JPS6025531A

JPS6025531A - Dry purification of exhaust gas

Info

Publication number: JPS6025531A
Application number: JP58133796A
Authority: JP
Inventors: Yoshio Kobayashi; 義雄小林
Original assignee: Hitachi Zosen Corp
Current assignee: Hitachi Zosen Corp
Priority date: 1983-07-21
Filing date: 1983-07-21
Publication date: 1985-02-08

Abstract

PURPOSE:To remove an acidic substance in exhaust gas at a high removal ratio by a dry process in the same degree as a wet process, by dispersing a fine granular Ca-absorbant with a specific particle size or less throughout high temp. exhaust gas before performing dust collection. CONSTITUTION:A powder of CaCO3, CaO or Ca(OH)2 is finely pulveized while particles are mutually collided by the energy of a high pressure air stream or an overheated steam stream in a jet mill 1 and a finely pulverized absorbent is directly introduced into high temp. exhaust gas along with the fluid stream from a dispersing machine 2 to be uniformly dispersed throughout the exhaust gas. The absorbent reacted with acidic substances such as SOx, HCl or HF is collected along with soot by a bag filter 3 while the purified gas is exhausted.

Description

【発明の詳細な説明】この発明は排ガスの乾式浄化法に関する。[Detailed description of the invention] This invention relates to a dry purification method for exhaust gas.

ボイラや廃棄物焼却炉から排出される高温排ガス中には
、硫黄酸化物（ＳＯｘ）、ＨＣ／、ＨＦなどの酸性の有
害物質が通常１０〜２０００１）ｐｍ含まれており、公
害対策上これら物質を除去することが義務付けられてい
る。従来、」二記酸性有害物質の除去方法としては、ア
ルカリ性の吸収剤を含む吸収液ないしはスラリーを湿度
の低下した排ガスと直接接触させて排ガスを洗浄する湿
式法が一般的であった。しかしこの方法の場合、除去率
が高い反面、廃水の処理に苦慮し、排ガスを再加熱する
必要があり、さらに設備費や運転費が高くつくうらみが
あった。High-temperature exhaust gas discharged from boilers and waste incinerators usually contains 10 to 20,001) pm of acidic harmful substances such as sulfur oxides (SOx), HC/HF, and these substances are is required to be removed. Conventionally, as a method for removing acidic harmful substances, a wet method was generally used, in which an absorbing liquid or slurry containing an alkaline absorbent is brought into direct contact with exhaust gas of reduced humidity to clean the exhaust gas. However, although this method has a high removal rate, it is difficult to treat wastewater, the exhaust gas needs to be reheated, and equipment and operating costs are high.

このような点から湿式法に代わって種々の方法が検討さ
れ、たとえば活性炭で有害物質を吸着しついで脱着する
活性炭吸着法や、消石灰スラリーを排ガス中に噴霧する
半乾式法が提案されているが、これらはいずれも高い脱
硝率を得ることができなかった。最近、高温の火炉内や
煙道内に石灰を直接分散させて酸性有害物質を除去する
方法が検討されている。しかしこの方法の場合も吸収剤
である粉体石灰の利用率が低くそのため除去率が低いき
らいがあり、したがって環境規制が極めて緩い特殊な場
合以外にはこの方法は実用化されていなかった。From this point of view, various methods have been considered in place of the wet method; for example, an activated carbon adsorption method in which harmful substances are adsorbed and then desorbed using activated carbon, and a semi-dry method in which slaked lime slurry is sprayed into the exhaust gas have been proposed. However, none of these methods could achieve a high denitrification rate. Recently, a method of removing acidic harmful substances by directly dispersing lime in a high-temperature furnace or flue has been studied. However, even in this method, the utilization rate of powdered lime, which is an absorbent, tends to be low, so the removal rate tends to be low, and therefore this method has not been put to practical use except in special cases where environmental regulations are extremely lax.

上記粉体石灰の利用率が低い理由は以下のとおりである
。すなわち排ガス中の酸性有害物質は生石灰および／ま
たは消石灰よりなる吸収剤とつぎの反応式に従って反応
し、吸収剤に吸収される。The reason why the utilization rate of the powdered lime is low is as follows. That is, acidic harmful substances in the exhaust gas react with an absorbent made of quicklime and/or slaked lime according to the following reaction formula, and are absorbed by the absorbent.

