JP4259633B2

JP4259633B2 - Method for producing smoke treatment agent

Info

Publication number: JP4259633B2
Application number: JP24295197A
Authority: JP
Inventors: 務上野; 朋弘石塚; 宏明土合; 真一郎中村
Original assignee: Hokkaido Electric Power Co Inc
Current assignee: Hokkaido Electric Power Co Inc
Priority date: 1997-09-08
Filing date: 1997-09-08
Publication date: 2009-04-30
Anticipated expiration: 2017-09-08
Also published as: JPH1176808A

Description

【０００１】
【発明の属する技術分野】
本発明は排煙処理剤さらに詳しくは石灰、重油等の燃料および各種廃棄物の燃焼、焙焼乾燥等に伴う排ガスの処理剤の製造方法に関する。
【０００２】
【従来の技術】
本発明者らはすでに石灰、石膏系排煙処理剤およびその製造方法について多くの提案を行ってきた（例えば特公平３−５９７３７号公報）。しかし、これらにおいては生石灰をあらかじめ水にとかして石灰乳として使用した（特公平７−２４７６３号公報）以外は原料に比較的高価な消石灰を使用し、原料混合処理後の養生時間が長いという問題点があった。
【０００３】
【発明が解決しようとする課題】
本発明の目的は上記従来の排煙処理剤の改良された製造方法を提供することである。
【０００４】
【課題を解決するための手段】
本発明者らは種々検討の結果、酸化カルシウム源として消石灰より安価な生石灰を用い、生石灰の消化時にシリカを含有する物質を添加することより非常に活性の高い生成物、アモルファスなカルシウムシリケート、が生成し、これが排煙処理剤の活性に寄与すること、および、この消化時に石膏がある量以上共存すると、活性物質の生成が妨げられることを見出した。すなわち本発明は次のようである。
【０００５】
１．酸化カルシウム、二酸化ケイ素、酸化アルミニウムおよび石膏を少なくとも含む排煙処理剤の製造方法において、生石灰に、非結晶性二酸化ケイ素を含む物質を、生石灰中の酸化カルシウム１００重量部当り二酸化ケイ素として２．４〜４５重量部になるように加え、水を加えて消化反応を行わせ、ついで上記消化反応により生石灰が消化した消石灰が排煙処理剤に対して３５％含有する組成になるよう酸化アルミニウム、石膏、および必要により二酸化ケイ素を含む物質を混合し、混練し、６〜１０ｍｍに整粒することを特徴とする排煙処理剤の製造方法。
【０００６】
２．上記非結晶性二酸化ケイ素を含む物質が石膏を含み、この際前記消化反応を行わせる系内に、石膏が生石灰中の酸化カルシウム１００重量部当り９重量部以下になるよう調整することを特徴とする上記１に記載の製造方法。
【０００７】
３．排煙処理剤中の酸化カルシウム、二酸化ケイ素、酸化アルミニウムおよび石膏が、生石灰、石炭灰および使用済脱硫剤より供給される上記１または２に記載の製造方法。
【０００８】
４．前記非結晶性二酸化ケイ素を含む物質が、ベントナイトまたは珪藻土である上記１に記載の製造方法。
【０００９】
【発明の実施の形態】
本発明で使用する生石灰は市販のものが利用でき、水和反応を促進するためには粉状物よりも３〜５ｍｍの粒状のものが好ましい。
【００１０】
非結晶性二酸化ケイ素を含む物質は、たとえば、含水ケイ酸、メタケイ酸アルミニウム、ケイ酸カルシウムおよび水ガラス等反応性の二酸化ケイ素を含有する化合物、クリストバライト、トリジマイト、カオリン、ベントナイト、タルク、パーライト、シラス、珪藻土、火山灰などの天然物、および高炉スラグ、石炭灰、使用済排煙処理剤などの副産物などがあげられる。工業薬品以外の原料で、本発明の排煙処理剤に使用可能なものの化学組成の一例を表１に示す。
【００１１】
【表１】

