Treatment method of chlorinated tail gas in titanium tetrachloride production process

Abstract

The present invention discloses a method for treating chlorinated tail gas in a titanium tetrachloride production process, comprising: mixing a dry base with water in a predetermined ratio to prepare a slurry; wherein the dry base is a material separated by magnetic separation during the crushing process of TiC-containing slag, the TiC-containing slag is a product of the carbonization process of TiO2-containing slag produced by smelting vanadium-titanium magnetite, and the dry base contains: Fe, TiC, CaO and MgO; the chlorinated tail gas is passed into the stirred slurry, the slurry is used to absorb the chlorine-containing components in the chlorinated tail gas, and the absorbed chlorinated tail gas meets the emission standards. The present invention can effectively utilize the byproducts of the TiC-containing slag in the crushing process, avoid the use of a large amount of additional absorbents, and save production costs.

Description

Technical Field

[0001] The invention relates to the technical field of chemical industry, and in particular to a method for treating chlorinated tail gas in a titanium tetrachloride production process. Background Art

[0002] During the smelting process of vanadium-titanium magnetite, high-titanium blast furnace slag is produced, in which the TiO2 content is about 20-24%. For this blast furnace slag, an effective utilization route of titanium-containing blast furnace slag based on the "high-temperature carbonization-low-temperature chlorination" process has been formed. High-temperature carbonization converts TiO2 in blast furnace slag into TiC in an electric furnace. The obtained TiC-containing slag is crushed and sent to a boiling chlorination furnace to react with Cl2 to produce TiCl4.

[0003] In actual production, there are two problems: First, the TiC-containing slag contains 1-4% metallic Fe, which can hardly be crushed by the vertical mill crushing process and needs to be discharged through a magnetic separation system. The material separated by magnetic separation contains components such as Fe, TiC and CaO, which are difficult to handle; second, the chlorinated tail gas contains uncondensed TiCl4, excess Cl2, HCl and other toxic and harmful gases, and the tail gas must be absorbed and treated before it meets the emission standards.

[0004] The existing chlorinated tail gas absorption method generally uses water washing first, and then neutralization and absorption with NaOH, Na2CO3, lime water, etc. In the process of producing titanium tetrachloride by boiling chlorination method, the reaction process is dynamic, and the amount of chlorinated tail gas generated is large. The existing method has the problems of high operating cost of absorbent and low added value of by-products after absorption. Summary of the invention

[0005] The main purpose of the present invention is to provide a method for solving the problems that the material separated by magnetic separation during the crushing of TiC-containing slag is difficult to handle and the cost of treating chlorinated tail gas is high.

[0006] According to one aspect of the present invention, a method for treating chlorinated tail gas in a titanium tetrachloride production process is proposed, comprising: mixing a dry base with water in a predetermined ratio to form a slurry; wherein the dry base is a material separated by magnetic separation during a crushing process of a TiC-containing slag, the TiC-containing slag is a product of a carbonization process of a TiO2-containing slag produced by smelting vanadium-titanium magnetite, and the dry base contains: Fe, TiC, CaO and MgO; the chlorinated tail gas is passed into the stirred slurry, the slurry is used to absorb the chlorine-containing components in the chlorinated tail gas, and the absorbed chlorinated tail gas meets the emission standards.

[0007] According to one embodiment of the present invention, the slurry is placed in a plurality of reactors, and the chlorinated tail gas is sequentially introduced into the slurries in the plurality of reactors.

[0008] According to one embodiment of the present invention, the chlorinated tail gas after being absorbed by the slurry is alkali washed, and then the chlorinated tail gas after alkali washing is discharged in compliance with the standards.

[0009] According to one embodiment of the present invention, after the slurry fails, the method further comprises: filtering the failed slurry to obtain a TiC-containing filter residue and an absorption liquid; returning the TiC-containing filter residue to a titanium tetrachloride production system as a chlorination raw material; recovering the valuable elements in the absorption liquid, and using the recovered clear liquid to prepare the slurry.

[0010] According to one embodiment of the present invention, the recovery of valuable elements in the absorption liquid includes: adjusting the pH value of the absorption liquid to 3.2-4.1, performing Fe 3+ hydrolyze; and filter the hydrolyzed product to obtain an iron hydroxide precipitate.

[0011] According to one embodiment of the present invention, when the slurry is used to absorb the chlorinated tail gas, the temperature of the slurry is set at 40-75°C.

[0012] According to one embodiment of the present invention, the dry basis comprises, by weight percentage, 15%-70% Fe, 5%-25% TiC, 10%-25% CaO and 2%-10% MgO.

[0013] According to one embodiment of the present invention, the volume ratio of the water to the dry basis is 3-10:1.