Ｃａ　Ｏ−１−Ｓ　Ｏ２−＋　Ｃａ　Ｓ　Ｏ３Ｃａ（Ｏ
Ｒ）２　＋ＳＯ’２　→ＣａＳＯ３＋Ｈ２ＯＣａＯ＋２
ＨＣ１→ＣａＣｌ２　＋Ｈ２０Ｃａ　（ＯＲ）　２　＋
２ＭＣｌ！→ＣａＣＡ’　２　＋２Ｈ２０ＳＯ３および
ＨＦについても上記反応式に準じて吸収剤に吸収される
。従来の吸収剤は粒径１００ミクロン程度ぜいぜい３０
〜５０ミクロンのものであり、そのため上記反応の速度
論的研究によると、上記酸性物質と吸収剤との反応速度
はすこメξる速いが、酸性物質が吸収剤の粒子内部に拡
散する速度が遅く、反応は粒子の表面ないしは表面から
１〜３ミクロンの部分でしか生ぜれも２０〜３０％以下
にすぎなかった。この場合湿式法と同程度の除去率を１
尋るには、７００℃以上の高温で吸収剤と排ガスの接触
時間を著しく長く保つ必要があるが、このような処理は
全く非実用的なものである。Ca O-1-S O2-+ Ca S O3Ca(O
R)2 +SO'2 →CaSO3+H2OCaO+2
HC1→CaCl2 +H20Ca (OR) 2 +
2MCl! →CaCA' 2 +2H20SO3 and HF are also absorbed by the absorbent according to the above reaction formula. Conventional absorbents have a particle size of about 100 microns at most 30
~50 microns, and therefore, according to kinetic studies of the above reaction, the reaction rate between the acidic substance and the absorbent is much faster, but the rate at which the acidic substance diffuses inside the particles of the absorbent is The reaction was slow, and the reaction occurred only at the surface of the particles or within 1 to 3 microns from the surface, and only less than 20 to 30% of the reaction occurred. In this case, the removal rate is 1
In order to achieve this, it is necessary to maintain the contact time between the absorbent and the exhaust gas at a high temperature of 700° C. or higher for an extremely long time, but such treatment is completely impractical.

本発明者は、上記のような実情に鑑み、湿式法に劣らな
い高い除去率（少なくとも９０チ）を得ることのできる
高温排ガスの乾式浄化法の開発を目的として研究を重ね
た結果、吸収剤の大きさが除去率に大きく影響するとい
う知見を得、この発明を完成するに至った。In view of the above-mentioned circumstances, the inventor of the present invention has conducted extensive research with the aim of developing a dry purification method for high-temperature exhaust gas that can obtain a removal rate as high as that of the wet method (at least 90 cm). This invention was completed based on the knowledge that the size of the particle size greatly affects the removal rate.

この発明による浄化法は、酸性物質を含む高温排ガス中
に粒径１０ミクロン以下の微粒子状のＣａ系吸着剤を分
散させ、ついで排ガスを集塵処理して、酸性物質を吸収
した吸収剤を煤塵とともに除去することを特徴とするも
のである。The purification method according to the present invention involves dispersing fine particulate Ca-based adsorbent with a particle size of 10 microns or less in high-temperature exhaust gas containing acidic substances, and then collecting the exhaust gas to remove the absorbent that has absorbed the acidic substances into soot. It is characterized in that it is removed along with the

どの発明において用いられる吸収剤は、石灰石すなわち
炭酸カルシウム、生石灰すなわち酸化カルシウム、消石
灰すなわち水酸化カルシウムのようなＣａ系吸収剤であ
る。高温ガスの温度は７００〜１２００℃好ましくは９
００〜１０５０℃である。ガス湿度が低すぎると、生石
灰または消石灰が排ガス中の炭酸ガスと反応して多量の
炭酸カルシウムを生成し、逆にガス温度が高すぎると、
Ｃａ系吸収剤が焼結して反応性を損なう。したがってガ
ス温度は上記７００〜１２００℃の範囲に限定される。The absorbents used in all inventions are Ca-based absorbents such as limestone or calcium carbonate, quicklime or calcium oxide, and slaked lime or calcium hydroxide. The temperature of the high temperature gas is 700-1200℃, preferably 9
00-1050°C. If the gas humidity is too low, quicklime or slaked lime will react with carbon dioxide gas in the exhaust gas to produce a large amount of calcium carbonate, while if the gas temperature is too high,
The Ca-based absorbent sinters and impairs reactivity. Therefore, the gas temperature is limited to the above range of 700 to 1200°C.

微粒子状のＣａｇ＆収剤としては、粒径１０ミクロン以
下のものが用いられる。また微粒子状吸収剤としては、
シャープな粒径分布曲線を描くものが好ましい。吸収剤
の粒径は小さくなればなるほどよいが、ジェットミルの
運転費を考慮に入れると、５ミクロン以下でシャープな
粒径分布曲線を有する吸収剤が特に好ましい。粗い粒子
を含む吸収剤は好ましくない。たとえば粒径４０ミクロ
ンの粒子を１０重量係含む吸収剤の場合、除去率は約８
％低下する。As the particulate Cag & collection agent, those having a particle size of 10 microns or less are used. In addition, as a particulate absorbent,
It is preferable that the particle size distribution curve is sharp. The smaller the particle size of the absorbent, the better; however, taking into consideration the operating costs of a jet mill, an absorbent having a sharp particle size distribution curve of 5 microns or less is particularly preferred. Absorbents containing coarse particles are not preferred. For example, for an absorbent containing 10 particles by weight of 40 microns, the removal rate is approximately 8
%descend.