本発明の製造方法における特徴はまず上記非結晶性二酸化ケイ素を含む物質を、生石灰の水による消化反応の際に共存させて、高活性の生成物（アモルファスなカルシウムシリケート）を生成させることである。この際、生石灰に加えるべき非結晶性二酸化ケイ素含有物質の割合は、生石灰中の酸化カルシウム１００重量部当り、二酸化ケイ素として０．０５〜６０重量部になるようにする。高純度の二酸化ケイ素を含む物質、例えば試薬の酸化ケイ素の場合であれば０．０５重量部でも、排煙処理活性に充分寄与することができるが、０．０５重量部未満では、その効果は期待できない。また、８０重量部をこえてもその効果は逓減し、不経済である。低純度の二酸化ケイ素含有物、例えば表１に示した原料の場合においても、上記６０重量部以下の範囲の使用で排煙処理に関し充分な効果を得ることができる。
【００１２】
上記非結晶性二酸化ケイ素共存における生石灰の消化反応の温度はきわめて急激に上昇し、沸騰状態になる。反応温度を故意に下げると、酸化ケイ素の活性化反応の進行が妨げられる。この反応温度は反応装置の保温、使用する水の温度の選定、生石灰の消化熱（６５．２ＫＪ／ｍｏｌＣａＯ）の利用等によって合理的に約８０℃以上に保持することが好ましい。
【００１３】
消化反応に使用する水の量は、原料生石灰１００重量部当り７０〜２００重量部である。
【００１４】
上記非結晶性二酸化ケイ素共存の生石灰の消化反応開始は、反応系の温度の急上昇により確認できるが、反応開始後数分ないし数１０分の間に、すでに反応系内にある物質も含めて所定の排煙処理剤組成になるように、酸化アルミニウム、石膏および必要により二酸化ケイ素を含む物質（原料）を加えて混合・混練する。
【００１５】
ここに排煙処理剤の組成としては、公知の、例えば特開平４−１９０８２０号公報記載の下記組成から選ぶことができる。
【００１６】
ＣａＯ２〜８０％
ＣａＳＯ₄ ０．１〜７０％
ＳｉＯ₂ ５〜８０％
Ａｌ₂Ｏ₃ ５〜７０％
【００１７】
上記混合物を、必要により粉砕または粉砕成形後、公知の方法で蒸気養生あるいはスラリー養生する。養生工程は処理剤中の活性物質の生成に必要な水分は充分に与えられた状態を経て活性化するためには不可欠な工程である。この養生は温度４０℃〜１８０℃、相対湿度５０〜１００％で行う。場合によっては養生を２段階で行い、第１段の養生後成形造粒、粉砕し、さらにほぼ同一条件で再度養生することもできる。
【００１８】
本発明の方法によれば下記実験例で示すように従来法にくらべてはるかに短時間の養生で高活性の排煙処理剤を得ることができた。
【００１９】
実験例
消石灰原料乾式脱硫剤（ＡＨ）は、消石灰３５重量部、石炭灰３５重量部、および石膏源としての使用済脱硫剤３０重量部を水４０重量部とともに混合・混練したのち約６ｍｍφ×１０ｍｍのペレット状に成形し、水蒸気雰囲気下で養生（０〜１０．５時間）を行い、乾燥させて調製した。
【００２０】
一方生石灰原料乾式脱硫剤（ＡＯ）は、生石灰を消石灰換算３５重量部、石炭灰１５重量部に水５０重量部を混合・消化した後使用済脱硫剤５０重量部を加えて混練し、以下ＡＨと同様の操作によって調製した。
【００２１】
脱硫性能試験では、常圧流通系において模擬排ガス（ＳＯ₂：２２５０ｐｐｍ，ＮＯ：７００ｐｐｍ，ＣＯ₂：１３％，Ｈ₂Ｏ：１０％，Ｎ₂：バランス）を用い、温度１３０℃、ＳＶ１０００ｈｒ^ー1（試料６０ｃｃ）の条件で、脱硫効率が８０％以上を維持する時間（ｍｉｎ．）を測定し図１の結果を得た。図１に示すようＡＯはＡＨにくらべ約１／２の養生時間で充分な脱硫活性を示した。
【００２２】
上記石炭灰および使用済脱硫剤は前記表１に示した組成とほぼ同一の組成を有するものである。
【００２３】
なお、消石灰、生石灰を消化させて調製した消石灰、および生石灰と石炭灰を混合・消化させて調製した消石灰の比表面積および脱硫性能試験の結果を表２に示した。これを見ると、生石灰と石炭灰を混合・消化させた試料は、比表面積および脱硫性能が著しく向上していることがわかる。このことから、消化熱を利用して、生石灰と石炭灰が反応することによって脱硫活性向上に寄与する物質を生成すると考えられた。
【００２４】
生成した物質を同定するために、各試料のＸＰＳ測定を行った。石炭灰のＳｉ_2Pのピークは１０３．０ｅＶに現れ、生石灰と石炭灰を混合・消化した試料は、１０１．５ｅＶにピークが現れた。解析の結果、１０３．０ｅＶのピークは石炭灰中に含まれるムライトに由来するものであり、１０１．５ｅＶのピークはカルシウムシリケートに帰属されるものと考えられ、このことから、カルシウムシリケートの形成が脱硫剤の活性向上に寄与したものと推察される。
【００２５】
【表２】

