JPS602896B2 - Method for removing mercury from smelting exhaust gas - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for efficiently and economically removing mercury from smelting exhaust gases, such as mercury-containing exhaust gases generated during the incineration of sulfide ores in zinc smelters.

Conventional methods for removing mercury from smelting exhaust gas include a) a method that takes advantage of the high affinity between selenium and mercury, b) a method of reacting metal sulfide with mercury, c) concentrated sulfuric acid, d) thiourea, There are gas cleaning methods such as Amilzansetka IJ, but these methods have the following problems.

b) A method that utilizes the affinity between selenium and mercury. For example, in the method of passing mercury-containing exhaust gas through a packed tower filled with metallic selenium, since metallic selenium is expensive, adsorbed mercury is stripped off and the selenium is activated. This necessitates a process of reuse, which is complicated. In addition, selenium is toxic and must be handled with care.In the method using metal sulfide as an absorbent, the metal sulfide is made into a slurry and brought into contact with a mercury-containing gas to absorb and remove mercury. In this case, the problem is that S03, which is contained in the exhaust gas other than SQ, is absorbed by the slurry liquid, increasing the acid concentration and reacting with metal sulfides to generate 2S gas.

Although there are several methods for removing mercury using oxidation, the method of oxidizing metallic mercury to mercury ions using an oxidizing agent and cleaning and removing it is not suitable for smelting exhaust gas containing a large amount of S02 gas. Further, in the cleaning method using sulfuric acid (c), mercury is precipitated as HgSO4 crystals by the reaction of the following formula, and is separated by a thickener.

However, the sulfuric acid concentration in this case needs to be 85-90%, but since the water contained in the exhaust gas lowers the sulfuric acid concentration, the liquid temperature must be lowered to 140-200% in order to maintain the sulfuric acid concentration. ℃, and the use of high-temperature, high-concentration sulfuric acid has the disadvantage that it is difficult to select the material for the equipment. In addition, in the method (d) using a slurry of thiourea and amylzanthate potash as the absorption liquid, the elemental sulfur produced by the decomposition of thiourea and amylzanthate potash adsorbs and reacts with mercury to remove HgS. The principle is that

However, the amount of elemental sulfur produced when these reagents decompose is only a small portion of the amount of reagent, and the amount of mercury adsorbed is small compared to the amount of reagent used, making it difficult to use economically. It's hard to call it a method. Therefore, the present inventors have carried out various tests and studies on methods for improving the above points and treating smelting exhaust gas containing high concentrations of mercury.As a result, we have developed a solution in which elemental sulfur is suspended. was found to be extremely effective in absorbing and removing mercury from smelting exhaust gas.

Elemental sulfur used as an absorbent must have a high degree of activity to remove mercury with high efficiency, but experiments with various types of sulfur have shown that highly active mercury, such as that produced by the Claus reaction, It has been determined that fine, highly active elemental sulfur is most suitable for this purpose. The present invention provides a method for removing mercury by contacting a solution containing extremely fine elemental sulfur produced by the Claus reaction or the like with mercury-containing smelting exhaust gas as an absorbing liquid, and causing the mercury in the gas to be adsorbed by sulfur. The high (large) specific gravity sulfur that adsorbs a large amount of mercury produced by the adsorption reaction is extracted from the system by wet classification, and the unreacted sulfur and the low specific gravity sulfur that has adsorbed some mercury remain in the absorption liquid. The present invention relates to a method for removing mercury from smelting exhaust gas, characterized by:

Next, an example of a process for industrially implementing the present invention will be described. The mercury-containing smelting exhaust gas is led to an absorption tower, and the mercury in the exhaust gas is adsorbed and removed by the sulfur in the absorption liquid.

As the absorption tower, devices such as a spray tower, a packed tower, and a wet tray tower can be considered. In order to remove sulfur that has adsorbed mercury and replace it with new sulfur, it is necessary to install several absorption towers and replace the entire amount of sulfur in one wind absorption tower from the tower where the amount of mercury adsorption has increased, or Sulfur that has adsorbed mercury has a high specific gravity, so wet classification is performed using this difference in specific gravity to separate sulfur into those that have adsorbed a large amount of mercury and those that have not. There is a way to take it out of the system. As will be described in Example 2 below, this latter method leaves sulfur with some mercury adsorbed in the absorption tower, so the mercury adsorption rate is faster than in the former case where the entire amount of sulfur is replaced with fresh sulfur. Become. Example 1
Using Claus sulfur obtained by blowing hydrogen sulfide into sulfurous acid water, make an aqueous solution of it for 35 minutes and use this as an absorption liquid for 1 hour.
When the gas was poured into a gas cleaning bottle equipped with a G-2 filter and the mercury concentration in the gas was analyzed before and after cleaning, the results shown in Table 1 were obtained.

The test conditions assume actual smelting exhaust gas, and the air amount is 2.
A mixture of 0 sulfur dioxide gas and 1 sulfur dioxide gas added per minute was used. Table 1 Example 2 Using Claus sulfur obtained as an intermediate product at a sulfur manufacturing plant, a solution was prepared for 23 days, and this was poured into a gas washing bottle with a G-2 filter as an absorbent for 0.8 days. Two tubes were prepared, connected in series, and mercury-containing gas was passed through them.

When the mercury concentration in the gas after cleaning was analyzed, the results shown in the graph of FIG. 1 were obtained. Note that the test conditions are the same as in Example 1. As is clear from the graph in FIG. 1, the mercury removal rate is low immediately after gas ventilation, and the mercury removal rate reaches its maximum when sulfur adsorbs some mercury.

Therefore, as mentioned above, the rate of mercury adsorption can be increased by separating the sulfur that has adsorbed mercury by wet classification and leaving the sulfur that has adsorbed only a small amount of mercury in the absorption liquid. . Example 3 Using Claus sulfur obtained at the same sulfur manufacturing plant as in Example 2, a solution was prepared for 60 minutes, and this was collected overnight as an absorption liquid, and then sprayed into a small-scale packed column to remove mercury. Mercury was removed from the contained gas.

The flow rate of the absorption liquid was 0.3 so/min, and the other conditions were the same as in Example 1. The packed tower had an internal cross section of 4 x 4 m, a packing thickness of 8 m, and a pressure loss of 50 to 7 m water columns. The results at this time are shown in the graph of FIG.

[Brief explanation of drawings]

FIGS. 1 and 2 are graphs showing changes in mercury removal rate when mercury in exhaust gas is removed using a sulfur-containing absorption liquid. Figure 1 Figure 2

Claims (1)

[Claims] 1. A method of removing mercury by contacting a solution containing extremely fine elemental sulfur produced by Claus reaction etc. with mercury-containing smelting exhaust gas as an absorption liquid to cause the mercury in the gas to be adsorbed to sulfur. The high specific gravity sulfur that adsorbs a large amount of mercury produced by the absorption reaction is extracted from the system by wet classification, while the end-reacted sulfur and the low specific gravity sulfur that has adsorbed some mercury remain in the absorption liquid. A method for removing mercury from smelting exhaust gas, characterized by: