JPS6047335B2 - Method for removing mercury and selenium from sulfuric acid sludge - Google Patents

Description

Detailed Description of the Invention The present invention is a simple process that requires a large amount of heat from sulfuric acid sludge containing mercury and selenium, which is produced when producing sulfuric acid from sulfur dioxide gas generated in a nonferrous metal refining process. The present invention relates to a method for removing mercury and selenium from sulfuric acid sludge, which simultaneously separates and removes mercury and selenium with high efficiency.

When using the dioxide-sulfur gas in the gas generated in nonferrous metal smelting as a raw material for sulfuric acid production, dry gas purification is first performed, and then water or diluted gas is purified by flowing down and circulating in cooling towers and cleaning towers as wet gas purification. Sulfuric acid sludge is a slurry produced by cooling gas with sulfuric acid and collecting dust during gas purification using dust in the gas.

This sulfuric acid sludge is mainly composed of fine particles of lead sulfate, in which selenium and mercury selenides are scattered, or they are scattered in the form of growth of lead sulfate as a core. Conventional methods for removing mercury and selenium from the sulfuric acid sludge include the following methods.

In other words, lime is added to sulfuric acid sludge, thoroughly mixed, and then roasted to volatilize and remove mercury. At the same time, selenium is converted into a soluble salt and contained in the roasted volatilization residue, and this residue is leached with dilute sulfuric acid. There is a combined dry and wet volatile extraction method that removes selenium as a solution. However, this method has the following problems.

(1) In order to separate the entire amount of sulfuric acid sludge produced from the solution, it is necessary to perform a preliminary step of filtering the solution, drying and pulverizing the remaining sulfuric acid sludge, and then mixing it with lime.

(2) From the preliminary process, the sulfuric acid sludge is heated and roasted in a roasting furnace.The mercury is removed by volatilization, and then the selenium, which has been converted into a soluble salt by mixing with lime, is extracted and a selenium solution is created. Therefore, the entire treatment process including the preliminary process becomes complicated and the operations become complicated.

(3) A large amount of heat is required to dry and roast the entire amount of the sulfuric acid sludge.

(4) In order to handle a large amount of sulfuric acid sludge, the equipment becomes large-sized and requires a completely sealed equipment to volatilize harmful metals.

The present inventors have solved the problems of the conventional methods described above, and provided a method for separating and removing mercury and selenium in sulfuric acid sludge with a simple process and high yield without requiring a large amount of heat. As a result of repeated research, it was discovered that mercury can be simultaneously removed as selenide by treating the sulfuric acid sludge with a combination of attrition treatment and flotation, thereby achieving the present invention.

That is, the gist of the present invention is that a sulfuric acid sludge containing mercury and selenium is subjected to an attrition treatment in an acidic sulfuric acid solution, and then the attrition-treated sulfuric acid sludge is subjected to a flotation treatment.
A method for removing mercury and selenium. The present invention further provides that the mercury concentration in the flotation tailings of the flotation treatment is 0.0.
If it is higher than 4%, sulfurizing agents such as hydrogen sulfide, sodium sulfide, and sodium thiosulfate are added to the flotation tailings to perform sulfidation treatment, and then flotation treatment is performed again to remove mercury from the tailings. The concentration can be reduced to 0.02-0.03%.

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a process diagram showing one embodiment of the present invention.

As mentioned above, when the mercury concentration in the flotation tailings is as high as 0.04% or more, the sulfidation treatment and flotation treatment steps enclosed by chain lines are added to this step. As shown in Table 1, the sulfuric acid concentration in the attrition treatment of the sulfuric acid sludge shown in FIG.
When the molar ratio is smaller than 50 da 1e, the yield becomes better.

The reason why the attrition treatment is performed in a sulfuric acid solution is that when sulfuric acid sludge is produced, Hg falls off as Se, and this Hg(7)Se remains stable in the sulfuric acid solution. be.

Regarding the valve concentration in attrition treatment, attrition treatment uses strong stirring to cause sulfuric acid sludge particles to collide with each other, causing a polishing effect on the surfaces of each particle, and the higher the valve concentration, the less effective it is. However, in the case of fine particles such as sulfuric acid sludge, when the bulb concentration is increased to 50% or more, the viscosity becomes high and fluidity decreases even with mechanical stirring, resulting in a reduction in its abrasive action. Conversely, if the bulb concentration is too low, it will naturally reduce the degree of particle collisions with each other. Therefore, the valve concentration is preferably in the range of 20 to 50%, taking into consideration the batch method and circulation method of attrition treatment. The attrition process is started at room temperature, but due to frictional heat, the temperature rises to 60-70°C in the batch method, but in the circulation method, the temperature rise is not as great as in the batch method.

Furthermore, the particles containing Se in the sulfuric acid sludge are 5p or less, and when this sludge is heated to 80°C, the average diameter of the particles increases to 30-45p. It is said that it is possible to
Even in the above-mentioned sludge treatment of the present invention, it is thought that coagulation of sludge particles occurs as the temperature rises. Thus, the sulfuric acid sludge particles are rubbed against each other by the attrition treatment, and their surfaces are successively peeled off, constantly exposing new surfaces to the sulfuric acid solution. That is, selenium is hydrophobic, and the higher the sulfuric acid concentration, the greater its hydrophobicity. The attrition-treated sulfuric acid sludge is separated into floating ore and tailings by flotation according to a conventional method. At that time, if flotation is carried out in an acidic environment with a pH of 3 or less, as shown in the examples, Mercury and selenium are transferred to the concentrate and removed simultaneously in high yields.