【００２６】
なお、Ｕ．Ｓ．Ｐ．４，９３１，２６４号には消石灰とフライアッシュのスラリー化によるカルシウムシリケートの生成について詳細に開示され、このスラリーによる脱硫方法がクレームされているが、本発明の方法は、生石灰を使用し、水の使用割合もはるかに少なくスラリー状態を経ないことから、この従来技術とは全く異質のものである。
【００２７】
〔実施例〕
以下、実施例をもって本発明を具体的に説明するが、本発明はこれらの実施例に限定されるものではない。
【００２８】
実施例１
市販の生石灰（ＣａＯ純度９８％）２６．５重量部に非結晶性二酸化ケイ素を含む物質として表１に示した使用済排煙処理剤０．５重量部（実施例１−１）、１．０重量部（実施例１−２）、２．０重量部（実施例１−３）、５．０重量部（実施例１−４）を添加（一次添加）し、１５℃の水を全原料乾物の５０％に相当する量だけ加え、蒸発しないように直ちに容器に蓋をして消化反応を行わせた。
混合物の温度が急激に上昇（消化開始）してから２分後に、前記使用済排煙処理剤を一次添加分と合わせて３０重量部になる量、および表１に示した細粒石炭灰（以下たんに石炭灰とする）３５重量部を添加（二次添加）し、約１０分間混練した。消化開始から混練終了までの混合物の温度は３００℃〜９０℃の範囲に保たれた。
得られた混合物を６ｍｍφの押出し成形機を用いて成形し、１００℃常圧で５時間蒸気養生し、２００℃で２時間乾燥後、６〜１０ｍｍに整粒して排煙処理剤を得た。
性能試験（脱ＳＯ₂および脱ＮＯ_X）は、前記実験例に示した条件で行い各性能は、８０％の除去率を維持した時間を、使用した生石灰中の酸化カルシウムのカルシウムｇ当りに換算した値（ｍｉｎ／ｇ−Ｃａ）で表３に示した。
【００２９】
【表３】

【００３０】
比較例１
一次添加および二次添加の使用済排煙処理剤の量を表３のように変えた以外は実施例１と同様にして排煙処理剤を得、その活性を測定して表３に示した。
【００３１】
表３によれば、一次添加における使用済排煙処理剤由来の石膏の量がこの方法において制限要因になることは明らかである。
【００３２】
実施例２
実施例１において、２分後の二次添加を６０分後の二次添加に変えた以外は実施例１と同様にして排煙処理剤を得た。この場合消化開始から二次添加までの混合物の温度は３００℃〜９０℃の範囲であり、二次添加後の約１０分間の混練においても９０℃〜３０℃の範囲に保たれた。
実施例１と同様の方法で得られた性能試験の結果を表４に示す。
【００３３】
【表４】

