An ultra-low-cost two-step titanium slag production process and system

Abstract

The application discloses a kind of ultra-low cost two-step method titanium slag production process and system.The process includes, titanium concentrate is sent into fluidized preheater after metering;Meanwhile, pre-baking is carried out to titanium concentrate using tail gas of fluidized reduction furnace and titanium slag electric furnace;In mixer, preheated titanium concentrate is fully mixed with metered reducing agent in mixer, to obtain mixed material;Then, mixed material is sent into fluidized reduction furnace through feeder to carry out first step reduction reaction, to obtain hot reduction material;Hot reduction material is directly added into titanium slag electric furnace to carry out second step smelting, titanium slag is discharged through slagging port of titanium slag electric furnace, and titanium slag finished product is obtained after titanium slag cooling, crushing and sorting.The application realizes comprehensive optimization in energy consumption, raw material consumption and equipment investment, so as to achieve the technical goal of ultra-low cost.

Description

Technical Field

[0001] This invention relates to an ultra-low-cost two-step titanium slag production process and an ultra-low-cost two-step titanium slag production system, belonging to the field of titanium slag smelting technology. Background Technology

[0002] Electricity consumption and reducing agent consumption are the most critical indicators affecting the production cost of titanium slag, with electricity consumption accounting for approximately 30% of the production cost. Reducing agent consumption accounts for about 12% of the total cost, and the remaining cost is due to titanium concentrate consumption. Since there is almost no TiO2 loss during the titanium slag production process, titanium concentrate consumption is determined by the TiO2 content in the titanium concentrate fed into the production unit. Therefore, there is essentially no room for adjustment regarding the impact of titanium concentrate consumption on the production cost of titanium slag. Thus, reducing electricity and reducing agent consumption has become a goal pursued by titanium slag production enterprises. However, despite years of efforts both domestically and internationally, these two indicators remain persistently high, hindering the development of the titanium slag industry and even the entire titanium industry.

[0003] Chinese patent application No. 201810267911.9 discloses a method for rapidly reducing titanium concentrate and separating high-titanium slag and acid-soluble titanium slag through low-temperature deep slag-iron separation. This technical solution involves raw material processing, pelletizing, and drying; then, in the reducing agent processing step, 30%–35% of the reducing agent is added to the pellets by weight to obtain the material to be reduced; next, the material to be reduced is added to a flame-insulated kiln and deeply reduced at 1080–1100℃ for 4–6 hours to achieve rapid slag-iron separation and reduction; then, a dry magnetic separator is used to separate the metallized pellets; finally, the high-titanium slag product is enriched. The reducing agent is composed of bituminous coal, anthracite, semi-coke, biomass materials, or biomass carbon with a particle size of 0–10 mm and a chemical composition by mass percentage of ≥45% fixed carbon, 5–20% ash, 15–35% volatile matter, 3–8% moisture, and the remainder being 0.3–1.0%. Summary of the Invention

[0004] The primary technical problem to be solved by this invention is to provide an ultra-low-cost two-step titanium slag production process.

[0005] Another technical problem to be solved by the present invention is to provide an ultra-low cost two-step titanium slag production system.

[0006] To achieve the above-mentioned technical objectives, the present invention adopts the following technical solution: According to a first aspect of the present invention, an ultra-low-cost two-step titanium slag production process is provided, comprising: Step 1: After metering, the titanium concentrate is fed into the fluidized bed preheater; at the same time, the tail gas from the fluidized bed reduction furnace and the titanium slag electric furnace is used to pre-bake the titanium concentrate; the moisture content can be reduced to less than 1%, the temperature can be increased to more than 200 degrees, the hourly material volume is 15-25 tons, and the actual processing capacity can be adjusted according to the production scale.

[0007] Step 2: In the mixer, the preheated titanium concentrate and the metered reducing agent are thoroughly mixed to obtain a mixture; the reducing agent ratio is 11-15% (the reducing agent ratio refers to the percentage of the reducing agent mass to the titanium concentrate mass).

