JP7589632B2 - Reaction vessel - Google Patents

Description

The present invention relates to a reaction vessel used, for example, in acid leaching treatment under high temperature and pressure.

In the wet smelting method of nickel oxide ore by the High Pressure Acid Leaching (hereinafter referred to as "HPAL") process, low-grade nickel ore is slurried, and sulfuric acid is added to the ore slurry under high temperature and pressure to leach valuable metals such as nickel and cobalt (leaching process). Since the obtained leachate contains impurities such as iron, the pH of the leachate is adjusted in a neutralization process to separate the impurity components into solid and liquid. Then, nickel and cobalt in the leachate are reacted with a sulfurizing agent such as _H2S gas to recover them as sulfides (sulfurization process). In addition, the liquid after recovering the valuable metals is neutralized until the pH reaches a level at which impurities can be removed, and is sent to a tailings dam (final neutralization process).

In the high-pressure sulfuric acid leaching reaction, which is the main reaction in the leaching process of the HPAL process, an autoclave is used to react the ore slurry with sulfuric acid under high temperature and pressure to produce a leachate that has leached nickel and cobalt.

The inner wall surface (inner wall) of the autoclave used in the leaching reaction is generally made of a material containing Ti (titanium). As described above, the leaching reaction using sulfuric acid occurs under high temperature and pressure inside the autoclave, so it needs to be made of a material that is corrosion-resistant. In particular, by making the inner wall out of Ti, corrosion resistance can be increased (for example, see Patent Document 1).

In addition, in an autoclave, a stirrer and baffle plates are installed in each chamber (each compartment) to promote reactions inside the device, allowing the solution to be stirred and mixed efficiently within the device.

Inside the autoclave, the leaching reaction is promoted by the stirring effect of the stirring device described above, but the resulting leachate contains impurities such as iron, and as it moves with the flow, it can wear away the inner surface of the autoclave. Furthermore, autoclaves are often made of clad steel containing Ti, and if wear damage occurs in the Ti parts, the slurry liquid produced by the leaching reaction can reach the steel parts, causing rapid corrosion and potentially causing serious damage to the autoclave body. Furthermore, this type of wear requires maintenance such as repairs and replacement of the inner walls, making it difficult to carry out efficient processing.

JP 2018-53321 A

Uenaka, et al., "Characteristics and Application Examples of Corrosion-Resistant Titanium Alloys," Nippon Steel & Sumitomo Metal Technical Report, 2013, No. 396, pp. 35-42

The present invention has been proposed in light of these circumstances, and aims to provide a technology that can effectively suppress corrosion, for example, in reaction vessels used for acid leaching treatment under high temperature and pressure.

The inventors of the present invention have conducted extensive research to solve the above-mentioned problems. As a result, they have discovered that corrosion can be effectively suppressed by attaching an anti-wear plate to the inner wall below the agitator in the reaction vessel. They have also discovered that so-called crevice corrosion can be effectively suppressed by specifying the material of the anti-wear plate in relation to the material (titanium material) that constitutes the inner wall of the autoclave.

(1) The first aspect of the present invention is a reaction vessel into which a slurry of a metal raw material is charged and into which a leaching process is carried out by adding sulfuric acid under high temperature and pressure to leach the metal contained in the metal raw material, the reaction vessel having at least its inner wall surface made of titanium material, a stirring device having a stirring shaft and a stirring blade, and a wear prevention plate attached to the inner wall below the stirring device.

(2) The second aspect of the present invention is a reaction vessel according to the first aspect, in which the wear protection plate is made of a titanium alloy.

(3) The third invention of the present invention is a reaction vessel according to the second invention, in which the titanium material constituting the inner wall surface contains palladium (Pd) in a predetermined ratio, and the titanium alloy constituting the wear protection plate does not contain Pd but contains nickel (Ni) in a predetermined ratio.

(4) The fourth aspect of the present invention is a reaction vessel according to any one of the first to third aspects, in which the wear protection plate has a thickness of 5 mm or more and 20 mm or less.