【００３４】
実施例１（表３）と比較すると二次添加のタイミングがおくれると活性がやや低下する傾向がうかがわれる。
【００３５】
実施例３
実施例１においては、非結晶性二酸化ケイ素を含む物質（一次添加物質）として使用済排煙処理剤を使用したが、本例では、石炭灰を使用し、二次添加物質として、さらに石炭灰と、使用済排煙処理剤を使用した。
排煙処理剤の調製の操作およびその間の温度も実施例１と同様である。
原料の使用割合、得られた剤の性能試験結果を表５に示す。
【００３６】
【表５】

【００３７】
実施例４
実施例３においては、実施例１と同様に二次添加を消化開始の２分後としたが、本例では、実施例２と同様に６０分後とし、使用原料の添加順序、使用割合は実施例３と同様にした。この場合、消化開始から二次添加までの混合物の温度は３００℃〜９０℃の範囲であり、二次添加後の約１０分間の混練においても９０℃〜３０℃の範囲に保たれた。得られた剤の性能試験結果を表６に示す。
【００３８】
【表６】

【００３９】
実施例５
実施例３において石炭灰の代わりに表１に示したベントナイトを用い、一次添加に１重量部、二次添加に３４重量部を用いた以外は実施例３と同様にして表５に示す性能を有する排煙処理剤を得た。
【００４０】
実施例６
実施例５においてベントナイトの代わりに表１に示した珪藻土を用いた以外は実施例５と同様にして表５に示す性能を有する排煙処理剤を得た。
【００４１】
比較例２
市販の消石灰（ＣａＯ含有率９８％）３５重量部、前記使用済排煙処理剤３０重量部、および前記石炭灰３５重量部を混合し、５０重量部の１５℃の水で１０分間混練した。
得られた混合物を６ｍｍφの押出し成形機を用いて成形し、１００℃常圧で１０時間蒸気養生し、２００℃で２時間乾燥後、６〜１０ｍｍに整粒して排煙処理剤を得た。
実施例１と同様に性能試験を行い、結果を表７に示した。
【００４２】
比較例３
実施例１で使用した生石灰２６．５重量部を実施例１と同量の１５℃の水で水分が蒸発しないように蓋をして消化し、消化開始から６０分後に実施例で使用した使用済排煙処理剤および石炭灰を、それぞれ３０重量部および３５重量部混合し、約１０分間混練した。
得られた混合物を６ｍｍφの押出し成形機を用いて成形し、１００℃常圧で５時間（比較例３−１）および、１０時間（比較例３−２）蒸気養生し、２００℃で２時間乾燥後、６〜１０ｍｍに整粒して排煙処理剤を得た。
実施例と同様に性能試験を行い、結果を表７に示した。
【００４３】
比較例４
実施例１で使用した生石灰、使用済排煙処理剤および石炭灰をそれぞれ２６．５重量部、３０重量部および３５重量部の割合で混合し、実施例１と同量の１５℃の水で水分が蒸発しないようにふたをして２０分間消化し、混練した。
得られた混合物を６ｍｍφの押出し成形機を用いて成形し、１００℃常圧で５時間（比較例４−１）および１０時間（比較例４−２）蒸気養生し、２００℃で２時間乾燥後、６〜１０ｍｍに整粒して排煙処理剤を得た。
実施例１と同様に性能試験を行い、結果を表７に示した。
【００４４】
【表７】