[0008] Step 3: Then, the mixture is fed into the fluidized bed reduction furnace via a feeder to carry out the first reduction reaction, and hot reduced material is obtained; Step 4: The hot-state reduced material is directly added to the titanium slag electric furnace for the second step of smelting. The titanium slag is discharged through the slag discharge port of the titanium slag electric furnace. After cooling, crushing and sorting, the finished titanium slag product is obtained.

[0009] Preferably, air is introduced into the fluidized bed reduction furnace, wherein the O2 content is 0.5% to 5%, so that the reducing agent undergoes incomplete combustion to generate CO.

[0010] Preferably, the reducing agent is a carbonaceous solid comprising anthracite, metallurgical coke, or petroleum coke.

[0011] Preferably, the reducing agent is a low-ash, low-sulfur reducing agent. The ash content is <6.5%, and the sulfur content is <0.5% (over 80% of the measured values ​​are between 0.1% and 0.2%), in order to control the impurity content in the titanium slag.

[0012] The preferred method involves reducing the fluidized bed reduction furnace for 2-3 hours.

[0013] Preferably, the fineness and carbon content of the reducing agent satisfy the following relationship: reducing agent <2mm percentage >80%, fixed carbon content >40%, volatile matter <45%, and total water <20%, to ensure sufficient contact and rapid reaction with titanium concentrate in a fluidized state.

[0014] Preferably, the temperature of the fluidized bed reduction furnace is set to 900℃-1300℃, more preferably 950-1250℃. From a thermodynamic perspective, although high temperature is beneficial to the Boudouard reaction and reduction rate, the core advantage of the fluidized bed reduction process lies in achieving efficient heat and mass transfer using gas-solid two-phase flow, which requires the material to remain in a solid particle state. This ensures the solid reduction of iron and stable fluidization of the material. Therefore, this temperature setting avoids excessively high temperatures that could lead to liquid reduction, while ensuring sufficient temperature to promote the reduction of ilmenite. The reduction rate of ilmenite FeTiO3 can reach over 85%, and the reduction degree of trivalent iron can reach over 60% (at which point solid reduction can be well completed without clogging the fluidized bed).

[0015] Preferably, the prebaking temperature is 200~300℃, and more preferably 250℃. At this temperature, the free water and crystal water in the titanium concentrate can be basically removed, and the moisture content entering the furnace is less than 0.5%, effectively avoiding hydrogen explosion during the subsequent high-temperature reduction process.

[0016] According to a second aspect of the present invention, an ultra-low cost two-step titanium slag production system is provided, comprising a fluidized bed preheater, a mixer, a feeder, a fluidized bed reduction furnace, a titanium slag electric furnace, a titanium slag cooling furnace, a titanium slag crusher, and a titanium slag separator, for realizing the aforementioned ultra-low cost two-step titanium slag production process.

[0017] Compared with existing technologies, this invention can significantly reduce costs, mainly due to the synergistic effect of the following core innovations: The fluidized bed reduction furnace achieves integrated combustion-reduction self-circulation. By controlling the oxygen content within the furnace, the solid reducing agent undergoes incomplete combustion, generating CO in situ and releasing a large amount of heat. Combustion and reduction are coupled within the same reactor, eliminating the need for complex coal gasification, gas purification, and external heating equipment found in traditional processes. Because no external heating or gasification system is required, equipment investment and operating costs are significantly reduced.

[0018] 2) Solid carbon regenerates CO via the Boudouard reaction. CO reduces iron oxides to produce CO2, which then reacts with carbon to produce CO again, forming a continuously scaled-up self-circulating reduction system (C+CO dual reduction self-circulation). This mechanism significantly improves reduction efficiency, shortens reduction time (2-3 hours), and reduces reducing agent consumption, thereby reducing process costs.

[0019] 3) The high temperature in the fluidized bed reduction furnace enhances the reduction, causing a significant negative shift in the Gibbs free energy ΔG of the carbothermic reduction reaction of titanium oxides, thus strengthening the spontaneous tendency of the reaction. Moreover, the high temperature exponentially increases the reaction rate constant, overcomes the solid-solid reaction energy barrier, promotes the rapid progress of the Boudouard reaction, and maintains a strong reducing atmosphere.

[0020] 4) Utilizing waste heat for efficient utilization and direct connection with hot state: On the one hand, the tail gas from the fluidized bed reduction furnace and titanium slag electric furnace is used to preheat the titanium concentrate to 200~300℃, recovering sensible heat and reducing subsequent energy consumption; on the other hand, the hot reduced material obtained in the first step of reduction, with a temperature of about 800-850 degrees, is directly added to the titanium slag electric furnace for smelting without intermediate processing such as cooling and briquetting, avoiding energy loss from repeated heating, which can reduce the electric furnace power consumption by about 30-40%, further reducing power consumption.

[0021] 5) Solid reducing agents are much cheaper than gaseous reducing agents (usually only 1 / 3 to 1 / 5 of the cost of gaseous reducing agents), and are widely available. They eliminate the need for large auxiliary systems such as external gas production, purification, and hot pressing. The process is short, the operation and control are simple (only the amount of oxygen needs to be adjusted), and the maintenance cost is low.

[0022] Therefore, this invention achieves comprehensive optimization in three dimensions: energy consumption, raw material consumption, and equipment investment, thereby achieving the technical goal of ultra-low cost. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the process steps for the ultra-low cost two-step titanium slag production process in an embodiment of the present invention. Detailed Implementation

[0024] The technical content of the present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0025] The technical concept in this invention embodiment is as follows: A two-step reduction process is employed. In the first step of the fluidized bed reduction furnace, the Gibbs free energy (ΔG) of the reduction reaction is shifted negatively. The thermodynamic essence of this is utilizing the buffering capacity of the C-CO-CO2 ternary system to establish a low oxidation potential at a lower temperature, which satisfies the requirements for titanium oxide reduction. This facilitates the reduction reaction and further reduces the energy required for the reaction. Furthermore, the material from the first step of reduction is directly fed into the titanium slag electric furnace for smelting without cooling, significantly reducing system heat loss and further lowering the production cost of titanium slag.

[0026] (First embodiment) like Figure 1 As shown, the ultra-low cost two-step titanium slag production process provided in the first embodiment of the present invention includes the following steps.

[0027] Step 1: Titanium concentrate with a TiO2 content greater than 45% (more preferably, TiO2 content of 44%-55%) is metered and fed into a fluidized bed preheater; at the same time, the titanium concentrate is pre-baked using the tail gas from the fluidized bed reduction furnace and the titanium slag electric furnace.

[0028] The titanium concentrate has a fineness of 100-250 mesh (approximately 150-74 μm, accounting for over 80%) to ensure uniform fluidization, a large reaction area, and to prevent adhesion and loss of flow. Under fluidized conditions, the titanium concentrate undergoes rapid heat exchange for 10-30 minutes, simultaneously removing some moisture and volatiles. The fluidizing gas velocity in the fluidization preheater is 0.2-1.5 m / s.

[0029] In this step, the exhaust gas from the fluidized bed reduction furnace and the titanium slag electric arc furnace are used to preheat the mixture to 200-300℃, reducing energy consumption for subsequent reduction. It should be noted that although the exhaust gas from the fluidized bed reduction furnace is typically 600-900℃ (containing CO, CO2, etc.), and the exhaust gas from the titanium slag electric arc furnace is typically 800-900℃ (mainly CO, with a content of up to 60%), controlling the preheating temperature below 400℃ here is to prevent CO or H2 from significantly reducing iron oxides. Furthermore, it also prevents spontaneous combustion of the reducing agent (the ignition point of pulverized coal is typically >400℃), ensuring safety during the mixing process.

[0030] Step 2: In the mixer, the preheated titanium concentrate and the metered reducing agent are thoroughly mixed to obtain a mixture.

