JPS5934219B2 - Method for removing mercury from smelting gas - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a comprehensive method for removing mercury from smelting gas, which makes it possible to completely prevent product contamination and environmental pollution caused by mercury in sulfur dioxide gas.

The raw material ore used in nonferrous smelting contains a small amount of mercury, and when this raw material ore is roasted or smelted, the mercury evaporates as mercury vapor and mixes into the smelting gas. There is a risk of contamination of the product sulfuric acid or environmental pollution due to release into the atmosphere, so it is necessary to remove it.

As methods for removing mercury from smelting gas, methods such as hot concentrated sulfuric acid washing, removal using mercuric chloride, mercury selenide production using selenium addition, and absorption using sulfides have been proposed and implemented. There are some things.

However, each of these methods has problems such as incomplete mercury removal, corrosion of equipment materials, danger of using musical instruments, and economical disadvantages. Not revealed.

When removing mercury, it must be possible to completely prevent product contamination and environmental pollution in a comprehensive manner, including the removal of mercury itself and the treatment of mercury-containing processed waste.

The present inventors have conducted studies in order to solve the problems of the above-mentioned conventional methods and provide a comprehensive mercury removal method that makes it possible to completely prevent product contamination and environmental pollution caused by mercury in smelting gas. As a result, it was discovered that the object could be achieved by using coke carrying lead sulfide as a mercury trapping agent, and the present invention was achieved.

That is, the gist of the present invention is that the particle size is 5 to 30.
After kneading the coke with lead sulfide with a moisture content of 15 to 25 parts, the coke carrying lead sulfide obtained by drying the coke with a moisture content of 1 to 3 parts is brought into contact with a non-ferrous smelting gas containing mercury to remove mercury from the coke. The coke saturated with collected mercury is heated to 400 to 500 °C in an inert atmosphere or 350 to 400 °C in an air atmosphere to generate mercury vapor, and the mercury vapor is cooled and condensed. A method for removing mercury from smelting gas, which comprises recovering metal mercury from smelting gas, circulating the exhaust gas into the non-ferrous smelting gas, and introducing lead-containing coke from which the collected mercury has been separated into a lead blast furnace. be.

That is, the present invention utilizes the known exchange reaction between lead sulfide and mercury, and involves bringing a mercury complement agent, in which lead sulfide is supported on the surface of coke as a carrier, into contact with mercury-containing smelting gas. The mercury in the smelting gas is complemented with coke through the exchange reaction and removed, the mercury is recovered as metallic mercury from the coke saturated with the complemented mercury, and the lead-containing coke is introduced into a lead blast furnace or the like. It is a comprehensive mercury removal method that does not generate any mercury-containing waste through reuse.

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

FIG. 1 is a process diagram of an embodiment of the present invention, and FIG. 2 is a flow rate of nitrogen gas of 2 cm/sec when mercury complement waste is heated to separate complement mercury as mercury vapor in the embodiment of FIG. 1.
c. A graph showing the relationship between the heating temperature of mercury complement waste and the mercury removal rate under a heating time of 120 min. Figure 3 also shows the relationship between the heating temperature of mercury complement waste and the mercury removal rate under a nitrogen flow rate of 2 cm/sec and a heating temperature of 450°C. FIG. 2 is a graph diagram showing the relationship between the heating time of mercury complement waste and the mercury removal rate.

Next, referring to FIG. 1, the steps of the present invention will be explained in detail.

The mercury complement agent used in the present invention has a particle size of 5 to 301r.
tm coke is put into chemically produced lead sulfide with a water content of 15 to 25 parts, and is forcibly kneaded, then dried to a level of 1 to 3 parts water, and then packed into a tower-shaped mercury removal tower.

In the above, if the moisture content of lead sulfide is less than 15 parts, it becomes hard and hard to stick to the coke surface, and if it is more than 25 parts, the fluidity becomes large and it easily flows off. If moisture is completely removed just before use, lead sulfide will easily separate from the coke, so the content is in the range of 1 to 3%.

In this way, by introducing the mercury-containing nonferrous smelting gas into the mercury removal tower filled with the mercury complement agent and bringing it into contact with the mercury complement agent, the mercury in the gas is almost completely removed by the exchange reaction. Complement to mercury complement agent, removed.

The reaction mechanism in which the mercury in the smelting gas is complemented by the mercury complement agent is thought to be as follows.

That is, when the smelting gas passes through the mercury removal tower, the mercury in the gas is first physically adsorbed on the lead sulfide surface of the mercury complement agent, and then, over time, the exchange reaction according to equation (1) progresses. It is successively diffused into lead sulfide, and is finally fixed and complemented in the form of mercury sulfide.