【００４５】
【発明の効果】
本発明の製造方法によれば、従来の方法で使用されていた原料の石灰源をより安価な生石灰に変え、しかもその消化反応熱を利用して他の原料中の二酸化ケイ素の活性化を図り排煙処理剤としての活性を向上させることができるため、この方法は石灰−石膏系排煙処理剤の製造に広く適用できその効果は大きい。
【図面の簡単な説明】
【図１】消石灰使用脱硫剤（ＡＨ）と、生石灰使用脱硫剤（ＡＯ）の活性の比較例を示した図である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a flue gas treating agent, and more particularly to a method for producing a flue gas treating agent accompanying combustion, roasting and drying of fuels such as lime and heavy oil and various wastes.
[0002]
[Prior art]
The present inventors have already made many proposals on lime, gypsum-based smoke treatment agents and methods for producing the same (for example, Japanese Patent Publication No. 3-59737). However, in these, quick lime is dissolved in water in advance and used as lime milk (Japanese Patent Publication No. 7-24863), and relatively expensive slaked lime is used as a raw material, and the curing time after the raw material mixing treatment is long. There was a point.
[0003]
[Problems to be solved by the invention]
An object of the present invention is to provide an improved method for producing the above conventional flue gas treating agent.
[0004]
[Means for Solving the Problems]
As a result of various studies, the present inventors have used quick lime that is cheaper than slaked lime as a calcium oxide source, and a product that is much more active than adding a substance containing silica during digestion of quick lime, amorphous calcium silicate, It was found that this contributes to the activity of the smoke treatment agent, and that the production of the active substance is hindered when a certain amount of gypsum coexists during the digestion. That is, the present invention is as follows.
[0005]
1. In the method for producing a flue gas treating agent containing at least calcium oxide, silicon dioxide, aluminum oxide, and gypsum, 2.4 wt. Of a substance containing amorphous silicon dioxide as quick lime as silicon dioxide per 100 parts by weight of calcium oxide in quick lime. It added to a 45 parts by weight, by adding water to perform the digestion reaction, then aluminum oxide so that the composition containing 35% with respect to hydrated lime flue gas treating agent quicklime was digested by the digestion reaction, the gypsum And, if necessary, a substance containing silicon dioxide is mixed, kneaded, and sized to 6 to 10 mm .
[0006]
2. The substance containing amorphous silicon dioxide contains gypsum, and in this case, the gypsum is adjusted to be 9 parts by weight or less per 100 parts by weight of calcium oxide in quick lime in the system in which the digestion reaction is performed. The manufacturing method according to 1 above.
[0007]
3. 3. The production method according to 1 or 2 above, wherein the calcium oxide, silicon dioxide, aluminum oxide and gypsum in the flue gas treating agent are supplied from quick lime, coal ash and a used desulfurizing agent.
[0008]
4). 2. The production method according to 1 above, wherein the substance containing amorphous silicon dioxide is bentonite or diatomaceous earth.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
As the quicklime used in the present invention, commercially available ones can be used, and in order to accelerate the hydration reaction, a granular one having a particle size of 3 to 5 mm is preferable to a powdery one.
[0010]
Substances containing amorphous silicon dioxide include, for example, hydrous silicic acid, aluminum metasilicate, calcium silicate and water glass, reactive silicon dioxide containing compounds, cristobalite, tridymite, kaolin, bentonite, talc, perlite, shirasu Natural products such as diatomaceous earth and volcanic ash, and by-products such as blast furnace slag, coal ash and spent smoke treatment agents. Table 1 shows an example of the chemical composition of raw materials other than industrial chemicals that can be used for the smoke treatment agent of the present invention.
[0011]
[Table 1]

A feature of the production method of the present invention is that a high-activity product (amorphous calcium silicate) is produced by coexisting a substance containing amorphous silicon dioxide in the digestion reaction of quicklime with water. . At this time, the ratio of the amorphous silicon dioxide-containing substance to be added to quicklime is 0.05 to 60 parts by weight as silicon dioxide per 100 parts by weight of calcium oxide in quicklime. In the case of a substance containing high-purity silicon dioxide, such as silicon oxide as a reagent, even 0.05 parts by weight can sufficiently contribute to the smoke treatment activity, but if it is less than 0.05 parts by weight, the effect is I can't expect it. Moreover, even if it exceeds 80 weight part, the effect diminishes and it is uneconomical. Even in the case of a low-purity silicon dioxide-containing material, for example, the raw materials shown in Table 1, a sufficient effect can be obtained with respect to the flue gas treatment when used in the range of 60 parts by weight or less.
[0012]
The temperature of the digestion reaction of quick lime in the presence of the amorphous silicon dioxide rises very rapidly and becomes a boiling state. If the reaction temperature is intentionally lowered, the activation reaction of silicon oxide is prevented. This reaction temperature is preferably kept at about 80 ° C. or more reasonably by keeping the temperature of the reaction apparatus, selecting the temperature of water to be used, utilizing the heat of digestion of quicklime (65.2 KJ / mol CaO), and the like.
[0013]
The amount of water used for the digestion reaction is 70 to 200 parts by weight per 100 parts by weight of raw quicklime.
[0014]
The start of the digestion reaction of quick lime coexisting with the amorphous silicon dioxide can be confirmed by a rapid rise in the temperature of the reaction system, but within a few minutes to several tens of minutes after the start of the reaction, including substances already in the reaction system. A material (raw material) containing aluminum oxide, gypsum and, if necessary, silicon dioxide is added and mixed and kneaded so that the composition of the flue gas treating agent is obtained.
[0015]
Here, the composition of the flue gas treating agent can be selected from known compositions described in, for example, JP-A-4-190820.
[0016]
CaO 2 -80%
CaSO ₄ 0.1 to 70%
SiO ₂ 5 ~80%
Al ₂ O ₃ 5 to 70%
[0017]
If necessary, the mixture is crushed or crushed and then steam-cured or slurry-cured by a known method. The curing process is an indispensable process for activating the moisture necessary for the production of the active substance in the treatment agent through a state where the moisture is sufficiently applied. This curing is performed at a temperature of 40 ° C. to 180 ° C. and a relative humidity of 50 to 100%. In some cases, the curing can be carried out in two stages, and after the first stage of curing, granulation and pulverization can be carried out, and further curing can be carried out under substantially the same conditions.
[0018]
According to the method of the present invention, as shown in the following experimental examples, it was possible to obtain a highly active smoke treatment agent with a much shorter curing time as compared with the conventional method.
[0019]
Experimental Example Slaked lime raw material dry desulfurization agent (AH) is about 6 mmφ × 10 mm after mixing and kneading 35 parts by weight of slaked lime, 35 parts by weight of coal ash, and 30 parts by weight of used desulfurization agent as a gypsum source together with 40 parts by weight of water. It was molded into a pellet shape, cured (0 to 10.5 hours) in a steam atmosphere, and dried to prepare.
[0020]
On the other hand, quick lime raw material dry desulfurization agent (AO) is mixed and digested with 35 parts by weight of quick lime in terms of slaked lime, 15 parts by weight of coal ash and 50 parts by weight of water. It was prepared by the same operation.
[0021]
In the desulfurization performance test, simulated exhaust gas (SO ₂ : 2250 ppm, NO: 700 ppm, CO ₂ : 13%, H ₂ O: 10%, N ₂ : balance) was used in a normal pressure flow system, the temperature was 130 ° C., and SV 1000 hr ^−1. The time (min.) During which the desulfurization efficiency was maintained at 80% or more was measured under the conditions of (sample 60 cc), and the result of FIG. 1 was obtained. As shown in FIG. 1, AO showed sufficient desulfurization activity with a curing time of about 1/2 compared to AH.
[0022]
The coal ash and the used desulfurization agent have substantially the same composition as that shown in Table 1 above.
[0023]
Table 2 shows the specific surface area and results of the desulfurization performance test of slaked lime, slaked lime prepared by digesting quick lime, and slaked lime prepared by mixing and digesting quick lime and coal ash. From this, it can be seen that the specific surface area and desulfurization performance of the sample mixed and digested with quicklime and coal ash are remarkably improved. From this, it was thought that the substance which contributes to desulfurization activity improvement is produced | generated when quick lime and coal ash react using digestion heat.
[0024]
In order to identify the produced substance, XPS measurement of each sample was performed. The peak of Si _2P in coal ash appeared at 103.0 eV, and the sample obtained by mixing and digesting quick lime and coal ash showed a peak at 101.5 eV. As a result of analysis, the peak of 103.0 eV is derived from mullite contained in coal ash, and the peak of 101.5 eV is considered to be attributed to calcium silicate. From this, formation of calcium silicate is It is assumed that it contributed to the improvement of the activity of the desulfurization agent.
[0025]
[Table 2]