[0014] According to one embodiment of the present invention, the particle size distribution on a dry basis is as follows: particles with a size less than 1 cm account for more than 80%, particles with a size of 1 cm-2 cm account for 0-20%, and particles with a size greater than 2 cm account for less than 5%.

[0015] In the chlorinated tail gas treatment method according to an embodiment of the present invention, the material separated by magnetic separation during the crushing process of the TiC-containing slag is used as a dry basis to prepare a slurry, and the slurry is used to absorb and treat the chlorinated tail gas. On the one hand, the problem that the material separated by magnetic separation is difficult to treat can be solved, and on the other hand, a large amount of additional absorbent can be avoided, saving the operating cost of the absorbent. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0017] Figure 1 A flow chart showing a method for treating chlorinated tail gas according to one embodiment of the present invention;

[0018] Figure 2 A flow chart showing a method for treating chlorinated tail gas according to another embodiment of the present invention is shown. DETAILED DESCRIPTION

[0019] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the embodiments of the present invention are further described in detail below in combination with specific embodiments and with reference to the accompanying drawings.

[0020] Figure 1 A flow chart of a method for treating chlorinated tail gas according to an embodiment of the present invention is shown. Figure 1 As shown, the chlorinated tail gas treatment method comprises:

[0021] Step S1, mixing a dry base with water in a predetermined ratio to form a slurry; wherein the dry base is a material separated by magnetic separation during the crushing process of the TiC-containing slag, the TiC-containing slag is a product of the carbonization process of the TiO2-containing slag produced by the smelting of vanadium-titanium magnetite, and the dry base contains: Fe, TiC, CaO and MgO;

[0022] Step S2, passing the chlorinated tail gas into the agitated slurry, using the slurry to absorb the chlorine-containing components in the chlorinated tail gas, and the chlorinated tail gas that has been absorbed meets the emission standards.

[0023] The material separated by magnetic separation is a by-product in the crushing process of TiC-containing slag. The by-product is used as a dry basis to prepare a slurry, and the slurry is used to absorb and treat the chlorinated tail gas, which can solve the treatment problem of the by-product and achieve the purpose of comprehensive resource utilization. It can also avoid the use of a large amount of additional absorbents, save the operating cost of the absorbent, and effectively treat the uncondensed TiCl4, excess Cl2, and HCl in the chlorinated tail gas, and stably achieve tail gas emission standards.

[0024] In terms of weight percentage, the dry basis may contain: 15%-70% Fe, 5%-25% TiC, 10%-25% CaO and 2%-10% MgO. In addition to Fe, TiC, CaO and MgO, the dry basis may also contain Al2O3 and SiO2.

[0025] The volume ratio of the water to the dry basis may be 3-10: 1. Such a volume ratio can ensure that the slurry has a suitable consistency, which is neither too thick to affect the diffusion of the chlorinated tail gas in the slurry nor too thin to affect the reaction efficiency between the chlorinated tail gas and the slurry.

[0026] When the slurry is used to absorb the chlorinated tail gas, the temperature of the slurry is made to be 40-75°C. Such a temperature can ensure a good reaction rate when the chlorinated tail gas reacts with the slurry. When the consistency of the slurry is appropriate, the slurry can be naturally maintained within the above temperature range due to the exothermic reaction of the chlorinated tail gas and the slurry, without the need for additional heating measures. In the case where the slurry is too thin, when the slurry is used to absorb the chlorinated tail gas, the temperature of the slurry is difficult to reach the above temperature range. At this time, additional heating measures are required to ensure that the temperature of the slurry reaches the above temperature range to ensure a suitable reaction rate.

[0027] In an embodiment of the present invention, the particle size distribution on the dry basis is such that particles with a size less than 1 cm account for more than 80%, particles with a size of 1 cm-2 cm account for 0-20%, and particles with a size greater than 2 cm account for less than 5%.

[0028] Such a particle size distribution can ensure that the slurry and the chlorinated tail gas are fully contacted for reaction. In general, the dry base separated by magnetic separation during the TiC slag crushing process can meet the above particle size distribution requirements. In the case where the particle size of the dry base is large, further crushing operations can be performed to ensure that the dry base meets the above particle size distribution requirements.

[0029] In some embodiments, the slurry is placed in multiple reactors, and the chlorinated tail gas is sequentially passed into the slurries of the multiple reactors. Thus, by using multiple stages of slurry for series absorption, it can be ensured that the chlorinated tail gas is fully absorbed and that the absorbed chlorinated tail gas meets the emission standards. 1-3 stages of slurry can be used, that is, 1-3 reactors are set to accommodate the slurry, so that the chlorinated tail gas is sequentially passed into the slurries of 1-3 reactors.