(5) The fifth aspect of the present invention is any one of the first to fourth aspects, in which the metal raw material is nickel oxide ore, and the reaction vessel is an autoclave used in a hydrometallurgical process for nickel oxide ore, in which sulfuric acid is added to a slurry of the nickel oxide ore to perform a leaching process under high temperature and high pressure.

The present invention can effectively suppress corrosion in reaction vessels in which acid leaching is performed under high temperature and pressure, for example.

It can also effectively suppress crevice corrosion.

FIG. 1 is a diagram showing an example of the configuration of an autoclave apparatus used for leaching treatment in a hydrometallurgical process for nickel oxide ore. FIG. 2 is a cross-sectional view perpendicular to the longitudinal direction of the autoclave apparatus, illustrating the manner in which anti-wear plates are installed.

A specific embodiment of the present invention (hereinafter, referred to as "the present embodiment") will be described in detail below. Note that the present invention is not limited to the following embodiment, and appropriate modifications can be made without departing from the gist of the present invention.

≪1. About the reaction vessel (autoclave device)≫
The reaction vessel according to the present embodiment is a reaction vessel into which a slurry of a metal raw material is charged and into which a leaching process is carried out to leach the metal contained in the metal raw material by adding sulfuric acid under high temperature and high pressure. The reaction vessel is equipped with a stirring device having a stirring shaft and a stirring blade from the viewpoint of increasing the efficiency of the reaction inside the reaction vessel.

Specific examples of such reaction vessels include autoclaves, which are reaction vessels used in a leaching process in which nickel and cobalt are leached from a nickel oxide ore slurry (ore slurry) using sulfuric acid under high temperature and high pressure in a hydrometallurgical process for nickel oxide ore based on the HPAL method.

In the hydrometallurgical process for nickel oxide ore, the ore slurry is loaded into an autoclave and leaching is carried out while stirring the ore slurry at a temperature of about 220°C to 280°C and a pressure of about 3 MPaG to 6 MPaG by adding an excess amount of sulfuric acid. The nickel oxide ore slurry to be leached contains about 10% to 50% by weight of iron. Therefore, the leaching process of the ore slurry in the autoclave causes wear on the inner wall of the autoclave as the reaction proceeds.

The reaction vessel according to this embodiment is characterized in that at least its inner wall surface is made of titanium material, and a wear protection plate is attached to the inner wall below the stirring device having a stirring shaft and stirring blades.

With such a reaction vessel, even when performing leaching treatment with an acid such as sulfuric acid under high temperature and pressure, corrosion can be effectively suppressed, especially below the stirring device. This can extend the life of the equipment and improve operating efficiency.

≪2. Autoclave equipment used in hydrometallurgical processes≫
1 is a diagram showing an example of the configuration of an autoclave apparatus used in a leaching treatment in a hydrometallurgical process for nickel oxide ore. Hereinafter, a more detailed explanation will be given by taking an autoclave apparatus as an example of a reaction vessel.

The autoclave device 1 contains a heated and pressurized raw material slurry (e.g., a slurry of nickel oxide ore), and by adding an acid such as sulfuric acid and stirring it, valuable metals contained in the solid matter in the slurry are leached under high temperature and pressure.

The autoclave apparatus 1 includes at least a plurality of compartments 10 and an agitator 20 provided in each compartment 10 for agitating the slurry. The compartments 10 are divided into a plurality of compartments by partitions 30 provided in the autoclave apparatus 1. In the example of the autoclave apparatus 1 shown in FIG. 1, five compartments 10 (10A, 10B, 10C, 10D, 10E) are provided, which are divided by four partitions 30 (30A, 30B, 30C, 30D). In each of the compartments 10A to 10E, an agitator 20 (20A, 20B, 20C, 20D, 20E) is provided. The number of compartments in the autoclave apparatus can be set appropriately depending on the raw materials, leaching conditions, etc.

In addition, in the autoclave apparatus 1, anti-wear plates 40 (40A, 40B, 40C, 40D, 40E) are attached to the inner wall below the agitator 20 in each compartment 10.

