Method for preparing pure iron fluxing agent with low carbon and sulfur content

Abstract

The invention belongs to the field of preparation of standard substances for detection, and particularly discloses a method for preparing a pure iron fluxing agent with low carbon and sulfur content. The method is characterized in that soluble pure iron is adopted as an anode, a titanium plate is adopted as a cathode, a FeCl2. 4H2O solution added with an electrolyte stabilizer is adopted as an electrolyte, and the pure iron plate with the ultralow carbon and sulfur content is prepared through hydrometallurgy electrolysis; an iron plate prepared through electrolysis is crushed into iron particles with the particle size being 1-3 mm in an impact mode, then grinding is conducted, surface oxide and hydrolysate are removed, then vacuum drying is conducted, and water vapor and gas in the iron particles are removed; and the dried iron particles are put into a rotary reduction furnace for high-temperature reduction, and the content of impurity elements in the pure iron is further reduced. Therefore, according to the method disclosed by the invention, five procedures of electrolysis, crushing, grinding, drying and reduction are combined, so that the contents of C and S elements in the prepared iron particles are both less than 5ppm, and the preparation of the pure iron fluxing agent with low carbon and sulfur contents is realized.

Description

Technical Field

[0001] The invention relates to the field of preparation of standard substances for detection, and in particular to a method for preparing a pure iron flux with low carbon and sulfur content. Background Art

[0002] Flux generally refers to various substances that can lower the softening, melting or liquefaction temperature of other substances. Generally, it can be divided into three categories: (1) In metallurgy, its main function is to combine with impurities in minerals to form slag and separate it from the metal to achieve the purpose of smelting. (2) The flux in the welding process is also called flux. (3) In analytical chemistry, its main function is to make insoluble substances become soluble substances to facilitate chemical analysis. For example, commonly used sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, potassium pyrosulfate, and a mixture of sodium carbonate and potassium nitrate, etc., are mixed with the sample and melted under heating to produce soluble substances, which are then acid-soluble or water-soluble for chemical analysis.

[0003] When the combustion method is used to determine the carbon and sulfur elements in metals and non-metals, non-metallic, conductive and magnetically conductive samples cannot burn in the high-frequency furnace. Fluxes are needed to reduce the melting point of the samples. In addition, the flux has an oxidative heat release effect during the combustion process, which helps to increase the combustion temperature of the sample. Commonly used fluxes include pure tungsten particles, pure iron powder or particles, pure tin particles, pure copper scraps or wires, tin foil, etc. Among them, pure iron type flux or flux based on iron is the necessary flux material for the current advanced infrared and other analyzers to determine carbon and sulfur. When the temperature is higher than 650℃, iron particles begin to oxidize and release a large amount of heat when passing oxygen. It has the characteristics of high calorific value, low melting heat, good air permeability, fast reaction, good melting state, and fully oxidizes and releases carbon and sulfur in the sample. The blank value is low, thereby ensuring the reliability of the carbon and sulfur analysis results. At the same time, it is easy to remove due to the generation of loose oxides. Therefore, the preparation of pure iron flux with low carbon and sulfur content plays a significant role in the detection of carbon and sulfur content in samples. Summary of the invention

[0004] In view of the technical problem that the high carbon and sulfur contents in pure iron flux may affect the accuracy of sample detection, the present invention provides a method for preparing pure iron flux with low carbon and sulfur contents; by adopting a method combining pure iron electrolysis, crushing electrolytic iron plates, grinding, vacuum drying and high-temperature reduction processes, the C and S contents in the obtained iron particles are both less than 5ppm, thereby realizing the preparation of pure iron flux with low carbon and sulfur contents.

[0005] In order to achieve the above object, the specific technical solution adopted by the present invention is as follows:

[0006] A method for preparing a low-carbon, low-sulfur pure iron flux comprises the following steps:

[0007] S1. Electrolysis: pure iron is used as the anode, titanium plate is used as the cathode, and FeCl2·4H2O solution with electrolyte stabilizer is added as the electrolyte for electrolysis. After the electrolysis is completed, the cathode plate is removed and the electrolytic iron plate is peeled off;

[0008] S2. Grinding and drying: The electrolytic iron plate is torn into iron particles by an impact crusher, and then ground to remove the surface oxides and hydrolysis products of the iron particles; after grinding, vacuum drying is performed to remove the residual water vapor during electrolysis;

[0009] S3. High temperature reduction: The iron particles obtained after grinding and drying are placed in a rotary reduction furnace for reduction, and the carbon and sulfur content in the iron particles is further reduced. After reduction, pure iron flux is obtained.

[0010] Furthermore, in step S1, the pure iron is industrial pure iron, which has low cost and a purity of 99.5-99.95wt%. The carbon and sulfur contents in the industrial pure iron must be less than 150ppm, and the contents of other elements can meet the requirements of industrial pure iron. The size of the anode plate is not less than 800*800mm 2 , thickness is 15-20mm; the cathode plate size is not less than 800*800mm 2 The plane size of the electrolytic iron plate is consistent with the size of the cathode plate, and the thickness is 2 to 4 mm.

[0011] Furthermore, in step S1, the electrolyte solute FeCl2·4H2O needs to be of high purity, and the ferrous ion concentration of the configured electrolyte is 50-200 g / L; the electrolyte pH is 1-4, preferably 2.0-2.8; the electrolyte temperature is 60-95°C, preferably 70-90°C; the cathode current density is 50-300 A / m 2 , preferably 150 to 250 A / m 2 .

[0012] Furthermore, the electrolyte stabilizer is a reducing additive that does not contain carbon or sulfur elements. The reducing additive is preferably ascorbic acid, which is used to promote the stability of the electrolyte and prevent the electrolyte from being oxidized and deteriorated, thereby making electrolysis impossible.

[0013] Furthermore, hydrochloric acid is used to adjust the pH value of the electrolyte during the preparation of the electrolyte. The pH value of the pure water solution is first adjusted to between 4 and 5, and then FeCl2·4H2O electrolyte and electrolyte stabilizer are added in sequence. After uniform dissolution, the pH value is further adjusted to the required range.

[0014] Furthermore, in step S1, the electrolyte circulation during the electrolysis process adopts a "top-in, bottom-out" liquid circulation flow method to prevent the electrolytic mud precipitated at the bottom of the electrolytic cell from rolling to the surface with the circulation of the electrolyte, thereby adhering to the surface of the electrolytic iron and hindering the deposition of the electrolytic iron.

[0015] Furthermore, in step S1, a temperature control system is used during the electrolysis process to obtain the required electrolyte temperature according to the change of electrolysis process parameters, thereby preventing gas elements in the liquid from entering the electrolytic iron during the electrolysis process and reducing the gas content in the pure iron.

[0016] Furthermore, in step S2, the electrolytic iron plate is crushed into iron particles with a particle size of 1 to 3 mm (ie, 1 to 3 mm in width and 1 to 3 mm in length).

[0017] Furthermore, in step S2, a rotary high-temperature vacuum drying oven is used to dry the iron particles, the drying temperature is 100-350°C, preferably 200-300°C; the drying time is not less than 2h, preferably 3-4h; the vacuum degree is not less than 1.0*10 -3 Pa.

[0018] Furthermore, in step S2, the iron particles obtained by crushing are ground by spin contact grinding.

[0019] Furthermore, in step S3, the rotation frequency of the rotary reduction furnace is 1 to 8 r / min, preferably 3 to 6 r / min; NH3 or H2 is selected as the reducing medium (reducing medium containing carbon element gas shall not be used), the medium flow rate is not less than 0.5 L / min, and is continuously introduced during the entire reduction stage.

[0020] Furthermore, in step S3, the reduction temperature is 700-900° C. and the reduction time is not less than 48 hours.

[0021] Furthermore, in step S3, the reduction process is to first put the iron particles into a cyclotron furnace, pass the reducing medium for half an hour to remove oxygen, and then gradually heat to a set temperature for reduction. After the reduction is completed and the temperature is lowered to below 150°C, the iron particles can be taken out, and the reducing medium is continuously passed during the heating and cooling process.

[0022] Furthermore, in step S3, the prepared pure iron flux is packaged in a vacuum or nitrogen atmosphere to isolate oxygen.

[0023] The present invention has the following beneficial effects:

[0024] The method for preparing a low-carbon and sulfur pure iron flux of the present invention selects low-cost industrial pure iron as an anode, thereby saving electrolysis cost; the electrolyzed pure iron is crushed, ground, dried and reduced, thereby solving the problem of a large amount of free and combined gaseous element contents remaining in the electrolytic iron; the method of electrolysis-crushing, grinding-drying-reduction is adopted, thereby reducing the C and S element contents in the electrolytic iron, thereby achieving the goal of preparing a low-carbon and sulfur pure iron flux. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The following are the results of gas element detection in the pure iron flux prepared in Example 1 of the present invention.

[0026] Figure 2 The following are the results of gas element detection in the pure iron flux prepared in Example 2 of the present invention.

