A method for preparing a desulfurizer by using ferrous chloride waste liquid

Abstract

The present application relates to a kind of methods for preparing desulfurizer with ferrous chloride waste liquid, comprising the following steps: 1) ferrous chloride waste liquid is mixed with carbide slag slurry, pH is controlled at 9-10, first precipitate is filtered out, and solution A is obtained;2) first precipitate is dissolved with ferrous chloride waste liquid, pH is controlled at 5-6, and solution B is obtained after filtration;3) solution A and solution B are mixed, oxidizing gas is introduced and stirred, after sufficient reaction, filtration is carried out, and secondary precipitate is obtained, secondary precipitate is washed with water, and hydroxyl ferric oxide desulfurizer is obtained after drying;In steps 1) and 2), the ferrous chloride waste liquid is ferrous chloride waste liquid generated in the production of titanium dioxide by chlorination method.The present application is to prepare hydroxyl ferric oxide desulfurizer using ferrous chloride waste liquid and carbide slag slurry in the chlorination method titanium dioxide process, which not only solves the problem of waste by-product resource treatment, but also reduces the production cost of hydroxyl ferric oxide.

Description

TECHNICAL FIELD

[0001] The application relates to a method for preparing a desulfurizing agent from ferrous chloride waste liquid, and belongs to the technical field of waste liquid treatment. BACKGROUND

[0002] In a chlorination method for producing titanium dioxide, a large amount of ferrous chloride acidic waste liquid is generated, the waste liquid contains many impurities, contains aluminum, manganese, chromium and other metal ions, and the concentration of ferrous chloride in the waste liquid is low, so it is difficult to recycle and utilize. In the prior art, the waste liquid is generally neutralized by lime, most of the metal ions form a precipitate, and after solid-liquid separation, waste slag is formed. Since the impurities are too many, the waste slag is difficult to recycle, a large amount of space is occupied for centralized stacking and treatment, and there is a risk of environmental pollution.

[0003] Iron hydroxyl oxide is a high-quality desulfurizing agent, and a traditional method is to prepare the iron hydroxyl oxide by reacting ferrous sulfate and sodium carbonate, and the raw material cost of sodium carbonate is high. Patent CN107381651A discloses a low-cost synthesis process of amorphous iron hydroxyl oxide, and the iron hydroxyl oxide is prepared by reacting ferrous chloride and calcium hydroxide. Since the calcium hydroxide with a monovalence of 1 / 3 of sodium carbonate is used as a neutralizing agent, the raw material cost is greatly reduced.

[0004] The application considers that the ferrous chloride waste liquid generated in the production of titanium dioxide by the chlorination method is used to prepare the iron hydroxyl oxide desulfurizing agent. However, due to the impurity problem of the ferrous chloride waste liquid, the ferrous chloride waste liquid cannot be directly used to prepare the iron hydroxyl oxide desulfurizing agent, and needs to be treated by removing impurities. In addition, the cost of using calcium hydroxide as a neutralizing agent is still high. SUMMARY

[0005] In view of the above problems, the application provides a method for preparing a desulfurizing agent from ferrous chloride waste liquid, and the specific scheme is as follows:

[0006] A method for preparing a desulfurizing agent from ferrous chloride waste liquid, comprising the following steps:

[0007] 1) The ferrous chloride waste liquid is mixed with carbide slag slurry, the pH value is controlled to be 9-10, the first precipitate is filtered out, and a solution A is obtained;

[0008] In this step, the ferrous ions in the ferrous chloride waste liquid and most of the metal ions form a precipitate, and at the same time, the insoluble impurities such as silicon aluminum oxide in the carbide slag slurry also enter the precipitate and are separated out by filtration. When the pH value is lower than 9, the degree of precipitation of the metal ions is low, and when the pH value is higher than 10, part of the precipitate will be redissolved and enter the solution A.

[0009] 2) The first precipitate is dissolved with ferrous chloride waste liquid, the pH value is controlled to be 5-6, and a solution B is obtained after filtration;

[0010] In this step, the ferrous iron in the primary precipitate is dissolved into solution B again, and the remaining impurities are not dissolved or are less dissolved, and are separated by filtration.

[0011] 3) mixing solution A and solution B, passing in oxidizing gas and stirring, after sufficient reaction, filtering to obtain secondary precipitate, washing the secondary precipitate with water, and drying to obtain hydroxyl ferric oxide desulfurizer;

[0012] In steps 1) and 2), the ferrous chloride waste liquid is ferrous chloride waste liquid produced in the production of titanium dioxide by chlorination method;

[0013] Preferably, in step 1), the amount of calcium carbide slag slurry added is 2.5-3.0wt% of the mass of the ferrous chloride waste liquid.