[0026]
In addition, U.S. S. P. No. 4,931,264 discloses in detail the formation of calcium silicate by slurrying slaked lime and fly ash, and claims a method for desulfurization with this slurry. The method of the present invention uses quick lime, This is quite different from this prior art because the ratio of the use of is much less and does not go through a slurry state.
[0027]
〔Example〕
EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited to these Examples.
[0028]
Example 1
Commercially used quicklime (CaO purity 98%) 26.5 parts by weight of used smoke treatment agent shown in Table 1 as a substance containing amorphous silicon dioxide 0.5 part by weight (Example 1-1), 0 parts by weight (Example 1-2), 2.0 parts by weight (Example 1-3), 5.0 parts by weight (Example 1-4) were added (primary addition), and water at 15 ° C. was completely added. An amount corresponding to 50% of the raw material dry matter was added, and the vessel was immediately capped to cause the digestion reaction so as not to evaporate.
2 minutes after the temperature of the mixture suddenly rises (starts digestion), the amount of the spent smoke treatment agent combined with the primary addition is 30 parts by weight, and fine coal ash shown in Table 1 ( 35 parts by weight (hereinafter simply referred to as coal ash) was added (secondary addition) and kneaded for about 10 minutes. The temperature of the mixture from the start of digestion to the end of kneading was kept in the range of 300 ° C to 90 ° C.
The obtained mixture was molded using an extrusion molding machine of 6 mmφ, steam-cured at 100 ° C. and normal pressure for 5 hours, dried at 200 ° C. for 2 hours, and then sized to 6 to 10 mm to obtain a flue gas treating agent. .
Performance tests (de-SO ₂ and de-NO _x ) were performed under the conditions shown in the above experimental examples, and each performance was calculated by converting the time during which the removal rate of 80% was maintained per gram of calcium oxide in calcium oxide used. The values (min / g-Ca) are shown in Table 3.
[0029]
[Table 3]

[0030]
Comparative Example 1
Except for changing the amount of spent smoke treatment agent for primary addition and secondary addition as shown in Table 3, a smoke treatment agent was obtained in the same manner as in Example 1, and its activity was measured and shown in Table 3. .
[0031]
According to Table 3, it is clear that the amount of gypsum derived from the used flue gas treating agent in the primary addition becomes a limiting factor in this method.
[0032]
Example 2
In Example 1, a flue gas treating agent was obtained in the same manner as in Example 1 except that the secondary addition after 2 minutes was changed to the secondary addition after 60 minutes. In this case, the temperature of the mixture from the start of digestion to the secondary addition was in the range of 300 ° C. to 90 ° C., and was maintained in the range of 90 ° C. to 30 ° C. even during the kneading for about 10 minutes after the secondary addition.
Table 4 shows the results of the performance test obtained by the same method as in Example 1.
[0033]
[Table 4]

[0034]
Compared to Example 1 (Table 3), it can be seen that the activity tends to decrease slightly when the timing of secondary addition is set.
[0035]
Example 3
In Example 1, the spent flue gas treating agent was used as the substance containing amorphous silicon dioxide (primary additive substance), but in this example, coal ash was used, and the secondary additive substance was further coal ash. And used spent flue gas treatment agent.
The operation for preparing the flue gas treating agent and the temperature during the preparation are the same as in Example 1.
Table 5 shows the ratio of raw materials used and the performance test results of the obtained agent.
[0036]
[Table 5]

[0037]
Example 4
In Example 3, the secondary addition was performed 2 minutes after the start of digestion as in Example 1. However, in this example, 60 minutes was performed in the same manner as in Example 2, Same as Example 3. In this case, the temperature of the mixture from the start of digestion to the secondary addition was in the range of 300 ° C. to 90 ° C., and was maintained in the range of 90 ° C. to 30 ° C. even during the kneading for about 10 minutes after the secondary addition. Table 6 shows the performance test results of the obtained agent.
[0038]
[Table 6]

