Method for preparing high purity vanadium pentoxide from vanadium-bearing shale by all-wet process

A method for preparing high purity vanadium pentoxide from vanadium-bearing shale by all-wet process, the method comprises the steps of:

• step 1, wet activation and compound leaching of the vanadium-bearing shale, including:
• step 1.1, grading activation of the vanadium-bearing shale, including:
• the vanadium-bearing shale is broken to a particle size less than 3 mm with 75˜95% to obtain a vanadium-bearing shale powder;
• then the vanadium-bearing shale powder is screened with a 0.45 mm standard screen to obtain a material under the screen and a material on the screen;
• mixing the activator with the material under the screen and the material on the screen respectively according to a mass ratio of (0.04˜0.07):1 to obtain a mixed material I and a mixed material II;
• then, adding water to the mixed material I and the mixed material II according to a liquid-solid ratio of 0.4˜0.6 L/kg and performing a slurry process to obtain a mixed slurry I and a mixed slurry II respectively;
• feeding the mixed slurry I into a mill for wet activation for 1-4 minutes to obtain an activated slurry I;
• feeding the mixed slurry II into the mill for wet activation for 10˜30 minutes to obtain an activated slurry II;
• finally, the activated slurry I and the activated slurry II are mixed to obtain a mixed activated slurry;
• step 1.2, compound leaching of the vanadium-bearing shale, including:
• the mixed activated slurry is added at a uniform rate from an upper port of a first feeding pipe (2) of a gradient continuous leaching system of vanadium-bearing shale, and a flow quantity of the mixed activated slurry added at a uniform rate is adjusted according to a flow time of the mixed activated slurry with 4˜8 hours in the gradient continuous leaching system of vanadium-bearing shale;
• then opening all steam conveying branch pipes (4) in the gradient continuous leaching system of vanadium-bearing shale, and adjusting a temperature of a tank (8) of a leaching device (1) to 98˜130° C.;
• then, adding an inorganic acid according to a mass ratio of the vanadium-bearing shale to the inorganic acid of 1:
• (0.275˜0.40), and adding 0.5-1 mol of a coordination agent per kg the vanadium-bearing shale, the inorganic acid is added at a uniform rate from an acid filling pipe (13) of a first leaching device (1), and the coordination agent is added at a uniform rate from the acid filling pipe (13) of a second leaching device (1);
• the mixed slurry output from a lower port of the last feeding pipe (2) of the gradient continuous leaching system of vanadium-bearing shale is subjected to a solid-liquid separation to obtain a vanadium-containing acid leachate and a leach residue;
• wherein the inorganic acid is a mixture obtained by a volume ratio of sulfuric acid to other inorganic acids except for the sulfuric acid with 1:(0˜1);
• wherein the other inorganic acids except for the sulfuric acid are more than one of phosphoric acid and hydrochloric acid;
• step 2, adjustment of pH of the vanadium-containing acid leachate, including:
• the adjustment of the pH of the vanadium-containing acid leachate is divided into two stages, and a pH adjusting device of the vanadium-containing acid leachate is the same for both stages;
• the pH adjusting device of the vanadium-containing acid leachate used in a first stage is called a first adjustment device;
• the pH adjusting device of the vanadium-containing acid leachate used in a second stage is called a second adjustment device;
• connecting mth-stage conditioning chamber of the first adjustment device to 1st-stage conditioning chamber of the second adjustment device;
• mth-stage acid recovery chamber of the second adjustment device is connected to 1st-stage acid recovery chamber of the first adjustment device;
• wherein the first stage of the adjustment of the pH of the vanadium-containing acid leachate is that a sodium sulfate solution is injected into an anode chamber and a cathode chamber of the first adjustment device, respectively;
• the vanadium-containing acid leachate is injected into an inlet of 1st-stage conditioning chamber of the first adjustment device, and water or low acid solution is injected into an inlet of 1st-stage acid recovery chamber of the first adjustment device;