[0014] Preferably, in step 2), the amount of ferrous chloride waste liquid used is 15-20 times the mass of the primary precipitate.

[0015] Preferably, in step 2), the concentration of ferrous chloride in solution B is controlled to be 10-15wt%.

[0016] In step 2), the dissolution of ferrous iron in the primary precipitate by the ferrous chloride waste liquid can increase the concentration of the ferrous chloride solution.

[0017] Preferably, in step 3), the mass ratio of solution B to solution A is 1:8-10.

[0018] Preferably, the reaction system used includes a first reaction kettle and a second reaction kettle; first, the ferrous chloride waste liquid is added to the first reaction kettle, then the calcium carbide slag slurry is uniformly added, and stirring is carried out at the same time; after the pH value rises to 9, the addition is stopped, and the stirring is continued; if the pH value rises to above 10, the ferrous chloride waste liquid is added to adjust the pH value to below 10; after filtration, the primary precipitate and solution A are obtained; the primary precipitate is added to the second reaction kettle, and the ferrous chloride waste liquid is uniformly added to the second reaction kettle at the same time; after the pH value drops to 6, the addition is stopped, and the stirring is continued; if the amount of ferrous chloride waste liquid added reaches 20 times the mass of the primary precipitate, and the pH value is still greater than 6, hydrochloric acid is added to adjust the pH value to below 6; after filtration, solution B is obtained.

[0019] Preferably, the reaction system used comprises a first tubular reactor and a second tubular reactor, the feeding end of the first tubular reactor is sequentially provided with a ferrous chloride waste liquid main feeding port and a plurality of carbide slag slurry feeding ports, and a ferrous chloride waste liquid auxiliary feeding port is arranged in the middle part; the feeding end of the second tubular reactor is sequentially provided with a primary ferrous chloride waste liquid main feeding port, a primary precipitation feeding port and a plurality of ferrous chloride waste liquid auxiliary feeding ports, and a hydrochloric acid feeding port is arranged in the middle part; a pH meter is arranged upstream of each feeding port, and the feeding amount of each feeding port is controlled according to the detection value of the pH meter.

[0020] The present application has the advantages that the present application uses ferrous chloride waste liquid and carbide slag slurry in the chlorination process of titanium dioxide to prepare the iron oxyhydroxide desulfurizer, which not only solves the problem of processing of waste resources, but also reduces the production cost of the iron oxyhydroxide desulfurizer. In addition, the present application can obtain high-quality iron oxyhydroxide desulfurizer, and can improve economic benefits. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 The schematic diagram of the reaction system in Example 5. DETAILED DESCRIPTION

[0022] The scheme of the present application will be described in detail below in combination with specific examples.

[0023] The following examples and comparative examples are based on the ferrous chloride waste liquid produced by a certain chlorination process titanium dioxide production line, the content of ferrous chloride in the waste liquid is 5wt%, the pH value of the waste liquid is 2, and the waste liquid also contains impurity metal ions such as chromium, aluminum, titanium and manganese.

[0024] In addition, the carbide slag slurry used is the waste slag produced after the hydrolysis of calcium carbide to produce acetylene gas, and the content of calcium hydroxide is 85wt%.

[0025] Example 1

[0026] Take 1000g of ferrous chloride waste liquid, slowly add 28g of carbide slag slurry, and stir at the same time, the pH value is detected to be 9.8, filter, and the weight of the precipitate after filtration is 37.5g, and solution A is obtained. The precipitate is dissolved with 520g of ferrous chloride waste liquid, fully stirred, and the pH value is detected to be 5.7, filtered, and solution B is obtained; take 800g of solution A and 90g of solution B, pass in air, continuously stir, and control the pH value to be 6-7 during the reaction, the reaction temperature is 60℃, fully react, filter, and the filter cake is dried to obtain the iron oxyhydroxide desulfurizer.

[0027] Example 2

[0028] Take 1000g ferrous chloride waste liquid, slowly add 25g carbide slag slurry, add the material while stirring, detect the pH value is 9.1, filter, the weight of the precipitate after filtration is 35.1g, and solution A is obtained. The precipitate is dissolved with 622g ferrous chloride waste liquid, fully stirred, and the pH value is detected as 6.5. A small amount of 30% hydrochloric acid is added to adjust the pH value to 6.0, filtration is performed, and solution B is obtained. Take 800g solution A and 80g solution B, and air is introduced. Stirring is continuously performed, and the pH value is controlled to be 6-7 during the reaction, and the reaction temperature is 60°C. After sufficient reaction, filtration is performed, and the filter cake is dried to obtain the hydroxyl iron oxide desulfurizer.

