Preparation method of high-purity chromium metal

Abstract

The invention relates to the technical field of preparation of high-purity chromium metal, in particular to a preparation method of high-purity chromium metal. The method comprises the following steps: (1) preparing a chromium trichloride solution; (2) purification: purifying the prepared chromium trichloride solution by an ion exchange method; (3) performing spray pyrolysis to prepare chromium sesquioxide; (4) gas-solid separation; and (5) chromium sesquioxide is reduced to prepare high-purity metal chromium. The method comprises the following steps: preparing a chromium trichloride solution by using metal chromium of 3N5, purifying the chromium trichloride solution by using an ion exchange method to remove heavy metal impurities in the chromium trichloride solution, and performing spray pyrolysis on the purified chromium trichloride solution to prepare high-purity chromium sesquioxide powder. Metal and interstitial element impurities such as oxygen, nitrogen and the like and low-melting-point metal impurities in the chromium sesquioxide are removed through a reduction method, and the purity of the prepared high-purity metal chromium reaches 99.999% or above. The preparation method is simple in process and few in control parameters, and the prepared chromium metal is high in purity.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high-purity metal chromium preparation, and particularly relates to a high-purity metal chromium preparation method. BACKGROUND

[0002] With the integrated chip process used in the electronic, semiconductor, communication and other industries becoming smaller and smaller, the purity of high-purity chromium used is required to be higher and higher. The preparation process of high-purity chromium is mostly electrolysis, chromium trioxide high-temperature carbon reduction, aluminum reduction, silicon reduction and other methods. The electrolysis method is generally used to prepare high-purity chromium of 4N or above. However, the electrolysis method has the following shortcomings: (1) the preparation and purification process of the electrolyte is complex. The purification of the trivalent chromium electrolytic solution generally needs to prepare a chrome ammonium alum solution, and then recrystallization purification is performed. The time is long, and the control conditions are harsh. Even so, it is difficult to prepare an electrolyte for preparing high-purity chromium of 5N; (2) the electrolysis process is complex. The process conditions of high-purity chromium are harsh, and it is difficult to form a plate. The circulation amount of the electrolyte is large, and the solution demand is high; (3) the current efficiency is low. The current efficiency of trivalent chromium electrolysis can only reach 20%-60%, and the energy consumption is high; (4) toxicity. A small amount of hexavalent chromium is still generated in the trivalent chromium electrolysis process. The hexavalent chromium has great toxicity, and the solution circulation amount is large; (5) according to the different raw material components, it is difficult to obtain high-purity chromium of 5N or above by one electrolysis, and the preparation process is complex.

[0003] Therefore, it is necessary to develop a method for preparing 5N high-purity chromium with little pollution. SUMMARY

[0004] In order to solve the problems in the prior art, the present application provides a high-purity metal chromium preparation method, which is as follows:

[0005] A high-purity metal chromium preparation method, comprising the following steps:

[0006] Step 1: Dissolving 3N5 metal chromium in a hydrochloric acid solution to obtain a chromium trichloride solution, wherein the 3N5 metal chromium is preferably chromium sheet;

[0007] Step 2: Purifying and removing impurities from the chromium trichloride solution by using ion exchange resin to obtain a purified solution;

[0008] Step 3: Adding the purified solution into a spray pyrolysis furnace, and atomizing the purified solution into mist droplets through a nozzle of the spray pyrolysis furnace. The mist droplets are pyrolyzed into a mixture of chromium trioxide powder and hydrogen chloride gas;

[0009] Step 4: Negative pressure extraction of the mixture of chromium trioxide powder and hydrogen chloride gas and addition of the mixture into a high-temperature gas-solid separation filter for gas-solid separation. The solid product is chromium trioxide powder;

[0010] Step 5: Reducing the chromium trioxide powder obtained in step 4 to prepare high-purity metal chromium.

[0011] Furthermore, the hydrogen chloride gas separated in step 4 enters a gas absorption device, which is filled with pure water. The hydrochloric acid solution obtained after absorption is circulated and used to dissolve 3N5 metallic chromium in step 1.

[0012] Furthermore, in step 1, the dissolution temperature is 20-60° C., the dissolution time is 20-100 min, the concentration of hydrochloric acid is 5-6 mol / L, and the chromium ion concentration in the chromium trichloride solution is 80-100 g / L.

[0013] Furthermore, the ion exchange resin in step 2 is a chelating resin, and the chromium trichloride solution is added to the ion exchange resin at a rate of 1-3BV / h for purification. After the purification and impurity removal in step 2 is completed, the ion exchange resin is regenerated with hydrochloric acid and then washed with pure water.

[0014] Furthermore, the spray pyrolysis furnace in step 3 is a vertical spray pyrolysis furnace with a height-to-diameter ratio greater than 10, and is pressurized by a metering pump or gas pressurized spraying.

[0015] Furthermore, in step 3, the spray pyrolysis furnace is first preheated to 700-800°C, and then the purification liquid is added. The addition rate of the purification liquid is 10-20L / h, and the spray pyrolysis temperature is 700-800°C.

[0016] Furthermore, the reduction method in step 5 is to perform carbon reduction and hydrogen reduction in sequence.

[0017] Compared with the prior art, the present invention has the following advantages:

[0018] 1. No additives are added during the preparation process of the present invention, thereby reducing the introduction of additional impurities.

[0019] 2. The present invention utilizes hydrochloric acid solution generated by spray pyrolysis to dissolve metal chromium flakes to prepare chromium trichloride, which has a simple preparation process and can recycle materials;

[0020] 3. The present invention uses ion exchange method to remove impurities in depth, remove trace heavy metal impurities in the solution, and purify the solution components, thus ensuring the purity of subsequent products;

[0021] 4. The chromium trichloride solution of the present invention adopts a spray pyrolysis method to prepare high-purity chromium trioxide, which has simple process control, uniform and controllable particle size of high-purity chromium trioxide powder, short reaction time, and low energy consumption; no pollutants are generated in the process, and no solid waste or waste liquid is generated, thereby achieving good economic and environmental benefits;

[0022] 5. The metal and interstitial element impurities such as oxygen, nitrogen and low-melting-point metal impurities are removed by reduction method. The high-purity metallic chromium prepared by the present invention has a purity of more than 99.999%, which can meet the requirements of high-end applications in the semiconductor field and other fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Embodiments of the present application will be further described below with reference to the drawings, in which:

[0024] Figure 1 A process flow diagram of the preparation of high-purity metallic chromium in an embodiment of the present application is shown. DETAILED DESCRIPTION

[0025] In order to make the objectives, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to specific embodiments and the accompanying drawings. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0026] A method for preparing high-purity metallic chromium, comprising the following steps:

[0027] Step 1: Dissolve 3N5 metallic chromium in a chromium dissolving tank using a hydrochloric acid solution to obtain a chromium chloride solution; the dissolving temperature is 20-60°C, the dissolving time is 20-100 min, the concentration of the hydrochloric acid is 5-6 mol / L, and the chromium ion concentration in the chromium chloride solution is 80-100 g / L;

[0028] Step 2: Purify and remove impurities in the chromium chloride solution using ion exchange resin to remove trace amounts of heavy metal impurities such as copper, iron, nickel, cobalt and zinc in the solution to obtain a purified solution; the ion exchange resin is a chelating resin, the chromium chloride solution is added to the ion exchange resin at a speed of 1-3 BV / h for purification, after the purification and impurity removal is completed, the ion exchange resin is regenerated with hydrochloric acid and then washed with pure water;

[0029] Step 3: Pump the purified solution into a spray pyrolysis furnace using a metering pump, and atomize the purified solution into mist droplets through a nozzle of the spray pyrolysis furnace; the size of the mist droplets can be adjusted to prepare products from nanometer to micrometer; the mist droplets are converted into a mixture of chromium oxide powder and hydrogen chloride gas through spray pyrolysis; the spray pyrolysis furnace is a vertical spray pyrolysis furnace with a height-diameter ratio >10, and the spray pyrolysis is performed by pressurization of the metering pump or pressurization of gas; first, preheat the spray pyrolysis furnace to 700-800°C, then pump in the purified solution, the pumping speed of the purified solution is 10-20 L / h, and the spray pyrolysis temperature is 700-800°C;

[0030] Step 4: Negative pressure extraction of the mixture of chromium oxide powder and hydrogen chloride gas out of the spray pyrolysis furnace body, and then addition into a high-temperature gas-solid separation filter for gas-solid separation; the hydrogen chloride gas is discharged from the upper end into a gas absorption device, the lower end of the gas-solid separation filter discharges the product, which is chromium oxide powder, the prepared chromium oxide powder has a D50 of about 5 μm, which meets the product use requirements; the separated hydrogen chloride gas enters the gas absorption device, which is in a three-stage series connection, the gas absorption device is fully sealed, the tail gas is discharged up to standard, the gas absorption device is filled with pure water, and the prepared hydrochloric acid solution after absorption is recycled for use in dissolving 3N5 metallic chromium in step 1.

[0031] Step 5: The chromium trioxide powder obtained in step 4 is placed in a reduction furnace for reduction to prepare high-purity metallic chromium. The reduction method is carbon reduction and hydrogen reduction, and the reduction raw material uses a high-purity raw material, such as carbon powder with a purity of 5N or above, to prepare metallic chromium with impurities meeting the requirements, remove gas impurities such as carbon, sulfur, oxygen, and nitrogen in the metallic chromium powder, and reduce the content of low-melting-point metals in the metallic chromium, thereby further improving the purity of the prepared high-purity metallic chromium.

[0032] Example 1

[0033] (1) Preparation of chromium solution: 6500 g of 3N5 metallic chromium is weighed and placed in a 100 L chromium dissolving tank, 60 L of recovered high-purity hydrochloric acid is slowly added, high-purity water is added to 75 L, the concentration of hydrochloric acid is 5 mol / L, heating to 40℃ and stirring, and the acid solution is adjusted until the added metallic chromium is almost completely dissolved, the dissolution time is 50 min, the volume is adjusted to 80 L, the solution is stirred uniformly, and the filtrate is a chromium chloride solution;

[0034] (2) Purification of chromium chloride solution: the chromium solution is subjected to ion exchange purification at a speed of 1 BV / h to obtain a purified chromium chloride solution.

[0035] (3) Spray pyrolysis: the spray pyrolysis furnace is first heated to 700℃, and the purified chromium chloride solution is pumped into the spray pyrolysis furnace by a metering pump at a flow rate of 10 L / h;

[0036] (4) Gas-solid separation: after the completion of spray pyrolysis, the mixed flue gas of chromium trioxide powder and hydrogen chloride gas produced by the spray pyrolysis furnace is extracted by negative pressure to enter the high-temperature gas-solid separation filter, the hydrogen chloride gas is discharged from the upper end to enter the gas absorption device, and the chromium trioxide powder collected at the lower end of the gas-solid separation device;

[0037] (5) Concentration of hydrochloric acid solution: the fan for negative pressure extraction is started when the spray pyrolysis of the chromium trioxide solution begins, and the hydrogen chloride gas is absorbed into the gas absorption device; the prepared hydrochloric acid solution is recycled to dissolve 3N5 metallic chromium to prepare a chromium chloride solution or used for other purposes.

[0038] (6) Reduction: the chromium trioxide powder is mixed with an appropriate proportion of 5N carbon powder and placed in a carbon reduction furnace for carbon reduction, and the obtained chromium powder is reduced in a hydrogen reduction furnace by passing hydrogen gas to obtain 5N high-purity metallic chromium.

[0039] Example 2

[0040] (1) Preparation of chromium solution: 15000g of 3N5 metallic chromium was weighed and placed in a 200L chromium dissolving tank, 130L of high-purity hydrochloric acid was slowly added, high-purity water was added to 140L, the concentration of hydrochloric acid was 5.5mol / L, heated to 60℃ and stirred, the acid was added slightly during stirring until the added metallic chromium was almost completely dissolved, the dissolution time was 30min, the volume was adjusted to 150L, stirred uniformly, the solution was filtered, and the filtrate was a chromium chloride solution;

[0041] (2) Purification of chromium chloride solution: the chromium solution was purified by ion exchange at a speed of 2BV / h to obtain a purified chromium chloride solution;

[0042] (3) Spray pyrolysis: the spray pyrolysis furnace was first heated to 750℃, and the purified chromium chloride solution was pumped into the spray pyrolysis furnace by a metering pump at a flow rate of 20L / h;

[0043] (4) Gas-solid separation: after the spray pyrolysis was completed, the mixed flue gas of chromium dioxide powder and hydrogen chloride gas produced by the spray pyrolysis furnace was extracted by negative pressure and entered the high-temperature gas-solid separation filter, the hydrogen chloride gas was discharged from the upper end and entered the gas absorption device, and the chromium dioxide powder collected at the lower end of the gas-solid separation device;

[0044] (5) Concentration of hydrochloric acid solution: the fan for negative pressure extraction was started when the spray pyrolysis of the chromium chloride solution was started, and the hydrogen chloride gas was absorbed into the gas absorption device; the prepared hydrochloric acid solution was recycled to dissolve 3N5 metallic chromium to prepare a chromium chloride solution or for other use;

[0045] (6) Reduction: the chromium dioxide powder was mixed with a proper proportion of 6N carbon powder and then placed in a carbon reduction furnace for carbon reduction, and the obtained chromium powder was reduced in a hydrogen reduction furnace by passing hydrogen gas to obtain 5N high-purity metallic chromium.

