JP2636926B2 - Method for removing zinc chloride from flue gas - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for removing zinc chloride from combustion exhaust gas generated when incinerating various industrial wastes containing a zinc compound.

(Prior art) In order to remove zinc chloride contained in the combustion exhaust gas of an incinerator by dry method, a method of adsorbing and removing it with an adsorbent such as activated carbon may be considered. Adsorbents that can be effectively adsorbed have not been developed. Also,
A method of cooling the combustion exhaust gas to condense the zinc chloride and remove the generated dust with a filter can be considered. The part passes through the filter as a gas and is released into the atmosphere, polluting the environment. In particular, when cooling such as the flue gas of an incinerator may cause condensation of the acid and cause corrosion of the piping, the flue gas is
Since it cannot be cooled down to below ℃, a large amount of zinc chloride is released into the atmosphere and pollutes the environment. Furthermore, when released into the atmosphere, zinc chloride is cooled and turned into dust, and dusted zinc chloride and water condensed by using it as nuclei are observed as white smoke, which may cause a problem. Excessive gas cooling also increases equipment costs, even when condensation of the acid in the exhaust gas cannot be considered, which is not preferable.

(Problems to be Solved by the Invention) The present invention solves the above-mentioned conventional problems, and efficiently removes zinc chloride contained in flue gas by a dry method until the concentration becomes about 1/10 of the conventional concentration. The present invention has been completed for the purpose of a method for removing zinc chloride from flue gas which does not cause dew condensation of acid in piping.

(SUMMARY for a) the invention, the filter in terms of the addition of SO _x gas in the combustion exhaust gas containing zinc chloride, to form a zinc sulfate to hold the flue gas temperature to 400 ° C. or less It is characterized by collecting.

Hereinafter, the present invention will be described in more detail with reference to FIG. 1. (1) is an incinerator, (2) is a cooler, (3) is a dust collector such as an electric dust collector, a bag filter, and a HEPA filter. It is a vessel. SO _x gas is introduced from the introduction port provided in front of the dust collector is in the combustion exhaust gas (3) (4). The SO _x gas may be introduced from a gas cylinder or may be generated by heating fuming sulfuric acid, heating sulfuric acid, or the like, but the SO _x gas may be added at any position before the dust collector (3). since may be performed, for example, combustible materials containing sulfur in incinerator by burning may generate sO _x gases. Thus when SO _x gas is added zinc sulfate is formed and in the combustion exhaust gas to.

The amount of SO _x gas added must be equal to or higher than the reaction equivalent,
SO ₂ is 0.47mg or more with respect to zinc chloride 1.0 mg, SO ₃ is 0.59mg
That is all. However, since the SO _x concentration is a risk of environmental pollution due to the release of corrosion and SO _x such as piping and excessively high, usually chloride SO _x concentration at the inlet of the dust collector (3) is precipitator by (3) 100-1 which can remove zinc
It may be supplied SO _x so as to maintain the 000 ppm. Note that H ₂ O or O ₂ may be supplied to the combustion exhaust gas as needed.
When zinc chloride reacts with SO _x in this way, zinc sulfate is formed in a very short time of about 0.1 to 1.0 seconds, but zinc sulfate must be kept at 740 ° C. or lower to decompose at 740 ° C. At a high temperature of 400 ° C. or higher, the saturated vapor pressure of zinc chloride is high, and some of the zinc chloride remains unreacted. Therefore, the temperature of the combustion exhaust gas is maintained at 400 ° C. or lower. The zinc sulfate thus formed is removed as dust by the dust collector.

(Example) As an apparatus shown in Fig. 1, an exhaust gas cooler (2) having an air mixer and a dust collector (3) having a HEPA filter was used, and SO2 of various concentrations was introduced from an inlet (4). _Two gases were blown, and the concentration of zinc chloride at the outlet of the dust collector (3) was measured. When the concentration of zinc chloride at the inlet of the dust collector (3) is about 10 ^-2 mg / Nl, the concentration of zinc chloride at the outlet of the dust collector (3) when SO ₂ gas is not added is 10 ^-4 mg / ^{N. N} l, but S
O ₂ dust collector in the case of the gas concentration of 100 ppm (3) the concentration of zinc chloride at the outlet of 10 ^-5 mg / ^N l, the SO ₂ gas concentration 25
When more than 0ppm less than 10 ^-5 mg / ^N l (instrument measurement limit or less for non-measurable) was reduced to the level of. This is shown graphically in FIG. Thus, according to the present invention, SO _x
It is possible to remove zinc chloride from the combustion exhaust gas to a level of 1/10 or less of the case of the conventional method in which no is added. Further, according to the present invention, the temperature of the combustion exhaust gas may be set to 400 ° C. or lower, and 150 to 400 ° C. where there is no possibility that dew condensation of the acid occurs.
Temperature range, so that the pipes and the like are not corroded.

(Effects of the Invention) As is clear from the above description, the present invention can efficiently remove zinc chloride in combustion exhaust gas to a level of 1/10 or less of the conventional level by a dry method. It is effective in preventing zinc chloride from escaping into the atmosphere from various incinerators since there is no possibility of dew condensation of the acid. Therefore, the present invention greatly contributes to industrial development as a method for removing zinc chloride from combustion exhaust gas that has eliminated the conventional problems.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an example of an apparatus used in the present invention, and FIG. 2 is a graph showing the relationship between the concentration of SO _{2 and the} concentration of zinc chloride in Examples. (1): incinerator, (2): cooler, (3): dust collector, (4): inlet.

Claims (1)

(57) [Claims] [Claim 1] was added SO _x gas in the combustion exhaust gas containing zinc chloride, it holds the flue gas temperature to 400 ° C. or less, characterized in that collected by the filter in terms of to form a zinc sulfate A method for removing zinc chloride from flue gas.