[0031] The reducing agent is a carbon-containing solid such as anthracite, metallurgical coke, or petroleum coke (with a cost far lower than gaseous CO, etc.), and it is a low-ash, low-sulfur reducing agent. The fineness and carbon content of the reducing agent meet the following relationship: <2mm accounts for more than 80% of the reducing agent, fixed carbon >40%, ash content <6.5%, and volatile matter appropriately higher than 45%, to ensure that the reducing agent has good fluidization characteristics and reactivity in the fluidized bed.

[0032] The ratio of reducing agent to titanium concentrate, based on fixed carbon, is 0.25~0.35 tons of reducing agent / ton of titanium concentrate, for example, 0.30 tons of reducing agent / ton of titanium concentrate. This ratio is calculated based on the theoretical carbon required for the incomplete reduction of iron oxides (FeO / Fe2O3) in the titanium concentrate, plus the excess carbon coefficient consumed by the process burn-off and the Boudouard reaction. The reducing agent consumption ranges from 11 kg to 300 kg / ton of titanium concentrate.

[0033] Step 3: Then, the mixture is fed into the fluidized bed reduction furnace via a feeder to carry out the first step of the reduction reaction, and hot reduced material is obtained.

[0034] In a fluidized bed reduction furnace, excess solid carbon in the reducing agent undergoes incomplete combustion with the introduced air (O2 content 0.5%~5%), releasing a large amount of heat and generating a large amount of CO.

[0035] If O2 is too low (<0.5%), carbon will not burn completely, resulting in insufficient CO production, insufficient temperature, and a slow reaction. If O2 is too high (>5%), some CO will be oxidized to CO2, weakening the reducing atmosphere or even creating an oxidizing atmosphere, causing the reduced iron to re-oxidize. This leads to the inability to effectively separate slag and iron in subsequent electric arc furnace smelting. Therefore, this invention utilizes the control of oxygen quantity to precisely control the reaction efficiency within the fluidized bed reduction furnace. That is, this invention uses solid carbon (not gas) to integrate "gasification" and "reduction" within the same fluidized bed reduction furnace, achieving incomplete combustion through oxygen limitation to generate CO in situ (not by directly introducing CO), eliminating the need for a large external coal gasification system. Furthermore, only the oxygen quantity needs to be controlled, without the need to control gasification temperature, pressure, etc., improving control precision, reducing process complexity, and lowering control costs.

[0036] Inside a fluidized bed reduction furnace, solid carbon and gaseous CO coexist. Solid carbon (reducing agent powder) adheres to the surface of the ore powder and directly reacts with oxygen to generate CO2; simultaneously, gaseous CO is regenerated through the Boudouard reaction (C + CO2 → 2CO). Gaseous CO then rapidly diffuses into the pores within the ore powder, reducing iron oxides and generating CO2; this CO2 then reacts with the external solid carbon to generate more gaseous CO. This creates a cyclical amplification effect, significantly increasing the reduction rate. If only gaseous CO is used, the regeneration of CO by solid carbon is lacking, and this cycle cannot be formed.

[0037] Therefore, the reduction process in a fluidized bed reduction furnace requires a sufficiently long reaction time, such as 2-3 hours, to amplify the reduction effect through such a cycle. This method is more energy-efficient than introducing CO gas. Because combustion and reduction occur in the same furnace, the heat released from the incomplete combustion of solid carbon is directly released within the reaction zone to heat the mineral powder, achieving direct utilization of sensible heat. The heat utilization efficiency can reach over 80%, making this method more energy-efficient than directly introducing CO (which requires additional air for combustion heat release and consumes the reducing agent itself, making it difficult to maintain a reducing atmosphere).

[0038] The temperature of the fluidized bed reduction furnace is set to 900-1300℃, preferably 950-1250℃. This is because the fluidized bed reduction furnace of the present invention needs to maintain "C+CO dual reduction" and "self-circulation". The Boudouard reaction has a larger equilibrium constant at high temperature, which can produce more CO and form a strong reducing atmosphere.