[0030] In some embodiments, the chlorinated tail gas after being absorbed by the slurry is alkali washed, and then the chlorinated tail gas after alkali washing is discharged in compliance with the standards. By adding a first stage of alkali washing before the chlorinated tail gas is discharged, it can be ensured that the chlorine-containing components in the chlorinated tail gas are completely absorbed during the failure of the slurry and the replacement of the slurry.

[0031] Figure 2 FIG. 2 is a flow chart showing a method for treating chlorinated tail gas according to another embodiment of the present invention. Figure 2 As shown, after the slurry fails, the method further comprises:

[0032] Filtering the failed slurry to obtain TiC-containing filter residue and absorption liquid;

[0033] Returning the TiC-containing filter residue as a chlorinated raw material to a titanium tetrachloride production system;

[0034] The valuable elements in the absorption liquid are recovered, and the clear liquid obtained after the recovery is used to prepare the slurry.

[0035] By returning the obtained TiC-containing filter residue as a raw material for chlorination for reuse and recovering the valuable elements in the absorption liquid, resources can be fully utilized and production costs can be further reduced.

[0036] In some embodiments, the recovering of valuable elements in the absorption liquid comprises:

[0037] Adjust the pH value of the absorption liquid to 3.2-4.1, and carry out Fe 3+ hydrolysis;

[0038] The hydrolyzed product is filtered to obtain an iron hydroxide precipitate and a filtrate.

[0039] The absorption liquid contains a large amount of Fe 3+ In addition, it may also contain Ca 2+ and Mg 2+ The corresponding purifier can be added to the filtrate to remove Ca 2+ and Mg 2+ Thus, a clear solution is obtained. Ca can be removed by precipitation, ion exchange, etc. 2 + and Mg 2+ , and recover the corresponding calcium-containing and magnesium-containing substances. Calcium chloride and magnesium chloride can be obtained by concentration, crystallization and filtration. After recovering the valuable elements in the absorption liquid, the obtained clear liquid can be replenished with new water and returned to pulping.

[0040] The chlorinated tail gas treatment method of the present invention can comprehensively utilize resources, reduce the cost of boiling chlorinated tail gas treatment, and is easy to operate and maintain as a whole.

[0041] The following is a description based on specific embodiments.

[0042] Example 1

[0043] The chlorinated tail gas treatment method of the present invention is adopted in a boiling chlorination system with a diameter of 1200 mm, and the chlorinated tail gas is absorbed by two-stage slurry.

[0044] In terms of weight percentage, the slurry contains 46.3% Fe, 17.1% TiC, 10.8% CaO, 5.7% Al2O3, 13.1% SiO2, 2.9% MgO and 4.1% other substances on a dry basis. The particle size distribution on a dry basis is: 100% of the particles are smaller than 1 cm.

[0045] About 10 tons of slurry was made according to the volume ratio of water: dry basis = 6:1, and loaded into two reaction tanks, 5 tons in each tank, and the slurry was stirred; the slurry temperature was kept at 60°C, and the chlorine-containing tail gas was washed and absorbed by two stages of slurry, and then discharged after a first-stage alkali wash. After testing, the absorption rate of chlorinated tail gas by the slurry reached 99.7%.

[0046] After the slurry is exhausted, the reaction tank is discharged and the TiC-containing filter residue and absorption liquid are obtained by filtration. The pH value of the absorption liquid is adjusted to 3.5 with quicklime and Fe 3+ Hydrolysis operation, after the hydrolysis is completed, ferric hydroxide is obtained by filtration; after iron removal, the filtrate is added with a purifier, and then further concentrated, crystallized and filtered to obtain calcium chloride and magnesium chloride.

[0047] Example 2

[0048] The chlorinated tail gas treatment method of the present invention is adopted in a boiling chlorination system with a diameter of 1200 mm, and the chlorinated tail gas is absorbed by two-stage slurry.

[0049] In terms of weight percentage, the slurry contains 70.1% Fe, 9.6% TiC, 5.7% CaO, 2.7% Al2O3, 6.2% SiO2, 2.4% MgO and 3.3% other substances on a dry basis. The particle size distribution on a dry basis is: 82% of the particles are smaller than 1 cm, 11% of the particles are between 1 cm and 2 cm, and 7% of the particles are larger than 2 cm.

[0050] About 10 tons of slurry was prepared according to the volume ratio of water: dry basis = 10:1, and loaded into two reaction tanks, 5 tons in each tank, and the slurry was stirred; the slurry temperature was kept at 40°C, and the chlorine-containing tail gas was washed and absorbed by two stages of slurry, and then discharged after a first-stage alkali wash. According to the test, the absorption rate of the slurry for chlorinated tail gas reached 98.6%.

