Method for smelting titanium concentrate by utilizing biomass

Abstract

The invention provides a method for smelting titanium concentrate by using biomass, which comprises the following steps: S1, biomass is prepared into biomass particles, and the carbon content of the biomass is greater than or equal to 40wt%; s2, the biomass particles and the titanium concentrate pellets are mixed and then subjected to pyrolysis in a gas-based shaft furnace, and thermal-state biomass carbon particles and thermal-state titanium concentrate metallized pellets are obtained; and S3, the thermal-state biomass carbon particles and the thermal-state titanium concentrate metallized pellets are subjected to reduction smelting. According to the method for smelting the titanium concentrate through the biomass, the hydrogen-rich gas is pyrolyzed through the biomass, the reducing capacity of reducing gas of a gas-based shaft furnace is enhanced, the air permeability of furnace burden in the gas-based shaft furnace is improved, and obtained biomass carbon can be directly added into an electric furnace to replace nut coke, pulverized coal and the like for reduction; and carbon dioxide generated in the biomass carbon combustion or reduction process is not included in carbon emission, so that near-zero carbon emission can be realized by using green electricity.

Description

Technical Field

[0001] The present invention relates to the technical field of titanium concentrate metallurgy, and in particular to a method for smelting titanium concentrate using biomass. Background Art

[0002] Titanium concentrate is the product of ilmenite (FeTiO3) after beneficiation and enrichment, in which the TiO2 content is 45wt% to 60wt%; therefore, titanium concentrate can be used as the main raw material for titanium extraction process and is widely used in the production of titanium dioxide, metallic titanium and titanium alloys.

[0003] The core of titanium concentrate smelting is the separation of titanium and iron. The mainstream process includes electric furnace smelting, which involves reducing titanium concentrate and coke in an electric arc furnace at high temperatures (>1600°C). Iron is reduced to pig iron, and titanium is enriched into a high-titanium slag (TiO2 >80%). This method is suitable for subsequent processing by chlorination or sulfuric acid methods. However, direct electric furnace smelting of titanium concentrate suffers from low reduction activity and efficiency, high power consumption, and high CO2 emissions. To address these issues, researchers have conducted numerous studies. For example, Chinese Patent Publication No. CN104087746A discloses a method for preparing titanium concentrate pellets using dust removal ash, Patent Publication No. CN106222402A discloses a method for producing titanium concentrate pellets using titanium concentrate supplemented with iron oxides, and Chinese Patent Publication No. CN103924062A addresses the low utilization rate and high dust emissions of fine-grained titanium concentrate (70% -200 mesh) in electric furnace smelting by proposing a pre-reduction process. However, the above method still has the above problems.

[0004] Therefore, it is of great significance to provide a smelting method for titanium concentrate with near-zero carbon emissions. Summary of the Invention

[0005] The technical problem solved by the present invention is to provide a method for smelting titanium concentrate using biomass, which has the advantages of high reduction activity, high reduction efficiency, low power consumption and low CO2 emissions.

[0006] In view of this, the present application provides a method for smelting titanium concentrate using biomass, comprising the following steps:

[0007] S1. preparing biomass into biomass particles, wherein the carbon content of the biomass is ≥40 wt%;

[0008] S2. mixing the biomass particles and the titanium concentrate pellets and pyrolyzing them in a gas-based shaft furnace to obtain hot biomass carbon particles and hot titanium concentrate metallized pellets;

[0009] S3, reducing and smelting the hot biomass carbon particles and the hot titanium concentrate metallized pellets.

[0010] In some specific embodiments, the density of the biomass particles is ≥1.5 g / cm 3 , compressive strength ≥2000N.

[0011] In some specific embodiments, the ash content of the biomass particles is ≤5%, and the sulfur content is ≤0.2%.

[0012] In some specific embodiments, the method for preparing the biomass particles is specifically as follows:

[0013] The biomass is dried at 100-120°C, crushed to ≤5mm and then thermoformed into pellets.

[0014] In some specific embodiments, the moisture content of the dried biomass is less than 12%, and the temperature of the thermoforming granulation is 150-300° C. and the pressure is 10-50 MPa.

[0015] In some specific embodiments, the diameter of the biomass particles is 10-20 mm.