[0039] This is because the carbothermic reduction reaction of titanium oxides in titanium concentrate (such as TiO2 + 2C → Ti + 2CO) has the following characteristics: 1) a strongly endothermic reaction (i.e., ΔH > 0); 2) an entropy-increasing reaction (i.e., ΔS > 0, because a large amount of CO gas is generated). According to the Gibbs free energy formula: ΔG = ΔH - TΔS, when the temperature T increases, ΔG rapidly becomes negative, the driving force of the reaction is greatly enhanced, and the reaction can proceed spontaneously and rapidly. On the other hand, the activation energy required for the direct reaction between solid carbon and titanium concentrate is extremely high. Increasing the temperature can cause the reaction rate constant to increase exponentially, shortening the reaction time from several hours to 2-3 hours. Therefore, the high temperature of the fluidized bed reduction furnace allows the ΔG of the titanium oxide reduction reaction to shift sufficiently negative, so as to obtain enough driving force to overcome the solid-solid reaction energy barrier kinetically, accelerate the Boudouard reaction, and maintain the C+CO self-circulation. Moreover, the high temperature allows the reduction products to be directly fed into the titanium slag electric furnace in a hot state, eliminating the cooling-reheating stage and achieving optimal overall energy consumption.

[0040] Step 4: The hot-state reduced material is directly added to the titanium slag electric furnace for the second step of smelting. The titanium slag is discharged through the slag discharge port of the titanium slag electric furnace. After cooling, crushing and sorting, the finished titanium slag product is obtained.

[0041] Example 1: S1: Titanium concentrate (TiO2 content is 45.6%), the titanium concentrate is metered at 2t / h and added to the fluidized bed pre-baking machine (fluidized bed preheater), and preheated to 250℃ by the tail gas of the fluidized bed reduction furnace and the titanium slag electric furnace. S2: The reducing agent is coke powder with 48.5% carbon content. The metering device is set to 1.8t / h. It is added to the mixer with titanium concentrate and mixed evenly to obtain a mixture. S3: The mixture is fed into the fluidized bed reduction furnace via a feeder. The temperature of the fluidized bed reduction furnace is set to 900-1300℃, the O2 content in the tail gas is less than 3%, and the reaction time is 3 hours to complete the first step of the reduction reaction, obtaining the hot reduced material. The discharge temperature is 1100℃, and the reduction degree of ferric iron is 68%. S4: The hot-reduced material obtained in step S3 is directly added to the titanium slag electric furnace and smelted by electric current. The tail gas temperature of the electric furnace is 867℃ and the smelting time is 3 hours. The titanium slag is then discharged from the titanium slag discharge port.

[0042] Finally, after cooling, crushing, and sorting, a titanium slag product with a TiO2 content of 88.6% is obtained. The power consumption per ton of titanium slag is reduced from 3100 kWh to 1800 kWh, and the amount of reducing agent is reduced from 250 kg / ton of slag to 180 kg / ton of slag. It can be seen that the process of this invention saves 300 kWh of electricity and 40 kg of reducing agent per ton of titanium slag, with a very significant energy-saving and consumption-reducing effect.

[0043] Therefore, this invention employs a solid reducing agent to achieve simultaneous coupling of combustion and reduction within a fluidized bed reduction furnace: by controlling oxygen-limited incomplete combustion, the high temperature and reducing gas (CO) required for the reaction are provided in situ; simultaneously, the synergistic amplification effect between the reducing gas and solid carbon creates a self-circulating strong reducing atmosphere, eliminating the need for external heating or external supply of reducing gas. This design not only eliminates the need for a complex gas production system and reduces equipment investment, but also fully leverages the low-cost advantage of solid reducing agents compared to gaseous reducing agents. In summary, this invention saves energy, simplifies the process, and reduces raw material costs, achieving comprehensive optimization in the three dimensions of energy consumption, investment, and operating costs.