[0046] Example 3

[0047] (1) Preparation of chromium solution: 10000g of 3N5 metallic chromium was weighed and placed in a 100L chromium dissolving tank, 90L of high-purity hydrochloric acid was slowly added, high-purity water was added to 95L, the concentration of hydrochloric acid was 5mol / L, heated to 50℃ and stirred, and the acid was added slightly during stirring until the added metallic chromium was almost completely dissolved, the dissolution time was 100min, the volume was adjusted to 100L, stirred uniformly, the solution was filtered, and the filtrate was a chromium chloride solution;

[0048] (2) Purification of chromium chloride solution: the chromium solution was purified by ion exchange at a speed of 3BV / h to obtain a purified chromium chloride solution;

[0049] (3) Spray pyrolysis: the spray pyrolysis furnace was first heated to 800℃, and the purified chromium chloride solution was pumped into the spray pyrolysis furnace by a metering pump at a flow rate of 15L / h;

[0050] (4) gas-solid separation: after the spray pyrolysis is completed, the mixed flue gas of the chromium trioxide powder and hydrogen chloride gas produced by the spray pyrolysis furnace is extracted from the spray pyrolysis furnace body by negative pressure and enters the high-temperature gas-solid separation filter, the hydrogen chloride gas is discharged from the upper end and enters the gas absorption device, and the chromium trioxide powder collected at the lower end of the gas-solid separation device is collected;

[0051] (5) hydrochloric acid solution concentration: when the spray pyrolysis with the chromium trioxide solution is started, the fan for negative pressure extraction is turned on, the hydrogen chloride gas is absorbed into the gas absorption device, and the prepared hydrochloric acid solution is recycled to dissolve 3N5 metal chromium to prepare the chromium trioxide solution or for other use;

[0052] (6) reduction: the chromium trioxide powder is mixed with 5N5 carbon powder in a proper ratio, and then is put into a carbon reduction furnace for carbon reduction, and the obtained chromium powder is reduced in a hydrogen reduction furnace by passing hydrogen gas to obtain 5N high-purity metal chromium.

[0053] The above describes some exemplary embodiments of the present application, and it can be understood that the above-described embodiments are only used to explain the present application and do not constitute a limitation on the protection scope of the present application. The features in these embodiments can be recombined in a suitable manner, and the schemes obtained thereby are still within the protection scope required by the present application. Based on the above-described embodiments, all other embodiments obtained by those skilled in the art without creative labor, i.e. all modifications, equivalent replacements and improvements, etc. made within the spirit and principles of the present application, are also within the protection scope required by the present application.

Claims

1. A method for preparing high-purity metallic chromium, characterized in that: The following steps are involved: Step 1: dissolving 3N5 metallic chromium in a hydrochloric acid solution to obtain a chromium trichloride solution; Step 2: purifying the chromium trichloride solution with an ion exchange resin to remove impurities to obtain a purified solution; Step 3: The purified liquid is added to the spray pyrolysis furnace, atomized into droplets through the nozzle of the spray pyrolysis furnace, and the droplets are pyrolyzed into a mixture of chromium oxide powder and hydrogen chloride gas; Step 4: extracting the mixture of the chromium oxide powder and hydrogen chloride gas under negative pressure and adding it to a high-temperature gas-solid separation filter for gas-solid separation, whereby the solid product is chromium oxide powder; Step 5: reducing the chromium oxide powder obtained in step 4 to prepare high-purity metallic chromium, wherein the purity of the high-purity metallic chromium is greater than 99.999%.

2. The method for preparing high-purity metallic chromium according to claim 1, characterized in that: The hydrogen chloride gas separated in step 4 enters a gas absorption device, which is filled with pure water. The hydrochloric acid solution obtained after absorption is circulated and used to dissolve 3N5 metallic chromium in step 1.

3. The method for preparing high-purity metallic chromium according to claim 1, characterized in that: In step 1, the dissolution temperature is 20-60° C., the dissolution time is 20-100 min, the concentration of hydrochloric acid is 5-6 mol / L, and the chromium ion concentration in the chromium trichloride solution is 80-100 g / L.

4. The method for preparing high-purity metallic chromium according to claim 1, characterized in that: The ion exchange resin described in step 2 is a chelating resin, and the chromium trichloride solution is added to the ion exchange resin at a speed of 1-3BV / h for purification. After the purification and impurity removal in step 2 is completed, the ion exchange resin is regenerated with hydrochloric acid and then washed with pure water.

5. The method for preparing high-purity metallic chromium according to claim 1, characterized in that: The spray pyrolysis furnace in step 3 is a vertical spray pyrolysis furnace with a height-to-diameter ratio greater than 10, and is pressurized by a metering pump or gas.

6. The method for preparing high-purity metallic chromium according to claim 5, characterized in that: In step 3, the spray pyrolysis furnace is first preheated to 700-800°C, and then the purification liquid is added. The addition rate of the purification liquid is 10-20L / h, and the spray pyrolysis temperature is 700-800°C.

7. The method for preparing high-purity metallic chromium according to claim 1, characterized in that: The reduction method in step 5 is to perform carbon reduction and hydrogen reduction in sequence.

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