[0027] Figure 3 The following are the results of gas element detection in the pure iron flux prepared in Example 3 of the present invention.

[0028] Figure 4 This is a physical picture of impurities adhering to the surface of electrolytic iron in Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0029] The technical solutions in the present invention are described clearly and completely below in conjunction with specific embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0030] Example 1

[0031] A method for preparing a low-carbon, low-sulfur pure iron flux comprises the following steps:

[0032] S1.Electrolytic iron making

[0033] Industrial pure iron (purity 99.5-99.95wt%, carbon and sulfur content less than 150ppm) is used as anode, titanium plate is used as cathode, FeCl2·4H2O is used as electrolyte, and a solution containing a small amount of electrolyte stabilizer ascorbic acid and hydrochloric acid as pH regulator is used as electrolyte for electrolysis. Before electrolysis, the surfaces of the anode and cathode plates are polished and cleaned with pure water; during electrolysis, the electrolyte flows out from the bottom of the electrolysis tank and is added to the top, and a liquid circulation flow mode of top-in and bottom-out is adopted; the ferrous ion concentration in the electrolyte is 100g / L, the initial pH value of the electrolyte is 2.0-2.2, the electrolyte temperature is 70°C, and the cathode current density is 200A / m 2 After 5 days of electrolysis, take out the cathode plate and peel off the electrolytic iron plate.

[0034] S2. Grinding and drying

[0035] The electrolytic iron plate is crushed into iron particles with a particle size of 1 to 3 mm by an impact crusher, and then put into a stainless steel drum for grinding for 2 hours to remove the surface oxides and hydrolysis products; after grinding, it is placed in a vacuum of 1.0*10 -3In the vacuum drying box of Pa, a double-cone rotary vacuum dryer model SZG-200 was used with a drying temperature of 200°C and a drying time of 3 h to remove the residual water vapor during electrolysis.

[0036] S3. High temperature reduction

[0037] The ground and dried iron particles are loaded into a rotary reduction furnace, using an atmosphere rotary furnace of model BJXG-5410. The reducing atmosphere H2 is selected as the reducing medium, and the medium flow rate is not less than 0.5L / min. During the reduction process, the reducing medium is ensured to be continuously introduced; the rotation frequency is set to 4r / min, the reduction temperature is 800℃, and the reduction time is 70h; the reduction process is to first pass the reducing medium for half an hour to remove oxygen, and then gradually heat to the set temperature for reduction. After the reduction is completed and the temperature is lowered to below 150℃, the iron particles can be taken out, and the reducing medium is continuously introduced during the heating and cooling process; after the reduction is completed, the iron particles are vacuumed and stored, and the gas elements of the reduced iron particles are detected by GDMS. The test results are as follows Figure 1 As shown, the C and S contents are both less than 5ppm.

[0038] Example 2

[0039] A method for preparing a low carbon and sulfur content pure iron flux is basically the same as Example 1, except that:

[0040] In step S1, the ferrous ion concentration in the electrolyte is 150 g / L, the initial pH value of the electrolyte is 2.2-2.4, the electrolyte temperature is 80°C, and the cathode current density is 100 A / m 2 ;

[0041] In step S2, the drying temperature is 150°C and the drying time is 4 hours;

[0042] In step S3, the reduction temperature is 700° C. and the reduction time is 80 h.

[0043] The gas element detection results of the obtained iron particles are as follows: Figure 2 As shown, the C and S contents are both less than 5ppm.

[0044] Example 3

[0045] A method for preparing a low carbon and sulfur content pure iron flux is basically the same as Example 1, except that:

[0046] In step S1, the concentration of ferrous ions in the electrolyte is 200 g / L, the initial pH value of the electrolyte is 2.0-2.2, the electrolyte temperature is 90°C, and the cathode current density is 150 A / m 2 ;

[0047] In step S3, the reduction temperature is 700° C. and the reduction time is 60 h.

[0048] The gas element detection results of the obtained iron particles are as follows: Figure 3 As shown, the C and S contents are both less than 5ppm.

[0049] Comparative Example 1

[0050] Compared with Example 1, this comparative example changes the circulation flow mode of the electrolyte in step S1, specifically, by changing "up in and down out" to "up out and down in". As a result, during the electrolysis process, the electrolyte circulates and rolls upward, driving the impurity mud deposited at the bottom of the electrolytic tank to the surface of the anode and cathode plates, almost completely covering the electrolytic iron deposited on the cathode plate. Figure 4 As shown, the continued deposition of electrolytic iron is hindered, and the impurities generated during the electrolysis process cannot be filtered and removed as the electrolyte circulates.