[0029] Example 3

[0030] Take 1000g ferrous chloride waste liquid, slowly add 30g carbide slag slurry, add the material while stirring, detect the pH value is 11.8, add a small amount of ferrous chloride waste liquid and stir, the pH value is reduced to 9.5, filter, the weight of the precipitate after filtration is 41.7g, and solution A is obtained. The precipitate is dissolved with 666g ferrous chloride waste liquid, fully stirred, and the pH value is detected as 6.1. Filtration is performed, and solution B is obtained. Take 800g solution A and 89g solution B, and air is introduced. Stirring is continuously performed, and the pH value is controlled to be 6-7 during the reaction, and the reaction temperature is 60°C. After sufficient reaction, filtration is performed, and the filter cake is dried to obtain the hydroxyl iron oxide desulfurizer.

[0031] Comparative Example 1

[0032] Take 1000g ferrous chloride waste liquid, add 17g carbide slag slurry, introduce air, continuously stir, and control the pH value to be 6-7 during the reaction, and the reaction temperature is 60°C. After sufficient reaction, filtration is performed, and the filter cake is dried to obtain the hydroxyl iron oxide desulfurizer.

[0033] Comparative Example 2

[0034] Take 1000g ferrous chloride waste liquid, add calcium hydroxide to adjust the pH value to 5, filter the precipitate, add 17g carbide slag slurry, introduce air, continuously stir, and control the pH value to be 6-7 during the reaction, and the reaction temperature is 60°C. After sufficient reaction, filtration is performed, and the filter cake is dried to obtain the hydroxyl iron oxide desulfurizer.

[0035] Comparative Example 3

[0036] Take 1000g ferrous chloride waste liquid, add calcium hydroxide to adjust the pH value to 5, filter the precipitate, add 15g calcium hydroxide, introduce air, continuously stir, and control the pH value to be 6-7 during the reaction, and the reaction temperature is 60°C. After sufficient reaction, filtration is performed, and the filter cake is dried to obtain the hydroxyl iron oxide desulfurizer.

[0037] The desulfurizer obtained in the above examples and comparative examples was sampled, the purity of the sample was detected by spectrophotometry, and the sample was subjected to penetration sulfur capacity detection according to HGT 5759-2020, and the comparison results were as follows:

[0038]

[0039] As can be seen from the comparison, the purity of the desulfurizer obtained in Examples 1-3 is greater than 99%, and the penetration sulfur capacity is greater than 50%, while the purity of the desulfurizer obtained in Comparative Examples 1 and 2 is low, mainly because the calcium carbide slag slurry carries a large amount of impurities; in addition, from the comparison of Comparative Examples 1 and 2, the impurities in the ferrous chloride waste liquid also have a greater impact on the purity of the desulfurizer. The purity of the desulfurizer obtained in Comparative Example 3 also reaches more than 99%, but it needs to use calcium hydroxide with a higher cost, and its penetration sulfur capacity is also lower than that of Examples 1-3, the reason may be that the concentration of the ferrous chloride solution is too low, the dissolution speed of calcium hydroxide is slow, the reaction speed is slow, the crystal nucleation speed is slow, the crystal grain growth particle size is large, which is not conducive to the formation of amorphous iron oxyhydroxide.

[0040] Example 4

[0041] This example provides a scheme for industrial preparation of iron oxyhydroxide desulfurizer, the reaction system used includes a first reaction kettle and a second reaction kettle; first, ferrous chloride waste liquid is added to the first reaction kettle, then calcium carbide slag slurry is uniformly added, and stirring is carried out at the same time, after the pH value rises to 9, the feeding is stopped, and the stirring is continued, if the pH value rises to more than 10, then ferrous chloride waste liquid is added to adjust the pH value to below 10; after filtration, a first precipitate and a solution A are obtained; the first precipitate is added to the second reaction kettle, and then ferrous chloride waste liquid is uniformly added to the second reaction kettle, and stirring is carried out at the same time, after the pH value drops to 6, the feeding is stopped, and the stirring is continued; if the feeding amount of the ferrous chloride waste liquid reaches 20 times the mass of the first precipitate, and the pH value is still greater than 6, then hydrochloric acid is added to adjust the pH value to below 6; after filtration, a solution B is obtained. Solution A and solution B are mixed in the reaction kettle in proportion, and air is introduced for reaction.