[0039]
Example 5
The performance shown in Table 5 was obtained in the same manner as in Example 3 except that bentonite shown in Table 1 was used instead of coal ash in Example 3, and 1 part by weight was used for primary addition and 34 parts by weight was used for secondary addition. A flue gas treating agent was obtained.
[0040]
Example 6
In Example 5, a smoke treatment agent having the performance shown in Table 5 was obtained in the same manner as in Example 5 except that diatomaceous earth shown in Table 1 was used instead of bentonite.
[0041]
Comparative Example 2
35 parts by weight of commercially available slaked lime (CaO content 98%), 30 parts by weight of the used flue gas treating agent, and 35 parts by weight of coal ash were mixed and kneaded with 50 parts by weight of 15 ° C. water for 10 minutes.
The obtained mixture was molded using an extrusion molding machine of 6 mmφ, steam-cured at 100 ° C. and normal pressure for 10 hours, dried at 200 ° C. for 2 hours, and then sized to 6 to 10 mm to obtain a flue gas treating agent. .
A performance test was conducted in the same manner as in Example 1, and the results are shown in Table 7.
[0042]
Comparative Example 3
26.5 parts by weight of quicklime used in Example 1 was digested with the same amount of water at 15 ° C. as in Example 1 so that the water did not evaporate, and used in the Example 60 minutes after the start of digestion. 30 parts by weight and 35 parts by weight of the finished flue gas treating agent and coal ash were mixed and kneaded for about 10 minutes.
The obtained mixture was molded using an extrusion molding machine of 6 mmφ, steam-cured at 100 ° C. normal pressure for 5 hours (Comparative Example 3-1) and 10 hours (Comparative Example 3-2), and heated at 200 ° C. for 2 hours. After drying, the particle size was adjusted to 6 to 10 mm to obtain a flue gas treating agent.
A performance test was conducted in the same manner as in the examples, and the results are shown in Table 7.
[0043]
Comparative Example 4
Quick lime, spent smoke treatment agent and coal ash used in Example 1 were mixed in a ratio of 26.5 parts by weight, 30 parts by weight and 35 parts by weight, respectively, and the same amount of 15 ° C. water as in Example 1 was used. The lid was capped to prevent evaporation of water, digested for 20 minutes, and kneaded.
The obtained mixture was molded using an extruder of 6 mmφ, steam-cured at 100 ° C. normal pressure for 5 hours (Comparative Example 4-1) and 10 hours (Comparative Example 4-2), and dried at 200 ° C. for 2 hours. Thereafter, the particle size was adjusted to 6 to 10 mm to obtain a flue gas treating agent.
A performance test was conducted in the same manner as in Example 1, and the results are shown in Table 7.
[0044]
[Table 7]

[0045]
【The invention's effect】
According to the production method of the present invention, the raw material lime source used in the conventional method is changed to cheaper quick lime, and the heat of digestion reaction is used to activate silicon dioxide in other raw materials. Since the activity as a flue gas treating agent can be improved, this method can be widely applied to the production of a lime-gypsum type flue gas treating agent, and its effect is great.
[Brief description of the drawings]
FIG. 1 is a view showing a comparative example of the activity of a slaked lime desulfurization agent (AH) and quick lime desulfurization agent (AO).

Claims

In the method for producing a flue gas treating agent comprising at least calcium oxide, silicon dioxide, aluminum oxide and gypsum,
The quicklime, the material comprising a non-crystalline silicon dioxide, added to a 2.4 to 45 parts by weight of calcium oxide per 100 parts by weight of silicon dioxide in quicklime, to perform the digestion reaction by adding water, then the Aluminum oxide, gypsum, and, if necessary, a substance containing silicon dioxide are mixed and kneaded so that the slaked lime digested by quick lime by the digestion reaction contains 35% of the flue gas treating agent , and the particle size is adjusted to 6 to 10 mm. A method for producing a flue gas treating agent.

The substance containing amorphous silicon dioxide contains gypsum, and in this case, the gypsum is adjusted to be 9 parts by weight or less per 100 parts by weight of calcium oxide in quicklime. The manufacturing method according to claim 1.

The manufacturing method according to claim 1 or 2, wherein calcium oxide, silicon dioxide, aluminum oxide and gypsum in the flue gas treating agent are supplied from quick lime, coal ash, and a used desulfurization agent.

The production method according to claim 1, wherein the substance containing amorphous silicon dioxide is bentonite or diatomaceous earth.