The interior wall surface (inner wall) of the autoclave apparatus 1 is made of titanium material. This increases the corrosion resistance of the apparatus when leaching with sulfuric acid is performed under high temperature and high pressure. The titanium material may be pure titanium with impurities such as iron of 0.35 mass% or less, or an alloy of titanium and other metals. Of these, titanium alloys containing a specified proportion of palladium (Pd), a platinum group element, are preferable. In particular, it is preferable to use ASTM SB-265 Gr17 (JIS standard: TP-240PdH), which is an ASTM standard that has high corrosion resistance and is economical.

ASTM SB-265 Gr17 selectively contains the following composition: palladium (Pd): 0.04-0.08 mass%, carbon (C): ≦0.08 mass%, iron (Fe): ≦0.20 mass%, hydrogen (H): ≦0.015 mass%, nitrogen (N): ≦0.03 mass%, oxygen (O): ≦0.18 mass%, with the remainder being titanium (Ti) and unavoidable impurities.

(Partitioned Room)
The compartment 10 is a space that serves as a reaction field in which treatment such as leaching treatment is performed on the raw material slurry in the autoclave apparatus 1. As described above, the autoclave apparatus 1 is configured with five compartments 10A to 10E that are divided into five by partition walls 30.

The compartments 10 are composed of the first compartment 10A, the second compartment 10B, etc., from the upstream side (left side of FIG. 1), and the fifth compartment 10E at the most downstream side (right side of FIG. 1). In the autoclave apparatus 1, raw material slurry is charged into the first compartment 10A at the most upstream side, and a solution such as sulfuric acid is supplied to the slurry through a pipe hanging down from the top of the first compartment 10A. In the first compartment 10A, valuable metals contained in the solid matter in the slurry are leached into the solution by stirring with the stirrer 20A described below.

In the first compartment 10A, the slurry is stirred to carry out the leaching process, and part of the slurry overflows the top of the partition wall 30A that separates the first compartment 10A from the second compartment 10B, and is transferred to the second compartment 10B. In the second compartment 10B, the leaching process proceeds sequentially by stirring with the agitator 20B, similar to the process in the first compartment 10A. In addition, in the second compartment 10B, a pipe can be hung from the top to supply a solution such as sulfuric acid or a slurry to be used for leaching.

The slurry is then transferred primarily by overflow to the third compartment 10C and the fourth compartment 10D, and the leaching process progresses in each compartment 10. The slurry is then subjected to the leaching process in the fifth compartment 10E, the most downstream compartment, in the same manner, and a slurry (leached slurry) containing the leachate obtained by leaching valuable metals is discharged through a leachate discharge pipe (not shown) provided in the fifth compartment 10E.

(Mixing device)
As described above, the compartment 10 is provided with the stirring device 20 for stirring the slurry therein. The stirring device 20 is installed in each of the first compartment 10A to the fifth compartment 10E, and stirs the slurry that is charged and transported inside each compartment 10.

As the agitation device 20, for example, one equipped with an agitation shaft 21 and multiple agitation blades 22, as shown in FIG. 1, can be used. The agitation device 20 can be suspended, for example, from the upper ceiling of each compartment 10, and installed so that the agitation shaft is located in the center of each compartment 10 when the autoclave apparatus 1 is viewed from above.

The agitator 20 rotates the agitator shaft 21 at a predetermined speed, for example, clockwise, and agitates the slurry with the agitator blades 22. Agitation by the agitator 20 in this manner generates a liquid flow in the slurry in the compartment 10 in a predetermined direction.

(Wear protection plate)
The wear protection plate 40 is a plate material for preventing wear on the bottom inner wall of the autoclave apparatus 1, and is provided for the purpose of protecting the apparatus. In the autoclave apparatus 1, the wear protection plate 40 is provided on the inner wall below the stirring device 20.

