Hydrogen sulfide gas evacuation tank

Abstract

To provide an evacuation tank having a structure capable of reducing a hole risk due to erosion generated in piping of a hydrogen sulfide gas flow.SOLUTION: There is provided a hydrogen sulfide gas evacuation tank that is installed in a sulfurization step in a hydrometallurgical smelting process for nickel oxide ore, the evacuation tank being an apparatus for performing gas-liquid separation of a sulfide slurry produced in the sulfurization step by a degassing treatment, obtaining gas-phase hydrogen sulfide gas and a slurry of solid-liquid components, and recovering the hydrogen sulfide gas, the hydrogen sulfide gas evacuation tank being characterized in that a conical baffle with an apex located at an upper portion and a doughnut-shaped baffle are located above a sulfide slurry inlet portion in the evacuation tank, and at least one combination of the conical baffle at an upper portion and at least one doughnut-shaped baffle at a lower portion is located.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] This invention relates to a manufacturing apparatus in the field of nickel hydrometallurgy, and more particularly to a structure of a degassing tank that degasses dissolved hydrogen sulfide contained in nickel sulfide slurry after a sulfurization reaction in a hydrometallurgy process based on high-temperature pressurized sulfuric acid leaching for recovering nickel from nickel oxide ore. [Background technology]

[0002] In the hydrometallurgy of nickel oxide ore, a high-pressure acid leaching method, also called HPAL (High Pressure Acid Leaching) method, in which leaching treatment is performed with sulfuric acid under high temperature and pressure conditions is known. Unlike the pyrometallurgy method in which the raw material nickel oxide ore is subjected to reduction and drying treatments, the high-pressure acid leaching method is a method that is advantageous in terms of energy and cost because it performs wet treatments throughout almost the entire process. Another advantage is that a mixed sulfide containing nickel and cobalt (also called nickel-cobalt mixed sulfide) in which the nickel content has been increased to about 50 to 60 mass % can be produced from a relatively low-quality nickel oxide ore raw material.

[0003] The above-mentioned high-pressure acid leaching method generally comprises a leaching step in which sulfuric acid is added to an ore slurry prepared by adding water to a raw material nickel oxide ore, and leaching treatment is carried out under high temperature and high pressure; a solid-liquid separation step in which a leachate containing nickel and cobalt is obtained by separating and removing a leach residue from the leachate slurry produced in the leaching step; a neutralization step in which a neutralizing agent is added to the leachate to separate and remove impurities contained in the leachate as a neutralized precipitate, thereby obtaining a neutralized final solution; and a nickel recovery step in which a sulfiding agent is added to the neutralized final solution to recover nickel and cobalt as a mixed sulfide thereof.

[0004] In the sulfurization step of the nickel recovery process, hydrogen sulfide gas is blown in as a sulfurizing agent to obtain a nickel-cobalt mixed sulfide, and the slurry produced from the sulfurization step contains dissolved hydrogen sulfide gas that was not used in the reaction. Since hydrogen sulfide gas is generally a toxic substance, in order to facilitate the handling of the slurry, Patent Documents 1 and 2 disclose a facility for degassing and recovering hydrogen sulfide contained in the slurry at the end of the sulfurization process. A gas-liquid separator as shown in Patent Document 3 is generally known for such facilities, and while it can separate gases effectively because it uses a cyclone, particles accelerated by the cyclone cause wear on the gas-liquid separator. The slurry produced from the sulfurization process contains a large amount of nickel-cobalt mixed sulfide as solid particles, which makes it particularly susceptible to wear, and it is therefore appropriate to make efforts such as making maximum use of baffles without using a cyclone.

[0005] However, in a typical vacuum degassing tank (see Figure 1), the operating conditions are kept below atmospheric pressure, and the hydrogen sulfide dissolved in the sulfide slurry is transferred to the gas phase as described above, resulting in gas-liquid separation. However, the degassed hydrogen sulfide gas may be accompanied by solid and liquid components of the sulfide slurry. This entrainment causes a very small amount of sulfide slurry to be mixed into the piping through which only hydrogen sulfide gas should flow, increasing the risk of holes being created due to erosion of the piping caused by the collision of slurry droplets. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2020-132945 A [Patent Document 2] Patent Publication No. 2022-098258 [Patent Document 3] JP 2008-036503 A Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention aims to provide a degassing tank having a structure capable of reducing the risk of holes being generated due to erosion in the piping for the hydrogen sulfide gas flow. [Means for solving the problem]

[0008] Therefore, in order to solve the above problems, the present inventors believed that by providing a cap-shaped baffle and a doughnut-shaped baffle above the slurry inlet into the degassing tank, these baffles would be able to trap the liquid and solid components accompanying the hydrogen sulfide gas degassed from the slurry, thereby preventing the liquid and solid components from flowing into the hydrogen sulfide gas flow. As a result of intensive research and development, they discovered a basic configuration of a reduced pressure degassing tank as shown in Figure 1, which is composed of a reduced pressure degassing tank 100 and a vacuum pump (not shown).

