WO2004090179A1

WO2004090179A1 - Method of recovering vanadium oxide flake from diesel oil fly-ash or orimulsion fly-ash

Info

Publication number: WO2004090179A1
Application number: PCT/KR2004/000742
Authority: WO
Inventors: Young-Ki Choi; Kyung-Ho Park; Dae-Hoo Kim; Sin-Won Han; Jong-Nam Lim; Park-Hyun Han; Ji-Hun Choi
Original assignee: KOREA AGENCY OF ENVIRONMENT
Current assignee: KOREA AGENCY OF ENVIRONMENT
Priority date: 2003-04-11
Filing date: 2004-03-31
Publication date: 2004-10-21
Anticipated expiration: 2005-10-11
Also published as: KR100516976B1; KR20040089324A

Abstract

Abstract Disclosed is a method of recovering a vanadium oxide flake from diesel oil fly-ash or Orimulsion fly-ash, including the steps of leaching a mixture of diesel oil fly-ash or Orimulsion fly-ash and water in an agitation leaching bath to dissolve vanadium and nickel, subjecting the leached mixture to solid-liquid separation to obtain a leached solution, adding a neutralizing agent to the leached solution to adjust pH to 5-6 to recover vanadium tetraoxide from the leached solution, drying the recovered vanadium tetraoxide at high temperatures to remove water contained in vanadium tetraoxide, and adding a flux to the dried vanadium tetraoxide and melting vanadium tetraoxide in a melting furnace, to prepare a vanadium oxide flake.

Description

METHOD OF RECOVERING VANADIUM OXIDE

FLAKE FROM DIESEL OIL FLY-ASH OR

ORIMULSION FLY-ASH

Technical Field

[1] The present invention relates, in general, to methods of recovering a vanadium oxide flake. More specifically, the present invention is directed to a method of recovering a vanadium pentoxide flake, which is a raw material for preparation of fer- rovanadium, from diesel oil fly-ash or Orimulsion fly-ash generated upon burning bunker oil or Orimulsion.

Background Art

[2] In general, diesel oil fly-ash is very light black powders having an apparent specific gravity of 0.4, recovered into an electric dust collector upon burning bunker oil fuel in a boiler, and contains 3-15% vanadium and 2-10% nickel.

[3] On the other hand, Orimulsion fly-ash is obtained upon burning an emulsion fuel comprising bitumen (residue remaining after volatile oil components in the petroleum are evaporated) mined in Orinoco province, Venezuela , in mixture with water and a surfactant. The Orimulsion fly-ash having an apparent specific gravity of about 0.2 consists of 5-20% vanadium, 1-5% nickel and 2-15% magnesium. Orimulsion has been spotlighted as a replacement for conventional fuel oil. For example, Youngnam Power Plant in Ulsan Province and F nam Power Plant in Yeosu , Korea , have plans to substitute Orimulsion for bunker oil as a boiler fuel in 2003 and 2004, respectively. In the future, the Orimulsion fly-ash is expected to be generated in drastically increased amounts.

[4] Such diesel oil fly-ash and Orimulsion fly-ash are classified into a special waste, because of containing large amounts of vanadium, nickel, etc., as heavy metals. Further, landfill treatment of the above fly-ash costs a great deal. In developed countries including USA and Japan , technologies for recovering valuable metals, in particular, vanadium, from the above fly-ash have been commercialized. In Korea , recovery of desired components from wastes has been carried out by means of conventional technologies.

[5] As for conventional methods of recovering vanadium contained in diesel oil fly- ash or Orimulsion fly-ash, diesel oil fly-ash or Orimulsion fly-ash is leached with sulfuric acid to dissolve vanadium and other valuable metals. Then, through a wet oxidation process using steam and air in a high-pressure reactor or using an oxidizing agent of NaClO , all the dissolved vanadium is oxidized to a pentavalent state. The

3 pentavalent vanadium-containing solution is added with a neutralizing agent, such as ammonia or caustic soda, and pH thereof is adjusted to 2.5-3 or 8. Thereafter, the solution is maintained at 80-120 ° C or higher for 1 hour or more, whereby vanadium is precipitated in the state of a red cake consisting mainly of vanadium pentoxide or ammonium vanadate and separated from the solution. The red cake or ammonium vanadate is melted at 800-1000 ° C and is prepared in the flake state, which is used as a preparation material of ferrovanadium. [6] F wever, the above method is disadvantageous in terms of use of expensive

NaClO to oxidize vanadium after leaching diesel oil fly-ash or Orimulsion fly-ash. In

3 addition, due to generation of chlorine gas upon oxidation, the work environment is degraded and the reactor made of metals is highly corroded. By using steam and air under high pressure, large quantities of electric power are consumed, thus increasing process costs.

[7] Further, hydrogen ions are generated upon oxidation of the vanadium ion, therefore lowering the pH of the leached solution. The above-mentioned method suffers from excessive consumption of the neutralizing agent, such as ammonia or caustic soda, to form the solution of pH 2.5-3.0 suitable for preparation of the red cake.

[8] Furthermore, since the temperature of the solution is maintained at 80 ° C or more for 1 hour or longer, large quantities of energy are consumed.

