JP4713062B2 - Exhaust gas treatment method - Google Patents

Description

【００２４】
＜ガス中水分及び処理温度による処理の比較＞
次に、酸性ガス処理剤としてＴＫ−ＳＰ１１１６ｍｇを用いて、排ガス中のＳＯ_２ガス濃度１５００ｐｐｍ、ＣＯ_２濃度９％の条件において、水分及び温度を種々変化させて処理したときのＳＯ_２除去率を求めた。結果を表２に示す。
【００２５】
【表２】

【００２６】
以上の結果からも分かるように、本発明の処理方法によれは、排ガス中水分が低い条件であっても効率的に酸性ガスを除去できた。
【００２７】
【発明の効果】
本発明によれば、酸性ガス成分を含む高温の排ガス中に酸性ガス処理剤を吹き込むことで、排ガス中水分が低い条件であっても酸性ガスを効率的に除去できるため、酸性ガス排出濃度を低減するとともに酸性ガス処理剤使用量を低減することができる。特に、所定の排ガス温度の領域に集塵機を設置することにより、高温時に酸性ガス処理剤を含む排ガス中煤塵を集塵することができ、ダイオキシン類の再合成や反応物の潮解による装置への不具合を起こす危険が低減される。また排ガスの温度を必要以上に下げる必要がなくなるため、排ガスの再加熱も不要になるメリットがある。
また、炭酸カルシウムスラリーを利用した湿式法と比べて、排ガス量が増えることも無く、設備費用や運転費用も少なく、経済的である。
【図面の簡単な説明】
【図１】 本発明の実施例で用いた装置の概要を示す図。[0001]
[Technical field to which the invention belongs]
The present invention relates to an acid gas treatment method capable of efficiently removing an acid gas component containing an acid gas component, particularly an acid gas component in exhaust gas such as waste incineration exhaust gas and power plant boiler gas.
[0002]
[Prior art]
Exhaust gas generated from refuse incinerators, thermal power plants and other boilers generally contains a large amount of acidic gas components such as sulfur oxides and hydrogen chloride. It is brought into contact with an acid gas treating agent consisting of a body to form a sulfate or chloride powder, which is separated by a bag filter or an electrostatic precipitator and then released into the atmosphere.
[0003]
Slaked lime used as an acid gas treating agent is usually blown into the flue immediately before the dust collector, reacts with the acid gas component in the exhaust gas, and the exhaust gas treatment is performed. The reactivity between slaked lime and acid gas components is affected by the temperature of the reaction site and the environment such as moisture. Generally, the lower the reaction temperature, the better the reactivity, and the more moisture, the better the reactivity.
[0004]
In recent years, the temperature of exhaust gas treatment has been kept low in order to reduce dioxins, which are extremely toxic substances contained in exhaust gas generated from waste incinerators, and as a result of the introduction of heat recovery boilers using exhaust gas. I came. Specifically, since dioxins are said to be re-synthesized in the vicinity of 250 ° C. to 300 ° C., the dust collection equipment of recent garbage incinerators uses an exhaust gas temperature to prevent re-synthesis of dioxins. A low-temperature bag filter system using a bag filter at 150 ° C. to 180 ° C. is adopted.
[0005]
Conventionally, the moisture in the exhaust gas was about 40% in the case of the temperature reduction method of the exhaust gas by direct water injection, but the number of facilities using a heat recovery boiler has increased, and has decreased to about 20%. Accordingly, in recent environments, the reactivity is improved due to the lowering of temperature, but the reactivity of the portion where moisture is reduced tends to deteriorate.
[0006]
Further, in the exhaust gas treatment using slaked lime, there is a problem that the SO ₂ removal performance is deteriorated. This is because when HCl and SO ₂ are mixed as acid gas components, HCl and slaked lime having high reactivity react first, and as a result, the reaction between SO ₂ and slaked lime becomes insufficient, and SO ₂ is discharged. In order to reduce the concentration, it was necessary to blow in more slaked lime.
Further, HCl and slaked lime react to become CaCl ₂ , but CaCl ₂ is a deliquescent substance, and therefore, when the temperature is lowered, it may deliquesce and adhere to the filter cloth of the bag filter.
[0007]
On the other hand, for the treatment of sulfur oxides in the acidic gas components of exhaust gas from power plant boilers, etc., a wet method is used in which it is treated in contact with a calcium carbonate slurry. However, there are drawbacks such as an increase in the amount of exhaust gas due to evaporation of moisture.
In either case, the moisture in the exhaust gas agglomerates and white smoke is generated when released into the atmosphere, and there is a problem that the exhaust gas needs to be reheated to prevent it.
[0008]
[Problems to be solved by the invention]
Then, this invention was made | formed for the purpose of solving the problem which said conventional acid gas processing method has, and providing the exhaust gas processing method which can remove efficiently the acid gas component in the acid gas in the conditions where moisture is low . Is.
[0009]
[Means for Solving the Problems]
As a result of intensive research on exhaust gas treatment methods under conditions where the moisture in the gas is low, the present inventors have found that the reaction between slaked lime and acidic gas components such as HCl and SO ₂ causes the moisture in the gas in a high temperature atmosphere of 300 ° C. or higher. The inventors have found that the reactivity is improved even under low conditions, and have completed the present invention based on this finding.
[0010]
That is, the present invention provides a method for treating sulfur oxide, which is one of acid gas components in exhaust gas under low moisture conditions (for example, 25% by weight or less), in which an acidic gas treating agent containing slaked lime is added to the flue. (sometimes hereinafter abbreviated as "first region".) exhaust gas temperature region to be a predetermined temperature range to look blown write, in the first region, characterized in that to stay the acid gas treating agent was blown An exhaust gas treatment method is provided. In the exhaust gas treatment method of the present invention, the first region in the flue is a region where the exhaust gas temperature is 250 ° C to 800 ° C (preferably 300 ° C to 400 ° C). The exhaust gas treatment method of the present invention is suitable for exhaust gas treatment with a moisture content of 20% or less.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the exhaust gas treatment method of the present invention will be described in detail.
[0012]