On the other hand, for lead, PbS + Hg0 → HgS + Pb
・・・・・・・・・・・・・・・(1) S in smelting gas
In the absence of O2 and water vapor, metallic lead is produced.

However, smelting gas usually contains water vapor, SO2,0
□ and a trace amount of S03, the above metallic lead is (2
) becomes PbSO4.

Note that SO2 in the gas that has arrived at the coke surface of the carrier
is oxidized to S03 by its catalytic action, but when water vapor is present, this SO3 immediately becomes sulfuric acid, and this sulfuric acid also participates in the sulfation of the metal lead.

Next, the mercury complement waste, which has been saturated by complementing mercury in the mercury removal tower, is put into a mercury separation furnace and heat-treated in an inert atmosphere or atmospheric atmosphere. It separates almost completely in the form of mercury vapor, leaving behind lead-containing coke.

In this case, the second heating condition in an inert atmosphere is
As shown in the mercury removal curve obtained in the heating temperature range of 200°C to 600°C in the figure, the mercury removal rate is low at temperatures below 400°C, and there is no improvement in the mercury removal rate at temperatures above 500°C, which requires energy. Since it is only consumed, the heating temperature range is 400 to 500°C.

Furthermore, as shown in the mercury removal curve obtained in the heating time range of up to 180 minutes in Figure 3, no improvement in the mercury removal rate was observed even if the heating time was longer than 30 minutes.
The heating time is preferably in the range of 30 to 60 minutes.

The atmospheric atmosphere should be below the ignition temperature (650°C) in order to prevent oxidation loss of coke, and the heating temperature to obtain a mercury removal rate of 98°C or higher is 350°C to 40°C.
It is in the range of 0°C.

In addition, in order to reuse the lead-containing coke from which the complement mercury has been separated in the lead blast furnace, it is better to oxidize the sulfide as well, which will contribute to reducing the capacity of the flue gas desulfurization equipment downstream of the lead blast furnace, and will also reduce SO2.
Since the gas can also be recovered as sulfuric acid, it is preferable to heat the mercury complement waste in an atmospheric atmosphere.

As described above, gas containing high concentration of mercury vapor is obtained by heat treatment of mercury complement waste in a mercury separation reactor, but this mercury vapor-containing gas is cooled and condensed in a condensation tower to remove the mercury vapor. Mercury vapor is recovered as metallic mercury and cooled, and the exhaust gas from the condensing tower still contains some SO2.
Since it contains gas and a trace amount of mercury, a closed system is used in which this exhaust gas is circulated to the above-mentioned smelting gas, so not even a trace amount of mercury is released into the atmosphere.

The remaining lead-containing coke, after almost complete separation of the complement mercury in the mercury separation furnace, is introduced into a lead blast furnace, where the lead is recovered and
Since coke is used as part of the reducing agent, there is no mercury-containing waste that could pollute the environment.

In addition, since this lead-containing coke does not substantially contain mercury, it eliminates the need for a mercury removal device downstream of the lead blast furnace.

On the other hand, in the mercury removal tower, the mercury is almost completely complemented by the mercury complementing agent, and the remaining smelting gas is sent to the sulfuric acid manufacturing factory as sulfuric acid raw material gas as in the usual method. Since the gas is substantially mercury-free as described above, the sulfuric acid produced is not contaminated with mercury.

As described above, the present invention provides a comprehensive pollution-free treatment method that can completely prevent product contamination and environmental pollution caused by mercury in non-ferrous smelting gas, and is extremely useful for pollution control and product quality improvement. be.

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 the gist thereof is exceeded.

Example 1 Hydrogen sulfide gas is blown into a saturated aqueous solution of lead acetate to produce lead sulfide, which is thoroughly washed with hydrogen sulfide saturated water to remove acetic acid and salts.

Next, excess water is removed by filtration, and coal coke with a particle size of 2 to 7g is added to the lead sulfide that has become muddy (moisture content is 15 to 25 parts), and the coke is forcibly kneaded to cause lead sulfide to adhere to the surface of the coke particles. The mercury complement agent was dried in air to a moisture content of 1 to 3%.

The lead sulfide grade of this mercury complement agent was 25%.

This mercury complement agent was filled in a glass reaction tube with a diameter of 35M and a height of 600rrvn at various heights, and mercury was added to a mixed gas consisting of 81g of nitrogen gas, 9% of oxygen gas, and 10% of sulfur dioxide gas. Gases containing various concentrations were collected at the inlet and outlet of the reaction tube, and the mercury concentration was measured by flameless atomic absorption spectrometry.