Disclosure of the Invention

[9] Accordingly, an object of the present invention is to alleviate the problems of conventional recovery treatments encountered in the prior art and to provide a method of recovering a vanadium, which is advantageous in terms of considerably decreased energy consumption to remarkably lower preparation cost of ferrovanadium, thus generating economic benefits.

[10] In order to achieve the above object, there is provided a method of recovering a vanadium oxide flake from diesel oil fly-ash or Orimulsion fly-ash, comprising the steps of leaching a mixture of diesel oil fly-ash or Orimulsion fly-ash and water in an agitation leaching bath to dissolve valuable metals, such as vanadium and nickel, followed by subjecting the leached mixture to solid-liquid separation, thereby separating a leached solution from insoluble residues; adding the leached solution with a neutralizing agent to adjust pH to 5-6 to precipitate, separate and recover vanadium tetraoxide from the leached solution, thereby preparing vanadium tetraoxide; drying the prepared vanadium tetraoxide at high temperatures to remove water contained in vanadium tetraoxide; and adding the dried vanadium tetraoxide with a flux and melting vanadium tetraoxide in a melting furnace to prepare a vanadium oxide flake, thereby recovering vanadium.

Brief Description of the Drawing

[11] FIG. 1 is a diagram showing a process of recovering a vanadium oxide flake according to the present invention.

Best Mode for Carrying Out the Invention

[12] Hereinafter, a detailed description will be given of a method of recovering a vanadium oxide flake according to the present invention, in conjunction with the appended FIG. 1.

[13] Referring to FIG. 1, there is shown a process for recovering a vanadium oxide flake according to the present invention. As shown in FIG. 1, diesel oil fly-ash or Orimulsion fly-ash is mixed with water or a weak sulfuric acid to dissolve valuable metals, such as vanadium and nickel, in an agitation leaching bath (ST 1), and a solid- liquid separation process is performed by use of a filter to separate a leached solution from insoluble residues (ST 2).

[14] As necessary, when pentavalent vanadium is present in an amount of 5% or more based on the total vanadium in the leached solution, it is reduced to a tertiary or tetravalent state in a reducing bath by use of Na SO , Fe (SO ) or SO gas as a

2 3 2 4 3 2 reducing agent (ST 3). Then, the leached solution is added with a neutralizing agent (NaOH or Na CO ) in a neutralizing bath to adjust pH thereof to 5.0-6.0. Thereby,

2 3 vanadium is precipitated as vanadium tetraoxide (ST 4). By means of another filter, vanadium tetraoxide (V O ) in the powder cake state is separated from the leached

2 4 solution and recovered (ST 5). In such a case, most nickel and magnesium remain in the above solution. [15] Powders of vanadium tetraoxide are dried in a dryer at 105-110 ° C to completely remove water (ST 6), and added with a flux and then melted in a melting furnace at 600-1000 ° C (ST 7). Consequently, vanadium pentoxide (V O ) is recovered in the

2 5 flake state. [16] The flux is selected from the group consisting of potassium nitrate, sodium carbonate or mixtures thereof. [17] As such, parts of the recovered vanadium flake are present in the form of vanadium tetraoxide, which functions to decrease the amount of the reducing agent to be used upon preparation of ferrovanadium.

[18] Meanwhile, since a large amount of nickel is present in the solution remaining after precipitation and separation of vanadium, together with magnesium in case of Orimulsion, it may be separated from the solution and recovered through a suitable post-treatment process, such as separation-precipitation process or solvent-extraction process.

[19] A better understanding of the present invention may be obtained through the following example which is set forth to illustrate a method of recovering vanadium pentoxide from diesel oil fly-ash and Orimulsion fly-ash, but is not to be construed as the limit of the present invention.

Example 1

[20] Recovering Vanadium Oxide Flake From Diesel Oil Fly-Ash

3

[21] 300 kg of diesel oil fly-ash was added to 1 m of process water and sufficiently agitated in an agitation leaching bath for 1 hour, and the resulting solution had pH 1.5-1.8. The above solution was further added with sulfuric acid and agitated, to obtain pH 1-1.5, after which a solid-liquid separation process was performed by use of a drum filter to separate the leached solution from insoluble resides. A concentration of vanadium in the leached solution was 16.7 g/1, corresponding to a leach yield of about 88 wt%.

[22] At this time, concentration of pentavalent vanadium in the leached solution was 4.8 g/1, which constituted 28.7 wt% of the total weight of vanadium. Therefore, Na SO as

2 3 a reducing agent was added in the amount of 20 wt% relative to the total weight of vanadium to reduce pentavalent vanadium to tetravalent vanadium. As a result, pentavalent vanadium concentration was decreased to 0.4 g/1.

[23] Thereafter, the tetravalent vanadium-containing leached solution was added with

20 wt% of caustic soda to adjust pH thereof to 5.2, and concentrated in a concentrating bath for 30 min or longer, to precipitate vanadium to the cake state, which was then recovered by use of a filter press.