Figure 2 is a cross-sectional view perpendicular to the longitudinal direction (the same direction from the first compartment to the fifth compartment) of the autoclave apparatus 1, and is a view for explaining the installation mode of the wear protection plate 40. As described above, in the autoclave apparatus 1, the stirring device 20 stirs and mixes the slurry to promote the reaction in each compartment 10, and iron and other substances in the slurry (including the leachate) also move in accordance with the flow generated by the stirring device 20. In particular, in the part directly below the stirring device 20, solids move along the bottom inner wall of the autoclave apparatus 1, causing wear of the bottom inner wall. In addition, the flow pattern of the stirring device 20 causes wear of the same part, creating a flow pattern in which particles move to the bottom surface, which may cause local wear and further accelerate wear.

Therefore, as shown in Figures 1 and 2, in the autoclave apparatus 1, a wear protection plate 40 is provided on the lower inner wall of the agitator 20. In this way, an apparatus provided with a wear protection plate 40 can effectively prevent wear on the inner wall, particularly below the agitator 20. This can extend the life of the autoclave apparatus 1 and improve operating efficiency.

The thickness of the wear protection plate 40 is not particularly limited, but is preferably 5 mm or more and 20 mm or less. If the thickness is less than 5 mm, the wear protection plate 40 itself may wear out in a short period of time, increasing the number of replacements and lengthening downtimes associated with replacement work, reducing operational efficiency. In addition, since the autoclave apparatus 1 generally has a circular cross section perpendicular to the longitudinal axis (see also FIG. 2), if the thickness of the wear protection plate 40 exceeds 20 mm, it becomes difficult to mold it to match the internal curvature of the autoclave apparatus 1.

The materials used to make the wear protection plate 40 will be described in detail later.

(Other configurations)
A raw material slurry charging pipe (not shown) for charging the raw material slurry is attached to the first compartment 10A of the compartments 10, and a slurry containing solids is charged through the raw material slurry charging pipe.

For example, when the autoclave apparatus 1 is used for leaching a raw material slurry containing at least a mixed sulfide of nickel and cobalt, the reactions during the leaching process of nickel sulfide and cobalt sulfide in each compartment 10 are represented by the following formulas (1) and (2).
NiS+ _2O2 → _NiSO4 ...(i)
CoS+ _2O2 → _CoSO4 ...(ii)

As shown in the above reaction formula, in leaching treatment under high temperature and pressure, it is common to provide various supply pipes, etc., in the compartment 10, for supplying gases (such as _O2 gas) required for the reaction into the slurry, or for supplying steam to maintain the high temperature and pressure state. In addition, in the leaching treatment of mixed sulfides of nickel and cobalt, an acid such as sulfuric acid is supplied to produce a sulfuric acid acidic leachate, so a pipe for supplying sulfuric acid is naturally provided. Water or slurry may also be supplied for the purpose of concentration adjustment, etc.

≪3. Materials for wear prevention plates (countermeasures against crevice corrosion)≫
As described above, the autoclave apparatus 1 is provided with the anti-wear plate 40 joined to the inner wall below the stirring device 20. By providing the anti-wear plate 40 in this manner, it is possible to effectively prevent the progression of wear caused by solid matter in the slurry that flows due to stirring.

However, a "gap" may occur between the inner wall of the autoclave apparatus 1 and the wear protection plate 40. Specifically, as shown in FIG. 2, the wear protection plate 40 is attached by welding so that it overlaps the inner wall of the autoclave apparatus 1 directly below the agitator 20, but the wear protection plate 40 itself wears over time as the apparatus is operated, and the welded portion also wears, causing cracks. When a crack occurs, slurry and the resulting leachate penetrate through the crack into the gap between the inner wall of the autoclave apparatus 1 and the wear protection plate 40, causing so-called "crevice corrosion" to occur in part of the space.

One possible method of preventing crevice corrosion is to increase the thickness of the equipment's inner walls to prevent the formation of gaps that cause crevice corrosion, but this does not prevent wear itself, and so the walls will eventually thin out, and there is also the possibility of problems with workability during manufacturing. It is also possible to prevent crevice corrosion by improving the sealing properties of the wear prevention plates to prevent liquid from entering, but this requires overlay repairs of the weld lines, which could extend the maintenance period and reduce operating efficiency.