[0051] Comparative Example 2

[0052] Compared with Example 1, the components of the electrolyte in this comparative example are changed as follows: no ascorbic acid is added to the electrolyte as a stabilizer. It is found that the oxidation deterioration rate of the electrolyte is significantly accelerated, resulting in frequent addition of hydrochloric acid and increased consumption of raw materials.

[0053] This specific implementation is only an explanation of the present invention, not a limitation of the present invention. Any changes made by those skilled in the art after reading the specification of the present invention will be protected by the patent law as long as they are within the scope of the claims of the present invention.

Claims

1. A method for preparing a low carbon and sulfur content pure iron flux, characterized in that: The following steps are involved: S1. Electrolysis: pure iron is used as the anode, titanium plate is used as the cathode, and FeCl2·4H2O solution with electrolyte stabilizer is added as the electrolyte for electrolysis. After the electrolysis is completed, the cathode plate is removed and the electrolytic iron plate is peeled off; S2. Grinding and drying: The electrolytic iron plate is torn into iron particles using an impact crusher, and then ground to remove the surface oxides and hydrolysis products of the iron particles; After grinding, vacuum drying is performed to remove the water vapor remaining during electrolysis; S3. High temperature reduction: The iron particles obtained after grinding and drying are placed in a rotary reduction furnace for reduction, and the carbon and sulfur content in the iron particles is further reduced. After reduction, pure iron flux is obtained.

2. The method for preparing a low carbon and sulfur content pure iron flux according to claim 1, characterized in that: In step S1, the pure iron is industrial pure iron, the carbon and sulfur contents in the industrial pure iron must be lower than 150 ppm, and other elements may meet the industrial pure iron standard.

3. The method for preparing a low carbon and sulfur content pure iron flux according to claim 1, characterized in that: In step S1, the purity of the FeCl2·4H2O must be high purity, the ferrous ion concentration of the prepared electrolyte is 50-200 g / L, the pH is 1-4, the electrolyte temperature is 60-95°C, and the cathode current density is 50-300 A / m 2 .

4. The method for preparing a low carbon and sulfur content pure iron flux according to claim 1, characterized in that: In step S1, the electrolyte stabilizer is a reducing additive that does not contain carbon or sulfur elements.

5. The method for preparing a low carbon and sulfur content pure iron flux according to claim 1, characterized in that: In step S1, hydrochloric acid is used to adjust the pH value of the electrolyte during the preparation of the electrolyte. The pH value of the pure water solution is first adjusted to between 4 and 5, and then an electrolyte stabilizer and FeCl2·4H2O electrolyte are added. After uniform dissolution, the pH value is further adjusted to the required range.

6. The method for preparing a low carbon and sulfur content pure iron flux according to claim 1, characterized in that: In step S1, during the electrolysis process, the electrolyte circulation adopts a liquid circulation flow mode of entering from the top and exiting from the bottom to reduce the enrichment of impurities at the cathode.

7. The method for preparing a low carbon and sulfur content pure iron flux according to claim 1, characterized in that: In step S2, the electrolytic iron plate is crushed into iron particles with a particle size of 1 to 3 mm.

8. The method for preparing a low carbon and sulfur content pure iron flux according to claim 1, characterized in that: In step S2, a rotary high-temperature vacuum drying oven is used to dry the iron particles. The drying temperature is 100-350°C, the drying time is not less than 2 hours, and the vacuum degree is not less than 1.0*10 -3 Pa.

9. The method for preparing a low carbon and sulfur content pure iron flux according to claim 1, characterized in that: In step S2, the iron particles obtained by crushing are ground by using a spin contact grinding method.

10. The method for preparing a low carbon and sulfur content pure iron flux according to claim 1, characterized in that: In step S3, the rotation frequency of the rotary reduction furnace is 1 to 8 r / min; NH3 or H2 is selected as the reducing medium, the medium flow rate is not less than 0.5 L / min, and is continuously introduced during the entire reduction stage.

11. The method for preparing a low carbon and sulfur content pure iron flux according to claim 1 or 10, characterized in that: In step S3, the reduction temperature is 700-900° C. and the reduction time is not less than 48 hours.

12. The method for preparing a low carbon and sulfur content pure iron flux according to claim 11, characterized in that: In step S3, the reduction process is to first put the iron particles into a cyclotron furnace, pass the reducing medium for half an hour to remove oxygen, and then gradually heat to a set temperature for reduction. After the reduction is completed and the temperature is lowered to below 150°C, the iron particles can be taken out, and the reducing medium is continuously passed during the heating and cooling process.

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