The exhaust gas targeted by the exhaust gas treatment method of the present invention is not particularly limited, but is a high-temperature exhaust gas discharged from a waste incinerator, a power generation boiler, etc. In addition to carbon dioxide in the gas, sulfurous acid, sulfur dioxide The treatment method of the present invention is applied to a flue that contains a sulfur oxide such as hydrogen chloride or an acidic gas such as hydrogen chloride.
[0013]
In the exhaust gas treatment method of the present invention, a basic substance powder containing slaked lime is used as the acid gas treating agent. Although it may be 100% slaked lime, it may contain a basic substance such as sodium bicarbonate.
The slaked lime may be industrial slaked lime, but in order to further improve the removal efficiency of the acidic gas component in the method of the present invention and to exhibit sufficient capacity, the BET specific surface area is 35 m ² / g or more and the pore volume is 0. It is preferable to use highly reactive slaked lime that is at least 15 cm ³ / g.
[0014]
Such an acid gas treating agent is blown into a flue for sending exhaust gas containing an acid gas component. Although the temperature of the exhaust gas sent through the flue gradually decreases, in the method of the present invention, it is important to blow the acid gas treating agent into the flue where the exhaust gas temperature is in the range of 250 ° C to 800 ° C. High processing performance can be obtained in such a temperature range. When the amount of water in the exhaust gas is small, if the temperature is lower than 250 ° C., the reactivity between slaked lime and acidic gas, particularly sulfur oxide, tends to decrease, and the processing efficiency tends to deteriorate. In addition, the treatment performance deteriorates even at a temperature higher than 800 ° C., but this is presumably because quick lime particles generated by dehydration from slaked lime are melted by thermal transformation and the particle structure changes.
[0015]
In the case of an exhaust gas containing a large amount of CO ₂ such as a combustion exhaust gas from a garbage incinerator or a power plant boiler, it is preferable to perform the treatment within an exhaust gas temperature range of 300 ° C to 400 ° C. That is, when the exhaust gas temperature exceeds 400 ° C., the reaction between slaked lime and CO ₂ occurs preferentially over the reaction with other acid gas components. A treatment agent needs to be blown in, and the amount of acid gas treatment agent and the amount of generated dust accompanying it increase.
[0016]
On the other hand, in order to avoid the problem of resynthesis of dioxins, the exhaust gas temperature in the dust collector is preferably 300 ° C. or higher, more preferably 350 ° C. or higher.
Note that the blowing of the acidic gas treating agent is generally performed by pneumatic transportation in a system in which exhaust gas continuously flows like a flue.
[0017]
As described above, in the exhaust gas treatment method of the present invention, the acidic gas treatment agent containing slaked lime and the acidic gas are reacted in a predetermined temperature range, and the acidic gas treatment is performed within such a temperature range. For the purpose of retaining the agent for a long time, it is effective to use a high-temperature filtration type dust collector such as a ceramic filter. Therefore, the dust collector is preferably installed in a flue whose exhaust gas temperature is in the range of 300 ° C to 400 ° C.
[0018]
By providing the dust collector in such a high exhaust gas temperature region, the contact time between the acidic gas component and the acidic gas treating agent can be extended, and the reactivity of the acidic gas treating agent can be improved.
Moreover, by collecting the dust in the exhaust gas containing the acid gas treating agent at high temperatures, the risk of causing malfunctions in the apparatus due to resynthesis of dioxins and deliquescence of reactants is reduced. Furthermore, since it is not necessary to lower the temperature of the exhaust gas more than necessary, it is not necessary to reheat the exhaust gas.
[0019]
【Example】
EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited at all by these examples. In the following examples, “%” means “% by weight” unless otherwise specified.
[0020]
<Examples and Comparative Examples>
As shown in FIG. 1, a test apparatus having a gas mixing unit 11 and a reaction unit 12 provided with an acidic gas treating agent fixing layer 13 in which an acidic gas treating agent is fixed in a heat-resistant mesh member was prepared. . A conduit between each gas supply unit (not shown) and the mixing unit 11 and a conduit between the mixing unit 11 and the reaction unit 12 are heating conduits, and a heating device is also installed in the reaction unit 12 to fix the acidic gas treatment agent fixed layer. 13 was heated to a predetermined temperature. In this state, the raw gas containing the acid gas component and the gas containing the predetermined moisture are mixed in the mixing unit 11 to obtain a reaction gas, the reaction gas is heated by a heating conduit, and heated to a predetermined temperature in the reaction unit 12 in advance. The acidic gas treatment agent fixed layer 13 was allowed to react with the acidic gas component, and the concentration of the treated gas after the reaction was measured with the analyzer 14 to obtain the acidic gas removal rate.
[0021]
SO ₂ gas is used as the acid gas component, JIS special slaked lime (BET specific surface area 15 m ² / g, pore volume 0.07 cm ³ / g, manufactured by Okutama Kogyo Co., Ltd.) and highly reactive slaked lime “ Tamacalc-sponge acal (TK-SP) "(BET specific surface area 45 m ² / g, pore volume 0.20 cm ³ / g, manufactured by Okutama Kogyo Co., Ltd.) was used.
The SO ₂ gas concentration in the exhaust gas was 1500 ppm, and the reaction time was 2 hours.
[0022]
<Comparison of treatment with acid gas treating agent and reaction temperature>
First, using 372 mg of each of the acidic gas treating agents described above, treatment was performed under various conditions of temperature of 8% moisture in the exhaust gas, and the SO ₂ removal rate was determined from the amount of SO ₂ after the treatment. The results are shown in Table 1.
[0023]
[Table 1]