[0009] In FIG. 1, reference numeral 100 denotes a vacuum degassing tank on which the present invention is based, reference numeral 100a denotes a tank body, reference numeral 101 denotes a sulfide slurry inlet insertion tube, reference numeral 101a denotes a sulfide slurry inlet, and reference numeral 112 denotes a conical baffle (also called a cap-shaped baffle) with its apex located at the top. The sulfide slurry discharged from the slurry inlet 101a is received on the baffle surface and subjected to gas-liquid separation. The gas component hydrogen sulfide gas is removed to the outside from a gas outlet 114 located at the top of the tank body 100a, and the liquid (slurry) component flows down the baffle surface and is removed to the outside from a slurry outlet 115 located at the bottom of the tank body 100a.

[0010] Reference numeral 113 denotes a doughnut-shaped baffle, which is an inverted truncated cone baffle consisting only of side surfaces with an inclination downward to a vertical line, and is arranged on the inner surface of the tank body 100a. The liquid component separated by the upper umbrella-shaped baffle is received on the surface of the doughnut-shaped baffle and subjected to gas-liquid separation again. Hydrogen sulfide gas from which the liquid component has been further removed is removed to the outside through a discharge port 114, and the residual liquid component is allowed to flow downward and removed to the outside through a sulfide slurry discharge port 115. Solid and liquid components are removed from the hydrogen sulfide gas removed to the outside as described above, and hydrogen sulfide gas containing as little solid and liquid components as possible can be removed to the outside. Furthermore, as a result of continuing research and development aimed at removing solid and liquid components from the hydrogen sulfide gas, the present invention as shown in FIG. 2 was completed.

[0011] A first aspect of the present invention is a hydrogen sulfide gas vacuum degassing tank that is installed in a sulfurization step in a hydrometallurgical smelting process for nickel oxide ore, the vacuum degassing tank being an apparatus that separates the sulfide slurry generated in the sulfurization step into gas and liquid by degassing treatment, obtains gas-phase hydrogen sulfide gas and a slurry of solid-liquid components, and recovers the hydrogen sulfide gas, characterized in that a conical baffle with an apex located at an upper part and a doughnut-shaped baffle are located above the sulfide slurry inlet part in the vacuum degassing tank, and at least one combination of the conical baffle located at an upper part and at least one doughnut-shaped baffle located at a lower part are located. Effect of the Invention

[0012] The present invention can reduce the risk of piping holes due to erosion that occurs in the piping for recovered hydrogen sulfide gas from the degassing tank, making it possible to extend the equipment maintenance interval and equipment life, and providing an industrially significant effect of increasing production efficiency. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is a schematic diagram of a basic vacuum degassing tank according to the present invention. [Diagram 2] FIG. 1 is a schematic explanatory diagram of a reduced pressure degassing tank according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] The vacuum degassing tank according to the present invention is generally cylindrical in shape, and the sulfide slurry is introduced into the tank from the side surface. The slurry is discharged from the inlet into the tank through the slurry inlet insertion pipe. Therefore, the slurry flows from the center of the tank to the bottom. The tank itself is depressurized from the top by a vacuum pump and is kept at a pressure below atmospheric pressure, so when the sulfide slurry flows into the tank, the dissolved hydrogen sulfide in the sulfide slurry moves to the gas phase and is recovered from the top of the tank as hydrogen sulfide gas. The remaining sulfide slurry is recovered from the bottom of the tank.

[0015] The vacuum degassing tank according to the present invention is provided with at least one combination of a conical baffle (also called a cap-shaped baffle) with an apex at the top and a doughnut-shaped baffle below it above the slurry inflow section into the degassing tank, so that liquids and solids entrained in the hydrogen sulfide gas degassed from the sulfide slurry are trapped on the baffle surface (in this case, the lower surface side of the baffle), preventing the liquids and solids from flowing into the hydrogen sulfide gas flow. This reduces the risk of holes being created by erosion in the piping for the hydrogen sulfide gas flow.