• turning on a DC power supply of the first adjustment device, wherein the DC power supply is set to constant voltage mode;
• the vanadium-containing acid leachate is injected into the inlet of the 1st-stage conditioning chamber of the first adjustment device, which flows through 2nd-stage conditioning chamber, 3rd-stage conditioning chamber, . . . , m−1th-stage conditioning chamber, mth-stage conditioning chamber, and then flows out of an outlet of the mth-stage conditioning chamber to obtain a pre-conditioning solution;
• the water is injected into the inlet of the 1st-stage acid recovery chamber of the first adjustment device, which flows through 2nd-stage acid recovery chamber, 3rd-stage acid recovery chamber, . . . , m−1th-stage acid recovery chamber, mth-stage acid recovery chamber, and then flows out of an outlet of the mth-stage acid recovery chamber to obtain a recovered acid solution;
• wherein the recovered acid solution is used in preparation of the inorganic acid as described in step 1.2 and a stripping regenerant as described in step 3.3;
• wherein the pH of the pre-conditioning solution is 0.5˜1.2;
• wherein the second stage of the adjustment of the pH of the vanadium-containing acid leachate is that the sodium sulfate solution is injected into the anode chamber and the cathode chamber of the second adjustment device, respectively;
• the pre-conditioning solution of the first adjustment device is injected into the inlet of the 1st-stage conditioning chamber of the second adjustment device, and water is injected into the inlet of the 1st-stage acid recovery chamber of the second adjustment device;
• turning on the DC power supply of the second adjustment device, wherein the DC power supply is set to constant current mode;
• the pre-conditioning solution is injected into the inlet of the 1st-stage conditioning chamber of the second adjustment device, which flows through the 2nd-stage conditioning chamber, the 3rd-stage conditioning chamber, . . . , the m−1th-stage conditioning chamber, the mth-stage conditioning chamber, and then flows out of the outlet of the mth-stage conditioning chamber to obtain a post-treatment solution;
• the water is injected into the inlet of the 1st-stage acid recovery chamber of the first adjustment device, which flows through the 2nd-stage acid recovery chamber, the 3rd-stage acid recovery chamber, . . . , the m−1th-stage acid recovery chamber, the mth-stage acid recovery chamber, and then flows out of the outlet of the mth-stage acid recovery chamber to obtain a low-acid solution;
• wherein the low-acid solution returns to the 1st-stage acid recovery chamber of the first adjustment device;
• wherein the pH of the post-treatment solution is 1.5˜2.5;
• step 3, purification and enrichment, including:
• step 3.1, according to a molar ratio of oxidant to vanadium ions in the post-treatment solution as (0.3˜0.5):1, the oxidant is added into the post-treatment solution, and stirring for 0.5-1 hours to obtain a feed solution;
• step 3.2, an organic phase is produced according to a volume ratio of hydroxime extractant to sulfonated kerosene as 1:(2˜9);
• then, according to a volume ratio of the feed solution to the organic phase as (2˜6):1, a loaded organic phase and a raffinate are obtained by countercurrent extraction in 2˜5 stages at an extraction temperature of 25˜60° C. and a single stage extraction time of 8˜20 minutes;
• after neutralization, the raffinate returns to the slurry process in step 1.2 and/or to the water using in the acid recovery chamber in step 2;
• step 3.3, according to a molar ratio of reductant and vanadium in the loaded organic phase as (1-5):1, the reductant is dissolved into the recovered acid solution as described in step 2 to obtain a stripping regenerant;
• wherein the reductant is one or more than one of oxalic acid, potassium oxalate, sodium oxalate, ammonium oxalate;
• step 3.4, according to a volume ratio of the loaded organic phase to the stripping regenerant as (3˜6):1, a regenerated organic phase and a vanadium-rich solution are obtained by countercurrent extraction in 2˜6 stages at an extraction temperature of 60-80° C. and a single stage extraction time of 15˜35 minutes;
• wherein the regenerated organic phase returns directly to step 3.2 as the organic phase for recycling;