Table 1 shows the gas concentration at 25°C, the filling height at 300 mm, and the gas flow rate at 17.3'-/plane superficial velocity of 3 Q Cm7-.
These are the measurement results when the mercury concentration in the inlet gas was varied.

Table 2 shows filling heights of 150 mm and 500 mm under the above conditions.
These are the measurement results when the question was asked.

Table 3 shows the measurement results tested at an inlet gas temperature of 50°C.

Next, the mercury supplementation waste agent (H
g9152PPm)10? was heated in a quartz reaction tube at eC of 400 to 500° C. while flowing nitrogen gas at a rate of 2 cm 7 , and mercury was almost completely separated.

In this nitrogen gas atmosphere, the heating temperature was set to 300 as a comparative example.
℃, the separation of mercury was insufficient as shown in Test No. 9.

The results of these measurements are shown in Table 4.

Table 5 shows the measurement results when the heating temperature was 450°C and the heating time was 30 to 120 minutes.

Table 6 shows the measurement results when the mercury complement waste was heated in an atmosphere with an oxygen partial pressure of 1 to 21 parts for a heating time of 60 min.

The effect of heating time is the same in an oxygen-containing atmosphere as in a nitrogen atmosphere.

As is clear from the above measurement results, when heated in an inert atmosphere (nitrogen atmosphere) and an atmosphere with a relatively low oxygen partial pressure, the mercury complement waste was tested in test numbers 116.10 to 1.
1 and 14-17 respectively, 400-
Complement mercury can be almost completely separated under conditions of 500°C and 30 to 60 min.

In addition, in the atmospheric environment, 30
Complement mercury can be almost completely separated at 0 to 350°C, but S02 gas is generated due to the oxidation reaction of sulfide.

Furthermore, the separated mercury vapor can be easily recovered as metallic mercury using a condenser, but since trace amounts of mercury are mixed into the exhaust gas, in actual operations, this exhaust gas is circulated to the smelting gas without causing environmental pollution. This is an extremely effective treatment method industrially.

In actual operation, as described above, the remaining lead-containing coke from which the complement mercury has been separated is introduced into a lead blast furnace, where the lead is recovered and the coke is used as part of the reducing agent.

Example 2 Lead sulfide produced in the same manner as Example 1 was prepared with a particle size of 2 to 7M.
Mercury complement agent (lead sulfide grade 1) attached to coal coke of
7.7%) was filled in a glass reaction tube with a diameter of 35 m and a height of 600 rrrm, and a mixed gas containing nitrogen gas and mercury vapor was charged into the reaction tube at 17.31%. / m1n1 at a superficial velocity of 30 cm/sec, and the mercury concentrations in the reaction tube inlet gas and outlet gas were measured in the same manner as in Example 1.

Table 7 shows the measurement results when the gas temperature was 27°C and the filling height was 200trvn.

The mercury complement waste obtained in the above mercury complement process (Hg75
23 ppm) LOP was taken, and it was heated in a quartz reaction tube with nitrogen gas flowing at a rate of 2 cm/sec to
When heated under conditions of 500° C. and heating time of 60 min, the complement mercury can be almost completely separated, and the measurement results are shown in Table 8.

[Brief Description of the Drawings] Figure 1 is a process diagram of one embodiment of the present invention, and Figure 2 is a process diagram of the embodiment of the present invention when mercury complement waste is heated to separate complement mercury as mercury vapor. Nitrogen gas flow rate 2 cm/5e
e1 A graph showing the relationship between the heating temperature and mercury removal rate of mercury complement waste under a heating time of 120 min. Figure 3 shows the original mercury at a nitrogen flow rate of 2 cm/sec and a heating temperature of 450°C. FIG. 3 is a graph showing the relationship between the heating time of complement waste and the mercury removal rate.

Claims (1)

[Claims] 1 Particle size 5~30wrLL: J) Coke with moisture 15~
The lead sulfide-supported coke obtained by kneading with 25 g of lead sulfide and drying to a moisture content of 1 to 3% is brought into contact with mercury-containing non-ferrous smelting gas to capture mercury in the coke. The coke saturated with mercury was heated in an inert atmosphere to
00 °C or in the range of 350 to 400 °C in the air atmosphere to generate mercury vapor, cool and condense the mercury vapor to recover it as metallic mercury, and circulate the exhaust gas to the nonferrous smelting gas, and A method for removing mercury from smelting gas characterized by introducing lead-containing coke from which captured mercury has been separated into a lead blast furnace.