吸収剤として石灰石または消石灰を用いた場合、これら
はつぎの反応式のように高温ガスによって熱分解を受け
てＣａＯを生じる。When limestone or slaked lime is used as an absorbent, it undergoes thermal decomposition by high temperature gas to produce CaO as shown in the following reaction formula.

Ｃａ　ＣＯ３→Ｃａ　Ｏ−１−ＣＯ２ｍ　−ｅ　１ｌ）
Ｃａ　（ＯＨ）　２−＋　Ｃａ　Ｑ　十Ｈ２０＠　ａ　
−＋２１生じたＣａＯはつきの反応式のように酸性物質
と反応する。Ca CO3 → Ca O-1-CO2m -e 1l)
Ca (OH) 2-+ Ca Q 1H20@a
-+21 The generated CaO reacts with an acidic substance as shown in the following reaction formula.

ＣａＯ＋５−０２→ＣａＳＯ３＠１１＠＋３）Ｃａ　Ｏ
−Ｊ−Ｓ　Ｏ３−＋　Ｃａ　Ｓ　Ｏ４ｍ　ａ　ｍ　（４
１ＣａＯ＋２Ｉ（ＣＩ！−＋ＣａＣＪ２　＋Ｈ２０５ｅ
ａ（５）ＣａＯ＋２ＨＦ’−＋ＣａＦ２＋Ｈ２０拳ｅｅ
ｆ６）式（３）で生じたＣａＳＯ３はさらにつぎのよう
に変化する。CaO+5-02→CaSO3@11@+3)CaO
-J-S O3-+ Ca S O4 m a m (4
1CaO+2I(CI!-+CaCJ2 +H205e
a(5) CaO+2HF'-+CaF2+H20 fistee
f6) CaSO3 generated in equation (3) further changes as follows.

Ｃａ５Ｏ３−）−１／　０２−＋ＣａＳＯ４＠＠＠　（
７＋この発明による浄化法のフローは第１図に示すとお
りである。同図において、粉砕機（１）としてはジェッ
トミルが好ましく用いられるが、これに限定されない。Ca5O3-)-1/ 02-+CaSO4@@@ (
7+ The flow of the purification method according to the present invention is as shown in FIG. In the figure, a jet mill is preferably used as the crusher (1), but the crusher is not limited thereto.

ジェットミルにおいて、石灰石、生石灰または消石灰の
粉体が高圧空気または過熱蒸気の気流エネルギーによっ
て互いに衝突させられて微粒子化せられる。微粒子状の
吸収剤は高圧空気または過熱蒸気とともに分散機（２）
において、高温排ガス中に直接導入され、これの気流エ
ネルギーによって排ガス中にＭＪ−に分散される。In a jet mill, limestone, quicklime, or slaked lime powder is atomized by colliding with each other by the airflow energy of high-pressure air or superheated steam. The particulate absorbent is sent to a disperser (2) along with high pressure air or superheated steam.
In the step, it is directly introduced into the high-temperature exhaust gas, and its airflow energy disperses MJ- into the exhaust gas.

分散した微粒子状の吸収剤は二次凝集をきたすおそれが
なく、上述した反応式に従って排ガス中の酸性有害物質
を吸収する。集塵装置（３）としてはバグフィルタが好
ましいが、これに代えで電気集塵機などを用いてももち
ろんよい。酸性物質を吸収した微粒子状の吸収剤と煤塾
の混合物はバグフィルタによって排ガスから除去される
。この場合バグフィルタ内部においても高温排ガスと吸
収剤の接触時間がかなり長く保たれ、酸性物質の吸収が
一層促進される。The dispersed particulate absorbent absorbs acidic harmful substances in the exhaust gas according to the reaction formula described above without causing secondary agglomeration. Although a bag filter is preferred as the dust collector (3), an electric dust collector or the like may of course be used instead. A mixture of particulate absorbent and soot that has absorbed acidic substances is removed from the exhaust gas by a bag filter. In this case, the contact time between the high-temperature exhaust gas and the absorbent is maintained for a considerably long time even inside the bag filter, and the absorption of acidic substances is further promoted.