• step 4 preparation of the high purity vanadium pentoxide, including:
• step 4.1, according to a molar ratio of vanadium ion in the vanadium-rich solution to an accelerator as 1:
• (0.01˜0.05), the accelerator is added into the vanadium-rich solution, and stirring for 0.5-1.5 hours to obtain a primary solution for vanadium precipitation;
• then, the pH of the primary solution is adjusted to 0.5-2 to obtain a reaction solution for vanadium precipitation;
• step 4.2, the reaction solution is transferred to a reaction vessel for vanadium precipitation valence conversion at a reaction temperature of 160˜220° C. and a reaction time of 4-8 hours, then cooled to room temperature;
• a solid-liquid separation is carried out to obtain a vanadium-containing hydroxide and a mother liquor after vanadium precipitation;
• wherein the mother liquor after vanadium precipitation is incorporated into the vanadium-containing acid leachate of step 1.2;
• step 4.3, the vanadium-containing hydroxide is roasted with chemical valence conversion under an oxygen-rich atmosphere at a roasting temperature of 300-500° C. and a roasting time of 0.5-2 hours to produce the high purity vanadium pentoxide;
• wherein the gradient continuous leaching system of vanadium-bearing shale described in step 1.2 consist of n the leaching devices (1), steam conveying pipes (5), n the steam conveying branch pipes (4) and n+1 the feeding pipes (2);
• with the purpose of convenient narration, relevant letters are uniformly described as follows:
• n indicates a number of the leaching devices (1), the steam conveying branch pipes (4) and the feeding pipes (2), n is a natural number from 2 to 10;
• h indicates a height of the tank (8) in the leaching device (1), its unit is mm;
• D indicates a diameter of the tank (8) in the leaching device (1), its unit is mm;
• wherein the leaching devices (1) in the gradient continuous leaching system of vanadium-bearing shale are setting in a ladder pattern with a height difference Δh1=(¾˜½) h;
• the upper port of the first feeding pipe (2) is connected to an external feeding bin, and the lower port of the first feeding pipe (2) is connected to the inlet of the first leaching device (1);
• the upper port of the second feeding pipe (2) is connected to the outlet of the first leaching device (1), and the lower port of the second feeding pipe (2) is connected to the inlet of the second leaching device (1);
• and so on, an upper port of the nth feeding pipe (2) is connected to an outlet of the n−1th leaching device (1), and a lower port of the nth feeding pipe (2) is connected to an inlet of the nth leaching device (1);
• an upper port of the n+1th feeding pipe (2) is connected to an outlet of the nth leaching device (1), and a lower port of the n+1th feeding pipe (2) is connected to next working procedure;
• each feeding pipe (2) is equipped with a gate valve (3) near the upper port;
• each leaching device (1) is equipped with the steam conveying branch pipe (4), an inlet of each steam conveying branch pipe (4) is connected to the steam conveying pipe (5), and an outlet of each steam conveying branch pipe (4) is located above a feed port of feeding pipe (2) in the corresponding leaching device (1);
• a distance between each steam conveying branch pipe (4) and an inner wall of the corresponding leaching device (1) is 1b=( 1/10˜⅛) D;
• wherein all leaching devices (1) consist of the tank (8), a cover plate (9), a drive motor (10), an upper slant lobe paddle (7), a lower straight lobe stirring paddle (6) and an acid filling tank (12);
• wherein the tank (8) is cylindrical, and a height of the tank (8) is h=( 4/3- 3/2) D;
• there is an inlet port on one side of the tank (8), a distance of the inlet port from a bottom is 1j=( 1/10-¼) h;
• there is an outlet port on the other side of the tank (8), a distance of the outlet port from the bottom is 1c=(¾˜⅘) h;
• there is a spherical tab (16) at a bottom center of the tank (8), a bottom diameter of the spherical tab (16) is dq=(⅖-⅔) D, a height of spherical tab (16) is hq=( 1/10˜⅖) D;
• an upper part of the tank (8) is fixed with the cover plate (9), wherein a center of cover plate (9) is equipped with the drive motor (10), wherein the drive motor (10) is connected to an upper part of a mixing shaft (14) via coupling, and a lower part of the mixing shaft (14) passing the cover plate (9) extends into the tank (8);