[0016] In some specific embodiments, the carbon content of the hot titanium concentrate metallized pellets is 3-12 wt%.

[0017] In some specific embodiments, the average metallization rate of the hot titanium concentrate metallized pellets is 65-75%.

[0018] In some specific embodiments, the reduction smelting is carried out in a closed electric furnace, and the hot biomass carbon particles and hot titanium concentrate metallized pellets are transferred from the gas-based vertical furnace to the closed electric furnace under inert gas protection.

[0019] In some specific embodiments, the reduction smelting time is 7.0 to 8.5 hours.

[0020] The present application provides a method for smelting titanium concentrate using biomass, which first prepares biomass into biomass particles, then mixes the biomass particles with titanium concentrate pellets and then pyrolyzes them in a gas-based vertical furnace, and finally reduces and smelts the obtained hot biomass carbon particles and hot titanium concentrate metallized pellets, and obtains high-titanium slag and molten iron after smelting; in the above process, the biomass is first pyrolyzed into biomass carbon in the gas-based vertical furnace, and the oxygen-free environment and high-temperature heat of the gas-based vertical furnace are utilized to pyrolyze the biomass and release hydrogen-rich gas, thereby increasing the effective reducing gas content in the gas-based vertical furnace, and the biomass carbon particles do not adhere to the titanium concentrate metallized pellets, thereby increasing the permeability of the charge and promoting the reduction of the titanium concentrate pellets, and then the hot biomass carbon particles and the hot titanium concentrate metallized pellets are deeply reduced in an electric furnace without adding other carbonaceous reducing agents, and combined with the use of green electricity, zero carbon emissions throughout the entire process are achieved; further, the biomass is first preheated in the gas-based vertical furnace, which is beneficial to reducing the power consumption of the electric furnace. DETAILED DESCRIPTION

[0021] In order to further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, rather than limiting the claims of the present invention.

[0022] In view of the problems of difficult reduction, low reduction efficiency, high power consumption and high CO2 emissions in the smelting of titanium concentrate in titanium slag furnaces in the prior art, the present application provides a method for smelting titanium concentrate using biomass, which first uses biomass to cooperate with a gas-based vertical furnace to pre-reduce titanium concentrate pellets, and pyrolyzes biomass to produce hydrogen-rich gas, thereby enhancing the reducing ability of the gas-based vertical furnace reducing gas and improving the permeability of the charge in the gas-based vertical furnace. The obtained biomass carbon can be directly added to the electric furnace to replace coke, coal powder and other reduction agents without introducing carbonaceous reducing agents that increase carbon emissions, and then the titanium concentrate pellets are reduced, thereby achieving titanium concentrate smelting with near-zero carbon emissions. Specifically, an embodiment of the present invention discloses a method for smelting titanium concentrate using biomass, comprising the following steps:

[0023] S1. preparing biomass into biomass particles, wherein the carbon content of the biomass is ≥40 wt%;

[0024] S2. mixing the biomass particles and the titanium concentrate pellets and pyrolyzing them in a gas-based shaft furnace to obtain hot biomass carbon particles and hot titanium concentrate metallized pellets;

[0025] S3, reducing and smelting the hot biomass carbon particles and the hot titanium concentrate metallized pellets.

[0026] In the process of using biomass to smelt titanium concentrate, the present application first prepares the biomass into biomass particles; in order to avoid affecting the efficiency of titanium concentrate smelting, the carbon content of the biomass is ≥40wt%, specifically, the carbon content of the biomass is 40-80wt%, more specifically, the carbon content of the biomass can be 40-50wt%; in addition to the above conditions, the biomass is conventional biomass in the prior art and can be selected from hazelnut shells, sawdust, sugarcane bagasse, reed stalks, etc. The method for preparing the biomass into biomass particles can be according to the method well known to those skilled in the art. In the present application, the method for preparing biomass particles is specifically as follows:

[0027] The biomass is dried at 100-120°C, crushed to ≤5mm and then thermoformed into pellets.

[0028] In the above process, the moisture content of the dried biomass is less than 12%. The temperature of the thermoforming granulation is 150-300°C and the pressure is 10-50 MPa; specifically, the temperature of the thermoforming granulation is 180-280°C and the pressure is 20-48 MPa, more specifically, the temperature of the thermoforming granulation is 200-240°C and the pressure is 25-38 MPa.