[24] As such, vanadium in the leached solution was recovered at a yield of 99.9 wt%, and parts of iron and nickel were precipitated and recovered together. The recovered vanadium cake was sufficiently dried upon performing a drying process, and then mixed with KNO at a suitable mixing ratio. Into a melting furnace of 900-1000 ° C,

3 the mixed vanadium flake was fed together with air, to obtain a vanadium oxide flake containing 60 wt% of vanadium (pentavalent vanadium 79%, tetravalent vanadium 21%).

[25] The contents and the recovery yields of the metals according to each process are shown in Table 1, below.

[26] TABLE 1 [27]

Example 2

[28] Recovering Vanadium Oxide Flake From Orimulsion Fly-Ash

3 [29] 300 kg of Orimulsion fly-ash was added to 1 m of process water and sufficiently agitated for 2 hours by use of an agitating machine, whereby 85% of vanadium was leached. As such, a concentration of vanadium was 41.1 g/1, wherein pentavalent vanadium had a concentration of 1.9 g/1, corresponding to only 4.6% of the total vanadium. Thus, a reducing agent for reducing the pentavalent state of vanadium to the tetravalent state was not additionally required.

[30] As shown in the following Table 2, nickel and magnesium were mostly dissolved. As such, pH of the leached solution was 2.6. The leached solution was subjected to solid-liquid separation by use of a drum filter. Then, the leached solution separated from insoluble residues was added with caustic soda to adjust pH thereof to 5.2-5.5 and concentrated for 30 min or more in a concentrating bath, whereby tetravalent vanadium in the leached solution was precipitated in the cake state and recovered by use of the filter press. In such a case, all vanadium in the leached solution was recovered, along with about 23% of nickel and 13% of calcium.

[31] The solution remaining after the vanadium tetraoxide cake was recovered was adjusted to pH 8.9 and concentrated for 30 min in the concentrating bath, after which a nickel hydroxide precipitate was recovered in the cake state. Thereafter, the remaining liquid was transferred to a wastewater disposal process.

[32] The recovered vanadium cake was sufficiently dried upon performing a drying process, and then mixed with Na CO and KNO as a flux at a suitable mixing ratio.

2 3 3

The mixed vanadium cake was fed together with air into a melting furnace of 900-1000 ° C, to obtain a vanadium oxide flake containing 57 wt% of vanadium (pentavalent vanadium 82%, tetravalent vanadium 18%). The contents and the recovery yields of the metals according to each process are shown in Table 2, below.

[33] TABLE 2 [34]

Industrial Applicability

[35] As described above, the present invention provides a method of recovering vanadium pentoxide from diesel oil fly-ash or Orimulsion fly-ash. In the method of the present invention, since the wet oxidation process using an oxidizing agent or using steam and air is not used, large quantities of energy are not required, therefore resulting in remarkably lowered preparation cost of ferrovanadium. As well, problems of hazardous work environment and reactor corrosion due to chlorine gas or ammonia gas generated by the oxidizing agent and the ammonia compound can be overcome.

[36] In addition, a considerable amount of tetravalent vanadium is present in a finally recovered vanadium pentoxide flake, and thus the amount of aluminum metal to be used as a reducing agent can be decreased upon preparation of ferrovanadium. Further, the inventive method is advantageous in terms of energy-saving effect, owing to not requiring a heating process of the leached solution.

[37] Although the preferred embodiments of the recovering method of vanadium pentoxide of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

Claims

[1] 1. A method of recovering a vanadium oxide flake from diesel oil fly-ash or

Orimulsion fly-ash, comprising the steps of: leaching a mixture of diesel oil fly-ash or Orimulsion fly-ash and water in an agitation leaching bath to dissolve valuable metals including vanadium and nickel, followed by subjecting the leached mixture to solid-liquid separation, thereby separating a leached solution from insoluble residues; adding the leached solution with a neutralizing agent to adjust pH to 5-6 at room temperature under atmospheric pressure to precipitate, separate and recover vanadium tetraoxide from the leached solution, thereby preparing vanadium tetraoxide; drying the prepared vanadium tetraoxide at high temperatures to remove water contained in vanadium tetraoxide; and adding the dried vanadium tetraoxide with a flux and melting vanadium tetraoxide in a melting furnace to prepare a vanadium oxide flake, thereby recovering vanadium.

[2] 2. The method of recovering a vanadium oxide flake from diesel oil fly-ash or

Orimulsion fly-ash as defined in claim 1, wherein a weak sulfuric acid is selectively used together with water in the leaching step.

[3] 3. The method of recovering a vanadium oxide flake from diesel oil fly-ash or

Orimulsion fly-ash as defined in claim 1, wherein a reducing agent is used to reduce pentavalent vanadium to tetravalent vanadium when pentavalent vanadium is present in an amount of 5 wt% or more based on the total weight of vanadium in the leached solution, in the leaching step.

[4] 4. The method of recovering a vanadium oxide flake from diesel oil fly-ash or

Orimulsion fly-ash as defined in claim 1, wherein the drying step is performed at 105-110 ° C

[5] 5. The method of recovering a vanadium oxide flake from diesel oil fly-ash or

Orimulsion fly-ash as defined in claim 1, wherein the flux is selected from the group consisting of potassium nitrate, sodium carbonate or mixtures thereof.