• a mid of the mixing shaft (14) is equipped with the upper slant lobe paddle (7), and a bottom of the mixing shaft (14) is connected to the lower straight lobe stirring paddle (6) via a hub (15);
• diameters of the upper slant lobe paddle (7) and the lower straight lobe stirring paddle (6) are dj=(⅓˜⅔) D, a distance between the lower straight lobe stirring paddle (6) and a top of the spherical tab (16) is 1t=( 1/20-⅛) h, and a distance between the upper slant lobe paddle (7) and the lower straight lobe stirring paddle (6) is 1i=(⅕-⅓) h;
• there is a lower acid filling pipe (13) on one side of the cover plate (9), a lower part of the lower acid filling pipe (13) passing the cover plate (9) extends into the tank (8), an upper part of the lower acid filling pipe (13) is connected to an outlet of the acid filling tank (12), an inlet of the acid filling tank (12) is connected to the lower part of the upper acid filling pipe (13), the upper part of the upper acid filling pipe (13) is connected to a relevant acid source;
• the upper acid filling pipe (13) and the lower acid filling pipe (13) are equipped with a butterfly valve (11) respectively;
• wherein a distance between the acid filling pipe (13) and right inner wall of the tank (8) is b2=( 1/10-⅛) D;
• wherein the pH adjusting device of the vanadium-containing acid leachate described in step 2 is that a cathode is connected to a negative terminal of the DC power supply and an anode is connected to a positive terminal of the DC power supply;
• the cathode and the anode are placed correspondingly on right side and left side of membrane stack;
• wherein the membrane stack consists of 1st cation exchange membrane, 1st anion exchange membrane, 2nd cation exchange membrane, 2nd anion exchange membrane, 3rd cation exchange membrane, . . . , mth cation exchange membrane, mth anion exchange membrane and m+1th cation exchange membrane in order from a direction of the anode to the cathode;
• wherein m is a positive integer from 10 to 1000;
• from the direction of the anode to the cathode, a gap between the anode and the 1st cation exchange membrane forms the anode chamber, a gap between the 1st cation exchange membrane and the 1st anion exchange membrane forms the 1st-stage conditioning chamber, a gap between the 1st anion exchange membrane and the 2nd cation exchange membrane forms the mth-stage acid recovery chamber, a gap between the 2nd cation exchange membrane and the 2nd anion exchange membrane forms the 2nd-stage conditioning chamber, a gap between the 2nd anion exchange membrane and the 3rd cation exchange membrane forms the m−1th stage acid recovery chamber, . . . , and so on;
• a gap between the m−1th stage cation exchange membrane and the m−1th stage anion exchange membrane forms the m−1th stage conditioning chamber, a gap between the m−1th stage anion exchange membrane and the mth stage cation exchange membrane forms the 2nd stage acid recovery chamber, a gap between the mth stage cation exchange membrane and the mth stage anion exchange membrane forms the mth-stage conditioning chamber, a gap between the mth stage anion exchange membrane and the m+1th stage cation exchange membrane forms the 1st-stage acid recovery chamber, a gap between the m+1th stage cation exchange membrane and the cathode forms the cathode chamber;
• wherein the 1st-stage conditioning chamber, the 2nd-stage conditioning chamber, the 3rd-stage conditioning chamber, . . . , the m−1th-stage conditioning chamber, and the mth-stage conditioning chamber are connected in sequence;
• wherein the 1st-stage acid recovery chamber, the 2nd-stage acid recovery chamber, the 3rd-stage acid recovery chamber, . . . , the m−1th-stage acid recovery chamber, the mth-stage acid recovery chamber are connected in sequence;
• wherein the pH adjusting device of the vanadium-containing acid leachate is obtained by forming a series circuit between the anode electrode chamber, the 1st-stage conditioning chamber, the mth-stage acid recovery chamber, the 2nd-stage conditioning chamber, the m−1th-stage acid recovery chamber, . . . , the m−1th-stage conditioning chamber, the 2nd-stage acid recovery chamber, the mth-stage conditioning chamber, the 1st-stage acid recovery chamber, the cathode electrode chamber and the DC power supply in the operating condition.