[0029] The diameter of the biomass particles prepared in this application is 10-20 mm, specifically, the diameter of the biomass particles is 12-15 mm; the diameter of the biomass particles will affect the subsequent pyrolysis process. If the diameter is too large, it may cause insufficient pyrolysis, and if it is too small, it will affect the air permeability of the gas-based vertical furnace. Furthermore, the density of the biomass particles is ≥1.5 g / cm 3 , compressive strength ≥ 2000N, ash content ≤ 5%, sulfur content ≤ 0.2%; Specifically, the density of the biomass particles is 1.7-2.0g / cm 3 , compressive strength 2500~2800N, ash content 0.5~3%, sulfur content ≤0.2%; the density of the biomass particles is to ensure that the biomass particles are more compact and avoid being too loose; if the compressive strength of the biomass particles is too low, the biomass particles will be easily crushed, blocking the vertical furnace channel and affecting the air permeability; the ash content of the biomass particles is to avoid slagging during electric furnace smelting, the slag volume is too large, the slag composition changes too much and affects the slag melting point; the sulfur content of the biomass particles is controlled to avoid being brought into the molten iron, so that the sulfur content in the molten iron is too high.

[0030] The present application then mixes the biomass particles and the titanium concentrate pellets and pyrolyzes them in a gas-based shaft furnace to obtain hot biomass carbon particles and hot titanium concentrate metallized pellets. In this process, the amount of biomass particles added is calculated based on the carbon content to meet the amount of FeO remaining in the amount of metallized titanium concentrate pellets reduced by one batch of electric furnace smelting, and is calculated according to the reaction formula:

[0031] FeO+C→Fe+CO;

[0032] In this application, the added carbon content is 1.1 to 1.3 times the theoretical amount calculated from the above reaction formula. The amount of biomass particles added can be determined based on the added carbon content. For example, the carbon content of the hot titanium concentrate metallized pellets is 3 to 12 wt %, and more specifically, the carbon content of the hot titanium concentrate metallized pellets is 5 to 10 wt %. The gas-based shaft furnace is a metallurgical reduction device known in the art, and its specific structure is not particularly limited in this application. Biomass particles are added to titanium concentrate pellets, and the process is carried out in an oxygen-free environment of a gas-based vertical furnace. The heat in the furnace pyrolyzes the biomass particles to generate biomass carbon particles. The pyrolysis gas released during the pyrolysis of the biomass particles is H2-rich gas, which is beneficial to increase the amount of reducing gas in the furnace and improve the H2 content. It is also beneficial to prevent the pyrolyzed biomass carbon particles from sticking to the metallized pellets, which is beneficial to loosen the material layer, increase the permeability of the charge, and promote the pre-reduction of the titanium concentrate pellets. In this process, the metallization rate of the titanium concentrate metallized pellets is increased by 1-3%. Specifically, the average metallization rate of the hot titanium concentrate metallized pellets is 65-75%. More specifically, the average metallization rate of the hot titanium concentrate metallized pellets is 69-72%.

[0033] According to the present invention, the hot biomass carbon particles and the hot titanium concentrate metallized pellets are finally subjected to electric furnace reduction smelting to obtain titanium slag and molten iron after melting. In this process, the reduction smelting is preferably carried out in a closed electric furnace, and inert gas protection is adopted during the transfer from the gas-based vertical furnace to the electric furnace. The reduction smelting time is 7.0 to 8.5 hours. Specifically, the reduction smelting time is 7.5 to 8.0 hours. The reduction smelting adopts green electricity, which is electricity produced by renewable energy (such as wind energy, solar energy, hydropower, etc.) or low-carbon clean energy.