[0042] Example 5

[0043] This example provides another scheme for industrial preparation of iron oxyhydroxide desulfurizer, as shown in Figure 1As shown, the reaction system used includes a first tubular reactor 1 and a second tubular reactor 2. The feed end of the first tubular reactor is sequentially provided with a ferrous chloride waste liquid main feed port and multiple calcium carbide slag slurry feed ports, and a ferrous chloride waste liquid auxiliary feed port is arranged in the middle. The feed end of the second tubular reactor is sequentially provided with a primary ferrous chloride waste liquid main feed port, a primary precipitation feed port, and multiple ferrous chloride waste liquid auxiliary feed ports, and a hydrochloric acid feed port is arranged in the middle. A pH meter is arranged upstream of each feed port, and the feed amount of each feed port is controlled according to the detection value of the pH meter. The discharge of the first tubular reactor is filtered to obtain solution A and primary precipitation, the primary precipitation enters the second tubular reactor, the discharge of the second tubular reactor is filtered to obtain solution B, and solution A and solution B are mixed in a certain proportion and then air is introduced for reaction. Solution A and solution B can be mixed in a reaction kettle and then air is introduced for reaction. The present scheme uses a tubular reactor to replace a reaction kettle, which is conducive to accurate control of the pH value during reaction and separation of impurities.

[0044] The following specific implementation can also be used. The discharge end of the first tubular reactor is connected to a first disc filter 3, the discharge port of the first disc filter is connected to a primary precipitation feed port of the second tubular reactor 2 through a screw feeder, the discharge end of the second tubular reactor 2 is connected to a second disc filter 4, the liquid discharge pipe of the first disc filter 3 and the liquid discharge pipe of the second disc filter 4 are connected to a third tubular reactor 5 through a parallel pipe, and the discharge end of the third tubular reactor 5 is connected to a third disc filter 6. The present scheme uses a tubular reactor system, which can realize continuous production and is conducive to improving production efficiency and improving the treatment efficiency of ferrous chloride wastewater.

Claims

1. A method for preparing a desulfurizing agent using ferrous chloride waste liquid, characterized in that, Includes the following steps: 1) Mix ferrous chloride waste liquid with calcium carbide slag slurry, control the pH value to 9-10, filter out the primary precipitate, and obtain solution A; 2) The primary precipitate is dissolved in ferrous chloride waste liquid, the pH value is controlled at 5-6, and solution B is obtained after filtration; 3) Mix solution A and solution B, introduce oxidizing gas and stir. After the reaction is complete, filter to obtain a secondary precipitate. Wash the secondary precipitate with water and dry it to obtain ferric hydroxide desulfurizer. In steps 1) and 2), the ferrous chloride waste liquid is the ferrous chloride waste liquid generated during the production of titanium dioxide by the chlorination process.

2. The method for preparing desulfurizing agent using ferrous chloride waste liquid according to claim 1, characterized in that: In step 1), the amount of calcium carbide slag slurry added is 2.5-3.0 wt% of the mass of ferrous chloride waste liquid.

3. The method for preparing desulfurizing agent using ferrous chloride waste liquid according to claim 2, characterized in that: In step 2), the amount of ferrous chloride waste liquid used is 15-20 times the mass of the first precipitation.

4. The method for preparing desulfurizing agent using ferrous chloride waste liquid according to claim 3, characterized in that: In step 2), the concentration of ferrous chloride in solution B is controlled to be 10-15 wt%.

5. The method for preparing desulfurizing agent using ferrous chloride waste liquid according to claim 4, characterized in that: In step 3), the mass ratio of solution B to solution A is 1:8-10.

6. The method for preparing desulfurizing agent using ferrous chloride waste liquid according to claim 5, characterized in that: The reaction system used includes a first reaction vessel and a second reaction vessel. First, ferrous chloride waste liquid is added to the first reaction vessel, followed by the uniform addition of calcium carbide slag slurry while stirring. Once the pH value rises to 9, the feeding is stopped, and stirring continues. If the pH value rises above 10, ferrous chloride waste liquid is added to adjust the pH value below 10. After filtration, a primary precipitate and solution A are obtained. The primary precipitate is added to the second reaction vessel, followed by the uniform addition of ferrous chloride waste liquid while stirring. Once the pH value drops to 6, the feeding is stopped, and stirring continues. If the amount of ferrous chloride waste liquid added reaches 20 times the mass of the primary precipitate and the pH value is still greater than 6, hydrochloric acid is added to adjust the pH value below 6. After filtration, solution B is obtained.

7. The method for preparing desulfurizing agent using ferrous chloride waste liquid according to claim 5, characterized in that: The reaction system used includes a first tubular reactor and a second tubular reactor. The feed end of the first tubular reactor has a main feed port for ferrous chloride waste liquid and multiple feed ports for calcium carbide slag slurry, and a secondary feed port for ferrous chloride waste liquid in the middle. The feed end of the second tubular reactor has a main feed port for primary ferrous chloride waste liquid, a primary precipitation feed port and multiple secondary feed ports for ferrous chloride waste liquid, and a hydrochloric acid feed port in the middle. A pH meter is installed upstream of each feed port, and the feed rate of each feed port is controlled according to the pH meter reading.

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