[0024]
<Comparison of treatment by moisture in gas and treatment temperature>
Next, using TK-SP 1116 mg as the acid gas treatment agent, the SO ₂ removal rate when the moisture and temperature were changed variously under the conditions of SO ₂ gas concentration of 1500 ppm and CO ₂ concentration of 9% in the exhaust gas was Asked. The results are shown in Table 2.
[0025]
[Table 2]

[0026]
As can be seen from the above results, according to the treatment method of the present invention, the acidic gas could be efficiently removed even under the condition of low moisture in the exhaust gas.
[0027]
【The invention's effect】
According to the present invention, the acidic gas treatment agent is blown into the high-temperature exhaust gas containing the acidic gas component, so that the acidic gas can be efficiently removed even under low moisture conditions in the exhaust gas. It is possible to reduce the amount of the acidic gas treating agent used while reducing the amount. In particular, by installing a dust collector in the specified exhaust gas temperature range, it is possible to collect the dust in the exhaust gas containing the acid gas treatment agent at high temperatures, which causes problems with equipment due to resynthesis of dioxins and liquefaction of the reactants. The risk of causing this is reduced. Moreover, since it is not necessary to lower the temperature of the exhaust gas more than necessary, there is an advantage that it is not necessary to reheat the exhaust gas.
Compared with the wet method using calcium carbonate slurry, the amount of exhaust gas does not increase, and the equipment and operating costs are low, which is economical.
[Brief description of the drawings]
FIG. 1 is a diagram showing an outline of an apparatus used in an embodiment of the present invention.

Claims (5)

In a method for treating sulfur oxide, which is one of acid gas components in exhaust gas having a moisture content of 25% by weight or less, generated from a waste incinerator or a thermal power plant boiler,
The acid gas treating agent containing hydrated lime, see write blown in a region the exhaust gas temperature of the flue is 300 to 400 ° C., an exhaust gas treatment method which comprises causing the residence. Exhaust gas treatment method according to claim 1, wherein the water content in the exhaust gas is 15 wt% or less. An exhaust gas treatment method according to claim 1 or 2 ,
Exhaust gas treatment method, characterized in that for retention of the acid gas treatment agent in the region by placing the filtration type dust collector to the area. The exhaust gas treatment method according to claim 3 , wherein the dust collector is installed in a region where the exhaust gas temperature in the flue is 350 ° C or higher. The exhaust gas treatment method according to any one of claims 1 to 4 , wherein slaked lime having a BET specific surface area of 35 m ² / g or more and a pore volume of 0.15 cm ³ / g or more is used as the slaked lime.

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