[0051] After the slurry is exhausted, the reaction tank is discharged and the TiC-containing filter residue and absorption liquid are obtained by filtration. The pH value of the absorption liquid is adjusted to 3.5 with quicklime and Fe 3+ Hydrolysis operation, after the hydrolysis is completed, ferric hydroxide is obtained by filtration; after iron removal, the filtrate is added with a purifier, and then further concentrated, crystallized and filtered to obtain calcium chloride and magnesium chloride.

[0052] Example 3

[0053] The chlorinated tail gas treatment method of the present invention is adopted in a boiling chlorination system with a diameter of 1200 mm, and the chlorinated tail gas is absorbed by two-stage slurry.

[0054] In terms of weight percentage, the slurry contains 15.8% Fe, 11.5% TiC, 24.4% CaO, 14.6% Al2O3, 23.2% SiO2, 8.6% MgO and 1.9% other substances on a dry basis. The particle size distribution on a dry basis is: 90% of the particles are smaller than 1 cm, 9% of the particles are between 1 cm and 2 cm, and 1% of the particles are larger than 2 cm.

[0055] About 10 tons of slurry was made according to the volume ratio of water: dry basis = 3:1, and loaded into two reaction tanks, 5 tons in each tank, and the slurry was stirred; the slurry temperature was kept at 75°C, and the chlorine-containing tail gas was washed and absorbed by two stages of slurry, and then discharged after a first-stage alkali wash. According to the test, the absorption rate of the slurry for chlorinated tail gas reached 98.8%.

[0056] After the slurry is exhausted, the reaction tank is discharged and the TiC-containing filter residue and absorption liquid are obtained by filtration. The pH value of the absorption liquid is adjusted to 3.5 with quicklime and Fe 3+ Hydrolysis operation, after the hydrolysis is completed, ferric hydroxide is obtained by filtration; after iron removal, the filtrate is added with a purifier, and then further concentrated, crystallized and filtered to obtain calcium chloride and magnesium chloride.

[0057] A person skilled in the art should understand that the discussion of any of the above embodiments is only exemplary and is not intended to imply that the scope of the disclosure of the embodiments of the present invention (including the claims) is limited to these examples; under the concept of the embodiments of the present invention, the technical features in the above embodiments or different embodiments can also be combined, and there are many other changes in different aspects of the embodiments of the present invention as described above, which are not provided in detail for the sake of simplicity. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the embodiments of the present invention should be included in the protection scope of the embodiments of the present invention.

Claims

1. A method for treating chlorinated tail gas in a titanium tetrachloride production process, characterized in that: include: Mixing a dry base with water in a predetermined ratio to form a slurry; wherein the dry base is a material separated by magnetic separation during the crushing process of the TiC-containing slag, the TiC-containing slag is a product of the carbonization process of the TiO2-containing slag produced by the smelting of vanadium-titanium magnetite, and the dry base contains: Fe, TiC, CaO and MgO; Passing the chlorinated tail gas into the agitated slurry, using the slurry to absorb the chlorine-containing components in the chlorinated tail gas, and the chlorinated tail gas that has been absorbed meets the emission standards; After the slurry fails, the method further comprises: Filtering the failed slurry to obtain TiC-containing filter residue and absorption liquid; Returning the TiC-containing filter residue as a chlorinated raw material to a titanium tetrachloride production system; The valuable elements in the absorption liquid are recovered, and the clear liquid obtained after the recovery is used to prepare the slurry.

2. The method according to claim 1, characterized in that The slurry is placed in a plurality of reactors, and the chlorinated tail gas is sequentially introduced into the slurries in the plurality of reactors.

3. The method according to claim 1, characterized in that The chlorinated tail gas absorbed by the slurry is alkali washed, and then the chlorinated tail gas after alkali washing is discharged in compliance with the standards.

4. The method according to claim 1, characterized in that: The recovering of the valuable elements in the absorption liquid comprises: Adjust the pH value of the absorption liquid to 3.2-4.1, and carry out Fe 3+ hydrolysis; The hydrolyzed product is filtered to obtain iron hydroxide precipitate.

5. The method according to claim 1, characterized in that When the slurry is used to absorb the chlorinated tail gas, the temperature of the slurry is made to be 40-75°C.

6. The method according to claim 1, characterized in that In terms of weight percentage, the dry basis comprises: 15%-70% Fe, 5%-25% TiC, 10%-25% CaO and 2%-10% MgO.

7. The method according to claim 1, characterized in that The volume ratio of the water to the dry basis is 3-10:

1.

8. The method according to claim 1, characterized in that The particle size distribution on the dry basis is such that particles with a size less than 1 cm account for more than 80%, particles with a size of 1 cm-2 cm account for 0-20%, and particles with a size greater than 2 cm account for less than 5%.

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