As the foaming agent, ordinary MIBC, Tau #250 (ethylene glycol type), etc. are used, and as the collecting agent, Eroflot #208 (dithiophosphate type), etc. are used. If the mercury concentration in the flotation tailings is as high as 0.04% or more, as shown in Figure 1, sulfidation treatment and flotation processes are added to the flotation tailings, and the resulting sulfide floatation is It will be reused together with refined tailings as a repeat ore for flotation.

In the above sulfiding treatment, hydrogen sulfide, soda sulfide, etc. are used as the sulfiding agent, and the amount added depends on the mercury concentration in the flotation tailings.
In other words, the amount of residual mercury is more than the stoichiometric amount. This sulfurization treatment reduces the mercury concentration in the flotation tailings to 0.02-0.
It can be reduced to 0.3%. Regarding sulfidation treatment when using hydrogen sulfide as a sulfiding agent, hydrogen sulfide gas is blown into the bottom of the flotation tailings valve while stirring to generate mercury sulfide, which is then sulfurized by the flotation tailings. It is separated from the sludge matrix as ore. The effects of the present invention are as follows.

(1) Attrition treatment and flotation are performed simply by adjusting the acidity and valve concentration of the sulfuric acid sludge as it is generated, so the process and operation are extremely simple and can be significantly shortened. be.

(2) Since both the above-mentioned attrition treatment and flotation are carried out at room temperature, a large amount of heat is not required, and mercury and selenium can be simultaneously removed in a solid state at a high yield.

(3) Since the removed substance is concentrated to about the amount of sulfuric acid sludge treated, its treatment is extremely easy.

(4) Flotation tailings is mostly lead sulfate, so it can be used as an advantageous lead resource. As described above, the present invention enables the production of mercury and selenium from sulfuric acid sludge containing mercury and selenium, which is generated when sulfuric acid is produced from sulfur dioxide gas generated in the nonferrous metal refining process, in a simple process that requires a large amount of heat, etc. The present invention provides a method for removing mercury and selenium from sulfuric acid sludge that makes it possible to simultaneously separate and remove them at a high yield without causing sludge, and is extremely useful for sulfuric acid production and resource reuse.

Next, the present invention will be explained in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist thereof.

Example 1 Hg0.51%, Se4.77%, Pb59. Attrition treatment was carried out for 4 hours in an attrition mill using a sulfuric acid acidic solution containing 30% sulfuric acid sludge as a bulb concentration and a sulfuric acid concentration of 100 DaIf, to attrition the sulfuric acid sludge particles, and then treatment. The sludge was diluted to a valve concentration of 10%, and a foaming agent MIBC3OO da IT and a collector Eroflot 208150 da IT were added to the amount of sulfuric acid sludge in a Denver type flotation machine to perform flotation treatment. (concentrate) and tailings were obtained.

The process diagram and flotation results of this example are shown in FIG. 2 and Table 2. The Hg:Se molar ratio of the sulfuric acid sludge in this example is 1:33. Table 1 shows the actual yield of mercury and selenium at 9
8% or more, indicating that high-grade lead concentrate can be obtained as flotation tailings. Example 2 Attrition treatment was carried out under the same conditions as in Example 1 using a sulfuric acid solution of 100 yIe of sulfuric acid concentration containing 30% sulfuric acid sludge containing 0.52% Hg, 4.6O% Se, and 58.97% Pb. After the treatment, the treated sludge was diluted to a valve concentration of 10%, and rough selection, fine selection, and flotation after sulfurization of the coarse tailings were performed using a Denver type flotation machine under the same conditions as in Example 1. Ta.

The flotation after rough selection, fine selection and sulfurization treatment is 20% each.
Minutes, 1 flour, 1 flour. The process diagram and flotation results of this example are shown in FIG. 1 and Table 3. Table 3 shows that the total yield of mercury and selenium is 98% or more, and that high-grade lead concentrate can be obtained from the flotation tailings.

Example 3 Hg0.31%, SeO. Using sulfuric acid sludge containing 42% Pb and 62.3O% Pb, attrition treatment, flotation treatment, and sulfidation treatment of purified tailings and flotation were carried out under the same conditions as in Example 2, but the selection of floating ore was omitted.

The process chart and flotation results of this example are shown in FIG. 3 and Table 4. Although the sulfuric acid sludge of this example has a lower grade of Se than that of Example 2, as shown in Table 4, the actual yield of mercury is 90% and that of selenium is 80% or more.

The lead quality of the flotation tailings is not much different from that in Example 2, and can be used as a raw material for lead smelting. Comparative example. Using the same sulfuric acid sludge as in Example 2, only crude refining and refining were performed under the same conditions as in Example 2, without attrition treatment, sulfidation treatment of coarse tailings, and reflotation, and the process diagram and The flotation results are shown in Figure 4 and Table 5.

Table 5 shows Examples 2 and 3 in which attrition treatment was performed.
This shows that the actual yields of mercury and selenium are extremely low compared to the above, and the separability of them from lead sulfate, the main component, is also poor.

[Brief explanation of the drawing]

Figure 1 is a process diagram of a basic embodiment of the present invention, and when the mercury concentration in the flotation tailings is high, 0.04% or more, this process includes sulfidation treatment and flotation treatment, which is surrounded by a chain line. This is an additional process.

Claims (1)

[Claims] 1. Removal of mercury and selenium from sulfuric acid sludge, characterized by subjecting sulfuric acid sludge containing mercury and selenium to attrition treatment in an acidic sulfuric acid solution, and then subjecting the attrition-treated sulfuric acid sludge to flotation treatment. Method. 2 Attrition treatment of sulfuric acid sludge containing mercury and selenium in an acidic sulfuric acid solution, then flotation treatment of the attrition treated sulfuric acid sludge, further sulfidation treatment of floating tailings from the flotation treatment, followed by flotation treatment. A method for removing mercury and selenium from sulfuric acid sludge.