[0034] The present application provides a method for smelting titanium concentrate using biomass, which utilizes the oxygen-free environment and high-temperature heat in a gas-based vertical furnace to pyrolyze biomass and release hydrogen-rich gas, thereby increasing the effective reducing gas content in the vertical furnace. The biomass carbon particles do not adhere to the metallized pellets of the titanium concentrate, which is beneficial to loosening the material layer, enhancing the permeability of the furnace charge, and promoting the reduction of the titanium concentrate pellets. The biomass carbon reducing agent is preheated in the gas-based vertical furnace to avoid absorbing heat in the electric furnace in a cold state, which is beneficial to reducing the power consumption of the electric furnace. Furthermore, in the titanium slag electric furnace smelting, the use of carbonaceous reducing agents that increase carbon emissions (accounting for approximately 5-10% of the mass of the titanium concentrate) is avoided, and instead a biomass carbon reducing agent that is not included in carbon emissions is used. When the titanium slag electric furnace uses green electricity, the titanium concentrate gas-based vertical furnace pre-reduction-titanium slag furnace smelting process achieves zero carbon emissions, reducing carbon dioxide emissions by 0.2-0.4tCO2 / t of titanium concentrate. Therefore, the present application utilizes carbon-neutral biomass to synergize with a gas-based vertical furnace-titanium slag electric furnace to smelt titanium concentrate, which is beneficial to promoting the reduction of titanium concentrate, reducing power consumption and deeply reducing carbon dioxide emissions, and can be widely used in titanium concentrate smelting enterprises.

[0035] In order to further understand the present invention, the method for smelting titanium concentrate using biomass provided by the present invention is described in detail below with reference to the examples. The protection scope of the present invention is not limited by the following examples.

[0036] Example 1

[0037] The hazelnut shells were dried at 120°C to a moisture content of less than 12%, crushed to ≤5mm particles using a grinder, and then thermoformed into hazelnut shell biomass pellets with a diameter of 12-15mm at a temperature of 240°C and a pressure of 38MPa. The hazelnut shell biomass pellets had a carbon content of about 50% and a density of about 1.7g / cm 3 , compressive strength 2800N, ash content 1-3%, sulfur content ≤0.2%;

[0038] Hazelnut shell biomass particles are mixed with titanium concentrate pellets (TFe 35%, TiO248%) and then added to a gas-based vertical furnace. The gas-based vertical furnace is used to reduce the titanium concentrate pellets to obtain hot titanium concentrate metallized pellets. The hazelnut shell biomass particles are pyrolyzed into hazelnut shell biochar in the furnace. Each kilogram of hazelnut shell biomass particles can produce 1.18L of reducing gas (CO+H2), and the generated CO:H2 ratio is 1:1.56. The average metallization rate of the titanium concentrate metallized pellets discharged from the furnace is 71.6%. In this process, the carbon content of the metallized pellets is about 5%, so the calculated addition amount of hazelnut shell biomass particles is 10%. If the electric furnace smelting capacity is 25t per furnace, 2.5t of hazelnut shell biomass particles are added.

[0039] Hazelnut shell biochar and hot titanium concentrate metallized pellets are directly hot-charged into a closed electric furnace for titanium slag reduction smelting and slag-iron separation. Green electricity is used for power supply, and inert gas protection is used during the transportation process. The smelting time is about 8.0 hours, and the power consumption is reduced from 1000kWh / t slag to 1500kWh / t slag. After melting and separation, high-titanium slag and molten iron are obtained, and the slag-iron separation effect is good, achieving zero carbon dioxide emissions from titanium concentrate smelting.

[0040] Comparative Example 1

[0041] When hazelnut shell biomass particles were not added, titanium concentrate pellets (TFe 35%, TiO2 48%) were pre-reduced in a gas-based shaft furnace to obtain hot titanium concentrate metallized pellets with an average metallization rate of 67.5%.

[0042] The hot titanium concentrate metallized pellets are directly hot-charged into a closed electric furnace for slag-iron separation and deep reduction of titanium slag. Inert gas is used for protection during the transportation process. The smelting time is about 10.0 hours, the power consumption is 2500kWh / t slag, and the carbon dioxide emissions are about 0.2tCO2 / t titanium concentrate.

[0043] Example 2

[0044] The reed stems were dried at 115°C to a moisture content of less than 12%, crushed to ≤5mm particles using a grinder, and then thermoformed and granulated at a temperature of 280°C and a pressure of 48 MPa to form reed stem biomass pellets with a diameter of 12-14mm. The reed stem biomass pellets had a carbon content of about 40% and a density of about 1.5g / cm 3 , compressive strength 2000N, ash content 0.5-2%, sulfur content ≤0.2%;