[0016] A detailed explanation will be given below with reference to FIG. FIG. 2 is an explanatory diagram showing one embodiment of a vacuum degassing tank according to the present invention, in which reference numeral 10 denotes a vacuum degassing tank according to the present invention, reference numeral 10a denotes a tank body, reference numeral 11 denotes a sulfide slurry inlet insertion tube, reference numeral 11a denotes a sulfide slurry inlet, and reference numeral 12 denotes a conical baffle (also called a cap-shaped baffle) with its apex located at the top. The sulfide slurry discharged from the inlet 11a is received on the baffle surface (in this case, the upper surface of the baffle) and subjected to gas-liquid separation. The gas component hydrogen sulfide gas is removed to the outside from a gas outlet 14 located at the top of the tank body 10a, and the liquid (slurry) component flows down the baffle surface (upper surface) and is removed to the outside from a slurry outlet 15 located at the bottom of the tank body 10a. Reference numeral 13 denotes a doughnut-shaped baffle, which is an inverted truncated cone-shaped baffle consisting only of side surfaces that is sloped vertically downward from the outer periphery inward. The baffle is arranged on the inner surface of the tank body 10a. The liquid component separated by the upper cap-shaped baffle 12 is received on the doughnut-shaped baffle surface (upper surface) and subjected to gas-liquid separation again. The hydrogen sulfide gas from which the liquid component has been further removed is removed to the outside from an outlet 14 at the top of the tank, and the residual liquid component is allowed to flow downward and removed to the outside from a sulfide slurry outlet 15 at the bottom of the tank.

[0017] Furthermore, in an embodiment of the present invention, at least one combination of a conical baffle (also called a cap-shaped baffle) 1 with an apex at the top and a doughnut-shaped baffle 2 (an inverted truncated cone baffle consisting of only side surfaces with a vertical line downwardly inclined from the outer periphery to the inside) is provided above the inlet 11a, so that liquids and solids entrained in the hydrogen sulfide gas degassed from the sulfide slurry are trapped on the baffle surface (the lower surface of the baffle in this case) of the cap-shaped baffle 1, and the inflow of liquids and solids into the hydrogen sulfide gas flow can be prevented. A similar process is also performed on the baffle surface (lower surface) of the doughnut-shaped baffle 2. The hydrogen sulfide gas removed to the outside as described above has had its solid and liquid components removed, and can be removed to the outside as hydrogen sulfide gas containing only small amounts of solid and liquid components.

[0018] The "conical baffle (cone-shaped baffle) 1" and the "donut-shaped baffle (inverted truncated cone baffle with only the side surface) 2" located above this inlet 11a are desirably made of a corrosion-resistant material such as stainless steel, nickel, Inconel, Monel, Hastelloy, etc., from the standpoint of corrosion resistance to hydrogen sulfide gas and durability. Also, the gas-liquid separation surface may be a member coated with a material that is corrosion-resistant to sulfides and hydrogen sulfide gas. EXAMPLES

[0019] The degassing tank according to the present invention as described above was used in a reduced pressure degassing tank installed in the sulfurization step of a hydrometallurgical process based on high-temperature pressurized sulfuric acid leaching for recovering nickel from nickel oxide ore, and it was confirmed that by providing a cap-shaped baffle 1 above the sulfide slurry inlet 11a into the tank body and a doughnut-shaped baffle 2 below it, the amount of liquid and solids accompanying the hydrogen sulfide gas recovered from the degassing tank was reduced and holes in the piping for the recovered hydrogen sulfide gas were no longer generated. [Explanation of symbols]

[0020] 1. Cone-shaped baffle / Umbrella-shaped baffle (baffle arranged above the inlet 11a) 2 Donut-shaped baffle / Inverted cone-shaped baffle 10. Decompression and degassing tank according to the present invention 10a, 100a tank body 11, 101 Sulfide slurry inlet pipe 11a, 101a Sulfide slurry inlet 12, 112 Conical baffle / Umbrella baffle (baffle with a peak at the top) 13, 113 Donut-shaped baffle / Inverted cone-shaped baffle (a baffle consisting of only sides with a slope downwards on the vertical line) 14, 114 Gas exhaust port 15, 115 Slurry outlet 100 Conventional vacuum degassing tank

Claims

[Claim 1] A vacuum degassing tank installed in a sulfurization step in a hydrometallurgical process for nickel oxide ore, comprising: The reduced pressure degassing tank is an apparatus for separating the sulfide slurry produced in the sulfurization step into gas and liquid through a degassing treatment, obtaining gaseous hydrogen sulfide gas and a slurry of solid-liquid components, and recovering the hydrogen sulfide gas; below a sulfide slurry inlet portion in the reduced pressure degassing tank, at least one or more combinations of a conical baffle having an apex disposed at an upper portion and an inverted truncated cone-shaped baffle consisting only of a side surface provided with an inclination perpendicularly downward from the outer periphery to the inside are disposed, the combination comprising the conical baffle at an upper portion and at least one inverted truncated cone-shaped baffle consisting only of a side surface at a lower portion; a hydrogen sulfide gas vacuum degassing tank, characterized in that at least one or more combinations of a conical baffle with an apex located at an upper part and an inverted truncated cone-shaped baffle consisting only of side surfaces with an inclination perpendicularly downward from the outer periphery to the inside are disposed above a sulfide slurry inlet portion inside the vacuum degassing tank, the combination comprising the conical baffle at an upper part and at least one inverted truncated cone-shaped baffle consisting only of side surfaces at a lower part.

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