The inventor therefore investigated a structure for the material of the wear protection plate 40 that would selectively cause corrosion on the wear protection plate 40 side, suppressing corrosion on the inner wall of the autoclave device 1, even if leaching slurry or leaching liquid penetrates into the gap between the inner wall of the autoclave device 1 and the wear protection plate 40, causing gap corrosion.

As described above, the inner wall of the autoclave device 1 is preferably made of a titanium material (titanium alloy) containing a predetermined ratio of Pd. If an abrasion protection plate is made of a titanium material of the same grade and joined to the autoclave device 1 made of this titanium material, crevice corrosion occurs on both the inner wall of the autoclave device 1 and the abrasion protection plate. In contrast, by joining an abrasion protection plate made of a material (titanium alloy) containing titanium of a grade with lower corrosion resistance than the titanium material that makes up the inner wall of the autoclave device 1, even if the leaching slurry or leachate enters the gap and causes crevice corrosion, crevice corrosion will selectively occur on the side of the abrasion protection plate 40, which has lower corrosion resistance.

That is, in the autoclave apparatus 1, a wear protection plate 40 made of a titanium alloy of a grade with lower corrosion resistance than the titanium material constituting the inner wall, specifically, a titanium alloy containing no Pd and a predetermined proportion of nickel (Ni), is joined to the inner wall of the autoclave apparatus 1. As a result, even if crevice corrosion occurs, it will occur selectively on the wear protection plate 40, and corrosion of the inner wall of the autoclave apparatus 1 can be suppressed. The reason for this effect is thought to be that the titanium alloy containing no Pd and a predetermined proportion of Ni is an electrochemically less noble material compared to the titanium alloy constituting the inner wall of the autoclave apparatus 1, and therefore exerts a so-called sacrificial corrosion protection effect.

For example, ASTM SB-265 Gr12, which is an ASTM standard, can be used as a titanium alloy that does not contain Pd but contains a certain amount of Ni. By forming the wear protection plate 40 from such a titanium alloy, when leaching treatment is performed by adding sulfuric acid under high temperature and high pressure, it has a certain degree of corrosion resistance in a corrosive environment, and because it has excellent mechanical properties, it exhibits excellent wear resistance. In addition, because it does not contain Pd, it is also economical.

The composition of ASTM SB-265 Gr12 selectively contains Pd: (-), C: ≦0.08 mass%, Fe: ≦0.30 mass%, H: ≦0.15 mass%, N: ≦0.03 mass%, O: ≦0.25 mass%, Ni: 0.6 to 0.9 mass%, and the remainder is Ti and unavoidable impurities.

Reference Signs List 1 Autoclave device 10, 10A to 10E Compartment chamber 20, 20A to 20E Stirring device 21 Stirring shaft 22 Stirring blade 30, 30A to 30D Partition wall 40, 40A to 40E Wear prevention plate

Claims (4)

A reaction vessel into which a slurry of a metal raw material is charged and into which a leaching process is carried out by adding sulfuric acid under high temperature and high pressure to leach metals contained in the metal raw material,
At least the inner wall surface is made of titanium material,
The apparatus is provided with a stirring device having a stirring shaft and a stirring blade,
A wear prevention plate is attached to the inner wall of the lower part of the stirring device,
The wear protection plate is made of a titanium alloy.
Reaction vessel. The titanium material constituting the inner wall surface contains palladium (Pd) at a predetermined ratio,
The titanium alloy constituting the wear protection plate does not contain Pd and contains nickel (Ni) in a predetermined ratio.
The reaction vessel of claim 1 . The wear protection plate has a thickness of 5 mm or more and 20 mm or less.
The reaction vessel according to claim 1 or 2 . the metal source is nickel oxide ore;
The reaction vessel is an autoclave used in a hydrometallurgical process for nickel oxide ore, in which sulfuric acid is added to a slurry of the nickel oxide ore to perform a leaching treatment under high temperature and high pressure.
The reaction vessel according to any one of claims 1 to 3 .

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