実施例１第２図に示す実験装置において、排ガス中のＳＯコ濃度
およびＨＣＩ濃度がそれぞれ約１１０００ＰＰになるよ
うに、二硫化炭素およびエチレンジ７０ライドが添加さ
れた燃料が、約１５０ＯＮｄ／Ｈの排ガスを発生する燃
焼炉α工）に供給された。炉（１１）で発生した温度約
１０５０℃の排ガスは、煙道（１２）のベンチュリ部（
１２ａ）を介して反応帯域（１３）に導かれた。排ガス
は約１０００℃に保たれた同帯域（１３）内に約１．２
秒間滞留した後、空気予熱器０４）ついでガスクーラ０
５１に通されて前者で空気と熱交換され後者で冷却され
て、最後にサンクロン集塵器口θに通されて除塵され、
系外に放出された。Example 1 In the experimental apparatus shown in FIG. 2, a fuel to which carbon disulfide and ethylene di70ride were added so that the SO concentration and HCI concentration in the exhaust gas were each about 11000 PP was used to reduce the exhaust gas concentration to about 150 ONd/H. was supplied to the combustion furnace (α) which generates The exhaust gas generated in the furnace (11) with a temperature of about 1050°C is passed through the venturi part (12) of the flue (12).
12a) into the reaction zone (13). The exhaust gas is kept at about 1,000℃ in the same zone (13).
After staying for seconds, air preheater 04) then gas cooler 0
51, heat exchanged with air in the former, cooled in the latter, and finally passed through the Sunclone dust collector port θ to remove dust.
Released outside the system.

石灰石はジェットミル（１７１で圧縮空気によって微粒
子化され、得られた微粒子状の吸収剤がジェットミル０
′７）からベンチュリ部（ＩＺａ）の入口側に直接導入
された。石灰石の供給量は化学当量比（供給した吸収剤
中のＣａＣＯ３のモル数）／（反応したＳＯ２のモル数
十反応したＨ（Ｊ’のモル数Ｘ　１／２　）　＝’ｌで
あった。The limestone is atomized by compressed air in a jet mill (171), and the resulting fine particulate absorbent is passed through a jet mill (171).
'7) directly into the inlet side of the venturi section (IZa). The amount of limestone supplied was a chemical equivalent ratio (number of moles of CaCO3 in the supplied absorbent)/(several tens of moles of reacted SO2, number of moles of reacted H (number of moles of J' X 1/2 ) ='l.

燃焼炉（ＩＩ）の出口および空気予熱器（１４）の入［
」においてそれぞれ排ガスのサンプリングを行ない、サ
ンプリングガスのＳＯ２濃度およびＨＣＩ濃度をそれぞ
れ分析した。分析値からＳＯ２除去率およびＩ（ＣＡ’
除去率を得、除去率と粒径の関係を第３■ 図に示した。なお同表中の吸収剤の粒径の表示は、その
表示の粒径を有する微粒子が９５チ以上含まれることを
意味する。The outlet of the combustion furnace (II) and the inlet of the air preheater (14) [
Exhaust gas was sampled at each of these stations, and the SO2 concentration and HCI concentration of the sampled gas were analyzed. From the analytical values, SO2 removal rate and I(CA'
The removal rate was obtained, and the relationship between removal rate and particle size is shown in Figure 3. In addition, the indication of the particle size of the absorbent in the same table means that 95 inches or more of fine particles having the indicated particle size are included.

以上のとおりで、この発明による乾式浄化法では、粒径
１０ミクロン以下の微粒子状の吸収剤を用いて高温排ガ
スを処理するので、　ｔＪｌ：ガスに含まれる酸性有害
物質を数秒〜数分という鎧い処理時間で吸収剤に吸収さ
せることができ、したがって高い除去率で酸性物質を除
去することができる。As described above, in the dry purification method according to the present invention, high-temperature exhaust gas is treated using a particulate absorbent with a particle size of 10 microns or less. The acidic substances can be absorbed into the absorbent in a short processing time, and therefore the acidic substances can be removed with a high removal rate.

【図面の簡単な説明】[Brief explanation of drawings]

第１図は排ガス浄化法のフロー図、第２図は実験装置の
フロー図、第３図は粒径と除去率の関係を示すグラフで
ある。以　上外４名FIG. 1 is a flowchart of the exhaust gas purification method, FIG. 2 is a flowchart of the experimental apparatus, and FIG. 3 is a graph showing the relationship between particle size and removal rate. 4 people other than the above

Claims

【特許請求の範囲】[Claims]

酸性物質を含む高温排ガス中に粒径１０ミクロン以下の
微粒子状のＣａ系吸収剤を分散させ、ついで排ガスを集
塵処理して、酸性物質を吸収した吸収剤を煤塵とともに
除去することを特徴とする、排ガスの乾式浄化法。It is characterized by dispersing fine particulate Ca-based absorbent with a particle size of 10 microns or less in high-temperature exhaust gas containing acidic substances, and then subjecting the exhaust gas to dust collection treatment to remove the absorbent that has absorbed acidic substances together with soot and dust. A dry purification method for exhaust gas.