[0044] <Second Embodiment> The second embodiment of the present invention provides an ultra-low-cost two-step titanium slag production system. The system includes a fluidized bed preheater, a mixer, a feeder, a fluidized bed reduction furnace, a titanium slag electric furnace, a titanium slag cooling furnace, a titanium slag crusher, and a titanium slag separator, used to implement the ultra-low-cost two-step titanium slag production process in the first embodiment.

[0045] The fluidization preheater is used to preheat the ore using the tail gas from the fluidization reduction furnace and the titanium slag electric furnace; The mixer is used to mix the preheated ore from the fluidized bed preheater with the solid reducing agent to make them uniformly mixed; In a fluidized bed reduction furnace, the mixed materials are fed into the furnace through a feeder. Under limited oxygen conditions (O2 content 0.5%~5%), the reducing agent undergoes incomplete combustion, releasing heat and generating CO in situ. CO reduces iron oxides in the ore to generate CO2, while solid carbon regenerates CO2 into CO through the Boudouard reaction, forming a continuous self-circulating synergistic reduction process, ultimately yielding hot reduced material.

[0046] The titanium slag electric furnace melts the directly fed hot reducing material, and then the titanium slag product is obtained through a titanium slag cooling furnace, titanium slag crusher and titanium slag separator.

[0047] The present invention has been described in detail above. Any obvious modifications made to this invention by those skilled in the art without departing from its essential content will constitute an infringement of the patent rights of this invention and will incur corresponding legal liability.

Claims

1. A two-step process for producing titanium slag with ultra-low cost, characterized in that... include Step 1: After being metered, the titanium concentrate is fed into the fluidized bed preheater; at the same time, the tail gas from the fluidized bed reduction furnace and the titanium slag electric furnace is used to pre-bake the titanium concentrate. Step 2: In the mixer, the preheated titanium concentrate and the metered reducing agent are thoroughly mixed to obtain a mixture. Step 3: Then, the mixture is fed into the fluidized bed reduction furnace via a feeder to carry out the first reduction reaction, and hot reduced material is obtained; Step 4: The hot-state reduced material is directly added to the titanium slag electric furnace for the second step of smelting. The titanium slag is discharged through the slag discharge port of the titanium slag electric furnace. After cooling, crushing and sorting, the finished titanium slag product is obtained.

2. The ultra-low cost two-step titanium slag production process as described in claim 1, characterized in that: Air is introduced into the fluidized bed reduction furnace, wherein the O2 content is 0.5% to 5%, so that the reducing agent undergoes incomplete combustion to generate CO.

3. The ultra-low cost two-step titanium slag production process as described in claim 2, characterized in that: The reducing agent is a carbonaceous solid containing anthracite, metallurgical coke, and petroleum coke.

4. The ultra-low cost two-step titanium slag production process as described in claim 3, characterized in that: The reducing agent is low-ash, low-sulfur coke powder with a carbon content of 48.5%.

5. The ultra-low cost two-step titanium slag production process as described in claim 3 or 4, characterized in that: The fluidized bed reduction furnace is used for reduction for 2-3 hours.

6. The ultra-low cost two-step titanium slag production process as described in claim 5, characterized in that: The fineness and carbon content of the reducing agent satisfy the following relationship: reducing agent <2mm percentage >80%, fixed carbon content >40%, volatile matter <45%, and total water <20%.

7. The ultra-low cost two-step titanium slag production process as described in claim 5, characterized in that: The temperature of the fluidized bed reduction furnace is set to 900℃-1300℃, preferably 950-1250℃.

8. The ultra-low cost two-step titanium slag production process as described in claim 7, characterized in that: The prebaking temperature is 200~300℃, preferably 250℃.

9. A two-step ultra-low-cost titanium slag production system, characterized in that... The system includes a fluidized bed preheater, a mixer, a feeder, a fluidized bed reduction furnace, a titanium slag electric furnace, a titanium slag cooling furnace, a titanium slag crusher, and a titanium slag separator, and is used to implement the ultra-low cost two-step titanium slag production process as described in any one of claims 1 to 8.

Images