, which is lower than the explosion limit of hydrogen (4.0-75.6%). The addition of argon ensures production safety. In the method of single CO2 injection, the injection gas is argon 200 mL / min and CO2 400 mL / min. The average generation rate of CO2 is 5.18×10 -6 mol / s.

[0042] It can be seen that under the premise of regulating the energy gas below the explosion limit, the average generation rate of the energy gas is lower than the generation rate of the H2-CO energy gas obtained by the method of spraying the H2O-CO2 mixed gas in Examples 1 and 3.

[0043] Table 1 Content of each component in steel slag

[0044]

[0045] Obviously, the above embodiments are only examples for clear explanation, and are not intended to limit the implementation methods. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from this are still within the protection scope of the invention.

Claims

1. A method for preparing H2-CO energy gas using steel slag, characterized in that: The preparation steps are as follows: Step 1: spraying a weak oxidizing gas onto the liquid surface of the molten steel slag to oxidize FeO in the steel slag, so that the iron oxide is converted into an easily separable magnetic phase and hydrogen and carbon monoxide gases are generated; Step 2: Separate and collect the gas after the reaction.

2. The method for preparing H2-CO energy gas using steel slag according to claim 1, characterized in that: The melting temperature of the steel slag in step 1 is 1400-1600°C.

3. The method for preparing H2-CO energy gas using steel slag according to claim 1, characterized in that: The chemical composition of the steel slag in step 1 is: 50.0-36.7% CaO, 25.0-18.3% SiO2, 20.0-25% FeO, 5.0-33.0% Al2O3, and 0-20% MgO.

4. The method for preparing H2-CO energy gas using steel slag according to claim 1, characterized in that: In step 1, the weak oxidizing gas is an Ar-H2O-CO2 mixed gas; the temperature of the Ar-H2O-CO2 mixed gas is between 100 and 125°C.

5. The method for preparing H2-CO energy gas using steel slag according to claim 1 or 4, characterized in that: In step 1, the Ar-H2O-CO2 mixed gas has an Ar partial pressure of 0.1-0.333, a water vapor partial pressure of 0.1-0.5, and a CO2 partial pressure of 0.1-0.

8.

6. The method for preparing H2-CO energy gas using steel slag according to claim 1 or 4, characterized in that: The Ar-H2O-CO2 mixed gas injection intensity is 120 m 3 / (min·t).

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