[0045] The hot-pressed reed biomass particles are mixed with titanium concentrate pellets (TFe 36%, TiO2 46%) and then added to a gas-based vertical furnace. The gas-based vertical furnace is used to reduce the titanium concentrate pellets to obtain hot titanium concentrate metallized pellets. The reed biomass particles are pyrolyzed into reed biochar in the furnace. Each kilogram of reed biomass particles can produce 1.22L of reducing gas (CO+H2), and the generated CO:H2 ratio is 1:1.80. The average metallization rate of the titanium concentrate metallized pellets discharged from the furnace is 68.6%. In this process, the carbon content of the metallized pellets smelted in the electric furnace is about 10%, so the calculated addition amount of reed biomass particles is 25%. If the electric furnace smelting capacity is 20t per furnace, 5t of reed biomass particles are added.

[0046] Reed stalk biochar and hot titanium concentrate metallized pellets are directly hot-charged into a closed electric furnace for titanium slag reduction smelting and slag-iron separation. Inert gas protection is used during the transportation process. The smelting time is about 8.5 hours, and the power consumption is reduced from 800kWh / t slag to 1800kWh / t slag. After melting, high-titanium slag and molten iron are generated, and the slag-iron separation effect is good, achieving zero carbon dioxide emissions from titanium concentrate smelting.

[0047] Comparative Example 2

[0048] When no reed straw biomass pellets are added, titanium concentrate pellets (TFe 36%, TiO2 46%) are pre-reduced in a gas-based vertical furnace, and the hot metallized pellets are directly hot-charged into a closed electric furnace for slag-iron separation and deep reduction of titanium slag. Inert gas is used for protection during the transportation process. The smelting time is about 11.0 hours, the power consumption is 2600kWh / t slag, and the carbon dioxide emissions are about 0.4tCO2 / t titanium concentrate.

[0049] Comparative Example 3

[0050] When using diced coke as a reducing agent, titanium concentrate pellets (TFe 36%, TiO2 46%) and 20% (weight ratio) diced coke are directly added to a closed electric furnace for vanadium-titanium slag reduction and slag-iron separation. The smelting time is about 30.0 hours, the power consumption is 3000 kWh / t slag, and the carbon dioxide emissions are about 1.0 tCO2 / t titanium concentrate. This method has a long smelting cycle, high power consumption and high carbon emissions.

[0051] The above embodiments are only intended to help understand the method and core concept of the present invention. It should be noted that, without departing from the principles of the present invention, a number of improvements and modifications may be made to the present invention by those skilled in the art, and such improvements and modifications also fall within the scope of protection of the claims of the present invention.

[0052] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for smelting titanium concentrate using biomass, comprising the following steps: S1. preparing biomass into biomass particles, wherein the carbon content of the biomass is ≥40 wt%; S2. mixing the biomass particles and the titanium concentrate pellets and pyrolyzing them in a gas-based shaft furnace to obtain hot biomass carbon particles and hot titanium concentrate metallized pellets; S3, reducing and smelting the hot biomass carbon particles and the hot titanium concentrate metallized pellets.

2. The method according to claim 1, characterized in that The density of the biomass particles is ≥1.5 g / cm 3 , compressive strength ≥2000N.

3. The preparation method according to claim 2, characterized in that The ash content of the biomass particles is ≤5%, and the sulfur content is ≤0.2%.

4. The method according to claim 1 or 3, characterized in that The preparation method of the biomass particles is specifically as follows: The biomass is dried at 100-120°C, crushed to ≤5mm and then thermoformed into pellets.

5. The method according to claim 4, characterized in that The moisture content of the dried biomass is less than 12%, the temperature of the hot forming granulation is 150-300° C., and the pressure is 10-50 MPa.

6. The method according to claim 1 or 5, characterized in that The diameter of the biomass particles is 10 to 20 mm.

7. The method according to claim 1, characterized in that The carbon content of the hot titanium concentrate metallized pellets is 3-12 wt%.

8. The method according to claim 1 or 7, characterized in that The average metallization rate of the hot titanium concentrate metallized pellets is 65-75%.

9. The method according to claim 8, characterized in that The reduction smelting is carried out in a closed electric furnace, and the hot biomass carbon particles and hot titanium concentrate metallized pellets are transferred from the gas-based vertical furnace to the closed electric furnace under inert gas protection.

10. The method according to claim 9, characterized in that The reduction smelting time is 7.0 to 8.5 hours.